A negative electrode material for an aqueous magnesium ion battery, a negative electrode sheet and a preparation method thereof

Abstract

A negative electrode material, a negative electrode sheet and a preparation method thereof for an aqueous magnesium ion battery belong to the field of new energy technology. The negative electrode material for the aqueous magnesium ion battery of the present invention is manganese vanadium oxide. Mn and multivalent V can both change valence in electrochemical reactions, and can provide a large number of electrons for reactions, thereby increasing the specific capacity. And the potential is suitable, and it can be used as a negative electrode material for an aqueous magnesium ion battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy, and in particular relates to a negative electrode material and a negative electrode sheet of an aqueous magnesium ion battery and a preparation method thereof. Background Art

[0002] Compared with traditional lead-acid and nickel-cadmium batteries, the ionic conductivity of aqueous electrolytes is much higher than that of organic electrolytes, and the impedance of electrolytes is smaller, which is conducive to high-rate charging and discharging, thereby improving electrochemical performance. Aqueous electrolytes are inherently safe and environmentally friendly, avoiding the disadvantages of organic electrolytes such as environmental pollution and flammability and explosion.

[0003] Aqueous magnesium-ion batteries are a promising energy storage and conversion system that can meet the growing demand for green, renewable and sustainable energy. The realization of high energy density and long-life systems is of great significance to fully realize the huge potential of aqueous magnesium batteries, which has attracted increasing attention and research from researchers around the world in the past few years. Moreover, the intrinsic advantages of magnesium have stimulated this potential, including high earth abundance (Mg is 1.94% and Li is 0.002%), low cost and environmental protection.

[0004] However, there are few studies on magnesium storage negative electrode materials using aqueous electrolyte systems. Developing and finding suitable negative electrode materials has become the key to improving the performance of rechargeable magnesium-ion batteries. Summary of the invention

[0005] Therefore, the present invention provides a negative electrode material, a negative electrode sheet and a preparation method thereof for an aqueous magnesium ion battery.

[0006] To this end, the present invention provides the following technical solutions.

[0007] In a first aspect, the present invention provides a negative electrode material for an aqueous magnesium ion battery, which is manganese vanadium oxide.

[0008] In a second aspect, the present invention provides a method for preparing a negative electrode material for an aqueous magnesium ion battery, comprising the following steps:

[0009] Step 1, mixing a manganese source and a vanadium source in water to obtain a mixed solution;

[0010] Step 2: subjecting the mixed solution to a hydrothermal reaction to obtain manganese vanadium oxide.

[0011] The manganese vanadium oxide prepared by the invention is in the form of flakes.

[0012] Furthermore, the molar ratio of the manganese source to the vanadium source is 1:(0.8-2.2).

[0013] Furthermore, the step 1 also includes: adjusting the pH value of the mixed solution to 5-6.

[0014] Furthermore, in step 2, the hydrothermal reaction temperature is 120 to 200° C., and the reaction time is 4 to 20 hours.

[0015] Furthermore, step 1 includes:

[0016] Mixing a manganese source with water and stirring at room temperature to obtain a manganese source solution;

[0017] Mixing the vanadium source with water, heating and stirring, to obtain a vanadium source solution;

[0018] The manganese source solution is added into the vanadium source solution, and the mixture is heated and stirred continuously to obtain a mixed solution.

[0019] The vanadium source solution is dissolved in hot water. Adding the manganese source solution into the vanadium source solution can prevent the vanadium source from cooling and precipitating, which would cause incomplete reaction.

[0020] Furthermore, step 1 satisfies at least one of the following conditions:

[0021] (1) Mixing a manganese source and water, and stirring for 0.2 to 1 h at room temperature;

[0022] (2) mixing the vanadium source with water, and heating and stirring at a temperature of 40° C. to 90° C.;

[0023] (3) mixing the vanadium source with water, and heating and stirring for 0.5 to 2 hours;

[0024] (4) Add the manganese source solution into the vanadium source solution, and continue heating and stirring at a temperature of 40° C. to 90° C. for 0.5 to 2 h.

[0025] Furthermore, the manganese source solution is added to the vanadium source solution at a dropping speed of 1 to 20 mL / min to slow down the reaction speed and avoid agglomeration of the precursor product.

[0026] Furthermore, the manganese source is a water-soluble manganese salt, and / or the vanadium source is a water-soluble vanadium salt.

[0027] Further, the manganese source is at least one of manganese chloride, manganese sulfate, manganese acetate or manganese nitrate;

[0028] The vanadium source includes one or more of ammonium metavanadate and sodium metavanadate.

[0029] In step 2, after the hydrothermal reaction, the product is filtered, and the precipitate is washed and dried to obtain manganese vanadium oxide.

[0030] In a third aspect, the present invention further provides a negative electrode plate for an aqueous magnesium ion battery, comprising the negative electrode material prepared by the above preparation method.

[0031] In a fourth aspect, the present invention further provides a method for preparing a negative electrode sheet of an aqueous magnesium ion battery, comprising the following steps:

[0032] The negative electrode material prepared according to the above preparation method is mixed with conductive carbon and polyvinylidene fluoride in a mass ratio of (6-8):(1-3):(1-2) to prepare an electrode slurry, and the polyvinylidene fluoride is dissolved in N-methylpyrrolidone. The electrode slurry is coated on a current collector and dried at 80-100° C. to obtain an aqueous magnesium ion battery negative electrode sheet.

[0033] Furthermore, the conductive carbon includes at least one of acetylene black, super P, graphite, carbon fiber, carbon nanotube, and graphene.

[0034] The current collector includes one of carbon cloth, carbon felt, stainless steel, titanium foil, aluminum foil and copper foil.

[0035] The technical solution of the present invention has the following advantages:

[0036] 1. The negative electrode material for aqueous magnesium ion batteries provided by the present invention is manganese vanadium oxide. Mn and multivalent V can both change valence in electrochemical reactions, and can provide a large number of electrons for reaction, thereby increasing the specific capacity. And the potential is suitable, and it can be used as a negative electrode material for aqueous magnesium ion batteries.

[0037] 2. The method for preparing the negative electrode material for an aqueous magnesium ion battery provided by the present invention comprises the following steps: step 1, mixing a manganese source and a vanadium source in water to obtain a mixed solution; step 2, subjecting the mixed solution to a hydrothermal reaction to obtain manganese vanadium oxide.

[0038] The manganese vanadium oxide is prepared by a one-step hydrothermal method. The manganese vanadium oxide can be precipitated quickly and the product has a good crystal form. The raw materials are extensive, the cost is low, and the preparation process is simple, which is beneficial to large-scale production and application.

[0039] 3. The method for preparing the negative electrode material for an aqueous magnesium ion battery provided by the present invention adjusts the pH value of the mixed solution to 5-6. By adjusting the pH range, the manganese-vanadium stoichiometric ratio in the product can be improved to be close to the added amount, thereby ensuring a more uniform product phase.

[0040] 4. The present invention provides a method for preparing a negative electrode material for an aqueous magnesium ion battery, wherein the molar ratio of the manganese source to the vanadium source is 1:(0.8-2.2), and the synthesized manganese vanadium oxide has a larger tunnel structure, which is beneficial to the deintercalation of magnesium ions in the material lattice, thereby reducing the impact on the host material lattice and improving the cycle stability and rate performance of the electrode.

[0041] The present invention uses cheap transition metal salts as raw materials, which are low in cost and widely available; using abundant water resources and cheap magnesium salts as electrolytes greatly reduces costs and avoids the shortcomings of organic electrolytes such as flammability, explosion and environmental pollution. While meeting green environmental protection requirements, it also improves the safety factor during production and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0043] Figure 1 The XRD pattern of the negative electrode material prepared in Example 1, the corresponding product is MnV 2 O 6 Material crystal structure;

[0044] Figure 2 This is a SEM morphology of the negative electrode material prepared in Example 1;

[0045] Figure 3 The constant current charge-discharge curve of the negative electrode sheet made of the negative electrode material of Example 1 at a current density of 0.5C in a three-electrode test system;

[0046] Figure 4 This is the XRD pattern of the negative electrode material prepared in Example 2. DETAILED DESCRIPTION

[0047] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0048] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0049] Example 1

[0050] This embodiment provides a method for preparing a negative electrode material for an aqueous magnesium ion battery, comprising the following steps:

[0051] Step (1), dissolving 1 mmol of manganese nitrate in 20 mL of water, stirring at room temperature for 20 min to obtain a manganese nitrate solution;

[0052] Step (2), dissolving 2 mmol of ammonium metavanadate in 20 mL of water, heating and stirring at 60° C. for 30 min to obtain an ammonium metavanadate solution;

[0053] Step (3), slowly adding the manganese nitrate solution into the ammonium metavanadate solution at a dropping speed of 1 mL / min, stirring at room temperature for 1 h to obtain a mixed solution;

[0054] Step (4), adjusting the pH of the mixed solution to 5 using aqueous ammonia;

[0055] Step (5), transferring the mixed solution to a reactor for hydrothermal reaction, maintaining the temperature at 180° C. for 16 h, filtering, washing and drying the precipitate to obtain manganese vanadium oxide.

[0056] Figure 1 The XRD pattern of the negative electrode material prepared in Example 1, the corresponding product is MnV 2 O 6 Material crystal structure.

[0057] Figure 2 This is the SEM morphology of the negative electrode material prepared in Example 1. It can be seen from the morphology that the manganese vanadium oxide product particles are uniform and the particle size is concentrated, and it is a relatively ideal negative electrode material.

[0058] Example 2

[0059] This example is substantially the same as Example 1, except that in step (2), 1 mmol of ammonium metavanadate is dissolved in 20 mL of water.

[0060] Figure 4 The XRD pattern of the negative electrode material prepared in Example 2, the corresponding product is still MnV 2 O 6 The material has a crystal structure, but there are certain impurity peaks.

[0061] Example 3

[0062] This embodiment is basically the same as embodiment 1, except that after the mixed solution is obtained in step (3), the pH of the mixed solution is not adjusted.

[0063] Example 4

[0064] This embodiment provides a method for preparing a negative electrode material for an aqueous magnesium ion battery, comprising the following steps:

[0065] Step (1), dissolving 1 mmol of manganese chloride in 20 mL of water, stirring at room temperature for 30 min, to obtain a manganese chloride solution;

[0066] Step (2), dissolving 2 mmol of ammonium metavanadate in 20 mL of water, heating and stirring at 70° C. for 30 min to obtain an ammonium metavanadate solution;

[0067] Step (3), slowly adding the manganese nitrate solution into the ammonium metavanadate solution at a dropping speed of 10 mL / min, stirring at room temperature for 1 h to obtain a mixed solution;

[0068] Step (4), adjusting the pH of the mixed solution to 6 using aqueous ammonia;

[0069] Step (5), transferring the mixed solution to a reactor for hydrothermal reaction, maintaining the temperature at 200° C. for 12 h, filtering, washing and drying the precipitate to obtain manganese vanadium oxide.

[0070] Comparative Example 1

[0071] This comparative example is substantially the same as Example 1, except that in step (1), manganese nitrate is replaced by ferric nitrate.

[0072] Test example

[0073] The negative electrode materials, conductive carbon and polyvinylidene fluoride prepared in Examples 1-3 and Comparative Example 1 were mixed in a mass ratio of 8:1:1, wherein polyvinylidene fluoride was dissolved in N-methylpyrrolidone to prepare an electrode slurry, which was coated on a carbon cloth and dried at 100°C to obtain a negative electrode sheet. A graphite rod was used as a counter electrode, a saturated calomel electrode was used as a reference electrode, and MgSO 4 The aqueous solution is used as the electrolyte and assembled into a three-electrode test system.

[0074] The above three-electrode test system was tested:

[0075] (1) Rate performance test process: Use Wuhan Blue Electric Battery Test System to perform rate performance test, the rate is 2C; the test steps are as follows: (the negative electrode is used as the working electrode) the battery is discharged to -1.1V at a constant current of 0.5C, charged to 0.5V at a constant current of 0.5C, and cycled 3 times; finally, discharged to -1.1V at 2C, and the time interval between each step is 10min.

[0076] (2) Cyclic performance test process: The test steps are as follows: (the negative electrode is used as the working electrode) the battery is discharged to -1.1V at a constant current of 1C, charged to 0.5V at a constant current of 1C, and cycled tested, with the time interval between each step being 10min.

[0077] (3) Potential test process: The test steps are as follows: (the negative electrode is used as the working electrode) the battery is discharged to -1.1V at a constant current of 0.5C, and charged to 0.3V at a constant current of 0.5C. The time interval between each step is 10 minutes. After integrating the capacity-voltage curve, the average discharge potential is obtained.

[0078] (4) The specific capacity test process is as follows: (the negative electrode is used as the working electrode) the battery is discharged to -1.1V at a constant current of 0.5C, and charged to 0.3V at a constant current of 0.5C. The time interval between each step is 10min, and the specific capacity of the material is obtained.

[0079] The test results are shown in Table 1.

[0080] Table 1

[0081]

[0082] As can be seen from Table 1, the manganese vanadium oxide of the present invention can greatly improve the stability, rate performance and specific capacity of aqueous magnesium ion batteries as negative electrode materials. The electrode sheet obtained by the product obtained when the molar ratio of manganese source to vanadium source in the raw material of Example 1 is 1:2 has higher specific capacity and stability, which can reach 230.2 mAh / g; while the specific capacity of the product obtained when the raw material molar ratio is 1:1 or without pH adjustment (Example 2 or 3) is reduced, which may be related to the presence of impurities in the product.

[0083] Figure 3 This is a constant current charge and discharge curve of the negative electrode sheet made of the negative electrode material of Example 1 at a current density of 0.5C in a three-electrode test system, and the specific capacity is 230.2 mAh / g.

[0084] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the scope of protection of the invention.

Claims

1. A negative electrode material for an aqueous magnesium ion battery, characterized in that: It is manganese vanadium oxide; The preparation method of the manganese vanadium oxide comprises the following steps: Step 1, mixing a manganese source and a vanadium source in water to obtain a mixed solution; the molar ratio of the manganese source to the vanadium source is 1:(2-2.2); adjusting the pH value of the mixed solution to 5-6; Step 2: subjecting the mixed solution to a hydrothermal reaction to obtain manganese vanadium oxide.

2. A method for preparing a negative electrode material for an aqueous magnesium ion battery according to claim 1, characterized in that: The following steps are involved: Step 1, mixing a manganese source and a vanadium source in water to obtain a mixed solution; Step 2: subjecting the mixed solution to a hydrothermal reaction to obtain manganese vanadium oxide.

3. The method for preparing a negative electrode material for an aqueous magnesium ion battery according to claim 2, characterized in that: The molar ratio of the manganese source to the vanadium source is 1:(2-2.2).

4. The method for preparing a negative electrode material for an aqueous magnesium ion battery according to claim 2, characterized in that: The step 1 also includes: adjusting the pH value of the mixed solution to 5-6.

5. The method for preparing a negative electrode material for an aqueous magnesium ion battery according to claim 2 or 3, characterized in that: In step 2, the hydrothermal reaction temperature is 120-200° C., and the reaction time is 4-20 hours.

6. The method for preparing a negative electrode material for an aqueous magnesium ion battery according to claim 2 or 3, characterized in that: Step 1 includes: Mixing a manganese source with water and stirring at room temperature to obtain a manganese source solution; Mixing the vanadium source with water, heating and stirring, to obtain a vanadium source solution; The manganese source solution is added into the vanadium source solution, and the mixture is heated and stirred continuously to obtain a mixed solution.

7. The method for preparing a negative electrode material for an aqueous magnesium ion battery according to claim 6, characterized in that: The dropping speed of the manganese source solution into the vanadium source solution is 1-20 mL / min.

8. The method for preparing a negative electrode material for an aqueous magnesium ion battery according to claim 2 or 3, characterized in that: The manganese source is at least one of manganese chloride, manganese sulfate, manganese acetate or manganese nitrate; The vanadium source includes one or more of ammonium metavanadate and sodium metavanadate.

9. A negative electrode plate for an aqueous magnesium ion battery, characterized in that: The negative electrode material comprises a negative electrode material prepared by the preparation method according to any one of claims 2 to 8.

10. A method for preparing a negative electrode sheet for an aqueous magnesium ion battery, characterized in that: The following steps are involved: The negative electrode material prepared by the preparation method according to any one of claims 2 to 8 is mixed with conductive carbon and polyvinylidene fluoride in a mass ratio of (6 to 8): (1 to 3): (1 to 2) to prepare an electrode slurry, and the electrode slurry is coated on a current collector and dried at 80 to 100° C. to obtain an aqueous magnesium ion battery negative electrode sheet.

Images