Manganese oxide-based positive electrode material of aqueous zinc ion battery and preparation method of manganese oxide-based positive electrode material

Abstract

The invention discloses a manganese oxide-based positive electrode material of an aqueous zinc ion battery and a preparation method of the manganese oxide-based positive electrode material. The preparation method specifically comprises the following steps: firstly, preparing a MnO2 nano-particle template; and preparing a MnO2 / MnOOH heterojunction material on the basis of the MnO2 nano particle template. The MnO2 / MnOOH heterojunction material is subjected to annealing treatment after being ground, and a MnO2 / Mn2O3 heterojunction material is obtained; and finally, grinding and mixing conductive carbon black, polyvinylidene fluoride and the MnO2 / Mn2O3 heterojunction material, adding N-methyl pyrrolidone, continuously grinding to obtain electrode slurry, coating conductive carbon paper with the electrode slurry, and drying to obtain the MnO2 / Mn2O3 heterojunction positive electrode material. According to the invention, the stability of the structure is enhanced by improving carrier transport, so that the zinc ion battery has high specific capacity and excellent cycle performance.

Description

Technical Field

[0001] The invention belongs to the technical field of positive electrode materials for aqueous zinc ion batteries, and in particular relates to a manganese oxide-based positive electrode material for aqueous zinc ion batteries and a preparation method thereof. Background Art

[0002] With the growth of global energy demand and the urgent need for environmental protection, the development and utilization of clean energy has become a key direction. Although aqueous zinc-ion batteries with metallic zinc negative electrodes have the advantages of high theoretical capacity, low cost, high safety and strong environmental protection, the development of aqueous zinc-ion batteries is still greatly limited by the performance of positive electrode materials. Therefore, the performance of positive electrode materials directly determines the energy storage performance of the battery and has become a hot topic in current research.

[0003] Currently, three types of cathode materials are considered as candidates for aqueous Zn-ion batteries: vanadium-based materials, manganese-based materials, and Prussian analogs. Among them, manganese-based oxides have attracted extensive research interest due to their high specific capacity (~300 mAh / g), valence state, polymorphism, as well as their high operating voltage (~1.23 V), low toxicity, and abundance.

[0004] However, despite the excellent application potential of manganese-based oxide cathode materials, their cycle stability is poor and their rate performance is limited, and they still face many technical challenges. In order to solve these problems, an effective strategy heterojunction structure has been proposed. The unique band arrangement and built-in electric field of the heterojunction interface can enhance the driving force for zinc ion migration, reduce transmission resistance, improve carrier distribution, and at the same time alleviate the volume change of the material, maintain structural stability, and extend battery life. In addition, regulating the interface geometry and chemical properties can further enhance the transmission kinetics, conductivity and ion diffusion rate, ensuring efficient coordinated transmission of ions and electrons. This fine regulation provides new ideas for the development of high-performance aqueous zinc-ion batteries and new energy storage materials.

[0005] In the prior art, a method using KNO 3 、MnSO 4 MnO was directly prepared by a one-step molten salt method using rGO and MnO as raw materials. 2 / Mn 2 O 3 Heterojunction positive electrode material method. However, the MnO obtained by this method 2 / Mn 2 O 3 Heterojunction positive electrode materials will affect the battery's cycle stability and rate performance due to problems such as uneven morphology. In addition, the reaction control of this method is not precise, and possible side reactions can easily generate unstable oxides, which further affect the electrochemical properties and practical applications of the materials. Summary of the invention

[0006] The object of the present invention is to provide a method for preparing a manganese oxide-based positive electrode material for an aqueous zinc ion battery, which enhances the stability of the structure by improving carrier transport, so that the zinc ion battery has a high specific capacity and excellent cycle performance.

[0007] Another object of the present invention is to provide a manganese oxide-based positive electrode material for an aqueous zinc ion battery.

[0008] The first technical solution adopted by the present invention is a method for preparing a manganese oxide-based positive electrode material for an aqueous zinc ion battery, which specifically comprises the following steps: Step 1, preparation of MnO 2 Nanoparticle templates; Step 2, based on MnO 2 Nanoparticle template preparation of MnO 2 / MnOOH heterojunction material; Step 3: MnO 2 / MnOOH heterojunction material is ground and evenly spread on Al 2 O 3 Annealing treatment was carried out in a crucible to obtain MnO 2 / Mn 2 O 3 Heterojunction materials; Step 4, conductive carbon black, polyvinylidene fluoride and MnO in step 3 2 / Mn 2 O 3 The heterojunction materials are ground and mixed, and N-methylpyrrolidone is added to continue grinding to obtain electrode slurry. The electrode slurry is coated on conductive carbon paper and dried to obtain MnO 2 / Mn 2 O 3 Heterojunction cathode material.

[0009] The first technical solution of the present invention is also characterized in that: Step 1 specifically includes the following steps: Step 1.1, KMnO 4 Dissolve in deionized water and perform the first magnetic stirring to obtain KMnO 4 Solution; Step 1.2, to KMnO 4 Adding ammonium halide to the solution, and performing a second magnetic stirring to stir evenly to obtain a mixed solution; Step 1.3, sealing the mixed solution into a reactor and performing a hydrothermal reaction, and after naturally cooling to room temperature, obtaining a reaction product A; Step 1.4, the reaction product A is first centrifuged and washed with deionized water, and then centrifuged and washed with anhydrous ethanol for a second time to obtain MnO2 Nanoparticle templates.

[0010] KMnO obtained in step 1.1 4 KMnO in solution 4 The concentration is 0.39mol / L~0.41mol / L, and the time of the first magnetic stirring is 18min~22min; The ammonium halide in step 1.2 includes NH 4 F or NH 4 Cl, the concentration of ammonium halide is 0.39mol / L~0.41mol / L. When the ammonium halide is NH 4 F, NH 4 F and KMnO 4 The mass ratio of ammonium halide is 1~2:4~8; when the ammonium halide is NH 4 When Cl, NH 4 Cl and KMnO 4 The mass ratio is 1~2:3~6; The second magnetic stirring time is 3min~7min; The temperature of the hydrothermal reaction in step 1.3 is 120°C to 160°C, and the time of the hydrothermal reaction is 9h to 12h; The number of times of the first centrifugal washing in step 1.4 is 2 to 3 times, and the number of times of the second centrifugal washing is 1 to 2 times.

[0011] Step 2 specifically includes the following steps: Step 2.1, preparing a divalent manganese salt solution; Step 2.2: MnO prepared in step 1 2 The nanoparticle template is dispersed in a divalent manganese salt solution and ultrasonically dispersed to obtain a uniform suspension; Step 2.3, sealing the suspension into a reactor and performing a hydrothermal reaction, and after naturally cooling to room temperature, obtaining a reaction product B; Step 2.4, the reaction product B is first centrifuged and washed with deionized water, and then centrifuged and washed with anhydrous ethanol for a second time, and then dried in air to obtain MnO 2 / MnOOH heterojunction material.

[0012] The divalent manganese salt solution in step 2.1 is MnCl 2 Solution, (CH 3 COO 2 Mn solution and MnSO 4 Any one of the solutions; the concentration of the divalent manganese salt solution is 0.05mol / L~0.15mol / L.

[0013] Step 2.2 MnO2 The mass ratio of the nanoparticle template to the solute in the divalent manganese salt solution is 1-2:5-15; The power of ultrasonic dispersion is 400w~600w, and the time of ultrasonic dispersion is 20min~30min; The temperature of the hydrothermal reaction in step 2.3 is 170°C to 200°C, and the time of the hydrothermal reaction is 9h to 12h; In step 2.4, the number of the first centrifugal washing is 2 to 3 times, and the number of the second centrifugal washing is 1 to 2 times; the drying temperature is 60°C to 80°C, and the drying time is 10h to 12h.

[0014] The annealing treatment in step 3 is specifically to uniformly spread MnO 2 Al / MnOOH heterojunction materials 2 O 3 The crucible is placed in a muffle furnace and annealed at a heating rate of 2°C / min~5°C / min from room temperature to 400°C~500°C. The annealing time is 1h~3h.

[0015] In step 4, conductive carbon black, polyvinylidene fluoride and MnO 2 / Mn 2 O 3 The heterojunction materials are ground and mixed to obtain a mixed material, in which the ratio of the three components in the mixed material is conductive carbon black: polyvinylidene fluoride: MnO 2 / Mn 2 O 3 Heterojunction material = 3~2:1:6~7, the ratio of N-methylpyrrolidone to mixed material is: 20μL:1mg; The drying temperature is 60℃~80℃, and the drying time is 9h~12h.

[0016] The second technical solution adopted by the present invention is that the manganese oxide-based positive electrode material of the aqueous zinc ion battery is prepared by the above-mentioned method for preparing the manganese oxide-based positive electrode material of the aqueous zinc ion battery. The beneficial effects of the present invention are: (1) The preparation method of the manganese oxide-based positive electrode material for aqueous zinc ion batteries of the present invention is to optimize the MnO by adjusting the concentration of the divalent manganese salt solution, the temperature of the hydrothermal reaction and the reaction time during the hydrothermal reaction in order to more finely control the surface to form a heterojunction. 2 The ratio of MnOOH ensures the smooth formation of MnO during high temperature annealing. 2 / Mn 2 O 3 Heterojunction. At the same time, the annealing conditions are adjusted to promote the 2 With Mn 2 O 3The mutual transformation and interface bonding between them ensure the stability and electrochemical properties of the material.

[0017] (2) The preparation method of the manganese oxide-based positive electrode material of the aqueous zinc ion battery of the present invention promotes the generation of more pores and defects on the surface of the material by adjusting the hydrothermal reaction conditions and optimizing the annealing treatment, thereby forming more reaction sites, increasing the specific surface area, and providing more reaction sites, thereby improving the specific capacity; at the same time, by adopting a composite conductive material, the electronic conductivity is improved, the resistance is reduced, and the energy transfer efficiency is improved.

[0018] (3) The preparation method of the manganese oxide-based positive electrode material of the aqueous zinc ion battery of the present invention is as follows: in the second hydrothermal reaction, part of MnO 2 The surface undergoes a dissolution-recrystallization reaction to form a MnOOH shell, which is then converted into Mn by annealing. 2 O 3 Shell layer. Thus, a core-shell structure is constructed. The shell material can effectively alleviate the cracks and disintegration caused by the volume expansion or contraction of the core material, thereby improving the mechanical stability of the material. At the same time, the shell layer can also effectively protect the core material and increase stability. At the same time, the interface between the shell and the core material helps to inhibit the decay of the internal structure, improve the cycle stability, and enable the battery to maintain good performance during repeated charge and discharge. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic flow chart of a method for preparing a manganese oxide-based positive electrode material for an aqueous zinc ion battery of the present invention; Figure 2 It is MnO prepared in step 1 of the present invention 2 SEM images of nanoparticle templates; Figure 3 It is MnO prepared in step 3 of the present invention. 2 / Mn 2 O 3 SEM image of heterojunction material; Figure 4 It is MnO prepared in step 3 of the present invention. 2 / Mn 2 O 3 XRD patterns of heterojunction materials; Figure 5 It is MnO prepared in step 3 of the present invention. 2 / Mn 2 O 3 TEM image of heterojunction material; Figure 6 is MnO in Example 6 of the present invention 2 / Mn 2 O 3The charge and discharge cycle curve of zinc-ion battery assembled with heterojunction cathode materials; Figure 7 is MnO in Example 6 of the present invention 2 / Mn 2 O 3 Curve of charge and discharge cycles of zinc-ion batteries assembled with heterojunction positive electrode materials. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0021] Example 1 The preparation method of the manganese oxide-based positive electrode material of the aqueous zinc ion battery of the present invention is as follows: Figure 1 As shown, the specific steps include: Step 1, preparation of MnO 2 Nanoparticle templates; Step 2, based on MnO 2 Nanoparticle template preparation of MnO 2 / MnOOH heterojunction material; Step 3: MnO 2 / MnOOH heterojunction material is ground and evenly spread on Al 2 O 3 Annealing treatment was carried out in a crucible to obtain MnO 2 / Mn 2 O 3 Heterojunction materials; Step 4, conductive carbon black, polyvinylidene fluoride and MnO in step 3 2 / Mn 2 O 3 The heterojunction materials are ground and mixed, and N-methylpyrrolidone is added to continue grinding to obtain electrode slurry. The electrode slurry is coated on conductive carbon paper and dried to obtain MnO 2 / Mn 2 O 3 Heterojunction cathode material.

[0022] The present invention optimizes the diffusion path of ions through a heterojunction structure, thereby enhancing the migration speed of ions and promoting efficient charging and discharging.

[0023] Example 2 In this embodiment, based on the embodiment 1, step 1 in the method for preparing the manganese oxide-based positive electrode material of the aqueous zinc ion battery of the present invention specifically comprises the following steps: Step 1.1, KMnO 4 Dissolve in deionized water and perform the first magnetic stirring for 18-22 minutes to obtain KMnO 4 Solution; Furthermore, KMnO 4 KMnO in solution 4 The concentration is 0.39mol / L~0.41mol / L.

[0024] Step 1.2, to KMnO 4 Add ammonium halide to the solution and perform a second magnetic stirring. The second magnetic stirring time is 3 min to 7 min. Stir evenly to obtain a mixed solution. Further, the ammonium halide includes NH 4 F or NH 4 Cl, the concentration of ammonium halide is 0.39mol / L~0.41mol / L. When the ammonium halide is NH 4 F, NH 4 F and KMnO 4 The mass ratio of ammonium halide is 1~2:4~8; when the ammonium halide is NH 4 When Cl, NH 4 Cl and KMnO 4 The mass ratio is 1~2:3~6.

[0025] Step 1.3, sealing the mixed solution into a reactor and performing a hydrothermal reaction, and after naturally cooling to room temperature, obtaining a reaction product A; Furthermore, the temperature of the hydrothermal reaction is 120°C to 160°C, and the time of the hydrothermal reaction is 9h to 12h.

[0026] Step 1.4, using deionized water to perform a first centrifugal washing on the reaction product A, the number of times of the first centrifugal washing is 2 to 3 times; The reaction product A was then centrifuged and washed for a second time using anhydrous ethanol. The number of times for the second centrifugation washing was 1 to 2 times to obtain MnO 2 Nanoparticle templates.

[0027] For the MnO prepared in step 1 2 Nanoparticle templates for sample observation, such as Figure 2 As shown, the MnO prepared by step 1 2The uneven size distribution of nanorods in the nanoparticle template and the irregularity of their morphology may reduce structural stability, affect cycle life, and limit electron and ion transport, reducing conductivity and specific capacity.

[0028] Example 3 In this embodiment, based on the embodiment 2, step 2 in the method for preparing the manganese oxide-based positive electrode material of the aqueous zinc ion battery of the present invention specifically comprises the following steps: Step 2.1, preparing a divalent manganese salt solution; Furthermore, the divalent manganese salt solution is MnCl 2 Solution, (CH 3 COO 2 Mn solution and MnSO 4 Any one of the solutions; the concentration of the prepared divalent manganese salt solution is 0.05mol / L~0.15mol / L.

[0029] Since MnCl 2 Solution, (CH 3 COO 2 Mn solution and MnSO 4 The solutions are all existing finished products, so the preparation process of the divalent manganese salt solution is not described in the present invention.

[0030] Step 2.2: MnO prepared in step 1 2 The nanoparticle template is dispersed in a divalent manganese salt solution and ultrasonically dispersed. The power of the ultrasonic dispersion is 400w-600w and the time is 20min-30min. After the ultrasonic dispersion is completed, a uniform suspension is obtained. Furthermore, MnO 2 The mass ratio of the nanoparticle template to the solute in the divalent manganese salt solution is 1-2:5-15.

[0031] Step 2.3, the suspension is sealed and placed in a reaction kettle, and a hydrothermal reaction is carried out, the temperature of the hydrothermal reaction is 170°C to 200°C, and the time of the hydrothermal reaction is 9h to 12h; after naturally cooling to room temperature, a reaction product B is obtained; Step 2.4, using deionized water to perform a first centrifugal washing on the reaction product B, the number of times of the first centrifugal washing is 2 to 3 times; The reaction product B was then centrifuged and washed for a second time using anhydrous ethanol. The second centrifugation washing was performed 1 to 2 times, and then dried in air to obtain MnO 2 / MnOOH heterojunction material.

[0032] Furthermore, the drying temperature is 60°C to 80°C, and the drying time is 10h to 12h.

[0033] Example 4 In this embodiment, based on the method for preparing the manganese oxide-based positive electrode material for an aqueous zinc ion battery of the present invention, the annealing treatment in step 3 is specifically to uniformly lay MnO 2 Al / MnOOH heterojunction materials 2 O 3 The crucible is placed in a muffle furnace and annealed at a heating rate of 2°C / min~5°C / min from room temperature to 400°C~500°C. The annealing time is 1h~3h.

[0034] During the annealing process in step 3, MnOOH is further converted into Mn 2 O 3 , forming Mn 2 O 3 shell, thus obtaining MnO 2 / Mn 2 O 3 Heterojunction structures, such as Figure 3 As shown in Figure 2, in this sample, the number of nanorods and nanoparticles increased significantly, the overall distribution became denser, and the outlines of the nanorods and particles became clearer. This phenomenon can be attributed to the addition of Mn 2+ The hydrothermal modification of MnO 2 The surface undergoes a dissolution-recrystallization reaction to form a MnOOH shell, which is further converted into Mn during the subsequent annealing process. 2 O 3 , forming Mn 2 O 3 shell, thus obtaining MnO 2 / Mn 2 O 3 The heterojunction structure affects the microstructure of the material. This morphological evolution may effectively increase the specific surface area and activity of the material, thereby improving its electrochemical performance.

[0035] Furthermore, in step 4, the conductive carbon black, polyvinylidene fluoride and MnO 2 / Mn 2 O 3 The heterojunction materials are ground and mixed to obtain a mixed material, in which the ratio of the three components in the mixed material is conductive carbon black: polyvinylidene fluoride: MnO 2 / Mn 2 O 3 Heterojunction material = 3~2:1:6~7.

[0036] The ratio of N-methylpyrrolidone to mixed materials is: 20 μL: 1 mg.

[0037] In step 4, the drying temperature is 60°C to 80°C, and the drying time is 9h to 12h.

[0038] Further analysis of MnO 2 / Mn 2 O 3 The heterojunction material is subjected to an X-ray diffraction experiment to obtain the XRD spectrum of the material, such as Figure 4 As shown, the material exhibits MnO 2 The characteristic diffraction peak of α-MnO 2 The diffraction peaks of the standard card (JCPDS 44-0141) are completely matched, indicating that MnO 2 The crystal structure is complete and stable.

[0039] MnO Removal 2 In addition to the diffraction peaks of Mn, additional diffraction peaks were detected at angles of 18.8°, 23.1°, 32.9°, 38.2°, 42.9°, 45.1°, 53.2° and 65.8°. 2 O 3 The standard diffraction peak of (JCPDS 41-1442) is completely matched. This result fully proves that the present invention can 2 As the substrate, MnO was successfully synthesized 2 / Mn 2 O 3 Composite positive electrode materials and ensure the effective formation of their crystalline phase structure.

[0040] In addition, the MnO prepared in step 3 2 / Mn 2 O 3 The heterojunction material is observed using a transmission electron microscope to generate a TEM image, such as Figure 5 As shown in the figure, it can be clearly observed that the material presents a typical core-shell structure. Among them, the outer layer of the rod-like structure clearly shows Mn 2 O 3 The lattice fringes of MnO 2 This feature clearly proves that Mn 2 O 3 Coated with MnO 2 surface, forming core-shell MnO 2 / Mn 2 O 3 Composite cathode material. The formation of this structure helps optimize the electron transfer path of the material and improve its electrochemical stability, thereby enhancing the overall performance.

[0041] Example 5 The manganese oxide-based positive electrode material of the aqueous zinc ion battery of the present invention is prepared by adopting the above-mentioned method for preparing the manganese oxide-based positive electrode material of the aqueous zinc ion battery.

[0042] Example 6 The method for preparing the manganese oxide-based positive electrode material of the aqueous zinc ion battery of this embodiment specifically comprises the following steps: Step 1, preparation of MnO 2 Nanoparticle templates; The specific steps are as follows: Step 1.1, KMnO 4 Dissolve in deionized water and perform the first magnetic stirring for 20 min to obtain KMnO 4 Solution; KMnO 4 The concentration of the solution is 0.4 mol / L; Step 1.2, to KMnO 4 Add NH 4 F, join NH 4 F and KMnO 4 The mass ratio of the two is 1:4 and magnetic stirring is performed for the second time. The stirring time is 5 minutes. After stirring evenly, a mixed solution is obtained. Step 1.3, the mixed solution is sealed and placed in a reaction vessel, and a hydrothermal reaction is carried out at a temperature of 140° C. for 12 h, and after naturally cooling to room temperature, a reaction product A is obtained; Step 1.4, the reaction product A is first centrifuged twice with deionized water, and then centrifuged twice with anhydrous ethanol to obtain MnO 2 Nanoparticle templates.

[0043] Step 2, based on MnO 2 Nanoparticle template preparation of MnO 2 / MnOOH heterojunction material; The specific steps are as follows: Step 2.1, prepare MnCl with a concentration of 0.1 mol / L 2 Solution; Step 2.2: MnO prepared in step 1 2 Nanoparticle templates dispersed in MnCl 2 Solution, MnO 2 Nanoparticle template and MnCl 2 The mass ratio of the solute in the solution was 2:15, and ultrasonic dispersion was performed at a power of 400 W for 20 min to obtain a uniform suspension; Step 2.3, the suspension is sealed and placed in a reaction vessel, and a hydrothermal reaction is carried out at a temperature of 180° C. for 12 h, and after naturally cooling to room temperature, a reaction product B is obtained; Step 2.4, the reaction product B is first centrifuged and washed twice with deionized water, and then centrifuged and washed twice with anhydrous ethanol, and then dried in air at a drying temperature of 60°C and a drying time of 12 h to obtain MnO 2 / MnOOH heterojunction material.

[0044] Step 3: MnO 2 The / MnOOH heterojunction material was ground into fine powder and evenly spread on the Al 2 O 3 Evenly spread MnO 2 Al / MnOOH heterojunction materials 2 O 3 The crucible was placed in a muffle furnace and annealed at a heating rate of 3°C / min from room temperature to 450°C for 2 h to obtain MnO 2 / Mn 2 O 3 Heterojunction materials; Step 4: Conductive carbon black, polyvinylidene fluoride and MnO in step 3 are mixed. 2 / Mn 2 O 3 The heterojunction materials are ground and mixed, conductive carbon black, polyvinylidene fluoride and MnO 2 / Mn 2 O 3 The ratio of heterojunction materials was 2:1:7. After mixing, N-methylpyrrolidone was added and the mixture was further ground to obtain electrode slurry. The electrode slurry was coated on conductive carbon paper and dried at 60°C for 12h to obtain MnO 2 / Mn 2 O 3 Heterojunction cathode material.

[0045] The MnO prepared in this example 2 / Mn 2 O 3 Heterojunction positive electrode, 12mm zinc foil negative electrode, ZnSO 4 The button aqueous zinc ion battery was assembled with the solution and glass fiber separator and the performance was tested.

[0046] like Figure 6 As shown in the figure, the charge and discharge cycles of the aqueous zinc ion battery composed of the above components were tested. Affected by the activation process, the specific capacity of the aqueous zinc ion battery first increased and then decreased in the initial cycle stage, and reached a maximum value of 557 mAh / g after 50 cycles, which is much higher than that of the traditional MnO 2 The specific capacity of the material as a positive electrode shows excellent energy storage performance. 2 O 3The introduction of enhances the diffusion of ions. After 150 cycles, the material specific capacity is stabilized at 359 mAh / g, and the capacity retention rate is 64.5%.

[0047] The MnO prepared in this example 2 / Mn 2 O 3 The high specific capacity of the heterojunction positive electrode is mainly due to MnO 2 / Mn 2 O 3 The core-shell heterojunction structure of the heterojunction material optimizes the electron transmission path, reduces the interface impedance and improves the conductivity.

[0048] like Figure 7 As shown in the figure, the charge and discharge cycles of the aqueous zinc ion battery were tested. The initial specific capacity of the material was 245 mAh / g. With the cycle activation, the maximum specific capacity reached 351 mAh / g after 500 cycles. Subsequently, after 1000 cycles, the capacity stabilized at 291 mAh / g, with a retention rate of 82.9%, showing excellent cycle stability. Compared with traditional MnO 2 The capacity of aqueous zinc-ion batteries is higher at the positive electrode, mainly due to the MnO 2 / Mn 2 O 3 The core-shell heterojunction structure of the heterojunction material, Mn 2 O 3 Provide additional active sites, and MnO 2 The synergistic effect enhances the diffusion dynamics. The stability of the core-shell structure further alleviates the volume expansion and structural collapse, and improves the cycle life and capacity retention rate. 2 / Mn 2 O 3 The heterojunction positive electrode performs excellently under high-rate cycling and has good application potential.

[0049] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0050] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a manganese oxide-based positive electrode material for an aqueous zinc ion battery, characterized in that: The specific steps include: Step 1, preparing a MnO2 nanoparticle template; Step 2, preparing a MnO2 / MnOOH heterojunction material based on a MnO2 nanoparticle template; Step 3, grinding the MnO2 / MnOOH heterojunction material and evenly spreading it in an Al2O3 crucible for annealing to obtain a MnO2 / Mn2O3 heterojunction material; Step 4, grind and mix the conductive carbon black, polyvinylidene fluoride and the MnO2 / Mn2O3 heterojunction material in step 3, add N-methylpyrrolidone and continue grinding to obtain electrode slurry, coat the electrode slurry on conductive carbon paper, and obtain MnO2 / Mn2O3 heterojunction positive electrode material after drying.

2. The method for preparing a manganese oxide-based positive electrode material for an aqueous zinc ion battery according to claim 1, wherein: The step 1 specifically comprises the following steps: Step 1.1, dissolving KMnO4 in deionized water, and performing a first magnetic stirring to obtain a KMnO4 solution; Step 1.2, adding ammonium halide to the KMnO4 solution, and performing a second magnetic stirring to stir evenly to obtain a mixed solution; Step 1.3, sealing the mixed solution into a reactor and performing a hydrothermal reaction, and after naturally cooling to room temperature, obtaining a reaction product A; Step 1.4, using deionized water to perform a first centrifugal washing on the reaction product A, and then using anhydrous ethanol to perform a second centrifugal washing on the reaction product A to obtain a MnO2 nanoparticle template.

3. The method for preparing a manganese oxide-based positive electrode material for an aqueous zinc ion battery according to claim 2, wherein: The KMnO4 concentration in the KMnO4 solution obtained in step 1.1 is 0.39 mol / L to 0.41 mol / L, and the first magnetic stirring time is 18 min to 22 min; In step 1.2, the ammonium halide includes NH4F or NH4Cl, and the concentration of the ammonium halide is 0.39 mol / L~0.41 mol / L. When the ammonium halide is NH4F, the mass ratio of NH4F to KMnO4 is 1~2:4~8; when the ammonium halide is NH4Cl, the mass ratio of NH4Cl to KMnO4 is 1~2:3~6; The second magnetic stirring time is 3min~7min; The temperature of the hydrothermal reaction in step 1.3 is 120°C to 160°C, and the time of the hydrothermal reaction is 9h to 12h; The number of times of the first centrifugal washing in step 1.4 is 2 to 3 times, and the number of times of the second centrifugal washing is 1 to 2 times.

4. The method for preparing a manganese oxide-based positive electrode material for an aqueous zinc ion battery according to claim 1, wherein: The step 2 specifically includes the following steps: Step 2.1, preparing a divalent manganese salt solution; Step 2.2, dispersing the MnO2 nanoparticle template prepared in step 1 in a divalent manganese salt solution, and performing ultrasonic dispersion to obtain a uniform suspension; Step 2.3, sealing the suspension into a reactor and performing a hydrothermal reaction, and after naturally cooling to room temperature, obtaining a reaction product B; Step 2.4, using deionized water to perform a first centrifugal washing on the reaction product B, and then using anhydrous ethanol to perform a second centrifugal washing on the reaction product B, and then drying in air to obtain a MnO2 / MnOOH heterojunction material.

5. The method for preparing a manganese oxide-based positive electrode material for an aqueous zinc ion battery according to claim 4, wherein: In the step 2.1, the divalent manganese salt solution is any one of a MnCl2 solution, a (CH3COO)2Mn solution and a MnSO4 solution; and the concentration of the divalent manganese salt solution is 0.05 mol / L to 0.15 mol / L.

6. The method for preparing a manganese oxide-based positive electrode material for an aqueous zinc ion battery according to claim 4, characterized in that: In the step 2.2, the mass ratio of the MnO2 nanoparticle template to the solute in the divalent manganese salt solution is 1-2:5-15; The power of the ultrasonic dispersion is 400w~600w, and the time of the ultrasonic dispersion is 20min~30min; The temperature of the hydrothermal reaction in step 2.3 is 170°C to 200°C, and the time of the hydrothermal reaction is 9h to 12h; In step 2.4, the number of the first centrifugal washing is 2 to 3 times, and the number of the second centrifugal washing is 1 to 2 times; the drying temperature is 60° C. to 80° C., and the drying time is 10 h to 12 h.

7. The method for preparing a manganese oxide-based positive electrode material for an aqueous zinc ion battery according to claim 1, characterized in that: The annealing treatment in step 3 is specifically to place the Al2O3 crucible evenly paved with the MnO2 / MnOOH heterojunction material in a muffle furnace, and perform annealing treatment from room temperature to 400℃~500℃ at a heating rate of 2℃ / min~5℃ / min, and the annealing treatment time is 1h~3h.

8. The method for preparing a manganese oxide-based positive electrode material for an aqueous zinc ion battery according to claim 1, characterized in that: In the step 4, the conductive carbon black, polyvinylidene fluoride and MnO2 / Mn2O3 heterojunction material are ground and mixed to obtain a mixed material, wherein the ratio of the three components in the mixed material is conductive carbon black: polyvinylidene fluoride: MnO2 / Mn2O3 heterojunction material = 3-2:1:6-7, and the ratio of N-methylpyrrolidone to the mixed material is: 20 μL:1 mg; The drying temperature is 60° C. to 80° C., and the drying time is 9 h to 12 h.

9. A manganese oxide-based positive electrode material for an aqueous zinc ion battery, characterized in that: The material is prepared by the method for preparing a manganese oxide-based positive electrode material for an aqueous zinc ion battery as described in any one of claims 1 to 8.

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