CN114956035A - Ultramicropore carbon material, sulfur positive electrode material and application research thereof in lithium-sulfur battery - Google Patents

Abstract

The invention provides ultra-microporous carbon materials, sulfur cathode materials and research on their application in lithium-sulfur batteries. The preparation method of the ultra-microporous carbon material includes: S1, dispersing a polymer compound containing carboxylate in water to obtain solution A; S2, dissolving CuCl ₂ ·2H ₂ O in water to obtain solution B; S3, dissolving the The solution A is slowly added to the solution B, and after the addition is completed, the first drying process is performed in sequence; S4, in the first inert atmosphere, the first calcination is performed on the first dried product to obtain the obtained solution. The ultra-microporous carbon material; the carboxylate-containing polymer compound includes sodium alginate and/or sodium carboxymethyl cellulose. Using the electrostatic interaction between polymer compounds containing carboxylate groups and Cu ²⁺ , a gel with a three-dimensional cross-linked structure was prepared, and ultra-microporous carbon materials were obtained after calcination; and the preparation process of ultra-microporous carbon materials Simple and conducive to mass production.

Description

Research on ultra-microporous carbon materials, sulfur cathode materials and their applications in lithium-sulfur batteries

technical field

The invention relates to the technical field of material preparation, in particular to an ultra-microporous carbon material, a sulfur positive electrode material and its application in a lithium-sulfur battery.

Background technique

Among the battery systems, lithium-sulfur batteries have attracted widespread attention due to their ultra-high theoretical energy density and specific discharge capacity, and are considered to be one of the next-generation rechargeable battery systems with promising development prospects. However, both the active sulfur and the final discharge product are electron/ionic insulators, and the conversion between the two has a severe volume expansion process, which seriously affects the structure of the cathode. In addition, the shuttle effect caused by the dissolution of the discharge intermediate polysulfide in the electrolyte seriously affects the cycling stability of the sulfur cathode.

At present, the common strategy is to load the active material sulfur in the nanopores of porous carbon, and the preparation methods include physical activation method, chemical activation method, template method, etc. The physical activation method usually requires the introduction of external activators, such as water vapor, CO ₂ , etc. This method can enhance the porosity of biomass carbon materials to a certain extent, thereby improving the electrochemical performance of the material, but this method requires instruments and equipment. higher, the energy consumption is larger, and the pore size of the prepared carbon material is difficult to control. The activators used in the chemical activation method are KOH, K ₂ CO ₃ , ZnCl ₂ , H ₃ PO ₄ , etc. In this method, the precursors are uniformly mixed with the activator by grinding or dipping, and activated at different temperatures to obtain carbon material. The chemical activation method has high efficiency in improving pores, but the use of a large number of corrosive reagents and the removal of chemical substances in the activated product make the preparation yield of carbon materials limited, which is not conducive to large-scale production. The template method introduces a certain template into the system, assembles the template with the precursor, and removes the template after carbonization. The carbon material prepared by this method can obtain porous carbon with uniform pore size, but the carbon material obtained at present cannot meet the requirements.

In view of this, the present invention is proposed.

SUMMARY OF THE INVENTION

The present invention aims to solve one of the technical problems in the related art at least to a certain extent. Therefore, an object of the present invention is to propose a method for preparing an ultra-microporous carbon material, which utilizes the electrostatic interaction between a polymer compound containing a -COOH group and Cu ²⁺ to prepare a three-dimensional cross-linked structure. Gel, after calcination, an ultra-microporous carbon material is obtained. The pore size of the ultra-microporous carbon material can be as small as 0.6 nm, and the pore size is uniform and easy to control. The above-mentioned pore structure has excellent physical confinement effect on small molecular sulfur. The sulfur cathode material obtained by compounding with sulfur has excellent electrochemical performance; and the preparation process of the ultra-microporous carbon material is simple, easy to control, and the pore-forming agent is easy to elute, can be recycled, and is conducive to large-scale production.

In one aspect of the present invention, the present invention provides a preparation method of an ultra-microporous carbon material, the preparation method comprising:

S1. Disperse the macromolecular compound containing carboxylate in water to obtain solution A;

S2. Dissolve CuCl ₂ ·2H ₂ O in water to obtain solution B;

S3, slowly adding the solution A to the solution B, and after the addition is completed, carry out standstill and the first drying treatment in sequence;

S4, in a first inert atmosphere, first calcining the first dried product to obtain the ultra-microporous carbon material;

The carboxylate-containing polymer compound includes sodium alginate and/or sodium carboxymethyl cellulose.

Further, the concentration of the solution A is 0.2-0.4 mol L ⁻¹ ;

The concentration of the solution B is 0.1-0.2 mol L ^-1 .

Further, the way of slowly adding the solution A to the solution B includes:

The solution A was injected into the solution B using a syringe pump, and the injection speed of the syringe pump was 50-100 mL h ^-1 .

Further, in an argon atmosphere, the temperature is raised to 700-900° C. at a heating rate of 5-10° C. min ⁻¹ to carry out the first calcination, and the time of the first calcination is 2h;

And/or, the first drying method includes: putting the standing product into a vacuum drying oven at 60-80° C. to dry.

Further, in step S4, the product obtained by the first calcination is soaked in HCl solution for 12 hours, and then washed and dried for a second time to obtain the ultra-microporous carbon material;

And/or, the concentration of the HCl solution is 5-10 mol L ⁻¹ .

In another aspect of the present invention, the present invention provides an ultra-microporous carbon material prepared by the aforementioned preparation method,

And/or, the pore size of the ultra-microporous carbon material is 0.6 nm, and the specific surface area is 1048.8 m ² g ^-1 .

In another aspect of the present invention, the present invention provides a method for preparing a sulfur cathode material, comprising: in a second inert atmosphere, a mixture of a second calcined elemental sulfur and the aforementioned ultra-microporous carbon material, the The conditions for the second calcination include: raising the temperature to 155°C at a heating rate of 1°C min ^-1 , and holding the temperature for 20h;

In a third inert atmosphere, the product obtained by the second calcination is thirdly calcined to obtain the sulfur cathode material, and the conditions of the third calcination include: keeping the temperature at 200° C. for 2-4 hours.

Further, based on the total mass of the elemental sulfur and the ultra-microporous carbon material, the content of the elemental sulfur is 30-50 wt%;

And/or, the second calcination is performed by placing the mixture of the elemental sulfur and the ultra-microporous carbon material in a closed container.

In another aspect of the present invention, the present invention provides a sulfur cathode material prepared by the aforementioned preparation method.

In another aspect of the present invention, the present invention provides a lithium-sulfur battery, comprising the aforementioned sulfur cathode material.

Compared with the prior art, the present invention can at least achieve the following beneficial effects:

The present invention utilizes the electrostatic interaction between a polymer compound containing a carboxylate (-COOH) group and Cu ²⁺ to prepare a gel with a three-dimensional cross-linked network structure by controlling the cross-linking concentration and cross-linking time. The gel is carbonized and pyrolyzed at high temperature, and after removing the metal oxide particles in the carbon material, an ultra-microporous carbon material with a pore size as small as 0.6 nm is obtained, and the pore size is uniform and easy to control. The ultra-microporous carbon material has excellent physical confinement effect on small molecular sulfur, and the prepared sulfur cathode material can be widely used in different battery systems. Moreover, the synthesis steps of the ultra-microporous carbon material of the present invention are simple and convenient, easy to regulate, and the pore-forming agent is easy to be washed out, can be recycled, and is favorable for large-scale production.

The carbon material prepared by the invention is an ultra-microporous carbon material, and through the nitrogen adsorption and desorption test, its nitrogen adsorption and desorption curve exhibits typical I-type adsorption and desorption curve characteristics, which proves that the material is an ultra-microporous carbon material. At the same time, the XRD test results show that the material has diffraction peaks of graphitized carbon, which proves that the material has good electrical conductivity and can be widely used in battery systems.

After compounding the ultra-microporous carbon material of the present invention with sulfur, a sulfur cathode material is obtained, a lithium-sulfur battery is assembled, and a constant current charge ^- discharge test is carried out. After 200 cycles, the discharge specific capacity remains 760.5mAh g ^-1 . The ultra-microporous carbon material has a certain confinement effect on small molecular sulfur, inhibits the "shuttle effect" and improves the electrochemical performance of lithium-sulfur batteries. performance.

Description of drawings

Fig. 1 is the SEM image of the ultra-microporous carbon material of embodiment 1;

Fig. 2 is the XRD pattern of the ultra-microporous carbon material of embodiment 1;

Fig. 3 is the nitrogen adsorption-desorption curve of the ultra-microporous carbon material of Example 1;

Fig. 4 is the pore size distribution curve of the ultra-microporous carbon material of embodiment 1;

5 is a cycle diagram of the lithium-sulfur battery of Example 1 at 0.1C;

6 is a cycle diagram of the lithium-sulfur battery of Example 1 at 1C.

Detailed ways

Embodiments of the present invention are described in detail below. The embodiments described below are exemplary, only for explaining the present invention, and should not be construed as limiting the present invention. If no specific technique or condition is indicated in the examples, the technique or condition described in the literature in the field or the product specification is used. The reagents or instruments used without the manufacturer's indication are conventional products that can be obtained from the market.

In one aspect of the present invention, the present invention provides a preparation method of an ultra-microporous carbon material, the preparation method comprising:

S1. Disperse the carboxylate-containing polymer compound in water to obtain solution A.

It should be noted that the carboxylate-containing polymer compound includes sodium alginate (SA) and/or sodium carboxymethylcellulose.

In some embodiments of the present invention, the concentration of the solution A is 0.2˜0.4 mol L ⁻¹ .

S2. Dissolve CuCl ₂ ·2H ₂ O in water to obtain solution B.

In some embodiments of the present invention, the concentration of the solution B is 0.1˜0.2 mol L ⁻¹ .

It can be understood that step S1 and step S2 can be interchanged, and the sequence is not limited.

S3. Slowly add the solution A into the solution B, and after the addition is completed, perform a standstill and a first drying treatment in sequence.

In some embodiments of the present invention, the way of slowly adding the solution A into the solution B includes: using a syringe pump to inject the solution A into the solution B, and the injection speed of the syringe pump is 50～100mL h ^-1 . Thus, copper ions (Cu ²⁺ ) and carboxylate groups are cross-linked, and a three-dimensional gel network structure in which copper ions are uniformly dispersed in SA can be prepared.

In some embodiments of the present invention, the first drying method includes: placing the standing product into a vacuum drying oven at 60-80° C. for drying.

S4. In a first inert atmosphere, first calcining the first dried product to obtain the ultra-microporous carbon material.

In some embodiments of the present invention, the first inert atmosphere is an ^argon atmosphere. The temperature of the first calcination is 700-900° C.), and the time of the first calcination is 2h. Thus, an ultra-microporous carbon material with suitable pore size can be obtained.

In some embodiments of the present invention, in step S4, the product obtained by the first calcination is soaked in an HCl solution for 12 hours, and then washed and dried for a second time to obtain the ultra-microporous carbon material; the concentration of the HCl solution It is 5～10mol L ^-1 . Thus, impurities in the ultra-microporous carbon material can be removed, and an ultra-microporous carbon material with higher purity can be obtained.

In some embodiments of the present invention, the second drying means includes drying using a blast drying oven.

The inventors of the present invention found that the active material sulfur is loaded in the nano-pores of porous carbon, which can not only improve the conductivity of the sulfur positive electrode, but also provide a confined space for the volume expansion of the sulfur positive electrode during the charging and discharging process, and suppress the polysulfide. Dissolution is one of the effective ways to improve the electrochemical performance of sulfur cathodes. If the pore size of porous carbon can be controlled within the ultra-micropore range (pore size < 0.7 nm), the confined space can effectively limit the conversion of active material sulfur to soluble long-chain polysulfides, and alleviate the dissolution of polysulfides The problem in the electrolyte reduces the possibility of the "shuttle effect", thereby significantly improving the cycling stability of the sulfur cathode.

The present invention utilizes the electrostatic interaction between a polymer compound containing a carboxylate (-COOH) group and Cu ²⁺ to prepare a gel with a three-dimensional cross-linked network structure by controlling the cross-linking concentration and cross-linking time. The gel is carbonized and pyrolyzed at high temperature, and after removing the metal oxide particles in the carbon material, an ultra-microporous carbon material with a pore size as small as 0.6 nm is obtained, and the pore size is uniform and easy to control. The ultra-microporous carbon material has excellent physical confinement effect on small molecular sulfur, and the prepared sulfur cathode material can be widely used in different battery systems. Moreover, the synthesis steps of the ultra-microporous carbon material of the present invention are simple and convenient, easy to regulate, and the pore-forming agent is easy to be washed out, can be recycled, and is favorable for large-scale production.

The carbon material prepared by the invention is an ultra-microporous carbon material, and through the nitrogen adsorption and desorption test, its nitrogen adsorption and desorption curve exhibits typical I-type adsorption and desorption curve characteristics, which proves that the material is an ultra-microporous carbon material. At the same time, the XRD test results show that the material has diffraction peaks of graphitized carbon, which proves that the material has good electrical conductivity and can be widely used in battery systems.

In some specific embodiments of the present invention, the preparation method of ultra-microporous carbon material comprises the following steps:

1) Weigh a certain amount of sodium alginate (SA) powder, disperse it in deionized water, and magnetically stir to form a uniform mixed solution A;

2) Weigh a certain amount of CuCl ₂ ·2H ₂ O and dissolve it in deionized water, and fully disperse it to form a uniform mixed solution B;

3) Use a syringe pump to inject the mixed solution A into the solution B at a certain speed. After the injection is completed, let it stand for several hours, and then put it into a 60-80 ℃ vacuum drying box to dry;

4) The dried product obtained in step 3) is calcined in a tube furnace, and in an inert atmosphere, the temperature is increased at a heating rate of 5-10 ℃ min ^-1 , the calcination temperature is 700-900 ℃, and the calcination is performed for 2 hours;

5) After soaking and stirring the carbon material obtained in step 4) with a certain concentration of HCl solution for a certain period of time, washing and suction filtration to obtain the carbon material, and finally drying in a blast drying oven to obtain the ultra-microporous carbon material.

In another aspect of the present invention, the present invention provides an ultra-microporous carbon material, the ultra-microporous carbon material is prepared by the aforementioned preparation method, and the ultra-microporous carbon material has an amorphous block structure , the pore size is 0.6nm, and the specific surface area is 1048.8m ² g ^-1 . Therefore, the ultra-microporous carbon material has excellent physical confinement effect on small molecular sulfur, and the sulfur cathode material prepared by compounding it with elemental sulfur has excellent electrochemical performance and can be used in battery systems.

In another aspect of the present invention, the present invention provides a method for preparing a sulfur cathode material, comprising: in a second inert atmosphere (for example, an argon atmosphere, etc.), the second calcined elemental sulfur is The mixture of microporous carbon materials, the conditions for the second calcination include: raising the temperature to 155°C at a heating rate of 1°C min ^-1 , and keeping the temperature for 20h;

In a third inert atmosphere (for example, it can be an argon atmosphere, etc.), the product obtained by the second calcination is thirdly calcined to obtain the sulfur cathode material, and the conditions of the third calcination include: at a temperature of 200° C. Incubate for 2 to 4 hours. Therefore, the above method is simple, convenient, and easy to implement. The ultra-microporous carbon material has a certain confinement effect on small molecular sulfur, inhibits the generation of the "shuttle effect", and improves the electrochemical performance of lithium-sulfur batteries. The ultra-microporous carbon material of the present invention is compounded with sulfur to obtain a sulfur positive electrode material, assemble a lithium ^- sulfur battery, and pass a constant current charge-discharge test. After 200 cycles, the discharge capacity remains 760.5mAh g ^-1 .

In some embodiments of the present invention, based on the total mass of the elemental sulfur and the ultra-microporous carbon material, the content of the elemental sulfur is 30-50 wt %.

In some embodiments of the present invention, the second calcination is performed by placing the mixture of the elemental sulfur and the ultra-microporous carbon material in a closed vessel.

In some specific embodiments of the present invention, the preparation method of the sulfur cathode material includes the following steps: grinding and mixing the aforementioned ultra-microporous carbon material with elemental sulfur according to a certain mass, then placing the mixture in a glass bottle, The temperature was raised in a muffle furnace, heated to 155 °C at a heating rate of 1 °C min ^-1 , and held for 20 h; then the material was transferred to a tube furnace, heated to 200 °C in an inert atmosphere, and held for 4 h.

In another aspect of the present invention, the present invention provides a sulfur cathode material prepared by the aforementioned preparation method.

In another aspect of the present invention, the present invention provides a lithium-sulfur battery, comprising the aforementioned sulfur cathode material.

It can be understood that the lithium-sulfur battery may include the structure that a conventional lithium-sulfur battery should have, such as a sulfur positive electrode, a negative electrode, an electrolyte, and a separator, wherein the sulfur positive electrode is prepared by using a sulfur positive electrode material.

In some embodiments of the present invention, the lithium-sulfur battery may be a coin cell.

In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments.

Example

Example 1

The preparation method of lithium-sulfur battery comprises the following steps:

1) Preparation of ultra-microporous carbon materials: 2 g of sodium alginate (SA) solution was dissolved in 125 mL of deionized water to form solution A, and 3.4421 g of CuCl ₂ ·2H ₂ O was dissolved in 100 mL of solution to form solution B, using injection The pump slowly added solution A to solution B dropwise at a rate of 50 mL h ^-1 to form a uniform gel, then transferred the gel to a vacuum drying oven and dried at 60 °C for 12 h. The dried sample was slowly heated to 800 °C at a heating rate of 5 °C min ^-1 in an argon (Ar) atmosphere, and kept for 2 h. After soaking the obtained carbon material in 3M HCl for 24 h, it was dried and washed to neutrality. The ultra-microporous carbon material Cu-SA was obtained;

2) Preparation of sulfur cathode material: The obtained ultra-microporous carbon material and sulfur powder were uniformly mixed in a mass ratio of 6:4, sealed in a glass bottle, filled with Ar atmosphere for protection, and then heated at 1 °C min ^-1 After the heating rate was raised to 155 °C, after holding for 20 h, it was transferred to a tube furnace and continued to heat up to 200 °C for 2 h to obtain the sulfur cathode material Cu-SA/S;

3) Slurry configuration: Mix the sulfur cathode material, the conductive agent and the binder polyvinylidene fluoride (PVDF) evenly, according to the mass ratio of Cu-SA/S:Super P:PVDF=8:1:1, respectively Take 0.21g of Cu-SA/S, 0.06g of conductive agent Super P, and 0.03g of PVDF, grind the weighed Cu-SA/S and Super P under the irradiation of infrared light for 30min, and divide the above mixture into several times after grinding. A small amount of 800uL of PVDF in N-methylpyrrolidone (NMP) solution was added, at room temperature, the small beaker was sealed, and the magnetic stirrer was stirred at the maximum speed for 12h;

4) Battery assembly: use a CR2025 coin-operated mold for assembly, the electrolyte used is 1M LiPF ₆ , the solvent is EC:DEC=1:1(v:v), the diaphragm is a polypropylene diaphragm with a diameter of 19mm, and the negative electrode is Lithium sheet, carry out the corresponding electrochemical test.

The SEM image (scanning electron microscope image) of FIG. 1 proves that the ultra-microporous carbon material of this embodiment is an amorphous bulk material, and the XRD image (X-ray diffraction image) of FIG. 2 proves that the ultra-microporous carbon material is graphitized carbon Material structure, good electrical conductivity. Figures 3 and 4 prove that the material is an ultra-microporous carbon material with a specific surface area of 1048.8 m ² g ^-1 and a micropore volume of 0.56 cm ³ g ^-1 . It can be seen from FIG. 5 that the charge-discharge capacity of the lithium-sulfur battery in this embodiment is 1670mAh g ^-1 in the first cycle of the 0.1C battery, and after 100 cycles, the battery capacity still remains at 997.2mAh g ^-1 . It can be seen from Figure 6 that at 1C, the charge-discharge capacity of the battery in the first cycle is 2000.8mAhg ^-1 , and after 200 cycles, the battery capacity remains at 720.1mAh g ^-1 .

Example 2

The preparation method of lithium-sulfur battery comprises the following steps:

1) Preparation of ultra-microporous carbon materials: 2 g of sodium alginate (SA) solution was dissolved in 250 mL of deionized water to form solution A, and 3.4421 g of CuCl ₂ ·2H ₂ O was dissolved in 200 mL of solution to form solution B, using injection The pump slowly added solution A to solution B dropwise at a rate of 50 mL h ^-1 to form a uniform gel, then transferred the gel to a vacuum drying oven and dried at 60 °C for 12 h. The dried sample was slowly heated to 800°C at a heating rate of 5°C min ^-1 in an Ar atmosphere, and kept for 2 hours. The obtained carbon material was soaked in 3M HCl for 24 hours, and then dried and washed to neutrality to obtain ultra-micropores. Carbon material Cu-SA;

2) Preparation of sulfur cathode material: The obtained ultra-microporous carbon material and sulfur powder were uniformly mixed in a mass ratio of 6:4, sealed in a glass bottle, filled with Ar atmosphere for protection, and then heated at 1 °C min ^-1 After the heating rate was increased to 155 °C, the temperature was kept for 20 h, and then transferred to a tube furnace to continue heating to 200 °C, and the temperature was kept for 2 h to obtain the sulfur cathode material Cu-SA/S;

3) Slurry configuration: Mix the sulfur cathode material, the conductive agent and the binder polyvinylidene fluoride (PVDF) evenly, according to the mass ratio of Cu-SA/S:Super P:PVDF=8:1:1, respectively Take 0.21g of Cu-SA/S, 0.06g of conductive agent Super P, and 0.03g of PVDF, grind the weighed Cu-SA/S and Super P under the irradiation of infrared light for 30min, and divide the above mixture into several times after grinding. A small amount of 800uL of PVDF in N-methylpyrrolidone (NMP) solution was added, at room temperature, the small beaker was sealed, and the magnetic stirrer was stirred at the maximum speed for 12h;

4) Battery assembly: use a CR2025 coin-operated mold for assembly, the electrolyte used is 1M LiPF ₆ , the solvent is EC:DEC=1:1(v:v), the diaphragm is a polypropylene diaphragm with a diameter of 19mm, and the negative electrode is Lithium sheet, carry out the corresponding electrochemical test.

After dilution, the size of the ultra-microporous carbon material in this embodiment is reduced. The lithium-sulfur battery in this embodiment has a charge-discharge capacity of 2100mAh g ^-1 in the first cycle of a 0.1C battery. After 100 cycles, the battery capacity remains the same. It remains at 873.8mAh g ^-1 ; the charge and discharge capacity of the 1C battery in the first cycle is 1800.8mAh g ^-1 , and after 200 cycles, the battery capacity remains at 623.2mAh g ^-1 .

Example 3

The preparation method of lithium-sulfur battery comprises the following steps:

1) Preparation of ultra-microporous carbon materials: 2 g of sodium alginate (SA) solution was dissolved in 125 mL of deionized water to form solution A, and 1.7211 g of CuCl ₂ ·2H ₂ O was dissolved in 100 mL of solution to form solution B, using The solution A was slowly added dropwise to the solution B at a rate of 50 mL h ^-1 by a syringe pump to form a uniform gel, and then the gel was transferred to a vacuum drying oven and dried at 60 °C for 12 h. The dried sample was slowly heated to 800°C at a heating rate of 5°C min ^-1 in an Ar atmosphere, and kept for 2 hours. The obtained carbon material was soaked in 3M HCl for 24 hours, and then dried and washed to neutrality to obtain ultra-micropores. Carbon material Cu-SA;

2) Preparation of sulfur cathode material: The obtained ultra-microporous carbon material and sulfur powder were uniformly mixed in a mass ratio of 6:4, sealed in a glass bottle, filled with Ar atmosphere for protection, and then heated at 1 °C min ^-1 After the heating rate was increased to 155 °C, the temperature was kept for 20 h, and then transferred to a tube furnace to continue heating to 200 °C, and the temperature was kept for 2 h to obtain the sulfur cathode material Cu-SA/S;

3) Slurry configuration: Mix the sulfur cathode material, the conductive agent and the binder polyvinylidene fluoride (PVDF) evenly, according to the mass ratio of Cu-SA/S:Super P:PVDF=8:1:1, respectively Take 0.21g of Cu-SA/S, 0.06g of conductive agent Super P, and 0.03g of PVDF, grind the weighed Cu-SA/S and Super P under the irradiation of infrared light for 30min, and divide the above mixture into several times after grinding. A small amount of 800uL of PVDF in N-methylpyrrolidone (NMP) solution was added, at room temperature, the small beaker was sealed, and the magnetic stirrer was stirred at the maximum speed for 12h;

4) Battery assembly: use a CR2025 coin-operated mold for assembly, the electrolyte used is 1M LiPF ₆ , the solvent is EC:DEC=1:1(v:v), the diaphragm is a polypropylene diaphragm with a diameter of 19mm, and the negative electrode is Lithium sheet, carry out the corresponding electrochemical test.

The lithium-sulfur battery of this embodiment has a charge-discharge capacity of 1600mAh g ^-1 in the first cycle of a 0.1C battery, and after 100 cycles, the battery capacity remains at 634.8mAh g ^-1 ; the charge-discharge capacity of a 1C battery in the first cycle is: 1400.5 mAh g ^-1 , the capacity of the battery remains at 508.8mAh g ^-1 after 200 cycles.

Example 4

The preparation method of lithium-sulfur battery comprises the following steps:

1) Preparation of ultra-microporous carbon materials: 2 g of sodium alginate (SA) solution was dissolved in 125 mL of deionized water to form solution A, and 5.163 g of CuCl ₂ ·2H ₂ O was dissolved in 100 mL of solution to form solution B, using The solution A was slowly added dropwise to the solution B at a rate of 50 mL h ^-1 by a syringe pump to form a uniform gel, and then the gel was transferred to a vacuum drying oven and dried at 60 °C for 12 h. The dried sample was slowly heated to 800°C at a heating rate of 5°C min ^-1 in an Ar atmosphere, and kept for 2 hours. The obtained carbon material was soaked in 3M HCl for 24 hours, and then dried and washed to neutrality to obtain ultra-micropores. Carbon material Cu-SA;

2) Preparation of sulfur cathode material: The obtained ultra-microporous carbon material and sulfur powder were uniformly mixed in a mass ratio of 6:4, sealed in a glass bottle, filled with Ar atmosphere for protection, and then heated at 1 °C min ^-1 After the heating rate was increased to 155 °C, the temperature was kept for 20 h, and then transferred to a tube furnace to continue heating to 200 °C, and the temperature was kept for 2 h to obtain the sulfur cathode material Cu-SA/S;

3) Slurry configuration: Mix the sulfur cathode material, the conductive agent and the binder polyvinylidene fluoride (PVDF) evenly, according to the mass ratio of Cu-SA/S:Super P:PVDF=8:1:1, respectively Take 0.21g of Cu-SA/S, 0.06g of conductive agent Super P, and 0.03g of PVDF, grind the weighed Cu-SA/S and Super P under the irradiation of infrared light for 30min, and divide the above mixture into several times after grinding. A small amount of 800uL of PVDF in N-methylpyrrolidone (NMP) solution was added, at room temperature, the small beaker was sealed, and the magnetic stirrer was stirred at the maximum speed for 12h;

4) Battery assembly: use a CR2025 coin-operated mold for assembly, the electrolyte used is 1M LiPF ₆ , the solvent is EC:DEC=1:1(v:v), the diaphragm is a polypropylene diaphragm with a diameter of 19mm, and the negative electrode is Lithium sheet, carry out the corresponding electrochemical test.

The lithium-sulfur battery of this embodiment has a charge and discharge capacity of 1500.4mAh g ^-1 in the first cycle of 0.1C battery, and after 100 cycles, the battery capacity gradually decays to 500.8mAh g ^-1 ; at 1C, the first cycle charge and discharge capacity of the battery It is: 1600.5mAh g ^-1 , after 200 cycles, the battery capacity remains at 308.8mAh g ^-1 , the discharge peak area of small molecular sulfur decreases, and macromolecular sulfur appears, which is related to the pore structure of ultra-microporous carbon materials. to the destruction.

Example 5

The preparation method of lithium-sulfur battery comprises the following steps:

1) Preparation of ultra-microporous carbon materials: 2 g of sodium alginate (SA) solution was dissolved in 125 mL of deionized water to form solution A, and 3.4421 g of CuCl ₂ ·2H ₂ O was dissolved in 100 mL of solution to form solution B, using A syringe pump slowly added solution A to solution B at a rate of 50 mL h ^-1 , and formed a uniform gel. The gel was then transferred to a vacuum drying oven and dried at 60 °C for 12 h. The dried sample was slowly heated to 800°C at a heating rate of 5°C min ^-1 in an Ar atmosphere, and kept for 2 hours. The obtained carbon material was soaked in 3M HCl for 24 hours, and then dried and washed to neutrality to obtain ultra-micropores. Carbon material Cu-SA;

2) Preparation of sulfur cathode material: The obtained ultra-microporous carbon material and sulfur powder were uniformly mixed at a mass ratio of 7:3, sealed in a glass bottle, filled with Ar atmosphere for protection, and then heated at 1 °C min ^-1 After the heating rate was increased to 155 °C, the temperature was kept for 20 h, and then transferred to a tube furnace to continue heating to 200 °C, and the temperature was kept for 2 h to obtain the sulfur cathode material Cu-SA/S;

3) Slurry configuration: Mix the sulfur cathode material, the conductive agent and the binder polyvinylidene fluoride (PVDF) evenly, according to the mass ratio of Cu-SA/S:Super P:PVDF=8:1:1, respectively Take 0.21g of Cu-SA/S, 0.06g of conductive agent Super P, and 0.03g of PVDF, grind the weighed Cu-SA/S and Super P under the irradiation of infrared light for 30min, and divide the above mixture into several times after grinding. A small amount of 800uL of PVDF in N-methylpyrrolidone (NMP) solution was added, at room temperature, the small beaker was sealed, and the magnetic stirrer was stirred at the maximum speed for 12h;

4) Battery assembly: use a CR2025 coin-operated mold for assembly, the electrolyte used is 1M LiPF ₆ , the solvent is EC:DEC=1:1(v:v), the diaphragm is a polypropylene diaphragm with a diameter of 19mm, and the negative electrode is Lithium sheet, carry out the corresponding electrochemical test.

The lithium-sulfur battery of this embodiment has a charge-discharge capacity of 1800.4mAh g ^-1 in the first cycle of 0.1C battery, and after 100 cycles, the battery capacity remains at 1000.5mAh g ^-1 ; at 1C, the charge-discharge capacity of the battery in the first cycle is : 2100.5mAh g ^-1 , after 200 cycles, the capacity of the battery remains at 800.9mAh g ^-1 , and the cycle performance is significantly improved compared to traditional lithium-sulfur batteries.

Example 6

The preparation method of lithium-sulfur battery comprises the following steps:

1) Preparation of ultra-microporous carbon materials: 2 g of sodium alginate (SA) solution was dissolved in 125 mL of deionized water to form solution A, and 3.4421 g of CuCl ₂ ·2H ₂ O was dissolved in 100 mL of solution to form solution B, using The solution A was slowly added dropwise to the solution B at a rate of 50 mL h ^-1 by a syringe pump to form a uniform gel, and then the gel was transferred to a vacuum drying oven and dried at 60 °C for 12 h. The dried sample was slowly heated to 800°C at a heating rate of 5°C min ^-1 in an Ar atmosphere, and kept for 2 hours. The obtained carbon material was soaked in 3M HCl for 24 hours, and then dried and washed to neutrality to obtain ultra-micropores. Carbon material Cu-SA;

2) Preparation of sulfur cathode material: The obtained ultra-microporous carbon material and sulfur powder were uniformly mixed at a mass ratio of 1:1, sealed in a glass bottle, filled with Ar atmosphere for protection, and then heated at 1 °C min ^-1 After the heating rate was increased to 155 °C, the temperature was kept for 20 h, and then transferred to a tube furnace to continue heating to 200 °C, and the temperature was kept for 2 h to obtain the sulfur cathode material Cu-SA/S;

3) Slurry configuration: Mix the sulfur cathode material, the conductive agent and the binder polyvinylidene fluoride (PVDF) evenly, according to the mass ratio of Cu-SA/S:Super P:PVDF=8:1:1, respectively Take 0.21g of Cu-SA/S, 0.06g of conductive agent Super P, and 0.03g of PVDF, grind the weighed Cu-SA/S and Super P under the irradiation of infrared light for 30min, and divide the above mixture into several times after grinding. A small amount of 800uL of PVDF in N-methylpyrrolidone (NMP) solution was added, at room temperature, the small beaker was sealed, and the magnetic stirrer was stirred at the maximum speed for 12h;

4) Battery assembly: use a CR2025 coin-operated mold for assembly, the electrolyte used is 1M LiPF ₆ , the solvent is EC:DEC=1:1(v:v), the diaphragm is a polypropylene diaphragm with a diameter of 19mm, and the negative electrode is Lithium sheet, carry out the corresponding electrochemical test.

The lithium-sulfur battery of this embodiment has a charge and discharge capacity of 1200.5mAh g ^-1 in the first cycle of 0.1C battery, and after 100 cycles, the battery capacity remains at 400.8mAh g ^-1 ; at 1C, the first cycle charge and discharge capacity of the battery is : 1600.4mAh g ^-1 , after 200 cycles, the capacity of the battery decays to 300.2mAh g ^-1 , which is due to the excessively loaded sulfur content. During the charging and discharging process, the sulfur volume expands, resulting in the ultra-microporous carbon material As a result of the damage to the structure, the active material sulfur falls off the electrode sheet, resulting in irreversible attenuation of the battery capacity.

The specific capacity of the lithium-sulfur batteries of Examples 1-6 after 100 cycles at 0.1C and the specific capacity after 200 cycles at 1C are shown in Table 1 below:

Table 1

As can be seen from Table 1, the electrochemical performance of the sulfur positive electrode material prepared by the ultra-microporous carbon material of Example 5 is the best, but its sulfur loading content is too low, but compared with the traditional sulfur positive electrode material, the present invention is The cycle performance of the sulfur cathode material is significantly improved.

The parts not covered above are applicable to the prior art.

In the description of this specification, description with reference to the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples", etc., mean specific features described in connection with the embodiment or example , structure, material or feature is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, those skilled in the art may combine and combine the different embodiments or examples described in this specification, as well as the features of the different embodiments or examples, without conflicting each other.

Although some specific embodiments of the present invention have been described in detail through examples, those skilled in the art should understand that the above examples are only for illustration, not for limiting the scope of the present invention. Various modifications or additions may be made to, or substituted for, the specific embodiments described, without departing from the direction of the invention or going beyond the scope defined by the appended claims. Those skilled in the art should understand that any modification, equivalent replacement, improvement, etc. made to the above embodiments according to the technical essence of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. A method for producing an ultra-microporous carbon material, comprising:

s1, dispersing a macromolecular compound containing carboxylate radicals in water to obtain a solution A;

s2, mixing CuCl ₂ ·2H ₂ Dissolving O in water to obtain a solution B;

s3, slowly adding the solution A into the solution B, and after the solution A is added, sequentially carrying out standing and first drying treatment;

s4, carrying out first calcination on the first dried product in a first inert atmosphere to obtain the ultramicropore carbon material;

the carboxylate-containing macromolecular compound comprises sodium alginate and/or sodium carboxymethyl cellulose.

2. The method according to claim 1, wherein the concentration of the solution A is 0.2 to 0.4mol L ^-1 ；

The concentration of the solution B is 0.1-0.2 mol L ^-1 。

3. The method of claim 1, wherein the slow addition of the solution a to the solution B comprises:

injecting the solution A into the solution B by using an injection pump, wherein the injection speed of the injection pump is 50-100 mL h ^-1 。

4. The method according to claim 1, wherein the temperature is controlled at 5 to 10 ℃ for min in an argon atmosphere ^-1 Raising the temperature to 700-900 ℃ at a heating rate to carry out the first calcination, wherein the time of the first calcination is 2 hours;

and/or, the first drying mode comprises the following steps: and (3) placing the product after standing in a vacuum drying oven at the temperature of 60-80 ℃ for drying.

5. The method according to any one of claims 1 to 4, wherein in step S4, the product obtained by the first calcination is immersed in an HCl solution for 12 hours, and then washed and second dried to obtain the ultra-microporous carbon material;

and/or the concentration of the HCl solution is 3-10 mol L ^-1 。

6. A microporous carbon material produced by the production method according to any one of claims 1 to 5,

and/or the ultra-microporous carbon material has a pore size of 0.6nm and a specific surface area of 1048.8m ² g ^-1 。

7. A method for producing a sulfur positive electrode material, comprising: second calcining a mixture of elemental sulfur and the nanoporous carbon material of claim 6 in a second inert atmosphere under conditions comprising: at 1 ℃ for min ^-1 The temperature is raised to 155 ℃ at the temperature raising rate, and the temperature is kept for 20 hours;

third calcining the product obtained by the second calcining in a third inert atmosphere to obtain the sulfur cathode material, wherein the conditions of the third calcining comprise: and preserving the heat for 2-4 hours at the temperature of 200 ℃.

8. The production method according to claim 7, wherein the elemental sulfur is contained in an amount of 30 to 50 wt% based on the total mass of the elemental sulfur and the ultra-microporous carbon material;

and/or placing the mixture of the elemental sulfur and the ultramicropore carbon material in a closed container for secondary calcination.

9. A sulfur positive electrode material, characterized in that it is produced by the production method according to claim 7 or 8.

10. A lithium-sulfur battery comprising the sulfur positive electrode material according to claim 9.

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