An ultra-high sulfur-containing lithium-sulfur battery cathode material and a preparation method thereof

Abstract

This invention discloses an ultra-high sulfur content lithium-sulfur battery cathode material and its preparation method, belonging to the technical field of lithium-sulfur battery cathode materials. The method includes the following steps: mixing acetylene black and sulfur, performing a first melt impregnation to obtain an acetylene black@sulfur material; adding a mixture of acetylene black and carbon nanotubes to the acetylene black@sulfur material, performing a second melt impregnation to obtain an acetylene black@sulfur@carbon nanotube material; preparing a nickel hydroxide suspension; dispersing the acetylene black@sulfur@carbon nanotube material into the nickel hydroxide suspension to form a dispersion; reacting the dispersion under sealed conditions; centrifuging, washing, and drying the reacted dispersion to obtain the acetylene black@sulfur@carbon nanotube@nickel hydroxide material. In this invention, the second melt impregnation process enhances the conductivity and electrolyte wettability of the material through the point-chain-like three-dimensional structure formed between the carbon nanotubes and acetylene black, reducing the polarization of the lithium-sulfur battery and further improving its performance.

Description

Technical Field

[0001] This invention belongs to the field of lithium-sulfur battery cathode material technology, specifically relating to an ultra-high sulfur content lithium-sulfur battery cathode material and its preparation method. Background Technology

[0002] Lithium-sulfur batteries possess advantages such as extremely high energy density and theoretical capacity, and their raw materials are abundant, making them a growing focus of research. However, several issues remain to be addressed: the "shuttle effect" of polysulfides during charge and discharge leads to capacity decay, and sulfur and polysulfides are not conductive. These problems hinder the widespread adoption of lithium-sulfur batteries.

[0003] To address the aforementioned issues, existing technologies often employ the method of injecting sulfur into porous carbon jackets. However, the interaction between mono- and polysulfides and non-polar carbon is relatively weak, resulting in less than ideal suppression of the "shuttle effect." Summary of the Invention

[0004] Purpose of the invention: In order to solve the above problems, the present invention provides an ultra-high sulfur content lithium-sulfur battery cathode material and its preparation method.

[0005] Technical solution: A method for preparing an ultra-high sulfur content lithium-sulfur battery cathode material, comprising the following steps:

[0006] Step 1: Mix 1.1~1.3g of acetylene black and 12.1~18.2g of sulfur, and perform a first melt impregnation at a temperature of 180~200℃ for 16~19h to obtain acetylene black@sulfur material; add a mixture of acetylene black and carbon nanotubes to the acetylene black@sulfur material and perform a second melt impregnation to obtain acetylene black@sulfur@carbon nanotube material;

[0007] Step 2: Dissolve tris(hydroxymethyl)aminomethane in a solution of ethanol and distilled water to obtain a mixed solution; add magnesium oxide and chitosan to the mixed solution to obtain a suspension; centrifuge the suspension to obtain magnesium oxide@chitosan; carbonize magnesium oxide@chitosan under carbonization conditions to obtain magnesium oxide@carbon; add the obtained magnesium oxide@carbon to a nickel nitrate aqueous solution and stir for 40-50 hours to obtain a nickel hydroxide suspension;

[0008] Step 3: Disperse the acetylene black@sulfur@carbon nanotube material into a nickel hydroxide suspension and form a dispersion under stirring conditions. React the dispersion under sealed conditions, centrifuge, wash, and dry the reacted dispersion to obtain the acetylene black@sulfur@carbon nanotube@nickel hydroxide material.

[0009] Furthermore, in step one, the mass of acetylene black in the mixture of acetylene black and carbon nanotubes is 0.5~0.8g, and the mass of carbon nanotubes is 0.8~1.2g.

[0010] Furthermore, in step one, the secondary melt impregnation temperature is 220~240℃, and the secondary melt impregnation time is 10~12h.

[0011] Further, in step two, the mass of tris(hydroxymethyl)aminomethane is 1-2 g, the mass of magnesium oxide is 0.1-0.3 g, the mass of chitosan is 0.1-0.3 g, and the mass of nickel nitrate is 0.3-0.4 mol / L.

[0012] Furthermore, the carbonization conditions in step two are: carbonization temperature of 400~500℃ and carbonization time of 2~4h under a nitrogen atmosphere.

[0013] Furthermore, the reaction conditions under sealed conditions in step three are: reaction temperature of 55~65℃ and reaction time of 10~15h.

[0014] Furthermore, the stirring conditions in step three are: a stirring speed of 200~300 r / min and a stirring time of 40~50 min.

[0015] In another technical solution, an ultra-high sulfur content lithium-sulfur battery cathode material is provided, which is prepared by the above-mentioned method for preparing an ultra-high sulfur content lithium-sulfur battery cathode material.

[0016] Beneficial effects:

[0017] (1) Based on the first melt impregnation, the present invention adds a second melt impregnation; in the second melt impregnation, acetylene black and carbon nanotubes are added. After the second melt impregnation, the arrangement between acetylene black and sulfur is improved. The sulfur surface is covered with more conductive carbon particles and more pores. After the carbon nanotubes are incorporated into the sulfur material, the material surface is attached in a linear manner. The point chain three-dimensional structure formed between the carbon nanotubes and acetylene black improves the conductivity of the material and the wettability of the electrolyte, reduces the polarization of the lithium-sulfur battery, and further improves the performance of the lithium-sulfur battery.

[0018] (2) In this invention, nickel hydroxide@carbon is coated on acetylene black@sulfur@carbon nanotube material to form a double core-shell structure nanosphere. The outer layer is a nickel hydroxide nanosheet layer and the inner layer is a highly conductive carbon-sulfur structure. The nickel hydroxide nanosheet layer confines sulfur and polysulfides in the shell layer, and the nickel hydroxide adsorbs polysulfides on the positive electrode side, which reduces the impedance and shuttle effect of lithium-sulfur battery, and shows excellent cycle stability and good electrochemical reaction kinetics. Attached Figure Description

[0019] Figure 1These are comparison graphs of the initial discharge capacity of Examples 1 to 4, and Comparative Examples 1 and 2;

[0020] Figure 2 This is a comparison chart of capacity retention rates after 100 cycles for Examples 1 to 4, and Comparative Examples 1 and 2. Detailed Implementation

[0021] Example 1

[0022] Step 1: Mix 1.1g of acetylene black and 12.1g of sulfur, and perform a first melt impregnation at a temperature of 180℃ for 16 hours to obtain acetylene black@sulfur material. Then, add a mixture of acetylene black and carbon nanotubes to the acetylene black@sulfur material, where the mass of acetylene black is 0.5g and the mass of carbon nanotubes is 0.8g. Perform a second melt impregnation at a temperature of 220℃ for 10 hours to obtain acetylene black@sulfur@carbon nanotube material.

[0023] Step 2: Dissolve 1g of tris(hydroxymethyl)aminomethane in a solution of ethanol and distilled water to obtain a mixed solution; add 0.1g of magnesium oxide and 0.1g of chitosan to the mixed solution to obtain a suspension; centrifuge the suspension to obtain magnesium oxide@chitosan; carbonize the magnesium oxide@chitosan at 400℃ for 2h under a nitrogen atmosphere to obtain magnesium oxide@carbon; add the obtained magnesium oxide@carbon to a 0.3 mol / L nickel nitrate aqueous solution and stir for 40h to obtain a nickel hydroxide suspension;

[0024] Step 3: Disperse the acetylene black@sulfur@carbon nanotube material into a nickel hydroxide suspension and stir at 200 r / min for 40 min to form a dispersion. React the dispersion at 55℃ under sealed conditions for 10 h. Centrifuge, wash and dry the dispersion after reaction to obtain the acetylene black@sulfur@carbon nanotube@nickel hydroxide material.

[0025] Example 2

[0026] Step 1: Mix 1.3g of acetylene black and 18.2g of sulfur, and perform a first melt impregnation at a temperature of 200℃ for 19 hours to obtain acetylene black@sulfur material. Then, add a mixture of acetylene black and carbon nanotubes to the acetylene black@sulfur material, where the mass of acetylene black is 0.8g and the mass of carbon nanotubes is 1.2g. Perform a second melt impregnation at a temperature of 240℃ for 12 hours to obtain acetylene black@sulfur@carbon nanotube material.

[0027] Step 2: Dissolve 2g of tris(hydroxymethyl)aminomethane in a solution of ethanol and distilled water to obtain a mixed solution; add 0.3g of magnesium oxide and 0.3g of chitosan to the mixed solution to obtain a suspension; centrifuge the suspension to obtain magnesium oxide@chitosan; carbonize the magnesium oxide@chitosan at 500℃ for 4h under a nitrogen atmosphere to obtain magnesium oxide@carbon; add the obtained magnesium oxide@carbon to a 0.4 mol / L nickel nitrate aqueous solution and stir for 50h to obtain a nickel hydroxide suspension;

[0028] Step 3: Disperse the acetylene black@sulfur@carbon nanotube material into a nickel hydroxide suspension and stir at 300 r / min for 50 min to form a dispersion. React the dispersion at 65℃ under sealed conditions for 15 h. Centrifuge, wash and dry the dispersion after reaction to obtain the acetylene black@sulfur@carbon nanotube@nickel hydroxide material.

[0029] Example 3

[0030] Step 1: Mix 1.2 g of acetylene black and 16.2 g of sulfur, and perform a first melt impregnation at a temperature of 190°C for 17 hours to obtain acetylene black@sulfur material. Then, add a mixture of acetylene black and carbon nanotubes to the acetylene black@sulfur material, where the mass of acetylene black is 0.6 g and the mass of carbon nanotubes is 1.0 g. Perform a second melt impregnation at a temperature of 230°C for 11 hours to obtain acetylene black@sulfur@carbon nanotube material.

[0031] Step 2: Dissolve 1.5g of tris(hydroxymethyl)aminomethane in a solution of ethanol and distilled water to obtain a mixed solution; add 0.2g of magnesium oxide and 0.2g of chitosan to the mixed solution to obtain a suspension; centrifuge the suspension to obtain magnesium oxide@chitosan; carbonize the magnesium oxide@chitosan at 450℃ for 3h under a nitrogen atmosphere to obtain magnesium oxide@carbon; add the obtained magnesium oxide@carbon to a 0.35mol / L nickel nitrate aqueous solution and stir for 45h to obtain a nickel hydroxide suspension;

[0032] Step 3: Disperse the acetylene black@sulfur@carbon nanotube material into a nickel hydroxide suspension and stir at 250 r / min for 45 min to form a dispersion. React the dispersion at 60℃ under sealed conditions for 12 h. Centrifuge, wash and dry the dispersion after reaction to obtain the acetylene black@sulfur@carbon nanotube@nickel hydroxide material.

[0033] Example 4

[0034] Step 1: Mix 1.15g of acetylene black and 13.2g of sulfur, and perform a first melt impregnation at a temperature of 182℃ for 17 hours to obtain acetylene black@sulfur material. Then, add a mixture of acetylene black and carbon nanotubes to the acetylene black@sulfur material, where the mass of acetylene black is 0.7g and the mass of carbon nanotubes is 1.1g. Perform a second melt impregnation at a temperature of 235℃ for 12 hours to obtain acetylene black@sulfur@carbon nanotube material.

[0035] Step 2: Dissolve 1.6g of tris(hydroxymethyl)aminomethane in a solution of ethanol and distilled water to obtain a mixed solution; add 0.1g of magnesium oxide and 0.1g of chitosan to the mixed solution to obtain a suspension; centrifuge the suspension to obtain magnesium oxide@chitosan; carbonize the magnesium oxide@chitosan at 460℃ for 3.5h under a nitrogen atmosphere to obtain magnesium oxide@carbon; add the obtained magnesium oxide@carbon to a 0.4mol / L nickel nitrate aqueous solution and stir for 50h to obtain a nickel hydroxide suspension;

[0036] Step 3: Disperse the acetylene black@sulfur@carbon nanotube material into a nickel hydroxide suspension and stir at 300 r / min for 50 min to form a dispersion. React the dispersion at 62℃ under sealed conditions for 12 h. Centrifuge, wash and dry the dispersion to obtain the acetylene black@sulfur@carbon nanotube@nickel hydroxide material.

[0037] Comparative Example 1

[0038] 1.1g of acetylene black and 12.1g of sulfur were mixed and melt-impregnated at a temperature of 180℃ for 16h to obtain acetylene black@sulfur material.

[0039] Comparative Example 2

[0040] 1.1g of acetylene black and 12.1g of sulfur were mixed and subjected to a first melt impregnation at a temperature of 180℃ for 16 hours to obtain acetylene black@sulfur material. A mixture of acetylene black and carbon nanotubes was added to the acetylene black@sulfur material, wherein the mass of acetylene black in the mixture was 0.5g and the mass of carbon nanotubes was 0.8g. A second melt impregnation was performed at a temperature of 220℃ for 10 hours to obtain acetylene black@sulfur@carbon nanotube material.

[0041] The materials obtained in Examples 1 to 4, and Comparative Examples 1 and 2, were used to prepare the positive electrodes for lithium-sulfur batteries. The obtained positive electrodes, existing lithium negative electrodes, and other materials were then assembled into lithium-sulfur batteries, and the electrochemical performance of the resulting lithium-sulfur batteries was tested. The test results are shown in Table 1.

[0042] Table 1

[0043]

[0044] As shown in the figure above, the initial discharge capacity of the lithium-sulfur batteries assembled with the materials obtained in Examples 1 to 4 is around 1200 mAh / g, which is higher than that of Comparative Examples 1 and 2. Furthermore, the capacity retention rate of the lithium-sulfur batteries obtained in Examples 1 to 4 after 100 cycles is over 79%, significantly higher than that of Comparative Examples 1 and 2. The reason why Examples 1 to 4 can achieve the above effects is as follows:

[0045] After a single melt impregnation process, acetylene black adheres to the sulfur surface and possesses electrical conductivity. A second melt impregnation process improves the arrangement of acetylene black and sulfur. Compared to the first impregnation, the sulfur surface is covered with more conductive carbon particles and more voids, further promoting electron transport and electrolyte wetting. This results in a higher discharge specific capacity for lithium-sulfur batteries and enhances their electrochemical kinetics. Furthermore, carbon nanotubes are incorporated into the second melt impregnation process. The carbon nanotubes, when incorporated into the sulfur material, form a linear attachment on the surface. The point-chain-like three-dimensional structure formed between the carbon nanotubes and acetylene black improves the material's conductivity and electrolyte wetting, reduces polarization in lithium-sulfur batteries, and further enhances battery performance.

[0046] The nickel hydroxide suspension obtained in step two is carbonized to form a nickel hydroxide@carbon material, with carbon coating the nickel hydroxide, exhibiting good conductivity. In step three, nickel hydroxide@carbon is coated onto acetylene black@sulfur@carbon nanotube material, forming a double-core-shell structured nanosphere. The outer layer is a nickel hydroxide nanosheet, and the inner layer is a highly conductive carbon-sulfur structure. The nickel hydroxide nanosheet confines sulfur and polysulfides within the shell, and the nickel hydroxide adsorbs polysulfides on the positive electrode side, reducing the impedance and shuttle effect of the lithium-sulfur battery, exhibiting excellent cycle stability and good electrochemical reaction kinetics.

Claims

1. A method for preparing an ultra-high sulfur content lithium-sulfur battery cathode material, characterized in that, Includes the following steps: Step 1: Take 1.1~1.3 g Acetylene black, 12.1~18.2 g The sulfur is mixed and then subjected to a single melt impregnation at a temperature of 180-200℃ for 16-19 minutes. h Acetylene black@sulfur material was obtained; a mixture of acetylene black and carbon nanotubes was added to the acetylene black@sulfur material and subjected to secondary melt impregnation to obtain acetylene black@sulfur@carbon nanotube material. Step 2: Dissolve tris(hydroxymethyl)aminomethane in a solution of ethanol and distilled water to obtain a mixed solution; add magnesium oxide and chitosan to the mixed solution to obtain a suspension; centrifuge the suspension to obtain magnesium oxide@chitosan; carbonize the magnesium oxide@chitosan under carbonization conditions to obtain magnesium oxide@carbon; add the obtained magnesium oxide@carbon to a nickel nitrate aqueous solution and stir for 40-50 minutes. h A nickel hydroxide suspension was obtained; Step 3: Disperse the acetylene black@sulfur@carbon nanotube material into a nickel hydroxide suspension and form a dispersion under stirring conditions. React the dispersion under sealed conditions, centrifuge, wash, and dry the reacted dispersion to obtain the acetylene black@sulfur@carbon nanotube@nickel hydroxide material.

2. The method for preparing an ultra-high sulfur content lithium-sulfur battery cathode material as described in claim 1, characterized in that, In step one, the mass of acetylene black in the mixture of acetylene black and carbon nanotubes is 0.5~0.

8. g The mass of carbon nanotubes ranges from 0.8 to 1.

2. g .

3. The method for preparing an ultra-high sulfur content lithium-sulfur battery cathode material as described in claim 1, characterized in that, In step one, the secondary melt impregnation temperature is 220~240℃, and the secondary melt impregnation time is 10~12 minutes. h .

4. The method for preparing an ultra-high sulfur content lithium-sulfur battery cathode material as described in claim 1, characterized in that, The mass of trihydroxymethylaminomethane in step two is 1~2. g The mass of magnesium oxide is 0.1~0.

3. g The mass of chitosan is 0.1~0.

3. g The nickel nitrate concentration is 0.3~0.4%. mol / L .

5. The method for preparing an ultra-high sulfur content lithium-sulfur battery cathode material as described in claim 1, characterized in that, The carbonization conditions in step two are as follows: carbonization temperature of 400~500℃ and carbonization time of 2~4 hours under a nitrogen atmosphere. h .

6. The method for preparing an ultra-high sulfur content lithium-sulfur battery cathode material as described in claim 1, characterized in that, The reaction conditions under sealed conditions in step three are: reaction temperature of 55~65℃ and reaction time of 10~15 minutes. h .

7. The method for preparing an ultra-high sulfur content lithium-sulfur battery cathode material as described in claim 1, characterized in that, The stirring conditions in step three are: a stirring speed of 200-300 rpm. r / min The stirring time is 40-50 seconds. min .

8. A cathode material for ultra-high sulfur content lithium-sulfur batteries, characterized in that, It is prepared by the method for preparing an ultra-high sulfur content lithium-sulfur battery cathode material as described in any one of claims 1 to 7.

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