Preparation method of nanoflower-like sulfurized polyacrylonitrile material and application in battery

Abstract

The application provides a preparation method of nano-flower-like sulfidized polyacrylonitrile material and application thereof in batteries. The nano-flower-like sulfidized polyacrylonitrile material is prepared by mixing acrylonitrile, a solvent and an azo initiator in a specific ratio, and then polymerizing the mixture at 50-100 DEG C to form a polymer, and then mixing the polymer with sulfur powder for sulfidization. When the nano-flower-like sulfidized polyacrylonitrile material is applied to lithium / sodium sulfur batteries, the overall composite specific capacity and rate performance are excellent.

Description

Technical Field

[0001] This invention relates to the field of sulfur battery technology, specifically to a method for preparing a nano-flower-like sulfurized polyacrylonitrile material and its application in batteries. Background Technology

[0002] Organic sulfur cathodes prepared using sulfurized polyacrylonitrile are helpful in designing and constructing lithium / sodium-sulfur batteries with high energy density and long cycle life. However, the composite specific capacity and rate performance of conventional organic sulfur cathodes are still low and need to be improved. Summary of the Invention

[0003] Therefore, it is necessary to provide a method for preparing nano-flower-like vulcanized polyacrylonitrile materials and their application in batteries, which can improve the composite specific capacity and rate performance of organic sulfur cathodes.

[0004] The present invention adopts the following technical solution:

[0005] This invention provides a nano-flower-like vulcanized polyacrylonitrile material, which is prepared by in-situ polymerization of acrylonitrile, solvent and azo initiator at 50-100°C to form a polymer, and then mixing the polymer with sulfur powder for vulcanization.

[0006] In some embodiments, the solvent is selected from at least one of acetone, methanol, ethanol, diethyl ether, chloroform, pyridine, tetrahydrofuran, and water.

[0007] In some embodiments, the azo initiator is selected from at least one of azobisisovalerate, azobisisoheptanenitrile, azoisobutylcyanoformamide, azobiscyclohexylformamide, dimethyl azobisisobutyrate, azobisisobutyramidine hydrochloride, azobisisovalerate, and azobisisopropylimidazoline hydrochloride.

[0008] In some of these embodiments, the volume ratio of acrylonitrile to solvent is 1:(0.5-5), and the amount of azo initiator is (0.1-1) mg / mL.

[0009] In some embodiments, the mass ratio of polymer to sulfur powder is 1:(2-20).

[0010] The present invention also provides a method for preparing the above-mentioned nano-flower-like vulcanized polyacrylonitrile material, comprising the following steps: adding acrylonitrile to a solvent, then adding an azo initiator, and carrying out an in-situ polymerization reaction at 50-100°C for 1-10 hours to obtain a polymer; mixing the polymer with sulfur powder at a mass ratio of 1:(2-20) and performing vulcanization treatment to obtain the final product.

[0011] In some embodiments, the vulcanization treatment is a two-step heat treatment performed in an inert gas atmosphere. The first heat treatment is performed at a temperature of 60–100°C for 1–3 hours, and the second heat treatment is performed at a temperature of 300–1000°C for 1–10 hours.

[0012] Preferably, the temperature of the second heat treatment is 300–400°C, and the duration is 1–6 hours.

[0013] In some embodiments, the sulfur powder is selected from at least one of pure sulfur powder, selenium-doped sulfur powder, and tellurium-doped sulfur powder.

[0014] The above-mentioned nano-flower-like vulcanized polyacrylonitrile material is used in the preparation of the positive electrode of a battery.

[0015] The present invention can also provide a battery comprising a positive electrode prepared from the above-mentioned nano-flower-shaped vulcanized polyacrylonitrile material.

[0016] In some embodiments, the battery is a lithium-sulfur battery or a sodium-sulfur battery.

[0017] Compared with the prior art, the core advantage of this invention is:

[0018] The nano-flower-like vulcanized polyacrylonitrile material of this invention is prepared by in-situ polymerization of acrylonitrile, solvent and azo initiator in a specific ratio at 50-100°C to form a polymer, and then mixing the polymer with sulfur powder for vulcanization. When applied to lithium / sodium-sulfur batteries, it exhibits excellent composite specific capacity and rate performance. Attached Figure Description

[0019] Figure 1 The image shows the SEM morphology of the nanoflower-shaped polyacrylonitrile prepared in Example 1.

[0020] Figure 2 The image shows the SEM morphology of the nanoflower-shaped vulcanized polyacrylonitrile material prepared in Example 1.

[0021] Figure 3 Comparison of SEM morphology of commercial polyacrylonitrile (Sigma-Aldrich) and the nanoflower-like polyacrylonitrile prepared in Example 1.

[0022] Figure 4 Comparison of SEM morphology of commercially available vulcanized polyacrylonitrile (Sigma-Aldrich) and the nanoflower-like vulcanized polyacrylonitrile material prepared in Example 1.

[0023] Figure 5 The graphs show the charge-discharge curves of the sulfurized polyacrylonitrile materials of Examples 2 and Comparative Examples 1 to 3 applied to lithium-sulfur batteries.

[0024] Figure 6The graphs show the charge-discharge curves of the sulfurized polyacrylonitrile materials of Examples 2 and Comparative Examples 1 to 3 applied to sodium-sulfur batteries. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to specific embodiments, so that those skilled in the art can more clearly understand the present invention. The following embodiments are only used to illustrate the present invention, and are not intended to limit the scope of the present invention. Based on the specific embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention. In the embodiments of the present invention, unless otherwise specified, all raw material components are commercially available products well known to those skilled in the art; in the embodiments of the present invention, unless specifically specified, the technical means used are conventional means well known to those skilled in the art.

[0026] Example 1

[0027] This embodiment provides a method for preparing vulcanized polyacrylonitrile material, including the following steps:

[0028] S1, acrylonitrile and acetone were mixed in a 1:1 volume ratio, and azobisisobutyronitrile (AIBN) was added to a concentration of 0.5 mg / mL. The mixture was then subjected to in-situ polymerization at 60°C for 6 hours to obtain the polymer. Subsequent morphology testing confirmed that it was a nano-flower-like polyacrylonitrile. Figure 1 As shown.

[0029] S2, the nano-flower-shaped polyacrylonitrile prepared in step S1 is mixed with sulfur powder at a mass ratio of 1:3, and then poured into a ceramic boat for vulcanization treatment. This vulcanization treatment process includes two heat treatment steps under an argon or nitrogen atmosphere:

[0030] The first step of heat treatment is at a temperature of 80℃ for 1 hour.

[0031] The second step involves heat treatment at 300℃ for 2.5 hours. After heat treatment, the mixture is cooled to room temperature to obtain nano-flower-like vulcanized polyacrylonitrile. Figure 2 As shown.

[0032] Example 2

[0033] This embodiment provides a method for preparing vulcanized polyacrylonitrile material. The process steps are basically the same as those in Example 1, except that in step S1, the volume ratio of acrylonitrile to acetone is 1:0.5.

[0034] Example 3

[0035] This embodiment provides a method for preparing vulcanized polyacrylonitrile material. The process steps are basically the same as those in Example 1, except that in step S1, the initiator azobisisobutyronitrile is added to a concentration of 0.2 mg / mL.

[0036] Example 4

[0037] This embodiment provides a method for preparing vulcanized polyacrylonitrile material. The process steps are basically the same as those in Example 1, except that in step S1, the initiator azobisisobutyronitrile is added to a concentration of 0.8 mg / mL.

[0038] Example 5

[0039] This embodiment provides a method for preparing vulcanized polyacrylonitrile material. The process steps are basically the same as those in Example 1, except that in step S1, the volume ratio of acrylonitrile to acetone is 1:3.

[0040] Example 6

[0041] This embodiment provides a method for preparing vulcanized polyacrylonitrile material. The process steps are basically the same as those in Example 1, except that in step S1, the volume ratio of acrylonitrile to acetone is 1:4.

[0042] Example 7

[0043] This embodiment provides a method for preparing vulcanized polyacrylonitrile material. The process steps are basically the same as those in Example 1, except that in step S1, the volume ratio of acrylonitrile to acetone is 1:5.

[0044] Morphology and application performance testing:

[0045] 1) Commercially available polyacrylonitrile from Sigma-Aldrich, Aladdin, and McLean were used as controls and vulcanized, referred to as Comparative Examples 1 to 3. The vulcanized polyacrylonitrile materials prepared in Examples 1 to 7 were subjected to SEM morphology testing. It was found that the vulcanized polyacrylonitrile materials prepared in the above experimental examples exhibited a nano-flower-like structure.

[0046] The SEM morphologies of commercially available polyacrylonitrile (Sigma-Aldrich), the nanoflower-like polyacrylonitrile prepared in Example 1, and the nanoflower-like vulcanized polyacrylonitrile materials are shown below. Figure 3 and 4 As shown.

[0047] 2) The vulcanized polyacrylonitrile material prepared in the above experimental example was mixed with conductive agent (Ketjen Black), binder sodium carboxymethyl cellulose, and styrene-butadiene rubber at a ratio of 8:1:0.5:0.5 to prepare a positive electrode slurry using water as a solvent. The positive electrode slurry was coated onto a current collector, dried, and stamped to obtain a novel organic sulfur material positive electrode sheet.

[0048] Assemble lithium / sodium-sulfur batteries: The entire battery assembly process is carried out in an inert gas glove box with water and oxygen content of less than 0.1 ppm.

[0049] The lithium-sulfur battery uses a multilayer polyolefin separator and a lithium-containing electrolyte (1M LiPF6, consisting of 1L of solvent with EC and DEC in a volume ratio of 3:7, containing 10wt% FEC of the total lithium-containing electrolyte). The organic sulfur positive electrode and metallic lithium are used as the counter electrode to assemble the lithium-sulfur battery.

[0050] Sodium-sulfur batteries use GF / A or GF / D separators and sodium-containing electrolytes (1M NaClO4, 1L of solvent consisting of EC and DEC in a volume ratio of 3:7, containing 10wt% FEC of the total sodium-containing electrolyte). The above-mentioned organic sulfur positive electrode is assembled with metallic sodium as the counter electrode.

[0051] The prepared lithium / sodium-sulfur batteries were subjected to constant current charge-discharge tests on the Xinwei Battery Testing Equipment. They were left to rest for 12 hours before the test. The voltage range of the lithium-sulfur batteries was 1-3V, and the voltage range of the sodium-sulfur batteries was 0.7-2.8V.

[0052] The test results are shown in the table below:

[0053]

[0054]

[0055] The above experimental results show that, compared with commercially available vulcanized polyacrylonitrile, the nano-flower-shaped polyacrylonitrile prepared by in-situ polymerization in Examples 1 to 7 and subjected to vulcanization treatment helps to increase the sulfur content of vulcanized polyacrylonitrile and significantly improves the composite specific capacity of lithium / sodium batteries.

[0056] Furthermore, when the nano-flower-shaped sulfurized polyacrylonitrile prepared by in-situ polymerization in Example 2 and the commercial polyacrylonitrile of Comparative Example 1 were tested for lithium / sodium-sulfur battery applications, the charge-discharge curves of the lithium / sodium-sulfur battery with the second reversible capacity at 0.1C were as follows: Figure 5 and 6 As shown.

[0057] Depend on Figure 5 and 6 It can be seen that the nano-flower-shaped sulfurized polyacrylonitrile prepared by in-situ polymerization in Example 2 exhibits a high composite discharge specific capacity and a small median voltage difference when applied to lithium / sodium-sulfur battery tests, which helps to accelerate reaction kinetics.

[0058] In addition, the inventors' team further investigated the effects of different solvents and initiators on the application performance of the prepared nano-flower-like vulcanized polyacrylonitrile. The experimental methods and procedures were the same as in Example 2, with the only difference being the composition of the in-situ polymerization solution. The specific experimental setup and test results are shown in the table below:

[0059]

[0060]

[0061] It is worth noting that, through extensive experimental investigation, this invention has discovered that:

[0062] 1) A nano-flower-like vulcanized polyacrylonitrile material is prepared by in-situ polymerization of acrylonitrile, solvent and azo initiator in a specific ratio at 50-100℃ to form a polymer, and then mixing the polymer with sulfur powder for vulcanization. When applied to lithium / sodium-sulfur batteries, it has excellent composite specific capacity and rate performance.

[0063] 2) Preferably, the volume ratio of acrylonitrile to solvent is 1:(0.5-5), the amount of azo initiator is (0.1-1) mg / mL, and the mass ratio of polymer to sulfur powder is 1:(2-20), which can ensure the thickness and uniformity of the nanoflower structure.

[0064] It should be noted that the above embodiments are only for further elaboration and explanation of the technical solution of the present invention, and are not intended to further limit the technical solution of the present invention. The method of the present invention is only a preferred embodiment and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A nanoflower-like sulfurized polyacrylonitrile material, characterized in that, The acrylonitrile, the solvent and the azo initiator are placed under the condition of 50-100 DEG C to form a polymer by in-situ polymerization, and then the polymer is mixed with sulfur powder to prepare the nano-flower-like vulcanized polyacrylonitrile material. The solvent is at least one selected from acetone, methanol, ethanol, diethyl ether, chloroform, pyridine, tetrahydrofuran and water. The volume ratio of acrylonitrile to solvent is 1:(0.5-5), and the concentration of azo initiator is (0.1-1) mg / mL. The mass ratio of polymer to sulfur powder is 1:(2-20). The vulcanization treatment is two-step heat treatment in an inert gas atmosphere, the first step heat treatment is at a temperature of 60-100 DEG C for 1-3 hours, and the second step heat treatment is at a temperature of 300-400 DEG C for 1-6 hours.

2. The nanoflowered sulfurized polyacrylonitrile material of claim 1, wherein, The azo initiator is at least one selected from azobis isovaleronitrile, azobis isoheptonitrile, azoisobutyronitrile carboxamide, azobiscyclohexyl cyanide, azobis dimethyl isobutyrate, azobis isobutyl amide hydrochloride, azobis dicyanopentanoic acid and azobis isopropyl imidazoline hydrochloride.

3. A process for producing the nanoflower-like sulfurized polyacrylonitrile material according to claim 1 or 2, characterized by, The method comprises the following steps: The acrylonitrile is added into the solvent, and then the azo initiator is added, and the in-situ polymerization reaction is carried out at 50-100 DEG C for 1-10 hours to obtain the polymer. The polymer and the sulfur powder are mixed in a mass ratio of 1:(2-20) to carry out the vulcanization treatment, and the nano-flower-like vulcanized polyacrylonitrile material is obtained. The solvent is at least one selected from acetone, methanol, ethanol, diethyl ether, chloroform, pyridine, tetrahydrofuran and water. The volume ratio of acrylonitrile to solvent is 1:(0.5-5), and the concentration of azo initiator is (0.1-1) mg / mL. The vulcanization treatment is two-step heat treatment in an inert gas atmosphere, the first step heat treatment is at a temperature of 60-100 DEG C for 1-3 hours, and the second step heat treatment is at a temperature of 300-400 DEG C for 1-6 hours.

4. The method for preparing the nano-flower-like vulcanized polyacrylonitrile material according to claim 3, characterized in that, The sulfur powder is at least one selected from pure sulfur powder, selenium-doped sulfur powder and tellurium-doped sulfur powder.

5. The nano-flower-like vulcanized polyacrylonitrile material of claim 1 or 2 is used in the preparation of a positive electrode of a battery.

6. A battery, characterized by The positive electrode is prepared from the nano-flower-like vulcanized polyacrylonitrile material of claim 1 or 2.

7. The battery of claim 6, wherein, The battery is a lithium-sulfur battery or a sodium-sulfur battery.

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