Six-fold symmetric snowflake-like graded nanowire assembly beta-MnO2 material and preparation method thereof
By preparing a six-fold symmetric, snowflake-like hierarchical nanowire assembly β-MnO2 material, the problems of structural degradation and slow ion diffusion of MnO2 in zinc-ion batteries were solved, achieving high specific surface area and excellent ion transport channels, thus improving electrochemical performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ANYANG INST OF TECH
- Filing Date
- 2026-02-04
- Publication Date
- 2026-05-01
AI Technical Summary
MnO2 suffers from structural degradation, capacity decay, slow ion diffusion kinetics, and low electronic conductivity in zinc-ion batteries, which limits its application in high-performance energy storage systems.
A six-fold symmetric, snowflake-like hierarchical nanowire assembly β-MnO2 material was prepared by hydrothermal reaction, filtration, drying and calcination to form a nanostructure with high specific surface area and excellent ion transport channels.
The electrochemical performance of MnO2 material was improved, the interfacial contact between the electrode and the electrolyte was enhanced, and the diffusion path of zinc ions was shortened, resulting in excellent electrochemical performance.
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Figure CN121948548A_ABST
Abstract
Description
Technical Field
[0001] This invention discloses a six-fold symmetric snowflake-like hierarchical nanowire assembly β-MnO2 material and its preparation method, belonging to the field of inorganic materials in the field of aqueous zinc-ion battery technology. Background Technology
[0002] To meet the urgent need for a global energy structure transition towards cleaner and lower-carbon energy, the development of efficient, stable, and environmentally friendly novel electrochemical energy storage systems has become a research hotspot. Electrode materials, as the core of energy storage devices, directly determine the performance of the entire system in terms of energy density, power density, and cycle life. Among numerous candidate materials, MnO2 is considered one of the most promising cathode materials due to its abundant resources, environmental friendliness, and high theoretical specific capacity. MnO2 possesses various crystal structures, including α, β, γ, δ, and λ. Different crystal forms exhibit differences in atomic arrangement, tunnel size, and connectivity, directly affecting ion migration behavior and electron transport paths, thus endowing the material with diverse electrochemical properties and providing the possibility of optimizing its performance through structural design.
[0003] However, MnO2 still faces many challenges in practical applications. Some crystal forms are prone to structural degradation or surface passivation during cycling, leading to rapid capacity decay; others are limited by slow ion diffusion kinetics or low electronic conductivity, exhibiting poor rate performance. These shortcomings severely restrict the large-scale application of MnO2 in high-performance energy storage systems. To address this, researchers have proposed various modification strategies, mainly including nanostructure manipulation, defect engineering, and composite material construction. From a practical application perspective, the overall performance of existing MnO2 materials is still insufficient, limiting its industrialization process. During synthesis, the choice of precipitant affects the ion precipitation rate and product morphology, thereby controlling the final structure of MnO2; simultaneously, the type and amount of manganese source also have a significant impact on crystal structure and chemical composition. Summary of the Invention
[0004] To overcome the technical shortcomings of MnO2 in zinc-ion battery applications, this invention provides a six-fold symmetric snowflake-like hierarchical nanowire assembly β-MnO2 material and its preparation method, belonging to the field of inorganic materials. Potassium permanganate solid, manganese nitrate aqueous solution, and ammonium bicarbonate solid are dissolved in deionized water, and the six-fold symmetric snowflake-like hierarchical nanowire assembly β-MnO2 material is obtained through hydrothermal reaction, filtration, drying, and calcination. This material exhibits a six-fold symmetric snowflake-like hierarchical structure formed by the self-assembly of nanowires. This structure possesses a high specific surface area and excellent ion transport channels, which is beneficial for providing abundant active sites, enhancing the interfacial contact between the electrode and the electrolyte, and shortening the diffusion path of zinc ions. This invention improves the electrochemical performance of MnO2 materials by optimizing the microstructure. The synthesis method is simple, low-cost, and suitable for large-scale industrial production.
[0005] The six-fold symmetric snowflake-like hierarchical nanowire assembly β-MnO2 material of this invention exhibits characteristic diffraction peaks at 2θ of 28.67°, 37.37°, 41.04°, 56.71°, and 72.37° in its XRD pattern; in its XPS pattern, the binding energies of Mn 2p orbitals are located at 641.6 eV and 653.09 eV, respectively, and the binding energies of O 1s orbitals are located at 528.78 eV and 530.58 eV, respectively; wherein Mn is +4 valence and O is +2 valence.
[0006] This invention also provides a method for preparing a six-fold symmetric, snowflake-like hierarchical nanowire assembly β-MnO2 material, comprising the following steps:
[0007] The first step is to disperse potassium permanganate solid in deionized water, then add 50% manganese nitrate aqueous solution and ammonium bicarbonate solid in sequence, and stir until the mixture is uniform.
[0008] The second step is to transfer the resulting mixed solution to a hydrothermal reactor, place it in an oven for constant temperature reaction, and allow it to cool naturally to room temperature after the reaction is complete.
[0009] The third step is to remove the reaction product, wash and filter it, and then dry it in an oven.
[0010] The fourth step involves calcining the dried product in an air atmosphere in a muffle furnace, and then cooling it to obtain the six-fold symmetrical snowflake-like hierarchical nanowire assembly β-MnO2 material.
[0011] Furthermore, in the above technical solution, in the first step, the molar ratio of potassium permanganate to manganese nitrate is 1:7.
[0012] Furthermore, in the above technical solution, in the first step, the molar ratio of potassium permanganate to ammonium bicarbonate is 1:16.
[0013] Furthermore, in the above technical solution, in the second step, the temperature of the isothermal reaction is 160°C, and the reaction time is 6 hours.
[0014] Furthermore, in the above technical solution, in the third step, the reaction product is washed with pure water. Specifically, the product is placed in pure water to form a suspension, ultrasonically treated for 3 minutes, and then filtered. This washing process is repeated a total of 3 times.
[0015] Furthermore, in the above technical solution, in the third step, the drying temperature is 80℃ and the drying time is 1 hour.
[0016] Furthermore, in the above technical solution, in the fourth step, the calcination temperature is 450℃ and the constant temperature calcination time is 5 hours; wherein, the time to heat up to 450℃ is 2 hours, and the time to naturally cool down to below 200℃ after calcination is 2 hours.
[0017] This invention also provides the application of the above-mentioned six-fold symmetric snowflake-like hierarchical nanowire assembly β-MnO2 material in the positive electrode of an aqueous zinc-ion battery.
[0018] Beneficial effects of the invention
[0019] 1. This invention prepares a six-fold symmetric snowflake-like hierarchical nanowire assembly β-MnO2 material. The synthesis steps are simple, the whole process is environmentally friendly and pollution is controllable, which is in line with the concept of green chemistry and has good potential for process scale-up and industrialization.
[0020] 2. This method achieves an organic combination of high specific surface area and efficient ion transport channels by constructing a β-MnO2 nanowire assembly with a six-fold symmetrical snowflake-like hierarchical structure. This structure not only provides abundant active sites but also enhances the contact between the electrode and the electrolyte interface, effectively shortening the diffusion path of zinc ions, thereby creating favorable conditions for electrochemical reaction kinetics.
[0021] 3. The six-fold symmetric snowflake-like hierarchical nanowire assembly β-MnO2 material prepared by the process of this invention exhibits excellent performance in the positive electrode of zinc-ion batteries and has good prospects for practical application. Attached Figure Description
[0022] Figure 1 The image shows the XRD pattern of the six-fold symmetric snowflake-like hierarchical nanowire assembly β-MnO2 material in Example 1.
[0023] Figure 2 This is a SEM image of the six-fold symmetric snowflake-like hierarchical nanowire assembly β-MnO2 material in Example 1;
[0024] Figure 3XPS images of the six-fold symmetric snowflake-like hierarchical nanowire assembly β-MnO2 material in Example 1; where: (a) is the full XPS spectrum; (b) is the XPS spectrum of Mn2p; and (c) is the XPS spectrum of O1s.
[0025] Figure 4 EDS image of the six-fold symmetric snowflake-like hierarchical nanowire assembly β-MnO2 material in Example 1;
[0026] Figure 5 The following is an elemental distribution diagram of the six-fold symmetric snowflake-like hierarchical nanowire assembly β-MnO2 material in Example 1; where: (a) is the overall elemental distribution diagram; (b) is the Mn elemental distribution diagram; and (c) is the O elemental distribution diagram.
[0027] Figure 6 The infrared spectrum of the six-fold symmetric snowflake-like hierarchical nanowire assembly β-MnO2 material in Example 1;
[0028] Figure 7 The image shows the Raman spectrum of the six-fold symmetric snowflake-like hierarchical nanowire assembly β-MnO2 material in Example 1.
[0029] Figure 8 The image shows the cyclic charge-discharge diagram of the six-fold symmetric snowflake-like hierarchical nanowire assembly β-MnO2 material in Example 5.
[0030] Figure 9 The cyclic voltammogram of the six-fold symmetric snowflake-like hierarchical nanowire assembly β-MnO2 material in Example 5;
[0031] Figure 10 The AC impedance diagram is shown for the six-fold symmetric snowflake-like hierarchical nanowire assembly β-MnO2 material in Example 5. Detailed Implementation
[0032] The present invention will be further described below through specific examples. However, these examples are merely exemplary and are not limited to the scope of protection of the present invention; they are merely embodiments.
[0033] In the following embodiments, unless otherwise specified, the reagents, materials and instruments used are all conventional reagents, materials and instruments, and are commercially available. The reagents involved can also be synthesized by conventional synthesis methods.
[0034] Example 1
[0035] The first step is to disperse 0.4741g of potassium permanganate and 7.5159g of 50% manganese nitrate aqueous solution in 60mL of deionized water and stir for 1 hour.
[0036] The second step is to add 3.7949g of ammonium bicarbonate to the above solution and continue stirring for 1 hour.
[0037] The third step is to transfer the resulting mixed solution to a 100mL hydrothermal reactor, place it in an oven, and react at a constant temperature of 160℃ for 6 hours. After the reaction is complete, allow it to cool naturally to room temperature.
[0038] The fourth step is to remove the reaction product from the hydrothermal reactor and perform a cleaning operation. The reaction product is placed in pure water to form a suspension, and then ultrasonically cleaned for 3 minutes in an ultrasonic cleaner. The suspension is then filtered, and the process is repeated a total of 3 times.
[0039] Fifth step: Place the cleaned product in an oven and dry it at 80°C for 1 hour.
[0040] The sixth step involves calcining the dried product in a muffle furnace. After calcination, the material is cooled to obtain a six-fold symmetrical, snowflake-like hierarchical nanowire assembly, β-MnO2. The calcination temperature is 450℃, with a heating program of 2 hours, a cooling period below 200℃ for 2 hours, and a constant-temperature calcination time of 5 hours.
[0041] Figure 1 XRD patterns of a six-fold symmetric snowflake-like hierarchical nanowire assembly of β-MnO2 were presented. The results showed that the obtained material had good crystallinity, and all diffraction peaks corresponded to the β-MnO2 standard card (PDF#01-071-4824), with no impurity phase peaks observed. Among them, the characteristic diffraction peaks located at 28.67°, 37.37°, 41.04°, 56.71°, and 72.37° corresponded to the (110), (101), (111), (211), and (301) crystal planes of β-MnO2, respectively.
[0042] Figure 2 This is a SEM image of a six-fold symmetric, snowflake-like hierarchical nanowire assembly of β-MnO2. The image reveals a six-fold symmetric, snowflake-like hierarchical structure. This morphology uses one-dimensional nanowires as the basic building blocks, preferentially growing along specific crystallographic directions and self-assembling to form a highly ordered six-fold symmetric hierarchical assembly, fully demonstrating crystal growth orientation and self-assembly behavior. This snowflake-like hierarchical structure possesses a large specific surface area and sufficient active sites, which helps enhance the interfacial contact between the electrode and the electrolyte and significantly shortens the ZnO2 electrolyte's surface area. 2+ The diffusion path.
[0043] Figure 3 XPS full spectrum of β-MnO2 material, a six-fold symmetric, snowflake-like hierarchical nanowire assembly. Figure 3 (a) The full spectrum confirms that the material is mainly composed of Mn and O elements, and no other metal impurities were detected. Figure 3 The Mn 2p spectrum in (b) shows that Mn 2p 3 / 2 and Mn 2p 1 / 2 The binding energies are located at 641.6 eV and 653.09 eV, respectively, and the spin-orbit splitting energy is 11.49 eV, consistent with the typical characteristics of MnO2. Through the analysis of Mn 2p... 3 / 2 Peak fitting can be performed to identify Mn. 4+ (642.5 eV) and Mn 3+ Characteristic peak at (641.2 eV). Mn 3+ / Mn 4+ The existence of redox couples provides a reaction basis for efficient energy storage and release. Further research... Figure 3 The O 1s spectrum analysis in (c) shows that the main peak at 528.78 eV belongs to lattice oxygen Mn–O–Mn, while the peak at 530.58 eV corresponds to surface adsorbed hydroxyl groups and oxygen vacancies.
[0044] Figure 4 The EDS diagram of the six-fold symmetric snowflake-like hierarchical nanowire assembly β-MnO2 material shows that characteristic peaks of Mn and O elements were detected in the analytical region, indicating that the main component of the synthesized material is manganese oxide.
[0045] Figure 5 This is an elemental distribution diagram of a six-fold symmetric, snowflake-like hierarchical nanowire assembly, β-MnO2. Strong signals for Mn and O elements were observed in the diagram, indicating a uniform distribution of manganese and oxygen in the test region.
[0046] Figure 6 The infrared spectrum of β-MnO2 material, a six-fold symmetrical, snowflake-like hierarchical nanowire assembly, is shown. It is located at 522.71 cm⁻¹. -1 The strong absorption peak at 709.8 cm⁻¹ is attributed to the bending vibration of the Mn–O bond in the MnO₆ octahedral framework, confirming the basic characteristics of the β-MnO₂ crystal structure; -1 The absorption peak at that point corresponds to the asymmetric stretching vibration of the Mn–O–Mn bridging bond, reflecting the covalent nature of the manganese-oxygen framework in the material.
[0047] Figure 7 The Raman spectrum of β-MnO2 material, a six-fold symmetric, snowflake-like hierarchical nanowire assembly, is located at 632.12 cm⁻¹. -1 The strong peak at 328 cm⁻¹ corresponds to the symmetric stretching vibration mode of the MnO₆ octahedron and is a characteristic Raman signal of β-MnO₂; -1 The peak at this point originates from the bending vibration of O–Mn–O. This type of structure can stabilize Mn through the Jahn–Teller effect. 3+ Species, promoting Mn3+ / Mn 4+ The formation of mixed valence states effectively improves the electronic conductivity of the material.
[0048] Example 2
[0049] The first step is to disperse 0.9482g of potassium permanganate and 6.4422g of 50% manganese nitrate aqueous solution in 60mL of deionized water and stir for 1 hour.
[0050] The second step is to add 3.7949g of ammonium bicarbonate to the above solution and continue stirring for 1 hour.
[0051] The third step is to transfer the resulting mixed solution to a 100mL hydrothermal reactor, place it in an oven, and react at a constant temperature of 160℃ for 6 hours. After the reaction is complete, allow it to cool naturally to room temperature.
[0052] The fourth step is to remove the reaction product from the hydrothermal reactor and perform a cleaning operation. The reaction product is placed in pure water to form a suspension, and then ultrasonically cleaned for 3 minutes in an ultrasonic cleaner. The suspension is then filtered, and the process is repeated a total of 3 times.
[0053] Fifth step: Place the cleaned product in an oven and dry it at 80°C for 1 hour.
[0054] The sixth step involves calcining the dried product in a muffle furnace. After calcination, the material is cooled to obtain a six-fold symmetrical, snowflake-like hierarchical nanowire assembly, β-MnO2. The calcination temperature is 450℃, with a heating program of 2 hours, a cooling period below 200℃ for 2 hours, and a constant-temperature calcination time of 5 hours.
[0055] Example 3
[0056] The first step is to disperse 1.4223g of potassium permanganate and 5.3685g of 50% manganese nitrate aqueous solution in 60mL of deionized water and stir for 1 hour.
[0057] The second step is to add 3.7949g of ammonium bicarbonate to the above solution and continue stirring for 1 hour.
[0058] The third step is to transfer the resulting mixed solution to a 100mL hydrothermal reactor, place it in an oven, and react at a constant temperature of 160℃ for 6 hours. After the reaction is complete, allow it to cool naturally to room temperature.
[0059] The fourth step is to remove the reaction product from the hydrothermal reactor and perform a cleaning operation. The reaction product is placed in pure water to form a suspension, and then ultrasonically cleaned for 3 minutes in an ultrasonic cleaner. The suspension is then filtered, and the process is repeated a total of 3 times.
[0060] Fifth step: Place the cleaned product in an oven and dry it at 80°C for 1 hour.
[0061] The sixth step involves calcining the dried product in a muffle furnace. After calcination, the material is cooled to obtain a six-fold symmetrical, snowflake-like hierarchical nanowire assembly, β-MnO2. The calcination temperature is 450℃, with a heating program of 2 hours, a cooling period below 200℃ for 2 hours, and a constant-temperature calcination time of 5 hours.
[0062] Example 4
[0063] The first step is to disperse 1.8964g of potassium permanganate and 4.2948g of 50% manganese nitrate aqueous solution in 60mL of deionized water and stir for 1 hour.
[0064] The second step is to add 3.7949g of ammonium bicarbonate to the above solution and continue stirring for 1 hour.
[0065] The third step is to transfer the resulting mixed solution to a 100mL hydrothermal reactor, place it in an oven, and react at a constant temperature of 160℃ for 6 hours. After the reaction is complete, allow it to cool naturally to room temperature.
[0066] The fourth step is to remove the reaction product from the hydrothermal reactor and perform a cleaning operation. The reaction product is placed in pure water to form a suspension, and then ultrasonically cleaned for 3 minutes in an ultrasonic cleaner. The suspension is then filtered, and the process is repeated a total of 3 times.
[0067] Fifth step: Place the cleaned product in an oven and dry it at 80°C for 1 hour.
[0068] The sixth step involves calcining the dried product in a muffle furnace. After calcination, the material is cooled to obtain a six-fold symmetrical, snowflake-like hierarchical nanowire assembly, β-MnO2. The calcination temperature is 450℃, with a heating program of 2 hours, a cooling period below 200℃ for 2 hours, and a constant-temperature calcination time of 5 hours.
[0069] Example 5
[0070] The six-fold symmetric snowflake-like hierarchical nanowire assembly β-MnO2 material prepared in Examples 1-4 was used as the positive electrode of an aqueous zinc-ion battery.
[0071] The first step is to weigh 0.16 g of six-fold symmetric snowflake-like hierarchical nanowire assembly β-MnO2 material and 0.02 g of acetylene black, and grind and mix them thoroughly in an agate mortar.
[0072] The second step involves dissolving 0.02 g of polyvinylidene fluoride in 0.6 mL of N-methylpyrrolidone to prepare an adhesive. After stirring evenly, the adhesive is added to the mixed powder obtained in the first step and further mixed into a uniform slurry.
[0073] The third step is to coat the obtained slurry onto the surface of a stainless steel foil with a thickness of 0.01 mm and dry it in an oven at 80 ℃ for 1 h.
[0074] The fourth step is to cut the stainless steel foil into 10 mm diameter discs after the active material has dried completely, which will be used as the positive electrode of the battery.
[0075] The fifth step involves assembling an aqueous zinc-ion battery using a zinc sheet as the negative electrode, glass fiber paper as the separator, and a mixed solution of 2 mol / L ZnSO4 and 0.2 mol / L MnSO4 as the electrolyte. After assembly, the battery is left to stand for 24 hours for subsequent electrochemical testing.
[0076] Figure 8 This is a charge-discharge cycle diagram of an aqueous zinc-ion battery using a six-fold symmetrical, snowflake-like hierarchical nanowire assembly of β-MnO2 as the positive electrode. The charge-discharge test currents were set at 50 mA / g, 100 mA / g, 200 mA / g, 300 mA / g, and 500 mA / g. The material prepared in Example 1 exhibited electrochemical self-activation behavior, with an initial discharge specific capacity of 250.73 mAh / g, which subsequently increased continuously during cycling, reaching a maximum discharge capacity of 402.27 mAh / g. This indicates that the material gradually undergoes structural reconstruction and interface optimization during the electrochemical process, forming a tunnel structure and active surface more conducive to Zn ion transport.
[0077] Figure 9 This is a cyclic voltammogram of an aqueous zinc-ion battery using a six-fold symmetrical, snowflake-like hierarchical nanowire assembly of β-MnO2 as the positive electrode. The curve shows a sharp oxidation peak, and reduction peaks are observed at approximately 1.2 V and 1.4 V. The peaks are prominent, and the peak spacing is small, indicating that the prepared material has low polarization.
[0078] Figure 10 This is the AC impedance curve of an aqueous zinc-ion battery using a six-fold symmetrical, snowflake-like hierarchical nanowire assembly β-MnO2 material as the positive electrode. The material prepared in Example 1 exhibits the lowest charge transfer resistance and solution resistance, indicating that it possesses a superior ion transport network.
[0079] Based on the disclosure in the foregoing specification, those skilled in the art can make appropriate changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention.
Claims
1. A six-fold symmetric snowflake-like hierarchical nanowire assembly β-MnO2 material, characterized in that its XRD pattern shows characteristic diffraction peaks at 2θ of 28.67°, 37.37°, 41.04°, 56.71° and 72.37°; in its XPS spectrum, the binding energies of Mn 2p orbitals are located at 641.6 eV and 653.09 eV, respectively, and the binding energies of O 1s orbitals are located at 528.78 eV and 530.58 eV, respectively; wherein Mn is +4 valence and O is +2 valence.
2. The method for preparing the six-fold symmetric, snowflake-like hierarchical nanowire assembly β-MnO2 material as described in claim 1, characterized in that, Includes the following steps: The first step is to disperse potassium permanganate solid in deionized water, then add 50% manganese nitrate aqueous solution and ammonium bicarbonate solid in sequence, and stir until the mixture is uniform. The second step is to transfer the resulting mixed solution to a hydrothermal reactor, place it in an oven for constant temperature reaction, and allow it to cool naturally to room temperature after the reaction is complete. The third step is to remove the reaction product, wash and filter it, and then dry it in an oven. The fourth step involves calcining the dried product in an air atmosphere in a muffle furnace, and then cooling it to obtain the six-fold symmetrical snowflake-like hierarchical nanowire assembly β-MnO2 material.
3. The preparation method according to claim 2, characterized in that: In the first step, the molar ratio of potassium permanganate to manganese nitrate is 1:
7.
4. The preparation method according to claim 2, characterized in that: In the first step, the molar ratio of potassium permanganate to ammonium bicarbonate is 1:
16.
5. The preparation method according to claim 2, characterized in that: In the second step, the isothermal reaction is carried out at a temperature of 160°C for 6 hours.
6. The preparation method according to claim 2, characterized in that: In the third step, the reaction product is washed with pure water. Specifically, the product is placed in pure water to form a suspension, sonicated for 3 minutes, and then filtered. This washing process is repeated a total of 3 times.
7. The preparation method according to claim 2, characterized in that: In the third step, the drying temperature is 80°C and the drying time is 1 hour.
8. The preparation method according to claim 2, characterized in that: In the fourth step, the calcination temperature is 450℃ and the constant temperature calcination time is 5 hours; of which, the time to heat up to 450℃ is 2 hours, and the time to cool down to below 200℃ after calcination is 2 hours.
9. The application of the six-fold symmetric snowflake-like hierarchical nanowire assembly β-MnO2 material as described in claim 1 in the positive electrode of an aqueous zinc-ion battery.