KR20130066770A - Manufacturing method of lifepo4 cathode active material for lithium battery and lifepo4 cathode active material using the method - Google Patents

Abstract

PURPOSE: A manufacturing method of a positive electrode active material is provided to control the size of the positive electrode active material by using cetyltrimethyl ammonium bromide when synthesizing a LiFePO4 positive electrode active material. CONSTITUTION: A manufacturing method of a positive electrode active material comprises: a step of dissolving lithium salt, ferrous salt, phosphate salt, and cetyltrimethylammonium bromide into an organic solvent; a step of putting the mixture solution into a reactor; a step of heating the reactor; a step of precipitating A LiFePO4 precursor by gravity difference through maintaining the temperature of the reactor; a step of cleaning and drying the precipitate; and a step of obtaining a LiFePO4 positive electrode active material by heat-treating the dried precipitate.

Description

Manufacturing method of lithium iron phosphate positive electrode active material for lithium ion battery and lithium iron phosphate positive electrode active material manufactured using the same {Manufacturing method of LiFePO4 cathode active material for lithium battery and LiFePO4 cathode active material using the method}

The present invention relates to a cathode active material for a lithium ion battery and a method of manufacturing the same, and more particularly, because a plurality of pores having a diameter of 2 to 300 nm are distributed on the surface and bulk of the particles to show porosity, and thus, depending on a charging or discharging operation. The plurality of pores allow insertion or desorption of cations on both the surface and the bulk of the particles, and by having uniform spherical particles having a micro size, the conventional LiFePO ₄ The tap density (apparent density) is improved compared to the positive electrode active material, and the absolute amount of the binder can be reduced when manufacturing a positive electrode for a lithium ion battery, and LiFePO ₄ A method of preparing a lithium iron phosphate (LiFePO ₄ ) positive electrode active material for a lithium ion battery capable of controlling the size of the positive electrode active material by using cetyltrimethylammonium bromide (CTAB) in synthesizing the positive electrode active material and a LiFePO ₄ positive electrode manufactured using the same It relates to an active material.

LiFePO ₄ positive electrode active material for lithium ion batteries has been used in the field of long-term use, such as hybrid electric vehicles, power tool batteries, power storage batteries due to the structural stability and thermal stability during charging and discharging.

However, LiFePO ₄ positive electrode active material, whose capacity is expressed by phase boundary movement due to diffusion of lithium ions during charging and discharging, uses nano-sized LiFePO ₄ having a high specific surface area as a positive electrode active material in order to increase diffusion rate of slow lithium ions. Therefore, the volume of the positive electrode active material is relatively increased, and thus the amount of the binder used is also increased, resulting in a decrease in the volumetric energy density.

The problem to be solved by the present invention is a plurality of pores having a diameter of 2 ~ 300nm is distributed on the surface and the bulk of the particles exhibit a porosity, so that the surface and bulk of the particles through the plurality of pores according to the charging or discharging operation It is possible to insert or desorption of cations in all, and to have a uniform spherical particle having a micro size, the conventional LiFePO ₄ The tap density (apparent density) is improved compared to the positive electrode active material, and the absolute amount of the binder can be reduced when manufacturing a positive electrode for a lithium ion battery, and LiFePO ₄ Is a method and LiFePO ₄ cathode active material it is manufactured by using the; (CTAB cetyltrimethylammonium bromide) for use by a cathode active material for lithium ion batteries capable of controlling LiFePO ₄ anode size active materials to provide cetyltrimethylammonium bromide when the positive electrode active material synthesized .

The present invention comprises the steps of dissolving lithium salts, iron salts, phosphate salts and cetyltrimethylammonium bromide in an organic solvent, lithium salts, iron salts, phosphate salts and cetyltrimethylammonium in a reactor that can be sealed inside Adding a mixed solution of bromide and covering the reactor with a cover to seal the reactor; By maintaining the temperature of the reactor at, the cetyltrimethylammonium bromide forms an inverted micelle, in which a hydrophilic group is located inside and a hydrophobic group is located outside, and lithium salts, iron salts, and phosphoric acid salts react to form spherical LiFePO _4. As the precursor is formed and distributed around the hydrophobic group to form a structure surrounding the reverse micelle, half In accordance with the progress as the LiFePO ₄ precursor it is gradually grown and have a spherical particle structure, a spherical shape of LiFePO ₄ precursor precipitate and steps cheomjeon the bottom of the reactor, which had sunk to the bottom of the reactor by the difference in specific gravity optionally Separating and separating the precipitate, optionally washing and drying the precipitate, and heat treating the dried precipitate to obtain a LiFePO ₄ positive electrode active material, wherein the precipitate according to the amount of cetyltrimethylammonium bromide added It provides a method for producing a LiFePO ₄ positive electrode active material for a lithium ion battery is controlled in size.

The lithium salt may be at least one salt selected from lithium acetate, lithium carbonate, lithium chloride, lithium hydroxide, lithium nitrate, and lithium sulfate, and the iron salt is selected from iron chloride, iron sulfate, iron citrate and iron nitrate. It may be at least one salt selected, and the phosphate salt may be at least one salt selected from ammonium phosphate and phosphoric acid.

Ethanol may be used as the organic solvent, and the target reaction temperature is preferably set to 78 to 200 ° C.

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

The heat treatment is preferably carried out in a reducing gas atmosphere or an inert gas atmosphere at a temperature of 500 ~ 900 ℃.

The method of manufacturing a LiFePO ₄ positive electrode active material for a lithium ion battery includes the steps of wet grinding prior to the heat treatment to remove salt components which are not removed in the cleaning process while micronizing the dried precipitate and having a uniform particle size. It may further include.

In addition, the present invention is produced by the above method, has a spherical structure, a plurality of pores having a diameter of 2 ~ 300nm on the surface and bulk of the particles are distributed to show porosity, the average particle diameter of the particles It provides a LiFePO ₄ positive electrode active material for a lithium ion battery having a size of 1 ~ 20㎛, which is capable of inserting or detaching cations on both the surface and the bulk of the particles through the plurality of pores according to a charging or discharging operation.

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

The specific surface area of the spherical structure particles may range from 0.1 to 100 m 2 / g.

According to the present invention, a plurality of pores having a diameter of 2 ~ 300nm is distributed on the surface and bulk of the particles to produce a uniform spherical LiFePO ₄ positive electrode active material exhibiting porosity and having a micro size, the conventional LiFePO ₄ It is possible to improve the tap density (apparent density) than the positive electrode active material, and to reduce the absolute amount of binder used in the production of a positive electrode for a lithium ion battery.

In addition, since a plurality of pores having a diameter of 2 ~ 300nm is distributed on the surface and the bulk of the particles and exhibits porosity, insertion of cations on both the surface and the bulk of the particles through the plurality of pores according to a charging or discharging operation or Desorption is possible.

In addition, LiFePO ₄ When synthesizing the positive electrode active material, the size of the positive electrode active material may be controlled by using cetyltrimethylammonium bromide (CTAB).

In addition, the LiFePO ₄ positive 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 schematic diagram showing the phase boundary movement of the LiFePO ₄ positive electrode active material during charge and discharge.
2 is a view showing a reactor for synthesizing a LiFePO ₄ precursor.
3 is a graph showing a vapor pressure curve according to the temperature in the reactor when ethanol is used as the organic solvent according to Experimental Example 1.
4 is a graph showing an X-ray diffraction (XRD) pattern of a LiFePO ₄ positive electrode active material prepared according to Experimental Example 1. FIG.
5 to 10 are scanning electron microscope (SEM) images showing a LiFePO ₄ positive electrode active material prepared according to Experimental Example 1. FIG.

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.

Hereinafter, nano size is used as a size in the range of 1 to 1000 nm as a size in nanometer (nm), and micro size is a size in the range of 1 to 1000 μm as a size in micrometer (μm). Used to mean the size of. In addition, bulk is used as what means all parts other than the surface which comprises a particle as a part which goes inward from the surface of a particle | grain.

As shown in FIG. 1, the LiFePO ₄ positive electrode active material undergoes a phase boundary transfer reaction by diffusion of lithium ions during charging and discharging. Conventionally, in order to increase the diffusion rate of lithium ions, the particle size is manufactured and used in a nano size, and the use amount of the binder is increased compared to the positive electrode active material due to the small size of the positive electrode active material, thereby reducing the volumetric energy density. A decrease in capacity appears.

However, in the present invention, a plurality of pores having a diameter of 2~300㎚ the surface and bulk of the particles are distributed by producing a cathode active material LiFePO ₄ having a uniform rectangle denotes a porous having a micro size, the conventional LiFePO ₄ It is possible to improve the tap density (apparent density) than the positive electrode active material, and to reduce the absolute amount of binder used in the production of a positive electrode for a lithium ion battery. In addition, LiFePO ₄ When synthesizing the positive electrode active material, the size of the positive electrode active material may be controlled by using cetyltrimethylammonium bromide (CTAB).

Method for producing a lithium iron phosphate (LiFePO ₄ ) positive electrode active material for a lithium ion battery according to a preferred embodiment of the present invention, the step of dissolving a lithium salt, iron salt, phosphate salt and cetyltrimethylammonium bromide in an organic solvent, and Putting a mixed solution of lithium salt, iron salt, phosphate salt and cetyltrimethylammonium bromide into a reactor capable of sealing the reactor, and then covering the reactor with a lid to seal the reactor; Ascending to a target reaction temperature equal to or higher than the boiling point of the organic solvent, and maintaining the temperature of the reactor at the target reaction temperature, the cetyltrimethylammonium bromide has an inverted micelle having a hydrophilic group on the inside and a hydrophobic group on the outside the formation, and lithium-based salts, iron salts, and phosphate salts the reaction of the spherical-type LiFePO ₄ precursor As the steps are distributed around the hydrophobic group which forms a structure surrounding said reverse micelles, while as the reaction proceeds, the LiFePO ₄ precursor is gradually grown and have a spherical particle structure, cheomjeon by the difference in specific gravity to the bottom of the reactor Selectively separating the precipitate, which is a spherical LiFePO ₄ precursor that has settled to the bottom of the reactor, washing and drying the precipitate that has been selectively separated, and heat treating the dried precipitate to obtain a LiFePO ₄ cathode active material. It includes a step, the size of the precipitate can be adjusted according to the content of the cetyltrimethylammonium bromide is added.

The lithium salt may be at least one salt selected from lithium acetate, lithium carbonate, lithium chloride, lithium hydroxide, lithium nitrate, and lithium sulfate, and the iron salt is selected from iron chloride, iron sulfate, iron citrate and iron nitrate. It may be at least one salt selected, and the phosphate salt may be at least one salt selected from ammonium phosphate and phosphoric acid.

Ethanol may be used as the organic solvent, and in this case, the target reaction temperature is preferably set to 78 to 200 ° C.

In addition, ethylene glycol may be used as the organic solvent, and in this case, the target reaction temperature is preferably set to 198 to 300 ° C.

The heat treatment is preferably carried out in a reducing gas atmosphere or an inert gas atmosphere at a temperature of 500 ~ 900 ℃.

The method of manufacturing a LiFePO ₄ positive electrode active material for a lithium ion battery includes the steps of wet grinding prior to the heat treatment to remove salt components which are not removed in the cleaning process while micronizing the dried precipitate and having a uniform particle size. It may further include.

The LiFePO ₄ positive electrode active material for a lithium ion battery manufactured using the method for preparing a LiFePO ₄ positive electrode active material for a lithium ion battery has particles having a spherical structure, and has a plurality of pores having a diameter of 2 to 300 nm on the surface and bulk of the particle. Are distributed to show porosity, and the average particle diameter of the particles is 1 to 20 µm, and insertion or desorption of cations is possible at both the surface and the bulk of the particles through the plurality of pores according to a charging or discharging operation.

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

The specific surface area of the spherical structure particles may range from 0.1 to 100 m 2 / g.

Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to the following Examples.

≪ Example 1 >

2 is a view schematically showing a reactor for synthesizing a LiFePO ₄ precursor.

Referring to FIG. 2, lithium salts, iron salts, phosphate salts and cetyltrimethylammonium bromide (CTAB) are dissolved in an organic solvent. At this time, lithium (Li), iron (Fe) and phosphorus (P) is added to the organic solvent by adjusting the content of the lithium salt, iron salt and phosphate salt to be mixed in a molar ratio of 1: 1: 1. .

The lithium salt is lithium acetate, lithium carbonate (Li ₂ CO ₃ ; lithium carbonate), lithium chloride (lithium chloride), lithium hydroxide, lithium nitrate (LiNO ₃ ; lithium nitrate) and lithium It is preferably at least one salt selected from lithium sulfate (Li ₂ SO ₄ ).

The iron salts are iron chloride (iron chloride), iron sulfate that;; (iron nitrate Fe (NO 3) 3) at least one selected from a salt (FeSO ₄ iron sulfate), salts (iron citrate) and iron nitrate to iron sheet desirable.

The phosphate salt is preferably at least one salt selected from ammonium phosphate and phosphoric acid (H ₃ PO ₄ ; phosphoric acid). The ammonium phosphate may be first ammonium phosphate (NH ₄ H ₂ PO ₄ ) or second ammonium phosphate ((NH ₄ ) ₂ HPO ₄ ).

The organic solvent is preferably at least one material selected from ethanol and ethylene glycol.

Cetyltrimethylammonium bromide (CTAB) has the opposite properties of hydrophilicity in the head and hydrophobicity in the head, and is spherical when the concentration of cetyltrimethylammonium bromide (CTAB) is below the critical micelle concentration as the solution evaporates. Or to form a reverse micelle in the form of a cylinder. 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.

The mixed solution 130 of lithium salt, iron salt, phosphate salt and cetyltrimethylammonium bromide (CTAB) is placed in a reactor 100 which can be completely sealed inside, and the reactor 100 is completely The reactor 100 is covered and sealed with a sealable cover 110. Since the reactor 100 is completely 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, 78 to 200 ° C. when ethanol is used as the organic solvent, and ethylene glycol is used as the organic solvent. In the case of 198-300 degreeC, it raises. The reaction temperature is preferably about 78 ~ 200 ℃ when using ethanol as the organic solvent, when the reaction temperature is less than 78 ℃ may not sufficiently react between the lithium salt, iron salt and phosphate salt, If it exceeds 200 ℃ it may be dangerous by the high vapor pressure it is preferable to react at the temperature in the above range.

When the temperature in the reactor 100 reaches the target reaction temperature, it is maintained at the reaction temperature for a predetermined time (for example, 1 to 48 hours) to react the lithium salt, iron salt and phosphate salt. Lithium salts, iron salts and phosphate salts are maintained for a sufficient time (eg, 1 to 48 hours) to allow sufficient reaction to occur. 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 LiFePO ₄ precursor. There is an advantage. While the lithium salt, the iron salt and the phosphate salt are reacting, it is preferable to stir at a predetermined stirring speed (eg, 10 to 500 rpm) using the stirrer 120 in view of uniform reaction and reaction promotion throughout the mixed solution. .

In the reaction process, cetyltrimethylammonium bromide (CTAB) forms a reverse micelle in which a hydrophilic group is located inside and a hydrophobic group is located outside, and a LiFePO ₄ precursor is distributed around the hydrophobic group to form a structure surrounding the reverse micelle. As the reverse micelle is seeded, the LiFePO ₄ precursor is gradually grown to have a spherical particle structure. By this principle, the size of the precipitate of LiFePO ₄ precursor can be adjusted according to the content of cetyltrimethylammonium bromide (CTAB) added.

After sufficient reaction, the temperature of the reactor 100 is cooled to obtain a precipitate which is a spherical LiFePO ₄ 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. Since the LiFePO ₄ precursor formed by the reaction has a large specific gravity and is heavy, it sinks to the bottom of the reactor 100 to form a precipitate.

The lime green precipitate, thus obtained LiFePO ₄ precursor, is selectively separated off. As a method of selectively separating the precipitate, it may be filtered using a filter or a method such as centrifugation.

The precipitates which have been selectively separated are washed at least once with an alcohol such as ethanol, water (H ₂ O), or the like. The salt component and the like remaining on the surface of the precipitate are removed by the cleaning process.

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 and the like.

After performing the drying process, a milling process such as ball milling or jet milling may be performed in order to micronize the precipitate and have a uniform particle size. The grinding may use a dry grinding process, but it is preferable to use a wet grinding (eg, wet ball milling) process that can remove impurities or the like which are not washed while remaining on the surface of the precipitate.

Taking a wet ball milling process as an example, it is charged to a ball milling machine (ball milling machine) in order to uniformly grind the precipitate and wet mixed with a solvent such as water and alcohol. The ball mill is rotated at a constant speed to uniformly mix the precipitate while mechanically crushing it. 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. The size of the balls, the milling time, and the rotation speed per minute of the ball miller are adjusted so as to be crushed to the target particle size. For example, the size of the balls may be set in a range of about 1 mm to 10 mm in consideration of the size of the particles, and the rotational speed of the ball miller may be set in a range of about 50 to 500 rpm. The ball milling is preferably performed for 1 to 48 hours in consideration of the target particle size and the like. By ball milling the precipitate is pulverized into finely sized particles, having a uniform particle size distribution, and evenly mixed. If a wet ball milling process is used, the milled precipitate is dried. The drying is preferably carried out for 30 minutes to 24 hours at a temperature of 60 ~ 120 ℃. In the wet ball milling process, the salt component deposited on the surface of the precipitate may be removed, and a high purity LiFePO ₄ cathode active material may be obtained in a subsequent heat treatment process.

The spherical LiFePO ₄ precursor thus obtained was heat-treated to prepare a LiFePO ₄ positive electrode active material. The heat treatment process may be performed in the following manner.

The LiFePO ₄ 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 2~50 ℃ / min, if the heating rate of the furnace is too slow, long that the productivity is poor so fast heating rate of the furnace, the LiFePO ₄ by a rapid temperature rise 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 a reducing gas atmosphere such as hydrogen (H ₂ ) or hydrogen (H ₂ ) mixed gas or in an inert gas atmosphere such as argon (Ar) and nitrogen (N ₂ ). Maintaining a predetermined time at the heat treatment temperature can obtain a LiFePO ₄ positive electrode active material.

Preferably, the heat treatment temperature is about 500 to 900 ° C. If the heat treatment temperature is too high, lithium (Li) may volatilize, grain growth may occur, and mechanical properties may decrease. When the heat treatment temperature is too low, Since the LiFePO ₄ precursor may not be converted into the LiFePO ₄ cathode active material, heat treatment at the heat treatment temperature in the above range is preferable. During heat treatment, the organic material cetyltrimethylammonium bromide (CTAB) is burned off, and pores are formed at sites where cetyltrimethylammonium bromide (CTAB) is located.

After performing the heat treatment process, the furnace temperature is lowered to unload the LiFePO ₄ cathode 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 LiFePO ₄ positive electrode active material prepared by the above method may be used as a positive electrode of a lithium ion battery. The positive electrode of a lithium ion battery may be prepared by mixing a LiFePO ₄ positive electrode active material with a binder and a conductive material according to a conventional method. As a method of manufacturing a cathode of a lithium ion battery as described above, a generally known method may be used, and it is not particularly limited. A cathode prepared using a LiFePO ₄ cathode active material may be used in a lithium ion battery.

The LiFePO ₄ positive electrode active material for a lithium ion battery prepared as described above has particles having a spherical structure, and a plurality of pores having a diameter of 2 to 300 nm are distributed on the surface and bulk of the particles, indicating porosity, and the average particle diameter of the particles It is about 1-20 micrometers. The spherical structure particles have a porosity of 1 to 50%, and the specific surface area of the spherical structure particles may range from 0.1 to 100 m 2 / g.

LiFePO ₄ positive electrode active material for a lithium ion battery is capable of inserting or detaching cations on both the surface and bulk of the particles through the plurality of pores according to a charging or discharging operation when used in a lithium ion battery. Only the surface of LiFePO ₄ as the positive electrode active material may permit insertion and desorption processes of the cation in the deep interior position of the cathode active material LiFePO ₄ according to the pores formed in the bulk (vulk).

Hereinafter, experimental examples according to the present invention are presented.

<Experimental Example 1>

Dissolve 1-5 g of cetyltrimethylammonium bromide (CTAB) in 35 ml of ethanol, dissolve 2.86 g of lithium acetate, lithium salt, and dissolve 11.31 g of iron nitrate, iron salt. , 3.2 g of phosphoric acid, phosphate salt, was added and mixed uniformly to form a clear yellow mixed solution. At this time, the content of lithium acetate, iron nitrate and phosphoric acid was adjusted so that lithium (Li), iron (Fe) and phosphorus (P) can be mixed in a ratio of 1: 1: 1.

The homogeneously mixed solution was placed in a reactor and sealed with a cover.

The temperature of the reactor was raised to a reaction temperature of 160 ° C. higher than the boiling point of ethanol by using heating means, and maintained at the reaction temperature for 7 hours to react lithium salts, iron salts and phosphate salts.

The reaction was maintained at a temperature of 160 ° C. for 7 hours to allow sufficient reaction to occur, and then the reactor temperature was cooled to room temperature to obtain a light green precipitate.

The precipitate was selectively separated off. The precipitate was selectively separated off by centrifugation.

The selectively separated precipitate was washed twice with ethanol. The washing consisted of dipping the precipitate in 300 ml of distilled water and stirring for 10 minutes at a stirring speed of 3800 rpm.

After the cleaning, the drying process was performed in a drying oven at a temperature of 80 DEG C for 24 hours.

And then charged to the drying step, coarse precipitates in an electric furnace, and heated to a temperature of 600 ℃ at a heating rate of 5 ℃ / min, in the hydrogen (H ₂₎ gas of 2% with argon (Ar), a mixed gas atmosphere of a gas of 98% 12 Heat treatment for a time to obtain a spherical LiFePO ₄ positive electrode active material.

3 is a graph showing a vapor pressure curve according to the temperature in the reactor when ethanol is used as the organic solvent according to Experimental Example 1.

4 is a graph showing an X-ray diffraction (XRD) pattern of a LiFePO ₄ positive electrode active material prepared according to Experimental Example 1. FIG.

Referring to FIG. 4, it was confirmed that the LiFePO ₄ cathode active material prepared according to Experimental Example 1 had a LiFePO ₄ crystal phase.

5 to 10 are scanning electron microscope (SEM) images showing a LiFePO ₄ positive electrode active material prepared according to Experimental Example 1. FIG. 5 is a case where 1 g of cetyltrimethylammonium bromide (CTAB) is used, FIG. 6 is a case where 2 g of cetyltrimethylammonium bromide (CTAB) is used, and FIG. 7 is a case where 3 g of cetyltrimethylammonium bromide (CTAB) is used. 8 illustrates a case where 4 g of cetyltrimethylammonium bromide (CTAB) is used, and FIG. 9 illustrates a case where 5 g of cetyltrimethylammonium bromide (CTAB) is used. FIG. 10 is a scanning electron microscope (SEM) photograph showing an enlarged view of FIG. 6.

5 to 10, the LiFePO ₄ positive electrode active material has particles having a spherical structure, and a plurality of pores having a diameter of 100 to 300 nm are distributed on the surface and bulk of the particles, indicating porosity, and the particle diameter of the particles. It was confirmed that it was about 1-20 micrometers. In addition, it was confirmed that the particle diameter of the LiFePO ₄ positive electrode active material increased as the content of cetyltrimethylammonium bromide (CTAB) increased.

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 (9)

Dissolving lithium salt, iron salt, phosphate salt and cetyltrimethylammonium bromide in an organic solvent;
Putting a mixed solution of lithium salt, iron salt, phosphate salt and cetyltrimethylammonium bromide into a reactor capable of sealing the inside, and sealing the reactor with a cover;
Heating the sealed reactor to raise a target reaction temperature equal to or higher than the boiling point of the organic solvent;
As the temperature of the reactor is maintained at the target reaction temperature, the cetyltrimethylammonium bromide forms an inverted micelle in which a hydrophilic group is located inside and a hydrophobic group is located outside, and lithium salt, iron salt, and phosphate salt react with each other. As the spherical LiFePO ₄ precursor is formed, it is distributed around the hydrophobic group to form a structure surrounding the reverse micelle, and as the reaction proceeds, the LiFePO ₄ precursor gradually grows to have a spherical particle structure, and the reactor is caused by specific gravity difference. Electrified at the bottom of the;
Selectively separating out the precipitate which is a spherical LiFePO ₄ precursor that sank to the bottom of the reactor;
Washing and drying the precipitate which has been selectively separated; And
Heat treating the dried precipitate to obtain a LiFePO ₄ positive electrode active material,
The method of manufacturing a LiFePO ₄ positive electrode active material for a lithium ion battery, characterized in that the size of the precipitate is adjusted according to the content of the cetyltrimethylammonium bromide added.
The method of claim 1, wherein the lithium salt is at least one salt selected from lithium acetate, lithium carbonate, lithium chloride, lithium hydroxide, lithium nitrate and lithium sulfate,
The iron salt is at least one salt selected from iron chloride, iron sulfate, iron citrate and iron nitrate,
The phosphate salt is a method for producing a LiFePO ₄ positive electrode active material for a lithium ion battery, characterized in that at least one salt selected from ammonium phosphate and phosphoric acid.
According to claim 1, using ethanol as the organic solvent, and the target reaction temperature process for producing a lithium ion battery positive electrode active material is LiFePO _4, characterized in that set to 78~200 ℃.
The method of claim 1, wherein the organic solvent using a glycol, wherein the production of the target reaction temperature of the lithium ion battery positive electrode characterized in that LiFePO ₄ is set to 198~300 ℃ active material.
The method of claim 1, wherein the heat treatment is a lithium ion battery, characterized in that at a temperature of 500~900 ℃ in a reducing gas atmosphere or inert gas atmosphere LiFePO ₄ method of producing a positive electrode active material.
The method of claim 1, further comprising the step of wet grinding prior to the heat treatment to remove the salt component that is not removed in the cleaning process while micronizing the dried precipitate to have a uniform particle size LiFePO for lithium ion battery ₄ Method for producing a positive electrode active material.
It is produced by the method according to claim 1, has a spherical structure, a plurality of pores having a diameter of 2 ~ 300nm on the surface and bulk of the particles are distributed to show porosity, the average particle diameter of the particles 1 ~ 20 μm, the LiFePO ₄ positive electrode active material for a lithium ion battery capable of inserting or detaching cations on both the surface and the bulk of the particles through the plurality of pores according to a charging or discharging operation.
The LiFePO ₄ positive electrode active material of claim 7, wherein the spherical particles have a porosity of 1 to 50%.
8. The LiFePO ₄ positive electrode active material for lithium ion batteries according to claim 7, wherein the specific surface area of the spherical structure particles is in the range of 0.1 to 100 m 2 / g.

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