Sulfur active material for ultra-high capacity secondary battery and preparation method and application thereof

Abstract

The invention discloses a sulfur active material for an ultrahigh-capacity secondary battery, which is prepared by the following steps: by taking nano-sized sulfur particles as a matrix, directionally coating a nano polymer layer on the surfaces of the nano-sized sulfur particles by using a non-ionic polymer compound, adding a siloxane solution, coating a silicon monoxide nano layer on the surfaces, and fully mixing in a glucose aqueous solution, thereby obtaining the sulfur active material for the ultrahigh-capacity secondary battery. And drying under a high-temperature condition to obtain a three-dimensional structure which is the sulfur active material for the ultra-high-capacity secondary battery. The invention also provides a preparation method and application of the sulfur active material for the ultrahigh-capacity secondary battery. The material has the characteristics of ultrahigh specific capacity, stable cycle performance, low cost and the like, the raw material selection flexibility is high, the price is low, and the preparation process is simple.

Description

Technical Field

[0001] The present invention relates to the technical field of rechargeable battery materials, and in particular to a sulfur active material for ultra-high capacity secondary batteries and a preparation method and application thereof. Background Art

[0002] Modern society's demand for energy has greatly promoted the development of energy storage technology. As the most successful energy storage device, lithium-ion batteries have broad application prospects in portable electronic devices, electric vehicles, space technology, defense industry, etc., and have become a research hotspot that has attracted widespread attention in recent years.

[0003] Lithium-sulfur metal battery is a very promising secondary battery. Its active material single sulfur has a theoretical discharge capacity of 1675mAh / g, and the theoretical energy density can reach 2600Wh / kg when lithium metal is used as the negative electrode, which is much larger than the secondary power lithium-ion battery of the LiFePO4 / graphite system and layered ternary lithium secondary battery system currently used. In addition, single sulfur has the advantages of low cost and environmental friendliness.

[0004] However, elemental sulfur has poor conductivity and volume expansion during the cycle, which will reduce the capacity and cycle performance of the battery. Therefore, it is very important to improve the sulfur active material to have both good conductivity and mechanical strength. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a sulfur active material for ultra-high capacity secondary batteries, which has the characteristics of ultra-high specific capacity, stable cycle performance and low cost.

[0006] The invention provides a sulfur active material for an ultra-high capacity secondary battery. Nano-sized sulfur particles are used as a matrix, a nano-polymer layer is directionally coated on the surface of the matrix, and then a silicon oxide nano-layer is coated, the mixture is fully mixed in a glucose aqueous solution, and then dried under high temperature conditions to obtain a three-dimensional structure that is a sulfur active material for an ultra-high capacity secondary battery.

[0007] Furthermore, the mass percentage concentration of the glucose aqueous solution is 5%.

[0008] The present invention also provides a method for preparing the above-mentioned sulfur active material for ultra-high capacity secondary battery, comprising the following steps:

[0009] (1) dispersing distilled sulfur in a mixed solution, and obtaining nano-sized sulfur particles dispersed in the mixed solution by wet ball milling; (2) adding a non-ionic polymer compound to the mixed solution, and obtaining sulfur nanoparticles with a surface covered with a nano-polymer layer in the suspension by a directional coating method; the non-ionic polymer compound is an aqueous solution composed of sulfur and a vinylamide polymer, and the mass ratio of sulfur to the vinylamide polymer in the aqueous solution is (1-4):1;

[0010] (3) centrifuging the obtained sulfur nanoparticles, filtering, washing with deionized water, and drying in a vacuum environment above 90° C. for 20 to 36 hours to obtain surface-modified sulfur nanoparticles;

[0011] (4) adding the modified sulfur nanoparticles into a siloxane solution, wherein the siloxane has the structural formula: Stirring for 1 to 4 hours, coating the surface of the modified sulfur nanoparticles with a silicon oxide nanolayer;

[0012]

[0013] The siloxane solution is not limited to the siloxane in the above reaction (the present invention uses siloxane to synthesize silicon dioxide on the surface of sulfur particles);

[0014] (5) centrifuging the sulfur nanoparticles obtained in step (4), filtering, washing with deionized water, and drying in a vacuum environment above 90° C. for 12 to 36 hours to obtain surface-coated sulfur nanoparticles;

[0015] (6) placing the surface-coated sulfur nanoparticles in a glucose aqueous solution and stirring them thoroughly for 2 to 4 hours;

[0016] (7) The sulfur nanoparticles obtained in step (6) are centrifuged, filtered, washed with deionized water, dried in a vacuum environment above 90° C. for 12 to 36 hours, and placed in a high temperature environment for 1 to 3 hours to obtain a sulfur active material with a three-dimensional structure.

[0017] Furthermore, the mixed solution in step (1) is composed of the following components in weight percentage: 20 wt % of ethanol and 80 wt % of deionized water.

[0018] Furthermore, in step (2), the non-ionic polymer compound is a 50 mg / 10 mL nano-sulfur mixed solution, the mass percentage concentration of sulfur in the nano-sulfur mixed solution is 10%, the mass percentage concentration of the vinylamide polymer is 5%, and the balance is deionized water.

[0019] Furthermore, the vacuum degree of step (3), step (5) and step (7) is controlled at -0.05Mpa.

[0020] Furthermore, in step (3), step (5) and step (7), the centrifugation step is performed at a speed of 3000 rpm and for 5 minutes.

[0021] Furthermore, the temperature of the high temperature environment in step (7) is controlled at 600-900°C.

[0022] The present invention also provides the use of the above-mentioned sulfur active material for ultra-high capacity secondary batteries in the preparation of secondary batteries.

[0023] The present invention uses nano-sized sulfur particles as a matrix, uses a non-ionic polymer compound to directionally coat the surface of the nano-sized sulfur particles with a nano-polymer layer, adds a siloxane solution, coats the surface with a silicon oxide nano-layer, and after being treated with a glucose aqueous solution, obtains a sulfur active material with a three-dimensional structure under high temperature conditions. The present invention ensures that the conductive layer coating on the surface of the sulfur nanoparticles is subsequently achieved at high temperature through the coating of the silicon oxide nano-functional layer, thereby realizing a composite sulfur positive electrode material with strong practicality. The present invention has the characteristics of ultra-high specific capacity, stable cycle performance, and low cost, high flexibility in raw material selection, low price, and simple preparation process.

[0024] The beneficial effects of the present invention are:

[0025] (1) The present invention uses distilled sulfur as raw material, which has high flexibility in raw material selection and low raw material price.

[0026] (2) The present invention uses nano-sized sulfur particles as a matrix, and then coats the surface with a nano-polymer layer and then a silicon oxide nano-layer. After being treated with a glucose aqueous solution, a three-dimensional structure is obtained under high temperature conditions, and the preparation process is simple.

[0027] (3) The three-dimensional structure of the sulfur active material of the present invention enhances the ion conduction capability and the electronic conductivity of the material.

[0028] (4) The present invention has both mechanical strength and excellent electrical conductivity, thereby improving the recycling performance of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0030] Figure 1 Cycling data, gram capacity, and coulombic efficiency for batteries based on sulfur active materials.

[0031] Figure 2 The voltage characteristics of lithium metal batteries based on sulfur active materials at the 1st, 50th, 75th, and 100th cycles. DETAILED DESCRIPTION

[0032] The technical solution of the present invention will be clearly and completely described below through specific implementation methods.

[0033] The invention discloses a sulfur active material for ultra-high capacity secondary batteries. The sulfur active material adopts nano-sized sulfur particles as a matrix, and the surface is directionally coated with a nano-polymer layer and then coated with a silicon oxide nano-layer. The three-dimensional structure obtained by fully mixing in a glucose aqueous solution and then drying under high temperature conditions is the sulfur active material for ultra-high capacity secondary batteries.

[0034] The mass percentage concentration of the glucose aqueous solution is 5%.

[0035] The specific steps of directional coating the surface with the nano polymer layer are: adding a non-ionic polymer compound (50 mg / 10 mL nano sulfur mixed solution) into the solution, performing a directional coating method, and obtaining sulfur nanoparticles with the surface covered with the nano polymer layer in the suspension.

[0036] The specific steps of coating the surface with a silicon oxide nano-layer are as follows: adding the modified sulfur nano-particles into a siloxane solution, stirring for 3 hours, and coating the surface of the modified sulfur nano-particles with a silicon oxide nano-layer.

[0037] Example 1

[0038] A method for preparing a sulfur active material for an ultra-high capacity secondary battery of this embodiment includes the following steps:

[0039] (1) dispersing distilled sulfur in a mixed solution, and performing wet ball milling to obtain nano-sized sulfur particles dispersed in the mixed solution, wherein the mixed solution is composed of the following components in weight percentage: 20 wt % of ethanol and 80 wt % of deionized water, and the wet ball milling is performed at a speed of 300-500 rpm for 3 hours;

[0040] (2) A non-ionic polymer compound is added to a mixed solution for directional coating to obtain sulfur nanoparticles with a surface covered with a nano polymer layer in a suspension, wherein the non-ionic polymer compound is a 50 mg / 10 mL nano-sulfur mixed solution; the non-ionic polymer compound is an aqueous solution composed of sulfur and a vinylamide polymer, and the mass ratio of sulfur to the vinylamide polymer in the aqueous solution is 2:1.

[0041] (3) centrifuging the obtained sulfur nanoparticles, filtering, washing with deionized water, and drying in a vacuum environment above 90 degrees for 24 hours to obtain surface-modified sulfur nanoparticles, the centrifugal speed is 3000 rpm, the time is 5 minutes, and the vacuum degree is controlled at -0.05 MPa;

[0042] (4) adding the modified sulfur nanoparticles into a siloxane solution, wherein the siloxane has the structural formula:

[0043] After stirring for 3 h, the surface of the modified sulfur nanoparticles was coated with a silicon oxide nanolayer;

[0044] (5) centrifuging the sulfur nanoparticles obtained in step (4), filtering, washing with deionized water, and drying in a vacuum environment above 90 degrees for 24 hours to obtain surface-coated sulfur nanoparticles, the centrifugal speed is 3000 rpm, the time is 5 minutes, and the vacuum degree is controlled at -0.05 MPa;

[0045] (6) The surface-coated sulfur nanoparticles were placed in a glucose aqueous solution (5 wt%) and stirred for 3 h;

[0046] (7) The sulfur nanoparticles obtained in step (6) are centrifuged, filtered, washed with deionized water, dried in a vacuum environment above 90 degrees for 24 hours, and placed in a high temperature environment for 2 hours to obtain a three-dimensional sulfur active material. The centrifugal speed is 3000 rpm, the time is 5 minutes, the vacuum degree is controlled at -0.05 MPa, and the temperature of the high temperature environment is controlled at 800°C.

[0047] refer to Figure 1 and 2 , using a battery cycle tester, adopting the constant current and constant voltage cycle test method commonly used for lithium batteries, and conducting tests in a normal temperature and pressure environment.

[0048] The capacitance in this embodiment is 800 mAh / g, and 90% of the capacity can be retained after 100 cycles. In comparison, the electrochemical capacity of NMC811 material is 200 mAh / g, and the electrochemical capacity of LCO material is 150 mAh / g. The electrochemical capacity of NMC532 is 160 mAh / g, and the electrochemical capacity of LFP is 140 mAh / g.

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art may make various modifications or equivalent substitutions to the present invention within the essence and protection scope of the present invention, and such modifications or equivalent substitutions should also be deemed to fall within the protection scope of the technical solution of the present invention.

Claims

1. A sulfur active material for ultra-high capacity secondary batteries, Features: Nano-sized sulfur particles are used as a matrix, a nano-polymer layer is directionally coated on the surface of the matrix, and then a silicon oxide nano-layer is coated, which is fully mixed in a glucose aqueous solution and then dried under high temperature conditions to obtain a three-dimensional structure that is a sulfur active material for ultra-high capacity secondary batteries.

2. The sulfur active material for an ultra-high capacity secondary battery according to claim 1, Features: The mass percentage concentration of the glucose aqueous solution is 5%.

3. The method for preparing the sulfur active material for ultra-high capacity secondary battery according to claim 1, Features: The steps include: (1) dispersing distilled sulfur in a mixed solution, and obtaining nano-sized sulfur particles dispersed in the mixed solution by wet ball milling; (2) adding a nonionic polymer compound to the mixed solution, and using a directional coating method to obtain sulfur nanoparticles with a surface covered with a nano polymer layer in the suspension; the nonionic polymer compound is an aqueous solution composed of sulfur and a vinylamide polymer, and the mass ratio of sulfur to the vinylamide polymer in the aqueous solution is (1-4):1; (3) centrifuging the obtained sulfur nanoparticles, filtering, washing with deionized water, and drying in a vacuum environment above 90° C. for 20 to 36 hours to obtain surface-modified sulfur nanoparticles; (4) adding the modified sulfur nanoparticles into the siloxane solution and stirring for 1 to 4 hours to coat the surface of the modified sulfur nanoparticles with a silicon oxide nanolayer; (5) centrifuging the sulfur nanoparticles obtained in step (4), filtering, washing with deionized water, and drying in a vacuum environment above 90° C. for 12 to 36 hours to obtain surface-coated sulfur nanoparticles; (6) placing the surface-coated sulfur nanoparticles in a glucose aqueous solution and stirring them thoroughly for 2 to 4 hours; (7) The sulfur nanoparticles obtained in step (6) are centrifuged, filtered, washed with deionized water, dried in a vacuum environment above 90° C. for 12 to 36 hours, and placed in a high temperature environment for 1 to 3 hours to obtain a sulfur active material with a three-dimensional structure.

4. The method for preparing a sulfur active material for an ultra-high capacity secondary battery according to claim 3, Features: The mixed solution described in step (1) is composed of the following components in weight percentage: 20 wt % of ethanol and 80 wt % of deionized water.

5. The method for preparing a sulfur active material for an ultra-high capacity secondary battery according to claim 3, Features: The non-ionic polymer compound in step (2) is a 50 mg / 10 mL nano-sulfur mixed solution, in which the mass percentage concentration of sulfur is 10%, the mass percentage concentration of the vinylamide polymer is 5%, and the balance is deionized water.

6. The method for preparing a sulfur active material for an ultra-high capacity secondary battery according to claim 3, Features: The vacuum degree of step (3), step (5) and step (7) is controlled at -0.05Mpa.

7. The method for preparing a sulfur active material for an ultra-high capacity secondary battery according to claim 3, Features: The centrifugation step in step (3), step (5) and step (7) is performed at a speed of 3000 rpm and for 5 minutes.

8. The method for preparing a sulfur active material for an ultra-high capacity secondary battery according to claim 3, Features: The temperature of the high temperature environment in step (7) is controlled at 600-900°C.

9. Use of the sulfur active material for ultra-high capacity secondary batteries according to claim 1 in preparing secondary batteries.

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