Cellulose cotton pulp for capacitor electrode and preparation method thereof
By adding hydrophilic cotton fibers, polypyrrole and sodium isyl hydroxyethylsulfonate to the cellulose cotton pulp, and using vacuum high-pressure impregnation and condensation reaction, the conductivity and electrochemical performance of the cellulose cotton pulp are improved, and the problem of poor conductivity of the cellulose cotton pulp is solved, and higher electrochemical performance is achieved.
Patent Information
- Application Number
- CN202510597786.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-09
- Publication Date
- 2025-07-11
AI Technical Summary
When existing cellulose cotton slurry is used as capacitor electrode material, the conductivity and energy density are poor, which limits the improvement of electrochemical performance.
By adding hydrophilic cotton fibers, polypyrrole (PPy) and sodium isyl hydroxyethylsulfonate (HESS) to the cellulose cotton pulp, Mg(NO3)2, Ca(NO3)2, and LiCl particles were loaded by vacuum high-pressure impregnation method, and combined with the condensation reaction between HESS and PPy, polymer compounds were formed to improve the conductivity and dispersion of cellulose cotton pulp.
It improves the conductivity and electrochemical performance of cellulose cotton pulp, enhances the charge transfer ability and electrochemical energy storage effect, and reduces the electrode resistance.
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of cellulose cotton pulp, and specifically relates to a cellulose cotton pulp for capacitor electrodes and a preparation method thereof. Background Art
[0002] With the rapid development of modern electronic devices, the demand for high-performance energy storage devices is increasing day by day. As a new type of energy storage element, supercapacitors have received extensive attention and applications in many fields due to their high power density, long cycle life, and fast charge and discharge characteristics. However, the performance bottleneck of traditional electrode materials limits the further improvement of the overall performance of supercapacitors.
[0003] As a natural polymer material, cellulose has received extensive attention in the field of materials science due to its renewable nature, good biocompatibility, and degradability. Especially cellulose cotton pulp, due to its uniform fiber structure and high purity, has become an ideal choice for preparing high-performance electrode materials. Through special treatment, cellulose cotton pulp can form a porous structure, providing rich ion transport channels, which helps to improve the energy density and power density of capacitors.
[0004] At present, some studies have applied cellulose materials to supercapacitor electrodes. However, cellulose itself has the disadvantages of poor conductivity and low energy density, which thus impose many limitations on the electrochemical performance of the electrodes. Based on this, the present invention is dedicated to providing a cellulose cotton pulp for capacitor electrodes and a preparation method thereof to improve its electrochemical performance. Summary of the Invention
[0005] The purpose of the present invention is to provide a cellulose cotton pulp for capacitor electrodes and a preparation method thereof, and solve the following technical problems:
[0006] How to improve the electrochemical performance of cellulose cotton pulp for capacitor electrodes.
[0007] The purpose of the present invention can be achieved through the following technical solutions:
[0008] In the first aspect, the present invention discloses a cellulose cotton pulp for capacitor electrodes, which comprises the following components in parts by weight: 70-90 parts of hydrophilic cotton fibers, 1-2 parts of polypyrrole (PPy), and 2-3 parts of sodium hydroxyethyl sulfonate (HESS);
[0009] Preferably, the hydrophilic cotton fibers are 80 parts, PPy is 1.5 parts, and HESS is 2.5 parts.
[0010] In the present invention, the hydrophilic cotton fibers are prepared according to the following preparation method:
[0011] Step 1: Prepare cotton fibers
[0012] A1. Treatment is carried out by the alkali method. The clean short cotton linter is directly immersed in a sodium hydroxide solution with a mass fraction of 20% - 30% without being crushed, and ultrasonically mixed for 2 hours, then heated to 120 °C and cooked for 2 hours, taken out and filtered, the filtrate is discarded, and the filter material is retained;
[0013] Preferably, the mass fraction of the sodium hydroxide solution is 25%;
[0014] Preferably, the short cotton linter used is Xinjiang short cotton linter.
[0015] A2. The filter material is repeatedly washed with deionized water to remove excess sodium hydroxide and impurities, and after washing, it is placed in a vacuum drying oven and dried at 120 °C for 6 hours to obtain cotton fibers.
[0016] Step 2. Magnesium nitrate (Mg(NO3)2) and calcium nitrate (Ca(NO3)2) are dissolved in a solvent system of N,N - dimethylacetamide / lithium chloride (DMAc / LiCl) to form an impregnating solution. The cotton fibers are placed in the impregnating solution and ultrasonically mixed, and then vacuum pressure impregnation is carried out under the conditions of a vacuum degree ≥ 10 -6 Torr, a pressure of 2 - 4 MPa, and an impregnation time of 20 - 30 minutes; after impregnation, it is filtered, 10 times the amount of water of the filter material is added to the obtained filter material, and then rotary evaporation is carried out using a rotary evaporation device. The rotary evaporation temperature is 80 °C, the rotary evaporation pressure is 60 mbar, and the rotary evaporation speed is 150 rpm, so as to remove N,N - dimethylacetamide and obtain a hydrophilic cotton fiber precursor;
[0017] Preferably, the vacuum degree is 0 -6 Torr, the pressure is 3 MPa, and the impregnation time is 25 minutes;
[0018] Furthermore, in the N,N - dimethylacetamide / lithium chloride solvent system, the dosage ratio of N,N - dimethylacetamide to lithium chloride is 100 mL / 8 g;
[0019] Furthermore, the dosage ratio of magnesium nitrate and calcium nitrate in the N,N - dimethylacetamide / lithium chloride solvent system to N,N - dimethylacetamide is 100 mL / 6 g.
[0020] Step 3. The hydrophilic cotton fiber precursor is placed in a vacuum drying oven and dried at 120 °C for 6 hours, then transferred to a crusher for crushing, and then transferred to a ball mill for grinding to finally obtain hydrophilic cotton fibers.
[0021] Cotton fibers are natural cellulose and are insoluble in water, alcohols, ketones and other conventional solvents. However, they have good solubility in the DMAc / LiCl solvent system. At the same time, Mg(NO3)2 and Ca(NO3)2 can also be uniformly dissolved in the DMAc / LiCl solvent system. Therefore, after the cotton fibers enter the impregnating solution, they can be in full and uniform contact with Mg(NO3)2, Ca(NO3)2, and LiCl in the impregnating solution. After vacuum pressure impregnation, Mg(NO3)2, Ca(NO3)2, and LiCl are deeply embedded into the gaps on the surface of the cotton fibers as hydrophilic particles. After removing DMAc and drying, the Mg(NO3)2, Ca(NO3)2, and LiCl particles will firmly adhere to the surface of the cotton fibers, achieving uniform loading of the hydrophilic particles.
[0022] In a second aspect, the present invention also discloses a method for preparing the cellulose cotton pulp for a capacitor electrode as described above, which is characterized by the following steps in sequence:
[0023] S1. Dissolve HESS in water to form a HESS solution, and add hydrophilic cotton fibers to the HESS solution. The mass ratio of HESS to water is 1 g: 80 mL; the sulfonic acid group (-SO3H) and its sodium salt form (-SONa) in HESS will undergo an esterification reaction or an etherification reaction with the hydroxyl groups in the cotton fibers, so that HESS is connected to the cotton fibers. As a surfactant intermediate, HESS has good water solubility and dispersibility. After being connected to the surface of the cotton fibers, it can improve the dispersibility and stability of the cotton fibers, which is beneficial to improving the compatibility of the cotton fibers with other substances during application, and further improving its functionality; stir in an ice-water bath at -10°C to -5°C for 30 min to obtain an ice mixture;
[0024] Preferably, the temperature of the ice-water bath is -8°C.
[0025] S2. Add PPy to the ice mixture for ultrasonic mixing reaction to cause a condensation reaction between PPy and HESS, and obtain a reaction solution after reacting for 2 h;
[0026] The condensation reaction is specifically as follows: As a conductive polymer, PPy first contacts HESS in the ice mixture through physical adsorption or charge interaction, and then the hydroxyethyl functional group in HESS undergoes a condensation reaction with the unsaturated bonds on the conjugated chain of PPy, so that PPy is connected to HESS to form a polymer compound. On the one hand, the dispersibility of PPy is improved, and on the other hand, it is beneficial to enhancing the electrochemical performance of the cotton fibers.
[0027] S3. Place the reaction solution in a freezer at a temperature between -50°C and -40°C for 5 hours to obtain a crystallized block. Under vacuum conditions, heat the crystallized block in a stepped manner. First, heat it at 10°C for 1 hour, then raise the temperature to 30°C and heat for 2 hours, and finally raise the temperature to 60°C and heat for 3 hours to complete freeze-drying, obtaining cellulose cotton pulp for capacitor electrodes.
[0028] Preferably, the pre-freezing temperature is -45°C.
[0029] Advantages of the present invention:
[0030] 1. In the cellulose cotton pulp for capacitor electrodes of the present invention, Mg(NO3)2, Ca(NO3)2, and LiCl particles are loaded on the surface of cotton fibers by the vacuum high-pressure impregnation method. These particles have excellent moisture absorption properties and can dissociate into ions with diffusion and transport capabilities after absorbing moisture, effectively improving the moisture power generation performance, reducing the resistance of the electrode, and enhancing the conductivity.
[0031] 2. HESS is added to the cellulose cotton pulp for capacitor electrodes of the present invention. -S03H and -SONa in HESS will undergo an esterification reaction or an etherification reaction with the hydroxyl groups in cotton fibers, connecting HESS to the cotton fibers. As a surfactant intermediate, HESS has good water solubility and dispersibility. After being connected to the surface of cotton fibers, it can improve the dispersibility and stability of cotton fibers, which is beneficial to improving the compatibility of cotton fibers with other substances during application, and thus improving its functionality.
[0032] 3. On the basis of adding HESS, PPy is also added to the cellulose cotton pulp for capacitor electrodes of the present invention. PPy has a large specific surface area, a large specific capacitance, and high conductivity. Through a condensation reaction, the hydroxyethyl functional group in HESS reacts with the unsaturated bonds on the conjugated chain in PPy, connecting PPy to HESS to form a polymer compound. On the one hand, the dispersibility of PPy is improved, and on the other hand, attaching to cotton fibers is beneficial to enhancing the electrochemical performance of cotton fibers. Detailed implementation methods
[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.
[0034] The experimental methods in the following embodiments are all conventional methods unless otherwise specified, and are carried out according to the technologies or conditions described in the literature in this field or according to the product instructions. The materials, reagents, etc. used in the following embodiments can be obtained from commercial channels unless otherwise specified.
[0035] Preparation Example 1
[0036] Preparation of cotton fiber:
[0037] Step 1: 2000 g of short cotton linter (purchased from Xinjiang Xinsai Cotton Industry Co., Ltd.) was repeatedly washed with clear water to remove impurities, and then dried in an oven to obtain 1769 g of clean short cotton linter;
[0038] Step 2: The clean short cotton linter was directly immersed in a sodium hydroxide solution with a mass fraction of 25% without crushing, and ultrasonically mixed for 2 h, then transferred to a steamer and heated to 120 °C for cooking for 2 h, and then the yellowish-black filtrate was filtered off, and the filter material was retained;
[0039] Step 3: The filter material was repeatedly washed with deionized water to remove excess sodium hydroxide and impurities until no sodium hydroxide was detected in the washing liquid. After washing, it was placed in a vacuum drying oven and dried at 120 °C for 6 h to obtain cotton fiber.
[0040] Preparation Example 2
[0041] Preparation of hydrophilic cotton fiber:
[0042] Step 1: 80 g of LiCl was added to a 1000 mL beaker and stirred evenly with a glass rod to form a DMAc / LiCl solvent system;
[0043] Step 2: 60 g of Mg(NO3)2 and 60 g of Ca(NO3)2 were added to the DMAc / LiCl solvent system and stirred evenly with a glass rod to form an impregnating solution;
[0044] Step 3: 400 g of the cotton fiber prepared in Preparation Example 1 was placed in the impregnating solution and ultrasonically mixed for 2 h, then added to a vacuum pressure impregnation tank. The vacuum degree of the vacuum pressure impregnation tank was set to 10 -6 Torr, the pressure was 3 MPa, and the impregnation time was 25 min. Then the switch was turned on for impregnation. After impregnation, filtration was carried out. 10 times the amount of water of the filter material was added to the obtained filter material, and then rotary evaporation was carried out using a rotary evaporation device. The rotary evaporation temperature was 80 °C, the rotary evaporation pressure was 60 mbar, and the rotary evaporation speed was 150 rpm to remove N,N-dimethylformamide to obtain a hydrophilic cotton fiber precursor;
[0045] Step 4: The hydrophilic cotton fiber precursor was placed in a vacuum drying oven and dried at 120 °C for 6 h, then transferred to a crusher for crushing, and then transferred to a ball mill for grinding to the nanometer level to finally obtain hydrophilic cotton fiber.
[0046] Comparative Preparation Example 1
[0047] Preparation of hydrophilic cotton fiber:
[0048] Compared with Preparation Example 2, the difference is only that Step 2 is cancelled and the impregnation solution in Step 3 is replaced with the solvent system of DMAc / LiCl prepared in Step 1, and other steps and conditions are exactly the same, and finally hydrophilic cotton fibers are obtained.
[0049] Comparative Preparation Example 2
[0050] Preparation of hydrophilic cotton fibers:
[0051] Compared with Preparation Example 2, the difference is only that Step 3 is "placing the cotton fibers prepared in Preparation Example 1 in the impregnation solution and ultrasonically mixing for 2 h to obtain a hydrophilic cotton fiber precursor"; other steps and conditions are exactly the same, and finally hydrophilic cotton fibers are obtained.
[0052] Comparative Preparation Example 3
[0053] Preparation of cotton fibers:
[0054] Directly take 400 g of the cotton fibers prepared in Preparation Example 1 as the cotton fibers of Comparative Preparation Example 3.
[0055] Example 1
[0056] Preparation of cellulose cotton pulp for capacitor electrodes:
[0057] Step 1: Add 2.5 g of HESS to a beaker containing 200 mL of water, stir evenly with a glass rod, then add 80 g of the hydrophilic cotton fibers prepared in Preparation Example 2, and stir the beaker in an ice-water bath at -8 °C for 30 min to obtain an ice mixture;
[0058] Step 2: Add 1.5 g of PPy to the ice mixture and carry out ultrasonic reaction for 2 h to obtain a reaction solution;
[0059] Step 3: Place the reaction solution in a refrigerator and pre-freeze it at -45 °C for 5 h to obtain a crystal block; under vacuum conditions, carry out stepwise heating on the crystal block, first heat at 10 °C for 1 h, then heat up to 30 °C for 2 h, and finally heat up to 60 °C for 3 h to complete freeze-drying and obtain cellulose cotton pulp for capacitor electrodes.
[0060] Example 2
[0061] Preparation of cellulose cotton pulp for capacitor electrodes:
[0062] Step 1: Add 2 g of HESS to a beaker containing 160 mL of water, stir evenly with a glass rod, then add 70 g of the hydrophilic cotton fibers prepared in Preparation Example 2, and stir the beaker in an ice-water bath at -5 °C for 30 min to obtain an ice mixture;
[0063] Step 2: Add 1 g of PPy to the ice mixture and carry out ultrasonic reaction for 2 h to obtain a reaction solution;
[0064] Step 3: Place the reaction solution in a refrigerator and pre-freeze it at -40°C for 5 h to obtain a crystallized block; under vacuum conditions, perform stepwise heating on the crystallized block, first heating at 10°C for 1 h, then raising the temperature to 30°C and heating for 2 h, and finally raising the temperature to 60°C and heating for 3 h to complete freeze-drying, obtaining the cellulose cotton pulp for capacitor electrodes.
[0065] Example 3
[0066] Preparation of cellulose cotton pulp for capacitor electrodes:
[0067] Step 1: Add 3 g of HESS to a beaker containing 240 mL of water, stir evenly with a glass rod, then add 90 g of the hydrophilic cotton fibers prepared in Preparation Example 2, and stir the beaker in an ice-water bath at -10°C for 30 min to obtain an ice mixture;
[0068] Step 2: Add 2 g of PPy to the ice mixture and perform ultrasonic reaction for 2 h to obtain a reaction solution;
[0069] Step 3: Place the reaction solution in a refrigerator and pre-freeze it at -50°C for 5 h to obtain a crystallized block; under vacuum conditions, perform stepwise heating on the crystallized block, first heating at 10°C for 1 h, then raising the temperature to 30°C and heating for 2 h, and finally raising the temperature to 60°C and heating for 3 h to complete freeze-drying, obtaining the cellulose cotton pulp for capacitor electrodes.
[0070] Comparative Example 1
[0071] Compared with Example 1, the difference is only that the hydrophilic cotton fibers prepared in Preparation Example 2 are replaced with the hydrophilic cotton fibers prepared in Comparative Preparation Example 1, and the other steps and conditions are exactly the same, finally obtaining the cellulose cotton pulp for capacitor electrodes.
[0072] Comparative Example 2
[0073] Compared with Example 1, the difference is only that the hydrophilic cotton fibers prepared in Preparation Example 2 are replaced with the hydrophilic cotton fibers prepared in Comparative Preparation Example 2, and the other steps and conditions are exactly the same, finally obtaining the cellulose cotton pulp for capacitor electrodes.
[0074] Comparative Example 3
[0075] Compared with Example 1, the difference is only that the hydrophilic cotton fibers prepared in Preparation Example 2 are replaced with the hydrophilic cotton fibers prepared in Comparative Preparation Example 3, and the other steps and conditions are exactly the same, finally obtaining the cellulose cotton pulp for capacitor electrodes.
[0076] Comparative Example 4
[0077] Directly use the hydrophilic cotton fibers prepared in Preparation Example 2 as the cellulose cotton pulp for capacitor electrodes in this comparative example.
[0078] Comparative Example 5
[0079] Directly use the cotton fiber obtained in Preparation Example 1 as the cellulose cotton pulp for the capacitor electrode in this comparative example.
[0080] Perform electrochemical performance tests on the cellulose cotton pulp for capacitor electrodes prepared in Examples 1-3 and Comparative Examples 1-5 respectively. The test method is as follows: Mix 90 g of cellulose cotton pulp for capacitor electrodes, 5 g of Super-P, and 5 g of polyvinylidene fluoride evenly, then add 200 g of N-methylpyrrolidone solvent and mix evenly to obtain a black slurry. Put the aluminum foil into a coating machine, pour the black slurry, and after coating evenly, transfer it to an oven and dry it at 40 °C for 4 h. Then put the dried aluminum foil into a punching machine to punch into electrode sheets, weigh them, put the electrode sheets into a drying bottle, transfer them to a vacuum drying oven and dry them at 110 °C for 6 h to obtain capacitor electrode sheets.
[0081] Adopt a standard three-electrode test system. Use the prepared capacitor electrode sheet as the working electrode, a platinum sheet electrode as the counter electrode, pour 3 mol / L KOH solution as the electrolyte into an electrolytic cell until it just covers the electrode sheet, then place the two electrodes parallel in the electrolyte, and place a silver-silver chloride electrode between the two electrodes as the reference electrode to perform galvanostatic charge-discharge (GCD), cyclic voltammetry scanning (CV), and electrochemical impedance spectroscopy (EIS). The specific test conditions are as follows:
[0082] GCD: The current density is 10 mA / cm 2 ;
[0083] CV: The scanning rate is 10 mV / s;
[0084] Obtain a curve graph based on the test results, and convert the curve graph into intuitive data and list it in Table 1 as follows:
[0085] Table 1
[0086] GCD CV EIS <![CDATA[Areal specific capacitance (mF / cm 2 )]]> Enclosed area (%) Impedance (Ω) Example 1 2618 21.5 62.5 Example 2 2595 20.6 65.2 Example 3 2602 20.9 64.6 Comparative Example 1 2032 15.2 125.6 Comparative Example 2 1965 14.6 126.9 Comparative Example 3 1525 12.6 135.2 Comparative Example 4 1569 12.9 135.8 Comparative Example 5 1025 6.8 150.6
[0087] Analyze the data in Table 1. It can be known that compared with Comparative Examples 1-5, Examples 1-3 have significantly larger area specific capacitance and closed area, and significantly smaller impedance. This shows that the capacitor electrode sheets of Examples 1-3 have stronger charge transfer ability, electrochemical energy storage effect, and lower resistance. Therefore, it can be shown that the cellulose cotton pulp for capacitor electrodes of the present invention has stronger electrochemical performance.
[0088] The above has described a specific embodiment of the present invention in detail, but the content described is only a preferred embodiment of the present invention and cannot be considered as limiting the scope of implementation of the present invention. All equivalent changes and improvements made according to the scope of the application of the present invention should still fall within the scope covered by the patent of the present invention.
Claims
1. A cellulose cotton pulp for capacitor electrodes, characterized in that, It comprises the following components in parts by weight: 70-90 parts of hydrophilic cotton fiber, 1-2 parts of polypyrrole, and 2-3 parts of sodium hydroxyethyl sulfonate; Among them, the hydrophilic cotton fiber is prepared according to the following preparation method: Step 1: Treat cotton linter with an alkali method to make cotton fiber; Step 2: Dissolve magnesium nitrate and calcium nitrate in a solvent system of N,N-dimethylformamide / lithium chloride to form an impregnating solution. Place the cotton fiber in the impregnating solution, ultrasonically mix it, and then use the vacuum pressure impregnation method for impregnation. After impregnation, filter, and use the azeotropic rotary evaporation method to remove N,N-dimethylformamide from the obtained filter material to obtain a hydrophilic cotton fiber precursor; Step 3: Dry, crush, and grind the hydrophilic cotton fiber precursor to obtain hydrophilic cotton fiber.
2. The cellulose cotton pulp for a capacitor electrode according to claim 1, wherein In Step 1, the specific steps of the alkali treatment are as follows: A1: Immerse the clean short cotton linter directly without crushing into a sodium hydroxide solution with a mass fraction of 20% - 30%, ultrasonically mix for 2 h, then heat to 120 °C and cook for 2 h, take out and filter, and retain the filter material; A2: Wash the filter material repeatedly with deionized water, and dry after washing to obtain cotton fiber.
3. The cellulose cotton pulp for a capacitor electrode according to claim 1, wherein In Step 2, in the solvent system of N,N-dimethylformamide / lithium chloride, the dosage ratio of N,N-dimethylformamide to lithium chloride is 100 mL / 8 g.
4. The cellulose cotton pulp for a capacitor electrode according to claim 3, wherein The dosage ratio of magnesium nitrate and calcium nitrate to N,N-dimethylformamide in the solvent system of N,N-dimethylformamide / lithium chloride is 100 mL / 6 g.
5. The cellulose cotton pulp for a capacitor electrode according to claim 1, wherein In Step 2, the parameters of the vacuum pressure impregnation method are: the degree of vacuum ≥ 10 -6 Torr, the pressure is 2 - 4 MPa, and the impregnation time is 20 - 30 min.
6. The cellulose cotton pulp for capacitor electrodes according to claim 1, wherein In Step 2, the specific steps of removing N,N-dimethylformamide by the azeotropic rotary evaporation method are as follows: Add water with a volume 10 times that of the filter material to the filter material, and then use a rotary evaporation device for rotary evaporation. The rotary evaporation temperature is 80 °C, the rotary evaporation pressure is 60 mbar, and the rotary evaporation speed is 150 rpm.
7. A preparation method of cellulose cotton pulp for a capacitor electrode as described in any one of claims 1-6, characterized in that, Proceed in the following steps in sequence: S1: Dissolve sodium hydroxyethyl sulfonate in water to form a sodium hydroxyethyl sulfonate solution, add the hydrophilic cotton fiber to the sodium hydroxyethyl sulfonate solution, and stir evenly in an ice bath to obtain an ice mixture; S2: Add polypyrrole to the ice mixture for ultrasonic mixing reaction, and obtain a reaction solution after reacting for 2 h; S3: Perform freeze-drying on the reaction solution to obtain cellulose cotton pulp for capacitor electrodes.
8. The preparation method of the cellulose cotton pulp for the capacitor electrode according to claim 7, characterized in that, In Step S1, the temperature of the ice bath is -10 °C to -5 °C, and the stirring time is 30 min.
9. The preparation method of the cellulose cotton pulp for the capacitor electrode according to claim 7, wherein, In Step S1, in the sodium hydroxyethyl sulfonate solution, the mass ratio of sodium hydroxyethyl sulfonate to water is 1 g:80 mL.
10. The preparation method of the cellulose cotton pulp for the capacitor electrode according to claim 7, characterized in that, In Step S3, the specific steps of the freeze-drying are as follows: B1: Place the reaction solution in a freezer at -50 °C to -40 °C for pre-freezing for 5 h to obtain a crystal block; B2: Under vacuum conditions, perform stepwise heating on the crystal block. First, heat at 10 °C for 1 h, then raise the temperature to 30 °C and heat for 2 h, and finally raise the temperature to 60 °C and heat for 3 h to complete freeze-drying.