Preparation and application of manganese-based positive electrode material based on in-situ introduction of oxygen defects by electrochemistry

Abstract

The application discloses a kind of preparation of manganese-based positive electrode material based on electrochemical in-situ introduction of oxygen defects.The preparation method is as follows: (1) the mixed solution of ethanol and ethylene glycol is added to potassium permanganate solution, stirred at 45 DEG C, centrifugal washing, and freeze-drying to obtain amorphous MnO2;(2) concentrated hydrochloric acid is added to potassium permanganate solution, then the powder in step (1) is added to the above mixed solution, hydrothermal reaction is carried out at 60~80 DEG C, after reaction, centrifugal washing and drying, amorphous MnO2 combined with layered δ-MnO2 powder is obtained;(3) the powder obtained in step (2), ketchen black and polyvinylidene fluoride are made into uniform slurry in the ratio of 7:2:1, then coated on stainless steel mesh, after drying, constant current charge-discharge cycle is carried out for one circle, to obtain manganese-based positive electrode material with electrochemical in-situ introduction of oxygen defects.The manganese-based positive electrode material prepared by the application can alleviate the Mn 2+ dissolution problem of manganese-based positive electrode material, so that the prepared aqueous zinc ion battery has excellent battery cycle performance.

Description

Technical Field

[0001] This invention belongs to the field of aqueous zinc-ion battery manufacturing technology, specifically relating to the preparation and application of a manganese-based cathode material based on the in-situ introduction of oxygen defects through electrochemical processes. Background Technology

[0002] With the current population growth and rapid industrial development, human society's demand for energy is increasing, leading to the continuous depletion of non-renewable resources and environmental degradation. Therefore, finding sustainable and environmentally friendly energy sources is urgent, and recyclable secondary batteries hold significant appeal for alleviating the energy crisis and environmental problems.

[0003] Currently, lithium-ion batteries dominate the market for portable electronic energy storage and power systems. However, limited lithium resources, high costs, and electrolyte safety have raised widespread concerns. Aqueous zinc-ion batteries (ZIBs) show promise as large-scale energy storage devices due to the relatively low electrochemical reduction potential (-0.763 V compared to a standard hydrogen electrode), high theoretical capacity (820 mAh / g), high natural abundance, and low toxicity of zinc metal anodes. The performance of the cathode material is crucial for achieving high performance in aqueous ZIBs. Manganese-based cathode materials, with their high operating voltage (1.3-1.4 V), high theoretical capacity (approximately 308 mAh / g based on a single-electron transfer reaction), and highly tunable polymorphic structure, are considered a more promising cathode material for practical applications in aqueous ZIBs.

[0004] However, in electrochemical reactions, manganese-based cathode materials contain Mn 2+ The dissolution and irreversible phase transition of manganese-based cathode materials severely restrict the long-cycle stability of batteries. Currently, researchers have proposed many solutions to address the structural instability of manganese-based cathode materials and have achieved some results. Introducing oxygen vacancies to enhance the structural stability and electrochemical activity of manganese-based cathode materials is an effective strategy. For example, patent CN110120525B mixes potassium permanganate with manganese acetate or manganese acetate tetrahydrate, then filters and dries the product to obtain manganese dioxide. The dried manganese dioxide is then treated with plasma to obtain oxygen-vacancy-rich manganese dioxide. This method uses plasma treatment to introduce oxygen vacancies, which is complex and costly. Patent CN115332511A calcines a mixture of sulfur powder and lithium-rich manganese-based cathode material in an inert gas atmosphere, depositing sulfur on the surface while simultaneously inducing in-situ formation of spinel and oxygen-vacancy surfaces. This method requires high-temperature calcination, making the preparation process energy-intensive and time-consuming.

[0005] Introducing oxygen defects in situ via electrochemical methods is simple and does not require complex preparation processes such as high-temperature treatment. It effectively improves the structural stability of cathode materials and therefore has great application prospects. Summary of the Invention

[0006] To address the issue of Mn content in manganese-based cathode materials during electrochemical cycling in aqueous zinc-ion batteries... 2+ To address the performance degradation caused by dissolution and irreversible phase transitions, this invention aims to provide a method for preparing and applying a manganese-based cathode material based on in-situ electrochemical introduction of oxygen vacancies. The oxygen vacancies introduced into this manganese-based cathode material effectively mitigate structural damage and capacity decay during battery cycling and enhance the material's electrochemical activity.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A manganese-based cathode material based on the in-situ introduction of oxygen defects through electrochemical methods is introduced in situ after one cycle of constant current charge-discharge.

[0009] This invention also provides a method for preparing the manganese-based cathode material based on the electrochemical in-situ introduction of oxygen vacancies, comprising the following steps:

[0010] (1) Add the homogeneous mixture of ethanol and ethylene glycol to the potassium permanganate solution at a certain rate, stir at 45 °C for 20-30 min until the reaction ends, centrifuge and wash, and freeze dry to obtain dark brown amorphous MnO2 powder.

[0011] (2) Add concentrated hydrochloric acid to potassium permanganate solution, and then add a certain mass of the powder obtained in step (1) to the above mixed solution. The mixture is then subjected to hydrothermal reaction at 60~80 °C for 12~15 h. After the reaction is complete, the mixture is centrifuged, washed and dried to obtain a black powder of amorphous MnO2 with layered δ-MnO2 on the surface.

[0012] (3) The powder obtained in step (2), Ketjen black and polyvinylidene fluoride are mixed in a ratio of 7:2:1 and an appropriate amount of 1-methyl-2-pyrrolidone is added to make a uniform slurry. Then, it is coated on a stainless steel mesh with a thickness of 100 μm. After drying, it is charged and discharged under constant current for one cycle to obtain a manganese-based cathode material with oxygen defects introduced in situ by electrochemical methods.

[0013] According to the above-mentioned preparation method of manganese-based cathode material based on the in-situ introduction of oxygen defects by electrochemical methods, preferably, in step (1), the volume fraction ratio of ethanol and ethylene glycol is 1:1 to 1:3.

[0014] According to the above-mentioned method for preparing manganese-based cathode materials based on the in-situ introduction of oxygen defects by electrochemical methods, preferably, in step (1), the dropping rate of the mixed solution of ethanol and ethylene glycol is 0.5~2 ml / min.

[0015] According to the above-mentioned method for preparing manganese-based cathode materials based on the in-situ introduction of oxygen defects by electrochemical methods, preferably, in step (1), the concentration of potassium permanganate solution is 0.01~0.05 mol / L.

[0016] According to the above-mentioned method for preparing manganese-based cathode materials based on the in-situ introduction of oxygen defects by electrochemical methods, preferably, in step (1), the powder prepared is amorphous manganese dioxide.

[0017] According to the above-mentioned method for preparing manganese-based cathode material based on the in-situ introduction of oxygen defects by electrochemical methods, preferably, in step (2), the volume ratio of concentrated hydrochloric acid to potassium permanganate solution is 1:40~1:60.

[0018] According to the above-mentioned method for preparing manganese-based cathode materials based on the in-situ introduction of oxygen defects by electrochemical methods, preferably, in step (2), the concentration of potassium permanganate solution is 0.002~0.008 mol / L.

[0019] According to the above-mentioned preparation method of manganese-based cathode material based on the in-situ introduction of oxygen defects by electrochemical methods, preferably, in step (2), the addition ratio of the powder obtained in step (1) is 1.5~2 g / L.

[0020] According to the above-mentioned method for preparing manganese-based cathode material based on in-situ electrochemical introduction of oxygen defects, preferably, in step (3), the current density used for electrochemical cycling is 0.1~0.5 A / g, and the voltage range for charging and discharging is 0.8~1.8 V.

[0021] This invention first prepares amorphous MnO2 by a simple redox reaction of potassium permanganate with a mixed solution of ethanol and ethylene glycol under constant temperature stirring conditions. Then, using the amorphous MnO2 as a core, a layered δ-MnO2 thin layer is uniformly grown on the amorphous MnO2 core through a hydrothermal reaction. The obtained material then introduces oxygen defects in situ through electrochemical means. Due to the introduction of oxygen defects and the lattice mismatch at the interface, the structural stability of the final manganese-based cathode material is greatly enhanced, thus achieving excellent electrochemical performance when used as a cathode material for aqueous zinc-ion batteries.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] (1) This invention is based on manganese-based cathode materials with in-situ electrochemical oxygen defects. By introducing stable oxygen defects into the material, the severe Mn content during battery cycling is effectively alleviated. 2+ and capacity decay.

[0024] (2) The present invention utilizes a simple low-temperature water bath oxidation-reduction and hydrothermal method to obtain high-performance manganese-based cathode materials. The preparation process is simple and the conditions are mild.

[0025] (3) The electrochemical in-situ introduction of oxygen defects used in this invention is simpler, more efficient and lower in cost than other oxygen defect introduction methods.

[0026] For example, the δA-MnO2 of the present invention at 0.1 A g -1 256 mAh g was obtained at the current density -1 It exhibits high specific capacity and good cycling stability at 0.5 A g. -1 After 100 cycles at low current density, the capacity retention is almost 100%, even at 1 A g. -1 After 500 cycles at a current density, the capacity retention rate is still 92%. Attached Figure Description

[0027] Figure 1 (a) SEM image of the sample prepared in Comparative Example 1, (b) SEM image of the sample prepared in Comparative Example 2, (c) SEM image of the sample prepared in Example 1.

[0028] Figure 2 The XRD patterns of the samples prepared in Comparative Example 1, Comparative Example 2 and Example 1 are compared.

[0029] Figure 3 (a) is a comparison of the high-resolution O 1s spectra of δA-MnO2 after one electrochemical cycle in Example 1; (b) is a comparison of the spin resonance (EPR) spectra of δA-MnO2 after one electrochemical cycle in Example 1; (c) is the high-resolution O 1s spectra of the sample with in-situ oxygen vacancies introduced by electrochemical methods in Example 1 during subsequent cycles; and (d) is the content of Mn in the electrolyte of the samples with in-situ oxygen vacancies introduced by δA-MnO2 in Comparative Example 1, Comparative Example 2, and Example 1 after different numbers of cycles.

[0030] Figure 4 The samples prepared in Comparative Example 1, Comparative Example 2, and Example 1 were measured at 0.1 mV s. -1 Comparison of CV curves at different scan rates.

[0031] Figure 5 This is the constant current charge-discharge curve of the sample prepared in Example 1.

[0032] Figure 6 The samples prepared in Comparative Example 1, Comparative Example 2 and Example 1 were measured at 1 A g. -1 Comparison of long-cycle performance at current densities.

[0033] Figure 7 The sample obtained in Example 2 was in 1 A g -1 Long-cycle performance at current density.

[0034] Figure 8 The sample obtained in Example 3 was in 1 A g -1 Long-cycle performance at current density. Detailed Implementation

[0035] The following embodiments further illustrate the content of the present invention; however, the scope of protection of the claims of the present invention is not limited by the embodiments.

[0036] Example 1

[0037] (1) Add 5 ml of ethanol and 5 ml of ethylene glycol into 100 ml of 0.01 mol / L potassium permanganate solution at a rate of 1 ml / min. After stirring at 45 °C for 30 min, the reaction is completed. After centrifugation and washing, the product is freeze-dried to obtain dark brown amorphous MnO2 powder.

[0038] (2) Add 1 ml of concentrated hydrochloric acid to 60 ml of 0.003 mol / L potassium permanganate solution, and then add 0.1 g of the powder obtained in step (1) to the above mixed solution. The mixture is hydrothermally reacted at 60 °C for 12 h. After the reaction is complete, the mixture is centrifuged, washed and dried to obtain a black powder with layered δ-MnO2 on the surface of amorphous MnO2, which is denoted as δA-MnO2.

[0039] (3) The powder obtained in step (2), Ketjen black, and polyvinylidene fluoride were mixed in a ratio of 7:2:1, and an appropriate amount of 1-methyl-2-pyrrolidone was added to prepare a uniform slurry. This slurry was then coated onto a 100 μm thick stainless steel mesh and dried. After drying, it was then coated with 0.1 Ag... -1 A manganese-based cathode material with in-situ electrochemical oxygen vacancies was obtained by one cycle of constant current charge-discharge at current density.

[0040] Example 2

[0041] (1) Add 5 ml of ethanol and 5 ml of ethylene glycol into 100 ml of 0.01 mol / L potassium permanganate solution at a rate of 1 ml / min. After stirring at 45 °C for 30 min, the reaction is completed. After centrifugation and washing, the product is freeze-dried to obtain dark brown amorphous MnO2 powder.

[0042] (2) Add 1 ml of concentrated hydrochloric acid to 60 ml of 0.006 mol / L potassium permanganate solution, and then add 0.1 g of the powder obtained in step (1) to the above mixed solution. The mixture is hydrothermally reacted at 60 °C for 12 h. After the reaction is complete, the mixture is centrifuged, washed and dried to obtain a black powder with layered δ-MnO2 on the surface of amorphous MnO2, which is denoted as δA-MnO2-2.

[0043] (3) The powder obtained in step (2), Ketjen black, and polyvinylidene fluoride were mixed in a ratio of 7:2:1, and an appropriate amount of 1-methyl-2-pyrrolidone was added to prepare a uniform slurry. This slurry was then coated onto a 100 μm thick stainless steel mesh and dried. After drying, it was then coated with 0.1 Ag... -1 A manganese-based cathode material with in-situ electrochemical oxygen vacancies was obtained by one cycle of constant current charge-discharge at current density.

[0044] Example 3

[0045] (1) Add 5 ml of ethanol and 5 ml of ethylene glycol into 100 ml of 0.02 mol / L potassium permanganate solution at a rate of 1 ml / min. After stirring at 45 °C for 30 min, the reaction is completed. After centrifugation and washing, the product is freeze-dried to obtain dark brown amorphous MnO2 powder.

[0046] (2) Add 1 ml of concentrated hydrochloric acid to 60 ml of 0.006 mol / L potassium permanganate solution, and then add 0.1 g of the powder obtained in step (1) to the above mixed solution. The mixture is hydrothermally reacted at 60 °C for 12 h. After the reaction is complete, the mixture is centrifuged, washed and dried to obtain a black powder with layered δ-MnO2 on the surface of amorphous MnO2, which is denoted as δA-MnO2-3.

[0047] (3) The powder obtained in step (2), Ketjen black, and polyvinylidene fluoride were mixed in a ratio of 7:2:1, and an appropriate amount of 1-methyl-2-pyrrolidone was added to prepare a uniform slurry. This slurry was then coated onto a 100 μm thick stainless steel mesh and dried. After drying, it was then coated with a 0.5 Ag... -1 A manganese-based cathode material with in-situ electrochemical oxygen vacancies was obtained by one cycle of constant current charge-discharge at current density.

[0048] Comparative Example 1

[0049] 1 ml of concentrated hydrochloric acid was added to 60 ml of 0.006 mol / L potassium permanganate solution. The mixture was then subjected to hydrothermal reaction at 60 °C for 12 h. After the reaction was completed, the mixture was centrifuged, washed and dried to obtain dark brown layered δ-MnO2 powder, denoted as δ-MnO2.

[0050] Comparative Example 2

[0051] A homogeneous mixture of 5 ml ethanol and 5 ml ethylene glycol was added to 100 ml of 0.02 mol / L potassium permanganate solution at a rate of 1 ml / min. The mixture was stirred at 45 °C for 30 min until the reaction was complete. The mixture was then centrifuged, washed, and freeze-dried to obtain a dark brown amorphous MnO2 powder, denoted as Amorphous-MnO2.

[0052] Sample structure characterization and battery performance testing

[0053] Figure 1 (a), (b) and (c) are SEM images of the samples prepared by Comparative Example 1, Comparative Example 2 and Example 1, respectively. It can be seen from the images that the morphologies of Comparative Example 1 and Comparative Example 2 are spherical and smooth irregular blocks, respectively, while Example 1 is an irregular block with uniformly loaded plate-like crystals, indicating that the amorphous MnO2 surface is successfully coated with layered δ-MnO2.

[0054] Figure 2 The sample structure of Comparative Example 1 is layered δ-MnO2 (JCPDS 42-1317), the crystallinity of the sample of Comparative Example 2 is very poor, while the diffraction peaks of the sample structure prepared in Example 1 are similar to those of layered δ-MnO2.

[0055] Figure 3 (a) A comparison of the high-resolution O 1s spectra of δA-MnO2 after one electrochemical cycle in Example 1 shows that a large number of oxygen defects were introduced after electrochemical cycling. (b) A comparison of the spin resonance (EPR) spectra of δA-MnO2 after one electrochemical cycle in Example 1 further illustrates that oxygen defects were successfully introduced in situ via electrochemical methods. (c) The high-resolution O 1s spectra of the sample with in situ oxygen defects introduced in Example 1 demonstrates that the oxygen defects introduced in situ via electrochemical methods can exist stably in subsequent cycles. (d) The changes in the Mn content in the electrolyte of the samples with in situ oxygen defects introduced in Comparative Examples 1, 2 and Example 1 after different number of cycles show that the in situ introduction of oxygen defects via electrochemical methods successfully suppressed the dissolution of Mn during battery cycling.

[0056] Figure 4 The samples prepared in Comparative Example 1, Comparative Example 2, and Example 1 were measured at 0.1 mV s. -1 Comparison of CV curves at different scanning rates revealed that the CV area of ​​the sample prepared in Example 1 was significantly larger than that of the control sample, indicating that it had higher electrochemical activity.

[0057] Figure 5 The constant current charge-discharge curve of the sample prepared in Example 1 is shown at 0.1 A g. -1 256 mAh g was obtained at the current density -1 High specific capacity, even at 2 A g -1 It can maintain 161 mAh g even at current density -1 Specific capacity.

[0058] Figure 6 The samples prepared in Comparative Examples 1, 2 and 1 were measured at 1 A g. -1The comparison of long-term cycling performance under current density showed that the sample prepared in Example 1 still had a capacity retention rate of 92% after 500 cycles, while the capacity retention rates of the control sample 1 and the control sample 2 were only 13% and 80%, respectively.

[0059] Figure 7 The sample obtained in Example 2 was in 1 A g -1 After 450 cycles at current density, there is still 101 mAh g. -1 Specific capacity.

[0060] Figure 8 The sample obtained in Example 3 was in 1 A g -1 After 400 cycles at current density, it still has 123 mAh g. -1 Specific capacity.

[0061] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for producing a manganese-based positive electrode material based on in-situ introduction of oxygen defects by electrochemistry, characterized by, The oxygen defects of the manganese-based positive electrode material are introduced in-situ after one cycle of constant current charge-discharge cycle, without high-temperature post-treatment, the manganese-based positive electrode material grows thin layers of layered δ-MnO2 on the amorphous MnO2 core through a hydrothermal reaction, the current density used in the cycle is 0.1-0.5 A / g, and the voltage range of the charge-discharge is 0.8-1.8 V.

2. The method for preparing a manganese-based positive electrode material based on in-situ introduction of oxygen defects according to claim 1, characterized in that, The method comprises the following steps: (1) a uniform mixed solution of ethanol and ethylene glycol is added to a potassium permanganate solution at a certain rate, the reaction is ended after stirring at 45 ℃ for 20-30 min, centrifugal washing is performed, and freeze-drying is performed to obtain a dark brown amorphous MnO2 powder; (2) concentrated hydrochloric acid is added to the potassium permanganate solution, then a certain mass of the powder obtained in step (1) is added to the mixed solution, a hydrothermal reaction is performed at 60-80 ℃ for 12-15 h, centrifugal washing is performed after the reaction is completed, and drying is performed to obtain a black powder of amorphous MnO2 with a surface combined layered δ-MnO2; (3) the powder obtained in step (2), Ketjen black and polyvinylidene fluoride are mixed at a ratio of 7:2:1, and an appropriate amount of 1-methyl-2-pyrrolidone is added to prepare a uniform slurry, then the slurry is coated on a stainless steel mesh with a thickness of 100 μm, after drying, one cycle of constant current charge-discharge cycle is performed to obtain a manganese-based positive electrode material with electrochemical in-situ introduced oxygen defects.

3. The method according to claim 2, wherein the manganese-based positive electrode material is prepared by in-situ introduction of oxygen defects based on electrochemistry. In step (1), the volume fraction ratio of ethanol and ethylene glycol is 1:1-1:

3.

4. The method according to claim 3, wherein the manganese-based positive electrode material is prepared by in-situ introducing oxygen defects based on electrochemistry. In step (1), the dropwise adding rate of the mixed solution of ethanol and ethylene glycol is 0.5-2 ml / min.

5. The method of claim 4, wherein the manganese-based positive electrode material is prepared by in-situ introduction of oxygen defects based on electrochemistry. In step (1), the concentration of the potassium permanganate solution is 0.01-0.05 mol / L.

6. The method of claim 5, wherein the manganese-based positive electrode material is prepared by in-situ introduction of oxygen defects based on electrochemistry. In step (1), the prepared powder is amorphous manganese dioxide.

7. The method according to claim 6, wherein the manganese-based positive electrode material is prepared by in-situ introduction of oxygen defects based on electrochemistry. In step (2), the volume ratio of concentrated hydrochloric acid to the potassium permanganate solution is 1:40-1:

60.

8. The method of claim 7, wherein the manganese-based positive electrode material is prepared by in-situ introduction of oxygen defects based on electrochemistry. In step (2), the concentration of the potassium permanganate solution is 0.002-0.008 mol / L.

9. The method of claim 8, wherein the manganese-based positive electrode material is prepared by in-situ introduction of oxygen defects based on electrochemistry. In step (2), the adding ratio of the powder obtained in step (1) is 1.5-2 g / L.

Images