阅读说明：本技术 制备锂二次电池用正极活性材料前体的方法和通过所述方法制备的正极活性材料前体 (Method for preparing positive active material precursor for lithium secondary battery and positive active material precursor prepared by the method ) 是由 李应周 郑志勋 睦德均 于 2020-02-28 设计创作，主要内容包括：本发明提供一种制备正极活性材料前体的方法、通过所述方法制备的正极活性材料前体以及二次电池用正极和包含所述正极的锂二次电池,所述制备正极活性材料前体的方法包含：将金属添加剂添加到反应器中的第一步骤,所述金属添加剂包含选自由第5族元素和第6族元素构成的组中的至少一种元素；和将包含镍原料、钴原料和锰原料的过渡金属水溶液、含铵离子的溶液和碱性水溶液添加到所述反应器中并进行共沉淀反应以制备平均粒径(D-(50))为3μm～5μm的正极活性材料前体的第二步骤。(The present invention provides a method of preparing a positive active material precursor, a positive active material precursor prepared by the method, and a positive electrode for a secondary battery and a lithium secondary battery including the positive electrode, the method of preparing the positive active material precursor comprising: a first step of adding a metal additive to the reactor, the metal additive comprising a metal selected from the group consisting of group 5 elements and group 6 elementsAt least one element of the group; and adding a transition metal aqueous solution comprising a nickel raw material, a cobalt raw material and a manganese raw material, an ammonium ion-containing solution and a basic aqueous solution to the reactor and performing a coprecipitation reaction to prepare an average particle diameter (D) 50 ) And a second step of preparing a precursor of the positive active material of 3 to 5 μm.)

1. A method of preparing a positive active material precursor, the method comprising:

a first step of adding a metal additive to the reactor, the metal additive including at least one element selected from the group consisting of group 5 elements and group 6 elements; and

adding a transition metal aqueous solution comprising a nickel raw material, a cobalt raw material and a manganese raw material, an ammonium ion-containing solution and an alkaline aqueous solution to the reactor and performing a coprecipitation reaction to prepare an average particle diameter (D)₅₀) And a second step of preparing a precursor of the positive active material of 3 to 5 μm.

2. The method of preparing a positive electrode active material precursor according to claim 1, wherein the metal additive is mixed in an amount such that the concentration of the metal additive is in the range of 0.0005M to 0.01M.

3. The method of preparing a positive electrode active material precursor according to claim 1, wherein the metal additive comprises at least one element selected from the group consisting of: tungsten (W), molybdenum (Mo), niobium (Nb), vanadium (V), tantalum (Ta),Chromium (Cr) and

4. the method of preparing a positive electrode active material precursor according to claim 1, wherein the metal additive comprises at least one element selected from the group consisting of: w, Mo and Nb.

5. The method of preparing a positive electrode active material precursor according to claim 1, wherein the metal additive comprises at least one selected from the group consisting of: li₂WO₄、Na₂WO₄、Li₂MoO₄And Na₂MoO₄。

6. The method of preparing a positive electrode active material precursor according to claim 1, wherein the metal additive of the first step is added by dissolving in the alkaline aqueous solution.

7. The method of preparing a positive electrode active material precursor according to claim 6, wherein the metal additive is added by dissolving in the alkaline aqueous solution in an amount such that the concentration of the metal additive is in the range of 0.0005M to 0.01M.

8. The method of preparing a positive electrode active material precursor according to claim 1, wherein the second step comprises the steps of: and after forming particle nuclei by adjusting the addition amounts of the ammonium ion-containing solution and the alkaline aqueous solution and performing a coprecipitation reaction at a pH of 11 to 13 for 1 to 60 minutes, growing particles by adjusting the addition amounts of the ammonium ion-containing solution and the alkaline aqueous solution and performing a coprecipitation reaction at a pH of 10 to 12 for 1 to 100 hours.

9. A positive electrode active material precursor containing nickel, cobalt, and manganese and doped with a metal element containing at least one element selected from the group consisting of group 5 elements and group 6 elements,

wherein the positive electrode active material precursor has an average particle diameter (D) of 3 to 5 [ mu ] m₅₀)，

Having a (D) of 0.5 to 1.5₉₀-D₁₀)/D₅₀And is and

the positive active material precursor includes the metal element in an amount of 100ppm to 4000ppm based on the total weight.

10. The positive electrode active material precursor according to claim 9, wherein (D)₉₀-D₁₀)/D₅₀In the range of 0.5 to 0.559.

11. The positive electrode active material precursor according to claim 9, wherein the metal element comprises at least one element selected from the group consisting of: tungsten (W), molybdenum (Mo), niobium (Nb), vanadium (V), tantalum (Ta)(Ta)、Chromium (Cr) and

12. the positive electrode active material precursor according to claim 9, wherein the metal element comprises at least one element selected from the group consisting of: w, Mo and Nb.

13. The positive electrode active material precursor according to claim 9, wherein the positive electrode active material precursor has an aspect ratio of 0.8 to 1.0.

14. A method for preparing a positive electrode active material, comprising a step of sintering after mixing a positive electrode active material precursor of claim 1 with a lithium raw material.

15. A positive electrode for a lithium secondary battery, comprising the positive electrode active material prepared by the method of claim 14.

16. A lithium secondary battery comprising the positive electrode according to claim 15.

Technical Field

Cross Reference to Related Applications

The present application claims priority from korean patent application No. 10-2019-0025285, filed on 5/3/2019, the contents of which are incorporated herein by reference.

Technical Field

The present invention relates to a method of preparing a positive active material precursor for a lithium secondary battery, a positive active material precursor prepared therefrom, and a lithium secondary battery prepared by using the positive active material precursor.

Background

As technology develops and the demand for mobile devices increases, the demand for secondary batteries as an energy source has significantly increased. Among these secondary batteries, lithium secondary batteries having high energy density, high voltage, long cycle life and low self-discharge rate have been commercialized and widely used.

Lithium transition metal composite oxides have been used as positive electrode active materials for lithium secondary batteries, and among these oxides, for example, LiCoO having high operating voltage and excellent capacity characteristics is mainly used₂The lithium cobalt composite metal oxide of (1). However, LiCoO₂Have very poor thermal properties due to an unstable crystal structure caused by delithiation. Furthermore, because of LiCoO₂Is expensive, so that a large amount of LiCoO is used₂There is a limitation as a power source for applications such as electric vehicles.

Lithium manganese complex metal oxides (LiMnO) have been developed₂Or LiMn₂O₄) Lithium iron phosphate compound (LiFePO)₄Etc.) or lithium nickel composite metal oxide (LiNiO)₂Etc.) as an alternative to LiCoO₂The material of (1). Among these materials, research and development of lithium nickel composite metal oxides, which can easily realize large-capacity batteries due to having a high reversible capacity of about 200mAh/g, have been more actively conducted. However, LiNiO₂Has the following limitation that LiNiO₂Having a specific LiCoO ratio₂Poor thermal stability, and when an internal short circuit occurs in a charged state due to external pressure, the positive electrode active material itself is decomposed to cause rupture and ignition of the battery. Therefore, LiNiO is maintained₂A lithium nickel cobalt oxide in which a part of nickel is replaced with cobalt (Co) and manganese (Mn) or aluminum (Al) has been developed as a method of improving low thermal stability while having excellent reversible capacity.

However, for lithium nickel cobalt metal oxide, it is necessary to prepare an electrode having a high density to increase the energy density per unit volume, and in order to increase the energy density, the average particle diameter (D) of lithium nickel cobalt metal oxide is required₅₀) Is 6 μm or less, and a method of preparing a positive electrode active material precursor having excellent sphericity and uniform particle size is required.

In general, as methods of preparing a cathode active material precursor, there are a method of preparing a cathode active material precursor by using a Continuous Stirred Tank Reactor (CSTR) and a method of preparing a cathode active material precursor by using a batch reactor. A Continuous Stirred Tank Reactor (CSTR) discharges a precursor composed of particles while adding and coprecipitating raw materials, whereas for a batch reactor, raw materials are added according to the volume of the reactor and reacted for a predetermined time, and the precursor is discharged after the reaction is completed.

Generally, a Continuous Stirred Tank Reactor (CSTR) process has an advantage in that it is easy to control a metal composition ratio, but since the addition of raw materials and the discharge of products continuously occur simultaneously, a residence time and a reaction time of a positive active material precursor formed in a reactor may vary, and thus, there is a limitation in that the size and composition of particles formed are not uniform.

Therefore, a batch method, which can easily control the size of particles and can prepare a positive electrode active material precursor having a uniform particle size, tends to be employed. However, the average particle diameter (D) is prepared in the case of using a batch reactor₅₀) In the case of a positive electrode active material precursor of 6 μm or less, it is necessary to control the concentration of the initial reaction solution initially added, the addition rate of the reaction solution, the reaction temperature, the reaction time, and the stirring speed, and in particular, there is a limitation in preparing a large amount of the positive electrode active material precursor because the synthesis must be performed by increasing the stirring speed. In addition, since the reaction time must be maintained to some extent to uniformly form the surface of the positive electrode active material precursor, the preparation time becomes long, and thus there are disadvantages as follows: the cathode active material precursor continues to grow during the reaction time, making it difficult to prepare a cathode active material precursor having a small particle size.

Therefore, it is required to develop a method for preparing a precursor of a positive electrode active material, which can easily synthesize a large amount of precursors having small particle diameters while reducing the preparation time.

Disclosure of Invention

Technical problem

One aspect of the present invention provides a method for preparing the average particle diameter (D)₅₀) A method of a positive electrode active material precursor of 3 to 5 μm, which suppresses the growth of positive electrode active material precursor particles by adding a metal additive to an initial reaction solution during the preparation of the positive electrode active material precursor.

Another aspect of the present invention provides a particle having an average particle diameter (D) of 3 μm to 5 μm prepared by the above method₅₀) And a positive active material precursor of uniform particle size.

Another aspect of the present invention provides a method for preparing a cathode active material by using the cathode active material precursor prepared as described above and a cathode active material prepared thereby.

Another aspect of the present invention provides a positive electrode and a lithium secondary battery including the positive electrode active material prepared as described above.

Technical scheme

According to an aspect of the present invention, there is provided a method of preparing a positive active material precursor, the method comprising: a first step of adding a metal additive to the reactor, the metal additive including at least one element selected from the group consisting of group 5 elements and group 6 elements; and adding a transition metal aqueous solution containing a nickel raw material, a cobalt raw material and a manganese raw material, an ammonium ion-containing solution and an alkaline aqueous solution to the reactor and performing a coprecipitation reaction to prepare an average particle diameter (D)₅₀) And a second step of preparing a precursor of the positive active material of 3 to 5 μm.

According to another aspect of the present invention, there is provided a positive electrode active material precursor including nickel, cobalt, and manganese, and doped with a metal element including at least one element selected from the group consisting of group 5 elements and group 6 elements, wherein the positive electrode active material precursor has an average particle diameter (D) of 3 μm to 5 μm₅₀) Having a (D) of 0.5 to 1.5₉₀-D₁₀)/D₅₀And the positive electrode active material precursor contains the metal element in an amount of 100ppm to 4000ppm based on the total weight.

According to another aspect of the present invention, there is provided a method of preparing a positive electrode active material, the method comprising the step of sintering after mixing the positive electrode active material precursor with a lithium raw material.

According to another aspect of the present invention, there are provided a positive electrode for a lithium secondary battery and a lithium secondary battery including the positive electrode active material prepared by the method of preparing a positive electrode active material.

Advantageous effects

According to the present invention, the average particle diameter (D) may be prepared by inhibiting the growth of particles of the positive electrode active material precursor by adding a metal additive to an initial reaction solution during the preparation of the positive electrode active material precursor₅₀) Has a small particle diameter of 3 to 5 μmA polar active material precursor.

In addition, since the growth of the particles of the positive electrode active material precursor can be suppressed by the metal additive even if the reaction time is increased for the surface uniformity of the positive electrode active material precursor, the positive electrode active material precursor having excellent uniformity and having a small particle diameter can be prepared.

Drawings

Fig. 1 is a Scanning Electron Microscope (SEM) photograph of the positive active material precursor prepared in example 1 of the present invention;

fig. 2 is an SEM photograph of the positive active material precursor prepared in example 2 of the present invention; and is

Fig. 3 is an SEM photograph of the positive electrode active material precursor prepared in comparative example 1 of the present invention.

Detailed Description

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

It should be understood that the words or terms used in the specification and claims should not be construed as meanings defined in common dictionaries, and it should be further understood that the words or terms should be interpreted as having meanings consistent with their meanings in the context of the relevant art and technical idea of the present invention based on the principle that the inventor can appropriately define the meanings of the words or terms to best explain the present invention.

Throughout the specification, the expression "average particle diameter (D)₅₀) "may be defined as the particle size at 50% cumulative volume in the particle size distribution curve. For example, average particle diameter (D)₅₀) Can be measured by using a laser diffraction method. For example, the average particle diameter (D) of the positive electrode active material is measured₅₀) In the method of (1), after dispersing particles of the positive electrode active material in a dispersion medium, the dispersion medium is introduced into a commercial laser diffraction particle size measuring instrument (e.g., Microtrac MT 3000) and irradiated with ultrasonic waves having a frequency of about 28kHz and an output power of 60W, and then an average particle diameter (D) at a cumulative volume of 50% can be calculated by the measuring instrument₅₀)。

Preparation of Positive active Material precursorMethod

The present inventors have found that the average particle diameter (D) can be prepared by inhibiting the growth of positive electrode active material precursor particles by adding a metal additive to an initial reaction solution during the preparation of a positive electrode active material precursor₅₀) A positive electrode active material precursor having a small particle size of 3 to 5 μm, and a large amount of the positive electrode active material precursor having a small particle size can be prepared by this method, thereby completing the present invention.

The method for preparing the precursor of the positive active material according to the present invention comprises: a first step of adding a metal additive to the reactor, the metal additive including at least one element selected from the group consisting of group 5 elements and group 6 elements; and adding a transition metal aqueous solution comprising a nickel raw material, a cobalt raw material and a manganese raw material, an ammonium ion-containing solution and a basic aqueous solution to the reactor and performing a coprecipitation reaction to prepare an average particle diameter (D)₅₀) And a second step of preparing a precursor of the positive active material of 3 to 5 μm.

Hereinafter, the respective steps will be described in more detail.

First, deionized water, an ammonium ion-containing solution, an alkaline aqueous solution, and a metal additive containing at least one element selected from the group consisting of group 5 elements and group 6 elements are added to a reactor, and the reactor is purged with nitrogen.

Preferably, as the reactor, a batch reactor may be used. Since the present invention uses a batch reactor as a reactor for preparing the positive active material precursor, reaction conditions such as concentration, temperature and residence time of reactants in the reactor are the same as compared to a Continuous Stirred Tank Reactor (CSTR), whereby a relatively uniform and deviation-free product can be prepared.

The pH value in the reactor may be adjusted by adding an initial reaction solution comprising deionized water, an ammonium ion-containing solution, and an aqueous alkaline solution to the reactor to a predetermined volume of the reactor.

The basic aqueous solution may comprise at least one selected from the group consisting of: NaOH, KOH and Ca (OH)₂And as a solvent, canSo as to use water or a mixture of water and an organic solvent (specifically, alcohol, etc.) which can be uniformly mixed with water. In this case, the concentration of the alkaline aqueous solution may be 2M to 15M, preferably 5M to 15M, and more preferably 8M to 13M. In the case where the concentration of the alkaline aqueous solution is 2M to 15M, precursor particles of a uniform size can be formed, the formation time of the precursor particles is fast, and the yield can also be excellent.

The ammonium ion-containing solution may comprise a compound selected from the group consisting of NH₄OH、(NH₄)₂SO₄、NH₄NO₃、NH₄Cl、CH₃COONH₄And (NH)₄)₂CO₃At least one of the group consisting of. As the solvent, water or a mixture of water and an organic solvent (specifically, alcohol or the like) which can be uniformly mixed with water can be used.

For example, the pH in the reactor may be adjusted to 11 to 13, preferably 12 to 13, and most preferably 12.3 to 12.8 by adding an initial reaction solution comprising deionized water, an ammonium ion-containing solution, and an aqueous alkaline solution to the reactor to a predetermined volume of the reactor.

According to the present invention, when the initial reaction solution comprising the ammonium ion-containing solution and the basic aqueous solution is added, the metal additive comprising at least one element selected from the group consisting of group 5 elements and group 6 elements may be added together. By the addition of the metal additive, since the metal additive accelerates the precipitation reaction of the transition metal hydroxide during the subsequent synthesis of the precursor particles of the positive electrode active material and preferentially provides the nuclei of the particles during the precipitation reaction, the coprecipitation reaction of the precursor can be performed while maintaining a state in which small-sized particles are uniformly distributed at the initial stage of the reaction. For example, with respect to the time of adding the metal additive, the metal additive may be added to the initial reaction solution as in the present invention or may be added during the coprecipitation reaction of the positive electrode active material precursor. However, in the case where the metal additive is added during the coprecipitation reaction, there is a limit in that the process cost is increased because a separate pipe for adding the metal additive must be additionally installed in the reactorAnd (5) preparing. In addition, in the case where the metal additive is added during the coprecipitation reaction, particle growth of the cathode active material may be affected, but since it does not affect the initial particle size control of the cathode active material precursor and unexpected fine powder generation and metal element doping may occur, it is not easy to prepare the average particle diameter (D) according to the present invention₅₀) A precursor of the positive electrode active material of 3 μm to 5 μm. Therefore, it is advantageous to add the metal additive together with the initial reaction solution in terms of reducing the processing cost and the particle size control of the cathode active material precursor.

The metal additive may contain at least one element selected from the group consisting of group 5 elements and group 6 elements, and for example, may contain at least one element selected from the group consisting of: tungsten (W), molybdenum (Mo), niobium (Nb), vanadium (V), tantalum (Ta),(Db), chromium (Cr) and(Sg). Since the metal additive contains at least one element selected from the group consisting of group 5 elements and group 6 elements, when the initial transition metal hydroxide precipitates, nucleation of particles becomes more dominant than crystal growth, and therefore, the coprecipitation reaction of the precursor can be performed while maintaining a state in which small-sized particles are uniformly distributed in the initial stage of the reaction. In addition, the metal additive may be at least one selected from the group consisting of: w, Mo and Nb, and may most preferably comprise at least one metal element selected from the group consisting of: w or Mo.

The metal additive may be added to the reactor in the form of a raw material containing at least one element selected from the group consisting of group 5 elements and group 6 elements, or may be added to the reactor after dissolving the metal additive in an alkaline aqueous solution. For example, the metal additive may be easily dissolved in water or an alkaline aqueous solution, and may be mixed in an amount such that the concentration of the metal additive in the initial reaction solution is in the range of 0.0005M to 0.01M, for example, 0.001M to 0.008M. In addition, in the case where the metal additive is added to the reactor after being dissolved in the alkaline aqueous solution, the metal additive may be added by being dissolved in the alkaline aqueous solution in an amount such that the concentration of the metal additive is in the range of 0.0005M to 0.01M, for example, 0.001M to 0.008M.

The metal additive may be added in an amount such that the concentration of the metal additive in the initial reaction solution is in the range of 0.0005M to 0.01M, for example 0.001M to 0.008M. In the case where the concentration of the metal additive added to the initial reaction liquid is less than the above range, the positive electrode active material precursor may be grown to a particle size of 6 μm or more because the effect of suppressing the particle growth due to the addition of the metal additive is insignificant. For example, in the case where the concentration of the metal additive added to the initial reaction solution is greater than the above range, since the metal additive is excessively contained during the synthesis of the precursor, it is possible to synthesize a precursor having an unintended composition, which may be present as an impurity.

For example, the metal additive may comprise at least one selected from the group consisting of: li₂MoO₄、Na₂MoO₄、Li₂WO₄And Na₂WO₄。

Subsequently, a transition metal aqueous solution containing a nickel raw material, a cobalt raw material and a manganese raw material, an ammonium ion-containing solution and a basic aqueous solution are added to a reactor and subjected to a coprecipitation reaction to prepare an average particle diameter (D)₅₀) A precursor of the positive electrode active material of 3 μm to 5 μm.

The aqueous transition metal solution may contain acetates, nitrates, sulfates, halides, sulfides, hydroxides, oxides or oxyhydroxides of the above-mentioned transition metals, and these materials are not particularly limited as long as they can be dissolved in water.

For example, it may be Co (OH)₂、CoOOH、Co(OCOCH₃)₂·4H₂O、Co(NO₃)₂·6H₂O or CoSO₄·7H₂The form of O contains the cobalt (Co), and any one thereof or a mixture of two or more thereof may be used.

In addition, Ni (OH) may be used₂、NiO、NiOOH、NiCO₃、2Ni(OH)₂·4H₂O、NiC₂O₂·2H₂O、Ni(NO₃)₂·6H₂O、NiSO₄、NiSO₄·6H₂The nickel (Ni) is contained in the form of O, a fatty acid nickel salt, or a nickel halide, and any one thereof or a mixture of two or more thereof may be used.

Further, the manganese (Mn) may be contained in the following form: oxides of manganese such as Mn₂O₃、MnO₂And Mn₃O₄(ii) a Manganese salts such as MnCO₃、Mn(NO₃)₂、MnSO₄Manganese acetate, manganese dicarboxylates, manganese citrate and manganese salts of fatty acids; an oxyhydroxide compound; and manganese chloride, and any one of them or a mixture of two or more thereof may be used.

Further, in the case where the finally prepared precursor contains another metal element (M) in addition to nickel (Ni), manganese (Mn) and cobalt (Co) (for example, M is at least one element selected from the group consisting of aluminum (Al), zirconium (Zr), chromium (Cr), titanium (Ti), magnesium (Mg), tantalum (Ta) and niobium (Nb)), the raw material containing the metal element (M) may be further added selectively during the preparation of the transition metal-containing solution.

The raw material containing the metal element (M) may contain an acetate, a nitrate, a sulfate, a halide, a sulfide, a hydroxide, an oxide, or a oxyhydroxide containing the metal element (M), and any one thereof or a mixture of two or more thereof may be used. For example, in the case where M is W, tungsten oxide may be used.

Preferably, the preparation of the positive active material precursor comprises the steps of: after forming particle cores by adjusting the addition amounts of the ammonium ion-containing solution and the basic aqueous solution and performing a coprecipitation reaction at a pH of 11 to 13 for 1 to 60 minutes, for example, 10 to 50 minutes, the particles are grown by adjusting the addition amounts of the ammonium ion-containing solution and the basic aqueous solution and performing the coprecipitation reaction at a pH of 10 to 12 for 1 to 100 hours, preferably 10 to 80 hours, and more preferably 20 to 40 hours.

In other words, at the start of the reaction, the ammonium ion-containing solution and the alkaline aqueous solution are first added to adjust the pH to a range of 11 to 13, for example, 11.7 to 12.7, and thereafter, the particle cores may be formed while the transition metal-containing solution is added to the reactor. In this case, since the pH value changes as the particle core is formed by adding the transition metal-containing solution, the pH value can be controlled to be maintained at 11 to 13 by continuously adding the ammonium ion-containing solution and the alkaline aqueous solution together with the transition metal-containing solution. If the pH value satisfies the above range, particle cores can be preferentially formed, and particle growth hardly occurs.

After the nucleation of the particles is completed, the pH is adjusted to be in the range of 10 to 12, for example, 10.5 to 11.7 by adjusting the addition amounts of the ammonium ion-containing solution and the alkaline aqueous solution, and the formed particle nuclei can be grown while adding the transition metal-containing solution. In this case, since the pH value changes as the particles are grown by adding the transition metal-containing solution, the pH value can be controlled to be maintained at 10 to 12 by continuously adding the ammonium ion-containing solution and the alkaline aqueous solution together with the transition metal-containing solution. If the pH value satisfies the above range, it may be difficult to form a new particle core, and the growth of the particles may occur preferentially.

In the case where the cathode active material precursor is prepared as described above, since the growth of the cathode active material precursor particles is inhibited by the metal additive, the average particle diameter (D) can be easily prepared₅₀) A precursor of the positive electrode active material of 3 μm to 5 μm.

Positive electrode active material precursor

Further, the present invention provides a positive electrode active material precursor prepared by the above-described methodPrepared by a method, containing nickel, cobalt and manganese, and doped with a metal element containing at least one element selected from the group consisting of group 5 elements and group 6 elements, wherein the positive electrode active material precursor has an average particle diameter (D) of 3 to 5 μm₅₀) Having a (D) of 0.5 to 1.5₉₀-D₁₀)/D₅₀And the positive electrode active material precursor contains the metal element in an amount of 100ppm to 4000ppm based on the total weight.

The average particle diameter (D) of the positive electrode active material precursor according to the present invention₅₀) Is 3 μm to 5 μm, wherein the positive electrode active material precursor is formed in such a manner as to have a small particle diameter, and not only the particle size distribution is uniform, but also the surface of the positive electrode active material is formed in a spherical shape.

The positive active material precursor may include a metal element in an amount of 100ppm to 4000ppm, preferably 100ppm to 2000ppm and most preferably 200ppm to 2000ppm based on the total weight. Since the growth of the precursor particles of the positive electrode active material is suppressed by the metal element, the average particle diameter (D) can be obtained₅₀) A precursor of a positive electrode active material having a nearly spherical shape and a diameter of 3 to 5 μm.

For example, the positive electrode active material precursor according to the present invention (D)₉₀-D₁₀)/D₅₀The value may be in the range of 0.5 to 1.5, preferably 0.5 to 1.0, more preferably 0.5 to 0.8 and most preferably 0.5 to 0.559, and in the range of (D) of the positive electrode active material precursor₉₀-D₁₀)/D₅₀In the case where the value is outside the above range, the particle size uniformity of the formed positive electrode active material precursor particles may be reduced. For example, in the case of the positive electrode active material precursor (D)₉₀-D₁₀)/D₅₀In the case where the value is greater than 1.5, the deviation of the particle size of the positive electrode active material precursor may be large.

The positive electrode active material precursor according to the present invention may preferably have an aspect ratio of 0.8 to 1.0, for example, 0.85 to 1.0. Preferably, the positive electrode active material precursor may have a spherical shape as the aspect ratio of the positive electrode active material precursor approaches 1. For example, in the case where the aspect ratio of the positive electrode active material precursor is less than 0.8, the sphericity of the precursor may be reduced.

The aspect ratio of the positive electrode active material precursor means a ratio of a diameter perpendicular to a major axis (a length of a minor axis passing through the center of the particle and perpendicular to the major axis) to a length of the positive electrode active material precursor particle (a length of the major axis passing through the center of the particle). In the present invention, a Scanning Electron Microscope (SEM) photograph magnified 2000 times is used to select 10 particle sizes and an average particle size (D)₅₀) The most similar particles, and the aspect ratio of the positive electrode active material was calculated by (short axis)/(long axis).

Positive electrode active material and method for producing positive electrode active material

Further, according to the present invention, there can be provided a positive electrode active material prepared by using the positive electrode active material precursor prepared by the above-described method.

Specifically, to prepare the cathode active material, a bimodal cathode active material precursor including an average particle diameter (D) may be mixed with a lithium-containing raw material and sintered to prepare the cathode active material₅₀) First positive electrode active material precursor particles having a core-shell structure and having a particle diameter (D) of 8 to 15 [ mu ] m₅₀) And second positive electrode active material precursor particles of 1 μm to less than 8 μm.

The lithium-containing raw material is not particularly limited as long as it is a compound containing a lithium source, but preferably at least one selected from the group consisting of: lithium carbonate (Li)₂CO₃) Lithium hydroxide (LiOH), LiNO₃、CH₃COOLi and Li₂(COO)₂。

The bimodal positive electrode active material precursor and the lithium-containing raw material may be mixed in an amount such that a molar ratio of Me to Li is in a range of 1:0.9 to 1: 1.8. In the case where the lithium-containing raw material is mixed in a ratio less than the above range, the capacity of the prepared cathode active material may be reduced, and in the case where the lithium-containing raw material is mixed in a ratio greater than the above range, since the particles are sintered in the sintering process, it may be difficult to prepare the cathode active material, the capacity may be reduced, and separation of the cathode active material particles may occur after sintering.

Subsequently, the mixture in which the bimodal positive electrode active material precursor and the lithium-containing raw material are mixed is sintered.

With the positive electrode active material precursor according to the present invention, even the average particle diameter (D) of the first positive electrode active material precursor particles₅₀) And the average particle diameter (D) of the second positive electrode active material precursor particles₅₀) In contrast, also because the average composition of the first cathode active material precursor particles and the composition of the second cathode active material precursor particles are different as described above, the different compositions of the small-particle size and large-particle size cathode active material precursors can compensate for the influence caused by temperature, that is, when the small-particle size and large-particle size cathode active material precursors are mixed and sintered at the same temperature, excessive sintering of the small-particle size cathode active material and uneven sintering in which sintering of the large-particle size cathode active material is insufficient may occur, whereby a cathode active material having good sintering uniformity can be prepared.

Sintering may be carried out at a temperature in the range of 700 ℃ to 950 ℃. For example, in the case where the sintering temperature is lower than 700 ℃, since raw materials may remain in the particles due to insufficient reaction, the high-temperature stability of the battery may be reduced and since the bulk density and crystallinity are reduced, the structural stability may be reduced. In the case where the sintering temperature is higher than 950 ℃, non-uniform growth of particles may occur, and the volume capacity of the battery may be reduced due to a decrease in the amount of particles per unit area caused by an excessive increase in the size of the particles. The sintering temperature may be more preferably in the range of 770 to 850 deg.c in consideration of particle size control, capacity and stability of the prepared cathode active material particles and reduction of lithium-containing byproducts.

The sintering may be performed for 6 to 13 hours. In the case where the sintering time is less than 6 hours, it may be difficult to obtain a high-crystallinity cathode active material because the reaction time is too short, and in the case where the sintering time is more than 13 hours, the size of particles may be excessively increased and the production efficiency may be reduced.

Positive electrode

In addition, the present invention provides a positive electrode for a lithium secondary battery comprising the positive electrode active material prepared by the above method.

Specifically, the present invention provides a positive electrode for a lithium secondary battery comprising a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, wherein the positive electrode active material layer comprises the positive electrode active material according to the present invention.

In this case, since the positive electrode material is the same as described above, a detailed description thereof will be omitted, and only the remaining configuration will be described in detail hereinafter.

The positive electrode current collector is not particularly limited as long as it has conductivity without causing adverse chemical changes in the battery, and for example, stainless steel, aluminum, nickel, titanium, fired carbon, or aluminum or stainless steel surface-treated with one of carbon, nickel, titanium, silver, or the like may be used. In addition, the cathode current collector may generally have a thickness of 3 to 500 μm, and fine irregularities may be formed on the surface of the current collector to improve adhesion to the cathode active material. The positive electrode current collector may be used in various shapes such as a film, a sheet, a foil, a mesh, a porous body, a foam, a nonwoven fabric body, and the like, for example.

In addition to the above-described cathode active material, the cathode active material layer may optionally further include a binder and a conductive agent, if necessary.

In this case, the content of the cathode active material may be 80 to 99 wt%, for example, 85 to 98.5 wt%, based on the total weight of the cathode active material layer. When the content of the positive electrode active material is within the above range, excellent capacity characteristics may be obtained.

The conductive agent is used to provide conductivity to the electrode, wherein any conductive agent may be used without particular limitation so long as it has suitable electronic conductivity without causing adverse chemical changes in the battery. Specific examples of the conductive agent may be graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black (Ketjen black), channel black, furnace black, lamp black, thermal black, and carbon fiber; powders or fibers of metals such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides such as titanium oxide; or a conductive polymer such as a polyphenylene derivative, and any one thereof or a mixture of two or more thereof may be used. The conductive agent may be included generally in an amount of 0.1 to 15 wt% based on the total weight of the positive electrode active material layer.

The binder improves the adhesion between the particles of the positive electrode active material and the adhesion between the positive electrode active material and the current collector. Specific examples of the binder may be polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP copolymer), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluorine-containing rubber, or various copolymers thereof, and any one of them or a mixture of two or more of them may be used. The binder may be included in an amount of 0.1 to 15 wt% based on the total weight of the positive electrode active material layer.

The positive electrode may be prepared according to a typical preparation method of a positive electrode, except for using the above-described positive electrode active material. Specifically, a composition for forming a positive electrode active material layer, which is prepared by dissolving or dispersing a positive electrode active material and optionally a binder and a conductive agent in a solvent, is coated on a positive electrode current collector, and then a positive electrode may be prepared by drying and rolling the coated positive electrode current collector.

The solvent may be a solvent generally used in the art. The solvent may contain dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and any one of them or a mixture of two or more of them may be used. In view of the coating thickness and manufacturing yield of the slurry, the amount of the solvent may be sufficient if the solvent can dissolve or disperse the positive electrode active material, the conductive agent, and the binder and can be made to have a viscosity that provides excellent thickness uniformity during the subsequent coating for preparing the positive electrode.

Further, as another method, a cathode may be prepared by casting a composition for forming a cathode active material layer on a separate support and then laminating a film separated from the support on a cathode current collector.

Lithium secondary battery

In addition, in the present invention, an electrochemical device including the cathode may be prepared. The electrochemical device may be specifically a battery or a capacitor, and may be, for example, a lithium secondary battery.

The lithium secondary battery specifically includes a positive electrode, a negative electrode disposed in a manner facing the positive electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte, wherein, since the positive electrode is the same as described above, a detailed description thereof will be omitted, and only the remaining configuration will be described in detail hereinafter.

In addition, the lithium secondary battery may further optionally include a battery container accommodating an electrode assembly of the positive electrode, the negative electrode and the separator, and a sealing member sealing the battery container.

In the lithium secondary battery, the anode includes an anode current collector and an anode active material layer disposed on the anode current collector.

The anode current collector is not particularly limited as long as it has high conductivity without causing adverse chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, copper or stainless steel surface-treated with one of carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. In addition, the anode current collector may generally have a thickness of 3 to 500 μm, and similar to the cathode current collector, fine irregularities may be formed on the surface of the current collector to improve adhesion to the anode active material. The negative electrode current collector may be used in various shapes, such as a film, a sheet, a foil, a mesh, a porous body, a foam, a nonwoven fabric body, and the like, for example.

The anode active material layer selectively contains a binder and a conductive agent in addition to the anode active material.

A compound capable of reversibly intercalating and deintercalating lithium may be used as the negative electrode active material. Specific examples of the anode active material may be as follows: carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; a (quasi) metal compound capable of alloying with lithium such as silicon (Si), aluminum (Al), tin (Sn), lead (Pb), zinc (Zn), bismuth (Bi), indium (In), magnesium (Mg), gallium (Ga), cadmium (Cd), a Si alloy, a Sn alloy, or an Al alloy; metal oxides, e.g. SiO, which can be doped and dedoped with lithium_β(0<β<2)、SnO₂Vanadium oxide and lithium vanadium oxide; or a composite material comprising a metal compound and a carbonaceous material, such as a Si-C composite material or a Sn-C composite material, and either one or a mixture of two or more thereof may be used. In addition, a metallic lithium thin film may be used as a negative electrode active material. Further, as the carbon material, both low crystalline carbon and high crystalline carbon may be used. Typical examples of the low crystalline carbon may be soft carbon and hard carbon, and typical examples of the high crystalline carbon may be amorphous, planar, flaky, spherical or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesophase carbon microbeads, mesophase pitch, and high temperature sintered carbon such as petroleum or coal tar pitch-derived coke.

The content of the anode active material may be 80 parts by weight to 99 parts by weight, based on the total weight of the anode active material layer.

The binder is a component contributing to binding between the conductive agent, the active material, and the current collector, and is generally added in an amount of 0.1 to 10 parts by weight, based on the total weight of the negative electrode active material layer. Examples of the binder may be polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluorine-containing rubber, and various copolymers thereof.

The conductive agent is a component for further improving the conductivity of the anode active material, wherein the conductive agent may be added in an amount of 10 parts by weight or less, for example, 5 parts by weight or less, based on the total weight of the anode active material layer. The conductive agent is not particularly limited as long as it has conductivity without causing adverse chemical changes in the battery, and for example, a conductive material such as graphite, e.g., natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black and thermal black; conductive fibers such as carbon fibers or metal fibers; carbon fluoride; metal powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides such as titanium oxide; or a polyphenylene derivative.

For example, the anode active material layer may be prepared by coating a composition for forming an anode prepared by selectively dissolving or dispersing a binder and a conductive agent and an anode active material in a solvent on an anode current collector and drying the coated anode current collector, or may be prepared by casting the composition for forming an anode on a separate support and then laminating a film separated from the support on the anode current collector.

In the lithium secondary battery, a separator separates a negative electrode and a positive electrode and provides a moving path of lithium ions, wherein any separator may be used as the separator without particular limitation as long as it is generally used in the lithium secondary battery, and in particular, a separator having a high moisture-retaining ability to an electrolyte and a low resistance to migration of electrolyte ions may be used. Specifically, it is possible to use: porous polymer films, for example, porous polymer films prepared from polyolefin-based polymers such as ethylene homopolymer, propylene homopolymer, ethylene/butene copolymer, ethylene/hexene copolymer, and ethylene/methacrylate copolymer; or have a laminated structure of two or more layers thereof. In addition, a typical porous nonwoven fabric, such as a nonwoven fabric formed of high-melting glass fibers or polyethylene terephthalate fibers, may be used. In addition, a coated separator including a ceramic component or a polymer material may be used to ensure heat resistance or mechanical strength, and a separator having a single-layer structure or a multi-layer structure may be selectively used.

In addition, the electrolyte used in the present invention may include an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, or a melt-type inorganic electrolyte, which may be used to manufacture a lithium secondary battery, but the present invention is not limited thereto.

Specifically, the electrolyte may include an organic solvent and a lithium salt.

Any organic solvent may be used as the organic solvent without particular limitation so long as it can serve as a medium through which ions participating in the electrochemical reaction of the battery can move. Specifically, the following solvents can be used as the organic solvent: ester solvents such as methyl acetate, ethyl acetate, gamma-butyrolactone and epsilon-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; or carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (MEC), Ethyl Methyl Carbonate (EMC), Ethylene Carbonate (EC), and Propylene Carbonate (PC); alcohol solvents such as ethanol and isopropanol; nitriles such as R-CN (where R is a linear, branched or cyclic C2-C20 hydrocarbon group and may contain double bonds, aromatic rings or ether linkages); amides, such as dimethylformamide; dioxolanes, such as 1, 3-dioxolane; or sulfolane. Among these solvents, a carbonate-based solvent may be used, and for example, a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant, which may increase charge/discharge performance of a battery, and a low-viscosity chain carbonate-based compound (e.g., ethylene carbonate, dimethyl carbonate, or diethyl carbonate) may be used. In this case, when the cyclic carbonate and the chain carbonate are mixed in a volume ratio of about 1:1 to about 1:9, the performance of the electrolyte may be excellent.

The lithium salt may be used without particular limitation so long as it is a compound capable of providing lithium ions for a lithium secondary battery. Specifically, LiPF may be used₆、LiClO₄、LiAsF₆、LiBF₄、LiSbF₆、LiAlO₄、LiAlCl₄、LiCF₃SO₃、LiC₄F₉SO₃、LiN(C₂F₅SO₃)₂、LiN(C₂F₅SO₂)₂、LiN(CF₃SO₂)₂LiCl, LiI or LiB (C)₂O₄)₂As the lithium salt. The lithium salt may be used in a concentration range of 0.1M to 2.0M. In the case where the concentration of the lithium salt is included in the above range, since the electrolyte may have appropriate conductivity and viscosity, excellent performance of the electrolyte may be obtained and lithium ions may be efficiently moved.

In order to improve the life characteristics of the battery, suppress the decrease in the capacity of the battery, and improve the discharge capacity of the battery, at least one additive such as halogenated alkylene carbonate compounds, e.g., ethylene difluorocarbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, (diethylene glycol dimethyl ether), hexamethylphosphoric triamide, nitrobenzene derivatives, sulfur, quinoneimine dye, N-substitutedOxazolidinone, N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additive may be included in an amount of 0.1 to 5 parts by weight, based on the total weight of the electrolyte.

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, the lithium secondary battery is suitable for portable devices such as mobile phones, notebook computers, and digital cameras, and electric vehicles such as Hybrid Electric Vehicles (HEVs).

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

The battery module or the battery pack may be used as a power source for at least one of medium-and large-sized devices: an electric tool; electric vehicles, including Electric Vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or an electrical power storage system.

The shape of the lithium secondary battery of the present invention is not particularly limited, but a cylindrical type, a prismatic type, a pouch type, or a coin type using a can may be used.

The lithium secondary battery according to the present invention may be used not only in a battery cell used as a power source for small-sized devices, but also as a unit cell in medium-and large-sized battery modules including a plurality of battery cells.

Hereinafter, the present invention will be described in detail based on specific examples. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these exemplary embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

Examples

Example 1

NiSO is added in an amount such that the molar ratio of nickel to cobalt to manganese is 90:5:5₄·6H₂O、CoSO₄·7H₂O and MnSO₄·H₂O was mixed in deionized water to prepare a transition metal-containing solution having a concentration of 2.3M.

The vessel containing the transition metal-containing solution was connected to a 20L reactor. In addition, 7.96M aqueous NaOH solution and 15% NH were prepared₄The aqueous OH solution was connected to the reactor.

3.8L of deionized water, 0.2L of ammonia, 0.063L of aqueous NaOH solution, and 2.8g of Na₂WO₄Was added to the reactor so that the molar concentration of tungsten contained in the initial reaction solution was 0.008M. The reactor was then purged with nitrogen at a rate of 5 mL/min to remove dissolved oxygen from the water and create a non-oxidizing atmosphere in the reactor. Thereafter, stirring was performed at a speed of 500rpm and a temperature of 50 ℃ to maintain the pH in the reactor at 12.5.

Thereafter, the concentration was adjusted to 6.3 mL/min and 4.2 mL/min, respectivelyThe transition metal-containing solution, aqueous NaOH solution and NH were added to the reactor at a rate of 0.46 mL/min₄The aqueous OH solution was subjected to a coprecipitation reaction for 30 minutes to form nuclei of the nickel manganese cobalt hydroxide particles. Subsequently, aqueous NaOH solution and NH added to the reactor₄The addition rates of the OH aqueous solution were adjusted to 3.8 mL/min and 0.46 mL/min, respectively, to grow the nickel manganese cobalt hydroxide particles at a pH of 11.4 for 1680 minutes, thereby preparing an average particle diameter (D)₅₀) 4.0 μm, average composition Ni_0.90Co_0.05Mn_0.05(OH)₂And 700ppm of W of the positive active material precursor.

Example 2

Except that 2.1g of Na as a metal additive was added in an amount such that the molarity of molybdenum contained in the initial solution was 0.008M₂MoO₄Except that the average particle diameter (D) was prepared in the same manner as in example 1₅₀) 4.0 μm, average composition Ni_0.90Co_0.05Mn_0.05(OH)₂And contains 340ppm of Mo.

Example 3

An average particle diameter (D) was prepared in the same manner as in example 1, except that 3.8L of deionized water, 0.2L of aqueous ammonia, and 0.063L of aqueous NaOH having W dissolved therein were used as initial reaction solutions₅₀) 4.0 μm, average composition Ni_0.90Co_0.05Mn_0.05(OH)₂And 700ppm of W of the positive active material precursor.

In this case, 2.8g of Na was added to the W-dissolved NaOH solution₂WO₄Was added to the NaOH solution so that the molar concentration of tungsten contained in the NaOH solution was 0.008M.

Example 4

Except that 0.07g of Na was added₂WO₄An average particle diameter (D) was prepared in the same manner as in example 1, except that the addition was made to the initial reaction solution so that the molar concentration of tungsten contained in the initial reaction solution was 0.0002M₅₀) Is composed of4.0 μm, average composition Ni_0.90Co_0.05Mn_0.05(OH)₂And contains 17.5ppm of W of the positive active material precursor.

Example 5

Except that 280g of Na was added₂WO₄An average particle diameter (D) was prepared in the same manner as in example 1, except that the addition was made to the initial reaction solution so that the molar concentration of tungsten contained in the initial reaction solution was 0.8M₅₀) 4.0 μm, average composition Ni_0.90Co_0.05Mn_0.05(OH)₂And 70000ppm of W as a positive active material precursor.

Comparative example 1

A positive electrode active material precursor was prepared in the same manner as in example 1, except that no metal additive was added to the reactor.

Comparative example 2

NiSO is added in an amount such that the molar ratio of nickel to cobalt to manganese is 90:5:5₄·6H₂O、CoSO₄·7H₂O and MnSO₄·H₂O was mixed in deionized water to prepare a transition metal-containing solution having a concentration of 2.3M. Mixing Na₂WO₄Mixed in deionized water to prepare an aqueous solution containing tungsten at a concentration of 0.06M.

A vessel containing the transition metal-containing solution and a vessel containing the tungsten-containing aqueous solution were connected to a 20L reactor, respectively.

After 3.8L of deionized water, 0.2L of aqueous ammonia, and 0.063L of aqueous NaOH solution were added to the reactor, the reactor was purged with nitrogen at a rate of 5 mL/min to remove dissolved oxygen from the water and form a non-oxidizing atmosphere in the reactor. Thereafter, stirring was performed at a speed of 500rpm and a temperature of 50 ℃ to maintain the pH in the reactor at 12.5.

Subsequently, a transition metal-containing solution, an aqueous tungsten-containing solution, an aqueous NaOH solution and NH were added to the reactor at rates of 6.3 mL/min, 0.88 mL/min, 4.2 mL/min and 0.46 mL/min, respectively₄Aqueous OH solution and run for 30 minutesThe coprecipitation reaction forms a core of the nickel manganese cobalt tungsten hydroxide particles.

Subsequently, aqueous NaOH solution and NH added to the reactor₄The addition rates of the OH aqueous solution were adjusted to 3.8 mL/min and 0.46 mL/min, respectively, to grow the nickel manganese cobalt tungsten hydroxide particles at a pH of 11.4 for 1680 minutes to prepare an average particle diameter (D)₅₀) 5.4 μm, average composition [ Ni ]_0.90Co_0.05Mn_0.05]_0.997W_0.003(OH)₂And 8000ppm of a positive active material precursor of W.

Experimental example 1: identification of surface characteristics of positive electrode active material precursor

The positive electrode active material precursors prepared in examples 1 to 5 and comparative examples 1 and 2 were photographed using a scanning electron microscope to identify the particle characteristics of the formed positive electrode active material precursors. In addition, a Scanning Electron Microscope (SEM) photograph was taken at a magnification of 2000 times, and the particle size and the average particle size (D) were selected₅₀) The most similar 10 particles, and the aspect ratio of each of the positive electrode active material precursor particles prepared in examples 1 to 5 and comparative examples 1 and 2 was calculated by (short axis)/(long axis). The aspect ratio of the positive electrode active material precursor calculated as described above is shown in table 1 below.

[ Table 1]

	Aspect ratio
		Example 1	0.89
Example 2	0.91
		Example 3	0.88
Example 4	0.73
		Example 5	0.89
Comparative example 1	0.72
		Comparative example 2	0.69

Referring to fig. 1 to 3, it can be confirmed that the positive active material precursors prepared in examples 1 and 2 have approximately spherical and uniform shapes. In contrast, with the positive electrode active material precursor prepared in comparative example 1, it was confirmed that the surface thereof was not uniform and was not formed into a spherical shape.

Further, referring to table 1, the positive electrode active material precursors prepared in examples 1 to 5 had an aspect ratio closer to 1 compared to the positive electrode active material precursors prepared in comparative examples 1 and 2, and thus, it can be confirmed that the sphericity of the positive electrode active material precursors prepared in examples 1 to 5 was superior to that of comparative examples 1 and 2.

Experimental example 2: examination of particle size distribution

In order to examine the particle size distribution of the positive electrode active material precursor particles prepared in examples 1 to 5 and comparative examples 1 and 2, the particle size of the positive electrode active material precursor formed in examples 1 to 5 and comparative examples 1 and 2 was measured using a particle size distribution meter (S-3500, Microtrac), and the results thereof are shown in table 2 below.

[ Table 2]

	D10(μm)	D50(μm)	D90(μm)	(D90-D10)/D50
					Example 1	3.04	3.94	5.08	0.518
Example 2	3.12	3.95	5.21	0.529
					Example 3	2.96	3.89	5.12	0.555
Example 4	4.07	5.54	7.35	0.592
					Example 5	3.12	4.03	5.22	0.521
Comparative example 1	4.10	5.32	7.08	0.560
					Comparative example 2	4.05	5.42	7.13	0.568

Referring to table 2, it can be confirmed that the average particle diameter (D) of the positive electrode active material precursors prepared in examples 1 to 5₅₀) Less than the average particle diameter (D) of the positive electrode active material precursor without the addition of the metal additive prepared in the comparative example₅₀). In addition, it was confirmed that the cathode active material precursors prepared in examples 1 to 3 and 5 had a more uniform particle size distribution than the cathode active material precursors prepared in comparative examples 1 and 2.

According to experimental examples 1 and 2, it was confirmed that when the metal additive was added to the initial reaction solution, a positive electrode active material precursor having an average particle diameter of 3 to 5 μm and excellent sphericity could be synthesized.