KR101375611B1 - Manufacturing method of lithium titanium oxide anode active material - Google Patents

Abstract

The present invention has a spherical structure, a plurality of pores having a diameter of 1 ~ 200nm is distributed on the surface and the bulk of the particles showing a porosity, the average particle diameter of the particles is 0.5 ~ 10㎛, filled or The present invention relates to a method of manufacturing a Li ₄ Ti ₅ O ₁₂ negative electrode active material capable of inserting or detaching ions on both the surface and bulk of the particles through the plurality of pores. According to the present invention, since a plurality of pores having a diameter of 1 to 200nm is distributed on the surface and bulk of the particles to show porosity, ions are formed at both the surface and the bulk of the particles through the plurality of pores according to a charging or discharging operation. Can be inserted or detached, and having uniform spherical particles having a size of 0.5 to 10 µm, the tap density (apparent density) is improved compared to the conventional Li ₄ Ti ₅ O ₁₂ negative electrode active material, and the absolute amount of binder used during the production of the negative electrode When it is used in the battery, it is possible to improve the power density by maximizing the reaction active site with the electrolyte due to the porous structure.

Description

Manufacturing method of lithium titanium oxide anode active material

The present invention relates to a method for producing a lithium titanium oxide anode active material, and more particularly, because a plurality of pores having a diameter of 1 ~ 200nm is distributed on the surface and bulk of the particles and exhibits porosity. It is possible to insert or detach ions on both the surface and the bulk of the particles through a plurality of pores, and to have uniform spherical particles having a size of 0.5 to 10 μm, so that the tap density is higher than that of a conventional Li ₄ Ti ₅ O ₁₂ anode active material. Apparent density) can be improved and the absolute amount of binder used can be reduced during the production of the negative electrode.When used in batteries, Li ₄ Ti ₅ O ₁₂ can be used to improve the power density by maximizing the active site of reaction with the electrolyte due to the porous structure. It relates to a method for producing a negative electrode active material.

When lithium is used as a negative electrode in a lithium secondary battery, stability is reduced due to the formation of a solid electrode interface (SEI) layer due to an irreversible reaction of charging and discharging, and a decrease in capacity and output occurs.

Li ₄ Ti ₅ O ₁₂ is used as a negative electrode active material to replace graphite in a lithium ion battery or a hybrid supercapacitor, and the Li ₄ Ti ₅ O ₁₂ negative electrode active material exhibits structural stability and stable operating voltage of 1.5V during charging and discharging.

The capacity of Li ₄ Ti ₅ O ₁₂ negative electrode active material is due to phase boundary shift due to diffusion of lithium ions during charging and discharging. Therefore, in order to increase the diffusion rate of lithium ions, Li ₄ Ti ₅ O ₁₂ having a high specific surface area with a nano size of less than 500 nm is used as an active material. However, the volume of the active material is relatively increased, and thus the content of the solvent and the binder used is also increased, resulting in a decrease in the volumetric energy density.

In addition, in the case of Li ₄ Ti ₅ O ₁₂ without pores, the output density is also reduced due to the reduction of the reaction active site with the electrolyte.

The problem to be solved by the present invention is a plurality of pores having a diameter of 1 ~ 200nm is distributed on the surface and the bulk of the particle exhibits porosity, so that the surface and bulk of the particle through the plurality of pores according to the charging or discharging operation Ion insertion or desorption is possible at all, and having uniform spherical particles having a size of 0.5 to 10 μm improves the tap density (apparent density) than the conventional Li ₄ Ti ₅ O ₁₂ negative electrode active material and makes binder It is possible to reduce the absolute amount of, and to provide a method for producing a Li ₄ Ti ₅ O ₁₂ negative electrode active material that can improve the output density by maximizing the reaction active site with the electrolyte due to the porous structure when used in the battery.

The present invention has a spherical structure, a plurality of pores having a diameter of 1 ~ 200nm is distributed on the surface and the bulk of the particles showing a porosity, the average particle diameter of the particles is 0.5 ~ 10㎛, filled or According to a discharge operation, a Li ₄ Ti ₅ O ₁₂ anode active material capable of inserting or detaching ions on both the surface and the bulk of the particles through the plurality of pores is provided.

The spherical structure particles have a porosity of 1 to 50%.

The specific surface area of the spherical structure particles may range from 0.1 to 200 m 2 / g.

In addition, the present invention, (a) mixing the organic compound, water and titanium salt in the first organic solvent and reacting to obtain a spherical TiO ₂ precursor of a white precipitate, and (b) a reactor capable of sealing the interior Putting the spherical TiO ₂ precursor together with a mixed solution of a second organic solvent and water to seal the reactor with a lid, and (c) heating the hermetically sealed reactor to be equal to or lower than the boiling point of the second organic solvent. (2) raising the target reaction temperature higher than the boiling point of the organic solvent, and (d) maintaining the temperature of the reactor at the target reaction temperature, thereby releasing organic components from the spherical TiO ₂ precursor to form spherical porous TiO. ₂ precursor is formed, (e) the first heat treatment of the spherical porous TiO ₂ precursor to form a spherical porous TiO ₂ and (f) mixing the spherical porous TiO ₂ and a lithium salt And a second heat treatment to provide a Li ₄ Ti ₅ O _12, the manufacturing method of the negative electrode active material including forming a porous anode active material Li ₄ Ti ₅ O ₁₂ of the rectangle.

As the reaction proceeds in the step (a), the head portion of the organic compound is combined with the Ti component to form a composition, and the reaction continues, while the tail portion of the organic compound is located inside and the head portion is located in the reverse micelle. As a result, the spherical reverse micelle is gradually grown to a seed, and has a spherical particle structure, and precipitates due to specific gravity to form a white precipitate.

The organic compound may be at least one amine organic compound selected from octylamine, decylamine, dodecylamine, tetradecylamine, and hexadecylamine.

The titanium salt may be at least one material selected from titanium butoxide, titanium isopropoxide and titanium chloride.

The organic compound and the titanium salt are preferably mixed in a molar ratio of 1: 1 to 1:10.

The mixed solution is preferably a solution in which an organic solvent and water are mixed at a ratio of 1: 0.1 to 1:10 by volume.

The lithium salt may be at least one material selected from lithium acetate, lithium hydroxide, lithium nitrate and lithium carbonate.

It is preferable that anhydrous ethanol is used as said 2nd organic solvent, and the said target reaction temperature is set to 78-200 degreeC.

Ethylene glycol is used as the organic solvent, and the target reaction temperature is preferably set to 198 to 300 ° C.

The first heat treatment is carried out in an oxidizing atmosphere at a temperature of 400 ~ 800 ℃, the second heat treatment is preferably carried out in an oxidizing atmosphere at a temperature of 600 ~ 1000 ℃.

According to the present invention, since a plurality of pores having a diameter of 1 to 200nm is distributed on the surface and bulk of the particles to show porosity, ions are formed at both the surface and the bulk of the particles through the plurality of pores according to a charging or discharging operation. Can be inserted or detached.

In addition, according to the present invention, by having uniform spherical particles having a size of 0.5 to 10 μm, the tap density (apparent density) is improved compared to the conventional Li ₄ Ti ₅ O ₁₂ negative electrode active material, and the absolute amount of binder used in the preparation of the negative electrode is reduced. Can be reduced.

In addition, according to the present invention, when used in a battery can maximize the reaction active site with the electrolyte due to the porous structure can improve the energy density and power density.

In addition, the particle size of the negative electrode active material may be controlled by controlling the content of the organic compound and the content of the titanium salt in the preparation of the Li ₄ Ti ₅ O ₁₂ negative electrode active material.

In addition, the Li ₄ Ti ₅ O ₁₂ negative electrode active material can be produced by a simple method, and since a low-cost starting material can be used, it is economical, and the process is simple and mass production is possible.

1 is a view illustrating a process of forming a spherical TiO ₂ precursor.
FIG. 2 schematically illustrates a reactor for synthesizing a TiO ₂ precursor having a spherical porous structure.
3 is a scanning electron microscope (SEM) photograph showing a spherical TiO ₂ precursor prepared according to the experimental example.
4 is a scanning electron microscope (SEM) photograph showing a spherical porous TiO ₂ precursor prepared according to the experimental example.
5 is a scanning electron microscope (SEM) photograph showing a spherical porous Li ₄ Ti ₅ O ₁₂ anode active material prepared according to the experimental example.
6 is a graph showing an X-ray diffraction (XRD) pattern of a spherical porous Li ₄ Ti ₅ O ₁₂ anode active material prepared according to the experimental example.
7 is a graph showing charge and discharge curves of a lithium ion battery prepared using a spherical porous Li ₄ Ti ₅ O ₁₂ negative electrode active material prepared according to the experimental example.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, it should be understood that the following embodiments are provided so that those skilled in the art will be able to fully understand the present invention, and that various modifications may be made without departing from the scope of the present invention. It is not. Wherein like reference numerals refer to like elements throughout.

In the following description, the bulk is used to mean all parts other than the surface constituting the particles as a portion directed from the surface of the particles to the inside.

The Li ₄ Ti ₅ O ₁₂ negative electrode active material undergoes phase boundary reaction by diffusion of lithium ions during charging and discharging, and has a slow diffusion rate of lithium ions. Therefore, in the related art, in order to shorten the moving distance of the ions, the size of the synthesized particles was manufactured to be smaller than the nano size of less than 500 nm. However, nano-sized particles of less than 500 nm have a low productivity because a large amount of solvent and a binder are required to make a slurry for electrode plate production in an electrode manufacturing process. In addition, nano-sized particles of less than 500nm is sensitive to moisture, and when exposed to air, excessive moisture is adsorbed on the surface of the particles, thereby degrading not only the electrode manufacturing process but also the characteristics of the battery.

In order to improve this problem, the present invention is to improve the energy density and output density by preparing a uniform spherical porous Li ₄ Ti ₅ O ₁₂ negative electrode active material having a size of 0.5 ~ 10㎛. The spherical porous Li ₄ Ti ₅ O ₁₂ negative electrode active material having a size of 0.5 to 10 μm may be used for a negative electrode of a lithium ion battery or a hybrid supercapacitor. The Li ₄ Ti ₅ O ₁₂ anode active material has a spherical shape and a porous shape, and has a size of 0.5 to 10 μm.

In the present invention, a plurality of pores having a diameter of 1 ~ 200nm is distributed on the surface and bulk of the particles to produce a uniform spherical Li ₄ Ti ₅ O ₁₂ negative electrode active material exhibiting porosity and having a micro size, the conventional Li ₄ Ti ₅ O ₁₂ Improved tap density (apparent density) than the negative electrode active material, maximizing the active site of the reaction with the electrolyte due to the reduction in the absolute amount of solvent and binder used in the electrode production and the porous structure can improve the output density.

Hereinafter, Li ₄ Ti ₅ O ₁₂ according to a preferred embodiment of the present invention The manufacturing method of a negative electrode active material is demonstrated.

An organic solvent, water (H ₂ O), and a titanium salt are mixed and reacted with the organic solvent. The organic solvent may be an organic solvent such as anhydrous ethanol or ethylene glycol. The water (H ₂ O) serves as a precipitant to precipitate the reaction product. The organic compound may be an amine organic compound, and the amine organic compound may be octylamine, decylamine, dodecylamine, dodecylamine, tetradecylamine, hexadecylamine, and hexadecylamine. Or mixtures thereof. The titanium salt may be titanium butoxide (titanium botoxide), titanium isopropoxide (titanium isopropoxide), titanium chloride (titanium chloride) or a mixture thereof. The organic compound and the titanium salt are preferably mixed in a molar ratio of about 1: 1 to about 1:10. The reaction is preferably performed for a predetermined time (eg, 10 minutes to 48 hours) while stirring at a predetermined rate (eg, 10 to 800 rpm) at a temperature of about -20 ° C to 40 ° C. By the reaction, a spherical TiO ₂ precursor, which is a white precipitate, is formed.

1 is a view illustrating a process of forming a spherical TiO ₂ precursor.

Referring to FIG. 1, the organic compound has the opposite property of having hydrophobicity in the head and hydrophobicity in the head, and as the reaction occurs, the head is combined with the Ti species to form a composition and the reaction continues. When the tails come together, they form a spherical reverse micelle. Inverted micelles refer to thermodynamically stable and uniform spherical structures of low molecular or high molecular weight materials having both amphiphilic, for example, hydrophilic and hydrophobic groups. In the reaction process, the organic compound forms an inverted micelle in which the tail is located inward and the head is located outward, and the Ti component is distributed around the head to form a structure surrounding the inverted micelle. As the seed grows gradually, it has a spherical particle structure. The reaction product of this spherical structure is settled by specific gravity to form a white precipitate. By this principle, the size of the white precipitate can be adjusted according to the content of the organic compound and the titanium salt.

When the reaction is carried out, a white precipitate, a spherical TiO ₂ precursor is formed, and the white precipitate formed after the reaction is filtered using a filter or selectively separated using a centrifuge or the like.

The spherical TiO ₂ precursor, which is an optional white precipitate, is washed and dried. The washing may use a material such as anhydrous ethanol, distilled water and the like. The drying may be carried out through a general drying process such as hot air drying, vacuum drying, spray drying. The drying is preferably carried out at a temperature of about 40 ~ 90 ℃ 10 minutes ~ 48 hours.

The dried spherical TiO ₂ precursor is added to a reaction apparatus as shown in FIG. 2 with a mixed solution of an organic solvent and water (distilled water) to react. Is out by the reaction of organic matter out of the TiO ₂ component precursor of the spherical structure is TiO ₂ precursor having the porous structure of the sphere is to be formed. The organic solvent may be an organic solvent such as anhydrous ethanol or ethylene glycol. The mixed solution is preferably a solution in which an organic solvent and water are mixed at a ratio of 1: 0.1 to 1:10 by volume. FIG. 2 schematically illustrates a reactor for synthesizing a spherical porous TiO ₂ precursor.

Referring to FIG. 2, a spherical TiO ₂ precursor and a mixed solution, which are dried products, are mixed in a reactor 100 capable of completely sealing the inside thereof, and a lid capable of completely sealing the reactor 100 such as a screw cap type ( The reactor 100 is covered with 110 and sealed. Since the reactor 100 is completely hermetically sealed by the cover 110, the reaction may be promoted by suppressing the amount of evaporation while increasing the vapor pressure in the reactor 100.

Using a heating means (not shown), the temperature of the reactor 100 is set at a target reaction temperature above the boiling point of the organic solvent (eg, when using ethanol as the organic solvent, for example, 78 to 200 ° C., ethylene glycol as the organic solvent). If used, the temperature is increased to 198 to 300 ° C. The reaction temperature is preferably about 78 ~ 200 ℃ when using ethanol as the organic solvent, if the reaction temperature is less than 78 ℃ sufficient reaction may not occur, if it exceeds 200 ℃ by high vapor pressure It may be dangerous to react at temperatures in this range.

When the temperature in the reactor 100 reaches the target reaction temperature, the organic component is released from the TiO ₂ precursor having a spherical structure by maintaining the reaction temperature for a predetermined time (for example, 1 to 48 hours) to have a spherical porous structure. Allow TiO ₂ precursor to form. During the reaction, the organic component, which was forming the reverse micelle, gradually escapes from the spherical TiO ₂ precursor and is dissolved in distilled water included in the mixed solution, and pores are formed at the site where the organic component is located. At this time, since the reactor 100 is sealed by the cover 110, the vapor pressure in the reactor 100 increases, but the amount of evaporation of the solution may be suppressed. Since the reactor 100 is sealed by the cover 110, it is possible to increase the pressure in the reactor 100, to react in a faster time than when the cover 110 is not used, and to obtain a spherical porous TiO ₂ precursor. There are advantages to it. While the reaction is performed, stirring at a predetermined stirring speed (eg, 10 to 500 rpm) using the stirrer 120 is preferable in terms of uniform reaction and reaction promotion.

After sufficient reaction, the temperature of the reactor 100 is cooled to obtain a spherical porous TiO ₂ precursor. Cooling of the reactor 100 may be cooled in a natural state by shutting off the power of the heating means, or may be cooled by setting a temperature drop rate (for example, 10 ° C / min) arbitrarily.

The spherical porous TiO ₂ precursor, which is a reaction product, is washed at least once with an alcohol such as anhydrous ethanol, water (H ₂ O), or the like. After washing, a drying process is performed. The drying process may be performed through a general drying process such as hot air drying, vacuum drying, spray drying. The drying is preferably carried out at a temperature of about 40 ~ 90 ℃ 10 minutes ~ 48 hours.

The spherical porous TiO ₂ precursor thus obtained is subjected to a heat treatment to remove residual organic components. The heat treatment process may be performed in the following manner.

A spherical porous TiO ₂ precursor is charged to a furnace, such as an electric furnace, and raised to the desired heat treatment temperature. In this case it is preferred heating rate of the furnace of about 1~50 ℃ / min, if the heating rate of the furnace is too slow, long that the productivity is poor so fast heating rate of the furnace is by the rapid temperature increase TiO ₂ Since thermal stress can be applied to the precursor, it is desirable to raise the temperature of the furnace at a rate of temperature rise within this range. At this time, the pressure in the furnace is preferably maintained at atmospheric pressure.

When the temperature of the furnace rises to the target heat treatment temperature, a constant time (for example, 1 to 48 hours) is maintained. The heat treatment is preferably performed in an oxidizing atmosphere such as air or oxygen (O ₂ ). If a certain time is maintained at the heat treatment temperature, the remaining organic components are removed to obtain spherical porous TiO ₂ .

The heat treatment temperature is preferably about 400 ~ 800 ℃, if the heat treatment temperature is too low, the organic component may remain without being removed, if the heat treatment temperature is too high energy consumption and may be uneconomical range within the above range It is preferable to perform heat treatment at the heat treatment temperature of. During the heat treatment, the organic component is burned out, and pores are formed at sites where the organic component is located.

After the heat treatment process, the furnace temperature is lowered to unload spherical porous TiO ₂ . The furnace cooling may be effected by shutting down the furnace power source to cool it in a natural state, or optionally by setting a temperature decreasing rate (for example, 10 DEG C / min). It is preferable to keep the pressure inside the furnace constant even while the furnace temperature is being lowered.

The spherical porous TiO ₂ thus prepared is mixed with a lithium salt. The lithium salt is preferably at least one material selected from lithium acetate, lithium hydroxide, lithium nitrate, and lithium carbonate. The mixing may use various methods such as ball milling and the like. In the example of the ball milling process, the spherical porous TiO ₂ and the lithium salt are charged into a ball milling machine in order to uniformly grind, and the spherical porous TiO ₂ is rotated at a constant speed using a ball milling machine. And the lithium salt are mechanically mixed uniformly. The ball used for ball milling may be a ball made of ceramics such as alumina or zirconia, and the balls may be all the same size or may be used together with balls having two or more sizes. Adjust the size of the ball, milling time and revolutions per minute of the ball mill. For example, the size of the ball may be set in the range of about 1 mm to 10 mm, the rotation speed of the ball mill may be set in the range of about 50 to 500 rpm, and ball milling is preferably performed for 1 to 48 hours. . Uniform mixing is achieved by ball milling.

The resultant mixture is heat treated to form a spherical porous Li ₄ Ti ₅ O ₁₂ negative electrode active material. The heat treatment process may be performed in the following manner.

The mixed result is charged to a furnace, such as an electric furnace, and raised to the desired heat treatment temperature. In this case, it is preferable that the temperature rise rate of the furnace is about 1 to 50 DEG C / min. If the temperature rise rate of the furnace is too slow, it takes a long time to decrease the productivity. If the temperature rise rate of the furnace is too fast, it is preferable to increase the temperature of the furnace at the heating rate within the above range. At this time, it is preferable that the pressure in the furnace is maintained at normal pressure.

When the temperature of the furnace rises to the target heat treatment temperature, a constant time (for example, 1 to 48 hours) is maintained. The heat treatment is preferably performed in an oxidizing atmosphere such as air or oxygen (O ₂ ). When a certain time is maintained at the heat treatment temperature, a reaction is performed between the spherical porous TiO ₂ and the lithium salt to obtain a spherical porous Li ₄ Ti ₅ O ₁₂ .

Preferably, the heat treatment temperature is about 600 to 1000 ° C. If the heat treatment temperature is too high, lithium (Li) may volatilize, and if the heat treatment temperature is too low, a reaction may occur between TiO ₂ and the lithium salt. Since it may not be converted into a Li ₄ Ti ₅ O ₁₂ negative electrode active material, it is preferable to heat-treat at a heat-treatment temperature in the above range.

After performing the heat treatment process, the furnace temperature is lowered to unload the spherical porous Li ₄ Ti ₅ O ₁₂ anode active material. The furnace cooling may be effected by shutting down the furnace power source to cool it in a natural state, or optionally by setting a temperature decreasing rate (for example, 10 DEG C / min). It is preferable to keep the pressure inside the furnace constant even while the furnace temperature is being lowered.

The prepared Li ₄ Ti ₅ O ₁₂ negative electrode active material has a spherical structure, a plurality of pores having a diameter of 1 ~ 200nm is distributed on the surface and bulk of the particles to show porosity, the average particle diameter of the particles It is about 500 nm-10 micrometers. The spherical structure particles may have a porosity of 1 to 50%, and the specific surface area of the spherical structure particles may range from 0.1 to 200 m 2 / g.

The Li ₄ Ti ₅ O ₁₂ negative electrode active material prepared by the above method may be used as a negative electrode of a lithium ion battery or a negative electrode of a hybrid supercapacitor.

The negative electrode of the lithium ion battery or the negative electrode of the hybrid supercapacitor may be prepared by mixing a Li ₄ Ti ₅ O ₁₂ negative electrode active material with a binder and a conductive material according to a conventional method. The negative electrode or hybrid supercapacitor manufacturing method of the lithium ion battery as described above can be used a generally known method, it is not particularly limited. The negative electrode manufactured using the Li ₄ Ti ₅ O ₁₂ negative electrode active material may be used in a lithium ion battery or a hybrid supercapacitor.

When the Li ₄ Ti ₅ O ₁₂ negative electrode active material is used in a lithium ion battery or a hybrid supercapacitor, ions may be inserted or detached from both the surface and the bulk of the particles through the plurality of pores according to a charging or discharging operation. In addition to the surface of the Li ₄ Ti ₅ O ₁₂ negative electrode active material as well as the pores formed in the bulk (vulk) in the deep position of the inside of the Li ₄ Ti ₅ O ₁₂ negative electrode active material can be inserted and desorption process.

Hereinafter, a method of manufacturing a negative electrode using the Li ₄ Ti ₅ O ₁₂ negative electrode active material will be described.

A negative electrode composition is prepared by mixing a Li ₄ Ti ₅ O ₁₂ negative electrode active material, a conductive material, a binder, and a solvent.

The negative electrode composition is Li ₄ Ti ₅ O ₁₂ cathode active material, the Li ₄ Ti ₅ O ₁₂ cathode active material, 100 parts by weight of conductive material, 2 to 20 parts by weight based on the Li ₄ Ti ₅ O ₁₂ cathode active material, relative to 100 parts by weight The binder may include 2 to 20 parts by weight, and 1 to 300 parts by weight of the solvent based on 100 parts by weight of the Li ₄ Ti ₅ O ₁₂ negative electrode active material. Since the composition for the negative electrode is dough, it may be difficult to uniformly mix (completely disperse) the electrode for a predetermined time (for example, 10 minutes to 12 hours) using a mixer such as a planetary mixer. The composition for negative electrodes suitable for manufacture can be obtained. Mixers, such as planetary mixers, enable the production of uniformly mixed negative electrode compositions.

The binder is polytetrafluoroethylene (PTFE), polyvinylidenefloride (PVDF), carboxymethylcellulose (CMC), polyvinyl alcohol (PVA), polyvinyl butyral (poly vinyl butyral (PVB), poly-N-vinylpyrrolidone (PVP), styrene butadiene rubber (SBR), polyamide-imide, polyimide, and the like. One or more selected species can be mixed and used.

The conductive material is not particularly limited as long as it is an electronic conductive material that does not cause chemical change, and examples thereof include natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, super-P black, carbon fiber, copper, and nickel. Metal powders such as aluminum, silver, or metal fibers.

The solvent may be an organic solvent such as ethanol (EtOH), acetone, isopropyl alcohol, N-methylpyrrolidone (NMP), propylene glycol (PG) or water.

A negative electrode composition comprising a Li ₄ Ti ₅ O ₁₂ negative electrode active material, a binder, a conductive material, and a solvent is pressed to form an electrode, or the negative electrode composition is coated on a metal foil to form an electrode, or the negative electrode composition It is pushed with a roller to form a sheet (sheet) and attached to a metal foil to form an electrode, the resultant formed in the electrode form is dried at a temperature of 100 ℃ to 350 ℃ to form a cathode.

Referring to the example of forming the negative electrode in more detail, the composition for the negative electrode can be molded by pressing using a roll press molding machine. The roll press molding machine aims at improving the electrode density through rolling and controlling the thickness of the electrode. The roll press molding machine includes a controller capable of controlling the thickness and the heating temperature of the rolls and rolls at the upper and lower ends, the winding &Lt; / RTI &gt; As the electrode in the roll state passes the roll press, the rolling process is carried out and the roll is rolled again to complete the electrode. At this time, it is preferable that the pressurization pressure of a press is 5-20 ton / cm <2>, and the temperature of a roll shall be 0-150 degreeC. The composition for the negative electrode, which has undergone the above press pressing process, is subjected to a drying process. The drying process is carried out at a temperature of 100 ° C to 350 ° C, preferably 150 ° C to 300 ° C. At this time, when the drying temperature is less than 100 ℃ is not preferable because the evaporation of the solvent is difficult, and when the high temperature drying over 350 ℃ may occur oxidation of the conductive material is not preferable. Therefore, it is preferable that drying temperature is 100 degreeC or more and does not exceed 350 degreeC. And the drying process is preferably carried out for about 10 minutes to 6 hours at the above temperature. This drying process improves the strength of the negative electrode by binding the powder particles while drying (solvent evaporation) the molded negative electrode composition.

In addition, looking at another example of forming a cathode, the composition for the cathode is a metal foil such as titanium foil (Ti foil), aluminum foil (Al foil), aluminum etching foil (Al etching foil), copper foil (Cu foil) ( It may be coated on a metal foil, or the composition for the negative electrode is pushed with a roller into a sheet state (rubber type) and attached to a metal foil to prepare a negative electrode shape. The aluminum etching foil means that the aluminum foil is etched in an uneven shape. The cathode is subjected to the drying process as described above. The drying process is carried out at a temperature of 100 ° C to 350 ° C, preferably 150 ° C to 300 ° C. At this time, when the drying temperature is less than 100 ℃ is not preferable because the evaporation of the solvent is difficult, and when the high temperature drying over 350 ℃ may occur oxidation of the conductive material is not preferable. Therefore, it is preferable that drying temperature is 100 degreeC or more and does not exceed 350 degreeC. And the drying process is preferably carried out for about 10 minutes to 6 hours at the above temperature. This drying process improves the strength of the negative electrode by binding the powder particles while drying (solvent evaporation) the negative electrode composition.

Hereinafter, experimental examples according to the present invention will be presented, and the present invention is not limited to the following experimental examples.

To 200 ml of anhydrous ethanol as a solvent, 1.15 g of dodecylamine and 1.12 ml of H ₂ O were mixed. 3.55 g of titanium isopropoxide was added to the solution, followed by reaction at room temperature with stirring at 400 rpm for 1 hour.

After the reaction, the white precipitate was selectively separated using a centrifuge, washed three times with anhydrous ethanol, and dried for 24 hours in a dryer at 60 ° C. to form a spherical TiO ₂ precursor.

3 is a scanning electron microscope (SEM) photograph showing the spherical TiO ₂ precursor thus prepared.

Referring to FIG. 2, it can be seen that particles having a uniform size are formed and the particles have a spherical shape.

1 g of the dried spherical TiO ₂ precursor was added to a mixed solution of 20 ml of anhydrous ethanol and 20 ml of H ₂ O, and reacted for 12 hours at a temperature of 160 ° C. in the reactor shown in FIG. ₂ precursors were formed.

The spherical porous TiO ₂ precursor was washed three times with anhydrous ethanol and dried in a drier at 60 ° C. for 24 hours.

4 is a scanning electron microscope (SEM) photograph showing the spherical porous TiO ₂ precursor thus prepared.

Referring to FIG. 4, it can be seen that spherical particles having a uniform size are formed, and micropores are observed on the surface of the particles.

The dried spherical porous TiO ₂ precursor was charged into a heat treatment apparatus, heated to 2 ° C./min, and heat-treated at 500 ° C. for 3 hours to remove remaining organics, and then cooled.

0.8 g of the heat treated porous TiO ₂ precursor and 1.02 g of lithium acetate were dry mixed.

The resultant mixture was charged to a heat treatment apparatus, heated to 2 ° C./min, heat treated at 800 ° C. for 12 hours, and cooled to prepare a spherical porous Li ₄ Ti ₅ O ₁₂ negative electrode active material.

5 is a scanning electron microscope (SEM) photograph showing a spherical porous Li ₄ Ti ₅ O ₁₂ negative electrode active material thus prepared.

Referring to FIG. 5, it can be seen that spherical particles having a uniform size are formed, and micropores are observed on the surface of the particles.

FIG. 6 is a graph showing an X-ray diffraction (XRD) pattern of a spherical porous Li ₄ Ti ₅ O ₁₂ anode active material.

Referring to FIG. 6, it was confirmed that the Li ₄ Ti ₅ O ₁₂ negative electrode active material prepared according to the experimental example had a Li ₄ Ti ₅ O ₁₂ crystal phase.

After weighing the prepared Li ₄ Ti ₅ O ₁₂ negative electrode active material, super-P carbon black (conductive material), polyvinylidene fluoride (Polyvinylidene fluoride) as a binder in a weight ratio of 80:10:10, A slurry was prepared using a high speed mixer with N-methylpyrrolidone (NMP) as a solvent.

The slurry was coated on aluminum foil and then dried at 120 ° C. for 1 hour.

The dried resultant was punched out to a diameter of 12 mm to use a negative electrode, and a lithium ion battery using a lithium foil as a positive electrode was prepared.

Figure 7 is a graph showing the charge and discharge curve of the lithium ion battery thus prepared.

Referring to FIG. 7, a charge and discharge curve in a voltage range of 1V to 3V shows a 1.5 V section flat voltage of a typical Li ₄ Ti ₅ O ₁₂ .

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, This is possible.

100: reactor
110: cover
120: stirrer
130: Mixed solution

Claims (13)

delete delete delete (a) mixing and reacting an organic compound, water, and a titanium salt with a first organic solvent to obtain a spherical TiO ₂ precursor as a white precipitate;
(b) putting the spherical TiO ₂ precursor together with a mixture of a second organic solvent and water in a reactor capable of sealing the inside and sealing the reactor with a cover;
(c) heating the sealed reactor to raise a target reaction temperature equal to or higher than the boiling point of the second organic solvent;
and (d) from the target reaction temperature according to maintain the temperature of the reactor, the organic component is forced out to form a porous TiO ₂ TiO ₂ precursor in the precursor of the rectangle of the rectangular;
(e) first heat treating the spherical porous TiO ₂ precursor to form a spherical porous TiO ₂ ; And
(f) Li ₄ Ti ₅ O The method of _12, a negative electrode active material comprises the step of mixing a porous TiO ₂ and a lithium based salt of the rectangle and the second heat treatment to form a porous Li ₄ Ti ₅ O _12, the negative electrode active material of the rectangle.
According to claim 4, As the reaction proceeds in the step (a) the head portion of the organic compound is combined with the Ti component to form a composition and the reaction is continued while the tail portion of the organic compound is located inside the head portion Li ₄ Ti ₅ O which forms a reverse micelle located outside, has a spherical particle structure as the spherical reverse micelle gradually grows as a seed, and precipitates by specific gravity to form a white precipitate. ₁₂ Method of manufacturing a negative electrode active material.
The method of claim 4, wherein the organic compound is at least one amine-based organic compound selected from octylamine, decylamine, dodecylamine, tetradecylamine and hexadecylamine of the Li ₄ Ti ₅ O ₁₂ negative electrode active material Manufacturing method.
In the titanium-based salt is the production of titanium butoxide, titanium isopropoxide and titanium Li ₄ Ti ₅ O ₁₂ cathode active material, characterized in that one or more materials that are selected from chloride to claim 4.
The method of claim 4, wherein the organic compound and the titanium-based salt in the molar ratio _{1: 1~1: Li 4 Ti 5} O 12 The method of the negative electrode active material comprising a step of mixing at a rate of 10.
The method of claim 4, wherein the mixed solution is 1 in the volume ratio of organic solvent and water: 0.1~1: Li ₄ Ti ₅ O ₁₂ The method of the negative electrode active material, characterized in that a solution mixed at a ratio of 10.
The method of claim 4, wherein the lithium-based salt is lithium acetate, lithium hydroxide, lithium nitrate, and Li ₄ Ti ₅ O ₁₂ The method of the negative electrode active material, characterized in that one or more materials that are selected from lithium carbonate.
In the second use of anhydrous ethanol as the organic solvent, and the target reaction temperature method for manufacturing a negative electrode active material Li ₄ Ti ₅ O _12, characterized in that set to 78~200 ℃ to claim 4.
The method for producing a Li ₄ Ti ₅ O ₁₂ negative electrode active material according to claim 4, wherein ethylene glycol is used as the organic solvent and the target reaction temperature is set at 198 to 300 ° C.
The method of claim 4, wherein the first heat treatment is performed in an oxidizing atmosphere at a temperature of 400~800 ℃, and the second heat treatment, characterized in that for performing in an oxidizing atmosphere at a temperature of 600~1000 ℃ Li ₄ Ti ₅ O ₁₂ Method of manufacturing a negative electrode active material.

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