WO2016089177A1 - Cathode active material, method for manufacturing same, and lithium secondary battery comprising same - Google Patents

Abstract

The present invention provides a cathode active material, a method for manufacturing the same, and a lithium secondary battery comprising the same, the cathode active material being manufactured by a manufacturing method comprising a step of forming a coating layer including a ceramic ion conductor on lithium composite metal oxide particles by mixing the lithium composite metal oxide particles with nano-sol of the ceramic ion conductor and performing heat treatment, wherein the coating layer including the ceramic ion conductor is formed, with a uniform thickness, on the surface of the lithium composite metal oxide particles, so that the cathode active material can minimize capacity reduction and improve life time characteristics when being applied to a secondary battery.

Description

Cathode active material, preparation method thereof, and lithium secondary battery comprising same

Citation with Related Applications

This application claims the benefit of priority based on Korean Patent Application No. 2014-0174080 dated December 5, 2014 and Korean Patent Application No. 2015-0172360 dated December 4, 2015, and all the patents disclosed in the documents of the Korean patent application. The contents are included as part of this specification.

Technical Field

The present invention relates to a positive electrode active material, a method of manufacturing the same, and a lithium secondary battery including the same.

Lithium secondary batteries have been widely used as power sources for portable devices since they emerged in 1991 as small, light and large capacity batteries. Recently, with the rapid development of electronics, telecommunications, and computer industry, camcorders, mobile phones, notebook PCs, etc. have emerged, and they are developing remarkably, and the demand for lithium secondary battery as a power source to drive these portable electronic information communication devices increases day by day. Doing.

Lithium secondary batteries have a problem in that their lifespan drops rapidly as they are repeatedly charged and discharged. In particular, this problem is more serious under high temperature or high voltage. This is due to a phenomenon in which the electrolyte is decomposed or the active material is deteriorated due to moisture or other effects in the battery, and the internal resistance of the battery is increased.

Accordingly, the positive electrode active material for lithium secondary batteries, which is currently actively researched and developed, is LiCoO ₂ having a layered structure. LiCoO ₂ is most commonly used due to its excellent lifespan characteristics and charge and discharge efficiency. However, LiCoO ₂ has a low structural stability and thus is not applicable to high capacity technology of batteries.

As a cathode active material for replacing this, various lithium transition metal oxides such as LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiFePO _4, or Li (Ni _x CoyMnz) O ₂ have been developed. Among them, LiNiO ₂ has the advantage of exhibiting battery characteristics of high discharge capacity, but the synthesis is difficult by a simple solid phase reaction, there is a problem of low thermal stability and low cycle characteristics. In addition, lithium manganese oxides such as LiMnO ₂ or LiMn ₂ O ₄ have advantages in that they are excellent in thermal safety and inexpensive, but have a small capacity and low temperature characteristics. In particular, in the case of LiMn ₂ O ₄ but a part merchandising products to low cost, since the Mn ^{+ 3} structure modification (Jahn-Teller distortion) due to the not good life property. In addition, LiFePO ₄ has a low price and excellent safety, and a lot of research is being made for hybrid electric vehicles (HEV), but it is difficult to apply to other fields due to low conductivity.

Due to this situation, Li (NixCoyMnz) O ₂ is the most recently attracting attention as an alternative cathode active material for LiCoO ₂ . (At this time, X, y, and z are atomic fractions of independent oxide composition elements, respectively, where 0 <x ≦ 1, 0 <y ≦ 1, 0 <z ≦ 1, and 0 <x + y + z = 1. This material is cheaper than LiCoO ₂ and has advantages in that it can be used for high capacity and high voltage, but has a disadvantage in that the rate capability and the service life at high temperature are poor.

Accordingly, the positive electrode active material is formed by doping a material such as Al, Ti, Sn, Ag, or Zn into the positive electrode active material, or by dry or wet coating a conductive metal on the surface of the positive electrode active material. Many attempts have been made to improve thermal stability, capacity characteristics, and cycle characteristics, but the degree of improvement is still insufficient.

The first technical problem to be solved by the present invention is to form a coating layer of a ceramic ion conductor having excellent lithium ion conductivity with respect to lithium composite metal oxide particles to a uniform thickness, in a battery generated due to the formation of a non-uniform coating layer It is to provide a method for producing a positive electrode active material that can minimize the reduction in capacity and improve the battery life characteristics.

The second technical problem to be solved by the present invention is to be produced by the above manufacturing method, to promote the movement of lithium ions on the surface of the lithium composite metal oxide particles, and at the same time can exhibit an impact absorbing effect during the pressing process during the production of the positive electrode By including the coating layer of the ceramic ion conductor, it is to provide a positive electrode active material that can improve the capacity characteristics and life characteristics when applying the battery.

The third technical problem to be solved by the present invention is to provide a positive electrode including the positive electrode active material.

The fourth technical problem to be solved by the present invention is to provide a lithium secondary battery, a battery module and a battery pack including the positive electrode.

In order to solve the above problems, according to an embodiment of the present invention, the lithium composite metal oxide particles are mixed with the nanosol of the ceramic-based ion conductor and heat treated, the coating layer comprising a ceramic-based ion conductor on the lithium composite metal oxide particles It provides a method for producing a positive electrode active material comprising the step of forming a.

In addition, according to another embodiment of the present invention, prepared by the manufacturing method, particles of a lithium composite metal oxide; And a coating layer positioned on the lithium composite metal oxide particles and including a ceramic ion conductor.

In addition, according to another embodiment of the present invention, a cathode including the cathode active material is provided.

Furthermore, according to another embodiment of the present invention, there is provided a lithium secondary battery, a battery module, and a battery pack including the positive electrode.

The method for producing a positive electrode active material according to the present invention utilizes a nano-sol of a ceramic ion conductor having excellent lithium ion ionicity, thereby promoting the movement of lithium ions to the surface of the lithium composite metal oxide particles and simultaneously pressing the positive electrode during the production of the positive electrode. It is possible to uniformly coat a ceramic-based ion conductor that can exhibit an impact absorption effect during the process. As a result, the cathode active material manufactured by the manufacturing method may exhibit improved lifespan characteristics with a minimized capacity reduction when the battery is applied.

The following drawings, which are attached to this specification, illustrate preferred embodiments of the present invention, and together with the contents of the present invention serve to further understand the technical spirit of the present invention, the present invention is limited to the matters described in such drawings. It should not be construed as limited.

1 is a photograph of a nano-sol of a ceramic ion conductor prepared in Preparation Example 1 under a transmission electron microscope.

Figure 2 shows the X-ray diffraction analysis (XRD) results of the nano-sol of the ceramic ion conductor prepared in Preparation Example 1.

FIG. 3 is a photograph of the surface of the cathode active material prepared in Example 1-1 using a Field-Emission Scanning Electron Microscope (FE-SEM). FIG.

Figure 4 is a photograph of the surface of the positive electrode active material prepared in Comparative Example 1-2 by FE-SEM.

5 is a graph showing the results of observing cycle characteristics of the lithium secondary batteries prepared in Examples 2-1 to 2-6 and Comparative Examples 2-1 and 2-2.

Hereinafter, the present invention will be described in more detail to aid in understanding the present invention.

The terms or words used in this specification and claims are not to be construed as being limited to their ordinary or dictionary meanings, and the inventors may appropriately define the concept of terms in order to best describe their invention. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention based on the principle that the present invention.

In the method of manufacturing a positive electrode active material according to an embodiment of the present invention, the lithium composite metal oxide particles are mixed with a nanosol of a ceramic ion conductor and heat treated to form a coating layer including a ceramic ion conductor on the lithium composite metal oxide particles. Forming a step.

In the nanosol of the ceramic ion conductor, the ceramic ion conductor may specifically include at least one of an ion conductive ceramic and a metal ceramic.

The ion conductive ceramic is specifically Y, Ca, or Yttria stabilized zirconia (YSZ ₎ , calcia stabilized zirconia (CSZ), scandia-stabilized zirconia (SSZ), or the like. Zirconia (ZrO ₂ ) -based oxides doped with Sc; Gd, Y or Sm doped, such as gadolinia doped ceria (GDC), samarium doped ceria (SDC), Yttria-doped ceria (YDC) Ceria (CeO ₂ ) based oxides; Lanthanum strontium gallate magnesite (LSGM), lanthanum strontium manganite (LSM), or lanthanum strontium cobalt ferrite (LSCF). Species alone or mixtures of two or more may be used.

In the ion conductive ceramics, the YSZ is a ceramic material made of zirconium oxide (zirconia) added with yttrium oxide (yttria) to be stable at room temperature. The YSZ may be part of the yttria is added by being Zr ^{4 +} ions to be substituted for the zirconia are Y ^3+. This is replaced by three O ² ions instead of four O ² ions, resulting in oxygen vacancy. Because of this oxygen deficiency, YSZ has O ² -ion conductivity, and the higher the temperature, the better the conductivity. Specifically, YSZ is Zr _(1-x) Y _x O _{2 -x / 2} , where 0.01 ≦ x ≦ 0.1, and more specifically 0.08 ≦ x ≦ 0.1. In addition, in this invention, normal temperature means the temperature range in 23 +/- 5 degreeC unless it is specifically defined.

In addition, the CSZ is a ceramic material made by adding calcium oxide (calcia) to zirconium oxide (zirconia) to be stable at room temperature. By adding calcia, the thermal stability of zirconia can be improved. The CSZ is a mixed state of a cubic crystal structure and a tetragonal crystal structure. The tetragonal crystal structure changes to a cubic crystal structure when the temperature rises, and changes to a tetragonal crystal structure when the temperature decreases. In this process, the expansion and contraction of the volume may be repeated.

Also, the SSZ is by the addition of scandium oxide (scandia) to zirconium oxide (zirconia) of a ceramic material so as to create a stable even at room temperature, specifically, the _{(ZrO 2) 1- 2x (Sc} 2 O 3) x, (ZrO 2) _1-2x (Sc ₂ O) _3x-z (Y ₂ O ₃ ) _z or (ZrO ₂ ) _{1-2x- z} (Sc ₂ O ₃ ) _x (CeO ₂ ) _z (where 0.01≤x≤0.2, 0.01 ≤ z ≤ 0.1).

In addition, the GDC is ceria doped with gadolinium oxide (Gd ₂ O ₃ ), and has high ion conductivity like LSGM. Specifically, Gd _0.1 Ce _0.9 O _1.95 can be mentioned.

In addition, the LSGM is a lanthanum-strontium-gallium-magnesium oxide doped with Sr and Mg and having high lithium ion conductivity, and specifically, ( La _x Sr _{1 -x} ) (Ga _y Mg _{1 -y} ) O _{3-. δ} (0.05 ≦ x <1 and 0.05 ≦ y <1, and δ may be defined as a value meaning a small deviation from perfect stoichiometry) and the like.

In addition, the LSM is a lanthanum manganate doped with Sr in LaMnO ₃ and has a manganese-based perovskite structure. Specifically LaSrMnO or La _(1-x) Sr _x MnO ₃ (0.01≤x≤0.3), or La _(1-y) Sr _y Mn _z O _{3 -δ} (0.05≤y≤1, 0.95≤z≤1.15 And δ can be defined as a value meaning a small deviation from the ideal stoichiometry).

In addition, the LSCF is a lanthanum ferrite doped with Sr and Co in LaFeO ₃ , and has excellent stability at high temperature and high ion conductivity.

On the other hand, the metal ceramic is manufactured by mixing and sintering a ceramic and a metal powder, and has both characteristics of a ceramic having high heat resistance and hardness, and a metal having plastic deformation or electrical conductivity. Specifically, in the metal ceramic, the ceramic may be the ion conductive ceramic described above, and the metal may be nickel, molybdenum, cobalt, or the like. More specifically, the metal ceramic may be a cermet such as nickel-yttria stabilized zirconia cermet (Ni-YSZ cermet).

In addition, in the method of manufacturing a positive electrode active material according to an embodiment of the present invention, the ceramic ion conductor may exhibit a peak of a single phase in X-ray diffraction analysis using Cu (Kα-ray).

In addition, in the method of manufacturing a positive electrode active material according to an embodiment of the present invention, the ceramic ion conductor is specifically YSZ, GDC, LSGM, It may include any one selected from the group consisting of LSM, CSZ, SSZ and Ni-YSZ or a mixture of two or more thereof, and more specifically any selected from the group consisting of YSZ, GDC, LSGM, SSZ and CSZ. It may be one or a mixture of two or more thereof.

In addition, in the method of manufacturing a cathode active material according to an embodiment of the present invention, the ceramic ion conductor may include YSZ, and the YSZ is Zr _(1-x) Y _x O _{2 -x / 2} ( At this time, 0.01 ≦ x ≦ 0.30, and more specifically 0.08 ≦ x ≦ 0.10). As described above, in the case of forming the coating layer of YSZ on the surface of the lithium composite metal oxide particles, Y enters the Zr site and has a superstructure, resulting in oxygen deficiency in the structure, resulting in a large amount of empty space on the surface of the cathode active material. Can occur. Such void space facilitates the insertion and desorption of lithium on the surface of the positive electrode active material, and as a result, greatly increases the lithium ion conductivity on the surface of the active material particles, thereby minimizing the capacity and output reduction of the battery.

In addition, the method of manufacturing a positive electrode active material according to an embodiment of the present invention, the ceramic ion conductor may be to include _{SSZ, (ZrO 2) 1- 2x} (Sc 2 O 3) x, (ZrO 2 ) _1-2x (Sc ₂ O) _3x-z (Y ₂ O ₃ ) _z , (ZrO ₂ ) _{1-2x- z} (Sc ₂ O ₃ ) _x (CeO ₂ ) _z (0.01≤x≤0.2, 0.01 ≦ z ≦ 0.l) and mixtures thereof, and may include SSZ selected from the group consisting of a mixture thereof.

In addition, in the method of manufacturing a positive electrode active material according to an embodiment of the present invention, the ceramic ion conductor has a CaO content in the total weight of CSZ of 1 mol% to 20 mol%, more specifically, 2 mol% to 17 mol%. It may be to include a CSZ.

In addition, in the method of manufacturing a cathode active material according to an embodiment of the present invention, the average particle diameter (D ₅₀ ) of the ceramic ion conductor may be 1 nm to 100 nm. Uniform dispersion in the sol is possible when having a particle size within this range. More specifically, the average particle diameter (D ₅₀ ) of the ceramic ion conductor may be 1 nm to 50 nm, and more specifically 1 nm to 5 nm.

In the present invention, the average particle diameter (D ₅₀ ) of the ceramic ion conductor may be defined as the particle size based on 50% of the particle size distribution. The average particle diameter (D ₅₀ ) of the particles according to an embodiment of the present invention can be measured using, for example, a laser diffraction method. In general, the laser diffraction method can measure the particle diameter of several mm from the submicron region, and high reproducibility and high resolution can be obtained. For example, the method for measuring the average particle diameter (D ₅₀ ) of the YSZ is introduced into a commercially available laser diffraction particle size measuring apparatus (eg, Microtrac MT 3000) for nanosols of YSZ, and outputs ultrasonic waves of about 28 kHz. was irradiated with W, it is possible to calculate the average particle diameter (D ₅₀₎ of from 50% based on the particle size distribution of the measuring device.

In addition, in the method of manufacturing a positive electrode active material according to an embodiment of the present invention, the nano-sol of the ceramic ion conductor is 50ppm to about the total weight of the positive electrode active material content of the ceramic ion conductor contained in the positive electrode active material to be finally prepared It may be used in an amount such that it is 300,000 ppm, more specifically 100 ppm to 10,000 ppm.

In the method of manufacturing a positive electrode active material according to an embodiment of the present invention, the nano-sol of the ceramic ion conductor is prepared by dissolving a precursor of the metal for forming a ceramic ion conductor in a glycol solvent and then adding water to hydrate it. Can be.

In the case of the dispersion prepared by dispersing the ceramic ion conductor powder on the nanoparticles in a solvent according to a conventional method, since the ceramic ion conductor is crystalline, it does not exhibit lithium ion conductivity and has very low reactivity with lithium. Therefore, it is difficult to form a uniform coating layer when coating the active material surface. On the other hand, when preparing a nano-sol of a ceramic ion conductor by the precursor reaction of the metal for forming a ceramic ion conductor as described above, a hydroxide-based ceramic type having a nano-scale particle size and amorphous, having a hydroxyl group on the surface An ion conductor is formed. Such a ceramic ion conductor not only exhibits lithium ion conductivity per se, but also has excellent reactivity with lithium, and enables uniform and efficient coating layer formation on a lithium composite metal oxide in an active material to be finally manufactured.

The glycol-based solvent that can be used in the preparation of the nanosol is a dihydric alcohol having two hydroxyl groups in the molecule, and specifically, may be ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol or polyethylene glycol, and any one of them. Or mixtures of two or more may be used.

As the precursor of the metal for forming the ceramic ion conductor, the metal-containing compound for forming the ceramic ion conductor, specifically, hydroxide, oxyhydroxide, alkoxide, carbonate, acetate, oxalate, citrate, nitrate, nitride, Sulfates, sulfides, halides or hydrates thereof, and the like, and any one or a mixture of two or more thereof may be used. In addition, the metal for forming the ceramic ion conductor may be a metal constituting the ceramic ion conductor, specifically, rare earth elements such as Y, Sc, Gd, Sm, Ce, or La; And one or more elements selected from the group consisting of Zr, or alkaline earth metal elements such as Ca, Mg, or Sr; Transition metals such as Mg, Co or Fe; And a mixed element with one or more elements selected from the group consisting of post-transition metals such as Ga. For example, precursors of YSZ include zirconium dinitrate dihydrate (ZrO (NO ₃ ) _{2 ·} 2H ₂ O) as a Zr-containing raw material and yttrium nitrate hexahydrate Y (NO ₃ ) ₃ · 6H as a raw material containing Y ₂ O can be used.

In addition, in the preparation of the nanosol, additives such as a chelating agent, a pH adjusting agent or a dispersing agent are further added to increase the solubility of the precursor of the metal for forming the ceramic ion conductor and to increase the dispersibility of the ceramic ion conductor to be manufactured. Can be.

Specifically, the pH adjusting agent may be an organic acid such as acetic acid, citric acid, lactic acid, or formic acid, or a basic compound such as ammonia, and may be included in an amount such that the pH of the nanosol is 6.5 to 8.

In addition, the dispersant may be a polymer dispersant or a surfactant in detail, and may be included in an amount of 1 part by weight or less, or 0.1 to 0.5 part by weight, based on 100 parts by weight of the ceramic ion conductor.

In addition, during the preparation of the nanosol, when dissolving the precursor of the metal for forming the ceramic-based ion conductor in a glycol-based solvent, a stirring or heat treatment process may be optionally further performed to increase the solubility. The stirring may be performed according to a conventional mixing process.

In addition, the heat treatment process may be carried out at a temperature of 120 ℃ or more below the boiling point of the glycol solvent, specifically 120 ℃ to 300 ℃, more specifically 120 ℃ to 200 ℃, even more specifically 120 ℃ to It may be carried out at 180 ℃.

In addition, after the heat treatment process, a cooling process may be further performed as necessary. In this case, the cooling process may be performed according to a conventional method such as natural cooling or cold wind cooling.

During the dissolution process of the precursor of the metal for forming the ceramic-based ion conductor as described above, an amorphous ceramic-based ion conductor at the nanoparticle level is generated by the reaction between the precursors.

Subsequently, a hydroxide process using water may be performed on the resulting reactant containing ceramic ion conductor. Wherein water; Alternatively, a mixed solvent of a solvent containing water and a hydroxyl group may be used, and the hydroxyl group-containing solvent may be specifically an alcohol (eg, methanol, ethanol, 1-propanol, 2-propanol, etc.), or a polyol (eg, ethylene glycol). , Propylene glycol, diethylene glycol, dipropylene glycol, polyethylene glycol, butane diol, glycerin, etc.), and any one or a mixture of two or more thereof may be used.

The hydroxide process may exhibit excellent reactivity with respect to lithium by binding water molecules to the ceramic ion conductor, and may form a uniform and highly efficient coating layer for the lithium composite metal oxide in the active material to be finally manufactured.

In addition, in the method of manufacturing a cathode active material according to an embodiment of the present invention, the nano-sol of the ceramic ion conductor may include aluminum (Al), niobium (Nb), titanium (Ti), tungsten (W), and molybdenum ( Mo), chromium (Cr), copper (Cu), vanadium (V) and zinc (Zn), any one selected from the group consisting of or a mixed metal of two or more thereof; Alternatively, the nanosol of the above metal may be further included.

The metals may be included in the form of an oxide in the coating layer of the positive electrode active material to be finally manufactured to further improve battery characteristics. Such metal may be included in an amount such that the concentration of the oxide of the metal included in the positive electrode active material to be finally produced is 50ppm to 300,000ppm, more specifically 100ppm to 10,000ppm.

The nanosol of the metal may be prepared by dissolving a metal precursor in a glycol-based solvent to react with a precursor of the nanosol of a ceramic ion conductor, and preparing a nanosol of the metal, followed by hydroxide addition of water. have.

Precursors of the metal are aluminum (Al), niobium (Nb), titanium (Ti), tungsten (W), molybdenum (Mo), chromium (Cr), copper (Cu), vanadium (V) and zinc (Zn). It may be any one selected from the group consisting of or a compound containing two or more of these mixed metals. Specifically, hydroxides, oxyhydroxides, alkoxides, carbonates, acetates, oxalates, citrates, nitrates, nitrides, sulfates, sulfides, halides or hydrates thereof, and the like, or any one or a mixture of two or more thereof. This can be used.

On the other hand, in the method for producing a positive electrode active material according to an embodiment of the present invention, the lithium composite metal oxide may be a composite metal oxide of lithium with one or more metals selected from the group consisting of nickel, manganese and cobalt. Specifically, the lithium composite metal oxide may include a compound of Formula 1 below:

<Formula 1>

Li _{1 + a} Ni _1-bc Mn _b Co _c O ₂

In Formula 1, 0 ≦ a ≦ 0.33, 0 ≦ b ≦ 0.5, and 0 ≦ c ≦ 0.5, more specifically 0 ≦ a ≦ 0.09, and even more specifically, a = 0. In Formula 1, when a is greater than 0.33, the effect of coating the ceramic-based ion conductor on the lithium composite metal particles may be less than about 10% of the difference in lifespan characteristics compared to the case of coating a conventional metal oxide. On the other hand, when a is less than or equal to 0.09, particularly 0 in Formula 1, the effect of coating the ceramic-based ion conductor on the lithium composite metal particles may be 30 to 70% higher than that of other metal oxides. have.

In the method of manufacturing a positive electrode active material according to an embodiment of the present invention, the lithium composite metal oxide is LiCoO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , and lithium in that the capacity characteristics and stability of the battery can be improved Nickel manganese cobalt oxide (eg, Li (Ni _0.6 Mn _0.2 Co _0.2 ) O ₂ , LiNi _{0 . 5} Mn _{0 . 3} Co _{0 . 2} O ₂ , or LiNi _{0 . 8} Mn _{0 . 1} Co _{0 . 1} O _2, etc.) may be any one selected from the group consisting of or a mixture of two or more thereof, more specifically lithium nickel manganese cobalt oxide.

In addition, the average particle diameter (D ₅₀ ) of the positive electrode active material according to an embodiment of the present invention may be 3 ㎛ to 25 ㎛, more specifically may be 5 to 25 ㎛. In the present invention, the average particle diameter (D ₅₀₎ of the lithium-metal composite oxide particles was measured by the same method described in the average particle diameter (D ₅₀₎ of the ceramic-based ion conductor.

The cathode active material according to an embodiment of the present invention may be primary particles of a lithium composite metal oxide, or secondary particles formed by assembling the primary particles. When the positive electrode active material is a primary particle of a lithium composite metal oxide, generation of surface impurities such as Li ₂ CO ₃ , LiOH, and the like caused by reaction with moisture in the air or CO ₂ is reduced, and thus there is a low risk of deterioration of battery capacity and gas generation. Also, excellent high temperature stability can be exhibited. In addition, when the cathode active material is secondary particles in which primary particles are assembled, output characteristics may be more excellent. In the case of secondary particles, the average particle size of the primary particles may be 10 nm to 200 nm. The form of such active material particles may be appropriately determined according to the composition of the lithium composite metal oxide constituting the active material.

In addition, in the method of manufacturing a positive electrode active material according to an embodiment of the present invention, the mixing of the particles of the lithium composite metal oxide and the ceramic ion conductor nanosol is, for example, a solvent and a dispersant in a ceramic ion conductor or a precursor thereof. After adding and stirring to form a colloidal ceramic ion conductor nanosol, the nanosol may be performed by surface treatment by various methods such as mixing, coating, spraying, or dipping with particles of a lithium composite metal oxide.

In addition, in the method of manufacturing a positive electrode active material according to an embodiment of the present invention, the heat treatment may be performed for 4 hours to 10 hours in the temperature range of 100 ℃ to 600 ℃. When the coating is performed under the above-described temperature conditions, a coating layer including a ceramic ion conductor and optionally a metal oxide may be formed on the surface of the lithium composite metal oxide particles by heat treatment.

In addition, the method of manufacturing a cathode active material according to an embodiment of the present invention may further include the step of firing after the heat treatment.

The firing process may be performed for 4 hours to 10 hours in the temperature range of 500 ℃ to 1000 ℃. When the firing process at the above temperature conditions is further performed, the oxidation of the metal is promoted, and the metal oxide selectively used in forming the ceramic-based ion conductor and the coating layer into the lithium composite metal oxide particles. The metal element of may have a concentration gradient that decreases toward the inside from the surface of the lithium composite metal oxide particles.

In this case, the metal element may exist up to about 500 nm from the surface of the lithium composite metal oxide particle. As such, when forming a composite with the lithium composite metal oxide particles, structural crystal collapse of the cathode active material may be prevented to improve structural stability and electrochemical properties.

The lithium composite metal oxide doped with the metal element may specifically include a compound of Formula 2 below:

<Formula 2>

ALi _{1 + a} Ni _1-bc Mn _b Co _c (1-A) M _'s M " _v O ₂

In Formula 2, M 'is a metal element derived from a ceramic ion conductor, specifically, Y, Zr, La, Sr, Ga, Mg, Sc, Gd, Sm, Ca, Ce, Co, Mn and Fe It may be any one selected from the group consisting of two or more mixed elements thereof, more specifically any one or two or more selected from the group consisting of Y, Zr, La, Sr, Ga, Sc, Gd, Sm and Ce It may be a mixed element, and more specifically, at least one element selected from the group consisting of Y and Zr.

In addition, in Formula 2, M ″ is derived from a metal nanosol which may be selectively included in the nanosol, and specifically, in the group consisting of Al, Nb, Ti, W, Mo, Cr, Cu, V, and Zn. Any one or two or more mixed elements selected, and more specifically, any one or two or more mixed elements selected from the group consisting of Al, Nb and Ti.

In Formula 2, 0 <A <1, 0≤a≤0.33, 0≤b≤0.5, 0≤c≤0.5, 0 <s≤0.2, 0≤v≤0.2, more specifically 0≤ a ≦ 0.09, and more specifically 0.9 <A <1, a = 0.

In addition, in Formula 2, M 'and M "may be each independently distributed in a concentration gradient gradually decreasing from the particle surface to the center in the particles of the lithium composite metal oxide. As a result, the concentration of the metal to be doped is distributed in a concentration gradient that gradually changes, so that there is no abrupt phase boundary region in the active material, so that the crystal structure is stabilized and thermal stability is increased. In the case of containing a concentration gradient that is distributed at a high concentration and decreases in concentration toward the particle center, it is possible to prevent a decrease in capacity while showing thermal stability.

Specifically, in the positive electrode active material according to an embodiment of the present invention, when the concentration of the doping elements M 'and M "represents a concentration gradient, the total atomic weight of each of the doping elements M' and M" included in the positive electrode active material is based on The concentration of M 'in a region within 10% by volume of the particle center (hereinafter simply referred to as' Rc ₁₀ region') and a region within 10% by volume of the particle surface (hereinafter simply referred to as' Rs ₁₀ region ') The difference may be 10 to 90 atomic% and the difference in concentration of M ″ may be 10 to 90 atomic%.

In the present invention, the concentration gradient structure and concentration of the doping element in the positive electrode active material particles are determined by an electron probe micro analyzer (EPMA), inductively coupled plasma-atomic emission spectrometer (ICP-). AES) or Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS), and more specifically, using EPMA to move from the center of the cathode active material to the surface. While measuring the atomic ratio of each metal (atomic ratio) can be measured.

In the method of manufacturing a positive electrode active material according to an embodiment of the present invention, a conventional wet mixing method is formed by forming a coating layer containing a ceramic ion conductor on a particle surface of a lithium composite metal oxide using a nanosol of a ceramic ion conductor. Compared to the case of use, the coating layer formed on the surface of the lithium composite metal oxide particles can be formed more uniformly, and by reducing the amount of solvent used, damage of the lithium composite metal oxide particles due to the solvent can be minimized. Can be.

In addition, the cathode active material manufactured by the manufacturing method includes specific composite particles having a single phase, that is, an amorphous ceramic-based ion conductor, thereby minimizing capacity reduction and output reduction of the secondary battery. In addition, due to the structural characteristics of the ceramic ion conductor, it is possible to minimize the cracking phenomenon of the positive electrode active material due to the shock absorbing effect during the positive electrode process, in particular the pressing process, thereby further improving the life characteristics when applied to the secondary battery. .

Accordingly, according to another embodiment of the present invention, a cathode active material prepared by the above-described manufacturing method is provided.

Specifically, the cathode active material may include particles of a lithium composite metal oxide, and a coating layer disposed on the particles of the lithium composite metal oxide and including a ceramic ion conductor. In this case, the particles of the lithium composite metal oxide and the ceramic ion conductor are the same as described above.

In the positive electrode active material according to an embodiment of the present invention, the coating layer may include a single-phase ceramic ion conductor. The single phase ceramic ion conductor exhibits a single phase peak upon XRD measurement.

In addition, in the cathode active material according to an embodiment of the present invention, the coating layer is any one or two or more selected from the group consisting of YSZ, CSZ, SSZ, GDC, LSGM, LSM and Ni-YSZ as the ceramic ion conductor. It may be to include the.

In addition, in the positive electrode active material according to an embodiment of the present invention, the coating layer is any one selected from the group consisting of YSZ, CSZ, SSZ, GDC and LSGM or a mixture of two or more thereof as a zirconia-based ceramic ion conductor. It may be.

In addition, the YSZ may be Zr _(1-x) Y _x O _{2 -x / 2,} 0.01 ≦ x ≦ 0.08, and more specifically 0.03 ≦ x ≦ 0.08. When the YSZ is included, Y may enter the Zr site to form a single phase first, and since the cathode active material structure has a superstructure, oxygen deficiency may occur in the structure to generate a lot of empty space. have. The movement path of lithium in the YSZ has a lot of space for Li to escape on the surface of the positive electrode active material due to the empty space due to oxygen deficiency inside the YSZ structure. In addition, when analyzing the ion conductivity of lithium ions by finding a path through which lithium ions can pass in YSZ, an energy difference of about 1.0 eV appears in an oxygen deficient section. Through this, when oxygen depletion paths are connected, lithium ion conductivity may be very high. When the cathode active material including YSZ is applied to a secondary battery due to such oxygen depletion, capacity reduction or output reduction may be minimized. In addition, due to the structurally formed void space, in the positive electrode process, particularly during the press (press) process, it has a shock absorbing effect can be minimized the cracking phenomenon of the positive active material.

Also, the SSZ is specifically _{(ZrO 2) 1- 2x (Sc} 2 O 3) x, (ZrO 2) 1-2x (Sc 2 O) 3x- z (Y 2 O 3) z, or (ZrO _{2) 1-2x-z} (Sc ₂ O ₃ ) _x (CeO ₂ ) _z , where 0.01 ≦ x ≦ 0.2, 0.01 ≦ _z ≦ 0.l.

In addition, the CSZ may be a CaO content of 2% to 17% by weight of the total CSZ weight.

In addition, in the cathode active material according to an embodiment of the present invention, the ceramic ion conductor may be included in the coating layer in an amount of 50 ppm to 300000 ppm, more specifically, 100 ppm to 10,000 ppm, based on the total weight of the cathode active material. have.

In addition, in the positive electrode active material according to an embodiment of the present invention, the coating layer further comprises an oxide containing at least one element of Al, Nb, Ti, Ca, W, Mo, Fe, Cr, Cu, V, and Zn. The oxide containing the above element may be included in the coating layer in an amount of 50 ppm to 300000 ppm, more specifically, 100 ppm to 10,000 ppm, based on the total weight of the positive electrode active material.

In addition, in the positive electrode active material according to an embodiment of the present invention, the coating layer may be formed in a thickness range of 1 to 5000nm from the outer surface of the lithium composite metal oxide particles.

In addition, in the positive electrode active material according to an embodiment of the present invention, the coating layer has an excellent thickness uniformity by using a nanosol in the manufacture. Specifically, the coating layer may have a thickness uniformity of 20 nm or less. In this case, the thickness uniformity means a thickness deviation between the maximum thickness value and the minimum thickness value.

In addition, the average particle diameter (D ₅₀ ) of the positive electrode active material according to an embodiment of the present invention may be 3㎛ to 30㎛, and also improve the rate characteristics and initial capacity characteristics of the battery according to the optimization of the specific surface area and the positive electrode mixture density In consideration of the effect, the average particle diameter (D ₅₀ ) of the cathode active material may be more specifically 5 μm to 10 μm.

The cathode active material according to an embodiment of the present invention may be primary particles of a lithium composite metal oxide, or secondary particles formed by assembling the primary particles. When the positive electrode active material is a primary particle of a lithium composite metal oxide, generation of surface impurities such as Li ₂ CO ₃ , LiOH, and the like caused by reaction with moisture in the air or CO ₂ is reduced, and thus there is a low risk of deterioration of battery capacity and gas generation. Also, excellent high temperature stability can be exhibited. In addition, when the cathode active material is secondary particles in which primary particles are assembled, output characteristics may be more excellent. In addition, in the case of secondary particles, the average particle diameter of the primary particles may be 10 nm to 200 nm. The form of such active material particles may be appropriately determined according to the composition of the lithium composite metal oxide constituting the active material.

According to another embodiment of the present invention, there is provided a positive electrode including the positive electrode active material prepared by the above manufacturing method.

The positive electrode may be manufactured by a conventional positive electrode manufacturing method known in the art, except for using the positive electrode active material described above. For example, a slurry is prepared by mixing and stirring a solvent, a binder, a conductive material, or a dispersant in a positive electrode active material, if necessary, and then coating (coating) the positive electrode current collector and drying to form a positive electrode active material layer to dry the positive electrode. It can manufacture.

The positive electrode current collector is a metal having high conductivity, and may be any metal as long as the slurry of the positive electrode active material is not easily reactive in a voltage range of a battery. Non-limiting examples of the positive electrode current collector include a foil made of aluminum, nickel, or a combination thereof.

In addition, the solvent for forming the positive electrode includes an organic solvent such as NMP (N-methyl pyrrolidone), DMF (dimethyl formamide), acetone, dimethyl acetamide or water, and these solvents alone or 2 It can mix and use species. The amount of the solvent used is sufficient to dissolve and disperse the positive electrode active material, the binder, and the conductive material in consideration of the coating thickness of the slurry and the production yield.

The binder includes vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, poly Vinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), liquor Fonned EPDM, styrene butadiene rubber (SBR), fluorine rubber, poly acrylic acid and polymers in which hydrogen thereof is replaced by Li, Na or Ca, or the like, or Various kinds of binder polymers such as various copolymers can be used. The binder may be included in an amount of 1 to 30 wt% based on the total weight of the cathode active material layer.

The conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery. Examples of the conductive material include graphite such as natural graphite and artificial graphite; Carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, farnes black, lamp black, thermal black carbon nanotubes or carbon fibers; Metal powder or metal fibers such as copper, nickel, aluminum, and silver; Conductive whiskers such as fluorocarbon, zinc oxide or potassium titanate; Conductive metal oxides such as titanium oxide; Or conductive polymers such as polyphenylene derivatives, and any one or a mixture of two or more thereof may be used. The conductive material may be included in an amount of 1 to 30 wt% based on the total weight of the positive electrode active material layer.

According to another embodiment of the present invention, there is provided a lithium secondary battery including the cathode active material manufactured by the above-described manufacturing method.

The lithium secondary battery specifically includes a separator interposed between the positive electrode, the negative electrode, the positive electrode and the negative electrode.

As the negative electrode active material used in the negative electrode, a carbon material, lithium metal, silicon, tin, or the like, in which lithium ions may be occluded and released, may be used. Preferably, a carbon material may be used, and as the carbon material, both low crystalline carbon and high crystalline carbon may be used. Soft crystalline carbon and hard carbon are typical of low crystalline carbon. Natural crystalline carbon is natural graphite, Kish graphite, pyrolytic carbon, liquid crystal pitch carbon fiber. High temperature calcined carbon such as (mesophase pitch based carbon fiber), meso-carbon microbeads, Mesophase pitches and petroleum or coal tar pitch derived cokes. In addition, the negative electrode current collector is generally made of a thickness of 3 ㎛ to 500 ㎛. Such a negative electrode current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery. For example, the surface of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel Surface-treated with carbon, nickel, titanium, silver, and the like, and aluminum-cadmium alloys may be used. In addition, like the positive electrode current collector, fine concavities and convexities may be formed on the surface to enhance the bonding strength of the negative electrode active material, and may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

The binder and the conductive material used for the negative electrode may be used as can be commonly used in the art as the positive electrode. The negative electrode may prepare a negative electrode by mixing and stirring the negative electrode active material and the additives to prepare a negative electrode active material slurry, and then applying the same to a current collector and compressing the negative electrode.

In addition, as the separator, conventional porous polymer films conventionally used as separators, for example, polyolefins such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer and ethylene / methacrylate copolymer, etc. The porous polymer film made of the polymer may be used alone or by laminating them, or a conventional porous nonwoven fabric, for example, a non-woven fabric made of high melting point glass fiber, polyethylene terephthalate fiber, or the like may be used. It is not.

The lithium salt which can be included as an electrolyte used in the present invention can be used without limitation, those which are commonly used in a lithium secondary battery electrolyte, such as the lithium salt, the anion is F ^-, Cl ^-, Br ^-, I ^{-, _{NO 3 -, N (CN)}} 2 -, BF 4 -, ClO 4 -, PF 6 -, (CF 3) 2 PF 4 -, (CF 3) 3 PF 3 -, (CF 3) 4 PF 2 -, ^{_{(CF 3) 5 PF -,}} (CF 3) 6 P -, CF 3 SO 3 -, CF 3 CF 2 SO 3 -, (CF 3 SO 2) 2 N -, (FSO 2) 2 N -, CF 3 _{CF 2 (CF 3) 2 CO} -, (CF 3 SO 2) 2 CH -, (SF 5) 3 C -, (CF 3 SO 2) 3 C -, CF 3 (CF 2) 7 SO 3 -, CF ₃ CO ₂ ^- may be any one selected from the group consisting of _{^{-, CH 3 CO 2 -,}} SCN - , and _{(CF 3 CF 2 SO 2)} 2 N.

Examples of the electrolyte used in the present invention include an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, and the like, which can be used in manufacturing a lithium secondary battery. no.

The lithium secondary battery having the above configuration may be manufactured by manufacturing an electrode assembly through a separator between a positive electrode and a negative electrode, placing the electrode assembly inside a case, and then injecting an electrolyte solution into the case.

As described above, since the lithium secondary battery including the cathode active material according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention rate, portable devices such as mobile phones, notebook computers, digital cameras, and hybrid electric vehicles It is useful in the field of electric vehicles.

Accordingly, according to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

The battery module or the battery pack is a power tool (Power Tool); Electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); Or it can be used as a power source for any one or more of the system for power storage.

Hereinafter, the present invention will be described in detail with reference to Examples. However, embodiments according to the present invention can be modified in many different forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

<Nanosol manufacturing>

Preparation Example 1

20 g zirconium dinitrate dihydrate (ZrO (NO ₃ ) ₂ .2H ₂ O) and 2.7 g yttrium nitrate hexahydrate (Y (NO ₃ ) _{3 in} 400 g ethylene glycol (C ₂ H ₆ O ₂ ) 6H ₂ O) was dissolved and stirred to prepare a mixed solution. The mixed solution was heated at a temperature of 160 ° C. for 5 hours with stirring, and then cooled to 90 ° C., and water was added thereto to obtain YSZ nanosol (Zr _(1-x) Y _× O _{) having} an average particle diameter (D ₅₀ ) of 10 nm. _{2- x / 2} , x value = 0.094 and weight ratio of Y: Zr in YSZ = 9: 91).

Production Example  2

Except for using calcium nitrate tetrahydrate (Ca (NO ₃ ) ₂ 4H ₂ O) in the amount of 0.85g instead of yttrium nitrate hexahydrate in Preparation Example 1 in the same manner as in Preparation Example 1 CSZ nanosol (CaO content = 5 mol%, Ca: Zr weight ratio = 2:98) was prepared.

Production Example  3

In the same manner as in Preparation Example 1 except for using the scandium nitrate hydrate (Sc (NO ₃ ) ₃ H ₂ O) in the amount of 2.55g instead of yttrium nitrate hexahydrate in Preparation Example 1 SSZ _nanosol ((ZrO ₂ ) _1-2x (Sc ₂ O ₃ ) _X , x value = 0.12, and a weight ratio of Sc: Zr in SSZ = 6: 94) were prepared.

Production Example  4

40 g of cerium nitrate hexahydrate (Ce (NO ₃ ) ₃ .6H ₂ O) and 6 g of gadolinium nitrate hexahydrate (Gd (NO) instead of zirconium dinitrate dihydrate and yttrium nitrate hexahydrate in Preparation Example 1 ₃ ) GDC nanosol (Gd _0.1 Ce _0.9 O _1.95 , Gd: Ce weight ratio in GDC = 14:86) was carried out in the same manner as in Preparation Example 1, except that ₃ · 6H ₂ O)) was used. Was prepared.

Production Example  5

Instead of zirconium dinitrate dihydrate and yttrium nitrate hexahydrate in Preparation Example 1, 10 g of lanthanum nitrate hexahydrate (La (NO ₃ ) ₃ .6H ₂ O), 1.55 g of strontium nitrate (Sr ( NO ₃ ) ₂ ), 6 g gallium nitrate hydrate (Ga (NO ₃ ) ₃ H ₂ O) and 1.55 g magnesium nitrate hexahydrate (Mg (NO ₃ ) ₂ .6H ₂ O) Except for LSGM nanosol ((La _x Sr _1-x ) (Ga _y Mg _1-y ) O ₃ , x = 0.75, y = 0.78, La: Sr in LSGM) A weight ratio of: Ga: Mg = 58: 12: 28: 2) was prepared.

Production Example  6

20 g of nickel chloride (NiCl ₂ ) was dispersed in 400 g of ethylene glycol (C ₂ H ₆ O ₂ ) solution, followed by stirring to prepare a mixed solution. The mixed solution was heated at a temperature of 160 ° C. for 5 hours with stirring, cooled to 90 ° C., and water was added to prepare Ni nanosols having an average particle diameter (D ₅₀ ) of 10 nm.

<Production of Lithium Composite Metal Oxide>

Preparation Example 7

89.46 g of LiOH (H ₂ O), Ni _{0 with an} average particle diameter of 5 μm _{. 6} Mn _{0 . 2} Co _{0 .2} (OH) ₂ is put into the center of 200g rpm for laboratory mixer to prepare a precursor by mixing at a speed of 18000rpm, 1 minute.

The precursor prepared above was placed in an alumina crucible and calcining was performed at about 860 ° C. for 6 hours in an air atmosphere. The cake obtained after firing was pulverized, and then classified using a 400 mesh sieve (American Tyler standard screen scale) to carry out LiNi _0.6 Mn _0.2 Co _0.2 O ₂ (average particle diameter (D _50). ): 5 m).

<Anode Active Material Manufacturing>

Example 1-1

LiNi ₀ prepared in Preparation Example 7 to include YSZ nanosol having an average particle diameter (D ₅₀ ) of 10 nm prepared in Preparation Example 1 in an amount of 0.2 wt% based on the total weight of the positive electrode active material to be manufactured _{. 6} Mn _{0 . 2} Co _{0 . 2} O ₂ (average particle diameter (D ₅₀ ): 5㎛) 50 g was mixed and mixed. The resulting mixture was heat treated at 400 ° C. for 6 hours, then induced and sieved to LiNi _{0 . 6} Mn _{0 . 2} Co _{0 . 2} O ₂ A cathode active material containing YSZ on the particle surface was prepared.

Example  1-2

In Example 1-1, except for using the CSZ nanosol prepared in Preparation Example 2 instead of the YSZ nanosol prepared in Preparation Example 1 was carried out in the same manner as in Example 1-1 to the cathode active material Was prepared.

Example  1-3

In Example 1-1, the positive electrode active material was carried out in the same manner as in Example 1-1 except for using the SSZ nanosol prepared in Preparation Example 3 instead of the YSZ nanosol prepared in Preparation Example 1. Was prepared.

Example 1-4

In Example 1-1, the positive electrode active material was carried out in the same manner as in Example 1-1 except for using the GDC nanosol prepared in Preparation Example 4 instead of the YSZ nanosol prepared in Preparation Example 1. Was prepared.

Example 1-5

In Example 1-1, except for using the LSGM nanosol prepared in Preparation Example 5 instead of the YSZ nanosol prepared in Preparation Example 1 was carried out in the same manner as in Example 1-1 to the cathode active material Was prepared.

Example 1-6

Except for using the YSZ nanosol in Example 1-1, Ni nanosol prepared in Preparation Example 6 further mixed so that the Ni content is 0.2% by weight relative to the total weight of the lithium composite metal oxide. In the same manner as in Example 1-1, on the surface side of LiNi _0.6 Mn _0.2 Co _0.2 O ₂ particles, a positive electrode active material having a surface treatment layer containing an YSZ ceramic ion conductor and NiO (average particle diameter (D ₅₀ ): 5 μm).

Comparative Example 1-1

A positive active material (average particle diameter (D ₅₀ ): 5 μm) was prepared in the same manner as in Example 1, except that YSZ nanosol was not added in Example 1-1.

Comparative Example 1-2

A positive electrode active material was prepared in the same manner as in Example 1-1, except for using an aqueous dispersion containing an average particle diameter (D ₅₀ ) of 50 nm YSZ powder instead of the YSZ nanosol in Example 1-1.

<Manufacture of Lithium Secondary Battery>

Example 2-1

Anode manufacturing

94% by weight of the positive electrode active material prepared in Example 1-1, 3% by weight of carbon black as the conductive material, and 3% by weight of polyvinylidene fluoride (PVdF) as the binder, N-methyl-2 Positive electrode slurry was prepared by addition to pyrrolidone (NMP). The positive electrode slurry was applied to a thin film of aluminum (Al), which is a positive electrode current collector having a thickness of about 20 μm, dried to prepare a positive electrode, and then roll rolled to prepare a positive electrode.

Cathode manufacturing

96.3 wt% graphite powder as negative electrode active material, 1.0 wt% super-p as conductive material, and 1.5 wt% and 1.2 wt% styrene butadiene rubber (SBR) and carboxymethylcellulose (CMC) as binders were added to NMP as a solvent. To prepare a negative electrode slurry. The negative electrode slurry was applied to a thin copper (Cu) thin film, which is a negative electrode current collector having a thickness of about 10 μm, dried to prepare a negative electrode, and then roll-rolled to prepare a negative electrode.

Non-aqueous  Manufacture of electrolyte

LiPF ₆ was added to a non-aqueous electrolyte solvent prepared by mixing ethylene carbonate and diethyl carbonate as a electrolyte in a volume ratio of 30:70 to prepare a 1 M LiPF ₆ non-aqueous electrolyte.

Lithium Secondary Battery Manufacturing

A cell was prepared by injecting a lithium salt-containing electrolyte solution through a separator of porous polyethylene between the positive electrode and the negative electrode prepared above.

Examples 2-2 to 2-6

A lithium secondary battery was manufactured by the same method as in Example 2-1, except for using the cathode active materials prepared in Examples 1-2 to 1-6, respectively.

Comparative Examples 2-1 and 2-2

A lithium secondary battery was manufactured by the same method as Example 2, except that the cathode active materials prepared in Comparative Examples 1-1 and 1-2 were used, respectively.

Experimental Example: Nanosol Analysis

The nanosol of the ceramic ion conductor prepared in Preparation Example 1 was observed using a transmission electron microscope (TEM), and X-ray diffraction analysis (XRD) was performed.

The results are shown in FIGS. 1 and 2.

As a result, it can be seen that the average particle diameter (D ₅₀ ) in the nanosol is 5 nm or less, and the amorphous YSZ without a crystal pattern is prepared in the hydroxide state.

Experimental Example: Analysis of Positive Electrode Active Material

The surface of the cathode active material prepared in Example 1-1 was observed using a Field-Emission Scanning Electron Microscope (FE-SEM), and the results are shown in FIG. 3.

YSZ nanoparticles from Figure 3 is LiNi _{0 . 6} Mn _{0 . 2} Co _{0 . 2} O ₂ It can be seen that the oxide is uniformly coated on the surface.

In addition, the surface of the cathode active material prepared in Example 1-6 was observed in the same manner as described above.

As a result, in the case of the active material of Example 1-6 LiNi _{0 . 6} Mn _{0 . 2} Co _{0 . 2} O ₂ It can be seen that a coating layer including NiO particles is formed on the oxide surface together with the YSZ nanoparticles.

In addition, the surface of the positive electrode active material prepared in Comparative Example 1-2 was observed using FE-SEM, and the results are shown in FIG. 4.

As shown in Figure 4, when the coating using the aqueous dispersion containing YSZ powder, unlike the coating surface of the positive electrode active material prepared in Example 1-1, the YSZ powder is LiNi _0.6 Mn _0.2 Co _0.2 O ₂ oxide It can be seen that the surface is unevenly coated.

Experimental Example: Analysis of Positive Electrode Active Material

XRD analysis was performed on the cathode active material prepared in Example 1-1, and the crystal structure of YSZ contained in the coating layer was confirmed. XRD analysis was also performed on ZrO ₂ for comparison.

XRD analysis was performed using Cu (Kα-ray) according to the following conditions.

Target: Cu (Kα-ray) Graphite Monochromator

Slit: divergent slit = 0.5 degree, receiving slit = 9.55mm, scattering slit = 5.89 degree

Measurement Zone and Step Angle / Measurement Time: -10.0 degrees <2θ <90 degrees, 0.5 seconds, 0.024 degrees where 2θ represents the diffraction angle.

As a result, YSZ showed a cubic crystal structure and showed a single-phase peak where 2 θ of the main peak existed at 29 to 31 degrees. On the other hand, ZrO ₂ showed a monoclinic crystal structure differently from YSZ, with a main peak between 27.5 and 28.5 degrees and a second peak between 31.1 and 31.8 degrees.

Experimental Example: Electrochemical Experiment

<Battery cycle characteristic evaluation>

Lithium secondary batteries (Examples 2-1 to 2-6 and Comparative Examples 2-1 and 2) including the cathode active materials prepared in Examples 1-1 to 1-6 and Comparative Examples 1-1 and 1-2, respectively In order to determine the rate of capacity reduction according to the number of cycles, the electrochemical evaluation experiment was performed as follows.

Specifically, the cycle characteristics evaluation was performed for the lithium secondary batteries prepared in Examples 2-1 to 2-6 and Comparative Examples 2-1 and 2-2 until the constant current (CC) of 4.25V of 0.5C at 25 ℃. After charging, the battery was charged at a constant voltage (CV) of 4.25V and charged for the first time until the charging current became 0.05 mAh. After standing for 20 minutes, the battery was discharged until it became 3.0V with a constant current of 1C (cut-off proceeded to 0.05C). This was repeated in 1 to 50 cycles. The results are shown in FIG.

As shown in FIG. 5, the lithium secondary batteries (Examples 2-1 to 2-6) including the positive electrode active materials of Examples 1-1 to 1-6, in which a coating layer was formed using nanosols, may have a surface coating layer. Significant improvement compared to lithium secondary batteries (Comparative Examples 2-1 and 2-2) each containing the active material of Comparative Example 1-1 and Comparative Example 1-2-, in which a coating layer was formed according to a conventional dry mixing method. Cycle characteristics.

Specifically, LiNi _{0 . 6} Mn _{0 . 2} Co _{0 . 2} O ₂ In the battery of Comparative Example 2-1 including the positive electrode active material of Comparative Example 1-1, in which the YSZ coating layer was not formed on the oxide surface, it can be confirmed that the capacity decreases as the number of battery cycles increases. In addition, LiNi _{0 . 6} Mn _{0 . 2} Co _{0 . 2} O ₂ When the YSZ coating layer was formed on the oxide surface, the battery of Example 2-1 including the positive electrode active material of Example 1-1 in which YSZ nanoparticles were uniformly coated, was prepared in Comparative Example 1-2 in which YSZ was unevenly coated. The capacity decrease was less than that of the battery of Comparative Example 2-2 containing the positive electrode active material.

From this by LiNi _{0 . 6} Mn _{0 . 2} Co _{0 . 2} O ₂ It was confirmed that the lithium secondary battery including the positive electrode active material in which the coating layer of the ceramic ion conductor was uniformly formed on the oxide surface, the capacity reduction was minimized, and as a result, exhibited better cycle characteristics.

Claims (29)

1. Mixing the lithium composite metal oxide particles with the nano-sol of the ceramic-based ion conductor and heat treatment, to form a coating layer comprising a ceramic-based ion conductor on the lithium composite metal oxide particles.
2. The method of claim 1,

   The ceramic ion conductor comprises a zirconia-based ceramics, ceria-based ceramics, lanthanum-based ceramics and any one or two or more mixtures selected from the group consisting of cermets thereof.
3. The method of claim 1,

   The ceramic ion conductor is yttria stabilized zirconia, gadolinia doped ceria, samarium doped ceria, lanthanum strontium cobalt ferrite, lanthanum strontium gallate magnesite, Lanthanum strontium manganate, Calcia stabilized zirconia, Scandia stabilized zirconia and Nickel-yttria stabilized zirconia cermet comprising any one or a mixture of two or more selected from the group consisting of.
4. The method of claim 1,

   The ceramic ion conductor includes a cathode active material comprising one or two or more selected from the group consisting of yttria stabilized zirconia, calcia stabilized zirconia, gadolinia doped ceria, lanthanum strontium gallate magnesite and scandia stabilized zirconia Manufacturing method.
5. The method of claim 4, wherein

   The yttria stabilized zirconia is Zr _(1-x) Y _x O _{2 -x / 2} (0.01≤x≤0.30) method of producing a positive electrode active material.
6. The method of claim 4, wherein

   The calcia stabilized zirconia is a method for producing a positive electrode active material containing CaO in 1 mol% to 20 mol% relative to the total weight of calcia stabilized zirconia.
7. The method of claim 4, wherein

   The scandia stabilized zirconia _{(ZrO 2) 1- 2x (Sc} 2 O 3) X, (ZrO 2) 1 - 2x (Sc 2 O 3) x -z (Y 2 O 3) z , and (Zr0 _{2) 1- 2x- z} (Sc ₂ O ₃ ) _x (CeO ₂ ) _z (0.01≤x≤0.2, 0.01≤z≤0.l) comprising any one or a mixture of two or more selected from the group consisting of Manufacturing method.
8. The method of claim 1,

   The ceramic ion conductor is a method of manufacturing a positive electrode active material that is amorphous.
9. The method of claim 1,

   The ceramic ion conductor is a method of producing a positive electrode active material having a hydroxide form.
10. The method of claim 1,

    Method for producing a positive electrode active material having an average particle diameter (D ₅₀ ) of the ceramic ion conductor is 1 nm to 100 nm.
11. The method of claim 1,

    The nanosol of the ceramic ion conductor is prepared by dissolving and reacting a precursor of a metal for forming a ceramic ion conductor in a glycol solvent and then adding water to prepare a cathode active material.
12. The method of claim 11,

    The glycol solvent is a method for producing a positive electrode active material comprising any one or a mixture of two or more selected from the group consisting of ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol and polyethylene glycol.
13. The method of claim 11,

    The method of manufacturing a positive electrode active material is further carried out a step of heat treatment at a temperature of 120 ℃ to below the boiling point of the glycol solvent before the addition of water after the dissolution of the precursor of the metal for forming a ceramic-based ion conductor.
14. The method of claim 1,

    The nano-sol of the ceramic ion conductor is used in an amount such that the content of the ceramic ion conductor is 50ppm to 300,000ppm with respect to the total weight of the positive electrode active material.
15. The method of claim 1,

    The nano-sol of the ceramic ion conductor may include aluminum (Al), niobium (Nb), titanium (Ti), tungsten (W), molybdenum (Mo), chromium (Cr), copper (Cu), vanadium (V), and Zinc (Zn) further comprises any one or two or more metals selected from the group consisting of, or is used in combination with a nanosol containing the above metals.
16. The method of claim 1,

    The heat treatment is a method of producing a positive electrode active material is carried out in a temperature range of 100 ℃ to 600 ℃.
17. It is prepared by the manufacturing method according to any one of claims 1 to 16,

    Particles of a lithium composite metal oxide; And a coating layer on the lithium composite metal oxide particles.

    The coating layer is a positive electrode active material containing a ceramic-based ion conductor.
18. The method of claim 17,

    The lithium composite metal oxide is a positive electrode active material comprising a compound of formula (1).

    <Formula 1>

    Li _{1 + a} Ni _1-bc Mn _b Co _c O ₂

    (In Formula 1, 0≤a≤0.33, 0≤b≤0.5 and 0≤c≤0.5)
19. The method of claim 18,

    In Chemical Formula 1, 0 ≦ a ≦ 0.09.
20. The method of claim 17,

    The ceramic ion conductor has a single phase peak during X-ray analysis.
21. The method of claim 17,

    The ceramic active material is an anode active material that is amorphous.
22. The method of claim 17,

    The coating layer further comprises a metal oxide including any one selected from the group consisting of Al, Nb, Ti, W, Mo, Cr, Cu, V and Zn or two or more metals thereof.
23. The method of claim 17,

    A cathode active material having an average particle diameter (D ₅₀ ) of 3 µm to 25 µm.
24. A positive electrode comprising the positive electrode active material according to claim 17.
25. Lithium secondary battery comprising a positive electrode according to claim 24.
26. A battery module comprising the lithium secondary battery according to claim 25 as a unit cell.
27. A battery pack comprising a battery module according to claim 26.
28. The method of claim 27,

    Battery pack that is used as a power source for medium and large devices.
29. The method of claim 28,

    The medium-to-large device is a battery pack that is selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles and power storage systems.

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