Preparation method for improving discharge potential of sulfenyl polymer material

Abstract

The invention provides a preparation method for improving the discharge potential of a sulfenyl polymer material. The core of the method is that transition metal fluoride is added when the sulfur-based polymer material is prepared, and the transition metal fluoride is uniformly distributed in the sulfur-based polymer material. As fluorine atoms have very strong electronegativity, the discharge potential of the sulfenyl polymer is effectively improved, and meanwhile, the transition metal fluoride serving as Lewis acid also has a catalytic effect and promotes an oxidation-reduction reaction, so that the electrochemical performance of a battery is remarkably improved.

Description

Technical Field

[0001] The invention discloses a preparation method for improving the discharge potential of a sulfur-based polymer material, and relates to the field of chemical power sources. Background Art

[0002] With the rapid development of electric vehicles, aerospace, and portable electronic devices, higher and higher requirements are placed on the energy density of batteries. Lithium-sulfur batteries have ultra-high theoretical energy density. The theoretical discharge mass specific capacity of lithium-sulfur batteries is as high as 1675mAh / g, which is much higher than the widely used lithium cobalt oxide batteries (<150mAh / g) in commercial applications, and also much higher than some traditional lithium-ion batteries. Therefore, it can meet the urgent demand for high energy density in these fields. The sulfur element used in lithium-sulfur batteries is abundant in the earth, low in price, and environmentally friendly, which is conducive to reducing the production cost of batteries. However, when sulfur is used as the positive electrode material, its electronic conductivity and ionic conductivity are poor, and sulfur and lithium sulfide have large volume expansion and contraction during the charging and discharging process, and the changes in the positive electrode morphology and structure lead to loss of active materials and self-discharge, which in turn affects the energy density and cycle life of the battery.

[0003] In this regard, this patent proposes a preparation method for improving the discharge potential of sulfur-based polymer materials. When transition metal fluorides are added, due to the strong electronegativity of fluorine atoms, the energy of LiF generated during the reaction is very low, so that the working potential of transition metal fluorides is higher than that of the same type of sulfides. Fluorides based on Fe, Co, Ni, and Cu have the most application prospects. The addition of transition metal fluorides in this innovative method effectively improves the discharge potential of sulfur-based polymers and the energy density of batteries. At the same time, transition metal fluorides, as Lewis acids, can also play a catalytic role, promote redox reactions, and significantly improve the electrochemical performance of batteries; it simplifies the preparation process of adding transition metal fluoride materials to sulfur-based polymers, making this technology easy to achieve large-scale production. Summary of the invention

[0004] To achieve the above object, the present invention adopts the following technical solution:

[0005] In a first aspect, the present invention provides a method for preparing a sulfur-based polymer material for improving the discharge potential, characterized in that the method is carried out according to the following steps:

[0006] S1: uniformly mixing elemental sulfur, transition metal fluoride and polymer and heating them together, and cooling them to room temperature after the heat treatment is completed to obtain a sulfur-based polymer containing metal fluoride;

[0007] S2: The obtained sulfur-based polymer material containing transition metal fluoride is mixed with conductive carbon and a binder in an appropriate proportion to form a pole piece, and the battery is assembled.

[0008] Preferably, in step S1, the ratio of elemental sulfur, transition metal fluoride and polymer is 10:(0.1-10):(0.01-5).

[0009] Preferably, in step S1, the elemental sulfur, transition metal fluoride and polymer material are mixed by sand milling, ball milling and air flow dispersion.

[0010] Preferably, the transition metal fluoride in step S1 is FeF2, FeF3, CoF2, NiF2, or MnF2.

[0011] Preferably, the polymer in step S1 is polyacrylonitrile, polyaniline, polyethylenedioxythiophene, poly(nitromethylpyrrole), polydopamine, polyethylene oxide, poly(m-aminothiophene), polyimide, polytetravinylpyridine, polyacrylic acid, 1,3-diisopropenylbenzene, poly(3-hexylthiophene-2,5-diyl), 1,3-diethinylbenzene, aminophenol-formaldehyde resin, poly(1,2,4,5-4-amino)benzene; the polymer is a homopolymer and a copolymer.

[0012] Preferably, the heating temperature in step S1 is 100-600° C.; the insulation time is 1-40 hours; and the heating rate is 1-20° C. / min.

[0013] Preferably, in step S2, the optional conductive carbon includes acetylene black, multi-walled and single-walled carbon nanotubes, SuperP, conductive graphite and Ketjen black; and the binder is selected from PAA, CMC, SBR, guar gum, PVDF and LA133.

[0014] In a second aspect, a method for preparing a sulfur-based polymer material containing transition metal fluorides is characterized in that the material is prepared by the preparation method described in any one of claims 1 to 7.

[0015] In a third aspect, the present invention provides a use of the sulfur-based polymer material containing transition metal fluorides described in the second aspect, 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.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] Improving the discharge potential is an effective means to construct high-performance sulfur-based polymer materials. By adding transition metal fluorides, the discharge potential in sulfur-based polymers can be increased, thereby improving the energy density and cyclability of the materials.

[0018] Adding transition metal fluorides as Lewis acids to sulfur-based polymers can act as catalysts, promote redox reactions, and significantly improve the electrochemical performance of the battery.

[0019] The present invention can quickly and conveniently prepare sulfur-based polymer materials containing transition metal fluorides, is easy to produce on a large scale, and plays an important role in promoting the practical application of lithium-sulfur batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The capacity-voltage curves of Example 1 and the comparative example. DETAILED DESCRIPTION

[0021] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and carefully in combination with preferred experimental examples below, but the protection scope of the present invention is not limited to the following specific embodiments.

[0022] 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.

[0023] 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.

[0024] Implementation Case 1

[0025] 8g of elemental sulfur, 5g of FeF2, and 2g of 15w molecular weight polyacrylonitrile (homopolymer) were ground in a mortar for 30 minutes, and then placed in a tube furnace at 300°C for 10 hours to obtain a sulfur-based polymer material containing transition metal fluorides. The obtained sulfur-based polymer material containing transition metal fluorides was used as the positive electrode and metallic lithium was used as the negative electrode to assemble a button battery. The electrochemical performance test was carried out in the voltage range of 1-3V. At a current density of 0.2C, the first discharge specific capacity reached 962.7mAh / g, such as Figure 1 The added transition metal fluoride significantly increases the discharge potential of the sulfur-based polymer material, and the energy density is significantly improved.

[0026] Implementation Case 2

[0027] 10g of elemental sulfur, 6g of CoF2, and 4g of polypyrrole (homopolymer) were placed in a mortar and ground for 30 minutes, and then placed in a tubular furnace at 360°C for 8h to obtain a sulfur-based polymer material containing transition metal fluorides. The obtained sulfur-based polymer material containing transition metal fluorides was used as the positive electrode and metallic lithium was used as the negative electrode to assemble a button battery and perform rate testing in the voltage range of 1-3V. The added transition metal fluoride can not only increase the discharge potential, but also has a certain catalytic effect, which significantly improves the electrochemical performance of the battery. At a rate of 3C, the discharge capacity of the material is 672mAh / g. When it returns to the initial condition at a rate of 0.2C, the discharge capacity is 936mAh / g. The sulfur-based polymer containing transition metal fluorides has good rate performance.

[0028] Comparative Example

[0029] 8g of elemental sulfur and 2g of 15w molecular weight polyacrylonitrile (homopolymer) were ground in a mortar for 20 minutes, and then placed in a tube furnace at 300°C for 10 hours to obtain a sulfur-based polymer material. The obtained sulfur-based polymer material was used as the positive electrode and metal lithium was used as the negative electrode to assemble a button battery. The electrochemical performance was tested in the voltage range of 1-3V. At a current density of 0.2C, the first discharge specific capacity reached 712.6mAh / g. Figure 1 shown.

Claims

1. A method for preparing a sulfur-based polymer material for improving the discharge potential, comprising the following steps: S1: uniformly mixing elemental sulfur, transition metal fluoride and polymer and heating them together, and cooling them to room temperature after the heat treatment is completed to obtain a sulfur-based polymer containing transition metal fluoride; S2: The obtained sulfur-based polymer material containing transition metal fluoride is mixed with conductive carbon and a binder in an appropriate proportion to form a pole piece, and the battery is assembled.

2. A method for preparing a sulfur-based polymer material for improving the discharge potential according to claim 1, characterized in that: In the step S1, the ratio of elemental sulfur, transition metal fluoride and polymer is 10:(0.1-10):(0.01-5).

3. The method for preparing a sulfur-based polymer material for improving the discharge potential according to claim 1, characterized in that: In the step S1, the elemental sulfur, transition metal fluoride and polymer material are mixed by sand milling, ball milling and air flow dispersion.

4. The method for preparing a sulfur-based polymer material for improving the discharge potential according to claim 1, characterized in that: The transition metal fluoride in step S1 is FeF2, FeF3, CoF2, NiF2, MnF2, CuF2.

5. The method for preparing a sulfur-based polymer material for improving the discharge potential according to claim 1, characterized in that: The sulfur-based polymer in step S1 is polyacrylonitrile, polyaniline, polyethylene dioxythiophene, polynitromethyl pyrrole, polydopamine, polyethylene oxide, poly-m-aminothiophene, polyimide, polytetravinyl pyridine, polyacrylic acid, 1,3-diisopropenylbenzene, poly(3-hexylthiophene-2,5-diyl), 1,3-diethynylbenzene, aminophenol-formaldehyde resin, poly(1,2,4,5-4-amino)benzene; the polymer is a homopolymer and a copolymer.

6. The method for preparing a sulfur-based polymer material for improving the discharge potential according to claim 1, characterized in that: The heating temperature in step S1 is 100-600° C.; the heat preservation time is 1-40 hours; and the heating rate is 1-20° C. / min.

7. The method for preparing a sulfur-based polymer material for improving discharge potential according to claim 1, characterized in that: In step S2, the optional conductive carbon includes acetylene black, multi-walled and single-walled carbon nanotubes, Super P, conductive graphite and Ketjen black; the binder is selected from PAA, CMC, SBR, guar gum, PVDF and LA133.

8. A method for preparing a sulfur-based polymer material containing transition metal fluorides, characterized in that: The preparation method is described in any one of claims 1 to 7.

9. A use of the sulfur-based polymer material containing transition metal fluoride as claimed in claim 8, characterized in that: It is prepared as positive electrode material and applied to lithium metal batteries, lithium ion batteries, sodium ion batteries, sodium metal batteries, potassium ion batteries and potassium metal batteries.

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