Lithium composite oxide

Abstract

To provide a lithium complex oxide improved in terms of life characteristics and capacity characteristics by maintaining a predetermined relationship with a mole fraction of nickel in an active material and a mass ratio between first particles and second particles and controlling a full width at half maximum value in XRD measurement to be within a predetermined range.SOLUTION: A lithium complex oxide includes a mixture of first particles of n1 (n1>40) aggregated primary particles and second particles of n2 (n2≤20) aggregated primary particles, and is represented by the composition shown in the following formula: LiaNixCoyMnzM1-x-y-zO2, wherein M is selected from: B, Ba, Ce, Cr, F, Mg, Al, Cr, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Sr, and combinations thereof, 0.9≤a≤1.3, 0.6≤x≤1.0, 0.0≤y≤0.4, 0.0≤z≤0.4, and 0.0≤1-x-y-z≤0.4.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a mixture of lithium composite oxides, and more specifically, to a lithium composite oxide that, when first particles and second particles having different numbers of aggregated primary particles are mixed, maintains a constant relationship between the range of the full width at half maximum (FWHM) of the (10⁴) peak of the XRD defined by a hexagonal lattice having an R-3m space group and the mole fraction of nickel in the lithium composite oxide and the mass ratio of the first particles to the second particles, thereby improving the life characteristics of a battery containing the lithium composite oxide according to the present invention. [Background technology]

[0002] With the miniaturization and increased performance of various devices, miniaturization, weight reduction, and higher energy density of lithium batteries are becoming increasingly important. In other words, high-voltage and high-capacity lithium batteries are gaining importance.

[0003] Research is being conducted on lithium composite oxides used as positive electrode active materials in lithium batteries, such as LiCoO2, LiMn2O4, LiNiO2, and LiMnO2. Of these lithium composite oxides, LiCoO2 is the most widely used due to its excellent lifespan and charge / discharge efficiency. However, it has disadvantages, such as poor structural stability and high cost due to the limited availability of cobalt resources used as a raw material, which limits its competitiveness.

[0004] Lithium manganese oxides such as LiMnO2 and LiMn2O4 have the advantages of excellent thermal stability and low cost, but they have the drawbacks of low capacity and poor high-temperature performance.

[0005] Furthermore, while LiNiO2-based cathode active materials exhibit high discharge capacity battery characteristics, their synthesis is difficult due to cation mixing issues between Li and transition metals, which significantly impacts their output (rate) characteristics.

[0006] To compensate for these shortcomings, the demand for nickel-rich systems (Ni-rich systems) with a Ni content of 60% or more has begun to increase as positive electrode active materials for secondary batteries. However, while the active materials of the aforementioned nickel-rich systems have the excellent advantage of exhibiting high capacity, as the Ni content increases, problems arise such as increased structural instability due to Li / Ni cation mixing, physical discontinuity between internal particles due to microcracks, and deepening electrolyte depletion, leading to a rapid deterioration of life characteristics at room temperature and high temperatures. [Overview of the project] [Problems that the invention aims to solve]

[0007] The occurrence of microcracks, known to be a cause of life degradation in nickel-rich positive electrode active materials, is said to be correlated with the size of the primary particles in the positive electrode active material. Specifically, it is known that the smaller the size of the primary particles, the more suppressed the occurrence of cracks due to repeated contraction and expansion of the particles. However, a decrease in primary particle size leads to a decrease in discharge capacity, and if the nickel content in the positive electrode active material increases, a decrease in primary particle size can worsen the life characteristics. Therefore, in order to improve the life characteristics of nickel-rich positive electrode active materials, it is necessary to consider the correlation between nickel content, primary particle size, and discharge capacity.

[0008] The present invention aims to provide a lithium composite oxide with improved lifetime characteristics and capacity characteristics by adjusting the full width at half maximum (FWHM) value within a predetermined range during XRD measurement, so as to solve the problems of the nickel-rich lithium composite oxide described above, and so as to maintain a constant relationship between the mole fraction of nickel in the active material and the mass ratio of the first and second particles. [Means for solving the problem]

[0009] To solve the above problems, the lithium composite oxide according to an embodiment of the present invention includes a mixture of a first particle in which n1 (n1>40) primary particles are aggregated and a second particle in which n2 (n2≦20) primary particles are aggregated, and is represented by the following [Chemical Formula 1] and has a range of the full width at half maximum FWHM (deg., 2θ) of the (104) peak in the XRD peak defined by the hexagonal lattice having the R-3m space group as shown in the following [Relational Expression 1].

[0010] [Chemical Formula 1]Li a Ni x Co y Mn z M 1-x-y-z O2 (In the formula, M is selected from the group consisting of B, Ba, Ce, Cr, F, Mg, Al, Cr, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Sr, and combinations thereof, 0.9≦a≦1.3, 0.6≦x≦1.0, 0.0≦y≦0.4, 0.0≦z≦0.4, 0.0≦1-x-y-z≦0.4.)

[0011] [Relational Expression 1]-0.025≦FWHM (104) -{0.04+(x 第1の粒子 -0.6)×0.25}≦0.025 (In the formula, FWHM (104) is represented by the following [Relational Expression 2].)

[0012] [Relational Expression 2]FWHM (104) ={(FWHM 化学式1のpowder(104) -0.1×mass ratio of the second particle) / mass ratio of the first particle}-FWHM Si powder(220) (In the formula, FWHM 化学式1のpowder(104) represents the full width at half maximum (FWHM) of the (104) peak observed around 44.5° (2θ) from the XRD measurement value of the lithium composite oxide. Also, FWHM Si powder(220) represents the full width at half maximum (FWHM) of the (220) peak observed around 47.3° (2θ) from the XRD measurement value of the Si powder. Also, x第1の粒子 =(x - x 第2の粒子 *Mass ratio of the second particle) / Mass ratio of the first particle, and the X 第2の粒子 represents the Ni molar ratio of the second particle. Note that the mass ratio means the ratio of the mass to the total mass of the first particle and the second particle combined.)

[0013] In SEM analysis, if particles exceeding n1 primary particles distinguishable by the naked eye are defined as "multi-particles" and particles of n2 or less are defined as "single particles", the lithium composite oxide according to an embodiment of the present invention has a bimodal structure of single-particle mixing in which large particles in the multi-particle form and small particles in the single-particle form are mixed.)

[0014] When applying a cathode active material having a bimodal structure of single-particle mixing to a secondary battery, compared with the case of applying a bimodal cathode active material in which small particles in the multi-particle form are mixed with large particles in the multi-particle form, the BET decreases, the generation of gas is suppressed, and the storage characteristics are improved.)

[0015] The second particle of the lithium composite oxide according to an embodiment of the present invention can have 20 or less, or 15 or less, or 10 or less, or 5 or less primary particles.)

[0016] As shown in the [Relationship 1], the lithium composite oxide according to an embodiment of the present invention has a range of the full width at half maximum FWHM of the (104) peak during XRD analysis, which maintains a certain relationship with the nickel content (x 第1の粒子 ) in the first particle and the mass ratio of the first particle and the second particle.)

[0017] According to the [Relationship 1], the optimal range of the FWHM of the lithium composite oxide according to an embodiment of the present invention is -0.25 to 0.25, or can be -0.20 to 0.20. When applying a lithium composite oxide having a bimodal structure of single-particle mixing within the optimal range of the FWHM to a secondary battery, excellent battery storage characteristics can be obtained.)

[0018] In the lithium composite oxide according to the embodiment of the present invention, during XRD analysis, deviations and errors occur in the full width at half maximum (FWHM) value due to various factors such as the condition of the analytical instrument, the X-ray source, and the measurement conditions. Therefore, as shown in [Relational Equation 2] above, correction is performed using the full width at half maximum (FWHM) of Si powder as a standard sample.

[0019] In the lithium composite oxide according to the embodiment of the present invention, the average particle size of the first particles can be 8 to 20 μm, 9 to 18 μm, 10 to 15 μm, or 10 to 13 μm.

[0020] In the lithium composite oxide according to the embodiment of the present invention, the average particle size of the second particles can be 0.1 to 7 μm, 2 to 5 μm, or 3 to 4 μm.

[0021] The crystal structure of the lithium composite oxide according to the embodiment of the present invention can be hexagonal α-NaFeO2 (R-3m space group).

[0022] In the lithium composite oxide according to the present invention, when the nickel content x in [Chemical Formula 1] is 0.97 to 0.99, the FWHM shown in [Relational Formula 2] (104) The range can be 0.108°(2θ) to 0.162°(2θ).

[0023] In the lithium composite oxide according to the present invention, when the nickel content x in [Chemical Formula 1] is 0.93 to 0.95, the FWHM shown in [Relational Formula 2] (104) The range can be 0.098°(2θ) to 0.152°(2θ).

[0024] In the lithium composite oxide according to the present invention, when the nickel content x in [Chemical Formula 1] is 0.87 to 0.89, the FWHM shown in [Relational Formula 2] (104)The range can be 0.083°(2θ) to 0.137°(2θ).

[0025] In the lithium composite oxide according to the present invention, when the nickel content x in [Chemical Formula 1] is 0.79 to 0.81, the FWHM represented by [Relational Formula 2] (104) The range can be 0.063°(2θ) to 0.117°(2θ).

[0026] Although not specifically described in this invention, during XRD analysis of the lithium composite oxide according to the present invention, various peaks such as (003) and (101) are observed in addition to the (104) peak, and each peak has a different FWHM value. During XRD analysis of the lithium composite oxide according to the present invention, in addition to the (104) peak, peaks detected at different positions may also have different FWHM ranges that maintain a certain relationship with the mole fraction of nickel and the mass ratio of the first particle to the second particle.

[0027] A method for producing a lithium composite oxide according to an embodiment of the present invention includes: a first step of synthesizing a first positive electrode active material precursor containing first particles formed by the aggregation of n1 (n1>40) primary particles, adding a lithium compound, and then calcining to produce a first positive electrode active material; a second step of synthesizing a second positive electrode active material precursor containing second particles formed by the aggregation of n2 (n2≦20) primary particles, adding a lithium compound, and then calcining; a third step of grinding the material formed in the second step to produce a second positive electrode active material; a fourth step of mixing the first positive electrode active material and the second positive electrode active material; and a fifth step of coating or doping the mixed material with substance M and then heat-treating it.

[0028] In the method for producing a lithium composite oxide according to an embodiment of the present invention, the lithium compound added in the first and second steps may be LiOH.

[0029] In the method for producing lithium composite oxide according to an embodiment of the present invention, the average particle size of the first positive electrode active material produced in the first step can be 8 to 20 μm, 9 to 18 μm, 10 to 15 μm, or 10 to 13 μm.

[0030] In the method for producing lithium composite oxide according to an embodiment of the present invention, the average particle size of the second positive electrode active material produced in the third step can be 0.1 to 7 μm, 2 to 5 μm, or 3 to 4 μm.

[0031] In the method for producing lithium composite oxide according to an embodiment of the present invention, the step of washing with water may be further included after calcination in the first step, after calcination in the second step, or after grinding in the third step.

[0032] In the method for producing lithium composite oxide according to an embodiment of the present invention, the step of washing with water after the heat treatment in the fifth step may be further included.

[0033] In the method for producing lithium composite oxide according to an embodiment of the present invention, in the fifth step, substance M is selected from the group consisting of B, Ba, Ce, Cr, F, Mg, Al, Cr, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Sr, and combinations thereof, but is not limited thereto. [Effects of the Invention]

[0034] The lithium composite oxide according to the present invention prevents microcracks in the first particle by maintaining a constant relationship between the range of the full width at half maximum (FWHM) value of the (10⁴) peak defined by a hexagonal lattice having an R-3m space group, and the mole fraction of nickel and the mass ratio of the first particle to the second particle. As a result, it improves the lifespan characteristics of batteries containing nickel-rich positive electrode active materials. [Brief explanation of the drawing]

[0035] [Figure 1] This is an SEM image of a lithium composite oxide according to an embodiment of the present invention. [Figure 2] The results of particle size analysis of the mixed mass ratio of large and small particles of the lithium composite oxide according to the embodiment of the present invention are shown. [Figure 3] The results of particle size analysis of the mixed mass ratio of large and small particles of the lithium composite oxide according to the embodiment of the present invention are shown. [Figure 4] This graph compares the characteristics of batteries with single-particle bimodal and multi-particle bimodal structures. [Figure 5] This graph compares the characteristics of batteries with single-particle bimodal and multi-particle bimodal structures. [Figure 6] The XRD analysis results of lithium composite oxides according to the examples and comparative examples of the present invention are shown. [Figure 7] The results of XRD analysis of Si powder according to an example of the present invention are shown. [Figure 8] This graph compares the battery characteristics of lithium composite oxides according to the examples and comparative examples of the present invention. [Figure 9] This graph compares the battery characteristics of lithium composite oxides according to the examples and comparative examples of the present invention. [Figure 10] This graph compares the battery characteristics of lithium composite oxides according to the examples and comparative examples of the present invention. [Figure 11] This graph compares the battery characteristics of lithium composite oxides according to the examples and comparative examples of the present invention. [Figure 12] This graph compares the battery characteristics of lithium composite oxides according to the examples and comparative examples of the present invention. [Figure 13] This graph compares the battery characteristics of lithium composite oxides according to the examples and comparative examples of the present invention. [Modes for carrying out the invention]

[0036] The present invention will be described in detail below based on examples. However, the present invention is not limited to the following examples.

[0037] <Meaning of measurement methods and terms> During the XRD measurements, a Cu-Kα1 X-ray source was used, and measurements were performed in the range of 10-70° (2θ) at 0.02° step intervals using the θ-2θ scan (Bragg-Brentano parafocusing geometry) method.

[0038] FWHM (104) and FWHM for Si powder (220) The measurement is calculated by fitting a Gaussian function, and Gaussian function fitting for FWHM measurement can be performed using various academic, publicly available, or commercial software well known to those skilled in the art.

[0039] For the silicon powder used, we used silicon powder (product number 215619) manufactured by Sigma-Aldrich.

[0040] The mixed mass ratio of large and small particles was confirmed by particle size analysis, as shown in Figures 2 and 3.

[0041] "FWHM range value" refers to FWHM (104) This means the value is -{0.04+(x-0.6)×0.25}, and "optimal range for FWHM" means that the FWHM value is between -0.025 and 0.025.

[0042] FWHM 大粒(104) " refers to large-particle FWHM (104) It means value, "FWHM 小粒(104) " refers to small-particle FWHM (104) It means value, "FWHM 混合(104) " is a lithium composite oxide FWHM manufactured by mixing large and small particles. (104) It means a value.

[0043] <Manufacturing Example 1> A positive electrode active material with a mole fraction of 0.80 for large Ni particles (multiple particles) and a positive electrode active material with a mole fraction of 0.85 for small Ni particles (single particles) were manufactured by the following method.

[0044] Synthesis of large-grained positive electrode active material First, nickel sulfate, cobalt sulfate, and manganese sulfate were prepared, and a precursor was synthesized by coprecipitation. After adding LiOH to the synthesized precursor, a lithium composite oxide was produced by calcination. Specifically, after mixing LiOH with the precursor, the furnace was heated at a rate of 1°C / min while maintaining an O2 atmosphere for 10 hours, and then allowed to cool naturally to produce the cathode active material.

[0045] Next, distilled water was added to the lithium composite oxide, followed by washing for 1 hour. The washed lithium composite oxide was then filtered and dried to obtain a large-grained positive electrode active material with an average diameter of 11-13 μm.

[0046] Method for synthesizing small, single-particle positive electrode active materials First, nickel sulfate, cobalt sulfate, and manganese sulfate were prepared, and a coprecipitation reaction was carried out to synthesize a precursor. After adding LiOH to the synthesized precursor, the lithium composite oxide was produced by calcination. Specifically, after mixing LiOH with the precursor, the temperature was increased at 1°C / min in a calcination furnace while maintaining an O2 atmosphere, and heat treatment was performed at 900°C for 10 hours, followed by natural cooling to produce the cathode active material.

[0047] Next, the lithium composite oxide was pulverized to a size of 3-4 μm using a pulverizer, then washed with distilled water for 1 hour. The washed lithium composite oxide was filtered and dried to obtain small, single-particle positive electrode active material.

[0048] Production of the final bimodal cathode active material by mixing large and small particles Next, the large-grained positive electrode active material and the small-grained positive electrode active material (single particles) were mixed together with a boron (B)-containing raw material (H3BO3) using a mixer, and a coating of B was applied. The B-containing raw material (H3BO3) was mixed to a concentration of 0.2% by weight relative to the total weight of the lithium composite oxide. The mixture was then heated in the same firing furnace at a rate of 2°C / min while maintaining an O2 atmosphere for 5 hours, and then allowed to cool naturally to obtain the lithium composite oxide.

[0049] SEM images of the manufactured lithium composite oxide were taken and are shown in Figure 1.

[0050] <Manufacturing Example> Battery Manufacturing A slurry was prepared by mixing the lithium secondary battery positive electrode active material produced in the manufacturing example with artificial graphite as a conductive material and polyvinylidene fluoride (PVdF) as a binder in a weight ratio of 85:10:5. The slurry was uniformly applied to a 15 μm thick aluminum foil and vacuum-dried at 135°C to produce a lithium secondary battery positive electrode.

[0051] A coin cell was manufactured using the aforementioned positive electrode, a lithium foil as the counter electrode, a porous polypropylene film with a thickness of 20 μm as the separator, and an electrolyte solution prepared by dissolving LiPF6 at a concentration of 1.15 M in a solvent containing a mixture of ethylene carbonate, diethyl carbonate, and ethyl methyl carbonate in a volume ratio of 3:1:6.

[0052] <Experimental Example 1> Figure 6 shows the XRD analysis results for Examples 1-1 to 1-4 and Comparative Examples 1-1 to 1-2, which were produced using the manufacturing method described in Manufacturing Example 1 above. All samples were confirmed to have a hexagonal α-NaFeO2 (R-3m space group) structure.

[0053] Furthermore, Figure 7 shows the results of analyzing Si powder using the same XRD apparatus and conditions for FWHM correction.

[0054] Next, FWHM (104)The values ​​were measured and are shown in Tables 1 and 2. [Table 1] [Table 2]

[0055] After producing a lithium composite oxide with a mole fraction of 0.80 for large Ni particles and a mole fraction of 0.85 for small Ni particles (single particles) using the manufacturing method described in Manufacturing Example 1 above, FWHM is performed based on the mass ratio of large particles, the mass ratio of small particles, and the Ni mole fraction. 混合(104) The FWHM range was calculated by measuring the FWHM and using the relational formula of the present invention. Next, a battery was manufactured according to the above-described manufacturing example, and its discharge capacity and life characteristics were measured, as shown in Table 3, Figure 8, and Figure 9 below. [Table 3]

[0056] According to Table 3, Figures 8 and 9, Examples 1-1 to 1-4, where the FWHM range value satisfies the optimal FWHM range, exhibited superior battery discharge capacity and lifespan. However, Comparative Examples 1-1 to 1-2, where the FWHM range value did not satisfy the optimal FWHM range, showed inferior battery discharge capacity and lifespan.

[0057] <Manufacturing Example 2> We manufactured a positive electrode active material with a mole fraction of 0.88 for large Ni particles (multiple particles) and a positive electrode active material with a mole fraction of 0.88 for small Ni particles (single particles).

[0058] Synthesis of large-particle positive electrode active material First, nickel sulfate, cobalt sulfate, and manganese sulfate were prepared, and a precursor was synthesized by coprecipitation. After adding LiOH to the synthesized precursor, a lithium composite oxide was produced by calcination. Specifically, after mixing LiOH with the precursor, the furnace was heated at 1°C / min while maintaining an O2 atmosphere for 10 hours, followed by natural cooling to produce a positive electrode active material. This produced a large-grained positive electrode active material with an average diameter of 11-13 μm.

[0059] Method for synthesizing small, single-particle positive electrode active materials First, nickel sulfate, cobalt sulfate, and manganese sulfate were prepared, and a coprecipitation reaction was carried out to synthesize a precursor. After adding LiOH to the synthesized precursor, the lithium composite oxide was produced by calcination. Specifically, after mixing LiOH with the precursor, the temperature was increased at 1°C / min in a calcination furnace while maintaining an O2 atmosphere, and heat treatment was performed at 900°C for 10 hours, followed by natural cooling to produce the cathode active material.

[0060] Next, the lithium composite oxide was pulverized to a size of 3-4 μm using a pulverizer to obtain small, single-particle positive electrode active material.

[0061] Production of the final bimodal cathode active material by mixing large and small particles Next, the large-grained positive electrode active material (multi-particle) and the small-grained positive electrode active material (single-particle) were mixed together with Al2O3 and ZrO2 using a mixer, and then coated with Al and Zr. The same firing furnace was heated at a rate of 2°C / min while maintaining an O2 atmosphere for 5 hours, after which it was allowed to cool naturally.

[0062] Next, distilled water was added to the lithium composite oxide, followed by washing for 1 hour, filtration, and drying to obtain the lithium composite oxide.

[0063] <Experimental Example 2> XRD analysis results for Examples 2-1 to 2-4 and Comparative Examples 2-1 to 2-2, which were produced by the manufacturing method described in Manufacturing Example 2 above, confirmed that all samples had a hexagonal α-NaFeO2 (R-3m space group) structure.

[0064] Next, FWHM (104) The values ​​were measured and are shown in Tables 4 and 5. [Table 4] [Table 5]

[0065] After producing a lithium composite oxide with a mole fraction of 0.88 for large Ni particles and 0.88 for small Ni particles (single particles) using the manufacturing method described in Manufacturing Example 2 above, FWHM is performed based on the mass ratio of large particles, the mass ratio of small particles, and the Ni mole fraction. 混合(104) The FWHM range was calculated by measuring the FWHM and using the relational formula of the present invention. Next, a battery was manufactured according to the above manufacturing example, and its discharge capacity and life characteristics were measured, as shown in Table 6, Figure 10, and Figure 11 below. [Table 6]

[0066] According to Table 6, Figure 10, and Figure 11, Examples 2-1 to 2-4, where the FWHM range value satisfies the optimal FWHM range, exhibited superior battery discharge capacity and lifespan. However, Comparative Examples 2-1 to 2-2, where the FWHM range value did not satisfy the optimal FWHM range, showed inferior battery discharge capacity and lifespan.

[0067] <Manufacturing Example 3> The lithium composite oxide was produced in the same manner as in Production Example 2 described above, except that the mole fraction of large Ni particles (multi-particle) was 0.94 and the mole fraction of small Ni particles (single-particle) was 0.92, and the Ti and Zr coatings were applied.

[0068] <Experimental Example 3> XRD analysis results for Examples 3-1 to 3-4 and Comparative Examples 3-1 to 3-2, which were produced by the manufacturing method described in Manufacturing Example 3 above, confirmed that all samples had a hexagonal α-NaFeO2 (R-3m space group) structure.

[0069] Next, FWHM (104) The values ​​were measured and are shown in Tables 7 and 8. [Table 7] [Table 8]

[0070] After producing a lithium composite oxide with a mole fraction of 0.94 for large Ni particles and a mole fraction of 0.92 for small Ni particles (single particles) using the manufacturing method described in Manufacturing Example 3 above, FWHM is performed based on the mass ratio of large particles, the mass ratio of small particles, and the Ni mole fraction. 混合(104) The FWHM range was calculated by measuring the FWHM and using the relational formula of the present invention. Next, a battery was manufactured according to the above manufacturing example, and its discharge capacity and life characteristics were measured, as shown in Table 9, Figure 12, and Figure 13 below. [Table 9]

[0071] According to Table 9, Figure 12, and Figure 13, Examples 3-1 to 3-4, where the FWHM range value satisfies the optimal FWHM range, exhibited superior battery discharge capacity and lifespan. However, Comparative Examples 3-1 to 3-2, where the FWHM range value did not satisfy the optimal FWHM range, showed inferior battery discharge capacity and lifespan.

[0072] <Experimental Example 4> Comparison of multi-particle bimodal and single-particle bimodal When manufacturing a bimodal positive electrode active material for high-nickel NCM by mixing large and small particles in a multi-particle form, using single-particle small particles in the mixture reduces BET, suppresses gas generation, and improves storage characteristics compared to using multi-particle small particles.

[0073] The gas generation rate and lifetime characteristics when using multi-particle mixed bimodal and single-particle mixed bimodal are compared and shown in Table 10, Figure 4, and Figure 5.

[0074] Figure 4 shows that in the case of a multi-particle bimodal mixture, the volume change of the pouch cell due to gas generation when left at high temperatures is more than twice as large compared to the case of a single-particle bimodal mixture. [Table 10]

Claims

1. The mixture comprises a first particle formed by the aggregation of n1 (n1 > 40) primary particles and a second particle formed by the aggregation of n2 (n2 ≤ 20) primary particles. As shown in [Chemical Formula 1] below, A lithium composite oxide in which the range of the full width at half maximum (FWHM) of the (104) peak in the XRD peak defined by a hexagonal lattice having an R-3m space group is shown by the following [Relationship 1]. [Chemical Formula 1] Li ａ Ni ｘ Co ｙ Mn ｚ M １－ｘ－ｙ－ｚ O ２ (In the formula, M is selected from the group consisting of B, Ba, Ce, Cr, F, Mg, Al, Cr, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Sr, and combinations thereof, where 0.9 ≤ a ≤ 1.3, 0.6 ≤ x ≤ 1.0, 0.0 ≤ y ≤ 0.4, 0.0 ≤ z ≤ 0.4, and 0.0 ≤ 1 - x - y - z ≤ 0.4.) [Relationship 1] -0.025 ≤ FWHM （１０４） -{0.04 + (x 第１の粒子 (-0.6) × 0.25 ≤ 0.025 (where FWHM （１０４） is represented by [Formula 2] as follows.) [Relational formula 2] FWHM （１０４） = {(FWHM 化学式１のｐｏｗｄｅｒ（１０４） (-0.1 × mass ratio of the second particle) / mass ratio of the first particle) - FWHM Ｓｉ ｐｏｗｄｅｒ（２２０） (In the formula, FWHM 化学式１のｐｏｗｄｅｒ（１０４） This shows the full width at half maximum (FWHM) of the (104) peak observed around 44.5° (2θ) from XRD measurements of lithium composite oxide. Also, FWHM Ｓｉ ｐｏｗｄｅｒ（２２０） This shows the full width at half maximum (FWHM) of the (220) peak observed around 47.3° (2θ) from XRD measurements of Si powder. Also, x 第１の粒子 = (x - x) 第２の粒子 *This is the ratio of the mass of the second particle to the mass of the first particle, and the aforementioned X 第２の粒子 This refers to the Ni molar ratio of the second particle. Furthermore, x represents the x in the aforementioned chemical formula 1. Furthermore, the Si powder is Si powder manufactured by Sigma-Aldrich (product code 215619). Furthermore, the aforementioned mass ratio refers to the ratio of the mass of the first and second particles to the total mass of the two particles combined.

2. The lithium composite oxide according to claim 1, wherein the average particle size of the first particles is 8 to 20 μm.

3. The lithium composite oxide according to claim 1, wherein the average particle size of the second particles is 0.1 to 7 μm.

4. The crystal structure of the aforementioned lithium composite oxide is hexagonal α-NaFeO ２ The lithium composite oxide according to claim 1.

5. When the nickel content x is 0.97 to 0.99, the FWHM shown in relational formula 2 （１０４） The lithium composite oxide according to claim 1, wherein the range satisfies 0.108°(2θ) to 0.162°(2θ).

6. When the nickel content x is 0.93 to 0.95, the FWHM shown in relational formula 2 （１０４） The lithium composite oxide according to claim 1, wherein the range is 0.098°(2θ) to 0.152°(2θ).

7. When the nickel content x is 0.87 to 0.89, the FWHM shown in relational formula 2 （１０４） The lithium composite oxide according to claim 1, wherein the range is 0.083°(2θ) to 0.137°(2θ).

8. When the nickel content x is 0.79 to 0.81, the FWHM shown in relational formula 2 （１０４） The lithium composite oxide according to claim 1, wherein the range is 0.063°(2θ) to 0.117°(2θ).

9. A method for producing a lithium composite oxide according to claim 1, A first step to produce a first positive electrode active material is to synthesize a first positive electrode active material precursor containing a first particle in which n1 (n1 > 40) primary particles are aggregated, add a lithium compound, and then calcine it; A second step involves synthesizing a second positive electrode active material precursor containing a second particle formed by the aggregation of n² (n² ≤ 20) primary particles, adding a lithium compound, and then calcining it; A third step of producing a second positive electrode active material by crushing the material formed in the second step; A fourth step of mixing the first positive electrode active material and the second positive electrode active material; and, A fifth step involves coating or doping the mixed substance with substance M, followed by heat treatment; A method for producing lithium composite oxides, including the above.

10. The method for producing a lithium composite oxide according to claim 9, wherein the lithium compound added in the first or second step is LiOH.

11. The method for producing a lithium composite oxide according to claim 9, wherein the average particle size of the first positive electrode active material produced in the first step is 8 to 20 μm.

12. The method for producing a lithium composite oxide according to claim 9, wherein the average particle size of the second positive electrode active material produced in the third step is 0.1 to 7 μm.

13. A method for producing a lithium composite oxide according to claim 9, further comprising the step of washing with water after calcination in the first step, after calcination in the second step, or after grinding in the third step.

14. A method for producing a lithium composite oxide according to claim 9, further comprising the step of washing with water after the heat treatment in the fifth step.

15. The method for producing a lithium composite oxide according to claim 9, wherein in the fifth step, substance M is selected from the group consisting of B, Ba, Ce, Cr, F, Mg, Al, Cr, V, Ti, Fe, Zr, Zn, Si, Y, Nb, Ga, Sn, Mo, W, P, Sr, and combinations thereof.

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