TMEDA-modified MnO2 cathode materials, their preparation methods and applications

Abstract

This invention belongs to the field of zinc-ion battery technology, specifically relating to a TMEDA-modified MnO2 cathode material, its preparation method, and its application. The method includes the following steps: Under magnetic stirring, divalent and heptavalent manganese sources are dissolved in deionized water to form a purple solution; the pH of the purple solution is adjusted with dilute acid, and the solution is made homogeneous by magnetic stirring; TMEDA is added to the solution and fully dissolved to obtain a mixed solution; the mixed solution undergoes a hydrothermal reaction to obtain a primary product; the primary product undergoes post-reaction processing to obtain the cathode material. Compared with existing technologies, this invention solves the problems of low intrinsic electronic conductivity, slow interlayer migration rate of zinc ions, and easy phase transformation and structural collapse during charge and discharge, leading to poor rate performance and rapid capacity decay during cycling, inherent in layered manganese dioxide. This method prepares a MnO2 cathode material with excellent cycle stability and high specific capacity.

Description

Technical Field

[0001] This invention belongs to the field of zinc-ion battery technology, specifically relating to a TMEDA-modified MnO2 cathode material, its preparation method, and its application. Background Technology

[0002] In recent years, clean energy sources such as wind, solar, and tidal power have developed rapidly. However, these energy sources are discontinuous and fluctuating in their spatial and temporal distribution, requiring large-scale energy storage systems for stable output and smooth regulation. Therefore, the construction of efficient energy storage facilities is increasingly urgent. Among various energy storage technologies, secondary metal-ion batteries are considered an important development direction for large-scale energy storage due to their advantages such as high energy density, stable operation, and low maintenance costs.

[0003] Compared to lithium-ion batteries, aqueous zinc-ion batteries benefit from abundant zinc resources, low raw material costs, the inherent high safety of non-flammable aqueous electrolytes, and the high theoretical specific capacity of zinc metal (820 mAh·g). -1 Zinc ions, with their characteristics such as high capacity and charge density, exhibit significant advantages in large-scale energy storage applications. Despite the large radius and high charge density of divalent zinc ions (and hydrated zinc ions), which can easily cause lattice distortion and structural collapse in cathode materials during insertion / extraction, and the challenges of dendrite growth and hydrogen evolution side reactions in zinc anodes, aqueous zinc-ion battery technology continues to advance. While significant progress has been made in the modification and protection of zinc anodes in zinc-ion battery material systems, the performance of cathode materials remains a key factor limiting overall energy density, rate performance, and cycle life. Current mainstream research directions include manganese-based oxides, vanadium-based oxides, and Prussian blue compounds; however, cathode materials that combine high capacity, long cycle life, low cost, and environmental friendliness are still very limited.

[0004] Among manganese-based cathode materials, layered manganese dioxide (MnO2) is considered a promising candidate material due to its abundant reserves, low cost, moderate operating voltage, and high theoretical capacity. In particular, its open layered structure provides a natural channel for zinc ion insertion / extraction, providing a good foundation for electrochemical lithium / zinc intercalation applications. However, layered manganese dioxide exhibits low intrinsic electronic conductivity, slow interlayer migration rate of zinc ions, and is prone to phase transformation and structural collapse during charge and discharge, resulting in poor rate performance and rapid capacity decay during cycling.

[0005] In the prior art, CN114516660A discloses a method for preparing a CTAB-induced δMnO2 nanoflower supercapacitor cathode material, its product, and its application. The preparation method includes the following steps: dissolving CTAB and potassium permanganate in water to obtain a reaction solution; transferring the reaction solution to a reaction vessel for hydrothermal reaction; naturally cooling to room temperature after the reaction; removing the solid precipitate from the reaction vessel; and successively washing and drying to obtain the target product. CN114516660A also discloses a molybdenum-doped manganese dioxide monolayer, its preparation and uses, and a zinc-ion battery containing it. 6+ Mo is doped in the form of single atoms on the MnO2 layers. 6+ The molybdenum element occupies the position of Mn in the [MnO6] octahedron on the plate; the manganese dioxide doped in the molybdenum element single-atom plate is a nanoflower-like structure with vertical cross-linking of nanosheets. However, these technologies do not fundamentally solve the problem of poor structural stability in MnO2 caused by the Jahn-Teller effect.

[0006] Therefore, it is necessary to develop a method to improve the properties of layered manganese dioxide so that it can be fully utilized in manganese-based cathode materials. Summary of the Invention

[0007] The purpose of this invention is to address at least one of the aforementioned problems by providing a TMEDA-modified MnO2 cathode material, its preparation method, and its applications. This addresses the issues in existing technologies where layered manganese dioxide exhibits low intrinsic electronic conductivity, slow zinc ion interlayer migration rate, and is prone to phase transformation and structural collapse during charge and discharge, leading to poor rate performance and rapid capacity decay during cycling. This solution improves the conductivity, ion diffusion capacity, and structural stability of layered manganese dioxide through strategies such as organic interlayer regulation and electronic structure optimization, resulting in a MnO2 cathode material with excellent cycle stability and high specific capacity.

[0008] The objective of this invention is achieved through the following technical solution: The first aspect of this invention discloses a method for preparing a TMEDA-modified MnO2 cathode material, comprising the following steps: (1) Under magnetic stirring, divalent manganese source and heptavalent manganese source were added to deionized water to dissolve and form a purple solution; (2) Adjust the pH of the purple solution obtained in step (1) with dilute acid and make the solution uniform by magnetic stirring; (3) Add TMEDA to the solution obtained by magnetic stirring in step (2) and dissolve it completely to obtain a mixed solution; (4) The mixed solution obtained in step (3) is subjected to a hydrothermal reaction to obtain the initial product; (5) The initial product obtained in step (4) is subjected to post-reaction processing to obtain the cathode material TMEDA-MnO2.

[0009] Preferred, including: The divalent manganese source is manganese sulfate; The heptavalent manganese source is potassium permanganate; The molar ratio of heptavalent manganese source, divalent manganese source and TMEDA is 6:1:0.35-0.5.

[0010] Preferably, in step (2), The dilute acid is dilute sulfuric acid or dilute hydrochloric acid; The pH of the purple solution was adjusted to 4-5 using dilute acid. After adjusting the pH, the magnetic stirring time is 30-60 minutes.

[0011] Preferably, in step (4), The temperature of the hydrothermal reaction is 120-180 ℃; The hydrothermal reaction takes 12-24 hours.

[0012] Preferably, in step (5), The post-reaction processing includes centrifugation, washing, and drying.

[0013] Preferred, including: The centrifugal separation speed is 8000 r / min; The washing process involves alternating between deionized water and ethanol for 3-5 cycles.

[0014] The second aspect of the present invention discloses a TMEDA-modified MnO2 cathode material, which is prepared by the preparation method described in any of the preceding claims.

[0015] Preferably, the positive electrode material TMEDA-MnO2 is: Nanoflowers composed of nanosheets.

[0016] Preferably, the particle size of the nanoflowers is: 100-1000 nm.

[0017] The third aspect of the present invention discloses the application of a TMEDA-modified MnO2 cathode material as described in any of the preceding claims in a zinc-ion battery.

[0018] The working principle of this invention is as follows: This invention utilizes a hydrothermal method to introduce TMEDA into MnO2 cathode material and modify its coordination. By introducing TMEDA into the MnO2 interlayer and constructing Mn-N coordination, the Jahn-Teller effect-induced distortion of the [MnO6] octahedron is effectively mitigated, thereby achieving a zinc-ion battery at 3 A·g -1 Stable cycling at current density. The electrochemical performance of the MnO2 cathode material is improved by stabilizing the layered structure through TMEDA and Mn coordination.

[0019] Compared with the prior art, the present invention has the following beneficial effects: (1) The TMEDA-modified coordinated MnO2 cathode material prepared according to the method of the present invention has excellent electrochemical performance by introducing TMEDA into MnO2. Since TMEDA has strong coordination and electron-donating ability, it can affect the electronic structure and stability of the material and enhance the kinetic performance of the material.

[0020] (2) The preparation method of the present invention has the advantages of good repeatability, simple operation, environmental friendliness and low cost, and has industrial application prospects.

[0021] (3) The cathode material of the present invention has good electrochemical performance, 0.2 A·g -1 It can release nearly 375 mAh·g at current density -1 It has a high specific capacity and high cycling stability (3 A·g). -1 The capacity retention rate is 84.86% after 1000 cycles at current density. Attached Figure Description

[0022] Figure 1 This is the X-ray diffraction (XRD) pattern of the pure MnO2 cathode material in Comparative Example 1 of the present invention.

[0023] Figure 2 This is the X-ray diffraction pattern (XRD pattern) of the TMEDA-modified MnO2 cathode material in Example 1 of the present invention.

[0024] Figure 3 The pure MnO2 cathode material in Comparative Example 1 of this invention was used at 0.2 A·g -1 Charge-discharge curves at current density.

[0025] Figure 4 The TMEDA-modified MnO2 cathode material in Example 1 of this invention is used at 0.2 A·g -1 Charge-discharge curves at current density.

[0026] Figure 5The MnO2 cathode materials before and after the introduction of TMEDA in Example 1 and Comparative Example 1 of this invention are at 3 A·g -1 Comparison curves of charge-length cycles at current density.

[0027] Figure 6 This is a scanning electron microscope (SEM) image of the TMEDA-modified MnO2 cathode material in Example 1 of the present invention.

[0028] Figure 7 The N 1s orbital spectra of the cathode materials of Example 1 and Comparative Example 1 are shown in the X-ray photoelectron spectroscopy (XPS).

[0029] Figure 8 The images show the Raman spectra of the cathode materials of Example 1 and Comparative Example 1. Detailed Implementation

[0030] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0031] Any preparation methods, materials, structures, or composition ratios not explicitly described in this technical solution are considered common technical features disclosed in the prior art.

[0032] All raw materials used in the following examples are commercially available.

[0033] The applicant's conceptualization process / the principle of this technical solution is as follows: Layered MnO2 cathode materials typically have an interlayer spacing of approximately 0.7 nm, providing ample space to accommodate other substances (such as TMEDA), facilitating the insertion and extraction of zinc ions, and exhibiting a high theoretical capacity (308 mAh·g). -1 MnO2 possesses advantages such as [missing information - likely related to chemical properties], making it an ideal cathode material for zinc-ion batteries. However, existing MnO2 cathode materials exhibit poor electrochemical stability and are prone to manganese dissolution. To overcome these shortcomings, the applicant proposes to employ a one-step hydrothermal method to introduce TMEDA into the interlayer of MnO2 and perform coordination modification to enhance structural stability and inhibit dissolution, thus creating an excellent organic-inorganic composite material for zinc-ion battery cathodes.

[0034] Specifically, this invention provides a method for introducing TMEDA into MnO2 cathode material using a hydrothermal method and modifying and coordinating it, thereby improving the electrochemical performance of MnO2 cathode material by stabilizing the layered structure through the coordination of TMEDA and Mn.

[0035] The preparation method includes the following steps: (1) Under magnetic stirring, weigh manganese sulfate and potassium permanganate and add them to a beaker containing deionized water and stir to dissolve them to form a purple solution; (2) Adjust the pH of the purple solution from step (1) with dilute acid and stir it with a magnetic stirrer for a period of time; (3) After stirring in step (2), add a certain amount of TMEDA and dissolve it completely to obtain a mixed solution; (4) Transfer the homogeneous mixed solution formed in step (3) to a polytetrafluoroethylene-lined stainless steel reactor and place it in an oven to react, thereby obtaining the initial product; (5) After centrifugation, the product is repeatedly washed with anhydrous ethanol and deionized water. The washed product is then dried in an oven to obtain the zinc-ion battery cathode material, which is named TMEDA-MnO2.

[0036] Furthermore, in steps (1) and (3), the molar ratio of potassium permanganate, manganese sulfate, and TMEDA is 6:1:0.35-0.5.

[0037] Furthermore, in step (2), the dilute acid used to adjust the pH is dilute sulfuric acid or dilute hydrochloric acid, adjusting the pH to 4 to 5.

[0038] Further, in step (2), the purple solution is adjusted to pH and then stirred for 30 to 60 minutes.

[0039] Further, in step (4), the mixed solution is transferred to a polytetrafluoroethylene-lined stainless steel reactor and kept at 120 to 180°C for 12 to 24 hours.

[0040] Furthermore, in step (5), the centrifugation speed is 8000 r / min, and the centrifugation is performed by alternating washing with deionized water and ethanol 3 to 5 times.

[0041] Furthermore, the TMEDA-modified MnO2 cathode material is a nanoflower material composed of nanosheets.

[0042] Furthermore, the nanoflower particle size ranges from 100 to 1000 nm.

[0043] The TMEDA-modified MnO2 cathode material is applied to the field of zinc-ion batteries.

[0044] Example 1 The method for preparing TMEDA-modified MnO2 cathode material for zinc-ion batteries provided in this embodiment includes the following steps: (1) Under magnetic stirring, weigh 1 mmol of manganese sulfate and 6 mmol of potassium permanganate and add them to a beaker containing 50 mL of deionized water and stir to dissolve, forming a purple solution; (2) Adjust the pH of the purple solution from step (1) to 4 with dilute sulfuric acid and stir with a magnetic stirrer for 30 min; (3) After stirring in step (2), add 0.35 mmol TMEDA and dissolve thoroughly to obtain a mixed solution; (4) The mixed solution was transferred to an 80 mL polytetrafluoroethylene-lined stainless steel reactor and placed in an oven at 120 °C for 12 h to obtain the initial product. (5) After centrifugation at 8000 r / min, the product was washed three times with anhydrous ethanol and deionized water, and then vacuum dried at 60℃ for 12 h to obtain the organic-inorganic composite zinc-ion battery cathode material.

[0045] The cathode material prepared by the above method has a nanoflower-like morphology, which greatly increases the specific surface area. Figure 6 .

[0046] Comparative Example 1 This example provides a method for preparing the original MnO2 cathode material, which is basically the same as that in Example 1, except that TMEDA is not added after stirring for 30 min in step (3).

[0047] Figure 1 The X-ray diffraction (XRD) pattern of the original MnO2 (without TMEDA) cathode material in Comparative Example 1 shows that the characteristic peaks correspond completely to the layered manganese dioxide standard card #01-080-1098. That is, the preparation method of Comparative Example 1 yielded pure-phase MnO2 cathode material.

[0048] Figure 2 The image shows the X-ray diffraction (XRD) pattern of the TMEDA-modified MnO2 (TMEDA-MnO2) cathode material in Example 1 of this invention. As can be seen from the image, the XRD peaks of TMEDA-MnO2 are sharp, and the peak positions correspond one-to-one with the standard spectrum without any new impurity peaks, indicating that the product introduced by TMEDA has high crystallinity and is a pure substance.

[0049] Figure 3 The original MnO2 cathode material in Comparative Example 1 of this invention was subjected to a temperature of 0.2 A·g. -1 Charge-discharge curves at current density. The figure shows that at 0.2 A·g... -1 The specific capacity at current density is 250 mAh·g -1 .

[0050] Figure 4 The TMEDA-modified MnO2 cathode material in Example 1 of this invention is used at 0.2 A·g -1 Charge-discharge curves at current density. The figure shows that at 0.2 A·g... -1The specific capacity at current density is 375 mAh·g -1 It represents a significant improvement over the original MnO2.

[0051] Figure 5 In Example 1 and Comparative Example 1 of this invention, the MnO2 cathode material before / after the introduction of TMEDA was used at 3 A·g -1 Long-cycle comparison curves at current density. The specific capacity of TMEDA-MnO2 material is significantly higher than that of original MnO2, and the capacity retention rate after 1000 cycles is 84.86%, which is higher than that of original MnO2 (56.21%). This indicates that the introduction of TMEDA significantly improves the rate performance and structural stability of MnO2.

[0052] Figure 6 This is a scanning electron microscope (SEM) image of TMEDA-modified MnO2 in Example 1 of the present invention. Figure 6 As shown, the nanosheets prepared in Example 1 of this invention form a nanoflower structure of approximately 500 nm, which is more conducive to increasing the specific surface area and accelerating the Zn synthesis. 2+ The transmission.

[0053] Figure 7 The images show the N 1s orbital spectra of the MnO2 cathode materials before and after the introduction of TMEDA in Example 1 and Comparative Example 1 of this invention. The results show that the TMEDA-modified MnO2 samples exhibit characteristic peaks belonging to Mn-N and CN at 400.3 and 399.7 eV, respectively. The Mn-N signal directly demonstrates the coordination interaction between TMEDA and the Mn sites.

[0054] Figure 8 The images show the Raman spectra of the MnO2 cathode materials before and after the introduction of TMEDA in Example 1 and Comparative Example 1 of this invention. The vibrational characteristics of the Mn-O bonds were analyzed using Raman spectroscopy to examine their impact on the distortion of the [MnO6] octahedron. The spectra are located at 450 cm⁻¹. -1 and 640 cm -1 The peaks at these locations correspond to E respectively. g (Corresponding to the four Mn-O bonds) and A 1g (Corresponding to axial Mn-O bond) vibration mode. Compared to MnO2, TMEDA-MnO2 exhibits lower A... 1g / E g The ratio indicates that the vibrational modes associated with axial distortion in the [MnO6] octahedron are effectively weakened, accompanied by equatorial Mn-O bond stretching, thus demonstrating that the introduction of TMEDA helps alleviate Jahn-Teller distortion.

[0055] Example 2 The method for preparing the zinc-ion secondary battery cathode material in this embodiment includes the following steps: (1) Under magnetic stirring, weigh 1 mmol of manganese sulfate and 6 mmol of potassium permanganate and add them to a beaker containing 50 mL of deionized water and stir to dissolve, forming a purple solution; (2) Adjust the pH of the purple solution from step (1) to 4 with dilute sulfuric acid and stir with a magnetic stirrer for 30 min; (3) After stirring in step (2), add 0.5 mmol TMEDA and dissolve thoroughly to obtain a mixed solution; (4) The mixed solution was transferred to an 80 mL polytetrafluoroethylene-lined stainless steel reactor and placed in an oven at 160 °C for 24 h to obtain the initial product. (5) After centrifugation at 8000 r / min, the product was washed three times with anhydrous ethanol and deionized water, and then vacuum dried at 60℃ for 12 h to obtain the organic-inorganic composite zinc-ion battery cathode material.

[0056] Comparative Example 2 The preparation method of the zinc-ion secondary battery cathode material in this comparative example includes the following steps: (1) Under magnetic stirring, weigh 1 mmol of manganese sulfate and 6 mmol of potassium permanganate and add them to a beaker containing 50 mL of deionized water and stir to dissolve, forming a purple solution; (2) Adjust the pH of the purple solution from step (1) to 4 with dilute sulfuric acid and stir with a magnetic stirrer for 30 min; (3) After stirring in step (2), add 0.35 mmol of ethylenediamine (EDA) and dissolve thoroughly to obtain a mixed solution; (4) The mixed solution was transferred to an 80 mL polytetrafluoroethylene-lined stainless steel reactor and placed in an oven at 160 °C for 24 h to obtain the initial product. (5) After centrifugation at 8000 r / min, the product was washed three times with anhydrous ethanol and deionized water, and then vacuum dried at 60℃ for 12 h to obtain the organic-inorganic composite zinc-ion battery cathode material.

[0057] Because EDA molecules are smaller and their interaction with MnO2 is weaker than that of TMEDA, EDA is not as effective as TMEDA in improving the structural stability of MnO2.

[0058] In summary, this invention relates to the field of zinc-ion battery cathode materials for energy storage, and discloses a tetramethylethylenediamine (TMEDA) modified coordination MnO2 cathode material and its preparation method. This cathode material is synthesized via a hydrothermal method. Due to the strong coordination and electron-donating capabilities of TMEDA, its introduction into the MnO2 interlayer and coordination with Mn elements affects the electronic structure of the material and enhances its structural stability, resulting in excellent electrochemical performance of the TMEDA-modified coordination MnO2 cathode material. The cathode material (TMEDA-MnO2) prepared by this invention exhibits good electrochemical performance when applied to zinc-ion batteries; at 0.2 A·g -1 It can release nearly 375 mAh·g at current density -1 It has a high specific capacity and high cycling stability (3 A·g). -1 With a capacity retention rate of 84.86% after 1000 cycles at current density, it is one of the ideal cathode materials for zinc-ion batteries.

[0059] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a TMEDA-modified MnO2 cathode material, characterized in that, Includes the following steps: (1) Under magnetic stirring, divalent manganese source and heptavalent manganese source were added to deionized water to dissolve and form a purple solution; (2) Adjust the pH of the purple solution obtained in step (1) with dilute acid and make the solution uniform by magnetic stirring; (3) Add TMEDA to the solution obtained by magnetic stirring in step (2) and dissolve it completely to obtain a mixed solution; (4) The mixed solution obtained in step (3) is subjected to a hydrothermal reaction to obtain the initial product; (5) The initial product obtained in step (4) is subjected to post-reaction processing to obtain the cathode material TMEDA-MnO2.

2. The method for preparing a TMEDA-modified MnO2 cathode material according to claim 1, characterized in that, include: The divalent manganese source is manganese sulfate; The heptavalent manganese source is potassium permanganate; The molar ratio of heptavalent manganese source, divalent manganese source and TMEDA is 6:1:0.35-0.

5.

3. The method for preparing a TMEDA-modified MnO2 cathode material according to claim 1, characterized in that, In step (2), The dilute acid is dilute sulfuric acid or dilute hydrochloric acid; The pH of the purple solution was adjusted to 4-5 using dilute acid. After adjusting the pH, the magnetic stirring time is 30-60 minutes.

4. The method for preparing a TMEDA-modified MnO2 cathode material according to claim 1, characterized in that, In step (4), The temperature of the hydrothermal reaction is 120-180 ℃; The hydrothermal reaction takes 12-24 hours.

5. The method for preparing a TMEDA-modified MnO2 cathode material according to claim 1, characterized in that, In step (5), The post-reaction processing includes centrifugation, washing, and drying.

6. The method for preparing a TMEDA-modified MnO2 cathode material according to claim 5, characterized in that, include: The centrifugal separation speed is 8000 r / min; The washing process involves alternating between deionized water and ethanol for 3-5 cycles.

7. A TMEDA-modified MnO2 cathode material, characterized in that, It is prepared by the preparation method described in any one of claims 1-6.

8. The TMEDA-modified MnO2 cathode material according to claim 7, characterized in that, The cathode material TMEDA-MnO2 is: Nanoflowers composed of nanosheets.

9. The TMEDA-modified MnO2 cathode material according to claim 8, characterized in that, The particle size of the nanoflowers is: 100-1000 nm.

10. The application of a TMEDA-modified MnO2 cathode material as described in any one of claims 7-9 in a zinc-ion battery.

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