A method for preparing molybdenum sulfide-doped hard carbon composite material

Abstract

The present invention discloses a method for preparing a molybdenum sulfide-doped hard carbon composite material, comprising: adding 1-5 parts of ammonium tetramolybdate to an organic solvent to form a 1-10wt% solution, then adding 100 parts of a 1-5wt% graphene oxide solution and 1-5% formic acid ethyl sulfide to disperse evenly, reacting at a temperature of 100-200°C for 1-6h, and then freeze-drying at a temperature of 40°C for 24h to obtain a porous molybdenum sulfide / graphene compound; adding the porous molybdenum sulfide / graphene compound to a 1-10wt% starch solution, dispersing evenly, spray-drying at an inlet temperature of 150°C, an outlet temperature of 80°C, and a flow rate of 1L / h, and then transferring to a tubular furnace. Under an inert atmosphere, the temperature is first raised to 500-800°C and maintained for 1-6h, then raised to 1000-1800°C, and sintered for 1-10h to obtain the result. The present invention can improve the energy density, fast charging performance, and cycle performance of hard carbon.

Description

Technical Field

[0001] The invention belongs to the field of secondary battery material preparation, and specifically relates to a method for preparing a molybdenum sulfide-doped hard carbon composite material. Background Art

[0002] At present, the negative electrode materials of sodium ion batteries on the market are mainly based on biomass hard carbon, but they have low specific capacity (300mAh / g) and low compaction density (1.0g / cm3), which results in low energy density. Although alloy materials such as molybdenum sulfide have high specific capacity and large interlayer spacing, the electronic conductivity of the material itself is poor and cannot be used purely. In addition, the expansion rate of the material after sodium embedding is also high, resulting in poor cycle performance. Therefore, it is necessary to dope it with hard carbon with high electronic conductivity and low expansion rate to give full play to their respective advantages and improve the energy density, fast charging performance and cycle performance of the material. For example, Chinese patent application No. 202210928908.3 discloses a sodium ion battery hard carbon-molybdenum disulfide negative electrode material and its preparation method. The material uses a hard carbon material coated with molybdenum disulfide as a structure to improve conductivity and cycle performance, but the preparation process is complicated and difficult to control, and molybdenum disulfide has a non-fluffy structure, which causes it to expand greatly, and the improvement of the cycle is not large. Summary of the Invention

[0003] The purpose of the present invention is to overcome the above-mentioned shortcomings and provide a method for preparing a molybdenum sulfide-doped hard carbon composite material that can improve the energy density and fast charging performance of hard carbon while taking into account the cycle performance.

[0004] A method for preparing a molybdenum sulfide-doped hard carbon composite material of the present invention comprises the following steps:

[0005] Step S1: According to the mass ratio of ammonium tetramolybdate: graphene oxide solution: ethyl formate sulfide = 1-5:100:1-5, 1-5 parts of ammonium tetramolybdate are added to an organic solvent to prepare a 1-10wt% solution, and then 100 parts of a 1-5wt% graphene oxide solution and 1-5 parts of ethyl formate sulfide are added and evenly dispersed, and the mixture is reacted at a temperature of 100-200°C for 1-6h, and then freeze-dried at a temperature of -40°C for 24h to obtain a porous molybdenum sulfide / graphene compound;

[0006] Step S2: According to the ratio of porous molybdenum sulfide / graphene compound to starch = 1-10:100, the porous molybdenum sulfide / graphene compound is added to a starch solution with a mass concentration of 1-10wt%, dispersed evenly, spray dried (inlet temperature 150°C, outlet temperature 80°C, flow rate 1L / h), and then transferred to a tubular furnace. Under an inert atmosphere, the temperature is first raised to 500-800°C and kept for 1-6h, then raised to 1000-1800°C, and the sintering time is 1-10h to obtain a molybdenum sulfide-doped hard carbon composite material.

[0007] The above-mentioned method for preparing a molybdenum sulfide-doped hard carbon composite material, wherein: the starch in step S1 is one of erythrocyte starch, corn starch, wheat starch, potato starch or pea starch.

[0008] Compared with the prior art, the present invention has obvious beneficial effects. From the above technical scheme, it can be seen that the molybdenum sulfide / graphene composite generated by the chemical method in the present invention has a porous structure, has the characteristics of low expansion, high electronic conductivity and high specific capacity, and is evenly mixed with the hard carbon precursor (starch), giving full play to the characteristics of the hard carbon itself with low expansion rate and good cycle performance, and the characteristics of molybdenum sulfide graphene with high specific capacity and high electronic conductivity, thereby improving the energy density of the material and its cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is the SEM image of the molybdenum sulfide-doped hard carbon composite material prepared in Example 1. DETAILED DESCRIPTION

[0010] Example 1:

[0011] A method for preparing a molybdenum sulfide-doped hard carbon composite material of the present invention comprises the following steps:

[0012] Step S1: 30 g of ammonium tetramolybdate was added to 150 g of ammonia water to prepare a 5 wt% solution, followed by adding 100 g of a 2 wt% graphene oxide solution and 3 g of ethyl formate sulfide to disperse evenly, and then subjected to a hydrothermal reaction at 150° C. for 3 h, followed by freeze drying at −40° C. for 24 h to obtain a porous molybdenum sulfide / graphene compound;

[0013] Step S2: Add 5 g of porous molybdenum sulfide / graphene compound to a 5 wt% erythrocyte starch solution with a mass concentration of 2000 g, disperse evenly, and spray dry (inlet temperature 150 ° C, outlet temperature 80 ° C, flow rate 1 L / h); the resulting material is transferred to a tubular furnace and first heated to 600 ° C and kept warm for 3 hours under an argon inert atmosphere, then heated to 1400 ° C and sintered for 5 hours to obtain.

[0014] Example 2:

[0015] A method for preparing a molybdenum sulfide-doped hard carbon composite material of the present invention comprises the following steps:

[0016] Step S1: 1 g of ammonium tetramolybdate was added to 100 g of ammonia water to prepare a 1 wt% solution, followed by adding 100 g of a 1 wt% graphene oxide solution and 1 g of ethyl formate sulfide to disperse evenly, and then subjected to a hydrothermal reaction at 100 ° C for 6 h, followed by freeze drying at -40 ° C for 24 h to prepare a porous molybdenum sulfide / graphene compound;

[0017] Step S2: Add 1 g of porous molybdenum sulfide / graphene compound to a 1 wt% wheat starch solution with a mass concentration of 10,000 g, disperse evenly, and spray dry (inlet temperature 150°C, outlet temperature 80°C, flow rate 1 L / h); the resulting material is transferred to a tubular furnace and first heated to 500°C under an argon inert atmosphere for 6 hours, then heated to 1000°C, and sintered for 10 hours.

[0018] Example 3:

[0019] A method for preparing a molybdenum sulfide-doped hard carbon composite material of the present invention comprises the following steps:

[0020] Step S1: 5 g of ammonium tetramolybdate was added to 500 g of ammonia water to prepare a 10 wt% solution, and then 100 g of a 5 wt% graphene oxide solution and 5 g of ethyl formate sulfide were added and dispersed evenly, and the mixture was subjected to a hydrothermal reaction at 200 ° C for 1 h, and then freeze-dried at -40 ° C for 24 h to obtain a porous molybdenum sulfide / graphene compound;

[0021] Step S2: Add 10g of porous molybdenum sulfide / graphene compound to 1000g of wheat starch solution with a mass concentration of 10wt%, disperse evenly, and spray dry (inlet temperature 150°C, outlet temperature 80°C, flow rate 1L / h); the obtained material is transferred to a tubular furnace and first heated to 800°C under an inert atmosphere for 1h, then heated to 1800°C and sintered for 1h to obtain a molybdenum sulfide-doped hard carbon composite material.

[0022] Comparative Example 1:

[0023] A method for preparing a graphene-doped hard carbon composite material, comprising:

[0024] Unlike Example 1, ammonium tetramolybdate and ethyl formate sulfide were not added, and molybdenum sulfide was not formed. The detailed preparation process was as follows: 100 g of a 3 wt% graphene oxide solution and 2000 g of a 5 wt% erythrocyte starch solution were evenly dispersed and spray-dried (inlet temperature 220°C, outlet temperature 100°C, flow rate 1 L / h). The resulting material was transferred to a tube furnace and heated to 600°C under an argon inert atmosphere for 3 hours, then to 1400°C and sintered for 5 hours to obtain a graphene-doped hard carbon composite material.

[0025] Comparative Example 2:

[0026] A method for preparing a molybdenum sulfide / graphene-doped hard carbon composite material, comprising:

[0027] The difference from Example 1 is that molybdenum sulfide is used instead of porous molybdenum sulfide. The detailed preparation process is as follows: 10g of molybdenum sulfide is added to 1000g of a 1wt% graphene solution and spray-dried (inlet temperature 220°C, outlet temperature 100°C, flow rate 1L / h) to obtain a molybdenum sulfide / graphene composite; 5g of the molybdenum sulfide / graphene compound complex is added to 2000g of a 5wt% erythrocyte starch solution, uniformly dispersed, and spray-dried (inlet temperature 150°C, outlet temperature 80°C, flow rate 1L / h); the resulting material is transferred to a tubular furnace and heated to 600°C under an argon inert atmosphere for 3h, then heated to 1400°C and sintered for 5h to obtain a molybdenum sulfide / graphene-doped hard carbon composite material.

[0028] Test example:

[0029] 1. SEM test

[0030] The molybdenum sulfide doped hard carbon composite material prepared in Example 1 was subjected to SEM testing, and the results were as follows: Figure 1 As shown in the figure, it can be seen that the hard carbon material prepared in Example 1 has a granular structure with uniform size distribution. The bright surface is a porous molybdenum sulfide compound with a particle size of 5-10 μm.

[0031] 2. Physical and chemical properties and button battery testing

[0032] The molybdenum sulfide-doped hard carbon composite materials prepared in Examples 1-3 and Comparative Examples 1-2 were tested for powder conductivity, tap density, specific surface area, trace element content (molybdenum) and specific capacity, and the interlayer spacing of the materials was tested by XRD.

[0033] Test method: GBT-24533-2019 "Graphite anode materials for lithium-ion batteries".

[0034] The molybdenum sulfide-doped hard carbon composite materials obtained in Examples 1-3 and Comparative Examples 1-2 were respectively assembled into button batteries A1, A2, A3, B1, and B2; the preparation method thereof was as follows: a binder, a conductive agent, and a solvent were added to the negative electrode material, stirred to make a slurry, coated on a copper foil, and dried and rolled to obtain the result. The binder used is LA132 binder, the conductive agent SP, the negative electrode material is the hard carbon material prepared in Examples 1-3 and Comparative Examples 1-2, respectively, the solvent is double distilled water, and the ratio is: negative electrode material: SP: LA132: double distilled water = 94g: 2g: 4g: 220mL, and a negative electrode plate is prepared; the electrolyte is NaPF6 / EC+DEC (volume ratio 1: 1, concentration 1.1mol / L), the metal sodium sheet is the counter electrode, and the diaphragm is polyethylene PE, polypropylene PP or polyethylene propylene PEP composite film. The simulated battery assembly is carried out in an argon-filled glove box, and the electrochemical performance is carried out on a Wuhan Blue Electric CT2001A battery tester. The charge and discharge voltage range is 0.00V to 2.0V, and the charge and discharge rate is 0.1C. At the same time, the rate (2C / 0.1C) and cycle performance (0.2C / 0.2C, 200 times) of its button battery are tested. The test results are as shown in Table 1 below:

[0035] Table 1

[0036]

[0037]

[0038] As shown in Table 1, the molybdenum sulfide-doped hard carbon composites prepared in Examples 1-3 exhibit significantly improved initial discharge capacity, initial efficiency, rate capability, and cycle performance compared to the comparative examples. This is because, in the present invention, molybdenum sulfide doping enhances the material's electronic conductivity and specific capacity, as well as its rate capability. Furthermore, the porous molybdenum sulfide composite reduces the material's irreversible capacity and swelling, improving cycle performance.

[0039] 3. Soft pack battery test:

[0040] The molybdenum sulfide-doped hard carbon composite material in Examples 1-3 and Comparative Examples 1-2 was used as the negative electrode, and the negative electrode sheet was prepared by slurry mixing and coating. 1 / 3 Mn 1 / 3 Ni 1 / 3 A 2Ah soft-pack battery was prepared using O2) as the positive electrode, NaPF6 (solvent is EC+DEC, volume ratio 1:1, concentration 1.3 mol / L) as the electrolyte, and celegard2400 as the separator.

[0041] Test cycle performance: charge and discharge current 1.0C / 1.0C, voltage range 1-4.0V, cycle number 500 times.

[0042] Test rate performance: Test the initial cycle DCR of the soft-pack battery and the constant current ratio under 2C charging conditions.

[0043] The test results are shown in Table 2.

[0044] Table 2

[0045] project Cycle retention rate (%) 2C constant current ratio (%) Initial DCR (mΩ) Example 1 95.4 91.4 11.34 Example 2 96.1 90.1 12.21 Example 3 94.9 92.4 10.65 Comparative Example 1 95.0 88.6 15.65 Comparative Example 2 90.9 89.9 14.78

[0046] As can be seen from Table 2, compared with the comparative example, the rate and cycle performance of the negative electrode sheets in Examples 1-3 are significantly better than those in the comparative example. The reasons for this are as follows: the example material has a large interlayer spacing and its powder conductivity improves the rate performance of the material; at the same time, the porous structure of the material itself is used to reduce expansion and improve the cycle performance; at the same time, the example material has a high powder conductivity, which improves the constant current ratio of the example battery and reduces its initial DCR.

[0047] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a molybdenum sulfide-doped hard carbon composite material, comprising the following steps: Step S1: According to the mass ratio of ammonium tetramolybdate: graphene oxide solution: ethyl formate sulfide = 1-5:100:1-5, 1-5 parts of ammonium tetramolybdate are added to an organic solvent to prepare a 1-10wt% solution, and then 100 parts of a 1-5wt% graphene oxide solution and 1-5 parts of ethyl formate sulfide are added and evenly dispersed, and the mixture is reacted at a temperature of 100-200°C for 1-6 hours, and then freeze-dried at a temperature of -40°C for 24 hours to obtain a porous molybdenum sulfide / graphene compound; Step S2: According to the ratio of porous molybdenum sulfide / graphene compound to starch = 1-10:100, the porous molybdenum sulfide / graphene compound is added to a starch solution with a mass concentration of 1-10wt%, and dispersed evenly. After spray drying at an inlet temperature of 150°C, an outlet temperature of 80°C, and a flow rate of 1L / h, the compound is transferred to a tubular furnace. Under an inert atmosphere, the temperature is first raised to 500-800°C and kept for 1-6h, and then raised to 1000-1800°C and sintered for 1-10h to obtain a molybdenum sulfide-doped hard carbon composite material.

2. The method for preparing a molybdenum sulfide-doped hard carbon composite material according to claim 1, wherein: The starch in step S1 is one of erythrocyte starch, corn starch, wheat starch, potato starch or pea starch.

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