Precursor for positive electrode active material for lithium secondary battery, positive electrode active material containing the same, and method for producing 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 particularly to a precursor for a positive electrode active material for a lithium secondary battery, a positive electrode active material for a lithium secondary battery containing the precursor, and a method for producing the same. [Background technology]

[0002] A lithium secondary battery generally comprises a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, a separator, and an electrolyte, and is charged and discharged by the intercalation-deintercalation of lithium ions. Lithium secondary batteries have advantages such as high energy density, large electromotive force, and high capacity, and are therefore used in a variety of fields. Furthermore, improving high-temperature performance, such as high-temperature storage characteristics and high-temperature cycle characteristics, is an important issue for lithium secondary batteries. For example, if the total internal pore volume is high after the cathode active material is applied to a current collector and rolled, the high-temperature performance of the cathode is likely to be reduced. Therefore, it is necessary to improve the high-temperature performance of lithium secondary batteries, such as fast-charging secondary batteries, by minimizing changes in electrode structure and total internal pore volume that occur during electrode rolling.

[0003] In addition, with the technological development and increasing demand for mobile devices, the demand for secondary batteries as an energy source is rapidly increasing. Among secondary batteries, lithium secondary batteries, which exhibit high energy density and working potential, long cycle life, and low self-discharge rate, have been commercialized and are widely used. In addition, as interest in environmental issues grows, there is growing interest in electric vehicles and hybrid electric vehicles that can replace vehicles that use fossil fuels such as gasoline vehicles and diesel vehicles, which are one of the main causes of air pollution, and active research is being conducted into using lithium secondary batteries as a power source for such electric vehicles and hybrid electric vehicles.

[0004] With technological development and increasing demand for electric vehicles, the demand for lithium 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 secondary batteries is rapidly increasing, and cobalt in the composite oxide in particular plays an important role in providing a positive electrode active material with high working voltage and excellent efficiency characteristics.

[0005] However, cobalt is expensive, which limits its use in large quantities in power sources such as electric vehicles. In recent years, the price of cobalt has risen sharply, gradually reducing the amount of cobalt contained. As a result, there is a need for a solution that can compensate for the stability and lifespan of cobalt.

[0006] Another method for improving the stability of a positive electrode active material has been proposed: a lithium transition metal oxide 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. However, lithium transition metal oxides having a concentration gradient cannot completely control cracks inside the particles that occur during charge and discharge, and the complex processes required to achieve this result in high processing costs and difficulties in quality control. Summary of the Invention [Problem to be solved by the invention]

[0007] It is possible to provide a precursor for a positive electrode active material that can be processed at low cost, with easy quality control, and that can produce a positive electrode active material with improved stability and life characteristics by controlling cracks inside particles that occur during charge and discharge. A positive electrode active material containing a positive electrode active material precursor having the above-mentioned advantages can be provided. It is possible to provide a method for producing a positive electrode active material having the above-mentioned advantages. [Means for solving the problem]

[0008] According to one embodiment of the present invention, the positive electrode active material precursor 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 In one embodiment, the positive electrode active material precursor may have at least one of a diffraction peak full width at half maximum in the (001) plane of 0.1 to 3.0, a diffraction peak full width at half maximum in the (100) plane of 0.1 to 2.8, a diffraction peak full width at half maximum in the (101) plane of 0.36 to 1.0, a diffraction peak full width at half maximum in the (102) plane of 0.1 to 2.0, and a diffraction peak full width at half maximum in the (110) plane of 0.1 to 3.0.

[0009] In one embodiment, the positive electrode active material precursor may have a structure in which at least one transition metal layer and one oxygen layer are laminated. In another embodiment, the positive electrode active material precursor may be composed of at least one primary particle, and the c-axis crystal 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 is <001> In one embodiment, the positive electrode active material includes LiOH, and the LiOH and the LiCO3 may satisfy the following formula 1: <Expression 1> 0.5≦[LiOH] / [Li2CO3]≦1.9 (In formula 1, [LiOH] means the content of LiOH, and [Li2CO3] means the content of Li2CO3.)

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

[0012] In one embodiment, the specific surface area is 1 to 30 m 2 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 <x<1.2、0.8<y<1、0<z<0.8、0<w<0.05、0≦v≦0.2である)

[0013] According to another embodiment of the present invention, a method for preparing a positive electrode active material includes: introducing an aqueous solution containing a sodium- or potassium-based substance to create an initial reaction condition in a reactor; introducing an aqueous metal salt solution containing at least one of nickel, cobalt, and manganese, a complex ion former, and a pH adjuster into the reactor to prepare a reaction solution; filtering the reaction solution to prepare a metal composite hydroxide; mixing the metal composite hydroxide and a lithium raw material to prepare a positive electrode active material precursor; 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 chloride, potassium chloride, and potassium sulfate. In one embodiment, in the step of adding an aqueous metal salt solution containing at least one of nickel, cobalt, and manganese, a complex ion forming agent, and a pH adjuster into the reactor, the ratio of the flow rate of the ammonia water 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 may be performed at 750 to 1100°C. In one embodiment, the calcination step may be performed for 5 to 30 hours. In one embodiment, the step of adding an aqueous metal salt solution containing at least one of nickel, cobalt, and manganese, a complex ion forming agent, and a pH adjuster into the reactor may 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 comprises: <001> The precursor can be grown by forming hydrogen bonds in the direction of the crystal structure.

[0017] According to another embodiment of the present invention, a positive electrode active material includes a precursor having the above-described advantages, and thus single particles are formed. This reduces cracks that occur at polycrystalline boundaries, thereby improving stability and life characteristics, and the content of residual Li2CO3 is limited within a predetermined range.

[0018] According to yet another embodiment of the present invention, a method for manufacturing a positive electrode active material can provide a method for manufacturing a positive electrode active material having the above-described advantages by controlling the content of a complex ion-forming agent. [Brief explanation of the drawings]

[0019] [Figure 1A]FIG. 1A shows SEM photographs of precursors for positive electrode active materials according to examples and comparative examples of the present invention. [Figure 1B] FIG. 1B shows SEM photographs of the precursors for positive electrode active materials according to examples and comparative examples of the present invention. [Figure 1C] FIG. 1C shows SEM photographs of the precursors for positive electrode active materials according to examples and comparative examples of the present invention. [Figure 2] FIG. 2 shows XRD peak intensity values according to examples of the present invention and comparative examples. [Figure 3A] FIG. 3A shows SEM photographs of positive electrode active materials for lithium secondary batteries according to examples of the present invention and comparative examples. [Figure 3B] FIG. 3B shows SEM photographs of the positive electrode active materials for lithium secondary batteries according to the examples of the present invention and the comparative examples. [Figure 3C] Fig. 3C shows an SEM photograph of a positive electrode active material for a lithium secondary battery according to an example of the present invention and a comparative example. (Fig. 3A) is a graph showing the capacity characteristics and life characteristics of a positive electrode active material for a lithium secondary battery according to an example of the present invention and a comparative example. (Fig. 3B) is a graph showing the capacity characteristics and life characteristics of a positive electrode active material for a lithium secondary battery according to an example of the present invention and a comparative example. [Figure 4A] FIG. 4A is a graph showing the capacity characteristics and life characteristics of positive electrode active materials for lithium secondary batteries according to examples of the present invention and comparative examples. [Figure 4B] FIG. 4B is a graph showing the capacity characteristics and life characteristics of the positive electrode active materials for lithium secondary batteries according to the examples of the present invention and the comparative examples. [Figure 5] FIG. 5 shows an SEM photograph of an active material precursor for a lithium secondary battery produced by adding ammonium sulfate in a comparative example of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] Terms such as first, second, and third are used to describe various parts, components, regions, layers, and / or sections, but are not limited thereto. These terms are used only to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Therefore, a first part, component, region, layer, or section described below can be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention.

[0021] The terminology used herein is for the purpose of referring to particular embodiments only and is not intended to limit the present invention. As used herein, the singular forms "a," "an," and "the" include the plural forms unless the context clearly dictates otherwise. As used in the specification, the term "comprising" embodies certain properties, regions, integers, steps, operations, elements, and / or components and does not exclude the presence or addition of other properties, regions, integers, steps, operations, elements, and / or components.

[0022] When an element is referred to as being "on" or "above" another element, it may be on or above the other element, with other elements interposed between them. In contrast, when an element is referred to as being "directly on" another element, there are no other elements interposed between them.

[0023] Unless otherwise defined, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by a person of ordinary skill in the art to which this invention belongs. Commonly used predefined terms are additionally interpreted to have a meaning consistent with the relevant technical literature and the presently disclosed content, and are not interpreted as having an ideal or very formal meaning unless defined.

[0024] Hereinafter, embodiments of the present invention will be described in detail, but these are presented as examples and are not intended to limit the present invention, which is defined only by the scope of the claims set forth below.

[0025] The 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 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. 001 may be a peak value that satisfies the range of 18.5±1.0° in the XRD peak value. 001 can refer to a c-axis grown precursor that grows by forming hydrogen bonds.

[0026] I 100 may be a peak value that satisfies the range of 33.0±1.0° in the XRD peak value, and I 101 can mean the peak value of the A-axis growth precursor, which is a peak value that falls within the range of 38.5±1.5° in the XRD peak value.

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

[0028] Above I 001 / I 100The ratio is one of the indices for determining whether a precursor has grown by forming hydrogen bonds in the 001 direction, and the higher the ratio, the more the precursor has grown by forming hydrogen bonds in the 001 direction. 001 / I 100 The ratio may be 0.5 to 6. Specifically, 001 / I 100 The ratio may be 2 to 6. Specifically, 001 / I 100 The ratio may be between 2.3 and 4.4. Above I 001 / I 100 The ratio satisfies the above range, which has the advantage that a single particle cathode active material can be obtained by calcining the precursor. If the ratio exceeds the upper limit, there is a problem in capacity when applied to a battery, and if the ratio is below the lower limit, there is a problem in forming the single particle cathode active material.

[0029] Above I 001 / I 101 The ratio is one of the indices for determining whether a precursor has grown by forming hydrogen bonds in the 001 direction, and the higher the ratio, the more the precursor has grown by forming hydrogen bonds in the 001 direction. 001 / I 101 The ratio may be 0.6 to 3. Specifically, 001 / I 101 The ratio may be 1.5 to 3. More specifically, 001 / I 101 The ratio may be between 1.5 and 1.8. Above I 001 / I 101 When the ratio satisfies the above range, cracks occurring at the polycrystalline boundaries are reduced, thereby improving stability and lifespan characteristics, and the content of residual Li2CO3 is limited. If the ratio exceeds the upper limit, there is a problem with capacity when applied to a battery, and if the ratio is below the lower limit, there is a problem with the size of the primary particles becoming thinner, increasing the boundaries of the crystal planes and increasing cracks.

[0030] Above I 001 / I 102The ratio is one of the indices for determining whether a precursor has grown by forming hydrogen bonds in the 001 direction, and the higher the ratio, the more the precursor has grown by forming hydrogen bonds in the 001 direction. 001 / I 102 The ratio may be 2.5 to 8. Specifically, 001 / I 102 The ratio may be between 4.9 and 6.7. Above I 001 / I 102 The ratio satisfies the above range, which has the advantage that a single particle cathode active material can be obtained by calcining the precursor. If the ratio exceeds the upper limit, there is a problem in capacity when applied to a battery, and if the ratio is below the lower limit, there is a problem in forming the single particle cathode active material.

[0031] Above I 001 / I 110 The ratio is one of the indicators for determining whether a precursor has grown by forming hydrogen bonds in the 001 direction, and the higher the ratio, the more the precursor has grown by forming hydrogen bonds in the 001 direction. 001 / I 110 The ratio may be 1.5 to 11. Specifically, 001 / I 110 The ratio may be 4.0 to 10.5. 001 / I 110 The ratio may be between 4.2 and 10.3. Above I 001 / I 110 When the ratio satisfies the above range, it is possible to obtain a single particle cathode active material by calcining the precursor. If the ratio exceeds the upper limit, there is a problem in capacity when applied to a battery, and if the ratio is below the lower limit, there is a problem in forming the single particle cathode active material.

[0032] Above I 001 / I 111 The ratio is one of the indicators for determining whether a precursor has grown by forming hydrogen bonds in the 001 direction, and the higher the ratio, the more the precursor has grown by forming hydrogen bonds in the 001 direction. 001 / I 111 The ratio may be 2 to 14. Specifically,001 / I 111 The ratio may be 7.0 to 13.5. 001 / I 111 The ratio may be between 7.4 and 13.0. Above I 001 / I 111 When the ratio satisfies the above range, it is possible to obtain a single particle cathode active material by calcining the precursor. If the ratio exceeds the upper limit, there is a problem in capacity when applied to a battery, and if the ratio is below the lower limit, there is a problem in forming the single particle cathode active material.

[0033] In one embodiment, I 100 / I 001 The ratio can be 0.1 to 3.1. 100 / I 001 The ratio can be between 0.23 and 0.44. 100 / I 101 The ratio can be 0.1 to 1.5. Specifically, I 100 / I 101 The ratio can be 0.34 to 0.78.

[0034] In one embodiment, I 100 / I 102 The ratio can be 1.0 to 7.3. 100 / I 102 In one embodiment, the ratio of I 100 / I 110 The ratio can be 1.5 to 3.2. 100 / I 110 In one embodiment, the ratio of I 100 / I 111 The ratio can be 2.5 to 5.3. 100 / I 111 The ratio can be 2.98 to 3.28. 100 / I 001 Ratio, I 100 / I 101 Ratio, I 100 / I 102Ratio, I 100 / I 110 Ratio, or I 100 / I 111 When the ratio satisfies the above range, it is advantageous in that single particles can be easily obtained during the preparation of the positive electrode active material.

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

[0036] Specifically, the full width at half maximum (FWHM) of the diffraction peak on the (001) plane can satisfy at least one of the following ranges: 0.27 to 0.42; 0.21 to 0.34; 0.37 to 0.55; 0.56 to 1.03; and 0.33 to 0.66; for the (110) plane.

[0037] In one embodiment, the cathode active material precursor may have a structure in which at least one transition metal layer and one oxygen layer are stacked. The transition metal layer may be composed of nickel, cobalt, manganese, or a mixture thereof. The transition metal layer may be stacked with the oxygen layer through hydrogen bonding to form dense aggregates. The dense aggregates favor the formation of single particles through a calcination process in the process of preparing the cathode active material, as described below.

[0038] In one embodiment, the positive electrode active material precursor may include at least one primary particle, and the primary particle may have a c-axis value of 300 nm to 700 nm. Specifically, as the transition metal layer dissolves and the electrostatic repulsion force of the (001) plane is reduced, the positive electrode active material precursor may have thick and large primary particles constituting the positive electrode active material precursor, and single particles may be synthesized even at a relatively low temperature during 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, may be in the range of 0.55 to 0.75. Specifically, the Span value may be in the range of 0.55 to 0.70, more specifically, in the range of 0.61 to 0.67.

[0040] The D10, D50, and D90 particle sizes refer to the particle sizes when precursor particles containing various particle distributions are accumulated to 10%, 50%, and 90% by volume, respectively. If the Span value range exceeds the upper limit of the range, the total specific surface area due to fine powder increases when applied to a battery, resulting in a decrease in initial charge / discharge efficiency. If the Span value range is below the lower limit of the range, the production yield decreases significantly and costs increase due to the need to process powder 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 the axial direction. For detailed descriptions of the positive electrode active material precursor, please refer to the above-mentioned descriptions to the extent not contradictory.

[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. By including Li2CO3 in the above range, there is an advantage in reducing residual lithium. If the Li2CO3 content exceeds the upper limit of the range, there are problems of deterioration in life characteristics and increased instability.

[0043] The single particle refers to a cathode active material in which the primary particles are all single-crystallized, eliminating the distinction between the primary particles, which are the primary structure of the single particle, and the secondary particles, which are aggregates of a plurality of primary particles aggregated by physical or chemical bonds between the primary particles. The single particle shape of the cathode active material for lithium secondary batteries reduces cracks that occur at polycrystalline boundaries, thereby providing a cathode active material with excellent stability and life characteristics.

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

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

[0046] When the content ratio of lithium hydroxide (LiOH) to lithium carbonate (LiCO) satisfies the above range, the resistance of the active material is reduced, and stability and life characteristics are improved. If the range of the above formula 1 exceeds the upper limit of the range, instability is increased, resulting in a problem of deterioration of life characteristics.

[0047] In one embodiment, the LiOH may be contained in an amount of 1000 to 4000 ppm by weight. Specifically, the LiOH may be contained in an amount of 1400 to 2000 ppm by weight. By containing the LiOH in the above range, it is possible to limit the amount of residual LiOH and reduce gas generation. If the LiOH content exceeds the upper limit of the range, 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 a lithium secondary battery may be 2.0 to 20 μm. 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) is above the upper limit, the total internal porosity after rolling increases, whereas if the average particle size (D50) is below the lower limit, stability is compromised.

[0050] In one embodiment, the specific surface area of the positive electrode active material for a lithium secondary battery is 1 to 30 m 2 Specifically, the specific surface area may be 5 to 10 m 2 / g.

[0051] If the specific surface area is above the upper limit of the range, a large amount of space is generated between the primary particles that gather to form secondary particles, whereas if the specific surface area is below the lower limit of the range, a large amount of space is generated between the primary particles that gather too 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 that satisfies the following chemical formula 1: <Chemical formula 1> Li x [Ni y Co z Mn w M v ]O2 In the above formula 1, M is one or more selected from Ba, Ca, Zr, Ti, Mg, Ta, Nb, and Mo, and <x<1.2、0.8<y<1、0<z<0.8、0<w<0.05、0≦v≦0.2である。

[0053] According to another embodiment of the present invention, a method for producing a positive electrode active material includes the steps of: introducing an aqueous solution containing a sodium- or potassium-based substance to form initial reaction conditions in a reactor; introducing into the reactor an aqueous metal salt solution containing at least one of nickel, cobalt, and manganese, a complex ion former, and a pH adjuster; 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] In the step of adding an aqueous solution containing a sodium or potassium-based substance to create an initial reaction condition in the reactor, the sodium or potassium-based substance may include at least one of sodium sulfate (NaSO), sodium chloride (NaClO), potassium sulfate (KSO), and potassium chloride (KClO). For example, the sodium-based substance may be sodium sulfate (NaSO).

[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. By including the sodium or potassium-based substance in the above range, there is an advantage in that the primary particles become thicker. If the amount exceeds the upper limit of the range, there is a problem in that the thickness of the primary particles increases significantly. If the amount falls below the lower limit of the range, there is a problem in that the thickness of the primary particles decreases significantly.

[0056] By creating initial reaction conditions in a reactor using the sodium- or potassium-based material, it was confirmed that primary particles tend to become thicker and larger when preparing a precursor for a positive electrode active material. In the case of a positive electrode active material prepared using the sodium- or potassium-based aqueous solution, it was confirmed that the crystals of the material using sodium sulfate were more uniform and exhibited a single crystal morphology.

[0057] In the step of preparing a reaction solution by adding an aqueous solution of a metal salt containing at least one of nickel, cobalt, and manganese, a complex ion former, and a pH adjuster to the reactor, the aqueous solution of the metal salt, the complex ion former, and the pH adjuster may be added in the aforementioned order at predetermined time intervals or simultaneously.

[0058] In the step of adding an aqueous metal salt solution containing at least one of nickel, cobalt, and manganese, a complex ion former, and a pH adjuster into the reactor, the aqueous metal salt solution may be a substance containing acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide, or oxyhydroxide of at least one of nickel, cobalt, and manganese. Non-limiting examples of the aqueous metal salt solution containing nickel include Ni(OH), NiO, NiOOH, NiCO·2Ni(OH)·4H2O, NiCO·2H2O, Ni(NO)·6H2O, NiSO, NiSO·6H2O, fatty acid nickel salt, nickel halide, or a combination thereof.

[0059] The cobalt-containing metal salt aqueous solution may be, but is not limited to, Co(OH)2, CoOOH, Co(OCOCH3)2·4H2O, Co(NO3)2·6H2O, CoSO4, Co(SO4)2·7H2O, or a combination thereof. The manganese-containing metal salt aqueous solution may be, but is not limited to, Mn2O3, MnO2, Mn3O4, MnCO3, Mn(NO3)2, MnSO4, manganese acetate, manganese dicarboxylate, manganese citrate, fatty acid manganese salt, manganese oxyhydroxide, manganese chloride, or a combination thereof.

[0060] In the step of preparing a reaction solution by adding an aqueous metal salt solution containing at least one of nickel, cobalt, and manganese, a complex ion former, and a pH adjuster into the reactor, the complex ion former 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 adding an aqueous solution of a metal salt containing at least one of nickel, cobalt, and manganese, a complex ion forming agent, and a pH adjuster to the reactor, the ratio of the flow rate of the aqueous ammonia solution to the flow rate of the aqueous metal solution may be 0.06 to 0.3, specifically, 0.1 to 0.2. When the flow rate of the metal aqueous solution satisfies the above range, it is possible to advantageously produce a positive electrode active material in a single particle form. If the flow rate of the metal aqueous solution is outside the above range, it is difficult to produce a positive electrode active material in a single particle form.

[0062] In one embodiment, the step of preparing a reaction solution by adding an aqueous metal salt solution containing at least one of nickel, cobalt, and manganese, a complex ion former, and a pH adjuster to the reactor may adjust the pH in the reactor to 10 to 12, specifically 10.5 to 11.5.

[0063] In one embodiment, the calcination step of calcining the positive electrode active material precursor may be performed at 750 to 1100° C. Specifically, the calcination step may be performed at 800 to 1000° C., more specifically, 780 to 950° C. By performing the calcination step within this temperature range, primary particles can be grown thickly without nucleation aggregation, which is advantageous in that a positive electrode active material having a single particle morphology can be produced.

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

[0065] According to another embodiment of the present invention, there is provided a lithium secondary battery including a positive electrode containing the above-described positive electrode active material; 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 includes a positive electrode active material, and the positive electrode active material 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 wt % to 99 wt % based on the total weight of the positive electrode active material layer.

[0067] The positive electrode active material layer may further include a binder and / or a conductive material, and the content of the binder and the conductive material may be 1 wt % to 5 wt % respectively based on the total weight of the positive electrode active material layer.

[0068] The binder serves to firmly adhere the positive electrode active material particles to each other and to the current collector. Representative examples of the binder include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, and nylon.

[0069] The conductive material is used to impart conductivity to the electrodes, and any material that is electron-conductive and does not undergo chemical changes in the battery that is constructed can be used. Examples of the conductive material include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, and carbon fiber; metal-based materials such as metal powders or metal fibers of copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; and 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 material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, a lithium metal alloy, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0073] The material capable of reversibly intercalating / deintercalating lithium ions may be any carbonaceous negative electrode active material commonly used in lithium ion secondary batteries, and representative examples thereof include crystalline carbon, amorphous carbon, or a combination of these.

[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 material capable of doping and dedoping lithium includes Si, SiO x(0 < x < 2), Si-Y alloy (where 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 (where 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), etc. may be mentioned.

[0076] Examples of the transition metal oxide include vanadium oxide, lithium vanadium oxide, etc. The negative electrode active material layer further contains a binder and may selectively further contain a conductive material.

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

[0078] The conductive material is used to impart conductivity to the electrode, and in the configured battery, any electron conductive material can be used without undergoing a chemical change.

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

[0080] The negative electrode and the positive electrode are manufactured by mixing an active material, a conductive material, and a binder in a solvent to produce an active material composition, and applying this composition to a current collector. Since such an electrode manufacturing method is well-known in the art, detailed description is omitted herein. Examples of the solvent include, but are not limited to, N-methylpyrrolidone.

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

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

[0083] The lithium salt is a substance that dissolves in an organic solvent, acts as a source of lithium ions in the battery, enables basic lithium secondary battery operation, and plays a role in facilitating the movement of lithium ions between the positive electrode and the negative electrode.

[0084] Depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. Such separators are made of polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more of these materials. Of course, mixed multilayer films such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator 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, into cylindrical, prismatic, coin, pouch, etc. types depending on the shape, and into bulk and thin film types depending on the size. The structure and manufacturing methods of these batteries are well known in this field, so detailed description will be omitted. [Example]

[0086] Preferred examples and comparative examples of the present invention will be described below, but the following examples are only preferred embodiments of the present invention and the present invention is not limited to the following embodiments.

[0087] Method for producing a positive electrode active material precursor for lithium secondary batteries 1A to 1C show SEM photographs of positive electrode active material precursors according to examples of the present invention and comparative examples. Figure 1A shows SEM photographs of the cathode active material precursor prepared in Example 1 (described later), Figure 1B shows SEM photographs of the cathode active material precursor prepared in Example 2 (described later), and Figure 1C shows SEM photographs of the cathode active material precursor prepared in Comparative Example 1 (described later). Referring to Figures 1A to 1C, it can be seen that the cathode active material precursors prepared in Examples 1 and 2 of the present invention tend to be thick and large.

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

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

[0090] Comparative Example 1 The same procedure as in Example 1 was carried out, except that water was introduced into a 100 L batch reactor in an amount of 15% of the total volume of the reactor, and no additional sodium sulfate was added. Evaluation example - precursor characteristics Table 1 below shows the XRD characteristics of the precursors and single crystals according to Examples 1 and 2 and Comparative Example 1. The XRD characteristics were measured using Rigaku's SMARTLAB equipment.

[0091] [Table 1]

[0092] FIG. 2 illustrates XRD peak intensity values according to examples of the present invention and comparative examples. 2, it can be seen that Examples 1 and 2 fall within the XRD peak intensity value range of the present invention, whereas Comparative Example 1 does not fall within the XRD peak intensity value range of the present invention.

[0093] Examples 3 and 4, and Comparative Example 2 - Positive Electrode Active Material The positive electrode active material precursors prepared in Examples 1 and 2 and Comparative Example 1 were heated in an oxygen atmosphere at a temperature increase rate of 2.5°C / min and then calcined at 780°C for 9 hours to prepare 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 with single crystal structure Table 2 below shows particle surface analysis and coin cell evaluation according to the content of the complex ion forming agent in Example 3, Example 4, and Comparative Example 2. For coin cell evaluation, a coin cell type (CR2032) half cell (coin cell) was assembled in a moisture-controlled dry room, and after cell assembly, it was aged at room temperature for 2 hours to impregnate the electrolyte and create an electrochemical equilibrium state. The coin cells were evaluated using a TOSCAT-3100 charger / discharger. First, formation was performed by applying a current density of 0.1C in the voltage range of 2.5V-4.25V and charging and discharging for one cycle, and then applying a current density of 0.3C in the same voltage range and charging and discharging. The initial discharge capacity and coulombic efficiency during the formation step, as well as the capacity retention rate during high temperature evaluation, are shown in the table below.

[0095] [Table 2]

[0096] 3A to 3C show SEM photographs of positive electrode active materials for lithium secondary batteries according to examples of the present invention and comparative examples. 3A to 3C show the positive electrode active materials of Example 3, Example 4, and Comparative Example 2, respectively, and it can be seen that Examples 3 and 4 of the present invention exhibit a more uniform and single-crystal morphology than Comparative Example 2. 4A and 4B are graphs showing the capacity characteristics and life characteristics of positive electrode active materials for lithium secondary batteries according to examples of the present invention and comparative examples. 4A and 4B, it can be seen that the positive electrode active materials of Examples 3 and 4 are superior in capacity characteristics and life characteristics to those of Comparative Example 2.

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

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

Claims

1. In the XRD peak value, 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 Ratio is 1.5 to 3.2, and I １００ / I １１1 A positive electrode active material precursor, wherein the ratio satisfies at least one of 2.5 to 5.

3. (In the XRD peak value, I ００１ is in the range of 18.5±1.0°, I １００ is in the range of 33.0±1.0°, I １０１ is in the range of 38.5±1.5°, I １０２ is in the range of 52.5±1.5°, 59±1.5°, I １１１ means a peak value that satisfies the range of 63±1.0°)

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

0.

3. 2. The positive electrode active material precursor according to claim 1, which has a structure in which at least one transition metal layer and one oxygen layer are laminated.

4. The positive electrode active material precursor according to claim 3 , wherein the transition metal layer and the oxygen layer form a stacked assembly through hydrogen bonding.

5. It is composed of at least one primary particle, 5. The positive electrode active material precursor according to claim 4, wherein the c-axis crystal constant of the primary particles is 300 nm to 700 nm.

6. At least one positive electrode active material precursor having hydrogen bonds in the <001> direction, 500 to 2000 ppm by weight of Li ２ CO ３ A positive electrode active material for a lithium secondary battery is a single particle comprising:

7. Contains LiOH, The LiOH and the Li ２ CO ３ The positive electrode active material for a lithium secondary battery according to claim 6, wherein R is a positive electrode active material for a lithium secondary battery, and R is a positive electrode active material for a lithium secondary battery. <Formula 1> 0.5≦[L-OH] / [L) ２ CO ３ ]≦1.9 (In formula 1, [LiOH] is the content of LiOH, [Li ２ CO ３ ] is Li ２ CO ３ (This means the content of

8. 7. The positive electrode active material for a lithium secondary battery according to claim 6, wherein the LiOH content is 1000 to 4000 ppm by weight.

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

10. Specific surface area is 1 to 30 m ２ The positive electrode active material for a lithium secondary battery according to claim 6, wherein the SiO2 content is 1 / g.

11. The positive electrode active material for a lithium secondary battery according to claim 6, wherein the positive electrode active material is 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 ]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 0.9<x<1.2, 0.8<y<1, 0<z<0.8, 0<w<0.05, 0≦v≦0.2)

12. administering an aqueous solution containing a sodium or potassium-based substance to create an initial reaction condition in the reactor; preparing a reaction solution by adding 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 prepare a positive electrode active material precursor; and a calcination step of calcining the positive electrode active material precursor, The aqueous solution containing the sodium or potassium-based substance contains 5 to 10 parts by weight of the sodium or potassium-based substance per 100 parts by weight of water.

13. The method for producing a positive electrode active material according to claim 12, wherein the sodium or potassium-based substance includes at least one of sodium sulfate, sodium chloride, potassium chloride, and potassium sulfate.

14. In the step of adding 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, 13. The method for producing a positive electrode active material according to claim 12, wherein the ratio of the flow rate of the ammonia water to the flow rate of the metal salt aqueous solution is 0.06 to 0.

3.

15. 15. The method for producing a positive electrode active material according to claim 14, wherein the flow rate of the metal salt aqueous solution is 2.5 to 3.5 L / hour.

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

17. The method for producing a positive electrode active material according to claim 12, wherein the calcination step is performed for 5 to 30 hours.

18. 13. The method for producing a cathode active material according to claim 12, wherein the step of adding an aqueous metal salt solution containing at least one of nickel, cobalt, and manganese, a complex ion forming agent, and a pH adjuster into the reactor adjusts the pH in the reactor to 10 to 12.

Images