Preparation method of a sulfidized polyacrylonitrile-acrylamide-based electrode material and application thereof

Abstract

This invention discloses a method for preparing polyacrylonitrile-acrylamide-based electrode materials and their battery applications. Preparation steps: 1. Prepare a mixture of acrylonitrile, acrylamide monomer, crosslinking agent, initiator, and solvent, and obtain the copolymer through free radical copolymerization; 2. Mix the copolymer with elemental sulfur, vulcanize under an inert atmosphere to remove unreacted sulfur, and obtain a vulcanized copolymer; 3. Mix the vulcanized copolymer, conductive agent, and binder to form a slurry, and coat it onto carbon-coated aluminum foil to obtain the positive electrode. This invention introduces acrylamide groups to enhance sulfur fixation through the synergistic effect of amide bonds and cyano groups, optimizing hydrophilicity and electrolyte wettability. When applied to lithium batteries, this positive electrode preferably exhibits a specific capacity exceeding 750 mAh / g, a capacity retention rate ≥88% at 2C rate, and a retention rate ≥85% after 200 cycles. This method is simple to operate, highly repeatable, and suitable for large-scale production, solving the problems of insufficient sulfur fixation and rapid cycle decay in traditional polyacrylonitrile-based materials.

Description

Technical Field

[0001] This invention belongs to the field of new energy materials and lithium-sulfur battery preparation technology, specifically relating to a method for synthesizing a polyacrylonitrile-acrylamide copolymer, and the application of the copolymer in preparing lithium-sulfur battery cathode materials after sulfidation. Background Technology

[0002] With the rapid development of the new energy industry, especially the increasing demand for high-energy-density batteries in fields such as low-altitude economy and electric vehicles, lithium-sulfur batteries have become one of the core candidate technologies to replace traditional lithium-ion batteries due to their advantages such as a theoretical energy density of up to 2600 Wh / kg and low raw material costs. However, the commercialization process of lithium-sulfur batteries is still limited by key pain points such as polysulfide shuttle effect, electrode volume expansion, and poor conductivity of active materials.

[0003] Polyacrylonitrile (PAN)-based vulcanized materials (SPAN) are one of the mainstream cathode materials for addressing the aforementioned pain points. They achieve a solid-solid reaction mechanism by forming covalent bonds between cyano groups (-C≡N) and sulfur, effectively suppressing polysulfide shuttle. However, traditional polyacrylonitrile homopolymers have inherent defects: first, the limited number of sulfur fixation sites on the cyano group means that insufficient sulfur fixation still exists under high sulfur loading; second, the material has poor hydrophilicity and insufficient electrolyte wettability, resulting in high ion transport resistance inside the electrode; and third, the polymer skeleton has limited flexibility, making it difficult to completely buffer volume expansion during charge and discharge, which easily leads to skeleton damage and active material shedding, affecting cycle stability. Summary of the Invention

[0004] I. Purpose of the Invention

[0005] To address the problems of insufficient sulfur fixation, poor hydrophilicity, and inadequate cycle stability of existing polyacrylonitrile homopolymers, this invention provides a method for preparing a sulfurized polyacrylonitrile-acrylamide-based electrode material. By introducing acrylamide groups through copolymerization, the synergistic effect of amide bonds and cyano groups is achieved, thereby improving the material's sulfur fixation capacity, hydrophilicity, and structural toughness. High-performance cathode materials are then prepared through sulfurization, ultimately improving the energy density, rate performance, and cycle durability of lithium-sulfur batteries.

[0006] II. Technical Solution

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for preparing a vulcanized polyacrylonitrile-acrylamide-based electrode material and its application, comprising the following steps:

[0009] (1) Copolymerization to prepare polyacrylonitrile-acrylamide copolymer: Prepare a homogeneous mixed solution containing acrylonitrile monomer, acrylamide monomer, crosslinking agent, initiator and solvent. Place the mixed solution under the corresponding initiation conditions for free radical copolymerization reaction. The reaction temperature is controlled at 10-100℃ and the reaction time is 1-12 hours. After the reaction is completed, the polyacrylonitrile-acrylamide copolymer product is obtained. The mass ratio of acrylonitrile to acrylamide monomer is (90-99):(1-10), the amount of initiator is (0.1-2) mg / mL, the volume ratio of crosslinking agent to total monomer is 0.01-5%, and the volume ratio of acrylonitrile to solvent is 1:(0.5-5). The technical features of this step are completely consistent with step (1) of claim 1 and claims 2-5. The adjustment of monomer ratio and initiation method in Examples 1-5 further verifies the rationality of this parameter range.

[0010] (2) Preparation of vulcanized copolymer by vulcanization: The polyacrylonitrile-acrylamide copolymer obtained in step (1) is thoroughly mixed with sulfur powder at a mass ratio of 1:(2-20). The mixture is placed in an inert gas (such as argon or nitrogen) atmosphere for vulcanization reaction at a reaction temperature of 300-450℃ for 1-10 hours. After the reaction is completed, the unreacted sulfur powder is removed by heat treatment (150-450℃ for 1-10 hours) and / or Soxhlet extraction. After cooling to room temperature, the vulcanized polyacrylonitrile-acrylamide copolymer is obtained. The technical features of this step are completely consistent with step (2) of claim 1 and claims 5-6. The vulcanization temperature and sulfur powder ratio adjustment in Examples 1-5 are all within the range of the claims.

[0011] (3) Preparation of vulcanized copolymer positive electrode: The vulcanized polyacrylonitrile-acrylamide copolymer (active material) prepared in step (2), conductive agent and binder are mixed in a mass ratio of (70-90):(5-20):(5-10), and an appropriate amount of solvent is added and stirred evenly to obtain a positive electrode slurry; the slurry is evenly coated on the surface of carbon-coated aluminum foil, and after drying and punching, the vulcanized polyacrylonitrile-acrylamide copolymer positive electrode is obtained; the technical features of this step are completely consistent with step (3) of claim 1 and claim 7, and the 8:1:1 ratio, SuperP conductive agent and PAA-Li binder in Example 1 are all specific embodiments within the scope of the claims.

[0012] Preferably, in step (1), the acrylamide monomer is selected from at least one of acrylamide, N-methylacrylamide, N,N-dimethylacrylamide, and 2-acrylamido-2-methylpropanesulfonic acid; among which acrylamide is the optimal choice, as it can take into account both the sulfur fixation effect and the copolymerization reaction activity.

[0013] Preferably, in step (1), the initiator is an ultraviolet (UV) photoinitiator or a thermal initiator; the UV photoinitiator is a benzoin ether compound, a benzophenone compound, an azo compound, an α-hydroxyalkyl phenyl ketone compound, or an acylphosphine oxide compound, with corresponding initiation conditions of UV irradiation at a wavelength of 250–420 nm, a reaction temperature of 10–50°C, and a reaction time of 1–12 h; the thermal initiator is an azo compound such as azobisisobutyronitrile or azobisisoheptanenitrile, or a peroxide compound such as benzoyl peroxide, with corresponding initiation conditions of constant temperature heating at 50–80°C and a reaction time of 1–4 h.

[0014] Preferably, in step (1), the solvent is selected from at least one of acetone, methanol, dichloromethane, ethanol, tetrahydrofuran, N,N-dimethylformamide, and water; among which acetone is the optimal choice, as it can ensure the full dissolution of the two monomers and the initiator and the homogeneity of the reaction system.

[0015] Preferably, in step (1), the crosslinking agent is selected from one of the acrylates; the volume ratio of acrylonitrile to crosslinking agent is 1:(0.5-5); among which triethylene glycol dimethacrylate is the optimal choice.

[0016] Preferably, in step (2), the sulfur powder is selected from at least one of pure sulfur powder, selenium-doped sulfur powder, and tellurium-doped sulfur powder; doping with selenium or tellurium can further enhance the conductivity of sulfur and its interaction with the copolymer.

[0017] Preferably, in step (3), the conductive agent is at least one of super carbon black, acetylene black, Ketjen black, carbon nanotubes, and graphene; and the binder is at least one of lithium polyacrylate (PAA-Li), polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), and polyimide (PI).

[0018] The present invention also protects the polyacrylonitrile-acrylamide copolymer, the vulcanized polyacrylonitrile-acrylamide copolymer positive electrode prepared by the above method, and the battery (lithium-sulfur battery or sodium-sulfur battery) containing the positive electrode.

[0019] III. Beneficial Effects

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. Acrylamide monomers contain amide bonds (-CONH2) which have strong polarity and hydrogen bond formation ability. If they are copolymerized with acrylonitrile, the copolymer can be endowed with multiple advantages: (1) Significant synergistic sulfur fixation effect: amide bonds can serve as additional sulfur fixation sites. The amide bonds of acrylamide groups in the copolymer and the cyano groups of acrylonitrile form dual sulfur fixation sites. Through the synergistic effect of covalent bonds and hydrogen bonds, sulfur and reaction intermediates can be firmly fixed, greatly suppressing the polysulfide shuttle effect. Compared with traditional polyacrylonitrile homopolymers, the sulfur fixation capacity is increased by more than 5%; (2) Optimized material hydrophilicity and wettability: The strong polarity of the amide bond significantly improves the hydrophilicity of the copolymer, enhances the wetting efficiency of the electrolyte inside the electrode, reduces the ion transport resistance, and greatly improves the rate performance of the battery. The capacity retention rate can reach more than 88% at a high current density of 1A / g; (3) Improved structural toughness and cycle stability: The flexible segments of the acrylamide group enhance the toughness of the polymer skeleton, which can effectively buffer 79% of the volume expansion / contraction during charging and discharging, avoid skeleton damage and active material shedding, and the capacity retention rate is ≥85% after 200 charge and discharge cycles. The cycle durability is better than that of traditional PAN-based materials.

[0022] 2. This invention introduces a crosslinking agent during the acrylonitrile polymerization stage to achieve controllable modification of the polyacrylonitrile skeleton at the molecular structure level, providing core support for subsequent vulcanization reactions and final electrode performance. Its advantages are specifically reflected in the following aspects: (1) Constructing a three-dimensional network structure to significantly improve the structural stability of the material: The crosslinking agent can form stable covalent crosslinking points between linear polyacrylonitrile molecular chains to construct a three-dimensional spatial network skeleton, fundamentally improving the defects of easy deformation and easy breakage of the linear structure of pure polyacrylonitrile, so that the material maintains structural integrity during high-temperature vulcanization and battery charging and discharging, effectively inhibiting electrode expansion, pulverization and shedding; (2) Enhancing the electrolyte resistance of the material and extending the battery cycle life: The crosslinking network can significantly reduce the swelling and dissolution of the polyacrylonitrile skeleton in ether and carbonate electrolytes. To avoid structural loosening and loss of active materials during long-term cycling, significantly improve the stability of the electrode interface, reduce battery internal resistance fluctuations, and improve cycle life and capacity retention; (3) Improve electron conduction and ion transport capabilities: The three-dimensional cross-linked structure provides a continuous pathway for electron transport and forms a pore structure that is conducive to the rapid diffusion of lithium ions, thereby improving the overall conductivity and ion conduction efficiency of the material, reducing battery polarization, and improving rate discharge performance; (4) Enhance the sulfur immobilization capacity and suppress polysulfide shuttle effect: The cross-linked network structure is more conducive to the formation of stable covalent bonds between sulfur and polyacrylonitrile at high temperatures, so that sulfur is firmly anchored on the polymer skeleton in the form of short chains, and no soluble long-chain polysulfides are generated during charging and discharging, thereby suppressing polysulfide shuttle from the source and improving the utilization rate of active materials.

[0023] 3. Compatible and controllable preparation process: The copolymerization reaction conditions are mild (10-100℃), and the copolymer structure can be precisely controlled by adjusting the monomer ratio and initiation method; the vulcanization and electrode preparation processes are compatible with existing battery production processes, requiring no major equipment modifications, and are suitable for large-scale production. Attached Figure Description

[0024] Figure 1 : The Fourier Transform Infrared (FT-IR) spectrum of the polyacrylonitrile-acrylamide copolymer prepared in Example 1 of this invention; Figure 2 Scanning electron microscope (SEM) image of the vulcanized polyacrylonitrile-acrylamide copolymer prepared in Example 1 of this invention; Figure 3 The charge-discharge cycle performance curve of the lithium-sulfur battery prepared in Example 1 of this invention at a current density of 0.1 A / g; Figure 4 The rate performance curves of the lithium-sulfur battery prepared in Example 1 of this invention at different current densities (0.1 A / g, 0.2 A / g, 0.5 A / g, 1 A / g, 2 A / g, 0.1 A / g); Figure 5 The long-cycle performance curve of the lithium-sulfur battery prepared in Example 1 of this invention at a current density of 1A / g. 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 do not limit the scope of protection of the present invention.

[0026] In this embodiment of the invention, all raw materials used are commercially available conventional products; the equipment used includes an ultraviolet initiation chamber (wavelength adjustable from 250 to 420 nm), a constant temperature oil bath, a tube furnace, a battery testing system (LAND CT2001A), etc., all of which are existing conventional equipment.

[0027] Example 1

[0028] A method for preparing a vulcanized polyacrylonitrile-acrylamide copolymer material includes the following steps:

[0029] S1. Preparation of polyacrylonitrile-acrylamide copolymer by copolymerization: Acrylonitrile and acrylamide were mixed at a mass ratio of 99:1, acetone solvent was added (acrylonitrile to solvent volume ratio 1:1), crosslinking agent TEGDMA was added (acrylonitrile to crosslinking agent volume ratio 995:5), and then UV photoinitiator I2959 was added. The mixture was stirred until completely dissolved, so that the initiator concentration was 0.5 mg / mL. The mixed solution was placed in a UV initiation chamber, and the UV wavelength was set to 365 nm and the reaction temperature to 20 °C. The polymerization was carried out under photoirradiation for 3 hours to obtain the polyacrylonitrile-acrylamide copolymer product (FT-IR image shown). Figure 1 Infrared spectroscopy characterization of the copolymer revealed the following results: a characteristic stretching vibration peak of the cyano group (-C≡N) appeared at 2243 cm⁻¹, confirming successful polymerization of the acrylonitrile monomer; symmetric and asymmetric stretching vibration peaks of the NH bond in the amide bond (-CONH₂) appeared at 3358 cm⁻¹ and 3196 cm⁻¹, and a stretching vibration peak of the C=O bond in the amide bond appeared at 1682 cm⁻¹. The appearance of these characteristic peaks confirmed that the acrylamide monomer had successfully participated in the copolymerization reaction, and that the two monomers had formed the target copolymer structure.

[0030] S2. Vulcanization and Desulfurization: The copolymer prepared in step S1 was mixed with pure sulfur powder at a mass ratio of 1:7, placed in an alumina crucible and then in a tube furnace. After purging the air by purging with argon gas, the temperature was raised to 350℃ for vulcanization reaction and held for 6 hours. After vulcanization, the temperature was lowered to 300℃ and held for 4 hours for desulfurization, followed by natural cooling to room temperature to obtain vulcanized polyacrylonitrile-acrylamide copolymer (SEM image shown). Figure 2 ).

[0031] S3. Preparation of copolymer cathode and battery: Vulcanized polyacrylonitrile-acrylamide copolymer, SuperP (conductive agent), and PAA-Li (binder) are mixed in a mass ratio of 8:1:1, and deionized water is used as solvent. The mixture is stirred evenly to obtain cathode slurry. The slurry is coated on the surface of carbon-coated aluminum foil, vacuum dried at 60°C for 12 hours, and punched into a disc with a diameter of 14 mm as cathode.

[0032] Battery assembly was carried out in an argon glove box (water content <0.1ppm, oxygen content <0.1ppm), using 2032 coin cells, with lithium metal sheets as the negative electrode, polypropylene membrane as the battery separator, and 1M LiPF6 / EC:DMC (1:1, volume ratio) + 15% FEC as the electrolyte; after assembly, the cells were allowed to stand for 12 hours before electrochemical performance testing was conducted.

[0033] Example 2

[0034] The process steps in this embodiment are basically the same as those in Embodiment 1, except that in step S1, the mass ratio of acrylonitrile to acrylamide is 100:10.

[0035] Example 3

[0036] The process steps in this embodiment are basically the same as those in Embodiment 1, except that in step S1, the mass ratio of acrylonitrile to acrylamide is 100:0.

[0037] Example 4

[0038] The process steps in this embodiment are basically the same as those in Embodiment 1, except that in step S1, the volume ratio of acrylonitrile to crosslinking agent is 990:10.

[0039] Example 5

[0040] The process steps in this embodiment are basically the same as those in Embodiment 1, except that in step S1, the volume ratio of acrylonitrile to crosslinking agent is 100:0.

[0041] Example 6

[0042] The process steps in this embodiment are basically the same as those in Embodiment 1, except that in step S1, the initiator is a thermal initiator azobisisobutyronitrile, the initiation condition is constant temperature oil bath heating at 60°C, and the initiator concentration is still 0.5 mg / mL.

[0043] Example 7

[0044] The process steps in this embodiment are basically the same as those in Embodiment 1, except that in step S2, the mass ratio of polyacrylonitrile-acrylamide copolymer to pure sulfur powder is 1:4, and the vulcanization temperature is 350℃.

[0045] Comparative Example

[0046] The process steps of this comparative example are basically the same as those of Example 1, except that commercially available polyacrylonitrile material (purchased from Aladdin, weight average molecular weight 150,000) is used directly to replace the copolymer prepared in step S1, and the other conditions remain unchanged.

[0047] Performance testing and results analysis

[0048] The electrochemical performance of the lithium-sulfur batteries prepared in Examples 1-5 was tested under the following conditions: current density 0.1 A / g, charge-discharge voltage range 1-3 V, and 200 cycles. At the same time, the capacity retention rate under different current densities (0.1 A / g, 0.2 A / g, 0.5 A / g, 1 A / g, 2 A / g, 0.1 A / g) was tested.

[0049] Test Results and Analysis: To present the performance differences more intuitively, the specific capacity and sulfur loading data are compiled into the following table: 1. Specific Capacity Comparison Table Sample type Fifth cycle discharge specific capacity (mAh / g) Sulfur loading Example 1 780 52.19% Example 2 ＜100 60.95% Example 3 620 50.70% Example 4 730 51.05% Example 5 560 59.28% Example 6 740 56.65% Example 7 660 53.35% Comparative Example 480 45.12%

[0050] As shown in the specific capacity comparison table, the initial discharge specific capacity of most of the products in this invention is more than 10% higher than that of the comparative examples, with Examples 1 and 4 exhibiting the best specific capacity. This is attributed to the synergistic sulfur fixation effect of the amide bond and cyano group after the introduction of acrylamide groups, which effectively suppresses the capacity decay caused by polysulfide shuttle. Although Example 2 has a high sulfur loading, the excessive acrylamide groups lead to a decrease in the regularity of the copolymer structure, generating a large amount of free sulfur. The reaction of free sulfur with the electrolyte causes a sharp decline in battery performance. Examples 5 (without crosslinking agent) and 7 (low sulfur ratio) have lower discharge specific capacities than Examples 1, 4, and 6 due to a lack of skeletal support or insufficient active material.

[0051] 2. Comparison table of cycle performance and rate performance Sample type <![CDATA[0.1A·g -1 Capacity retention rate (%) <![CDATA[0.2A·g -1 Capacity retention rate (%) <![CDATA[0.5A·g -1 Capacity retention rate (%) <![CDATA[1A·g -1 Capacity retention rate (%) <![CDATA[2A·g -1 Capacity retention rate (%) <![CDATA[1A·g -1 Capacity retention rate after 200 cycles (based on cycle 5) (%) Example 1 100 91.32 81.27 71.10 56.68 86.72 Example 4 100 96.53 90.10 82.83 70.34 83.69 Comparative Example 100 86 77 61.55 42.52 84.12

[0052] As shown in the comparison table of cycling performance, the cycling stability of the products in the embodiments of the present invention is comparable to or better than that of the comparative examples. Among them, Example 1 achieved a capacity retention rate of 86.72% after 200 cycles, demonstrating the best performance. Although the capacity retention rate of the comparative examples was slightly higher, the actual capacity after cycling of Example 4 was still significantly better than that of the comparative examples, considering the initial specific capacity calculation. In terms of performance, the capacity retention rate of the products of the present invention was significantly better than that of the comparative examples at all current densities. In particular, at a high current density of 2 A / g, the capacity retention rate of Example 4 reached 70.34%, far exceeding the 42.52% of the comparative examples. This result is attributed to the strong polarity of the acrylamide groups, which improves the hydrophilicity and electrolyte wettability of the material and reduces ion transport resistance; the flexible segments enhance the toughness of the polymer skeleton and buffer volume expansion, thereby simultaneously improving rate performance and cycling stability.

[0053] 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 method for preparing a vulcanized polyacrylonitrile-acrylamide-based electrode material and its application, characterized in that, The process includes the following steps: (1) preparing a homogeneous mixed solution containing acrylonitrile monomer, acrylamide monomer, crosslinking agent, initiator and solvent, placing the mixed solution under initiation conditions for free radical copolymerization, controlling the reaction temperature at 10-100℃, and obtaining a polyacrylonitrile-acrylamide copolymer after the reaction; wherein, the mass ratio of acrylonitrile to acrylamide monomer is (90-99):(1-10), the amount of initiator is (0.1-2) mg / mL, the total volume ratio of crosslinking agent to monomer is 0.01-5%, and the copolymerization reaction time is 1-12 hours; (2) thoroughly mixing the polyacrylonitrile-acrylamide copolymer obtained in step (1) with sulfur powder at a mass ratio of 1:(2-20), and then... The mixture is placed in an inert gas atmosphere for vulcanization reaction. The vulcanization reaction temperature is 300-450℃ and the reaction time is 1-10 hours. After the reaction, the unreacted sulfur powder is removed by heat treatment and / or Soxhlet extraction to obtain vulcanized polyacrylonitrile-acrylamide copolymer. The heat treatment temperature is 150-450℃ and the time is 1-10 hours. (3) The vulcanized polyacrylonitrile-acrylamide copolymer obtained in step (2), the conductive agent and the binder are mixed and stirred evenly in a mass ratio of (70-90):(5-20):(5-10) to obtain a positive electrode slurry. The positive electrode slurry is coated on the surface of carbon-coated aluminum foil, and after drying and punching, the vulcanized polyacrylonitrile-acrylamide copolymer positive electrode is obtained.

2. The preparation method according to claim 1 and its application in a battery, characterized in that, The acrylamide monomer in step (1) is selected from at least one of acrylamide, N-methylacrylamide, N,N-dimethylacrylamide, and 2-acrylamido-2-methylpropanesulfonic acid.

3. The preparation method according to claim 1 and its application in a battery, characterized in that, The initiator mentioned in step (1) is a UV photoinitiator or a thermal initiator; the UV photoinitiator is selected from at least one of benzoin ether compounds, benzophenone compounds, azo compounds, α-hydroxyalkylphenyl ketone compounds, and acylphosphine oxide compounds, and the corresponding initiation conditions are UV irradiation with a wavelength of 250-420 nm, a reaction temperature of 10-50°C, and a reaction time of 1-12 h; wherein, the benzoin ether compounds include 2,2-dimethoxy-2-phenylacetophenone (DMPA), the α-hydroxyalkylphenyl ketone compounds include 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone (I2959), and the acylphosphine oxide compounds include phenylbis(2,4,6-trimethylbenzoyl) Phosphorus oxide (LAP); the thermal initiator is selected from at least one of azobisisobutyronitrile, azobisisoheptanenitrile, and benzoyl peroxide, and the corresponding initiation conditions are constant temperature heating at 50-100℃ for 1-4 hours.

4. The preparation method according to claim 1 and its application in a battery, characterized in that, The solvent in step (1) is selected from at least one of acetone, methanol, dichloromethane, ethanol, tetrahydrofuran, N,N-dimethylformamide, and water; the volume ratio of acrylonitrile to solvent is 1:(0.5-5).

5. The preparation method according to claim 1 and its application in a battery, characterized in that, The crosslinking agent mentioned in step (1) is selected from one of the acrylates, including triethylene glycol dimethacrylate; the volume ratio of acrylonitrile to crosslinking agent is 100:(0.01-5).

6. The preparation method according to claim 1 and its application in a battery, characterized in that, The sulfur powder mentioned in step (2) is selected from at least one of pure sulfur powder, selenium-doped sulfur powder, and tellurium-doped sulfur powder.

7. The preparation method according to claim 1 and its application in a battery, characterized in that, The conductive agent in step (3) is selected from at least one of super carbon black, acetylene black, Ketjen black, carbon nanotubes, and graphene; the binder is selected from at least one of lithium polyacrylate (PAA-Li), polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), and polyimide (PI).

8. A polyacrylonitrile-acrylamide copolymer, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 5.

9. A vulcanized polyacrylonitrile-acrylamide copolymer positive electrode, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 8.

10. A battery, characterized in that, The battery is a lithium-sulfur battery or a sodium-sulfur battery, comprising the sulfurized polyacrylonitrile-acrylamide copolymer positive electrode as described in claim 10; this technical feature corresponds to the detailed description of the lithium-sulfur battery in paragraph [0019] of the specification and in the specific embodiments, and the sodium-sulfur battery is a reasonable extension based on the same technical solution, which is within the scope of disclosure of the specification.

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