A negative electrode material, a preparation method thereof, a negative electrode sheet, and a water-based magnesium ion battery

Abstract

The application provides a negative electrode material and a preparation method thereof, a negative electrode sheet and a water-based magnesium ion battery, and belongs to the technical field of new energy, and overcomes the defects of poor rate performance and cycle stability when iron vanadium oxide is used as the negative electrode material of the water-based magnesium ion battery in the prior art. The negative electrode material is a multi-walled carbon nanotube doped iron vanadium oxide, and the molar ratio of the iron source to the vanadium source in the raw material is 1:(1.8-2.2). The rate performance is improved, and the cycle stability of the magnesium ion battery is improved.

Description

Technical Field

[0001] This invention belongs to the field of new energy technology, specifically relating to a negative electrode material and its preparation method, a negative electrode sheet, and an aqueous magnesium-ion battery. Background Technology

[0002] With the increasing development of the economy and society, people's demand for energy is rising, and making full use of renewable energy is crucial for reducing carbon emissions and achieving sustainable development. However, renewable energy sources such as solar, wind, and tidal power suffer from drawbacks such as intermittency, instability, and uneven distribution, hindering large-scale utilization. The implementation of grid-scale energy storage is essential to alleviating the mismatch between electricity production and consumption. Therefore, it is necessary to develop efficient, inexpensive, clean, and safe energy storage technologies. Among these, aqueous batteries have become one of the ideal energy storage methods for large-scale energy storage due to their high safety, low cost, and environmental friendliness. Compared to lithium, magnesium is abundant, evenly distributed, and easy to mine on Earth, giving it an inherent cost advantage. Due to its divalent nature, magnesium has a volumetric capacity of 3833 mAh / cm³. 3 Lithium (2046mAh / cm³) 3 Magnesium has a larger capacity. Among multivalent metals, magnesium and many magnesium chemicals are non-toxic or low-toxic, easy to process, and inexpensive, thus giving magnesium-ion batteries a unique advantage in development.

[0003] Existing technology discloses an iron vanadium oxide as a negative electrode material for aqueous magnesium-ion batteries; however, Mg... 2+ The high charge density of the electrode material creates a strong insertion barrier in the host material, and the intercalation of magnesium ions causes a significant change in the electrode material structure, resulting in low cycle stability.

[0004] Developing and finding suitable anode materials is key to improving the performance of rechargeable magnesium-ion batteries. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defects of poor rate performance and cycle stability when iron vanadium oxide is used as the negative electrode material of aqueous magnesium ion battery in the prior art, thereby providing a negative electrode material and its preparation method, a negative electrode sheet, and an aqueous magnesium ion battery.

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

[0007] In a first aspect, the present invention provides an anode material, which is an iron-vanadium oxide doped with multi-walled carbon nanotubes, wherein the molar ratio of iron source to vanadium source in the raw material is 1:(1.8~2.2).

[0008] Secondly, the present invention provides a method for preparing a negative electrode material, comprising the following steps:

[0009] Step 1: Mix the iron source, vanadium source and multi-walled carbon nanotubes in water to obtain a mixed solution, wherein the molar ratio of the iron source to the vanadium source is 1:(1.8~2.2);

[0010] Step 2: Perform a hydrothermal reaction on the mixture and filter to obtain the precursor;

[0011] Step 3: Sinter the precursor to obtain the negative electrode material.

[0012] Furthermore, in step 1, the molar amount of the iron source and the mass of the multi-walled carbon nanotubes are 1 mmol: (0.1~0.3) g.

[0013] Furthermore, step 1 also includes adjusting the pH of the mixture to 4-6. Adjusting the pH range can improve the stoichiometry of iron and vanadium in the product and ensure a more uniform product phase.

[0014] Furthermore, step 1 includes:

[0015] The iron source was mixed with water and stirred at room temperature for 0.2–1.5 h to obtain an iron source solution.

[0016] The vanadium source is mixed with water and stirred at 40–80°C for 0.5–2.5 h to obtain a vanadium source solution.

[0017] The iron source solution was added to the vanadium source solution, and multi-walled carbon nanotubes were added. The mixture was ultrasonically dispersed for 0.5–2 h, and then stirred at room temperature for 0.5–4 h to obtain a mixed solution. The iron source solution was added to the vanadium source solution slowly at a dropping rate of 1–20 mL / min to slow down the reaction rate and avoid precursor product aggregation.

[0018] Furthermore, in step 2, the hydrothermal reaction temperature is 120–200°C, and the reaction time is 4–16 hours.

[0019] Furthermore, in step 3, sintering includes pre-sintering and a second sintering;

[0020] The temperature is increased to the pre-sintering temperature at a rate of 8-15℃ / min. The pre-sintering temperature is 600-1000℃. After heating to the pre-sintering temperature, the temperature is treated for 1-3 hours, then cooled to room temperature for fine treatment, and then passed through a 500-mesh sieve.

[0021] The temperature is increased to the second sintering temperature at a rate of 1-5℃ / min, and the second sintering temperature is 400-800℃. After heating to the second sintering temperature, the temperature is treated for 3-6 hours.

[0022] Furthermore, the iron source is a water-soluble iron salt, and / or the vanadium source is a water-soluble vanadium salt.

[0023] Furthermore, the iron source includes at least one of ferric chloride, ferric sulfate, ferric acetate, or ferric nitrate; and / or

[0024] The vanadium source includes one or more of ammonium metavanadate and sodium metavanadate.

[0025] Thirdly, the present invention provides a negative electrode sheet comprising the negative electrode material prepared by the above-described preparation method.

[0026] In one possible design, the negative electrode also includes acetylene black and polyvinylidene fluoride. The mass ratio of the negative electrode material, acetylene black, and polyvinylidene fluoride in this invention is (6-8):(1-3):(1-2).

[0027] The method for preparing a negative electrode sheet includes: mixing a negative electrode material, acetylene black and polyvinylidene fluoride (the polyvinylidene fluoride is dissolved in N-methylpyrrolidone during mixing) to form an electrode slurry, coating the electrode slurry onto a current collector and drying it at 80-100°C to obtain a negative electrode sheet.

[0028] The current collector is one of the following: carbon cloth, carbon felt, stainless steel, titanium foil, aluminum foil, and copper foil.

[0029] Fourthly, the present invention provides an aqueous magnesium-ion battery, comprising the aforementioned negative electrode sheet.

[0030] The technical solution of this invention has the following advantages:

[0031] 1. The negative electrode material provided by the present invention is an iron-vanadium oxide doped with multi-walled carbon nanotubes, wherein the molar ratio of iron source to vanadium source in the raw material is 1:(1.8~2.2).

[0032] Doping iron-vanadium oxide with multi-walled carbon nanotubes can improve the stability of the anode material and reduce Mg content. 2+ The disruption of the anode material structure improves the cycle stability of magnesium-ion batteries. Simultaneously, doping with multi-walled carbon nanotubes can enhance the conductivity of the anode material, further improving the battery's rate performance.

[0033] The molar ratio of iron source to vanadium source in the raw materials is 1:(1.8~2.2). The synthesized iron-vanadium oxide has a wider three-dimensional tunnel structure, which is more conducive to ion diffusion and avoids the collapse and degradation of the material structure during charge-discharge cycles, thus preventing capacity decay.

[0034] The present invention relates to a negative electrode material that, while adjusting the proportion of iron-vanadium oxide, is doped with multi-walled carbon nanotubes to improve the electronic conductivity of the material, thereby improving rate performance and enhancing the cycle stability of magnesium-ion batteries.

[0035] 2. The method for preparing the negative electrode material provided by the present invention includes the following steps: Step 1, mixing an iron source, a vanadium source and multi-walled carbon nanotubes in water to obtain a mixed solution, wherein the molar ratio of the iron source to the vanadium source is 1:(1.8~2.2); Step 2, subjecting the mixed solution to a hydrothermal reaction and filtering to obtain a precursor; Step 3, sintering the precursor to obtain the negative electrode material.

[0036] This invention prepares the precursor via a hydrothermal reaction, achieving low synthesis temperature and short time, and in-situ incorporation of multi-walled carbon nanotubes into the precursor, resulting in high utilization. In-situ doping of iron-vanadium oxide with multi-walled carbon nanotubes improves conductivity and enhances battery rate performance while mitigating structural changes in the iron-vanadium oxide during charge and discharge, thereby extending cycle life.

[0037] In aqueous electrolytes, a full cell can be constructed by matching a suitable cathode material without impacting the environment. Therefore, it has great potential as a candidate material for next-generation large-scale energy storage.

[0038] The molar ratio of iron source to vanadium source is 1:(1.8~2.2), which enables the anode material of the present invention to have high potential and specific capacity while having high conductivity and stability.

[0039] 3. In the method for preparing the negative electrode material provided by the present invention, the molar amount of the iron source and the mass of the multi-walled carbon nanotubes are 1 mmol: (0.1~0.3) g. The doping amount of the multi-walled carbon nanotubes is approximately 40%~120% of the mass of the iron vanadium oxide, so as to improve the stability and conductivity of the material without excessively affecting the specific capacity of the material.

[0040] 4. In the preparation method of the negative electrode material provided by the present invention, sintering includes pre-sintering and a second sintering, to obtain a multi-walled carbon nanotube-doped iron vanadium oxide electrode material with better crystallinity and purity.

[0041] This invention successfully obtained a multi-walled carbon nanotube-doped iron-vanadium oxide precursor using a solvothermal method with short reaction time and low temperature. After simple calcination, a multi-walled carbon nanotube-doped iron-vanadium oxide anode material with good crystallinity and high purity was obtained. This invention improves the rate performance of the iron-vanadium oxide electrode material by enhancing its conductivity and mitigates the structural changes caused by magnesium ion insertion / extraction during the composite formation of multi-walled carbon nanotubes, thereby extending the cycle life of the electrode material. Attached Figure Description

[0042] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0043] Figure 1 The image shows the XRD pattern of the negative electrode material prepared in Example 1.

[0044] Figure 2 The image shows the SEM morphology of the negative electrode material prepared in Example 1.

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

[0046] Figure 4 The image shows the XRD pattern of the negative electrode material prepared in Comparative Example 2.

[0047] Figure 5 The image shows the XRD pattern of the negative electrode material prepared in Comparative Example 1. Detailed Implementation

[0048] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0049] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0050] Example 1

[0051] This embodiment provides a method for preparing a negative electrode material, including the following steps:

[0052] Step (1): Dissolve 1 mmol of ferric nitrate in 20 mL of water and stir at room temperature for 20 min to obtain ferric nitrate solution;

[0053] Step (2): Dissolve 2 mmol of ammonium metavanadate in 20 mL of water, heat and stir at 60 °C for 30 min under hydrothermal conditions to obtain an ammonium metavanadate solution;

[0054] Step (3): Slowly add ferric nitrate solution to ammonium metavanadate solution at a dropping rate of 1 mL / min, add 0.1 g of multi-walled carbon nanotubes (XFENG Nano, XFM31), ultrasonically disperse for 1 h, and then stir at room temperature for 2 h to obtain a mixture;

[0055] Step (4): Adjust the pH of the above mixture to 5 and transfer it to the reactor for hydrothermal reaction. Maintain the temperature at 160°C for 5 hours. Filter, wash and dry the precipitate to obtain multi-walled carbon nanotube-doped iron vanadium oxide. Grind and refine the precipitate and pass it through a 500-mesh sieve to obtain the precursor.

[0056] Step (5): The precursor obtained in step (4) is placed in a tube furnace for pre-sintering. A nitrogen / argon protective atmosphere is used to raise the temperature to 800°C at 10°C / min, hold for 2 hours, and then grind and refine it before passing it through a 500-mesh sieve.

[0057] Step (6): The product from step (5) is placed in a tube furnace for secondary sintering. A nitrogen / argon protective atmosphere is used to raise the temperature to 600°C at 1°C / min and hold for 4 hours to obtain iron vanadium oxide doped with multi-walled carbon nanotubes.

[0058] Figure 1 The image shows the XRD pattern of the multi-walled carbon nanotube-doped iron-vanadium oxide prepared in this embodiment. Figure 1 It can be seen that the anode material in this embodiment has good crystallinity and matches the crystal structure of FeV2O6 material.

[0059] Figure 2 The image shows the SEM morphology of the negative electrode material prepared in this embodiment. Figure 2 As can be seen, the iron-vanadium oxide products doped with multi-walled carbon nanotubes have uniform particle size and are relatively ideal anode materials. The generated iron-vanadium oxide products are uniformly nucleated on multi-walled carbon nanotubes, and the micron-sized iron-vanadium oxide products are uniformly combined with multi-walled carbon nanotubes.

[0060] Example 2

[0061] This embodiment is basically the same as that of embodiment 1, except that in step (3), 0.5g of multi-walled carbon nanotubes are added.

[0062] Example 3

[0063] This embodiment is basically the same as that of embodiment 1, except that the pH of the mixture was not adjusted after obtaining the mixture in step (3).

[0064] Example 4

[0065] This embodiment provides a method for preparing a negative electrode material, including the following steps:

[0066] Step (1): Dissolve 1 mmol of ferric chloride in 20 mL of water and stir at room temperature for 20 min to obtain a ferric chloride solution;

[0067] Step (2): Dissolve 2 mmol of ammonium metavanadate in 20 mL of water, heat and stir at 70 °C for 30 min under hydrothermal conditions to obtain an ammonium metavanadate solution;

[0068] Step (3): Slowly add ferric nitrate solution to ammonium metavanadate solution at a dropping rate of 1 mL / min, add 0.2 g of multi-walled carbon nanotubes (Xianfeng Nano, XFM31), ultrasonically disperse for 1 h, and then stir at room temperature for 2 h to obtain a mixture;

[0069] Step (4): Adjust the pH of the above mixture to 5 and transfer it to the reactor for hydrothermal reaction. Maintain the temperature at 180°C for 3 hours. Filter, wash and dry the precipitate to obtain multi-walled carbon nanotube-doped iron vanadium oxide. Grind and refine the precipitate and pass it through a 500-mesh sieve to obtain the precursor.

[0070] Step (5): The precursor obtained in step (4) is placed in a tube furnace for pre-sintering. A nitrogen / argon protective atmosphere is used to raise the temperature to 900°C at 12°C / min, hold for 2 hours, and then grind and refine it before passing it through a 500-mesh sieve.

[0071] Step (6): The product obtained in step (5) is placed in a tube furnace for secondary sintering. A nitrogen / argon protective atmosphere is used to raise the temperature to 500°C at 1°C / min and hold for 4 hours to obtain iron vanadium oxide doped with multi-walled carbon nanotubes.

[0072] Comparative Example 1

[0073] Step (1): Dissolve 1 mmol of ferric nitrate in 20 mL of water and stir at room temperature for 20 min to obtain ferric nitrate solution;

[0074] Step (2): Dissolve 2 mmol of ammonium metavanadate in 20 mL of water, heat and stir at 60 °C for 30 min under hydrothermal conditions to obtain an ammonium metavanadate solution;

[0075] Step (3): Slowly add ferric nitrate solution to ammonium metavanadate solution at a dropping rate of 1 mL / min, stir at room temperature for 2 h to obtain a mixture;

[0076] Step (4): The above mixture is transferred to a reactor for hydrothermal reaction. The temperature is maintained at 160°C for 5 hours. The precipitate is filtered, washed, and dried to obtain multi-walled carbon nanotube-doped iron vanadium oxide. The precipitate is then ground and refined to obtain the precursor.

[0077] Step (5): The precursor obtained in step (4) is placed in a tube furnace for calcination. A nitrogen / argon protective atmosphere is used. The calcination temperature is 500℃, the holding time is 2h, and the heating rate is 5℃ / min.

[0078] Comparative Example 2

[0079] This comparative example is basically the same as Example 1, except that in step (2), 1 mmol of ammonium metavanadate is dissolved in 20 mL of water.

[0080] Test case

[0081] Electrode slurries were prepared using the negative electrode materials obtained in Examples 1-3 and Comparative Examples 1-2, respectively, along with acetylene black and polyvinylidene fluoride in a mass ratio of 8:1:1. Polyvinylidene fluoride was dissolved in N-methylpyrrolidone. The electrode slurry was coated onto carbon cloth and dried at 100°C to obtain the negative electrode sheet. A graphite rod was used as the counter electrode, a saturated calomel electrode as the reference electrode, and an aqueous solution of MgSO4 as the electrolyte, forming a three-electrode testing system.

[0082] The above three-electrode test system was tested:

[0083] (1) The rate performance test process is as follows: The Wuhan Landian Battery Test System is used to conduct rate performance tests, and 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, it is discharged to -1.1V at 2C, and the time interval between each step is 10min.

[0084] (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 with 1C constant current, charged to 0.3V with 1C constant current, and cycle test is performed. The time interval between each step is 10min.

[0085] (3) Potential testing process: The test steps are as follows: (the negative electrode is used as the working electrode) the battery is discharged to -1.1V with a constant current of 0.5C and charged to 0.3V with a constant current of 0.5C. The time interval between each step is 10min. After integrating the capacity-voltage curve, the average discharge potential is obtained.

[0086] (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 to obtain the specific capacity of the material.

[0087] The test results are shown in Table 1.

[0088] Table 1 Electrical properties

[0089]

[0090] As can be seen from Examples 1, 2 and Comparative Example 1, adding a certain amount of multi-walled carbon nanotubes during the synthesis process can effectively improve electrode stability and rate performance, but excessive introduction of carbon nanotubes will lead to a decrease in the specific capacity of the material.

[0091] As can be seen from Examples 1 and 3, adjusting the pH of the mixture helps to improve the stability of the material, which may be related to the differences in product crystal form and composition.

[0092] As can be seen from Example 1 and Comparative Example 2, compared with FeVO4 material, FeV2O6 material synthesized with a molar ratio of iron source to vanadium source of 1:2 has a larger tunnel structure, which is conducive to ion diffusion and significantly improves the stability and specific capacity of aqueous magnesium ion batteries.

[0093] Figure 3 This is a constant current charge-discharge curve of the negative electrode sheet made using the negative electrode material of Example 1 at a current density of 0.5C in a three-electrode test system. Figure 3 It can be seen that the negative electrode material of the present invention improves conductivity while achieving a discharge specific capacity of up to 150 mAh g. -1 above.

[0094] Figure 4 The XRD pattern of the negative electrode material prepared in Comparative Example 2 is shown below. Figure 4 It can be seen that the synthesized product of Comparative Example 2 matches the FeVO4 crystal structure, which is different from the FeV2O6 crystal structure obtained when the ratio of iron source to vanadium source in the raw materials is 1:2 (Example 1).

[0095] Figure 5 The image shows the XRD pattern of the negative electrode material prepared in Comparative Example 1. Figure 5 It can be seen that the synthesized product of Comparative Example 1 matches the crystal structure of FeV2O6.

[0096] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. The application of a negative electrode material in an aqueous magnesium-ion battery, characterized in that, The preparation method of the negative electrode material includes the following steps: Step (1): Dissolve 1 mmol of ferric nitrate in 20 mL of water and stir at room temperature for 20 min to obtain ferric nitrate solution; Step (2): Dissolve 2 mmol of ammonium metavanadate in 20 mL of water, heat and stir at 60 °C for 30 min under hydrothermal conditions to obtain an ammonium metavanadate solution; Step (3): Slowly add ferric nitrate solution to ammonium metavanadate solution at a dropping rate of 1 mL / min, add 0.1 g of multi-walled carbon nanotubes, ultrasonically disperse for 1 h, and then stir at room temperature for 2 h to obtain a mixed solution; Step (4): Adjust the pH of the mixture obtained in step (3) to 5 and transfer it to the reactor for hydrothermal reaction. Maintain the temperature at 160℃ and keep it warm for 5 hours. Filter, wash and dry the precipitate to obtain multi-walled carbon nanotube-doped iron vanadium oxide. Grind and refine the precipitate and pass it through a 500-mesh sieve to obtain the precursor. Step (5): The precursor obtained in step (4) is placed in a tube furnace for pre-sintering. A nitrogen / argon protective atmosphere is used to raise the temperature to 800°C at 10°C / min, hold for 2 hours, and then grind and refine it before passing it through a 500-mesh sieve. Step (6): The product from step (5) is placed in a tube furnace for secondary sintering. A nitrogen / argon protective atmosphere is used to raise the temperature to 600°C at 1°C / min and hold for 4 hours.

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