A high-entropy doped manganese oxide / metal solid solution heterojunction and its preparation method, electrode sheet and zinc ion battery

Abstract

The present invention belongs to the technical field of zinc ion battery positive electrode materials, and specifically relates to a high-entropy doped manganese oxide / metal solid solution heterojunction and its preparation method, electrode sheet and zinc ion battery. The present invention uses manganese acetate tetrahydrate, multiple metal salts and trimesic acid as raw materials to prepare a precursor, and synthesizes a high-entropy manganese oxide / metal solid solution heterojunction through high-temperature calcination heat treatment. The chemical formula is: Mn x (M 1a M 2b ) y (M 3c M 4d M 5e ) z O / IMC, where Mn represents manganese, and M1-M5 represent doping metal elements other than manganese. By varying the type of doping metal element, this invention optimizes the material's crystal and electronic structure, enabling regulation of product ion and electron transport kinetics. This resulting zinc-ion battery exhibits excellent rate performance and cycle stability, demonstrating broad application prospects and significant economic value in the zinc-ion battery field.

Description

Technical Field

[0001] The present invention belongs to the technical field of zinc ion battery positive electrode materials, and particularly relates to a high-entropy doped manganese oxide / metal solid solution heterojunction and a preparation method thereof, an electrode sheet and a zinc ion battery. Background Art

[0002] Zinc-ion batteries (ZIBs) are a promising energy storage technology in the post-lithium-ion era due to their high safety, abundant zinc resources, environmental friendliness, and wide application. 2+ Large ionic radius and high charge density will produce strong electrostatic repulsion with the host material, resulting in structural collapse and slow kinetics, which will hinder the embedding process and reduce the cycling stability. Therefore, the development of cathode materials with high energy density and structural stability is imperative. Manganese-based oxides, as representative cathode materials, have multiple oxidation states with high energy density. Their different crystal structures also provide flexible options for optimizing electrochemical performance. To date, various manganese-based oxides (MnO2, Mn2O3, Mn3O4, and MnO) have been explored for use in ZIBs. Among them, MnO has the highest theoretical capacity and has the potential to achieve ultra-high energy density. However, Zn 2+ Transport is hampered by the compact [MnO6] octahedral arrangement in its rocksalt (NaCl-type) structure, while electronic transport is suppressed by its wide band gap and strong electron correlation of Mn 3d orbitals, hindering its development.

[0003] The development of multi-scale ion / electron transport channels has attracted widespread attention. In the current research context, new material modification strategies have emerged, mainly including two technical paths: heterostructure construction and ion doping regulation. Specifically, heterostructures accelerate electron migration through external interface modulation, while ion doping optimizes ion migration through internal lattice distortion. However, there are few reports on the synergistic combination of the two. Heterojunctions are interface structures formed between different materials, and their unique electronic properties are derived from interface effects. Metal element-metal oxide heterostructures use electronic structure differences to achieve unique functions. Their interface effects optimize charge transfer through a three-layer mechanism: (1) Band structure differences lead to electron-hole separation, improving charge storage and transport efficiency; (2) Electronic polarization and charge density gradients induce electron redistribution, activating electrochemical reaction sites; (3) Built-in electric fields regulate the ion migration energy barrier and improve carrier dynamics. While heterojunction engineering has significantly improved the performance of functional materials, its development is hampered by two major bottlenecks: the difficulty in achieving precise nanoscale control of the heterojunction interface, which often leads to localized charge accumulation; and the mismatch in electron / ion transport capabilities between components (e.g., poor synergy between highly conductive and highly ion-diffusive phases), which exacerbates concentration polarization. Therefore, a shift toward synergistic, multidimensional modulation strategies is crucial.

[0004] In recent years, innovative concepts of high entropy (i.e., element types ≥ 5) have emerged in the field of doping, which exhibit high electrochemical activity due to lattice distortion and diffusion delay effects. By introducing elements with different ionic radii and chemical properties, the host material undergoes lattice distortion, resulting in defects and unsaturated coordination, thereby promoting carrier transport. This lattice distortion also causes lattice reconstruction, resulting in more continuous ion migration pathways and lowered energy barriers. In addition, the higher activation energy required for multi-element diffusion leads to a diffusion delay effect, which slows down atomic migration, effectively suppresses phase transitions, and stabilizes ion channels during charge and discharge cycles. However, it is necessary to be wary of local optimization traps, where single parameter improvements are difficult to achieve the overall optimal state and may even lead to adverse effects. For example, doping Zn 2+ The initial activity of manganese oxide was enhanced at the expense of its cycling stability. Therefore, combining heterostructure engineering with high-entropy doping strategies can achieve synergistic modulation of electronic and crystal structures, which is crucial for optimizing electron / ion transport kinetics. At the same time, elucidating the multicomponent cooperative mechanism provides an innovative approach to addressing the inherent limitations of manganese-based materials. Summary of the Invention

[0005] To address the limited ion / electron transport in manganese oxide-based zinc-ion batteries, the present invention uses manganese acetate tetrahydrate, various metal salts, and trimesic acid as raw materials to prepare a precursor. A high-entropy doped manganese oxide / metal solid solution heterojunction is synthesized through high-temperature calcination and successfully applied as a positive electrode material for zinc-ion batteries. Results show that the high-entropy doping strategy induces lattice distortion, promoting ion transport, while the heterojunction strategy influences the electronic structure, promoting electron transport. The synergistic effect of these two strategies effectively addresses the irreversible phase transition and structural collapse of MnO during zinc storage, resulting in excellent cycling stability and rate characteristics as a positive electrode material for zinc-ion batteries.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] The first aspect of the present invention provides a high entropy doped manganese oxide / metal solid solution heterojunction, the chemical formula of which is Mn x (M 1a M 2b )y(M 3c M 4d M 5e ) z O / IMC, wherein Mn represents manganese, M1, M2, M3, M4, and M5 represent doping metal elements other than manganese, and the doping metal elements are selected from up to five metal elements in the second to fifth periods of the periodic table, 0≤a≤0.025, 0≤b≤0.025, 0≤c≤0.1, 0≤d≤0.1, and 0≤e≤0.1.

[0008] Furthermore, M1 and M2 represent substitutional doping metal elements other than manganese, a+b=y; M3, M4, and M5 represent interstitial doping metal elements other than manganese, c+d+e=z; 0.8≤x≤1, 0≤y≤0.05, 0≤z≤0.15, x+y+z=1.

[0009] Furthermore, in the chemical formula, IMC represents a metal solid solution, which is composed of at least two metal elements among M1, M2, M3, M4, and M5.

[0010] Furthermore, the doping metal elements are selected from at most five elements of magnesium, calcium, cobalt, nickel, copper, zinc, barium and bismuth.

[0011] Furthermore, the high entropy doped manganese oxide phases M1, M2, M3, M4, and M5 in the heterojunction are magnesium, zinc, cobalt, nickel, and copper, respectively, corresponding to the diffraction peaks (111), (200), (220), (311), and (222); the metal solid solution phase is Cu 0.603 Co 0.327 Ni 0.07 , corresponding to diffraction peaks (111), (200) and (220).

[0012] A second aspect of the present invention provides a method for preparing a high-entropy doped manganese oxide / metal solid solution heterojunction, characterized in that it comprises the following steps:

[0013] Step 1, respectively weighing manganese acetate tetrahydrate and polyvinyl pyrrolidone, adding them to a solvent, and stirring at room temperature for 0.5 to 2 hours to obtain solution a; weighing trimesic acid, adding them to a solvent, and stirring at room temperature for 0.5 to 2 hours to obtain solution b; weighing other metal salts, adding them to a solvent, and stirring at room temperature for 0.5 to 2 hours to obtain solution c; the solvents are all mixed solutions of ethanol and water in a volume ratio of 1:1;

[0014] Step 2: Slowly pour solution b into solution a and continue stirring at room temperature for 1-2 hours to obtain suspension d;

[0015] Step 3: Slowly add solution c to suspension d, stir continuously at room temperature for 2-5 hours, and let it stand for 12-24 hours to obtain a precipitate;

[0016] Step 4: vacuum filter the obtained precipitate and wash it with ethanol and water for 3 to 6 times, and then dry the product in a vacuum drying oven at 80° C. for 10 to 15 hours to obtain a heterojunction precursor;

[0017] Step 5: heat-treating the precursor obtained in step 4 under nitrogen to obtain a high-entropy doped manganese oxide / metal solid solution heterojunction.

[0018] Furthermore, the weight average molecular weight of polyvinyl pyrrolidone is 10-50 kDa, and the molar ratio of manganese acetate tetrahydrate, metal salt, and trimesic acid is (2-3): (0-1.5):5.

[0019] Furthermore, in step 1, the metal salts are copper acetate, cobalt acetate tetrahydrate, nickel acetate tetrahydrate, magnesium acetate and zinc acetate, and the molar ratio of manganese acetate tetrahydrate, copper acetate, cobalt acetate tetrahydrate, nickel acetate tetrahydrate, magnesium acetate and zinc acetate is 2.499: (0~0.24): (0~0.104): (0~0.104): (0~0.208): (0~0.208).

[0020] Furthermore, during the heat treatment process in step five, the calcination temperature is 600-800°C, the holding time is 2-4 h, and the heating rate is 2-5°C / min.

[0021] The third aspect of the present invention provides an electrode sheet comprising an electrode active material, conductive carbon, a binder, and a dispersing solvent, wherein the electrode active material is the high-entropy doped manganese oxide / metal solid solution heterojunction provided by the first aspect of the present invention.

[0022] The fourth aspect of the present invention provides a zinc ion battery, comprising positive and negative electrode sheets, an electrolyte, and a battery separator, wherein the positive electrode sheet of the zinc ion battery is the above-mentioned electrode sheet.

[0023] Beneficial effects of the present invention:

[0024] This invention addresses the limited ion / electron transport issues inherent in manganese oxide (MnO)-based zinc-ion batteries by proposing an innovative solution. First, a high-entropy doping strategy is employed to induce a lattice distortion effect, significantly enhancing the material's ion transport capacity. Second, a heterojunction structure is employed to manipulate the electronic band structure, effectively enhancing electronic conductivity. The synergistic effect of these two approaches not only addresses key issues associated with conventional MnO materials during zinc ion storage, such as irreversible phase transitions and structural collapse, but also enables the cathode material to exhibit exceptional cycling stability and superior rate performance. Furthermore, through the precise design of the ratios of multiple metal elements, this invention achieves synergistic optimization of the material's crystal and electronic structures, providing a novel design approach for the development of high-performance zinc-ion battery cathode materials. This material, characterized by a simple preparation process and excellent electrochemical performance, demonstrates broad application prospects and significant economic benefits in the zinc-ion battery field. 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 following briefly introduces the drawings required for use in the embodiments or the description of the prior art; obviously, the drawings described below are some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 Scanning electron microscope images of high-entropy doped manganese oxide / metal solid solution heterojunctions prepared in different embodiments, wherein: a is embodiment 1, b is embodiment 2, and c is embodiment 3;

[0027] Figure 2 This is a scanning electron microscope photograph of the material prepared in Comparative Example 6 of the present invention;

[0028] Figure 3 XRD Rietveld refinement spectra of materials prepared in different embodiments and comparative examples of the present invention, wherein: a is embodiment 1, b is embodiment 2, c is embodiment 3, and d is comparative example 4;

[0029] Figure 4 The half-peak width of the crystal plane (200) of the material prepared in Examples 1 to 3 of the present invention and Comparative Example 4;

[0030] Figure 5 High-resolution XPS spectrum of the high-entropy doped manganese oxide / solid solution heterojunction prepared in Example 1, where: a is the Co 2p orbital, b is the Ni 2p orbital, and c is the Cu 2p orbital;

[0031] Figure 6 XRD spectra of materials prepared in different comparative examples, where a is comparative example 2, b is comparative example 3, c is comparative example 4, and d is comparative example 5;

[0032] Figure 7 This is the EDS spectrum of the high-entropy doped manganese oxide / metal solid solution heterojunction material prepared in Example 1 of the present invention;

[0033] Figure 8 Density of state curves of the materials prepared in Examples 1 to 3 of the present invention and Comparative Examples 1 to 3;

[0034] Figure 9 Bader charge analysis of the high entropy doped manganese oxide / metal solid solution heterojunction material prepared in Example 1 of the present invention;

[0035] Figure 10 The materials prepared in Examples 1 to 3 and Comparative Example 1 of the present invention are Zn 2+ The adsorption energy value of

[0036] Figure 11 The Zn content of the materials prepared in Comparative Example 1 and Example 1 is 2+ Migration path and energy barrier value, where: a is comparative example 1, b is example 1, and c is the energy barrier value;

[0037] Figure 12 The rate performance curves of the materials prepared in Examples 1 to 3 of the present invention are as follows;

[0038] Figure 13 The stability performance curves of the materials prepared in Examples 1 to 3 of the present invention;

[0039] Figure 14 This is the performance curve of the high-entropy doped manganese oxide / metal solid solution heterojunction high-loading electrode prepared in Example 1 of the present invention;

[0040] Figure 15 This is the stability performance curve of the high-load electrode of the high-entropy doped manganese oxide / metal solid solution heterojunction prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0041] To make the purpose, technical effects, and technical solutions of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention are clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention. Based on the embodiments disclosed in the present invention, other embodiments obtained by ordinary technicians in this field without making any creative efforts should fall within the scope of protection of the present invention.

[0042] Example 1:

[0043] This embodiment provides a method for preparing a HE-MnO / IMC high entropy doped manganese oxide / metal solid solution heterojunction, comprising the following steps:

[0044] Step 1. Weigh 2.499 mmol of manganese acetate tetrahydrate and 0.15 g of 40 kDa polyvinyl pyrrolidone respectively, add them to 50 mL of a mixed solvent of ethanol and water with a volume ratio of 1:1, and stir at room temperature for 2 h to obtain solution a; weigh 5.353 mmol of trimesic acid and add it to 100 mL of a mixed solvent of ethanol and water with a volume ratio of 1:1, and stir at room temperature for 2 h to obtain solution b; weigh 0.24 mmol of copper acetate, 0.104 mmol of cobalt acetate tetrahydrate, 0.104 mmol of nickel acetate tetrahydrate, 0.208 mmol of zinc acetate, and 0.208 mmol of magnesium acetate respectively and add them to 50 mL of a mixed solvent of ethanol and water with a volume ratio of 1:1, and stir at room temperature for 2 h to obtain solution c;

[0045] Step 2: Slowly pour solution b into solution a and continue stirring at room temperature for 2 h to obtain suspension d;

[0046] Step 3: Slowly add solution c to suspension d, stir continuously at room temperature for 5 h, and let it stand for 24 h to obtain a precipitate;

[0047] Step 4: vacuum filter the obtained precipitate and wash it with ethanol and water for 6 times, then dry the product in a vacuum drying oven at 80° C. for 15 h to obtain a heterojunction precursor;

[0048] Step 5: The precursor obtained in step 4 is placed in nitrogen for heat treatment, the temperature is raised to 700 ° C, the holding time is 4 h, and the heating rate is 2 ° C / min, thereby obtaining a HE-MnO / IMC high entropy doped manganese oxide / metal solid solution heterojunction.

[0049] Example 2:

[0050] This embodiment provides a method for preparing an ME-MnO / Cu entropy-doped manganese oxide / metal solid solution heterojunction, comprising the following steps:

[0051] Step 1. Weigh 2.499 mmol of manganese acetate tetrahydrate and 0.15 g of 40 kDa polyvinyl pyrrolidone respectively, add them to 50 mL of a 1:1 volume ratio of ethanol and water mixed solvent, and stir at room temperature for 1 hour to obtain solution a; weigh 5.353 mmol of trimesic acid and add it to 100 mL of a 1:1 volume ratio of ethanol and water mixed solvent, and stir at room temperature for 1 hour to obtain solution b; weigh 0.24 mmol of copper acetate, 0.208 mmol of zinc acetate, and 0.208 mmol of magnesium acetate respectively and add them to 50 mL of a 1:1 volume ratio of ethanol and water mixed solvent, and stir at room temperature for 1 hour to obtain solution c;

[0052] Step 2: Slowly pour solution b into solution a and continue stirring at room temperature for 1 hour to obtain suspension d;

[0053] Step 3: Slowly add solution c to suspension d, stir continuously at room temperature for 4 h, and let it stand for 18 h to obtain a precipitate;

[0054] Step 4: vacuum filter the precipitate obtained in step 3, then wash it with ethanol and water 5 times, and then place the product in a vacuum drying oven at 80°C for 12 hours to obtain a heterojunction precursor;

[0055] Step 5: The precursor obtained in step 4 is placed in nitrogen for heat treatment, the temperature is raised to 700 ° C, the holding time is 3 h, and the heating rate is 3 ° C / min, thereby obtaining the ME-MnO / Cu entropy-doped manganese oxide / metal solid solution heterojunction.

[0056] Example 3:

[0057] This embodiment provides a method for preparing LE-MnO low entropy manganese oxide, comprising the following steps:

[0058] Step 1. Weigh 2.499 mmol of manganese acetate tetrahydrate and 0.15 g of 40 kDa polyvinyl pyrrolidone respectively, add them to 50 mL of a 1:1 volume ratio of ethanol and water mixed solvent, and stir at room temperature for 1 hour to obtain solution a; weigh 5.353 mmol of trimesic acid and add it to 100 mL of a 1:1 volume ratio of ethanol and water mixed solvent, and stir at room temperature for 1 hour to obtain solution b; weigh 0.208 mmol of zinc acetate and 0.208 mmol of magnesium acetate respectively and add them to 50 mL of a 1:1 volume ratio of ethanol and water mixed solvent, and stir at room temperature for 1 hour to obtain solution c;

[0059] Step 2: Slowly pour solution b into solution a and continue stirring at room temperature for 1 hour to obtain suspension d;

[0060] Step 3: Slowly add solution c to suspension d, stir continuously at room temperature for 4 h, and let it stand for 16 h to obtain a precipitate;

[0061] Step 4: vacuum filter the precipitate obtained in step 3, then wash it with ethanol and water four times, and then place the product in a vacuum drying oven at 80°C for 12 hours to obtain a low-entropy doped manganese oxide precursor;

[0062] Step 5: The precursor obtained in step 4 is placed in nitrogen for heat treatment, the temperature is raised to 700 ° C, the holding time is 2 h, and the heating rate is 3 ° C / min, thereby obtaining LE-MnO low-entropy doped manganese oxide.

[0063] Example 4:

[0064] This embodiment provides a method for preparing a battery using HE-MnO / IMC as a positive electrode material, comprising the following steps:

[0065] A. Preparation of electrodes:

[0066] HE-MnO / IMC, Ketjen black, and polyvinylidene fluoride were weighed in a mass ratio of 7:2:1, and a slurry was prepared using N,N-dimethylformamide. The slurry was evenly applied on a stainless steel mesh, and the stainless steel mesh was placed in a vacuum drying oven at 80°C and dried for 12 h to obtain an electrode sheet with HE-MnO / IMC as the active material.

[0067] B. Preparation of batteries:

[0068] Zinc foil was selected as the negative electrode, HE-MnO / IMC electrode sheet as the positive electrode, 2 M ZnSO4 and 0.2 M MnSO4 as the electrolyte, and glass fiber as the battery separator to assemble a zinc ion battery.

[0069] Example 5:

[0070] This embodiment provides a method for preparing a battery with ME-MnO / Cu as the positive electrode material, comprising the following steps:

[0071] A. Preparation of electrodes:

[0072] ME-MnO / Cu, acetylene black, and polytetrafluoroethylene (PTFE) in a mass ratio of 7:2:1 were weighed and made into a slurry using N-methylpyrrolidone. The slurry was evenly applied on a stainless steel mesh, which was then dried in a vacuum drying oven at 80 °C for 12 h to obtain an electrode sheet with ME-MnO / Cu as the active material.

[0073] B. Preparation of batteries:

[0074] Zinc foil was selected as the negative electrode, ME-MnO / Cu electrode sheet as the positive electrode, 2 M ZnSO4 and 0.2 M MnSO4 as the electrolyte, and glass fiber as the battery separator to assemble a zinc ion battery.

[0075] Example 6:

[0076] This embodiment provides a method for preparing a battery using LE-MnO as a positive electrode material, comprising the following steps:

[0077] A. Preparation of electrodes:

[0078] LE-MnO, acetylene black, and polytetrafluoroethylene (PTFE) were weighed in a mass ratio of 7:2:1. A slurry was prepared using N-methylpyrrolidone and evenly applied on a stainless steel mesh. The stainless steel mesh was then dried in a vacuum drying oven at 80 °C for 12 h to obtain an electrode sheet with LE-MnO as the active material.

[0079] B. Preparation of batteries:

[0080] Zinc foil was selected as the negative electrode, LE-MnO electrode sheet as the positive electrode, 2 M ZnSO4 and 0.2 M MnSO4 as the electrolyte, and glass fiber as the battery separator to assemble a zinc ion battery.

[0081] Comparative Example 1:

[0082] This comparative example provides a method for preparing MnO manganous oxide, comprising the following steps:

[0083] Step 1: Weigh 2.499 mmol of manganese acetate tetrahydrate and 0.15 g of 40 kDa polyvinyl pyrrolidone respectively, add them to 50 mL of a 1:1 volume ratio ethanol and water mixed solvent, and stir at room temperature for 2 h to obtain solution a; weigh 5.353 mmol of trimesic acid and add it to 100 mL of a 1:1 volume ratio ethanol and water mixed solvent, and stir at room temperature for 2 h to obtain solution b;

[0084] Step 2: Slowly pour solution b into solution a and stir continuously at room temperature for 2 h to obtain suspension c. After standing for 24 h, a precipitate is obtained.

[0085] Step 3: vacuum filter the precipitate obtained in step 2, then wash it with ethanol and water 6 times, and then place the product in a vacuum drying oven at 80°C for 15 hours to obtain a manganese oxide precursor;

[0086] Step 4: heat-treat the precursor obtained in step 3 under nitrogen, raise the temperature to 700°C, keep the temperature for 4 h, and increase the temperature at a rate of 2°C / min to obtain manganous oxide.

[0087] Comparative Example 2:

[0088] This comparative example provides a method for preparing HE-MnO high entropy doped manganese oxide, comprising the following steps:

[0089] Step 1. Weigh 2.499 mmol of manganese acetate tetrahydrate and 0.15 g of 40 kDa polyvinyl pyrrolidone respectively, add them to 50 mL of a mixed solvent of ethanol and water with a volume ratio of 1:1, and stir at room temperature for 2 h to obtain solution a; weigh 5.353 mmol of trimesic acid and add it to 100 mL of a mixed solvent of ethanol and water with a volume ratio of 1:1, and stir at room temperature for 2 h to obtain solution b; weigh 0.0315 mmol of copper acetate, 0.0315 mmol of cobalt acetate tetrahydrate, 0.0315 mmol of nickel acetate tetrahydrate, 0.208 mmol of zinc acetate, and 0.208 mmol of magnesium acetate respectively, add them to 50 mL of a mixed solvent of ethanol and water with a volume ratio of 1:1, and stir at room temperature for 2 h to obtain solution c;

[0090] Step 2: Slowly pour solution b into solution a and continue stirring at room temperature for 2 h to obtain suspension d;

[0091] Step 3: Slowly add solution c to suspension d, stir continuously at room temperature for 5 h, and let it stand for 24 h to obtain a precipitate;

[0092] Step 4: vacuum filter the obtained precipitate and wash it with ethanol and water 6 times, and then dry the product in a vacuum drying oven at 80° C. for 15 h to obtain a high-entropy doped manganese oxide precursor;

[0093] Step 5: The precursor obtained in step 4 is placed in nitrogen for heat treatment, the temperature is raised to 700 ° C, the holding time is 4 h, and the heating rate is 2 ° C / min, thereby obtaining HE-MnO / IMC high entropy doped manganese oxide.

[0094] Comparative Example 3:

[0095] Step 1: Weigh 0.24 mmol of copper acetate, 0.104 mmol of cobalt acetate tetrahydrate, 0.104 mmol of nickel acetate tetrahydrate, 0.208 mmol of zinc acetate, 0.208 mmol of magnesium acetate, and 0.15 g of 40 kDa polyvinyl pyrrolidone, respectively, and add them to 50 mL of a 1:1 volume ratio ethanol and water mixed solvent, and stir at room temperature for 2 h to obtain solution a; weigh 5.353 mmol of trimesic acid and add it to 100 mL of a 1:1 volume ratio ethanol and water mixed solvent, and stir at room temperature for 2 h to obtain solution b;

[0096] Step 2: Slowly pour solution b into solution a and continue stirring at room temperature for 5 h to obtain suspension c. After standing for 24 h, a precipitate is obtained.

[0097] Step 3: The precipitate obtained in step 2 was vacuum filtered, then washed with ethanol and water 6 times, and then placed in a vacuum drying oven at 80 ° C for 15 h to obtain an IMC solid solution precursor;

[0098] Step 4: The precursor obtained in step 3 is placed in nitrogen for heat treatment, the temperature is raised to 700 ° C, the holding time is 4 h, and the heating rate is 2 ° C / min to obtain the product.

[0099] Comparative Example 4:

[0100] This comparative example provides a method for preparing a heterojunction, comprising the following steps:

[0101] Step 1. Weigh 2.499 mmol of manganese acetate tetrahydrate and 0.15 g of 40 kDa polyvinyl pyrrolidone respectively, add them to 50 mL of a mixed solvent of ethanol and water with a volume ratio of 1:1, and stir at room temperature for 2 h to obtain solution a; weigh 5.353 mmol of trimesic acid and add it to 100 mL of a mixed solvent of ethanol and water with a volume ratio of 1:1, and stir at room temperature for 2 h to obtain solution b; weigh 0.24 mmol of copper acetate, 0.104 mmol of cobalt acetate tetrahydrate, 0.104 mmol of nickel acetate tetrahydrate, 0.208 mmol of zinc acetate, and 0.208 mmol of magnesium acetate respectively and add them to 50 mL of a mixed solvent of ethanol and water with a volume ratio of 1:1, and stir at room temperature for 2 h to obtain solution c;

[0102] Step 2: Slowly pour solution b into solution a and continue stirring at room temperature for 2 h to obtain suspension d;

[0103] Step 3: Slowly add solution c to suspension d, stir continuously at room temperature for 5 h, and let it stand for 24 h to obtain a precipitate;

[0104] Step 4: vacuum filter the obtained precipitate and wash it with ethanol and water for 6 times, then dry the product in a vacuum drying oven at 80° C. for 15 h to obtain a heterojunction precursor;

[0105] Step 5: The precursor obtained in step 4 is placed in nitrogen for heat treatment, the temperature is raised to 1000°C, the holding time is 4 h, and the heating rate is 2°C / min, thereby obtaining a heterojunction.

[0106] Comparative Example 5:

[0107] The present invention provides a method for preparing a heterojunction, comprising the following steps:

[0108] Step 1. Weigh 2.499 mmol of manganese acetate tetrahydrate, 0.24 mmol of copper acetate, 0.104 mmol of cobalt acetate tetrahydrate, 0.104 mmol of nickel acetate tetrahydrate, 0.208 mmol of zinc acetate, 0.208 mmol of magnesium acetate, and 0.15 g of 40 kDa polyvinyl pyrrolidone, respectively, and add them to 50 mL of a 1:1 volume ratio ethanol and water mixed solvent, and stir at room temperature for 2 h to obtain solution a; weigh 5.353 mmol of trimesic acid and add it to 100 mL of a 1:1 volume ratio ethanol and water mixed solvent, and stir at room temperature for 2 h to obtain solution b;

[0109] Step 2: Slowly pour solution b into solution a and stir continuously at room temperature for 5 h to obtain suspension c. After standing for 24 h, a precipitate is obtained.

[0110] Step 3: After vacuum filtration, the obtained precipitate was washed with ethanol and water for 6 times, and then the product was placed in a vacuum drying oven at 80° C. for 15 h to obtain a heterojunction precursor;

[0111] Step 4: The precursor obtained in step 3 is placed in nitrogen for heat treatment, the temperature is raised to 700 ° C, the holding time is 4 h, and the heating rate is 2 ° C / min, so as to obtain a product heterojunction.

[0112] Comparative Example 6:

[0113] This comparative example provides a method for preparing a heterojunction, comprising the following steps:

[0114] Step 1. Weigh 2.499 mmol of manganese acetate tetrahydrate and 0.15 g of 270 kDa polyvinyl pyrrolidone respectively, add them to 50 mL of a mixed solvent of ethanol and water with a volume ratio of 1:1, and stir at room temperature for 2 h to obtain solution a; weigh 5.353 mmol of trimesic acid and add it to 100 mL of a mixed solvent of ethanol and water with a volume ratio of 1:1, and stir at room temperature for 2 h to obtain solution b; weigh 0.24 mmol of copper acetate, 0.104 mmol of cobalt acetate tetrahydrate, 0.104 mmol of nickel acetate tetrahydrate, 0.208 mmol of zinc acetate, and 0.208 mmol of magnesium acetate respectively and add them to 50 mL of a mixed solvent of ethanol and water with a volume ratio of 1:1, and stir at room temperature for 2 h to obtain solution c;

[0115] Step 2: Slowly pour solution b into solution a and continue stirring at room temperature for 2 h to obtain suspension d;

[0116] Step 3: Slowly add solution c to suspension d, stir continuously at room temperature for 5 h, and let it stand for 24 h to obtain a precipitate;

[0117] Step 4: vacuum filter the obtained precipitate and wash it with ethanol and water for 6 times, then dry the product in a vacuum drying oven at 80° C. for 15 h to obtain a heterojunction precursor;

[0118] Step 5: The precursor obtained in step 4 is placed in nitrogen for heat treatment, the temperature is raised to 700°C, the holding time is 4 hours, and the heating rate is 2°C / min, thereby obtaining a heterojunction.

[0119] Figure 1 Scanning electron micrographs of high-entropy doped manganese oxide / metal solid solution heterojunctions prepared in different examples, where a is Example 1, b is Example 2, and c is Example 3. The particles exhibit a pomegranate-shaped morphology. This unique structure increases the contact area between the electrode material and the electrolyte, facilitating sufficient electrolyte wetting and thereby enhancing ion / electron transport kinetics.

[0120] Figure 2 This is a scanning electron microscope image of the material prepared in Comparative Example 6. Compared to the well-dispersed pomegranate-shaped particles in Example 1, this material exhibits severe agglomeration. This indicates that the use of high-molecular-weight polyvinylpyrrolidone (PVP) reduces steric efficiency due to its long, curled chains and significantly increases the risk of bridging flocculation, ultimately forming irregular particles that are prone to agglomeration. This agglomerated structure may reduce the material's effective specific surface area and the number of surface active sites, thereby hindering its electrochemical performance.

[0121] Figure 3 The X-ray Rietveld refinement spectra of the materials prepared in Examples 1, 2, 3 and Comparative Example 1 confirm the formation of a high-entropy doped manganese oxide / metal solid solution heterojunction; in step 1, the type of acetate added has an important influence on the formation of the heterojunction. Figure 3 In Example 1, a high entropy doped manganese oxide and a metal solid solution heterojunction containing Cu, Co, and Ni (HE-MnO / IMC) is formed; Figure 3 b. In Example 2, a medium entropy doped manganese oxide and Cu single substance heterojunction (ME-MnO / Cu) is formed; Figure 3 The material formed in Example 3 is low-entropy doped manganese oxide (LE-MnO). Figure 3 The d comparative example 1 forms undoped manganese oxide (MnO). The difference in crystal structure proves that Cu, Co, Ni, Zn, and Mg will be doped into manganese oxide; at the same time, some Cu, Co, and Ni will be reduced at high temperature to form a crystal structure of Cu 0.603 Co 0.327 Ni 0.07 This is attributed to the thermodynamically driven entropic stabilization effect during high-temperature calcination, which causes the system to spontaneously evolve toward a low Gibbs free energy and high entropy state, ultimately forming a heterostructure of high-entropy-doped manganese oxide and an intermetallic compound. The coexistence of high-entropy-doped manganese oxide and an intermetallic compound in this system is a natural manifestation of thermodynamic equilibrium.

[0122] Table 1

[0123]

[0124] Table 1 is Figure 3 The corresponding X-ray Rietveld refined crystallographic data. Lattice parameter analysis shows that the volume of LE-MnO shrinks by 0.19% compared with MnO, which is mainly due to the smaller ionic radius of Zn 2+ and Mg 2+ ions preferentially replace Mn 2+Lattice sites, corresponding to substitutional doping, where the ionic radius mismatch leads to reduced bond lengths and lattice compression. In contrast, ME-MnO / Cu and HE-MnO / IMC exhibit 0.20% and 0.24% volume expansion compared to LE-MnO, which is due to the Cu 2+ 、Co 2+ and Ni 2+ It occupies the interstitial sites of the octahedron, corresponds to interstitial doping, and expands the interlayer spacing.

[0125] Figure 4 Gaussian fitting of the half-maximum width (FWHM) of the diffraction peak of manganese oxide (200) crystal plane was prepared for different examples and comparative example 1, where a is example 1, b is example 2, c is example 3, and d is comparative example 1. Data analysis shows that the half-maximum width of LE-MnO on the (200) crystal plane is the largest (0.66°), indicating that Zn 2+ / Mg 2+ The introduction of controllable defects by substitutional doping reduces crystallinity and improves reaction activity. In contrast, the half-peak widths of ME-MnO / Cu and HE-MnO / IMC are smaller (0.45° and 0.22°, respectively), which is consistent with the gap doping characteristics and optimized long-range order, and is conducive to the construction of a three-dimensional electronic conduction network through charge compensation. This result once again confirms that Zn 2+ and Mg 2+ It belongs to substitutional doping, replacing Mn sites; Cu 2+ 、Co 2+ and Ni 2+ It is interstitial doping and enters the lattice gap.

[0126] Figure 5 This is a high-resolution XPS spectrum of the high-entropy doped manganese oxide / metal solid solution heterojunction prepared in Example 1, where: a is the Co 2p orbital, b is the Ni 2p orbital, and c is the Cu 2p orbital. The valence distribution of HE-MnO / IMC was further analyzed. The Co 2p spectrum revealed that the Co element has a mixed valence of +2 and 0, accounting for 70.9% and 29.1% respectively; similar phenomena were found for Ni 2p and Cu 2p. This further illustrates that part of the Co / Ni / Cu is doped into manganese oxide in the form of +2 valence to form high-entropy doped manganese oxide; part of the Co / Ni / Cu precipitates and forms an intermetallic compound solid solution in the form of a single substance, forming a heterojunction with the high-entropy doped manganese oxide.

[0127] Figure 6 The XRD spectra of the materials prepared in Comparative Examples 2, 3, 4 and 5 are shown in FIG. Figure 6In Comparative Example 2, by reducing the amount of copper, cobalt, and nickel salts, a single-phase structure containing only high-entropy-doped manganese oxide was formed after calcination, without a solid solution heterojunction. This shows that controlling the salt concentration has a significant impact on the synthesis of high-entropy-doped manganese oxide / metal solid solution heterojunctions.

[0128] Figure 6 In Comparative Example 3, IMC was synthesized without adding manganese salt. XRD revealed that in addition to the characteristic peaks of IMC, there were also peaks of Co / Ni elements, which were different from the single-phase characteristic peaks of the IMC part in Example 1. This further indicates that manganous oxide can accommodate Co / Ni elements to form high-entropy doped manganous oxide.

[0129] Figure 6 Comparative Example 4, a HE-MnO / IMC synthesized at 1000°C, shows a shift in the IMC toward the characteristic peaks of Co / Ni elements. This is attributed to the increased calcination temperature, which causes the Co / Ni elements doped into the manganese oxide to further precipitate and reduce to their elemental form. This decreases the configurational entropy of the manganese oxide, depriving it of its high-entropy doping properties and adversely affecting its electrochemical performance. Therefore, calcination temperature has a significant impact on the synthesis of high-entropy doped manganese oxide / metal solid solution heterojunctions.

[0130] Figure 6 In Comparative Example 5, all acetates were mixed in a one-pot process, and the relative content of IMC in the resulting heterojunction was significantly higher than that in Example 1. This indicates that during the one-pot synthesis process, the ion exchange reaction was insufficient, resulting in the formation of a precursor structure with uneven distribution of metal elements. This unevenness reduces the content of the target metal doped in the MnO matrix in the final product, while increasing the proportion of metal precipitated to form an independent IMC phase. This shows that the preparation method of adding acetate in steps has an important influence on the synthesis of high-entropy doped manganese oxide / metal solid solution heterojunctions.

[0131] Figure 7 Elemental mapping of the high-entropy doped manganese oxide heterojunction prepared in Example 1. This shows the uniform distribution of C, Mn, Mg, Cu, Zn, Co, and Ni, as well as abundant nanoscale heterojunction interfaces. This intuitively confirms the successful synthesis of high-entropy doping and solid solution heterojunctions.

[0132] Figure 8Density of states spectra of the materials prepared in Examples 1 to 3 and Comparative Examples 1 to 3. MnO exhibits wide bandgap characteristics, confirming its semiconductor characteristics with poor conductivity. IMC exhibits continuous energy levels, proving that it is a good electronic conductor. Continuous energy level distributions were observed in both HE-MnO and HE-MnO / IMC, indicating that the heterojunction and high entropy doping strategies significantly improved the conductivity of MnO. In addition, HE-MnO / IMC showed a higher density of states near the Fermi level, indicating the presence of a large number of free electrons involved in charge transport, which benefited from the synergistic effect of high entropy doping and heterojunction engineering, affecting the electronic structure of MnO.

[0133] Figure 9 This is the Bader charge analysis of the high entropy doped manganese oxide / metal solid solution heterojunction prepared in Example 1. The study found that during the discharge process, the valence of Co and Ni changes with the change of Zn 2+ In contrast, the valence of Cu, Zn, and Mg changed little. This suggests that Co and Ni are the main active elements in IMCs, utilizing their redox properties to balance charges and promote electron transfer.

[0134] Figure 10 The materials prepared in Examples 1 to 3 and Comparative Example 1 were Zn 2+ The adsorption energy of Zn on HE-MnO / IMC 2+ The adsorption energy of ZnO (-2.06 eV) is significantly higher than that of ME-MnO / Cu (-1.56 eV), LE-MnO (-1.09 eV) and MnO (-0.54 eV). This indicates that high entropy doping and changes in the heterogeneous interface optimize the electronic structure of MnO and enhance the adsorption of ZnO. 2+ The higher adsorption energy enables the material to effectively capture Zn in the electrolyte. 2+ , for the subsequent Zn 2+ Intercalation reaction provides favorable conditions.

[0135] Figure 11 The Zn content of the materials prepared in Comparative Example 1 and Example 1 is 2+ Migration paths and energy barriers. By comparing Zn 2+ The energy barriers of migration in MnO and HE-MnO / IMC further understand the influence of high entropy doping strategy on ion migration pathway. The migration energy barrier of HE-MnO / IMC is much lower than that of MnO, which indicates that the doping ions increase the disorder in MnO, which is beneficial to the migration of Zn 2+ In addition, the low energy barrier of HE-MnO / IMC is Zn 2+ The migration provides the driving force, thereby improving the electrochemical performance.

[0136] Figure 12 and Figure 13 The materials prepared in Examples 1 to 3 and Comparative Example 1 were subjected to constant current charge and discharge tests in a Neware device with a voltage window set to 0.8-1.9 V; the long cycle stability test was conducted at 5.0 A g -1 The rate performance test was carried out at a current density of 0.2-5.0 A g -1 It was observed that HE-MnO / IMC has excellent rate performance; and the long cycle stability test showed that at 5.0 A g -1 At a current density of 1.5 GHz, the battery still has a capacity retention rate of 92.3% after 10,000 cycles, proving that HE-MnO / IMC with faster ion / electron transport kinetics exhibits the best electrochemical performance and can maintain a stable material structure during rapid charge and discharge.

[0137] Figure 14 and Figure 15 Performance curves of the high entropy doped manganese oxide / metal solid solution heterojunction prepared in Example 1 at high loadings. -2 The performance test was carried out under different mass loading conditions. -1 When the loading amount increases, the areal capacity increases significantly (from 0.68 to 1.60 to 1.74 mAh cm -2 ), while the energy density also increased accordingly (from 0.94 to 2.11 to 2.26 mWh cm -2 ), showing good scalability. -1 Lower pair 6.5 mg cm -2 Long-term cycling tests of the electrode revealed negligible capacity fade over 80 cycles with an average Coulombic efficiency of 99.1%, confirming its stability.

[0138] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the same. Although the present invention has been described in detail with reference to the above embodiments, a person skilled in the art may still modify or make equivalent substitutions to the specific implementations of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the scope of protection of the claims of the present invention to be approved.

Claims

1. A high entropy doped manganese oxide / metal solid solution heterojunction, characterized in that: The chemical formula of the high entropy doped manganese oxide / metal solid solution heterojunction is Mn x (M 1a M 2b ) y (M 3c M 4d M 5e ) z O / MSS, Mn represents manganese, M1, M2, M3, M4, M5 represent five doping metal elements other than manganese, 0 <a≤0.025,0<b≤0.025,0<c≤0.1,0<d≤0.1,0<e≤0.1; Wherein, M3, M4, and M5 represent cobalt, nickel, and copper metal elements, and M1 and M2 are selected from two metal elements other than manganese, copper, cobalt, and nickel in the second to fifth periods of the periodic table; MSS stands for Metal Solid Solution, the metal solid solution phase is Cu 0.603 Co 0.327 Ni 0.07 .

2. The high entropy doped manganese oxide / metal solid solution heterojunction according to claim 1, characterized in that: M1 and M2 represent substitutional doping metal elements other than manganese, a+b=y; M3, M4, and M5 represent interstitial doping metal elements, c+d+e=z; 0.8≤x<1,0 <y≤0.05,0<z≤0.15,x+y+z=1。 3. The high entropy doped manganese oxide / metal solid solution heterojunction according to claim 1, characterized in that: The high entropy doped manganese oxide phases M1, M2, M3, M4, and M5 in the heterojunction are magnesium, zinc, cobalt, nickel, and copper, respectively, with corresponding diffraction peaks (111) (200) (220) (311) (222); the metal solid solution phase Cu 0.603 Co 0.327 Ni 0.07 Corresponding diffraction peaks (111) (200) (220).

4. The method for preparing a high entropy doped manganese oxide / metal solid solution heterojunction according to any one of claims 1 to 3, characterized in that: The following steps are involved: Step 1: Weigh manganese acetate tetrahydrate and polyvinyl pyrrolidone respectively, add them to a solvent, and stir at room temperature for 0.5 to 2 hours to obtain solution a; weigh trimesic acid, add them to a solvent, and stir at room temperature for 0.5 to 2 hours to obtain solution b; weigh other metal salts, add them to a solvent, and stir at room temperature for 0.5 to 2 hours to obtain solution c; Step 2: Slowly pour solution b into solution a and continue stirring at room temperature for 1-2 hours to obtain suspension d; Step 3: Slowly add solution c to suspension d, stir continuously at room temperature for 2-5 hours, and let it stand for 12-24 hours to obtain a precipitate; Step 4: vacuum filter the obtained precipitate and wash it with ethanol and water for 3 to 6 times, and then dry the product in a vacuum drying oven at 80° C. for 10 to 15 hours to obtain a heterojunction precursor; Step 5: heat-treating the precursor obtained in step 4 under nitrogen to obtain a high-entropy doped manganese oxide / metal solid solution heterojunction.

5. The method for preparing a high entropy doped manganese oxide / metal solid solution heterojunction according to claim 4, characterized in that: The weight average molecular weight of the polyvinyl pyrrolidone is 10-50 kDa; The molar ratio of manganese acetate tetrahydrate, metal salt and trimesic acid is (2-3): (0-1.5):

5.

6. The method for preparing a high entropy doped manganese oxide / metal solid solution heterojunction according to claim 4, characterized in that: During the heat treatment process in step 5, the calcination temperature is 600-800°C, the holding time is 2-4 h, and the heating rate is 2-5°C / min.

7. An electrode sheet comprising an electrode active material, conductive carbon, a binder, and a dispersing solvent, characterized in that: The electrode active material is the high entropy doped manganese oxide / metal solid solution heterojunction according to any one of claims 1 to 3.

8. A zinc ion battery comprising positive and negative electrode sheets, an electrolyte, and a battery separator, characterized in that: The positive electrode sheet of the zinc ion battery is the electrode sheet described in claim 7.

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