Preparation method of sulfur-based composite material coated with self-repairing functional layer

Abstract

The invention provides the preparation method of the sulfur-based composite material coated with the self-repairing functional layer, and the electrochemical performance of the sulfur-based composite material is remarkably improved through the method. The method comprises the following steps: dispersing an amino structure compound containing a polyethylene glycol (PEG) chain segment, an aldehyde structure compound and a sulfur-based composite material in a solvent according to a certain proportion, and initiating a Schiff polymerization reaction of an aldehyde group and an amino group by adding a proper amount of a catalyst to generate a porous polymer containing an imino group; therefore, an ultrathin coating layer with a self-repairing function is formed on the surface of the sulfur-based composite material in situ. According to the technology, the negative influence of volume expansion and shuttle effect of the sulfur-based composite material on the battery is greatly relieved, and the cycle performance and the rate capability of the battery are improved.

Description

Technical Field

[0001] The invention belongs to the field of chemical power sources, and in particular to a method for preparing a sulfur-based composite material coated with a self-repairing functional layer. Background Art

[0002] Covalent organic frameworks (COFs) are a class of long-range ordered porous crystalline polymers formed by organic building units based on covalent bonds. They are mainly composed of non-metallic lightweight elements (C, N, O and S, etc.) and have the advantages of structural order, larger specific surface area, designable regular pores, and functional modifiable properties. The design principle of COFs can create a backbone with a clear chemical structure and adjustable pore size and pores and geometric shapes. It can achieve precise control of the position of COFs building units and a variety of functional groups in two-dimensional and three-dimensional space. At the same time, a highly ordered crystalline network structure can be obtained, thereby achieving directional control of the physical and chemical properties of COFs. Constructing COFs with functional groups is of great significance, especially for lithium-ion battery applications.

[0003] Based on this, we innovatively use the topological structure design combined with the specific covalent bond polymerization between monomers to guide the growth of the ordered structure to achieve the optimization characteristics of ion conductivity. The porous imine-based polymerization coating containing polyethylene glycol segments is conducive to the self-repair of the ultra-thin functional layer, and the polyethylene glycol segment functionalized structure can achieve rapid lithium ion transport. This method significantly improves the conduction efficiency of lithium ions in the positive electrode material, improves the ion diffusion capacity of the material, and alleviates the impact of volume expansion and shuttle effect, providing a new solution for the development of high-performance batteries. Summary of the invention

[0004] In a first aspect, a method for preparing a sulfur-based composite material coated with a self-repairing functional layer comprises the following steps:

[0005] S1: taking a proper proportion of a halogenated oxygen-containing compound and a hydroxyl structure compound, dispersing them in a solvent, and adding a proper amount of a catalyst to initiate substitution and polymerization reactions to generate a compound containing a polyethylene glycol chain segment structure, and then adding an ammonia compound to generate an amino structure compound containing a polyethylene glycol chain segment;

[0006] S2: taking an appropriate amount of an aldehyde-containing structural compound, an amino-containing structural compound with a polyethylene glycol segment and a sulfur-based composite material and dispersing them in a solvent, and adding an appropriate amount of a catalyst to initiate Schiff polymerization of aldehyde and amino groups to form a porous imine polymer-coated sulfur-based composite material containing a polyethylene glycol segment;

[0007] S3: Sulfur-based composites include sulfur-based polymers and carbon-sulfur composites;

[0008] S4: Equip the battery with the porous imine-coated sulfur-based composite material containing polyethylene glycol segments as the positive electrode material.

[0009] Preferably, the halogenated oxygen-containing compound in step S1 is an oxygen-containing halogenated hydrocarbon: bis(2-methoxyethoxy)methane, 2-methoxyethoxymethyl chloride, 1-bromo-2-(2-methoxyethoxy)ethane, 1-iodo-2-(2-methoxyethoxy)ethane, 2-(2-ethoxyethoxy)ethane; hydroxyl structure compounds such as Figure 1 As shown; the solvent is water, NMP, DMF, chloroform, acetonitrile, ether and acetone; the catalyst is: potassium carbonate, potassium hydroxide, sodium hydroxide, lithium hydroxide, hydrochloric acid, sulfuric acid, nitric acid and acetic acid; the ammonia compound is ammonia water, hydrazine, ammonia methanol and ammonium chloride; n in (CH2CH2O)n in the generated polyethylene glycol segment is 1-1000.

[0010] Preferably, the aldehyde-containing structural compound in step S2 is Figure 2 As shown; the molar ratio of the aldehyde structure compound to the amino structure compound containing the polyethylene glycol segment is 1:100-100:1; the mass ratio of the positive electrode material of the polyethylene glycol segment porous imine compound and the sulfur-based compound is 1:100-100:1.

[0011] Preferably, the sulfur-based polymer material in step S3 is sulfurized polyacrylonitrile, dimethyl trisulfide, sulfurized polyacrylic acid, phenyl polysulfide, sulfurized polytetravinylpyridine, diallyl sulfide, sulfurized aminophenol-formaldehyde resin, and sulfurized poly(1,2,4,5-4-amino)benzene; the carbon-sulfur composite material is: porous carbon / sulfur, hollow carbon / sulfur, graphene and its derivatives / sulfur, carbon nanotubes and their derivatives / sulfur, and carbon nanofibers / sulfur.

[0012] In a second aspect, a self-repairing functional layer-coated sulfur composite positive electrode material is provided, characterized in that it is prepared by the preparation method described in any one of claims 1 to 3.

[0013] In the third aspect, a method for in-situ improving the cycle capacity of sulfur-based compound positive electrode materials as described in the second aspect is characterized in that it is applied to lithium metal batteries, lithium ion batteries, sodium ion batteries, sodium metal batteries, potassium ion batteries, and potassium metal batteries.

[0014] Compared with the prior art, the present invention has the following significant advantages:

[0015] (1) Efficient ion transport: The introduction of a functionalized polyethylene glycol chain improves the efficiency of lithium ion transport. The oxygen atoms in the polyethylene glycol chain can provide a fast lithium ion transfer channel, improving the rate performance of the battery.

[0016] (2) Alleviate the impact of volume expansion: Since the coating has a self-repairing function, the coating fracture caused by volume expansion during the charge and discharge process can be self-repaired, which is helpful to alleviate the impact of volume expansion. This feature plays an important role in improving the stability and cycle life of the battery.

[0017] (3) Economic sustainability: The self-healing functional layer coated sulfur-based composite material prepared by this innovative method not only shows excellent economy and efficiency, but also perfectly fits the environmental protection concept of green production. In addition, it also significantly reduces the difficulty of large-scale production, paving a solid path for the battery industry to move towards a sustainable future. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is the discharge rate diagram of lithium-sulfur battery.

[0019] Figure 2 It is a schematic diagram of the structure of a hydroxyl-containing structural compound.

[0020] Figure 3 Schematic diagram of the structure of compounds containing aldehyde structures.

[0021] Figure 4 Schematic diagram of the structure of PEG-NHNH2.

[0022] Figure 5 Schematic diagram of the structure of porous imine polymer with polyethylene glycol chain segments.

[0023] Figure 6 It is the rate data of the battery. DETAILED DESCRIPTION

[0024] In order to facilitate the understanding of the present invention, the present invention will be described in more comprehensive and detailed manner below in conjunction with the accompanying drawings and preferred experimental examples, but the protection scope of the present invention is not limited to the following specific embodiments.

[0025] Unless otherwise defined, all the professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0026] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0027] Implementation Case 1

[0028] Take 0.25 mol of 1-bromo-2-(2-methoxyethoxy)ethane, 0.1 mol of diethyl 2,5-dihydroxyterephthalate and 0.045 mol of potassium carbonate, dissolve them in 500 mL of anhydrous acetonitrile, and a substitution reaction occurs to introduce oxygen into the benzene ring to generate PEG-CH2CH3. Dissolve 0.45 mol of PEG-CH2CH3 in 400 mL of ethanol and 50 ml of hydrazine hydrate to obtain the final product PEG-NHNH2, such as Figure 3 As shown. Take 0.05 mol of 1,3,5-triformylbenzene and 0.15 mol of PEGNHNH2 and add them into water, then take 30 g of graphene and its derivatives / sulfur and disperse them. Add 0.01 acetic acid as an initiator to promote the polymerization reaction between aldehyde groups and amino groups to generate a polyethylene glycol segment porous polymer as shown. Figure 4 As shown, and in situ coated on the carbon-sulfur composite material as shown Figure 5 As shown. The prepared porous imine-based polymer coated carbon-sulfur composite material is used as the positive electrode material. We use this material as the positive electrode and lithium metal as the negative electrode to assemble a Li-S battery soft pack, as shown Figure 6 As shown, a rate charge and discharge test was carried out. At a rate of 1C, the discharge specific capacity of the material was 849 mAh / g.

[0029] Implementation Case 2

[0030] Take 0.3 mol of 2-methoxyethoxymethyl chloride, 0.15 mol of 2-hydroxyterephthalic acid and 0.08 mol of potassium hydroxide, dissolve in 500 mL of DMF, and a substitution reaction occurs to introduce oxygen into the benzene ring to generate PEG-CH3. Dissolve 0.45 mol of PEG-CH3 in 400 mL of ethanol and 60 ml of ammonia methanol to obtain the final product PEG-NH2. Take 0.1 mol of 4-acetylbenzoic acid and 0.15 mol of PEG-NH2 and add them to the DMF organic solvent, then take 20 g of dimethyl trisulfide and disperse it therein. Add 0.05 mol of hydrochloric acid as an initiator to promote the polymerization reaction between the aldehyde group and the amino group to generate a porous imine polymer of a polyethylene glycol segment, and in situ coat it on the sulfide polyacrylic acid positive electrode material. The prepared porous imine-coated sulfide polyacrylonitrile material is used as the positive electrode material. We used this material as the positive electrode and metallic lithium as the negative electrode to assemble a Li-S battery soft pack and tested it at a current density of 0.1C. The Li-S battery can remain stable after 200 cycles, and the coulombic efficiency remains at 99.6%, effectively alleviating the impact of volume expansion.

[0031] Implementation Case 3

[0032] Take 0.4 mol of 1-(2-chloroethoxy)-2-(2-methoxyethoxy)ethane, 0.3 mol of 2,5-dihydroxy-1,4-phenylenediacetic acid and 0.06 mol of sodium hydroxide, dissolve in 600 mL of NMP, and a substitution reaction occurs to introduce oxygen into the benzene ring to generate PEG-CH3. Dissolve 0.45 mol of PEG-CH2CH3 in 400 mL of ethanol and 50 ml of ammonium chloride to obtain the final product PEG-NHNH2. Take 0.15 mol of acetylphenylacetic acid and 0.3 mol of PEG-NH2 and add them to the NMP organic solvent, then take 10 g of sulfide polyacrylic acid and disperse it therein. Add 0.05 mol of acetic acid as an initiator to promote the polymerization reaction between the aldehyde group and the amino group to generate a porous imine polymer of the polyethylene glycol segment, and in situ coat it on the sulfide polyacrylic acid positive electrode material. The above-prepared porous imine-coated sulfide polyacrylic acid material is used as the positive electrode material. We use this material as the positive electrode and metal lithium as the negative electrode to assemble a Li-S battery soft pack. At a current density of 0.5C, the Li-S battery can be cycled for 150 cycles and remain stable. As mentioned above, although the present invention has been shown and described with reference to specific preferred embodiments, it should not be interpreted as limiting the present invention itself. Various changes in form and details may be made without departing from the spirit and scope of the present invention as defined in the appended claims.

Claims

1. A method for preparing a sulfur-based composite material coated with a self-repairing functional layer, comprising the following steps: S1: taking a proper proportion of a halogenated oxygen-containing compound and a hydroxyl structure compound, dispersing them in a solvent, and adding a proper amount of a catalyst to initiate substitution and polymerization reactions to generate a compound containing a polyethylene glycol chain segment structure, and then adding an ammonia compound to generate an amino structure compound containing a polyethylene glycol chain segment; S2: taking an appropriate amount of an aldehyde-containing structural compound, an amino-containing structural compound with a polyethylene glycol segment and a sulfur-based composite material and dispersing them in a solvent, and adding an appropriate amount of a catalyst to initiate Schiff polymerization of aldehyde and amino groups to form a porous imine polymer-coated sulfur-based composite material containing a polyethylene glycol segment; S3: Sulfur-based composites include sulfur-based polymers and carbon-sulfur composites; S4: Equip the battery with the porous imine-coated sulfur-based composite material containing polyethylene glycol segments as the positive electrode material.

2. The method for preparing a sulfur-based composite material coated with a self-repairing functional layer according to claim 1, characterized in that: In step S1, the halogenated oxygen-containing compound is an oxygen-containing halogenated hydrocarbon: bis(2-methoxyethoxy)methane, 2-methoxyethoxymethyl chloride, 1-bromo-2-(2-methoxyethoxy)ethane, 1-iodo-2-(2-methoxyethoxy)ethane, 2-(2-ethoxyethoxy)ethane; the hydroxy structure compound is: p-methylphenol, 2,4,6-tri-tert-butylphenol, diphenol propane, p-hydroxybenzoic acid, 2,5-dihydroxy terephthalate, 2,8-naphthalenediol-6-sulfonate sodium; the solvent is water, NMP, DMF, chloroform, acetonitrile, ether and acetone; the catalyst is: potassium carbonate, potassium hydroxide, sodium hydroxide, lithium hydroxide, hydrochloric acid, sulfuric acid, nitric acid and acetic acid; the ammonia compound is ammonia water, hydrazine, ammonia methanol and ammonium chloride; and n in (CH2CH2O)n in the generated polyethylene glycol segment is 1-1000.

3. According to the method for preparing a sulfur-based composite material coated with a self-healing functional layer according to claim 1, the aldehyde-containing structural compound in step S2 is: p-tolualdehyde, 2,4,6-trimethylbenzaldehyde, terphenyl dialdehyde, 4-formylphenylboric acid, benzaldehyde, tris(4-formylphenyl)amine, terephthalaldehyde, 4,6-dihydroxybenzaldehyde, 1,3,5-tris(p-formylphenyl)benzene, biphenyl dicarboxaldehyde, 2-hydroxy-1-naphthaldehyde; the molar ratio of the aldehyde-containing structural compound to the amino structural compound containing a polyethylene glycol segment is 1:100-100:1; the mass ratio of the positive electrode material of the porous imine compound containing a polyethylene glycol segment and the sulfur-based compound is 1:100-100:

1.

4. According to the method for preparing a sulfur-based composite material coated with a self-healing functional layer according to claim 1, the sulfur-based polymer material in step S3 is sulfurized polyacrylonitrile, dimethyl trisulfide, sulfurized polyacrylic acid, phenyl polysulfide, sulfurized polytetravinyl pyridine, diallyl sulfide, sulfurized aminophenolic resin, and sulfurized poly(1,2,4,5-4-amino)benzene; the carbon-sulfur composite material is: porous carbon / sulfur, hollow carbon / sulfur, graphene and its derivatives / sulfur, carbon nanotubes and their derivatives / sulfur, and carbon nanofibers / sulfur.

5. A self-repairing functional layer coated sulfur-based composite material, characterized in that The material is prepared by the method for preparing a sulfur-based composite material coated with a self-repairing functional layer as described in any one of claims 1 to 4.

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