Method for coating surface of carbon-sulfur positive electrode material with zinc sulfide in situ

Abstract

The invention discloses a method for in-situ coating of zinc sulfide on the surface of a carbon-sulfur positive electrode material, and belongs to the technical field of chemical power sources. The invention aims to improve the electrochemical performance and stability. The method comprises the following steps: dissolving zinc salt and sulfide in deionized water to respectively form solutions; adding the carbon-sulfur material into the zinc salt solution, stirring, standing, slowly dropwise adding the sulfide solution, and quickly stirring, so that the nano zinc sulfide is coated on the surface of the carbon-sulfur material; finally filtering and drying to obtain a product. The method is simple and convenient, coating is uniform and controllable, the specific discharge capacity in practical application reaches up to 1301 mAh / g, and 0.1 C charge-discharge cycle is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical power sources, and in particular relates to a method for in-situ coating of zinc sulfide on the surface of a carbon-sulfur positive electrode material. Background Art

[0002] With the advent of the energy age, lithium-ion batteries (LIBs) have successfully occupied the portable electronic device consumer market with their outstanding performance such as high energy density (150-250Wh kg-1), good cycle stability (more than 1000 cycles) and high operating voltage (about 4V). However, in the face of the growing energy demand of electric vehicles and smart cars and the needs of grid applications, the positive electrode materials used in traditional lithium-ion batteries, such as lithium transition metal oxides / phosphates (including LiCoO2, ternary lithium, LiFePO4, etc.) and graphite anodes, have gradually shown limitations in charge storage capacity and energy density. This situation has prompted researchers to actively explore advanced alternative positive electrode materials that surpass current LIBs in order to achieve a paradigm shift in the field of electrochemistry.

[0003] In the exploration of advanced high-energy-density batteries, lithium-sulfur batteries have a larger theoretical specific capacity (1675 mAh g -1 ) and theoretical energy density (2500Wh kg -1 ), in fact, lithium-sulfur batteries can provide 400-600Wh kg -1 The effective energy density of lithium-sulfur batteries is about twice that of traditional LIBs. In addition, sulfur cathodes are abundant, natural, cheap and non-toxic, which makes lithium-sulfur batteries extremely competitive in the market. However, in the research and development of lithium-sulfur batteries, how to improve the utilization rate of sulfur in the battery has always been an issue that cannot be effectively solved. Therefore, it is necessary for us to propose a method for in situ coating of zinc sulfide on the surface of carbon-sulfur positive electrode materials. This preparation method is simple and efficient, and the electrostatic self-assembly of zinc sulfide on the surface of the carbon-sulfur positive electrode can effectively improve the specific energy and rate performance of the carbon-sulfur positive electrode and the effective utilization rate of elemental sulfur in the positive electrode. Summary of the invention

[0004] In order to solve the technical problems existing in the above-mentioned background technology, the present invention provides a method for in-situ coating of zinc sulfide on the surface of a carbon-sulfur positive electrode material.

[0005] The present invention adopts the following technical solution: a method for in-situ coating of zinc sulfide on the surface of a carbon-sulfur positive electrode material, comprising the following steps:

[0006] Step 1, measuring a predetermined amount of zinc salt, dissolving it in deionized water to form a zinc salt aqueous solution; adding the surface-treated carbon-sulfur cathode material to the zinc salt aqueous solution and stirring evenly, and after being evenly dispersed, allowing the solution to stand;

[0007] Step 2, measuring a predetermined amount of sulfide, dissolving it in deionized water to form a sulfide aqueous solution, then dropping the sulfide aqueous solution into the solution and stirring at a predetermined rate, filtering after the dropwise addition is completed, and placing the obtained filter cake in an oven and baking it to dryness.

[0008] Preferably, the zinc salt is zinc sulfate, zinc nitrate, zinc chloride, zinc fluorosilicate, zinc fluoroborate, zinc gluconate and zinc acetate; the concentration of the zinc salt is 0.1-5 mol / L; the speed of mechanical stirring is 200-20000 rpm / min; and the solution is allowed to stand for 3-50 h.

[0009] Preferably, the sulfide is sodium sulfide, ammonium sulfide, sodium persulfate, ammonium persulfate; the concentration of the sulfide aqueous solution is 0.1-5 mol / L; the speed of mechanical stirring is 200-30000 rpm / min; the drop rate is 0.1-20 ml / min; the baking temperature of the oven is 20-90°C; and the baking time is 5-2000 h.

[0010] Preferably, it is used in lithium metal batteries, lithium ion batteries, sodium ion batteries, sodium metal batteries, potassium ion batteries, and potassium metal batteries.

[0011] Beneficial effects of the present invention:

[0012] 1. Important breakthrough in process scale-up and industrialization: This preparation method not only ensures the excellent performance of the material through the clever use of the solution method, but more importantly, it greatly promotes the scale-up and industrialization of the preparation process. This innovation enables us to easily achieve the preparation of high-capacity materials from laboratory level to kilogram level and even ton level, effectively reducing production costs and improving production efficiency, opening up broad prospects for the widespread application and commercial production of carbon-sulfur materials.

[0013] 2. Unique surface modification technology improves discharge performance: Another highlight of this patent is the precise precipitation of zinc sulfide on the surface of the carbon-sulfur cathode material by precipitation method, and the formation of a nano-sulfur coating layer. This innovative surface modification strategy cleverly utilizes the catalytic effect of zinc sulfide and significantly accelerates the efficient conversion of long-chain sulfur to short-chain sulfur during the discharge process. This transformation not only optimizes the discharge reaction path, but also effectively improves the discharge specific capacity of the material, making the battery show excellent performance in terms of energy density and cycle stability, providing strong technical support for improving the overall performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is the charge and discharge curve of carbon-sulfur positive electrode material. DETAILED DESCRIPTION

[0015] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0016] Embodiment 1

[0017] The present embodiment discloses a method for in-situ coating of zinc sulfide on the surface of a carbon-sulfur cathode material, comprising the following steps: selecting zinc sulfate as a zinc source, weighing 100 and dissolving it in 500 mL of deionized water to form a zinc sulfate aqueous solution with a concentration of 1.36 mol / L. 50 g of pre-treated carbon-sulfur cathode material is added to the above solution, and a magnetic stirrer is used to stir at a speed of 800 rpm / min for 30 minutes until the carbon-sulfur material is completely dispersed and uniform. The mixed solution is allowed to stand for 24 hours to ensure that zinc ions are fully adsorbed on the surface of the carbon-sulfur material. 60 g of sodium sulfide is weighed and dissolved in 400 mL of deionized water to form a sulfide aqueous solution with a concentration of 2 mol / L. A separating funnel is used to slowly drip the sodium sulfide solution into the zinc sulfate-carbon-sulfur mixed solution after standing at a speed of 5 ml / min, and the agitator is turned on at the same time, and the speed is adjusted to 1500 rpm / min to ensure rapid and uniform mixing. After the addition is completed, stirring is continued for 30 minutes, followed by filtering and collecting the filter cake. Place the filter cake in an oven at 60°C and bake for 12 hours until completely dry to obtain a zinc sulfide-coated carbon-sulfur positive electrode material. Use the prepared carbon-sulfur material as the positive electrode material. Select lithium metal as the negative electrode and PP diaphragm as the battery diaphragm. According to the conventional battery assembly process, assemble the positive electrode, negative electrode and diaphragm into a lithium metal battery. Carry out charge and discharge tests in the voltage range of 1.8-2.6V. At 0.1C, the reversible discharge specific capacity is as high as 1300mAh / g.

[0018] Embodiment 2

[0019] This embodiment discloses a method for in-situ coating of zinc sulfide on the surface of a carbon-sulfur cathode material, comprising the following steps:

[0020] Zinc nitrate was selected as the zinc source and configured into a 3 mol / L zinc nitrate aqueous solution (219 g zinc nitrate was weighed and dissolved in 500 mL deionized water). 75 g of pre-treated carbon-sulfur cathode material was added to the solution and stirred at 1200 rpm / min for 45 minutes using a mechanical stirrer to ensure uniform dispersion of the material. The mixed solution was allowed to stand for 48 hours to promote the adsorption of zinc ions on the surface of the carbon-sulfur material. An ammonium persulfate aqueous solution with a concentration of 1.5 mol / L was prepared (142 g ammonium persulfate was weighed and dissolved in 500 mL deionized water). The ammonium persulfate solution was dripped into the zinc nitrate-carbon-sulfur mixture at a speed of 2 ml / min by a peristaltic pump control, and the stirring speed was adjusted to 2500 rpm / min. After the addition was completed, stirring was continued for 1 hour, and the filter cake was collected by filtration. The filter cake was placed in an oven at 80 ° C and baked for 48 hours to obtain the product. The carbon-sulfur material prepared above was used as the cathode material. Lithium metal was selected as the negative electrode and PP diaphragm was used as the battery diaphragm. According to the conventional battery assembly process, the positive electrode, negative electrode and separator are assembled into a lithium metal battery. The charge and discharge test is carried out in the voltage range of 1.8-2.6V. At 0.1C, the reversible discharge specific capacity is as high as 1301mAh / g.

[0021] Embodiment 3

[0022] This embodiment discloses a method for in-situ coating of zinc sulfide on the surface of a carbon-sulfur cathode material, comprising the following steps:

[0023] Use zinc acetate as a zinc source and prepare a 0.5 mol / L zinc acetate aqueous solution (weigh 68 g zinc acetate and dissolve it in 1 L deionized water). Add 30 g of pre-treated carbon-sulfur cathode material to the solution and stir at 400 rpm / min for 1 hour to ensure that the material is evenly dispersed. Let the mixed solution stand for 10 hours to promote the adsorption of zinc ions. Prepare a 0.3 mol / L ammonium sulfide aqueous solution (such as weighing 22.8 g ammonium sulfide and dissolving it in 500 mL deionized water). Use a dropping funnel to add the ammonium sulfide solution to the zinc acetate-carbon-sulfur mixture at a rate of 10 ml / min, and adjust the stirring speed to 1000 rpm / min. After the addition is complete, continue stirring for 60 minutes and then filter. Place the filter cake in a 40 ° C oven and bake for 72 hours to obtain a carbon-sulfur cathode material uniformly coated with zinc sulfide. The prepared carbon-sulfur material is used as the cathode material. Lithium metal is selected as the negative electrode and PP diaphragm is used as the battery diaphragm. According to the conventional battery assembly process, the positive electrode, negative electrode and separator are assembled into a lithium metal battery. The charge and discharge test is carried out in the voltage range of 1.8-2.6V. At 0.1C, the reversible discharge specific capacity is as high as 1301mAh / g. Figure 1A method for in-situ coating of zinc sulfide on the surface of a carbon-sulfur cathode material is used in lithium metal batteries, lithium ion batteries, sodium ion batteries, sodium metal batteries, potassium ion batteries, and potassium metal batteries.

[0024] The above is a detailed introduction to a method for in-situ coating of zinc sulfide on the surface of a carbon-sulfur positive electrode material provided by the present invention. It is worth noting that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical details recorded in the aforementioned embodiments, or to make equivalent replacements for some of the technical features therein. Any equivalent replacements, modifications, etc. made within the core ideas and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for in-situ coating of zinc sulfide on the surface of a carbon-sulfur cathode material, characterized in that: The following steps are involved: Step 1, measuring a predetermined amount of zinc salt, dissolving it in deionized water to form a zinc salt aqueous solution; adding the surface-treated carbon-sulfur cathode material to the zinc salt aqueous solution and stirring evenly, and after being evenly dispersed, allowing the solution to stand; Step 2, measuring a predetermined amount of sulfide, dissolving it in deionized water to form a sulfide aqueous solution, then dropping the sulfide aqueous solution into the solution and stirring at a predetermined rate, filtering after the dropwise addition is completed, and placing the obtained filter cake in an oven and baking it to dryness.

2. A method for in-situ coating of zinc sulfide on the surface of a carbon-sulfur cathode material according to claim 1, characterized in that: The zinc salt is zinc sulfate, zinc nitrate, zinc chloride, zinc fluorosilicate, zinc fluoroborate, zinc gluconate and zinc acetate; the concentration of the zinc salt is 0.1-5 mol / L; the speed of mechanical stirring is 200-20000 rpm / min; and the solution is left standing for 3-50 hours.

3. A method for in-situ coating of zinc sulfide on the surface of a carbon-sulfur cathode material according to claim 2, characterized in that: The sulfide is sodium sulfide, ammonium sulfide, sodium persulfate, ammonium persulfate; the concentration of the sulfide aqueous solution is 0.1-5 mol / L; the speed of mechanical stirring is 200-30000 rpm / min; the drop speed is 0.1-20 ml / min; the baking temperature of the oven is 20-90° C.; and the baking time is 5-2000 h.

4. The method of in-situ coating of zinc sulfide on the surface of a carbon-sulfur cathode material according to claim 1, characterized in that: Used in lithium metal batteries, lithium ion batteries, sodium ion batteries, sodium metal batteries, potassium ion batteries, and potassium metal batteries.

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