Preparation method of SbCo / Co alloy modified carbon nanotube composite and application thereof in lithium-sulfur battery

Abstract

The application discloses a preparation method of SbCo / Co alloy modified carbon nanotube composite material, which comprises the following steps: 1) mixing Co(NO3)2.6H2O, polyethylene glycol, antimony compound, boric acid, urea and deionized water, stirring the mixture until it is clear, drying, grinding, and obtaining a precursor powder; 2) pyrolyzing the precursor powder under an inert gas atmosphere at 800-1000 DEG C for 3-8 h, and obtaining the SbCo / Co alloy modified carbon nanotube composite material. The interaction between Sb and Co elements can effectively improve the physical and chemical properties of single elements, the obtained SbCo / Co nanoparticles can effectively improve the chemical adsorption of polysulfides and effectively catalyze the mutual conversion of polysulfides. In addition, the unique structure of the carbon nanotube can further improve the electron transfer, and it has abundant internal space to load sulfur and buffer volume expansion. After loading S, the SbCo / Co@CNT carbon nanotube functional hybrid material exhibits excellent electrochemical performance, including excellent cycle stability and rate performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery cathode materials, and particularly relates to a preparation method of a SbCo / Co alloy modified carbon nanotube (SbCo / Co @ CNT) composite material and application of the SbCo / Co alloy modified carbon nanotube (SbCo / Co @ CNT) composite material in a high-performance lithium-sulfur Li-S battery. BACKGROUND

[0002] With the development of new energy vehicles and mobile electronic devices, humans have put forward higher requirements for energy storage methods. Among many energy storage methods, lithium-sulfur batteries have attracted widespread attention due to their high theoretical energy density (2600 Wh kg -1 ). However, the current commercial Li-S batteries still face many challenges, such as poor conductivity of sulfur (S8) and lithium sulfide (Li2S), volume change during battery operation, and "shuttle effect" caused by polysulfides, which leads to low utilization efficiency of sulfur and rapid capacity decay of the battery. Solving the above problems is the key to improving the performance of Li-S batteries.

[0003] Among many solutions, developing effective porous materials plays an important role in improving the performance of Li-S batteries. Such materials have a certain composition and structure, which can optimize the conductivity of the battery, reduce volume change and "shuttle effect".

[0004] Traditional porous materials often attach sulfur single elements to carbon nanospheres, carbon nanotubes and two-dimensional graphene. This strategy can enhance the conductivity of the material and the physical adsorption of polysulfides (LiPSs). However, due to the limited physical adsorption capacity of such materials, they can only partially improve the performance of the battery. Due to the above problems, modifying the surface structure of the porous material to further improve the performance of the Li-S battery has become a research hotspot in recent years.

[0005] The method of modifying the surface structure of the porous material often combines the adsorption of sulfur to LiPSs and electrochemical catalysis, and attaches the resulting electrical material to the positive electrode of the battery. This strategy can optimize the reaction kinetics of the sulfur positive electrode. Researchers have explored hybrid composite materials attached with metal oxides, metal carbides, metal nitrides, metal phosphides and metal sulfides, which have significantly improved the performance of Li-S batteries. However, these materials limit the electronic conduction efficiency of Li-S batteries, affecting the adsorption balance of LiPSs on the positive electrode surface. If the adsorption and diffusion balance of LiPSs can be achieved, it is expected to further improve the performance of Li-S batteries. Based on this, the present application is developed. SUMMARY

[0006] The present application aims to overcome the defects of the prior art, and provides a preparation method of SbCo / Co alloy modified carbon nanotube (SbCo / Co@CNT) composite material. The method adjusts the proportion of Co(NO3)2·6H2O, polyethylene glycol (PEG), antimony compound and CH4N2O in the hydrolysis reaction, and wet-synthesizes the precursor to obtain the SbCo / Co alloy modified carbon nanotube positive electrode composite material with high conductivity and catalytic performance.

[0007] Another object of the present application is to provide the application of the SbCo / Co alloy modified carbon nanotube prepared by the above method in lithium-sulfur batteries. The SbCo / Co alloy modified carbon nanotube is used as a sulfur carrier to load elemental sulfur in the nanotube by in-situ pyrolysis to obtain a composite electrode material, and is used as a lithium-sulfur battery positive electrode material to improve the performance of the lithium-sulfur battery.

[0008] To achieve the above object, the present application adopts the following technical scheme:

[0009] A preparation method of SbCo / Co alloy modified carbon nanotube (SbCo / Co@CNT) composite material, comprising the following steps:

[0010] 1) Co(NO3)2·6H2O, polyethylene glycol (PEG), antimony compound, boric acid (H3BO3), urea (CH4N2O) and deionized water are mixed, and the mixture is stirred vigorously (stirring for 10-15 min) until it is clear, dried, ground, and a precursor powder is obtained;

[0011] 2) The precursor powder is pyrolyzed at 800-1000℃ for 3-8 h under an inert gas atmosphere (such as argon), and the reduction of Co 2+ and Sb 3+ is carried out, that is, the carbon nanotube with trace SbCo / Co alloy nanoparticles attached is obtained.

[0012] Specifically, the antimony compound includes but is not limited to one or two of H6KO6Sb, SbCl3, etc.; the molar ratio of Co(NO3)2·6H2O to antimony compound can be in the range of 1-10:1.

[0013] Further, the mass ratio of polyethylene glycol to Co(NO3)2·6H2O can be in the range of 20-40:1. The polyethylene glycol is preferably PEG 2000.

[0014] Further, the mass ratio of boric acid to Co(NO3)2·6H2O can be in the range of 0-15:1, preferably 5-12:1.

[0015] Further, the mass ratio of the urea to Co(NO3)2·6H2O can be 200-500:1, preferably 250-360:1. In step 1), the drying temperature can be 100-200℃.

[0016] The application provides an SbCo / Co alloy modified carbon nanotube composite material (SbCo / Co@CNT) prepared by the above method, with a diameter of 100-150 nm.

[0017] The application uses the carbon nanotube loaded with sulfur after being attached with trace SbCo / Co alloy nanoparticles as a positive electrode material of a lithium-sulfur battery. Specifically, the application also provides application of the SbCo / Co alloy modified carbon nanotube composite material in a high-performance lithium-sulfur battery. In the application, the SbCo / Co alloy modified carbon nanotube composite material and elemental sulfur are mixed at a mass ratio of 1:1-10, and then reacted in a hydrothermal reactor at 140-170℃ for 10-14h. After cooling to room temperature, the reaction product is heated at 180-220℃ for 0.4-1h in a tube furnace under an argon atmosphere to remove excess S, thereby obtaining a lithium-sulfur battery positive electrode material (SbCo / Co@CNT-S powder). The lithium-sulfur battery positive electrode material is used to prepare a lithium-sulfur battery.

[0018] The application also provides a lithium-sulfur battery positive electrode material, which is obtained by mixing the SbCo / Co alloy modified carbon nanotube composite material and elemental sulfur at a mass ratio of 1:1-10, and then reacting in a hydrothermal reactor at 140-170℃ for 10-14h, and then heating at 180-220℃ for 0.4-1h in a tube furnace under an argon atmosphere.

[0019] In the application, the interaction between Sb and Co elements can effectively improve the physical and chemical properties of single elements, the obtained SbCo / Co nanoparticles can effectively improve the chemical adsorption of polysulfides and effectively catalyze the mutual transformation of polysulfides. In addition, the unique structure of the carbon nanotube can further improve the electron transfer, and it has abundant internal space to load sulfur and buffer volume expansion. After loading sulfur, the SbCo / Co@CNT carbon nanotube functional hybrid material exhibits excellent electrochemical performance, including excellent cycle stability and rate performance.

[0020] Compared with the prior art, the application has the following advantages and beneficial effects:

[0021] 1) The present application loads SbCo / Co alloy nanoparticles inside carbon nanotubes by in-situ pyrolysis, and prepares a multilayer hybrid hollow SbCo / Co@CNT composite material with controllable morphology, uniform size and good structural stability; by controlling the addition ratio of Co(NO3)2·6H2O and antimony compound, SbCo / Co@CNT and Co@CNT can be prepared using this step.

[0022] 2) After loading sulfur, the multilayer hybrid hollow SbCo / Co@CNT nanotube composite material prepared by the present application has excellent multilayer absorption and protection effect, and exhibits excellent electrochemical performance as a Li-S battery positive electrode material, including good cycle stability and high reversible specific capacity. The SbCo / Co@CNT functional composite material prepared by the present application exhibits excellent electrochemical performance, and also exhibits very excellent rate performance at a current density of 1C. At a current density of 0.1C, 0.2C, 0.5C, 1C and 2C, the SbCo / Co@CNT functional composite material prepared by the present application exhibits specific capacities of 1416 mAh g -1 , 1204 mAh g -1 , 1033 mAh g -1 , 922 mAh g -1 and 658 mAh g -1 , respectively. When the current density returns to 0.1C, the specific capacity is still as high as 1247 mAh g -1 , and the capacity retention rate is 88%. Similarly, after 100 cycles of charging and discharging at a current density of 0.1C, the specific capacity is still as high as 1096.5 mAh g -1 , which is much higher than other materials reported in the literature (Co@CNT: 772.6 mAh g -1 ; CNT: 627.0 mAh g -1 ). At a high current density of 1C, the SbCo / Co@CNT functional composite material prepared by the present application still has a charging and discharging capacity of 1020.2 mAh g -1 , and after 500 cycles of charging and discharging, the charging and discharging capacity is maintained at 948.7 mAh g⁻¹, with an average cycle decay of only 0.014%, which exhibits extremely excellent cycle stability.

[0023] 3) The multilayer hybrid hollow SbCo / Co@CNT nanotube composite material prepared by the preparation method of the present application has a wide application prospect in high-performance Li-S batteries, and can be further applied to the field of related electronic devices. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a low-magnification SEM image of the SbCo / Co@CNT prepared in Example 1.

[0025] Figure 2 High-magnification SEM images of the SbCo / Co@CNT prepared in Example 1;

[0026] Figure 3 XPS images of the SbCo / Co@CNT prepared in Example 1;

[0027] Figure 4 The cycle charge-discharge images of the three materials at different rates of 0.1C, 0.2C, 0.5C, 1C and 2C, from top to bottom are SbCo / Co@CNT-S, Co@CNT-S and CNT-S;

[0028] Figure 5 is the long-life cycle discharge times of the three materials under 1C charge-discharge conditions, from top to bottom are SbCo / Co@CNT-S, Co@CNT-S and CNT-S;

[0029] Figure 6 is the specific capacity of the three materials after 100 cycles under 0.1C charge-discharge conditions, from top to bottom are SbCo / Co@CNT-S, Co@CNT-S and CNT-S. DETAILED DESCRIPTION

[0030] The technical solutions of the present application are further described in detail below in combination with examples, but the protection scope of the present application is not limited thereto.

[0031] In the following examples, the raw materials used are ordinary commercially available products that can be directly purchased or prepared by conventional methods in the art.

[0032] Room temperature refers to 25±5℃.

[0033] Example 1

[0034] The preparation of SbCo / Co@CNT specifically includes the following steps:

[0035] Add 34.2 mg of Co(NO3)2·6H2O and 30.8 mg of H6KO6Sb (molar ratio of Co(NO3)2·6H2O to H6KO6Sb is 1:1, both are 0.117 mmol) to 150 mL of deionized water containing 11 g of urea, 0.3 g of boric acid and 1 g of PEG-2000, and stir the mixture vigorously until it is clear; evaporate the above solution at 100℃ until dry; grind the above solid and heat it to 900℃ at a heating rate of 5℃ / min under argon atmosphere for 5 h to obtain SbCo / Co@CNT.

[0036] The SEM images of the prepared SbCo / Co@CNT are as follows Figure 1 and 2As shown in FIG. 1. Figure 1 and 2 It can be seen that the SbCo / Co@CNT is a nanotube with uniform size, and the diameter thereof is about 100-150 nm.

[0037] Figure 3 XPS diagram of the SbCo / Co@CNT prepared in the embodiment is given; according to the analysis of the characteristic peaks in the diagram, it can be seen that the material is composed of carbon, cobalt, nitrogen and antimony elements.

[0038] Preparation of the SbCo / Co@CNT loaded with sulfur, specifically comprising the following steps:

[0039] 0.1 gram of the prepared SbCo / Co@CNT is mixed with 0.4 gram of sulfur powder and then ground uniformly; the mixture is heated to 156℃ in a hydrothermal reactor and kept for 12 hours. After the reaction is completed, the mixture is cooled to room temperature; the mixture is then transferred into a tube furnace and heated to 200℃ under an argon atmosphere for pyrolysis for 1 hour (the heating rate is 2℃ / min), thereby obtaining a SbCo / Co@CNT-S positive electrode material.

[0040] The SbCo / Co@CNT-S positive electrode material prepared is mixed with a conductive agent (Super-P) and a binder (PVDF) in a mass ratio of 7:2:1, and then N-methyl pyrrolidone (NMP) is added and stirred to coat the mixture on an aluminum foil to prepare an electrode sheet, which is dried in a vacuum drying box for 12 hours.

[0041] In an argon atmosphere glove box, the electrode sheet is used as a positive electrode, a lithium metal sheet is used as a negative electrode, and a DME-DOL (volume ratio 1:1) mixture containing 1M LiTFSI and 2 wt% LiNO3 is used as an electrolyte to assemble a 2032 type button cell, which is then tested. The test conditions are as follows: the charge and discharge current density is 0.1C, 0.2C, 0.5C, 1C, 2C (1C=1675mA / g), and the charge and discharge cutoff voltage is 1.7-2.8V. The cycle number-capacity performance curve obtained by the test is shown in FIG. 2. Figures 4-6

[0042] Comparative Example 1

[0043] Preparation of Co@CNT, specifically comprising the following steps:

[0044] 65 milligrams of Co(NO3)2·6H2O is added to 150 mL of deionized water containing 11 grams of urea, 0.3 grams of boric acid and 1 gram of PEG-2000, and the mixture is stirred vigorously until it is clear; the above solution is evaporated at 100℃; the above solid is ground and heated to 900℃ at a heating rate of 5℃ / min under an argon atmosphere for pyrolysis for 5 hours, thereby obtaining Co@CNT. ​

[0045] Preparation of Co@CNT supported sulfur, specifically comprising the following steps:

[0046] The prepared Co@CNT was taken 0.1 gram, mixed with 0.4 gram of sulfur powder and ground uniformly; the mixture was heated to 156℃ in a hydrothermal reactor and kept for 12 h, and after the reaction was completed, it was cooled to room temperature; the mixture was transferred to a tube furnace and heated to 200℃ again under argon atmosphere and pyrolyzed for 1 h (heating rate 2℃ / min), obtaining Co@CNT-S positive electrode material.

[0047] The prepared Co@CNT-S positive electrode material was mixed with conductive agent (Super-P) and binder (PVDF) in a mass ratio of 7:2:1, and N-methyl pyrrolidone NMP was added and stirred, then coated on aluminum foil to make electrode sheet, and dried in a vacuum drying box for 12 hours.

[0048] In an argon atmosphere glove box, the above electrode sheet was used as the positive electrode, lithium sheet as the negative electrode, and DME-DOL (volume ratio 1:1) mixed solution containing 1M LiTFSI and 2 wt% LiNO3 as the electrolyte to assemble 2032 type button cell, and then test. The test conditions were: charge-discharge current density was 0.1C, 0.2C, 0.5C, 1C, 2C (1C=1675mA / g), and charge-discharge cutoff voltage was 1.7-2.8V. The cycle number-specific capacity performance curve obtained by testing is shown in Figure 6 After 100 cycles of charge-discharge at a current density of 0.1C, the specific capacity was 772.6 mAh g -1 .

[0049] Comparative Example 2

[0050] Preparation of CNT, specifically comprising the following steps:

[0051] 0.3 gram of boric acid, 11 gram of urea and 1 gram of PEG-2000 were added to 150 mL of deionized water, and the mixture was stirred vigorously until clear; the above solution was evaporated at 100℃; the above solid was ground and heated to 900℃ under argon atmosphere at a heating rate of 5℃ / min for pyrolysis for 5 h, obtaining CNT.

[0052] Preparation of CNT supported sulfur, specifically comprising the following steps:

[0053] The prepared CNT was taken 0.1 gram, mixed with 0.4 gram of sulfur powder and ground uniformly; the mixture was heated to 156℃ in a hydrothermal reactor and kept for 12 h, and after the reaction was completed, it was cooled to room temperature; the mixture was transferred to a tube furnace and heated to 200℃ again under argon atmosphere and pyrolyzed for 1 h (heating rate 2℃ / min), obtaining CNT-S positive electrode material.

[0054] The prepared CNT-S positive electrode material was mixed with a conductive agent (Super-P) and a binder (PVDF) in a mass ratio of 7:2:1, and then N-methyl pyrrolidone (NMP) was added and stirred to coat the aluminum foil to make an electrode sheet, which was dried in a vacuum drying oven for 12 hours.

[0055] In an argon atmosphere glove box, the above electrode sheet was used as the positive electrode, and a lithium metal sheet was used as the negative electrode. A 2032 type button cell was assembled using a DME-DOL (volume ratio 1:1) mixture containing 1M LiTFSI and 2 wt% LiNO3 as the electrolyte, and then tested. The test conditions were: the charge and discharge current density was 0.1C, 0.2C, 0.5C, 1C, 2C (1C = 1675 mA / g), and the charge and discharge cutoff voltage was 1.7-2.8V. The cycle number-specific capacity performance curve obtained by the test is shown in FIG. 1. After 100 cycles of charge and discharge at a current density of 0.1C, the specific capacity was 627.0 mAh g -1 . Figure 6

[0056] Figure 4 The cycle charge and discharge graphs of the three materials at different rates are shown in FIG. 2, from top to bottom in order: SbCo / Co@CNT-S, Co@CNT-S, CNT-S. Figure 4 As shown in FIG. 2, at a current density of 1C, the SbCo / Co@CNT functional composite material also showed very excellent rate performance, and exhibited specific capacities of 1416 mAh g -1 , 1204 mA g -1 , 1033 mAh g -1 , 922 mAh g -1 , and 658 mAh g -1 at current densities of 0.1C, 0.2C, 0.5C, 1C, and 2C, respectively; when the current density returned to 0.1C, the specific capacity was still as high as 1247 mAh g -1 , with a capacity retention rate of 88%. The Co@CNT exhibited specific capacities of 1099.5 mAh g -1 , 916.1 mAh g -1 , 736.7 mAh g -1 , 579.4 mAhg -1 , 389. 5 mAh g -1 at current densities of 0.1C, 0.2C, 0.5C, 1C, and 2C, respectively; when the current density returned to 0.1C, the specific capacity was 955.6 mAh g -1 ​.932.3 mAh g -1 , 733.2 mAh g -1 , 553.2 mAh g -1 , 432.5 mAh g -1 , 246.1 mAh g -1 , 762.8 mAh g -1 .

[0057] Figure 5 shows the long-life cycle discharge times of the three materials at 1C, from top to bottom, SbCo / Co@CNT-S, Co@CNT-S, CNT-S. Figure 5 As can be seen: at a high current density of 1C, the charge-discharge capacity of the SbCo / Co@CNT functional composite material is still as high as 1020.2 mAh g -1 ; after 500 charge-discharge cycles, the charge-discharge capacity is maintained at 948.7 mAh g -1 , with an average cycle decay of only 0.014%, exhibiting extremely excellent cycle life. At 1C, the charge-discharge capacities of Co@CNT and CNT after 500 long cycles are only 614.4 mAh g -1 , 354.5 mAh g -1 .

[0058] Figure 6 shows the specific capacity of the three materials after 100 cycles at 0.1C, from top to bottom, SbCo / Co@CNT-S, Co@CNT-S, CNT-S. The SbCo / Co@CNT functional composite material exhibits excellent electrochemical performance, with a specific capacity of 1096.5 mAh g -1 after 100 cycles of charge-discharge at a current density of 0.1C, which is much higher than other materials reported in the literature (Co@CNT: 772.6 mAh g -1 , CNT: 627.0 mAh g -1 ), see Figure 6 .

[0059] Example 2

[0060] Preparation of SbCo / Co@CNT, which is different from Example 1 in that SbCl3 is used instead of H6KO6Sb, and specifically includes the following steps:

[0061] SbCo / Co@CNT was prepared by adding 36.4 mg of Co(NO3)2·6H2O and 28.6 mg of SbCl3 (molar ratio of Co(NO3)2·6H2O to SbCl3 was 1:1, both were 0.125 mmol) into 150 mL of deionized water containing 11 g of urea, 0.3 g of boric acid and 1 g of PEG-2000, and the mixture was stirred vigorously until it was clear; the above solution was evaporated at 100℃; after grinding the above solid, it was heated to 900℃ at a heating rate of 5℃ / min under argon atmosphere for pyrolysis for 5 h to obtain SbCo / Co@CNT.

[0062] Preparation of SbCo / Co@CNT loaded with sulfur, specifically comprising the following steps:

[0063] The prepared SbCo / Co@CNT was taken 0.1 g, mixed with 0.4 g of sulfur powder and ground uniformly; the above mixture was heated to 156℃ in a hydrothermal reactor and kept for 12 h. After the reaction was completed, it was cooled to room temperature; the above mixture was transferred to a tube furnace and heated to 200℃ under argon atmosphere for pyrolysis for 1 h (heating rate 2℃ / min) to obtain SbCo / Co@CNT-S positive electrode material.

[0064] The prepared SbCo / Co@CNT-S positive electrode material was made into an electrode sheet according to the method of Example 1, and assembled into a button cell, and the electrochemical performance test was carried out under the same conditions. The results showed that its performance was equivalent to that of Example 1.

[0065] In summary, the multilayer hybrid hollow SbCo / Co@CNT nanotube composite material prepared by the present application has excellent multilayer absorption and protection effect after loading sulfur, and exhibits excellent electrochemical performance as a Li-S battery positive electrode material, including good cycle stability and high reversible specific capacity.

Claims

1. A method for preparing an SbCo / Co alloy decorated carbon nanotube composite, characterized in that, Comprising the following steps: 1) mixing Co(NO3)2·6H2O, polyethylene glycol, antimony compound, boric acid, urea and deionized water, stirring the mixture until clear, drying, grinding to obtain a precursor powder; 2) pyrolyzing the precursor powder at 800-1000℃ for 3-8 h under an inert gas atmosphere to obtain the SbCo / Co alloy modified carbon nanotube composite material.

2. The method for preparing the SbCo / Co alloy-modified carbon nanotube composite material as described in claim 1, characterized in that, The antimony compound is one or both of H6KO6Sb and SbCl3; the molar ratio of Co(NO3)2·6H2O to antimony compound ranges from 1-10:

1.

3. The method for preparing the SbCo / Co alloy-modified carbon nanotube composite material as described in claim 1, characterized in that, The mass ratio of polyethylene glycol to Co(NO3)2·6H2O ranges from 20-40:

1.

4. The method for preparing the SbCo / Co alloy-modified carbon nanotube composite material as described in claim 1, characterized in that, The mass ratio of boric acid to Co(NO3)2·6H2O ranges from 0-15:1, with the range excluding 0.

5. The method for preparing the SbCo / Co alloy-modified carbon nanotube composite material as described in claim 1, characterized in that, The mass ratio of urea to Co(NO3)2·6H2O ranges from 200-500:

1.

6. The method for preparing the SbCo / Co alloy-modified carbon nanotube composite material as described in claim 1, characterized in that, In step 1), the drying temperature is 100-200℃.

7. The SbCo / Co alloy modified carbon nanotube composite material prepared by the method of any one of claims 1-6.

8. The use of the SbCo / Co alloy modified carbon nanotube composite material of claim 7 in lithium-sulfur batteries.

9. Use of the SbCo / Co alloy decorated carbon nanotube composite material according to claim 8 in lithium-sulfur batteries, characterized in that, Mix the SbCo / Co alloy modified carbon nanotube composite material and elemental sulfur at a mass ratio of 1:1-10, incubate at 140-170℃ for 10-14 h, then transfer to a tube furnace and incubate at 180-220℃ under an argon atmosphere for 0.4-1 h to obtain a lithium-sulfur battery anode material.

10. A lithium-sulfur battery cathode material, characterized in that, Mix the SbCo / Co alloy modified carbon nanotube composite material of claim 7 and elemental sulfur at a mass ratio of 1:1-10, incubate at 140-170℃ for 10-14 h, then transfer to a tube furnace and incubate at 180-220℃ under an argon atmosphere for 0.4-1 h to obtain a lithium-sulfur battery anode material.

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