Organic sulfur cathode materials, methods of making, and use in batteries

Abstract

The application provides an organic sulfur positive electrode material, a preparation method thereof and application thereof in a battery. The organic sulfur positive electrode material is prepared by electrostatic spinning of polyacrylonitrile, a solvent and an additive in a specific proportion as a precursor, and then mixing the precursor with selenium-doped sulfur powder and heat treatment. When the organic sulfur positive electrode material prepared by the application is applied to a lithium / sodium sulfur battery, the overall rate capability and the composite discharge specific capacity can be improved.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to an organic sulfur cathode material, its preparation method, and its application in batteries. Background Technology

[0002] Lithium / sodium-sulfur batteries have attracted widespread attention due to their high theoretical energy density and other advantages, and are expected to develop into the next generation of high-energy and long-cycle-life rechargeable batteries. Among them, sulfurized polyacrylonitrile (SPCI) has gained significant attention due to its high sulfur utilization efficiency, good cycle stability, and the fact that its quasi-solid-phase conversion process can effectively reduce the formation of higher-order polysulfides and suppress the shuttle effect. Furthermore, the organic framework of SPCI can effectively overcome the volume expansion problem during sulfur conversion, making organic sulfur cathodes prepared using SPCI highly promising.

[0003] However, the organic sulfur cathode prepared by conventional sulfurized polyacrylonitrile has an active material content of less than 50% and poor conductivity, resulting in poor composite theoretical capacity and high-rate performance. Summary of the Invention

[0004] Therefore, it is necessary to provide an organic sulfur cathode material, its preparation method, and its application in batteries, which can improve the rate performance and composite discharge specific capacity of sulfur batteries.

[0005] The present invention adopts the following technical solution:

[0006] This invention provides an organic sulfur cathode material, which is prepared by electrospinning a fiber precursor using polyacrylonitrile, a solvent, and additives, followed by heat treatment of the fiber precursor mixed with selenium-doped sulfur powder. The active material content containing selenium and sulfur is greater than 50%. The solvent is selected from at least one of N,N-dimethylformamide, dimethyl sulfoxide, sulfolane, ethyl nitrate, acetone, tetrahydrofuran, methanol, and ethanol. The additive is selected from at least one of triallyl isocyanurate, 1,3-diisopropenylbenzene, α-methylstyrene, 1,3-diisopropenylbenzene, trithiocyanate, 1,3-diacetylenebenzene, tetrafluorohydroquinone, tetrafluoroo-benzoquinone, and tetrafluoro-p-benzoquinone.

[0007] In some of these embodiments, the mass ratio of polyacrylonitrile, solvent, and additive is 1:(5-10):(1-5).

[0008] Preferably, the additive is triallyl isocyanurate, and the mass ratio of polyacrylonitrile, solvent and additive is 1:10:1.

[0009] In some embodiments, the mass ratio of selenium to sulfur in the selenium-doped sulfur powder is 1:(10-30), and the mass ratio of the spinning fiber precursor to the selenium-doped sulfur powder is 1:(3-10).

[0010] The present invention also provides a method for preparing the above-mentioned organic sulfur cathode material, comprising the following steps: mixing polyacrylonitrile, solvent and additives to obtain a spinning solution; electrospinning the spinning solution to obtain a spinning fiber precursor; mixing the spinning fiber precursor with selenium-doped sulfur powder evenly, performing a sulfurization treatment, and cooling to obtain the final product.

[0011] In some embodiments, the electrospinning process parameters are as follows: the electrospinning voltage range is 3 to 25 kV, the spinning solution injection speed is 0.01 to 0.1 mL / min, and the distance between the receiving roller and the injection nozzle is 10 to 20 cm.

[0012] Preferably, the vulcanization treatment includes a two-step heat treatment under an inert gas atmosphere: the first heat treatment is performed at a temperature of 150–200°C for 1–3 hours; the second heat treatment is performed at a temperature of 300–600°C for 1–6 hours.

[0013] The present invention also provides an organic sulfur cathode, which is prepared using the above-mentioned organic sulfur cathode material.

[0014] The present invention also provides a lithium-sulfur battery comprising the above-mentioned organic sulfur cathode and a lithium-containing electrolyte.

[0015] The present invention also provides a sodium-sulfur battery comprising the above-mentioned organic sulfur cathode and a sodium-containing electrolyte.

[0016] Compared with the prior art, the core advantage of this invention is:

[0017] This invention utilizes a specific ratio of polyacrylonitrile, solvent, and additives to prepare a precursor via electrospinning. The precursor is then mixed with selenium-doped sulfur powder and heat-treated to obtain an organic sulfur cathode material. When applied to lithium / sodium-sulfur batteries, this material exhibits improved rate performance and composite discharge capacity. Attached Figure Description

[0018] Figure 1 The graph shows a comparison of the cycle performance of lithium-sulfur batteries prepared and assembled using the organic sulfur cathode materials of Example 1 and Comparative Examples 1 to 3 under 0.1C conditions.

[0019] Figure 2 The graph shows a comparison of the cycle performance of sodium-sulfur batteries prepared and assembled using the organic sulfur cathode materials of Examples 1 and 1 to 3 under 0.1C conditions.

[0020] Figure 3 The graph shows a comparison of the rate performance of lithium-sulfur batteries prepared and assembled using the organic sulfur cathode materials of Example 2 and Comparative Examples 1 and 2.

[0021] Figure 4The graph shows a comparison of the rate performance of sodium-sulfur batteries prepared and assembled using the organic sulfur cathode materials of Example 2 and Comparative Examples 1 and 2. Detailed Implementation

[0022] The technical concept of this invention is to provide a novel organic sulfur cathode material, its preparation method, and its application in batteries, which can improve the rate performance and composite discharge specific capacity of sulfur batteries.

[0023] 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.

[0024] Key materials source and physicochemical parameters:

[0025] Preparation method of selenium-doped sulfur powder: Selenium powder and sulfur powder are ball-milled at a mass ratio of 1:15 for 6 hours at a speed of 500 r / min. The ball-milled powder is then sealed in a tube and placed in a box furnace at 260℃ for 12 hours to obtain selenium-doped sulfur powder.

[0026] Polyacrylonitrile: Commercial polyacrylonitrile (150,000 molecular weight, brand Sigma-Aldrich).

[0027] Triallyl isocyanurate: Commercially available triallyl isocyanurate (98% with 500ppm BHTstabilizer, brand name Aladdin).

[0028] Example 1

[0029] This embodiment provides a method for preparing an organic sulfur cathode material, including the following steps:

[0030] S1. Polyacrylonitrile, triallyl isocyanurate and N,N-dimethylformamide are added in a mass ratio of 1:1:10 and stirred until homogeneous. Then, triallyl isocyanurate is added and stirred until homogeneous at room temperature to obtain the spinning solution.

[0031] S2, use the spinning solution prepared in step S1 to prepare electrospun fibers. The electrospinning process parameters are: electrospinning voltage is 18kV, spinning solution injection speed is 0.05mL / min, and the distance between the receiving roller and the injection nozzle is 15cm.

[0032] S3. The electrospun fibers prepared in step S2 are mixed with selenium-doped sulfur powder at a mass ratio of 1:4. The mixture is then poured into a ceramic boat for stepwise heat treatment. Under an argon or nitrogen atmosphere, the temperature of the first heat treatment is 155℃ and the time is 3h; the temperature of the second heat treatment is 300℃ and the time is 3h. After the heat treatment is completed, the mixture is cooled to room temperature to obtain a novel organic sulfur material.

[0033] Example 2

[0034] This embodiment provides a method for preparing an organic sulfur cathode material, the process steps of which are basically the same as those in Example 1, with the only difference being:

[0035] In step S1, the mass ratio of polyacrylonitrile, triallyl isocyanurate, and N,N-dimethylformamide is 1:1:5.

[0036] Example 3

[0037] This embodiment provides a method for preparing an organic sulfur cathode material, the process steps of which are basically the same as those in Example 1, with the only difference being:

[0038] In step S1, the mass ratio of polyacrylonitrile, triallyl isocyanurate, and N,N-dimethylformamide is 1:1:8.

[0039] Example 4

[0040] This embodiment provides a method for preparing an organic sulfur cathode material, the process steps of which are basically the same as those in Example 1, with the only difference being:

[0041] In step S1, the mass ratio of polyacrylonitrile, triallyl isocyanurate, and N,N-dimethylformamide is 1:2:10.

[0042] Example 5

[0043] This embodiment provides a method for preparing an organic sulfur cathode material, the process steps of which are basically the same as those in Example 1, with the only difference being:

[0044] In step S1, the mass ratio of polyacrylonitrile, triallyl isocyanurate, and N,N-dimethylformamide is 1:3:8.

[0045] Example 6

[0046] This embodiment provides a method for preparing an organic sulfur cathode material, the process steps of which are basically the same as those in Example 1, with the only difference being:

[0047] In step S1, the mass ratio of polyacrylonitrile, triallyl isocyanurate, and N,N-dimethylformamide is 1:4:10.

[0048] Example 7

[0049] This embodiment provides a method for preparing an organic sulfur cathode material, the process steps of which are basically the same as those in Example 1, with the only difference being:

[0050] In step S1, the mass ratio of polyacrylonitrile, triallyl isocyanurate, and N,N-dimethylformamide is 1:5:5.

[0051] Example 8

[0052] This embodiment provides a method for preparing an organic sulfur cathode material, the process steps of which are basically the same as those in Example 1, with the only difference being:

[0053] In step S1, the mass ratio of polyacrylonitrile, triallyl isocyanurate, and N,N-dimethylformamide is 1:5:10.

[0054] Comparative Example 1

[0055] This comparative example provides a method for preparing an organic sulfur cathode material, the process steps of which are basically the same as those in Example 1, the only difference being:

[0056] In step S1, a spinning solution is prepared using only polyacrylonitrile and N,N-dimethylformamide at a mass ratio of 1:10.

[0057] Comparative Example 2

[0058] This comparative example provides a method for preparing an organic sulfur cathode material, the process steps of which are basically the same as those in Example 1, the only difference being:

[0059] In step S1, a spinning solution is prepared using only polyacrylonitrile and N,N-dimethylformamide at a mass ratio of 1:8.

[0060] Comparative Example 3

[0061] This comparative example provides a method for preparing an organic sulfur cathode material, the process steps of which are basically the same as those in Example 1, the only difference being:

[0062] In step S1, a spinning solution is prepared using only polyacrylonitrile and N,N-dimethylformamide at a mass ratio of 1:5.

[0063] Comparative Example 4

[0064] This comparative example provides a method for preparing an organic sulfur cathode material, the process steps of which are as follows: In step S1, a spinning solution is prepared using polyacrylonitrile and N,N-dimethylformamide at a mass ratio of 1:10. Furthermore, in step S3, the selenium-doped sulfur powder is replaced with elemental sulfur powder.

[0065] Comparative Example 5

[0066] This comparative example provides a method for preparing an organic sulfur cathode material, the process steps of which are basically the same as those in Example 1, the only difference being:

[0067] In step S1, a spinning solution is prepared using only polyacrylonitrile, triallyl isocyanurate, and N,N-dimethylformamide in a mass ratio of 1:10:5.

[0068] Application performance testing:

[0069] The novel organic sulfur material prepared in the above experimental examples was mixed with a conductive agent (Ketjen Black), a 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 the novel organic sulfur material positive electrode sheet.

[0070] 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.

[0071] The lithium-sulfur battery uses a multilayer polyolefin separator and a lithium electrolyte (1M LiPF6, 1L of solvent with a volume ratio of EC and DEC of 3:7, containing 10wt% FEC in the total electrolyte). The above-mentioned organic sulfur positive electrode and metallic lithium are used as the counter electrode to assemble the lithium-sulfur battery.

[0072] Sodium-sulfur batteries use GF / A or GF / D separators and sodium electrolyte (1M NaCIO4, 1L of solvent with a volume ratio of EC and DEC of 3:7, containing 10wt% FEC in the total electrolyte). The above organic sulfur positive electrode and metallic sodium are used as counter electrodes to assemble sodium-sulfur batteries.

[0073] 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.

[0074] The test results are summarized in the table below:

[0075]

[0076]

[0077] Further comparisons were made of the cycle performance tests of batteries prepared and assembled using the organic sulfur cathode materials of Examples 1 and Comparative Examples 1-3 in 0.1C lithium / sodium-sulfur batteries. Figure 1 and 2 As shown.

[0078] Depend on Figure 1 and 2It can be seen that the lithium-sulfur battery composite specific capacity prepared and assembled using the organic sulfur cathode material of Example 1 is significantly higher than that of Comparative Examples 1 to 3, which is equivalent to an overall composite specific capacity increase of about 20%. In addition, the performance comparison of sodium-sulfur batteries shows that the organic sulfur cathode material of Example 1 is also suitable for sodium-sulfur batteries and exhibits superior cycle stability and high discharge specific capacity.

[0079] Further comparisons were made of the rate performance of batteries assembled using the organic sulfur cathode materials of Example 2 and Comparative Examples 1 and 2. The test results are as follows: Figure 3 and 4 As shown.

[0080] Depend on Figure 3 and 4 It can be seen that the lithium-sulfur battery assembled using the organic sulfur cathode material of Example 2 still has a composite specific capacity close to 400 at 8C. However, compared to Example 2, the lithium-sulfur batteries assembled using Comparative Examples 1 and 2 have almost no discharge capacity at high rates of 7C and 8C, and exhibit poor performance at other rates. Meanwhile, comparing the rate performance of sodium-sulfur batteries, it was found that the sodium-sulfur battery assembled using the organic sulfur cathode material of Example 2 still exhibits extremely excellent rate performance.

[0081] In addition, the inventors' team further investigated the effects of different solvents and additives on the application performance of the prepared organic sulfur cathode material. The experimental methods and procedures were the same as in Example 2, with the only difference being the composition of the spinning solution. The specific experimental setup and test results are shown in the table below:

[0082]

[0083] In fact, the organic sulfur cathode material of this invention requires the following conditions to be guaranteed during its preparation process in order to achieve superior rate performance in lithium / sodium-sulfur batteries:

[0084] 1) In the spinning solution, the mass ratio of polyacrylonitrile, solvent and additive is controlled as 1:(5~10):(1~5). The process parameters for electrospinning are: electrospinning voltage range of 3~25kV, spinning solution injection speed of 0.01~0.1mL / min, and distance between receiving roller and spray nozzle of 10~20cm.

[0085] 2) During the vulcanization process, the mass ratio of the spinning fiber precursor to the selenium-doped sulfur powder is controlled at 1:(3~10). The vulcanization treatment includes two-step heat treatment under an inert gas atmosphere: the temperature of the first heat treatment is 150~200℃ and the duration is 1~3h; the temperature of the second heat treatment is 300~600℃ and the duration is 1~6h.

[0086] 3) Introduction of additives, with the following selection range: at least one of triallyl isocyanurate, 1,3-diisopropenylbenzene, α-methylstyrene, 1,3-diisopropenylbenzene, trithiocyanate, 1,3-diacetylenebenzene, tetrafluorohydroquinone, tetrafluoroo-benzoquinone, and tetrafluoro-p-benzoquinone.

[0087] 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. An organic sulfur positive electrode material, characterized by, The organic sulfur cathode material is prepared by electrospinning polyacrylonitrile, solvent and additives to prepare a spinning fiber precursor, and then mixing the spinning fiber precursor with selenium-doped sulfur powder and heat treating it. The active material content containing selenium and sulfur is greater than 50%. The solvent is selected from at least one of N,N-dimethylformamide, dimethyl sulfoxide, sulfolane, and tetrahydrofuran; The additive is triallyl isocyanurate; The mass ratio of polyacrylonitrile, solvent and additive is 1:(5~10):(1~5); The mass ratio of the fiber precursor to selenium-doped sulfur powder is 1:(3~10).

2. The organic sulfur cathode material of claim 1, wherein, The mass ratio of polyacrylonitrile, solvent, and additives is 1:10:

1.

3. A method of producing an organic sulfur cathode material as claimed in claim 1 or 2, characterized in that, Includes the following steps: A spinning solution is prepared by mixing polyacrylonitrile, solvent and additives; The spinning solution is electrospinned to obtain a fiber precursor. The spinning fiber precursor is mixed evenly with selenium-doped sulfur powder, subjected to vulcanization treatment, and cooled to obtain the final product.

4. The method for preparing the organic sulfur cathode material according to claim 3, characterized in that, The electrospinning process parameters are as follows: the electrospinning voltage range is 3~25 kV, the spinning solution injection speed is 0.01~0.1 mL / min, and the distance between the receiving roller and the injection nozzle is 10~20 cm.

5. The method for preparing the organic sulfur cathode material according to claim 3, characterized in that, The vulcanization process includes a two-step heat treatment under an inert gas atmosphere: The first heat treatment is performed at a temperature of 150~200℃ for 1~3 hours. The second heat treatment is carried out at a temperature of 300~600℃ for 1~6 hours.

6. An organic sulfur positive electrode characterized by comprising: It is prepared using the organic sulfur cathode material described in claim 1 or 2.

7. A lithium-sulfur battery, characterized by, It comprises the organic sulfur cathode and lithium-containing electrolyte as described in claim 6.

8. A sodium-sulfur battery characterized by comprising: It comprises the organic sulfur cathode as described in claim 6 and a sodium-containing electrolyte.

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