KR101202079B1 - Method of preparing core-shell type cathode active materials for lithium secondary batteries through a high-temperature spray dryer and the facility - Google Patents

Abstract

PURPOSE: A manufacturing method of a core-shell type cathode active material is provided to obtain excellent physical properties, and high productivity and reproducibility. CONSTITUTION: A manufacturing method of a core-shell type cathode active material comprises: a step(S100) of manufacturing a coating precursor solution; a step(S200) of manufacturing a coating solution in which a complex with a metal ion and a complex-inducing agent by adding metal salt into the coating precursor solution; a step(S300) of forming a coating layer on the surface of lithium metal oxide particle by spreading the coating solution on a lithium metal oxide particle forming core part; and a step of removing solvent in the coating solution and high-temperature spraying drying. [Reference numerals] (AA) Start; (BB) End; (S100) Manufacturing a coating precursor solution mixed with complex derivative, pH stabilizer, and solvent; (S200) Manufacturing a coating precursor solution with a formed complex by adding metal salt; (S300) Forming a coating layer on the surface of lithium metal oxide particle by spreading a coating solution on the surface of lithium metal oxide particles; (S400) Removing solvent in a coating solution, and spray-drying at high temperature in order to remove polymers in the complex; (S500) Forming core-shell type lithium metal oxide powder

Description

Method of preparing a cathode active material for a core-shell type lithium secondary battery by high temperature spray drying, and a spray drying apparatus therefor {Method of preparing core-shell type cathode active materials for lithium secondary batteries through a high-temperature spray dryer and the facility}

The present invention relates to a method for manufacturing a cathode active material for a core-shell lithium secondary battery by high temperature spray drying and a drying apparatus thereof. More specifically, the present invention relates to a method for producing a cathode active material for a core-shell-type lithium secondary battery that forms a metal oxide shell portion on a lithium metal oxide core using a complex forming reaction, and a spray drying apparatus thereof.

A lithium secondary battery is an energy storage device including a cathode active material that provides lithium ions during charging, an anode active material that receives lithium ions, an electrolyte that is a lithium ion transfer medium, a separator that separates the cathode and the anode, and other components.

Lithium secondary battery has high energy density and driving voltage, and it is not only a high-performance energy source for IT devices such as mobile phones, tablet PCs, notebook PCs, and game machines, but also for driving energy sources of next-generation eco-friendly vehicles such as HEV, PHEV, EV, solar, wind It is expected to be applied in various fields throughout the industry of large capacity power storage systems such as power generation.

Since the first commercialization of Sony in 1991, lithium secondary batteries have been continuously developed based on battery structure, parts and material development, and have become an indispensable part of modern life. Various characteristics such as high energy density and driving voltage of the lithium secondary battery are most affected by the positive electrode active material among the components of the battery. Therefore, in the lithium secondary battery industry, efforts are being made to develop new cathode materials to improve battery characteristics.

Currently, the most commonly used material as a cathode active material for lithium secondary batteries is lithium cobalt oxide (LiCoO ₂ ) having a layered structure. Lithium cobalt oxide is excellent in various characteristics required for secondary batteries, that is, high voltage, high capacity, high rate characteristics, cycle characteristics, charge and discharge reversibility, voltage flatness, but cobalt metal, which is the main material of lithium cobalt oxide, is compared with other transition metals. It is expensive, has limited resources due to reserves, and environmental regulations due to environmental pollution.

Accordingly, lithium nickel oxide (LiNiO ₂ ) and spinel structure lithium manganese oxide (LiMn ₂ O ₄ ) having a layered structure such as lithium cobalt oxide as a cathode active material that can replace lithium cobalt oxide. , Multi-component lithium manganese-nickel-cobalt oxide in which a part of nickel is substituted with a transition metal, lithium iron phosphate (LiFePO ₄ ) having an olivine structure, and the like have been introduced.

However, each of these positive electrode active materials has its own disadvantages, and none of them have a limit to be used alone. Thus, studies have been introduced to mix two or more kinds of positive electrode active materials or to modify the surface of the positive electrode active material.

For example, Japanese Patent Laid-Open No. 2001-143705 discloses a positive electrode active material in which lithium cobalt oxide and lithium manganese oxide are mixed. However, simply mixing a lithium manganese oxide with excellent safety is not enough improvement effect. In Japanese Patent Laid-Open No. 2007-012441, in order to improve overcharge characteristics, a positive electrode having a positive electrode active material layer having two or more layers is applied, and an olivine type lithium iron phosphate or a spinel type lithium manganese oxide is proposed for the positive electrode current collector layer. . Although the improvement effect of the overcharge characteristic is expected, since the thickness of these oxide layers is formed to several micrometers, and there exists an active material layer with low electrical conductivity, there exists a problem that a high current discharge characteristic falls. Japanese Laid-Open Patent Publication No. 2006-318815 discloses a technique for coating the surface of secondary particles with lithium salt, lithium oxide, or the like for the purpose of improving the durability of lithium nickel oxide. However, since it is difficult to coat the entire surface of each of the positive electrode active material secondary particles to a certain thickness, the improvement effect is not obvious.

On the other hand, Korean Patent Publication No. 2010-0102382 discloses that the surface of the Lix [Ni _{1- y- z} Co _y Al _z ] O ₂ oxide with a carbon or an organic compound (including conductive polymer) coating to improve the stability and high rate characteristics than conventional An improved method for producing a positive electrode active material has been proposed. However, there is a problem that productivity is limited due to complicated processes and long manufacturing time. Korean Patent Laid-Open Publication No. 2010-0036896 discloses a wet coating to form a layer of aluminum oxide on the surface of Li _x Ni _y M _{1 - y} O ₂ to increase the filling capacity, decrease the irreversible capacity, and increase the stability. There is a problem that productivity is limited to a complicated manufacturing process for maintaining the coating strength. Korean Patent Laid-Open Publication No. 2005-0048452 proposes a wet coating method of indium and tin oxide on a LiMn ₂ O ₄ surface by using a chelating agent for the purpose of improving the surface electrical conductivity of the cathode active material, stabilizing the structure, and improving the electronic conductivity. Due to the complexity of the manufacturing process for forming a uniform and stable coating layer, a long process time, there is a problem that productivity is reduced. Republic of Korea Patent Publication No. 2010-0052116 and Republic of Korea Patent No. 889622 propose a dry coating for the production of a positive electrode active material for lithium secondary battery with improved thermal stability, overcharge characteristics. However, dry coating is very limited in size and shape of particles, and in particular, since the size of additives must be adjusted to a nano level to form a uniform coating layer, there is a problem in that productivity decreases due to an increase in material cost and process constraints. .

As such, no effective solution has been reported to date, and thus, there is an urgent need to develop a method for reforming a cathode active material capable of compensating for the disadvantages without deteriorating the characteristics of an existing cathode active material and to develop an excellent mass production facility therefor.

Therefore, the technical problem to be achieved by the present invention is to provide a method for producing a core-shell type positive electrode active material by high temperature spray drying with high reproducibility and productivity, and a drying apparatus thereof.

In order to achieve the above technical problem, a method of manufacturing a cathode active material for a core-shell lithium secondary battery by high temperature spray drying, the method for producing a cathode active material for a core-shell lithium secondary battery, includes: (a) a pH stabilizer, a complex inducing agent, and a solvent Preparing a coating precursor solution by mixing a mixture, (b) adding a salt of a metal forming a shell portion to the coating precursor solution to prepare a coating solution having a complex in which a metal ion and a complex inducing agent are combined; c) applying the coating solution to the surface of the lithium metal oxide particles forming the core portion to form a coating layer in which the complex precipitates on the surface of the lithium metal oxide particles, and (d) obtaining the lithium metal oxide powder having the coating layer formed thereon. Removing the solvent in the coating solution, and performing hot spray drying to remove the polymer in the complex. It shall be.

In the present invention, the step (d) is the step of performing the primary drying while (d-1) the hot air heated to 350 ℃ heated by a low temperature hot air heater, and (d-2) 900 by the high temperature heater Secondary drying is carried out while the hot air is heated at a high temperature of (° C.), and (d-3) tertiary drying is performed when the lithium metal oxide powder dried at a high temperature falls and is completely dried in a temperature range of 400 to 600 ° C. It is preferable that it consists of.

In the present invention, in the step (d), the hot spray drying is two heat sources, it is preferable that the temperature range is 350 ℃ ~ 900 ℃.

In the present invention, the coating precursor solution is preferably pH 10 to pH 12.

In the present invention, the complex inducing agent is characterized in that the chelating agent.

In the present invention, the salt of the metal forming the shell portion is any one or two selected from the group consisting of a composite metal of aluminum, titanium, yttrium, magnesium, indium, tin, zinc, cobalt, zirconium and lithium-transition metal. The above is a salt of the mixed metal.

In the present invention, the lithium metal oxide forming the core portion is any one or a mixture of two or more selected from the group consisting of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium manganese-nickel oxide and lithium composite metal oxide. It is characterized by that.

In the present invention, the lithium metal oxide particles forming the core portion preferably have an average particle diameter of 1 µm to 25 µm.

In order to achieve the above technical problem, a high-temperature spray drying apparatus for preparing a cathode active material for a core-shell lithium secondary battery includes a low temperature hot air heater for supplying heating air at 350 ° C. in a drying apparatus for manufacturing a cathode active material for a core-shell lithium secondary battery. And a mixed solution supply device for supplying a mixed solution of lithium metal oxide and a solvent in which precipitation and agglomeration have been completed, and a plurality of drying spaces for drying the mixed solution sprayed and supplied from the mixed solution supply device. It characterized in that it comprises a cyclone for recovering the lithium metal oxide powder dried by the drying device body for supplying air heated to 900 ℃ for high temperature drying.

In the present invention, the drying apparatus main body, the drying apparatus main body is located at the upper end of the drying apparatus main body, a nozzle for mixing the mixed solution and the ambient air at room temperature to be injected into the dryer, and heated to 350 ℃ A secondary drying space having a primary drying space in which the mixed solution is dried by air and a high temperature heater positioned at a lower end of the primary drying space and capable of heating up to 900 ° C., wherein the mixed solution dried at the primary drying space is dried at a high temperature. And a tertiary drying space located at a lower end of the secondary drying space and completely dried while the powder produced by high temperature drying in the secondary drying space falls, and a powder recovery space in which the completely dried powder is moved to a cyclone, and the powder And a tank in which residual dry powder remaining in the recovery space is collected.

According to one aspect of the present invention, since it is possible to disperse various metal elements at the atomic level, it is possible to form a homogeneous shell structure on the surface of the ultrafine oxide powder. As a result, the shell portion can be formed to a thickness of several nm to several tens of nm.

In addition, according to another aspect of the present invention, it is possible to homogeneously mix and disperse various kinds of metal salts to ensure excellent reproducibility in the production of the cathode active material powder of the core-shell structure. In particular, in the present invention, unlike the drying process for removing the solvent in the coating solution, the primary powder grinding, and the long-term heat treatment at a high temperature and the secondary powder grinding to remove the polymer complex inducing agent, in the present invention within a few seconds at a high temperature Because of the high temperature spray drying method that can remove the solvent and the polymer complex inducing agent in a very short time, the manufacturing process is simple and the productivity is very excellent, which has the advantage of facilitating mass production.

In addition, according to another aspect of the present invention, since the heat treatment time is very short to suppress particle growth of the core-shell cathode active material powder, it is possible to maintain the powder characteristics of the core material. If the particles of the powder are large during the heat treatment, the tap density is lowered, so that the electrode density is lowered and the energy storage capacity per volume is lowered during the manufacturing of the lithium secondary battery electrode. However, when the high temperature spray drying method of the present invention is applied, these problems are solved. I can solve it.

In addition, according to another aspect of the present invention, as a cathode active material of a lithium secondary battery, not only the surface coating of the lithium composite metal oxide, but also can be applied to all fields to produce a composite oxide powder of the core-shell structure using a wet chemical reaction. Through this, it is possible to overcome the limitations of existing materials and to expand the field of application and to apply to new applications.

1 is a flow chart showing a process for producing a core-shell composite oxide powder by high temperature spray drying according to the present invention
2 is a detailed flowchart of the high temperature spray drying process of FIG.
3 is a structural diagram of a high temperature spray drying apparatus for performing the high temperature spray drying process of FIG.
4 is an X-RD photograph of lithium manganese oxide powder before (A) and after (B) the shell portion formation according to the embodiment
5 is a FE-SEM photograph of lithium manganese oxide powder before (A) and after (B) the shell portion formation according to the embodiment
6 is a FE-TEM photograph of the lithium manganese oxide powder produced by each Example
7 is a TEM-EDS photograph showing the surface (A) of the lithium manganese oxide powder produced by the example, the manganese element distribution (B) of the powder surface, and the aluminum element distribution (C) of the shell portion;

Hereinafter, the present invention will be described in detail with reference to examples, and detailed description will be made with reference to the accompanying drawings to help understand the present invention. However, embodiments according to the present invention may 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 clearly and easily describe the present invention to those skilled in the art. Like reference numerals in the drawings refer to like elements.

In the method for producing a cathode active material for a core-shell type lithium secondary battery by high temperature spray drying according to the present invention, after depositing and agglomerating a complex on a lithium metal oxide core using a complex formation reaction, a metal oxide shell is formed on the surface of the core through heat treatment. How to form wealth. A method of manufacturing a cathode active material for a core-shell type lithium secondary battery by high temperature spray drying according to the present invention will be described with reference to FIG. 1.

1 is a flow chart showing a process for producing a core-shell composite oxide powder by high temperature spray drying according to the present invention. Referring to Figure 1, first to prepare a coating precursor solution by mixing a pH stabilizer, a complex inducing agent and a solvent (S100).

The complex inducing agent is a compound which forms a complex by reacting with a metal ion generated from a salt of a metal forming a shell, and any compound known in the art as a complex inducing agent which forms a complex by combining with a metal ion is particularly limited. Is not. Preferably, a chelating agent can be used that can provide two or more unshared pairs of electrons to the metal ion. For example, ethylene-diamine tetraacetic acid (EDTA), nitrilotriacetic acid (NTA), 1,2-cyclo-hexadiamine tetraacetic acid (CyDTA), and the like, and most preferably, EDTA can be used.

In addition, the pH stabilizer is used to adjust the pH of the coating precursor solution in order to help dissolution of the complex inducing agent, the specific type of pH stabilizer may be used in the art according to the type of complex inducing agent. For example, since the EDTA is well dissolved in an aqueous solution under strong base conditions, in this case, as a pH stabilizer, tetramethylammonium hydroxide (TMAH) may be used. The pH of the coating precursor solution controlled by the pH stabilizer may vary depending on the specific type of complex inducing agent or pH stabilizer used and the pH may be 10-12. In addition, distilled water, pure water (DI water), or the like may be used as a solvent of the coating precursor solution.

When the coating precursor solution is prepared in step S100, a metal salt forming a shell portion is added to the coating precursor solution to prepare a coating solution in which a complex in which a metal ion and a complex inducing agent are combined is formed (S200).

In the present invention, the shell portion of the positive electrode active material is formed of a metal oxide, the raw material for providing a metal element to the metal oxide is a metal salt. Thus, the salt form is not particularly limited as long as it is in a form capable of ionizing in the coating precursor solution. For example, there may be, but are not limited to, sulfates, nitrates, hydrochlorides, hydroxides, and the like. The metal salt also includes a hydrate of the metal salt.

In the metal salt, the metal may include aluminum, titanium, yttrium, magnesium, indium, tin, zinc, cobalt, zirconium, or a composite metal of lithium-transition metal, and the metal salts may be used alone or in combination of two or more. Can be used. Selection of the metal salt can be appropriately selected by those skilled in the art in consideration of the specifications required according to the type and use of the battery.

That is, when the metal salt is added to the coating precursor solution, it is ionized, and the metal ions combine with the complex inducing agent present in the coating precursor solution to form a complex.

When the coating solution in which the complex is formed in step S200 is prepared, the coating solution in which the complex is deposited is formed on the surface of the lithium metal oxide particles by applying the coating solution in which the complex is formed to the surface of the lithium metal oxide particles forming the core part (S300). ).

The method of applying the coating solution to the lithium metal oxide may be any method conventional in the art without limitation, and for example, may be impregnation, spraying, or the like. When the impregnation is explained by way of example, when the prepared coating solution is impregnated with lithium metal oxide, the complex present in the coating solution precipitates uniformly on the surface of the lithium metal oxide. The complex precipitates on the lithium metal oxide surface at a thickness of several nm to several tens of nm. The precipitated complexes aggregate with each other to form a relatively stable coating layer. The time required to form the coating layer of the complex on the surface of the lithium metal oxide varies depending on the specific components of the complex, and may be, for example, 1 hour to 1 day.

Lithium metal oxide used as the core of the positive electrode active material in the present invention may be used without limitation as long as it is used as a positive electrode active material in the art. For example, lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium manganese-nickel-cobalt oxide, lithium composite metal oxide, or the like may be used alone or in combination of two or more thereof. It is preferable that the average particle diameter of the said lithium metal oxide is 1 micrometer-25 micrometers.

When the coating layer is formed by the step S300, hot spray drying is performed in a temperature range of 350 ° C. to 900 ° C. in order to remove the polymer contained in the precipitate of the solvent and the complex in the coating solution, leaving only the lithium metal oxide in the coating layer (S400). The step S400 will be described in detail by subdividing the step into three after a detailed description of the high temperature spray drying apparatus to be described below.

And when the high temperature spray drying is completed by the step S400, the production of the cathode active material for a core-shell-type lithium secondary battery, which is a lithium metal oxide powder having a homogeneous metal oxide shell portion, is completed (S500).

In order to perform the high temperature spray drying process, a high temperature spray drying apparatus is used. Referring to Figure 3 with respect to the high temperature spray drying apparatus according to the present invention.

3 is a structural diagram of a high temperature spray drying apparatus for performing the high temperature spray drying process of FIG. 1. Referring to Figure 3, the solvent and the high temperature spray drying apparatus according to the present invention is a low-temperature hot air heater 10 for supplying a heating air of about 350 ℃ largely, the precipitation and aggregation of the complex is completed lithium metal with a coating layer is formed Mixing solution supply device 20 for supplying a coating solution containing an oxide, and a spray drying apparatus main body 30 having three drying spaces and drying the mixed solution with heating air of about 350 ℃ to 900 ℃ And, a cyclone 40 for recovering the completely dried powder, a dust collector 50 including a dust collector 50 to finally recover the dry powder of fine powder and discharge the clean air containing no fine powder to the outside, and a dust collector. And a blower 60 for sucking air to recover the dry powder of the fine powder 50.

When the low temperature hot air heater 10 is described in detail above, the low temperature hot air heater 10 is heated to about 350 ° C. while the outside air filtered through the filter 10 a passes through the hot air heater 10 c by the blower 10 b. The heated air is connected to the upper side of the spray drying apparatus main body 30 through the inlet pipe 10d and introduced into the drying apparatus.

In addition, when the mixed solution supply device 20 is described in detail, the mixed solution supply device 20 is mixed with a tank 20a for storing a solution in which a lithium metal oxide powder and a solvent in which the precipitation and aggregation of the complex are completed are mixed. It is composed of a stirring device 20b for stirring so that the solution does not sink under the container, a pump 20c for supplying the solution at a constant speed, and a tube 20d connected to the nozzle 30a.

In addition, when the spray drying apparatus main body 30 is described in detail, the spray drying apparatus main body 30 is located at the top of the main body and mixes the mixed solution supplied from the mixed solution supply device 20 with ambient air at room temperature to dry the inside of the dryer apparatus. Nozzle 30a for spraying to the air, and the air warmed at 350 ° C introduced through the inlet pipe 10d to the high temperature drying section and prevents the dry powder from flowing backward due to the heat of the high temperature drying section to descend to the bottom. The mixed solution is passed through a dry powder backflow prevention plate 30b, a primary drying space 30c in which the mixed solution is dried by air warmed at 350 ° C, and a high temperature heater 30d capable of heating up to about 900 ° C. The secondary drying space 30e to be dried, and the third drying space 30f having a temperature range of 400 to 600 ° C. completely dried while the heated powder falls, and the outside air filtered through the filter 30g are introduced into the inlet pipe 30h. Through A powder recovery space 30j having a discharge pipe 30i which flows in and cools the hot air inside the drying apparatus and moves the powder dried by the suction force of the cyclone 40 to the cyclone 40, and the cyclone It consists of a tank (30k) for collecting the remaining dry powder except the powder moved to 40.

The high temperature spray drying apparatus according to the present invention can minimize the size of the solution particles sprayed through the nozzle 30a by simultaneously blowing external air when the mixed solution is injected into the drying apparatus through the nozzle 30a, After three successive drying processes covering the primary drying space 30c, the secondary drying space 30e, and the tertiary drying space 30f, the contact area with the heated air increases to precipitate the solvent and the complex in the mixed solution. The polymer contained in can be removed in seconds. The cyclone 40 has a tank 40a for collecting completely dried powder and recovers 95% or more of the dried powder, and the remaining 5% is a tank provided in the high temperature spray drying apparatus main body 30. 30k and the dust collector 50 are recovered.

On the other hand, with reference to Figure 2 with respect to step S400, the high temperature spray drying process as follows.

FIG. 2 is a detailed flowchart of the high temperature spray drying process of FIG. 1. Referring to Figure 2, when the coating layer is formed by the step S300, the mixed solution supply device 20 nozzles (30a) a mixed solution in which the lithium metal oxide powder and the solvent is mixed and the precipitation of the complex is complete Spraying through, and the heated air heated to about 350 ℃ by the low temperature hot air heater 10 is introduced through the inlet pipe (10d) and the primary drying is carried out in the primary drying space (30c) (S400-1). When the primary drying is made by the step S400-1, the high temperature heater 30d supplies high-temperature heating air corresponding to about 900 ° C. to the secondary drying space 30e, and the lithium metal oxide powder and the solvent that are primary dried are The mixed solution that is mixed is subjected to secondary drying at high temperature in the secondary drying space 30e (S400-2). When the secondary drying is made by step S400-2, complete drying is performed in the tertiary drying space 30f in the 400 to 600 ° C temperature range while the lithium metal oxide powder dried at a high temperature falls (S400-3). After the high temperature spray drying process as described above, the mixed solution supplied from the mixed solution supply device 20 removes all of the polymers contained in the precipitate of the solvent and the complex in the coating solution, leaving only lithium metal oxide.

The solvent is removed through the operation of the above-mentioned high temperature spray drying apparatus, the metal ions of the complex react with the oxygen element to form a metal oxide, and the other elements of the complex are removed by vaporization through the decomposition and oxidation reaction, thereby lithium metal The oxide particle surface has a shell portion formed of a metal oxide.

The conventional hot air spray drying apparatus has a single heat source and a maximum drying temperature of about 350 ° C., so that a large amount of liquid solution needs to be completely dried in order to heat the outside air, and a large capacity heater is exposed to the heated air. Expensive rotary atomizer, which makes the size of the sprayed solution in mic (μm) unit to increase the surface area of the solution, increases the width of the dryer body and lengthens the body to increase the exposure time to heated air. There is a problem losing. When the rotary atomizer is rotated at high speed to form a fine spray of the solution, the sprayed solution adheres to the inside wall of the dryer without drying, and the recovery rate of the powder is low. The shape and size of the can be increased. In addition, the amount of heat supplied to maintain a uniform hot air temperature inside the large spray dryer must be large, and energy efficiency is very low compared to the powder drying throughput.

On the other hand, the high temperature spray drying apparatus according to the present invention is divided into two heat sources for heating the air to about 350 ℃ (low temperature) and about 900 ℃ (high temperature), the solution sprayed into the spray dryer sequentially The solvent in the solution is easily removed while passing through the air portion heated to a high temperature, and there is a space where the heated powder particles can stay for a certain time without an additional heat source, thereby obtaining completely dried powder particles. Therefore, it is possible to heat external inlet air primarily with a small heater capacity, and because the high temperature heater and the high temperature heating space are in close proximity, there is no heat loss generated during the movement of the heated air, and the powder heated to a high temperature is completely dried while falling. Therefore, a powder can be prepared by drying a large amount of the mixed solution with a small heat source. In addition, since the drying efficiency is high, it is possible to use a nozzle atomizer (cheap atomizer) which is several times less expensive than a rotary sprayer, and has the advantage of reducing the size of the drying spray device body by more than half.

Therefore, the cathode active material of the lithium metal oxide having the metal oxide shell portion according to the present invention may have a uniform shell portion to exhibit high battery performance.

As described above, in the cathode active material according to the present invention, since the shell portion is formed on the surface of the lithium metal oxide at a nano level, the particle size distribution of the formed cathode active material powder is very uniform. In addition, the method of forming the shell portion is also very simple by using a complex forming reaction, and the powder is dried within a few seconds by applying a high temperature spray drying process capable of simultaneously performing a drying process and a heat treatment process, Since there is no change in particle shape and size, unlike the prior art, no additional grinding process is required after powder drying, and thus productivity and reproducibility are excellent.

Hereinafter, the present invention will be described in detail with reference to Examples.

Example

After mixing TMAH, a pH stabilizer, to pure water, EDTA, a complex inducer, was added, and a coating precursor solution was prepared by adjusting pH to 11. Al (NO ₃ ) ₂ ˜9H ₂ O was added to the prepared coating precursor solution, followed by stirring to prepare a coating solution. Lithium manganese oxide (LiMn ₂ 0 ₄ ) powder was added to the coating solution, followed by stirring for 1 hour.

Precipitation and agglomeration of the complex were completed, and dried with a hot spray drying apparatus according to the present invention to remove the solvent in the coating solution containing a lithium metal oxide having a coating layer. The low temperature hot air heater 10 first heats the solution sprayed through the nozzle 30a by heating the external inlet air to 350 ° C. and then flowing it through the inlet pipe 10d, and the high temperature heater 30d is air to 900 ° C. The solvent was removed by heating, and the powder was completely dried while the powder heated in the body portion of the drying apparatus was dropped to prepare a cathode active material. At this time, the injection rate of the solution was 45cc / min, the nozzle flow rate is 25NL / min, the nozzle pressure was 6kgf / cm ² , the recovery rate of the dry powder was about 95%.

XRD analysis, FE-SEM analysis, FE-TEM analysis, TEM-EDS analysis were performed to examine the characteristics of the lithium manganese oxide powder which is the cathode active material for a lithium secondary battery recovered through the above process. Referring to the following test example and Figures 4 to 7 as follows.

4 is an X-RD photograph of lithium manganese oxide powder before (A) and after (B) shell formation according to an embodiment, and FIG. 5 is lithium before (A) and after (B) formation of shell portion according to an embodiment. FE-SEM picture of the manganese oxide powder, Figure 6 is a FE-TEM picture of the lithium manganese oxide powder each produced by the embodiment, Figure 7 is a surface (A) of the lithium manganese oxide powder produced by the embodiment, It is a TEM-EDS photograph which shows the manganese element distribution figure (B) of the powder surface and the aluminum element distribution figure (C) of a shell part.

Test Example

(One) XRD  analysis

In Example, the crystal structure was analyzed by XRD to determine the phase change of the oxide powder dried by the hot spray drying apparatus after the coating of the additive on the surface of the core oxide powder, and the results are shown in FIG. 4. Referring to FIG. 4, as can be seen before forming the shell portion of the upper graph (A) (RAW LMO) and after forming the shell portion of the lower graph (B) (Al 2wt%), the crystal of the lithium metal oxide of the core portion is determined. It was confirmed that there was no structural change. From this, it can be seen that after coating of the additive and hot spray drying according to the present invention, the aluminum oxide coating layer is present only on the surface of the core and does not diffuse into the core, thereby maintaining the original physical properties.

(2) FE - SEM  analysis

FE-SEM 30000 times measurement before (A) and after (B) formation of lithium manganese oxide used in Examples to determine the shape of the powder before and after shell formation in the cathode active material powder prepared by the high temperature spray drying apparatus The photo is shown in FIG. Referring to Figure 5, it can be seen that the shape and size of the oxide powder before and after the shell portion did not change.

(3) FE - TEM  analysis

6 shows FE-TEM photographs measured at various scales of the cathode active material particles prepared in Examples in order to determine the shape and thickness of the shell portion formed on the surface of the oxide powder. Referring to FIG. 6, it can be seen that aluminum oxide is formed on the surface of lithium manganese oxide as a core to form a coating layer with a nano thickness.

(4) TEM-EDS Analysis

The TEM-EDS measurement photograph of the lithium manganese oxide prepared in Example is shown in FIG. 7 to determine whether the aluminum oxide constituting the shell portion is uniformly distributed on the oxide powder surface. In FIG. 7, (A) shows the particle surface of the powder after the shell portion is formed, (B) shows the distribution of manganese elements in the lithium manganese oxide powder as a core material, and (C) shows the distribution of the aluminum elements constituting the shell portion, respectively. will be. Referring to FIG. 7, it can be seen that a homogeneous coating layer is formed from the homogeneous distribution of aluminum oxide on the surface of the lithium manganese oxide serving as the core part.

Therefore, the lithium metal oxide powder, which is a cathode active material of the core-shell structure, manufactured according to the present invention, may have excellent physical properties, and have high productivity, compared to the conventional lithium metal oxide powder prepared by a complex, high cost, and low efficiency process. It has the advantage of ensuring reproducibility.

In the above described with reference to the accompanying drawings, preferred embodiments of the present invention in detail. However, embodiments of the present invention may be variously modified or applied by those skilled in the art, the scope of the technical idea according to the present invention should be determined by the claims below. will be.

Description of the Related Art
10: low temperature hot air heater 10a, 30g: filter
10b, 60: blower 10c: hot air heater
10d, 30h: Inlet pipe 20: Mixed solution supply device
20a, 30k, 40a: tank 20b: stirring device
20c: pump 20d: tube
30: spray drying apparatus main body 30a: nozzle
30b: non-return plate 30c: primary drying space
30d: high temperature heater 30e: secondary drying space
30f: tertiary drying space 30i: discharge pipe
30j: powder recovery space 40: cyclone
50: dust collector

Claims (10)

In the manufacturing method of the positive electrode active material for a core-shell lithium secondary battery,
(a) mixing a pH stabilizer, a complex inducer and a solvent to prepare a coated precursor solution,
(b) adding a salt of a metal forming a shell to the coating precursor solution to prepare a coating solution having a complex in which a metal ion and a complex inducing agent are combined;
(c) applying the coating solution to the surface of the lithium metal oxide particles forming the core portion to form a coating layer in which the complex precipitates on the surface of the lithium metal oxide particles;
(d) removing the solvent in the coating solution to obtain the lithium metal oxide powder having the coating layer formed thereon, and performing hot spray drying to remove the polymer in the complex
Method for producing a cathode active material for a core-shell-type lithium secondary battery comprising a. The method of claim 1,
The step (d)
(d-1) primary drying is performed while spraying heated air heated to 350 ° C. by a low temperature hot air heater;
(d-2) the secondary drying is performed while the heated air of 900 ° C. is supplied by the high temperature heater,
(d-3) a step of tertiary drying in which the lithium metal oxide powder dried at a high temperature falls and is completely dried in a temperature range of 400 to 600 ° C.
Method for producing a cathode active material for a core-shell lithium secondary battery, characterized in that made. The method of claim 1,
In the step (d)
The high temperature spray drying has two heat sources, the temperature range is 350 ℃ ~ 900 ℃ method for producing a cathode active material for a lithium secondary battery, characterized in that the secondary battery. The method of claim 1,
The coating precursor solution is a pH 10 to pH 12 method for producing a cathode active material for a core-shell type lithium secondary battery. The method of claim 1,
The complex inducing agent is a method for producing a cathode active material for a core-shell type lithium secondary battery, characterized in that the chelating agent. The method of claim 1,
The salt of the metal forming the shell portion is any one or two or more metals selected from the group consisting of aluminum, titanium, yttrium, magnesium, indium, tin, zinc, cobalt, zirconium, and lithium-transition metal complex metals. Method for producing a cathode active material for a core-shell lithium secondary battery, characterized in that the salt. The method of claim 1,
The lithium metal oxide forming the core portion is any one or a mixture of two or more selected from the group consisting of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium manganese-nickel oxide and lithium composite metal oxide. A method for producing a cathode active material for a core-shell lithium secondary battery. The method of claim 7, wherein
The lithium metal oxide particles forming the core part have a mean particle diameter of 1 μm to 25 μm, wherein the cathode-active material for a core-shell type lithium secondary battery is prepared. In the drying device for producing a cathode active material for a core-shell lithium secondary battery,
Low temperature hot air heater which supplies heating air of 350 degreeC,
A mixed solution supply device for supplying a mixed solution of a lithium metal oxide and a solvent in which precipitation and aggregation of the complex are completed;
A drying device main body having a plurality of drying spaces for drying the mixed solution sprayed from the mixed solution supply device and supplying air heated at 900 ° C. for high temperature drying;
Cyclone for recovering the lithium metal oxide powder dried by the drying device body
A high temperature spray drying apparatus for producing a cathode active material for a core-shell type lithium secondary battery, comprising: a. The method of claim 9,
The drying device main body,
Located at the top of the drying apparatus main body and a nozzle for mixing the mixed solution and the outside air at room temperature to be injected into the dryer;
Primary drying space in which the mixed solution is dried by the air warmed to 350 ℃,
Located at the bottom of the primary drying space, and equipped with a high temperature heater capable of heating up to 900 ℃, the secondary drying space in which the mixed solution dried in the primary drying space high temperature drying,
Located in the bottom of the secondary drying space, the third drying space is completely dried while the powder produced by the high temperature drying in the secondary drying space falls;
A powder recovery space in which the completely dried powder is moved to a cyclone,
Tank for collecting the residual dry powder remaining in the powder recovery space
A high temperature spray drying apparatus for producing a cathode active material for a core-shell type lithium secondary battery, comprising: a.

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