KR100398468B1 - Sulfur positive electrode for lithium battery and it's fabrication method - Google Patents

Abstract

The present invention relates to a sulfur positive electrode for a lithium battery and a manufacturing method thereof.

In a sulfur positive electrode for a lithium battery comprising a mixture of an active material consisting of a sulfur-based component and a polymer electrolyte used as a battery conductive material and an ion conductor, the total amount of the mixture is 100% by weight. It has a content of 60 to 80% by weight, the sulfur electrode is a sulfur positive electrode for lithium batteries having a discharge capacity of 70% or more of the theoretical discharge capacity (1675mAh / sulfur g); In the method for producing a sulfur positive electrode for a lithium battery comprising a mixture of an active material consisting of a sulfur-based component and a polymer electrolyte used as a battery conductive material and an ion conductor, when the total mixture is 100% by weight Mixing a mixture consisting of 60 to 80% by weight of the base component, 8 to 35% by weight of polyethylene oxide (PEO) and 15 to 30% by weight of carbon with an acentonitile (ACN); and the mixed mixture It relates to a method for manufacturing a sulfur positive electrode for a lithium battery comprising the step of manufacturing a sulfur electrode in a thin film form.

Therefore, the present invention includes a 60 to 80% by weight sulfur base component, the positive electrode for a lithium battery in which the content of PEO and carbon contained in the sulfur electrode is properly adjusted, the current collector may exhibit excellent discharge capacity, and also can exhibit a discharge capacity It is an excellent invention in the lithium sulfur battery manufacturing industry because the electrode can be easily manufactured by directly manufacturing the positive electrode to the current collector to which the unevenness is applied.

Description

Sulfur positive electrode for lithium battery and manufacturing method thereof {Sulfur positive electrode for lithium battery and it's fabrication method}

The present invention relates to a sulfur positive electrode for a lithium battery and a method for manufacturing the same, and more specifically, containing a sulfur base component of 60 to 80% by weight, and can have an excellent discharge capacity by appropriately adjusting the content of PEO and carbon contained in the sulfur electrode. The present invention relates to a positive electrode for a lithium battery and a method of manufacturing the same.

As the miniaturization of electronic products and communication devices is rapidly progressing all over the world, and the necessity of electric vehicles is increasing, the development of secondary batteries used as mobile power sources for these products is actively progressing, and such battery performance is improved. This is greatly demanded. Accordingly, studies on batteries having a large discharge capacity or energy density, which are important factors of secondary battery performance, are being conducted.

Looking at the electrode, which is a factor that determines the performance of the secondary battery, the electrode material should first have a high energy density or discharge capacity per unit mass, have thermal and chemical stability within a certain temperature range, and have excellent oxidation / reduction. It must be reversible and have sufficient electrochemical electrical and ion conductivity. In addition, the electrode material should be non-toxic, inexpensive and readily available. Among them, the most important thing for the performance of the battery is the discharge capacity, that is, the energy density. In order to develop a secondary battery having excellent performance, an electrode having a large discharge capacity per unit weight (Ah / kg) must be developed.

However, in general, in the case of lead batteries, nickel / cadmium batteries, and nickel hybrid batteries used in electric vehicles, there are advantages in that they can be charged and discharged many times without deteriorating performance, but they have a relatively low energy density per unit mass. There is this. In addition, in the case of Ni / MH batteries which are generally used secondary batteries, the highest electrode capacity is about 500 mAh / g, which is magnesium-based, and in the case of Li batteries, V ₂ O ₅ shows the largest capacity, about 400 mAh / g or so. However, sulfur (S) is a very promising material as an electrode material because of its low atomic weight and low price. In particular, the Li / S battery pair has a theoretical energy density of 2800 Wh / kg (1675 mAh / g), which is much higher than other battery systems. Therefore, many researchers have tried to construct lithium secondary batteries using sulfur. Rauh et al. (RD Rauh, GFPerson and SB Brummer, J. Electrochem. Soc., 6, 1761-1766 (1977)) used a carbon electrode as an anode and dissolved sulfur in an organic electrolyte to construct a cell. Yamin (E.Peled and H. Yamin, J. Power Sources, 9, 281-287 (1983)) converted organic solvents to construct a cell. However, high discharge capacity could not be obtained due to the reaction of organic solvent and sulfur. In order to solve the problem of the organic solvent, a study using a solid polymer electrolyte has been conducted. In US Pat. No. 5,686,201, Chu et al. (MYChu, Okakland, Calif, US Patent No. 5,686,201), prepared a positive electrode of a lithium battery using 50wt% sulfur, 16wt% carbon, 34wt% (PEO) ₄₉ LiTFSi at 90 ℃ Energy densities of up to 1500 mAh / g.sulfur (750 mAh / g. Cathode) were obtained.

Cairns (D.Marmorstein, THYu, KAStiebel, FRMcLarnon, J.Hou, EJCairns, J. Power Sources, 89 p.219-226, 2000) are 75wt% sulfur, 7.5wt% carbon, 15wt% PEGDME 430 (mAh / g. Cathode, 570 mAh / g.sulfur) was obtained at 23 ° C. using / LiTFSi (30: 1) and 2.5 wt% PEO.

Hyo-Jun Ahn (Hyo-Jun Ahn, Patent Application No. 10-1999-0017811), etc., prepared a lithium battery positive electrode with a composition of 40 wt% sulfur, 19.2 wt%, 36 wt% PEO, and 4.8 wt% Li (CF ₃ SO ₃ ). The discharge capacity was about 1540 (mAh / g.sulfur) at 90 ° C.

However, in the previous study, when the Li / S battery was composed of up to 75wt% of sulfur and its discharge characteristics were examined, its utilization was low. Thus, to increase the content of sulfur to prepare the electrode. In the case of high sulfur electrodes, if the energy density per sulfur is the same, the energy density per positive electrode increases. Increasing the content of sulfur decreases the content of PEO (poly (ethylene oxide)), which is an ion conductor, and carbon, which is an electrical conductor. Sulfur is an electrical insulator, so the carbon in the electrical conductor must be adequate and PEO, an ion conductor, must also be above a certain amount for excellent discharge capacity. If the composition is not appropriate, the discharge capacity is reduced because PEO or carbon does not play a role. In addition, the reduction of PEO that acts as a binder lowers the mechanical strength of the electrode, making it brittle, making it difficult to manufacture the electrode. Therefore, how to adjust the composition ratio of the sulfur electrode at high content and how to maintain the proper mechanical strength of the electrode will determine the characteristics of the battery.

Sulfur electrode is a conductive powder such as carbon, graphite, copper, and nickel that can be used as sulfur and an electric conductor, and a polymer electrolyte that can be used as an ion conductor (PEO (Poly (ethylene oxide)), PAN (Polyacrylonitrile) , PVdF (Poly (vinylidene -fluoride)) should be mixed well.

Accordingly, an object of the present invention is to provide a method for manufacturing a high content sulfur electrode for a lithium secondary battery.

Another object of the present invention is to provide a sulfur electrode for a lithium battery, which exhibits excellent discharge capacity by appropriately constituting a composition of a sulfur electrode.

1 shows a discharge curve of a lithium battery composed of a positive electrode containing 60% by weight of sulfur prepared according to the present invention.

Figure 2 shows the discharge curve of a lithium battery containing 60% by weight of sulfur produced according to the present invention and the sulfur electrode according to the carbon content as a positive electrode.

Figure 3 shows the discharge curve of a lithium battery composed of a positive electrode containing 70% by weight of sulfur prepared by the present invention.

4 shows a discharge curve of a lithium battery composed of a positive electrode containing 80% by weight of sulfur prepared according to the present invention.

FIG. 5 shows a discharge curve of a lithium battery constructed by applying an unevenness to an aluminum foil of a current collector with a positive electrode containing 80 wt% sulfur and 10 wt% carbon prepared according to the present invention.

FIG. 6 illustrates a discharge curve of a lithium battery including 80 wt% sulfur prepared according to the present invention and using a sulfur electrode according to a carbon content as a positive electrode and applying an unevenness to an aluminum foil of a current collector.

FIG. 7 illustrates a discharge curve of a lithium battery in which a positive electrode containing 80 wt% sulfur and 10 wt% carbon prepared by the present invention is configured using an Al current collector.

The present invention relates to a sulfur positive electrode for a lithium battery comprising a mixture of an active material consisting of a sulfur-based component and a polymer electrolyte used as a battery conductive material and an ion conductor, wherein the sulfur is 100% by weight. The base component is 60 to 80% by weight, PEO (polyethylene oxide) 8 to 35% by weight to optimize the mechanical strength and electrical properties of the sulfur positive electrode; 15-30% by weight of carbon; And lithium salt 2 to 8 wt% of any one selected from LiCF ₃ SO _3, LiClO _4, LiBF _4, LiAsF _{4, and} LiPF ₆ , wherein the sulfur electrode is 70-100% of the theoretical discharge capacity (1675 mAh / g of sulfur). The present invention relates to a sulfur positive electrode for a lithium battery having a discharge capacity of. A sulfur positive electrode for a lithium battery comprising a mixture of an active material composed of a sulfur-based component and a polymer electrolyte used as a battery conductive material and an ion conductor. In the production method of, the content of the sulfur base component when the total mixture to 100% by weight has a 60 to 80% by weight, in order to optimize the mechanical strength and electrical properties of the sulfur positive electrode PEO (Polyethylene oxide) 8 35 wt%; 15-30% by weight of carbon; And mixing 2 to 8% by weight of a lithium salt of any one selected from LiCF ₃ SO _3, LiClO _4, LiBF _4, LiAsF _{4, and} LiPF _{6 with} Acentonitile (ACN); And a method of manufacturing a sulfur positive electrode for a lithium battery, comprising the steps of preparing the mixed mixture as a sulfur electrode in a thin film form. The sulfur positive electrode according to the present invention includes crystalline sulfur, amorphous sulfur, and CS (C: Sulfur active materials composed of sulfur base components such as carbon, S: sulfur), MS (M: transition metal, S: sulfur) and the like, metal or electric conductive materials such as carbon and graphite, and PEO (Poly (ethylene oxide)), It consists of a mixture of ionic conductors such as polyacrylonitrile (PAN) and poly (vinylidene fluoride) (PVD) -based solid polymer electrolytes, and has a discharge capacity of 80% or more of the theoretical discharge capacity (1675 mAh / gsulfur) at 90 ° C. .

When the content of each component is 100% by weight of the mixture as a whole, the content of the sulfur base component is 60 to 80% by weight, about 15 to 35% by weight of the electrically conductive material, 10 to 30% by weight of the ion conductor In percent.

In addition, the present invention was to increase the discharge efficiency by mixing the carbon, an electrically conductive material in an appropriate amount in the case of 80% by weight sulfur-containing positive electrode with a low sulfur content of the active material.

Therefore, the sulfur positive electrode may further include 5 to 20% by weight of polyethylene oxide (PEO) and 3 to 17% by weight of carbon in order to optimize mechanical strength, electrical conductivity and ionic conductivity.

In addition, in the case of a 60% by weight sulfur positive electrode, it is preferable to further include 8 to 35% by weight of polyethylene oxide (PEO) and 15 to 30% by weight of carbon in order to optimize the mechanical strength and electrical properties.

In the case of the 80% by weight sulfur positive electrode, it is preferable to further include 8 to 12% by weight of polyethylene oxide (PEO) and 10 to 12% by weight of carbon by optimizing the mechanical strength and electrical properties.

In addition, the sulfur positive electrode according to the present invention may further include a lithium salt such as LiCF ₃ SO _3, LiClO _4, LiBF _4, LiAsF _4, LiPF _{6 of} about 2 to 8% by weight in order to increase the conductivity of the ion conductor. Can be.

Looking at the manufacturing method of the present invention by process, 60%, 70%, 80% sulfur and electrically conductive materials carbon and ionic conductors PEO (polyethylene oxide) and Li salt mixed in ACN (Acentonitile) and stirred evenly dispersed over a day It was made. It was made into a film and dried at 50 DEG C in vacuum for at least 12 hours.

In addition, if manufactured by the same method as in the above and Chu et al. In the present invention, after the high-sulfur electrode is manufactured, the mechanical strength of the electrode is low, so that it is difficult to maintain the form of the sulfur film. Unevenness was given to the current collector to give adhesion between the current collector and the sulfur electrode. The lithium battery was constructed by using a sulfur positive electrode prepared in the present invention, a Li metal ribbon as a negative electrode, and a polyethylene oxide (PEO) electrolyte as a polymer electrolyte.

In addition, in order to investigate the discharge capacity of the sulfur electrode according to the present invention, the discharge test of the lithium battery prepared as described above at 90 ℃, to obtain a discharge capacity of 1489mAh / g (S) with a 60% sulfur electrode.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1 Preparation of Sulfur-Containing Positive Electrode of 60% by Weight

60 wt% sulfur, 20 wt% carbon, 17 wt% PEO, and 3 wt% Li salt were mixed and dissolved in acetonitrile (ACN) and stirred for at least one day. The homogeneously mixed mixture was prepared in a thin film form by glass casting, and then dried in a vacuum at 50 ° C. for at least 12 hours to remove moisture in the electrode, thereby preparing an electrode.

Example 2 70 wt% sulfur-containing positive electrode

In the same manner as in Example 1, a sulfur positive electrode consisting of 70% by weight sulfur, 15% by weight carbon, 12.25% by weight PEO, 2.25% by weight Li salt was prepared.

Example 3 Preparation of 80 wt% Sulfur-Containing Positive Electrode

In the same manner as in Example 1, a sulfur positive electrode consisting of 80% by weight sulfur, 10% by weight carbon, 8.5% by weight PEO, 1.5% by weight Li salt was prepared.

Example 4 80 wt% sulfur-containing positive electrode was prepared by mixing 5 wt% carbon using a current collector

In the same manner as in Example 1, after preparing a sulfur positive electrode consisting of 80% by weight sulfur, 5% by weight carbon, 13% by weight polyethylene oxide (PEO), 2% by weight Li salt is used as a current collector instead of a glass plate Glass casting was performed on aluminum foil.

Example 5 80 wt% sulfur-containing positive electrode was prepared by mixing 10 wt% carbon using a current collector

In the same manner as in Example 4, a sulfur positive electrode made of 80 wt% sulfur, 10 wt% carbon, 8 wt% polyethylene oxide (PEO), and 2 wt% Li salt was prepared.

Example 6 80 wt% sulfur-containing positive electrode was prepared by mixing 15 wt% carbon using a current collector

In the same manner as in Example 4, a sulfur positive electrode consisting of 80% by weight sulfur, 15% by weight carbon, 3% by weight PEO (polyethylene oxide), 2% by weight Li salt was prepared.

Example 7 80 wt% sulfur-containing positive electrode was prepared by mixing 10 wt% carbon using a current collector

In the same manner as in Example 1, after fabricating a sulfur positive electrode consisting of 80% by weight sulfur, 10% by weight carbon, 8% by weight polyethylene oxide (PEO), 2% by weight Li salt after the Al current collector (current instead of a glass plate) Glass casting on the collector).

Example 8 Lithium Battery with Sulfur Electrode According to the Present Invention (60 wt% Sulfur-Containing Electrode)

In order to examine the discharge characteristics of the sulfur positive electrode according to the present invention, a lithium battery comprising a sulfur positive electrode / polymer solid electrolyte / negative electrode according to the present invention was prepared. The positive electrode was prepared in Example 1, the negative electrode was used a lithium metal ribbon, the electrolyte was used a polyethylene oxide (PEO) film.

Discharge test was carried out at 90 ℃, discharge current was 50mA / g (S). Figure 1 shows the discharge curve as a result of the experiment, the discharge capacity was found to be about 1490mAh / g (S) at 90 ℃, the discharge voltage is composed of two flat sections of 2.4V and 2.1V. Thus, while maintaining an appropriate discharge voltage at 90 degreeC, the high discharge capacity which is about 89% of the theoretical discharge capacity of 1675 mAh / g is shown.

Example 9 Lithium Battery with Sulfur Electrode according to the Present Invention (70 wt% Sulfur-Containing Electrode)

A lithium battery was manufactured in the same manner as in Example 8 using the sulfur electrode prepared in Example 2, and a discharge test was performed. FIG. 3 shows the results, showing a discharge curve shape similar to that of Example 7, but with a discharge capacity of about 1337 mAh / g (about 80% of theory), which is slightly lower than that of Example 7. It is shown.

Example 10 Lithium Battery (80 wt% Sulfur-Containing Electrode) Having a Sulfur Electrode according to the Present Invention

A lithium battery was manufactured in the same manner as in Example 8 using the sulfur electrode prepared in Example 3, and a discharge test was performed. 4 shows the result, and the discharge capacity shows a discharge capacity of about 883 mAh / g (about 53% of theory).

Example 11 Lithium Battery with Sulfur Electrode According to the Present Invention (80 wt% Sulfur, 5 wt% Carbon-Containing Electrode)

The lithium battery was manufactured in the same manner as in Example 8 using the sulfur electrode prepared according to Example 4, and discharge experiments were performed.

Example 12 A lithium battery having a sulfur electrode according to the present invention (80 wt% sulfur, 10 wt% carbon-containing electrode)

A lithium battery was manufactured in the same manner as in Example 8 using the sulfur electrode prepared in Example 5, and a discharge test was performed. FIG. 5 shows the result, and the discharge capacity shows a discharge capacity of about 1047 mAh / g (about 63% of theory).

[Example 13] A lithium battery having a sulfur electrode according to the present invention (80 wt% sulfur, 15 wt% carbon-containing electrode)

A lithium battery was manufactured in the same manner as in Example 8 using the sulfur electrode prepared in Example 6, and a discharge test was performed.

Example 14 Lithium Battery (80 wt% Sulfur-Containing Electrode) Having a Sulfur Electrode according to the Present Invention

A lithium battery was manufactured in the same manner as in Example 8 using the sulfur electrode prepared according to Example 7, and a discharge test was performed. 7 shows the result, and the discharge capacity shows a discharge capacity of about 1026 mAh / g (about 61% of theory).

As described in the above embodiment, the positive electrode for a lithium battery including a sulfur base component of 60 to 80% by weight, and appropriately adjusting the content of PEO and carbon included in the sulfur electrode exhibits excellent discharge capacity. In addition, it is a very useful invention in the lithium sulfur battery manufacturing industry because there is an effect that it is possible to simply manufacture the electrode by directly manufacturing the positive electrode to the current collector that can exhibit the discharge capacity or the uneven current collector.

Claims (12)

In a sulfur positive electrode for a lithium battery, comprising a mixture of an active material consisting of a sulfur-based component and a polymer electrolyte used as a battery conductive material and an ion conductor, When the total amount of the mixture to 100% by weight of the sulfur base component content of 60 to 80% by weight, PEO (polyethylene oxide) 8 to 35% by weight in order to optimize the mechanical strength and electrical properties of the sulfur positive electrode; 15-30% by weight of carbon; And lithium salt 2 to 8 wt% of any one selected from LiCF ₃ SO _3, LiClO _4, LiBF _4, LiAsF _{4, and} LiPF ₆ , wherein the sulfur electrode is 70-100% of the theoretical discharge capacity (1675 mAh / g of sulfur). Sulfur positive electrode for a lithium battery, characterized in that it has a discharge capacity of. delete delete delete delete delete In the method for producing a sulfur positive electrode for a lithium battery comprising a mixture of an active material consisting of a sulfur-based component and a polymer electrolyte used as a battery conductive material and an ion conductor, When the total amount of the mixture to 100% by weight of the sulfur base component content of 60 to 80% by weight, PEO (polyethylene oxide) 8 to 35% by weight in order to optimize the mechanical strength and electrical properties of the sulfur positive electrode; 15-30% by weight of carbon; And mixing 2 to 8% by weight of a lithium salt of any one selected from LiCF ₃ SO _3, LiClO _4, LiBF _4, LiAsF _{4, and} LiPF _{6 with} Acentonitile (ACN); And A method of manufacturing a sulfur positive electrode for a lithium battery, comprising the step of preparing the mixed mixture as a sulfur electrode in a thin film form. delete delete The method of claim 7, wherein the preparing of the mixture in the form of a thin film is a sulfur positive electrode manufacturing method for a lithium battery, characterized in that the mixture is stirred and poured into a current collector to dry. The method of claim 10, wherein the current collector is any one selected from an aluminum plate and a copper plate having excellent electrical conductivity. The method for manufacturing a sulfur positive electrode for a lithium battery according to claim 10, wherein irregularities are formed on the surface of the current collector.