KR20020068782A - Cathode Having Minute Metal Included Carbon and Method Of Manufacturing The Same - Google Patents

Abstract

PURPOSE: Provided is a cathode containing metallic fine particles-contained carbon, which can increase the capacity of a primary or a secondary battery and improve the lifetime of the battery and charge/discharge velocity. CONSTITUTION: The cathode is produced by a process comprising the steps of: wetting carbon by applying a metal salt-dissolved solution to the carbon; drying the wet carbon; heat-treating the dried metal-contained carbon under argon, nitrogen, hydrogen, or a mixed gas thereof at 200-900deg.C to prepare the carbon containing the metallic fine particles with a particle size of less than 1 micrometer; coating a current collector with an active material containing the metallic fine particles-contained carbon, a conductive polymer, and a sulfur-contained material. The metallic fine particles are made of at least one metal component selected from the group consisting of copper, iron, and silver.

Description

Cathode having minute metal included carbon and method of manufacturing the same

The present invention relates to a positive electrode including carbon containing metal fine particles and a method of manufacturing the same, and specifically, obtained by mixing an active material represented by carbon containing metal fine particles having a very small particle size and an organic sulfur compound or unit sulfur. It relates to a hybrid positive electrode and a method of manufacturing the same.

A system using a redox reaction of sulfur as a positive electrode material for improving the capacity of a lithium secondary battery has been proposed. Sulfur accepts two electrons as the bond between the sulfur atoms breaks, and then releases two electrons as the bond between the sulfur atoms forms, and has a high theoretical capacity of about 1680 mAh / g. However, the redox reaction of sulfur is difficult to reversible reaction and has a problem that electron transfer is difficult because sulfur itself is an insulator. Instead of using unit sulfur, it has also been proposed to use organic sulfur compounds containing or capable of forming disulfide, which are more reactive and exhibit more reversible charge and discharge behavior.

Electrochemical reactions of organic sulfur compounds require electrons to be transferred to the organic sulfur compounds. When conductive polymers are added, the conductive polymers act as molecular current collectors to facilitate electron transfer to organic sulfur compounds. It is known to act as a catalyst and to act as a catalyst. However, organic sulfur compounds also have a problem that does not exhibit a rapid redox reaction at room temperature.

Q. Chi and F. Matsumoto et al. Published a research paper on lithium secondary batteries using organic sulfur compounds containing disulfide groups. They especially studied the reactivity of copper current collectors with organic sulfur compounds. (J. Electrochem. Soc. 145, 2369 (1989), Electrochemical Behavior and Surface Morphologic Changes of Copper Substrates in the Presence of 2,5-Dimercapto-1,3,4-thiadiazole, Q. Chi et al., Langmuir, 15, 857 (1999), Studies of the Adsorption Behavior of 2,5-Dimercapto-1,3,4-thiadiazole and 2-Mercapto-5-methyl-1,3,4-thiadiazole at Gold and Copper Electrode Surfaces, F Matsumoto et al.) However, the above two studies merely disclose a hybrid electrode including an active material represented by an organic sulfur compound, carbon as a conductive agent, and polyaniline as a catalyst, but include metal particles as a component in the hybrid electrode. It is not.

N. Oyama et al. Prepared a polymer positive electrode by dissolving DMcT (dimercapto-dithiodiazole), a type of organic sulfur compound, and polyaniline, a kind of conductive polymer, in a solvent called NMP (N-methyl pyrrolidone), and applying it to a current collector together with carbon. It is reported about a technique for implementing an improved capacity by adding a copper salt to a lithium secondary battery comprising the same. (J. Electrochem. Soc., 144, L47 (1997), Effects of Adding Copper (II) Salt to Organosulfur Cathodes for Rechargeable Lithium Batteries, N. Oyama et al.) This is in the form of ions, not in the form of metals.

U.S. Patent No. 5,665,492 to T. Sotomura et al. Discloses a technique in which a current collector of a positive electrode using an organic sulfur compound as an active material is used as copper or silver foil or a metal foil other than the foil mentioned above as a current collector. . In this case, copper or silver metal powder is added to realize the improved capacity. It is suggested that the added metal powder dissolves during the filling process to form a complex with the organic sulfur compound, thereby increasing capacity and improving lifetime. However, in the above patent, since the copper or silver metal powder is added to the anode as it is, there is a disadvantage that the size of the metal particles is about tens of micrometers and is very large. If the particle size is large, the effective surface area of the metal particles is narrow, so that the organic sulfur compound cannot be contacted with a sufficiently large area, so that the effect of increasing the capacity due to the addition thereof is not large enough.

U.S. Patent No. 6,057,056 to H. J. Kim et al. Discloses a technique for producing a positive electrode using an organic sulfur compound, a metal compound, and a copper current collector. The secondary battery using the positive electrode thus produced shows improved capacity and good reversibility. However, the patent also adds the metal particles to the anode as it is, the size of the particles is very large.

As described above, the size of the metal powder added to prepare the hybrid electrode in the prior art is composed of large particles having a level of several μm to several tens of μm. In order to obtain the expected effect of the addition of the metal powder, the metal powder must be well mixed with the organic sulfur compound as the active material and carbon as the conductive agent. However, the metal powder used in the above-described prior art is difficult to mix well with organic sulfur compounds and carbon because of the large particle size. Therefore, the metal powder is difficult to be uniformly distributed in the electrode, thereby reducing the reactivity with the organic sulfur compound.

In addition, when the copper salt is simply mixed with the active material of the positive electrode, anion forming the copper salt may be included in the positive electrode active material, which may cause side reactions during the redox reaction. There is a possibility.

Accordingly, the present invention has been made in view of the above problems to provide a hybrid electrode prepared by containing metal fine particles having a very small particle size in carbon used as a conductive agent.

Another object of the present invention is to provide a method for easily manufacturing the above-described positive electrode.

Still another object of the present invention is to provide an energy storage device having an improved capacity and lifespan by promoting the electron transfer reaction of a substance containing sulfur such as an organic sulfur compound or unit sulfur by employing the above-described anode.

1 is an X-ray diffraction diagram of copper-supported carbon powder.

2 shows voltage curves during discharge of unit cells prepared in Example 1 and Comparative Example 1. FIG.

In order to achieve the above object, in the present invention

Current collectors; And

Provided is a cathode coated on the current collector, including a conductive polymer, an active material including sulfur, and an active material including carbon containing metal fine particles having a particle size of 1 μm or less.

In particular, the metal fine particles are preferably at least one metal component selected from the group consisting of copper, iron, and silver, and more preferably, the particle size of the metal fine particles is 100 nm or less.

Another object of the present invention described above

Adding a solution of a metal salt dissolved in carbon to wet the carbon;

Drying the wet carbon;

Preparing carbon containing metal fine particles having a particle size of 1 μm or less comprising heat-treating the dried metal-containing carbon in argon, nitrogen, hydrogen, or a mixed gas atmosphere thereof; And

It is achieved by a method for producing a positive electrode comprising coating on the current collector an active material comprising a material containing carbon, a conductive polymer and sulfur containing the metal fine particles.

Another object of the present invention described above

Coating an active material including a conductive polymer, a material containing sulfur, and a carbon on a current collector;

It is also achieved by a method for producing a positive electrode comprising immersing a current collector obtained in a solution in which a metal salt is dissolved and flowing a current to precipitate metal fine particles having a particle size of 1 μm or less on the current collector.

Another object of the present invention is a current collector; And

Is achieved by an energy storage device coated on the current collector and including a positive electrode comprising a conductive polymer, a material containing sulfur and an active material comprising carbon containing metal fine particles having a particle size of 1 μm or less. .

Examples of such energy storage devices include primary lithium batteries, secondary lithium batteries, and capacitors.

The present invention is made of a hybrid electrode by including a very small metal particles of several tens of nanometers in the carbon used as a conductive material, and employing it as a positive electrode to improve the capacity, charging and discharging speed and life of the battery and increase the stability It is related to storage.

That is, in the present invention, by mixing the fine metal particles with a material containing sulfur such as an organic sulfur compound or unit sulfur to prepare a hybrid positive electrode, it is possible to improve the capacity, charge and discharge rate and life of the battery using the conventional positive electrode. In particular, the development of a technique of incorporating metal particles into carbon has made it possible to produce metal particles of much smaller size than in the prior art, which allows the metal components to be evenly distributed in the hybrid anode and contains sulfur. It can be easily reacted with the material to facilitate the electron transfer reaction of such a sulfur-containing material.

In particular, the carbon-supported metal particles have a very small particle size as compared to the unsupported metal powder or metal black. Thus, the effective surface area of the metal particles is increased, thereby increasing the capacity per electrode weight. In addition, the small metal particles may be evenly distributed in the hybrid anode and thus contact with a sulfur-containing material, especially an organic sulfur compound, through a larger area. That is, the activation of the electron transfer reaction of the material containing sulfur, the stability due to complex formation with the material containing sulfur is increased due to the metal particles supported on the carbon of a very small size.

Various methods can be applied as a method of containing metal fine particles in carbon. For example, impregnation method, deposition method, incipient wetness method, ion-exchange method, colloidal adsorption method, etc. are mentioned.

Hereinafter, a process of manufacturing carbon containing metal particles by an impregnation method will be described in detail.

Slowly add a solution of the desired metal salt dissolved in carbon as a support. At this time, the solvent used for the preparation of the solution is generally water, but any organic solvent that can dissolve the metal salt is possible. The weight ratio of the metal to carbon can be easily adjusted by changing the concentration of the solution. When comparing the cell capacity and the cycle performance, the preferred ratio is 10/1 to 1/10, more preferably 5/1 to 1 / 5.

After the carbon is all wetted with the solution, the solvent is removed to dry the powder obtained. The powder thus obtained is preferably made into a fine powder form using a mortar or the like. It can then be chemically or thermally reduced to finally obtain the carbon on which the metal particles are supported. The heat treatment temperature and time can be controlled in various ways, thereby changing the particle size of the metal. The heat treatment temperature is suitably in the range of 200 to 900 ° C, preferably 400 to 600 ° C. In addition, the heat treatment atmosphere may be an inert atmosphere such as argon or nitrogen, or an atmosphere in which 0-100% of hydrogen is mixed. In addition, a single metal species such as copper, iron and silver, as well as mixtures or alloys of different metals containing them, may also be supported on carbon.

The method for producing a positive electrode containing metal fine particles by the deposition method is as follows.

First, a conductive polymer, an organic sulfur compound or a material containing sulfur such as unit sulfur and a slurry containing carbon are coated on a current collector to form a film, followed by drying to prepare an electrode for copper precipitation. The copper metal particles are precipitated on the electrode thus prepared. For example, in order to precipitate the copper fine particles, the copper sulfate solution and sulfuric acid are mixed to flow an appropriate amount of current to complete the precipitation of the copper metal particles. At this time, dextrin, gelatin, brightener including sulfur, sulfonic acid and the like may be used as an additive. In addition to gastric precipitating solution, CuCN, KCN, and K ₂ CO ₃ solutions may be mixed and current may be precipitated to precipitate copper metal particles. At this time, Na ₂ SO ₃ can be used as an additive.

In addition to the precipitates described above, a variety of precipitates may be used for the precipitation of the metal fine particles, as well as various precipitation methods such as electroless plating may be used for the precipitation of small-sized metal particles.

The production method of the anode using carbon containing metal fine particles is as follows.

A sulfur-containing material is dissolved in a solvent such as NMP, acetonitrile, methyl sulfoxide, tapineol, acetone, tetrahydrofuran, methanol, ethanol and the like to prepare a slurry. In order to improve the conductivity of the electrode is prepared according to the above-described method to add carbon containing the metal fine particles. The resulting active material slurry is applied to a copper plated current collector and then the solvent is dried to form an electrode on which the carbon containing a conductive polymer, a sulfur-containing material, and metal fine particles is mixed on the current collector.

As the conductive polymer, at least one compound selected from the group consisting of polyaniline, polypyrrole, polythiophene, polyvinylene phenylene and polyacene may be preferably used.

Organic sulfur compounds that can be used include dimercapto-1,3,4-dithiazole having two or more thiol groups, dimethyl ethylenediamine, ethylenediamine, polyethylene Polyethylene imine derivatives, trithiocyanuric acid, piperazine, 2,4-dithiopyrimidine, 1,2-ethanedithiol (1 , 2-ethanedithiol), 2-mercaptoethyl sulfide, trithiocyanuric acid, etc. can be used, and 2-mercaptothiazoline having a thiol group attached thereto (2- mercaptothiazoline), 2-mercaptobenzimidazole, 2-mercaptoppyrimidine, 1,2,4-triazole-3-thiol (1,2,4-triazole-3 -thiol), 2-mercaptopyridine, 2-mercapto-5-methyl-1,3,4-thiadiazole (2-mercapto-5-methyl-1,3,4-thiadiazole) , 2-mercaptoben The oxazole (2-mercaptobenzoxazole), 2- mercapto-1-methyl-imidazole may be used as (2-mercapto-1-methylimidazole). It is also possible to add unit sulfur instead of the organic sulfur compounds as described above.

The amount of the conductive polymer and the sulfur-containing material is preferably in the range of 1:10 to 10: 1 by weight. If the content of the conductive polymer is used in the above range, the cycle performance is improved but the cell capacity tends to be decreased. If the content of the conductive polymer is less than the above range, the cell capacity is increased but the cycle performance is decreased. Therefore, it is preferable to add it at the above-mentioned mixing ratio. More preferably, the addition ratio thereof is 1: 1 to 4: 1.

A method of manufacturing a lithium secondary battery using the prepared cathode is as follows.

In this way, a unit cell is manufactured in a structure in which a separator or a polymer electrolyte is sandwiched between a positive electrode containing carbon containing metal fine particles on a current collector and a lithium or carbon negative electrode. In the case of the stacked cell, the anode, the electrolyte, and the cathode are fabricated in order. After attaching a tab to an uncoated portion of the electrode, a lithium secondary battery is manufactured by sealing by packaging using an aluminum can or an aluminum pack.

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

<Example 1>

A solution of 29.5 g of Cu (NO ₃ ) ₂ dissolved in 50 ml of distilled water was slowly added to 10 g of acetylene black. After all the carbon was sufficiently wetted with solution, all distilled water was evaporated in a 110 ° C. convection oven. Then, using a mortar to make a fine powder and dried in a 110 ℃ convection oven for one day. The dried powder was reduced by heat treatment at 500 ° C. for 2 hours in an Ar atmosphere containing 10% (volume ratio) hydrogen.

The X-ray diffraction diagram of the carbon powder thus prepared and supported with the copper fine particles is shown in FIG. 1. Only diffraction peaks due to the surface centered cubic structure of Cu metal can be seen, which means that all of the copper ions are reduced to copper metal and no other impurities are present. It can be seen from the line width of the (111) main peak that the average size of the supported copper particles is 15 nm. A hybrid positive electrode and a lithium secondary battery were manufactured using the copper supported carbon prepared above as described below.

2 g of dimercapto-1,3,4-dithiazole having two thiol groups, 1 g of polyaniline (35% oxidized), and 1 g of acetylene black loaded with copper fine particles were mixed with NMP 12 g, which was then added to a copper plated current collector. After the film formation, it was dried under vacuum at 60 ° C. for 3 hours to complete the electrode. A unit cell was prepared by stacking the prepared hybrid positive electrode, polyacrylonitrile-based polymer electrolyte, and metallic lithium (cell A).

<Example 2>

2 g of dimercapto-1,3,4-dithiazole having two thiol groups, 1 g of polyaniline (35% oxidized), and 1 g of acetylene black were mixed with NMP 12 g, which was then formed into a current collector, followed by vacuum at 60 ° C. Drying for 3 hours to prepare an electrode for copper precipitation. Copper metal fine particles were precipitated on the electrode thus prepared in the following manner.

200-250 gdm- ³ copper sulfate solution and 25-50 gdm- ³ sulfuric acid solution for copper precipitation were mixed, and 20-50 mAcm <^-2> current was passed at the temperature of about 20-40 degreeC, and the precipitation of the copper metal particle was completed. At this time, dextrin, gelatin, brightener including sulfur and sulfonic acid were added in small amounts as additives to prepare a cathode in which copper fine particles were precipitated.

<Example 3>

2 g of dimercapto-1,3,4-dithiazole having two thiol groups, 1 g of polyaniline (35% oxidized), and 1 g of acetylene black were mixed with NMP 12 g, which was then formed into a current collector, followed by vacuum at 60 ° C. Drying for 3 hours to prepare an electrode for copper precipitation. Copper metal fine particles were precipitated on the electrode thus prepared in the following manner.

^{40~50 gdm -3 CuCN, 20~30 gdm -3} KCN, 5~25 gdm -3 K 2 CO 3 solution, the copper metal particles flowing a current of 10~40mAcm ^-2 at a temperature of 40~70 ℃ Mix Precipitated. At this time, a small amount of Na ₂ SO ₃ was added as an additive to prepare a cathode in which copper metal fine particles precipitated.

<Example 4>

A solution obtained by dissolving 14.8 g of Cu (NO ₃ ) ₂ and 21.65 g of Fe (NO ₃ ) _{2 in} 50 ml of distilled water was slowly added to 10 g of acetylene black. After all the carbon was sufficiently wetted with solution, all distilled water was evaporated in a 110 ° C. convection oven. After the use of the induction to make a fine powder and dried in a 110 ℃ convection oven for one day. The dried powder was reduced to 500 ° C. for 3 hours in an Ar atmosphere containing 10% (volume ratio) hydrogen. Carbon particles carrying an copper ratio of 1: 1 in an atomic ratio were obtained. (Weight ratio of carbon to alloy = 50:50).

Comparative Example 1

2 g of dimercapto-1,3,4-dithiazole, 1 g of polyaniline (35% oxidized), and 1 g of acetylene black were mixed with 12 g of NMP, which was then deposited on a copper plated current collector, and then Drying over time gave an electrode. This was laminated with a polyacrylonitrile-based polymer electrolyte and metallic lithium to prepare a unit cell (cell B).

2 shows the voltage curves during discharging of the battery produced via Example 1 and the battery prepared by Comparative Example 1. FIG. Compared with the case of cell B, cell A exhibits about twice the discharge capacity. This means that the copper supported on carbon participates in the discharge capacity and activates the reaction in which the S-S bond of the organic sulfur compound is broken.

According to the present invention, when a mixed positive electrode is prepared by mixing carbon containing metal fine particles having a fine size with a material containing sulfur, the metal particles act as an active material together with a material containing sulfur to increase the capacity of the positive electrode. do. When the battery is charged, the metal particles are oxidized, and when discharged, the metal particles are reduced to metal again to contribute to capacity. In addition, the metal particles serve to activate the electron transfer reaction of the material containing sulfur. Thus, the capacity of the substance containing sulfur can be fully utilized. Finally, the metal particles may be dissolved during the filling process to form a complex with a substance containing sulfur such as an organic sulfur compound or unit sulfur, and the formation of the complex may prevent the substance containing sulfur from being dissolved in the electrolyte. This means that the life of a battery manufactured using a material containing sulfur as an active material can be improved.

Although the present invention has been described above according to an embodiment of the present invention, it will be apparent to those skilled in the art that various modifications may be made without departing from the spirit of the present invention.

Claims (11)

Current collectors; And A positive electrode comprising an active material coated on the current collector, the active polymer including a conductive polymer, a material containing sulfur and carbon containing metal fine particles having a particle size of 1 μm or less. The anode according to claim 1, wherein the sulfur-containing material is an organic sulfur compound or unit sulfur. The anode according to claim 1, wherein the metal fine particles are composed of at least one metal component selected from the group consisting of copper, iron, and silver. The anode according to claim 1, wherein the weight ratio of the metal fine particles to carbon is in the range of 10/1 to 1/10. The anode according to claim 1, wherein the particle size of the metal fine particles is 100 nm or less. Adding a solution of a metal salt dissolved in carbon to wet the carbon; Drying the wet carbon; Preparing carbon containing metal fine particles having a particle size of less than or equal to 1 μm comprising heat treating the dried metal-containing carbon under argon, nitrogen, hydrogen, or a mixed gas atmosphere thereof; And A method of manufacturing a positive electrode comprising coating an active material comprising a material containing carbon, a conductive polymer, and sulfur containing the metal fine particles on a current collector. The method according to claim 6, wherein the heat treatment temperature is in the range of 200 to 900 ° C. 7. The method of claim 6, further comprising pulverizing the dried metal-containing carbon. Coating an active material including a conductive polymer, a material containing sulfur, and a carbon on a current collector; A method for producing a positive electrode, comprising the step of dipping a current collector obtained by dissolving a metal salt and flowing a current to precipitate metal fine particles having a particle size of 1 μm or less on the current collector. An energy storage device comprising an anode according to claim 1. The energy storage device of claim 10, wherein the energy storage device is a primary lithium battery, a secondary lithium battery, or a capacitor.