Ionic liquid-based eutectic electrolyte and its application in aqueous zinc-iodine battery

Abstract

The application discloses a eutectic electrolyte based on ionic liquid and application thereof in a water-based zinc-iodine battery, and belongs to the technical field of eutectic electrolytes. First, a sulfonic acid pyrrolidone copolymer is prepared by radical polymerization with 2-acrylamido-2-methylpropanesulfonic acid and N-vinylpyrrolidone as monomers, then a stable eutectic liquid phase system is constructed by regulating the amount of deionized water with zinc sulfate heptahydrate as a zinc salt and 1-ethyl-3-methylimidazolium chloride as a core functional component, and then the sulfonic acid pyrrolidone copolymer is introduced to prepare the eutectic electrolyte based on ionic liquid. When the electrolyte is used for assembling the water-based zinc-iodine battery, the iodine-based four-electron transfer reaction can be stably realized, the migration of iodide and the disorderly growth of zinc dendrites are effectively inhibited, and the water-based zinc-iodine battery has long-term cycle stability.

Description

Technical Field

[0001] This invention belongs to the field of eutectic electrolyte technology, specifically eutectic electrolytes based on ionic liquids and their application in aqueous zinc-iodine batteries. Background Technology

[0002] Aqueous zinc-iodine batteries, with their core advantages such as high theoretical energy density, abundant zinc reserves, and low manufacturing costs, have become one of the most competitive candidate technologies in the field of large-scale electrochemical energy storage. However, the energy storage process of traditional aqueous zinc-iodine batteries relies on I0... - The two-electron transfer reaction of / I₂ significantly limits the improvement of energy density. In contrast, unlocking the four-electron transfer reaction of iodine (I₂) - / I2 / I + This can significantly improve the theoretical specific capacity of the cathode, providing a key path to overcome the high specific energy bottleneck of zinc-iodine batteries.

[0003] However, four-electron zinc-iodine batteries face extremely severe dynamic failure problems during actual long-term operation. The electrolyte, as the core medium for ion transport and interfacial reactions within the battery, directly determines the stability of the four-electron reaction and the uniformity of interfacial deposition. In traditional aqueous electrolyte systems, the high-valence I₂ generated at the positive electrode during charging and discharging... + Hydrolysis quenching is prone to occur, and a large number of intermediate polyiodides that are highly soluble in water are also generated. These free polyiodides easily migrate across the membrane to the surface of the zinc anode, changing the interfacial electric field distribution. This easily exacerbates the uneven deposition of zinc ions, promotes the rapid nucleation and disordered growth of zinc dendrites, and forms a vicious cycle between the loss of active iodine in the positive electrode and the damage to the physical structure of the zinc anode, resulting in a decrease in the long-cycle stability of the battery.

[0004] Therefore, under high specific energy four-electron reaction conditions, how to effectively suppress the distortion of the zinc negative electrode electric field and the disordered growth of zinc dendrites caused by the migration of iodine species, and thus construct a high-performance electrolyte system that can maintain stable positive electrode conversion and uniform negative electrode deposition for a long time, has become a key technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a eutectic electrolyte based on ionic liquids and its application in aqueous zinc-iodine batteries. By synergistically introducing a 1-ethyl-3-methylimidazolium chloride eutectic matrix and a sulfonic acid-based pyrrolidone copolymer into the electrolyte system, the efficient operation of the electrochemical reaction is achieved by optimizing the ion transport environment and stabilizing the electrode interface state. This constructs an electrolyte system that can stabilize iodine-based four-electron conversion and suppress zinc ion dendrite formation, thus endowing aqueous zinc-iodine batteries with good high specific capacity and long-term cycle stability.

[0006] The objective of this invention can be achieved through the following technical solutions: The eutectic electrolyte based on ionic liquids comprises, by mass parts, the following raw materials: 10-20 parts of zinc sulfate heptahydrate; 10-20 parts of 1-ethyl-3-methylimidazolium chloride; 25-100 parts deionized water; 1-3 parts of sulfonate-based pyrrolidone copolymer.

[0007] Furthermore, the eutectic electrolyte based on ionic liquids is obtained by mixing and compounding zinc sulfate heptahydrate, 1-ethyl-3-methylimidazolium chloride, deionized water, and sulfonic acid pyrrolidone copolymer, as follows: Zinc sulfate heptahydrate and 1-ethyl-3-methylimidazolium chloride were placed in a reaction vessel and stirred at 60-70°C for 10-12 hours. Deionized water was added, and the reaction was continued at the same temperature for 20-40 minutes. Sulfonic acid pyrrolidone copolymer was added, and the reaction was continued at the same temperature for 1-2 hours to obtain a eutectic electrolyte based on ionic liquid.

[0008] Furthermore, the sulfonate-based pyrrolidone copolymer was obtained through free radical polymerization using 2-acrylamido-2-methylpropanesulfonic acid and N-vinylpyrrolidone as monomers, isopropanol as a chain transfer agent, and ammonium persulfate aqueous solution as an initiator. The specific process is as follows: 2-Acrylamido-2-methylpropanesulfonic acid, N-vinylpyrrolidone, deionized water and isopropanol were placed in a reaction vessel under nitrogen atmosphere and stirred at 40-60℃ for 20-40 min. A 5wt% ammonium persulfate aqueous solution was slowly added, and the reaction was continued at 70-80℃ for 4-6 h. After precipitation, washing and drying, sulfonate-based pyrrolidone copolymer was obtained.

[0009] This invention also provides the application of an ionic liquid-based eutectic electrolyte in an aqueous zinc-iodine battery, using a zinc sheet as the negative electrode, an iodine composite positive electrode as the positive electrode, glass fiber as the separator, and an ionic liquid-based eutectic electrolyte as the electrolyte to prepare an aqueous zinc-iodine battery.

[0010] Furthermore, the iodine composite positive electrode sheet is obtained by mixing and grinding iodine composite positive electrode material, polyvinylidene fluoride and N-methyl-2-pyrrolidone, uniformly coating it on carbon paper, vacuum drying, pressing it into a sheet and cutting it into a circular electrode sheet.

[0011] Furthermore, the mass ratio of iodine composite cathode material, polyvinylidene fluoride, and N-methyl-2-pyrrolidone is 8:1:1.

[0012] Furthermore, the iodine composite cathode material is obtained by uniformly mixing activated carbon, carbon nanotubes and elemental iodine, and then allowing it to stand under vacuum.

[0013] Furthermore, the mass ratio of carbon nanotubes, elemental iodine, and activated carbon is 1:3:6.

[0014] The beneficial effects of this invention are: 1. The ionic liquid-based eutectic electrolyte prepared in this invention achieves a synergistic effect of solvation structure regulation and active species stabilization through the compounding of 1-ethyl-3-methylimidazolium chloride and sulfonic acid-based pyrrolidone copolymer. The chloride ions in the ionic liquid possess excellent coordination properties, optimizing the electrolyte solvation environment and regulating the system's water activity, which is beneficial for the stable formation and transformation of iodine-containing intermediates. The pyrrolidone ring in the copolymer can bind and stabilize the iodine-based active species in the system through polar interactions. This synergistic effect effectively improves the problems of poor iodine species transformation kinetics and easy loss, enhances the reversibility of redox reactions, and can stably achieve I... - / I2 / I + The four-electron conversion reaction effectively improves the reversible specific capacity and energy density of aqueous zinc-iodine batteries.

[0015] 2. The ionic liquid-based eutectic electrolyte prepared by this invention, with optimized water content, can effectively improve the wetting performance with the zinc anode surface and enhance the interface adhesion. At the same time, the sulfonic acid groups in the copolymer can optimize the transport and distribution of zinc ions through electrostatic interaction, guiding the uniform deposition of zinc ions. The above synergistic effect can effectively reduce the roughness of the zinc anode interface, inhibit the disordered growth of zinc dendrites, significantly improve the long-cycle stability of the battery, effectively extend the battery life, and meet the stable operation requirements of four-electron aqueous zinc-iodine batteries. Attached Figure Description

[0016] Figure 1 The cyclic voltammetry curves are obtained by testing the zinc-iodine batteries assembled with the electrolytes prepared in Comparative Example 1 and Example 2 at a scan rate of 0.1 mV / s.

[0017] Figure 2 The image shows the AFM image of the zinc electrode after 200 charge-discharge cycles in the electrolytes prepared in Comparative Example 1 and Example 2.

[0018] Figure 3 The contact angle measurement diagrams of the electrolytes prepared in Comparative Example 1 and Example 2 on the zinc electrode are shown.

[0019] Figure 4 The linear sweep voltammetry (LSV) curves were obtained by testing the electrolytes prepared in Comparative Example 1 and Example 2 with a three-electrode test system constructed using a zinc sheet as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode at a scan rate of 1 mV / s.

[0020] Figure 5The Tafel curves were obtained by testing the electrolytes prepared in Comparative Example 1 and Example 2 with a three-electrode test system consisting of a zinc sheet as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode at a scan rate of 0.5 mV / s. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1: This example provides a eutectic electrolyte based on ionic liquids, prepared through the following steps: S1: Using 6g of 2-acrylamido-2-methylpropanesulfonic acid and 6g of N-vinylpyrrolidone as monomers and 8g of isopropanol as chain transfer agent, the monomers and chain transfer agent were placed in a reactor under nitrogen atmosphere protection with 40mL of deionized water. The reactor was stirred at 200r / min for 20min at 40℃. 2g of 5wt% ammonium persulfate aqueous solution was slowly added as an initiator. The reaction was continued at 70℃ with the same stirring rate for 4h. After free radical polymerization, the mixture was cooled to room temperature. The reaction solution was added to anhydrous ethanol to precipitate the precipitate. The precipitate was filtered, washed twice with anhydrous ethanol, dried under vacuum at 60℃ to constant weight, and ground to obtain sulfonate-based pyrrolidone copolymer.

[0023] S2: Place 10g of zinc sulfate heptahydrate and 10g of 1-ethyl-3-methylimidazolium chloride in a reaction vessel and stir at 200r / min for 10h at 60℃. Add 25g of deionized water and continue the reaction for 20min at the same temperature and stirring rate. Add 1g of sulfonated pyrrolidone copolymer and continue the reaction for 1h at the same temperature and stirring rate. After the reaction is completed, cool to room temperature to obtain a eutectic electrolyte based on ionic liquid.

[0024] Example 2: This example provides a eutectic electrolyte based on ionic liquids, prepared through the following steps: S1: Using 8g of 2-acrylamido-2-methylpropanesulfonic acid and 8g of N-vinylpyrrolidone as monomers and 12g of isopropanol as chain transfer agent, the monomers and chain transfer agent were placed in a reactor under nitrogen atmosphere protection with 50mL of deionized water. The mixture was stirred at 250r / min for 30min at 50℃. 3g of 5wt% ammonium persulfate aqueous solution was slowly added as an initiator. The reaction was continued at 75℃ with the same stirring rate for 5h. After free radical polymerization, the mixture was cooled to room temperature. The reaction solution was added to anhydrous ethanol to precipitate the precipitate. The precipitate was filtered, washed three times with anhydrous ethanol, dried under vacuum at 70℃ to constant weight, and ground to obtain sulfonate-based pyrrolidone copolymer.

[0025] S2: Place 15g of zinc sulfate heptahydrate and 15g of 1-ethyl-3-methylimidazolium chloride in a reaction vessel and stir at 250r / min for 11h at 65℃. Add 56g of deionized water and continue the reaction for 30min at the same temperature and stirring rate. Add 2g of sulfonated pyrrolidone copolymer and continue the reaction for 1.5h at the same temperature and stirring rate. After the reaction is completed, cool to room temperature to obtain a eutectic electrolyte based on ionic liquid.

[0026] Example 3: This example provides a eutectic electrolyte based on ionic liquids, prepared through the following steps: S1: Using 10g of 2-acrylamido-2-methylpropanesulfonic acid and 10g of N-vinylpyrrolidone as monomers and 16g of isopropanol as chain transfer agent, the monomers and chain transfer agent were placed in a reactor under nitrogen atmosphere protection with 60mL of deionized water. The reactor was stirred at 300r / min for 40min at 60℃. 4g of 5wt% ammonium persulfate aqueous solution was slowly added as an initiator. The reaction was continued at 80℃ with the same stirring rate for 6h. After free radical polymerization, the mixture was cooled to room temperature. The reaction solution was added to anhydrous ethanol to precipitate the precipitate. The precipitate was filtered, washed four times with anhydrous ethanol, and dried under vacuum at 80℃ to constant weight. The precipitate was then ground to obtain the sulfonate-based pyrrolidone copolymer.

[0027] S2: Place 20g of zinc sulfate heptahydrate and 20g of 1-ethyl-3-methylimidazolium chloride in a reaction vessel and stir at 300r / min for 12h at 70℃. Add 100g of deionized water and continue the reaction for 40min at the same temperature and stirring rate. Add 3g of sulfonated pyrrolidone copolymer and continue the reaction for 2h at the same temperature and stirring rate. After the reaction is completed, cool to room temperature to obtain a eutectic electrolyte based on ionic liquid.

[0028] The ionic liquid-based eutectic electrolytes prepared in Examples 1-3 above used 2-acrylamido-2-methylpropanesulfonic acid and N-vinylpyrrolidone as monomers, isopropanol as a chain transfer agent, and ammonium persulfate aqueous solution as an initiator. Through a free radical copolymerization process, sulfonic acid-based pyrrolidone copolymers were obtained. Subsequently, zinc sulfate heptahydrate and 1-ethyl-3-methylimidazolium chloride were mixed at a constant temperature and stirred. Utilizing the synergistic effect of imidazole cations and chloride ions in the ionic liquid, the hydrogen bond network of the zinc salt's water of crystallization was broken, and chloride ions and zinc ions underwent coordination complexation to construct a stable homogeneous complex system. Then, deionized water was added for liquid phase regulation and reconstruction to form a eutectic liquid phase system. Finally, the sulfonic acid-based pyrrolidone copolymer was added to allow the polymer chain segments to fully swell, stretch, and disperse in the liquid phase, introducing the polar sulfonic acid groups and pyrrolidone rings on the long-chain backbone and side chains into the system, thus obtaining the ionic liquid-based eutectic electrolyte.

[0029] Example 4: This example provides the application of ionic liquid-based eutectic electrolytes in aqueous zinc-iodine batteries. Step 1: Thoroughly grind activated carbon (Kuraray, brand name YP-50F) and carbon nanotubes (Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., brand name XFM13), add elemental iodine and mix evenly (mass ratio of carbon nanotubes, elemental iodine and activated carbon is 1:3:6). Transfer the mixed material to a sealed container and let it stand under vacuum at 90℃ for 12h to obtain iodine composite cathode material. Mix and grind iodine composite cathode material, polyvinylidene fluoride and N-methyl-2-pyrrolidone at a mass ratio of 8:1:1, coat evenly on carbon paper, dry under vacuum at 60℃ for 8h, press into sheets at 12MPa for 40s, cut into circular electrode sheets with a diameter of 12mm and a thickness of 40μm to obtain iodine composite cathode sheet.

[0030] Step 2: Cut zinc foil (Nantong Xinxiang Zinc Industry, 100μm thick) into 14mm diameter discs to serve as the negative electrode, iodine composite positive electrode sheet as the positive electrode, glass fiber (Whatman, brand GF / D) as the separator, and ionic liquid-based eutectic electrolyte as the electrolyte. Assemble the 2032 type button zinc-iodine battery in the following order: positive electrode shell - positive electrode - electrolyte - glass fiber - electrolyte - negative electrode - gasket - negative electrode shell.

[0031] The ionic liquid-based eutectic electrolytes prepared in Examples 1-3 were used to prepare an aqueous zinc-iodine battery according to the scheme in Example 4.

[0032] Comparative Example 1: The difference from Example 2 is that an equal amount of sodium chloride is used to replace 1-ethyl-3-methylimidazolium chloride in step S2, while the other steps remain unchanged. An electrolyte is prepared using this electrolyte and an aqueous zinc-iodine battery is prepared according to the scheme in Example 4.

[0033] Comparative Example 2: The difference from Example 2 is that the sulfonate-based pyrrolidone copolymer prepared in step S1 is removed in step S2, while the other steps remain unchanged, and an electrolyte is prepared. This electrolyte is then used to prepare an aqueous zinc-iodine battery according to the scheme in Example 4.

[0034] The zinc-iodine batteries prepared in the above embodiments and comparative examples were subjected to performance tests, and the test results are shown in Table 1: Sample preparation: The aqueous zinc-iodine full cells prepared in the above examples and comparative examples were placed in a constant temperature environment of 25°C for 24 hours, and then put into the test state.

[0035] Cyclic stability performance: The battery charge-discharge test system was used to perform constant current charge-discharge tests on the sample. The working voltage range was set to 0.8V-1.7V and the charge-discharge rate was 0.5C. The battery's first discharge specific capacity and first coulombic efficiency, as well as the discharge specific capacity and coulombic efficiency after 200 charge-discharge cycles were recorded.

[0036] Table 1 Performance Tests of Aqueous Zinc-Iodine Batteries As shown in Table 1, Examples 1 through 3 all exhibited good electrochemical performance, with Example 2 showing the best performance. This indicates that when the deionized water content is too low, as in Example 1, although the system has good cycle stability, the excessively high electrolyte viscosity may hinder zinc ion migration, resulting in a decrease in the initial specific capacity. Conversely, when the deionized water content is too high, as in Example 3, although the initial ion transport is faster, the excessively high water activity may significantly exacerbate the leaching and loss of iodine species at the positive electrode and the hydrogen evolution and corrosion problems at the zinc negative electrode, leading to the most significant capacity decay during cycling.

[0037] In Comparative Example 1, replacing 1-ethyl-3-methylimidazolium chloride with an equal amount of sodium chloride resulted in a significant decrease in electrochemical performance. This may be because the system lacks the steric hindrance effect of imidazolium cations and the strong coordination effect of chloride ions, making it difficult to construct a stable eutectic liquid phase structure. It can only form a traditional aqueous electrolyte, which cannot effectively regulate the zinc ion solvation structure and inhibit the activity of water molecules. This may lead to the loss of active materials and accelerated hydrolysis failure. At the same time, the uniformity of zinc ion deposition deteriorates, increasing the risk of zinc dendrite growth, thereby reducing the battery capacity and cycle stability.

[0038] In Comparative Example 2, the battery's cycle stability decreased after the removal of the sulfonic acid-based pyrrolidone copolymer. This may be because the sulfonic acid groups introduced by the sulfonic acid-based pyrrolidone copolymer have strong polarity and electrostatic effects, which may help guide the uniform deposition of zinc ions. At the same time, the pyrrolidone ring has good polarity and complexing ability, which may interact with polyiodides in the system, reducing the degree of iodine species ionization and migration, further optimizing the interface environment between the electrolyte and the electrode, and improving the stability of the battery during cycling.

[0039] Depend on Figure 1 It can be seen that in the electrolyte of Example 2, two sets of characteristic redox peaks with sharp peak shapes and good symmetry appear in the potential ranges of 1.28 / 1.22V and 1.72 / 1.66V, respectively, corresponding to I - The reversible transformation between I2 and I2 / ICl constitutes a complete four-electron reaction process. The curve of the comparative electrolyte shows a broad peak and a weak current response, reflecting the slow transformation of iodine species and the high degree of polarization.

[0040] Depend on Figure 2 It can be seen that after cycling with the electrolyte of Comparative Example 1, the height difference on the surface of the zinc electrode reached 595.2 nm, indicating a high surface roughness. In contrast, in the electrolyte system of Example 2, the height difference on the surface of the zinc electrode was only 122.2 nm. This shows that the electrolyte of Example 2 can effectively induce uniform deposition of zinc ions, reduce the surface roughness of the electrode, and reduce the risk of zinc dendrite growth.

[0041] Depend on Figure 3 It can be seen that the contact angle of the zinc foil surface decreased significantly from 82° to 54°. This indicates that the electrolyte prepared in Example 2 can effectively improve the surface hydrophilicity of the zinc foil, making it exhibit stronger adsorption capacity for the zinc substrate, which is conducive to ion transport and lays the interfacial foundation for subsequent uniform deposition of zinc ions and suppression of dendrite growth.

[0042] Depend on Figure 4 It can be seen that the electrolyte prepared in Example 2 can broaden the electrochemical window from 2.54V in Comparative Example 1 to 2.77V, thereby effectively suppressing the occurrence of hydrogen evolution side reaction and improving the electrochemical stability of the system.

[0043] i represents the current density, and the vertical axis is the logarithm of the absolute value of the current density. Figure 5 It can be seen that the potential of the zinc electrode in the electrolyte of Example 2 is -0.772V, and the potential in the electrolyte of Comparative Example 1 is -0.875V. The value of its ordinate changes from -2.6367mA / cm in Example 2. 2 It becomes -1.955 mA / cm in Comparative Example 1. 2 The system in Example 2 exhibited a more positive corrosion potential and a lower current density, indicating that the corrosion behavior of the zinc electrode in this electrolyte environment was significantly suppressed.

[0044] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A eutectic electrolyte based on ionic liquids, characterized in that, The following raw materials are included by weight: 10-20 parts of zinc sulfate heptahydrate; 10-20 parts of 1-ethyl-3-methylimidazolium chloride; 25-100 parts deionized water; 1-3 parts of sulfonate-based pyrrolidone copolymer.

2. The eutectic electrolyte based on ionic liquid according to claim 1, characterized in that, The eutectic electrolyte based on ionic liquids is obtained by mixing and compounding zinc sulfate heptahydrate, 1-ethyl-3-methylimidazolium chloride, deionized water and sulfonic acid pyrrolidone copolymer.

3. The eutectic electrolyte based on ionic liquid according to claim 2, characterized in that, The specific process of mixing and compounding is as follows: Zinc sulfate heptahydrate and 1-ethyl-3-methylimidazolium chloride were placed in a reaction vessel and stirred at 60-70°C for 10-12 hours. Deionized water was added, and the reaction was continued at the same temperature for 20-40 minutes. Sulfonic acid pyrrolidone copolymer was added, and the reaction was continued at the same temperature for 1-2 hours to obtain a eutectic electrolyte based on ionic liquid.

4. The eutectic electrolyte based on ionic liquid according to claim 3, characterized in that, The sulfonate-based pyrrolidone copolymer is obtained by free radical polymerization using 2-acrylamido-2-methylpropanesulfonic acid and N-vinylpyrrolidone as monomers, isopropanol as a chain transfer agent, and ammonium persulfate aqueous solution as an initiator.

5. The eutectic electrolyte based on ionic liquid according to claim 4, characterized in that, The specific process of the free radical polymerization reaction is as follows: 2-Acrylamido-2-methylpropanesulfonic acid, N-vinylpyrrolidone, deionized water and isopropanol were placed in a reaction vessel under nitrogen atmosphere and stirred at 40-60℃ for 20-40 min. A 5wt% ammonium persulfate aqueous solution was slowly added, and the reaction was continued at 70-80℃ for 4-6 h. After precipitation, washing and drying, sulfonate-based pyrrolidone copolymer was obtained.

6. The application of the ionic liquid-based eutectic electrolyte as described in any one of claims 1-5 in an aqueous zinc-iodine battery, characterized in that, An aqueous zinc-iodine battery was prepared using zinc sheet as the negative electrode, iodine composite positive electrode as the positive electrode, glass fiber as the separator, and ionic liquid-based eutectic electrolyte as the electrolyte.

7. The application according to claim 6, characterized in that, The iodine composite positive electrode sheet is prepared by mixing and grinding iodine composite positive electrode material, polyvinylidene fluoride and N-methyl-2-pyrrolidone, uniformly coating it on carbon paper, vacuum drying, pressing it into a sheet and cutting it into a circular electrode sheet.

8. The application according to claim 7, characterized in that, The mass ratio of the iodine composite cathode material, polyvinylidene fluoride, and N-methyl-2-pyrrolidone is 8:1:

1.

9. The application according to claim 8, characterized in that, The iodine composite cathode material is obtained by uniformly mixing activated carbon, carbon nanotubes and elemental iodine, and then allowing it to stand under vacuum.

10. The application according to claim 9, characterized in that, The mass ratio of the carbon nanotubes, elemental iodine, and activated carbon is 1:3:6.

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