NiCoSe / carbon cloth / S composite lithium-sulfur battery positive electrode material and preparation method thereof

Abstract

The application belongs to the technical field of preparation of lithium-sulfur battery electrode materials, and particularly relates to a NiCoSe / carbon cloth / S composite lithium-sulfur battery positive electrode material and a preparation method thereof. The application synthesizes a CoNiSe / carbon cloth composite material with a honeycomb structure by using an in-situ growth and heat treatment method, and the composite material is used for a lithium-sulfur battery positive electrode after loading of sulfur. The positive electrode material uses a carbon fiber cloth as a three-dimensional carbon material conductive network, NiCoSe is compounded on the carbon fiber cloth to form a NiCoSe / carbon cloth composite material, and elemental sulfur is loaded on the NiCoSe / carbon cloth composite material, and the NiCoSe is a cobalt-nickel bimetallic selenide with a honeycomb structure. The electrode material prepared by the application has more excellent conductivity and stability compared with traditional flexible electrode materials. By compounding the double transition metal selenide on the carbon cloth, the adsorption of the carbon cloth to polysulfides is improved, the "shuttle effect" is inhibited, and the cycle stability and electrochemical performance of the battery are greatly improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of preparation of lithium-sulfur battery electrode materials, and particularly relates to a NiCoSe / carbon cloth / S composite lithium-sulfur battery positive electrode material and a preparation method thereof. BACKGROUND

[0002] Lithium-sulfur batteries are active materials with sulfur as the active material, have high theoretical specific capacity and energy density, sulfur is abundant in the earth, has low price, can reduce the cost of the battery, and therefore development of lithium-sulfur batteries has great application prospect. Even though lithium-sulfur batteries have many advantages, but the problems faced still restrict large-scale development and commercial application. The host material of sulfur is mainly carbon material, such as carbon nanotubes, graphene and porous carbon material as the matrix material to load sulfur element. The structure of elemental sulfur changes in the charging and discharging process, which will cause the volume expansion of the electrode, affect the capacity and electrochemical performance of lithium-sulfur batteries. In order to solve the problems of poor sulfur conductivity, soluble polysulfide shuttle effect, volume expansion in the electrochemical reaction process and the like faced by lithium-sulfur batteries, many researchers composite sulfur and many carbon materials to prepare sulfur-carbon electrodes, which enhances the overall conductivity and stability, such as carbon nanotubes, carbon spheres, graphene, carbon fiber cloth and the like all show good electrochemical performance. Directly constructing a conductive network by using carbon material can alleviate the poor conductivity of elemental sulfur itself, thereby improving the conductivity of the material.

[0003] The research on lithium-sulfur batteries in the prior art still faces many problems, the ion conductivity and electronic conductivity of S and Li2S are poor, which makes the conversion kinetics of sulfur slow, the reaction rate is poor, and further reduces the utilization rate of active material; the high-order polysulfide produced by the sulfur conversion reaction is dissolved in the ether-based electrolyte, and the dissolved polysulfide tends to diffuse to the anode under the driving of the concentration gradient, since the lithium metal anode has strong reducing property, the diffused polysulfide is directly reduced to insoluble Li2S and Li2S2 particles. These particles attached to the surface of the metal lithium will cause capacity reduction and coulombic efficiency reduction. At the same time, the dissolved polysulfide will increase the viscosity of the electrolyte, thereby slowing down the transmission of lithium ions; the conversion reaction of sulfur is accompanied by a large volume change. The structural change will cause the electrode material to have a large volume expansion, and the repeated volume change will destroy its own performance and structure, reduce the stability of the electrode material, and rapidly reduce the capacity of the electrode.

[0004] The traditional carbon material can only solve the problem of poor polysulfide adsorption by controlling its microstructure, has single property, and the effect is not good, and the electrochemical performance still needs to be improved. The polar material has good chemical adsorption to polysulfide, and can catalyze the conversion of polysulfide, therefore, the combination of polar and non-polar materials can significantly improve the electrochemical performance of the electrode material. SUMMARY

[0005] To solve the problems existing in the prior art, the application provides a NiCoSe / carbon cloth / S composite lithium-sulfur battery positive electrode material and a preparation method thereof.

[0006] To achieve the above object, the application adopts the following technical scheme:

[0007] A NiCoSe / carbon cloth / S composite lithium-sulfur battery positive electrode material, the positive electrode material is carbon fiber cloth as a three-dimensional carbon material conductive network, and a cobalt-nickel double metal selenide (NiCoSe) with a honeycomb structure is compounded, and elemental sulfur is loaded on the composite material. On the basis of this structure, the flexible carbon fiber cloth can realize efficient ion and electron transmission, and has a certain physical adsorption capacity for polysulfides. In addition, the honeycomb polar NiCoSe double metal selenide compounded on the carbon fiber cloth can improve the chemical adsorption of polysulfides and act as a catalyst for the redox reaction of sulfur elements, accelerating the electrochemical reaction kinetics process, thereby improving the electrochemical performance of the lithium-sulfur battery.

[0008] The application synthesizes a CoNiSe / carbon cloth composite material with a honeycomb structure by in-situ growth and heat treatment, and the composite material is used for a lithium-sulfur battery positive electrode after loading sulfur. The electrode material prepared by the application has more excellent conductivity and stability compared with traditional flexible electrode materials. By compounding the double transition metal selenide on the carbon cloth, the adsorption of polysulfides by the carbon cloth is improved, the "shuttle effect" is inhibited, and the cycle stability and electrochemical performance of the battery are greatly improved.

[0009] A preparation method of a NiCoSe / carbon cloth / S composite lithium-sulfur battery positive electrode material, specifically comprising the following steps:

[0010] (1) A cut carbon cloth is prepared and is ultrasonically treated in acetone, ethanol and deionized water for 10-30 min respectively, and is then dried in an oven at 80 DEG C, and is calcined at 900 DEG C for 2-3 h under an argon atmosphere;

[0011] (2) Cobalt salt and nickel salt are added to a methanol solution, and are stirred for 10-20 min;

[0012] (3) 2-methylimidazole is added to the methanol solution, and is stirred and dissolved;

[0013] (4) The solution in step (3) is added to the mixed solution in step (2), and is stirred for 20-30 min, and then is transferred into a reaction kettle together with the pretreated carbon cloth in step (1) for reaction;

[0014] (5) The carbon cloth after heat treatment in step (4) is washed with ethanol for 2-4 times, and the washed carbon cloth is dried in an oven at 80 DEG C.

[0015] (6) Put the carbon cloth dried in step (5) and selenium source into a tube furnace for selenization;

[0016] (7) Dissolve sulfur powder in carbon disulfide and stir to obtain a uniform solution;

[0017] (8) Put the carbon cloth treated in step (6) into the uniform solution in step (7) and stand for 4-6 min, and then put into an oven for drying to obtain a CoNiSe / carbon cloth / S composite lithium-sulfur battery positive electrode material.

[0018] According to the application, in step (2), the cobalt salt is cobalt nitrate hexahydrate, the nickel salt is nickel nitrate hexahydrate, the molar ratio of the cobalt salt to the nickel salt is (1.0-2.0):(0.5-1.5), the mass-volume ratio of the cobalt salt to methanol is (0.3-0.6):(20-40), and the mass-volume ratio of the nickel salt to methanol is (0.15-0.45):(10-30), unit: g / mL; further preferably, the molar ratio of the cobalt salt to the nickel salt is 1.0:1.0, the mass-volume ratio of the cobalt salt to methanol is 0.3:20, and the mass-volume ratio of the nickel salt to methanol is 0.3:20, unit: g / mL.

[0019] According to the application, in step (3), the mass-volume ratio of 2-methylimidazole to methanol is (1.64-4.92):(10-30), unit: g / mL; further preferably, the mass-volume ratio of 2-methylimidazole to methanol is 3.28:20, unit: g / mL.

[0020] According to the application, in step (4), the reaction temperature in the high-pressure reaction kettle is 100-150 DEG C, and the reaction time is 8-16 h; further preferably, the reaction temperature in the high-pressure reaction kettle is 120 DEG C, and the reaction time is 14 h.

[0021] According to the application, in step (6), the selenium source is selenium powder, the carbon cloth is placed in a tube furnace with 0.3-0.6 g of selenium powder for selenization, the temperature is 500-600 DEG C, and the holding time is 2-3 h; further preferably, the carbon cloth is placed in a tube furnace with 0.5 g of selenium powder for selenization, the temperature is 600 DEG C, and the holding time is 3 h.

[0022] Beneficial effects

[0023] The application discloses a NiCoSe / carbon cloth / S composite lithium-sulfur battery positive electrode material and a preparation method thereof.

[0024] The positive electrode material is a carbon fiber cloth as a three-dimensional carbon material conductive network, and a cobalt-nickel bimetallic selenide (NiCoSe) with a honeycomb structure is compounded, and elemental sulfur is loaded on the composite material. On the basis of this structure, the flexible carbon fiber cloth can realize efficient ion and electron transmission, and has a certain physical adsorption capacity for polysulfides. In addition, the honeycomb-like polar NiCoSe bimetallic selenide is compounded on the carbon fiber cloth, which can improve the chemical adsorption of polysulfides, and also act as a catalyst for the redox reaction of sulfur element, accelerate the electrochemical reaction kinetics process, thereby improving the electrochemical performance of the lithium-sulfur battery.

[0025] The preparation process described in the application is very simple, easy to operate, and the prepared composite material has a honeycomb-like morphology, a large specific surface area, is beneficial to the loading of sulfur, increases the loading amount of sulfur, the three-dimensional honeycomb structure can also enhance the adsorption of polysulfides, inhibit the shuttle effect of polysulfides, and the prepared electrode material also has excellent cycle stability, providing a new idea for flexible electrode materials. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The XRD pattern of the NiCoSe / carbon cloth composite material obtained by the application;

[0027] Figure 2 The SEM image of the NiCoSe / carbon cloth composite material obtained by the application;

[0028] Figure 3 The long cycle performance curve of the lithium-sulfur battery prepared by the NiCoSe / carbon cloth / S composite positive electrode material of the application. DETAILED DESCRIPTION

[0029] Hereinafter, the application will be described in detail. Before the description, it should be understood that the terms used in the specification and the appended claims should not be construed as being limited to the general and dictionary meanings and should be construed as having meanings and concepts corresponding to the technology to which the application pertains based on the principle that the inventor is allowed to define appropriate terms in order to best explain the application. Therefore, the description presented herein is merely a preferred example in which all features are provided for the purpose of illustration only and is not intended to limit the scope of the application, so it should be understood that other equivalents or modifications thereof can be obtained by those skilled in the art without departing from the spirit and scope of the application.

[0030] The following examples are merely listed as examples of embodiments of the application and do not constitute any limitation on the application, and those skilled in the art can understand that modifications within the scope of the spirit and concept of the application fall within the protection scope of the application. Unless otherwise specified, the reagents and instruments used in the following examples are commercially available products.

[0031] Example 1

[0032] A NiCoSe / carbon cloth / S composite lithium-sulfur battery positive electrode material is prepared by the following method:

[0033] A piece of cut carbon cloth is prepared by ultrasonicating with acetone, ethanol, and deionized water for 15 minutes each, and then drying in an oven at 80°C. Then, under an argon atmosphere, the carbon cloth is calcined at 900°C for 2 hours. 0.3 g of cobalt nitrate hexahydrate and 0.3 g of nickel nitrate hexahydrate are added to 20 ml of a methanol solution, stirred for 10-20 minutes, and a solution A is prepared. 3.28 g of 2-methylimidazole is added to 20 ml of methanol, stirred and dissolved, and a solution B is prepared. Solution B is added to solution A, stirred for 20-30 minutes, and then placed in a reaction kettle together with the pretreated carbon cloth at 120°C for 14 hours. The heat-treated carbon cloth is washed with ethanol for 2-4 times, and then dried in an oven at 80°C. The dried carbon cloth is placed in a tube furnace with 0.5 g of selenium powder, heat-treated at 600°C for 3 hours, and then placed in a solution formed by sulfur powder (0.3 g) and carbon disulfide (10 mL) to load sulfur, and then dried in an oven to obtain a CoNiSe / carbon cloth / S composite lithium-sulfur battery positive electrode material.

[0034] It is detected that the lithium-sulfur battery positive electrode material obtained in this example has an initial discharge capacity of 575 mAh / g at a current density of 1 C.

[0035] Example 2

[0036] A NiCoSe / carbon cloth / S composite lithium-sulfur battery positive electrode material is prepared by the following method:

[0037] A piece of cut carbon cloth is prepared by ultrasonicating with acetone, ethanol, and deionized water for 10 minutes each, and then drying in an oven at 80°C. Then, under an argon atmosphere, the carbon cloth is calcined at 900°C for 3 hours. 0.6 g of cobalt nitrate hexahydrate and 0.3 g of nickel nitrate hexahydrate are added to 35 ml of a methanol solution, stirred for 10-20 minutes, and a solution A is prepared. 4.92 g of 2-methylimidazole is added to 35 ml of methanol, stirred and dissolved, and a solution B is prepared. Solution B is added to solution A, stirred for 20-30 minutes, and then placed in a reaction kettle together with the pretreated carbon cloth at 120°C for 16 hours. The heat-treated carbon cloth is washed with ethanol for 2-4 times, and then dried in an oven at 80°C. The dried carbon cloth is placed in a tube furnace with 0.5 g of selenium powder, heat-treated at 600°C for 2 hours, and then placed in a solution formed by sulfur powder (0.5 g) and carbon disulfide (15 mL) to load sulfur, and then dried in an oven to obtain a CoNiSe / carbon cloth / S composite lithium-sulfur battery positive electrode material.

[0038] The lithium-sulfur battery positive electrode material obtained in this embodiment has an initial discharge capacity of 520 mAh / g at a current density of 1 C.

[0039] Example 3

[0040] A NiCoSe / carbon cloth / S composite lithium-sulfur battery positive electrode material is prepared by the following method:

[0041] A piece of cut carbon cloth is prepared by ultrasonic treatment in acetone, ethanol and deionized water for 10 min, and then dried in an oven at 80℃. Then, the carbon cloth is calcined at 900℃ for 3 h under an argon atmosphere. 0.6 g of cobalt nitrate hexahydrate and 0.6 g of nickel nitrate hexahydrate are added to 35 ml of a methanol solution, and stirred for 10-20 min to prepare solution A. 6.56 g of 2-methylimidazole is added to 35 ml of a methanol solution, and stirred to dissolve, to prepare solution B. Solution B is added to solution A, and stirred for 20-30 min. The mixture is then transferred into a reaction kettle together with the pretreated carbon cloth, and reacted at 120℃ for 16 h. The heat-treated carbon cloth is washed with ethanol for 2-4 times, and then dried in an oven at 80℃. The dried carbon cloth is placed in a tube furnace together with 0.5 g of selenium powder, and heat-treated at 600℃ for 2 h. The heat-treated carbon cloth is then placed in a solution formed by 0.3 g of sulfur powder and 10 mL of carbon disulfide, and allowed to stand to load sulfur. The carbon cloth is then dried in an oven to obtain a CoNiSe / carbon cloth / S composite lithium-sulfur battery positive electrode material.

[0042] The lithium-sulfur battery positive electrode material obtained in this embodiment has an initial discharge capacity of 496 mAh / g at a current density of 1 C.

[0043] Experimental Example

[0044] The NiCoSe / carbon cloth composite material obtained in the present application is subjected to performance testing, and the results are as follows.

[0045] The XRD pattern of the NiCoSe / carbon cloth composite material is shown in Figure 1 The results show that the composite material obtained in the present application has a high degree of crystallinity, and the NiCoSe / carbon cloth is composed of two phases. The diffraction peaks of the NiCoSe / carbon cloth material are related to NiSe2 (JCPDE NO: 65-5016) and CoSe2 (JCPDE NO: 65-3327).

[0046] The SEM pattern of the NiCoSe / carbon cloth composite material is shown in Figure 2As shown in the figure, the results show that the NiCoSe / carbon cloth composite material obtained by the application has a honeycomb-like morphology, has a large specific surface area, is beneficial to the loading of sulfur, and improves the loading capacity of sulfur, and the three-dimensional honeycomb structure can also enhance the adsorption of polysulfides.

[0047] The long cycle performance curve of the lithium-sulfur battery prepared by the NiCoSe / carbon cloth / S composite positive electrode material is as shown in the figure Figure 3 As shown in the figure, the results show that the lithium-sulfur battery positive electrode material obtained by the application has good capacity retention and good cycle stability.

[0048] The above examples are only used to illustrate the technical solutions of the application, but not to limit it; although the application has been described in detail with reference to the foregoing examples, the technical solutions recorded in the foregoing examples can still be modified or some technical features can be replaced by equivalents for ordinary skilled in the art; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions claimed by the application.

Claims

1. A preparation method of a NiCoSe / carbon cloth / S composite lithium-sulfur battery positive electrode material, characterized in that, The positive electrode material uses carbon fiber cloth as a three-dimensional carbon material conductive network, the carbon fiber cloth is compounded with NiCoSe to form a NiCoSe / carbon cloth composite material, elemental sulfur is loaded on the NiCoSe / carbon cloth composite material, and the NiCoSe is a cobalt-nickel bimetallic selenide with a honeycomb structure; the positive electrode material has a three-dimensional honeycomb structure. The specific steps of the preparation method are as follows: (1) A piece of cut carbon cloth is ultrasonically treated with acetone, ethanol and deionized water respectively, dried, and then calcined to obtain pretreated carbon cloth; (2) Cobalt salt and nickel salt are added to a methanol solution and stirred to dissolve; (3) 2-methylimidazole is added to the methanol solution and stirred to dissolve; (4) The solution obtained in step (3) is added to the solution obtained in step (2), stirred, and then transferred into a reaction container together with the pretreated carbon cloth in step (1) to react, to obtain heat-treated carbon cloth; (5) The heat-treated carbon cloth obtained in step (4) is washed and dried; (6) The dried carbon cloth in step (5) is selenized with a selenium source; (7) Sulfur powder is dissolved in carbon disulfide to obtain a uniform solution after stirring; (8) The selenized carbon cloth in step (6) is placed in the uniform solution in step (7) and left to stand, and then dried to obtain a CoNiSe / carbon cloth / S composite lithium-sulfur battery positive electrode material.

2. The preparation method of the NiCoSe / carbon cloth / S composite lithium-sulfur battery positive electrode material according to claim 1, characterized in that, In step (1), the calcination conditions are as follows: 900 DEG C under an argon atmosphere, and calcination for 2-3 h.

3. The preparation method of the NiCoSe / carbon cloth / S composite lithium-sulfur battery positive electrode material according to claim 1, characterized in that, In step (2), the cobalt salt is cobalt nitrate hexahydrate, and the nickel salt is nickel nitrate hexahydrate.

4. The preparation method of the NiCoSe / carbon cloth / S composite lithium-sulfur battery positive electrode material according to claim 3, characterized in that The molar ratio of the cobalt salt to the nickel salt is (1.0-2.0):(0.5-1.5), the mass-volume ratio of the cobalt salt to methanol is (0.3-0.6):(20-40), and the mass-volume ratio of the nickel salt to methanol is (0.15-0.45):(10-30).

5. The preparation method of the NiCoSe / carbon cloth / S composite lithium-sulfur battery positive electrode material according to claim 1, characterized in that, In step (3), the mass-volume ratio of 2-methylimidazole to methanol is (1.64-4.92):(10-30).

6. The preparation method of the NiCoSe / carbon cloth / S composite lithium-sulfur battery positive electrode material according to claim 1, characterized in that, In step (4), the reaction container is a high-pressure reaction kettle, the reaction temperature in the high-pressure reaction kettle is 100 DEG C-150 DEG C, and the reaction time is 8-16 h.

7. The preparation method of the NiCoSe / carbon cloth / S composite lithium-sulfur battery positive electrode material according to claim 1, characterized in that, In step (5), the heat-treated carbon cloth is washed with ethanol for 2-4 times, and then placed in an oven for drying at 80 DEG C. 8.The method for preparing the NiCoSe / carbon cloth / S composite lithium-sulfur battery cathode material of claim 1, characterized in that, In step (6), the selenium source is selenium powder, the carbon cloth is selenized with 0.3-0.6 g of selenium powder in a tube furnace at a temperature of 500 DEG C-600 DEG C for 2-3 h.

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