Preparation method of high-stability manganese oxide anode for zinc ion battery

Abstract

The application discloses a preparation method of a high-stability manganese oxide positive electrode of a zinc ion battery, and belongs to the technical field of novel battery material preparation. The method comprises the following steps: dissolving potassium permanganate and a divalent manganese salt in a mixed solution of water and N,N dimethylformamide; the obtained mixed solution is heated, stirred and refluxed; after the reaction is completed, the mixed solution is filtered and washed with water and alcohol, and drying is not needed; the mixed solution is transferred into an acidic solution, and the next step of reaction is performed under the assistance of ultrasonic waves; after the reaction is completed, the mixed solution is washed with water and alcohol, and vacuum drying is performed; and a manganese oxide material pre-embedded with hydrated protons is obtained. The manganese oxide material prepared by the method has a small molar mass / size of the pre-embedded hydrated protons, a formed interlayer hydrogen bond network and a strong O-H bond formed with a metal layer, and thus has high rate performance and excellent cycle stability, and can be popularized and applied in the field of zinc ion battery electrode materials.

Description

Technical Field

[0001] This invention belongs to the field of novel battery material preparation technology, and specifically relates to a method for preparing a highly stable manganese oxide cathode for zinc-ion batteries. Background Technology

[0002] In recent years, aqueous zinc-ion batteries have attracted much attention due to their high safety, abundant zinc resources, and low cost. Developing high-stability, high-energy-density aqueous zinc-ion battery systems is currently a research hotspot. The cathode material, as the core component, is key to limiting the overall performance of the battery; therefore, finding cathode materials with high electrochemical performance is crucial for the development of aqueous zinc-ion batteries. Among many cathode material systems, manganese oxide (MCO) is considered a promising cathode material for aqueous zinc-ion batteries due to its abundant reserves, low price, and high theoretical capacity. However, in practical applications, the high charge density and large-size zinc ions repeatedly intercalating and deintercalating in the MCO lattice cause the MCO structure to easily distort during charge and discharge. Furthermore, the Jan Taylor effect of trivalent manganese leads to manganese dissolution, limiting the further development of MCO materials in aqueous zinc-ion batteries. Therefore, preparing highly stable MCO materials is of great significance for constructing high-performance aqueous zinc-ion batteries.

[0003] Currently, there are numerous methods for preparing manganese oxide materials, resulting in materials with diverse morphologies, and they have made rapid progress as cathode materials for zinc-ion batteries. However, preparing highly stable manganese oxide cathode materials for aqueous zinc-ion batteries remains challenging. Existing research generally employs a series of methods to improve the electronic structure, conductivity, and interface of manganese oxide materials, thereby enhancing the zinc storage capacity of the manganese oxide cathode, including pre-intercalation strategies (pre-intercalation of metal ions, organic molecules, or polymer molecules), composites, the creation of manganese / oxygen vacancies, and coating techniques. Through a search of publicly available literature both domestically and internationally, we found few reports on the preparation of manganese oxide materials using pre-intercalated non-metallic ions. Summary of the Invention

[0004] To address the shortcomings of existing manganese oxide cathode materials in zinc-ion battery applications, the present invention aims to provide a method for preparing a highly stable manganese oxide cathode for zinc-ion batteries by improving the preparation technology of manganese oxide materials. This method is characterized by its simplicity, ease of operation, mild reaction conditions, and high controllability. The resulting manganese oxide cathode for zinc-ion batteries exhibits high specific capacity, rate performance, and cycle stability.

[0005] To achieve the above technical objectives, considering that protons have the lightest molar mass and the smallest ionic radius, pre-intercalated hydrated protons can not only reduce the resistance to interlayer ion migration, but also form strong OH bonds with oxygen atoms in the metal layer and hydrogen bond networks with interlayer lattice water, giving them significant advantages as a cathode material for zinc-ion batteries. Therefore, through extensive experimental research and continuous improvement, the following technical solution was finally obtained:

[0006] A method for preparing a highly stable manganese oxide cathode for zinc-ion batteries, the method comprising the following steps:

[0007] Step 1: Dissolve potassium permanganate and divalent manganese salt in a mixture of water and N,N-dimethylformamide;

[0008] Step 2: The above-obtained mixture is heated and stirred under reflux at a temperature of 65–90°C. After the reaction is complete, the reaction product is washed without drying.

[0009] Step 3: Disperse the reaction product obtained in Step 2 in H... + The reaction is carried out in an acidic solution with a concentration of 0.5–3 mol / L, and ultrasonic-assisted reaction is performed. The ultrasonic-assisted reaction can be carried out in an ultrasonic cleaner. The reaction temperature is 20–30℃. After every 25–35 minutes of reaction, the ultrasonic treatment is stopped for 4–6 minutes, and the acidic solution is added to increase the concentration gradient of the reaction. The reaction is carried out for a total of 2–4 hours. After the reaction is completed, the reaction product is washed and dried to obtain a high-stability manganese oxide cathode material for zinc-ion batteries.

[0010] More preferably, in the method for preparing the high-stability zinc-ion battery manganese oxide cathode as described above, the divalent manganese salt is selected from one or more of the following: manganese chloride tetrahydrate, manganese nitrate hexahydrate, manganese sulfate monohydrate, and manganese acetate tetrahydrate.

[0011] More preferably, in the method for preparing the high-stability zinc-ion battery manganese oxide cathode as described above, the molar ratio of potassium permanganate and divalent manganese salt in step 1 is 2:(1-3).

[0012] More preferably, in the method for preparing the high-stability zinc-ion battery manganese oxide cathode as described above, the volume ratio of water to N,N-dimethylformamide in step 1 is 1:(5-10), and the molar ratio of potassium permanganate to N,N-dimethylformamide is 1:(900-1600).

[0013] More preferably, in the method for preparing the high-stability zinc-ion battery manganese oxide cathode as described above, the heating, stirring, and reflux reaction time in step 2 is 3–6 hours.

[0014] More preferably, in the method for preparing the high-stability zinc-ion battery manganese oxide cathode as described above, the acidic solution in step 3 is a mixed acid solution of one or more inorganic acids, including hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid.

[0015] More preferably, in the method for preparing the high-stability zinc-ion battery manganese oxide cathode as described above, the ultrasonic power of the ultrasonic-assisted reaction in step 3 is 300-800W, and the frequency is 25-40kHz.

[0016] More preferably, in the preparation method of the high-stability zinc-ion battery manganese oxide cathode as described above, after the reaction in step 3 is completed, the electrode is washed 2 to 5 times alternately with deionized water and ethanol.

[0017] More preferably, in the method for preparing the high-stability zinc-ion battery manganese oxide cathode as described above, the reaction product obtained in step 3 is dried in a vacuum drying oven at a temperature of 55–65°C for 8–16 hours.

[0018] In addition, the present invention also provides a zinc-ion battery manganese oxide cathode material prepared by the above method.

[0019] Compared with existing technologies, the method for preparing manganese oxide cathode for zinc-ion batteries provided by this invention has the following advantages and significant advancements:

[0020] (1) This invention utilizes the weak alkalinity of N,N-dimethylformamide aqueous solution to avoid the addition of strong alkali, thereby controlling the weak alkaline environment of the reaction. In addition, this invention utilizes the characteristic of N,N-dimethylformamide to assist the oxidation of divalent manganese salts by potassium permanganate, which has a significant advantage in controlling the morphology and structure of manganese oxide materials.

[0021] (2) Breaking the current research hotspot of manganese oxide cathode modification in zinc-ion batteries - the regulation strategy of metal ion pre-intercalation, this invention utilizes the small size, light molar mass, hydrogen bond network between molecules, and strong OH bond formed with the metal layer of hydrated protons, which not only stabilizes the structure of manganese oxide during charging and discharging, but also reduces the steric hindrance of interlayer ion diffusion. More importantly, it is conducive to the Groot conduction of protons.

[0022] (3) The high-stability zinc-ion battery manganese oxide cathode synthesized in this invention helps to suppress the formation of basic zinc sulfate, an intermediate product, during the discharge process, and further stabilizes the structural stability of the material during the electrochemical reaction.

[0023] (4) Compared with other synthesis methods, the heating reflux method and microwave synthesis method used in this invention have the advantages of being time-saving, efficient, energy-saving and environmentally friendly. The preparation process of this invention is simple, easy to operate, and can be mass-produced.

[0024] (5) The high-stability zinc-ion battery manganese oxide cathode synthesized in this invention has high discharge specific capacity, high rate performance and excellent cycle stability in slightly acidic water-washed electrolyte. It has the advantages of easy operation and simple synthesis. It can provide innovative technical support and theoretical support for the development of high-stability aqueous zinc-ion batteries, and has important academic significance and application value. Attached Figure Description

[0025] Figure 1 This is a SEM image of the highly stable zinc-ion battery manganese oxide cathode material prepared in Example 1 of this invention;

[0026] Figure 2 This is the XRD pattern of the highly stable zinc-ion battery manganese oxide cathode material prepared in Example 1 of this invention;

[0027] Figure 3 The TGA curve of the highly stable zinc-ion battery manganese oxide cathode material prepared in Example 1 of this invention;

[0028] Figure 4 This is the cycle stability curve of the high-stability zinc-ion battery manganese oxide cathode material prepared in Example 1 of this invention;

[0029] Figure 5 The mass change-time curve of the high-stability zinc-ion battery manganese oxide cathode material prepared in Example 1 of this invention was tested using an electrochemical quartz crystal microbalance.

[0030] Figure 6 The TGA curves of the zinc-ion battery manganese oxide cathode material prepared in Comparative Example 1 are shown.

[0031] Figure 7 The cycling stability curves of the zinc-ion battery manganese oxide cathode material prepared in Comparative Example 1 are shown.

[0032] Figure 8 The mass change-time curve of the zinc-ion battery manganese oxide cathode material prepared in Comparative Example 1 was measured using an electrochemical quartz crystal microbalance. Detailed Implementation

[0033] This invention proposes a microwave synthesis technique assisted by a heating reflux method to prepare a highly stable manganese oxide cathode material for zinc-ion batteries. As a zinc-ion battery cathode material, its unique interlayer and metal layer structure design and morphological structure stabilize the crystal structure of the material during charge and discharge, and facilitate the rapid intercalation and deintercalation of zinc ions and protons between the two-dimensional layers, significantly improving the zinc storage capacity and cycle stability of the manganese oxide material. The preparation method of this invention is described in detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of this invention is not limited to the following embodiments.

[0034] Example 1:

[0035] A method for preparing a highly stable manganese oxide cathode material for zinc-ion batteries, specifically comprising the following steps:

[0036] Step 1: Weigh 0.158 g (0.001 mol) of potassium permanganate and 0.287 g of manganese nitrate hexahydrate and dissolve them in 12.5 mL of deionized water. Stir at room temperature for 30 min, then add 87.5 mL of N,N-dimethylformamide (1.132 mol) to the mixed solution and stir at room temperature for another 30 min.

[0037] Step 2: Transfer the above reaction solution to a three-necked round-bottom flask and heat under reflux with stirring at 80°C for 4.5 hours. Filter and wash with water and ethanol; drying is not required.

[0038] Step 3: Transfer the product obtained in Step 2 to 30 mL of 1.2 mol / L nitric acid solution. Under ultrasonic assistance, control the ultrasonic power at 600 W, the frequency at 25 kHz, the reaction temperature at 20 °C, and the reaction time at 3.0 h. After every 30 min of reaction, stop the ultrasonic treatment for 5 min, and simultaneously add 10 mL of 1.2 mol / L nitric acid solution to the system. After the reaction is complete, wash the product alternately with deionized water and ethanol 3-4 times. Dry the product in a vacuum drying oven at 60 °C for 12 h to obtain the high-stability zinc-ion battery manganese oxide cathode material of this invention.

[0039] Example 2:

[0040] A method for preparing a highly stable manganese oxide cathode material for zinc-ion batteries, specifically comprising the following steps:

[0041] Step 1: Weigh 0.158g of potassium permanganate and 0.144g of manganese nitrate hexahydrate and dissolve them in 20mL of deionized water. Stir at room temperature for 30min, then add 100mL of N,N-dimethylformamide (1.299mol) to the mixed solution and stir at room temperature for another 30min.

[0042] Step 2: Transfer the above reaction solution to a three-necked round-bottom flask and heat under reflux with stirring at 75°C for 5.0 h. Filter and wash with water and ethanol; drying is not required.

[0043] Step 3: Transfer the product obtained in Step 2 to 30 mL of 1.5 mol / L nitric acid solution. Under ultrasonic-assisted conditions, control the ultrasonic power at 500 W and the frequency at 30 kHz, the reaction temperature at 20 °C, and the reaction time at 2.0 h. After every 30 min of reaction, stop the ultrasonication for 5 min, and simultaneously add 10 mL of 1.5 mol / L nitric acid solution to the system. After the reaction is complete, wash the product alternately with deionized water and ethanol 3-4 times. Dry the product in a vacuum drying oven at 60 °C for 12 h to obtain the high-stability zinc-ion battery manganese oxide cathode material of this invention.

[0044] Example 3:

[0045] A method for preparing a highly stable manganese oxide cathode material for zinc-ion batteries, specifically comprising the following steps:

[0046] Step 1: Weigh 0.158g of potassium permanganate and 0.144g of manganese nitrate hexahydrate and dissolve them in 12.5mL of deionized water. Stir at room temperature for 30min, then add 75mL of N,N-dimethylformamide (0.974mol) to the mixed solution and stir at room temperature for another 30min.

[0047] Step 2: Transfer the above reaction solution to a three-necked round-bottom flask and heat under reflux with stirring at 70°C for 5.5 hours. Filter and wash with water and ethanol; drying is not required.

[0048] Step 3: Transfer the product obtained in Step 2 to a 1.5 mol / L, 30 mL hydrochloric acid solution. Under ultrasonic-assisted conditions, control the ultrasonic power at 400 W, the frequency at 35 kHz, the reaction temperature at 25 °C, and the reaction time at 3.0 h. After every 30 min of reaction, stop the ultrasonication for 5 min, and simultaneously add 10 mL of 1.5 mol / L hydrochloric acid solution to the system. After the reaction is complete, wash the product alternately with deionized water and ethanol 3-4 times. Dry the product in a vacuum drying oven at 60 °C for 12 h to obtain the high-stability zinc-ion battery manganese oxide cathode material of this invention.

[0049] Example 4:

[0050] A method for preparing a highly stable manganese oxide cathode material for zinc-ion batteries, specifically comprising the following steps:

[0051] Step 1: Weigh 0.158g of potassium permanganate and 0.256g of manganese acetate tetrahydrate and dissolve them in 20mL of deionized water. Stir at room temperature for 30min, then add 120mL of N,N-dimethylformamide (1.559mol) to the mixed solution and stir at room temperature for another 30min.

[0052] Step 2: Transfer the above reaction solution to a three-necked round-bottom flask and heat under reflux with stirring at 70°C for 6.0 h. Filter and wash with water and ethanol; drying is not required.

[0053] Step 3: Transfer the product obtained in Step 2 to a 1.5 mol / L, 30 mL hydrochloric acid solution. Under ultrasonic-assisted conditions, control the ultrasonic power at 700 W, the frequency at 30 kHz, the reaction temperature at 30 °C, and the reaction time at 2.0 h. After every 30 min of reaction, stop the ultrasonication for 5 min, and simultaneously add 10 mL of 1.5 mol / L hydrochloric acid solution to the system. After the reaction is complete, wash the product alternately with deionized water and ethanol 3-4 times. Dry the product in a vacuum drying oven at 60 °C for 12 h to obtain the high-stability zinc-ion battery manganese oxide cathode material of this invention.

[0054] Comparative Example 1

[0055] A method for preparing manganese oxide cathode material for zinc-ion batteries, specifically comprising the following steps:

[0056] Step 1: Weigh 0.158g of potassium permanganate and 0.287g of manganese nitrate hexahydrate and dissolve them in 12.5mL of deionized water. Stir at room temperature for 30min, then add 87.5mL of N,N-dimethylformamide to the mixed solution and stir again at room temperature for 30min.

[0057] Step 2: Transfer the above reaction solution to a three-necked round-bottom flask and heat under reflux with stirring at 80°C for 4.5 hours. Filter and wash with water and ethanol; drying is not required.

[0058] Step 3 Transfer the product obtained in step 2 to 30 mL of deionized water. Under ultrasound-assisted conditions, the ultrasound power was controlled at 600W, the frequency at 25kHz, the reaction temperature at 20℃, and the reaction time at 3.0h. Ultrasound was stopped for 5min after every 30min of reaction. At the same time, add 10 mL of deionized water to the system. After the reaction is complete, the product is washed 3-4 times alternately with deionized water and ethanol. The product is then dried in a vacuum drying oven at 60°C for 12 hours.

[0059] like Figure 1 The image shown is a SEM image of the high-stability zinc-ion battery manganese oxide cathode material prepared in Example 1 of this invention. It can be seen that the nanosheets have a three-dimensional interconnected nanoflower structure, and the flower balls also form a cross-linked network porous structure, which can provide a rich chemical reaction interface during zinc storage, shorten the diffusion path of ions, and alleviate the structural changes caused by stress during ion insertion and extraction.

[0060] like Figure 2The image shown is the XRD pattern of the high-stability zinc-ion battery manganese oxide cathode material prepared in Example 1 of the present invention. It can be seen that the manganese oxide material synthesized in the present invention is a δ-type layered manganese oxide with low crystallinity and a lattice spacing of about 0.73 nm, which is consistent with the lattice spacing of manganese oxide with hydrated protons.

[0061] like Figure 3 The figure shows the TGA curve of the highly stable manganese oxide cathode material for zinc-ion batteries prepared in Example 1 of this invention. The physical adsorbed water and interlayer lattice water were quantified, revealing a crystal water content as high as 7.28%, which is beneficial for stabilizing the structure of manganese oxide and the Groot conduction of protons.

[0062] like Figure 4 The figure shows the cycle stability curve of the high-stability zinc-ion battery manganese oxide cathode material prepared in Example 1 of this invention, 0.3Ag. -1 Activated for 30 cycles at low current density, the capacity reached 341 mAh g. -1 In 3.0Ag -1 After 600 cycles at high current density, the capacity still reaches 79mAh g. -1 It has a high capacitance retention rate.

[0063] like Figure 5 The figure shows the mass change-time curve of the high-stability zinc-ion battery manganese oxide cathode material prepared in Example 1 of this invention, measured using an electrochemical quartz crystal microbalance. The change in electrode mass is related to the insertion / extraction of protons / zinc ions and the dissolution / deposition of basic zinc sulfate during charging and discharging, reflecting the reversibility of the electrochemical reaction during charging and discharging. Figure 5 The results show that the electrochemical reaction process is highly reversible, indicating that the manganese oxide structure is stable.

[0064] like Figure 6 The figure shows the TGA curve of the manganese oxide cathode material for zinc-ion batteries prepared in Comparative Example 1. The physical adsorption water and interlayer lattice water were quantified, revealing a relatively low crystal water content of only 3.46%, which is detrimental to the stable structure of manganese oxide and the Groot conduction of protons.

[0065] like Figure 7 As shown, the cycle stability curve of the zinc-ion battery manganese oxide cathode material prepared in Comparative Example 1 is displayed. (0.3Ag) -1 Activated for 30 cycles at low current density, the capacity reaches 324mAh g. -1 In 3.0Ag -1 After 600 cycles at high current density, the capacity decayed to 55mAh g. -1 It has low capacitance retention and poor structural stability of manganese oxide.

[0066] like Figure 8The figure shows the mass change-time curve of the zinc-ion battery manganese oxide cathode material prepared in Comparative Example 1, as measured by an electrochemical quartz crystal microbalance. Figure 8 The results show that the electrochemical reaction process has poor reversibility, indicating that the manganese oxide structure is unstable.

[0067] Table 1 shows the zinc ion content in the electrodes of the two manganese oxide materials prepared in Example 1 and Comparative Example 1 of this invention, used as positive electrode materials for aqueous zinc-ion batteries, after 5, 15, 30, and 60 cycles, measured by inductively coupled plasma (ICP-PAP). The results indicate that the manganese oxide positive electrode material prepared in this invention can suppress the formation of basic zinc sulfate during discharge and exhibits high structural stability.

[0068] Table 1. Zinc ion content in the electrode after 5-60 cycles of manganese oxide material as positive electrode material in aqueous zinc-ion batteries.

[0069] Example 1 0.0645 0.0699 0.0710 0.0713 Comparative Example 1 0.0410 0.0520 0.0512 0.0514

Claims

1. A method for preparing a highly stable manganese oxide positive electrode for zinc-ion batteries, characterized in that, The method includes the following steps: Step 1: Dissolve potassium permanganate and divalent manganese salt in a mixture of water and N,N-dimethylformamide; Step 2: The above-obtained mixture is heated and stirred under reflux at a temperature of 65–90°C. After the reaction is complete, the reaction product is washed without drying. Step 3: Disperse the reaction product obtained in Step 2 in H... + The reaction was carried out in an acidic solution with a concentration of 0.5–3 mol / L, with ultrasound assistance at a reaction temperature of 20–30 °C. After every 25–35 minutes of reaction, the ultrasound was stopped for 4–6 minutes, and the acidic solution was added to increase the concentration gradient. The reaction was carried out for a total of 2–4 hours. After the reaction was completed, the reaction product was washed and dried to obtain a highly stable manganese oxide cathode material for zinc-ion batteries.

2. The method for preparing the high-stability manganese oxide cathode for zinc-ion batteries according to claim 1, characterized in that, The divalent manganese salt is selected from one or more of the following: manganese chloride tetrahydrate, manganese nitrate hexahydrate, manganese sulfate monohydrate, and manganese acetate tetrahydrate.

3. The method for preparing the high-stability manganese oxide cathode for zinc-ion batteries according to claim 1, characterized in that, In step 1, the molar ratio of potassium permanganate to divalent manganese salt is 2:(1-3).

4. The method for preparing the high-stability manganese oxide positive electrode for zinc-ion batteries according to claim 1, characterized in that, In step 1, the volume ratio of water to N,N-dimethylformamide is 1:(5-10), and the molar ratio of potassium permanganate to N,N-dimethylformamide is 1:(900-1600).

5. The method for preparing the high-stability manganese oxide cathode for zinc-ion batteries according to claim 1, characterized in that, The heating, stirring, and reflux reaction time in step 2 is 3 to 6 hours.

6. The method for preparing the high-stability manganese oxide positive electrode for zinc-ion batteries according to claim 1, characterized in that, The acidic solution mentioned in step 3 is a mixed acid solution of one or more inorganic acids, including hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid.

7. The method for preparing the high-stability manganese oxide cathode for zinc-ion batteries according to claim 1, characterized in that, The ultrasonic power of the ultrasonic-assisted reaction in step 3 is 300-800W, and the frequency is 25-40kHz.

8. The method for preparing the high-stability manganese oxide cathode for zinc-ion batteries according to claim 1, characterized in that, After the reaction in step 3 is completed, wash with deionized water and ethanol alternately 2 to 5 times.

9. The method for preparing the high-stability manganese oxide positive electrode for zinc-ion batteries according to claim 1, characterized in that, The reaction product obtained in step 3 is dried in a vacuum drying oven at a temperature of 55-65℃ for 8-16 hours.

10. A zinc-ion battery manganese oxide cathode material prepared by the method according to any one of claims 1-9.

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