Amorphous MoS 5+x Method for preparing magnesium ion battery cathode material and application

Abstract

The application relates to the field of battery materials and discloses amorphous MoS 5+x A preparation method and application of a positive electrode material. First, ammonium polysulfide molybdate is prepared by using molybdate, a reducing agent and a certain amount of ammonium polysulfide as reaction raw materials; the ammonium polysulfide molybdate is dissolved in deionized water, stirred, then oxalic acid is added dropwise into the solution, continuous stirring is carried out, washing and centrifugation are carried out, and drying is carried out in a vacuum oven to obtain molybdenum polysulfide (MoS 5+x ), which is stored in a dryer and used as a positive electrode material of a magnesium ion battery. The amorphous MoS 5+x The positive electrode material has excellent electrochemical performance, and its super-high reversible capacity, superior coulomb efficiency and long cycle life all exceed those of current mainstream positive electrode materials of magnesium ion batteries. The significant magnesium storage performance of the amorphous MoS 5+x positive electrode material has a wide application prospect in magnesium ion batteries and other electrochemical energy storage devices.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of battery materials, in particular to an amorphous MoS 5+x Preparation method and application of positive electrode material. BACKGROUND

[0002] Lithium-ion batteries have many well-known advantages, such as high energy density, mature manufacturing process and wide application range, but these advantages cannot cover up some performance defects. For example, the power density of lithium-ion batteries performs poorly at high-rate discharge, limiting their performance in applications that require rapid energy release. In addition, due to the risk of thermal runaway of lithium-ion batteries, which may cause the battery to overheat, even cause fire or explosion, the safety problem of lithium-ion batteries has always been a concern. At the same time, due to the limited resources of lithium, the cost of lithium-ion batteries has been high, which has hindered their application in large-scale energy storage to some extent.

[0003] In contrast, magnesium-ion batteries (MIBs for short) are considered as a promising electrochemical energy storage technology due to their unique advantages. First, magnesium is abundant and low in price, which gives magnesium-ion batteries a significant advantage in cost. Second, the environmental friendliness of magnesium-ion batteries is an important reason for their attention, which meets the current pursuit of green and sustainable energy. Most importantly, compared with lithium metal electrodes, magnesium electrodes have little tendency to form dendrites, which can cause short circuits and further safety problems. Therefore, magnesium-ion batteries have a significant advantage in safety.

[0004] These advantages make magnesium-ion batteries a promising electrochemical energy storage device, which may replace traditional lithium-ion batteries in the future, providing safer, more efficient and environmentally friendly energy solutions for large-scale grid energy storage, electric vehicles and portable electronic devices. However, the poor performance of the positive electrode material is currently the weakness of MIBs. Therefore, it is urgent to develop new positive electrode materials to promote its development. The main reason for the poor performance of MIBs positive electrode is the Mg 2+ ion. Mg 2+ + 2+ has two positive charges, resulting in strong interaction with the positive electrode, making it difficult to insert into the positive electrode lattice, causing poor diffusion dynamics. In addition, limited by the crystal structure, the reaction energy barrier of Mg 2+ in the crystalline positive electrode material is significantly enhanced. Compared with crystalline materials, amorphous materials can provide three-dimensional diffusion channels, and the diffusion energy barrier can be effectively reduced to improve the magnesium storage capacity. Compared with MoS2, molybdenum polysulfide has the characteristics of polysulfide, which not only contains S 2- ​​and also contains S2 2- , anions can occur redox reaction at the same time, provide higher storage magnesium capacity, is a promising rechargeable magnesium ion battery anode material. Therefore, amorphous molybdenum polysulfide is considered to be an ideal choice for high-performance rechargeable magnesium ion battery anode material.

[0005] To this end, the present application provides an amorphous MoS 5+x Preparation method and application of magnesium ion battery anode material, so as to realize the performance optimization of magnesium ion battery and obtain high-energy-density magnesium ion battery anode material. SUMMARY

[0006] In view of the deficiencies of the prior art, the present application provides an amorphous MoS 5+x Preparation method of anode material, which can not only improve the performance of magnesium ion battery, but also provide strong technical support for its application in large-scale power grid energy storage, electric vehicles and portable electronic devices.

[0007] To achieve the above object, the present application is realized by the following technical scheme: an amorphous MoS 5+x Preparation method of anode material, comprising the following steps:

[0008] S1: Molybdate, reducing agent and a certain amount of ammonium polysulfide are used as raw materials to prepare ammonium polysulfide molybdate;

[0009] S2: Dissolve ammonium polysulfide molybdate in deionized water, stir, then add oxalic acid dropwise to the above solution, continue to stir, wash and centrifuge, dry in a vacuum oven to obtain molybdenum polysulfide (MoS 5+x ), and store in a desiccator;

[0010] Preferably, in the S1 step, the reducing agent includes but is not limited to hydroxylamine hydrochloride, hydrazine hydrate, sodium borohydride.

[0011] Preferably, in the S2 step, the type of acid includes but is not limited to oxalic acid, hydrochloric acid, glacial acetic acid.

[0012] Preferably, a magnesium ion battery, the positive electrode of the magnesium ion battery is composed of an amorphous MoS 5+x Anode material.

[0013] Preferably, the negative electrode of the magnesium ion battery includes but is not limited to magnesium metal, magnesium alloy.

[0014] Preferably, the electrolyte of the battery is an electrolyte suitable for magnesium ion battery, including but not limited to (PhMgCl)2-AlCl3 / THF electrolyte, Mg(TFSI)2-MgCl2 electrolyte, (R-PhOMgCl)2-AlCl3 / THF electrolyte.

[0015] Preferably, the battery is in 0.1Ag -1 At that current density, after 90 charge-discharge cycles, it can provide 685mAh g. -1 It has reversible capacity and a coulombic efficiency ≥95% during charge and discharge processes, at 1Ag -1 At a rate increase of [value missing], the specific capacity remains at 200mAh g. -1 above.

[0016] This invention provides amorphous MoS2 5+x Preparation methods and applications of cathode materials. They possess the following beneficial effects:

[0017] 1. The amorphous MoS₂ of the present invention 5+x The cathode material exhibits outstanding electrochemical performance, with its high reversible capacity, superior coulombic efficiency, and long cycle life surpassing current mainstream magnesium-ion battery cathode materials. This performance optimization enables amorphous MoS₂... 5+x Cathode materials have broad application prospects in high-performance magnesium-ion batteries and other energy storage devices.

[0018] 2. The preparation method of this invention employs a strategy of low-temperature synthesis of the precursor followed by acid addition and stirring, resulting in a simple operation process and easily controllable reaction conditions. This characteristic enables the method to be readily implemented in large-scale production, further improving production efficiency. Attached Figure Description

[0019] Figure 1 MoS2 obtained in Example 1 5+x TEM images of the cathode material; TEM image of the MoS3 cathode material prepared in Comparative Example 1; TEM image of the MoS2 cathode material prepared in Comparative Example 2.

[0020] Figure 2 MoS2 obtained in Example 1 5+x XRD patterns of cathode materials; XRD patterns of MoS3 cathode materials prepared in Comparative Example 1; XRD patterns of MoS2 cathode materials prepared in Comparative Example 2.

[0021] Figure 3 MoS2 obtained in Example 1 5+x Raman spectra of cathode materials; Raman spectra of MoS3 cathode material prepared in Comparative Example 1; Raman spectra of MoS2 cathode material prepared in Comparative Example 2.

[0022] Figure 4 MoS2 obtained in Example 1 5+x EDS spectrum of cathode material.

[0023] Figure 5 MoS2 obtained in Example 1 5+xRate capability plots of full cells assembled with the cathode material of Example 1, the MoS3 cathode material of Comparative Example 1, and the MoS2 cathode material of Comparative Example 2, and metallic magnesium at 0.1 Ag -1 Cycle performance plots.

[0024] Figure 6 MoS3 cathode material of Example 1, the MoS3 cathode material of Comparative Example 1, and the MoS2 cathode material of Comparative Example 2, and metallic magnesium at 0.1 Ag 5+x Rate capability plots of full cells assembled with the cathode material of Example 1, the MoS3 cathode material of Comparative Example 1, and the MoS2 cathode material of Comparative Example 2, and metallic magnesium at 0.1 Ag DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the specification of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0026] Embodiment:

[0027] Please refer to the drawings in the specification of the present application Figure 1 - the drawings in the specification of the present application Figure 6 :

[0028] Embodiment 1:

[0029] First, 8.0 g of ammonium molybdate tetrahydrate and 6.0 g of hydroxylamine hydrochloride were weighed and dissolved in 120 mL of deionized water, and after stirring, they were mixed with 120 mL of ammonium polysulfide solution to obtain a mixed solution. Then, the mixed solution was placed in a 50°C oven for 1 hour, and after standing for 1 hour, it was washed and centrifuged to obtain a filtrate. The filtrate was placed in a 90°C oven for 4 hours, and after standing for 1 hour, it was washed and centrifuged. Next, 40 mL of ammonium polysulfide was added dropwise to the filtrate, and it was stirred vigorously, and after standing for 12 hours, it was filtered to collect ammonium dithiomolybdate raw material, and the black crystals were further washed with 30 mL of ice water, isopropyl alcohol, carbon disulfide, and diethyl ether twice each. Then the black crystals were dried in a vacuum oven at room temperature, and then stored in a desiccator. Finally, 0.15 g of ammonium dithiomolybdate was dissolved in 50 mL of deionized water, and 12.5 mL of 1M oxalic acid was added dropwise to the above solution, which was stirred for 2 hours, centrifuged and dried to prepare amorphous MoS3 5+x material.

[0030] Embodiment 2:

[0031] First, 8.0 g of ammonium molybdate tetrahydrate and 6.0 g of hydroxylamine hydrochloride were dissolved in 120 mL of deionized water, and after stirring, they were mixed with 120 mL of ammonium polysulfide solution to obtain a mixed solution. Then, the mixed solution was placed in a 50°C oven for 1 hour, and after standing for 1 hour, it was washed and centrifuged to obtain a filtrate. The filtrate was placed in a 90°C oven for 4 hours, and after standing for 1 hour, it was washed and centrifuged. Next, 40 mL of ammonium polysulfide was added dropwise to the filtrate, and after stirring vigorously, it was allowed to stand for 12 hours. After that, the ammonium dithiomolybdate raw material was collected by filtration, and the black crystals were further washed with 30 mL of ice water, isopropyl alcohol, carbon disulfide, and diethyl ether twice each. Then, the black crystals were dried in a vacuum oven at room temperature, and then stored in a desiccator. Finally, 0.15 g of ammonium dithiomolybdate was dissolved in 50 mL of deionized water, and 12.5 mL of 1M glacial acetic acid was added dropwise to the above solution, stirred for 2 hours, and centrifuged and dried to prepare amorphous MoS5 cathode material. 5+x material.

[0032] Example 3:

[0033] First, 8.0 g of ammonium molybdate tetrahydrate and 6.0 g of hydroxylamine hydrochloride were dissolved in 120 mL of deionized water, and after stirring, they were mixed with 120 mL of ammonium polysulfide solution to obtain a mixed solution. Then, the mixed solution was placed in a 50°C oven for 1 hour, and after standing for 1 hour, it was washed and centrifuged to obtain a filtrate. The filtrate was placed in a 90°C oven for 4 hours, and after standing for 1 hour, it was washed and centrifuged. Next, 40 mL of ammonium polysulfide was added dropwise to the filtrate, and after stirring vigorously, it was allowed to stand for 12 hours. After that, the ammonium dithiomolybdate raw material was collected by filtration, and the black crystals were further washed with 30 mL of ice water, isopropyl alcohol, carbon disulfide, and diethyl ether twice each. Then, the black crystals were dried in a vacuum oven at room temperature, and then stored in a desiccator. Finally, 0.15 g of ammonium dithiomolybdate was dissolved in 50 mL of deionized water, and 12.5 mL of 1M glacial acetic acid was added dropwise to the above solution, stirred for 2 hours, and centrifuged and dried to prepare amorphous MoS5 cathode material. 5+x material.

[0034] Summary: The above three examples describe in detail the method of successfully preparing MoS5 cathode material using different reducing agents and acids. These examples show that the preparation method of the present invention has the advantages of simple operation, mild reaction conditions, high product purity, and high yield, and can effectively prepare amorphous MoS5 cathode material with excellent electrochemical performance, which is suitable for energy storage fields such as magnesium ion batteries. 5+x

[0035] Comparative Example 1:

[0036] ​Into a 500 mL flask, 7 g of ammonium molybdate tetrahydrate, 30 mL of water, ammonia water were placed, stirred at 70 °C oil bath for 60 min, poured into 550 mL of ammonium sulfide solution, added at 70 °C oil bath for 2 h, the solution was red, cooled, filtered with isopropyl alcohol, diethyl ether, (NH4)2MoS4was obtained. 4， Into 20 mL of deionized water, 70 mL of (NH4)2MoS4was added and stirred for 1 hour, HCl was added dropwise into the above solution until the PH was equal to 3, stirred for 2 hours, centrifuged and dried to prepare amorphous MoS3cathode material.

[0037] Comparative Example 2:

[0038] Into 50 mL of deionized water, 60 mg of ammonium molybdate tetrahydrate was added, after ultrasonic for 5 min, 1.7 mL of hydrazine hydrate was added into the above solution, then stirred for 20 min, then the dark red solution was quickly transferred into a 50 mL reactor, reacted in a 150 °C oven for 6 hours, finally washed with water and ethanol for 5 times to prepare amorphous MoS2cathode material.

[0039] The cathode materials obtained in Examples 1-3 and Comparative Example 1 were mixed with acetylene black and PVDF in a weight ratio of 7:2:1 to form a slurry, the slurry was evenly coated on a copper foil, the electrode sheet was cut and pressed to obtain an electrode sheet, which was directly used as a positive electrode, a magnesium sheet was used as a negative electrode, and an organic electrolyte was (PhMgCl)2-AlCl3 / THF electrolyte containing 1-butyl-1-methylpyridinium chloride ([BMP]Cl), and a button cell was assembled.

[0040] Figure 1 The MoS3cathode material obtained in Example 1 was used as a positive electrode material. 5+x TEM images of the positive electrode material (a), (b), the MoS3cathode material obtained in Comparative Example 1 (c), (d), and the MoS2cathode material obtained in Comparative Example 2 (e), (f). The materials in a, b were uniform nanoparticles with a diameter of about 12-58 nm, the materials in c, d were also uniform nanoparticles with a diameter of about 12-52 nm, the size was comparable, and the materials in e, f were uniform nanospheres assembled by nanosheets with an average size of 80-100 nm.

[0041] Figure 2 The MoS3cathode material obtained in Example 1 was used as a positive electrode material. 5+x XRD patterns of the positive electrode material, the MoS3cathode material obtained in Comparative Example 1, and the MoS2cathode material obtained in Comparative Example 2. It can be seen from the XRD pattern results that MoS3, MoS3, and MoS2 all have amorphous characteristics. 5+x

[0042] Figure 3 ​MoS2 obtained in Example 1 5+x Raman spectra of the cathode materials, the Raman spectra of the MoS3 cathode material obtained in Comparative Example 1, and the Raman spectra of the MoS2 cathode material obtained in Comparative Example 2. As can be seen from the figures, amorphous MoS2... 5+x 130 to 250 cm in Raman diagram -1 The Raman peaks are attributed to Mo-Mo stretching vibrations, 250 to 400 cm⁻¹. -1 The Raman peak is attributed to the Mo-S stretching vibration. In the Raman spectrum of amorphous MoS3, it is located at 277 cm⁻¹. -1 and 347cm -1 The two Raman peaks are attributed to the Mo-S stretching vibrations in MoS3. The Raman vibration peaks of amorphous MoS2 are different, located at 140 cm⁻¹. -1 188cm -1 and 339cm -1 The J1, J2, and J3 modes correspond to the metallic 1T phase, while the other three are located at 275.7 cm⁻¹. -1 370cm -1 and 400cm -1 The three peaks correspond to the E1g, E2g, and A1g vibrational modes of the semiconductor 2H phase.

[0043] Figure 4 MoS2 obtained in Example 1 5+x EDS spectra of the cathode material. The EDS results show that the molybdenum-sulfur molar ratio of this cathode material is 1:5.7, confirming the polysulfide-rich characteristics of MoS₂. 5+x Successful preparation.

[0044] Figure 5 MoS2 obtained in Example 1 5+x Button batteries assembled with magnesium oxide using the following cathode materials: MoS3 cathode material obtained in Comparative Example 1 and MoS2 cathode material obtained in Comparative Example 2, in 0.1 Ag... -1 The current density cycling performance graph after 90 cycles of Mg 2+ Embedding / Extraction, MoS₂ obtained in Example 1 5+x The cathode material can still provide 685mAh g -1 The ultra-high reversible capacity is significantly higher than the 350 mAh g⁻¹ provided by the MoS₃ cathode material in Comparative Example 1. -1 Compared with the MoS2 cathode material of Comparative Example 2, which provides 239 mAh g⁻¹ -1 This indicates that the increase in the number of sulfide ions plays a key positive role in improving magnesium storage capacity.

[0045] Figure 6 MoS2 obtained in Example 1 5+xThe coin cells assembled with the positive material of MoS3 obtained in Comparative Example 1 and metal magnesium were subjected to 90 cycle rate performance tests at different current densities, and the MoS3 positive material had the best rate performance (even at a rate of 1 A g 5+x -1, the specific capacity was still 200 mAh g -1 -1, which was significantly better than the MoS3 prepared in Comparative Example 1 and the MoS2 prepared in Comparative Example 2. -1

[0046] Although embodiments of the present application have been described, it is understood that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents.​

Claims

1. Amorphous MoS 5+x A method for producing a positive electrode material, characterized by, Comprise the following steps: S1: take molybdate, reducing agent and a certain amount of ammonium polysulfide as reaction raw materials to prepare ammonium polysulfide molybdate; S2: Dissolve ammonium molybdate polysulfide in deionized water, stir, then add oxalic acid dropwise to the above solution, continue to stir, wash and centrifuge, dry in a vacuum oven, obtain molybdenum polysulfide MoS 5+x , store in a desiccator; In the S2 step, the stirring time of the oxalic acid after being added into the ammonium polysulfide molybdate solution is 1.5-2 hours. In the S1 step, the reducing agent comprises hydroxylamine hydrochloride, hydrazine hydrate or sodium borohydride.

2. A magnesium-ion battery, characterized by, The positive electrode of the magnesium ion battery is prepared from the amorphous MoS 5+x Positive electrode material composition.

3. The magnesium-ion battery of claim 2, wherein, The negative electrode of the magnesium ion battery is magnesium metal or magnesium alloy.

4. The magnesium-ion battery of claim 2, wherein, The electrolyte of the battery is an electrolyte suitable for magnesium ion batteries.

5. The magnesium-ion battery of claim 4, wherein, The battery can provide a high reversible capacity of 685mAh g -1 after 90 charge-discharge cycles at a current density of 0.1Ag -1 , and the coulombic efficiency in the charge-discharge process is ≥95%, and the specific capacity is still 200mAh g -1 above at a rate of 1Ag -1 .

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