Flexible electrode material and preparation method and application thereof

Abstract

The invention provides a flexible electrode material as well as a preparation method, application and a preparation method thereof. The preparation method comprises the following steps: (1) dispersing cellulose nanofibers in water to form a cellulose nanofiber suspension, adding carbon nanotubes, and uniformly mixing to prepare a cellulose nanofiber / carbon nanotube dispersion liquid; (2) immersing carbon cloth into the cellulose nanofiber / carbon nanotube dispersion liquid to obtain a carbon cloth / cellulose nanofiber / carbon nanotube substrate material; and (3) immersing the carbon cloth / cellulose nanofiber / carbon nanotube substrate material into a potassium permanganate solution, adding concentrated sulfuric acid, and performing hydrothermal treatment to obtain the flexible electrode material. The preparation method comprises the following steps: preparing carbon cloth substrate materials with different hydrophilicity by adjusting the mixed concentration of cellulose nanofibers / carbon nanotubes; the cellulose nanofibers play a role in interface regulation and control, and the non-uniform pore structure of the cellulose nanofibers and the carbon nanotubes can provide pore diameters in a larger range and provide more active sites, so that the overall performance of the battery is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer nanocomposite materials, and in particular to a flexible electrode material and a preparation method and application thereof. Background Art

[0002] Currently, zinc-manganese electrochemistry is booming in the primary battery market (developed in 1860), and there is growing interest in developing flexible, environmentally friendly, safe, miniature and high-performance zinc-manganese batteries due to the development of portable and implantable electronic devices. The most common flexible substrates for depositing manganese dioxide are carbon cloth, conductive polymer films, conductive oxide films, graphene films, carbon nanotube films and conductive polyurethane foam. However, the poor interfacial compatibility between flexible substrates and electrode materials may weaken the bonding between electrode materials and reduce the affinity for manganese dioxide deposition, thereby affecting the cycle stability and overall performance of the battery. Many technologies have been used to improve the conductivity and flexibility of flexible substrates as electrode material supports to improve battery performance. Specifically, the charge retention capacity and transfer efficiency of the battery are improved by adding conductive materials and introducing oxygen-containing groups or other reactive groups. The ion transport rate and specific surface area are optimized by adjusting the pore structure and pore size of the flexible substrate. Studies have highlighted the profound impact of electrode wetting characteristics on the electrochemical performance of zinc batteries.

[0003] Hydrophilic electrode substrates have the potential to enhance electrolyte mobility and mitigate the formation of local acidic environments. This mitigates the effect of local acidification on MnO2, thereby reducing its dissolution. In addition, the appropriate amount of water molecules on the electrode surface reduces the Zn 2+ Ion diffusion barrier. Excess water molecules and Zn 2+ Forming octahedral ligand [Zn(H2O)6] 2+ [Zn(H2O)6] 2+ It reduces the strong electrostatic repulsion between zinc ions and raw materials, but excessive amounts will also affect Zn 2+ Insertion of the anode. Therefore, finding a suitable hydrophilic electrode is crucial to probing battery performance.

[0004] A Chinese patent document discloses "a manganese-based composite positive electrode for zinc-ion batteries and its preparation method and application", and its publication number is CN 117558866A. This patent document uses ethanol as a carbon source and uses a chemical vapor deposition method to in-situ grow carbon nanotubes on a carbon cloth substrate to prepare a composite substrate and provide a three-dimensional conductive network; MnO2 is deposited on the composite substrate using an electrodeposition method to obtain a manganese-based composite positive electrode for a zinc-ion battery. The prepared manganese-based composite positive electrode for a zinc-ion battery has a good three-dimensional conductive network, which improves the rate performance of the battery, and the three-dimensional nanosphere structure provides a large specific surface area and a large number of voids, which reserves sufficient space for the volume expansion of manganese dioxide, thereby improving the capacity and cycle stability of the battery. However, the interface compatibility of the manganese-based composite positive electrode for zinc-ion batteries prepared by this patent is poor, which may weaken the binding between electrode materials. The Chinese patent literature discloses "a hydrophobic zinc ion battery diaphragm based on inorganic oxides and its application in zinc batteries", and its publication number is CN 117438741A. The hydrophobic diaphragm is composed of inorganic oxides and binders. The preparation method is that the mass ratio of inorganic oxide (Ta2O5, Al2O3 or La2O3, etc.) and binder (PVDF) is (8-10): 1, stirring to make them evenly mixed; placing the slurry on a glass plate, using a scraper to evenly coat it; drying; using deionized water to separate the diaphragm from the glass plate to obtain a hydrophobic diaphragm. The diaphragm is hydrophobic and can isolate a large amount of free water, while the surface contains a porous structure, and electrolyte ions can be freely transmitted. It is self-assembled with a hydrophilic glass fiber diaphragm. The "hydrophobic-hydrophilic-hydrophobic" diaphragm is used for long-life zinc ion batteries. The hydrophilic diaphragm can store a large amount of electrolyte to ensure the high-performance cycle of the zinc battery, and the hydrophobic diaphragm can isolate a large amount of free water to prevent electrode corrosion or dissolution. However, the hydrophobic zinc ion battery separator prepared by this patent has poor cycle stability when applied to zinc-manganese batteries. Summary of the invention

[0005] In view of the shortcomings of the prior art mentioned above, the object of the present invention is to provide a flexible electrode material and a preparation method and application thereof, so as to solve the problem that the interface compatibility between the flexible substrate and the electrode material in the existing flexible zinc-manganese battery is poor, which may weaken the bonding between the electrode materials and reduce the affinity of manganese dioxide deposition, thereby affecting the cycle stability and overall performance of the battery.

[0006] To achieve the above objectives and other related objectives, the present invention provides a method for preparing a flexible electrode material, comprising: (1) dispersing cellulose nanofibers in water to form a cellulose nanofiber suspension, adding carbon nanotubes to the cellulose nanofiber suspension, and mixing them evenly to obtain a cellulose nanofiber / carbon nanotube dispersion; (2) immersing the carbon cloth into a cellulose nanofiber / carbon nanotube dispersion to obtain a carbon cloth / cellulose nanofiber / carbon nanotube substrate material; (3) The carbon cloth / cellulose nanofiber / carbon nanotube substrate material is immersed in a potassium permanganate solution, concentrated sulfuric acid is added, and a carbon cloth / cellulose nanofiber / carbon nanotube / manganese dioxide electrode material is obtained after a hydrothermal reaction, namely the flexible electrode material. The effect of concentrated sulfuric acid is to affect the purity of manganese dioxide and to reduce the generation of other valence states of manganese.

[0007] In the above technical solution of the present application, carbon cloth is selected as a flexible substrate, which has good flexibility, mechanical strength and low processing cost. Cellulose nanofibers are natural polysaccharide materials with a large number of hydroxyl groups, which make nanocellulose compatible with aqueous solutions. Carbon nanotubes have excellent conductivity and high specific surface area, which can increase the contact area between the electrode and the electrolyte and improve the electrochemical reaction rate. They are an excellent electrode material. Cellulose is one of the most abundant natural renewable resources in nature, with the advantages of being renewable, cheap, environmentally friendly, and biodegradable. The present application found that the cellulose nanofibers prepared by cellulose have the characteristics of high rigidity, high modulus, high specific surface area, and rich surface active groups in addition to the properties of cellulose. They can be used to prepare flexible conductive materials with carbon nanotubes, and are widely used in electronic fields such as batteries, sensors, supercapacitors, and electromagnetic shielding. The use of cellulose nanofibers to construct multifunctional composite electrode materials has dual significance for reducing environmental pollution and slowing down energy consumption.

[0008] This application enhances the specific capacity and cycle stability of zinc-ion batteries by adjusting the hydrophilicity of the electrode interface. As a new functional material, cellulose nanofibers have been relatively rarely used in the battery field in recent years. By introducing nanocellulose to regulate the hydrophilicity of the electrode interface, this method can significantly improve the contact performance between the electrode and the electrolyte. It is an innovative application exploration and can deeply study and understand the interaction between the electrode / electrolyte interface. This has important scientific significance for improving battery performance and designing new battery materials.

[0009] The present invention uses cellulose nanofibers / carbon nanotubes to adjust the interfacial hydrophilicity and conductivity of carbon cloth, and uses them to construct MnO2 flexible electrodes to explore the influence of carbon cloth wetting characteristics on the performance of flexible batteries, so as to improve the specific capacity and cycle stability of zinc batteries. It is then assembled into zinc ion batteries with zinc foil to test their electrochemical performance. The presence of cellulose nanofibers / carbon nanotubes effectively reduces the surface Zn 2+The migration barrier of MnO2 can be improved. In addition, optimizing the surface wettability can promote the interaction between MnO2 and carbon cloth, thereby improving the physical and chemical adsorption between the two. The good wettability of the electrode material enables the effective transportation of zinc ions and hydrogen ions in the electrolyte, thereby reducing the dissolution of MnO2 by reducing the local acidification of the MnO2 electrode surface, so that the zinc ion battery has more excellent and stable electrochemical performance. The present invention will play an important role in the design and manufacture of zinc ion batteries.

[0010] Preferably, in step (1), the mass ratio of cellulose nanofibers to carbon nanotubes in the cellulose nanofiber suspension is 1:(0.5-4), specifically 1:4, 1:2, 1:1, 2:1.

[0011] Preferably, in step (1), the cellulose nanofiber suspension and the carbon nanotubes are mixed under stirring and ultrasonically dispersed to form a cellulose nanofiber / carbon nanotube dispersion.

[0012] Preferably, in step (1), the frequency of ultrasonic dispersion is 60-100 KHz and the time is 5 min.

[0013] Preferably, in step (2), vacuum impregnation is performed for 30 to 60 minutes, wherein the carbon cloth is completely immersed in the cellulose nanofiber / carbon nanotube dispersion.

[0014] Preferably, in step (3), the concentration of the potassium permanganate solution is 0.005-0.015 mol / L, more preferably 0.01 mol / L, the concentration of concentrated sulfuric acid is 98.3%, and the temperature of the hydrothermal reaction is 85-100°C. Preferably, after step (3), a post-treatment process is further included, wherein the product obtained by the hydrothermal reaction is first subjected to ultrasonic treatment, and then washed with water. The purpose of the ultrasonic treatment is to remove unstable manganese dioxide on the surface of the product.

[0015] The present invention also provides a flexible electrode material prepared by the above preparation method.

[0016] Preferably, the hydrophilic angle of the flexible electrode material is 92.13~101.95.

[0017] The present invention also provides an application of a flexible electrode material as a flexible positive electrode in the preparation of a flexible zinc ion battery.

[0018] The flexible electrode material prepared by the present invention has excellent flexibility and charge storage capacity, so that it has high application prospects in the field of flexible zinc ion batteries.

[0019] The present invention also provides a flexible zinc ion battery, comprising a flexible positive electrode, a negative electrode, a separator and an electrolyte solution, wherein the flexible positive electrode is the above-mentioned flexible electrode material.

[0020] The flexible positive electrode in the zinc ion battery of the present application adopts the above-mentioned flexible electrode material, thereby making the zinc ion battery have good electrochemical performance and cycle stability, and can continuously power electronic devices such as timers and mobile phones.

[0021] Preferably, the negative electrode is zinc foil, the electrolyte solution is zinc sulfate / manganese sulfate solution, and the separator is glass fiber paper.

[0022] Preferably, the concentration of zinc sulfate in the electrolyte solution is 1 mol / L, and the concentration of manganese sulfate is 0.1 mol / L.

[0023] Preferably, the flexible zinc ion battery has a -1 The maximum specific capacity at the current density is 261.32 mAh / g.

[0024] When the mass ratio of cellulose nanofibers to carbon nanotubes is 1:2, the hydrophilic angle of the flexible electrode material is 97.04±4.91°. 2+ The diffusion barrier in the carbon cloth / cellulose nanofiber / carbon nanotube / MnO2 electrode material is only 0.3574 eV. The flexible zinc ion battery prepared by the present invention has a diffusion barrier of only 0.3574 eV in 0.1 Ag -1 The specific capacity at the current density is 261.32 mAh / g. After 1000 cycles, the capacity retention rate of the prepared flexible zinc-ion battery is 87%.

[0025] Experiments have shown that the electrochemical performance of zinc batteries changes in a parabolic trend as the contact angle of the carbon cloth changes from hydrophilic to hydrophobic.

[0026] As described above, the present invention has the following beneficial effects: (1) The present invention prepares carbon cloth substrate materials with different hydrophilicities by adjusting the mixed concentration of cellulose nanofibers / carbon nanotubes; the cellulose nanofibers not only play a role in interface regulation, but also can provide a wider range of pore sizes with the non-uniform pore structure of carbon nanotubes, providing more active sites for different types of reactions, thereby improving the overall performance of the battery; with the addition of cellulose nanofibers / carbon nanotubes, the interfacial hydrophilicity of the carbon cloth substrate material changes; the excellent surface wettability of the carbon cloth not only enhances the adsorption of manganese dioxide, but also reduces the diffusion capacity of zinc ions on the electrode surface; (2) The present invention is based on the rich oxygen-containing functional groups on the surface of cellulose nanofibers, which have excellent hydrophilicity and can be mixed with carbon nanotubes to adjust the hydrophilicity and conductivity of the electrode interface; the wettability adjustment of cellulose nanofibers / carbon nanotubes on carbon cloth can enhance the adsorption of MnO2 at the electrode interface, slow down the dissolution of MnO2 at the electrode-electrolyte interface, and reduce the Zn 2+ The diffusion potential of Zn 2+ The adsorption and penetration of zinc ion batteries improves the capacity and cycle performance of zinc ion batteries. (3) The flexible zinc ion battery of the present invention has excellent electrochemical performance and cycle stability. -1 The maximum specific capacity under current density is 261.32 mAh / g, and after 1000 cycles, the capacity retention rate of the prepared zinc ion battery is 87%. The present invention further broadens the development of flexible zinc ion batteries, and is also in line with the concept of sustainable development of contemporary new energy, and is expected to provide a new power supply platform for wearable electronic devices, electronic skin, human motion monitoring and other equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Shown are the contact angles of the flexible electrode materials prepared in Examples 1 to 4 and the comparative example.

[0028] Figure 2 Shown is the GCD curve of a flexible zinc ion battery using the flexible electrode materials prepared in Examples 1 to 4 and the comparative example as a flexible positive electrode.

[0029] Figure 3 Shown is a schematic diagram of the flexible zinc-ion battery in Example 3 that can continuously power a timer. DETAILED DESCRIPTION

[0030] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0031] It should be noted that the process equipment or devices not specifically specified in the following embodiments are all conventional equipment or devices in the art.

[0032] In addition, it should be understood that one or more method steps mentioned in the present invention do not exclude the existence of other method steps before or after the combination step or the insertion of other method steps between these explicitly mentioned steps, unless otherwise specified; it should also be understood that the combination connection relationship between one or more devices / apparatuses mentioned in the present invention does not exclude the existence of other devices / apparatuses before or after the combination device / apparatus or the insertion of other devices / apparatuses between these explicitly mentioned two devices / apparatuses, unless otherwise specified. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or the scope of the present invention. Changes or adjustments in their relative relationships should also be regarded as the scope of the present invention without substantially changing the technical content.

[0033] The flexible zinc ion batteries in the following embodiments of the present application all include a flexible positive electrode, a negative electrode, a separator and an electrolyte solution, wherein the flexible positive electrode is the flexible electrode material prepared in each embodiment and comparative example; the negative electrode is zinc foil, the electrolyte solution is a zinc sulfate / manganese sulfate solution, and the separator is glass fiber paper; the concentration of zinc sulfate in the electrolyte solution is 1 mol / L, and the concentration of manganese sulfate is 0.1 mol / L.

[0034] Example 1 The present invention provides a method for preparing a flexible electrode material, comprising the following steps: (1) Preparation of cellulose nanofiber / carbon nanotube dispersion 100 mg of cellulose nanofibers were added to distilled water and stirred for 30 min at room temperature using a magnetic stirrer to mix them evenly. Then, 50 mg of carbon nanotubes were added to the CNF suspension and then sonicated in a cell disruptor for 30 min to obtain a uniform cellulose nanofiber / carbon nanotube dispersion. (2) Preparation of carbon cloth / cellulose nanofiber / carbon nanotube substrate materials The carbon cloth was soaked in acetone, ethanol and distilled water in turn to remove dust, grease and impurities, and then the carbon cloth was placed in an oven at 60°C to dry for use; the dried carbon cloth was immersed in a cellulose nanofiber / carbon nanotube dispersion and vacuum impregnated for 30 min to obtain a carbon cloth / cellulose nanofiber / carbon nanotube flexible substrate; (3) Preparation of carbon cloth / cellulose nanofibers / carbon nanotubes / manganese dioxide electrodes 0.1106 g KMnO4 was dissolved in 70 mL deionized water and stirred magnetically until completely dissolved. Then, the carbon cloth / cellulose nanofiber / carbon nanotube flexible substrate (i.e., the substrate obtained in step (2) of Example 1) was transferred to the KMnO4 solution, heated to 90°C for 2 hours, and 500 μL of concentrated sulfuric acid was added at 40°C. The carbon cloth / cellulose nanofiber / carbon nanotube flexible substrate was collected, washed with water 3 times, ultrasonicated for 3 min, and finally vacuum dried at 60°C for 1 h to obtain a carbon cloth / cellulose nanofiber / carbon nanotube / manganese dioxide electrode material, and the sample was recorded as CF2T1.

[0035] like Figure 1 As shown in FIG. 1 , the hydrophilic angle of the carbon cloth / cellulose nanofiber / carbon nanotube substrate material prepared in this embodiment is 48.70 ± 5.72°. Figure 2 As shown, the flexible zinc ion battery (CF2T1-M) formed by using the carbon cloth / cellulose nanofiber / carbon nanotube / manganese dioxide electrode material prepared in this embodiment as a flexible positive electrode and assembling it with a negative electrode, a separator and an electrolyte solution has a specific capacity of 137.45 mAh / g at a current density of 0.1 A / g.

[0036] Example 2 The present invention provides a method for preparing a flexible electrode material, comprising the following steps: (1) Preparation of cellulose nanofiber / carbon nanotube dispersion 50 mg of cellulose nanofibers were added to distilled water and stirred for 30 min at room temperature using a magnetic stirrer to make them uniform. Then, 50 mg of carbon nanotubes were added to the CNF suspension and then sonicated in a cell disruptor for 30 min to obtain a uniform cellulose nanofiber / carbon nanotube dispersion. (2) Preparation of carbon cloth / cellulose nanofiber / carbon nanotube substrate materials The carbon cloth was soaked in acetone, ethanol and distilled water in turn to remove dust, grease and impurities, and then placed in an oven at 60°C to dry for later use. The dried carbon cloth was immersed in a cellulose nanofiber / carbon nanotube dispersion and vacuum impregnated for 30 min to obtain a carbon cloth / cellulose nanofiber / carbon nanotube flexible substrate; (3) Preparation of carbon cloth / cellulose nanofibers / carbon nanotubes / manganese dioxide electrodes 0.1106 g KMnO4 was dissolved in 70 mL deionized water and stirred magnetically until completely dissolved. Then, the carbon cloth / cellulose nanofiber / carbon nanotube flexible substrate (i.e., the substrate obtained in step (2) of Example 1) was transferred to the KMnO4 solution, heated to 90°C for 2 hours, and 500 μL of concentrated sulfuric acid was added at 40°C. The carbon cloth / cellulose nanofiber / carbon nanotube flexible substrate was collected, washed with water 3 times, ultrasonicated for 3 min, and finally vacuum dried at 60°C for 1 h to obtain a carbon cloth / cellulose nanofiber / carbon nanotube / manganese dioxide electrode material, and the sample was recorded as CF1T1.

[0037] like Figure 1 As shown in FIG. 1 , the hydrophilic angle of the carbon cloth / cellulose nanofiber / carbon nanotube substrate material prepared in this embodiment is 83.53 ± 3.22°. Figure 2 As shown, the flexible zinc ion battery (CF1T1-M) formed by using the carbon cloth / cellulose nanofiber / carbon nanotube / manganese dioxide electrode material prepared in this embodiment as a flexible positive electrode and assembling it with a negative electrode, a separator and an electrolyte solution has a specific capacity of 181.44 mAh / g at a current density of 0.1 A / g.

[0038] Example 3 The present invention provides a method for preparing a flexible electrode material, comprising the following steps: Preparation of cellulose nanofiber / carbon nanotube dispersion 25 mg of cellulose nanofibers were added to distilled water and stirred at room temperature for 30 min using a magnetic stirrer to make them uniform. Then, 50 mg of carbon nanotubes were added to the CNF suspension and then sonicated in a cell disruptor for 30 min to obtain a uniform cellulose nanofiber / carbon nanotube dispersion. (2) Preparation of carbon cloth / cellulose nanofiber / carbon nanotube substrate materials The carbon cloth was soaked in acetone, ethanol and distilled water in turn to remove dust, grease and impurities, and then placed in an oven at 60°C to dry for later use. The dried carbon cloth was immersed in a cellulose nanofiber / carbon nanotube dispersion and vacuum impregnated for 30 min to obtain a carbon cloth / cellulose nanofiber / carbon nanotube flexible substrate; (3) Preparation of carbon cloth / cellulose nanofibers / carbon nanotubes / manganese dioxide electrodes 0.1106 g KMnO4 was dissolved in 70 mL deionized water and stirred magnetically until completely dissolved. Then, the carbon cloth / cellulose nanofiber / carbon nanotube flexible substrate (i.e., the substrate obtained in step (2) of Example 1) was transferred to the KMnO4 solution, heated to 90°C for 2 hours, and 500 μL of concentrated sulfuric acid was added at 40°C. The carbon cloth / cellulose nanofiber / carbon nanotube flexible substrate was collected, washed with water 3 times, ultrasonicated for 3 min, and finally vacuum dried at 60°C for 1 h to obtain a carbon cloth / cellulose nanofiber / carbon nanotube / manganese dioxide electrode material, and the sample was recorded as CF1T2.

[0039] like Figure 1 As shown in FIG. 1 , the hydrophilic angle of the carbon cloth / cellulose nanofiber / carbon nanotube substrate material prepared in this embodiment is 97.04 ± 4.91°. Figure 2 As shown, the flexible zinc ion battery (CF1T2-M) formed by using the carbon cloth / cellulose nanofiber / carbon nanotube / manganese dioxide electrode material prepared in this embodiment as a flexible positive electrode and assembling it with a negative electrode, a separator and an electrolyte solution has a specific capacity of 261.32 mAh / g at a current density of 0.1 A / g.

[0040] The schematic diagram of the flexible zinc ion battery in this embodiment continuously supplying power to the timer is shown in FIG. Figure 3 As shown, from Figure 3 It can be seen that the prepared flexible zinc-ion battery can continuously power an electronic watch for 99 min, indicating that it has good application prospects in portable electronic devices.

[0041] Example 4 The present invention provides a method for preparing a flexible electrode material, comprising the following steps: (1) Preparation of cellulose nanofiber / carbon nanotube dispersion 12.5 mg CNF was added to distilled water and stirred for 30 min at room temperature using a magnetic stirrer to make it uniform. Then, 50 mg carbon nanotubes were added to the CNF suspension and then sonicated in a cell disruptor for 30 min to obtain a uniform cellulose nanofiber / carbon nanotube dispersion. (2) Preparation of carbon cloth / cellulose nanofiber / carbon nanotube substrate materials Soak the carbon cloth in acetone, ethanol and distilled water in turn to remove dust, grease and impurities, and then put the CC into an oven at 60°C to dry for use. Immerse the dried carbon cloth in the cellulose nanofiber / carbon nanotube dispersion and vacuum impregnate for 30 minutes to obtain a carbon cloth / cellulose nanofiber / carbon nanotube flexible substrate; (3) Preparation of carbon cloth / cellulose nanofibers / carbon nanotubes / manganese dioxide electrodes 0.1106 g KMnO4 was dissolved in 70 mL deionized water and stirred magnetically until completely dissolved. Then, the carbon cloth / cellulose nanofiber / carbon nanotube flexible substrate (i.e., the substrate obtained in step (2) of Example 1) was transferred to the KMnO4 solution, heated to 90°C for 2 hours, and 500 μL of concentrated sulfuric acid was added at 40°C. The carbon cloth / cellulose nanofiber / carbon nanotube flexible substrate was collected, washed with water 3 times, ultrasonicated for 3 min, and finally vacuum dried at 60°C for 1 h to obtain a carbon cloth / cellulose nanofiber / carbon nanotube / manganese dioxide electrode material, and the sample was recorded as CF1T4.

[0042] like Figure 1 As shown in FIG. 1 , the hydrophilic angle of the carbon cloth / cellulose nanofiber / carbon nanotube substrate material prepared in this embodiment is 130.85 ± 3.36°. Figure 2 As shown, the flexible zinc ion battery (CF1T4-M) formed by using the carbon cloth / cellulose nanofiber / carbon nanotube / manganese dioxide electrode material prepared in this embodiment as a flexible positive electrode and assembling it with a negative electrode, a separator and an electrolyte solution has a specific capacity of 219.97 mAh / g at a current density of 0.1 A / g.

[0043] Comparative Example This comparative example provides a method for preparing a carbon cloth / manganese dioxide electrode material, comprising the following steps: (1) Soaking the carbon cloth in acetone, ethanol and distilled water in turn to remove dust, grease and impurities, and then drying the carbon cloth in an oven at 60°C for later use to obtain a carbon cloth flexible substrate; (2) Dissolve 0.1106 g KMnO4 in 70 mL deionized water and stir magnetically until completely dissolved; transfer the carbon cloth flexible substrate obtained in step (1) to the KMnO4 solution, heat to 90°C for 2 hours, and add 500 μL concentrated sulfuric acid at 40°C. Collect the carbon cloth flexible substrate, wash it with water 3 times, ultrasonicate it for 3 min, and finally vacuum dry it at 60°C for 1 h to obtain the carbon cloth / manganese dioxide electrode material, and the sample is recorded as CC.

[0044] like Figure 1 As shown in FIG. 1 , the hydrophilic angle of the carbon cloth / manganese dioxide electrode material prepared in this embodiment is 139.27 ± 3.2°. Figure 2 As shown, the flexible zinc ion battery (CC-M) formed by using the carbon cloth / cellulose nanofiber / carbon nanotube / manganese dioxide electrode material prepared in this comparative example as a flexible positive electrode and assembling it with a negative electrode, a separator and an electrolyte solution has a specific capacity of 114.51 mAh / g at a current density of 0.1 A / g.

[0045] In summary, the present invention regulates the hydrophilicity of the carbon cloth interface through cellulose nanofibers, and prepares a flexible zinc ion battery. The cellulose nanofiber surface is rich in oxygen-containing functional groups. The cellulose nanofiber not only plays a role in interface regulation, but also can provide a wider range of pore sizes with the non-uniform pore structure of carbon nanotubes, providing more active sites for different types of reactions, thereby improving the electrochemical performance of the battery. The excellent surface wettability of the carbon cloth not only enhances the adsorption of manganese dioxide, but also reduces the diffusion capacity of zinc ions on the electrode surface. The zinc ion battery thus assembled has excellent electrochemical performance and cycle stability. The present invention further broadens the development of zinc ion batteries, and is also in line with the concept of sustainable development of contemporary new energy.

[0046] The above is only a preferred embodiment of the present invention, and is not any formal or substantial limitation of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the method of the present invention, and these improvements and supplements should also be regarded as the protection scope of the present invention. Any technician familiar with this profession, without departing from the spirit and scope of the present invention, can make some changes, modifications and evolutions of the technical content disclosed above, which are equivalent embodiments of the present invention; at the same time, any changes, modifications and evolutions of any equivalent changes made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a flexible electrode material, characterized in that: include: (1) dispersing cellulose nanofibers in water to form a cellulose nanofiber suspension, adding carbon nanotubes to the cellulose nanofiber suspension, and mixing them evenly to obtain a cellulose nanofiber / carbon nanotube dispersion; (2) immersing the carbon cloth into a cellulose nanofiber / carbon nanotube dispersion to obtain a carbon cloth / cellulose nanofiber / carbon nanotube substrate material; (3) Immersing the carbon cloth / cellulose nanofiber / carbon nanotube substrate material in a potassium permanganate solution, adding concentrated sulfuric acid, and performing a hydrothermal reaction to obtain a carbon cloth / cellulose nanofiber / carbon nanotube / manganese dioxide electrode material, which is the flexible electrode material.

2. The preparation method according to claim 1, characterized in that: In step (1), the mass ratio of cellulose nanofibers to carbon nanotubes in the cellulose nanofiber suspension is 1:(0.5-4); the cellulose nanofiber suspension and the carbon nanotubes are mixed under stirring, and ultrasonically dispersed to form a cellulose nanofiber / carbon nanotube dispersion; the frequency of the ultrasonic dispersion is 60-100 KHz, and the time is 5 min.

3. The preparation method according to claim 1, characterized in that: In step (2), vacuum impregnation is performed for 30 to 60 minutes.

4. The preparation method according to claim 1, characterized in that: In step (3), the concentration of the potassium permanganate solution is 0.005-0.015 mol / L, the concentration of concentrated sulfuric acid is 98.3%, and the temperature of the hydrothermal reaction is 85-100°C.

5. The preparation method according to claim 1, characterized in that: After step (3), a post-treatment process is also included, wherein the post-treatment process is to firstly ultrasonically treat the product obtained by the hydrothermal reaction, and then wash it with water.

6. A flexible electrode material obtained by the preparation method according to any one of claims 1 to 5.

7. The flexible electrode material according to claim 6, characterized in that: The hydrophilic angle of the flexible electrode material is 92.13~101.

95.

8. Use of the flexible electrode material as claimed in claim 6 as a flexible positive electrode in the preparation of a flexible zinc ion battery.

9. A flexible zinc ion battery, characterized in that: It comprises a flexible positive electrode, a negative electrode, a separator and an electrolyte solution, wherein the flexible positive electrode is the flexible electrode material as claimed in claim 6; the negative electrode is a zinc foil, the electrolyte solution is a zinc sulfate / manganese sulfate solution, and the separator is a glass fiber paper; the concentration of zinc sulfate in the electrolyte solution is 1 mol / L, and the concentration of manganese sulfate is 0.1 mol / L.

10. The flexible zinc ion battery according to claim 9, characterized in that: The flexible zinc-ion battery has a -1 The maximum specific capacity at the current density is 261.32 mAh / g.

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