KR20230027580A - Method for sulfur-carbon composite and sodium-sulfur battery including the composite - Google Patents

Abstract

A sulfur-carbon composite manufacturing method and a sodium-sulfur battery including the composite are provided. The sulfur-carbon composite is manufactured by mixing solid sulfur (S_8) and phthalic acid or phthalate to form a mixture and heat-processing the mixture in a reducing atmosphere to carbonize the phthalic acid or the phthalate to be carbon and impregnate sulfur into the carbon.

Description

Method for manufacturing sulfur-carbon composite and sodium-sulfur battery including the composite {Method for sulfur-carbon composite and sodium-sulfur battery including the composite}

The present invention relates to a sodium-sulfur battery, and more particularly to a cathode for a sodium-sulfur battery.

Recently, with the rapid development of electronic devices and electric vehicles, the demand for secondary batteries is increasing. In particular, with the trend of miniaturization and weight reduction of portable electronic devices, there is a growing demand for secondary batteries having high energy densities that can meet the trend.

A lithium-sulfur battery among secondary batteries uses a sulfur-based compound having a sulfur-sulfur combination as a cathode active material and a carbon-based material in which lithium ions are intercalated and deintercalated as a cathode active material. am. In the anode of such a lithium-sulfur battery, the oxidation number of sulfur decreases as the bond between sulfur is broken during the reduction reaction (during discharge), and the oxidation number of sulfur increases during the oxidation reaction (during charging) to form a bond between sulfur and sulfur again. Oxidation-reduction reactions are used to store and generate electrical energy.

These lithium-sulfur batteries have the advantage of being able to express high energy density per weight, and the element sulfur used in the cathode active material has high energy density compared to its mass, is inexpensive, and is harmless to the human body. have Therefore, as a next-generation secondary battery that will replace the lithium secondary battery market in the future, lithium-sulfur batteries are in the limelight, and are expected to exert great influence in, for example, large-capacity power storage devices (ESS) and drone markets.

However, lithium-sulfur batteries have limitations in that sulfur (lithium polysulfide) is eluted into the electrolyte during battery operation, and in some cases, the life span of the battery is shortened due to precipitation of lithium sulfide, and price competitiveness due to limited lithium resources. I have this lower problem.

Republic of Korea Patent Publication No. 10-2006-0023470

The problem to be solved by the present invention is to provide a cathode for a sodium-sulfur battery having high capacity and stable life characteristics, a manufacturing method thereof, and a sodium-sulfur battery including the same.

In order to achieve the above object, one aspect of the present invention provides a method for preparing a sulfur-carbon composite. First, a mixture is formed by mixing solid sulfur (S ₈ ) and phthalic acid or phthalate. The mixture is heat treated in a reducing atmosphere to carbonize the phthalic acid or phthalate to carbon and impregnate sulfur into the carbon to form a sulfur-carbon complex.

The phthalic acid may be terephthalic acid. Carbon obtained by carbonizing the phthalic acid or phthalate may be crystalline carbon. The crystalline carbon may have a crystal structure of fullerite C60. The phthalic acid or phthalate can be obtained by decomposing waste plastic, PET.

The mixture may further include PAN (Polyacrylonitrile).

In order to achieve the above object, another aspect of the present invention provides a sodium-sulfur battery manufacturing method. First, a positive electrode active material layer is prepared using the sulfur-carbon composite obtained through the sulfur-carbon composite manufacturing method. Assemble a battery including the positive active material layer, a negative active material layer in which an oxidation reaction of sodium occurs during discharge, and an electrolyte disposed between the positive active material layer and the negative active material layer.

The positive electrode active material layer may further include a conductive material and a binder. The electrolyte may be a sodium salt dissolved in an organic solvent.

According to the present invention, in preparing the sulfur-carbon composite used as a positive electrode active material, the carbon precursor is carbonized and sulfur is impregnated into the carbon at the same time to suppress the elution of polysulfide, thereby improving battery life. As crystalline carbon is obtained using phthalic acid or phthalate, the electrical activity of the sulfur-carbon composite can be improved. In addition, by further using PAN as a carbon precursor, it is possible to form a porous amorphous carbon region and also improve the electrical activity of the sulfur-carbon composite.

The technical effects of the present invention are not limited to those mentioned above, and other technical effects not mentioned will be clearly understood by those skilled in the art from the description below.

1 is a schematic cross-sectional view of a unit cell of a sodium-sulfur battery according to an embodiment of the present invention.
Figure 2a is an XRD (X-ray Diffraction) graph of a sulfur-carbon composite according to Preparation Examples A2 and A3 and a carbon composite according to Comparative Example A1, Figure 2b is a sulfur-carbon according to Preparation Examples A1 and Preparation Example A2 It is an XRD graph of the composite, and FIG. 2c is an XRD graph of the sulfur-carbon composite according to Preparation Example A4.
Figure 3a is a Raman graph of sulfur-carbon composites according to Preparation Examples A1 and A2, Figure 3b is a Raman graph of sulfur-carbon composites according to Preparation Example A4, Figure 3c is a sulfur-carbon composite according to Comparative Example A2 is the Raman graph of
4a and 4b are SEM (Scanning Electron Microscope) images of the sulfur-carbon composite powder according to Preparation Example A4.
5 is a SEM (Scanning Electron Microscope) image of a sulfur-carbon composite powder according to Preparation Example A2.
6 is a TEM (Transmission Electron Microscopy)-elemental mapping image of a sulfur-carbon composite powder according to Preparation Example A2.
7a and 7b show cyclic voltammetry (CV) curves for sulfur-carbon composite powders according to Preparation Example A2 and Preparation Example A1, respectively.
8 is a graph showing charge/discharge curves (a), a discharge capacity graph (b), and rate characteristics (c) in multiple cycles of half-cells according to Preparation Examples B1 and B2.
9 is a graph of first charge and discharge characteristics (a), rate characteristics (b), charge and discharge curves in multiple cycles (c), and discharge capacity in multiple cycles of half cells according to Preparation Examples B1 and B2 ( It is a graph showing d).

Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

While the present invention is susceptible to various modifications and variations, specific embodiments thereof are shown by way of illustration in the drawings and will be described in detail below. However, it is not intended to limit the present invention to the particular form disclosed, but rather the present invention includes all modifications, equivalents and substitutions consistent with the spirit of the present invention as defined by the claims.

1 is a schematic cross-sectional view of a unit cell of a sodium-sulfur battery according to an embodiment of the present invention.

Referring to FIG. 1 , a sodium-sulfur battery includes an anode active material layer 40, a cathode active material layer 10, and a separator 20 interposed therebetween. An electrolyte (not shown) may be disposed between the negative active material layer 40 and the positive active material layer 10 . In addition, the negative active material layer 40 may be disposed on the negative current collector 60 , and the positive active material layer 10 may be disposed on the positive current collector 50 .

The cathode current collector 50 is carbon paper (gas diffusion layer), nickel mesh (Ni mesh), stainless mesh (Stainless mesh), nickel foam (Ni foam), glass fiber (glass filter), aluminum foil, carbon nanotube layer or graphene layer.

The cathode active material layer 10 is a layer in which a sulfur reduction reaction occurs during battery discharge, and may contain a sulfur-carbon composite as a cathode active material.

The sulfur-carbon composite may be obtained by mixing a carbon precursor and solid sulfur (S ₈ ) and then performing heat treatment of carbonizing the carbon precursor. The sulfur-carbon complex obtained through this method can adsorb polysulfide generated during the sulfur reduction reaction and suppress the elution of polysulfide into the electrolyte. As a result, life characteristics of the battery can be greatly improved.

The carbon precursor may include phthalic acid or phthalate. The phthalic acid may be terephthalic acid (TPA), and the phthalate may be terephthalate. In addition, the carbon precursor may further include polyacrylonitrile (PAN). Phthalic acid or TPA (terephtalic acid) can be obtained by decomposing PET, a waste plastic. In this case, it is also possible to reduce resources by promoting recycling of waste plastics. Phthalic acid or phthalate and PAN may be included in a weight ratio of 2:1 to 1:2. In one example, phthalic acid or phthalate and PAN may be included in a weight ratio of 1:1.

In the sulfur-carbon composite manufacturing method, when the solid sulfur (S ₈ ) is 100 parts by weight, the carbon precursor may be used in an amount of 20 to 40, specifically 22 to 30 parts by weight.

A heat treatment for carbonizing the carbon precursor may exceed 200°C. As an example, it may be 250 to 500 ° C, specifically 300 ° C or higher. At this heat treatment temperature, the carbon precursor is sufficiently carbonized and at the same time the carbon adsorbs sulfur to form a sulfur-carbon complex in which carbon and sulfur are sufficiently dispersed. Oxygen derived from the carbon precursor may also be dispersed in the sulfur-carbon composite.

In the sulfur-carbon composite, carbon obtained by carbonizing the phthalic acid or phthalate may be crystalline carbon. The crystalline carbon may have a crystal structure of fullerite C60. This crystalline carbon may also have an I _G / _ID of 1 or more in a Raman spectrum. Meanwhile, carbon obtained by carbonizing PAN may be amorphous carbon. In this case, crystalline carbon may be dispersed in the amorphous carbon matrix. Also, in the sulfur-carbon composite, carbon may be porous carbon.

In addition, heat treatment for carbonizing the carbon precursor may be performed in an inert gas atmosphere, specifically, an argon atmosphere.

When only phthalic acid or phthalate is heat-treated, it becomes a light material that is easily dispersed, but when heat-treated in a state mixed with sulfur, sulfur is liquefied and phthalic acid or phthalate is not dispersed, and a strong bond is formed between phthalic acid or phthalate in liquefied sulfur and Alternatively, sulfur may be impregnated at the same time as the phthalate is carbonized. At this time, phthalic acid or phthalate forms platy carbon crystals, and sulfur may be impregnated into the carbon crystals. This may appear similarly when PAN is added along with phthalic acid or phthalate as a carbon precursor.

In this way, in preparing the sulfur-carbon composite used as a positive electrode active material, the battery life can be improved by suppressing the elution of polysulfide by impregnating sulfur into carbon simultaneously with carbonization of the carbon precursor, while phthalic acid or phthalic acid or As crystalline carbon is obtained using phthalate, the electrical activity of the sulfur-carbon composite can be improved. In addition, by further using PAN as a carbon precursor, it is possible to form a porous amorphous carbon region and also improve the electrical activity of the sulfur-carbon composite.

The positive electrode active material layer 10 may further contain a conductive material and a binder. The conductive material may be a carbon material such as natural graphite, artificial graphite, cokes, carbon black, carbon nanotubes, or graphene. The binder is a thermoplastic resin, for example, a fluororesin such as polyvinylidene fluoride, polytetrafluoroethylene, tetrafluoroethylene, a vinylidene fluoride copolymer, hexafluoropropylene, and/or a polyolefin resin such as polyethylene and polypropylene. can include

The anode active material layer 40 may be formed of sodium metal or a sodium alloy as an electrode in which an oxidation reaction of sodium occurs during discharging of the battery. In one example, the negative active material layer 40 may be a sodium foil or a layer including conductive carbon impregnated with sodium ions or sodium metal. As an example, it may be a porous carbon layer impregnated with sodium ions or sodium metal. In this case, the porous carbon may be hard carbon, soft carbon, graphene, or carbon nanotubes.

The anode current collector 60 may include carbon paper (gas diffusion layer), nickel mesh (Ni mesh), stainless mesh (Stainless mesh), nickel foam (Ni foam), glass fiber (glass filter), carbon nanotube layer or graphite It may be a pinned layer. However, the negative electrode active material layer 40 is not limited thereto and may serve as the negative electrode current collector 60 .

The separator 20 separates or insulates the positive active material layer 10 and the negative active material layer 40 from each other and enables sodium ions to be transported between the positive active material layer 10 and the negative active material layer 40. can The separator 20 may be porous and made of a non-conductive or insulating material. Specifically, the separator 20 may be a material having a form such as a porous film made of a material such as a polyolefin resin such as polyethylene or polypropylene, a fluororesin, or a nitrogen-containing aromatic polymer, a nonwoven fabric, or a woven fabric.

The electrolyte is a liquid or solution-phase electrolyte, and may be a non-aqueous electrolyte, that is, a sodium salt dissolved in an organic solvent.

The organic solvent may be an aprotic solvent, specifically, an ether-based solvent. The ether-based solvent is an alkylene glycol dialkyl ether-based solvent, specifically, methylene glycol dimethyl ether (methylene glycol dimehtyl ether or dimethoxymethane), propylene glycol dimethyl ether (propylene glycol methyl ether or 1,2-dimethoxypropane), EGDE ( Ethylene glycol diethyl ether), DEGDME (diethylene glycol dimethyl ether), DEGDEE (diethylene glycol diethyl ether), triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, or these may be a combination of These solvents are less flammable and can improve battery safety.

The sodium salt is an ion containing a sodium ion, specifically, an imide-based sodium salt, more specifically, a sodium bissulfonyl imide salt, such as NaN(CF ₃ SO ₂ ) ₂ (NaTFSI), NaN(C ₂ F ₅ SO ₂ ) ₂ , NaN(CF ₃ SO ₂ ) (C ₂ F ₅ SO ₂ ) or NaN(SO ₂ F) ₂ (NaFSI). The sodium salt may be contained in a concentration of 0.3 to 2M, 0.5 to 1.5M as a rescue, and more specifically, 0.8 to 1.2M.

Hereinafter, in order to explain the present invention in more detail, preferred experimental examples according to the present invention will be described in more detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms.

Sulfur-carbon composite preparation examples

<Preparation Example A1: Preparation of sulfur-carbon composite from S+PAN>

Sulfur powder (S ₈ powder) and DPAN (Dehydrogenated Polyacrylonitrile) were quantified at a weight ratio of 4:1, stirred, and heat-treated for 3 hours in an inert gas atmosphere at 300 ° C. to prepare a sulfur-carbon composite.

<Preparation Example A2: Preparation of sulfur-carbon composite from S+PAN+TPA>

TPA (terephtalic acid) and DPAN (dehydrogenated polyacrylonitrile) were quantified in a weight ratio of 1:1 and stirred to obtain a mixed powder. Thereafter, the sulfur powder (S ₈ powder) and the mixed powder were mixed in a weight ratio of 4: 1 (sulfur: TPA: DPAN = 4: 0.5: 0.5), stirred, and then heat-treated for 3 hours in an inert gas atmosphere at 300 ° C. A sulfur-carbon composite was prepared.

<Preparation Example A3: Preparation of sulfur-carbon composite from S/PAN/TPA>

A sulfur-carbon composite was prepared in the same manner as in Preparation Example A2, except for heat treatment in an inert gas atmosphere at 200 °C.

<Preparation Example A4: Preparation of sulfur-carbon composite from S+TPA>

의 불활성 기체 분위기에서 3시간동안 열처리하여 황-탄소 복합체를 제조하였다.TPA (terephtalic acid) and sulfur powder (S8 powder) were quantified in a weight ratio of 1: 1 and stirred to obtain a mixed powder, and then the mixed powder was 300

A sulfur-carbon composite was prepared by heat treatment in an inert gas atmosphere for 3 hours.

<Preparation Example A5: Addition of TPA after Preparation of Sulfur-Carbon Composite from S+PAN>

A sulfur-carbon composite was prepared by mixing TPA (terephtalic acid) with the sulfur-carbon composite obtained in Preparation Example A1 at a weight ratio of 4:1.

<Comparative Example A1: Preparation of carbon composite from PAN+TPA>

TPA (terephtalic acid) and DPAN (dehydrogenated polyacrylonitrile) were quantified and stirred at a weight ratio of 1:1 to obtain a mixed powder, and then heat-treated in an inert gas atmosphere at 300 °C for 3 hours to obtain a carbon composite.

<Comparative Example A2: Preparation of sulfur-carbon composite from S + phthalimide acid>

A sulfur-carbon composite was prepared in the same manner as in Preparation Example A4, except that phthalimide acid was used instead of terephtalic acid (TPA).

Half cell manufacturing examples

<Production Example B1>

After mixing the sulfur-carbon composite obtained in Preparation Example A1, super p carbon as a conductive agent, and PVdF (polyvinylidene difluoride) as a binder in a weight ratio of 70:20:10 in NMP (N-Methyl-2-pyrrolidone), aluminum It was cast on a foil and dried at 80° C. to prepare a positive electrode active material layer on the aluminum foil. At this time, the loading amount of the positive electrode active material layer was 4-5 mg/cm ³ . A coin cell of R2032 type including a cathode active material layer formed on the aluminum foil as a cathode current collector, a cathode of sodium foil, and an electrolyte (0.5M NaPF ₆ in propylene carbonate (PC) + 2% fluorinated ethylene carbonate (FEC)) manufactured.

<Production Example B2>

A coin cell was manufactured in the same manner as in Preparation Example B1, except that the sulfur-carbon composite obtained in Preparation Example A2 was used instead of the sulfur-carbon composite obtained in Preparation Example A1.

<Production Example B3>

Preparation Example except for using the sulfur-carbon composite obtained in Preparation Example A5 instead of the sulfur-carbon composite obtained in Preparation Example A1, super p carbon as a conductive agent, and polyvinylidene difluoride (PVdF) as a binder in a weight ratio of 70:20:10 A coin cell was manufactured using the same method as in B1.

The contents described in Preparation Examples A1, A2, A3, A5, and A5, Comparative Examples A1 and A2, and the contents described in Preparation Examples B1, B2, and B3 are summarized in Table 1 below.

Sulfur-carbon composite production example Semi-cell manufacturing example ingredient
(weight ratio) for carbonization
heat treatment temperature Additional materials after heat treatment Production Example A1 S+PAN (4:1) 300℃ - Preparation Example B1 Production Example A2 S+PAN+TPA (4:0.5:0.5) 300℃ - Production Example B2 Production Example A3 S+PAN+TPA(4:0.5:0.5) 200℃ - - Manufacturing example A4 S+TPA (1:1) 300℃ - - Manufacturing example A5 S+PAN (4:1) 300℃ TPA Production Example B3 Comparative Example A1 PAN+TPA (1:1) 300℃ - - Comparative Example A2 S+phthalimide acid (1:1) 300℃ - -

Figure 2a is an XRD (X-ray Diffraction) graph of a sulfur-carbon composite according to Preparation Examples A2 and A3 and a carbon composite according to Comparative Example A1, Figure 2b is a sulfur-carbon according to Preparation Examples A1 and Preparation Example A2 It is an XRD graph of the composite, and FIG. 2c is an XRD graph of the sulfur-carbon composite according to Preparation Example A4.

Referring to FIG. 2a, when heat treatment is performed at 200 degrees after mixing sulfur and carbon precursors PAN and TPA (Production Example A3), peaks corresponding to sulfur are seen as they are, indicating that sulfur remains as it is. However, since sulfur is not confirmed when the heat treatment temperature is 300 degrees, it can be assumed that sulfur is impregnated into carbon as carbonization of the carbon precursor is completed. On the other hand, when heat treatment was performed at 300 degrees after mixing PAN and TPA, which are carbon precursors, without adding sulfur (Comparative Example A1), carbonization was seen to have progressed, but sulfur was impregnated into carbon. Unlike Preparation Example A2, shows a peak at the position From this, when sulfur is impregnated into carbon, it seems that 2θ shows a peak near 25 degrees in XRD.

Referring to FIG. 2B, when heat treatment is performed at 300 degrees after mixing sulfur and carbon precursors PAN and TPA (Preparation Example A2) and when heat treatment is performed at 300 degrees after mixing sulfur and PAN (Preparation Example A1) All of them showed peaks at similar positions, such as showing a peak at 2θ near 25 degrees in XRD. Accordingly, it was assumed that sulfur was impregnated into the carbon in both preparations.

Referring to FIG. 2c, when sulfur and TPA, a carbon precursor, were mixed at a weight ratio of 1:1 and then heat treated at 300 degrees (Preparation Example A4), XRD peaks similar to those of fullerite C60 were shown.

Figure 3a is a Raman graph of sulfur-carbon composites according to Preparation Examples A1 and A2, Figure 3b is a Raman graph of sulfur-carbon composites according to Preparation Example A4, Figure 3c is a sulfur-carbon composite according to Comparative Example A2 is the Raman graph of

Referring to FIG. 3A, the sulfur-carbon composites according to Preparation Examples A1 and A2 show peaks of sulfur along with carbon, indicating that carbon and sulfur coexist. At this time, the sulfur-carbon composite according to Preparation Example A1 has an intensity ratio of I _G /I _D of the G-band to the D-band of about 0.5, and the sulfur-carbon composite according to Preparation Example A2 has I _G /I Since _D is about 0.9, it can be seen that the sulfur-carbon composite according to Preparation Example A2 has better carbon crystallinity as it further includes TPA as a carbon precursor.

Referring to FIG. 3B, the sulfur-carbon composite according to Preparation Example A4, that is, when sulfur and TPA are mixed and then heat-treated, is the intensity ratio of the G-band to the D-band, I _G /I _D is about 3.5 - 4, so it can be seen that the carbon crystallinity is very excellent.

Referring to FIG. 3c, the sulfur-carbon composite according to Comparative Example A2, that is, the sulfur-carbon composite obtained by mixing sulfur and phthalimide acid and then heat-treating, is the intensity ratio of the G-band to the D-band, I _G / It can be seen that I _D indicates very low carbon crystallinity of about 0.4.

When simultaneously referring to FIGS. 3b and 3c , it can be seen that very good carbon crystallinity can be obtained when TPA is used compared to when phthalimide acid is used.

4a and 4b are SEM (Scanning Electron Microscope) images of the sulfur-carbon composite powder according to Preparation Example A4.

Referring to Figures 4a and 4b, the sulfur-carbon composite according to Preparation Example A4, that is, when sulfur and TPA were mixed and then heat-treated, the particle shape of the sulfur-carbon composite was found to be plate-like. It was assumed that when TPA was carbonized by heat treatment, plate-shaped particles were generated, and sulfur was impregnated into the plate-shaped particles.

5 is a SEM (Scanning Electron Microscope) image of a sulfur-carbon composite powder according to Preparation Example A2.

Referring to FIG. 5, it can be seen that the shape of the particles of the sulfur-carbon composite powder has a polygonal shape, and has a shape in which spherical small particles are aggregated and compounded on the surface.

6 is a TEM (Transmission Electron Microscopy)-elemental mapping image of a sulfur-carbon composite powder according to Preparation Example A2.

Referring to FIG. 6 , it can be seen that sulfur and carbon are uniformly dispersed and the complexation is almost completely performed. In addition, it can be seen that oxygen originating from the carbon precursor is also dispersed in the sulfur-carbon composite particles.

The properties of the sulfur-carbon composites according to Preparation Example A1 and Preparation Example A5 are shown in Table 2 below.

average pore diameter total pore volume total surface area Tab Density Preparation Example A1 (heat treatment after mixing S + PAN) 2.182 nm 2.494 cm ³ g ^-1 4.571 m ² g ^-1 ~0.52 g cm ^-3 Preparation Example A5 (S+PAN after mixing and heat treatment
add TPA) 2.105 nm 2.294 cm ³ g ^-1 4.450 m ² g ^-1 ~0.71 g cm ^-3

7a and 7b show cyclic voltammetry (CV) curves for sulfur-carbon composite powders according to Preparation Example A2 and Preparation Example A1, respectively.

7a and 7b, when heat treatment is performed at 300 degrees after mixing sulfur and PAN (Production Example A1), compared to when heat treatment is performed at 300 degrees after mixing sulfur and carbon precursors PAN and TPA (Production Example It can be seen that the sulfur-carbon composite of A2) exhibits better electrochemical reactivity.

8 is a graph showing charge/discharge curves (a), a discharge capacity graph (b), and rate characteristics (c) in multiple cycles of half-cells according to Preparation Examples B1 and B2. 9 is a graph of first charge and discharge characteristics (a), rate characteristics (b), charge and discharge curves in multiple cycles (c), and discharge capacity in multiple cycles of half cells according to Preparation Examples B1 and B2 ( It is a graph showing d).

In this evaluation, 1C was 1200 mAhg ^-1 , and charging and discharging of the battery was repeated at a rate in the range of 0.05C-5C in a voltage range of 0.6 - 2.8 V. In addition, in FIGS. 8(a) and 8(b), 50 cycles were performed at a current density of 0.1C for a plurality of cycles. In FIG. 8(c), 3 cycles were performed for each current density in stages from a current density of 0.05C to 5C.

Referring to FIG. 8, when the sulfur-carbon composite obtained by mixing sulfur and PAN and heat treatment at 300 degrees was used as a cathode active material (Preparation Example B1), the initial capacity was only 424.67 mAhg ^-1 , but compared to sulfur and When the sulfur-carbon composite obtained by mixing PAN and TPA, which are carbon precursors, and heat treatment at 300 degrees was used as a cathode active material (Preparation Example B2), it can be seen that the initial capacity is greatly improved to 1306.99 mAhg ^-1 , and further It can be seen that excellent rate performance (capacity was much higher at each current density) and life characteristics (capacity retention rate: 69.4% in the case of Preparation Example B1 and 79.81% in the case of Preparation Example B2).

Referring to FIG. 9, compared to the case where the sulfur-carbon composite obtained by mixing sulfur and PAN and heat treatment at 300 degrees was used as a cathode active material (Production Example B1), heat treatment was performed at 300 degrees after mixing sulfur and PAN. In the case of using the obtained sulfur-carbon composite and non-heat treated TPA (Preparation Example B3), it was found to have better charge and discharge characteristics, rate performance, and lifespan characteristics.

Referring to FIGS. 8 and 9 at the same time, compared to the case of using the sulfur-carbon composite obtained by mixing sulfur and PAN and then heat-treating at 300 degrees and non-heat-treated TPA (Preparation Example B3), the sulfur and carbon precursor PAN When the sulfur-carbon composite obtained by mixing and TPA and heat treatment at 300 degrees was used as a cathode active material (Preparation Example B2), it can be seen that the initial capacity is better, and the rate performance and lifespan characteristics are better. can

In the above, the present invention has been described in detail with preferred embodiments, but the present invention is not limited to the above embodiments, and various modifications and changes are made by those skilled in the art within the technical spirit and scope of the present invention. this is possible

Claims (9)

After forming a mixture by mixing solid sulfur (S ₈ ) and phthalic acid or phthalate,
Heat-treating the mixture in a reducing atmosphere to carbonize the phthalic acid or phthalate to carbon and impregnate sulfur into carbon to form a sulfur-carbon complex,
Sulfur-carbon composite manufacturing method. According to claim 1,
The phthalic acid is terephthalic acid, sulfur-carbon composite manufacturing method. According to claim 1,
The carbon obtained by carbonizing the phthalic acid or phthalate is crystalline carbon, sulfur-carbon composite manufacturing method. According to claim 3,
The crystalline carbon has a crystal structure of fullerite C60, sulfur-carbon composite manufacturing method. According to claim 1,
The phthalic acid or phthalate is obtained by decomposing waste plastic PET, sulfur-carbon composite manufacturing method. According to claim 1,
The mixture further comprises PAN (Polyacrylonitrile), sulfur-carbon composite manufacturing method. Preparing a positive electrode active material layer using the sulfur-carbon composite obtained through the method of preparing a sulfur-carbon composite according to any one of claims 1 to 6; and
Assembling a battery including the positive electrode active material layer, a negative electrode active material layer in which an oxidation reaction of sodium occurs during discharge, and an electrolyte disposed between the positive electrode active material layer and the negative electrode active material layer, manufacturing a sodium-sulfur battery method. According to claim 7,
The cathode active material layer further comprises a conductive material and a binder, sodium-sulfur battery manufacturing method. According to claim 7,
The electrolyte is a method of manufacturing a sodium-sulfur battery in which a sodium salt is dissolved in an organic solvent.

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