Precursor for positive electrode active material for lithium secondary battery, positive electrode active material containing the same, and method for producing a positive electrode active material

Abstract

The present invention relates to a positive electrode active material precursor for a lithium secondary battery, a positive electrode active material for a lithium secondary battery, and a method for producing a positive electrode active material, wherein the positive electrode active material precursor for a lithium secondary battery has an XRD peak value of I 001 / I 100 Ratio is 0.5 to 6, I 001 / I 101 Ratio is 0.6 to 3, I 001 / I 102 Ratio is 2.5 to 8, I 001 / I 110 Ratio is 1.5 to 11, I 001 / I 111 Ratio is 2-14, I 100 / I 001 Ratio is 0.1 to 3.1, I 100 / I 101 Ratio is 0.1 to 1.5, I 100 / I 102 Ratio is 1.0 to 7.3, I 100 / I 110 Ratios between 1.5 and 3.2, and I 100 / I 111 The ratio can satisfy at least one of 2.5 to 5.3.

Description

[Technical Field]

[0001] The present invention relates to a secondary battery, and more specifically to a precursor for a lithium secondary battery positive electrode active material, a lithium secondary battery positive electrode active material containing the same, and a method for producing the same. [Background technology]

[0002] Lithium-ion secondary batteries generally consist of a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, a separator membrane, and an electrolyte. Charging and discharging are performed by the insertion and deintercalation of lithium ions. Because lithium-ion secondary batteries have advantages such as high energy density, high electromotive force, and high capacity, they are applied in a variety of fields. Furthermore, improving high-temperature performance, such as high-temperature storage characteristics and high-temperature cycling characteristics, in lithium secondary batteries is a crucial challenge to address. For example, if the total internal pore volume is high after the positive electrode active material is applied to a current collector and rolled, there is a high probability that the high-temperature performance of the positive electrode will deteriorate. Therefore, it is necessary to improve the high-temperature characteristics during the development of positive electrode materials for lithium secondary batteries, such as rapid-charging secondary batteries, by minimizing the changes in electrode structure and total internal pore volume that occur during electrode rolling.

[0003] Furthermore, with the technological development and increasing demand for mobile devices, the demand for secondary batteries as an energy source has surged. Among secondary batteries, lithium-ion batteries, which exhibit high energy density and operating potential, long cycle life, and low self-discharge rate, have been commercialized and are widely used. Furthermore, as concern for environmental issues increases, interest in electric vehicles and hybrid electric vehicles, which can replace fossil fuel vehicles such as gasoline and diesel vehicles—one of the main causes of air pollution—is growing, and research into using lithium-ion batteries as a power source for these electric vehicles and hybrid electric vehicles is actively being conducted.

[0004] With the technological development and increasing demand for electric vehicles, the demand for lithium-ion secondary batteries as an energy source for large batteries is rapidly increasing. Interest in lithium nickel cobalt manganese composite oxide as a positive electrode active material for lithium-ion secondary batteries is rapidly increasing, and among the composite oxides, cobalt in particular plays an important role in providing a positive electrode active material with a high operating voltage and excellent efficiency characteristics.

[0005] However, because cobalt is expensive, there are limitations to its use in large quantities in power sources such as electric vehicles. In recent years, the price of cobalt has risen sharply, and the cobalt content has gradually decreased, creating a need for solutions that can compensate for the resulting lack of stability and lifespan.

[0006] Furthermore, as another method to improve the stability of the positive electrode active material, lithium transition metal oxides having a concentration gradient in which the concentration of the transition metal component gradually changes from the surface to the interior of the positive electrode active material have been proposed. However, lithium transition metal oxides with a concentration gradient have the problem that cracks inside the particles that occur during the charge-discharge process cannot be completely controlled, and complex processes are used to achieve this, resulting in high processing costs and difficulties in quality control. [Overview of the project] [Problems that the invention aims to solve]

[0007] In the processing of positive electrode active materials, it is possible to provide a precursor for positive electrode active materials that has low processing costs, is easy to control in terms of quality, and can produce positive electrode active materials with improved stability and lifespan characteristics by controlling cracks inside the particles that occur during the charge and discharge process. A positive electrode active material can be provided that includes a precursor for positive electrode active material having the advantages described above. A method for producing a positive electrode active material having the aforementioned advantages can be provided. [Means for solving the problem]

[0008] According to one embodiment of the present invention, the positive electrode active material precursor has, in XRD peak values, I 001 / I 100 has a ratio of 0.5 to 6, I 001 / I 101 has a ratio of 0.6 to 3, I 001 / I 102 has a ratio of 2.5 to 8, I 001 / I 110 has a ratio of 1.5 to 11, I 001 / I 111 has a ratio of 2 to 14, I 100 / I 001 has a ratio of 0.1 to 3.1, I 100 / I 101 has a ratio of 0.1 to 1.5, I 100 / I 102 has a ratio of 1.0 to 7.3, I 100 / I 110 has a ratio of 1.5 to 3.2, and I 100 / I 111 can satisfy at least one of a ratio of 2.5 to 5.3. In one embodiment, the positive electrode active material precursor can satisfy at least one of the following: the full width at half maximum of a diffraction peak on the (001) plane is in the range of 0.1 to 3.0, the full width at half maximum of a diffraction peak on the (100) plane is 0.1 to 2.8, the full width at half maximum of a diffraction peak on the (101) plane is 0.36 to 1.0, the full width at half maximum of a diffraction peak on the (102) plane is 0.1 to 2.0, and the full width at half maximum of a diffraction peak on the (110) plane is in the range of 0.1 to 3.0.

[0009] In one embodiment, the positive electrode active material precursor can have a structure in which at least one transition metal layer and at least one oxygen layer are laminated. In another embodiment, the positive electrode active material precursor is composed of at least one primary particle, and the c-axis lattice constant of the primary particle may be 300 nm to 700 nm.

[0010] According to another embodiment of the present invention, the positive electrode active material may be a single particle including at least one positive electrode active material precursor having a hydrogen bond in the <001> direction and containing 500 to 2000 ppm by weight of Li2CO3. In one embodiment, the positive electrode active material contains LiOH, and the LiOH and the Li2CO3 can satisfy the following Formula 1. <Formula 1> 0.5 ≤ [LiOH] / [Li2CO3] ≤ 1.9 (In formula 1, [LiOH] represents the LiOH content, and [Li2CO3] represents the Li2CO3 content.)

[0011] In one embodiment, the LiOH may contain 1000 to 4000 ppm by weight. In one embodiment, the average particle size (D50) of the positive electrode active material may be 2 to 20 μm.

[0012] In one embodiment, the specific surface area is 1 to 30 m². 2 It may also be / g. In one embodiment, the positive electrode active material may be a lithium-nickel composite oxide represented by the following chemical formula 1. <Chemical formula 1> Li x [Ni y Co z Mn w M v ]O2 (In the above chemical formula 1, M is one or more selected from Ba, Ca, Zr, Ti, Mg, Ta, Nb, and Mo, and 0.9 <x<1.2、0.8<y<1、0<z<0.8、0<w<0.05、0≦v≦0.2である)

[0013] A method for producing a positive electrode active material according to another embodiment of the present invention includes the steps of: preparing initial reaction conditions in a reactor by administering an aqueous solution containing a sodium or potassium-based substance; preparing a reaction solution by administering an aqueous solution of a metal salt containing at least one of nickel, cobalt, and manganese, a complex ion forming agent, and a pH adjusting agent into the reactor; preparing a metal composite hydroxide by filtering the reaction solution; preparing a positive electrode active material precursor by mixing the metal composite hydroxide and a lithium raw material; and calcining the positive electrode active material precursor, wherein the aqueous solution containing the sodium or potassium-based substance may contain 5 to 10 parts by weight of the sodium or potassium-based substance per 100 parts by weight of water.

[0014] In one embodiment, the sodium or potassium-based substance may include at least one of sodium sulfate, sodium hydrochloride, potassium hydrochloride, and potassium sulfate. In one embodiment, in the step of administering an aqueous metal salt solution containing at least one of nickel, cobalt, and manganese, a complex ion forming agent, and a pH adjusting agent into the reactor, the flow rate ratio of aqueous ammonia to the flow rate of the aqueous metal salt solution may be 0.06 to 0.3.

[0015] In one embodiment, the flow rate of the metal salt aqueous solution may be 2.5 to 3.5 L / hour. In one embodiment, the calcination step can be carried out at 750 to 1100°C. In one embodiment, the calcination step can be carried out for 5 to 30 hours. In one embodiment, the step of administering a metal salt aqueous solution containing at least one of nickel, cobalt, and manganese, a complex ion forming agent, and a pH adjusting agent into the reactor can adjust the pH in the reactor to 10 to 12. [Effects of the Invention]

[0016] A precursor for a positive electrode active material according to one embodiment of the present invention is <001> This provides a precursor that has grown by forming hydrogen bonds in a specific direction.

[0017] According to another embodiment of the present invention, a positive electrode active material can be provided in which the stability and lifetime characteristics are improved by reducing cracks occurring at polycrystalline boundaries, thereby forming a single particle containing a precursor having the advantages described above, and the residual Li2CO3 content is limited to a predetermined range.

[0018] A method for producing a positive electrode active material according to yet another embodiment of the present invention can provide a method for producing a positive electrode active material having the advantages described above by controlling the content of the complex ion forming agent. [Brief explanation of the drawing]

[0019] [Figure 1A]Figure 1A shows SEM images of cathode active material precursors according to the examples and comparative examples of the present invention. [Figure 1B] Figure 1B shows SEM images of cathode active material precursors according to the examples and comparative examples of the present invention. [Figure 1C] Figure 1C shows SEM images of cathode active material precursors according to the examples and comparative examples of the present invention. [Figure 2] Figure 2 shows the XRD peak intensity values ​​for the embodiments and comparative examples of the present invention. [Figure 3A] Figure 3A shows SEM images of positive electrode active materials for lithium secondary batteries according to examples and comparative examples of the present invention. [Figure 3B] Figure 3B shows SEM images of positive electrode active materials for lithium secondary batteries according to examples and comparative examples of the present invention. [Figure 3C] Figure 3C shows SEM images of positive electrode active materials for lithium secondary batteries according to examples and comparative examples of the present invention. [Figure 4A] Figure 4A is a graph showing the capacity characteristics and life characteristics of positive electrode active materials for lithium secondary batteries according to examples and comparative examples of the present invention. [Figure 4B] Figure 4B is a graph showing the capacity characteristics and life characteristics of positive electrode active materials for lithium secondary batteries according to examples and comparative examples of the present invention. [Figure 5] Figure 5 shows an SEM image of a lithium secondary battery active material precursor produced by adding ammonium sulfate in a comparative example of the present invention. [Modes for carrying out the invention]

[0020] The terms first, second, and third are used to describe various parts, components, regions, layers, and / or sections, but are not limited to these. These terms are used solely to distinguish one part, component, region, layer, or section from other parts, components, regions, layers, or sections. Accordingly, the first part, component, region, layer, or section described below may be referred to as the second part, component, region, layer, or section without departing from the scope of the invention.

[0021] The technical terms used herein are for the sole purpose of referring to specific embodiments and are not intended to limit the invention. The singular form used herein also includes the plural form unless the wording explicitly indicates the opposite. The meaning of “includes” as used in this specification is to embody specific characteristics, regions, integers, steps, operations, elements, and / or components, and does not exclude the presence or addition of other characteristics, regions, integers, steps, operations, elements, and / or components.

[0022] When referring to one part being "on top of" or "on" another part, it may be on top of or on top of the other part, and the other part may be between them. In contrast, when referring to one part being "directly on top of" another part, the other part is not intervening between them.

[0023] Although not defined differently, all terms used herein, including technical and scientific terms, have the same meaning as that commonly understood by a person of ordinary skill in the art to which this invention pertains. Commonly used predefined terms are further interpreted as having the meaning consistent with the relevant technical literature and the present disclosure, and are not interpreted as having an ideal or highly formal meaning unless otherwise defined.

[0024] Embodiments of the present invention will be described in detail below. However, these are presented as examples only and do not limit the present invention, which is defined only by the scope of the claims described later.

[0025] A positive electrode active material precursor for a lithium secondary battery according to one embodiment of the present invention has an XRD peak value of I 001 / I 100 The ratio is 0.5-6, I 001 / I 101 The ratio is 0.6 to 3, I 001 / I 102 The ratio is 2.5 to 8, I 001 / I 110 The ratio is 1.5 to 11, I 001 / I 111 The ratio is 2-14, I 100 / I 001 The ratio is 0.1 to 3.1, I 100 / I 101 The ratio is 0.1 to 1.5, I 100 / I 102 The ratio is 1.0 to 7.3. 100 / I 110 The ratio is 1.5 to 3.2, and I 100 / I 111 The ratio can satisfy at least one of the following conditions: 2.5 to 5.3. Specifically, I 001 The XRD peak value may be a peak value that satisfies the range of 18.5 ± 1.0°. More specifically, the I 001 This can refer to a C-axis growth precursor that has grown by forming hydrogen bonds.

[0026] I 100 The XRD peak value may also be a peak value that satisfies the range of 33.0 ± 1.0°, I 101 In terms of XRD peak values, a peak value that satisfies the range of 38.5 ± 1.5° can be considered the peak value of the A-axis growth precursor.

[0027] I 102 The XRD peak value may also be a peak value that satisfies the range of 52.5 ± 1.5°, I 110 The XRD peak value may also be a peak value that satisfies the range of 59±1.5°, I 111 The peak value may also satisfy the range of 63±1.0°.

[0028] The above I 001 / I 100The ratio is one of the indicators used to determine whether a precursor has grown by forming hydrogen bonds in the 001 direction. A higher ratio indicates a precursor that has grown by forming hydrogen bonds in the 001 direction. 001 / I 100 The ratio may be 0.5 to 6. Specifically, the above I 001 / I 100 The ratio may be between 2 and 6. Specifically, the above I 001 / I 100 The ratio may be between 2.3 and 4.4. The above I 001 / I 100 The ratio, by satisfying the aforementioned range, has the advantage of allowing the acquisition of single-particle positive electrode active material by precursor calcination. If the ratio exceeds the upper limit, there are capacity issues when applied to batteries, and if the ratio falls below the lower limit, there are difficulties in producing single-particle positive electrode active material.

[0029] The above I 001 / I 101 The ratio is one of the indicators used to determine whether a precursor has grown by forming hydrogen bonds in the 001 direction. A higher ratio indicates a precursor that has grown by forming hydrogen bonds in the 001 direction. 001 / I 101 The ratio may be 0.6 to 3. Specifically, the above I 001 / I 101 The ratio may be 1.5 to 3. More specifically, the above I 001 / I 101 The ratio can be between 1.5 and 1.8. The above I 001 / I 101 By keeping the ratio within the aforementioned range, cracks occurring at polycrystalline boundaries are reduced, resulting in improved stability and lifetime characteristics, as well as the advantage of limiting the residual Li2CO3 content. If the ratio exceeds the upper limit, there are capacity issues when applied to batteries, and if the ratio falls below the lower limit, the primary particle size becomes thinner, increasing the number of crystal plane boundaries and thus increasing the number of cracks.

[0030] The above I 001 / I 102Said ratio is one of the indicators for determining a precursor grown by forming hydrogen bonds in the 001 direction. A higher ratio means a precursor grown by forming hydrogen bonds in the 001 direction. Said I 001 / I 102 ratio may be 2.5 to 8. Specifically, said I 001 / I 102 ratio may be 4.9 to 6.7. Said I 001 / I 102 When the ratio satisfies the aforementioned range, there is an advantage that a single-particle positive electrode active material can be obtained by calcining the precursor. If the ratio exceeds the upper limit, there is a problem with the capacity when applied to a battery; if the ratio is lower than the lower limit, it is difficult to form the positive electrode active material into single particles.

[0031] Said I 001 / I 110 Said ratio is one of the indicators for determining a precursor grown by forming hydrogen bonds in the 001 direction. A higher ratio means a precursor grown by forming hydrogen bonds in the 001 direction. Said I 001 / I 110 ratio may be 1.5 to 11. Specifically, said I 001 / I 110 ratio may be 4.0 to 10.5. More specifically, said I 001 / I 110 ratio may be 4.2 to 10.3. Said I 001 / I 110 When the ratio satisfies the aforementioned range, there is an advantage that a single-particle positive electrode active material can be obtained by calcining the precursor. If the ratio exceeds the upper limit, there is a problem with the capacity when applied to a battery; if the ratio is lower than the lower limit, it is difficult to form the positive electrode active material into single particles.

[0032] Said I 001 / I 111 Said ratio is one of the indicators for determining a precursor grown by forming hydrogen bonds in the 001 direction. A higher ratio means a precursor grown by forming hydrogen bonds in the 001 direction. Said I 001 / I 111 ratio may be 2 to 14. Specifically, said I001 / I 111 ratio may be 7.0 to 13.5. More specifically, said I 001 / I 111 ratio may be 7.4 to 13.0. Said I 001 / I 111 ratio satisfying the aforementioned range has the advantage that a single-particle positive electrode active material can be obtained by precursor firing. When the ratio exceeds the upper limit, there is a problem with the capacity when applied to a battery, and when the ratio is below the lower limit, there is a problem that it is difficult to form the positive electrode active material into single particles.

[0033] In one embodiment, I 100 / I 001 ratio may satisfy 0.1 to 3.1. Specifically, I 100 / I 001 ratio may satisfy 0.23 to 0.44. I 100 / I 101 ratio may satisfy 0.1 to 1.5. Specifically, I 100 / I 101 ratio may satisfy 0.34 to 0.78.

[0034] In one embodiment, I 100 / I 102 ratio may satisfy 1.0 to 7.3. Specifically, I 100 / I 102 ratio may satisfy 1.13 to 2.95. In one embodiment, I 100 / I 110 ratio may satisfy 1.5 to 3.2. Specifically, I 100 / I 110 ratio may satisfy 1.83 to 2.37. In one embodiment, I 100 / I 111 ratio may satisfy 2.5 to 5.3. Specifically, I 100 / I 111 ratio may satisfy 2.98 to 3.28. Said I 100 / I 001 ratio, I 100 / I 101 ratio, I 100 / I 102Ratio, I 100 / I 110 Ratio, or I 100 / I 111 The ratio satisfying the aforementioned range has the advantage of making it easy to obtain single particles during the production of the positive electrode active material.

[0035] In one embodiment, the positive electrode active material precursor can satisfy at least one of the following conditions: diffraction peak full width at half maximum (FWHM) in the (001) plane is in the range of 0.1 to 3.0, diffraction peak full width at half maximum in the (100) plane is in the range of 0.1 to 2.8, diffraction peak full width at half maximum in the (101) plane is in the range of 0.36 to 1.0, diffraction peak full width at half maximum in the (102) plane is in the range of 0.1 to 2.0, and diffraction peak full width at half maximum in the (110) plane is in the range of 0.1 to 3.0.

[0036] Specifically, the Full Width At Half Maximum (FWHM) can satisfy at least one of the following ranges: the diffraction peak FWHM at the (001) plane is in the range of 0.27 to 0.42, the diffraction peak FWHM at the (100) plane is in the range of 0.21 to 0.34, the diffraction peak FWHM at the (101) plane is in the range of 0.37 to 0.55, the diffraction peak FWHM at the (102) plane is in the range of 0.56 to 1.03, and the diffraction peak FWHM at the (110) plane is in the range of 0.33 to 0.66.

[0037] In one embodiment, the positive electrode active material precursor may have a structure in which at least one transition metal layer and an oxygen layer are laminated. The transition metal layer may consist of nickel, cobalt, manganese, or a mixture thereof. The transition metal layer can be laminated with the oxygen layer through hydrogen bonding to form a dense aggregate. This dense aggregate plays a role in favorably facilitating the formation of single particles through the calcination process in the positive electrode active material manufacturing process described later.

[0038] In one embodiment, the positive electrode active material precursor comprises at least one primary particle, the primary particle having a c-axis value of 300 nm to 700 nm. Specifically, as the dissolution of the transition metal layer and the electrostatic repulsion of the (001) plane decrease, the primary particles constituting the positive electrode active material precursor can be formed to be thicker and larger, and single particles can be synthesized even at relatively low temperatures during the synthesis of the positive electrode active material.

[0039] In one embodiment, the Span value ((D90-D10) / D50), which is the ratio of the difference between the D90 particle size and the D10 particle size to the D50 particle size of the positive electrode active material precursor, can satisfy the range of 0.55 to 0.75. Specifically, the Span value can satisfy the range of 0.55 to 0.70, and more specifically, the range of 0.61 to 0.67.

[0040] The D10, D50, and D90 particle sizes refer to the particle sizes when precursor particles, which have a distribution of various particles, are accumulated to 10%, 50%, and 90% by volume, respectively. If the range of the Span value exceeds the upper limit of the range, there is a problem that the overall specific surface area increases due to the fine powder when applied to a battery, reducing the initial charge-discharge efficiency. If the range of the Span value falls below the lower limit of the range, there is a problem that the production yield decreases significantly and costs increase because it is necessary to process powders with very small particle size deviations industrially.

[0041] In another embodiment of the present invention, the positive electrode active material for a lithium secondary battery is: <001> The positive electrode active material precursor may be formed by calcining at least one positive electrode active material precursor having hydrogen bonds in a particular direction. A detailed description of the positive electrode active material precursor can be found above, to the extent that it does not contradict the previous description.

[0042] In one embodiment, the positive electrode active material for a lithium secondary battery may be a single particle containing 500 to 2000 ppm by weight of Li2CO3. Specifically, the Li2CO3 content may be 800 to 1800 ppm. Including Li2CO3 within the above range has the advantage of reducing residual lithium. If the range of Li2CO3 exceeds the upper limit, there are problems of deterioration of lifespan characteristics and increased instability.

[0043] The term "single particle" refers to a positive electrode active material in which the distinction between a primary particle, which is a single-particle primary structure formed by the entire primary particle being single-crystallized, and a secondary particle, which is an aggregate formed by the physical or chemical bonding between multiple primary particles, disappears. By having the single-particle shape, the positive electrode active material for lithium secondary batteries can reduce cracks that occur at polycrystalline boundaries, thereby providing a positive electrode active material with excellent stability and lifespan characteristics.

[0044] In one embodiment, the positive electrode active material for a lithium secondary battery contains LiOH and can satisfy the following formula 1. <Expression 1> 0.5 ≤ [LiOH] / [Li2CO3] ≤ 1.9 (In formula 1, [LiOH] represents the LiOH content, and [Li2CO3] represents the Li2CO3 content.)

[0045] Equation 1 above can satisfy the range of 0.5 to 1.9. Specifically, Equation 1 above can satisfy the range of 1.1 to 1.75.

[0046] When the ratio of lithium hydroxide (LiOH) to lithium carbonate (Li2CO3) satisfies the aforementioned range, it reduces the resistance of the active material, which has the advantage of improving stability and lifetime characteristics. If the range of Equation 1 exceeds the upper limit of the aforementioned range, it increases instability and leads to a deterioration of lifetime characteristics.

[0047] In one embodiment, the LiOH may be present in a weight percentage of 1000 to 4000 ppm. Specifically, the LiOH may be present in a weight percentage of 1400 to 2000 ppm. Including the LiOH within the aforementioned range has the advantage of limiting residual LiOH and reducing gas generation. If the LiOH range exceeds the upper limit, there is a problem of increased instability due to increased gas generation.

[0048] In one embodiment, the average particle size (D50) of the positive electrode active material for the lithium secondary battery may be 2.0 to 20 μm. More specifically, the average particle size (D50) may be 3.6 to 4.4 μm. More specifically, the average particle size (D50) may be 3.80 to 4.06 μm.

[0049] If the average particle size (D50) exceeds the upper limit, there is a problem of increased total internal pores after rolling. If the average particle size (D50) falls below the lower limit, there is a problem of stability.

[0050] In one embodiment, the specific surface area of ​​the positive electrode active material for lithium secondary batteries is 1 to 30 m². 2 It may also be / g. Specifically, the specific surface area is 5 to 10 m². 2 / g is also acceptable.

[0051] If the specific surface area exceeds the upper limit of the range, there is a problem in that a large amount of space is generated between primary particles as they gather to form secondary particles. If the specific surface area falls below the lower limit of the range, there is a problem in that primary particles gather very densely to form secondary particles.

[0052] In one embodiment, the positive electrode active material for a lithium secondary battery may be a lithium-nickel composite oxide satisfying the following chemical formula 1. <Chemical formula 1> Li x [Ni y Co z Mn w M v ]O2 In the above chemical formula 1, M is one or more selected from Ba, Ca, Zr, Ti, Mg, Ta, Nb, and Mo, and 0.9 <x<1.2、0.8<y<1、0<z<0.8、0<w<0.05、0≦v≦0.2である。

[0053] A method for producing a positive electrode active material according to another embodiment of the present invention includes the steps of: administering an aqueous solution containing a sodium or potassium-based substance to form initial reaction conditions in a reactor; administering an aqueous solution of a metal salt containing at least one of nickel, cobalt, and manganese, a complex ion forming agent, and a pH adjusting agent into the reactor; filtering the reaction solution to produce a metal composite hydroxide; mixing the metal composite hydroxide and a lithium raw material to produce a positive electrode active material precursor; and calcining the positive electrode active material precursor.

[0054] The step of administering an aqueous solution containing a sodium or potassium-based substance to establish initial reaction conditions in the reactor may include at least one of the following as the sodium or potassium-based substance: sodium sulfate (Na2SO4), sodium hydrochloride (NaClO3), potassium sulfate (K2SO4), and potassium hydrochloride (KClO3). For example, the sodium-based substance may be sodium sulfate (Na2SO4).

[0055] In one embodiment, the aqueous solution containing the sodium or potassium-based substance may contain 5 to 10 parts by weight of the sodium or potassium-based substance per 100 parts by weight of water. Including the sodium or potassium-based substance within the aforementioned range has the advantage of increasing the thickness of the primary particles. If the amount exceeds the upper limit of the range, there is a problem of a significant increase in the thickness of the primary particles. If the amount falls below the lower limit of the range, there is a problem of a significant decrease in the thickness of the primary particles.

[0056] By creating initial reaction conditions in the reactor using the aforementioned sodium or potassium-based substance, it can be confirmed that the primary particles tend to become thicker and larger during the production of the positive electrode active material precursor. Furthermore, in the case of the positive electrode active material produced through the aforementioned sodium or potassium-based aqueous solution, it can be confirmed that the crystals of the material using sodium sulfate are more uniform and exhibit a single-crystal morphology.

[0057] The step of preparing a reaction solution by administering an aqueous metal salt solution containing at least one of nickel, cobalt, and manganese, a complex ion forming agent, and a pH adjusting agent into the reactor can be performed by administering the aqueous metal salt solution, the complex ion forming agent, and the pH adjusting agent in the order described above, with predetermined time intervals between them, or by administering them simultaneously.

[0058] In the step of administering an aqueous metal salt solution containing at least one of nickel, cobalt, and manganese, a complex ion forming agent, and a pH adjusting agent into the reactor, the aqueous metal salt solution may be a substance containing at least one of nickel, cobalt, and manganese, such as an acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide, or oxyhydroxide. The aqueous metal salt solution containing nickel may, in non-limiting examples, be Ni(OH)2, NiO, NiOOH, NiCO3·2Ni(OH)2·4H2O, NiC2O4·2H2O, Ni(NO3)2·6H2O, NiSO4, NiSO4·6H2O, fatty acid nickel salts, nickel halides, or combinations thereof.

[0059] The aqueous solution of the metal salt containing cobalt may, in non-limiting examples, be Co(OH)2, CoOOH, Co(OCOCH3)2·4H2O, Co(NO3)2·6H2O, CoSO4, Co(SO4)2·7H2O, or a combination thereof. The aqueous solution of the metal salt containing manganese may, in non-limiting examples, be Mn2O3, MnO2, Mn3O4, MnCO3, Mn(NO3)2, MnSO4, manganese acetate, manganese dicarboxylate salts, manganese citrate, manganese fatty acid salts, manganese oxyhydroxide, manganese chloride, or a combination thereof.

[0060] In the step of preparing a reaction solution by administering an aqueous metal salt solution containing at least one of nickel, cobalt, and manganese, a complex ion forming agent, and a pH adjusting agent into the reactor, the complex ion forming agent may be capable of forming a complex with at least one ion of nickel, cobalt, and manganese.

[0061] In one embodiment, in the step of preparing a reaction solution by administering an aqueous metal salt solution containing at least one of nickel, cobalt, and manganese, a complex ion forming agent, and a pH adjusting agent into the reactor, the ammonia water flow rate relative to the flow rate of the aqueous metal solution may be 0.06 to 0.3. Specifically, the ammonia water flow rate relative to the flow rate of the aqueous metal solution may be 0.1 to 0.2. When the flow rate of the aforementioned metal aqueous solution satisfies the aforementioned range, it has the advantage of being able to produce a positive electrode active material with a single particle shape. If it falls outside the aforementioned range, there is a problem in that a positive electrode active material with a single particle shape cannot be realized.

[0062] In one embodiment, the step of preparing a reaction solution by administering an aqueous metal salt solution containing at least one of nickel, cobalt, and manganese, a complex ion forming agent, and a pH adjusting agent into the reactor can adjust the pH in the reactor to 10-12, specifically 10.5-11.5.

[0063] In one embodiment, the calcination step of calcining the positive electrode active material precursor can be carried out at 750 to 1100°C. Specifically, the calcination step can be carried out at 800 to 1000°C, more specifically at 780 to 950°C. By carrying out the calcination step within this temperature range, it is possible to grow primary particles thickly without nucleation aggregation, and to produce a positive electrode active material having a single-particle morphology.

[0064] In one embodiment, the calcination step of calcining the positive electrode active material precursor can be carried out for 5 to 30 hours. Specifically, the calcination step can be carried out for 8 to 12 hours.

[0065] According to another embodiment of the present invention, a lithium secondary battery is provided which comprises a positive electrode containing the positive electrode active material described above; a negative electrode; and an electrolyte.

[0066] The positive electrode includes a current collector and a positive electrode active material layer located on the current collector. The positive electrode active material layer contains a positive electrode active material, which may include the positive electrode active material for a lithium secondary battery according to the embodiment described above. In the positive electrode active material layer, the content of the positive electrode active material may be 90% to 99% by weight relative to the total weight of the positive electrode active material layer.

[0067] The positive electrode active material layer may further contain a binder and / or a conductive material. In this case, the content of the binder and the conductive material may be 1% to 5% by weight, respectively, relative to the total weight of the positive electrode active material layer.

[0068] The binder plays a role in ensuring that the positive electrode active material particles adhere well to each other and that the positive electrode active material adheres well to the current collector. Typical examples of binders that can be used include, but are not limited to, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylic styrene-butadiene rubber, epoxy resin, and nylon.

[0069] The conductive material is used to impart conductivity to the electrodes, and any electronically conductive material that does not undergo chemical changes can be used in the battery that is constructed. Examples of conductive materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjenblack, and carbon fibers; metallic materials such as metal powders or metal fibers of copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; or conductive materials containing mixtures thereof.

[0070] The positive electrode current collector may be, but is not limited to, aluminum foil, nickel foil, or a combination thereof.

[0071] The negative electrode includes a current collector and a negative electrode active material layer formed on the current collector, and the negative electrode active material layer includes a negative electrode active material.

[0072] The negative electrode active material includes a substance capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a substance capable of doping and dedoping lithium, or a transition metal oxide.

[0073] As a material capable of reversibly intercalating / deintercalating the lithium ions, any carbon-based negative electrode active material commonly used in lithium-ion secondary batteries can be used as a carbon material. Typical examples include crystalline carbon, amorphous carbon, or a combination of both.

[0074] As the lithium metal alloy, an alloy of lithium and a metal selected from the group consisting of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn can be used.

[0075] The substances that can dope and dedope lithium include Si and SiO x(0<x<2), Si-Y alloy (wherein Y is an element selected from the group consisting of alkali metals, alkaline earth metals, group 13 elements, group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Si), Sn, SnO₂, Sn-Y (wherein Y is an element selected from the group consisting of alkali metals, alkaline earth metals, group 13 elements, group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Sn), and the like.

[0076] Examples of the transition metal oxide include vanadium oxide, lithium vanadium oxide, and the like. The negative electrode active material layer further comprises a binder, and may optionally further comprise a conductive material.

[0077] The binder serves to well adhere the negative electrode active material particles to each other, and also to well adhere the negative electrode active material to a current collector.

[0078] The conductive material is used for imparting conductivity to an electrode, and any electronically conductive material that does not cause chemical changes in the constructed battery can be used.

[0079] As the current collector, one selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrates coated with conductive metal, and combinations thereof can be used.

[0080] The negative electrode and the positive electrode are produced by mixing an active material, a conductive material and a binder in a solvent to prepare an active material composition, and applying the composition to a current collector. Such electrode production methods are well known in the art, so detailed descriptions thereof are omitted herein. As the solvent, N-methylpyrrolidone and the like can be used, but the solvent is not limited thereto.

[0081] The electrolyte comprises a non-aqueous organic solvent and a lithium salt.

[0082] The aforementioned non-aqueous organic solvent acts as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0083] The aforementioned lithium salt dissolves in organic solvents and acts as a source of lithium ions within the battery, enabling the operation of a basic lithium secondary battery and facilitating the movement of lithium ions between the positive and negative electrodes.

[0084] Depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. Such separators may be polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more layers of these materials. Mixed multilayer films such as polyethylene / polypropylene two-layer separators, polyethylene / polypropylene / polyethylene three-layer separators, and polypropylene / polyethylene / polypropylene three-layer separators can also be used.

[0085] Lithium secondary batteries are classified into lithium-ion batteries, lithium-ion polymer batteries, and lithium polymer batteries depending on the type of separator and electrolyte used. They are further classified by shape into cylindrical, prismatic, coin-type, pouch-type, etc., and by size into bulk type and thin-film type. Since the structure and manufacturing methods of these batteries are well known in this field, a detailed explanation will be omitted. [Examples]

[0086] The following describes preferred embodiments and comparative examples of the present invention. However, the following embodiments represent only one preferred embodiment of the present invention, and the present invention is not limited to these embodiments.

[0087] Method for producing a positive electrode active material precursor for lithium secondary batteries Figures 1A to 1C illustrate SEM images of cathode active material precursors according to the embodiments and comparative examples of the present invention. Figure 1A shows an SEM image of the positive electrode active material precursor produced by Example 1, Figure 1B shows an SEM image of the positive electrode active material precursor produced by Example 2, and Figure 1C shows an SEM image of the positive electrode active material precursor produced by Comparative Example 1, which will be described later. Referring to Figures 1A to 1C, it can be confirmed that the positive electrode active material precursor produced by Examples 1 and 2 of the present invention tends to be thicker and larger.

[0088] Example 1 After adding water to a 100L batch reactor to a volume of 15% of the total reactor volume, sodium sulfate was added to the reactor at a ratio of 5 parts by weight per 100 parts by weight of water. Then, while stirring at a speed of 400 rpm, the internal temperature was set to 30-50°C, and nitrogen gas was introduced into the reactor to create an inert atmosphere. Subsequently, a 2.5M aqueous solution of metal sulfates, mixed with nickel sulfate, cobalt sulfate, and manganese sulfate in a molar ratio of 0.8:0.1:0.1, along with 25% sodium hydroxide and 28% aqueous ammonia, was prepared. The flow rate of the metal sulfate aqueous solution was adjusted to 3 L / hour, the flow rate of the ammonia water was adjusted to a ratio of 0.1 to the flow rate of the metal sulfate aqueous solution, and the amount of sodium hydroxide (NaOH) solution administered was adjusted so that the hydrogen ion concentration (pH) in the reactor was approximately 11.0 to 12.0. Subsequently, the reactants were added at a stirring speed of 500 rpm, with an average residence time of 20 hours for the entire solution. The reaction temperature was maintained at 40-70°C, and nitrogen gas was added to maintain an inert atmosphere. After the reaction was complete, the formed solution was washed with water and solid-liquid separated using a filter press, and residual moisture was removed using high-pressure fresh air. The solid-liquid separated active material was dried at 100-200°C using a fluidized bed dryer. A cathode active material precursor was produced by mixing the hydroxide particles obtained by the method described above with lithium hydroxide in an equivalent ratio of 1.05 with the hydroxide.

[0089] Example 2 After adding water to a 100L batch reactor to a volume of 15% of the total reactor volume, sodium sulfate was added to the reactor at a ratio of 10 parts by weight per 100 parts by weight of water. Then, while stirring at a speed of 400 rpm, the internal temperature was set to 30-50°C, and nitrogen gas was introduced into the reactor to adjust it to an inert atmosphere. Subsequently, a 2.5M aqueous solution of metal sulfates, mixed with nickel sulfate, cobalt sulfate, and manganese sulfate in a molar ratio of 0.8:0.1:0.1, along with 25% sodium hydroxide and 28% aqueous ammonia, was prepared. The flow rate of the metal sulfate aqueous solution was adjusted to 3 L / hour, the flow rate of the ammonia water was adjusted to a ratio of 0.2 to the flow rate of the metal sulfate aqueous solution, and the amount of sodium hydroxide (NaOH) solution administered was adjusted so that the hydrogen ion concentration (pH) in the reactor was approximately 11.5 to 12.5. Subsequently, the reactants were added at a stirring speed of 400 rpm, with an average residence time of 20 hours for the entire solution. The reaction temperature was maintained at 40-70°C, and nitrogen gas was added to maintain an inert atmosphere. After the reaction was complete, the formed solution was washed with water and solid-liquid separated using a pressure filter (Filter Press), and residual moisture was removed using high-pressure fresh air. The solid-liquid separated active material was dried at 100-200°C using a fluidized bed dryer. A cathode active material precursor was produced by mixing the hydroxide particles obtained by the method described above with lithium hydroxide in an equivalent ratio of 1.05 with the hydroxide.

[0090] Comparative Example 1 The procedure was carried out in the same manner as in Example 1, except that after adding water to a 100L batch reactor at a volume of 15% of the total reactor volume, no additional sodium sulfate was added. Evaluation Example - Precursor Properties Table 1 below shows the XRD characteristics and single crystals of the precursors related to Examples 1 and 2, and Comparative Example 1. The aforementioned XRD characteristics were measured using Rigaku's SMARTLAB equipment.

[0091] [Table 1]

[0092] Figure 2 illustrates the XRD peak intensity values ​​for embodiments and comparative examples of the present invention. As can be seen in Figure 2, Examples 1 and 2 fall within the XRD peak intensity value range of the present invention, while Comparative Example 1 does not fall within the XRD peak intensity value range of the present invention.

[0093] Examples 3, 4, and Comparative Example 2 - Cathode Active Material The cathode active material precursors formed in Examples 1 and 2 and Comparative Example 1 were heated in an oxygen atmosphere at a heating rate of 2.5°C / min, and then calcined at 780°C for 9 hours to produce lithium composite metal oxides having a uniform single-crystal structure.

[0094] Evaluation Example - Particle surface analysis and coin cell evaluation of positive electrode active material for lithium batteries having a single crystal structure Table 2 below shows the particle surface analysis and coin cell evaluation according to the complex ion-forming agent content for Examples 3, 4, and Comparative Example 2. For coin cell evaluation, coin cell type (CR2032) half-cells (coin cells) were assembled in a moisture-controlled dry room. After cell assembly, they were aged at room temperature for 2 hours to allow electrolyte impregnation and electrochemical equilibrium to be achieved. Coin cells were evaluated using a TOSCAT-3100 charger / discharger. First, the formation process involved charging and discharging for one cycle with a current density of 0.1C in the voltage range of 2.5V-4.25V, followed by charging and discharging with a current density of 0.3C in the same voltage range. The initial discharge capacity, cefficiency, and high-temperature capacity retention rate during evaluation at high temperatures are shown in the table below.

[0095] [Table 2]

[0096] Figures 3A to 3C show SEM images of positive electrode active materials for lithium secondary batteries according to examples and comparative examples of the present invention. Figures 3A to 3C show the positive electrode active materials of Example 3, Example 4, and Comparative Example 2, respectively, confirming that Examples 3 and 4 of the present invention exhibit a more uniform single-crystal morphology compared to Comparative Example 2. Figures 4A and 4B are graphs showing the capacity characteristics and life characteristics of positive electrode active materials for lithium secondary batteries according to examples and comparative examples of the present invention. Figures 4A and 4B confirm that the positive electrode active materials of Examples 3 and 4 exhibit superior capacity characteristics and lifetime characteristics compared to Comparative Example 2.

[0097] Evaluation Example - Properties of sodium sulfate as a complex ion forming agent Figure 5 shows an SEM image of a lithium secondary battery active material precursor produced by adding ammonium sulfate in a comparative example of the present invention. Figure 5 shows an SEM image of a lithium secondary battery active material precursor produced by adding ammonium sulfate to the reactor. Figures 1A and 1B are SEM images of a positive electrode active material precursor produced using sodium sulfate under initial reaction conditions, and Figure 5 is an SEM image of a positive electrode active material precursor produced using sodium sulfate under initial reaction conditions. Figures 1A, 1B, and 5 show that the primary particles produced by adding sodium sulfate (Figures 1A and 1B) tend to be thicker and larger than the precursor produced by adding ammonium sulfate (Figure 5). Furthermore, the crystals of the material using sodium sulfate are more uniform and exhibit a single-crystal morphology, confirming that it is preferable to use sodium sulfate as one of the initial reaction conditions compared to ammonium sulfate.

[0098] Although preferred embodiments have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art that utilize the basic concepts defined in the following claims also fall within the scope of the present invention.

Claims

1. A cathode active material precursor for producing a lithium-nickel composite oxide represented by the following chemical formula 1, At the XRD peak value, I ００１ / I １００ The ratio is 2 to 6, and the I 001 / I 101 ratio satisfies 1.5 to 3. The transition metal layer and the oxygen layer are stacked together through hydrogen bonds to form an aggregate. It consists of at least one primary particle, The primary particle has a crystal constant value of 300 nm to 700 nm along its c axis, which is a cathode active material precursor. (At the XRD peak value, I ００１ The range is 18.5 ± 1.0°, I １００ The range is 33.0 ± 1.0°, I １０１ (This refers to the peak value that satisfies the range of 38.5 ± 1.5°) <Chemical formula 1> Li x [Ni y Co z Mn w M v ]O 2 (In the above chemical formula 1, M is one or more selected from Ba, Ca, Zr, Ti, Mg, Ta, Nb, and Mo, and the following conditions apply: 0.9 < x < 1.2, 0.8 < y < 1, 0 < z < 0.8, 0 < w < 0.05, 0 ≤ v ≤ 0.2)

2. The positive electrode active material precursor according to claim 1, wherein the diffraction peak full width at half maximum (FWHM) on the (001) plane is in the range of 0.1 to 3.0, the diffraction peak full width at half maximum on the (100) plane is in the range of 0.1 to 2.8, the diffraction peak full width at half maximum on the (101) plane is in the range of 0.36 to 1.0, the diffraction peak full width at half maximum on the (102) plane is in the range of 0.1 to 2.0, and the diffraction peak full width at half maximum on the (110) plane is in the range of 0.1 to 3.

0.

3. A single particle formed by mixing and calcining the positive electrode active material precursor and lithium raw material according to claim 1 or 2, which is a lithium-nickel composite oxide represented by chemical formula 1, Li in weight percent of 500-2000 ppm ２ CO ３ A positive electrode active material for lithium secondary batteries, including the above.

4. Contains LiOH, The aforementioned LiOH and the aforementioned Li ２ CO ３ is the positive electrode active material for a lithium secondary battery according to claim 3, which satisfies the following formula 1. <Formula 1> 0.5≦[L-OH] / [L) ２ CO ３ ]≦1.9 (In formula 1, [LiOH] is the LiOH content, [Li ２ CO ３ ] is Li ２ CO ３ (This refers to the content of)

5. The positive electrode active material for lithium secondary batteries according to claim 3, comprising 1000 to 4000 ppm by weight of LiOH.

6. The positive electrode active material for a lithium secondary battery according to claim 3, wherein the average particle size (D50) is 2 to 20 μm.

7. Specific surface area of ​​1 to 30 m² ２ The positive electrode active material for a lithium secondary battery according to claim 3, wherein the value is / g.

8. A step of administering an aqueous solution containing a sodium or potassium-based substance to establish initial reaction conditions in the reactor; A step of preparing a reaction solution by administering an aqueous solution of a metal salt containing at least one of nickel, cobalt, and manganese, a complex ion forming agent, and a pH adjusting agent into the reactor; A step of filtering the reaction solution to produce a metal composite hydroxide; A step of mixing the metal composite hydroxide and lithium raw material to produce a positive electrode active material precursor according to claim 1 or 2; and The process includes a calcination step of calcining the positive electrode active material precursor, A method for producing a positive electrode active material, wherein the aqueous solution containing the sodium or potassium-based substance comprises 5 to 10 parts by weight of the sodium or potassium-based substance per 100 parts by weight of water.

9. The method for producing a positive electrode active material according to claim 8, wherein the sodium or potassium-based substance comprises at least one of sodium sulfate, sodium hydrochloride, potassium hydrochloride, and potassium sulfate.

10. In the step of administering an aqueous metal salt solution containing at least one of nickel, cobalt, and manganese, a complex ion forming agent, and a pH adjusting agent into the reactor, The method for producing a positive electrode active material according to claim 8, wherein the ratio of the flow rate of aqueous ammonia to the flow rate of the aqueous metal salt solution is 0.06 to 0.

3.

11. The method for producing a positive electrode active material according to claim 10, wherein the flow rate of the metal salt aqueous solution is 2.5 to 3.5 L / hour.

12. The method for producing a positive electrode active material according to claim 8, wherein the firing step is performed at 750 to 1100°C.

13. The method for producing a positive electrode active material according to claim 8, wherein the firing step is performed for 5 to 30 hours.

14. The method for producing a positive electrode active material according to claim 8, wherein the step of administering an aqueous metal salt solution containing at least one of nickel, cobalt, and manganese, a complex ion forming agent, and a pH adjusting agent into the reactor adjusts the pH in the reactor to 10 to 12.

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