A manganese-vanadium bimetallic three-phase positive electrode material and a preparation method of a zinc ion battery water system thereof

Abstract

The application provides a preparation method of a zinc ion battery positive electrode material. The method uses self-made porous Mn-MOF as a sacrifice template to introduce a vanadium source, and in a protective atmosphere, in-situ constructs a MnO-MnV2O4-V2O3 ternary heterostructure through high-temperature carbonization treatment. The prepared Mn-MOF has porous nanometer characteristics, a large specific surface area and rich pore structures, can realize efficient loading and uniform dispersion of the vanadium source, and further forms a ternary composite material with synergistic action of double active sites. In the continuous charge and discharge cycle process, the double active sites can significantly increase the number of electrochemical active sites, and the ternary hetero-interface can strengthen the interface orbital hybridization effect, effectively improve the electronic conductivity of the material, and thus significantly improve the discharge specific capacity and cycle stability of the zinc ion battery.

Description

Technical Field

[0001] This invention relates to the field of aqueous battery electrode material preparation technology, specifically to a method for preparing MnO-MnV2O4-V2O3 composite cathode material for aqueous zinc-ion batteries using a MOF sacrificial template method. Background Technology

[0002] With the continuous development of portable electronic devices, flexible electronic devices, and energy storage technologies, the market is placing increasingly higher demands on the lightweight, flexibility, integration, and high safety performance of energy storage devices. Lithium-ion batteries, due to their high energy density, have been widely used in various electronic devices, but they have significant shortcomings in application: limited and unevenly distributed lithium resources lead to continuously rising raw material costs; the use of organic electrolyte systems makes them prone to safety issues such as leakage, combustion, and thermal runaway; and battery production, use, and recycling pose certain environmental risks. Therefore, developing new energy storage systems that are safer, have more abundant resources, lower costs, and are environmentally friendly has become an important development direction in the current energy storage field.

[0003] Aqueous zinc-ion batteries, using aqueous electrolytes as the medium, offer significant advantages such as high intrinsic safety, environmental friendliness, and low manufacturing costs. Meanwhile, zinc metal anodes possess characteristics such as high theoretical specific capacity, good compatibility with aqueous electrolytes, high hydrogen evolution potential, and excellent chemical stability. Furthermore, zinc resources are abundant and inexpensive, making aqueous zinc-ion batteries highly promising for applications in flexible devices, portable electronic devices, and large-scale energy storage, and they are considered one of the most promising new energy storage systems. Currently, the commercial application and performance improvement of aqueous zinc-ion batteries are mainly limited by the insufficient overall performance of the cathode materials. Existing aqueous zinc-ion battery cathode materials generally suffer from low specific capacity, poor cycle stability, easy structural degradation, and short lifespan, making it difficult to meet practical application requirements. Currently, the most researched and applied cathode materials mainly include manganese-based materials, vanadium-based materials, organic materials, and Prussian blue analogues. However, all of these materials have inherent defects: Prussian blue analogues have low reversible specific capacity, which cannot meet the requirements of high energy density; organic cathode materials have problems such as complex synthesis processes, high preparation costs, and limited reversible capacity, which are not conducive to large-scale applications; manganese-based materials are prone to Jahn-Teller distortion during charge and discharge, and manganese ion dissolution occurs, leading to material structure damage and rapid capacity decay; vanadium-based materials have problems such as vanadium species dissolution and poor intrinsic electronic conductivity, which seriously affect the cycle life and rate performance of the battery.

[0004] To improve the stability and conductivity of cathode materials, existing technologies typically employ methods such as constructing heterostructures, coating, or introducing carbon layers to suppress the dissolution of active materials and enhance electronic conductivity. Metal-organic frameworks (MOFs) possess advantages such as high specific surface area, tunable pore structure, and uniform metal site dispersion. Carbon-supported metal oxide composites can be prepared through high-temperature pyrolysis, making them ideal precursors and templates for preparing heterostructured electrode materials. However, existing MOF-derived materials still suffer from significant technical limitations: monometallic MOF-derived materials possess only a single active site, lacking the synergistic effect between bimetallic active sites, making it difficult to achieve a balance between high capacity and high stability; reported bimetallic Mn-V-based materials are mostly simple two-phase structures with weak interfacial interactions, and fail to fully utilize the orbital hybridization effect at the heterostructure interface for effective control of charge transfer dynamics. This prevents optimization of charge transport, suppression of structural distortion, and dissolution of active materials at the electronic structure level, resulting in overall battery performance that still cannot meet practical application requirements. Therefore, in order to address the technical challenges of existing aqueous zinc-ion battery cathode materials, such as low specific capacity, poor cycle stability, easy dissolution of active materials, and slow charge transfer kinetics, it is of great significance to develop MOF-derived three-phase Mn-V oxide / carbon composite materials with optimized interface electronic structure to achieve synergistic effects of multiple active sites, strong coupling of heterogeneous interfaces, and enhanced conductive network. This is of great significance for breaking through existing technical bottlenecks, improving the overall performance of aqueous zinc-ion batteries, and promoting their practical application and industrialization. Summary of the Invention

[0005] The purpose of this invention is to overcome the technical defects of existing aqueous zinc-ion battery cathode materials and provide a method for preparing a manganese-vanadium bimetallic three-phase cathode material. This method introduces a vanadium source using porous Mn-MOF as a sacrificial template and constructs a ternary heterostructure of MnO-MnV₂O₄-V₂O₃ in situ, achieving synergistic optimization of the active sites, interface structure, and microstructure of the cathode material. Simultaneously, this invention also provides the manganese-vanadium bimetallic three-phase cathode material prepared by this method and an aqueous zinc-ion battery containing this cathode material. This cathode material features a large specific surface area, abundant pore structure, excellent electronic conductivity, and good cycle stability. The aqueous zinc-ion battery prepared using this cathode material exhibits high reversible specific capacity, ultra-long cycle life, and excellent rate performance.

[0006] A method for preparing a manganese-vanadium bimetallic three-phase cathode material includes the following steps: (1) Dissolve 100-200 parts of manganese acetate tetrahydrate in 10-30 mL of deionized water by weight to obtain a manganese salt aqueous solution; at the same time, dissolve 100-200 parts of 2,5-dihydroxy-1,4-benziquinone and 0.1-0.5 g of polyvinylpyrrolidone (PVP) in 20-100 mL of anhydrous ethanol to obtain an organic ligand ethanol solution; mix the above manganese salt aqueous solution and organic ligand ethanol solution, transfer to a 100 mL stainless steel high-pressure reactor lined with polytetrafluoroethylene, heat treat at 150-250 °C for 10-15 h, and after the reaction is completed, cool naturally to room temperature. The resulting light red product is washed multiple times with deionized water and anhydrous ethanol, and then dried in a 60 °C electric thermostatic drying oven for 24 h to obtain a porous Mn-MOF precursor.

[0007] (2) Weigh 100-200 parts by weight of the porous Mn-MOF precursor obtained in step 1 and disperse it uniformly in 20-50 mL of anhydrous ethanol to obtain Mn-MOF ethanol dispersion; take another 100-200 parts of ammonium metavanadate and dissolve it in 40 mL of deionized water to obtain ammonium metavanadate aqueous solution; stir the ammonium metavanadate aqueous solution at 50-80 °C for 0.5-1 h and slowly add it dropwise to the Mn-MOF ethanol dispersion, continue stirring at room temperature for 1-3 h, transfer the mixture to a 100 mL stainless steel high-pressure reactor lined with polytetrafluoroethylene, heat treat it at 150-250 °C for 10-15 h, cool it naturally to room temperature after the reaction is completed, wash the black-red product with deionized water and anhydrous ethanol several times, and dry it in a 65 °C electric thermostatic drying oven for 24 h to obtain MnV-MOF composite precursor.

[0008] (3) The MnV-MOF composite precursor obtained in step 2 was placed in a tube furnace and heated at 5 °C·min under an argon protective atmosphere. -1 The temperature was increased to 800 °C at a heating rate, and the mixture was held for annealing for 2 h. After naturally cooling to room temperature, the resulting black product was collected, which is the MnO-MnV2O4-V2O3 manganese vanadium bimetallic three-phase cathode material. Attached Figure Description

[0009] Figure 1 SEM images of MnO-MnV2O4-V2O3 Figure 2 XRD patterns of MnO-MnV2O4-V2O3 Figure 3 MnO-MnV2O4-V2O3 in 4A·g -1 Long loop graph below Figure 4 Rate performance diagram of MnO-MnV2O4-V2O3 Detailed Implementation The following content provides a further detailed explanation and complete supplementary description of the technical solution, technical principles, material design concept, and performance advantages of the present invention. Unless otherwise expressly defined and limited in the present invention, all technical terms, scientific terms, and process descriptions used in the present invention have meanings generally understood and accepted by those skilled in the art.

[0010] To address the inherent technical defects of traditional aqueous zinc-ion battery cathode materials in practical applications, especially the problems of irreversible Jahn-Teller distortion, poor intrinsic electronic conductivity, easy dissolution and loss of manganese ions, and easy structural collapse of manganese-based oxides during long-term charge-discharge cycles, which ultimately lead to rapid capacity decay, shortened cycle life, and poor rate performance, this invention provides a three-phase composite cathode material derived from bimetallic Mn-V MOF and its design concept.

[0011] To fundamentally overcome the aforementioned technical bottlenecks, this invention, through the rational construction of a three-phase heterostructure and leveraging the strong interfacial coupling and interfacial orbital hybridization effect induced by VO-Mn bridging bonds, successfully achieves the directional and efficient transfer and redistribution of electrons between vanadium and manganese active sites. For example... Figure 1 As shown, the material exhibits a spherical morphology of aggregated MnO-MnV2O4-V2O3 nanowires; XRD testing confirmed that it is indeed composed of three phases: MnO, MnV2O4, and V2O3 (Figure 2).

[0012] The aforementioned electronic structure regulation mechanism can effectively suppress Mn in the material. 3+ The proportion and formation trend of the electrode material significantly alleviate the structural damage caused by Jahn-Teller distortion, while greatly accelerating the charge transfer kinetic rate and enhancing the ion diffusion capability. Ultimately, this achieves a synergistic improvement in the structural stability and electrochemical kinetic performance of the electrode material, breaking through the core technical challenge of traditional single-phase or two-phase materials that cannot simultaneously achieve high capacity and long lifespan from the principle level.

[0013] Through the synergistic optimization of multiple factors, including multi-metal active site coupling, heterogeneous interface electronic structure regulation, porous carbon framework enhancement effect, and precise construction of microstructure and pore structure, the MnO-MnV2O4-V2O3 composite electrode material prepared in this invention exhibits extremely excellent electrochemical performance. For example... Figure 3 As shown, at 4 A·g -1 At high current densities, this material can still stably release 268.9 mAh·g after 10,000 ultra-long-term deep cycles. -1 Its high reversible specific capacity highlights outstanding cycle stability, structural reliability and excellent long service life characteristics.

[0014] At the same time, such as Figure 4 As shown, the material exhibits performance at concentrations of 0.1, 0.2, 0.4, 0.5, 1, 2, and 4 A·g. -1 At different current densities, the reversible specific capacities reached 383, 376, 363, 352, 334, 320 and 301 mAh·g, respectively. -1 When the current density drops back to 0.1 A·g -1 At that time, its capacity can be restored to 372 mAh·g -1 The capacity recovery rate is as high as 97.1%, and the rate performance is extremely excellent. To fully demonstrate the effective introduction of vanadium, the successful construction of the three-phase heterostructure, the strong coupling effect between the phases, and to characterize and verify the high specific capacity, excellent rate performance, excellent cycling stability, and fast kinetic characteristics of the material prepared by this invention, this invention uses material analysis and testing methods to systematically test and elucidate the microstructure, crystal structure, and electrochemical performance of the sample. The relevant experimental data, characterization spectra, and performance curves are all detailed in the accompanying drawings and subsequent specific embodiments of this application.

Claims

1. A method for preparing a manganese-vanadium bimetallic three-phase cathode material, characterized in that, Includes the following steps: S1: Preparation of porous Mn-MOF precursor: By weight, 100-200 parts of manganese acetate tetrahydrate are dissolved in 10-30 mL of deionized water to obtain a manganese salt aqueous solution; simultaneously, 100-200 parts of 2,5-dihydroxy-1,4-benzylquinone and 0.1-0.5 g of polyvinylpyrrolidone are dissolved in 20-100 mL of anhydrous ethanol to obtain an organic ligand ethanol solution; the manganese salt aqueous solution and the organic ligand ethanol solution are mixed and transferred to a stainless steel high-pressure reactor lined with polytetrafluoroethylene, and heat-treated at 150-250 ℃ for 10-15 h. After naturally cooling to room temperature, the product is washed multiple times with deionized water and anhydrous ethanol and dried at 60 ℃ for 24 h to obtain a porous Mn-MOF precursor; S2: Preparation of MnV-MOF composite precursor: Weigh 100-200 parts by weight of the porous Mn-MOF precursor obtained in step S1, and uniformly disperse it in 20-50 mL of anhydrous ethanol to obtain Mn-MOF ethanol dispersion; separately take 100-200 parts of ammonium metavanadate, dissolve it in 40 mL of deionized water to obtain ammonium metavanadate aqueous solution; stir the ammonium metavanadate aqueous solution at 50-80 ℃ for 0.5-1 h, and then slowly add it dropwise to the Mn-MOF ethanol dispersion, stir at room temperature for 1-3 h, transfer the mixture to a stainless steel high-pressure reactor lined with polytetrafluoroethylene, heat treat it at 150-250 ℃ for 10-15 h, and after naturally cooling to room temperature, wash the product multiple times with deionized water and anhydrous ethanol, and dry it at 65 ℃ for 24 h to obtain MnV-MOF composite precursor; S3: High-temperature carbonization preparation of three-phase cathode material: The MnV-MOF composite precursor obtained in step S2 is placed in a tube furnace and heated at 5 °C·min under an argon protective atmosphere. -1 The temperature was increased to 800 °C and held for 2 h. After naturally cooling to room temperature, the black product was collected, which is the MnO-MnV2O4-V2O3 manganese vanadium bimetallic three-phase cathode material.

2. The method for preparing the manganese-vanadium bimetallic three-phase cathode material according to claim 1, characterized in that, In steps S1 and S2, the volume of the polytetrafluoroethylene-lined stainless steel high-pressure reactor is 100 mL.

3. A manganese-vanadium bimetallic three-phase cathode material, characterized in that, The cathode material is prepared by the preparation method described in claim 1 or 2. It is a ternary heterostructure of MnO-MnV2O4-V2O3, which forms an interfacial orbital hybridization effect through VO-Mn bridging bonds and has the characteristics of porous structure and synergistic effect of manganese and vanadium bimetallic active sites.

4. A method for preparing a positive electrode sheet for an aqueous zinc-ion battery, characterized in that, Includes the following steps: (a) Titanium sheets with a size of 1×2 cm were ultrasonically washed with deionized water for 20-40 min and ultrasonically washed with anhydrous ethanol for 10-30 min, and dried at 50-80 ℃ to obtain pretreated titanium sheets. (b) Weigh 60-80 parts by weight of the manganese-vanadium bimetallic three-phase cathode material as described in claim 3, 5-10 parts of acetylene black, and 5-10 parts of polytetrafluoroethylene, mix and stir evenly to obtain electrode slurry. (c) Place the pretreated titanium sheet obtained in step a on an automatic coating machine, and uniformly coat the electrode slurry obtained in step b onto the surface of the titanium sheet, with a coating amount of 2-4 mg / cm². 2 The sample was then placed in a vacuum drying oven and dried at 70-90 ℃ for 10-15 h to obtain the positive electrode sheet for an aqueous zinc-ion battery.

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