A kind of Co 8 NiS 8 / Ni 3 S 2 -CNF catalytic material and its preparation method and application

Abstract

The present invention discloses a Co8NiS8 / Ni3S2-CNF catalytic material, a preparation method thereof and an application thereof. The method comprises the steps of: 1. Dissolving Ni(NO3)2·6H2O, Co(NO3)2·6H2O and urea in a mixed solution of isopropanol and deionized water, transferring the mixture to a hydrothermal autoclave after stirring evenly, keeping the temperature at 100-120 °C until the reaction is sufficient, then washing and drying to obtain a basic carbonate powder; 2. Taking the basic carbonate and thioacetamide in a ratio of (0.2-0.3 g):(0.4-0.6 g):(50-60 mL), adding them to absolute ethanol, transferring the mixture to a hydrothermal autoclave after stirring, keeping the temperature at 120-130 °C, then washing and drying to obtain a NiCo2S4 powder; 3. Dispersing the NiCo2S4 powder and bacterial cellulose BC in deionized water according to a mass ratio of 5:1, and drying to obtain a NiCo2S4 / BC composite material; 4. Carbonizing the NiCo2S4 / BC composite material to obtain a Co8NiS8 / Ni3S2-CNF composite material, which has a good adsorption effect and can improve the electrochemical performance of a Li-S battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-sulfur batteries, and specifically relates to a Co 8 NiS 8 / Ni 3 S 2 -CNF catalytic material and its preparation method and application. Background Art

[0002] The continuous consumption of traditional fossil fuels has caused a potential energy shortage crisis. To reduce the dependence on fossil fuels, solar energy, wind energy, and energy storage systems have been widely used. As a new type of energy storage system, lithium-ion batteries have been widely used, but their actual energy density is only 200 mAh g -1 , which cannot meet the growing market demand. Therefore, it is necessary to develop the next-generation secondary batteries with higher energy density than lithium-ion batteries; as a new type of energy storage system, lithium-sulfur batteries have a high theoretical mass specific capacity (1675 mAh g -1 ) and theoretical mass energy density (2600 Wh kg -1 ), and have the advantages of environmental friendliness and low price. However, it has problems such as poor conductivity of the positive electrode material, polysulfide shuttle effect, and volume expansion. According to research, compared with non-polar carbon materials and polymer materials, polar materials can increase the tap density of the sulfur positive electrode. Although metal oxides have an excellent binding ability with polysulfides, too strong a binding energy will destroy the polysulfides. Metal compounds have a higher binding energy for polysulfides, especially metal sulfides have a more moderate binding energy compared to metal oxides, and the electronic conductivity of metal sulfides is also higher than that of oxides at room temperature. At the same time, the catalytic function of a single active site of metal sulfides may not contribute equally to polysulfides. Especially, bimetallic sulfides contain multiple active sites, so they may enhance the redox reactions of polysulfides with different molecular structures such as lithium polysulfide at the same time, and are expected to improve the specific capacity of lithium-sulfur batteries. Summary of the Invention

[0003] The purpose of the present invention is to provide a Co 8 NiS 8 / Ni 3 S 2 -CNF catalytic material and its preparation method and application. The prepared Co 8 NiS 8 / Ni 3 S 2 -CNF has a good adsorption effect on sulfides and can improve the electrochemical performance of Li-S batteries.

[0004] To achieve the above purpose, the present invention adopts the following technical solutions to achieve:

[0005] A Co 8 NiS 8 / Ni 3 S 2 -CNF catalytic material preparation method, including the following steps:

[0006] Step 1: First, take Ni(NO 3 ) 2 ·6H 2 O, Co(NO 3 ) 2 ·6H 2 O, urea, isopropanol and deionized water in the proportions of (1 - 3 g):(2 - 4 g):(10 - 15 g):60 mL:12 mL. Then dissolve Ni(NO 3 ) 2 ·6H 2 O, Co(NO 3 ) 2 ·6H 2 O and urea in the mixed solution of isopropanol and deionized water, stir evenly and transfer to a hydrothermal reactor, keep warm at 100 - 120 °C until the reaction is complete, then wash and dry to obtain basic carbonate powder;

[0007] Step 2: First, take basic carbonate, thioacetamide and absolute ethanol in the proportions of (0.2 - 0.3 g):(0.4 - 0.6 g):(50 - 60 mL). Then dissolve basic carbonate and thioacetamide in absolute ethanol, stir evenly and transfer to a hydrothermal reactor, keep warm at 120 - 130 °C until the reaction is complete, then wash and dry to obtain NiCo 2 S 4 powder;

[0008] Step 3: Take NiCo 2 S 4 powder and bacterial cellulose BC in a mass ratio of 5:1. Then take deionized water according to the ratio of the mass of NiCo 2 S 4 powder to the volume of deionized water of 1:1. Then disperse bacterial cellulose BC and NiCo 2 S 4 powder in deionized water in sequence, stir evenly and dry to obtain NiCo 2 S 4 / BC composite material;

[0009] Step 4: Disperse NiCo 2 S 4The Co 8 NiS 8 / Ni 3 S 2 -CNF composite material was placed in a tubular furnace and first heated from room temperature to 200 °C at a heating rate of 5 °C / min, then heated to 600 - 700 °C at a heating rate of 2 °C / min, and then cooled to room temperature with the furnace to obtain

[0010] Furthermore, the stirring in Step 1 was carried out using a magnetic stirrer for 30 min.

[0011] Furthermore, the heat preservation time in Step 1 was 12 - 16 h.

[0012] Furthermore, the stirring in Step 2 was carried out using a magnetic stirrer for 15 min.

[0013] Furthermore, the heat preservation time in Step 2 was 6 - 12 h.

[0014] Furthermore, the washing in both Step 1 and Step 2 was carried out by alternately washing with deionized water and absolute ethanol 3 - 5 times.

[0015] Furthermore, the drying in Steps 1 - 3 was carried out at 60 °C for 12 - 24 h.

[0016] A Co 8 NiS 8 / Ni 3 S 2 -CNF composite material.

[0017] A Co 8 NiS 8 / Ni 3 S 2 -CNF's application in the separator of Li-S batteries.

[0018] The present invention has the following beneficial effects:

[0019] The present invention prepares NiCo 2 S 4 powder through a simple process, and after uniformly mixing the NiCo 2 S 4 powder with BC single, uses high-temperature carbonization to improve the conductivity of the NiCo 2 S 4 material; meanwhile, since hydroxylated BC has a fine network structure and can still maintain the network structure after carbonization, therefore, during the carbonization process, the strong conductive network of hydroxylated BC can relieve NiCo 2 S 4Agglomeration makes more active sites exposed, improving the adsorption effect on polysulfides. It can be seen that the present invention not only has a simple preparation process and a short preparation cycle, but also the prepared Co 8 NiS 8 / Ni 3 S 2 -CNF has a good adsorption effect on sulfides.

[0020] Utilizing the property that Co 8 NiS 8 / Ni 3 S 2 -CNF has a good adsorption effect on sulfides, it is used as a modified layer of the Li-S battery separator, improving the specific capacity and cycle stability of the Li-S battery, making the Li-S battery have excellent electrochemical performance, providing a broad prospect for the commercial application of the Li-S battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 : XRD pattern of Co 8 NiS 8 / Ni 3 S 2 -CNF prepared in Example 1 of the present invention;

[0022] Figure 2 : SEM image of NiCo 2 S 4 / BC prepared in Example 1 of the present invention;

[0023] Figure 3 : SEM image of Co 8 NiS 8 / Ni 3 S 2 -CNF prepared in Example 1 of the present invention;

[0024] Figure 4 : Comparison diagram of the rate performance of the Li-S battery assembled with the Co 8 NiS 8 / Ni 3 S 2 -CNF modified separator and the commercial separator;

[0025] Figure 5 : Comparison diagram of the cycle performance of the Li-S battery assembled with the Co 8 NiS 8 / Ni 3 S 2 -CNF modified separator and the commercial separator at a current density of 0.2C. DETAILED DESCRIPTION OF THE INVENTION

[0026] The following further elaborates on the specific content of the present invention in conjunction with embodiments, but it does not limit the present invention.

[0027] Example 1

[0028] Step 1: Respectively take 1.2 g of Ni(NO 3 ) 2 ·6H 2 O, 2.4 g of Co(NO 3 ) 2 ·6H 2 O and 15 g of urea and dissolve them in a mixed solution of 60 mL of isopropanol and 12 mL of deionized water. After stirring with a magnetic stirrer for 30 min, transfer it to a hydrothermal autoclave, keep it at 120 °C for 15 h, then wash it alternately with absolute ethanol and deionized water 3 times, and finally dry it at 60 °C for 12 h to obtain basic carbonate;

[0029] Step 2: Respectively take 0.2 g of basic carbonate and 0.4 g of thioacetamide and dissolve them in 60 mL of absolute ethanol. After stirring with a magnetic stirrer for 15 min, transfer it to a hydrothermal autoclave, keep it at 120 °C for 6 h, then wash it alternately with absolute ethanol and deionized water 3 times, and finally dry it at 60 °C for 12 h to obtain NiCo 2 S 4 powder;

[0030] Step 3: Take 40 mg of bacterial cellulose BC and disperse it evenly in 200 mL of deionized water, then add 200 mg of NiCo 2 S 4 powder and stir evenly, then dry it at 60 °C for 12 h to remove excess moisture, obtaining NiCo 2 S 4 / BC composite;

[0031] Step 4: Place the NiCo 2 S 4 / BC composite in a tube furnace, first heat it from room temperature to 200 °C at a heating rate of 5 °C / min, then heat it to 600 °C at a heating rate of 2 °C / min, and then cool it to room temperature with the furnace to obtain Co 8 NiS 8 / Ni 3 S 2 -CNF composite.

[0032] It can be seen from Figure 1 that NiCo 2 S 4 in the NiCo 2 S 4 / BC composite generates bimetallic sulfide Co8 NiS 8 and Ni 3 S 2 , which can provide more active sites as a separator modification material and alleviate the "shuttle effect".

[0033] From Figure 2 it can be seen that the particle size of NiCo 2 S 4 / BC is about 4 - 5 μm, and the bacterial cellulose BC connects the NiCo 2 S 4 particles, which can prevent the agglomeration of NiCo 2 S 4 particles. 2 S 4

[0034] From Figure 3 it can be seen that after the bacterial cellulose BC in NiCo 2 S 4 / BC is carbonized, carbon nanofibers are generated, making NiCo 2 S 4 have high conductivity.

[0035] Mix Co 8 NiS 8 / Ni 3 S 2 -CNF, acetylene black and PVDF by grinding, and then add NMP to prepare a uniform slurry. Coat the slurry evenly on the polypropylene separator of a commercial lithium-sulfur battery and dry it to obtain a Co 8 NiS 8 / Ni 3 S 2 -CNF modified separator. Assemble a Li-S battery using the modified separator and conduct various performance tests. The results are as follows:

[0036] From Figure 4 it can be seen that when Co 8 NiS 8 / Ni 3 S 2 -CNF is used as the modification layer of the Li-S battery separator, the initial capacity of the Li-S battery reaches 1300 mAh g at 0.1C -1 , and at 2C, its capacity can still reach 730 mAh g -1 . It can be seen that the Li-S battery has a high active sulfur utilization rate.

[0037] From Figure 5 it can be seen that 8 NiS 8 ​ / Ni 3 S 2 When the Li-S battery uses the -CNF as the separator modification layer, the capacity of the Li-S battery can still reach 754.3 mAh g after 100 cycles at 0.2C. -1 However, the capacity of the conventional Li-S battery is only 322.6 mAh g after 100 cycles. -1 .

[0038] Example 2

[0039] Step 1: Take 1 g of Ni(NO 3 ) 2 ·6H 2 O, 2 g of Co(NO 3 ) 2 ·6H 2 O and 10 g of urea and dissolve them in a mixed solution of 60 mL of isopropanol and 12 mL of deionized water. After stirring with a magnetic stirrer for 30 min, transfer the solution to a hydrothermal reactor, keep it at 100 °C for 12 h, then wash it 4 times alternately with absolute ethanol and deionized water, and finally dry it at 60 °C for 14 h to obtain basic carbonate.

[0040] Step 2: Take 0.22 g of basic carbonate and 0.45 g of thioacetamide and dissolve them in 50 mL of absolute ethanol. After stirring with a magnetic stirrer for 15 min, transfer the solution to a hydrothermal reactor, keep it at 125 °C for 8 h, then wash it 4 times alternately with absolute ethanol and deionized water, and finally dry it at 60 °C for 14 h to obtain NiCo 2 S 4 powder.

[0041] Step 3: Take 20 mg of bacterial cellulose BC and disperse it evenly in 100 mL of deionized water. Then add 100 mg of NiCo 2 S 4 powder and stir evenly. Then dry it at 60 °C for 14 h to remove the excess water and obtain NiCo 2 S 4 / BC composite.

[0042] Step 4: Place the NiCo 2 S 4 / BC composite in a tube furnace. First, heat it from room temperature to 200 °C at a heating rate of 5 °C / min, then heat it to 680 °C at a heating rate of 2 °C / min, and then cool it to room temperature with the furnace to obtain Co 8 NiS 8 / Ni 3 S 2 -CNF composite.

[0043] Example 3

[0044] Step 1: Weigh 1.5 g of Ni(NO 3 ) 2 ·6H 2 O, 2.5 g of Co(NO 3 ) 2 ·6H 2 O and 12 g of urea, and dissolve them in a mixed solution of 60 mL of isopropanol and 12 mL of deionized water. After stirring with a magnetic stirrer for 30 min, transfer the solution to a hydrothermal reactor, keep it at 110 °C for 13 h, then wash it 5 times alternately with absolute ethanol and deionized water, and finally dry it at 60 °C for 16 h to obtain basic carbonate;

[0045] Step 2: Weigh 0.24 g of basic carbonate and 0.5 g of thioacetamide, and dissolve them in 55 mL of absolute ethanol. After stirring with a magnetic stirrer for 15 min, transfer the solution to a hydrothermal reactor, keep it at 130 °C for 10 h, then wash it 5 times alternately with absolute ethanol and deionized water, and finally dry it at 60 °C for 16 h to obtain NiCo 2 S 4 powder;

[0046] Step 3: Disperse 10 mg of bacterial cellulose BC evenly in 50 mL of deionized water, then add 10 mg of NiCo 2 S 4 powder and stir evenly. Then dry it at 60 °C for 16 h to remove the excess water and obtain NiCo 2 S 4 / BC composite;

[0047] Step 4: Place the NiCo 2 S 4 / BC composite in a tube furnace. First, heat it from room temperature to 200 °C at a heating rate of 5 °C / min, then heat it to 700 °C at a heating rate of 2 °C / min, and then cool it to room temperature with the furnace to obtain Co 8 NiS 8 / Ni 3 S 2 -CNF composite.

[0048] Example 4

[0049] Step 1: Weigh 2 g of Ni(NO 3 ) 2 ·6H 2 O, 3 g of Co(NO 3 ) 2 ·6H 20 and 13 g of urea are dissolved in a mixed solution of 60 mL of isopropanol and 12 mL of deionized water. After stirring with a magnetic stirrer for 30 min, it is transferred to a hydrothermal reactor, kept at 120 °C for 14 h, then washed alternately with absolute ethanol and deionized water 3 times, and finally dried at 60 °C for 18 h to obtain basic carbonate;

[0050] Step 2: 0.25 g of basic carbonate and 0.55 g of thioacetamide are respectively dissolved in 60 mL of absolute ethanol. After stirring with a magnetic stirrer for 15 min, it is transferred to a hydrothermal reactor, kept at 120 °C for 12 h, then washed alternately with absolute ethanol and deionized water 3 times, and finally dried at 60 °C for 18 h to obtain NiCo 2 S 4 powder;

[0051] Step 3: 60 mg of bacterial cellulose BC is dispersed evenly in 300 mL of deionized water, and then 300 mg of NiCo 2 S 4 powder is added and stirred evenly. After drying at 60 °C for 18 h to remove excess moisture, NiCo 2 S 4 / BC composite is obtained;

[0052] Step 4: The NiCo 2 S 4 / BC composite is placed in a tubular furnace. First, it is heated from room temperature to 200 °C at a heating rate of 5 °C / min, then heated to 620 °C at a heating rate of 2 °C / min, and then cooled to room temperature with the furnace to obtain Co 8 NiS 8 / Ni 3 S 2 -CNF composite.

[0053] Example 5

[0054] Step 1: 2.5 g of Ni(NO 3 ) 2 ·6H 2 O, 3.5 g of Co(NO 3 ) 2 ·6H 2 O and 14 g of urea are dissolved in a mixed solution of 60 mL of isopropanol and 12 mL of deionized water. After stirring with a magnetic stirrer for 30 min, it is transferred to a hydrothermal reactor, kept at 115 °C for 16 h, then washed alternately with absolute ethanol and deionized water 4 times, and finally dried at 60 °C for 20 h to obtain basic carbonate;

[0055] Step 2: Weigh 0.28 g of basic carbonate and 0.6 g of thioacetamide respectively, dissolve them in 55 mL of absolute ethanol, stir with a magnetic stirrer for 15 min, then transfer to a hydrothermal reactor, keep the temperature at 120 °C for 7 h, then wash alternately with absolute ethanol and deionized water for 4 times, and finally dry at 60 °C for 20 h to obtain NiCo 2 S 4 powder;

[0056] Step 3: Disperse 30 mg of bacterial cellulose BC evenly in 150 mL of deionized water, then add 30 mg of NiCo 2 S 4 powder and stir evenly, then dry at 60 °C for 20 h to remove the excess moisture, obtaining NiCo 2 S 4 / BC composite;

[0057] Step 4: Place the NiCo 2 S 4 / BC composite in a tubular furnace, first heat from room temperature to 200 °C at a heating rate of 5 °C / min, then heat to 640 °C at a heating rate of 2 °C / min, and then cool to room temperature with the furnace to obtain Co 8 NiS 8 / Ni 3 S 2 -CNF composite.

[0058] Example 6

[0059] Step 1: Weigh 3 g of Ni(NO 3 ) 2 ·6H 2 O, 4 g of Co(NO 3 ) 2 ·6H 2 O and 11 g of urea, dissolve them in a mixed solution of 60 mL of isopropanol and 12 mL of deionized water, stir with a magnetic stirrer for 30 min, then transfer to a hydrothermal reactor, keep the temperature at 105 °C for 15 h, then wash alternately with absolute ethanol and deionized water for 5 times, and finally dry at 60 °C for 24 h to obtain basic carbonate;

[0060] Step 2: Weigh 0.3 g of basic carbonate and 0.4 g of thioacetamide respectively, dissolve them in 50 mL of absolute ethanol, stir with a magnetic stirrer for 15 min, then transfer to a hydrothermal reactor, keep the temperature at 130 °C for 9 h, then wash alternately with absolute ethanol and deionized water for 5 times, and finally dry at 60 °C for 24 h to obtain NiCo 2 S 4 powder;

[0061] Step 3: Disperse 50 mg of bacterial cellulose BC evenly in 250 mL of deionized water, and then add 50 mg of NiCo 2 S 4 powder. After stirring evenly, dry it at 60 °C for 24 h to remove excess moisture and obtain the NiCo 2 S 4 / BC composite material;

[0062] Step 4: Place the NiCo 2 S 4 / BC composite material in a tube furnace. First, heat it from room temperature to 200 °C at a heating rate of 5 °C / min, then heat it to 660 °C at a heating rate of 2 °C / min, and then cool it to room temperature with the furnace to obtain the Co 8 NiS 8 / Ni 3 S 2 -CNF composite material.

[0063] Example 7

[0064] Step 1: Weigh 2.8 g of Ni(NO 3 ) 2 ·6H 2 O, 3.7 g of Co(NO 3 ) 2 ·6H 2 O and 10 g of urea and dissolve them in a mixed solution of 60 mL of isopropanol and 12 mL of deionized water. After stirring with a magnetic stirrer for 30 min, transfer the solution to a hydrothermal autoclave, keep it at 100 °C for 16 h, then wash it alternately with absolute ethanol and deionized water 3 times, and finally dry it at 60 °C for 22 h to obtain the basic carbonate;

[0065] Step 2: Weigh 0.26 g of basic carbonate and 0.6 g of thioacetamide and dissolve them in 50 mL of absolute ethanol. After stirring with a magnetic stirrer for 15 min, transfer the solution to a hydrothermal autoclave, keep it at 125 °C for 11 h, then wash it alternately with absolute ethanol and deionized water 3 times, and finally dry it at 60 °C for 22 h to obtain the NiCo 2 S 4 powder;

[0066] Step 3: Disperse 40 mg of bacterial cellulose BC evenly in 200 mL of deionized water, and then add 200 mg of NiCo 2 S 4 powder. After stirring evenly, dry it at 60 °C for 22 h to remove excess moisture and obtain the NiCo 2 S 4 / BC composite material;

[0067] Step 4: Place the NiCo2 S 4 The Co 8 NiS 8 / Ni 3 S 2 -CNF composite material was placed in a tube furnace and first heated from room temperature to 200 °C at a heating rate of 5 °C / min, then heated to 650 °C at a heating rate of 2 °C / min, and then cooled to room temperature with the furnace to obtain the Co

Claims

1. A Co 8 NiS 8 / Ni 3 S 2 -CNF catalytic material preparation method, It is characterized in that It includes the following steps: Step 1: First, take Ni(NO 3 ) 2 ·6H 2 O, Co(NO 3 ) 2 ·6H 2 O, urea, isopropanol, and deionized water in the ratio of (1 - 3 g) : (2 - 4 g) : (10 - 15 g) : 60 mL : 12 mL in sequence. Then dissolve Ni(NO 3 ) 2 ·6H 2 O, Co(NO 3 ) 2 ·6H 2 O and urea in the mixed solution of isopropanol and deionized water. After stirring evenly, transfer it to a hydrothermal autoclave, keep it at 100 - 120 °C until the reaction is complete, then wash and dry to obtain basic carbonate powder; Step 2: First, take basic carbonate, thioacetamide, and absolute ethanol in the ratio of (0.2 - 0.3 g) : (0.4 - 0.6 g) : (50 - 60 mL) in sequence. Then dissolve the basic carbonate and thioacetamide in absolute ethanol, transfer the mixture to a hydrothermal autoclave after stirring evenly, keep it at 120 - 130 °C until the reaction is complete, and then wash and dry to obtain NiCo 2 S 4 powder; Step 3: Take NiCo 2 S 4 powder and bacterial cellulose BC in a mass ratio of 5:1, and then take deionized water according to the ratio of the mass of NiCo 2 S 4 powder to the volume of deionized water of 1:

1. Then, disperse bacterial cellulose BC and NiCo 2 S 4 powder in deionized water in sequence. After stirring evenly, dry to obtain NiCo 2 S 4 / BC composite material; Step 4: Place the NiCo 2 S 4 / BC composite material in a tube furnace, first heat it from room temperature to 200 °C at a heating rate of 5 °C / min, then heat it to 600 - 700 °C at a heating rate of 2 °C / min, and then cool it to room temperature with the furnace to obtain Co 8 NiS 8 / Ni 3 S 2 -CNF composite material.

2. The Co 8 NiS 8 / Ni 3 S 2 -CNF catalytic material preparation method, It is characterized in that The stirring in step 1 is carried out with a magnetic stirrer for 30 min.

3. The Co 8 NiS 8 / Ni 3 S 2 -CNF catalytic material preparation method, It is characterized in that The heat preservation time of step 1 is 12 - 16 h.

4. The Co 8 NiS 8 / Ni 3 S 2 -CNF catalytic material preparation method, It is characterized in that The stirring in step 2 is carried out with a magnetic stirrer for 15 min.

5. The Co 8 NiS 8 / Ni 3 S 2 -CNF catalytic material preparation method, It is characterized in that The heat preservation time of step 2 is 6 - 12 h.

6. The Co 8 NiS 8 / Ni 3 S 2 -CNF catalytic material preparation method, It is characterized in that The washing in both step 1 and step 2 is carried out by alternately washing with deionized water and absolute ethanol for 3 - 5 times.

7. The Co 8 NiS 8 / Ni 3 S 2 -CNF catalytic material preparation method, It is characterized in that The drying in steps 1 - 3 is carried out at 60 °C for 12 - 24 h.

8. A Co 8 NiS 8 / Ni 3 S 2 -CNF composite material prepared by the method according to any one of claims 1 to 7.

9. An application of Co 8 NiS 8 / Ni 3 S 2 -CNF in the separator of a Li-S battery.

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