KR101359861B1 - Composite particle having metal oxide infiltrated in pores or hydrophilic surface of particle - Google Patents

Abstract

The present invention is a composite in which a metal oxide is infiltrated in the pores of the particles or the hydrophilic surface of the particles, the metal oxide is a composite characterized in that the metal precursor of the metal oxide is formed by reacting with water present in the pores or on the hydrophilic surface ; And it provides an electrochemical device using the complex as an electrode active material.

In addition, the present invention is a method of infiltrating the metal oxide in the pores of the porous particles or on the hydrophilic surface of the hydrophilic particles, the first step of hydrating the porous particles or hydrophilic particles; And a second step of contacting and reacting a metal precursor capable of reacting with water to form a metal oxide with water in the hydrated particles.

Description

COMPOSITE PARTICLE HAVING METAL OXIDE INFILTRATED IN PORES OR HYDROPHILIC SURFACE OF PARTICLE} Incorporating Metal Oxides Into Pores of Particles or Hydrophilic Surfaces of Particles

1 is a typical hard carbon; It is a graph showing the X-ray diffraction pattern of the hard carbon / titania composite prepared in Example 1.

2 is a typical hard carbon; Hardcarbon / titania composites prepared in Example 1; A graph showing the moisture content of hard carbon containing fumed titania.

3 is a graph showing specific capacitance when the three materials are used as a negative electrode active material of a lithium secondary battery.

4 is a typical activated carbon; Activated carbon / titania composite prepared in Example 3; It is a graph showing the water content of activated carbon containing fumed titania.

5 is a graph showing specific capacitance when the three materials are used as an electrode active material of an ion adsorption-desorption electrochemical device.

The present invention relates to a composite in which a metal oxide is infiltrated in the pores of particles or the hydrophilic surface of the particles, and can be used as an electrode active material of an electrochemical device.

Electrochemical devices are devices that accumulate and store power and send it to external electrical circuits. Examples include batteries for converting chemical energy into electrical energy by a redox reaction, and energy storage devices (eg, electric double layer capacitors) of an adsorption-and-desorption method in which charge is absorbed and desorbed on a positive electrode surface to store energy. Supercapacitors, pseudocapacitors, etc.).

The electrochemical device may include a separator, an electrolyte, and an exterior material for accommodating the two electrodes, the cathode and the anode being positioned between the two electrodes to electrically insulate the two electrodes.

In one example of the battery, the rechargeable lithium battery is charged and discharged by an intercalation-deintercalation mechanism of lithium ions. For example, occlusion and desorption of lithium ions during charge and discharge occurs between the graphite layers of the negative electrode, and in the case of metal oxides, may also occur between layers in the form of anatase crystals.

On the other hand, the energy storage element of the adsorption-desorption method is a device for storing energy by the surface adsorption of charge. At this time, the adsorption of charge occurs at the interface between the electrode and the electrolyte. In general, the core material of an electrochemical device based on adsorption and desorption is an electrode. The electrode is generally composed of a current collector and an electrode active material adhered to the current collector, in which the current collector and the electrode active material respectively serve to conduct electrons and adsorb charges from the electrolyte.

Representative electrode active material of the energy storage device of the adsorption-desorption method is activated carbon. Adsorption-and-desorption type energy storage devices such as electric double layer capacitors (EDLC) have excellent speeds and are used as devices requiring high output or auxiliary power supplies, but they have limited energy density due to their low energy density. .

In general, the manufacturing process of the battery electrode includes a step of applying and drying a slurry (slurry) in which a common electrode active material, a binder, water or an organic solvent and the like in an appropriate amount and thickness on a thin metal foil. The slurry often retains moisture even after drying. In particular, in the case of an electrode material having a porous or hydrophilic surface such as hard carbon, the slurry has high moisture adsorption power even in a relatively dry environment in which an electrochemical device is assembled. It will exist.

As described above, the moisture contained in the electrode during the manufacturing process or the material characteristics reacts with the fluorine component in the salt dissolved in the electrolyte to form hydrofluoric acid, and the formed hydrofluoric acid causes unnecessary electrode surface reaction such as melting the positive electrode active material, thereby reducing battery performance. There is a problem. In addition, in the lithium ion battery, the moisture present in the electrode reacts with lithium to generate hydrogen gas, thereby degrading the performance of the battery or increasing the pressure in the battery, thereby causing a risk of explosion. Therefore, moisture removal is very important in electrode production.

Various methods for removing water from a battery have been proposed, but the method of removing water by assembling or adsorbing moisture from an electrode during assembly is mainly used. For example, in order to catch moisture generated after cell assembly, a method of including alumina, zeolite, and silica particles, which are moisture absorbing materials, in an electrode or a separator, is mainly used.

In another method of removing moisture from an electrode, hot air at an appropriate speed is blown up and down the coated electrode at an appropriate amount of air to dry the electrode. However, in the above technique, the solvent vaporizes on the surface of the electrode first, and as a result, when the solidification is completed, it is difficult for the solvent molecules to escape to the surface, resulting in high residual moisture, or solid content of the slurry used. There is a problem that the drying process is difficult depending on the content and the total volatilization. In addition, there is a problem in that pinholes on the surface of the electrode and a crater shape (Deffect) occur due to the internal solvent molecules rapidly exiting.

The present invention utilizes that water is adsorbed on the hydrophilic surface or pores of particles having a hydrophilic surface or a large pore well-developed pore, such as hard carbon or activated carbon. By reacting with metal precursors and substituting metal oxides (eg, titania), metal oxides are infiltrated into particle pores such as carbon materials or on hydrophilic surfaces to provide a complex of adsorbed metals.

The present invention is a composite in which the metal oxide is infiltrated into the pores of the particles or the hydrophilic surface of the particles, the metal oxide is characterized in that the metal precursor of the metal oxide is formed by reacting with the moisture present in the pores or on the hydrophilic surface Complex; And it provides an electrochemical device using the complex as an electrode active material.

In addition, the present invention is a method of infiltrating the metal oxide in the pores of the porous particles or on the hydrophilic surface of the hydrophilic particles, the first step of hydrating the porous particles or hydrophilic particles; And a second step of contacting and reacting a metal precursor capable of reacting with water to form a metal oxide with water in the hydrated particles.

Hereinafter, the present invention will be described in detail.

Hard carbon is used as an electrode active material of an electrochemical device capable of converting chemical energy into electrical energy by a redox reaction like a battery. The surface of the hard carbon has a functional group such as a hydroxyl group that can adsorb moisture well, and the water content of the hard carbon increases up to about 2,000 ppm even in a relatively dry environment in which batteries are assembled. Moisture adsorbed on the hard carbon has a decisive effect on the battery using the hard carbon as an electrode active material, causing a decrease in performance, and the property of absorbing moisture will not change unless the surface of the hard carbon is modified.

On the other hand, activated carbon is an aggregate of amorphous carbons having a large internal surface area (internal surface area of approximately 1,000 m / g), and the functional group of the carbon atoms on the surface strongly adsorbs with the adsorbable molecules of the surrounding liquid and gas. Moisture can be adsorbed on internal surfaces such as pores. The activated carbon is used as an electrode active material of an electrochemical device that stores energy by surface adsorption of electric charge, such as an electric double layer capacitor.

On the other hand, titanium tetrachloride reacts with water to form hydrochloric acid with titania.

TiCl ₄ + 2H ₂ O-> TiO ₂ + 4HCl

Titania can also be used as an electrode active material and it is reported that the adsorption and desorption of lithium is much easier when the particle size is nano-size (Angewandte Chemie vol. 44 page. 797 year 2005). For this report, the Solzel reaction of methoxy titania was used to form nano-sized titania.

The present invention utilizes that water is adsorbed on the hydrophilic surface or pores of particles having a hydrophilic surface or a large pore well-developed pore, such as hard carbon or activated carbon. By reacting with the metal precursor and replacing it with a metal oxide (eg, titania), the metal oxide is infiltrated inside the particle pores or a hydrophilic surface, such as a carbon material, to provide an adsorbed composite.

Since the present invention modifies the inside or surface of the particles with metal oxides by reaction with moisture adsorbed on or inside the pores of the particles, the particles to be infiltrated in the present invention are porous particles or hydrophilic materials that may have a high water content. Particles are preferred. Porous particles contain moisture in the pores due to the adsorption force due to porosity, and the hydrophilic particles can easily adsorb moisture in the particle surface due to material properties such as having a hydrophilic functional group such as a hydroxyl group. The porous particles or the hydrophilic particles may have a moisture content of 100 ppm or more in the air by the above characteristics.

Representative examples of the porous particles or hydrophilic particles include hard carbon and activated carbon, which increase the water content to about 2000 ppm even in a relatively dry environment. In addition, the general electrode active materials such as lithium manganese oxide (lithiated magnesium oxide), lithium cobalt oxide (lithiated cobalt oxide), lithium nickel oxide (lithiated nickel oxide), carbon (carbon), petroleum coke, graphite (graphite) In this case, lithium is a porous particle capable of adsorption and desorption and moisture can be adsorbed.

The composite in which the metal oxide is infiltrated in accordance with the present invention is a water adsorption capacity of the particles to be infiltrated; The degree of spontaneity of the chemical reaction with the water used; It may have a metal oxide content of 1% to 98% by weight based on the reaction conditions.

According to the present invention, since the metal oxide infiltrated into the particle pores or the hydrophilic surface is formed by the reaction of the metal precursor with the water and the metal oxide inside the particle pores or the hydrophilic surface, it may be formed in a nano size, the particle diameter is 1 to May be 10 nm.

It is preferable that the metal oxide infiltrated into the particle pores or the hydrophilic surface can be charged and discharged. For example, it is preferable that the metal oxide can convert chemical energy into electrical energy by redox reaction like lithium metal oxide. For example, metal oxides such as titania may occlude / desorse charges and thus may serve as electrode active materials such as negative electrode active materials. Therefore, the composite having the metal oxide infiltrated to serve as the electrode active material can be used as the electrode active material.

Meanwhile, the metal oxide may be amorphous or crystalline, and may be crystallized by sintering to act as an electrode active material.

In addition, when the particles to be infiltrated in the composite according to the present invention is a material used as an electrode active material, such as hard carbon or activated carbon, the metal oxide is infiltrated so that the composite has an electrode capacity when used as an electrode active material of an electrochemical device. It can be increased, and the water removal effect in the electrode active material such as hard carbon or activated carbon can also be exerted (see FIGS. 2, 3 and 4). Therefore, the metal oxide and the particles to be infiltrated are preferably an electrode active material capable of charging and discharging.

On the other hand, an electrode active material (e.g., activated carbon) that stores energy by surface adsorption of charge has a small electric capacity (capacitance value) because charge is adsorbed only on the surface, whereas chemical energy is converted into electrical energy by a redox reaction. The electrode active material (eg, metal oxide) to be converted has a large capacitance because charges such as lithium ions enter the particles and contribute to the capacitance as a whole particle. Therefore, when metal oxide is infiltrated into the electrode active material that stores energy by surface adsorption of electric charges, it may contribute to an increase in capacitance. For example, metal oxides such as titania may occlude / desorption lithium ions, and thus the capacitance may be increased in the case of a composite in which titania is infiltrated into activated carbon (see FIG. 5).

In addition, the metal oxide infiltrated into the composite provided by the present invention may have a nano size as described above, and thus may more effectively act to increase the capacitance of the electrochemical device.

According to the present invention, the composite in which the metal oxide is infiltrated is removed by the reaction of the water adsorbed on the particles to be infiltrated with the metal precursor of the metal oxide, and the water content is 70% compared to the water content of the initial porous particles or the hydrophilic particles. It may be reduced or more than 1500ppm water content of the composite.

In addition, the present invention can adsorb the moisture at any position where the moisture can be adsorbed in the porous particles or hydrophilic particles and the adsorbed moisture can be replaced with the metal oxide by reacting with the metal precursor of the metal oxide. Therefore, the composite in which the metal oxide is infiltrated according to the present invention may be modified with a metal oxide at a position where water adsorption is possible, thereby preventing further water adsorption.

According to the present invention, the metal oxide infiltrated inside the particle pores or the hydrophilic surface is preferably a metal selected from the group consisting of metals having four or more cycles, such as Fe, Sn, and Ti. This is because when the metal of the metal oxide is a transition metal of 4 cycles or more, the charge / sucking / desorbing of the charge is possible, and thus it can be generally used as an electrode active material. Non-limiting examples of the metal oxides are titania, tin oxide, iron oxide and the like.

Method for infiltrating the metal oxide in the pores of the porous particles or the hydrophilic surface of the hydrophilic particles provided by the present invention comprises a first step of hydrating the porous particles or hydrophilic particles; And a second step of contacting and reacting a metal precursor capable of reacting with water to form a metal oxide with water in the hydrated particles.

At this time, when the porous particles and the hydrophilic particles spontaneously contain water, the hydration step may be omitted, and this case also belongs to the scope of the present invention.

The particles may be exposed to high temperature or high pressure steam to hydrate the porous or hydrophilic particles in large quantities.

In the present invention, the metal precursor may form a metal oxide directly by reacting with moisture, or may form a metal oxide by heat treatment after forming a hydrate.

In addition, the metal oxide formed by reacting the metal precursor with water may be amorphous, and may be sintered at a temperature to crystallize.

In the present invention, the metal precursor which forms the metal oxide by reacting with water or forms a hydrate immediately and then forms a metal oxide by heat treatment spontaneously reacts with water, and preferably has a lower oxidizing power than water (H ₂ 0). Non-limiting examples of the metal precursors include metal salts, preferably metal chlorides such as TiCl ₄ , SnCl ₄ , SnCl ₂ , FeCl ₂ , FeCl ₃ or compounds having a combination of Ti, Sn and CNO ₃ ⁻ or more than 4 cycles. There are metal compounds composed of transition metals.

The metal precursor of the metal oxide preferably has a high vapor pressure and reacts with moisture in a gaseous state. When the metal precursor of the metal oxide is in contact with moisture in the gas phase, the accessibility to moisture existing in the microstructure of the substrate, such as pores in the substrate, is increased, which is effective for removing moisture. Non-limiting examples of the metal precursor is a metal chloride having a high vapor pressure, such as TiCl ₄ , SnCl ₄ , SnCl ₂ , FeCl ₂ , FeCl ₃ .

Meanwhile, the water present in the pores or on the hydrophilic surface by reacting with the metal precursor is preferably water adsorbed to the particles.

In the present invention, the metal precursor is reacted with water, followed by heat treatment.

In order to remove moisture and other impurities remaining after the reaction, the heat treatment may be performed at 100 degrees or more for 30 minutes to 10 hours. In the case where a hydrate is formed by the reaction between the metal precursor and water, the hydrate may be heat treated at 500 ° C. for 30 minutes to 10 hours to change the hydrate to a metal oxide.

The condition of the heat treatment step is not particularly limited, and may be performed in an atmosphere containing oxygen. Since the metal oxide formed by the reaction of the metal precursor with water may be amorphous or incomplete metal oxide, the metal oxide may be annealed in the form of rutile or anatase or incomplete metal oxide by heat treatment in an atmosphere containing oxygen. Can be burned to increase the yield of complete metal oxides.

The present invention will be described in detail with reference to the following Examples. However, these examples are presented for understanding the present invention and do not limit the scope of the present invention.

Example 1 Preparation of Hard Carbon / Titania Composites

After exposing the hard carbon that is easily adsorbed to moisture to a certain temperature and humidity to adsorb a certain amount of water, it is placed in a chamber containing titanium tetrachloride (TiCl ₄ ) and sealed, and then sealed in the pores of the hard carbon according to the following reaction formula. Titania (TiO ₂ ) formed an infiltrated complex.

TiCl ₄ + 2H ₂ O-> TiO ₂ + 4HCl

As a result of adding about 500 degrees of heat to the complex for 1 hour in an oxygen-containing environment to remove water and other impurities remaining after the reaction with hydrochloric acid, only titania crystallized in the form of anatase was infiltrated into hard carbon. The remaining complex was obtained.

Figure 1 is a graph showing the X-ray diffraction pattern of the hard carbon containing the titania prepared in Example 1 and the existing hard carbon. According to the present invention, the peak around 25 degrees from the hard carbon containing titania is a peak of the anatase crystal of titania, indicating that the titania is included in the hard carbon.

Example  2: The lithium secondary battery  Produce

83.5% by weight of the hard carbon / titania composite prepared in Example 1 and 9.25% by weight of graphite (MCMB1028, Osaka gas) as active materials, 1% by weight of super-P as a conductive material, and 6.5% by weight of PVdF as a binder. A four-component mixture slurry was prepared by adding to NMP. The mixture slurry was coated and dried on a copper thin film having a thickness of about 20 μm, which is a negative electrode current collector, to prepare a negative electrode. The battery was assembled by stacking by using the negative electrode and lithium metal as the positive electrode, and lithium secondary battery using ethyl methyl carbonate (EMC) in which 1 M lithium phosphate hexafluoro (LiPF ₆ ) was dissolved. Paper was prepared.

Comparative Example 1

A lithium secondary battery was manufactured in the same manner as in Example 2, except that general hard carbon was used instead of the hard carbon / titania composite prepared in Example 1.

Experimental Example 1: Comparison of Physical Properties of General Hard Carbon and Hard Carbon / Titania Composites

The water content of the general hard carbon used in Comparative Example 1 and the hard carbon / titania composite prepared in Example 1 was measured and shown in FIG. 2. As a result of comparison, it was found that the water content of the hard carbon / titania composite according to the present invention was reduced by about 70% compared to the conventional hard carbon.

Experimental Example  2: General Hard Carbon Hard carbon Of Titania  Complex As electrode active material  Used The lithium secondary battery  Stock Capacity Comparison

The discharge specific capacitances of the lithium secondary batteries prepared in Example 2 and Comparative Example 1 are shown in FIG. 3. When the discharge specific capacitance was calculated per total electrode weight, Example 2 showed a relatively high discharge capacity compared to Comparative Example 1. From this, it can be seen that using the hard carbon / titania composite provided in the present invention as an electrode active material increases the battery capacity.

Example 3: Preparation of Activated Carbon / Titania Composites

Activated carbon (MSP-20, Kansai Chemical Co., Ltd.), a carbon material that easily adsorbs moisture, was exposed to an environment of constant temperature and humidity to adsorb a certain amount of moisture, and then sealed in a chamber containing titanium tetrachloride. Because of the high vapor pressure of titanium tetrachloride, the titanium tetrachloride gas molecules react with the water on the surface or inside of the carbon material to react to form titania and hydrochloric acid. At this time, titania and hydrochloric acid are adsorbed to the carbon material.

Subsequently, heat was applied to the resultant at about 500 degrees in air to remove hydrochloric acid and water remaining after the reaction. As a result, only the titania crystallized in the form of anatase was infiltrated with activated carbon to obtain a complex.

Example  4: electrochemical device manufacturing

A four-component mixture slurry was prepared by adding 60 wt% of activated carbon impregnated in Example 3 as an active material, 20 wt% of a conductive material, 15 wt% of PTFE and 5 wt% of CMC as a binder to water as a solvent. The mixture slurry was applied to an aluminum thin film having a thickness of 20 μm, which is a current collector, and dried to prepare an electrode.

The electrode and the separator were assembled using a stacking method, and an electrochemical device was prepared by injecting ethyl methyl carbonate (EMC) in which 1 M of lithium phosphate hexafluoro (LiPF ₆ ) was dissolved.

Comparative Example 2

A four-component electrode and an electrochemical device were manufactured in the same manner as in Example 3, using the existing activated carbon instead of the activated carbon impregnated with titania prepared in Example 3.

Comparative Example 3

Except for the production of a five-component electrode using a mixture of activated carbon and fumed titania (not sintered) in a ratio of 9: 1 (weight ratio), instead of the activated carbon impregnated with titania prepared in Example 3, In the same manner, an electrochemical device was manufactured.

Experimental Example  3. Titania  Evaluation of Physical Properties of Activated Carbon Containing

The moisture content of the activated carbon used in Example 3 and Comparative Examples 1 and 2 was measured and shown in FIG. 4.

Experimental Example 4. Performance Evaluation of Ion Adsorption and Desorption Electrochemical Devices

In order to evaluate the performance of the electrochemical device containing activated carbon impregnated with the titania nanoparticles prepared in Example 4, it was performed as follows.

The specific capacitance measured using the ion adsorption-and-desorption electrochemical device prepared in Example 4 and Comparative Examples 2 and 3 is shown in FIG. 5. When the discharge specific capacitance was calculated as the total electrode weight, Example 4 showed a relatively high discharge capacity compared to Comparative Examples 2 and 3. This suggests that the new material introduced in the present invention changes the surface properties of activated carbon which is a basic active material and at the same time the new material-titania-contributes to the capacity.

As described above, the present invention removes moisture contained in or in the pores of porous particles or hydrophilic particles that are easily absorbed, and at the same time to modify the inside or surface of the pores of the particles to provide a substance that is no longer adsorbed. can do.

In addition, when a metal oxide capable of charging and discharging charges is infiltrated inside or on the surface of particles, the metal oxide may be formed in a nano size, and the material according to the present invention may be used as an electrode active material of an electrochemical device. Can be. This can increase the capacitance of the electrochemical device. Particularly, in the case of activated carbon, the output is good when used as an electrode active material of an electrochemical device, but there is a problem in that the capacity is lowered. Dose effect can be increased.

Various modifications may be made without departing from the spirit and scope of the invention as set forth in the claims.

Claims (23)

A composite in which a metal oxide is infiltrated in the pores of a particle or on a hydrophilic surface of the particle, wherein the metal oxide is formed by reacting a metal precursor of the metal oxide with moisture present in the pores or on a hydrophilic surface. Electrochemical device used as. The electrochemical device according to claim 1, wherein the metal oxide is crystalline or completely metal oxide by heat treatment. The electrochemical device according to claim 1, wherein the particles to be infiltrated are activated carbon or hard carbon. The electrochemical device according to claim 1, wherein the metal oxide is capable of charging and discharging electric charges. The electrochemical device according to claim 1, wherein the metal oxide and the particles to be infiltrated are electrode active materials capable of charging and discharging. The electrochemical device according to claim 1, wherein the composite is used as an electrode active material capable of charging and discharging. The electrochemical device according to claim 1, wherein the metal oxide is nano sized. The electrochemical device according to claim 1, wherein the metal oxide has a particle diameter of 1 to 10 nm. The electrochemical device according to claim 1, wherein the metal of the metal oxide is a metal selected from the group consisting of four or more cycle metals. The electrochemical device according to claim 1, wherein the metal oxide is selected from the group consisting of titania, tin oxide, and iron oxide. The electrochemical device according to claim 1, wherein the composite has a metal oxide content of 1% to 98% by weight relative to the composite. The electrochemical device according to claim 1, wherein the water present in the pores or on the hydrophilic surface is water adsorbed on the particles. The electrochemical device according to claim 1, wherein the water-adsorbed pores or the hydrophilic surface is modified with the metal oxide to further suppress water absorption. The electrochemical device according to claim 1, wherein the water present in the pores or on the hydrophilic surface before the metal oxide is formed is 100ppm to 20,000ppm in the total content. The electrochemical device according to claim 1, wherein the water present in the composite after formation of the metal oxide is 1500 ppm or less. The electrochemical device according to claim 1, wherein the metal precursor has a high vapor pressure and reacts with moisture in a gaseous state. The electrochemical device according to claim 1, wherein the metal precursor is a metal salt. The electrochemical device according to claim 1, wherein the metal precursor is a metal chloride. The electrochemical device of claim 1, wherein the metal precursor is selected from the group consisting of TiCl ₄ , SnCl ₄ , SnCl ₂ , FeCl _2, and FeCl ₃ . delete The electrochemical device of claim 1, wherein the electrochemical device is a lithium secondary battery or an electric double layer capacitor. delete delete

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