阅读说明：本技术 一种新型多孔碳阴极锂硫电池的制备方法 (Preparation method of novel porous carbon cathode lithium-sulfur battery ) 是由 刘久清 席阳 刘萌 于 2019-04-03 设计创作，主要内容包括：本发明公布了一种新型多孔碳阴极锂硫电池的制备方法,包括以下步骤：(1)槟榔渣先后经浸泡、洗涤、干燥、机械处理、碳化、活化、再次洗涤、最终干燥工序获得多孔碳；(2)用多孔碳制备硫/多孔碳复合材料；(3)用硫/多孔碳复合材料制备多孔碳阴极；(4)用多孔碳阴极装配锂硫电池。本发明用废弃的槟榔渣成功制备了大比表面积与大孔容的多孔碳,并用这种多孔碳制得了性能优异的多孔碳阴极与相应的锂硫电池。(The invention discloses a preparation method of a novel porous carbon cathode lithium-sulfur battery, which comprises the following steps: (1) sequentially carrying out soaking, washing, drying, mechanical treatment, carbonization, activation, secondary washing and final drying on the areca residue to obtain porous carbon; (2) preparing a sulfur/porous carbon composite material by using porous carbon; (3) preparing a porous carbon cathode by using a sulfur/porous carbon composite material; (4) a lithium sulfur battery was assembled with a porous carbon cathode. The invention successfully prepares porous carbon with large specific surface area and large pore volume by using the waste betel nut residues, and prepares a porous carbon cathode with excellent performance and a corresponding lithium-sulfur battery by using the porous carbon.)

1. A preparation method of a novel porous carbon cathode lithium-sulfur battery is characterized by comprising the following steps:

step one, taking betel nut residues, soaking the betel nut residues in deionized water for 1-5 days, then washing the betel nut residues with the deionized water for 3-6 times, and then drying the betel nut residues in an oven at the temperature of 80-160 ℃ for 12-24 hours;

step two, mechanically treating the dried areca residue obtained in the step one to obtain easily carbonized areca residue;

step three, putting the easy-carbonized areca-nut residues obtained in the step two into a tubular electric furnace, introducing protective gas, heating to 400-;

step four, mixing the carbonized areca residue obtained in the step three with an activating agent in a proportion of 1: grinding the powder into powder in a mortar according to the mass ratio of 0.25-4, putting the powder into a tubular electric furnace, introducing protective gas, heating to 900 ℃ at the heating rate of 1-10 ℃/min, and carrying out heat preservation and calcination for 1-4 h to obtain activated areca residue;

step five, washing the activated areca residue obtained in the step four in an acid solution for 3-5 times, then continuing to wash in deionized water for 2-4 times, and then drying in an oven at 60-130 ℃ for 24-48 h to obtain porous carbon;

step six, mixing the sublimed sulfur and the porous carbon obtained in the step five according to the mass ratio of 1-5: 1, mixing, grinding for 20-50 min, placing in a closed container prepared by special materials, introducing protective gas, then placing in a muffle furnace, heating to 80-200 ℃ at a heating rate of 2-15 ℃/min, carrying out heat preservation and calcination for 3-8 h, heating to 200-500 ℃ at a heating rate of 2-10 ℃/min, continuing to carry out heat preservation and calcination for 2-8 h, and then cooling to obtain a sulfur-carbon composite material;

step seven, blending and grinding the sulfur-carbon composite material obtained in the step six, a conductive material and a binder for 10-30 min, adding an organic solvent, and continuously grinding for 20-40 min to obtain anode slurry; coating the positive slurry on the current collector, and drying in an oven at 60-120 ℃ for 12-48 h to obtain a porous carbon cathode;

and step eight, sequentially packaging the prepared porous carbon cathode, the diaphragm, the electrolyte and the metal lithium anode in an anhydrous and oxygen-free environment to obtain the novel porous carbon cathode lithium-sulfur battery.

2. The method for preparing a novel porous carbon cathode lithium sulfur battery as claimed in claim 1, wherein the mechanical treatment in step two is one or more of ball milling, shearing or extrusion.

3. The method for preparing a novel porous carbon cathode lithium sulfur battery as claimed in claim 1, wherein the easily carbonized areca residue obtained in step two is one of filament, strip, granule or powder.

4. The method of claim 1, wherein the shielding gas in step three, step four, and step six is one of argon, nitrogen, or helium.

5. The method of claim 1, wherein in step four, the activator is KOH, KCl, FeCl₃、Fe₂O₃Or ZnCl₂One kind of (1).

6. The method of claim 1, wherein in step five the acid solution is one of sulfuric acid, hydrochloric acid or nitric acid.

7. The method for preparing a novel porous carbon cathode lithium-sulfur battery as claimed in claim 1, wherein in the sixth step, the special material is one of polytetrafluoroethylene, perfluoroether rubber, chlorinated polyether or polyborodiphenylsiloxane.

8. The method for preparing a novel porous carbon cathode lithium-sulfur battery as claimed in claim 1, wherein the mass ratio of the sulfur-carbon composite material, the conductive material and the binder in step seven is 6-9: 0-3: 1; the conductive material is Super P, high-conductivity acetylene black, Ketjen black or one of carbon black; the binder is one of PVDF, PTFE and PVA; the organic solvent is NMP.

9. The method for preparing a novel porous carbon cathode lithium sulfur battery as claimed in claim 1, wherein in step seven, the current collector can be one of foamed nickel, carbon paper or aluminum foil, the positive slurry is coated by one of spraying, brushing or blade coating, and the coating amount is 0.2-3 mg cm^-2。

10. The method for preparing a novel porous carbon cathode lithium-sulfur battery as claimed in claim 1, wherein in step eight the separator can be one of PP film, PE film, PEI film, PVDF-HFP film; the electrolyte consists of lithium salt and solvent, wherein the lithium salt is selected from LiClO₄、LiTFSI、LiNO₃、LiFSI、LiCF₃SO₃、LiPF₆The solvent is one or more selected from dimethyl sulfoxide, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1-ethyl-3-methyl tetrafluoroborate imidazole and N, N-dimethylformamide.

Technical Field

The invention relates to a preparation method of a novel porous carbon cathode lithium-sulfur battery, and belongs to the technical field of lithium-sulfur batteries.

Background

Lithium sulfur batteries are expected to outperform the most advanced lithium ion batteries as potential power sources, and have recently attracted considerable attention due to their potentially high energy density. Among them, lithium-sulfur batteries have low cost, no pollution, and high specific capacity (1675 mAh g)^-1) High energy density (2600W h kg)^-1) And good safetyAnd can be considered as an electrochemical energy system having great prospects, in addition, the sulfur-based material used as the positive electrode active material is a cheap and environmentally friendly material, however, there is a problem in that the conductivity of sulfur is 5 × 10^-30S/cm, sulfur approaches a non-conductor, and as a result, it is difficult to move electrons generated by the electrochemical reaction. Therefore, it is desirable to use conductive materials, such as carbon, that provide smooth electrochemical reaction sites. In this case, there are the following problems: in the case where the conductive material and sulfur are simply mixed for use, sulfur flows out to the electrolyte during the oxidation-reduction reaction to reduce the battery life, and in the case where a suitable electrolyte solution is not selected, lithium polysulfide, which is a reducing substance of sulfur, is eluted, so that sulfur can no longer participate in the electrochemical reaction. Therefore, there is a need to develop a technology for reducing the amount of sulfur flowing out to an electrolyte and improving the performance of a battery. Porous carbon is the most common cathode material in lithium-sulfur battery research because of its advantages of low cost, good electrical conductivity, strong adsorption capacity, proper pore channel structure, etc.

Every year, a large amount of areca nuts are consumed in the areas of Hunan and Hainan, and accordingly, a large amount of areca nut residues are generated, which causes great damage to the environment. The betel nut is a biological material rich in carbon and nitrogen, and the nitrogen-doped porous carbon with large specific surface area and large pore volume can be obtained by carbonization and activation. The large specific surface area can provide more active sites, and is beneficial to the decomposition of discharge products. The large pore volume can contain more discharge products, and is beneficial to improving the discharge specific capacity of the lithium-sulfur battery.

Disclosure of Invention

The invention aims to provide a method for manufacturing a porous carbon cathode lithium-sulfur battery and the lithium-sulfur battery manufactured by the method. The porous nitrogen-doped porous carbon with large specific surface area is prepared by taking areca residue as a carbon source and is applied to the preparation of the battery cathode.

The invention is realized by the following technical scheme:

the invention provides a method for manufacturing a porous carbon cathode lithium-sulfur battery, which comprises the following steps:

step one, taking betel nut residues, soaking the betel nut residues in deionized water for 1-5 days, then washing the betel nut residues with the deionized water for 3-6 times, and then drying the betel nut residues in an oven at the temperature of 80-160 ℃ for 12-24 hours;

step two, mechanically treating the dried areca residue obtained in the step one to obtain easily carbonized areca residue;

step three, putting the easy-carbonized areca-nut residues obtained in the step two into a tubular electric furnace, introducing protective gas, heating to 400-;

step four, mixing the carbonized areca residue obtained in the step three with an activating agent in a proportion of 1: grinding the powder into powder in a mortar according to the mass ratio of 0.25-4, putting the powder into a tubular electric furnace, introducing protective gas, heating to 900 ℃ at the heating rate of 1-10 ℃/min, and carrying out heat preservation and calcination for 1-4 h to obtain activated areca residue;

step five, washing the activated areca residue obtained in the step four in an acid solution for 3-5 times, then continuing to wash in deionized water for 2-4 times, and then drying in an oven at 60-130 ℃ for 24-48 h to obtain porous carbon;

step six, mixing the sublimed sulfur and the porous carbon obtained in the step five according to the mass ratio of 1-5: 1, mixing, grinding for 20-50 min, placing in a closed container prepared by special materials, introducing protective gas, then placing in a muffle furnace, heating to 80-200 ℃ at a heating rate of 2-15 ℃/min, carrying out heat preservation and calcination for 3-8 h, heating to 200-500 ℃ at a heating rate of 2-10 ℃/min, continuing to carry out heat preservation and calcination for 2-8 h, and then cooling to obtain a sulfur-carbon composite material;

step seven, blending and grinding the sulfur-carbon composite material obtained in the step six, a conductive material and a binder for 10-30 min, adding an organic solvent, and continuously grinding for 20-40 min to obtain anode slurry; coating the positive slurry on the current collector, and drying in an oven at 60-120 ℃ for 12-48 h to obtain a porous carbon cathode;

and step eight, sequentially packaging the prepared porous carbon cathode, the diaphragm, the electrolyte and the metal lithium anode in an anhydrous and oxygen-free environment to obtain the novel porous carbon cathode lithium-sulfur battery.

Preferably, the mechanical treatment in the second step is one or more of ball milling, shearing and extrusion.

Preferably, the easily carbonized areca residue obtained in the second step is one of filiform, strip, granular or powdery.

Preferably, the protective gas in the third step, the fourth step and the sixth step is one of argon, nitrogen or helium.

Preferably, the activating agent in the fourth step is KOH, KCl, FeCl₃、Fe₂O₃Or ZnCl₂One kind of (1).

Preferably, the acid solution in the fifth step is one of sulfuric acid, hydrochloric acid or nitric acid.

Preferably, the special material in the sixth step is one of polytetrafluoroethylene, perfluoroether rubber, polybenzimidazole, chlorinated polyether or polyborodiphenylsiloxane.

Preferably, the mass ratio of the sulfur-carbon composite material, the conductive carbon and the binder in the seventh step is 6-9: 0-3: 1; the conductive material is Super P, high-conductivity acetylene black, Ketjen black or one of carbon black; the binder is one of PVDF, PTFE and PVA; the organic solvent is NMP.

Preferably, the current collector in the seventh step can be one of nickel foam, carbon paper or aluminum foil, the coating mode of the positive electrode slurry is one of spraying, brushing and blade coating, and the coating amount is 0.2-3 mg cm^-2。

Preferably, the separator in the eighth step may be one of a PP film, a PE film, a PEI film, a PVDF film, and a PVDF-HFP film; the electrolyte consists of lithium salt and solvent, wherein the lithium salt is selected from LiClO₄、LiTFSI、LiNO₃、LiFSI、LiCF₃SO₃、LiPF₆The solvent is one or more selected from dimethyl sulfoxide, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1-ethyl-3-methyl tetrafluoroborate imidazole and N, N-dimethylformamide.

The innovation points of the invention are as follows:

the waste betel nut residues are used as a carbon source to prepare porous carbon with large specific surface area and large pore volume, so that the porous carbon cathode and the lithium-sulfur battery with excellent performance are prepared.

The invention has many advantages over the prior art.

1. The betel nut residue is used as a carbon source to prepare porous carbon, and the porous carbon is applied to a cathode of a lithium-sulfur battery. The betel nut dregs are common wastes in Hunan and Hainan areas, and cause serious damage to the environment. The use of betel nut dregs as a carbon source is an action of changing waste into valuable and is beneficial to environmental protection.

2. The porous carbon prepared from the areca residue has large specific surface area and large pore volume, and is beneficial to improving the cycle performance and the discharge specific capacity of the lithium-sulfur battery.

The present invention will be described in further detail with reference to the following embodiments, which are illustrative only and not limiting, and the scope of the present invention is not limited thereby.

Description of the drawings:

fig. 1 is a scanning electron micrograph of porous carbon prepared from areca residue for a lithium sulfur battery cathode.

Example 1: selecting 30 g of areca residue, firstly soaking in deionized water for 2 days, then washing in deionized water for 3 times, drying in a 100 ℃ oven for 12 hours, then cutting the areca residue into filaments with the diameter of about 3 mm, putting the filaments into a tubular electric furnace in an argon environment, and starting to heat up. The temperature rise speed is 2 ℃/min, the temperature is raised to 500 ℃, and the carbonized material is taken out after heat preservation and calcination are carried out for 3 h. 10 g of carbonized material was ground to a powder by blending with 30 g of KOH. And (3) placing the ground blended powder into an argon environment tubular electric furnace, continuously heating to 600 ℃ at the heating rate of 3 ℃/min, carrying out heat preservation and calcination for 4 h, and taking out the activated material. And (3) washing the activated material with hydrochloric acid and deionized water respectively for 3 times, and drying in an oven at 120 ℃ for 24 hours to obtain the dried porous carbon.

Mixing sublimed sulfur and porous carbon according to a mass ratio of 3: 1, mixing, grinding for 20 min, placing in a closed container prepared from polytetrafluoroethylene, adopting argon protection, then placing in a muffle furnace, heating to 155 ℃ at a heating rate of 4 ℃/min, carrying out heat preservation and calcination for 6 h, heating to 300 ℃ at a heating rate of 5 ℃/min, continuing to carry out heat preservation and calcination for 3h, and then cooling to obtain the sulfur-carbon composite material.

Grinding 70 g of sulfur-carbon composite material, 20 g of Super P and 10 g of PVDF in an agate mortar for 25 min, adding 500 g of NMP, continuously grinding for 30 min to obtain anode slurry, coating the anode slurry on foamed nickel by using a brush, wherein the coating amount is 1.0 mg cm^-2And then drying in an oven at 80 ℃ for 24 h to prepare the porous carbon cathode. In a glove box in an argon environment, 0.5M LiTFSI is dissolved in tetraglyme to prepare the required electrolyte, and then the porous carbon cathode, the PP film, the electrolyte and the lithium sheet are sequentially packaged to prepare the lithium-sulfur battery.

The carbon material prepared in this example had a specific surface area of 1381 m²g^-1Pore volume of 0.63 cm³g^-1. Super P is a carbon material commonly used in the cathode of the lithium-sulfur battery at present, and the specific surface area of the Super P is only 60 m²g^-1Pore volume of only 0.25 cm³g^-1. The lithium sulfur battery prepared in this example and the Super P-based lithium sulfur battery were subjected to charge and discharge tests at a voltage ranging from 1.5 to 3V. The first discharge capacity of the lithium-sulfur battery prepared in the embodiment reaches 1341 mA h g at the current density of 0.2C^-1And the first discharge capacity of the Super P-based lithium-sulfur battery is only 1156 mA h g^-1. At a high current density of 5C, the first discharge capacity of the lithium-sulfur battery prepared in the embodiment is still high, namely 849 mA h g^-1And after 500 times of charge and discharge, the discharge capacity of the Super P-based lithium-sulfur battery is only 678 mA h g of first discharge capacity^-1And after 500 times of charging and discharging, the attenuation of each circle is 0.09%.