CN115692639A - CoSe 2 Positive electrode material of/NC-CNT/S lithium-sulfur battery and preparation method thereof - Google Patents

Abstract

The invention belongs to the technical field of preparation of lithium-sulfur battery electrode materials, and in particular relates to a CoSe ₂ /NC-CNT/S lithium-sulfur battery positive electrode material and a preparation method thereof. The anode material of the present invention is prepared by forming a CoSe ₂ /NC-CNT composite material from CoSe ₂ and Co-NC-CNT materials, and the simple substance S is uniformly loaded on the CoSe ₂ /NC-CNT composite material. This unique structure is conducive to expanding the electrode/electrolyte interface area, improving the electrochemical activity of the material, regulating the volume change of the electrode material during charge and discharge, and realizing the rapid diffusion of electrons and the rapid transfer of electrolyte ions, which contribute to the high performance of lithium-sulfur batteries. The exploration and design of electrode materials has opened up new ideas.

Description

A kind of CoSe2/NC-CNT/S lithium-sulfur battery cathode material and preparation method thereof

technical field

The invention belongs to the technical field of preparation of lithium-sulfur battery electrode materials, and in particular relates to a CoSe ₂ /NC-CNT/S lithium-sulfur battery positive electrode material and a preparation method thereof.

Background technique

With the rapid development of portable electronics and electric vehicles, energy storage devices, such as lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), and zinc-ion batteries (ZIBs), have received increasing attention. Among them, lithium-sulfur battery has become an important member. Lithium-sulfur batteries are considered to be one of the most promising green energy sources due to their good electrochemical performance and environmental friendliness.

So far, there are many positive electrode sulfur carrier materials for lithium-sulfur batteries, such as metal sulfides, metal oxides, and metal selenides. Among them, transition metal selenides (TMDs) have attracted extensive attention due to their high theoretical capacity and good cycle stability. Compared with metal oxides/sulfides, TMDs have higher electronic conductivity and richer redox reactions. In recent years, selenide materials have been considered as potential candidates for lithium sulfur due to their abundant resources and large theoretical capacity. This kind of battery has many advantages, such as excellent theoretical energy density (2600Wh kg ^-1 ), high theoretical specific capacity (1675 mAhg ^-1 ), abundant materials, low cost, safety and environmental protection. However, due to the insulation problem of the final discharge products (S and _Li2S2 / _Li2S ), and the dissolution of _intermediate product sulfides in the electrolyte, the shuttle effect of polysulfides is caused, which affects the application of batteries.

Contents of the invention

In order to solve the problems in the above-mentioned prior art, the present invention provides a CoSe ₂ /NC-CNT/S lithium-sulfur battery positive electrode material and a preparation method thereof, a CoSe ₂ /NC-CNT/S described in the present invention The positive electrode material can suppress and alleviate the large volume change during the cycle, so that it has excellent cycle stability, which opens up new ideas for the exploration and design of high-performance electrode materials for lithium-sulfur batteries.

To achieve the above object, the present invention adopts the following technical solutions:

A CoSe ₂ /NC-CNT/S lithium-sulfur battery cathode material, based on the synthesis of ZIF-8@ZIF-67 core-shell structure material, under high temperature conditions, a large amount of nitrogen doping is produced under the catalysis of Co particles carbon nanotubes, and _CoSe2 was further synthesized on nitrogen-doped carbon nanotubes. This unique structure is conducive to expanding the electrode/electrolyte interface area, improving the electrochemical activity of the material, regulating the volume change during charge and discharge, and realizing the rapid diffusion of electrons and the rapid transfer of electrolyte ions.

The method for the above-mentioned CoSe ₂ /NC-CNT/S lithium-sulfur battery cathode material specifically includes the following steps:

(1) Preparation of ZIF-8@ZIF-67 core-shell structure material: using cobalt nitrate hexahydrate and 2-methylimidazole as the main raw materials, methanol as the solvent, centrifugation, washing and drying to obtain ZIF-8@ZIF-67 core Shell structural materials;

(2) Preparation of Co-NC-CNT composite material: carbonize the ZIF-8@ZIF-67 core-shell structure material obtained in step (1) under inert gas, and keep it at 700℃~900℃ for 3h to obtain Co-NC -CNT composite materials;

(3) Preparation of CoSe ₂ /NC-CNT composite material: the Co-NC-CNT material obtained in step (2) was mixed with selenium powder at a ratio of 1:2 and ground evenly, annealed in an inert atmosphere, and kept at 350°C for 6 h, That is, the CoSe ₂ /NC-CNT composite material is obtained;

(4) Preparation of CoSe ₂ /NC-CNT/S material: Mix CoSe ₂ /NC-CNT/S obtained in step (3) with sulfur powder at a ratio of 1:1.5 and grind evenly into a glass bottle, and seal it with aluminum foil. Annealing under atmosphere, holding at 155°C for 12h, then removing the aluminum foil, and holding at 200°C for 30min in an inert gas to obtain CoSe ₂ /NC-CNT/S material.

Beneficial effect

The invention discloses a CoSe ₂ /NC-CNT/S lithium-sulfur battery cathode material and a preparation method thereof. Compared with the prior art, the invention has the following advantages:

1. The present invention provides a method for preparing a CoSe ₂ /NC-CNT/S lithium-sulfur battery cathode material. This method has the advantages of low energy consumption and low cost.

2. The CoSe ₂ /NC-CNT/S lithium-sulfur battery anode material of the present invention is rich in carbon nanotubes. This unique structure is conducive to expanding the electrode/electrolyte interface area, improving the electrochemical activity of the material, regulating the volume change during charge and discharge, and realizing the rapid diffusion of electrons and the rapid transfer of electrolyte ions.

3. Compared with other metal compounds, the raw materials prepared by the present invention are cheap and widely sourced; during the preparation process, waste liquid and waste materials that cannot be processed are not produced, the energy consumption is low, the environment is friendly, and the operability is strong. provides a new direction.

Description of drawings

Fig. 1 is the SEM spectrum of CoSe ₂ /NC-CNT/S lithium-sulfur battery cathode material in embodiment 2;

Fig. 2 is the XRD schematic diagram of CoSe ₂ /NC-CNT/S lithium-sulfur battery cathode material in embodiment 2;

FIG. 3 is a rate diagram of the CoSe ₂ /NC-CNT/S lithium-sulfur battery positive electrode material in Example 2 under different current densities.

Fig. 4 is a long-term cycle diagram of the CoSe ₂ /NC-CNT/S lithium-sulfur battery cathode material in Example 2 under 1C condition.

Detailed ways

Hereinafter, the present invention will be described in detail. Before proceeding with the description, it should be understood that the terms used in this specification and appended claims should not be construed as limited to ordinary and dictionary meanings, but should be best interpreted while allowing the inventor to properly define the terms On the basis of the principles of the present invention, explanations are made based on meanings and concepts corresponding to the technical aspects of the present invention. Accordingly, the descriptions set forth herein are preferred examples for illustrative purposes only and are not intended to limit the scope of the invention, so that it should be understood that other, etc. price or improvement.

The following examples are only listed as examples of embodiments of the present invention, and do not constitute any limitation to the present invention. Those skilled in the art can understand that modifications within the scope of not departing from the essence and design of the present invention all fall into the protection of the present invention. scope. Unless otherwise specified, the reagents and instruments used in the following examples are all commercially available products.

Example 1

A CoSe ₂ /NC-CNT/S lithium-sulfur battery cathode material, prepared by the following method:

(1) ZIF-8@ZIF-67 core-shell structure material. Weigh 2.98g of zinc nitrate hexahydrate and 3.08g of 2-methylimidazole, put them into 75ml of methanol respectively, and mark them as A and B solutions. Pour solution B into solution A, stir for 24 hours, centrifuge, wash and dry, and first obtain white ZIF-8 material.

Weigh 0.25g ZIF-8, 2.91g cobalt nitrate hexahydrate, and 3.08g 2-methylimidazole, put them into 50ml methanol respectively, and mark them as A, B, and C solutions. First introduce solution B into solution A, then put solution C into the mixture of A and B, and stir for 24 hours. Centrifuge, wash and dry to obtain the ZIF-8@ZIF-67 core-shell structure material.

(2) Preparation of Co-NC-CNT materials. The ZIF-8@ZIF-67 core-shell structure material obtained in step (1) was carbonized under an inert gas, and kept at 700°C for 3 hours to obtain a Co-NC-CNT material.

(3) Preparation of CoSe ₂ /NC-CNT composite material. The Co-NC-CNT material obtained in step (2) was mixed with selenium powder at a ratio of 1:2 and ground evenly, annealed in an inert atmosphere, and kept at 350°C for 6 h to obtain a CoSe ₂ /NC-CNT composite material.

(4) Preparation of CoSe ₂ /NC-CNT/S material. Mix the CoSe ₂ /NC-CNT and sulfur powder obtained in step (3) at a ratio of 1:1.5 and grind them evenly into a glass bottle, seal it with aluminum foil, anneal it in an inert atmosphere, keep it at 155°C for 12h, and then put it in an inert gas The CoSe ₂ /NC-CNT/S material was obtained by keeping it at 200°C for 30 minutes.

The prepared CoSe ₂ /NC-CNT/S material is used as the positive electrode material of the lithium-sulfur battery. The positive electrode material is mixed with acetylene black and PVDF in a ratio of 7:2:1, and a certain amount of solvent (nitromethylpyrrolidone) is added dropwise. After uniform mixing, ball milling, drying, slicing and weighing, the prepared electrode sheet is used for battery assembly to obtain a battery for testing.

Example 2

A CoSe ₂ /NC-CNT/S lithium-sulfur battery cathode material, prepared by the following method:

(1) ZIF-8@ZIF-67 core-shell structure material. Weigh 2.98g of zinc nitrate hexahydrate and 3.08g of 2-methylimidazole, put them into 75ml of methanol respectively, and mark them as A and B solutions. Pour solution B into solution A, stir for 24 hours, centrifuge, wash and dry, and first obtain white ZIF-8 material.

Weigh 0.25g ZIF-8, 2.91g cobalt nitrate hexahydrate, and 3.08g 2-methylimidazole, put them into 50ml methanol respectively, and mark them as A, B, and C solutions. First introduce solution B into solution A, then put solution C into the mixture of A and B, and stir for 24 hours. Centrifuge, wash and dry to obtain the ZIF-8@ZIF-67 core-shell structure material.

(2) Preparation of Co-NC-CNT materials. The ZIF-8@ZIF-67 core-shell structure material obtained in step (1) was carbonized under an inert gas, and kept at 800°C for 3 hours to obtain a Co-NC-CNT composite material.

(3) Preparation of CoSe ₂ /NC-CNT materials. The Co-NC-CNT composite material obtained in step (2) was mixed with selenium powder at a ratio of 1:2 and ground evenly, annealed in an inert atmosphere, and kept at 350°C for 6 h to obtain CoSe ₂ /NC-CNT material.

(4) Preparation of CoSe ₂ /NC-CNT/S material. Mix the CoSe ₂ /NC-CNT and sulfur powder obtained in step (3) at a ratio of 1:1.5 and grind them evenly into a glass bottle, seal it with aluminum foil, anneal it in an inert atmosphere, and keep it at 155°C for 12 hours; then remove the aluminum foil, The CoSe ₂ /NC-CNT/S material was obtained by inert gas at 200°C for 30 minutes.

The SEM spectrum of the obtained CoSe ₂ /NC-CNT/S lithium-sulfur battery cathode material is shown in Figure 1. From Figure 1, it can be seen that there are a large number of carbon nanotubes on the basis of the ZIF-8@ZIF-67 core-shell structure Generated, which will facilitate the transport and migration of electrons.

The XRD schematic diagram of the obtained CoSe ₂ /NC-CNT/S lithium-sulfur battery cathode material is shown in Figure 2. From Figure 2, it can be seen that the peak corresponds to the peak of the PDF card (09#0234) of CoSe ₂ .

The prepared CoSe ₂ /NC-CNT/S positive electrode material was used as the positive electrode material of the lithium-sulfur battery. The positive electrode material was mixed with acetylene black and PVDF in a ratio of 7:2:1, and a certain amount of solvent (nitromethylpyrrolidone ) after mixing evenly, ball milling, drying, slicing and weighing, and using the prepared electrode sheet for battery assembly to obtain a battery for testing. Test the performance of the battery, as follows:

Test method: Carry out long-term cycle test on the battery at a current density of 1C; perform rate test at different current densities of 0.2C, 0.5C, 1C, 2C, and 3C.

Test results: In Figure 3, under the condition of high current density of 1C, the initial specific capacity can be as high as 1137 mAh g ^-1 , and after nearly 120 cycles of high current, there is still a large specific capacity of 765 mAh g ^-1 Capacity, which shows that it has excellent long-term cycle performance, and also has good Coulombic efficiency; from the rate cycle diagram in Figure 4, at different current densities of 0.2C, 0.5C, 1C, 2C, and 3C, there are 1100, Specific capacities of 991, 865, 773, 713 mAh g ^-1 . Finally, when the current density returns to 0.2C, the capacity reaches 962mAh g ^-1 . It can be seen that after experiencing a large current cycle, it still maintains a good specific capacity, indicating that it has good cycle stability. At the same time, under the current density of 2C and 3C, the change of specific capacity is small, which also proves that it has good high-current cycle performance.

Example 3

A CoSe ₂ /NC-CNT/S lithium-sulfur battery cathode material, prepared by the following method:

(1) ZIF-8@ZIF-67 core-shell structure material. Weigh 2.98g zinc nitrate hexahydrate and 3.08g

2-Methylimidazole, put into 75ml of methanol respectively, and marked as A, B solution. Pour solution B into solution A, stir for 24 hours, centrifuge, wash and dry, and first obtain white ZIF-8 material. Weigh 0.25g ZIF-8, 2.91g cobalt nitrate hexahydrate, and 3.08g 2-methylimidazole, put them into 50ml methanol respectively, and mark them as A, B, and C solutions. First introduce solution B into solution A, then put solution C into the mixture of A and B, and stir for 24 hours. Centrifuge, wash and dry to obtain the ZIF-8@ZIF-67 core-shell structure material.

(2) Preparation of Co-NC-CNT composites. The ZIF-8@ZIF-67 core-shell structure material obtained in step (1) was carbonized under an inert gas, and kept at 900°C for 3 hours to obtain a Co-NC-CNT composite material.

(3) Preparation of CoSe ₂ /NC-CNT materials. The Co-NC-CNT material obtained in step (2) was mixed with selenium powder at a ratio of 1:2 and ground evenly, annealed in an inert atmosphere, and kept at 350°C for 6 h to obtain a CoSe ₂ /NC-CNT composite material.

(4) Preparation of CoSe ₂ /NC-CNT/S material. Mix the CoSe ₂ /NC-CNT material obtained in step (3) with sulfur powder at a ratio of 1:1.5 and grind it evenly into a glass bottle, seal it with aluminum foil, anneal it in an inert atmosphere, and keep it at 155°C for 12 hours; then remove the aluminum foil, In inert gas at 200° C. for 30 minutes, the CoSe ₂ /NC-CNT/S material is obtained.

The prepared CoSe ₂ /NC-CNT/S is used as the positive electrode material of lithium-sulfur battery. The positive electrode material is mixed with acetylene black and PVDF in a ratio of 7:2:1, and a certain amount of solvent (nitromethylpyrrolidone) is added dropwise to mix After uniformity, ball milling, drying, slicing and weighing, the prepared electrode sheet is used for battery assembly to obtain a battery for testing.

The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art can still understand the foregoing embodiments. Modifications are made to the technical solutions described, or equivalent replacements are made to some of the technical features; 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 in the present invention.

Claims (10)

1. A CoSe ₂ /NC-CNT/S lithium-sulfur battery positive electrode material, characterized in that the positive electrode material is selenized by Co-NC-CNT material to form a CoSe ₂ /NC-CNT composite material, and the single substance S is evenly loaded on Made on CoSe ₂ /NC-CNT composites. 2. The CoSe ₂ /NC-CNT/S lithium-sulfur battery cathode material according to claim 1, wherein the Co-NC-CNT material is prepared from a ZIF-8@ZIF-67 core-shell structure material. 3. A method for preparing a CoSe ₂ /NC-CNT/S lithium-sulfur battery cathode material, characterized in that it comprises the following steps: (1) Preparation of ZIF-8@ZIF-67 core-shell structure material: Zinc nitrate hexahydrate, cobalt nitrate hexahydrate and 2-methylimidazole were used as the main raw materials, and methanol was used as the solvent to prepare ZIF-8@ZIF-67 core Shell structural materials; (2) Preparation of Co-NC-CNT material: the ZIF-8@ZIF-67 core-shell structure material obtained in step (1) was carbonized at high temperature under inert gas to obtain Co-NC-CNT material; (3) Preparation of CoSe ₂ /NC-CNT composite material: the Co-NC-CNT material obtained in step (2) is mixed with selenium powder and ground evenly, and annealed in an inert atmosphere to obtain CoSe ₂ /NC-CNT composite material ; (4) Preparation of CoSe ₂ /NC-CNT/S material: Mix the CoSe ₂ /NC-CNT obtained in step (3) with sulfur powder and grind evenly, seal it, and anneal it in an inert atmosphere; keep it warm in an inert gas after unsealing , that is, the CoSe ₂ /NC-CNT/S material is obtained. 4. The preparation method of CoSe ₂ /NC-CNT/S lithium-sulfur battery cathode material according to claim 3, characterized in that, in the step (1), the ZIF-8@ZIF-67 core-shell structure material The preparation method is as follows: Preparation of ZIF-8 material: Weigh zinc nitrate hexahydrate and 2-methylimidazole, put them in methanol respectively, and mark them as A and B solutions, pour B solution into A solution, stir, centrifuge, wash and dry to obtain ZIF-8 material; Preparation of ZIF-8@ZIF-67 core-shell structure material: Weigh ZIF-8 material, cobalt nitrate hexahydrate, and 2-methylimidazole, put them into methanol respectively, and mark them as C, D, and E solutions. The solution was poured into solution C to obtain a mixed solution, and then solution E was poured into the mixed solution, stirred, centrifuged, washed and dried to obtain a ZIF-8@ZIF-67 core-shell structure material. 5. CoSe according to claim ₄ The preparation method of /NC-CNT/S lithium-sulfur battery cathode material is characterized in that, in the preparation of ZIF-8 material step, the weight of zinc nitrate hexahydrate and 2-methylimidazole The ratio is 1:1.03~1:04; in the step of preparing ZIF-8@ZIF-67 core-shell structure material, the weight ratio of ZIF-8 material, cobalt nitrate hexahydrate, and 2-methylimidazole is 1:11.6:12.32. 6. The preparation method of CoSe ₂ /NC-CNT/S lithium-sulfur battery cathode material according to claim 3, characterized in that, in the step (2), the high-temperature carbonization condition is: 700°C-900°C Keep warm for 3h. 7. The preparation method of CoSe ₂ /NC-CNT/S lithium-sulfur battery cathode material according to claim 3, characterized in that, in the step (3), the weight ratio of Co-NC-CNT material to selenium powder The ratio is 1:2; the annealing condition is: 350°C for 6h. 8. The preparation method of CoSe ₂ /NC-CNT/S lithium-sulfur battery cathode material according to claim 3, characterized in that, in the step (4), the weight ratio of CoSe ₂ /NC-CNT to sulfur powder The ratio is 1:1.5, the annealing condition is: 155°C for 12h; the holding condition is: 200°C for 30min. 9. An application of a CoSe ₂ /NC-CNT/S lithium-sulfur battery cathode material, characterized in that it is used to prepare a lithium-sulfur battery cathode material. 10. The application of the CoSe ₂ /NC-CNT/S lithium-sulfur battery cathode material according to claim 9, characterized in that the cathode material comprises a component: CoSe ₂ /NC-CNT/S lithium-sulfur battery cathode material , acetylene black, PVDF, solvent; the positive electrode material is prepared by the following method: CoSe ₂ /NC-CNT/S lithium-sulfur battery positive electrode material is mixed with acetylene black and PVDF in proportion, and a certain amount of solvent is added dropwise, after mixing evenly Ball milling, drying, slicing and weighing to obtain the electrode sheet of the positive electrode material.

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