Gel electrolyte taking betaine as cross-linked substance as well as preparation method and application of gel electrolyte

Abstract

The invention discloses a gel electrolyte taking betaine as a cross-linked product and a preparation method and application thereof, and the preparation method comprises the following steps: (1) taking a certain amount of water, adding two monomers of acrylic acid and acryloyloxyethyl trimethyl ammonium chloride (DAC) into the water, dissolving the monomers in the water, and uniformly stirring; (2) adding betaine and inorganic salt into the clear and transparent solution in the step (1), and uniformly stirring; (3) adding a photoinitiator into the clarified solution obtained in the step (2), stirring, transferring into an ultrasonic machine, carrying out ultrasonic defoaming, putting into a glass clamping plate mold, and initiating gel formation through ultraviolet light; the prepared flexible gel electrolyte has good mechanical performance and electrochemical performance at the same time, and has wide application prospects in the field of flexible energy storage.

Description

Technical Field

[0001] The present invention belongs to the field of supercapacitors and new energy technologies, and specifically relates to a preparation method and application of a betaine-based flexible gel electrolyte having both high mechanical and electrochemical properties, in particular to a gel electrolyte with betaine as a cross-linked material, and a preparation method and application thereof. Background Art

[0002] Gel electrolyte is a semi-solid electrolyte material, mainly composed of polymer chains, salt solutions and various additives. It has a three-dimensional network structure and good mechanical stability. Compared with traditional liquid electrolytes, it is safer and has attracted widespread attention in the materials industry. The economic cost of gel electrolytes prepared using special conductive fillers is too high, the preparation cycle is long, and it is not conducive to large-scale production. At the same time, gel electrolytes also face the problem that mechanical properties and electrochemical properties cannot be taken into account at the same time, which limits their further promotion and use.

[0003] Supercapacitors are a new type of energy storage device with high power density, fast charge and discharge, long cycle life and wide temperature range. Supercapacitors with gel as electrolyte are flexible and can be used under various special conditions. However, gel electrolytes mainly rely on free ions as conductive materials, and low ionic conductivity will limit the electrochemical performance of the device to a certain extent.

[0004] Therefore, it is of great significance to develop a gel electrolyte that is easy to prepare, low-cost, has excellent mechanical properties and good ionic conductivity, and apply it to the field of flexible energy storage. Summary of the invention

[0005] In view of the defects in the prior art, the purpose of the present invention is to design a polyacrylic acid / DAC flexible gel electrolyte based on betaine as a crosslinker, and to use the special molecular structure left after different betaines are ionized in water to make it act as a crosslinking material, a conductive promoter, and a low-temperature resistant agent at the same time, and to participate in the construction of a competitive balance between a flexible network dominated by electrostatic interaction and a rigid network dominated by metal coordination. The invention successfully broadens the role of betaine in gel electrolytes. The prepared betaine gel electrolyte has excellent mechanical and electrochemical properties, and also has many properties such as low-temperature resistance and high transparency.

[0006] A preparation method and application of a gel electrolyte using betaine as a cross-linked material, comprising the following steps:

[0007] (1) Take a certain amount of water, add two monomers, acrylic acid and DAC, into it, dissolve the monomers in the water, and stir evenly.

[0008] (2) Add betaine and inorganic salts into the clear and transparent solution in step (1), and stir evenly.

[0009] (3) Add a photoinitiator into the clear solution in step (2), stir, transfer it to an ultrasonic machine, remove bubbles by ultrasonic treatment, place it in a glass splint mold, and form a gel by ultraviolet light initiation.

[0010] Furthermore, in step (1), the mass ratio of the two monomers, acrylic acid and acryloyloxyethyltrimethylammonium chloride, is 1:0.1 - 2, and the total addition amount is 10% - 50% of the mass of the solvent.

[0011] Furthermore, in step (2), the types of betaine are one or more of anhydrous betaine, betaine hydrochloride, betaine phosphate, and betaine citrate, and the addition amount is 5% - 40% of the mass of the solvent.

[0012] Furthermore, in step (2), the types of inorganic salts selected are one or more of anhydrous magnesium chloride, anhydrous calcium chloride, anhydrous manganese chloride, anhydrous cobalt chloride, aluminum chloride hexahydrate, chromium chloride, anhydrous iron chloride, zirconium oxychloride octahydrate, and titanium tetrachloride, and the addition amount is 5% - 50% of the mass of the solvent.

[0013] Furthermore, in step (3), the photoinitiator is one or more of 2 - hydroxy - 4′-(2 - hydroxyethoxy)-2 - methylpropiophenone, 2 - hydroxy - 2 - methyl - 1 - phenyl - 1 - propanone, and 2,4,6 - trimethylbenzoyl - diphenylphosphine oxide, and the added mass is 0.1% - 0.3% of the total mass of the monomers.

[0014] Furthermore, in step (3), the final precursor solution after adding the photoinitiator is ultrasonically treated to remove the bubbles therein, and the ultrasonic time is 5 - 10 min.

[0015] Furthermore, in all steps, the stirring time after adding the corresponding solid or liquid solute is 10 - 30 min.

[0016] The assembly of the supercapacitor includes a betaine gel electrolyte prepared by the above method and a sandwich structure composed of two electrodes, and subsequent device performance tests are carried out.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention broadens the role of betaine. After betaine ionizes in water, the remaining zwitterionic structure is connected to the positive and negative ion groups in the polymer side chain through electrostatic interaction, and at the same time participates in the coordination of metal ions, making the two main effects reach a competitive balance, ensuring the uniformity and stability of the gel three - dimensional network, and endowing the hydrogel with excellent mechanical properties.

[0019] The present invention expands the number of free ions through a variety of ion source channels, mainly from the ionization of betaine, inorganic salts, monomer acryloyloxyethyl trimethyl ammonium chloride, etc. While ensuring that the mechanical properties are not affected, the ionic conductivity is improved, and to a certain extent, the contradiction between the mechanical properties and electrochemical properties of the gel electrolyte is balanced.

[0020] The betaine used in the present invention forms strong hydrogen bonds with free water in the solution, thus ensuring that the formed gel has good low-temperature resistance.

[0021] The raw materials used in the experiment of the betaine gel electrolyte prepared by the present invention have low economic cost, mild synthesis conditions, and simple preparation methods, which are conducive to large-scale industrial production and application. The assembled supercapacitor has excellent electrochemical properties and has a wide application prospect in the field of flexible energy storage. Description of the Drawings

[0022] Figure 1 It is the infrared spectrum diagram of the betaine flexible gel electrolyte in Example 7.

[0023] Figure 2 It is the scanning electron microscope diagram of the betaine flexible gel electrolyte in Example 7.

[0024] Figure 3 It is the X-ray photoelectron spectroscopy diagram of the betaine flexible gel electrolyte in Example 7.

[0025] Figure 4 It is the stress-strain curve diagram of the betaine flexible gel electrolyte with the monomer mass ratio (Figure a) and the content of betaine hydrochloride (Figure b) as variables in Examples 1-9.

[0026] Figure 5 It is the bar chart of the change in ionic conductivity of the betaine flexible gel electrolyte with the monomer mass ratio (Figure a) and the content of betaine hydrochloride (Figure b) as variables in Examples 1-9.

[0027] Figure 6 It is the differential scanning calorimetry diagram of the betaine flexible gel electrolyte from -80°C to 20°C in Example 7.

[0028] Figure 7 It is the ultraviolet transmittance diagram of the betaine flexible gel electrolyte in Example 7.

[0029] Figure 8 It is the physical diagram of the supercapacitor device with a sandwich structure assembled by the betaine flexible gel electrolyte combined with a flexible carbon electrode in Example 7.

[0030] Figure 9Cyclic voltammogram of the supercapacitor assembled with the betaine flexible gel electrolyte in Example 7 at different scanning rates.

[0031] Figure 10 Galvanostatic charge-discharge curves of the supercapacitor assembled with the betaine flexible gel electrolyte in Example 7 at different current densities. Detailed implementation manners

[0032] The present invention will be described in detail below in conjunction with specific embodiments.

[0033] Example 1 Preparation of flexible gel electrolyte:

[0034] Measure 7 ml of deionized water, fix the total monomer mass at 30 wt%, add the monomers acrylic acid and DAC to the water so that their mass ratio is 10:1, and stir at room temperature for 10 min until the solution is homogeneous and transparent; then add 0.75 g of betaine hydrochloride and 1.5 g of zirconium oxychloride octahydrate thereto in sequence, then add 5 mg of photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone thereto, and stir at room temperature for 10 min; transfer it to an ultrasonic machine and ultrasonicate for 5 min to remove bubbles, and finally pour the transparent solution into a glass splint with a thickness of 2 mm and initiate it with ultraviolet light for 5 min to obtain the betaine flexible gel electrolyte, which is used for subsequent structural characterization and performance testing.

[0035] Example 2 Preparation of flexible gel electrolyte:

[0036] Measure 7 ml of deionized water, fix the total monomer mass at 30 wt%, add the monomers acrylic acid and DAC to the water so that their mass ratio is 7:3, and stir at room temperature for 10 min until the solution is homogeneous and transparent; then add 0.75 g of betaine hydrochloride and 1.5 g of zirconium oxychloride octahydrate thereto in sequence, then add 5 mg of photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone thereto, and stir at room temperature for 10 min; transfer it to an ultrasonic machine and ultrasonicate for 5 min to remove bubbles, and finally pour the transparent solution into a glass splint with a thickness of 2 mm and initiate it with ultraviolet light for 5 min to obtain the betaine flexible gel electrolyte, which is used for subsequent structural characterization and performance testing.

[0037] Example 3 Preparation of flexible gel electrolyte:

[0038] Measure 7 ml of deionized water, fix the total mass of the monomers at 30 wt%, add the monomers acrylic acid and DAC to the water such that their mass ratio is 1:1, and stir at room temperature for 10 min until the solution is homogeneous and transparent; then successively add 0.75 g of betaine hydrochloride and 1.5 g of zirconium oxychloride octahydrate thereto, then add 5 mg of the photoinitiator 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone thereto, and stir at room temperature for 10 min; transfer to an ultrasonic machine and ultrasonicate for 5 min to remove bubbles, and finally pour the transparent solution into glass splints of different thicknesses and initiate with ultraviolet light for 5 min to obtain the betaine flexible gel electrolyte, which is used for subsequent structural characterization and performance testing.

[0039] Preparation of the flexible gel electrolyte in Example 4:

[0040] Measure 7 ml of deionized water, fix the total mass of the monomers at 30 wt%, add the monomers acrylic acid and DAC to the water such that their mass ratio is 2:3, and stir at room temperature for 10 min until the solution is homogeneous and transparent; then successively add 0.75 g of betaine hydrochloride and 1.5 g of zirconium oxychloride octahydrate thereto, then add 5 mg of the photoinitiator 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone thereto, and stir at room temperature for 10 min; transfer to an ultrasonic machine and ultrasonicate for 5 min to remove bubbles, and finally pour the transparent solution into glass splints of different thicknesses and initiate with ultraviolet light for 5 min to obtain the betaine flexible gel electrolyte, which is used for subsequent structural characterization and performance testing.

[0041] Preparation of the flexible gel electrolyte in Example 5:

[0042] Measure 7 ml of deionized water, fix the total mass of the monomers at 30 wt%, add the monomers acrylic acid and DAC to the water such that their mass ratio is 3:7, and stir at room temperature for 10 min until the solution is homogeneous and transparent; then successively add 0.75 g of betaine hydrochloride and 1.5 g of zirconium oxychloride octahydrate thereto, then add 5 mg of the photoinitiator 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone thereto, and stir at room temperature for 10 min; transfer to an ultrasonic machine and ultrasonicate for 5 min to remove bubbles, and finally pour the transparent solution into glass splints of different thicknesses and initiate with ultraviolet light for 5 min to obtain the betaine flexible gel electrolyte, which is used for subsequent structural characterization and performance testing.

[0043] Preparation of the flexible gel electrolyte in Example 6:

[0044] Measure 7 ml of deionized water, fix the total mass of the monomers at 30 wt%, add the monomers acrylic acid and DAC to the water such that their mass ratio is 1:1, and stir at room temperature for 10 min until the solution is homogeneous and transparent; then add 0.35 g of betaine hydrochloride and 1.5 g of zirconium oxychloride octahydrate thereto in sequence, then add 5 mg of the photoinitiator 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone thereto, and stir at room temperature for 10 min; transfer to an ultrasonic machine and ultrasonicate for 5 min to remove air bubbles, and finally pour the transparent solution into glass splints of different thicknesses and initiate with ultraviolet light for 5 min to obtain the betaine flexible gel electrolyte, which is used for subsequent structural characterization and performance testing.

[0045] Preparation of the flexible gel electrolyte in Example 7:

[0046] Measure 7 ml of deionized water, fix the total mass of the monomers at 30 wt%, add the monomers acrylic acid and DAC to the water such that their mass ratio is 1:1, and stir at room temperature for 10 min until the solution is homogeneous and transparent; then add 1.5 g of betaine hydrochloride and 1.5 g of zirconium oxychloride octahydrate thereto in sequence, then add 5 mg of the photoinitiator 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone thereto, and stir at room temperature for 10 min; transfer to an ultrasonic machine and ultrasonicate for 5 min to remove air bubbles, and finally pour the transparent solution into glass splints of different thicknesses and initiate with ultraviolet light for 5 min to obtain the betaine flexible gel electrolyte, which is used for subsequent structural characterization and performance testing.

[0047] Preparation of the flexible gel electrolyte in Example 8:

[0048] Measure 7 ml of deionized water, fix the total mass of the monomers at 30 wt%, add the monomers acrylic acid and DAC to the water such that their mass ratio is 1:1, and stir at room temperature for 10 min until the solution is homogeneous and transparent; then add 2 g of betaine hydrochloride and 1.5 g of zirconium oxychloride octahydrate thereto in sequence, then add 5 mg of the photoinitiator 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone thereto, and stir at room temperature for 10 min; transfer to an ultrasonic machine and ultrasonicate for 5 min to remove air bubbles, and finally pour the transparent solution into glass splints of different thicknesses and initiate with ultraviolet light for 5 min to obtain the betaine flexible gel electrolyte, which is used for subsequent structural characterization and performance testing.

[0049] Preparation of the flexible gel electrolyte in Example 9:

[0050] Measure 7 ml of deionized water, fix the total mass of the monomers at 30 wt%, add monomer acrylic acid and DAC to the water such that their mass ratio is 1:1, and stir at room temperature for 10 min until the solution is homogeneous and transparent; then sequentially add 2.5 g of betaine hydrochloride and 1.5 g of zirconium oxychloride octahydrate thereto, then add 5 mg of photoinitiator 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone thereto, and stir at room temperature for 10 min; transfer to an ultrasonic machine and ultrasonicate for 5 min to remove air bubbles, and finally pour the transparent solution into glass splints of different thicknesses and initiate with ultraviolet light for 5 min to obtain a betaine flexible gel electrolyte, which is used for subsequent structural characterization and performance testing.

[0051] Preparation of the flexible gel electrolyte of Example 10:

[0052] Measure 7 ml of deionized water, fix the total mass of the monomers at 10 wt%, add monomer acrylic acid and DAC to the water such that their mass ratio is 1:1, and stir at room temperature for 10 min until the solution is homogeneous and transparent; then sequentially add 1.5 g of betaine hydrochloride and 1.5 g of zirconium oxychloride octahydrate thereto, then add 5 mg of photoinitiator 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone thereto, and stir at room temperature for 10 min; transfer to an ultrasonic machine and ultrasonicate for 5 min to remove air bubbles, and finally pour the transparent solution into glass splints of different thicknesses and initiate with ultraviolet light for 5 min to obtain a betaine flexible gel electrolyte, which is used for subsequent structural characterization and performance testing.

[0053] Preparation of the flexible gel electrolyte of Example 11:

[0054] Measure 7 ml of deionized water, fix the total mass of the monomers at 50 wt%, add monomer acrylic acid and DAC to the water such that their mass ratio is 1:1, and stir at room temperature for 10 min until the solution is homogeneous and transparent; then sequentially add 1.5 g of betaine hydrochloride and 1.5 g of zirconium oxychloride octahydrate thereto, then add 5 mg of photoinitiator 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone thereto, and stir at room temperature for 10 min; transfer to an ultrasonic machine and ultrasonicate for 5 min to remove air bubbles, and finally pour the transparent solution into glass splints of different thicknesses and initiate with ultraviolet light for 5 min to obtain a betaine flexible gel electrolyte, which is used for subsequent structural characterization and performance testing.

[0055] Preparation of the flexible gel electrolyte of Example 12:

[0056] Measure 7 ml of deionized water, fix the total mass of the monomers at 30 wt%, add acrylic acid and DAC as monomers to the water, with a mass ratio of 1:1, and stir at room temperature for 10 min until the solution is homogeneous and transparent; then add 1.5 g of phosphobetaine and 1.5 g of aluminum chloride hexahydrate to it in sequence. Next, add 5 mg of the photoinitiator 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone into it and stir at room temperature for 10 min; transfer it to an ultrasonic machine and ultrasonicate for 5 min to remove air bubbles. Finally, pour the transparent solution into glass splints with different thicknesses and initiate with ultraviolet light for 5 min to obtain the betaine flexible gel electrolyte, which is used for subsequent structural characterization and performance testing.

[0057] Assemble the betaine gel electrolyte prepared in Example 7 and the carbon electrode material into a supercapacitor in a sandwich structure. Specifically: cut the gel into thin slices with a length of 2 cm, a width of 2 cm, and a thickness of 2 mm, sandwich them between two carbon electrodes with a length of 2 cm and a width of 2 cm, and press them tightly so that the three do not slide relative to each other under natural conditions. After successfully forming the device, proceed with the testing of the subsequent device.

[0058] Figure 1 It is the infrared spectrum of the betaine flexible gel electrolyte obtained in Example 7. Among them, at 1727 cm -1 , 953 cm -1 , the -C=O and -N + (CH3)3 characteristic peaks of two monomers, acrylic acid and acryloyloxyethyltrimethylammonium chloride, respectively, and at 1614 cm -1 , 1407 cm -1 are the -COO- and -C-N characteristic peaks of betaine, successfully proving the successful introduction of various raw materials into the gel electrolyte.

[0059] Figure 2 It is the scanning electron micrograph of the betaine flexible gel electrolyte obtained in Example 7. It can be seen from the figure that the prepared gel electrolyte presents a porous structure, which is a structure conducive to ion migration.

[0060] Figure 3 It is the X-ray photoelectron spectroscopy of the betaine flexible gel electrolyte in Example 7. It can be seen from it the chemical components contained in the gel electrolyte and the chemical states of each element, also proving the introduction of each substance.

[0061] Figure 4The stress-strain curves of the gel electrolytes prepared in Examples 1-9 are shown respectively with the monomer mass ratio and the content of betaine hydrochloride as variables. The mechanical properties of the prepared hydrogels were tested and compared using a universal testing machine. As can be seen from the figure, with the increase of the mass of DAC monomer under the condition that the total mass of monomers, the mass of betaine hydrochloride and the mass of zirconium oxychloride octahydrate are fixed, the mechanical properties of the gel electrolyte show a trend of first increasing and then decreasing; with the addition of betaine hydrochloride under the condition that the total mass of monomers, the monomer mass ratio and the mass of zirconium oxychloride octahydrate are fixed, the mechanical properties of the gel electrolyte also show a trend of first increasing and then decreasing. This is mainly because a certain amount of DAC provides more cross-linking sites for betaine hydrochloride, promoting the competitive balance of the two networks. At this time, the best mechanical properties are obtained for the gel in Example 7, with a tensile stress of 3.1 Mpa and a tensile strain of 2200%.

[0062] Figure 5 The bar chart of the conductivity change of the gel electrolytes prepared in Examples 1-9 is shown respectively with the monomer mass ratio and the content of betaine hydrochloride as variables. The conductivity of the prepared hydrogels was tested and compared using an electrochemical workstation. As can be seen from the figure, with the increase of the mass of DAC monomer under the condition that the total mass of monomers, the mass of betaine hydrochloride and the mass of zirconium oxychloride octahydrate are fixed, the conductivity of the gel electrolyte shows a trend of first increasing and then decreasing; with the addition of betaine hydrochloride under the condition that the total mass of monomers, the monomer mass ratio and the mass of zirconium oxychloride octahydrate are fixed, the mechanical properties of the gel electrolyte also show a trend of first increasing and then decreasing. This is mainly because an appropriate ion concentration can promote the improvement of conductivity, while an excessive ion concentration hinders ion transfer and reduces conductivity instead. At this time, the best conductivity is obtained for the gel in Example 7, which is 15.4 S / m.

[0063] Figure 6 The differential scanning calorimetry chart of the gel prepared in Example 7 shows a crystallization peak of free water at -55 °C during the cooling process, indicating that the gel has good low-temperature resistance.

[0064] Figure 7 The ultraviolet transmission chart of the gel prepared in Example 7 shows that the gel can maintain a transmittance of 92.9% at a wavelength of 400 nm, having excellent transparency.

[0065] Figure 8 The schematic diagram and the physical picture of the sandwich structure composed of the gel prepared in Example 7 and a carbon electrode are shown. The assembled device can be bent at any angle, having good flexibility.

[0066] From the results of Examples 1-9, it can be seen that the betaine gel electrolyte prepared in Example 7 has both the best mechanical properties and the best ionic conductivity. Therefore, the supercapacitor composed of it as the gel electrolyte is taken as a representative for subsequent performance testing.

[0067] Figure 9 With Figure 10 The main performance test graphs of the supercapacitors composed for Example 7 at 6 different scanning rates and 6 different current densities respectively can illustrate that the assembled devices have good electrochemical performance.

[0068] It should be understood that those skilled in the art can make improvements or transformations according to the above description, and all such improvements and transformations should fall within the protection scope of the appended claims of the present invention.

Claims

1. A method for preparing a gel electrolyte with betaine as a crosslinking agent, characterized in that, It includes the following steps: (1) Take a certain amount of water, add two monomers, acrylic acid and acryloyloxyethyl trimethyl ammonium chloride (DAC), dissolve the monomers in the water, and stir evenly to obtain a clear and transparent solution; (2) Add betaine and inorganic salts to the clear and transparent solution in step (1), and stir evenly to obtain a clear solution; (3) Add a photoinitiator to the clear solution in step (2), stir and then transfer it to an ultrasonic machine to remove bubbles by ultrasonic treatment. Place it in a glass splint mold and initiate gel formation through ultraviolet light.

2. The preparation method according to claim 1, characterized in that: In step (1), the mass ratio of the two monomers, acrylic acid and DAC, is 1:0.1 - 2, and the total addition amount is 10% - 50% of the mass of the solvent.

3. The preparation method according to claim 1, characterized in that: In step (2), the type of betaine is one or more of anhydrous betaine, betaine hydrochloride, betaine phosphate, and betaine citrate, and the addition amount is 5% - 40% of the mass of the solvent.

4. The preparation method according to claim 1, wherein: In step (2), the type of the selected inorganic salt is one or more of anhydrous magnesium chloride, anhydrous calcium chloride, anhydrous manganese chloride, anhydrous cobalt chloride, aluminum chloride hexahydrate, chromium chloride, anhydrous iron chloride, zirconium oxychloride octahydrate, and titanium tetrachloride, and the addition amount is 5% - 50% of the mass of the solvent.

5. The preparation method according to claim 1, wherein: In step (3), the photoinitiator is one or more of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and the addition amount is 0.1% - 0.3% of the total mass of the monomers.

6. The preparation method according to claim 1, characterized in that: In step (3), the final precursor solution after adding the photoinitiator is ultrasonically treated to remove the bubbles therein, and the ultrasonic time is 5 - 10 min.

7. The preparation method according to claim 1, characterized in that: In all steps, the stirring time after adding the corresponding solid or liquid solute is 10 - 30 min.

8. A betaine flexible gel electrolyte prepared by the preparation method according to any one of claims 1 - 7.

9. Application of the betaine flexible gel according to claim 8 as a solid electrolyte in a supercapacitor.

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