Method for preparing hexagonal manganese ore mn(o,oh)2 and its application

Abstract

The application provides a preparation method of hexagonal manganese ore Mn(O,OH)2 and application thereof, and belongs to the technical field of inorganic energy material preparation, and the preparation method comprises the following steps: (1) a predetermined amount of water, a divalent manganese salt, an oxidizing agent and a surfactant are mixed and treated to obtain a mixed solution; (2) the mixed solution is placed in a polytetrafluoroethylene reaction kettle, and is hydrothermally treated at 140-180 DEG C for 6-12 h; and the product is subjected to centrifugal and drying treatment to obtain the hexagonal manganese ore Mn(O,OH)2. The hexagonal manganese ore Mn(O,OH)2 is directly synthesized by using a one-step hydrothermal method with the divalent manganese salt, the oxidizing agent and the surfactant as reaction raw materials. The preparation method has the advantages of low reaction temperature, simple process, convenient operation and low production cost. The prepared hexagonal manganese ore Mn(O,OH)2 is used as a zinc ion battery positive electrode material to assemble a zinc ion battery, and the zinc ion battery has excellent electrochemical performance.

Description

Technical Field

[0001] This invention belongs to the field of inorganic energy material preparation technology, specifically relating to a method for preparing hexagonal manganese ore Mn(O,OH)2 and its application. Background Technology

[0002] Among numerous novel battery systems, aqueous zinc-ion batteries have gradually gained popularity in academia and industry due to their advantages such as low cost, environmental friendliness, high safety, large volumetric capacity, and high reversibility in aqueous systems. However, the limited availability of cathode materials and problems such as electrode material dissolution have slowed the rapid development of aqueous zinc-ion batteries. Therefore, it is necessary to find a new inorganic cathode material to solve the problems of electrode material dissolution and low battery performance.

[0003] Nsutite, also known as hexagonal manganese ore, has the following composition: (Mn) 4+ Mn 2+ (O,OH)2. Hexagonal manganese ore, associated with pyrolusite, manganese potassium ore, calcium manganese ore, and manganese barium ore, exhibits excellent discharge efficiency and is a major mineral component of high-quality discharge manganese ore. During the charging and discharging process of aqueous zinc-ion batteries, hydrogen evolution and corrosion occur to a certain extent, causing the pH to gradually decrease and the system to become slightly acidic, leading to a gradual decline in battery performance after multiple cycles. Hexagonal manganese ore Mn(O,OH)2 is alkaline and, to some extent, inhibits the decrease in pH during charging and discharging, thus contributing to long-term performance stability. However, no synthesis methods for hexagonal manganese ore Mn(O,OH)2 have been reported, nor has its application in aqueous zinc-ion batteries been observed. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a method for preparing hexagonal manganese ore Mn(O,OH)2.

[0005] The present invention also provides an application of the hexagonal manganese ore Mn(O,OH)2 prepared by the above preparation method.

[0006] The technical solution adopted by this invention to solve its technical problem is as follows:

[0007] A method for preparing hexagonal manganese ore Mn(O,OH)2 includes the following steps:

[0008] (1) Mix a predetermined amount of water, divalent manganese salt, oxidant and surfactant to obtain a mixed solution;

[0009] (2) The mixed solution was placed in a polytetrafluoroethylene reactor and hydrothermally heated at 140-180℃ for 6-12 hours. The product was centrifuged and dried to obtain hexagonal manganese ore Mn(O,OH)2.

[0010] Preferably, the volume ratio of water to surfactant is 15-20 mL: 0-0.01 g, and the morphology of hexagonal manganese ore Mn(O,OH)2 is controlled by adjusting the amount of surfactant.

[0011] Preferably, the molar ratio of the divalent manganese salt to the oxidant is 1-2:1.5-3.

[0012] Preferably, the mixing process is as follows: PVP is added to water and stirred until dissolved, then divalent manganese salt is added and stirred until dissolved, and finally an oxidant is added and stirred for 10-20 minutes.

[0013] Preferably, the divalent manganese salt is manganese chloride.

[0014] Preferably, the oxidant is sodium chlorate.

[0015] Preferably, the centrifugation and drying process specifically involves: centrifuging the product three times with deionized water, discarding the transparent filtrate to obtain a black solid product, placing the black solid product in an oven at 50-70°C for 8-10 hours, and then grinding and collecting the sample.

[0016] An application of hexagonal manganese ore Mn(O,OH)2 prepared by the above preparation method, wherein the hexagonal manganese ore Mn(O,OH)2 can be used as a positive electrode material for zinc-ion batteries.

[0017] As can be seen from the above technical solution, this invention provides a method for preparing hexagonal manganese ore Mn(O,OH)2 and its application. Compared with the prior art, its advantages are: this invention, for the first time, uses divalent manganese salt, oxidant, and surfactant as reaction raw materials. The oxidant oxidizes divalent manganese ions to a higher valence state to form a stable hexagonal manganese ore structure. The morphology of hexagonal manganese ore Mn(O,OH)2 is controlled by the surfactant, and hexagonal manganese ore Mn(O,OH)2 can be directly synthesized using a one-step hydrothermal method. This preparation method has advantages such as low reaction temperature, simple process, convenient operation, and low production cost. The hexagonal manganese ore Mn(O,OH)2 prepared by this invention was used as a positive electrode material in zinc-ion batteries. The results show that hexagonal manganese ore Mn(O,OH)2 has excellent electrochemical performance. Attached Figure Description

[0018] Figure 1 These are the XRD patterns of the two hexagonal manganese ore Mn(O,OH)2 prepared in Examples 1 and 2.

[0019] Figure 2 This is a SEM image of Mn(O,OH)2 prepared in Example 1.

[0020] Figure 3This is a SEM image of Mn(O,OH)2 prepared in Example 2.

[0021] Figure 4 It is at 0.4mV s -1 CV diagrams of the two hexagonal manganese ore Mn(O,OH)2 prepared in Examples 1 and 2.

[0022] Figure 5 The graphs show the rate performance of the two hexagonal manganese ore Mn(O,OH)2 prepared in Examples 1 and 2.

[0023] Figure 6 The graphs show the long-cycle performance of the two hexagonal manganese ore Mn(O,OH)2 prepared in Examples 1 and 2.

[0024] Figure 7 These are EIS performance diagrams of the two hexagonal manganese ore Mn(O,OH)2 prepared in Examples 1 and 2. Detailed Implementation

[0025] The technical solutions and effects of the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0026] This invention provides a method for preparing hexagonal manganese ore Mn(O,OH)2, comprising the following steps:

[0027] (1) Mix a predetermined amount of water, divalent manganese salt, oxidant and surfactant to obtain a mixed solution;

[0028] (2) The mixed solution was placed in a polytetrafluoroethylene reactor and hydrothermally heated at 140-180℃ for 6-12 hours. The product was centrifuged and dried to obtain hexagonal manganese ore Mn(O,OH)2.

[0029] This invention, for the first time, uses divalent manganese salt, an oxidant, and a surfactant as reactants. The oxidant oxidizes divalent manganese ions to a higher valence state to form a stable hexagonal manganese ore structure. The morphology of hexagonal manganese ore Mn(O,OH)₂ is then controlled by the surfactant, allowing for direct synthesis of hexagonal manganese ore Mn(O,OH)₂ via a one-step hydrothermal method. This preparation method offers advantages such as low reaction temperature, simple process, convenient operation, and low production cost. The hexagonal manganese ore Mn(O,OH)₂ prepared by this invention was used as a positive electrode material in zinc-ion batteries. Results showed that hexagonal manganese ore Mn(O,OH)₂ exhibits excellent electrochemical performance.

[0030] Furthermore, the volume ratio of water to surfactant was 15–20 mL: 0–0.01 g. The morphology of hexagonal manganese ore Mn(O,OH)₂ was controlled by adjusting the amount of surfactant. When no surfactant was added (i.e., the amount of surfactant was 0), the obtained hexagonal manganese ore Mn(O,OH)₂ exhibited a dense hexagonal disc structure; when a surfactant was added, the obtained hexagonal manganese ore Mn(O,OH)₂ exhibited a spherical structure. The two different morphologies of hexagonal manganese ore Mn(O,OH)₂ were used as positive electrode materials in zinc-ion batteries, and the results showed that both morphologies of hexagonal manganese ore Mn(O,OH)₂ exhibited excellent electrochemical performance. Among them, the hexagonal manganese ore Mn(O,OH)₂ with a dense hexagonal disc structure had a larger specific surface area, which was more conducive to Zn during charge and discharge. 2+ and H + The insertion and extraction of these molecules can provide higher specific capacity and more insertion / extraction sites, thus resulting in superior electrochemical performance.

[0031] Furthermore, the molar ratio of the divalent manganese salt to the oxidant is 1-2:1.5-3.

[0032] Furthermore, the mixing process involves adding PVP to water and stirring until dissolved, then adding divalent manganese salt and stirring until dissolved, and finally adding an oxidant and stirring for 10–20 minutes.

[0033] Furthermore, the divalent manganese salt is manganese chloride.

[0034] Furthermore, the oxidant is sodium chlorate.

[0035] Furthermore, the product was centrifuged three times with deionized water, the transparent filtrate was discarded, and a black solid product was obtained. The black solid product was placed in an oven at 50-70°C and dried for 8-10 hours, then ground and collected.

[0036] Example 1

[0037] A method for preparing hexagonal manganese ore Mn(O,OH)2 includes the following steps:

[0038] (1) Add 0.01g PVP to 20mL of water and stir until dissolved. Then add 1mmol of manganese chloride and stir until dissolved. Finally add 1.5mmol of sodium chlorate and stir for 10min to obtain a mixed solution.

[0039] (2) The mixed solution was placed in a polytetrafluoroethylene reactor and hydrothermally reacted at 140°C for 12 hours. The product was centrifuged three times with deionized water, and the transparent filtrate was discarded to obtain a black solid product. The black solid product was placed in an oven at 70°C and dried for 8 hours. The sample was then ground and collected to obtain hexagonal manganese ore Mn(O,OH)2, labeled as Nsutite-PVP.

[0040] Example 2

[0041] A method for preparing hexagonal manganese ore Mn(O,OH)2 includes the following steps:

[0042] (1) Add 1 mmol of manganese chloride to 20 mL of water and stir until dissolved. Then add 1.5 mmol of sodium chlorate and stir for 10 min to obtain a mixed solution.

[0043] (2) The mixed solution was placed in a polytetrafluoroethylene reactor and hydrothermally reacted at 140°C for 12 hours. The product was centrifuged three times with deionized water, and the transparent filtrate was discarded to obtain a black solid product. The black solid product was placed in an oven at 70°C and dried for 8 hours. The sample was then ground and collected to obtain hexagonal manganese ore Mn(O,OH)2, labeled as Nsutite-NO.

[0044] X-ray diffraction and SEM analyses were performed on the hexagonal manganese ore Mn(O,OH)2 prepared in Examples 1 and 2. The results are as follows:

[0045] Figure 1 The X-ray powder diffraction patterns of hexagonal manganese ore Mn(O,OH)2 prepared in Examples 1 and 2 show that the product has only one set of XRD diffraction peaks corresponding to Mn(O,OH)2, and the peak positions of the two samples can be matched one-to-one with the peak positions of the PDF (17-0510) card number, indicating that the prepared samples do not contain other impurities and are pure phase Mn(O,OH)2.

[0046] Figure 2 SEM images of Mn(O,OH)2 obtained in Example 1, where a: low magnification, b: high magnification. Figure 2 In (a), Nsutite-PVP appears spherical, approximately 5 micrometers in diameter, with numerous nanorod-like structures distributed on its surface. Further magnification reveals these to be nanorods, which self-assemble to form a large sphere. Figure 2 (b) In the high-magnification SEM, the nanorod-like structures were found to be approximately 100 nm wide and 800 nm long. The neat and clean morphology is attributed to the fact that PVP, as a surfactant, helps the product to form good morphological characteristics.

[0047] Figure 3SEM images of Mn(O,OH)2 prepared in Example 2 are shown, where a: low magnification, b: back view of the hexagonal flower, c: front view of the hexagonal flower, and d: side view of the hexagonal disk close-packed structure. From image 3(a), the low magnification shows that Nsutite-NO has a hexagonal disk-like structure with a central hexagonal part from which nanorods grow in six directions. The entire disk is approximately 6 micrometers wide. From image 3(b), the back view of the hexagonal flower shows that the nanorods extend uniformly from the center, and the layers are tightly stacked. From image 3(c), the front view of the hexagonal flower shows that the hexagonal disk grows nanorods along the six corners of the hexagonal flower, and the layers are also tightly stacked. From image 3(d), the side view of the hexagonal disk close-packed structure shows that the length of each side is approximately 500 nm, and the thickness of each hexagonal layer is approximately 25 nm.

[0048] The hexagonal manganese ore Mn(O,OH)2 prepared in Examples 1 and 2 were assembled into batteries for battery performance experiments. The assembly process was conducted indoors, and the steps were as follows: first, the positive electrode shell was placed, then a titanium foil coated with hexagonal manganese ore Mn(O,OH)2 was placed in the center as the positive electrode, followed by a Whatman separator, and then 150 μL of electrolyte (2M ZnSO4 + 0.1M MnSO4 + 0.01M L-serine) was added. Next, a polished zinc sheet was placed, followed by a gasket and a spring, and finally the negative electrode shell was placed, and the battery was sealed using a sealing machine. It was important to ensure that the zinc sheet, gasket, and spring did not touch the inner wall of the positive electrode shell during placement after the electrolyte was added. Performance testing was then conducted after standing at room temperature for 8 hours.

[0049] Figure 4 For 0.4mV s -1 CV diagrams of the two hexagonal manganese ore Mn(O,OH)2 prepared in Examples 1 and 2, where a: Nsutite-PVP, b: Nsutite-NO, c: the first CV diagram of Nsutite-PVP and Nsutite-NO. From Figure 4 (a) found that Nsutite-PVP at 0.4 mV s -1 At the specified scan rate, the CV curves from the first to the fifth scan essentially overlapped, demonstrating excellent reversibility. The oxidation peaks appearing around 1.80 and 1.70 V correspond to Zn, respectively. 2+ and H + The extraction process, with reduction peaks appearing around 1.19 and 1.35V, corresponds to the Zn extraction. 2+ and H + The embedding process. From Figure 4 (b) It was found that Nsutite-NO, at a scan rate of 0.4 mV s⁻¹, showed almost identical CV values ​​for the first 5 cycles, demonstrating good reversibility. The oxidation peaks appearing at 1.80 and 1.70 V corresponded to Zn. 2+ and H+ The extraction process; the reduction peaks appearing at 1.19 and 1.35 V correspond to Zn, respectively. 2+ and H + The embedding process. From Figure 4 (c) shows that the peak area of ​​the Nsutite-NO sample is higher than that of the Nsutite-PVP sample, indicating that Nsutite-NO has a higher specific capacity and corresponding to better zinc storage performance. The elution positions of the redox peaks of both samples remain unchanged, indicating that the surfactant PVP does not affect the redox peak positions of the materials, and no significant deviation occurs on the charge-discharge platform.

[0050] Figure 5 The graph shows the rate performance of the two hexagonal manganese ore Mn(O,OH)2 prepared in Examples 1 and 2. As can be seen from the graph, at 0.3, 0.5, 0.8, 1.0, and 2.0 Å g... -1 At current densities of 760, 580, 400, 260, and 120 mAh g⁻¹, Nsutite-NO exhibited values ​​of 760, 580, 400, 260, and 120 mAh g⁻¹. -1 The discharge specific capacity of Nsutite-PVP was 580, 350, 240, 200, and 90 mAh g. -1 Both samples exhibited high discharge specific capacities, and their coulombic efficiencies remained around 99%. Furthermore, the rate performance of the Nsutite-NO electrode material was superior to that of Nsutite-PVP, indicating that the morphological advantages resulting from the dense hexagonal disc structure manifested as better performance at different rates.

[0051] Figure 6 The two hexagonal manganese ore Mn(O,OH)2 prepared in Examples 1 and 2 were subjected to 2Ag -1 Long-cycle performance at current density. The graph shows that after several activation cycles, the discharge specific capacities of Nsutite-NO and Nsutite-PVP remained at 150 and 110 mAh g, respectively. -1 The coulombic efficiency remains around 99%. Among them, Nsutite-NO exhibits superior long-cycle performance.

[0052] Figure 7 The figures show the EIS performance of the two hexagonal manganese ore Mn(O,OH)2 prepared in Examples 1 and 2. As can be seen from the figures, Nsutite-NO exhibits a smaller semicircle diameter and a lower Rct resistance, indicating superior performance. Both belong to the Warburg impedance type; equivalent circuit diagrams are shown in the inner figures.

[0053] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the invention. Those skilled in the art will understand that implementing all or part of the above-described embodiments and making equivalent changes in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A method for preparing hexagonal manganese ore Mn(O,OH)2, characterized in that: The steps include the following: (1) Add 0.01g PVP to 20mL of water and stir until dissolved. Then add 1mmol of manganese chloride and stir until dissolved. Finally add 1.5mmol of sodium chlorate and stir for 10min to obtain a mixed solution. (2) The mixed solution was placed in a polytetrafluoroethylene reactor and hydrothermally reacted at 140°C for 12 hours. The product was centrifuged three times with deionized water, and the transparent filtrate was discarded to obtain a black solid product. The black solid product was placed in an oven at 70°C and dried for 8 hours. The sample was then ground and collected to obtain hexagonal manganese ore Mn(O,OH)2. The hexagonal manganese ore Mn(O,OH)2 is spherical with a diameter of about 5 micrometers and many nanorod-shaped substances are distributed on the surface of the sphere. These nanorods self-assemble to eventually form a large sphere. The width of the nanorod structure is about 100 nm and the length is about 800 nm.

2. A method for preparing hexagonal manganese ore Mn(O,OH)2, characterized in that: The steps include the following: (1) Add 1 mmol of manganese chloride to 20 mL of water and stir until dissolved. Then add 1.5 mmol of sodium chlorate and stir for 10 min to obtain a mixed solution. (2) The mixed solution was placed in a polytetrafluoroethylene reactor and hydrothermally reacted at 140°C for 12 hours. The product was centrifuged three times with deionized water, and the transparent filtrate was discarded to obtain a black solid product. The black solid product was placed in an oven at 70°C and dried for 8 hours. The sample was then ground and collected to obtain hexagonal manganese ore Mn(O,OH)2. The hexagonal manganese ore Mn(O,OH)2 has a hexagonal flower disc structure with a regular hexagonal center. Nanorods grow in six directions. The width of the entire flower disc is about 6 micrometers. The nanorods extend uniformly from the center and are tightly stacked between layers. The length of each side is about 500 nm, and the thickness of each hexagonal layer is about 25 nm.

3. An application of hexagonal manganese ore Mn(O,OH)2 as described in claim 1 or 2, characterized in that: The hexagonal manganese ore Mn(O,OH)2 is used as the positive electrode material for zinc-ion batteries.

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