KR101890338B1 - Manufacturing method of a positive electrode active material for rechargable lithium battery, positive electrode active material for rechargable lithium battery manufacture using the same, and rechargable lithium battery including the same - Google Patents

Abstract

The present invention relates to a method for producing a porous structure, comprising the steps of: preparing a first porous structure and a second porous structure by mixing a metal hydroxide, a lithium compound and an additive; filling a mixture of the first porous structure and the second porous structure into a firing vessel and firing And cooling and pulverizing the fired mixture, wherein the first porous structure and the second porous structure have different average particle diameters, and a method for manufacturing a cathode active material for a lithium secondary battery manufactured using the same Active material and a lithium secondary battery comprising the same.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive electrode active material for a lithium secondary battery, a positive electrode active material for a lithium secondary battery manufactured using the same, and a lithium secondary battery comprising the same. BACKGROUND ART THE SAME, AND RECHARGABLE LITHIUM BATTERY INCLUDING THE SAME}

The present invention relates to a method for producing a cathode active material for a lithium secondary battery, a cathode active material for a lithium secondary battery manufactured using the same, and a lithium secondary battery comprising the cathode active material.

BACKGROUND ART Lithium secondary batteries have been actively studied for increasing the capacity of lithium secondary batteries as application fields are expanded from small-sized devices such as portable electronic communication devices to large-sized devices such as electric vehicles and energy storage devices. Accordingly, in order to improve the energy density of a lithium secondary battery, development of a high-capacity electrode active material has been progressed.

Generally, a lithium secondary battery is manufactured by using a material capable of reversible intercalation / deintercalation of lithium ions as a cathode active material and an anode active material, and charging an electrolyte between the anode and the cathode including the cathode active material and the anode active material.

As a cathode active material of such a lithium secondary battery, a lithium composite metal compound or the like is used as a cathode active material of a lithium secondary battery. Such a cathode active material is manufactured by loading powdery raw material into a firing vessel and then firing at a high temperature .

The largest portion of the production process of the cathode active material for a lithium secondary battery is a firing process. Therefore, it is important to reduce the cost of the firing process in order to secure price competitiveness in the production of the cathode active material for a lithium secondary battery.

However, if the amount of the raw material loaded in the plastic container is increased to improve the productivity, the carbon dioxide generated during the firing process is not smoothly discharged. Since the carbon dioxide not discharged increases the amount of impurities remaining on the surface of the cathode active material produced by reacting with the raw material, when the lithium secondary battery is applied to the lithium secondary battery, the lifetime characteristics of the battery deteriorate.

The present embodiments provide a method for producing a positive electrode active material for a lithium secondary battery having improved productivity while securing excellent lifetime characteristics of the lithium secondary battery and a lithium secondary battery including the positive electrode active material produced thereby.

A method of manufacturing a cathode active material for a lithium secondary battery according to an embodiment of the present invention includes:

Preparing a first porous structure and a second porous structure by mixing a metal hydroxide, a lithium compound, and an additive; filling the mixture of the first porous structure and the second porous structure into a firing vessel and firing the mixture; And cooling and pulverizing the resulting mixture, wherein the first porous structure and the second porous structure have different average particle diameters.

The average particle size of the first porous structure may be 0.2 to 0.4 times the average particle size of the second porous structure.

The average particle diameter of the second porous structure may range from 20 mm to 100 mm.

The shape of the first porous structure and the second porous structure may be at least one of a spherical shape, a cylindrical shape, a rectangular parallelepiped shape, a cube shape, a donut shape, a briquette shape, and a mixed shape thereof.

The content ratio of the first porous structure and the second porous structure in the mixture of the first porous structure and the second porous structure may range from 10:90 to 40:60.

The density of the mixture of the first porous structure and the second porous structure may range from 1.5 g / cc to 3.0 g / cc.

The metal hydroxide may include a compound represented by the following formula (1) or (2).

[Chemical Formula 1]

M 1 _x M 2 _y M 3 _z (OH) _{2 + δ}

Wherein M1, M2 and M3 are selected from the group consisting of Ni, Co, Mn and combinations thereof, and 0? X? 1, 0? Y? 1, 0? Z? 1, lt; = 0.02, 0 < x + y + z &lt; = 1)

(2)

M 1 _x M 2 _y M 3 _z (OH) _{2 + δ}

Wherein M1, M2 and M3 are selected from the group consisting of Ni, Co, Al and combinations thereof, 0.8? X? 1, 0? Y? 0.2, 0? Z? 0.2, 0.0? lt; = 0.02, 0 < x + y + z &lt;

The lithium compound may be lithium carbonate or lithium hydroxide.

The additive may be an oxide of Fe, Na, Mg, Ca, Ti, V, Cr, Cu, Zn, Ge, La, Ce, Ta, Sr, Al, Ag, Ba, Zr, Nb, Mo, Hydroxides, hydroxides, and combinations thereof.

Wherein the step of preparing the first porous structure and the second porous structure further comprises a step of adding a binder containing at least one of polyvinyl alcohol (PVA), polyvinyl butyral (PVB) and water Or by mixing them.

The content of at least one of the polyvinyl alcohol (PVA) and the polyvinyl butyral (PVB) ranges from 0 wt% to 1 wt% based on the mixture of the metal hydroxide, the lithium compound and the additive. .

The water content may range from 10% to 15% by weight, based on the mixture of metal hydroxide, lithium compound and additive.

In addition, the present invention may include a cathode active material for a lithium secondary battery manufactured by the above-described production method.

Also, the lithium secondary battery according to an embodiment of the present invention may include a cathode, a cathode, and an electrolyte including the cathode active material for the lithium secondary battery.

Since the method of manufacturing a cathode active material for a lithium secondary battery according to an embodiment of the present invention can easily discharge carbon dioxide generated in a firing process, the amount of raw materials that can be loaded on the firing vessel can be significantly increased, Excellent productivity can be ensured in production of active material.

In addition, the lithium secondary battery including the cathode active material thus produced can secure excellent lifetime characteristics.

FIG. 1 illustrates a porous structure manufactured in the course of preparing a cathode active material for a lithium secondary battery according to an embodiment of the present invention. Referring to FIG.
Fig. 2 shows the state in which the porous structure of Fig.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention may be embodied in many different forms and is not limited to the embodiments described herein.

In order to clearly illustrate the present invention, parts not related to the description are omitted, and the same or similar components are denoted by the same reference numerals throughout the specification.

In addition, since the sizes and thicknesses of the respective components shown in the drawings are arbitrarily shown for convenience of explanation, the present invention is not necessarily limited to those shown in the drawings.

Also, throughout the specification, when an element is referred to as " including " an element, it is understood that the element may include other elements as well, without departing from the other elements unless specifically stated otherwise.

The inventors of the present invention have conducted intensive studies to improve the productivity of the cathode active material while realizing a lithium secondary battery having excellent lifespan characteristics and as a result have found that mixing a metal hydroxide, a lithium compound, and an additive to form a first And the second porous structure are manufactured, and the mixture is calcined and pulverized to produce a cathode active material. The present invention has been accomplished on the basis of these findings.

That is, a method of manufacturing a cathode active material according to an embodiment of the present invention includes: preparing a first porous structure and a second porous structure by mixing a metal hydroxide, a lithium source, and an additive; Filling the mixture in a firing vessel and firing the fired mixture; and cooling and pulverizing the fired mixture, wherein the first porous structure and the second porous structure have different average particle diameters.

First, the steps of preparing the first and second porous structures by mixing the metal hydroxide, the lithium compound, and the additive are described.

The first porous structure and the second porous structure may be prepared by, for example, adding a metal hydroxide, a lithium compound, and an additive to a mixer, mixing the mixture, and then adding water and a binder to granulate the mixture. Alternatively, a metal hydroxide, a lithium compound, and an additive may be put in a molding container and pressed. Even in the case of manufacturing the porous structure by pressurization, water, a binder and the like can be added.

As the mixer, for example, a granulator or an intensive mixer may be used, and the pressurizing process may be performed using, for example, a press.

In the present embodiment, the average particle size of the first porous structure and the second porous structure can be adjusted by adjusting the mixing rate (rpm, etc.), the amount of powder input, and the amount of water added when the porous structure is manufactured using the above- Can be adjusted.

The first porous structure and the second porous structure having different average particle diameters are prepared by appropriately adjusting these conditions and then mixed to prepare a mixture of the first and second porous structures.

At this time, the average particle size of the first porous structure may be about 0.2 to 0.4 times the average particle size of the second porous structure. When the average particle diameter of the first porous structure has a size that satisfies the above range with respect to the average particle diameter of the second porous structure, voids of several mm or more are formed between the prepared first porous structure and the second porous structure included in the firing vessel . Since the emission of carbon dioxide generated in the firing process can be facilitated through the pores, it is preferable that the average particle diameter of the first porous structure satisfies the above range.

The average diameter of the second porous structure may range from 20 mm to 100 mm. When the average particle diameter of the second porous structure satisfies the above range, the first porous structure and the second porous structure are formed in the sintering container in such a manner that voids of several mm or more are formed so as to facilitate the discharge of carbon dioxide in the sintering process Can be filled.

In the case where the porous structure is manufactured by preparing the porous structure including the first porous structure and the second porous structure having different average particle sizes and then mixing and firing the mixture, the amount of the powder to be filled in the firing container is preferably in the range of The productivity can be improved because it can be increased by about 10% to 20% or more as compared with the case where the structure is fired and then fired.

On the other hand, in the step of producing the cathode active material for a lithium secondary battery, the firing step is generally carried out in an oxygen-containing atmosphere. At this time, the oxygen-containing gas flowing from the outside must be easily circulated in the firing container, for example, the fire-resistant container. In this case, the raw material filled in the firing vessel is in contact with oxygen, and the firing efficiency can be improved.

In the firing process, steam and carbon dioxide, which are reaction byproducts, are generated. Among these byproducts, carbon dioxide is heavier than the oxygen-containing gas used for controlling the firing atmosphere, and thus remains in the firing vessel and reacts with the lithium oxide on the surface of the cathode active material during the cooling process to form lithium carbonate.

However, if the concentration of lithium carbonate on the surface of the cathode active material increases, the dispersibility of the cathode active material in slurry production may deteriorate. In addition, when such a cathode active material is applied to a lithium secondary battery, there is a problem in that the capacity of the battery is reduced to deteriorate the life characteristics. Therefore, it is necessary to smoothly discharge the carbon dioxide generated during the firing process.

To this end, the present invention has developed a method for producing a cathode active material for a lithium secondary battery by preparing a first porous structure and a second porous structure having different average particle diameters as described above, and then putting the mixture into a firing step . In this case, a gap of several mm or more can be formed in the mixture of the first and second porous structures to be filled in the firing vessel. Through these pores, the flow of oxygen can be smoothly performed, the firing efficiency can be increased, and the carbon dioxide generated in the firing process can be easily discharged. As a result, the amount of powder that can be filled per unit firing vessel in the firing process can be increased, and productivity is also significantly improved.

On the other hand, the shapes of the first porous structure and the second porous structure may be any shape or irregular shape as long as the atmosphere gas can flow in the firing process and the reaction by-products can be discharged. The first porous structure and the second porous structure may be at least one of a spherical shape, a cylindrical shape, a rectangular parallelepiped shape, a cube shape, a donut shape, a briquette shape, and a mixed shape thereof. In the present embodiment, the first porous structure and the second porous structure are preferably spherical.

If the first and second porous structures are spherical, the average particle size of the first and second porous structures may range from 5 mm to 100 mm. When the average particle diameter of the first and second porous structural bodies is less than 5 mm, the size of the pores formed between the first and second porous structural bodies is small, so that gas does not smoothly flow in and out, When the particle diameter exceeds 100 mm, deformation of the first and second porous structures occurs in the firing step, and the contact area between the firing container and the first and second porous structures increases, thereby reducing the life of the firing container .

That is, the first and second porous structural bodies may be manufactured to have a specific range size of 500 times or more of the particle size of metal hydroxide or lithium compound, and then mixed and filled into the firing vessel to form the first and second porous structural bodies A void may be formed in the mixture to perform a firing process for producing the cathode active material.

Oxygen required for the reaction can be easily introduced through the pores to increase the firing efficiency, and the reaction by-products can smoothly discharge the water vapor and the carbon dioxide from the firing vessel.

In addition, the density of the mixture of the first porous structure and the second porous structure may be in the range of, for example, 1.5 g / cc to 3.0 g / cc. In the present specification, the density of the mixture of the first and second porous structures is defined as follows.

Density of the mixture of the first and second porous structures = (sum of the weights of the first and second porous structures) / (sum of the volumes of the first and second porous structures)

By manufacturing the mixture of the first and second porous structural bodies so as to have a high density, the amount of powder to be filled per unit firing vessel in the firing step can be remarkably increased, and productivity can be improved remarkably.

When the density of the mixture of the first and second porous structures is less than 1.5 g / cc, the amount of the raw material to be filled per unit firing vessel is greatly different from the case of firing only with the first porous structure or firing only with the second porous structure There is a problem that the productivity is not improved. Also, when the density of the mixture of the first and second porous structures is 3.0 g / cc or more, the discharge of carbon dioxide and water vapor generated in the first and second porous structure mixture in the firing process is not smooth, There is a problem that the capacity per unit weight of the cathode active material decreases.

Next, the metal hydroxide used in the production of the porous structure is a secondary particle having an average particle diameter of 10 탆 to 20 탆 in the form of aggregated primary particles of 1 탆 or less.

Here, the metal hydroxide may include a compound represented by the following formula (1) or (2).

[Chemical Formula 1]

M 1 _x M 2 _y M 3 _z (OH) _{2 + δ}

M1, M2 and M3 are selected from the group consisting of Ni, Co, Mn and combinations thereof, and 0? X? 1, 0? Y? 1, 0? Z? 1, 0.0? 0.02, 0 < x + y + z &lt; = 1.

(2)

M 1 _x M 2 _y M 3 _z (OH) _{2 + δ}

Wherein M1, M2 and M3 are selected from the group consisting of Ni, Co, Al and combinations thereof, 0.8 = x? 1, 0? Y? 0.2, 0? Z? 0.2, 0.0? 0.02, 0 < x + y + z &lt; = 1.

Such a metal hydroxide can be produced by a conventional method known in the art and is not particularly limited. For example, the metal hydroxide can be produced by a solid phase reaction method, coprecipitation method, sol-gel method, hydrothermal synthesis method or the like.

The amount of the metal hydroxide to be added may be in the range of 67 to 72% by weight based on the entire mixture, and may be in the range of 67 to 70% by weight.

In the lithium compound used for the production of the porous structure, the lithium carbonate or lithium hydroxide is a secondary particle having an average particle diameter of several micrometers in the form of aggregated primary particles of 1 탆 or less, for example, lithium carbonate or hydroxide Lithium.

The amount of the lithium compound to be added may range from 28% by weight to 33% by weight, specifically from 28% by weight to 30% by weight, based on the whole mixture.

The additive may be selected from the group consisting of Fe, Na, Mg, Ca, Ti, V, Cr, Cu, Zn, Ge, La, Ce, Ta, Sr, Al, Ag, Ba, Zr, Ga, and B oxides or hydroxides, and combinations thereof. However, the present invention is not limited thereto. In the present embodiment, the additive may include Zr (OH) _4, and it may be contained in an amount ranging from 0.01% by weight to 1% by weight based on the entire mixture of the metal hydroxide and the lithium compound. The additive can improve the stability by substituting the metal ion of the cathode active material and acts as an oxide form on the surface of the cathode active material to prevent the reaction with the electrolyte solution.

Also, the step of preparing the porous structure may be carried out by further adding a binder capable of binding the metal hydroxide and the lithium compound to mix.

Such a binder may comprise at least one of, for example, polyvinyl alcohol (PVA), polyvinyl butyral (PVB) and water.

The content of at least one of the polyvinyl alcohol (PVA) and the polyvinyl butyral (PVB) ranges from 0.0 wt% to 1 wt% based on the mixture of the metal hydroxide, the lithium compound and the additive. . Such a binder is a substance which helps binding in the process of producing the first or second porous structure but is burned in the firing process. Therefore, when an excessive amount of the binder is added, carbon dioxide is generated in a large amount during the firing process, and the residual lithium carbonate concentration on the surface of the cathode active material may increase, so that the content of the binder preferably satisfies the above range.

Also, the content of water may be in the range of 10 wt% to 15 wt% based on the mixture of the metal hydroxide, the lithium compound, and the additive. If the content of water is less than 10% by weight, binding of the first or second porous structure is difficult. When the content of water is more than 15% by weight, the viscosity of the mixture of the metal hydroxide, the lithium compound and the additive becomes low and it is difficult to produce the first or second porous structure in a spherical shape.

Fig. 1 shows an exemplary shape of the first or second porous structure manufactured by the above-described method. Referring to FIG. 1, the first or second porous structure 100 may include a precursor 10 and lithium carbonate 20. In the present invention, the first porous structure and the second porous structure have the same shape, but differ only in the size of the average particle size. Thus, both the first porous structure and the second porous structure may have a shape as shown in Fig.

Next, the step of filling and firing the porous structure in a firing vessel is performed.

The firing may be performed by, for example, performing an oxygen-containing gas or an inert gas atmosphere at a temperature ranging from 400 to 1100 for 10 hours to 30 hours, but is not limited thereto. The temperature and time of firing may be appropriately changed as necessary.

As the firing container, for example, alumina, mullite, or a material having a coating layer formed thereon can be used, and any material that is inert to the raw material and has durability under the firing temperature can be used without limitation.

Further, the firing container to be disposed in the firing furnace, for example, the firing chamber may be one, or two or more firing containers may be stacked and fired in two or more layers.

Thereafter, the calcined porous structure is cooled and pulverized.

The cooling and pulverization can be carried out by a conventional method known in the art and are not particularly limited.

That is, the cooling can be performed at a cooling rate of, for example, 1 / min to 10 / min from the firing temperature to at least 200. The cooled porous structure is pulverized to obtain a cathode active material for a lithium secondary battery.

The cathode active material prepared according to one embodiment of the present invention can be usefully used for the anode of a lithium secondary battery. The rechargeable lithium secondary battery includes a cathode and an electrolyte including a cathode active material prepared by the above-described method together with a cathode.

Specifically, the lithium secondary battery according to an embodiment of the present invention may include an electrode assembly including a cathode, a cathode, and a separator disposed between the anode and the cathode.

The negative electrode may be prepared by preparing a composition for forming a negative electrode active material layer by mixing a negative electrode active material, a binder and a conductive material, and then applying the composition to an anode current collector such as copper.

As the negative electrode active material, a material capable of intercalating / deintercalating lithium is used. Examples of the negative active material include lithium metal, lithium alloy, coke, artificial graphite, natural graphite, Lt; / RTI &gt;

Examples of the binder include polyvinyl alcohol, carboxymethylcellulose / styrene-butadiene rubber, hydroxypropylene cellulose, diacetylene cellulose, polyvinyl chloride, polyvinylpyrrolidone, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene Polypropylene and the like can be used, but the present invention is not limited thereto. The binder may be mixed in an amount of 1 to 30% by weight based on the total amount of the composition for forming the negative electrode active material layer.

The conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, and specifically includes graphite such as natural graphite and artificial graphite; Carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used. The conductive material may be mixed in an amount of 0.1 to 30% by weight based on the total amount of the composition for forming the anode active material layer.

The anode includes the cathode active material prepared by the method for producing a cathode active material according to an embodiment. That is, the cathode active material, the binder and optionally the conductive material may be mixed to prepare a composition for forming a cathode active material layer, and then the composition may be applied to a cathode current collector such as aluminum. Further, the conductive material, binder and solvent are used in the same manner as in the case of the above-mentioned anode.

As the electrolyte to be filled in the lithium secondary battery, a non-aqueous electrolyte or a known solid electrolyte may be used, and a lithium salt dissolved therein may be used.

The lithium salt may be, for example, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiSbF ₆ , LiAlO ₄ , LiAlCl ₄ , LiCl, and LiI may be used.

Examples of the solvent of the non-aqueous electrolyte include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate; Chain carbonates such as dimethyl carbonate, methyl ethyl carbonate and diethyl carbonate; Esters such as methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate and? -Butyrolactone; Ethers such as 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 1,2-dioxane and 2-methyltetrahydrofuran; Nitriles such as acetonitrile; Amides such as dimethylformamide, and the like can be used, but the present invention is not limited thereto. These may be used singly or in combination. Particularly, a mixed solvent of cyclic carbonate and chain carbonate can be preferably used.

As the electrolyte, a gelated polymer electrolyte in which an electrolyte solution is impregnated with a polymer electrolyte such as polyethylene oxide or polyacrylonitrile, or an inorganic solid electrolyte such as LiI or Li ₃ N can be used.

The separator may be an olefin-based polymer such as polypropylene, which is chemically resistant and hydrophobic; A sheet or a nonwoven fabric made of glass fiber, polyethylene or the like can be used. When a solid electrolyte such as a polymer is used as the electrolytic solution, the solid electrolytic solution may also serve as a separation membrane.

Hereinafter, the present invention will be described in more detail with reference to experimental examples. These experimental examples are only for illustrating the present invention, and the present invention is not limited thereto.

Example  One

(1) Production of Porous Structure and Cathode Active Material

1) Preparation of Porous Structure

Ni ₀ as metal hydroxide _{. 6} Co _{0 . 2} was prepared in the Mn _{0 .2} (OH) _2, Li-Zr as Li ₂ CO _3, the additive as a raw material (OH) _2, and preparing, in the average particle diameter 8mm by putting them on the disk granules concentrator a first porous structure.

Also, a second porous structure having an average particle diameter of 20 mm was prepared by using a disk granulator using the same material as that of the first porous structure.

2) Preparation of cathode active material

The first porous structure and the second porous structure prepared in 1) were mixed at a ratio of 30:70 to prepare a mixture. The mixture was filled in a saggar of mullite material, and then sintered at 900 ° C in an air atmosphere sintering furnace . The state in which the porous structure is loaded in the firing vessel is shown in Fig.

The sintered material was pulverized and classified according to the firing to prepare a cathode active material for a lithium secondary battery.

(2) Production of lithium secondary battery

The positive electrode active material for a lithium secondary battery prepared in (1) above, 2 wt% of a conductive material (Denka Black), 2 wt% of a binder (PVDF) and 1 wt% of a thickener (CMC) (NMP) solvent to prepare a slurry.

The slurry was uniformly applied to an aluminum (Al) current collector, compressed by a roll press, and vacuum-dried in a 100 ° C vacuum oven for 12 hours to prepare a positive electrode.

Lithium metal (Li-metal) was used as a counter electrode, and a mixed solvent of ethylene carbonate (EC: Ethylene Carbonate): dimethyl carbonate (DMC, Dimethyl Carbonate) ₆ solution was used.

Using each of the above components, a 2032 half-coin cell was fabricated according to a conventional manufacturing method.

Comparative Example  One

A cathode active material and a half cell were fabricated in the same manner as in Example 1, except that only the second porous structure prepared in (1) 2) of Example 1 was filled in an inner shell and fired. At this time, the filling amount of the porous structure packed in the inner shell is shown in Table 1 below.

Comparative Example  2

A precursor of the metal hydroxide form including nickel, cobalt, and manganese was prepared by coprecipitation.

A lithium secondary battery and a half-cell were prepared in the same manner as in Example 1, except that Li ₂ CO ₃ , which is a lithium raw material, was prepared and uniformly mixed with the precursor to fill the saggar.

At this time, the filling amount of the mixture filled in the inner wall is shown in Table 1 below.

Experimental Example  1 - Residue on the surface of the cathode active material Lithium sheep  Measure

The residual lithium content on the surface of the cathode active material prepared according to Example 1 and Comparative Examples 1 and 2 was measured by acid-base titration using dilute hydrochloric acid (HCl). The results are shown in Table 1 below.

Experimental Example  2 - Evaluation of life characteristics

The lifetime characteristics of the half-cells produced according to Example 1 and Comparative Examples 1 and 2 were evaluated.

First, charging and discharging were performed at 0.1 C in a range of 2.5 V to 4.25 V at 25 캜 using a charge / discharge device (Maccor) to which a constant current was applied. The initial discharge capacity and initial charge / discharge efficiency were shown in Table 1 . The same method was repeated 50 times to calculate the discharge capacity ratio at 50 times to one discharge capacity to determine the capacity retention rate, which was defined as the cycle life.

division Example 1 Comparative Example 1 Comparative Example 2 Load per unit in the unit (kg) 7 6 3 Average particle size of porous structure (mm) 20, 8 20 - Residual LiOH (ppm) 700 700 1000 Residual Li ₂ CO ₃ (ppm) 1530 1500 2500 Initial discharge capacity
(mA / g, @ 0.1 C) 176 176 175 Initial Charge / Discharge Efficiency (%) 91 91 90 Capacity retention rate (%)
(50 ^th / 1 ^st @ 1C) 98 98 97

Referring to Table 1, it can be seen that the amount of lithium hydroxide and lithium carbonate remaining on the surface of the cathode active material produced according to Example 1 and Comparative Example 1 in which the porous structure was manufactured and fired was reduced by 30% or more . Therefore, it can be confirmed that when the cathode active material is manufactured after the porous structure is manufactured, the effect of reducing the residual lithium content on the surface is excellent.

However, in the case of Example 1 in which the first and second porous structural bodies were produced and then mixed to produce the cathode active material, as compared with Comparative Example 1 in which the cathode active material was produced by firing only the second porous structural body, It can be confirmed that the load is increased by about 16%.

It is also confirmed that the lithium secondary battery including the cathode active material produced in the same manner as in Example 1 does not deteriorate the lifetime characteristics and has excellent lifetime characteristics.

Therefore, when the cathode active material is manufactured according to an embodiment of the present invention, the residual lithium content of the surface can be reduced, and the amount of the raw material that can be filled per unit firing vessel can be increased The productivity can be remarkably improved.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. As will be understood by those skilled in the art. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

10: precursor
20: Lithium carbonate
100: a first porous structure or a second porous structure

Claims (15)

Preparing a first porous structure and a second porous structure by mixing a metal hydroxide, a lithium compound, and an additive;
Filling a mixture of the first porous structure and the second porous structure into a firing vessel and firing the mixture; And
Cooling and pulverizing the calcined mixture;
Lt; / RTI &gt;
Wherein the first porous structure and the second porous structure are formed of a porous material,
Wherein the average particle diameters are different from each other.
The method according to claim 1,
Wherein the average particle size of the first porous structure is 0.2 to 0.4 times the average particle size of the second porous structure.
The method according to claim 1,
Wherein the second porous structural body has an average particle diameter ranging from 20 mm to 100 mm.
The method according to claim 1,
The shape of the first porous structure and the second porous structure may be,
Wherein the cathode active material is at least one selected from the group consisting of a sphere, a cylinder, a rectangular parallelepiped, a cube, a donut, a briquette, and a mixture thereof.
The method according to claim 1,
Wherein the content ratio of the first porous structure and the second porous structure in the mixture of the first porous structure and the second porous structure is in the range of 10:90 to 40:60 by weight.
The method according to claim 1,
Wherein the density of the mixture of the first porous structure and the second porous structure,
Lt; RTI ID = 0.0 &gt; g / cc. &Lt; / RTI &gt;
The method according to claim 1,
Wherein the metal hydroxide comprises a compound represented by the following formula (1) or (2).
[Chemical Formula 1]
M 1 _x M 2 _y M 3 _z (OH) _{2 + δ}
Wherein M1, M2 and M3 are selected from the group consisting of Ni, Co, Mn and combinations thereof, and 0? X? 1, 0? Y? 1, 0? Z? 1, lt; = 0.02, 0 < x + y + z < = 1)
(2)
M 1 _x M 2 _y M 3 _z (OH) _{2 + δ}
Wherein M1, M2 and M3 are selected from the group consisting of Ni, Co, Al and combinations thereof, 0.8? X? 1, 0? Y? 0.2, 0? Z? 0.2, 0.0? lt; = 0.02, 0 &lt; x + y + z &lt;
The method according to claim 1,
The lithium compound,
Lithium carbonate or lithium hydroxide.
The method according to claim 1,
Preferably,
Oxides or hydroxides of Fe, Na, Mg, Ca, Ti, V, Cr, Cu, Zn, Ge, La, Ce, Ta, Sr, Al, Ag, Ba, Zr, Nb, Mo, Ga, Wherein the positive electrode active material is at least one selected from the group consisting of a combination of a positive electrode active material and a negative electrode active material.
The method according to claim 1,
Wherein the step of fabricating the first porous structure and the second porous structure comprises:
Wherein the binder is carried out by further adding and mixing a binder containing at least one of polyvinyl alcohol (PVA), polyvinyl butyral (PVB) and water.
11. The method of claim 10,
Wherein the content of at least one of the polyvinyl alcohol (PVA) and the polyvinyl butyral (PVB) is in the range of 0 wt% to 1 wt% based on the mixture of the metal hydroxide, the lithium compound and the additive A method for producing a cathode active material.
11. The method of claim 10,
Wherein the water content is in the range of 10 wt% to 15 wt% based on the mixture of the metal hydroxide, the lithium compound and the additive.
The method according to claim 1,
Wherein the firing step is performed under an oxygen-containing gas.
14. The cathode active material for a lithium secondary battery according to any one of claims 1 to 13.
anode;
cathode; And
Comprising an electrolyte,
Wherein the positive electrode comprises the positive electrode active material of claim 14.

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