A weakly crystalline molybdenum disulfide embedded mesoporous carbon pore material and its preparation method and application

Abstract

The present invention discloses a weakly crystalline molybdenum disulfide embedded mesoporous carbon pore material, its preparation method and application. The solvothermal confinement growth method is adopted, including: adding sodium molybdate dihydrate and mesoporous carbon into a solvent and mixing evenly, slowly evaporating the solvent under the condition of water / oil bath to obtain a sodium molybdate / mesoporous carbon precursor. This precursor and a sulfur source are added to a non-polar solvent in proportion, and the mixture is placed in a high-pressure reaction kettle and heated and reacted at 150-250 °C for 6-30 hours. After the reaction, centrifugation or filtration is carried out, and the obtained black precipitate is washed with deionized water and ethanol, and dried overnight in vacuo at 100 °C to obtain a few-layer weakly crystalline molybdenum disulfide embedded mesoporous carbon pore material. The above pore material of the present invention has advantages such as high initial Coulomb efficiency, obvious charge-discharge voltage plateau, high specific capacity and good cycling performance as the anode material of lithium / sodium ion batteries. Among them, the solvothermal confinement growth method has the advantages of simple operation, easy process control and high yield.

Description

Technical Field

[0001] The present invention belongs to the field of lithium / sodium ion battery materials, and particularly relates to a weakly crystalline molybdenum disulfide embedded mesoporous carbon pore material, a preparation method thereof, and an application thereof. Background Art

[0002] Energy storage technology is an important driving force for promoting the development of the new energy industry and is also an important foundation for supporting the wide application of new energy in the fields of transportation, electricity, industry, etc. Lithium-ion batteries are the main energy storage technology in the current market, widely used in mobile devices such as mobile phones and laptop computers, and gradually developing towards large-scale energy storage fields such as electric vehicles. However, with the continuous development of advanced electronic devices and electric transportation systems, traditional lithium-ion batteries are difficult to meet people's energy demands due to the limited lithium storage specific capacity of their electrodes, and the increasingly scarce available lithium resources and rising prices greatly limit their application in large-scale energy storage fields. Therefore, it is urgent to develop high-performance lithium-ion batteries and new battery energy storage systems.

[0003] In recent years, sodium-ion batteries have been considered as one of the most promising energy storage devices in the field of large-scale energy storage due to reasons such as rich sodium resources. As an important component of lithium / sodium ion batteries, electrode materials are the main factors determining their performance. Exploring electrode materials with high lithium and sodium storage specific capacities has become the key to developing high-performance lithium / sodium ion batteries.

[0004] Transition metal sulfide molybdenum disulfide has attracted much attention from scientific researchers as an electrode material due to its unique two-dimensional structure, flat discharge platform, high theoretical specific capacity, and low cost. In particular, its few-layer weakly crystalline structure can significantly promote the rapid insertion and extraction of alkali metal ions, as well as the full contact between the electrode and the electrolyte and effectively weaken the metal-sulfur bond binding energy, thus being more conducive to the progress of electrochemical reactions. However, when molybdenum disulfide is used as a lithium / sodium ion battery material, it often causes material pulverization due to its poor electrical conductivity and large volume changes during charge and discharge processes, which in turn leads to attenuation of lithium and sodium storage capacities. Embedding molybdenum disulfide in the carbon pores of mesoporous carbon is an effective strategy to solve its capacity attenuation problem. The carbon pore walls surrounding molybdenum disulfide can effectively alleviate the volume changes of the active material during charge and discharge processes, and carbon materials can improve the electronic conductivity of the overall electrode material. Summary of the Invention

[0005] Aiming at the above technical problems, the main object of the present invention is to provide a weakly crystalline molybdenum disulfide embedded mesoporous carbon pore material, which has the advantages of high initial Coulomb efficiency, high specific capacity, and good cycling performance. The formed few-layer weakly crystalline molybdenum disulfide embedded mesoporous carbon pore structure can play the following roles:

[0006] (1) Promote the rapid deintercalation and intercalation of alkali metal ions, ensure sufficient contact between the electrode and the electrolyte, and effectively weaken the metal-sulfur bond binding energy, thereby improving the electrochemistry reaction kinetics;

[0007] (2) Alleviate the volume change of the active material during charge and discharge, and avoid capacity decay during the cycling process;

[0008] (3) Establish a conductive network to improve the electronic conductivity of the overall electrode material.

[0009] Another object of the present invention is to provide a preparation method of the above-mentioned weakly crystalline molybdenum disulfide embedded in mesoporous carbon pore materials, which is simple to operate and the process is easy to control.

[0010] Another object of the present invention is to provide the application of the above-mentioned weakly crystalline molybdenum disulfide embedded in mesoporous carbon pore materials as or in the preparation of lithium / sodium ion battery anode materials, which has good lithium / sodium storage performance as lithium / sodium ion battery anode materials.

[0011] The above objects of the present invention are achieved by the following technical solutions:

[0012] The present invention provides a weakly crystalline molybdenum disulfide embedded in mesoporous carbon pore material, which has a three-dimensional interconnected tubular structure, wherein the molybdenum disulfide is embedded in the mesoporous carbon pore structure in a few-layer weakly crystalline crystal structure, and is prepared by a solvothermal confinement growth method.

[0013] The present invention also provides a preparation method of the above-mentioned weakly crystalline molybdenum disulfide embedded in mesoporous carbon pore material, which adopts a solvothermal confinement growth method and includes the following steps:

[0014] Step 1: Sodium molybdate dihydrate and mesoporous carbon are added to a solvent in a mass ratio of 5:1 - 1:10 and mixed evenly. Under the condition of water / oil bath, the solvent in the above mixture is slowly evaporated to dryness to obtain a sodium molybdate / mesoporous carbon precursor;

[0015] Step 2: The sodium molybdate / mesoporous carbon precursor obtained in Step 1 and a sulfur source are added to a non-polar solvent in a mass ratio of 2:1 - 1:10. The obtained mixture is placed in a high-pressure reaction kettle and heated and reacted at 150 - 250 °C for 6 - 30 hours. After the solvothermal reaction is completed, the black precipitate is obtained by centrifugation or filtration and washed with deionized water and ethanol, and dried overnight in vacuum at 100 °C to obtain the product.

[0016] Preferably, in Step 1, the solvent is deionized water and / or absolute ethanol.

[0017] Preferably, in Step 2, the sulfur source is selected from one or more combinations of thioacetamide, thiourea, and L-cysteine.

[0018] Preferably, in step 2, the non-polar solvent is selected from one or more combinations of n-hexane, isooctane, benzene, toluene, carbon tetrachloride, and dichloromethane.

[0019] The present invention also provides the application of the above-mentioned weakly crystalline molybdenum disulfide embedded in mesoporous carbon channels material as or in the preparation of a negative electrode material for lithium / sodium ion batteries.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] In the present invention, molybdenum disulfide is embedded in mesoporous carbon channels in a few-layer weakly crystalline structure. Using it as a negative electrode material for lithium / sodium ion batteries has the advantages of high initial Coulomb efficiency, obvious charge and discharge voltage platforms, high specific capacity, and good cycle performance. At the same time, the solvothermal confinement growth preparation method is adopted, which is simple in operation, easy to control in process, and has a high yield, with strong practicability. Description of the Drawings

[0022] Figure 1 It is a scanning electron microscope image of the few-layer weakly crystalline molybdenum disulfide embedded in mesoporous carbon channels material in Example 1.

[0023] Figure 2 It is a transmission electron microscope image of the few-layer weakly crystalline molybdenum disulfide embedded in mesoporous carbon channels material in Example 1.

[0024] Figure 3 It is a transmission electron microscope selected area electron diffraction pattern of the few-layer weakly crystalline molybdenum disulfide embedded in mesoporous carbon channels material in Example 1.

[0025] Figure 4 It is a charge and discharge performance graph of lithium storage of the few-layer weakly crystalline molybdenum disulfide embedded in mesoporous carbon channels material in Example 2.

[0026] Figure 5 It is a cycle performance graph of lithium storage of the few-layer weakly crystalline molybdenum disulfide embedded in mesoporous carbon channels material in Example 2.

[0027] Figure 6 It is a charge and discharge curve graph of sodium storage of the few-layer weakly crystalline molybdenum disulfide embedded in mesoporous carbon channels material in Example 3.

[0028] Figure 7 It is a cycle performance graph of sodium storage of the few-layer weakly crystalline molybdenum disulfide embedded in mesoporous carbon channels material in Example 3.

[0029] Figure 8 It is a transmission electron microscope image of nickel sulfide embedded in mesoporous carbon channels material in Example 4. Detailed Embodiments

[0030] The present invention will be further described below in conjunction with specific embodiments and the accompanying drawings. These embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0031] Example 1

[0032] In this example, a few-layer weakly crystalline molybdenum disulfide embedded mesoporous carbon channel material was prepared as follows:

[0033] First step: 0.5 g of sodium molybdate dihydrate and 0.5 g of mesoporous carbon CMK-3 were added to 50 mL of deionized water and ultrasonically mixed evenly. Under the condition of heating and vacuumizing in a water bath at 60 °C, the solvent in the above mixture was slowly evaporated to dryness to obtain a sodium molybdate / mesoporous carbon precursor.

[0034] Second step: 0.3 g of the precursor obtained in the first step and 0.6 g of thioacetamide were added to 60 mL of n-hexane solvent. The above mixture was placed in a high-pressure reaction kettle and heated and reacted at 180 °C for 24 hours. After the reaction kettle was cooled to room temperature, it was centrifuged at 9000 rpm and washed four times with deionized water and ethanol to obtain a black precipitate. The black precipitate was dried overnight in a vacuum at 100 °C to obtain the product.

[0035] It can be seen from Figure 1-3 that this material is a three-dimensional interconnected tubular structure ( Figure 1 ), the pore structure of the mesoporous carbon is basically intact, and a few-layer weakly crystalline molybdenum disulfide exists inside the pipeline ( Figure 2 and 3 ).

[0036] Example 2

[0037] The few-layer weakly crystalline molybdenum disulfide embedded mesoporous carbon channel material prepared in Example 1, binder polyvinylidene fluoride (PVDF), and conductive agent (Super-P) were ground and dispersed in N-methylpyrrolidone solvent in a mass ratio of 80:10:10 to make a slurry. The slurry was evenly coated on a 9-μm-thick copper foil by a coater, and then heated and dried in an oven at 30 °C. After drying was completed, the copper foil coated with the slurry was cut into a circular electrode sheet with a diameter of 14 mm by a mechanical slicer, and the active material loading on the electrode sheet was about 1.2 mg. A lithium metal sheet was used as the counter electrode, glass fiber (Whatman) was used as the separator, and lithium hexafluorophosphate (1 M, LiPF 6 ) dissolved in a mixed solvent of ethylene carbonate, diethyl carbonate, and ethyl methyl carbonate with a mass ratio of 1:1:1 was used as the electrolyte, and a CR2032 coin cell was assembled in a glove box with the contents of water and oxygen both less than 0.5 ppm. After the coin cell was stationary for 10 h, the electrochemical performance was tested by a Blue Power battery tester (Land2001A) (voltage range: 0.005 - 3 V).

[0038] Figure 4 When the prepared few-layer weakly crystalline molybdenum disulfide embedded mesoporous carbon channel material is used as the anode material of a lithium-ion battery, the charge-discharge curve at a current density of 100 mA / g shows that the first reversible specific capacity of this material is as high as 1005 mAh / g, and the first Coulombic efficiency is 74.87%; Figure 5 This is the corresponding cycle performance curve of this material. After 100 cycles at a current density of 100 mA / g, the reversible specific capacity can reach 1100 mAh / g, and the capacity retention rate is 109.5%, showing excellent cycle performance.

[0039] Example 3

[0040] The few-layer weakly crystalline molybdenum disulfide embedded mesoporous carbon channel material prepared in Example 1, binder polyvinylidene fluoride (PVDF), and conductive agent (Super-P) were ground and dispersed in N-methylpyrrolidone solvent in a mass ratio of 80:10:10 to form a slurry. The slurry was evenly coated on a 9-μm thick copper foil using a coater, and then dried by heating in an oven at 30 °C. After drying, the copper foil coated with the slurry was cut into circular electrode sheets with a diameter of 14 mm using a mechanical slicer, and the active material loading on the electrode sheets was about 1.2 mg. Using a sodium metal sheet as the counter electrode, a glass fiber (Whatman) as the separator, and sodium perchlorate (1 M, NaClO 4 ) dissolved in a mixed solvent of propylene carbonate and ethylene carbonate with a mass ratio of 1:1 as the electrolyte, and assembled into a CR2032 coin cell in a glove box with the contents of water and oxygen both less than 0.5 ppm. After the coin cell was left stationary for 10 h, electrochemical performance tests (voltage range: 0.005 - 3 V) were carried out using a Blue Power battery tester (Land2001A).

[0041] Figure 6 When the prepared few-layer weakly crystalline molybdenum disulfide embedded mesoporous carbon channel material is used as the anode material of a sodium-ion battery, the charge-discharge curve at a current density of 50 mA / g shows that the first reversible specific capacity of this material is as high as 504 mAh / g, and the first Coulombic efficiency is 68.52%; Figure 7 This is the corresponding cycle performance curve of this material. After 100 cycles at a current density of 50 mA / g, the reversible specific capacity can reach 428.5 mAh / g, and the capacity retention rate is 85%, showing excellent cycle performance.

[0042] Example 4

[0043] In this example, a nickel sulfide embedded mesoporous carbon channel material was prepared by a solvothermal confinement growth method, specifically as follows:

[0044] Step 1: Add 0.5 g of nickel chloride and 0.5 g of mesoporous carbon CMK-3 into 50 mL of deionized water, ultrasonically mix them evenly, and under the condition of heating and vacuumizing in a water bath at 60 °C, slowly evaporate the solvent in the above mixture to dryness to obtain a nickel chloride / mesoporous carbon precursor.

[0045] Step 2: Take 0.3 g of the precursor obtained in the first step and 0.6 g of thioacetamide and add them into 60 mL of n-hexane solvent. Place the above mixture in a high-pressure reactor and heat it at 180 °C for 24 hours. After the reactor cools down to room temperature, centrifuge at 9000 rpm and wash it four times with deionized water and ethanol to obtain a black precipitate. The black precipitate is dried overnight in vacuo at 100 °C to obtain a nickel sulfide-embedded mesoporous carbon channel material.

[0046] Figure 8 It is the transmission electron micrograph of the prepared nickel sulfide-embedded mesoporous carbon channel material. It can be seen that some of the mesoporous carbon channels are deformed due to the embedding of nickel sulfide. Different from the three-dimensional interconnected tubular structure of the few-layer weakly crystalline molybdenum disulfide-embedded mesoporous carbon channel material prepared in Example 1, it further proves that the few-layer weakly crystalline molybdenum disulfide-embedded mesoporous carbon channel material prepared by the present invention has the advantages of high initial Coulomb efficiency, high specific capacity and good cycle performance when used as the anode material of lithium / sodium ion batteries.

[0047] The above description of the embodiments is to enable those of ordinary skill in the art to understand and use the present invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative labor. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art according to the principles of the present invention without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. Preparation method of weakly crystalline molybdenum disulfide embedded mesoporous carbon channel material, characterized in that, it is prepared by solvothermal confinement growth method, including the following steps: Step 1: Sodium molybdate dihydrate and mesoporous carbon with a mass ratio of 5:1 - 1:10 are added to a solvent and mixed evenly. Under the condition of water / oil bath, the solvent in the above mixture is slowly evaporated to dryness to obtain a sodium molybdate / mesoporous carbon precursor; Step 2: The sodium molybdate / mesoporous carbon precursor obtained in Step 1 and a sulfur source are added to a non-polar solvent according to a mass ratio of 2:1 - 1:

10. The obtained mixture is put into a high-pressure reactor and heated and reacted at 150 - 250 °C for 6 - 30 hours. After the solvothermal reaction ends, the black precipitate is obtained by centrifugation or filtration and then washed with deionized water and ethanol, and dried overnight in vacuum at 100 °C to obtain; the sulfur source is selected from one or a combination of two or more of thioacetamide, thiourea, and L-cysteine; the non-polar solvent is selected from one or a combination of two or more of n-hexane, isooctane, benzene, toluene, carbon tetrachloride, and dichloromethane.

2. Weakly crystalline molybdenum disulfide embedded mesoporous carbon channel material, characterized in that, it is prepared by the preparation method of the weakly crystalline molybdenum disulfide embedded mesoporous carbon channel material described in Claim 1. The weakly crystalline molybdenum disulfide embedded mesoporous carbon channel material has a three-dimensional interconnected tubular structure, wherein molybdenum disulfide is embedded in the mesoporous carbon channel in a few-layer weakly crystalline crystal structure.

3. Application of the weakly crystalline molybdenum disulfide embedded mesoporous carbon channel material described in Claim 2 in the preparation of anode materials for lithium / sodium ion batteries.

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