Positive electrode active material, positive electrode, and lithium secondary battery containing the same

Abstract

To provide a single-crystal type positive electrode active material which can exhibit relatively high battery performance and can have a uniform particle size distribution by inducing uniform particle growth even without any harsh calcination condition or disintegration process and by reducing inter-particle agglomeration.SOLUTION: A positive electrode active material comprises a lithium composite oxide capable of intercalation / deintercalation of lithium, where the lithium composite oxide includes at least lithium and transition metal and has D10, D50, D90 and Dmax satisfying all of Formulas 1 to 3 in the following: D90 / D10≤3.62 [Formula 1]; Dmax-D90<2.0 μm [Formula 2]; and Dmax / Dmin<5.19 [Formula 3].SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a positive electrode active material and a lithium secondary battery containing the same, and more specifically, to a single-crystal type positive electrode active material having a uniform particle size distribution and high sharpness of the particle size distribution, a positive electrode, and a lithium secondary battery containing the same. [Background technology]

[0002] Batteries store electricity by using electrochemically reactive materials at the positive and negative electrodes. A typical example of such a battery is the lithium-ion secondary battery, which stores electrical energy through the difference in chemical potential that occurs when lithium ions are intercalated / deintercalated at the positive and negative electrodes.

[0003] The lithium secondary battery is manufactured by using materials capable of reversible intercalation / deintercalation of lithium ions as positive electrode and negative electrode active materials, and by filling the space between the positive electrode and the negative electrode with an organic electrolyte or a polymer electrolyte.

[0004] Lithium composite oxides are used as positive electrode active materials in lithium secondary batteries, and examples of composite oxides such as LiCoO2, LiMn2O4, LiNiO2, and LiMnO2 are being studied.

[0005] Among the positive electrode active materials, LiCoO2 is the most widely used due to its excellent lifespan characteristics and charge / discharge efficiency. However, it has the disadvantage of limited price competitiveness because the cobalt used as a raw material is expensive.

[0006] Lithium manganese oxides such as LiMnO2 and LiMn2O4 have advantages such as excellent thermal safety and low cost, but they have the drawbacks of low capacity and poor high-temperature characteristics. LiNiO2-based cathode active materials have the advantage of exhibiting high discharge capacity, but they are not only difficult to synthesize due to the active cation mixing of Li and Ni, but the synthesized cathode active materials also have the problem of very poor rate characteristics and lifetime characteristics.

[0007] As a result, in order to improve the low rate characteristics and lifetime characteristics of LiNiO2 while maintaining its high reversible capacity, ternary lithium composite oxides such as NCM (Ni-Co-Mn) and NCA (Ni-Co-Al), or quaternary lithium composite oxides such as NCMA (Ni-Co-Mn-Al), have been developed in which some of the nickel is replaced with cobalt, manganese, and / or aluminum. Since the reversible capacity decreases as the nickel content in such ternary or quaternary lithium composite oxides decreases, research has recently been actively conducted to increase the nickel content in lithium composite oxides.

[0008] Furthermore, while typical ternary or quaternary lithium composite oxides have a secondary particle structure in which tens to hundreds or more primary particles are aggregated, it has been reported that reducing the number of primary particles constituting the secondary particles can improve the stability (such as lifetime characteristics) of the positive electrode active material. Lithium composite oxides with a reduced number of primary particles in this way are also called single-crystal lithium composite oxides or single-particle lithium composite oxides.

[0009] For example, Non-Patent Document 1 describes a lithium composite oxide (LiNi) with a single-crystal structure having a particle size of 2-3 μm. 0.5 Mn 0.3 Co 0.2 The report discloses that O2) exhibits some improvement in stability compared to a polycrystalline lithium composite oxide having the same composition.

[0010] However, as disclosed in Non-Patent Document 1, if the firing temperature is excessively increased or the amount of lithium relative to the transition metal in the lithium composite oxide is excessively increased in order to single-crystallize the lithium composite oxide constituting the positive electrode active material, the cation mixing phenomenon within the crystal structure may increase.

[0011] In particular, when cation mixing increases in single-crystal lithium composite oxides, the formation of phases other than the layered crystal structure (e.g., rock-salt phase) can alter the surface resistance characteristics of the lithium composite oxide or cause premature degradation.

[0012] Furthermore, when single crystallization of lithium composite oxides is induced simply through harsh firing conditions (for example, over-firing at high firing temperatures), uniform particle growth is difficult to induce, resulting in aggregation between particles and making it impossible to obtain a cathode active material with a uniform particle size distribution.

[0013] Furthermore, after synthesizing secondary particles formed by the aggregation of multiple primary particles, a positive electrode active material containing a single-crystal lithium composite oxide can be produced through a crushing process. However, the crushing process not only drastically increases the processing cost of the positive electrode active material, but also carries the risk of damaging the surface of the lithium composite oxide during the crushing process. Such defects on the surface of the lithium composite oxide can alter its surface resistance properties. In addition, side reactions with the electrolyte can occur through these surface defects, generating gas, and cracks may develop along these surface defects.

[0014] Therefore, there is a need to develop single-crystal type cathode active materials that can reduce interparticle aggregation by inducing uniform particle growth, thereby achieving a uniform particle size distribution without the need for a separate crushing process after calcination of the precursor. [Prior art documents] [Patent Documents]

[0015] [Non-Patent Document 1] Journal of The Electrochemical Society, Volume 164, Number 7, A1534-A1544 (Published May 23, 2017) [Overview of the Initiative] [Problems that the invention aims to solve]

[0016] In the lithium-ion battery market, the growth of lithium-ion batteries for electric vehicles is driving the market, and this is leading to a sustained increase in the demand for positive electrode active materials used in lithium-ion batteries.

[0017] For example, while lithium-ion batteries using lithium iron phosphate (LFP) have traditionally been the primary choice due to safety considerations, there has recently been a growing trend towards the use of nickel-based lithium composite oxides, which offer a higher energy capacity per unit weight compared to LFP. Of course, relatively cheaper LFP is still sometimes used to reduce costs.

[0018] Furthermore, nickel-based lithium composite oxides, which are mainly used as positive electrode active materials in high-capacity lithium secondary batteries, generally have ternary compositions such as NCM (Ni-Co-Mn) and NCA (Ni-Co-Al), or quaternary compositions such as NCMA (Ni-Co-Mn-Al).

[0019] As mentioned above, in order to achieve high capacity for such ternary or quaternary nickel-based lithium composite oxides, reducing the number of primary particles that make up the secondary particles can improve the stability (lifetime characteristics, etc.) of the positive electrode active material.

[0020] However, with commercially available processes to date, harsh firing conditions can cause changes in the crystal structure of lithium composite oxides. Furthermore, uniform particle growth is difficult to induce under harsh firing conditions, which ultimately necessitates a crushing process, leading to a sharp increase in the processing cost of the cathode active material.

[0021] Therefore, the present invention aims to provide a single-crystal type positive electrode active material that can have a uniform particle size distribution and exhibit relatively high battery performance by reducing the aggregation phenomenon between particles by inducing uniform particle growth without harsh firing conditions and crushing processes.

[0022] Furthermore, the present invention aims to provide a positive electrode active material with high particle size distribution sharpness due to uniform particle growth and a reduction in interparticle aggregation phenomena.

[0023] Another object of the present invention is to provide a lithium secondary battery using the positive electrode active material defined in this application.

[0024] The objects of the present invention are not limited to those mentioned above, and other objects and advantages of the present invention not mentioned can be understood from the following description and will be further made clear from the embodiments of the present invention. It will also be readily apparent that the objects and advantages of the present invention can be realized by the means and combinations set forth in the claims. [Means for solving the problem]

[0025] According to one aspect of the present invention, a positive electrode active material is provided which includes a lithium composite oxide capable of lithium intercalation / deintercalation, wherein the lithium composite oxide satisfies all of the following formulas 1 to 3.

[0026] [Formula 1] D 90 / D 10 ≤3.62 [Formula 2] D max -D 90 <2.0 μm [Formula 3] D max / D min <5.19 (In the above Formula 1 to the above Formula 3, the D 10 is the particle size of the lithium composite oxide at which the volume accumulation amount is 10% in the volume accumulation particle size distribution graph obtained by laser diffraction particle size distribution measurement, and the D 50 is the particle size of the lithium composite oxide at which the volume accumulation amount is 50% in the volume accumulation particle size distribution graph, and the D 90 is the particle size of the lithium composite oxide at which the volume accumulation amount is 90% in the volume accumulation particle size distribution graph, and D min is the minimum particle size of the lithium composite oxide in the volume accumulation particle size distribution graph, and the D max is the maximum particle size of the lithium composite oxide in the volume accumulation particle size distribution graph.)

[0027] The lithium composite oxide constituting the positive electrode active material according to the above example may have a uniform particle size distribution and be a single crystal type with a high sharpness of the particle size distribution.

[0028] In the present invention, the D 50 of the lithium composite oxide is preferably 2 μm to 8 μm, and the D max of the lithium composite oxide is preferably 15 μm or less.

[0029] In one example, the lithium composite oxide can satisfy at least one or both selected from the following Formula 4 and Formula 5.

[0030] [Formula 4] D 50 / D 10 <1.19 [Formula 5] D max -D50 <7.8μm In the present invention, the lithium composite oxide comprises at least lithium and a transition metal. In the present invention, the transition metal may comprise at least one, at least two, at least three, or all of the following selected from the group consisting of nickel, cobalt, manganese, and aluminum.

[0031] The positive electrode active material of the present invention may be represented by the following chemical formula 1, which is the lithium composite oxide. [Chemical formula 1] Li a Ni 1-(b+c+d) Co b M1 c M2 d O2 (Here, M1 is at least one selected from Mn and Al, and M2 is at least one selected from the group consisting of Na, K, Mg, Ca, Ba, Mn, B, Ce, Hf, Ta, Cr, F, Al, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Sr, Ge, Nd, Gd, and Cu, and M1 and M2 are distinct from each other, with 0.5 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.20, 0 ≤ c ≤ 0.30, and 0 ≤ d ≤ 0.10.)

[0032] In the present invention, the lithium composite oxide may exist in at least one form selected from single particles and secondary particles formed by the aggregation of multiple primary particles. Furthermore, the secondary particles may be in a state in which 1 to 10 primary particles are aggregated.

[0033] Furthermore, according to another aspect of the present invention, a positive electrode containing the positive electrode active material described above is provided. Furthermore, according to yet another aspect of the present invention, a lithium secondary battery is provided in which the positive electrode described above is used. [Effects of the Invention]

[0034] According to the present invention, by using a combination of a molten salt-based flux and a metal oxide-based dopant during the precursor calcination stage, uniform particle growth can be induced without harsh calcination conditions or a crushing process, thereby obtaining a positive electrode active material with reduced interparticle aggregation.

[0035] The positive electrode active material obtained through this process has a uniform particle size distribution, and in particular, it has the advantage of high particle size distribution sharpness. When using a positive electrode active material with such a sharp particle size distribution, the capacity characteristics and life characteristics of lithium secondary batteries can be improved.

[0036] In addition to the effects described above, the specific effects of the present invention will be described together with the following descriptions of embodiments for carrying out the invention. [Brief explanation of the drawing]

[0037] [Figure 1] This is an SEM image of the positive electrode active material according to Example 1. [Figure 2] This is an SEM image of the positive electrode active material according to Example 2. [Figure 3] This is an SEM image of the cathode active material according to Example 3. [Figure 4] This is an SEM image of the positive electrode active material according to Comparative Example 1. [Figure 5] This is an SEM image of the positive electrode active material according to Comparative Example 2. [Figure 6] This is an SEM image of the positive electrode active material according to Comparative Example 3. [Modes for carrying out the invention]

[0038] For the sake of easier understanding of the present invention, certain terms are defined herein for convenience. Unless otherwise defined herein, scientific and technical terms used herein have meanings that are generally understood by those of ordinary skill in the art. Furthermore, unless otherwise specified in the context, singular terms should be understood to include their plural forms, and plural terms should be understood to include their singular forms.

[0039] positive electrode active material A positive electrode active material according to one aspect of the present invention allows for reversible intercalation / deintercalation of lithium ions and includes a lithium composite oxide.

[0040] The positive electrode active material of the present invention preferably has a layered crystalline structure belonging to the R-3m space group, and the lithium composite oxide is a composite metal oxide capable of lithium ion intercalation / deintercalation. The lithium composite oxide having a layered crystalline structure preferably shows a specific peak in the region where 2θ is 18° to 20° in the rotation pattern obtained from XRD analysis.

[0041] The positive electrode active material of the present invention comprises a lithium composite oxide containing at least lithium and a transition metal. The transition metal may include at least one, at least two, at least three, or all of nickel, cobalt, manganese, and aluminum.

[0042] Preferably, the lithium composite oxide may be a lithium nickel-based composite oxide containing nickel. Alternatively, the lithium composite oxide may be a lithium nickel-based composite oxide containing nickel and cobalt.

[0043] In one embodiment, in order to improve the low rate characteristics and lifetime characteristics while maintaining the high reversible capacity of LiNiO2, the lithium nickel-based composite oxide may be a ternary type lithium composite oxide such as NCM (Ni-Co-Mn) and NCA (Ni-Co-Al), in which part of the nickel is replaced with cobalt, manganese, and / or aluminum, or a quaternary type lithium composite oxide such as NCMA (Ni-Co-Mn-Al). The ternary or quaternary type lithium composite oxide may further contain dopants other than nickel, cobalt, manganese, and aluminum. In another embodiment, the lithium nickel-based composite oxide may be a cobalt-free type lithium composite oxide that does not contain cobalt in the bulk particles. The cobalt-free type lithium composite oxide may further contain dopants other than nickel, cobalt, manganese, and aluminum.

[0044] In the present invention, the lithium composite oxide is preferably represented by the following chemical formula 1. [Chemical formula 1] Li a Ni 1-(b+c+d) Co b M1 c M2 d O2 Here, M1 is at least one selected from Mn and Al, and M2 is at least one selected from the group consisting of Na, K, Mg, Ca, Ba, Mn, B, Ce, Hf, Ta, Cr, F, Al, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Sr, Ge, Nd, Gd, and Cu, and M1 and M2 are distinct from each other, with 0.5 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.20, 0 ≤ c ≤ 0.30, and 0 ≤ d ≤ 0.10.

[0045] In the lithium composite oxide, the ratio of lithium to the total elements other than lithium (Ni+Co+M1+M2), represented by 'a', is preferably 0.5 or more and 1.5 or less, more preferably 0.75 or more and 1.25 or less, even more preferably 0.90 or more and 1.1 or less, and particularly preferably 0.95 or more and 1.05 or less.

[0046] In one embodiment, the lithium composite oxide may be a lithium-nickel composite oxide in which the mole fraction of nickel relative to the total elements other than lithium is 70% or more. In this case, the positive electrode active material of the present invention preferably has b+c+d of 0.30 or less in the chemical formula 1. That is, the lithium composite oxide according to the above embodiment is a lithium-nickel composite oxide having a layered crystalline structure belonging to the R-3m space group, in which the mole fraction of nickel relative to the total elements other than lithium is 70% or more.

[0047] Furthermore, according to other embodiments, the mole fraction of nickel relative to the total elements other than lithium in the lithium composite oxide is more preferably 75% or more (in this case, b+c+d is 0.25 or less), even more preferably 80% or more (in this case, b+c+d is 0.20 or less), even more preferably 85% or more (in this case, b+c+d is 0.15 or less), and particularly preferably 90% or more (in this case, b+c+d is 0.10 or less).

[0048] When the lithium composite oxide contains cobalt, the mole fraction of cobalt relative to the total elements other than lithium in the secondary particles is preferably 20% or less, more preferably 15% or less, even more preferably 10% or less, and particularly preferably 5% or less. When the lithium composite oxide contains cobalt, b in chemical formula 1 is greater than 0, and when the lithium composite oxide is a cobalt-free type lithium composite oxide that does not contain cobalt, b in chemical formula 1 is 0.

[0049] When the lithium composite oxide contains manganese and / or aluminum, the mole fraction of manganese and / or aluminum relative to the total elements other than lithium in the lithium composite oxide is preferably 30% or less, more preferably 20% or less, even more preferably 15% or less, even more preferably 10% or less, and particularly preferably 5% or less. When the lithium composite oxide contains manganese and / or aluminum, c in the chemical formula 1 is greater than 0.

[0050] In the above chemical formula 1, M2 represents a dopant present in the secondary particle. The dopant may exist in a doped state within the crystal lattice of the primary particle. In addition, in the above chemical formula 1, M2 may selectively contain elements derived from a molten salt-based flux and / or a metal oxide-based dopant used in the calcination step of the lithium composite oxide precursor.

[0051] If the lithium composite oxide contains a dopant, d in chemical formula 1 is greater than 0, and if the lithium composite oxide does not contain a dopant, d in chemical formula 1 is 0.

[0052] Furthermore, the dopant content relative to all elements other than lithium in the secondary particles is smaller than the content of nickel, cobalt, and M1. For example, the mole fraction of the dopant relative to all elements other than lithium in the secondary particles is preferably 10% or less, more preferably 5% or less, more preferably 4% or less, more preferably 3% or less, more preferably 2% or less, more preferably 1% or less, more preferably 0.5% or less, more preferably 0.4% or less, more preferably 0.3% or less, more preferably 0.2% or less, and particularly preferably 0.1% or less.

[0053] If the secondary particles selectively contain a dopant, the dopant may contain at least one selected from the group consisting of Na, K, Mg, Ca, Ba, Mn, B, Ce, Hf, Ta, Cr, F, Al, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Sr, Ge, Nd, Gd, and Cu.

[0054] The upper and lower limits of the nickel, cobalt, M1, and M2 content defined in the above chemical formula 1 can be appropriately selected within the range that satisfies the definition described above.

[0055] The positive electrode active material of the present invention may exist in at least one form selected from single particles and secondary particles formed by the aggregation of multiple primary particles, wherein the lithium composite oxide may exist as an aggregate of single particles and secondary particles. However, if the aggregation phenomenon between particles is reduced by inducing uniform particle growth during the manufacturing process of the positive electrode active material, the aggregate will have an even more uniform particle size distribution as the proportion of single particles to secondary particles increases, and in particular, a positive electrode active material with high particle size distribution sharpness can be obtained. When a positive electrode active material with such a sharp particle size distribution is used, the capacity characteristics and life characteristics of the lithium secondary battery can be improved. Here, a narrow peak width in the particle size distribution observed in the volume cumulative particle size distribution graph can indicate high particle size distribution sharpness.

[0056] When the aforementioned single particles aggregate to exist as secondary particles, each of the single particles constituting the secondary particles can be referred to as a primary particle. In this case, the composition of the single particles, primary particles, and secondary particles can all be represented by the aforementioned chemical formula 1. Furthermore, the single particles, primary particles, and secondary particles all exist as particles capable of lithium intercalation / deintercalation.

[0057] The single particles and primary particles may have a rod shape, an elliptical shape, and / or an amorphous shape. Furthermore, unless specifically intended in the manufacturing process, primary particles of various shapes may exist within the same cathode active material. The primary particles refer to particle units that, when observed at a magnification of 5,000x to 20,000x using a scanning electron microscope, do not exhibit visible grain boundaries.

[0058] The average particle size of the single particle and the primary particle is preferably 0.5 μm to 10 μm, more preferably 0.5 μm to 8 μm, more preferably 0.5 μm to 6 μm, more preferably 0.5 μm to 5 μm, more preferably 1 μm to 10 μm, more preferably 1 μm to 8 μm, more preferably 1 μm to 6 μm, more preferably 1 μm to 5 μm, more preferably 2 μm to 10 μm, more preferably 2 μm to 8 μm, more preferably 2 μm to 6 μm, or particularly preferably 2 μm to 5 μm. In this case, the average particle size of the single particle and the primary particle can be the average value of the length in the long axis direction and the length in the short axis direction of the single particle and the primary particle ([long axis length + short axis length] / 2).

[0059] Furthermore, the lithium composite oxide is a single-crystal type lithium composite oxide. Here, "single-crystal type" means that the smallest particle unit constituting the lithium composite oxide, which is a single particle or primary particle, exists as a single crystallite.

[0060] If secondary particles are present in the aggregate, the average particle size of the secondary particles is preferably 0.5 μm to 15 μm, more preferably 1.0 μm to 12 μm, even more preferably 1.0 μm to 10 μm, even more preferably 2.0 μm to 12 μm, and particularly preferably 2.0 μm to 10 μm. Here, the average particle size of the secondary particles can be calculated as the average value of the particle sizes of the secondary particles confirmed from the SEM image. The average particle size of the secondary particles can vary depending on the number of primary particles that constitute the secondary particles.

[0061] The particle size distribution of the lithium composite oxide in the positive electrode active material can be measured using the laser diffraction method. For example, after dispersing secondary particles in a dispersion medium, the particles can be introduced into a commercially available laser diffraction particle size analyzer (e.g., Microtrac MT 3000), and after irradiating with ultrasound at approximately 28 kHz at an output of 60 W, a volume-cumulative particle size distribution graph can be obtained. From there, the particle sizes corresponding to 10%, 50%, and 90% of the volume-cumulative amount, the minimum particle size in the volume-cumulative particle size distribution graph, and the maximum particle size in the volume-cumulative particle size distribution graph can be calculated.

[0062] Here, the particle size of the lithium composite oxide (single particle or secondary particle) corresponding to 50% of the cumulative volume is defined as the average particle size (D 50 ) will be defined as D 10 In the volume cumulative particle size distribution graph obtained by laser diffraction particle size distribution measurement, the particle size of the lithium composite oxide (single particle or secondary particle) where the volume cumulative amount is 10% is D 50 In the volume cumulative particle size distribution graph, the particle size of the lithium composite oxide (single particle or secondary particle) where the volume cumulative amount is 50% is D 90 D is the particle size of the lithium composite oxide (single particle or secondary particle) at which the cumulative volume amount in the volume cumulative particle size distribution graph becomes 90%. minIn the volume cumulative particle size distribution graph, the lithium composite oxide (single particle or secondary particle) has a minimum particle size, and D max This is defined as the maximum particle size of the lithium composite oxide (single particle or secondary particle) in the volume cumulative particle size distribution graph.

[0063] In one embodiment, the D of lithium composite oxide 50 The particle size is preferably 2 μm to 8 μm, more preferably 3 μm to 7 μm, and even more preferably 4 μm to 6 μm, and the lithium composite oxide D max The particle size is preferably 15 μm or less, more preferably 14 μm or less, and even more preferably 13 μm or less.

[0064] Furthermore, the D of the lithium composite oxide min The particle size is preferably 0.5 μm to 4 μm, more preferably 1 μm to 4 μm, and even more preferably 2 μm to 3.2 μm. 10 It is preferably 1 μm to 4 μm, more preferably 2 μm to 4 μm, and even more preferably 2.5 μm to 3.5 μm, D 90 The particle size is preferably 6 μm to 15 μm, more preferably 8 μm to 12 μm, and even more preferably 9 μm to 12 μm.

[0065] D as defined above min , D 10 , D 50 , D 90 and D max The upper and lower limits can be appropriately selected within the range that satisfies the following equations 1 to 3, 1 to 4, 1 to 3 and 5, or 1 to 5. Equations 1 through 5 below are calculated based on single particles and aggregates containing secondary particles.

[0066] In the present invention, the lithium composite oxide is D 10 and D 90 The following equation 1 is satisfied. [Formula 1] D 90 / D 10 ≤3.62 D 90 / D 10 By having a value of 3.62 or less, the particle size difference between lithium composite oxides having relatively small particle sizes and lithium composite oxides having relatively large particle sizes among the positive electrode active materials can be reduced. D 90 / D 10 It may be within the ranges of 3.3-3.8, 3.3-3.7, 3.4-3.65, 3.42-3.62, or 3.45-3.62.

[0067] In the positive electrode active material of the present invention, the lithium composite oxide is D 90 and D max The following equation 2 is satisfied. [Formula 2] D max -D 90 <2.0μm D max -D 90 This means the difference between the largest particle size in the aggregate and the particle size that represents 90% of the volume accumulation, and D max -D 90 A particle size of less than 2.0 μm indicates high sharpness in the particle size distribution. D max -D 90 The particle size is less than 2.0 μm, preferably 1.9 μm or less, and more preferably 1.8 μm or less. In addition, in order to ensure appropriate sharpness of the particle size distribution, D max -D 90 The particle size is preferably 0.75 μm, and more preferably greater than 1 μm.

[0068] In the positive electrode active material of the present invention, the lithium composite oxide is D min and D max The following equation 3 is satisfied. [Formula 3] D max / D min <5.19 D max / D min D is the ratio of the largest particle size to the smallest particle size in the aggregate. max / D min As the size increases, the deviation between the smallest and largest particle sizes in the aggregate increases, which reduces the uniformity of the particle size distribution and lowers the sharpness of the particle size distribution.

[0069] D max / D min It is less than 5.19, preferably 5.1 or less, more preferably 5.0 or less, even more preferably 4.95 or less, and particularly preferably 4.92 or less. In addition, in order to ensure appropriate sharpness of the particle size distribution, D max / D min It is preferable that this value is greater than 2 or 3.

[0070] According to the present invention, by using a combination of a molten salt-based flux and a metal oxide-based dopant in the calcination stage of the lithium composite oxide precursor, uniform particle growth can be induced without harsh calcination conditions or a crushing process, thereby obtaining a positive electrode active material with reduced interparticle aggregation.

[0071] The positive electrode active material obtained through this process has a uniform particle size distribution, and in particular, it has the advantage of high particle size distribution sharpness. When using a positive electrode active material with such a sharp particle size distribution, the capacity characteristics and life characteristics of lithium secondary batteries can be improved.

[0072] Thus, a positive electrode active material having a uniform particle size distribution and high sharpness of the particle size distribution preferably satisfies all of Equations 1 to 3.

[0073] Furthermore, in order to further improve the uniformity and sharpness of the particle size distribution of the lithium composite oxide among the positive electrode active material in the present invention, the lithium composite oxide is D10 and D 50 and D max and can satisfy at least one or both selected from the following Formula 4 and Formula 5.

[0074] [Formula 4] D 50 / D 10 <1.19

[0075] D 50 / D 10 is the ratio of the particle size (average particle diameter) that is 50% of the volume accumulation amount in the aggregate to the particle size that is 10% of the volume accumulation amount, and D 50 / D 10 As it becomes larger, the deviation between D close to the average particle diameter and the minimum particle size in the volume accumulation particle size distribution graph becomes larger, so the uniformity of the particle size distribution decreases and the sharpness of the particle size distribution becomes lower. 10

[0076] D 50 / D 10 is preferably less than 1.19, more preferably 1.18 or less, still more preferably 1.17 or less, or particularly preferably 1.16 or less. Also, in order to ensure appropriate sharpness of the particle size distribution, D 50 / D 10 is preferably greater than 1.

[0077] [Formula 5] D max -D 50 <7.8 μm

[0078] D max -D 50 means the difference between the maximum particle size in the aggregate and the particle size (average particle diameter) that is 50% of the volume accumulation amount, and D max -D 90 Similar to the above D max -D 50 By having a value less than 7.8 μm, the sharpness of the particle size distribution can be improved. ​

[0079] D max -D 50 The particle size is preferably less than 7.8 μm, more preferably 7.6 μm or less, even more preferably 7.4 μm or less, and particularly preferably 7.2 μm or less. In addition, in order to ensure appropriate sharpness of the particle size distribution, D max -D 50 It is preferable that the particle size be greater than 3 μm, and more preferably greater than 4 μm.

[0080] As described above, the lithium composite oxide may exist in at least one form selected from single particles and secondary particles formed by the aggregation of multiple primary particles, and thereby the positive electrode active material may exist as an aggregate of single particles and secondary particles. That is, the positive electrode active material can be defined as an aggregate of multiple lithium composite oxides having the same and / or different grain boundary densities.

[0081] The grain boundary density can be calculated by substituting the number of primary particles (P) placed on a hypothetical straight line (L) that crosses the center of the lithium composite oxide in the longitudinal direction in a cross-sectional SEM image of the lithium composite oxide into the following equation 6.

[0082] [Formula 6] Grain boundary density = (Number of interface surfaces (B) between primary particles placed on the imaginary straight line (L) / Number of primary particles (P) placed on the imaginary straight line (L))

[0083] For example, if the lithium composite oxide is a single particle, the number of interfaces (grain boundaries) between primary particles placed on a hypothetical straight line is 0, so the grain boundary density has a value of 0. On the other hand, if the number of primary particles (P) placed on the hypothetical straight line (L) is 2, and the number of interfaces (B) between primary particles placed on the hypothetical straight line (L) is 1, the grain boundary density has a value of 0.5.

[0084] The closer the average grain boundary density of the lithium composite oxide present in the aggregate is to 0, the higher the proportion of lithium composite oxide present as single particles relative to secondary particles in the aggregate.

[0085] Furthermore, in the present invention, the lithium composite oxide present as secondary particles in the aggregate is preferably in a state in which 2 to 100 primary particles are aggregated, more preferably in a state in which 2 to 50 primary particles are aggregated, even more preferably in a state in which 2 to 30 primary particles are aggregated, even more preferably in a state in which 2 to 20 primary particles are aggregated, and particularly preferably in a state in which 2 to 10 primary particles are aggregated.

[0086] Lithium-ion battery The lithium secondary battery of the present invention uses the positive electrode of the present invention. According to another aspect of the present invention, a positive electrode can be provided comprising a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector. Here, the positive electrode active material layer may include positive electrode active materials according to various embodiments of the present invention. Therefore, since the positive electrode active material is the same as described above, a detailed explanation will be omitted for convenience, and only the remaining undescribed components will be explained below.

[0087] The positive electrode current collector is not particularly limited as long as it does not induce chemical changes in the battery and is conductive. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc. may be used. The positive electrode current collector may also have a thickness of 3 to 500 μm, and fine irregularities can be formed on the surface of the current collector to increase the adhesion strength of the positive electrode active material. For example, it may be used in various forms such as film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0088] The positive electrode active material layer may be manufactured by applying a positive electrode slurry composition, which includes a conductive material and, if necessary, a binder, together with the positive electrode active material, to the positive electrode current collector.

[0089] In this case, the positive electrode active material may be present in an amount of 80 wt% to 99 wt%, more specifically, 85 wt% to 98.5 wt%, relative to the total weight of the positive electrode active material layer. When present within this content range, excellent capacity characteristics can be observed, but the material is not necessarily limited to this range.

[0090] The conductive material is used to impart conductivity to the electrodes and can be used without particular limitations as long as it has electronic conductivity without causing chemical changes in the battery it is configured in. Specific examples include graphite such as natural graphite or artificial graphite, carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber, metal powders or metal fibers such as copper, nickel, aluminum, and silver, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, or conductive polymers such as polyphenylene derivatives. One of these may be used alone or a mixture of two or more. The conductive material may be included in an amount of 0.1 wt% to 15 wt% relative to the total weight of the positive electrode active material layer.

[0091] The binder plays a role in improving the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, of which one or more may be used. The binder may be included in an amount of 0.1 to 15 wt% relative to the total weight of the positive electrode active material layer.

[0092] The positive electrode of the present invention comprises the positive electrode active material of the present invention. The positive electrode may be manufactured by a conventional method for manufacturing a positive electrode, except that the positive electrode active material is used. Specifically, the positive electrode may be manufactured by coating a positive electrode slurry composition, prepared by dissolving or dispersing the positive electrode active material and selectively a binder and a conductive material in a solvent, onto a positive electrode current collector, followed by drying and rolling.

[0093] The solvent may be any solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and one or more of these may be used individually or in mixtures of two or more. The amount of solvent used should be such that it dissolves or disperses the cathode active material, conductive material, and binder, and then provides a viscosity that allows for excellent thickness uniformity during coating for cathode manufacturing, taking into consideration the coating thickness and production yield of the slurry.

[0094] In other embodiments, the positive electrode may be manufactured by casting the positive electrode slurry composition onto a separate support, peeling it off the support, and then laminating the resulting film onto the positive electrode current collector.

[0095] Furthermore, according to yet another aspect of the present invention, an electrochemical element including the aforementioned positive electrode may be provided. Specifically, the electrochemical element may be a battery, a capacitor, or the like, and more specifically, a lithium secondary battery.

[0096] The lithium secondary battery may specifically include a positive electrode, a negative electrode positioned opposite the positive electrode, and a separator and electrolyte interposed between the positive and negative electrodes. Here, since the positive electrode is as described above, for convenience, a detailed explanation will be omitted, and only the remaining components not mentioned above will be described in detail below.

[0097] The lithium secondary battery may further selectively include a battery container for housing the electrode assembly comprising the positive electrode, the negative electrode, and the separator, and a sealing member for sealing the battery container. The negative electrode may include a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

[0098] The negative electrode current collector is not particularly limited as long as it has high conductivity without inducing chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. The negative electrode current collector may also typically have a thickness of 3 μm to 500 μm, and, similar to the positive electrode current collector, fine irregularities can be formed on the surface of the current collector to strengthen the bonding force of the negative electrode active material. For example, it may be used in various forms such as film, sheet, foil, net, porous material, foam, and nonwoven fabric.

[0099] The negative electrode active material layer may be manufactured by applying a negative electrode slurry composition, which includes the negative electrode active material together with a conductive material and, if necessary, a selective binder, to the negative electrode current collector.

[0100] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and SiO2. β Examples include lithium-doped and dedoped metal oxides such as (0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide, or composites containing the metallic compound and carbonaceous material, such as Si-C composites or Sn-C composites. One or more of these mixtures may be used. A metallic lithium thin film may also be used as the negative electrode active material. Furthermore, low-crystalline carbon and high-crystalline carbon may all be used as the carbon material. Typical examples of low-crystalline carbon include soft carbon and hard carbon, while typical examples of high-crystalline carbon include amorphous, plate-like, flaky, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes. The aforementioned negative electrode active material may be present in an amount of 80 wt% to 99 wt% based on the total weight of the negative electrode active material layer.

[0101] The binder may be added in an amount of 0.1 wt% to 10 wt% based on the total weight of the negative electrode active material layer, as a component that assists in bonding between the conductive material, active material, and current collector. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0102] The conductive material may be added as a component to further improve the conductivity of the negative electrode active material, in an amount of 10 wt% or less, preferably 5 wt% or less, based on the total weight of the negative electrode active material layer. Such a conductive material is not particularly limited as long as it has conductivity without inducing a chemical change in the battery, and for example, graphite such as natural graphite or artificial graphite, carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black, conductive fibers such as carbon fibers and metal fibers, metal powders such as carbon fluoride, aluminum, and nickel powder, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, and conductive materials such as polyphenylene derivatives may be used.

[0103] In one embodiment, the negative electrode active material layer may be manufactured by coating a negative electrode slurry composition, which is prepared by dissolving or dispersing a negative electrode active material and a binder and conductive material selectively in a solvent, onto a negative electrode current collector and then drying it, or by casting the negative electrode slurry composition onto a separate support, peeling it off the support, and then laminating the resulting film onto the negative electrode current collector.

[0104] In other embodiments, the negative electrode active material layer may be manufactured by coating a negative electrode slurry composition, prepared by dissolving or dispersing a negative electrode active material and a binder and conductive material selectively in a solvent, onto a negative electrode current collector and drying it, or by casting the negative electrode slurry composition onto a separate support, peeling it off the support, and laminating the resulting film onto the negative electrode current collector.

[0105] On the other hand, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Generally, any separator commonly used in lithium secondary batteries can be used without particular limitations, and it is especially preferable that the separator has low resistance to ion movement of the electrolyte and excellent electrolyte moisture absorption capacity. Specifically, porous polymer films, such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or laminated structures of two or more layers thereof may be used. Alternatively, ordinary porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, may be used. Furthermore, to ensure heat resistance or mechanical strength, coated separators containing ceramic components or polymeric substances may be used, and may be selectively used as single-layer or multi-layer structures.

[0106] Furthermore, the electrolytes used in this application include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries. Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0107] The organic solvent can be any solvent that serves as a medium through which ions involved in the electrochemical reaction of the battery can move, without any particular limitations. Specifically, the organic solvent may be an ester solvent such as methyl acetate, ethyl acetate, γ-butyrolactone, or ε-caprolactone; an ether solvent such as dibutyl ether or tetrahydrofuran; a ketone solvent such as cyclohexanone; an aromatic hydrocarbon solvent such as benzene or fluorobenzene; dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), or propylene carbonate (propylene Carbonate solvents such as carbonate (PC), alcohol solvents such as ethyl alcohol and isopropyl alcohol, nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, and may include a double-bonded aromatic ring or ether bond), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, or sulfolanes may be used. Among these, carbonate solvents are preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant that can improve the charge and discharge performance of the battery, and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferred. In this case, the electrolyte performance can be improved by mixing the cyclic carbonate and the linear carbonate in a volume ratio of about 1:1 to about 1:9.

[0108] The lithium salt may be any compound capable of providing lithium ions for use in a lithium secondary battery, without any particular limitations. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3), LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2, etc. The concentration of the lithium salt is preferably within the range of 0.1 to 2.0 M. When the concentration of the lithium salt falls within this range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and lithium ions can move effectively.

[0109] In the present invention, when the electrolyte used is a solid electrolyte, a solid inorganic electrolyte such as a sulfide-based solid electrolyte, oxide-based solid electrolyte, nitride-based solid electrolyte, or halogen-based solid electrolyte may be used, and preferably a sulfide-based solid electrolyte may be used.

[0110] As the material for the sulfide-based solid electrolyte, a solid electrolyte containing Li, element X (where X is at least one selected from P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In) and S may be used. Examples of the sulfide-based solid electrolyte materials include Li2S-P2S5, Li2S-P2S-LiX (where X is a halogen element such as I or Cl), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-ZmSn (where m and n are integers and Z is Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, and Li2S-SiS2-Li p MO q(Here, p and q are integers, and M is P, Si, Ge, B, Al, Ga, or In.)

[0111] The solid electrolyte, preferably a sulfide-based solid electrolyte, may be amorphous or crystalline, or a mixture of amorphous and crystalline materials.

[0112] As a material for oxide-based solid electrolytes, Li7La3Zr2O 12 Li 7-x La3Zr 1-x Nb x O 12 Li 7-3x La3Zr2Al x O 12 Li 3x La 2 / 3-x TiO3, Li 1+x Al x Ti 2-x (PO4)3, Li 1+x Al x Ge 2-x (PO4)3, Li3PO4, Li 3+x PO 4-x N x (LiPON), Li 2+2x Zn 1-x Examples include GeO4 (LISICON).

[0113] The aforementioned solid electrolyte may be arranged as a separate layer (solid electrolyte layer) between the positive electrode and the negative electrode. Furthermore, the solid electrolyte may be partially included in the positive electrode active material layer of the positive electrode independently of the solid electrolyte layer, or partially included in the negative electrode active material layer of the negative electrode independently of the solid electrolyte layer.

[0114] In addition to the electrolyte components, the electrolyte may further contain one or more additives for the purpose of improving battery life characteristics, suppressing the decrease in battery capacity, and improving battery discharge capacity, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphate triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additive may be present in an amount of 0.1 to 5 wt% relative to the total weight of the electrolyte.

[0115] As described above, the lithium secondary battery containing the positive electrode active material according to the present invention exhibits excellent discharge capacity, output characteristics, and life characteristics in a stable manner, making it useful in portable devices such as mobile phones, laptop computers, and digital cameras, as well as in the electric vehicle field, such as hybrid electric vehicles (HEVs).

[0116] The external shape of the lithium secondary battery according to the present invention is not particularly limited, but it may be cylindrical, rectangular, pouch-shaped, or coin-shaped using a can. Furthermore, the lithium secondary battery can be used not only as a battery cell used as a power source for small devices, but may also be preferably used as a unit battery in medium-to-large battery modules containing multiple battery cells.

[0117] According to yet another aspect of the present invention, a battery module and / or a battery pack including the lithium secondary battery as a unit cell can be provided.

[0118] The battery module or battery pack can be used as a power source for one or more medium-to-large devices, including power tools, electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs), or power storage systems.

[0119] The present invention will be described in more detail below with reference to examples. However, these examples are for illustrative purposes only and should not be construed as limiting the scope of the present invention.

[0120] The positive electrode current collector is not particularly limited as long as it does not induce chemical changes in the battery and is conductive. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc. may be used. The positive electrode current collector may also have a thickness of 3 to 500 μm, and fine irregularities can be formed on the surface of the current collector to increase the adhesion strength of the positive electrode active material. For example, it may be used in various forms such as film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0121] The positive electrode active material layer may be manufactured by applying a positive electrode slurry composition, which includes a conductive material and, if necessary, a binder, together with the positive electrode active material, to the positive electrode current collector.

[0122] In this case, the positive electrode active material may be present in an amount of 80 wt% to 99 wt%, more specifically, 85 wt% to 98.5 wt%, relative to the total weight of the positive electrode active material layer. When present within this content range, excellent capacity characteristics can be observed, but the material is not necessarily limited to this range.

[0123] The conductive material is used to impart conductivity to the electrodes and can be used without particular limitations as long as it has electronic conductivity without causing chemical changes in the battery it is configured in. Specific examples include graphite such as natural graphite or artificial graphite, carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber, metal powders or metal fibers such as copper, nickel, aluminum, and silver, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, or conductive polymers such as polyphenylene derivatives. One of these may be used alone or a mixture of two or more. The conductive material may be included in an amount of 0.1 wt% to 15 wt% relative to the total weight of the positive electrode active material layer.

[0124] The binder plays a role in improving the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, of which one or more may be used. The binder may be included in an amount of 0.1 to 15 wt% relative to the total weight of the positive electrode active material layer.

[0125] The positive electrode may be manufactured by a conventional positive electrode manufacturing method, except that the positive electrode active material is used. Specifically, the positive electrode may be manufactured by applying a positive electrode slurry composition, prepared by dissolving or dispersing the positive electrode active material and selectively a binder and conductive material in a solvent, onto a positive electrode current collector, followed by drying and rolling.

[0126] The solvent may be any solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and one or more of these may be used individually or in mixtures of two or more. The amount of solvent used should be such that it dissolves or disperses the cathode active material, conductive material, and binder, and then provides a viscosity that allows for excellent thickness uniformity during coating for cathode manufacturing, taking into consideration the coating thickness and production yield of the slurry.

[0127] In other embodiments, the positive electrode may be manufactured by casting the positive electrode slurry composition onto a separate support, peeling it off the support, and then laminating the resulting film onto the positive electrode current collector.

[0128] Furthermore, according to yet another aspect of the present invention, an electrochemical element including the aforementioned positive electrode may be provided. Specifically, the electrochemical element may be a battery, a capacitor, or the like, and more specifically, a lithium secondary battery.

[0129] The lithium secondary battery may specifically include a positive electrode, a negative electrode positioned opposite the positive electrode, and a separator and electrolyte interposed between the positive and negative electrodes. Here, since the positive electrode is as described above, for convenience, a detailed explanation will be omitted, and only the remaining components not mentioned above will be described in detail below.

[0130] The lithium secondary battery may further selectively include a battery container for housing the electrode assembly comprising the positive electrode, the negative electrode, and the separator, and a sealing member for sealing the battery container. The negative electrode may include a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

[0131] The negative electrode current collector is not particularly limited as long as it has high conductivity without inducing chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. The negative electrode current collector may also typically have a thickness of 3 μm to 500 μm, and, similar to the positive electrode current collector, fine irregularities can be formed on the surface of the current collector to strengthen the bonding force of the negative electrode active material. For example, it may be used in various forms such as film, sheet, foil, net, porous material, foam, and nonwoven fabric.

[0132] The negative electrode active material layer may be manufactured by applying a negative electrode slurry composition, which includes the negative electrode active material together with a conductive material and, if necessary, a selective binder, to the negative electrode current collector.

[0133] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and SiO2. βExamples include lithium-doped and dedoped metal oxides such as (0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide, or composites containing the metallic compound and carbonaceous material, such as Si-C composites or Sn-C composites. One or more of these mixtures may be used. A metallic lithium thin film may also be used as the negative electrode active material. Furthermore, low-crystalline carbon and high-crystalline carbon may all be used as the carbon material. Typical examples of low-crystalline carbon include soft carbon and hard carbon, while typical examples of high-crystalline carbon include amorphous, plate-like, flaky, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes. The aforementioned negative electrode active material may be present in an amount of 80 wt% to 99 wt% based on the total weight of the negative electrode active material layer.

[0134] The binder may be added in an amount of 0.1 wt% to 10 wt% based on the total weight of the negative electrode active material layer, as a component that assists in bonding between the conductive material, active material, and current collector. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0135] The conductive material may be added as a component to further improve the conductivity of the negative electrode active material, in an amount of 10 wt% or less, preferably 5 wt% or less, based on the total weight of the negative electrode active material layer. Such a conductive material is not particularly limited as long as it has conductivity without inducing a chemical change in the battery, and for example, graphite such as natural graphite or artificial graphite, carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black, conductive fibers such as carbon fibers and metal fibers, metal powders such as carbon fluoride, aluminum, and nickel powder, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, and conductive materials such as polyphenylene derivatives may be used.

[0136] In one embodiment, the negative electrode active material layer may be manufactured by coating a negative electrode slurry composition, which is prepared by dissolving or dispersing a negative electrode active material and a binder and conductive material selectively in a solvent, onto a negative electrode current collector and then drying it, or by casting the negative electrode slurry composition onto a separate support, peeling it off the support, and then laminating the resulting film onto the negative electrode current collector.

[0137] In other embodiments, the negative electrode active material layer may be manufactured by coating a negative electrode slurry composition, prepared by dissolving or dispersing a negative electrode active material and a binder and conductive material selectively in a solvent, onto a negative electrode current collector and drying it, or by casting the negative electrode slurry composition onto a separate support, peeling it off the support, and laminating the resulting film onto the negative electrode current collector.

[0138] On the other hand, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Generally, any separator commonly used in lithium secondary batteries can be used without particular limitations, and it is especially preferable that the separator has low resistance to ion movement of the electrolyte and excellent electrolyte moisture absorption capacity. Specifically, porous polymer films, such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or laminated structures of two or more layers thereof may be used. Alternatively, ordinary porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, may be used. Furthermore, to ensure heat resistance or mechanical strength, coated separators containing ceramic components or polymeric substances may be used, and may be selectively used as single-layer or multi-layer structures.

[0139] Furthermore, the electrolytes used in this application include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries. Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0140] The organic solvent can be any solvent that serves as a medium through which ions involved in the electrochemical reaction of the battery can move, without any particular limitations. Specifically, the organic solvent may be an ester solvent such as methyl acetate, ethyl acetate, γ-butyrolactone, or ε-caprolactone; an ether solvent such as dibutyl ether or tetrahydrofuran; a ketone solvent such as cyclohexanone; an aromatic hydrocarbon solvent such as benzene or fluorobenzene; dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), or propylene carbonate (propylene Carbonate solvents such as carbonate (PC), alcohol solvents such as ethyl alcohol and isopropyl alcohol, nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, and may include a double-bonded aromatic ring or ether bond), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, or sulfolanes may be used. Among these, carbonate solvents are preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant that can improve the charge and discharge performance of the battery, and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferred. In this case, the electrolyte performance can be improved by mixing the cyclic carbonate and the linear carbonate in a volume ratio of about 1:1 to about 1:9.

[0141] The lithium salt may be any compound capable of providing lithium ions for use in a lithium secondary battery, without any particular limitations. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3), LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2, etc. The concentration of the lithium salt is preferably within the range of 0.1 to 2.0 M. When the concentration of the lithium salt falls within this range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and lithium ions can move effectively.

[0142] In the present invention, when the electrolyte used is a solid electrolyte, a solid inorganic electrolyte such as a sulfide-based solid electrolyte, oxide-based solid electrolyte, nitride-based solid electrolyte, or halogen-based solid electrolyte may be used, and preferably a sulfide-based solid electrolyte may be used.

[0143] As the material for the sulfide-based solid electrolyte, a solid electrolyte containing Li, element X (where X is at least one selected from P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In) and S may be used. Examples of the sulfide-based solid electrolyte materials include Li2S-P2S5, Li2S-P2S-LiX (where X is a halogen element such as I or Cl), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-ZmSn (where m and n are integers and Z is Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, and Li2S-SiS2-Li p MO q(Here, p and q are integers, and M is P, Si, Ge, B, Al, Ga, or In.) The solid electrolyte, preferably a sulfide-based solid electrolyte, may be amorphous or crystalline, or a mixture of amorphous and crystalline materials.

[0144] As a material for oxide-based solid electrolytes, Li7La3Zr2O 12 Li 7-x La3Zr 1-x Nb x O 12 Li 7-3x La3Zr2Al x O 12 Li 3x La 2 / 3-x TiO3, Li 1+x Al x Ti 2-x (PO4)3, Li 1+x Al x Ge 2-x (PO4)3, Li3PO4, Li 3+x PO 4-x N x (LiPON), Li 2+2x Zn 1-x Examples include GeO4 (LISICON).

[0145] The aforementioned solid electrolyte may be arranged as a separate layer (solid electrolyte layer) between the positive electrode and the negative electrode. Furthermore, the solid electrolyte may be included in part within the positive electrode active material layer of the positive electrode independently of the solid electrolyte layer, or in part within the negative electrode active material layer of the negative electrode independently of the solid electrolyte layer.

[0146] In addition to the electrolyte components, the electrolyte may further contain one or more additives for the purpose of improving battery life characteristics, suppressing the decrease in battery capacity, and improving battery discharge capacity, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphate triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additive may be present in an amount of 0.1 to 5 wt% relative to the total weight of the electrolyte.

[0147] As described above, the lithium secondary battery containing the positive electrode active material according to the present invention exhibits excellent discharge capacity, output characteristics, and life characteristics in a stable manner, making it useful in portable devices such as mobile phones, laptop computers, and digital cameras, as well as in the electric vehicle field, such as hybrid electric vehicles (HEVs).

[0148] The external shape of the lithium secondary battery according to the present invention is not particularly limited, but it may be cylindrical, rectangular, pouch-shaped, or coin-shaped using a can. Furthermore, the lithium secondary battery can be used not only as a battery cell used as a power source for small devices, but may also be preferably used as a unit battery in medium-to-large battery modules containing multiple battery cells.

[0149] According to yet another aspect of the present invention, a battery module and / or a battery pack including the lithium secondary battery as a unit cell can be provided.

[0150] The battery module or battery pack can be used as a power source for one or more medium-to-large devices, including power tools, electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs), or power storage systems.

[0151] The present invention will be described in more detail below with reference to examples. However, these examples are for illustrative purposes only and should not be construed as limiting the scope of the present invention.

[0152] Manufacturing Example 1. Manufacturing of positive electrode active material Example 1 NiCoMn(OH)2 hydroxide precursor (Ni:Co:Mn=95:4:1(at%)) of lithium composite oxide was synthesized by a known co-precipitation method using nickel sulfate, cobalt sulfate, and manganese sulfate. The average particle size (D) of the lithium composite oxide hydroxide precursor was determined. 50 The diameter was 3.0 μm.

[0153] Next, the first hydroxide precursor and LiOH (Li / (Ni+Co+Mn)mol ratio=1.05) were mixed, and then heat-treated (primary calcination) was performed in an O2 atmosphere at 790°C for 12 hours to obtain a lithium composite oxide. Before the primary calcination, 4.0 mol% NaNO3 and 0.1 mol% ZrO2 as a metal oxide dopant were added.

[0154] After the primary calcination was completed, the lithium composite oxide was added to distilled water, stirred for 1 hour, and then dried in a vacuum dryer at 120°C for 12 hours.

[0155] Next, the material was heat-treated (secondary calcination) in an O2 atmosphere at 700°C for 12 hours to obtain a positive electrode active material containing a lithium composite oxide.

[0156] Example 2 NiCoMn(OH)2 hydroxide precursor (Ni:Co:Mn=95:4:1(at%)) of lithium composite oxide was synthesized by a known co-precipitation method using nickel sulfate, cobalt sulfate, and manganese sulfate. The average particle size (D) of the lithium composite oxide hydroxide precursor was determined. 50 The diameter was 3.0 μm.

[0157] Next, the first hydroxide precursor and LiOH (Li / (Ni+Co+Mn)mol ratio=1.05) were mixed, and then heat-treated (primary calcination) was performed in an O2 atmosphere at 790°C for 12 hours to obtain a lithium composite oxide. Before the primary calcination, 3.0 mol% of NaNO3 and 0.1 mol% of ZrO2 as a metal oxide dopant were added.

[0158] After the primary calcination was completed, the lithium composite oxide was added to distilled water, stirred for 1 hour, and then dried in a vacuum dryer at 120°C for 12 hours.

[0159] Next, the material was heat-treated (secondary calcination) in an O2 atmosphere at 700°C for 12 hours to obtain a positive electrode active material containing a lithium composite oxide.

[0160] Example 3 NiCoMn(OH)2 hydroxide precursor (Ni:Co:Mn=95:4:1(at%)) of lithium composite oxide was synthesized by a known co-precipitation method using nickel sulfate, cobalt sulfate, and manganese sulfate. The average particle size (D) of the lithium composite oxide hydroxide precursor was determined. 50 The diameter was 3.0 μm.

[0161] Next, the first hydroxide precursor and LiOH (Li / (Ni+Co+Mn)mol ratio=1.05) were mixed, and then heat-treated (primary calcination) was performed in an O2 atmosphere at 790°C for 12 hours to obtain a lithium composite oxide. Before the primary calcination, 5.0 mol% NaNO3 and 0.1 mol% ZrO2 as a metal oxide dopant were added.

[0162] After the primary calcination was completed, the lithium composite oxide was added to distilled water, stirred for 1 hour, and then dried in a vacuum dryer at 120°C for 12 hours.

[0163] Next, the material was heat-treated (secondary calcination) in an O2 atmosphere at 700°C for 12 hours to obtain a positive electrode active material containing a lithium composite oxide.

[0164] Example 4 NiCoMn(OH)2 hydroxide precursor (Ni:Co:Mn=95:4:1(at%)) of lithium composite oxide was synthesized by a known co-precipitation method using nickel sulfate, cobalt sulfate, and manganese sulfate. The average particle size (D) of the lithium composite oxide hydroxide precursor was determined. 50 The diameter was 3.0 μm.

[0165] Next, the first hydroxide precursor and LiOH (Li / (Ni+Co+Mn)mol ratio=1.05) were mixed, and then heat-treated (primary calcination) was performed in an O2 atmosphere at 790°C for 12 hours to obtain a lithium composite oxide. Before the primary calcination, 8.0 mol% NaNO3 and 0.1 mol% ZrO2 as a metal oxide dopant were added.

[0166] After the primary calcination was completed, the lithium composite oxide was added to distilled water, stirred for 1 hour, and then dried in a vacuum dryer at 120°C for 12 hours.

[0167] Next, the material was heat-treated (secondary calcination) in an O2 atmosphere at 700°C for 12 hours to obtain a positive electrode active material containing a lithium composite oxide.

[0168] Comparative Example 1 NiCoMn(OH)2 hydroxide precursor (Ni:Co:Mn=95:4:1(at%)) of lithium composite oxide was synthesized by a known co-precipitation method using nickel sulfate, cobalt sulfate, and manganese sulfate. The average particle size (D) of the lithium composite oxide hydroxide precursor was determined. 50 The diameter was 3.0 μm.

[0169] Next, the first hydroxide precursor and LiOH (Li / (Ni+Co+Mn)mol ratio=1.05) were mixed, and then heat-treated (primary calcination) was performed in an O2 atmosphere at 790°C for 12 hours to obtain a lithium composite oxide. Before the primary calcination, 2.0 mol% of NaNO3 and 0.1 mol% of ZrO2 as a metal oxide dopant were added.

[0170] After the primary calcination was completed, the lithium composite oxide was added to distilled water, stirred for 1 hour, and then dried in a vacuum dryer at 120°C for 12 hours.

[0171] Next, the material was heat-treated (secondary calcination) in an O2 atmosphere at 700°C for 12 hours to obtain a positive electrode active material containing a lithium composite oxide.

[0172] Comparative Example 2 NiCoMn(OH)2 hydroxide precursor (Ni:Co:Mn=95:4:1(at%)) of lithium composite oxide was synthesized by a known co-precipitation method using nickel sulfate, cobalt sulfate, and manganese sulfate. The average particle size (D) of the lithium composite oxide hydroxide precursor was determined. 50 The diameter was 3.0 μm.

[0173] Next, the first hydroxide precursor and LiOH (Li / (Ni+Co+Mn)mol ratio=1.05) were mixed, and then heat-treated (primary calcination) was performed in an O2 atmosphere at 790°C for 12 hours to obtain a lithium composite oxide. At this time, 4.0 mol% of NaNO3 was added before the primary calcination.

[0174] After the primary calcination was completed, the lithium composite oxide was added to distilled water, stirred for 1 hour, and then dried in a vacuum dryer at 120°C for 12 hours.

[0175] Next, the material was heat-treated (secondary calcination) in an O2 atmosphere at 700°C for 12 hours to obtain a positive electrode active material containing a lithium composite oxide.

[0176] Comparative Example 3 NiCoMn(OH)2 hydroxide precursor (Ni:Co:Mn=91:8:1(at%)) of lithium composite oxide was synthesized by a known co-precipitation method using nickel sulfate, cobalt sulfate, and manganese sulfate. The average particle size (D) of the lithium composite oxide hydroxide precursor was determined. 50 The diameter was 3.0 μm.

[0177] Next, the first hydroxide precursor and LiOH (Li / (Ni+Co+Mn)mol ratio=1.05) were mixed, and then heat-treated (primary calcination) was performed in an O2 atmosphere at 790°C for 12 hours to obtain a lithium composite oxide. At this time, 0.1 mol% of ZrO2 was added as a metal oxide dopant before the primary calcination.

[0178] After the primary calcination was completed, the lithium composite oxide was added to distilled water, stirred for 1 hour, and then dried in a vacuum dryer at 120°C for 12 hours.

[0179] Next, the material was heat-treated (secondary calcination) in an O2 atmosphere at 700°C for 12 hours to obtain a positive electrode active material containing a lithium composite oxide.

[0180] Comparative Example 4 NiCoMn(OH)2 hydroxide precursor (Ni:Co:Mn=95:4:1(at%)) of lithium composite oxide was synthesized by a known co-precipitation method using nickel sulfate, cobalt sulfate, and manganese sulfate. The average particle size (D) of the lithium composite oxide hydroxide precursor was determined. 50The diameter was 3.0 μm.

[0181] Next, the first hydroxide precursor and LiOH (Li / (Ni+Co+Mn)mol ratio=1.05) were mixed, and then heat-treated (primary calcination) was performed in an O2 atmosphere at 790°C for 12 hours to obtain a lithium composite oxide. Before the primary calcination, 10.0 mol% NaNO3 and 0.1 mol% ZrO2 as a metal oxide dopant were added.

[0182] After the primary calcination was completed, the lithium composite oxide was added to distilled water, stirred for 1 hour, and then dried in a vacuum dryer at 120°C for 12 hours.

[0183] Next, the material was heat-treated (secondary calcination) in an O2 atmosphere at 700°C for 12 hours to obtain a positive electrode active material containing a lithium composite oxide.

[0184] Manufacturing Example 2: Manufacturing of Lithium-ion Secondary Batteries (Half-Cells) A cathode slurry was prepared by dispersing 94 wt% of each of the cathode active materials produced according to Production Example 1, 3 wt% of carbon black, and 3 wt% of PVDF binder in 30 g of N-methyl-2-pyrrolidone (NMP). The cathode slurry was uniformly coated onto a 15 μm thick aluminum thin film and vacuum-dried at 135°C to produce a cathode for a lithium secondary battery.

[0185] A half-cell was manufactured using a lithium foil as the counter electrode to the positive electrode, a porous polyethylene membrane (Celgard 2300, thickness: 25 μm) as the separator, and an electrolyte containing ethylene carbonate and ethyl methyl carbonate mixed in a volume ratio of 3:7 with LiPF6 present at a concentration of 1.15 M.

[0186] Experimental Example 1: Analysis of particle size distribution of positive electrode active material The particle size distribution of lithium composite oxides among the positive electrode active materials produced according to Production Example 1 was analyzed using a known laser diffraction method. Specifically, after dispersing each positive electrode active material in a dispersion medium, an ultrasonic wave of approximately 28 kHz was irradiated at an output of 60 W using a laser diffraction particle size analyzer (Microtrac MT 3000), and a volume cumulative particle size distribution graph was obtained.

[0187] Next, from the volume cumulative particle size distribution graph, the particle sizes corresponding to 10%, 50%, and 90% of the volume cumulative amount (each, D 10 , D 50 , D 90 ), the minimum particle size (D) of the volume cumulative particle size distribution graph. min ) and the maximum particle size (D) in the volume cumulative particle size distribution graph. max ) was calculated. The results of the above analysis are shown in Tables 1 and 2 below.

[0188] [Table 1]

[0189] [Table 2]

[0190] Experimental Example 2. Evaluation of the electrochemical properties of lithium secondary batteries (half-cells). For lithium secondary batteries (half-cells) manufactured in Manufacturing Example 2, the initial charge capacity, initial discharge capacity, initial efficiency, and 1.0C / 0.1C rate characteristics were measured through charge-discharge experiments using an electrochemical analyzer (Toyo, Toscat-3100) at 25°C, a voltage range of 3.0V to 4.3V, and a discharge rate of 1.0C / 0.1C.

[0191] Furthermore, the same lithium secondary battery (half-cell) was subjected to 50 charge-discharge cycles using an electrochemical analyzer (Toyo, Toscat-3100) at 45°C, a voltage range of 3.0V to 4.3V, and 1C / 1C. The ratio of the discharged capacity at the 50th cycle to the initial capacity (cycle capacity retention) was then measured. The measurement results are shown in Table 3 below.

[0192] [Table 3]

[0193] Referring to the results in Table 3, it can be confirmed that the electrochemical properties of lithium secondary batteries using the positive electrode active materials of Examples 1 to 4, which have a uniform particle size distribution and high particle size distribution sharpness, have been improved. In particular, improvements in the life characteristics related to the stability of lithium secondary batteries using the positive electrode active materials of Examples 1 to 4 can be confirmed.

[0194] Although embodiments of the present invention have been described above, a person with ordinary skill in the art can modify and change the present invention in various ways, such as by adding, changing, deleting, or adding components, without departing from the spirit of the invention as described in the claims, and this can also be said to be within the scope of the rights of the present invention.

Claims

1. It contains lithium composite oxides that allow for lithium intercalation / deintercalation, The lithium composite oxide comprises at least lithium and a transition metal, The lithium composite oxide is D １０ and D ５０ and D ９０ and D ｍａｘ The positive electrode active material satisfies all of the following equations 1 to 3. [Formula 1] 3.42≦D ９０ / D １０ ≦3.62 [Formula 2] D ｍａｘ -D ９０ <2.0μm [Formula 3] D ｍａｘ / D ｍｉｎ <5.19 (In the above formulas 1 to 3, the D １０ This is the particle size of the lithium composite oxide at which the cumulative volume amount is 10% in the volume cumulative particle size distribution graph obtained by laser diffraction particle size distribution measurement, and D ５０ This is the particle size of the lithium composite oxide at which the cumulative volume amount in the volume cumulative particle size distribution graph becomes 50%, and D ９０ D is the particle size of the lithium composite oxide at which the cumulative volume amount reaches 90% in the volume cumulative particle size distribution graph. ｍｉｎ In the volume cumulative particle size distribution graph, this is the smallest particle size of the lithium composite oxide, and D ｍａｘ This represents the maximum particle size of the lithium composite oxide in the volume cumulative particle size distribution graph.

2. The lithium composite oxide is the D ５０ The positive electrode active material according to claim 1, wherein the particle size is 2 μm to 8 μm.

3. The lithium composite oxide is the D ｍａｘ The positive electrode active material according to claim 1, wherein the particle size is 15 μm or less.

4. The lithium composite oxide is the D １０ and the aforementioned D ５０ The positive electrode active material according to claim 1, wherein the following formula 4 is satisfied. [Formula 4] D ５０ / D １０ <1.19

5. The lithium composite oxide is the D ５０ and the aforementioned D ｍａｘ The positive electrode active material according to claim 1, wherein the following formula 5 is satisfied. [Formula 5] D ｍａｘ -D ５０ <7.8μm

6. The positive electrode active material according to claim 1, wherein the transition metal is at least one selected from the group consisting of nickel, cobalt, and manganese.

7. The lithium composite oxide is the positive electrode active material according to claim 1, represented by the following chemical formula 1. [Chemical formula 1] Li ａ Ni １－（ｂ＋ｃ＋ｄ） Co ｂ M1 ｃ M2 ｄ O ２ (Here, M1 is at least one selected from Mn and Al. M2 is at least one selected from the group consisting of Na, K, Mg, Ca, Ba, Mn, B, Ce, Hf, Ta, Cr, F, Al, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Sr, Ge, Nd, Gd, and Cu. M1 and M2 are different from each other. (0.5 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.20, 0 ≤ c ≤ 0.30, 0 ≤ d ≤ 0.10.)

8. The positive electrode active material according to claim 1, wherein in the above chemical formula 1, b + c + d is 0.30 or less.

9. The positive electrode active material according to claim 1, wherein the lithium composite oxide exists in at least one form selected from single particles and secondary particles formed by the aggregation of multiple primary particles.

10. The positive electrode active material according to claim 9, wherein the secondary particles are in a state in which 2 to 10 primary particles are aggregated.

11. A positive electrode comprising the positive electrode active material according to any one of claims 1 to 10.

12. A lithium secondary battery using the positive electrode described in claim 11.

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