Positive electrode active material for non-aqueous electrolyte secondary batteries and non-aqueous electrolyte secondary batteries

Abstract

To provide a positive electrode active material that can suppress thermal runaway, and a non-aqueous electrolyte secondary battery using the same. [Solution] The positive electrode active material for a non-aqueous electrolyte secondary battery is Li[Li x (Ni 1-y-z-w Co y Mn z M w ) 1-x ]O2(wherein M is one or more elements other than Li, Ni, Co, Mn and O, and -0.1≦x≦0.15, 0

Description

[Technical Field]

[0001] This disclosure relates to a positive electrode active material for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery. [Background technology]

[0002] Lithium-ion rechargeable batteries are attracting attention as power sources for electronic devices such as AV equipment and personal computers, due to their advantages of being small, lightweight, having high energy density, high charge / discharge voltage, and large charge / discharge capacity.

[0003] Lithium-ion secondary batteries typically use flammable organic solvents as their electrolyte, thus requiring high thermal stability. For example, in lithium-ion secondary batteries, when heat is applied while the battery is charged, oxygen is released from the positive electrode active material crystal. This oxygen reacts with the electrolyte, which is known to cause thermal runaway.

[0004] In particular, active materials containing Ni, Co, and Mn have been widely used as positive electrode active materials in recent years. In such positive electrode active materials, the higher the Ni content, the earlier the phase transition reaction of the positive electrode active material occurs in the low-temperature range, and oxygen is rapidly released, making the positive electrode active material more susceptible to thermal runaway. On the other hand, there is a growing demand for materials with high Ni content that have a large battery capacity, and as a result, there is a tendency for the thermal stability inherent in materials with high Ni content to decrease.

[0005] Therefore, in order to suppress such thermal runaway of the positive electrode active material, for example, Patent Document 1 proposes a positive electrode active material containing a lithium transition metal composite oxide containing 80 mol% or more of Ni and 0.1 mol% or more and 1.5 mol% or less of B with respect to the total number of moles of metal elements excluding Li. On at least the particle surface of the lithium transition metal composite oxide, B and at least one element (M1) selected from Groups 4 to 6 are present. The molar fraction of M1 with respect to the total number of moles of metal elements excluding Li on the surface of particles smaller than the 30% particle size is larger than the molar fraction of M1 with respect to the total number of moles of metal elements excluding Li on the surface of particles with a volume-based particle size larger than the 70% particle size. Patent Document 1 describes that by using such a composite oxide in a lithium ion secondary battery, the self-heating rate can be suppressed even at high temperatures.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, in the positive electrode active material of Patent Document 1, by coating the particle surface of the positive electrode active material with a boron compound, a certain inhibitory effect is expected against thermal runaway caused by the reaction between oxygen released from the positive electrode active material and the electrolyte. However, this alone is not sufficient to suppress thermal runaway, and there is still room for improvement.

[0008] Therefore, a method for suppressing thermal runaway is required other than the method of coating the surface of the positive electrode active material with a compound as described above.

[0009] The present disclosure has been made in view of the above circumstances, and an object thereof is to provide a positive electrode active material capable of suppressing thermal runaway in a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery using the same.

Means for Solving the Problems

[0010] The inventors of the present invention have intensively studied to solve the above-mentioned problems. As a result, a composite oxide represented by the general formula Li 1+x Ni 1-y-z-w Co y Mn z M w O2 (where M is one or more elements other than Li, Ni, Co, Mn, and O, and -0.1 ≦ x ≦ 0.15, 0 ≦ y ≦ 0.4, 0 ≦ z ≦ 0.4, 0 ≦ w ≦ 0.1). When the differential thermogravimetric curve obtained by heating the composite oxide from 50°C to 600°C at 5°C / min per minute for a sample with the counter electrode charged to 4.30V with lithium is separated into a plurality of peaks, in the temperature range of 150°C or higher and 350°C or lower, there are a first peak where the value of the differential thermogravimetry at the peak top shows the maximum value, and among the peaks whose peak tops are at a temperature more than 20°C away from the temperature showing the peak top of the first peak, a second peak where the value of the differential thermogravimetry at the peak top shows the maximum value. When a positive electrode active material in which the value of the differential thermogravimetry of the first peak with respect to the value of the differential thermogravimetry of the second peak is 1 or more and 9 or less is used in a non-aqueous electrolyte secondary battery, it has been found that the maximum oxygen release rate (hereinafter referred to as "maximum oxygen release rate") from the positive electrode active material can be suppressed, and furthermore, thermal runaway can be suppressed. Specifically, the present disclosure provides the following.

[0011] (1) The general formula Li 1+x Ni 1-y-z-w Co y Mn z M wO2 (where M is one or more elements other than Li, Ni, Co, Mn, and O, -0.1 ≦ x ≦ 0.15, 0 ≦ y ≦ 0.4, 0 ≦ z ≦ 0.4, 0 ≦ w ≦ 0.1), and when the differential thermogravimetric curve obtained by raising the temperature of a sample charged to 4.30 V with lithium as the counter electrode from 50 °C to 600 °C at 5 °C / min is separated into a plurality of peaks, in the temperature range of 150 °C or higher and 350 °C or lower, there are a first peak where the value of the differential thermogravimetry at the peak top shows the maximum value, and among the peaks showing the peak top at a temperature separated from the temperature showing the peak top of the first peak by 20 °C or more, a second peak where the value of the differential thermogravimetry at the peak top shows the maximum value, and the value of the differential thermogravimetry at the peak top of the first peak with respect to the value of the differential thermogravimetry at the peak top of the second peak is 1 or more and 9 or less. A positive electrode active material for a non-aqueous electrolyte secondary battery.

[0012] (2) The positive electrode active material for a non-aqueous electrolyte secondary battery according to (1), wherein in the composite oxide, 0 < x ≦ 0.15.

[0013] (3) The positive electrode active material for a non-aqueous electrolyte secondary battery according to (1) or (2), wherein the value of the differential thermogravimetry at the peak top of the first peak is 3% / min or less.

[0014] (4) A non-aqueous electrolyte secondary battery including a positive electrode containing the positive electrode active material according to (1) or (2).

Advantages of the Invention

[0015] According to the present disclosure, it is possible to provide a positive electrode active material capable of suppressing thermal runaway when used in a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery using the same.

Brief Description of the Drawings

[0016] [Figure 1] It is a DTG curve of the composite oxide sample of Example 1. [Figure 2] It is a DTG curve of the composite oxide sample of Example 2. [Figure 3]This is the DTG curve for the composite oxide sample of Example 3. [Figure 4] This is the DTG curve for the composite oxide sample of Example 4. [Figure 5] This is the DTG curve for the composite oxide sample of Example 5. [Figure 6] This is the DTG curve for the composite oxide sample of Example 6. [Figure 7] This is the DTG curve for the composite oxide sample of Example 7. [Figure 8] This is the DTG curve for the composite oxide sample of Example 8. [Figure 9] This is the DTG curve for the composite oxide sample of Example 9. [Figure 10] This is the DTG curve for the composite oxide sample of Example 10. [Figure 11] This is the DTG curve for the composite oxide sample of Example 11. [Figure 12] This is the DTG curve for the composite oxide sample of Example 12. [Figure 13] This is the DTG curve for the composite oxide sample of Example 13. [Figure 14] This is the DTG curve for the composite oxide sample of Comparative Example 1. [Modes for carrying out the invention]

[0017] The embodiments of this disclosure will be described below, but this disclosure is not limited in any way by the description of the embodiments and can be implemented with appropriate modifications.

[0018] <Cathode active material for nonaqueous electrolyte secondary batteries> The positive electrode active material for a non-aqueous electrolyte secondary battery according to the embodiments of this disclosure is of the general formula Li 1+x Ni 1-y-z-w Co y Mn z M wThe material contains a composite oxide represented by O2 (wherein M is one or more elements other than Li, Ni, Co, Mn, and O, and -0.1≦x≦0.15, 0≦y≦0.4, 0≦z≦0.4, 0≦w≦0.1), and when a sample of this composite oxide is charged to 4.30V with lithium as the counter electrode, and the temperature is increased from 50℃ to 600℃ at 5℃ / min, the differential thermogravimetric curve obtained is separated into multiple peaks, and in the temperature range of 150℃ to 350℃, there is a first peak in which the value of differential thermogravimetric at the peak top is the maximum value, and a second peak in which the value of differential thermogravimetric at the peak top is the maximum value among the peaks in which the peak top is located at a temperature 20℃ or more away from the temperature in which the peak top of the first peak is located, and the value of differential thermogravimetric at the peak top of the first peak is between 1 and 9.

[0019] When oxygen release from the positive electrode active material occurs at multiple temperature ranges that are far apart from each other, the oxygen release per temperature range is suppressed compared to when the oxygen release from the positive electrode active material occurs at only one narrow temperature range. As a result, the reaction with the electrolyte is also suppressed, and the amount of heat generated decreases. Therefore, by ensuring that oxygen release from the positive electrode active material occurs at multiple temperature ranges that are far apart from each other, thermal runaway of the positive electrode active material can be suppressed.

[0020] The inventors of this invention confirmed by TG-MS that when TG measurements were performed on a composite oxide, almost all of the weight loss at temperatures up to around 350°C was due to oxygen release. As a result, oxygen release from the positive electrode active material occurs in the temperature range of 150°C to 350°C, while the positive electrode active material does not undergo any other reactions in this temperature range. Therefore, when the differential thermogravimetric curve (hereinafter sometimes referred to as the "DTG curve") of the positive electrode active material is separated into multiple peaks, it is determined that in the temperature range of 150°C to 350°C, there is a first peak which is the largest, and a second peak which is separated from it by a temperature of 20°C or more, and the magnitude of the first peak is 9 times or less the magnitude of the second peak, indicating that oxygen release from the positive electrode active material occurs in multiple temperature ranges that are separated from each other.

[0021] On the other hand, in the DTG curve, if it cannot be separated into multiple peaks (consisting of a single peak), or if it can be separated into multiple peaks but the magnitude of the first peak is much larger than the magnitude of the second peak, then oxygen release from the positive electrode active material occurs within a single narrow temperature range, making thermal runaway more likely.

[0022] The requirements for a positive electrode active material to exhibit such a DTG curve involve numerous factors, including the elemental composition, crystal structure, crystallinity, and synthesis conditions of the positive electrode active material, and can also change depending on the balance of these factors. Materials that tend to exhibit such a DTG curve include those with the general formula Li 1+x Ni 1-y-z-w Co y Mn z M w A composite oxide represented by O2 (wherein M is one or more elements other than Li, Ni, Co, Mn, and O, and -0.1 ≤ x ≤ 0.15, 0 ≤ y ≤ 0.4, 0 ≤ z ≤ 0.4, 0 ≤ w ≤ 0.1) is an example, but even if a compound has such a composition, the two predetermined peaks of the DTG curve do not necessarily satisfy the above requirements. In other words, the two predetermined peaks of the DTG curve do not depend solely on the composition of the compound.

[0023] The following describes the mechanism by which a composite oxide releases oxygen in a charged state where a large amount of lithium is desorbed from the crystal structure, and the crystal structure is generally unstable. 1-x-δ Let's take NiO2 as an example. When such a composite oxide is used as the positive electrode active material and heated in a charged state, the crystalline state undergoes a phase transition from a layered rock salt structure (R-3m) to a spinel structure (Fd-3m) or rock salt structure (Fm3m) within a specific temperature range, as shown in equations (1) and (2) below. The temperature of these phase transitions depends on the charging depth, but occurs in a temperature range of approximately 190-310°C. Furthermore, as is clear from equations (1) and (2), it is thought that this process proceeds while generating oxygen gas.

[0024] Formula (1): Li 1-x-δ NiO2 (Layered rock salt structure R-3m) →{(1-x-δ) / (1-δ)}Li 1-δ NiO2 (Layered rock salt structure 1 R-3m) +{x / 3(1-δ)}Ni3O4 (Spinel structure Fd-3m) +{x / 3(1-δ)}O2↑

[0025] Formula (2): ·{(1-x-δ) / (1-δ)}Li 1-δ NiO2 (Layered rock salt structure 1 R-3m) →(1-x-δ)LiNiO2 (Layered rock salt structure 2 R-3m) +{δ(1-x-δ) / (1-δ)}NiO(Rock salt structure 1 Fm3m) +{δ(1-x-δ) / 2(1-δ)}O2↑ ·{x / 3(1-δ)}Ni3O4 (Spinel structure Fd-3m) →{x / 3(1-δ)}NiO (rock salt structure 2 Fm3m) +{x / 6(1-δ)}O2↑

[0026] Note that, although the "-" in R-3m should normally be placed above the 3, for convenience it is written as above. Similarly, although the "-" in Fd-3m should normally be placed above the 3, for convenience it is written as above.

[0027] The inventors believed that the rapid generation of this oxygen gas would have a significant impact on the thermal stability of a charged non-aqueous electrolyte secondary battery.

[0028] When a charged non-aqueous electrolyte secondary battery overheats and its temperature rises, the oxygen gas generated by the reactions in equations (1) and (2) primarily oxidizes (including combustion) the organic electrolyte within the battery. Since this reaction is exothermic, the temperature of the non-aqueous electrolyte secondary battery rises. This temperature rise further oxidizes the electrolyte and generates heat, leading to an uncontrollable temperature increase and ultimately thermal runaway.

[0029] The increase in temperature is proportional to the difference between the amount of heat generated per unit time in the non-aqueous electrolyte secondary battery and the amount of heat dissipated per unit time from the non-aqueous electrolyte secondary battery. Therefore, by preventing the heat generation amount and heat flow from being concentrated in a short time according to Formula (1) and Formula (2), the temperature increase can be suppressed, and the safety can be enhanced by preventing thermal runaway, which is uncontrollable.

[0030] From the above, the inventors considered that it is most important to suppress the oxygen release rate from the positive electrode active material in order to suppress thermal runaway that becomes uncontrollable. And for that purpose, it can be said that it is effective to adjust so that oxygen release of the composite oxide occurs in a plurality of temperature ranges as in the present disclosure and to control so that rapid oxygen release does not occur in a narrow temperature range.

[0031] [Chemical Structure] As the composite oxide, those represented by the general formula Li[Li x (Ni 1-y-z-w Co y Mn z M w ) 1-x O2 (where M is one or more elements other than Li, Ni, Co, Mn, and O, and -0.1 ≤ x ≤ 0.15, 0 < y ≤ 0.4, 0 ≤ z ≤ 0.4, 0 ≤ w ≤ 0.1) are not particularly limited as long as they are represented by the formula.

[0032] In the present disclosure, the reason why the composite oxide as the positive electrode active material shows a plurality of peaks is not necessarily clear and is not limited to a specific theory, but the inventors consider as follows. In such a composite oxide, at a high SOC charge state, most of the Ni in the positive electrode active material is oxidized to a high-valence Ni<Q000031>and is reduced in the temperature range of 150°C to 350°C to become Ni / 2+ state. At this time, since the ionic radius of Ni 2+ is almost the same as that of Li + , Ni 2+ will move to the Li layer. The inventors believe that this reduction of Ni 4+ and Ni 2+The migration of Ni to the Li layer occurs almost simultaneously, and we thought that if we could suppress this migration, we could also suppress the reduction. 2+ For Ni to move to the Li layer 2+ It is necessary to move from the oxygen octahedron position in the metal layer where it exists, through the empty oxygen tetrahedron position in contact with it, and then to the empty oxygen octahedron position in the Li layer that is in contact with it. Therefore, Ni 2+ If the energy barrier for Ni to move to empty tetrahedron or octahedron positions can be increased, then more energy will be required for the movement, and thus it will be reduced at a higher temperature. 2+ By distributing the height of the barrier required for the movement of Ni, it is possible to distribute the temperature range in which high-valence Ni is reduced. This suppresses the amount of Ni reduced in one narrow temperature range, thereby suppressing the amount of oxygen released, and thus lowering the DTG peak in one narrow temperature range. Therefore, it has been found that if a composite oxide exhibits this phenomenon depending on the ratio of Li, Ni, Co, Mn and element M, the type of element M, the crystallinity of the composite oxide, and the synthesis conditions of the composite oxide, then when used as a positive electrode active material, it is possible to distribute the temperature range in which oxygen is released over multiple ranges while maintaining the basic functions (charge capacity and cycle characteristics) of a non-aqueous electrolyte secondary battery, and as described above, the peak value of DTG can be lowered.

[0033] Specifically, it depends on the combination of other elements contained in the composite oxide, the crystallinity of the composite oxide, and the synthesis conditions, but if the composite oxide contains Co, the temperature is between approximately 230 and 270°C. 3+ and Co 4+ Co 2+ It is thought to be reduced to form a spinel structure of Co3O4 and remain in the oxygen tetrahedron position of the Li layer. This oxygen tetrahedron position is Ni 2+ This is the pathway for the movement of oxygen to the octahedral position, and this position is Co 2+ By occupying Ni 2+This is thought to make it easier to suppress the movement of oxygen to the octahedral position. Therefore, in such cases, when a composite oxide is used as the positive electrode active material, it may be possible to distribute the temperature range in which oxygen is released over multiple ranges while maintaining the basic functions (charge capacity and cycle characteristics) of a non-aqueous electrolyte secondary battery, and as mentioned above, to lower the peak value of DTG.

[0034] In the general formula, the value of x is not particularly limited as long as it is within the range of -0.10 ≤ x ≤ 0.15, but for example, -0.095 or greater, -0.09 or greater, -0.085 or greater, -0.08 or greater, -0.075 or greater, -0.07 or greater, -0.065 or greater, -0.06 or greater, -0.055 or greater, -0.05 or greater, -0.045 or greater, -0.04 or greater, -0.035 or greater, -0.03 or greater, -0.025 or greater, -0.02 or greater, -0.015 or greater, -0.01 or greater, -0.0095 or greater. -0.009 or higher, -0.0085 or higher, -0.008 or higher, -0.0075 or higher, -0.007 or higher, -0.0065 or higher, -0.006 or higher, -0.0055 or higher, -0.005 or higher, -0.0045 or higher, -0.004 or higher, -0.0035 or higher, -0.003 or higher, -0.0025 or higher, -0.002 or higher, -0.0015 or higher, -0.001 or higher, 0 or higher, 0.001 or higher, 0.0015 or higher, 0.002 or higher, 0.0025 or higher, 0.003 or higher, 0.0035 or higher, 0.004 or higher, 0.0045 or higher, 0.005 or higher, 0.0055 or higher, 0.006 or higher, 0.0065 or higher, 0.007 or higher, 0.0075 or higher, 0.008 or higher, 0.0085 or higher, 0.009 or higher, 0.0095 or higher, 0.01 or higher, 0.015 or higher, 0.02 or higher, 0.025 or higher, 0.03 or higher, 0.035 or higher, 0.04 or higher, 0.045 or higher, 0.05 or higher, 0.055 or higher, 0.06 or higher, 0.065 or higher, 0.07 or higher, Preferably, the values ​​are 0.075 or higher, 0.08 or higher, 0.085 or higher, 0.09 or higher, 0.095 or higher, 0.1 or higher, 0.102 or higher, 0.105 or higher, 0.107 or higher, 0.11 or higher, 0.112 or higher, 0.115 or higher, 0.117 or higher, 0.122 or higher, 0.125 or higher, 0.127 or higher, 0.13 or higher, 0.132 or higher, 0.135 or higher, 0.137 or higher, 0.14 or higher, 0.142 or higher, 0.145 or higher, 0.147 or higher, and 0.15 or higher.On the other hand, the values ​​of x are: 0.147 or less, 0.145 or less, 0.142 or less, 0.14 or less, 0.137 or less, 0.135 or less, 0.132 or less, 0.13 or less, 0.127 or less, 0.125 or less, 0.122 or less, 0.12 or less, 0.117 or less, 0.115 or less, 0.112 or less, 0.11 or less, 0.107 or less, 0.105 or less, 0.102 or less, 0.1 or less, 0.095 or less, 0.09 or less, 0.085 or less, 0.08 or less, 0. 075 or less, 0.07 or less, 0.065 or less, 0.06 or less, 0.055 or less, 0.05 or less, 0.045 or less, 0.04 or less, 0.035 or less, 0.03 or less, 0.025 or less, 0.02 or less, 0.015 or less, 0.0 1 or less, 0.0095 or less, 0.009 or less, 0.0085 or less, 0.008 or less, 0.0075 or less, 0.007 or less, 0.0065 or less, 0.006 or less, 0.0055 or less, 0.005 or less, 0.0045 or less, 0 .004 or less, 0.0035 or less, 0.003 or less, 0.0025 or less, 0.002 or less, 0.0015 or less, 0.001 or less, 0 or less, -0.001 or less, -0.0015 or less, -0.002 or less, -0.0025 or less , -0.003 or less, -0.0035 or less, -0.004 or less, -0.0045 or less, -0.005 or less, -0.0055 or less, -0.006 or less, -0.0065 or less, -0.007 or less, -0.0075 or less, -0. Preferably, the values ​​of x are 0.08 or less, -0.0085 or less, -0.009 or less, -0.0095 or less, -0.01 or less, -0.015 or less, -0.02 or less, -0.025 or less, -0.03 or less, -0.035 or less, -0.04 or less, -0.045 or less, -0.05 or less, -0.055 or less, -0.06 or less, -0.065 or less, -0.07 or less, -0.075 or less, -0.08 or less, -0.085 or less, -0.09 or less, and -0.095 or less. A value of x being within the required range means that the Li content is within the required range. By setting the value of x to a value greater than or equal to the required value, the Li content can be increased, the Li vacancies can be reduced, the first reduction of Ni occurring between approximately 200 and 250°C can be suppressed, and the rate of the second reduction occurring between approximately 260 and 320°C can be increased. As a result, the peak top on the low-temperature side of the differential thermogravimetric curve tends to decrease, while the peak top on the high-temperature side tends to increase.By keeping the value of x below the required value, a certain amount of vacancies in Li can be ensured, thereby suppressing a decrease in charging capacity.

[0035] In the general formula, the value of 1-yzw is not particularly limited as long as it is a combination of y, z, and w within their possible ranges, but for example, it could be 0.6 or greater, 0.605 or greater, 0.61 or greater, 0.615 or greater, 0.62 or greater, 0.625 or greater, 0.63 or greater, 0.635 or greater, 0.64 or greater, 0.645 or greater, 0.65 or greater, 0.655 or greater, 0.66 or greater, 0.665 or greater, 0.67 or greater, 0.675 or greater, 0.68 or greater, 0. It is preferable that the values ​​are 685 or higher, 0.69 or higher, 0.695 or higher, 0.70 or higher, 0.705 or higher, 0.71 or higher, 0.715 or higher, 0.72 or higher, 0.725 or higher, 0.73 or higher, 0.735 or higher, 0.74 or higher, 0.745 or higher, 0.75 or higher, 0.755 or higher, 0.76 or higher, 0.765 or higher, 0.77 or higher, 0.775 or higher, 0.78 or higher, 0.785 or higher, 0.79 or higher, or 0.795 or higher. On the other hand, the value of 1-yzw may be less than or equal to 1, less than or equal to 0.995, less than or equal to 0.99, less than or equal to 0.985, less than or equal to 0.98, less than or equal to 0.975, less than or equal to 0.97, less than or equal to 0.965, less than or equal to 0.96, less than or equal to 0.955, less than or equal to 0.95, less than or equal to 0.945, less than or equal to 0.94, less than or equal to 0.935, less than or equal to 0.93, less than or equal to 0.925, less than or equal to 0.92, less than or equal to 0.915, less than or equal to 0.91, less than or equal to 0.905, less than or equal to 0.90, less than or equal to 0.895, less than or equal to 0.89, less than or equal to 0.885, less than or equal to 0.88, less than or equal to 0.875, less than or equal to 0.87, less than or equal to 0.865, less than or equal to 0.86, less than or equal to 0.855, less than or equal to 0.85, less than or equal to 0.845, or less than or equal to 0.84. A 1-yzw value within the required range means that the Ni content is within the required range. By setting the 1-yzw value above the required value, the amount of Ni moving within the composite oxide can be increased. On the other hand, by setting the 1-yzw value below a certain level, depending on the balance with other elements, it may be possible to include elements with functional properties that can inhibit the movement of some Ni.

[0036] In the general formula, the value of y is not particularly limited as long as it is within the range 0 ≤ y ≤ 0.4, but for example, greater than 0, 0.001 or greater, 0.0015 or greater, 0.002 or greater, 0.0025 or greater, 0.003 or greater, 0.0035 or greater, 0.004 or greater, 0.0045 or greater, 0.005 or greater, 0.0055 or greater, 0.006 or greater, 0.0065 or greater, 0.007 or greater, 0.0075 or greater, 0.008 or greater, 0.0085 or greater, 0.009 or greater, 0.0095 or greater, 0.01 or greater, 0.015 or greater, 0.02 or greater, 0.025 or greater, 0.03 or greater, 0.035 or greater, 0.04 or greater, 0.045 or higher, 0.05 or higher, 0.055 or higher, 0.06 or higher, 0.065 or higher, 0.07 or higher, 0.075 or higher, 0.08 or higher, 0.085 or higher, 0.09 or higher, 0.095 or higher, 0.1 or higher, 0.102 or higher, 0.105 or higher, 0.107 or higher, 0.11 or higher, 0.112 or higher, 0.115 or higher, 0.117 or higher, 0.12 or higher, 0.122 or higher, 0.125 or higher, 0.127 or higher, 0.13 or higher, 0.132 or higher, 0.135 or higher, 0.137 or higher, 0.14 or higher, 0.142 or higher, 0.145 or higher, 0.147 or higher, 0.15 or higher, 0.152 Above, 0.155 or above, 0.157 or above, 0.16 or above, 0.162 or above, 0.165 or above, 0.167 or above, 0.17 or above, 0.172 or above, 0.175 or above, 0.177 or above, 0.18 or above, 0.182 or above, 0.185 or above, 0.187 or above, 0.19 or above, 0.192 or above, 0.195 or above, 0.197 or above, 0.2 or above, 0.202 or above, 0.205 or above, 0.207 or above, 0.21 or above, 0.212 or above, 0.215 or above, 0.217 or above, 0.222 or above, 0.225 or above, 0.227 or above, 0.23 or above, 0.232 or above , 0.235 or higher, 0.237 or higher, 0.24 or higher, 0.242 or higher, 0.245 or higher, 0.247 or higher, 0.25 or higher, 0.252 or higher, 0.255 or higher, 0.257 or higher, 0.26 or higher, 0.262 or higher, 0.265 or higher, 0.267 or higher, 0.27 or higher, 0.272 or higher, 0.275 or higher, 0.277 or higher, 0.28 or higher, 0.282 or higher, 0.285 or higher, 0.287 or higher, 0.29 or higher, 0.292 or higher, 0.295 or higher, 0.297 or higher, 0.3 or higher, 0.302 or higher, 0.305 or higher, 0.307 or higher, 0.31 or higher, 0.312 or higher, 0.Preferably, the values ​​are 315 or higher, 0.317 or higher, 0.32 or higher, 0.322 or higher, 0.325 or higher, 0.327 or higher, 0.33 or higher, 0.332 or higher, 0.335 or higher, 0.337 or higher, 0.34 or higher, 0.342 or higher, 0.345 or higher, 0.347 or higher, 0.352 or higher, 0.355 or higher, 0.357 or higher, 0.36 or higher, 0.362 or higher, 0.365 or higher, 0.367 or higher, 0.372 or higher, 0.375 or higher, 0.377 or higher, 0.38 or higher, 0.382 or higher, 0.385 or higher, 0.387 or higher, 0.39 or higher, 0.392 or higher, 0.395 or higher, and 0.397 or higher. On the other hand, the values ​​of y are 0.397 or less, 0.395 or less, 0.392 or less, 0.39 or less, 0.387 or less, 0.385 or less, 0.382 or less, 0.38 or less, 0.377 or less, 0.375 or less, 0 .372 or less, 0.367 or less, 0.365 or less, 0.362 or less, 0.36 or less, 0.357 or less, 0.355 or less, 0.352 or less, 0.35 or less, 0.347 or less, 0.345 or less, 0.342 or less Below, 0.34 or less, 0.337 or less, 0.335 or less, 0.332 or less, 0.33 or less, 0.327 or less, 0.325 or less, 0.322 or less, 0.32 or less, 0.317 or less, 0.315 or less, 0.3 12 or less, 0.31 or less, 0.307 or less, 0.305 or less, 0.302 or less, 0.3 or less, 0.297 or less, 0.295 or less, 0.292 or less, 0.29 or less, 0.287 or less, 0.285 or less, 0. 282 or less, 0.28 or less, 0.277 or less, 0.275 or less, 0.272 or less, 0.27 or less, 0.267 or less, 0.265 or less, 0.26 or less, 0.257 or less, 0.255 or less, 0.252 or less , 0.25 or less, 0.247 or less, 0.245 or less, 0.242 or less, 0.24 or less, 0.237 or less, 0.235 or less, 0.232 or less, 0.23 or less, 0.227 or less, 0.225 or less, 0.222 0.22 or less, 0.217 or less, 0.215 or less, 0.212 or less, 0.21 or less, 0.207 or less, 0.205 or less, 0.202 or less, 0.2 or less, 0.197 or less, 0.195 or less, 0.19 2 or less, 0.19 or less, 0.187 or less, 0.185 or less, 0.182 or less, 0.18 or less, 0.177 or less, 0.175 or less, 0.172 or less, 0.17 or less, 0.167 or less, 0.165 or less, 0.162 or less, 0.16 or less, 0.155 or less, 0.152 or less, 0.15 or less, 0.147 or less, 0.145 or less, 0.142 or less, 0.14 or less, 0.137 or less, 0.135 or less, 0.132 or less, 0.13 or less, 0.127 or less, 0.125 or less, 0.122 or less, 0.12 or less, 0.117 or less, 0.115 or less, 0.112 or less, 0.11 or less, 0.107 or less, 0.105 or less, 0.102 or less, 0.1 or less, 0.095 or less, 0.09 or less, 0.085 or less, 0.08 or less, 0.075 or less, 0.07 or less, 0.065 or less, 0 Preferably, the values ​​are 0.06 or less, 0.055 or less, 0.05 or less, 0.045 or less, 0.04 or less, 0.035 or less, 0.03 or less, 0.025 or less, 0.02 or less, 0.015 or less, 0.01 or less, 0.0095 or less, 0.009 or less, 0.0085 or less, 0.008 or less, 0.0075 or less, 0.007 or less, 0.0065 or less, 0.006 or less, 0.0055 or less, 0.005 or less, 0.0045 or less, 0.004 or less, 0.0035 or less, 0.003 or less, 0.0025 or less, 0.002 or less, 0.0015 or less, and 0.001 or less. A value of y being within the required range means that the Co content is within the required range. By setting the value of y to a value greater than or equal to the required value, Co is increased, which in turn increases Ni. 4+ This can increase the amount of reduction in the second round. On the other hand, even if the value of y is set above a certain level, the increase in the amount of reduction in the second round may be capped, so it should be kept below the required value.

[0037] In the general formula, the value of z is not particularly limited as long as it is within the range of 0 ≤ z ≤ 0.4, but for example, 0.001 or more, 0.0015 or more, 0.002 or more, 0.0025 or more, 0.003 or more, 0.0035 or more, 0.004 or more, 0.0045 or more, 0.005 or more, 0.0055 or more, 0.006 or more, 0.0065 or more, 0.007 or more, 0.0075 or more, 0.008 or more, 0.0085 or more, 0.009 or more, 0.0095 or more, 0.01 or more, 0.015 or more, 0.02 or more, 0.025 or more, 0.03 or more, 0.035 or more, 0.04 or more, 0. 0.45 or higher, 0.05 or higher, 0.055 or higher, 0.06 or higher, 0.065 or higher, 0.07 or higher, 0.075 or higher, 0.08 or higher, 0.085 or higher, 0.09 or higher, 0.095 or higher, 0.1 or higher, 0.102 or higher, 0.105 or higher, 0.107 or higher, 0.11 or higher, 0.112 or higher, 0.115 or higher, 0.117 or higher, 0.12 or higher, 0.122 or higher, 0.125 or higher, 0.127 or higher, 0.13 or higher, 0.132 or higher, 0.135 or higher, 0.137 or higher, 0.14 or higher, 0.142 or higher, 0.145 or higher, 0.147 or higher, 0.15 or higher, 0.152 or higher , 0.155 or higher, 0.157 or higher, 0.16 or higher, 0.162 or higher, 0.165 or higher, 0.167 or higher, 0.17 or higher, 0.172 or higher, 0.175 or higher, 0.177 or higher, 0.18 or higher, 0.182 or higher, 0.185 or higher, 0.187 or higher, 0.19 or higher, 0.192 or higher, 0.195 or higher, 0.197 or higher, 0.2 or higher, 0.202 or higher, 0.205 or higher, 0.207 or higher, 0.21 or higher, 0.212 or higher, 0.215 or higher, 0.217 or higher, 0.222 or higher, 0.225 or higher, 0.227 or higher, 0.23 or higher, 0.232 or higher, 0.235 or higher, 0.237 or higher, 0.24 or higher, 0.242 or higher, 0.245 or higher, 0.247 or higher, 0.25 or higher, 0.252 or higher, 0.255 or higher, 0.257 or higher, 0.26 or higher, 0.262 or higher, 0.265 or higher, 0.267 or higher, 0.27 or higher, 0.272 or higher, 0.275 or higher, 0.277 or higher, 0.28 or higher, 0.282 or higher, 0.285 or higher, 0.287 or higher, 0.29 or higher, 0.292 or higher, 0.295 or higher, 0.297 or higher, 0.3 or higher, 0.302 or higher, 0.305 or higher, 0.307 or higher, 0.31 or higher, 0.312 or higher, 0.Preferably, the values ​​are 315 or higher, 0.317 or higher, 0.32 or higher, 0.322 or higher, 0.325 or higher, 0.327 or higher, 0.33 or higher, 0.332 or higher, 0.335 or higher, 0.337 or higher, 0.34 or higher, 0.342 or higher, 0.345 or higher, 0.347 or higher, 0.352 or higher, 0.355 or higher, 0.357 or higher, 0.36 or higher, 0.362 or higher, 0.365 or higher, 0.367 or higher, 0.372 or higher, 0.375 or higher, 0.377 or higher, 0.38 or higher, 0.382 or higher, 0.385 or higher, 0.387 or higher, 0.39 or higher, 0.392 or higher, 0.395 or higher, and 0.397 or higher. On the other hand, the values ​​of z are 0.397 or less, 0.395 or less, 0.392 or less, 0.39 or less, 0.387 or less, 0.385 or less, 0.382 or less, 0.38 or less, 0.377 or less, 0.375 or less, 0 .372 or less, 0.367 or less, 0.365 or less, 0.362 or less, 0.36 or less, 0.357 or less, 0.355 or less, 0.352 or less, 0.35 or less, 0.347 or less, 0.345 or less, 0.342 or less Below, 0.34 or less, 0.337 or less, 0.335 or less, 0.332 or less, 0.33 or less, 0.327 or less, 0.325 or less, 0.322 or less, 0.32 or less, 0.317 or less, 0.315 or less, 0.3 12 or less, 0.31 or less, 0.307 or less, 0.305 or less, 0.302 or less, 0.3 or less, 0.297 or less, 0.295 or less, 0.292 or less, 0.29 or less, 0.287 or less, 0.285 or less, 0. 282 or less, 0.28 or less, 0.277 or less, 0.275 or less, 0.272 or less, 0.27 or less, 0.267 or less, 0.265 or less, 0.26 or less, 0.257 or less, 0.255 or less, 0.252 or less , 0.25 or less, 0.247 or less, 0.245 or less, 0.242 or less, 0.24 or less, 0.237 or less, 0.235 or less, 0.232 or less, 0.23 or less, 0.227 or less, 0.225 or less, 0.222 0.22 or less, 0.217 or less, 0.215 or less, 0.212 or less, 0.21 or less, 0.207 or less, 0.205 or less, 0.202 or less, 0.2 or less, 0.197 or less, 0.195 or less, 0.19 2 or less, 0.19 or less, 0.187 or less, 0.185 or less, 0.182 or less, 0.18 or less, 0.177 or less, 0.175 or less, 0.172 or less, 0.17 or less, 0.167 or less, 0.165 or less, 0.162 or less, 0.16 or less, 0.155 or less, 0.152 or less, 0.15 or less, 0.147 or less, 0.145 or less, 0.142 or less, 0.14 or less, 0.137 or less, 0.135 or less, 0.132 or less, 0.13 or less, 0.127 or less, 0.125 or less, 0.122 or less, 0.12 or less, 0.117 or less, 0.115 or less, 0.112 or less, 0.11 or less, 0.107 or less, 0.105 or less, 0.102 or less, 0.1 or less, 0.095 or less, 0.09 or less, 0.085 or less, 0.08 or less, 0.075 or less, 0.07 or less, 0.065 or less, 0 Preferably, the values ​​are 0.06 or less, 0.055 or less, 0.05 or less, 0.045 or less, 0.04 or less, 0.035 or less, 0.03 or less, 0.025 or less, 0.02 or less, 0.015 or less, 0.01 or less, 0.0095 or less, 0.009 or less, 0.0085 or less, 0.008 or less, 0.0075 or less, 0.007 or less, 0.0065 or less, 0.006 or less, 0.0055 or less, 0.005 or less, 0.0045 or less, 0.004 or less, 0.0035 or less, 0.003 or less, 0.0025 or less, 0.002 or less, 0.0015 or less, and 0.001 or less. A value of z within the required range means that the Mn content is within the required range. By setting the value of z above the required value, the formation of Li2MnO3 is facilitated, increasing the number of Li vacancies and promoting the migration of Ni and Co into the Li layer. By setting the value of z below the required value, the increase in Li2MnO3 formation can suppress the decrease in charging capacity caused by an excessive increase in Li vacancies.

[0038] In the general formula, the value of w is not particularly limited as long as it is within the range of 0 ≤ w ≤ 0.1, but for example, 0.001 or more, 0.0012 or more, 0.0015 or more, 0.0017 or more, 0.002 or more, 0.0022 or more, 0.0025 or more, 0.0027 or more, 0.003 or more, 0.0032 or more, 0.0035 or more, 0.0037 or more, 0.004 or more, 0.0042 or more. Above, 0.0045 or higher, 0.0047 or higher, 0.005 or higher, 0.0052 or higher, 0.0055 or higher, 0.0057 or higher, 0.006 or higher, 0.0062 or higher, 0.0065 or higher, 0.0067 or higher, 0.007 or higher, 0.0072 or higher, 0.0075 or higher, 0.0077 or higher, 0.008 or higher, 0.0082 or higher, 0.0085 or higher, 0.0087 or higher, 0 0.009 or higher, 0.0092 or higher, 0.0095 or higher, 0.0097 or higher, 0.01 or higher, 0.012 or higher, 0.015 or higher, 0.017 or higher, 0.02 or higher, 0.022 or higher, 0.025 or higher, 0.027 or higher, 0.03 or higher, 0.032 or higher, 0.035 or higher, 0.037 or higher, 0.04 or higher, 0.042 or higher, 0.045 or higher, 0.047 or higher, 0.0 Preferably, the values ​​are 5 or higher, 0.052 or higher, 0.055 or higher, 0.057 or higher, 0.06 or higher, 0.062 or higher, 0.065 or higher, 0.067 or higher, 0.07 or higher, 0.072 or higher, 0.075 or higher, 0.077 or higher, 0.08 or higher, 0.082 or higher, 0.085 or higher, 0.087 or higher, 0.09 or higher, 0.092 or higher, 0.095 or higher, and 0.097 or higher.On the other hand, the values ​​of w are 0.097 or less, 0.095 or less, 0.092 or less, 0.09 or less, 0.087 or less, 0.085 or less, 0.082 or less, 0.08 or less, 0.077 or less, 0.075 or less, 0.072 or less, 0.07 or less, 0.067 or less, 0.065 or less, 0.062 or less, 0.06 or less, 0.057 or less, 0.055 or less, 0. 052 or less, 0.05 or less, 0.047 or less, 0.045 or less, 0.042 or less, 0.04 or less, 0.037 or less, 0.035 or less, 0.032 or less, 0.03 or less, 0. 027 or less, 0.025 or less, 0.022 or less, 0.02 or less, 0.017 or less, 0.015 or less, 0.012 or less, 0.01 or less, 0.0097 or less, 0.0095 or less , 0.0092 or less, 0.009 or less, 0.0087 or less, 0.0085 or less, 0.0082 or less, 0.008 or less, 0.0077 or less, 0.0075 or less, 0.0072 less than or equal to 0.007, less than or equal to 0.0067, less than or equal to 0.0065, less than or equal to 0.0062, less than or equal to 0.006, less than or equal to 0.0057, less than or equal to 0.0055, less than or equal to 0.0052, 0.00 It is preferable that the value of w is 5 or less, 0.0047 or less, 0.0045 or less, 0.0042 or less, 0.004 or less, 0.0037 or less, 0.0035 or less, 0.0032 or less, 0.003 or less, 0.0027 or less, 0.0025 or less, 0.0022 or less, 0.002 or less, 0.0017 or less, 0.0015 or less, 0.0012 or less, or 0.001 or less. A value of w within the required range means that the content of element M is within the required range. By setting the value of w to be greater than or equal to the required value, the effects of adding element M can be realized. By setting the value of w to be less than or equal to the required value, the content of Ni, Co, and Mn can be ensured, and battery performance, including high charging capacity, can be maintained.

[0039] In the formula, element M is not particularly limited as long as it is one or more elements other than Li, Ni, Co, Mn, and O, but for example, Al, Ti, Mg, Zn, Nb, W, Mo, Sb, V, Cr, Ca, Fe, Ga, Sr, Y, Ru, In, Sn, Ta, Bi, Zr, B, etc. can be used. The type of element M should be selected according to the purpose of addition. Also, if element M contains multiple elements, the value of w represents the total amount of the multiple elements.

[0040] Among these, it is preferable to use Al as element M. When Al is used as element M, Al is fixed to a specific site and forms a stable structure. As a result, Li in the vicinity of Al + Li becomes difficult to move, + and Ni 2+ Cationic mixing is suppressed, and higher temperatures are required for oxygen release in some parts of the complex oxide. Therefore, when the complex oxide contains Al, the peak in the DTG curve caused by oxygen release occurring between approximately 200 and 250°C becomes broader compared to when it does not contain Li2MnO3, making it easier to suppress thermal runaway.

[0041] w contains only Al AlThe value is not particularly limited, but for example, it could be 0 or greater, 0.001 or greater, 0.0012 or greater, 0.0015 or greater, 0.0017 or greater, 0.0022 or greater, 0.0025 or greater, 0.0027 or greater, 0.003 or greater, 0.0032 or greater, 0.0035 or greater, 0.0037 or greater, 0.004 or greater, 0.0042 or greater, 0.0045 or greater, 0. 0.0047 or higher, 0.005 or higher, 0.0052 or higher, 0.0055 or higher, 0.0057 or higher, 0.0062 or higher, 0.0065 or higher, 0.0067 or higher, 0.007 or higher, 0.0072 or higher, 0.0075 or higher, 0.0077 or higher, 0.008 or higher, 0.0082 or higher, 0.0085 or higher, 0.0087 or higher, 0.009 or higher, 0. 0.092 or higher, 0.0095 or higher, 0.0097 or higher, 0.01 or higher, 0.012 or higher, 0.015 or higher, 0.017 or higher, 0.02 or higher, 0.022 or higher, 0.025 or higher, 0.027 or higher, 0.03 or higher, 0.032 or higher, 0.035 or higher, 0.037 or higher, 0.04 or higher, 0.042 or higher, 0.045 or higher, 0.047 or higher, 0.05 or higher, 0 Preferably, the values ​​are 0.052 or higher, 0.055 or higher, 0.057 or higher, 0.06 or higher, 0.062 or higher, 0.065 or higher, 0.067 or higher, 0.07 or higher, 0.072 or higher, 0.075 or higher, 0.077 or higher, 0.08 or higher, 0.082 or higher, 0.085 or higher, 0.087 or higher, 0.09 or higher, 0.092 or higher, 0.095 or higher, and 0.097 or higher.On the other hand, the values ​​of w are: 0.1 or less, 0.097 or less, 0.095 or less, 0.092 or less, 0.09 or less, 0.087 or less, 0.085 or less, 0.082 or less, 0.08 or less, 0.077 or less, 0.075 or less, 0.072 or less, 0.07 or less, 0.067 or less, 0.065 or less, 0.062 or less, 0.06 or less, 0.057 or less, 0.055 or less. Below, 0.052 or less, 0.05 or less, 0.047 or less, 0.045 or less, 0.042 or less, 0.04 or less, 0.037 or less, 0.035 or less, 0.032 or less, 0.03 or less Lower, 0.027 or less, 0.025 or less, 0.022 or less, 0.02 or less, 0.017 or less, 0.015 or less, 0.012 or less, 0.01 or less, 0.0097 or less, 0.009 5 or less, 0.0092 or less, 0.009 or less, 0.0087 or less, 0.0085 or less, 0.0082 or less, 0.008 or less, 0.0077 or less, 0.0075 or less, 0.0 072 or less, 0.007 or less, 0.0067 or less, 0.0065 or less, 0.0062 or less, 0.006 or less, 0.0057 or less, 0.0055 or less, 0.0052 or less, 0. It is preferable that the values ​​are 0.005 or less, 0.0047 or less, 0.0045 or less, 0.0042 or less, 0.004 or less, 0.0037 or less, 0.0035 or less, 0.0032 or less, 0.003 or less, 0.0027 or less, 0.0025 or less, 0.0022 or less, 0.002 or less, 0.0017 or less, 0.0015 or less, 0.0012 or less, and 0.001 or less. Al The fact that the value is within the required range means that the Al content is within the required range. Al By setting the value of to above the required value, the peak caused by oxygen release occurring between approximately 200 and 250°C in the DTG curve, which is obtained by adding Al, can be broadened, thereby suppressing thermal runaway. Al By keeping the value below the required value, the content of Ni, Co, and Mn can be ensured, and battery performance, including high charging capacity, can be maintained.

[0042] In the general formula, the value of z+w is not particularly limited as long as it is within the range of 0≦z≦0.4 and 0≦w≦0.1, but for example, 0 or greater, greater than 0, 0.001 or greater, 0.0015 or greater, 0.002 or greater, 0.0025 or greater, 0.003 or greater, 0.0035 or greater, 0.004 or greater, 0.0045 or greater, 0.005 or greater, 0.0055 or greater, 0.006 or greater, 0.0065 or greater, 0.007 or greater, 0.0075 or greater, 0.008 or greater, 0.0085 or greater, 0.009 or greater, 0.0095 or greater, 0.01 or greater, 0.015 or greater, 0.02 or greater, 0.025 or greater, 0.03 or greater, 0 .035 or more, 0.04 or more, 0.045 or more, 0.05 or more, 0.055 or more, 0.06 or more, 0.065 or more, 0.07 or more, 0.075 or more, 0.08 or more, 0.085 or more, 0.09 or more, 0.095 or more, 0.1 or more, 0.102 or more, 0.105 or more, 0.107 0.11 or more, 0.112 or more, 0.115 or more, 0.117 or more, 0.12 or more, 0.122 or more, 0.125 or more, 0.127 or more, 0.13 or more, 0.132 or more, 0.135 or more, 0.137 or more, 0.14 or more, 0.142 or more, 0.145 or more, 0.147 or more Above, 0.15 or higher, 0.152 or higher, 0.155 or higher, 0.157 or higher, 0.16 or higher, 0.162 or higher, 0.165 or higher, 0.167 or higher, 0.17 or higher, 0.172 or higher, 0.175 or higher, 0.177 or higher, 0.18 or higher, 0.182 or higher, 0.185 or higher, 0.187 or higher, 0.19 or higher, 0.192 or higher, 0.195 or higher, 0.197 or higher, 0.2 or higher, 0.202 or higher, 0.205 or higher, 0.207 or higher, 0.21 or higher, 0.212 or higher, 0.215 or higher, 0.217 or higher, 0.22 or higher, 0.222 or higher, 0.225 or higher, 0.227 or higher, 0.23 or higher, 0.232 or higher, 0.235 or higher, 0.237 or higher, 0.24 or higher, 0.242 or higher, 0.245 or higher, 0.247 or higher, 0.25 or higher, 0.252 or higher, 0.255 or higher, 0.257 or higher, 0.26 or higher, 0.262 or higher, 0.265 or higher, 0.267 or higher, 0.27 or higher, 0.272 or higher, 0.275 or higher, 0.277 or higher, 0.28 or higher, 0.282 or higher, 0.285 or higher, 0.287 or higher, 0.29 or higher, 0.292 or higher, 0.295 or higher, 0.297 or higher, 0.3 or higher, 0.302 or higher, 0.305 or higher, 0.307 or higher, 0.31 or higher, 0.312 or higher, 0.315 or higher, 0.317 or higher, 0.322 or higher, 0.325 or higher, 0.327 or higher, 0.33 or higher, 0.332 or higher, 0.335 or higher, 0.337 or higher, 0.342 or higher, 0.345 or higher, 0.347 or higher, 0.35 or higher, 0.352 or higher, 0.355 or higher, 0.35 7 or higher, 0.36 or higher, 0.362 or higher, 0.365 or higher, 0.367 or higher, 0.372 or higher, 0.375 or higher, 0.377 or higher, 0.38 or higher, 0.382 or higher, 0.385 or higher, 0.387 or higher, 0.39 or higher, 0.392 or higher, 0.395 or higher, 0.397 or higher, 0.4 or higher, 0.402 or higher, 0.405 or higher , 0.407 or higher, 0.41 or higher, 0.412 or higher, 0.415 or higher, 0.417 or higher, 0.422 or higher, 0.425 or higher, 0.427 or higher, 0.43 or higher, 0.432 or higher, 0.435 or higher, 0.437 or higher, 0.44 or higher, 0.442 or higher, 0.445 or higher, 0.447 or higher, 0.45 or higher, 0.452 or higher, 0 Preferably, the values ​​are 0.455 or higher, 0.457 or higher, 0.46 or higher, 0.462 or higher, 0.465 or higher, 0.467 or higher, 0.47 or higher, 0.472 or higher, 0.475 or higher, 0.477 or higher, 0.48 or higher, 0.482 or higher, 0.485 or higher, 0.487 or higher, 0.49 or higher, 0.492 or higher, 0.495 or higher, and 0.497 or higher. On the other hand, the values ​​of z+w are: 0.5 or less, 0.497 or less, 0.495 or less, 0.492 or less, 0.49 or less, 0.487 or less, 0.485 or less, 0.482 or less, 0.48 or less, 0.477 or less, 0.475 or less, 0.472 or less, 0.467 or less, 0.465 or less, 0.462 or less, 0.46 or less, 0.457 or less, 0.455 or less, 0.452 or less, 0.45 or less, 0.447 or less, 0.445 or less, 0.442 or less, 0.44 or less, 0. 437 or less, 0.435 or less, 0.432 or less, 0.43 or less, 0.427 or less, 0.425 or less, 0.422 or less, 0.42 or less, 0.417 or less, 0.415 or less, 0.412 or less, 0.41 or less, 0.407 or less, 0 .405 or less, 0.402 or less, 0.4 or less, 0.397 or less, 0.395 or less, 0.392 or less, 0.39 or less, 0.387 or less, 0.385 or less, 0.382 or less, 0.38 or less, 0.377 or less, 0.375 or less, 0.Below 372, below 0.367, below 0.365, below 0.362, below 0.36, below 0.357, below 0.355, below 0.352, below 0.35, below 0.347, below 0.345, below 0.342, below 0.34, below 0.337, below 0.335, below 0.332, below 0.33, below 0.327, below 0.325, below 0.322, below 0.32, below 0.317, below 0.315, below 0.312, below 0.31, below 0.307, below 0.305, below 0.302, below 0.3, below 0.297, below 0.295, below 0.292, 0. Below 29, below 0.287, below 0.285, below 0.282, below 0.28, below 0.277, below 0.275, below 0.272, below 0.27, below 0.267, below 0.265, below 0.26, below 0.257, below 0.255, below 0.252, below 0.25, below 0.247, below 0.245, below 0.242, below 0.24, below 0.237, below 0.235, below 0.232, below 0.23, below 0.227, below 0.225, below 0.222, below 0.22, below 0.217, below 0.215, below 0.212, below 0.21, 0.20 Below 7, below 0.205, below 0.202, below 0.2, below 0.197, below 0.195, below 0.192, below 0.19, below 0.187, below 0.185, below 0.182, below 0.18, below 0.177, below 0.175, below 0.172, below 0.17, below 0.167, below 0.165, below 0.162, below 0.16, below 0.155, below 0.152, below 0.15, below 0.147, below 0.145, below 0.142, below 0.14, below 0.137, below 0.135, below 0.132, below 0.13, below 0.127, below 0.125 Below, below 0.122, below 0.12, below 0.117, below 0.115, below 0.112, below 0.11, below 0.107, below 0.105, below 0.102, below 0.1, below 0.095, below 0.09, below 0.085, below 0.08, below 0.075, below 0.07, below 0.065, below 0.06, below 0.055, below 0.05, below 0.045, below 0.04, below 0.035, below 0.03, below 0.025, below 0.02, below 0.015, below 0.01, below 0.0095, below 0.009, below 0.0085, below 0.008, 0.Preferably, the values ​​are 0.0075 or less, 0.007 or less, 0.0065 or less, 0.006 or less, 0.0055 or less, 0.005 or less, 0.0045 or less, 0.004 or less, 0.0035 or less, 0.003 or less, 0.0025 or less, 0.002 or less, 0.0015 or less, and 0.001 or less.

[0043] The form of the composite oxide is not particularly limited and may be particulate, for example. When particulate matter is used, the particles may aggregate as primary particles to form secondary particles, remain as primary particles, or be a mixture of secondary and primary particles. As long as the primary particles have the same particle size distribution, the temperature at which oxygen is released from the composite oxide does not change significantly regardless of the state in which they exist.

[0044] The average particle diameter of the primary particles of the composite oxide is not particularly limited, but is preferably, for example, 80 nm or more, 100 nm or more, 120 nm or more, 150 nm or more, 170 nm or more, 200 nm or more, 250 nm or more, 300 nm or more, 350 nm or more, 400 nm or more, or 450 nm or more. By having an average particle diameter of the composite oxide that is greater than or equal to the required value, the oxygen release temperature can be increased. On the other hand, the average particle diameter of the primary particles is preferably 15 μm or less, 14.5 μm or less, 14 μm or less, 13.5 μm or less, 13 μm or less, 12.5 μm or less, 12 μm or less, 11.5 μm or less, 11 μm or less, 10.5 μm or less, 10 μm or less, 9.5 μm or less, 9 μm or less, 8.5 μm or less, 8 μm or less, 7.5 μm or less, 7 μm or less, 6.5 μm or less, 6 μm or less, 5.5 μm or less, 5 μm or less, or 4.5 μm or less. By keeping the average particle diameter of the primary particles below the required value, the energy density can be increased, and particle breakage and a decrease in rate characteristics associated with the cycle can be suppressed. The average particle diameter of the primary particles of the composite oxide is calculated by observing electron microscope images using a field emission scanning electron microscope (JSM-7100F: manufactured by JEOL Ltd.) with an acceleration voltage of 10kV and magnification from 3000 to 20000x. Specifically, one field of view in which 100 or more primary particles with discernible outlines are visible is randomly selected, and electron microscope images are obtained of all particles with discernible outlines within that field of view, changing the magnification within the aforementioned range as needed. Then, the spherical equivalent diameter is calculated from these electron microscope images using image processing software (e.g., ImageJ), and this is used as the particle diameter of the primary particles.

[0045] Furthermore, the average particle size (D50) of the composite oxide is not particularly limited, but is preferably, for example, 80 nm or more, 100 nm or more, 120 nm or more, 150 nm or more, 170 nm or more, 200 nm or more, 250 nm or more, 300 nm or more, 350 nm or more, 400 nm or more, or 450 nm or more. By having D50 above the required value, the oxygen release temperature can be increased, and in addition, the electrode density can be improved. On the other hand, for D50, the following ranges apply: 25 μm or less, 24.5 μm or less, 24 μm or less, 23.5 μm or less, 23 μm or less, 22.5 μm or less, 22 μm or less, 21.5 μm or less, 21 μm or less, 20.5 μm or less, 20 μm or less, 19.5 μm or less, 19 μm or less, 18.5 μm or less, 18 μm or less, 17.5 μm or less, 17 μm or less, 16.5 μm or less, 16 μm or less, 15.5 μm or less, 15 Preferably, the particle size is ≤μm, ≤14.5μm, ≤14μm, ≤13.5μm, ≤13μm, ≤12.5μm, ≤12μm, ≤11.5μm, ≤11μm, ≤10.5μm, ≤10μm, ≤9.5μm, ≤9μm, ≤8.5μm, ≤8μm, ≤7.5μm, ≤7μm, ≤6.5μm, ≤6μm, ≤5.5μm, ≤5μm, or ≤4.5μm. By keeping the D50 of the composite oxide below the required value, the energy density of the non-aqueous electrolyte secondary battery using this composite oxide can be increased, and particle breakage and rate characteristic degradation associated with cycling can be suppressed. D50 is measured by volume using a wet laser method with a laser particle size distribution analyzer (Microtrac HRA, manufactured by Nikkiso Co., Ltd.).

[0046] [DTG curve] The DTG curve of the composite oxide in this disclosure is obtained when the composite oxide is charged using the charging method described below and the temperature is increased from 50°C to 600°C at a rate of 5°C / minute.

[0047] The differential thermogravimetric curve obtained in this way is fitted using a log-normal distribution function and the peaks are separated to calculate the temperature and weight loss rate (oxygen release rate) at the peak top of each peak.

[0048] Specifically, the thermal analysis gravimetric curve was obtained using a thermogravimetric differential thermal analysis (TG-DTA) instrument (DTG-60H, manufactured by Shimadzu Corporation) in the method described below, and then the first and second peaks were analyzed.

[0049] (Sample preparation) A 2032 type coin cell with a lithium counter electrode is fabricated according to the method described below. Under 25°C conditions, it is charged with a constant current of 0.3C up to 4.30V, then charged with a constant voltage until the current reaches 0.05C. After charging is complete, a 20-minute pause is allowed, followed by a constant current discharge at 0.3C down to 2.50V, then a constant current discharge at 0.1C, followed by a 20-minute pause. This charging and discharging cycle is repeated twice. Next, it is charged with a constant current of 0.3C up to 4.30V, then charged with a constant voltage until the current reaches 0.05C, followed by a 20-minute pause after charging is complete.

[0050] The charged coin cell is disassembled in a glove box (dew point: -70°C or below) to prevent short circuits, and the positive electrode is separated. The separated positive electrode is washed with dimethyl carbonate (DMC) for 10 minutes and dried under vacuum in a side box. Then, in the same glove box, the positive electrode mixture is scraped off the aluminum foil using a spatula. 15 mg of the obtained positive electrode mixture powder is filled into an aluminum TG measurement container, the lid is closed, and it is sealed using a crimping machine.

[0051] The resulting aluminum measuring container is removed from the glove box and placed on the measuring balance of the TG-DTA device.

[0052] (TG-DTA measurement) Reference: Pt container filled with 15-20 mg of Al2O3 Maximum temperature: 600℃ Heating rate: (1) 25℃ (room temperature) ~ 50℃: 1℃ / min (2) 50℃~600℃: 5℃ / min Measurement environment: N2 gas atmosphere (200 ml / min)

[0053] Immediately before measurement, a small hole is made in the lid of a sealed aluminum measuring container in a TG-DTA apparatus under an N2 gas atmosphere, and then the heating is started. By using this method, the cathode composite powder to be measured can be measured without being exposed to the atmosphere.

[0054] Based on the obtained results, a DTG curve is created with temperature on the horizontal axis and the differential thermogravimetric index (DTG), which is the derivative of the weight change (TG) with respect to time (DTG, representing the rate of weight loss and corresponding to the oxygen release rate of the complex oxide in the range of 150-350°C), on the vertical axis.

[0055] In this DTG curve, among the peaks with peak tops between 150 and 350°C, the peak where the differential thermogravimetric value at its peak top is maximized is defined as the first peak. The value of the differential thermogravimetric value at the peak top is defined as the oxygen release rate (% / min). Furthermore, among the peaks with peak tops at temperatures 20°C or more away from the peak top temperature of the first peak, the peak where the value of the differential thermogravimetric value at its peak top is maximized is defined as the second peak.

[0056] Next, we calculate the differential thermogravimetric value at the peak top of the first peak relative to the differential thermogravimetric value at the peak top of the second peak.

[0057] [First peak] The first peak is the peak where the differential thermogravimetric value at the peak top is maximized in the temperature range of 150°C to 350°C, when the DTG curve obtained as described above is separated into multiple peaks.

[0058] The value of the differential thermogravimetric at the peak top of the first peak is not particularly limited, but is preferably, for example, 3% or less, 2.9% or less, 2.8% or less, 2.7% or less, 2.6% or less, 2.5% or less, 2.4% or less, 2.3% or less, 2.2% or less, 2.1% or less, or 2% or less.

[0059] [Second peak] The second peak is the peak whose peak top is located at a temperature more than 20°C away from the temperature at which the peak top of the first peak is located, and which shows the maximum value of the differential thermogravimetric value at the peak top.

[0060] The temperature at the peak of the second peak only needs to be at least 20°C higher than the temperature at the peak of the first peak; there is no limit to how high or low it can be. In other words, the temperature at the peak of the second peak may be at least 20°C higher or at least 20°C lower than the temperature at the peak of the first peak.

[0061] The temperature at which the peak top of the second peak is indicated is preferably 21°C or higher, 22°C or higher, 23°C or higher, 24°C or higher, 25°C or higher, 26°C or higher, 27°C or higher, 28°C or higher, 29°C or higher, 30°C or higher, 31°C or higher, 32°C or higher, 33°C or higher, 34°C or higher, 35°C or higher, 36°C or higher, 37°C or higher, 38°C or higher, 39°C or higher, or 40°C or higher, compared to the temperature at which the peak top of the first peak is indicated. On the other hand, the temperature indicating the peak top of the second peak may be, for example, 160°C or less, 155°C or less, 150°C or less, 145°C or less, 140°C or less, 135°C or less, 130°C or less, 125°C or less, 120°C or less, 115°C or less, 110°C or less, 105°C or less, 100°C or less, 95°C or less, 90°C or less, 85°C or less, 80°C or less, 75°C or less, or 60°C or less from the temperature indicating the peak top of the first peak.

[0062] [Ratio of differential thermogravimetric values] In the positive electrode active material of this disclosure, the value of the differential thermoweight of the first peak relative to the value of the differential thermoweight of the second peak (differential thermoweight of the first peak / differential thermoweight of the second peak) is not particularly limited as long as it is between 1 and 9, but for example, 8.9 or less, 8.8 or less, 8.7 or less, 8.6 or less, 8.5 or less, 8.4 or less, 8.3 or less, 8.2 or less, 8.1 or less, 8 or less, 7.9 or less, 7.8 or less, 7.7 or less, 7.6 or less, 7.5 or less, 7.4 or less, 7.3 or less, 7.2 or less, 7.1 or less, 7 or less, 6.9 or less, 6.8 or less, 6.7 or less, 6.6 or less, 6.5 or less, 6.4 or less, 6.3 or less, 6.2 or less, 6.1 or less. Preferably, the values ​​are 6 or less, 5.9 or less, 5.8 or less, 5.7 or less, 5.6 or less, 5.5 or less, 5.4 or less, 5.3 or less, 5.2 or less, 5.1 or less, 5 or less, 4.9 or less, 4.8 or less, 4.7 or less, 4.6 or less, 4.5 or less, 4.4 or less, 4.3 or less, 4.2 or less, 4.1 or less, 4 or less, 3.9 or less, 3.8 or less, 3.7 or less, 3.6 or less, 3.5 or less, 3.4 or less, 3.3 or less, 3.2 or less, 3.1 or less, 3 or less, 2.9 or less, 2.8 or less, 2.7 or less, 2.6 or less, 2.5 or less, 2.4 or less, 2.3 or less, 2.2 or less, 2.1 or less, 2 or less, 1.9 or less, 1.8 or less, 1.7 or less, and 1.6 or less. On the other hand, the differential thermogravimetric value of the first peak relative to the differential thermogravimetric value of the second peak may be 1.1 or greater, 1.2 or greater, 1.3 or greater, 1.4 or greater, 1.5 or greater, 1.6 or greater, 1.7 or greater, 1.8 or greater, or 1.9 or greater.

[0063] <Method for manufacturing positive electrode active material for non-aqueous electrolyte secondary batteries> The positive electrode active material for a non-aqueous electrolyte secondary battery according to the embodiments of this disclosure can be manufactured, for example, by performing the following steps in this order. Note that the following describes a method for producing a composite oxide containing 30 mol% or more Ni among elements other than Li as an example; for other composite oxides, conventional methods shall be followed.

[0064] Step 1: Synthesize a precursor complex compound containing at least a transition metal, and prepare a mixture by mixing the precursor complex compound with a lithium compound. Step 2: The mixture prepared in Step 1 is fired. Step 3: If necessary, the composite oxide obtained by calcination in Step 2 is subjected to a water washing treatment. Step 4: If necessary, the composite oxide obtained in Step 2 or 3 is subjected to surface treatment. Step 5: Mix multiple types of composite oxides with varying primary particle size, average particle size, etc., by changing the conditions in Steps 1-3 as needed.

[0065] [Process 1] First, a precursor complex compound is synthesized as an aggregate of primary particles containing at least a transition metal. The method for synthesizing the precursor complex compound is not particularly limited. For example, an aqueous solution containing an aqueous solution of a transition metal and various aqueous solutions of compounds containing other elements according to the composition of the desired complex oxide is dropped dropwise into a reaction vessel that is being stirred with an alkaline aqueous solution such as sodium hydroxide solution or ammonia solution as the mother liquor. Sodium hydroxide and the like are also dropped dropwise, and the pH is monitored and controlled to stay within an appropriate range. The compound is then coprecipitation by a wet reaction to obtain, for example, a hydroxide, an oxide obtained by calcining a hydroxide, a carbonate, etc.

[0066] Furthermore, in the reaction for synthesis, it is preferable to create a nitrogen atmosphere in the reaction vessel using an inert gas, or more preferably nitrogen gas for industrial purposes, from the time the alkaline aqueous solution which will serve as the mother liquor is prepared, and to keep the oxygen concentration in the reaction vessel system and the solution as low as possible. If the oxygen concentration is too high, there is a risk that the co-precipitated hydroxide may be over-oxidized by the residual oxygen exceeding a predetermined amount, or that the formation of aggregates by crystallization may be hindered.

[0067] The aqueous solution of the transition metal is not particularly limited, but for example, an acidic aqueous solution is preferred, and in the case of a nickel compound, a sulfuric acid aqueous solution such as nickel sulfate aqueous solution is more preferred. Furthermore, one or more transition metals can be used as the aqueous solution.

[0068] The nickel compound is not particularly limited, but one or more can be selected from, for example, nickel sulfate, nickel oxide, nickel hydroxide, nickel nitrate, nickel carbonate, nickel chloride, nickel iodide, and metallic nickel.

[0069] The cobalt compound is not particularly limited, but one or more selected from, for example, cobalt sulfate, cobalt oxide, cobalt hydroxide, cobalt nitrate, cobalt carbonate, cobalt chloride, cobalt iodide, and metallic cobalt can be used.

[0070] The manganese compound is not particularly limited, but for example, one or more selected from manganese sulfate, manganese oxide, manganese hydroxide, manganese nitrate, manganese carbonate, manganese chloride, manganese iodide, and metallic manganese can be used.

[0071] The aluminum compound is not particularly limited, but examples include aluminum sulfate, aluminum oxide, aluminum hydroxide, aluminum nitrate, aluminum carbonate, aluminum chloride, aluminum iodide, sodium aluminate, and metallic aluminum.

[0072] The titanium compound is not particularly limited, but for example, one or more selected from titanyl sulfate, titanium dioxide, titanium hydroxide, titanium nitrate, titanium carbonate, titanium chloride, titanium iodide, and metallic titanium can be used.

[0073] The iron compound is not particularly limited, but one or more selected from, for example, iron sulfate, iron oxide, iron hydroxide, iron nitrate, iron carbonate, iron chloride, iron iodide, and metallic iron can be used.

[0074] The niobium compound is not particularly limited, but one or more selected from, for example, niobium oxide, niobium chloride, lithium niobate, niobium iodide, etc., can be used.

[0075] The tungsten compound is not particularly limited, but one or more selected from, for example, tungsten oxide, sodium tungstate, ammonium paratungstate, hexacarbonyltungsten, tungsten sulfide, etc., can be used.

[0076] The magnesium compound is not particularly limited, but one or more selected from, for example, magnesium sulfate, magnesium oxide, magnesium hydroxide, magnesium nitrate, magnesium carbonate, magnesium chloride, magnesium iodide, and metallic magnesium can be used.

[0077] The zinc compound is not particularly limited, but one or more selected from, for example, zinc sulfate, zinc oxide, zinc hydroxide, zinc nitrate, zinc carbonate, zinc chloride, zinc iodide, and metallic zinc can be used.

[0078] For other elements, one or more selected from sulfates, oxides, hydroxides, nitrates, carbonates, chlorides, iodides, and metals may be used.

[0079] The proportions of each compound should be adjusted so that the amounts of each element reach the desired ratio, taking into account the composition of the target composite oxide.

[0080] The appropriate pH range for synthesizing precursor complex compounds is not particularly limited and can be determined to obtain the desired shape, such as secondary particle size and density. Generally, a range of 10 to 13 is sufficient.

[0081] The precursor complex compound obtained by the wet reaction is preferably subjected to washing, dehydration, and drying.

[0082] Washing the precursor complex compound removes impurities such as sulfate, carbonate, and sodium that may have been incorporated into the aggregated particles or adhered to the surface during the reaction. For small amounts, washing can be performed using a Buchner funnel or by sending the reaction suspension through a press filter for washing and dehydration. While pure water, sodium hydroxide solution, sodium carbonate solution, etc., can be used for washing, pure water is preferred industrially. However, if there is a large amount of residual sulfate, a sodium hydroxide solution with pH controlled according to the residual amount may be used.

[0083] Next, the synthesized precursor complex compound and the lithium compound are mixed in a predetermined ratio to prepare a mixture. The mixing may be performed using a solvent system, in which the precursor complex compound and the lithium compound are each prepared as an aqueous solution and these solutions are mixed in a predetermined ratio, or it may be performed using a non-solvent system, in which the powder of the precursor complex compound and the powder of the lithium compound are weighed in a predetermined ratio and mixed dry.

[0084] The lithium compound is not particularly limited, and various lithium salts can be used. Specifically, one or more lithium compounds can be selected from, for example, anhydrous lithium hydroxide, lithium hydroxide hydrate, lithium nitrate, lithium carbonate, lithium acetate, lithium bromide, lithium chloride, lithium citrate, lithium fluoride, lithium iodide, lithium lactate, lithium oxalate, lithium phosphate, lithium pyruvate, lithium sulfate, and lithium oxide. Among these, it is preferable to use one or more selected from anhydrous lithium hydroxide and lithium hydroxide hydrate.

[0085] The mixing ratio of the lithium compound and the precursor complex compound is not particularly limited, but can be appropriately adjusted so that the amount of lithium and the total amount of each element are in the desired ratio, taking into consideration the composition of the target complex oxide.

[0086] [Process 2] As described above, when producing composite oxides containing at least a transition metal, lithiation and crystal growth occur during calcination. Of these, the lithiation reaction requires a certain oxygen partial pressure. The lithiation reaction yields a composite oxide containing lithium. Subsequently, raising the temperature to a predetermined level promotes crystal growth.

[0087] The maximum temperature of the mixture during firing is preferably 650°C to 1100°C, 670°C to 1000°C, or 700°C to 980°C. Furthermore, the firing time at the maximum temperature is preferably 1 to 24 hours, 1 to 20 hours, 1 to 15 hours, 1 to 10 hours, 2 to 9 hours, or 3 to 8 hours. By setting the firing temperature to be above the melting point of the lithium compound in the mixture, and setting the maximum temperature and time to achieve the desired crystal growth or particle growth of the lithium-containing composite oxide, the desired composite compound can be obtained.

[0088] In general, calcination is carried out by weighing lithium compounds, precursor complex compounds, and, if necessary, compounds of element M, mixing them in a mixer, and then filling the resulting mixed powder into containers such as crucibles or saggars. However, particularly in the lithiumation reaction, it becomes difficult to vent the generated gases to the outside and to diffuse the required oxygen concentration, especially as the mixed powder approaches the bottom of the container. As a result, it becomes difficult to achieve reaction uniformity and control the primary particle size.

[0089] Therefore, when manufacturing the composite oxide according to the embodiment of this disclosure, it is preferable to first pre-fire it in step 2 under the following predetermined conditions, and then perform the main firing under the predetermined conditions. However, pre-fire is not an essential step.

[0090] In the pre-calcination of step 2, it is preferable to employ a calcination method that particularly promotes the lithiumization reaction. Specifically, this method involves creating a state where the mixture is more easily heated, allowing for the easy discharge of gases generated from the lithium compound, and diffusing gases with a high oxygen partial pressure into the mixture (particles). For example, it is possible to achieve the desired properties by pre-calcining a smaller amount of mixture.

[0091] In step 2, the mixture can be pre-fired by filling saggers or crucibles with the mixture and firing it in a stationary furnace, roller hearth kiln, or pusher furnace, but a rotary kiln can be used to fire the mixture while it is flowing.

[0092] The maximum temperature of the mixture to be pre-calcined is not particularly limited, and is preferably adjusted according to the type of lithium compound used in the preparation of the mixture. This ensures that the precursor complex compound and the lithium compound in the mixture react reliably, allowing the lithiation reaction to proceed reliably and uniformly, preventing the generation of improper phases, and enabling the acquisition of the desired complex oxide.

[0093] The atmosphere for pre-calcination is not particularly limited; any oxidizing atmosphere that ensures the lithiumization reaction proceeds reliably and uniformly is acceptable. For example, it is preferable to use a decarboxylated oxidizing gas atmosphere with a carbon dioxide concentration of 30 ppm or less, or an oxygen atmosphere with an oxygen concentration of 80 vol% or more, or 90 vol% or more.

[0094] The pre-firing time is not particularly limited and should be any time that ensures the lithiumization reaction proceeds reliably and uniformly. For example, 1 to 10 hours or 2 to 8 hours is preferable.

[0095] The pre-calcined mixture is then subjected to a final calcination at a higher temperature to promote crystal and particle growth. During this process, it is necessary to ensure reliable and uniform crystal growth to obtain a composite oxide with the desired crystalline structure.

[0096] The atmosphere for the final firing is not particularly limited, but any atmosphere that ensures reliable and uniform crystal growth and has an oxygen partial pressure such that the transition metals contained in the mixture to be fired are not reduced, preferably with low moisture content and carbon dioxide concentration, is acceptable. For example, it is preferable to use a decarboxylated oxidizing gas atmosphere with a carbon dioxide concentration of 30 ppm or less, or an oxygen atmosphere with an oxygen concentration of preferably 80 vol% or more, or 90 vol% or more.

[0097] The temperature for the main firing is not particularly limited as long as it is higher than the pre-firing temperature, and can be adjusted depending on the composition of the composite oxide to be obtained. For example, it is preferable to adjust the maximum temperature to 700°C to 1100°C, 710°C to 1000°C, or 720°C to 980°C. By keeping the maximum temperature within the required range, it is possible to obtain a composite oxide with a desired crystal structure with reduced unreacted components, and it is also possible to prevent a decrease in the battery characteristics of a non-aqueous electrolyte secondary battery using the obtained composite oxide as the positive electrode. Furthermore, for example, when obtaining a composite oxide in which the Ni content is 20 mol% to 80 mol% of the elements other than Li, it is preferable to fire the mixture at a temperature in which the maximum temperature does not exceed 1100°C.

[0098] The firing time is not particularly limited and should be sufficient to form a composite oxide having the desired crystal structure. For example, 1 to 15 hours, 2 to 12 hours, or 2 to 10 hours are preferred.

[0099] [Step 3] The composite oxide obtained in step 2 may contain impurities such as unreacted lithium compounds or lithium compounds that appear on the particle surface from the crystalline structure during the calcination process. Therefore, these impurities can be removed or reduced by, for example, washing with water and heat treatment. Step 3 is not an essential component.

[0100] [Step 4] By adding and mixing a predetermined elemental compound to the composite oxide obtained in step 2 or 3, and then subjecting it to heat treatment, the surface of the primary and / or secondary particles of the composite oxide can be surface-treated with a compound of lithium and the added element, resulting in effects such as a reduction in lithium compound remaining on the particle surface, improved lithium ion conductivity, and reduced reaction resistance. Step 4 is not an essential component.

[0101] The elemental compounds added for the surface treatment described above can be selected from, for example, aluminum compounds, boron compounds, tungsten compounds, manganese compounds, cobalt compounds, phosphorus compounds, niobium compounds, strontium compounds, antimony compounds, zirconium compounds, titanium compounds, etc., and one or more of these can be used.

[0102] [Step 5] If the composite oxide obtained in any of steps 2 to 4 does not individually possess multiple specific peaks as described above, or if it satisfies certain requirements for specific peaks but the thermal runaway suppression effect is to be further enhanced, then the manufacturing conditions of the composite oxide (conditions in steps 1 to 4) are changed to mix multiple types of composite oxides with different primary particle sizes and average particle sizes. Note that if the composite oxide obtained in any of steps 2 to 4 individually satisfies certain requirements for specific peaks, step 5 is not an essential component.

[0103] <Nonaqueous electrolyte secondary battery> The non-aqueous electrolyte secondary battery according to the embodiments of this disclosure comprises a positive electrode containing the above-mentioned composite oxide as a positive electrode active material, and the non-aqueous electrolyte secondary battery is composed of an electrolyte solution containing a positive electrode, a negative electrode, and an electrolyte.

[0104] When manufacturing the positive electrode, a conductive agent and a binder are added to the composite oxide according to the embodiment of this disclosure and mixed according to a conventional method. Preferably, the conductive agent is acetylene black, carbon black, graphite, etc. Preferably, the binder is polytetrafluoroethylene, polyvinylidene fluoride, etc.

[0105] The negative electrode is not particularly limited, but can be a negative electrode active material such as lithium metal, graphite, or low-crystallinity carbon material, as well as one or more nonmetals or metal elements selected from Si, Al, Sn, Pb, Zn, Bi, and Cd, alloys containing them, or chalcogen compounds containing them.

[0106] The solvent for the electrolyte is not particularly limited, but an organic solvent containing one or more selected from carbonates such as ethylene carbonate, propylene carbonate, dimethyl carbonate, and diethyl carbonate, or ethers such as dimethoxyethane, can be used.

[0107] As an electrolyte, in addition to lithium hexafluoride phosphate (LiPF6), one or more lithium salts selected from, for example, lithium perchlorate and lithium tetrafluoroborate, can be used dissolved in a solvent. [Examples]

[0108] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples.

[0109] <Preparation of complex oxide samples> The composite oxide samples of Examples 1 to 13 and Comparative Example 1 were prepared by the method described below.

[0110] [Preparation of precursor complex hydroxides] (Preparation of Precursor Complex Hydroxide 1) A mixed aqueous solution was obtained by mixing nickel sulfate aqueous solution, cobalt sulfate aqueous solution, and manganese sulfate aqueous solution so that the molar ratio of Ni, Co, and Mn was Ni:Co:Mn = 83:5:12. In the reaction vessel, 10 L of pure water to which 300 g of sodium hydroxide aqueous solution and 500 g of ammonia aqueous solution had been added was prepared as the mother liquor. The reaction vessel was then filled with nitrogen gas at a flow rate of 0.7 L / min to create a nitrogen atmosphere, and the reaction was carried out under a nitrogen atmosphere.

[0111] Subsequently, while rotating the stirring blade at 1000 rpm, the mixed aqueous solution, sodium hydroxide aqueous solution, and ammonia aqueous solution were simultaneously added dropwise at a predetermined rate. The amount of alkaline solution added was adjusted so that the pH would be 11.5. Through a crystallization reaction, Ni, Co, and Mn crystallized and coprecipitation occurred to form aggregated particles, yielding a coprecipitate.

[0112] Subsequently, the slurry in the reactor was separated into solid and liquid phases, and then washed with pure water to reduce residual impurities. The resulting coprecipitate was then dried in an atmospheric environment at 100°C for 10 hours, and the composition formula Ni was obtained. 0.83 Co 0.05 Mn 0.12 A nickel-cobalt-manganese composite hydroxide represented by (OH)2 was obtained. The D50 of the obtained composite hydroxide precursor was 14.2 μm.

[0113] (Preparation of precursor complex oxide 2) A mixed aqueous solution was obtained by mixing nickel sulfate aqueous solution, cobalt sulfate aqueous solution, and manganese sulfate aqueous solution so that the molar ratio of Ni, Co, and Mn was Ni:Co:Mn = 83:12:5. In the reaction vessel, 10 L of pure water to which 330 g of sodium hydroxide aqueous solution and 500 g of ammonia aqueous solution had been added was prepared as the mother liquor. The reaction vessel was then filled with nitrogen gas at a flow rate of 0.7 L / min to create a nitrogen atmosphere, and the reaction was carried out under a nitrogen atmosphere.

[0114] Subsequently, while rotating the stirring blade at 1100 rpm, the mixed aqueous solution, sodium hydroxide aqueous solution, and ammonia aqueous solution were simultaneously added dropwise at a predetermined rate. The amount of alkaline solution added was adjusted so that the pH would be 12.6. Through a crystallization reaction, Ni, Co, and Mn crystallized and coprecipitationd to form aggregated particles, yielding a coprecipitate.

[0115] Subsequently, the slurry in the reactor was separated into solid and liquid phases, and then washed with pure water to reduce residual impurities. The resulting coprecipitate was then dried in an atmospheric environment at 100°C for 10 hours, and the composition formula Ni was obtained. 0.83 Co 0.12 Mn 0.05 A nickel-cobalt-manganese composite hydroxide represented by (OH)2 was obtained by coprecipitation. The D50 of the obtained composite hydroxide precursor was 4.0 μm.

[0116] [Example 1] Precursor composite hydroxide 1, lithium hydroxide, and aluminum hydroxide were weighed and mixed so that Li / (Ni+Co+Mn+Al) = 1.030 and Al / (Ni+Co+Mn+Al) = 2.0 mol%. Then, the mixture was heat-treated at 570°C for 6 hours under an oxygen atmosphere, and further calcined at 805°C for 6 hours under an oxygen atmosphere (oxygen concentration: 97 vol%). The resulting calcined product was pulverized to obtain lithium nickel composite oxide powder.

[0117] The obtained lithium nickel composite oxide powder and pure water adjusted to a liquid temperature of 25°C were mixed in a ratio of 1500 g / L to prepare a slurry. After stirring for 10 minutes, the slurry was dehydrated to obtain a cake-like compound. The cake-like compound was dried in a vacuum dryer at 75°C for 2 hours and then at 120°C for 10 hours.

[0118] After drying, 1000 ppm of boric acid was added to the lithium nickel composite oxide and mixed with it. The mixture was then heat-treated at 325°C for 2 hours under an oxygen atmosphere (oxygen concentration: 97 vol%) to obtain the composite oxide sample of Example 1. The Li / (Ni+Co+Mn+Al) ratio of the obtained composite oxide sample was 1.009.

[0119] [Example 2] The composite oxide sample of Example 2 was obtained in the same manner as in Example 1, except that the precursor composite hydroxide 1, lithium hydroxide, and aluminum hydroxide were weighed so that Li / (Ni+Co+Mn+Al) = 1.050 and Al / (Ni+Co+Mn+Al) = 2.0 mol%. The Li / (Ni+Co+Mn+Al) of the obtained composite oxide sample was 1.023.

[0120] [Example 3] A composite oxide sample of Example 3 was obtained in the same manner as in Example 1, except that the precursor composite hydroxide 1, lithium hydroxide, and aluminum hydroxide were weighed so that Li / (Ni+Co+Mn+Al) = 1.070 and Al / (Ni+Co+Mn+Al) = 2.0 mol%. The Li / (Ni+Co+Mn+Al) of the obtained composite oxide sample was 1.045.

[0121] [Example 4] A composite oxide sample of Example 4 was obtained in the same manner as in Example 1, except that the precursor composite hydroxide 1, lithium hydroxide, and aluminum hydroxide were weighed so that Li / (Ni+Co+Mn+Al) = 1.090 and Al / (Ni+Co+Mn+Al) = 2.0 mol%. The Li / (Ni+Co+Mn+Al) of the obtained composite oxide sample was 1.06.

[0122] [Example 5] Precursor composite hydroxide 1, lithium hydroxide, and aluminum hydroxide were weighed and mixed so that Li / (Ni+Co+Mn+Al) = 1.010 and Al / (Ni+Co+Mn+Al) = 3.0 mol%. Then, the mixture was heat-treated at 570°C for 6 hours under an oxygen atmosphere, and further calcined at 810°C for 6 hours under an oxygen atmosphere (oxygen concentration: 97 vol%). The resulting calcined product was pulverized to obtain lithium nickel composite oxide. The composite oxide sample of Example 5 was obtained in the same manner as in Example 1 thereafter. The Li / (Ni+Co+Mn+Al) of the obtained composite oxide sample was 1.001.

[0123] [Example 6] The composite oxide sample of Example 6 was obtained in the same manner as in Example 5, except that the precursor composite hydroxide 1, lithium hydroxide, and aluminum hydroxide were weighed so that Li / (Ni+Co+Mn+Al) = 1.030 and Al / (Ni+Co+Mn+Al) = 3.0 mol%. The Li / (Ni+Co+Mn+Al) of the obtained composite oxide sample was 1.012.

[0124] [Example 7] The composite oxide sample of Example 7 was obtained in the same manner as in Example 5, except that the precursor composite hydroxide 1, lithium hydroxide, and aluminum hydroxide were weighed so that Li / (Ni+Co+Mn+Al) = 1.050 and Al / (Ni+Co+Mn+Al) = 3.0 mol%. The Li / (Ni+Co+Mn+Al) of the obtained composite oxide sample was 1.032.

[0125] [Example 8] The composite oxide sample of Example 8 was obtained in the same manner as in Example 5, except that the precursor composite hydroxide 1, lithium hydroxide, and aluminum hydroxide were weighed so that Li / (Ni+Co+Mn+Al) = 1.030 and Al / (Ni+Co+Mn+Al) = 1.0 mol%. The Li / (Ni+Co+Mn+Al) of the obtained composite oxide sample was 1.008.

[0126] [Example 9] Precursor composite hydroxide 2 and lithium hydroxide were weighed and mixed so that Li / (Ni+Co+Mn) = 1.050. The mixture was then further calcined at 860°C for 12 hours under an oxygen atmosphere (oxygen concentration: 97 vol%). The resulting calcined product was pulverized to obtain lithium nickel composite oxide powder.

[0127] The obtained lithium nickel composite oxide powder was further calcined at 700°C for 7 hours under an oxygen atmosphere (oxygen concentration: 97 vol%).

[0128] The lithium nickel composite oxide, after calcination, was mixed with 500 ppm of boric acid as a boron compound, and then heat-treated at 330°C for 7 hours under air to obtain the composite oxide sample of Example 9. The Li / (Ni+Co+Mn) ratio of the obtained composite oxide sample was 1.015.

[0129] [Example 10] The composite oxide sample of Example 10 was obtained in the same manner as in Example 9, except that the precursor composite hydroxide 2 and lithium hydroxide were weighed so that Li / (Ni+Co+Mn) = 1.060. The Li / (Ni+Co+Mn) of the obtained composite oxide sample was 1.029.

[0130] [Example 11] The composite oxide sample of Example 11 was obtained in the same manner as in Example 9, except that the precursor composite hydroxide 2 and lithium hydroxide were weighed so that Li / (Ni+Co+Mn) = 1.070. The Li / (Ni+Co+Mn) of the obtained composite oxide sample was 1.048.

[0131] [Example 12] Precursor composite hydroxide 2 and lithium hydroxide were weighed and mixed so that Li / (Ni+Co+Mn) = 1.070. The mixture was then further calcined at 860°C for 12 hours under an oxygen atmosphere (oxygen concentration: 97 vol%). The resulting calcined product was pulverized to obtain lithium nickel composite oxide powder.

[0132] The obtained lithium nickel composite oxide powder was mixed with 0.5 mol% of aluminum oxide powder, Al2O3, and heat-treated at 700°C for 7 hours under air. The composite oxide sample of Example 12 was then obtained in the same manner as in Example 9. The Li / (Ni+Co+Mn+Al) ratio of the obtained composite oxide sample was 1.012.

[0133] [Example 13] Precursor composite hydroxide 2 and lithium hydroxide were weighed and mixed so that Li / (Ni+Co+Mn) = 1.050. The mixture was then calcined at 860°C for 12 hours under an oxygen atmosphere (oxygen concentration: 97 vol%). The resulting calcined product was pulverized to obtain lithium nickel composite oxide powder.

[0134] A lithium metal composite oxide was obtained by adding 0.8 mol% of aluminum oxide powder (Al2O3) to the obtained lithium nickel composite oxide powder and heat-treating it at 600°C for 7 hours under air.

[0135] A slurry was prepared by mixing heat-treated lithium nickel composite oxide powder with pure water adjusted to a liquid temperature of 25°C in a ratio of 1500 g / L. The slurry was stirred for 10 minutes, then dehydrated to obtain a cake-like compound. Subsequently, it was dried in a vacuum dryer at 75°C for 2 hours and then at 120°C for 10 hours.

[0136] After drying, 500 ppm of boric acid was added to the lithium nickel composite oxide and mixed with it. The mixture was then heat-treated at 300°C for 7 hours under air to obtain the composite oxide sample of Example 13. The Li / (Ni+Co+Mn+Al) ratio of the obtained composite oxide sample was 0.989.

[0137] [Comparative Example 1] Precursor composite hydroxide 2, lithium hydroxide, and aluminum hydroxide were weighed and mixed so that Li / (Ni+Co+Mn+Al) = 1.050. The mixture was then calcined at 860°C for 12 hours under an oxygen atmosphere (oxygen concentration: 97 vol%). The resulting calcined product was pulverized to obtain lithium nickel composite oxide powder.

[0138] The obtained lithium nickel composite oxide powder was mixed with 0.8 mol% of aluminum oxide powder, Al2O3, and heat-treated at 700°C for 7 hours under air. The composite oxide sample of Comparative Example 1 was then obtained in the same manner as in Example 9. The Li / (Ni+Co+Mn+Al) ratio of the obtained composite oxide sample was 1.

[0139] <Rating> The obtained samples were evaluated using the following method.

[0140] [Compositional analysis of precursor compounds and complex oxides] The compositions of the precursor complex compound and complex oxide sample were determined by the following method: 0.2 g of the complex oxide sample was heated and dissolved in 25 ml of 20% hydrochloric acid solution. After cooling, the solution was transferred to a 100 ml volumetric flask, and pure water was added to prepare the adjusted solution. The elements of the obtained adjusted solution were quantified using ICP-AES (Optima 8300, PerkinElmer Japan Co., Ltd.).

[0141] [Average particle size of precursor compound (D50)] The particle size distribution was measured using a wet laser method with a laser-type particle size distribution analyzer (Microtrac HRA, manufactured by Nikkiso Co., Ltd.), based on volume.

[0142] [Thermogravimetric differential thermal analysis] To confirm the oxygen release behavior of the complex oxide sample, thermogravimetric differential thermal analysis (TG-DTA) was performed using a thermogravimetric differential thermal analysis instrument (DTG-60H, manufactured by Shimadzu Corporation).

[0143] (Sample preparation) Following the method described below, a 2032 type coin cell with a lithium counter electrode was fabricated. Under conditions of 25°C, it was charged with a constant current of 0.3C up to 4.30V, followed by constant voltage charging until the current value reached 0.05C. After charging was complete, a 20-minute pause was allowed, followed by constant current discharge at 0.3C down to 2.50V, then constant current discharge at 0.1C, followed by a 20-minute pause. This charge-discharge cycle was repeated twice. Next, it was charged with a constant current of 0.3C up to 4.30V, followed by constant voltage charging until the current value reached 0.05C, and a 20-minute pause was allowed after charging was complete.

[0144] A charged coin cell was disassembled in a glove box (dew point: below -70°C) to prevent short circuits, and the positive electrode was separated. The separated positive electrode was washed with DMC for 10 minutes and dried under vacuum in a side box. Then, in the same glove box, the positive electrode mixture was scraped off the aluminum foil using a spatula. 15 mg of the obtained positive electrode mixture powder was filled into an aluminum TG measurement container, the lid was closed, and it was sealed using a crimping machine.

[0145] The aluminum measuring container obtained in this manner was removed from the glove box and placed on the measuring balance of the TG-DTA apparatus.

[0146] (TG-DTA measurement) Reference: Pt container filled with 15-20 mg of Al2O3 Maximum temperature: 600℃ Heating rate: (1) 25℃ (room temperature) ~ 50℃: 1℃ / min (2) 50℃~600℃: 5℃ / min Measurement environment: N2 gas atmosphere (200 ml / min)

[0147] Immediately before measurement, a small hole was made in the lid of a sealed aluminum measuring container inside the TG-DTA apparatus, which was in an N2 gas atmosphere, and then the heating process was started.

[0148] Based on the obtained results, a DTG curve is created with temperature on the horizontal axis and the differential thermogravimetric index (DTG), which is the derivative of the weight change (TG) with respect to time (DTG, representing the rate of weight loss and corresponding to the oxygen release rate of the complex oxide in the range of 150-350°C), on the vertical axis.

[0149] In this DTG curve, among the peaks with peak tops between 150 and 350°C, the peak showing the maximum value of the differential thermogravimetric peak top was defined as the first peak (P1). The value of the differential thermogravimetric peak top was defined as the oxygen release rate (% / min). Furthermore, among the peaks with peak tops at temperatures 20°C or more away from the temperature showing the peak top of the first peak, the peak showing the maximum value of the differential thermogravimetric peak top was defined as the second peak (P2). Figures 1 to 13 show the DTG curves of the composite oxide samples of Examples 1 to 13, respectively. Figure 14 shows the DTG curve of the composite oxide sample of Comparative Example 1.

[0150] [Analysis of crystal structure by Rietveld analysis] Using an X-ray diffractometer [SmartLab, Rigaku Corporation], XRD diffraction data was obtained for a composite oxide sample under the following X-ray diffraction conditions. Rietveld analysis was then performed using the XRD diffraction data, referencing "RAYoung, ed., 'The Rietveld Method', Oxford University Press (1992)". Specifically, the proportion of lithium contained in sites 3a and 3b, as well as the unit cell volume, were calculated. (X-ray diffraction conditions) Source: Cu-Kα Acceleration voltage and current: 45kV and 200mA Sampling width: 0.02 degrees. Scan width: 15deg.~122deg. Scan speed: 1.0 step / second Divergence slit: 2 / 3 degree. Light-receiving slit width: 0.15 mm Scattering slit: 2 / 3 degree.

[0151] [Evaluation of the charging capacity of coin cells using composite oxide samples] In this specification, 2032 type coin cells using a composite oxide sample as the positive electrode active material were manufactured using the positive electrode, negative electrode, and electrolyte prepared by the following methods.

[0152] (positive electrode) Acetylene black and graphite were used as conductive agents in a 1:1 ratio (by weight), and polyvinylidene fluoride was used as a binder. The composite oxide sample, conductive agent, and binder were blended in a ratio of 90:6:4 (by weight) for the composite oxide sample, conductive agent, and binder. These were mixed with N-methylpyrrolidone and coated onto aluminum foil. This was dried at 110°C to produce a sheet, which was then punched out to 15mmΦ and cut at 3t / cm 2 The rolled material was used as the positive electrode.

[0153] (Negative electrode) A 500 μm thick lithium foil, punched out to a diameter of 16 mm, was used as the negative electrode.

[0154] (electrolyte) A mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC) was prepared with a volume ratio of EC:DMC = 1:2, and a solution was prepared by mixing 1 mol / L of LiPF6 with this solvent to create the electrolyte.

[0155] (Separator) A 0.5mm thick separator (Celgard #2400, manufactured by Celgard) punched out to a diameter of 20mm was used.

[0156] (Measurement of total charging capacity) Using coin cells manufactured by the method described above, constant current charging was performed at 25°C at 0.3C until the voltage reached 4.30V, followed by constant voltage charging until the current value reached 0.05C. After charging was complete, a 20-minute rest period was observed, followed by constant current discharge at 0.3C until the voltage reached 2.50V, then constant current discharge at 0.1C, followed by a 20-minute rest period. This charging and discharging cycle was repeated twice. Next, constant current charging was performed at 0.3C until the voltage reached 4.30V, followed by constant voltage charging until the current value reached 0.05C. The total charging capacity (mAh / g) was calculated as follows during the operation. ·1st charge / discharge 0.3C at 4.3V (constant voltage charging until the current reaches 0.05C) 20 minute break Discharge to 2.5V at 0.3C, then discharge again to 2.5V at 0.1C. 20 minute break ·Second charge and discharge 0.3C at 4.3V (constant voltage charging until the current reaches 0.05C) 20 minute break Discharge to 2.5V at 0.3C, then discharge again to 2.5V at 0.1C. • Third charge 0.3C at 4.3V (constant voltage charging until the current reaches 0.05C) Total charging capacity = 1st charge capacity + (2nd charge capacity - 1st discharge capacity at 0.3C - 1st discharge capacity at 0.1C) + (3rd charge capacity - 2nd discharge capacity at 0.3C - 2nd discharge capacity at 0.1C)

[0157] Table 1 shows the composition of the composite oxide constituting the samples of Examples 1 to 13 and Comparative Example 1, the proportion of lithium contained in the 3a and 3b sites, the unit cell volume, the total charging capacity, the peak top temperature of the first peak of the DTG curve, the differential thermogravimetric index (oxygen release rate), and the reduction rate of differential thermogravimetric index compared to Comparative Example 1, the peak top temperature and differential thermogravimetric index (oxygen release rate) of the second peak, and the ratio of the thermogravimetric derivative at the peak top of the first peak to the thermogravimetric derivative at the peak top of the second peak (differential thermogravimetric index at the peak top of the first peak / differential thermogravimetric index at the peak top of the second peak).

[0158] Table 1

Claims

1. General formula Li １＋ｘ Ni １－ｙ－ｚ－ｗ Co ｙ Mn ｚ M ｗ O ２ (wherein M is one or more elements other than Li, Ni, Co, Mn, and O, and -0.1 ≤ x ≤ 0.15, 0 ≤ y ≤ 0.4, 0 ≤ z ≤ 0.4, 0 ≤ w ≤ 0.1) The compound oxide includes the above, When the differential thermogravimetric curve obtained by heating the aforementioned composite oxide sample, with lithium as the counter electrode, up to 4.30V, from 50°C to 600°C at a rate of 5°C / min, is separated into multiple peaks, In a temperature range of 150°C to 350°C, there is a first peak where the value of differential thermogravimetric analysis at the peak top is maximized, and a second peak where the value of differential thermogravimetric analysis at the peak top is maximized, among peaks whose peak tops are located at temperatures 20°C or more away from the temperature at which the peak top of the first peak is located. The differential thermogravimetric value at the peak top of the first peak is 1 or more and 9 or less, relative to the differential thermogravimetric value at the peak top of the second peak. Positive electrode active material for non-aqueous electrolyte secondary batteries.

2. In the aforementioned composite oxide, 0 < x ≤ 0.15 The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1.

3. The differential thermogravimetric value at the peak top of the first peak is 3% / min or less. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 or 2.

4. The positive electrode comprises a positive electrode containing the positive electrode active material described in claim 1 or 2. Nonaqueous electrolyte secondary battery.

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