A modified manganese dioxide positive electrode material and its preparation method and application

Abstract

The present invention discloses a modified manganese dioxide positive electrode material and a preparation method and application thereof, and relates to the field of electrochemical energy storage technology. The modified manganese dioxide positive electrode material comprises p-dinitrobenzene surface-modified manganese dioxide. The modified manganese dioxide positive electrode material provided by the present invention has multiple active sites, and can optimize the battery energy storage characteristics in an aqueous zinc ion battery, and improve the battery's specific capacity, rate performance and cycle life.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical energy storage, and in particular to a modified manganese dioxide positive electrode material and a preparation method and application thereof. Background Art

[0002] As a new electrochemical energy storage technology, aqueous zinc-ion batteries have attracted widespread attention due to their high safety, low cost and environmental protection characteristics. They have the advantages of being clean, safe and renewable. Aqueous zinc-ion batteries exhibit excellent electrochemical performance during the charge and discharge process and are an ideal choice to replace traditional batteries.

[0003] The positive electrode materials of aqueous zinc-ion batteries mainly include vanadium-based materials, manganese-based materials and organic materials. Among them, manganese-based materials have higher theoretical specific capacity and working potential, can store more energy, and show a higher voltage platform during the charge and discharge process, thereby improving the energy density and performance of aqueous zinc-ion batteries. However, manganese-based materials have the problem of poor structural stability, which affects the cycle stability of zinc-ion batteries. Summary of the invention

[0004] The main purpose of the present invention is to provide an organic-modified manganese dioxide positive electrode material and a preparation method and application thereof, aiming to solve the problems of low capacity and poor structural stability of existing manganese-based materials, thereby improving the energy density and cycle stability of zinc ion batteries.

[0005] To achieve the above object, the present invention provides a modified manganese dioxide positive electrode material, wherein the modified manganese dioxide positive electrode material comprises manganese dioxide surface-modified with p-dinitrobenzene.

[0006] The present invention also provides a method for preparing the modified manganese dioxide positive electrode material as described above, comprising the following steps:

[0007] The p-dinitrobenzene solution is mixed with the manganese dioxide aqueous solution to obtain a mixed solution, and the mixed solution is heated for reaction and then dried to obtain a modified manganese dioxide positive electrode material.

[0008] In one embodiment, in the mixed solution, the mass ratio of manganese dioxide to p-dinitrobenzene is (0.7-0.9): (0.3-0.1); and / or,

[0009] The solvent of the p-dinitrobenzene solution includes at least one of dimethylformamide, dimethyl sulfoxide, deionized water and ethanol.

[0010] In one embodiment, the mixing time is 1 to 3 hours; and / or,

[0011] The temperature of the heating reaction is 40-80°C; and / or,

[0012] The heating reaction time is 10 to 24 hours.

[0013] The present invention also provides a positive electrode sheet, which is made of the modified manganese dioxide positive electrode material or the modified manganese dioxide positive electrode material prepared by the preparation method of the modified manganese dioxide positive electrode material.

[0014] The present invention also provides a method for preparing the positive electrode sheet as described above, comprising the following steps:

[0015] The modified manganese dioxide positive electrode material is mixed with acetylene black, polyvinylidene fluoride and N-methylpyrrolidone to obtain a slurry;

[0016] The slurry is coated on a current collector and dried to obtain a positive electrode sheet.

[0017] In one embodiment, in the step of mixing the modified manganese dioxide positive electrode material with acetylene black, polyvinylidene fluoride and N-methylpyrrolidone to obtain a slurry,

[0018] The mass ratio of the modified manganese dioxide positive electrode material, acetylene black and polyvinylidene fluoride is (6-8): (3-1):1.

[0019] In one embodiment, in the step of applying the slurry to carbon cloth and drying to obtain a positive electrode sheet:

[0020] The drying temperature is 60-65°C; and / or,

[0021] The drying time is 6 to 12 hours.

[0022] In one embodiment, in the positive electrode sheet, the loading amount of the modified manganese dioxide positive electrode material is 2.0-10.0 mg / cm 2 .

[0023] The present invention also provides a zinc ion battery, which includes a battery positive electrode, a battery negative electrode and an electrolyte, and the battery positive electrode includes the positive electrode sheet as described above or the positive electrode sheet prepared by the preparation method of the positive electrode sheet as described above.

[0024] In the technical solution of the present invention, p-dinitrobenzene (PDNB) is used to modify the surface of manganese dioxide (MnO2) to obtain p-dinitrobenzene modified manganese dioxide (PDNB@MnO2), and p-dinitrobenzene molecules can introduce multiple active groups to provide additional theoretical specific capacity for MnO2. As an organic substance, p-dinitrobenzene itself has energy storage capacity and stability, and after surface modification with MnO2, it can further improve the manganese dissolution and Jan-Taylor distortion problems of the MnO2 electrode through a synergistic mechanism, and improve the specific capacity and structural stability of the PDNB@MnO2 positive electrode, so it has excellent electrochemical performance in aqueous zinc ion batteries. The modified manganese dioxide positive electrode material provided by the present invention has multiple active sites and can react with Zn 2+ / H + Give full play to the co-embedded synergistic effect, optimize the battery energy storage characteristics, and improve the battery's specific capacity and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0026] Figure 1 This is a scanning electron microscope image of the modified manganese dioxide positive electrode material prepared in Example 1 of the present invention;

[0027] Figure 2 This is an X-ray diffraction test diagram of the modified manganese dioxide positive electrode material prepared in Example 1 of the present invention;

[0028] Figure 3 This is a charge and discharge long cycle diagram of a zinc-manganese battery prepared with the modified manganese dioxide positive electrode material in Example 1 of the present invention at a current density of 0.2 A / g;

[0029] Figure 4 This is a charge and discharge long cycle diagram of a zinc-manganese battery prepared with the modified manganese dioxide positive electrode material in Example 2 of the present invention at a current density of 0.2 A / g;

[0030] Figure 5 This is a charge and discharge cycle test diagram of a zinc-manganese battery prepared with the modified manganese dioxide positive electrode material in Example 3 of the present invention at a current density of 4.0 A / g;

[0031] Figure 6 This is a cyclic voltammetry test diagram of a battery prepared using the modified manganese dioxide positive electrode material in Example 3 of the present invention;

[0032] Figure 7The charge and discharge test curves of the zinc-manganese battery prepared with the modified manganese dioxide positive electrode material in Comparative Example 1 and Example 3 of the present invention at different current densities;

[0033] Figure 8 This is a charge and discharge performance diagram of the zinc-manganese battery based on unmodified manganese dioxide positive electrode material in Comparative Example 1 of the present invention at different cycle numbers.

[0034] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0037] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features limited to "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the "and / or" or "and / or" appearing in the full text include three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or solutions that satisfy both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in the field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0038] As a new electrochemical energy storage technology, aqueous zinc-ion batteries have attracted widespread attention due to their high safety, low cost and environmental protection characteristics. They have the advantages of being clean, safe and renewable. Aqueous zinc-ion batteries exhibit excellent electrochemical performance during the charge and discharge process and are an ideal choice to replace traditional batteries.

[0039] The positive electrode materials of aqueous zinc-ion batteries mainly include vanadium-based materials, manganese-based materials and organic materials. Among them, manganese-based materials have higher theoretical specific capacity and working potential, can store more energy, and show a higher voltage platform during the charge and discharge process, thereby improving the energy density and performance of aqueous zinc-ion batteries. However, manganese-based materials have the problem of poor structural stability, which affects the cycle stability of zinc-ion batteries.

[0040] In view of this, the present invention provides a modified manganese dioxide positive electrode material, wherein the modified manganese dioxide positive electrode material comprises manganese dioxide surface-modified with p-dinitrobenzene.

[0041] In the technical solution of the present invention, p-dinitrobenzene (PDNB) is used to modify the surface of manganese dioxide (MnO2) to obtain p-dinitrobenzene modified manganese dioxide (PDNB@MnO2), and p-dinitrobenzene molecules can introduce multiple active groups to provide additional theoretical specific capacity for MnO2. As an organic substance, p-dinitrobenzene itself has energy storage capacity and stability, and after surface modification with MnO2, it can further improve the manganese dissolution and Jan-Taylor distortion problems of the MnO2 electrode through a synergistic mechanism, and improve the specific capacity and structural stability of the PDNB@MnO2 positive electrode, so it has excellent electrochemical performance in aqueous zinc ion batteries. The modified manganese dioxide positive electrode material provided by the present invention has multiple active sites and can react with Zn 2+ / H + Give full play to the co-embedded synergistic effect, optimize the battery energy storage characteristics, and improve the battery's specific capacity and stability.

[0042] The present invention further provides a method for preparing the modified manganese dioxide positive electrode material as described above, comprising the following steps:

[0043] The p-dinitrobenzene solution is mixed with the manganese dioxide aqueous solution to obtain a mixed solution, and the mixed solution is heated for reaction and then dried to obtain a modified manganese dioxide positive electrode material.

[0044] In the technical solution of the present invention, a p-dinitrobenzene solution is mixed with a manganese dioxide aqueous solution so that p-dinitrobenzene and manganese dioxide can be better dispersed in the mixed solution. During the heating reaction, p-dinitrobenzene can be evenly attached to the surface of manganese dioxide to obtain a p-dinitrobenzene-modified manganese dioxide positive electrode material. When the p-dinitrobenzene-modified manganese dioxide positive electrode material is used as a positive electrode material for a zinc ion battery, it can react with Zn 2+ / H + Give full play to the co-embedded synergistic effect, optimize the battery energy storage characteristics, and improve the battery's specific capacity and rate performance.

[0045] Further, the solvent of the p-dinitrobenzene solution includes at least one of dimethyl sulfoxide (DMSO), ethanol, dimethylformamide (DMF) and deionized water. It is understandable that the p-dinitrobenzene solution includes a solvent and a solute, the solute is p-dinitrobenzene, and the solvent can be an organic solvent, preferably, at least one of dimethyl sulfoxide (DMSO), ethanol, dimethylformamide (DMF) and deionized water. In some embodiments, the solvent is dimethyl sulfoxide, that is, the p-dinitrobenzene solution is a dimethyl sulfoxide solution of p-dinitrobenzene, and dimethyl sulfoxide is an excellent solvent that can better promote the interaction between p-dinitrobenzene and manganese dioxide. Therefore, dissolving p-dinitrobenzene in DMSO can prolong its shelf life and reduce the loss caused by decomposition or deterioration.

[0046] In some embodiments, the mass ratio of manganese dioxide to p-dinitrobenzene in the mixed solution is (0.7-0.9): (0.3-0.1). The present invention does not limit the concentration of p-dinitrobenzene in the p-dinitrobenzene solution, nor does it limit the concentration of manganese dioxide in the manganese dioxide aqueous solution. As long as the mass ratio of manganese dioxide to p-dinitrobenzene in the mixed solution after the p-dinitrobenzene solution and the manganese dioxide aqueous solution are mixed, it can be (0.7-0.9): (0.3-0.1). Under this condition, the obtained modified manganese dioxide positive electrode material can enable the battery to have better rate performance when used as the positive electrode material of the zinc ion battery.

[0047] Furthermore, when the p-dinitrobenzene solution is mixed with the manganese dioxide aqueous solution, the mixing time is 1 to 3 hours. Specifically, the mixing time is 1 hour, 2 hours, 3 hours, etc. The purpose of mixing is to allow the p-dinitrobenzene and manganese dioxide in the solution to be fully dispersed in the solution, so that the p-dinitrobenzene can be evenly attached to the surface of the manganese dioxide.

[0048] Further, in the step of drying the mixed solution after heating the reaction, heating can accelerate the reaction. In some embodiments, the temperature of the heating reaction is 40-80°C, and the time of the heating reaction is 10-24h. Specifically, the temperature of the heating reaction is 40°C, 50°C, 65°C, 80°C, etc., and the time of the heating reaction is 10h, 15h, 20h, 24h, etc. The above-mentioned heat-relieving temperature and time can make the p-dinitrobenzene and manganese dioxide fully combined. The drying can be carried out by centrifugal drying or other methods. The centrifugal drying method can better remove the solvent and avoid the solvent from adhering to the obtained modified manganese dioxide positive electrode material.

[0049] The present invention also provides a positive electrode sheet, which is made of the modified manganese dioxide positive electrode material or the modified manganese dioxide positive electrode material prepared by the preparation method of the modified manganese dioxide positive electrode material.

[0050] In some embodiments, the positive electrode sheet can be prepared by the following method:

[0051] The modified manganese dioxide positive electrode material is mixed with acetylene black, polyvinylidene fluoride and N-methylpyrrolidone to obtain a slurry;

[0052] The slurry is coated on a current collector and dried to obtain a positive electrode sheet.

[0053] In the above preparation method, acetylene black is used as a conductive agent to improve the conductivity of the electrode material, ensuring that the current generated by the active material can be smoothly transmitted to the current collector; polyvinylidene fluoride is used as a binder to bond the active material and the conductive agent to the current collector to prevent them from falling off during the use of the battery; N-methylpyrrolidone is used as an organic solvent to mix the modified manganese dioxide positive electrode material with acetylene black and polyvinylidene fluoride into a uniform slurry for easy coating; the current collector mainly collects the current generated by the active material and transmits it to the external circuit.

[0054] In some embodiments, the mass ratio of the modified manganese dioxide positive electrode material, acetylene black, and polyvinylidene fluoride is (6-8): (3-1): 1. Specifically, the mass ratio of the modified manganese dioxide positive electrode material, acetylene black, and polyvinylidene fluoride can be 8:1:1, 7:2:1, 6:3:1, etc. The use of the above ratio of modified manganese dioxide positive electrode material, acetylene black, and polyvinylidene fluoride to prepare the slurry can make the obtained positive electrode sheet have better electrochemical performance.

[0055] In some embodiments, when the modified manganese dioxide positive electrode material is mixed with acetylene black, polyvinylidene fluoride and N-methylpyrrolidone, the modified manganese dioxide positive electrode material can be mixed with acetylene black first, then the N-methylpyrrolidone solution of polyvinylidene fluoride is added and mixed, and finally N-methylpyrrolidone is added to a pre-calculated volume.

[0056] In the step of applying the slurry to a current collector such as a carbon cloth or a stainless steel mesh, a titanium mesh, and drying to obtain a positive electrode sheet, the drying temperature is 60-65°C, and the drying time is 6-12h. Specifically, the drying temperature can be 60°C, 62°C, 65°C, etc., and the drying time can be 6h, 8h, 12h, etc. The higher the temperature, the faster the evaporation of the solvent and water, thereby improving the drying efficiency, but too high a temperature may cause thermal decomposition or chemical reaction of the components in the slurry, affecting the performance of the positive electrode sheet. The longer the drying time, the more thoroughly the water and solvent in the coating evaporate, thereby obtaining a drier and more stable positive electrode sheet, but if the drying time is too long, it will lead to a waste of energy. Preferably, the slurry is applied to a carbon cloth and dried at 60°C for 8 hours to obtain a dry and stable positive electrode sheet.

[0057] In zinc-ion batteries, the loading of the positive electrode material (positive electrode sheet) describes the mass distribution of the active material on the electrode. It is usually described by how many milligrams (mg) of active material (modified manganese dioxide positive electrode material) are loaded per square meter (cm²) of electrode area. The size of the loading is directly related to the energy density, discharge performance and cost of the battery. A higher loading usually means that the electrode can store more energy, so the battery has a higher energy density. The appropriate loading can ensure that the electrode provides a stable current during the discharge process.

[0058] Preferably, in some embodiments of the present application, in the positive electrode sheet, the loading amount of the modified manganese dioxide positive electrode material is 2.0-10.0 mg / cm 2 In the technical solution of the present application, the surface of manganese dioxide is modified to obtain a p-dinitrobenzene surface-modified manganese dioxide positive electrode material, and its mass loading can reach 8 mg / cm 2 It has a high mass loading and exhibits excellent specific capacity and stable cycle performance.

[0059] The present invention also provides a zinc ion battery, which includes a battery positive electrode, a battery negative electrode and an electrolyte, and the battery positive electrode includes the above-mentioned positive electrode sheet or a positive electrode sheet prepared by the above-mentioned method for preparing the positive electrode sheet.

[0060] In some embodiments, the positive electrode sheet can be used to prepare an aqueous zinc-manganese ion battery, the electrolyte includes zinc sulfate and manganese sulfate, and the battery negative electrode includes zinc foil. The zinc foil can be commercial high-purity zinc foil, the concentration of zinc sulfate in the electrolyte is preferably 1-3 mol / L, the concentration of manganese sulfate is preferably 0.1-0.5 mol / L, and the solvent of the electrolyte is distilled water.

[0061] The p-dinitrobenzene surface-modified manganese dioxide positive electrode material prepared by the present invention has excellent electrochemical performance in aqueous zinc ion batteries. At a low current density of 200 mA / g, a high specific capacity of 250 mAh / g can be obtained; at a high current density of 1 A / g, the specific capacity is 200 mAh / g, and good rate performance is shown. Compared with commercial MnO2 (CMO), its stability is significantly better than that of commercial manganese dioxide positive electrode materials. Therefore, the positive electrode sheet prepared by the p-dinitrobenzene surface-modified manganese dioxide positive electrode material in the present invention can not only improve the specific capacity and rate performance of zinc ion batteries, but also promote the commercial development of zinc-manganese batteries.

[0062] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments and drawings. It should be understood that the following embodiments are only used to explain the present invention and are not used to limit the present invention.

[0063] Example 1

[0064] A positive electrode sheet is provided, which is prepared by the following method:

[0065] (1) Preparation of positive electrode material: 30 mg of p-dinitrobenzene, 70 mg of manganese dioxide and 20 mL of dimethyl sulfoxide aqueous solution were mixed for 2 h, and then the mixture was heated at 60 ° C for 20 h, centrifuged and dried to obtain a modified manganese dioxide positive electrode material;

[0066] In the mixed solution of p-dinitrobenzene and manganese dioxide, the mass ratio of p-dinitrobenzene to manganese dioxide is 3:7 (the mass concentration of manganese dioxide is 3.5 mg / mL);

[0067] Among them, the mass concentration of dimethyl sulfoxide in the dimethyl sulfoxide aqueous solution is 5 mg / mL;

[0068] (2) Preparation of positive electrode sheet: 100 mg of the modified manganese dioxide positive electrode material prepared in step (1) was mixed evenly with 50 mg of acetylene black and 16.67 mg of polyvinylidene fluoride, and 8 ml of N-methylpyrrolidone was added to obtain a slurry; the slurry was evenly coated on the carbon cloth current collector, and the loading amount of the positive electrode material was 7 mg / cm 2 , and heat-bake in an oven at 60 °C for 8 h to obtain a positive electrode sheet.

[0069] Example 2

[0070] A positive electrode sheet is provided, which is prepared by the following method:

[0071] (1) Preparation of positive electrode material: 20 mg of p-dinitrobenzene, 80 mg of manganese dioxide and 20 mL of ethanol solution were mixed for 2 h, and then the mixture was heated at 60 ° C for 22 h and centrifuged to obtain a modified manganese dioxide positive electrode material;

[0072] In the mixed solution of p-dinitrobenzene and manganese dioxide, the mass ratio of p-dinitrobenzene to manganese dioxide is 2:8 (the mass concentration of manganese dioxide is 4.0 mg / mL);

[0073] (2) Preparation of positive electrode sheet: 100 mg of the modified manganese dioxide positive electrode material prepared in step (1) was mixed evenly with 28.5 mg of acetylene black and 14.3 mg of polyvinylidene fluoride, and 8 ml of N-methylpyrrolidone was added to obtain a slurry; the slurry was evenly coated on the stainless steel mesh current collector, and the loading amount of the positive electrode material was 8 mg / cm 2 , and heat-bake in an oven at 60 °C for 8 h to obtain a positive electrode sheet.

[0074] Example 3

[0075] A positive electrode sheet is provided, which is prepared by the following method:

[0076] (1) Preparation of positive electrode material: 10 mg of p-dinitrobenzene, 90 mg of manganese dioxide and 20 mL of N-methylpyrrolidone solution were mixed for 2 h, and then the mixture was heated at 60 ° C for 24 h and centrifuged to obtain a modified manganese dioxide positive electrode material;

[0077] In the mixed solution of p-dinitrobenzene and manganese dioxide, the mass ratio of p-dinitrobenzene to manganese dioxide is 1:9 (the mass concentration of manganese dioxide is 4.5 mg / mL);

[0078] (2) Preparation of positive electrode sheet: 100 mg of the modified manganese dioxide positive electrode material prepared in step (1) was mixed evenly with 25 mg of acetylene black and 12.5 mg of polyvinylidene fluoride, and 8 ml of N-methylpyrrolidone was added to obtain a slurry; the slurry was evenly coated on the titanium mesh current collector, and the loading amount of the positive electrode material was 6 mg / cm 2 , and heat-bake in an oven at 60 °C for 8 h to obtain a positive electrode sheet.

[0079] Comparative Example 1

[0080] Except that p-dinitrobenzene is not added, other steps are the same as those in Example 1.

[0081] The modified manganese dioxide positive electrode materials prepared in Examples 1 to 3 were tested by scanning electron microscopy. Since the results are similar, only the test results of Example 1 are used as an example. The results are as follows: Figure 1 The modified manganese dioxide is in the shape of nano needles.

[0082] The modified manganese dioxide positive electrode materials prepared in Examples 1 to 3 were subjected to X-ray diffraction tests, with the horizontal axis representing the diffraction angle 2θ and the vertical axis representing the intensity. Since the results are similar, only the test results of Example 1 are used as an example below. The results are as follows: Figure 2 The modified manganese dioxide positive electrode material prepared in Example 1 exhibits characteristic peaks of manganese dioxide, corresponding to the standard PDF card 44-0141, and no new diffraction peaks or peak position shifts appear. This proves that the p-dinitrobenzene organic matter only performs surface modification on manganese dioxide, rather than intercalation modification of manganese dioxide.

[0083] Preparation of batteries

[0084] The positive electrode sheets provided in Examples 1 to 3 and Comparative Example 1 were cut into original sheets with a diameter of 10 mm as the positive electrode of the battery, and a high-purity zinc foil (10 mm diameter round sheet) with a thickness of 20 to 100 microns was used as the negative electrode of the battery. The electrolyte solutes were zinc sulfate and manganese sulfate, wherein the concentration of zinc sulfate in the electrolyte was 1 to 2 mol / L, and the concentration of manganese sulfate was 0.05 to 0.50 mol / L. The diaphragm used a glass fiber diaphragm with a diameter of 16 mm to better infiltrate the zinc sulfate & manganese sulfate electrolyte. The positive electrode shell, gasket, positive electrode sheet, diaphragm infiltrated with electrolyte, zinc negative electrode, gasket, shrapnel, and negative electrode shell were sequentially discharged and pressurized to prepare a CR2025 type aqueous zinc-manganese battery.

[0085] Electrochemical testing

[0086] (1) The zinc-manganese battery prepared by using the p-dinitrobenzene-modified manganese dioxide positive electrode sheet in Example 1 was subjected to a charge and discharge long cycle test at a current density of 0.2 A / g. The results are as follows: Figure 3 As shown, the battery prepared by the positive electrode sheet in Example 1 can obtain a high specific capacity of 250 mAh / g at a current density of 0.2A / g, and has good cycle stability. Therefore, the good surface modification between dinitrobenzene and manganese dioxide effectively inhibits the dissolution of manganese atoms in manganese dioxide and irreversible lattice distortion, thereby improving the structural stability of manganese dioxide.

[0087] (2) The battery prepared with the positive electrode sheet in Example 2 was subjected to a long charge and discharge cycle test at a current density of 0.2 A / g. The results are as follows: Figure 4 As shown, the battery prepared by the positive electrode sheet in Example 2 has a specific capacity of 400 mAh / g at a current density of 0.2 A / g, and still has an excellent capacity retention rate after 100 cycles. Therefore, p-dinitrobenzene can effectively regulate the interfacial reaction between manganese dioxide and the electrolyte, especially the reversible deintercalation reaction between zinc ions and hydrogen ions and manganese dioxide, thereby improving the energy density and cycle life of zinc-manganese batteries.

[0088] (3) The battery prepared with the positive electrode sheet in Example 3 was subjected to a long charge and discharge cycle test at a current density of 4.0 A / g. The results are as follows: Figure 5 As shown, the battery prepared by the positive electrode sheet in Example 3 still has a good specific capacity of 200 mAh / g at a high current density of 4.0 A / g, and still has a specific capacity of nearly 180 mAh / g after 1800 cycles. Figure 3-5 It can be seen that manganese dioxide modified with p-dinitrobenzene in different proportions exhibits different reactivity, and the specific capacity and cycle life are optimal when the ratio of manganese dioxide: p-dinitrobenzene is 8:2.

[0089] (4) Figure 6The linear cyclic voltammetry test diagram of the battery prepared from the positive electrode sheet in Example 3, the scanning rates are 0.2 mV / s, 0.4 mV / s, 0.6 mV / s, 0.8 mV / s, 1.0 mV / s, 1.2 mV / s, respectively. Figure 6 It can be seen that the p-dinitrobenzene-modified manganese dioxide positive electrode has good shape retention at different scan rates, proving that p-dinitrobenzene can significantly improve the reaction kinetics and rate performance of zinc-manganese batteries, especially the fast charging performance.

[0090] (5) Figure 7 Figure a is a charge and discharge test curve of the zinc-manganese battery prepared by the positive electrode sheet in Comparative Example 1 at different current densities. Figure 7 Figure b is a charge and discharge test curve of the zinc-manganese battery prepared with the positive electrode sheet in Example 3 at different current densities. The current densities used for constant current charge and discharge are 0.2A / g, 0.5A / g, 1.0A / g, 1.5A / g, 2.0A / g, 3.0A / g, and 5.0A / g from right to left. Figure 7 It can be seen that the modification of p-dinitrobenzene makes manganese dioxide have significantly increased specific capacity and rate performance, indicating that the p-dinitrobenzene-modified manganese dioxide positive electrode has excellent energy density and fast charging performance.

[0091] (6) Figure 8 The figure is the charge and discharge performance diagram of the zinc-manganese battery based on the unmodified manganese dioxide positive electrode sheet in Comparative Example 1 at different cycle numbers. The cycle numbers are 1, 5, 10, 25, 50, 100 and 150 respectively, and the current density is 0.5A / g. Figure 8 It can be seen that as the cycle progresses, the specific capacity of the manganese dioxide positive electrode in the comparative example at 0.5 A / g decays very seriously, indicating that the battery made without using p-dinitrobenzene-modified manganese dioxide as the positive electrode material has low specific capacity and structural stability.

[0092] The above are only preferred embodiments of the present invention, and do not limit the patent scope of the present invention. For those skilled in the art, the present invention may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the patent protection scope of the present invention.

Claims

1. A method for preparing a modified manganese dioxide positive electrode material, characterized in that: The following steps are involved: Mixing a p-dinitrobenzene solution with a manganese dioxide aqueous solution to obtain a mixed solution, heating the mixed solution for reaction and then drying the mixed solution to obtain a modified manganese dioxide positive electrode material, wherein the modified manganese dioxide positive electrode material comprises manganese dioxide modified on the surface of p-dinitrobenzene; In the mixed solution, the mass ratio of manganese dioxide to p-dinitrobenzene is (0.7-0.9): (0.3-0.1); The solvent of the p-dinitrobenzene solution includes at least one of dimethylformamide, dimethyl sulfoxide, deionized water and ethanol; The temperature of the heating reaction is 40-80° C., and the time of the heating reaction is 10-24 hours.

2. The method for preparing the modified manganese dioxide positive electrode material according to claim 1, characterized in that: The mixing time is 1 to 3 hours.

3. A positive electrode sheet, characterized in that: The positive electrode sheet is made of a modified manganese dioxide positive electrode material prepared by the preparation method of the modified manganese dioxide positive electrode material according to claim 1 or 2.

4. A method for preparing a positive electrode sheet as claimed in claim 3, characterized in that: The following steps are involved: The modified manganese dioxide positive electrode material is mixed with acetylene black, polyvinylidene fluoride and N-methylpyrrolidone to obtain a slurry; The slurry is coated on a current collector and dried to obtain a positive electrode sheet.

5. The method for preparing a positive electrode sheet according to claim 4, characterized in that: In the step of mixing the modified manganese dioxide positive electrode material with acetylene black, polyvinylidene fluoride and N-methylpyrrolidone to obtain a slurry, The mass ratio of the modified manganese dioxide positive electrode material, acetylene black and polyvinylidene fluoride is (6-8): (3-1):

1.

6. The method for preparing a positive electrode sheet according to claim 4, characterized in that: In the step of applying the slurry to carbon cloth and drying to obtain a positive electrode sheet: The drying temperature is 60-65°C; and / or, The drying time is 6 to 12 hours.

7. The method for preparing a positive electrode sheet according to claim 4, characterized in that: In the positive electrode sheet, the loading amount of the modified manganese dioxide positive electrode material is 2.0-10.0 mg / cm 2 .

8. A zinc ion battery, characterized in that: The zinc ion battery comprises a battery positive electrode, a battery negative electrode and an electrolyte, and the battery positive electrode comprises the positive electrode sheet according to claim 3 or a positive electrode sheet prepared by the method for preparing the positive electrode sheet according to any one of claims 4 to 7.

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