KR101853836B1 - Positive electrode active material for rechargable lithium battery, method for manufacturing the same, and rechargable lithium battery including the same - Google Patents

Abstract

Provided is a positive electrode active material for lithium secondary batteries. More specifically, the present invention relates to a positive electrode active material for lithium secondary batteries, a production method thereof, and a lithium secondary battery comprising the same. The positive electrode active material is a secondary particle in which lithium metal oxide particles are aggregated, wherein the lithium metal oxide particles have a nickel-layered structure. Ti and B in the structure are simultaneously doped. A doping ratio of the lithium metal oxide particles based on 1 mole of metal in the whole lithium metal oxide satisfies the following condition respectively, 0.0001 <=Ti<= 0.05 and 0.00005 <=B<= 0.025. The average density of the secondary particles is 0.97 or more and 1 or less, and the BET value of the secondary particles is 0.5 m2/g or less.

Description

TECHNICAL FIELD The present invention relates to a positive electrode active material for a lithium secondary battery, a method for producing the same, and a lithium secondary battery including the same. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive active material for a lithium secondary battery,

A cathode active material for a lithium secondary battery, and a lithium secondary battery comprising the same.

2. Description of the Related Art In recent years, portable electronic devices such as AV devices and personal computers have been rapidly made portable and wireless, and as a driving power source therefor, there is a growing demand for secondary batteries having small and lightweight high energy densities. In recent years, development and commercialization of electric vehicles and hybrid vehicles have been made for the global environment, and thus there is a growing demand for lithium ion secondary batteries having excellent storage characteristics. Under such circumstances, a lithium ion secondary battery having a large charge / discharge capacity and an excellent life characteristic has been attracting attention.

Conventionally, LiMn ₂ O ₄ of a spinel type structure, LiMnO ₂ of a zigzag layer type structure, LiCoO ₂ and LiNiO ₂ of a layered rock salt type structure are generally used as a cathode active material useful for a high energy type lithium ion secondary battery having a voltage of 4 V class Among them, a lithium ion secondary battery using LiNiO2 is attracting attention as a battery having a high charge / discharge capacity.

However, this material is inferior in durability in charging and discharging cycles, and further improvement in characteristics is required.

In order to solve the above-mentioned problem, a secondary particle aggregated with lithium metal compound particles simultaneously doped with Ti and B in a nickel-based layered structure is provided as a cathode active material.

The present invention also provides a method for producing the positive electrode active material, and a lithium secondary battery in which the positive electrode active material is applied to a positive electrode.

In one embodiment of the present invention, secondary particles in which lithium metal compound particles simultaneously doped with Ti and B are aggregated in a nickel-based layered structure are provided as a cathode active material.

Specifically, the lithium metal oxide particles are a nickel-based layered structure, and Ti and B in the structure include simultaneously doped lithium metal oxides.

The doping ratio of the lithium metal oxide particles is 0.0001? Ti? 0.05 and 0.00005? B? 0.025, respectively, on the basis of the molar ratio.

More specifically, the lithium metal composite oxide particle may be a nickel-based layered structure including nickel and cobalt.

For example, the lithium metal oxide particles may be represented by the following formula (1).

[Chemical Formula 1]

Li _{1 + W} (Ni _a Co _b Ti _x B _y Me _z ) _{1-W 2} O ₂

Wherein Me is at least one element selected from the group consisting of an alkali metal, an alkali metal, an alkaline earth metal, a transition metal, a group 13 element, or a group 14, -0.5? W? 0.5, 0.5? A < <b <0.5, 0.0001? x? 0.05, 0.00005? y? 0.025, and 0? z? In the formula 1, 2.0? X / y? 20.0, 0.005? X? 0.05, and 0.0025? Y? 0.05.

On the other hand, the lithium metal oxide powder is an index of compactness and includes particles having an internal pore ratio of 1% or less.

In addition, the lithium metal oxide powder includes particles having a circularity of 0.9 or more.

The BET specific surface area of the lithium metal oxide is less than 0.5 m ² / g.

In another embodiment of the present invention, there is provided a process for preparing a dry mixture of a Ti supply material, a B supply material, a nickel-based metal hydroxide precursor, and a lithium feed material; And firing the dry mixture to form secondary particles in which lithium metal oxide particles are aggregated. The present invention also provides a method for producing a cathode active material for a lithium secondary battery.

However, the stoichiometric molar ratio of the dry mixture is controlled so that the doping ratio of the lithium metal oxide particles is 0.0001? Ti? 0.05 and 0.00005? B? 0.025, respectively, independently on the basis of the molar ratio.

As the nickel-based metal hydroxide precursor, hydroxides including nickel and cobalt can be used.

The firing temperature of the dry mixture may be 700 to 1,050 ° C.

In another embodiment of the present invention, there is provided a positive electrode comprising: a positive electrode including a positive electrode collector and a positive electrode active material layer disposed on the positive electrode collector; A negative electrode comprising a negative electrode active material; And an electrolyte, wherein the cathode active material layer includes a cathode active material, and the cathode active material uses the same one as described above.

The lithium secondary battery had a capacity retention rate of 98% or more relative to the initial (100%) after 30 cycles when a voltage of 4.3 to 3.0 V was applied at 0.1 C / 0.1 C to Li + / Li at 25 캜, The maintenance rate may be 94% or more of the initial (100%), and the capacity maintenance rate after 100 cycles may be 100% or more of the initial (100%).

Further, when a voltage of 4.3 to 3.0 V is applied at 1 C / 1C to Li + / Li at 25 占 폚, the formation discharge capacity may be 190 mAh / g or more.

Meanwhile, the cathode active material layer may include a conductive material, a binder, or a combination thereof.

The optimum dopant combination (Ti and B) capable of exhibiting a stable cycle characteristic by suppressing the change of the crystal structure even during the course of the cycle can be applied to the nickel-based radar structure which is rich in Ni and capable of exhibiting a high capacity with respect to the positive electrode active material. Of the doping concentration), but it is possible to suggest an optimal doping ratio that can mitigate the decrease in the initial discharge capacity due to the excessive dopant content.

1 is an image showing a cathode active material particle prepared in Example 2. Fig.
FIG. 2 is an image showing the cathode active material particles produced in Comparative Example 1. FIG.
3 is an image showing a cathode active material particle produced through Comparative Example 4. FIG.
4 is an SEM image of Example 1. Fig.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

Cathode active material

In one embodiment of the present invention, secondary particles in which lithium metal compound particles simultaneously doped with Ti and B are aggregated in a nickel-based layered structure are provided as a cathode active material. Specifically, the lithium metal oxide particles are a nickel-based layered structure.

In addition, Ti and B in the structure may include simultaneously doped lithium metal oxides. The doping ratio of the lithium metal oxide particles is in the range of 0.0001? Ti? 0.05 and 0.00005? B? 0.025,

This is because, in the nickel-based radar structure in which Ni is abundantly contained in the positive electrode active material to exhibit a high capacity, an optimal dopant combination (Ti And B), with an optimal doping ratio (0.0001? Ti? 0.05, 0.00005? B? 0.025) that can mitigate the decrease in initial discharge capacity due to excessive dopant content.

Concretely, when Ti and B are simultaneously doped in the nickel-based layered structure. The effect of stabilizing the crystal structure is more excellent than when only Ti or B is doped alone.

When such stable particles are gathered to form secondary particles, the internal particle spacing (voids) is reduced. As a result, the total pore volume in the secondary particles is reduced, and collapse of the secondary particles during driving of the battery can be suppressed.

However, depending on the doping ratio of each element, the cycle life characteristics and the initial capacity characteristics of the battery tend to be different from each other. Specifically, as the doping ratio of Ti and B increases, the cycle life characteristics of the battery are improved, but the charging capacity and efficiency tend to decrease.

In this connection, the doping ratio of 0.0001 &lt; = Ti = 0.05 and 0.00005 &lt; = B &lt; = 0.025, which is defined in advance, can be improved by improving the effect of improving the cycle life characteristics of the battery, Ratio.

Hereinafter, the cathode active material provided in one embodiment of the present invention will be described in more detail.

The lithium metal composite oxide particle has a layered structure including nickel and cobalt, and may be represented by, for example, the following chemical formula (1).

[Chemical Formula 1]

Li _{1 + W} (Ni _a Co _b Ti _x B _y Me _z ) _{1-W 2} O ₂

Wherein Me is at least one element selected from the group consisting of an alkali metal, an alkali metal, an alkaline earth metal, a transition metal, a Group 13 element and a Group 14, and -0.5? W? b < 0.5, 0.0001? x? 0.05, 0.00005? y? 0.025, and 0? z?

That is, the lithium metal oxide particle is a layered structure including nickel and cobalt, and has a molar content of Ni of 50 mol% or more, 0.0001? Ti? 0.05, and 0.00005? B? Doped, and may additionally include Me doping. Of course, Me doping can be omitted (when z = 0).

In Formula 1, 2.0? X / y? 20.0. When the respective doping ratios of Ti and B satisfy the above relational expression, the capacity loss due to doping can be minimized while optimizing the effect of improving the cycle life characteristics of the battery, and this fact is confirmed in the following evaluation examples.

In the above formula (1), 0.005? X? 0.05, and 0.0025? Y? 0.025. Of course, this case also can be 2.0? X / y? 20.0.

On the other hand, the ratio of the average internal pore of the lithium metal oxide powder may be 1% or less. The pore ratio can be measured by a pixel method, and a detailed method is discussed in Evaluation Example 1. When the internal pore ratio is low, the density is high. When the range is satisfied, it can be seen that the cyclic characteristics are excellent as a result of confirming through this embodiment.

Further, the average particle circularity of the lithium metal oxide powder is 0.9 or more.

The average circularity means how close the circle shape is to the particle shape. In the present invention, the average circularity can be measured by a binary method, and a detailed measurement method will be described in Evaluation Example 2. In the present invention, it can be seen that the higher the degree of circularity, the higher the cycle. This is because the smaller the size of the primary particle is, the smaller the particle size of the primary particle is.

The BET specific surface area of the lithium metal oxide is 0.5 m ² / g or less. More specifically, it may be 0.4 m ² / g or less. When these ranges are satisfied, it can be seen that the voids of the particles are suppressed, and it can be seen that they are dense particles.

It can be seen that the size of the pores is smaller or the volume of the pores is smaller than that of the Ti or B single doping. As a result, the structure can be collapsed during operation of the cell, or the particles can be prevented from being broken during the pressing process.

Method for producing cathode active material

In another embodiment of the present invention, there is provided a process for preparing a dry mixture of a Ti supply material, a B supply material, a nickel-based metal hydroxide precursor, and a lithium feed material; And firing the dry mixture to form secondary particles in which lithium metal oxide particles are aggregated. The present invention also provides a method for producing a cathode active material for a lithium secondary battery.

However, the stoichiometric molar ratio of the dry mixture is controlled so that the doping ratio of the lithium metal oxide particles is 0.0001? Ti? 0.05 and 0.00005? B? 0.025, respectively, independently on the basis of the molar ratio.

According to this series of processes, the above-described cathode active material can be obtained.

Hereinafter, the description of the finally obtained material will be omitted, and the characteristics of raw materials, processes, etc. used in each of the above steps will be described.

Manufacturing process of raw material mixture

In the process of preparing the mixture of raw materials, a material including elements to be doped is mixed together with a nickel-based metal hydroxide precursor and a lithium supplying material.

Specifically, the Ti-supplying material and the B-supplying material are mixed together with the nickel-based metal hydroxide precursor and the lithium supplying material, and the mixing method at this time is not limited to all the methods of dry-making.

Examples of the nickel-based metal hydroxide precursor include hydroxides including nickel and cobalt, for example, those represented by the following formula (2).

???????? Ni _a Co _b Me _z (OH) ₂ ?????

Wherein Me is at least one element selected from the group consisting of an alkali metal, an alkali metal, an alkaline earth metal, a transition metal, a Group 13 element and a Group 14, 0.5? A <1, 0? B? 0.5, 0.01.

The precursor may have a roundness of 0.9 or more. The description thereof is as described above.

When such a nickel-based metal hydroxide precursor is used, secondary particles in which the lithium metal oxide particles represented by the above-mentioned formula (1) are collected can be finally obtained.

Mixture of raw materials

The firing temperature of the dry mixture may be 700 to 1,050 ° C. When firing is performed within this range, Li, Ti, and B in the nickel-based metal hydroxide precursor are evenly distributed, so that secondary particles aggregated with desired lithium metal oxide particles can be formed.

However, if it exceeds the above range, undesirable phenomenon such as generation of reaction impurities and generation of large particles may occur, and if it is less than the above range, the reaction may not be completely performed and desired material may not be formed.

Lithium secondary battery

Another embodiment of the present invention provides a lithium secondary battery comprising a cathode, a cathode, and an electrolyte solution containing the cathode active material.

The positive electrode includes a positive electrode collector and a positive electrode active material layer formed on the positive electrode collector. The cathode active material layer includes the above-described cathode active material, and optionally, a binder, a conductive material, or a combination thereof.

The lithium secondary battery had a capacity retention rate of 98% or more relative to the initial (100%) after 30 cycles when a voltage of 4.3 to 3.0 V was applied at 0.1 C / 0.1 C to Li + / Li at 25 캜, The retention rate may be 94% or more of the initial (100%) and 100% of the initial (100%) capacity retention rate after 100 cycles.

Further, when a voltage of 4.3 to 3.0 V is applied at 1 C / 1C to Li + / Li at 25 占 폚, the formation discharge capacity may be 190 mAh / g or more.

Such excellent cell performance is supported by the evaluation examples described later.

Hereinafter, a redundant description of the above-mentioned positive electrode active material will be omitted, and the remaining constitution of the lithium secondary battery will be described.

As the collector, aluminum may be used, but the present invention is not limited thereto.

The binder may be selected from, for example, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers comprising ethylene oxide, Styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, and the like can be used.

The conductive material is used for imparting conductivity to the electrode. Any conductive material can be used without causing any chemical change in the battery. Examples of the conductive material include metal powders such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, copper, nickel, aluminum and silver, metal fibers and the like, and conductive materials such as polyphenylene derivatives May be used alone or in combination.

The negative electrode includes a current collector and a negative electrode active material layer formed on the current collector.

The current collector may be a copper foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foil, a copper foil, a polymer substrate coated with a conductive metal, or a combination thereof.

The negative electrode active material layer includes a negative electrode active material, a binder composition, and / or a conductive material.

The negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, a lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

Descriptions of the negative electrode active material, the binder composition and the conductive material will be omitted.

The electrolyte includes a non-aqueous organic solvent and a lithium salt. The non-aqueous organic solvent and the lithium salt can be used as long as they are compatible with each other, so that detailed explanation is omitted.

Examples of the present invention, comparative examples thereof, and evaluation examples thereof will be described below. The following examples are only illustrative of the present invention and are not intended to limit the scope of the present invention.

Example 1

(1) Preparation of cathode active material

The desired LiNi _{0 . 8865} Co _{0 . 0985} Ti _{0 . 005} B _{0 . To} be a stoichiometric molar ratio of O ₂ , the Ni-based metal hydroxide precursor Ni _{0 .} A _{9 0 .1} Co (OH) _2, lithium source material of LiOH, Ti feed material is TiO _2, and B raw materials of B ₂ O _3, and mixed in a dry process.

Dried mixture was filled in a mullite saggar and fired in a box-type sintering furnace in an air atmosphere at a firing temperature of 790 for a total of 10 hours. Thereafter, it was naturally cooled to room temperature.

The material thus obtained was pulverized and classified to obtain an average particle size of 15 占 퐉, which was obtained as the cathode active material of Example 1.

(2) Production of lithium secondary battery (Half-cell)

Were uniformly mixed in an N-methyl-2-pyrrolidone solvent such that the mass ratio of the cathode active material to the conductive material (Denka black) and the binder (PVDF) of Example 1 was 94: 3: 3 (active material: conductive material: binder) .

The above mixture was spread evenly on an aluminum foil, compressed by a roll press, and vacuum-dried in a 100-200 vacuum oven for 12 hours to prepare a positive electrode. Li-metal was used as a counter electrode, and 1 mol of LiPF ₆ solution in a mixed solvent of ethylene carbonate (EC): ethyl methyl carbonate (EMC) = 1: 2 was used as a liquid electrolytic solution according to a conventional manufacturing method A half-coin cell was prepared.

Example 2

LiNi _{0 . 8865} Co _{0 . 0985} Ti _{0 . 01} B _{0 .} Object ₀₀₅ to O ₂ by dry mixing the raw materials and the remainder of the active material by the same process as in Example 1 to prepare a half-cell for making and including the same.

Example 3

LiNi _{0 . 8865} Co _{0 . 0985} Ti _{0 . 05} B _{0 . An} active material was prepared by dry mixing the raw materials with the aim of O ₂ and the remainder in the same manner as in Example 1 to prepare a half-cell including the same.

Comparative Example 1

LiNi _{0 . 8865} Co _{0 . 0985} Ti _{0 . 01} &lt; / RTI &_gt; O2, and the remaining materials were prepared in the same manner as in Example 1 to prepare a half-cell.

Comparative Example 2

LiNi _{0 . 8865} Co _{0 . 0985} B _{0 .} Object ₀₀₅ to O ₂ by dry mixing the raw materials and the remainder of the active material by the same process as in Example 1 to prepare a half-cell for making and including the same.

Comparative Example 3

LiNi _{0 . 8865} Co _{0 . 0985} Ti _{0 . 01} B _{0 . 01} &lt; / RTI &_gt; O2, and the remaining materials were prepared in the same manner as in Example 1 to prepare a half-cell.

Comparative Example 4

LiNi _{0 . 8865} Co _{0 . 0985} O ₂ , and the remainder was prepared in the same manner as in Example 1 to prepare an active material, and a half cell comprising the same was prepared.

Evaluation example 1 (particle inner pore ratio, particle density)

The measurement was carried out by SEM (scanning electron microscope / scanning electron microscope).

The SEM detects the secondary electrons scattered in the sample by the irradiated energy, and uses the principle that the displayed dye is changed according to the amount of the detected secondary electrons, so that light and shade are generated and are combined and imaged.

Thus, the name card difference can be defined by a pixel-based program such as Photoshop, and the area of the pore and the bulk can be obtained by obtaining the area of the area formed by the boundary. Normally, the bulk portion has a large amount of electrons scattered, so that the bulk portion has a bright color and the pore portion has a dark color.

The color of the pore is close to the color outside the particle, not the particle, which is closer to black as the secondary particles are not scattered.

The density of the particles can be any program that can be known by the ratio occupied by the pore area in the particle in the particle and can obtain the area with the difference of the measured particle color pixel as a boundary. Typically, Photoshop is available and can be obtained through the following steps.

1) Use the magic stick function to check the area (A) calculated from the measurement log after clicking the bulk part inside the particle to specify the color range of the same color as the color of the bulk part by ± 5

2) Using the magic stick function, click on the pore inside the particle to specify the same color area of the same color as the pore and set the pigment tolerance within ± 5, select all the pores inside the particle, Check the area (B) calculated by summing in the plane

3) Determine the ratio of the fore part to the total area of the particle (C) through the relation A / (A + B)

1 is an image showing a cathode active material particle prepared in Example 2. Fig.

FIG. 2 is an image showing the cathode active material particles produced in Comparative Example 1. FIG.

3 is an image showing a cathode active material particle produced through Comparative Example 4. FIG.

Compared with FIG. 1, FIG. 2 and FIG. 3 show that the ratio of the void space in the cathode active material is high.

The cross-section of each of the cathode active materials of Comparative Example 4, Comparative Example 1 and Example 2 was observed by an electron scanning microscope. It was found that the relatively bright portion in a single particle was defined as A, the relatively dark And the area of the pore portion is B, it can be confirmed that the ratio of A / (A + B) is the largest in Example 2.

However, it can be seen that the size of the secondary particle internal pores becomes larger and the volume occupied by the pores becomes larger as compared with Comparative Example 1 in which Ti alone is doped only and Comparative Example 4 which is not doped at all.

Evaluation example  2 (particle circularity)

The circularity can be obtained as follows.

After particle images were taken with a scanning electron microscope (SEM) or a transmission electron microscope (TEM), particles having a size of D40 or more of the powder to be measured were randomly selected,

1) Draw a first circle inside the particle that can contain the maximum internal area of the particle.

2) Draw a second circle containing the entire area of the particle except for the area included in the first circle, with the longest axis of the particle as the diameter.

3) A circularity value? Is obtained by a ratio? /? Between the length? Of the first circle and the length? Of the diameter of the second circle.

The reason why the particle size in the measured powder is more than D40 is that in the case of small particles of Dmin to less than D40, the shape of the particles tends to be irregular in almost all of the test samples, so that the difference of the particle sphericality by the dopant can not be clearly confirmed Because.

The difference in sphericality of the particles due to the dopant can be confirmed from the particles of D40 or more in which the reaction is completed when the precursor is synthesized. In general, particles that are not completely reacted in the precursor state have a morphology of irregular shape, so that they have an irregular shape when they are calcined. Therefore, it is preferable to obtain the average circularity in the particles of D40 or more in which the reaction is completed in the precursor state.

These compactness and circularity are parameters of a single particle unit. Therefore, in order to be applied to a powder, this measurement can be applied to the number of n particles, divided by n, and then the average can be applied as a powder characteristic.

In this case, n is usually the total number of particles randomly distributed within the SEM image 1000 magnification or 3000 magnification, and is usually 20-30.

4 is an SEM image of Example 1. Fig. It can be seen that almost all of the particles having a particle size of D40 or more have a spherical shape.

Compactness Circularity BET (m ² / g) Example 1 0.999 0.97 0.32 Example 2 0.999 0.98 0.29 Example 3 0.999 0.97 0.30 Comparative Example 1 0.968 0.98 0.69 Comparative Example 2 0.957 0.97 0.62 Comparative Example 3 0.999 0.97 0.30 Comparative Example 4 0.87 0.98 0.78

Thus, it can be seen that, when Ti is doped alone, and when B and Ti are simultaneously doped, the size and volume of the internal pores are both reduced, and the secondary particles are solidified.

Furthermore, such a solid secondary particle will minimize secondary cell structure collapse even if the charge / discharge cycle of the battery is continued, and the battery conduction network will be maintained, thereby minimizing battery capacity decrease.

Evaluation Example 2 (Evaluation of battery characteristics)

Actually, each battery of Examples 1 to 3 and Comparative Examples 1 to 4 was charged and discharged once, charged and discharged once for 30 times, charged and discharged for 50 times, charged and discharged for 100 times, , The discharge capacity and the capacity retention rate were evaluated and recorded in Table 1.

However, each battery was subjected to a voltage of 4.3 to 3.0 V at 1 C / 1C relative to Li + / Li at 25 占 폚.

Ti B 1st Discharge 30th Discharge 50th Discharge 100th Discharge 1st / 30th ratio 1st / 50th ratio 1st / 100th ratio Example 1 0.005 0.0025 210.78 208.93 199.08 169.76 99.12% 94.45% 80.54% Example 2 0.01 0.005 200.78 208.93 199.08 173.83 99.12% 94.45% 82.47% Example 3 0.05 0.0025 195.24 208.99 200.28 172.29 99.15% 95.02% 81.74% Comparative Example 1 0.01 211.09 206.86 182.89 165.27 98.14% 86.77% 78.41% Comparative Example 2 0.005 212.82 196.34 180.66 147.76 93.15% 85.71% 70.10% Comparative Example 3 0.01 0.01 187.47 208.93 200.49 169.80 99.12% 95.12% 80.56% Comparative Example 4 214.03 190.00 175.39 145.46 90.14% 83.21% 69.01%

* discharge unit: mAh / g

One) Advantages of doping

According to Table 1, when the cathode active material doped with Ti, B, or a combination thereof was used (Examples 1 to 3 and Comparative Examples 1 to 3 ), It is confirmed that the capacity retention ratio is improved with the progress of the cycle of the battery.

2) Benefits of Ti and B Co-doping

Further, in the doped cathode active material, when Ti and B were simultaneously doped (Examples 1 to 3 and Comparative Example 4) than in the case where only B or Ti was doped (Comparative Examples 1 and 2) It can be confirmed that the capacity retention rate is improved.

Concretely, the B doping ratio was set to 0.01 and the Ti doping ratio was set to 0.05 as compared with Comparative Example 1 in which the B doping ratio was 0.01 and the single doping was Comparative Example 2 in which the Ti doping ratio was 0.005, In the case of Example 2, the cycle characteristics were further improved.

In this connection, simultaneous doping with a Ti doping ratio of 0.0001 to 0.05 and a B doping ratio of 0.00005 to 0.025 is considered to be advantageous in exhibiting excellent cycle characteristic improving effect.

3) Advantages of limiting Ti and B simultaneous doping ratios

Furthermore, even in the case of simultaneous doping of Ti and B, when the Ti doping ratio is fixed to 0.01 and the B doping ratio is changed to 0.005 (Example 2) and 0.01 (Comparative Example 3), respectively, It is confirmed that the capacity retention ratio after 50 cycles is improved, but the capacity retention ratio and the initial capacity characteristic after 100 cycles are lowered.

As the B doping ratio is increased, the cycle life characteristics of the battery are improved, but the initial characteristics may be lowered. Accordingly, by appropriately adjusting the simultaneous doping ratios of Ti and B, the cycle life characteristics and the initial characteristics of the battery can be harmoniously improved.

Specifically, in Examples 1 to 3 and Comparative Example 3, in Examples 1 to 3 in which the doping ratio (x) of Ti to the doping ratio (y) of B is 2? X / / y = 1, the initial characteristic deterioration is suppressed while maximizing the cycle life characteristic.

It is therefore seen that it is advantageous that the doping ratio (x) of Ti to the doping ratio (y) of B satisfies an appropriate range.

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.

Claims (16)

delete The lithium metal oxide particles are aggregated secondary particles,
The lithium metal oxide particle is a nickel-based layered structure,
The average density of the secondary particles was 0.999,
The BET specific surface area value of the secondary particles is 0.5 m ² / g or less,
Wherein the lithium metal oxide particles are simultaneously doped with Ti and B in the structure,
The doping ratio of the lithium metal oxide particles is 0.0001? Ti? 0.05, and 0.00005? B? 0.025 or less, independently for each mole of metal in the total lithium metal oxide,
Wherein the nickel-based layered structure is a nickel-based layered structure including nickel and cobalt.
3. The method of claim 2,
Wherein the secondary particles have an average circularity of 0.9 or more.
3. The method of claim 2,
Wherein the secondary particles have a BET specific surface area value of 0.4 m ² / g or less.
3. The method of claim 2,
Wherein the lithium metal oxide particles are represented by the following formula (1)
Cathode active material for lithium secondary battery:
[Chemical Formula 1]
Li _{1 + W} (Ni _a Co _b Ti _x B _y Me _z ) _{1-W 2} O ₂
In Formula 1,
Me is at least one element selected from alkali metals, alkaline earth metals, transition metals, Group 13 elements, or Group 14,
0.5? A? 1, 0? B? 0.5, 0.0001? X? 0.05, 0.00005? Y? 0.025, and 0? Z?
6. The method of claim 5,
Wherein in Formula 1, 2.0? X / y? 20.0,
Cathode active material for lithium secondary battery.
6. The method of claim 5,
Wherein 0.005? X? 0.05 in the formula (1)
Cathode active material for lithium secondary battery.
6. The method of claim 5,
Wherein 0.0025? Y? 0.025 in the formula (1)
Cathode active material for lithium secondary battery.
Preparing a dry mixture of a Ti feedstock, a B feedstock, a nickel-based metal hydroxide precursor, and a lithium feedstock; And
Calcining the dry mixture to form secondary particles into which lithium metal oxide particles have been aggregated,
Wherein the dry mixture is controlled to have a stoichiometric molar ratio such that the doping ratio of the lithium metal oxide particles is 0.0001? Ti? 0.05 and 0.00005? B? 0.025,
(Method for producing positive electrode active material for lithium secondary battery).
10. The method of claim 9,
Wherein the nickel-based metal hydroxide precursor comprises nickel and cobalt.
(Method for producing positive electrode active material for lithium secondary battery).
10. The method of claim 9,
The firing temperature of the dry mixture is 700 to 1,050 DEG C,
(Method for producing positive electrode active material for lithium secondary battery).
A positive electrode including a positive electrode collector and a positive electrode active material layer disposed on the positive electrode collector;
A negative electrode comprising a negative electrode active material; And
An electrolyte,
Wherein the cathode active material layer comprises a cathode active material,
Wherein the cathode active material is a secondary particle in which lithium metal oxide particles are aggregated, the lithium metal oxide particle is a nickel-based layered structure, Ti and B in the structure are simultaneously doped, and the doping ratio of the lithium metal oxide particle is, , 0.00001?? Ti? 0.05, and 0.00005? B? 0.025, the average density of the secondary particles is 0.999, and the BET ratio of the secondary particles The surface area value is not more than 0.5 m ² / g
Lithium secondary battery.
13. The method of claim 12,
In the lithium secondary battery,
Wherein the capacity retention rate after 30 cycles at a voltage of 4.3 to 3.0 V at 0.1 C / 0.1 C for Li ⁺ / Li at 25 캜 is 98% or more relative to the initial (100%).
Lithium secondary battery.
13. The method of claim 12,
In the lithium secondary battery,
Wherein the capacity retention ratio after 50 cycles at a voltage of 4.3 to 3.0 V at 0.1 C / 0.1 C for Li ⁺ / Li at 25 캜 is 94% or more relative to the initial (100%).
Lithium secondary battery.
13. The method of claim 12,
In the lithium secondary battery,
Wherein a formation discharge capacity is 190 mAh / g or more when a voltage of 4.3 to 3.0 V is applied at 1 C / 1C to Li ⁺ / Li at 25 占 폚.
Lithium secondary battery.

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