Method for producing highly conductive sulfur-based positive electrode material for secondary batteries and method for producing secondary batteries

Abstract

A highly conductive sulfur-based positive electrode material for a secondary battery and a secondary battery are provided. [Solution] The present invention relates to a highly conductive sulfur-based positive electrode material for secondary batteries and a secondary battery, and the sulfur-based positive electrode material is formed by using highly isotactic polyacrylonitrile as a precursor, mixing it uniformly with elemental sulfur, and then heating it to cause a chemical reaction. Highly isotactic polyacrylonitrile is synthesized by radical polymerization or inclusion polymerization of acrylonitrile monomer under the action of a template. Compared with the prior art, the highly isotactic polyacrylonitrile of the present invention has a higher crystallinity and lower thermal decomposition and cyclization temperatures than atactic polyacrylonitrile, and the conductivity of the prepared sulfur-based positive electrode material S@pPAN is 10 -3 S / cm, and the sulfur content is 40-70wt%. When used as a positive electrode material for secondary batteries, the electrical conductivity of the entire material is significantly improved, and the active material utilization rate, cycle stability, and rate characteristics of the sulfur positive electrode are significantly improved, and the reversible specific capacity of the positive electrode material reaches 700mAh / g. The effect is remarkable, the manufacturing process is simple, it is easy to amplify, and it is highly practical.

Description

[Technical Field]

[0001] The present invention relates to a sulfur-based positive electrode material, and more particularly to a highly conductive sulfur-based positive electrode material for secondary batteries, such as lithium-sulfur batteries, sodium-sulfur batteries, potassium-sulfur batteries, magnesium-sulfur batteries, calcium-sulfur batteries, and aluminum-sulfur batteries, which are assembled using the sulfur-based positive electrode material, and the secondary batteries. [Background technology]

[0002] Secondary batteries using lithium, sodium, potassium, magnesium, or aluminum as the anode and sulfur as the cathode have significant advantages, including high energy density, abundant sulfur resources, low cost, and environmental friendliness. Lithium-sulfur batteries, for example, have attracted widespread attention due to their theoretical energy density of up to 2600 Wh / kg and their low cost and environmental friendliness. However, due to the insulating properties of sulfur, the actual energy density differs significantly from the theoretical value. To ensure proper operation of sulfur cathodes, a large amount of conductive additive must be added during cathode fabrication, which reduces the specific capacity of the entire material. Furthermore, during cycling, the intermediate product lithium polysulfide dissolves in the electrolyte, creating a "shuttle effect" that further reduces the active material.

[0003] As early as 2002, sulfur-modified polyacrylonitrile (sulfur-based positive electrode material S@pPAN) was first reported, produced by chemically reacting sulfur with polyacrylonitrile (PAN) (Non-Patent Document 1). This positive electrode material does not have the shuttle effect of dissolving polysulfide ions in carbonate ester electrolytes, has high charge / discharge efficiency, and has low self-discharge. However, when conventional atactic polyacrylonitrile is used as a precursor, the resulting S@pPAN positive electrode material has low conductivity, with a low conductivity of approximately 10 -7 ~10 -4 The resulting dielectric constant is at the S / cm level, and the cycle stability and rate characteristics of the material are low, affecting the use of secondary batteries.

[0004] Patent Document 1 discloses a method for producing a polyacrylonitrile-sulfur composite material, in which 85% or more of sp 2 By using the polyacrylonitrile-sulfur composite with a mixed ratio as the electrode active material, it is possible to improve the intrinsic conductivity, form a relatively low ohmic resistance, increase the charge / discharge rate, obtain a stable capacitance, and increase the sulfur utilization rate.

[0005] Patent Document 2 discloses a method for producing polyacrylonitrile-sulfur composites, in which a matrix material and specific reactants are added in advance to prevent agglomeration of polyacrylonitrile particles and achieve a particularly uniform distribution of composite particles. This method can produce polyacrylonitrile-sulfur composites with excellent electrochemical cycle stability and high discharge rates. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Chinese Patent Application Publication No. 104350072 [Patent Document 2] Chinese Patent Application Publication No. 104334613 [Non-patent literature]

[0007] [Non-Patent Document 1] J.Wang,et al.,Advanced materials,2002,13-14,963 Summary of the Invention [Problem to be solved by the invention]

[0008] Through research, the applicant of the present invention found that although the two patents, Patent Document 1 and Patent Document 2, improve the performance of the manufactured materials to a certain extent, they achieve this by improving the sintering process or adding conductive materials, and do not start from the structure of polyacrylonitrile itself.

[0009] Therefore, it is of great significance to improve the cycle stability and rate performance of secondary batteries by fabricating highly conductive S@pPAN cathode materials without adding other materials.

[0010] The present invention starts from the structure of PAN itself, and by controlling the polymerization process of acrylonitrile monomer, it is possible to produce polyacrylonitrile with a high isotactic fraction, and then to increase the degree of cyclization during the chemical reaction with sulfur, thereby greatly improving the conductivity of the composite material and achieving excellent electrochemical performance. Moreover, the process is simple and effective.

[0011] The present invention aims to provide a highly conductive sulfur-based positive electrode material for secondary batteries, which realizes significant improvements in the conductivity of the entire material, the utilization rate of the active material in the sulfur positive electrode, the cycle stability, and the rate characteristics, and a secondary battery. [Means for solving the problem]

[0012] The object of the present invention is achieved by the following technical solutions.

[0013] The first aspect of the present invention provides a highly conductive sulfur-based cathode material for secondary batteries, which is formed by adopting highly isotactic polyacrylonitrile as a precursor, mixing it with elemental sulfur, and then heating it to cause a chemical reaction.

[0014] Preferably, the highly isotactic polyacrylonitrile is synthesized by subjecting acrylonitrile monomers to inclusion polymerization or radical polymerization under the action of a template.

[0015] Preferably, the highly isotactic polyacrylonitrile has an isotactic fraction (isotactic mm content) of 40 to 99%, where the polyacrylonitrile with an isotactic fraction of 40 to 60% is prepared by radical polymerization under the action of a template, and the polyacrylonitrile with an isotactic fraction of 60 to 99% is prepared by inclusion polymerization.

[0016] More preferably, the highly isotactic polyacrylonitrile is polyacrylonitrile having an isotactic fraction of 50 to 90%.

[0017] Preferably, the radical polymerization reaction includes the following steps: mixing acrylonitrile monomer, an initiator, and a template, stirring at room temperature for 0.5 to 5 hours, and then raising the temperature to 50 to 100°C and polymerizing for 2 to 24 hours to obtain the highly isotactic polyacrylonitrile. More preferably, the mass ratio of acrylonitrile monomer, initiator, and template is 1:0.01 to 0.1:10 to 50, the template is one or more selected from MgCl2, FeCl3, CoCl2, NiCl2, and MgBr2, and the initiator is one or more selected from potassium persulfate, sodium persulfate, ammonium persulfate, azodiisobutyronitrile, and benzamide.

[0018] Preferably, the inclusion polymerization reaction process includes the following steps: freezing the acrylonitrile / urea inclusion compound at -60°C for 3 to 40 days, irradiating it with high-energy rays at liquid nitrogen temperature to initiate the reaction, raising the temperature to -60 to -100°C after irradiation to carry out a chain growth reaction, carrying out the reaction for 2 to 48 hours, and then terminating the reaction with water or methanol to obtain a polymer. More preferably, the type of high-energy rays used for the irradiation reaction is one of β-, γ-, and X-rays.

[0019] Preferably, the mass ratio of the elemental sulfur to the highly isotactic polyacrylonitrile is 2 to 16:1.

[0020] Preferably, the conditions for heating to cause the chemical reaction are heating to 250 to 450°C and maintaining the temperature for 1 to 16 hours.

[0021] In the present invention, the heat-induced chemical reaction can be carried out in the presence of an added shielding gas, which can be nitrogen gas or argon gas, or can be carried out without the addition of a separate shielding gas, in which case the H2S generated during the reaction process plays a protective role.

[0022] Preferably, the sulfur content in the above-mentioned sulfur-based positive electrode material for secondary batteries is 35 to 70 wt %, and more preferably, the sulfur content is 40 to 60 wt %.

[0023] A second aspect of the present invention provides a secondary battery including the above-mentioned highly conductive sulfur-based positive electrode material for secondary batteries.

[0024] Preferably, the negative electrode of the secondary battery is lithium, sodium, potassium, magnesium, calcium, or aluminum, and the corresponding secondary batteries are lithium-sulfur batteries, sodium-sulfur batteries, potassium-sulfur batteries, magnesium-sulfur batteries, calcium-sulfur batteries, and aluminum-sulfur batteries, each of which is assembled using a sulfur-based positive electrode material.

[0025] The third aspect of the present invention provides a sulfur positive electrode for a secondary battery, which is prepared by uniformly dispersing a binder, the aforementioned highly conductive sulfur-based positive electrode material for a secondary battery, and a conductive agent in a solvent in a mass ratio of 7-9:0.5-1.5:0.5-1.5, applying the dispersion to a current collector, drying, and pressing to obtain a sulfur positive electrode for a secondary battery.

[0026] Preferably, the solvent comprises one of H2O, DMF, and NMP. [Effects of the Invention]

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The sulfur-based cathode material S@pPAN, which is manufactured using atactic polyacrylonitrile as a precursor, has an electronic conductivity of 10 -7 ~10 -4 The conductivity of the S@pPAN produced by this invention is only at the S / cm level, which affects the cycle characteristics and rate characteristics of the material. The present invention starts with a polyacrylonitrile precursor and constructs a highly isotactic polyacrylonitrile (isotactic fraction of 40% or more, preferably 50-90%). This type of PAN has a low temperature for thermal decomposition and cyclization reaction, a high degree of crystallinity, and a regular morphology. Therefore, the thermal decomposition and cyclization reaction levels at the same temperature are higher than those of conventional PAN, improving the conductivity of the entire material and significantly improving the utilization rate of the active material in the sulfur positive electrode, cycle stability, and rate characteristics. The conductivity of the S@pPAN produced by this invention is 10 -3 The reversible specific capacity of the sulfur-based positive electrode material with a sulfur content of around 45 wt% can reach 700 mAh / g, which is highly effective, simple to process, easy to amplify, and highly practical. [Brief explanation of the drawings]

[0029] [Figure 1] 1A and 1B are scanning electron micrographs of highly isotactic polyacrylonitrile (a), atactic polyacrylonitrile (b), a corresponding sulfur-based positive electrode material S@pPAN (c) prepared using highly isotactic polyacrylonitrile as a precursor, and a corresponding sulfur-based positive electrode material S@pPAN (d) prepared using atactic polyacrylonitrile as a precursor in Example 1 and Comparative Example 1. [Figure 2] 1A and 1B are transmission electron micrographs of the highly isotactic polyacrylonitrile (S@pPAN) in Example 1 (a) and the corresponding sulfur-based positive electrode material S@pPAN (b) prepared using the highly isotactic polyacrylonitrile as a precursor. [Figure 3] 1 shows the carbon nuclear magnetic resonance spectra of the highly isotactic polyacrylonitrile (a) and the atactic polyacrylonitrile (b) obtained in Example 1. [Figure 4]1 shows infrared spectra of highly isotactic polyacrylonitrile (a) and atactic polyacrylonitrile (b) obtained in Example 2. [Figure 5] 1 shows XRD spectra of highly isotactic polyacrylonitrile (a) and atactic polyacrylonitrile (b) obtained in Example 2. [Figure 6] 1 shows DSC spectra of highly isotactic polyacrylonitrile and atactic polyacrylonitrile obtained in Example 2. [Figure 7] FIG. 1 is a comparison diagram of the electrical conductivity of the sulfur-based positive electrode material S@pPAN prepared using the highly isotactic polyacrylonitrile obtained in each example as a precursor. [Figure 8] FIG. 1 is a comparison diagram of the cycles of the sulfur-based positive electrode material S@pPAN prepared using the highly isotactic polyacrylonitrile and atactic polyacrylonitrile obtained in Example 2 as precursors. [Figure 9] FIG. 1 is a comparative graph of the rates of the sulfur-based positive electrode material S@pPAN prepared using the highly isotactic polyacrylonitrile and atactic polyacrylonitrile obtained in Example 2 as precursors. DETAILED DESCRIPTION OF THE INVENTION

[0030] A highly conductive sulfur-based cathode material for secondary batteries is formed by mixing highly isotactic polyacrylonitrile as a precursor with elemental sulfur and then heating it to cause a chemical reaction.

[0031] In some embodiments, the highly isotactic polyacrylonitrile is synthesized by radical polymerization of acrylonitrile monomer under the influence of inclusion polymerization or template. In some embodiments, the highly isotactic polyacrylonitrile is polyacrylonitrile having an isotactic fraction (isotactic mm content) of 40 to 99%. Here, polyacrylonitrile having an isotactic fraction of 40 to 60% is prepared by radical polymerization under the influence of template, and polyacrylonitrile having an isotactic fraction of 60 to 99% is prepared by inclusion polymerization. Preferably, the highly isotactic polyacrylonitrile is polyacrylonitrile having an isotactic fraction of 50 to 90%.

[0032] In some embodiments, the radical polymerization reaction includes the following steps: mixing acrylonitrile monomer, an initiator, and a template, stirring at room temperature for 0.5 to 5 hours, and then raising the temperature to 50 to 100°C and polymerizing for 2 to 24 hours to obtain the highly isotactic polyacrylonitrile. Preferably, the mass ratio of acrylonitrile monomer, initiator, and template is 1:0.01 to 0.1:10 to 50, the template can be one or more selected from MgCl2, FeCl3, CoCl2, NiCl2, and MgBr2, and the initiator can be one or more selected from potassium persulfate, sodium persulfate, ammonium persulfate, azodiisobutyronitrile, and benzamide.

[0033] In some embodiments, the inclusion polymerization reaction step includes the following steps: freezing the acrylonitrile / urea inclusion compound at -60°C for 3 to 40 days, irradiating it with high-energy rays at liquid nitrogen temperature to initiate the reaction, raising the temperature to -60 to -100°C after irradiation to carry out a chain growth reaction, reacting for 2 to 48 hours, and then terminating the reaction with water or methanol to obtain a polymer. Preferably, the type of high-energy rays used for the irradiation reaction is one of β-, γ-, and X-rays.

[0034] In some embodiments, the weight ratio of elemental sulfur to highly isotactic polyacrylonitrile is 2-16:1.

[0035] In some embodiments, the conditions for heating to cause a chemical reaction include heating to 250 to 450° C. and maintaining the temperature for 1 to 16 hours.

[0036] In the present invention, the heat-induced chemical reaction can be carried out in the presence of an added shielding gas, which can be nitrogen gas or argon gas, or can be carried out without the addition of a separate shielding gas, in which case the H2S generated during the reaction process plays a protective role.

[0037] In some embodiments, the sulfur content in the sulfur-based positive electrode material for secondary batteries is 35 to 70 wt %, and preferably the sulfur content is 40 to 60 wt %.

[0038] A secondary battery comprising the highly conductive sulfur-based positive electrode material for secondary batteries described above.

[0039] In the present invention, the negative electrode of the secondary battery can be lithium, sodium, potassium, magnesium, calcium, or aluminum, and the corresponding secondary batteries are lithium-sulfur batteries, sodium-sulfur batteries, potassium-sulfur batteries, magnesium-sulfur batteries, calcium-sulfur batteries, and aluminum-sulfur batteries, each of which is assembled using a sulfur-based positive electrode material.

[0040] In the present invention, the sulfur positive electrode for secondary batteries can be prepared by uniformly dispersing a binder, the above-mentioned highly conductive sulfur-based positive electrode material for secondary batteries, and a conductive agent in a solvent in a mass ratio of 7-9:0.5-1.5:0.5-1.5, applying the dispersion to a current collector, drying, and pressing to obtain a sulfur positive electrode for secondary batteries.

[0041] In some embodiments, the solvent comprises one of H2O, DMF, and NMP.

[0042] The present invention will be described in detail below with reference to the drawings and specific examples.

[0043] Comparison 1

[0044] 6 ml of acrylonitrile monomer was added to 30 ml of a water / DMSO mixed solvent (volume ratio of water to DMSO: 4:1). Next, 0.1 g of AIBN was added to the mixture as an initiator, and nitrogen gas was introduced to remove the air inside. The mixture was heated to 70°C and magnetically stirred for 12 hours, yielding a white powder precipitate. The white precipitate was washed alternately with methanol and water, and then placed in a vacuum dryer and dried for 24 hours to obtain atactic polyacrylonitrile.

[0045] 2 g of the resulting atactic polyacrylonitrile and 16 g of elemental sulfur were added to ethanol and ball-milled for 3 hours. After drying, the resulting powder was heated at 300 °C for 5 hours in a nitrogen gas atmosphere in a tube furnace to obtain the sulfur-based cathode material S@pPAN. The sulfur content in the material was 45.19 wt%, and the electronic conductivity of the material was 3.2 × 10 -7 S / cm.

[0046] 1 and 2, the SEM and TEM photographs of the prepared atactic polyacrylonitrile were compared with the highly isotactic polyacrylonitrile prepared in the present invention, and it was found that the highly isotactic polyacrylonitrile had a more uniform particle size distribution, better sphericity, and a smoother surface. As shown in Figure 3, NMR testing revealed that the isotactic fraction of atactic polyacrylonitrile was 26%, while the highly isotactic polyacrylonitrile prepared in Example 2 had an isotactic fraction of up to 55%.

[0047] Battery assembly and testing: A sulfur cathode was prepared using the sulfur-based cathode material obtained in Comparative Example 1, and a lithium-sulfur secondary battery was assembled using lithium metal as the anode. The electrolyte was 1M LiPF6 / EC:DMC (1:1 volume ratio, EC: ethylene carbonate, DMC: dimethyl carbonate), and the charge / discharge cutoff voltage was 1-3V (vs. Li + 8, the initial reversible specific capacity under the condition of a 0.2C rate was 712 mAh / g, the specific capacity after 200 cycles was 547 mAh / g, and the capacity retention rate was 76.8%. [Example]

[0048] 30g of anhydrous CoCl2 was added to a three-neck flask, cooled in cold water for 30 minutes, and then filled with argon gas. Next, 7g of acrylonitrile monomer and 0.15g of AIBN initiator were added and the polymerization reaction was initiated by magnetic stirring at 60°C for 4 hours. After the reaction time was 6 hours, the resulting white powder was washed alternately with methanol and water, and then dried in a vacuum oven for 24 hours to obtain highly isotactic polyacrylonitrile (isotactic fraction 55%).

[0049] 1 and 2 are SEM and TEM images of the highly isotactic polyacrylonitrile and positive electrode material prepared in this example and the atactic polyacrylonitrile and sulfur-based positive electrode material S@pPAN in Comparative Example 1. It can be seen that the highly isotactic polyacrylonitrile has a more uniform particle size distribution, better sphericity, and a smoother surface.

[0050] As shown in Figure 3, the isotactic fraction of the highly isotactic polyacrylonitrile reached 55%, which is a significant improvement in the isotactic fraction (mm) compared to the atactic polyacrylonitrile (26%) prepared in Comparative Example 1.

[0051] 2 g of the resulting atactic polyacrylonitrile and 16 g of elemental sulfur were added to ethanol and ball-milled for 3 hours. After drying, the resulting powder was heated at 300 °C for 10 hours in a nitrogen gas atmosphere in a tube furnace to obtain the sulfur-based cathode material S@pPAN. The sulfur content in the material was 41.1 wt%, and the electronic conductivity of the material was 1.2 × 10 -3 S / cm.

[0052] Battery assembly and testing: A sulfur cathode was prepared using the sulfur-based cathode material obtained in Example 1, and a lithium-sulfur secondary battery was assembled using lithium metal as the anode. The electrolyte was 1M LiPF6 / EC:DMC (1:1 volume ratio, EC: ethylene carbonate, DMC: dimethyl carbonate), and the charge / discharge cutoff voltage was 1 to 3 V (vs. Li + The initial specific capacity under the condition of 0.2 C rate was 635 mAh / g. [Example]

[0053] 30g of anhydrous cobalt chloride was added to a three-neck flask, cooled in cold water for 30 minutes, and then filled with argon gas. Next, 7g of acrylonitrile monomer and 0.15g of AIBN initiator were added and the polymerization reaction was initiated by magnetic stirring at 70°C for 4 hours. After the reaction had continued for 6 hours, the resulting white powder was washed alternately with methanol and water, and then dried in a vacuum oven for 24 hours to obtain highly isotactic polyacrylonitrile (isotactic fraction 55%).

[0054] Highly isotactic polyacrylonitrile has a much higher isotactic fraction than atactic polyacrylonitrile and has a more regular morphology, so its crystallinity is also far higher than that of atactic polyacrylonitrile, which causes deviations in the characteristic peaks of the corresponding group (-AN) and material, as shown in Figures 4 and 5.

[0055] Figure 6 shows the DSC spectrum analysis results for the highly isotactic polyacrylonitrile prepared in this example and the atactic polyacrylonitrile in Comparative Example 1. It can be seen that the dehydrogenation cyclization reaction already occurs at a temperature of around 277°C for the highly isotactic polyacrylonitrile, while the cyclization temperature for the atactic polyacrylonitrile reaches a maximum of 292°C. This explains why the cyclization reaction occurs more easily in the highly isotactic polyacrylonitrile. Similarly, the sintering temperature and time also result in a higher degree of cyclization, which further increases the conductivity of the prepared sulfur-based cathode material.

[0056] The prepared highly isotactic polyacrylonitrile (2 g) and elemental sulfur (16 g) were added to ethanol and ball-milled for 3 hours. After drying, the resulting powder was heated at 300°C for 5 hours in a nitrogen gas atmosphere in a tube furnace to obtain the sulfur-based cathode material S@pPAN. The sulfur content in the material was 45.13 wt%, and the electronic conductivity of the material was 8.4 × 10 -6 S / cm.

[0057] Battery assembly and testing: A sulfur cathode was prepared using the sulfur-based cathode material obtained in Example 2, and a lithium-sulfur secondary battery was assembled using lithium metal as the anode. The electrolyte was 1M LiPF6 / EC:DMC (1:1 volume ratio, EC: ethylene carbonate, DMC: dimethyl carbonate), and the charge / discharge cutoff voltage was 1 to 3 V (vs. Li + / Li). Referring to FIG. 8, the initial reversible specific capacity under 0.2C rate conditions was 721 mAh / g, the specific capacity after 200 cycles was 661 mAh / g, and the capacity retention rate was 91.7%, which was significantly higher than the capacity retention rate of Comparative Example 1. Referring to FIG. 9, rate performance tests were performed on the positive electrode materials prepared in the Examples and Comparative Example 1 under different rate conditions. It can be seen that as the rate increased, the rate performance of the positive electrode material prepared in the Examples became better than that of the positive electrode material in Comparative Example 1. [Example]

[0058] 30g of anhydrous CoCl2 was added to a three-neck flask, cooled in cold water for 30 minutes, and then filled with argon gas. Next, 7g of acrylonitrile monomer and 0.15g of AIBN initiator were added and the polymerization reaction was initiated by magnetic stirring at 70°C for 4 hours. After the reaction time was 6 hours, the resulting white powder was washed alternately with methanol and water, and then dried in a vacuum oven for 24 hours to obtain highly isotactic polyacrylonitrile (isotactic fraction 55%).

[0059] The resulting highly isotactic polyacrylonitrile (2 g) and elemental sulfur (16 g) were added to ethanol and ball-milled for 3 hours. After drying, the resulting powder was heated at 350°C for 5 hours in a nitrogen gas atmosphere in a tube furnace to obtain the sulfur-based cathode material S@pPAN. The sulfur content in the material was 40.20 wt%, and the electronic conductivity of the material was 6.7 × 10 -5 S / cm.

[0060] Battery assembly and testing: A sulfur cathode was prepared using the sulfur-based cathode material obtained in Example 3, and a lithium-sulfur secondary battery was assembled using lithium metal as the anode. The electrolyte was 1M LiPF6 / EC:DMC (1:1 volume ratio, EC: ethylene carbonate, DMC: dimethyl carbonate), and the charge / discharge cutoff voltage was 1 to 3 V (vs. Li + The initial reversible specific capacity under a 0.2 C rate condition was 630 mAh / g. [Example]

[0061] 30g of anhydrous CoCl2 was added to a three-neck flask, cooled in cold water for 30 minutes, and then filled with argon gas. Next, 7g of acrylonitrile monomer and 0.15g of AIBN initiator were added and the polymerization reaction was initiated by magnetic stirring at 70°C for 4 hours. After the reaction time was 6 hours, the resulting white powder was washed alternately with methanol and water, and then dried in a vacuum oven for 24 hours to obtain highly isotactic polyacrylonitrile (isotactic fraction 55%).

[0062] The resulting highly isotactic polyacrylonitrile (2 g) and elemental sulfur (16 g) were added to ethanol and ball-milled for 3 hours. After drying, the resulting powder was heated at 350°C for 10 hours in a nitrogen gas atmosphere in a tube furnace to obtain the sulfur-based cathode material S@pPAN. The sulfur content in the material was 38.71 wt% and the conductivity was 8.7 × 10 -3 S / cm.

[0063] Battery assembly and testing: A sulfur cathode was prepared using the sulfur-based cathode material obtained in Example 4, and a lithium-sulfur secondary battery was assembled using lithium metal as the anode. The electrolyte was 1M LiPF6 / EC:DMC (1:1 volume ratio, EC: ethylene carbonate, DMC: dimethyl carbonate), and the charge / discharge cutoff voltage was 1 to 3 V (vs. Li + The initial reversible specific capacity under a 0.2 C rate condition was 600 mAh / g. [Example]

[0064] 30g of anhydrous CoCl2 was added to a three-neck flask, cooled in cold water for 30 minutes, and then filled with argon gas. Next, 7g of acrylonitrile monomer and 0.15g of AIBN initiator were added and the polymerization reaction was initiated by magnetic stirring at 70°C for 4 hours. After the reaction time was 6 hours, the resulting white powder was washed alternately with methanol and water, and then dried in a vacuum oven for 24 hours to obtain highly isotactic polyacrylonitrile (isotactic fraction 55%).

[0065] The resulting highly isotactic polyacrylonitrile (2 g) and elemental sulfur (16 g) were added to ethanol and ball-milled for 3 hours. After drying, the resulting powder was heated in an argon gas atmosphere in a tube furnace at 400°C for 5 hours to obtain the sulfur-based cathode material S@pPAN. The sulfur content in the material was 39.78 wt%, and the electronic conductivity of the material was 5.4 × 10 -3 S / cm.

[0066] Battery assembly and testing: A sulfur cathode was prepared using the sulfur-based cathode material obtained in Example 5, and a lithium-sulfur secondary battery was assembled using lithium metal as the anode. The electrolyte was 1M LiPF6 / EC:DMC (1:1 volume ratio, EC: ethylene carbonate, DMC: dimethyl carbonate), and the charge / discharge cutoff voltage was 1-3 V (vs. Li + The initial reversible specific capacity under a 0.2 C rate condition was 622 mAh / g. [Example]

[0067] 30g of anhydrous CoCl2 was added to a three-neck flask, cooled in cold water for 30 minutes, and then filled with argon gas. Next, 7g of acrylonitrile monomer and 0.15g of AIBN initiator were added and the polymerization reaction was initiated by magnetic stirring at 70°C for 4 hours. After the reaction time was 6 hours, the resulting white powder was washed alternately with methanol and water, and then dried in a vacuum oven for 24 hours to obtain highly isotactic polyacrylonitrile (isotactic fraction 55%).

[0068] The resulting highly isotactic polyacrylonitrile (2 g) and elemental sulfur (16 g) were added to ethanol and ball-milled for 3 hours. After drying, the resulting powder was heated in an argon gas atmosphere in a tube furnace at 400°C for 10 hours to obtain the sulfur-based cathode material S@pPAN. The sulfur content in the material was 35.75 wt% and the conductivity was 9.8 × 10 -3 It was S / cm.

[0069] Battery assembly and testing: A sulfur cathode was prepared using the sulfur-based cathode material obtained in Example 6, and a sodium-sulfur secondary battery was assembled using sodium metal as the anode. The electrolyte was 1M LiPF6 / EC:DMC (1:1 volume ratio, EC:ethylene carbonate, DMC:dimethyl carbonate), and the charge / discharge cutoff voltage was 1 to 2.7 V (vs. Li + The initial reversible specific capacity under a 0.2 C rate condition was 554 mAh / g. [Example]

[0070] 30g of anhydrous MgCl2 was added to a three-neck flask, cooled in cold water for 20 minutes, and then filled with argon gas. Next, 7g of acrylonitrile monomer and 0.15g of BPO initiator were added and the polymerization reaction was initiated with magnetic stirring at 70°C for 4 hours. After the reaction time was 6 hours, the resulting white powder was washed alternately with methanol and water, and then dried in a vacuum oven for 24 hours to obtain highly isotactic polyacrylonitrile (isotactic fraction 42%).

[0071] The resulting highly isotactic polyacrylonitrile (2 g) and elemental sulfur (16 g) were added to ethanol and ball-milled for 3 hours. After drying, the resulting powder was heated at 300°C for 10 hours in a nitrogen gas atmosphere in a tube furnace to obtain the sulfur-based cathode material S@pPAN. The sulfur content in the material was 42.16 wt%, and the resulting conductivity was 6.7 × 10 -4 It was S / cm.

[0072] Battery assembly and testing: A sulfur cathode was prepared using the sulfur-based cathode material obtained in Example 7, and a lithium-sulfur secondary battery was assembled using lithium metal as the anode. The electrolyte was 1M LiPF6 / EC:DMC (1:1 volume ratio, EC: ethylene carbonate, DMC: dimethyl carbonate), and the charge / discharge cutoff voltage was 1-3 V (vs. Li + The initial reversible specific capacity under a 0.2 C rate condition was 653 mAh / g. [Example]

[0073] 30g of anhydrous NiCl2 was added to a three-neck flask, cooled in cold water for 30 minutes, and then filled with argon gas. Next, 7g of acrylonitrile monomer and 0.15g of AIBN initiator were added and the polymerization reaction was initiated by magnetic stirring at 70°C for 4 hours. After the reaction time was 6 hours, the resulting white powder was washed alternately with methanol and water, and then dried in a vacuum oven for 24 hours to obtain highly isotactic polyacrylonitrile (isotactic fraction 60%).

[0074] The resulting highly isotactic polyacrylonitrile (2 g) and elemental sulfur (16 g) were added to ethanol and ball-milled for 3 hours. After drying, the resulting powder was heated at 300°C for 10 hours in an argon gas atmosphere in a tube furnace to obtain the sulfur-based cathode material S@pPAN. The sulfur content in the material was 40.52 wt%, and the resulting conductivity was 2.2 × 10 -3 S / cm.

[0075] Battery assembly and testing: A sulfur cathode was prepared using the sulfur-based cathode material obtained in Example 8, and a lithium-sulfur secondary battery was assembled using lithium metal as the anode. The electrolyte was 1M LiPF6 / EC:DMC (1:1 volume ratio, EC: ethylene carbonate, DMC: dimethyl carbonate), and the charge / discharge cutoff voltage was 1-3 V (vs. Li + The initial reversible specific capacity under a 0.2 C rate condition was 628 mAh / g. [Example]

[0076] 10 g of acrylonitrile and 12 g of urea were homogeneously mixed and frozen at -60°C for 3 days to obtain an acrylonitrile / urea inclusion compound. The prepared acrylonitrile / urea inclusion compound was then cooled to the temperature of liquid nitrogen and dissolved in 2.0 × 10 15 Bq 60 The inclusion compound was then irradiated with Co γ-rays (8 kGy x 3 h). The inclusion compound was then removed from the γ-rays and the temperature was raised to -100°C to allow the chain growth reaction. After 4 hours, cold methanol was added to the reaction system to dissolve and remove the urea, terminating the polymerization reaction. The residue was then filtered and repeatedly washed with distilled water and methanol until the unreacted monomer and urea were completely removed. Finally, the polymer was vacuum dried to obtain a white powder of highly isotactic polyacrylonitrile (isotactic fraction 63%).

[0077] The resulting highly isotactic polyacrylonitrile (2 g) and elemental sulfur (16 g) were added to ethanol and ball-milled for 3 hours. After drying, the resulting powder was heated at 300°C for 10 hours in a nitrogen gas atmosphere in a tube furnace to obtain the sulfur-based cathode material S@pPAN. The sulfur content in the material was 42.51 wt%, and the resulting conductivity was 3.1 × 10 -3 S / cm.

[0078] Battery assembly and testing: A sulfur cathode was prepared using the sulfur-based cathode material obtained in Example 9, and a lithium-sulfur secondary battery was assembled using lithium metal as the anode. The electrolyte was 1M LiPF6 / EC:DMC (1:1 volume ratio, EC: ethylene carbonate, DMC: dimethyl carbonate), and the charge / discharge cutoff voltage was 1-3 V (vs. Li + The initial reversible specific capacity under a 0.2 C rate condition was 658 mAh / g.

[0079] A sulfur cathode was prepared using the sulfur-based cathode material obtained in Example 9, and a magnesium-sulfur secondary battery was assembled using metallic magnesium as the anode. The electrolyte was 0.4 M (PhMgCl)2-AlCl3 / THF ((PhMgCl)2: phenyl magnesium chloride), and the charge / discharge cutoff voltage was 0.4 to 2.4 V (vs. MgCl). 2+ The initial reversible specific capacity under a 0.1C rate condition was 620 mAh / g. [Example]

[0080] 10 g of acrylonitrile and 12 g of urea were homogeneously mixed and frozen at -60°C for 12 days to obtain an acrylonitrile / urea inclusion compound. The prepared acrylonitrile / urea inclusion compound was then cooled to the temperature of liquid nitrogen and dissolved in 2.0 × 10 15 Bq 60The inclusion compound was then irradiated with Co γ-rays (8 kGy x 3 h). The inclusion compound was then removed from the γ-rays and the temperature was raised to -100°C to allow the chain growth reaction. After 4 hours, cold methanol was added to the reaction system to dissolve and remove the urea, terminating the polymerization reaction. The residue was then filtered and repeatedly washed with distilled water and methanol until the unreacted monomer and urea were completely removed. Finally, the polymer was vacuum dried to obtain a white powder of highly isotactic polyacrylonitrile (isotactic fraction 78%).

[0081] The resulting highly isotactic polyacrylonitrile (2 g) and elemental sulfur (16 g) were added to ethanol and ball-milled for 3 hours. After drying, the resulting powder was heated at 300°C for 10 hours in a nitrogen gas atmosphere in a tube furnace to obtain the sulfur-based cathode material S@pPAN. The sulfur content in the material was 40.23 wt%, and the resulting conductivity was 4.1 × 10 -3 S / cm.

[0082] Battery assembly and testing: A sulfur cathode was prepared using the sulfur-based cathode material obtained in Example 10, and a lithium-sulfur secondary battery was assembled using lithium metal as the anode. The electrolyte was 1M LiPF6 / EC:DMC (1:1 volume ratio, EC: ethylene carbonate, DMC: dimethyl carbonate), and the charge / discharge cutoff voltage was 1-3 V (vs. Li + The initial reversible specific capacity under a 0.2 C rate condition was 617 mAh / g.

[0083] A sulfur cathode was prepared using the sulfur-based cathode material obtained in Example 10, and a calcium-sulfur secondary battery was assembled using metallic calcium as the anode. The electrolyte was 1 M Ca(ClO4)2 / DMSO (DMSO: dimethyl sulfoxide), and the charge / discharge cutoff voltage was 0.7 to 2.7 V (vs. Ca 2+ The initial reversible specific capacity under a 0.1 C rate condition was 605 mAh / g. [Example]

[0084] 10 g of acrylonitrile and 12 g of urea were homogeneously mixed and frozen at -60°C for 28 days to obtain an acrylonitrile / urea inclusion compound. The prepared acrylonitrile / urea inclusion compound was then cooled to the temperature of liquid nitrogen and dissolved in 2.0 × 10 15 Bq 60 The inclusion compound was then irradiated with Co γ-rays (8 kGy x 3 h). The inclusion compound was then removed from the γ-rays and the temperature was raised to -100°C to allow the chain growth reaction. After 4 hours, cold methanol was added to the reaction system to dissolve and remove the urea, terminating the polymerization reaction. The residue was then filtered and repeatedly washed with distilled water and methanol until the unreacted monomer and urea were completely removed. Finally, the polymer was vacuum dried to obtain a white powder of highly isotactic polyacrylonitrile (isotactic fraction >99%).

[0085] The resulting highly isotactic polyacrylonitrile (2 g) and elemental sulfur (16 g) were added to ethanol and ball-milled for 3 hours. After drying, the resulting powder was heated at 300°C for 10 hours in a nitrogen gas atmosphere in a tube furnace to obtain the sulfur-based cathode material S@pPAN. The sulfur content in the material was 39.75 wt%, and the resulting conductivity was 7.3 × 10 -3 It was S / cm.

[0086] Battery assembly and testing: A sulfur cathode was prepared using the sulfur-based cathode material obtained in Example 11, and a lithium-sulfur secondary battery was assembled using lithium metal as the anode. The electrolyte was 1M LiPF6 / EC:DMC (1:1 volume ratio, EC: ethylene carbonate, DMC: dimethyl carbonate), and the charge / discharge cutoff voltage was 1-3 V (vs. Li + The initial reversible specific capacity under a 0.2 C rate condition was 607 mAh / g.

[0087] A sulfur cathode was prepared using the sulfur-based cathode material obtained in Example 11, and an aluminum-sulfur secondary battery was assembled using metallic aluminum as the anode. The electrolyte was NMBPBr / AlCl ionic liquid (1:1.3 molar ratio, NMBPBr: N-butyl-N-methyl-piperidinium bromide), and the charge / discharge cutoff voltage was 0.01 to 1.3 V (vs. Al 3+The initial reversible specific capacity under a 0.2 C rate condition was 607 mAh / g. [Example]

[0088] 10 g of acrylonitrile and 12 g of urea were homogeneously mixed and frozen at -60°C for 28 days to obtain an acrylonitrile / urea inclusion compound. The prepared acrylonitrile / urea inclusion compound was then cooled to the temperature of liquid nitrogen and dissolved in 2.0 × 10 15 Bq 60 The inclusion compound was then irradiated with Co γ-rays (8 kGy x 3 h). The inclusion compound was then removed from the γ-rays and the temperature was raised to -100°C to allow the chain growth reaction. After 16 hours, cold methanol was added to the reaction system to dissolve and remove the urea, terminating the polymerization reaction. The residue was then filtered and repeatedly washed with distilled water and methanol until the unreacted monomer and urea were completely removed. Finally, the polymer was vacuum dried to obtain a white powder of highly isotactic polyacrylonitrile (isotactic fraction >99%).

[0089] The resulting highly isotactic polyacrylonitrile (2 g) and elemental sulfur (16 g) were added to ethanol and ball-milled for 3 hours. After drying, the resulting powder was heated at 300°C for 10 hours in a nitrogen gas atmosphere in a tube furnace to obtain the sulfur-based cathode material S@pPAN. The sulfur content in the material was 41.76 wt%, and the resulting conductivity was 6.5 × 10 -3 It was S / cm.

[0090] Battery assembly and testing: A sulfur cathode was prepared using the sulfur-based cathode material obtained in Example 12, and a lithium-sulfur secondary battery was assembled using lithium metal as the anode. The electrolyte was 1M LiPF6 / EC:DMC (1:1 volume ratio, EC: ethylene carbonate, DMC: dimethyl carbonate), and the charge / discharge cutoff voltage was 1-3 V (vs. Li + The initial reversible specific capacity under a 0.2 C rate condition was 647 mAh / g.

[0091] A sulfur cathode was prepared using the sulfur-based cathode material obtained in Example 12, and a sodium-sulfur secondary battery was assembled using sodium metal as the anode. The electrolyte was 1M NaPF6 / EC:DMC (1:1 volume ratio, EC:ethylene carbonate, DMC:dimethyl carbonate), and the charge / discharge cutoff voltage was 0.7 to 2.7 V (vs. Na + The initial reversible specific capacity under the 0.1 C rate condition was 588 mAh / g. [Example]

[0092] 10 g of acrylonitrile and 12 g of urea were homogeneously mixed and frozen at -60°C for 28 days to obtain an acrylonitrile / urea inclusion compound. The prepared acrylonitrile / urea inclusion compound was then cooled to the temperature of liquid nitrogen and dissolved in 2.0 × 10 15 Bq 60 The inclusion compound was then irradiated with Co γ-rays (8 kGy x 3 h). The inclusion compound was then removed from the γ-rays and the temperature was raised to -100°C to allow the chain growth reaction. After 48 h, cold methanol was added to the reaction system to dissolve and remove the urea, terminating the polymerization reaction. The residue was then filtered and repeatedly washed with distilled water and methanol until the unreacted monomer and urea were completely removed. Finally, the polymer was vacuum dried to obtain a white powder of highly isotactic polyacrylonitrile (isotactic fraction >99%).

[0093] The resulting highly isotactic polyacrylonitrile (2 g) and elemental sulfur (16 g) were added to ethanol and ball-milled for 3 hours. After drying, the resulting powder was heated at 300°C for 10 hours in a nitrogen gas atmosphere in a tube furnace to obtain the sulfur-based cathode material S@pPAN. The sulfur content in the material was 42.69 wt%, and the resulting conductivity was 5.5 × 10 -3 S / cm.

[0094] Battery assembly and testing: A sulfur cathode was prepared using the sulfur-based cathode material obtained in Example 13, and a lithium-sulfur secondary battery was assembled using lithium metal as the anode. The electrolyte was 1M LiPF6 / EC:DMC (1:1 volume ratio, EC: ethylene carbonate, DMC: dimethyl carbonate), and the charge / discharge cutoff voltage was 1-3 V (vs. Li+ The initial reversible specific capacity under a 0.2 C rate condition was 661 mAh / g.

[0095] A sulfur cathode was prepared using the sulfur-based cathode material obtained in Example 13, and a potassium-sulfur secondary battery was assembled using potassium metal as the anode. The electrolyte was 1M KPF6 / EC:DMC (1:1 volume ratio, EC:ethylene carbonate, DMC:dimethyl carbonate), and the charge / discharge cutoff voltage was 0.9 to 2.9 V (vs. K). + The initial reversible specific capacity under a 0.1 C rate condition was 560 mAh / g.

[0096] The above-described embodiments are described to facilitate understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to the embodiments and can apply the general principles described herein to other embodiments without any creative effort. Therefore, the present invention is not limited to the above-described embodiments. Any changes and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention are within the scope of protection of the present invention.

Claims

1. The method includes the steps of: using highly isotactic polyacrylonitrile as a precursor, mixing it with elemental sulfur, and then heating it to cause a chemical reaction to form a highly conductive sulfur-based positive electrode material for secondary batteries; A method for producing a highly conductive sulfur-based positive electrode material for a secondary battery, wherein the highly isotactic polyacrylonitrile is polyacrylonitrile having an isotactic fraction of 40 to 99%.

2. 2. The method for producing a highly conductive sulfur-based positive electrode material for secondary batteries according to claim 1, wherein the highly isotactic polyacrylonitrile is polyacrylonitrile having an isotactic fraction of 50 to 90%.

3. 2. The method for producing a highly conductive sulfur-based positive electrode material for secondary batteries according to claim 1, wherein the mass ratio of the elemental sulfur to the highly isotactic polyacrylonitrile is 2 to 16:

1.

4. 2. The method for producing a highly conductive sulfur-based positive electrode material for secondary batteries according to claim 1, wherein the heating conditions for the chemical reaction are heating to 250 to 450°C and maintaining the temperature for 1 to 16 hours.

5. 2. The method for producing a highly conductive sulfur-based positive electrode material for secondary batteries according to claim 1, wherein the sulfur content in the sulfur-based positive electrode material for secondary batteries is 35 to 80 wt %.

6. 2. The method for producing a highly conductive sulfur-based positive electrode material for secondary batteries according to claim 1, wherein the sulfur content is 40 to 70 wt %.

7. 2. The method for producing a highly conductive sulfur-based positive electrode material for secondary batteries according to claim 1, wherein the shielding gas used in the heating and chemical reaction is one of nitrogen gas and argon gas.

8. 8. A method for producing a secondary battery, comprising the step of producing a highly conductive sulfur-based positive electrode material for a secondary battery by the method for producing a highly conductive sulfur-based positive electrode material for a secondary battery according to claim 1.

9. 9. The method for producing a secondary battery according to claim 8, wherein the negative electrode of the secondary battery is made of lithium, sodium, potassium, magnesium, calcium or aluminum.

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