Positive electrode active material for non-aqueous electrolyte secondary batteries

Abstract

To provide a cathode active material for non-aqueous electrolyte secondary battery capable of constituting a non-aqueous electrolyte secondary battery having excellent output characteristics, and a manufacturing method thereof.SOLUTION: A cathode active material for non-aqueous electrolyte secondary battery contains lithium transition metal composite oxide having a layered structure containing at least one metal element M1 of lithium, nickel, titanium and zirconium. The lithium transition metal composite oxide has a composition that a ratio D50 / DSEM with respect to an average particle diameter DSEM based on an electron microscope observation of 50% particle diameter D50 in a cumulative grain size distribution according to a volume reference is 1 or more and 4 or less, a ratio of a mol number of nickel with respect to a total mol number of a metal other than lithium is 0.3 or more and less than 1, and a ratio of a mol number of the metal element M1 with respect to the total mol number of the metal other than lithium is 0.025 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Positive electrode active materials for non-aqueous electrolyte secondary batteries, including nickel-cobalt manganese lithium, are used in large power equipment such as electric vehicles, and improved power output characteristics are required for these positive electrode active materials. To obtain high power output characteristics, positive electrode active materials having a structure of secondary particles (hereinafter also referred to as aggregated particles) formed by the aggregation of many primary particles are considered effective. However, in positive electrode active materials containing aggregated particles, cracks may occur in the aggregated particles due to pressurization during the formation of the positive electrode, expansion and contraction of the positive electrode active material during charging and discharging, and the desired power output characteristics may not be obtained. In connection with this, a method for manufacturing positive electrode active materials containing lithium transition metal composite oxide particles (hereinafter also referred to as single particles) that reduce the number of primary particles constituting a single particle or a single secondary particle has been proposed (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2017-188443 [Patent Document 2] Japanese Patent Publication No. 2017-188444 [Overview of the project] [Problems that the invention aims to solve]

[0004] One aspect of this disclosure aims to provide a positive electrode active material for a non-aqueous electrolyte secondary battery and a method for producing the same, which can constitute a non-aqueous electrolyte secondary battery having excellent output characteristics. [Means for solving the problem]

[0005] The first embodiment is a lithium, nickel, and at least one metallic element M of titanium and zirconium. 1 The lithium transition metal composite oxide comprises a layered structure containing the following, wherein the lithium transition metal composite oxide has a 50% particle size D in the cumulative particle size distribution based on volume. 50 Average particle size D based on electron microscope observations SEM Ratio D 50 / D SEM The ratio of the number of moles of nickel to the total number of moles of metals other than lithium is 0.3 or more and less than 1, and the ratio of the number of metal elements M to the total number of moles of metals other than lithium is 1 or more and 4 or less, and the ratio of the number of moles of nickel to the total number of moles of metals other than lithium is 0.3 or more and less than 1, and the ratio of the number of moles of metal elements M to the total number of moles of metals other than lithium 1 This is a positive electrode active material for a non-aqueous electrolyte secondary battery having a composition in which the ratio of the number of moles of is 0.025 or less. [Effects of the Invention]

[0006] According to one aspect of this disclosure, it is possible to provide a positive electrode active material for a non-aqueous electrolyte secondary battery and a method for producing the same, which can constitute a non-aqueous electrolyte secondary battery having excellent output characteristics. [Brief explanation of the drawing]

[0007] [Figure 1] This is an example of a scanning electron microscope (SEM) image of the positive electrode active material according to Example 1. [Figure 2] This is an example of an SEM image of the positive electrode active material according to Example 2. [Figure 3] This is an example of an SEM image of the positive electrode active material according to Example 3. [Figure 4] This is an example of an SEM image of the positive electrode active material related to Comparative Example 1. [Figure 5] This is an example of an SEM image of the positive electrode active material related to Comparative Example 2. [Figure 6] This is an example of an SEM image of the positive electrode active material related to Comparative Example 3. [Figure 7] This is an example of an SEM image of the positive electrode active material related to Comparative Example 4. [Figure 8] This is an example of an SEM image of the positive electrode active material according to Example 4. [Figure 9]This is an example of a SEM image of the positive electrode active material according to Example 5. [Figure 10] This is an example of a SEM image of the positive electrode active material according to Example 6. [Figure 11] This is an example of a SEM image of the positive electrode active material according to Comparative Example 5. [Figure 12] This is an example of a SEM image of the positive electrode active material according to Comparative Example 6. [Figure 13] This is an example of a SEM image of the positive electrode active material according to Comparative Example 7. [Figure 14] This is an example of a SEM image of the positive electrode active material according to Comparative Example 8. [Figure 15] This is an equivalent circuit model in AC impedance measurement.

Mode for Carrying Out the Invention

[0008] In this specification, the term "step" includes not only an independent step but also a step in which, even if it cannot be clearly distinguished from other steps, the intended purpose of the step is achieved. Also, the content of each component in the composition means the total amount of the plurality of substances corresponding to each component in the composition when there are a plurality of substances corresponding to each component in the composition, unless otherwise specified. Hereinafter, embodiments of the present invention will be described in detail. However, the embodiments shown below are examples of a positive electrode active material for a non-aqueous electrolyte secondary battery and a method for manufacturing the same for embodying the technical idea of the present invention, and the present invention is not limited to the positive electrode active material for a non-aqueous electrolyte secondary battery and the method for manufacturing the same shown below.

[0009] Positive electrode active material for non-aqueous electrolyte secondary battery Lithium, nickel, and at least one metal element M of titanium and zirconium 1 including a lithium transition metal composite oxide having a layered structure, and the lithium transition metal composite oxide has a 50% particle size D in the cumulative particle size distribution based on volume 50 average particle size D based on electron microscope observation SEM ratio D to 50 / D SEMThe ratio of the number of moles of nickel to the total number of moles of metals other than lithium is 0.3 or more and less than 1, and the ratio of the number of metal elements M to the total number of moles of metals other than lithium is 1 or more and 4 or less, and the ratio of the number of moles of nickel to the total number of moles of metals other than lithium is 0.3 or more and less than 1, and the ratio of the number of moles of metal elements M to the total number of moles of metals other than lithium 1 This is a positive electrode active material for a non-aqueous electrolyte secondary battery having a composition in which the ratio of the number of moles of is 0.025 or less.

[0010] Lithium, nickel, and at least one metallic element M of titanium and zirconium 1 This includes the total number of moles of metals other than lithium, and the metal element M 1 Ratio D has a composition in which the ratio of the number of moles is less than or equal to a predetermined value. 50 / D SEM A positive electrode active material comprising single-particle lithium transition metal composite oxide particles having a predetermined range exhibits excellent output characteristics in a non-aqueous electrolyte secondary battery composed of this material. This is because, for example, compared to single-particle lithium transition metal composite oxide particles that do not contain titanium and zirconium, the inclusion of at least one of titanium and zirconium improves lithium conductivity, thus improving the output characteristics.

[0011] The lithium transition metal composite oxide particles that constitute the positive electrode active material have a ratio of D 50 / D SEM The ratio D may be between 1 and 4. 50 / D SEM A value of 1 indicates a single particle, and the closer it is to 1, the fewer primary particles make up the composite oxide particle. Ratio D 50 / D SEM From the viewpoint of output characteristics, a value of 3.5 or less is preferred, 3 or less is more preferred, 2.5 or less is even more preferred, and 2 or less is particularly preferred. Also, ratio D 50 / D SEM The lower limit can be, for example, 1.1 or higher.

[0012] In lithium transition metal composite oxide particles, the average particle size D is determined by electron microscopy observation. SEM From a durability standpoint, the particle size is, for example, between 0.1 μm and 20 μm. Average particle size D based on electron microscope observation. SEMFrom the viewpoint of output characteristics, the lower limit is preferably 0.3 μm or more, more preferably 0.5 μm or more, and the upper limit is preferably 15 μm or less, more preferably 10 μm or less, even more preferably 8 μm or less, and particularly preferably 5 μm or less.

[0013] Average particle size D based on electron microscope observation SEM This is determined by using a scanning electron microscope (SEM) to observe particles at magnifications ranging from 1000x to 10000x depending on their particle size, selecting 100 primary particles whose outlines can be confirmed, calculating the spherical equivalent diameter for the selected particles using image processing software, and then determining the arithmetic mean of the obtained spherical equivalent diameters.

[0014] 50% particle size D of lithium transition metal composite oxide particles 50 For example, the particle size is 1 μm or more and 30 μm or less, preferably 1.5 μm or more, more preferably 3 μm or more, and from the viewpoint of output characteristics, preferably 10 μm or less, and more preferably 5.5 μm or less.

[0015] 50% particle size D 50 This is determined using a laser diffraction particle size distribution analyzer, as the particle size corresponding to 50% of the volume accumulation from the small diameter side in the volume-based cumulative particle size distribution measured under wet conditions. Similarly, the 90% particle size D described later is determined. 90 and 10% particle size D 10 These are determined as particle sizes corresponding to 90% and 10% of the volume accumulation from the smaller diameter side, respectively.

[0016] 90% particle size D in the volume-based cumulative particle size distribution of lithium transition metal composite oxide particles 90 10% particle size D 10 The ratio to D indicates, for example, the extent of the particle size distribution; a smaller ratio value indicates that the particle sizes are more uniform. 90 / D 10 For example, it may be 4.5 or less. Ratio D 90 / D 10 From the viewpoint of output characteristics, it is preferably 4 or less, and more preferably 3.9 or less. Also, ratio D 90 / D 10The lower limit can be, for example, 1.2 or higher.

[0017] Lithium transition metal composite oxides have a composition of lithium (Li), nickel (Ni), and at least one of the metallic elements M, titanium (Ti), and zirconium (Zr). 1 It contains and has a layered structure. The lithium transition metal composite oxide may have a ratio of the number of moles of nickel to the total number of moles of metals other than lithium (hereinafter also simply referred to as the [nickel ratio]) of, for example, 0.3 or more and less than 1. The lower limit of the nickel ratio is preferably 0.31 or more, more preferably 0.32 or more. The upper limit of the nickel ratio is preferably 0.98 or less, more preferably 0.8 or less, and particularly preferably 0.6 or less.

[0018] Lithium transition metal composite oxides are composed of at least one of the metallic elements M, titanium, and zirconium. 1 It includes. Lithium transition metal composite oxides have a ratio of the total number of moles of metals other than lithium to the number of metal elements M 1 The ratio of the number of moles is, for example, 0.025 or less, preferably 0.0001 to 0.022, and more preferably 0.0003 to 0.021, from the viewpoint of output characteristics. Metal element M 1 In the case of titanium, from the viewpoint of output characteristics, it is preferably 0.0004 to 0.015, and more preferably 0.0009 to 0.011. 1 In the case of zirconium, from the viewpoint of output characteristics, it is preferably 0.004 to 0.022, and more preferably 0.009 to 0.021.

[0019] Lithium transition metal composite oxides consist of at least one metallic element M selected from the group consisting of cobalt (Co), manganese (Mn), and aluminum (Al). 2 It may further contain: Lithium transition metal composite oxides contain at least one metallic element M selected from the group consisting of cobalt, manganese, and aluminum. 2 If it includes, the metal element M relative to the total number of moles of metals other than lithium. 2The ratio of the number of moles is, for example, greater than 0 and less than or equal to 0.75. 2 If it contains cobalt, it is preferably 0.05 or more and 0.5 or less, and more preferably 0.1 or more and 0.4 or less. Metal element M 2 If it contains manganese, the amount is preferably 0.05 or more and 0.5 or less, and more preferably 0.1 or more and 0.4 or less. Metal element M 2 If it contains aluminum, the amount is preferably 0.05 or more and 0.5 or less, and more preferably 0.1 or more and 0.4 or less.

[0020] Lithium transition metal composite oxides are composed of lithium, nickel, and the metallic element M. 1 and metallic element M 2 Other metal elements M 3 It may further contain: Metal element M 3 Examples include boron (B), sodium (Na), magnesium (Mg), silicon (Si), phosphorus (P), sulfur (S), potassium (K), calcium (Ca), vanadium (V), chromium (Cr), zinc (Zn), strontium (Sr), yttrium (Y), niobium (Nb), molybdenum (Mo), indium (In), tin (Sn), barium (Ba), lanthanum (La), cerium (Ce), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), etc., and may be at least one selected from the group consisting of these. Lithium transition metal composite oxides are composed of the metal element M 3 If it includes, the metal element M relative to the total number of moles of metals other than lithium. 3 The ratio of the number of moles is, for example, greater than 0 and 0.1 or less, preferably 0.005 or more and 0.05 or less, and more preferably 0.01 or more and 0.04 or less.

[0021] In lithium transition metal composite oxides, the ratio of moles of lithium to the total number of moles of other metals is, for example, 0.95 to 1.5, preferably 1 to 1.3.

[0022] The lithium transition metal composite oxide may have a composition represented by, for example, the following formula (1). Li p Ni w M 1 x M 2 y M 3 z O 2+α (1) (In formula (1), p, w, x, y, z, and α satisfy 0.95 ≤ p ≤ 1.5, 0.3 ≤ w < 1, 0 < x ≤ 0.025, 0 ≤ y ≤ 0.75, 0 ≤ z ≤ 0.1, w + x + y + z ≤ 1, -0.1 ≤ α ≤ 0.1, M 1 represents at least one of Ti and Zr, M 2 represents at least one selected from Co, Mn, and Al, M 3 represents at least one selected from the group consisting of B, Na, Mg, Si, P, S, K, Ca, V, Cr, Zn, Sr, Y, Nb, Mo, In, Sn, Ba, La, Ce, Nd, Sm, Eu, and Gd.)

[0023] Method for manufacturing a positive electrode active material for a non-aqueous electrolyte secondary battery The lithium transition metal composite oxide can be referred to, for example, in JP-A-2017-188443 (US Patent Publication 2017-0288221), JP-A-2017-188444 (US Patent Publication 2017-0288222), JP-A-2017-188445 (US Patent Publication 2017-0288223), etc., but specifically, it can be prepared as follows. The method for preparing the lithium transition metal composite oxide may include, for example, a precursor preparation step of preparing a precursor and a synthesis step of synthesizing the lithium transition metal composite oxide.)

[0024] In the precursor preparation step, a precursor containing an oxide containing nickel is prepared. The precursor may be appropriately selected and prepared from commercially available products. Examples of the method for obtaining an oxide containing nickel include a coprecipitation method in which a nickel salt is dissolved in a solvent, and a precipitate having a target composition is obtained by adjusting the temperature, pH, adding a complexing agent, etc., and an oxide containing nickel is obtained by heat-treating these precipitates. An example of the method for manufacturing an oxide containing nickel will be described below.)

[0025] A method for obtaining nickel-containing oxides by coprecipitation may include a seed generation step of adjusting the pH of a nickel solution to obtain seed crystals, a crystallization step of growing the generated seed crystals to obtain nickel-containing hydroxides, and an oxidation step of heat-treating the obtained nickel-containing hydroxides to obtain nickel-containing oxides. For details on such a method for obtaining nickel-containing oxides, see, for example, Japanese Patent Publication No. 2003-292322 and Japanese Patent Publication No. 2011-116580 (US Patent Publication No. 2012-270107).

[0026] In the seed generation process, a liquid medium containing seed crystals is prepared by adjusting the pH of a nickel ion-containing solution to, for example, 11 to 13. The seed crystals may contain nickel hydroxides. Examples of nickel ion-containing solutions include nickel sulfate, nitrate, hydrochloride, etc. The temperature inside the tank during the seed generation process can be, for example, 20°C to 80°C. The atmosphere during the seed generation process can be a low-oxidizing atmosphere, for example, by maintaining an oxygen concentration of 10% by volume or less.

[0027] In the seed generation process, the seed crystal may contain nickel as well as the aforementioned metal element M as needed. 1 , metallic element M 2 and metallic element M 3 It may contain hydroxides containing nickel ions. In that case, instead of a solution containing nickel ions, nickel ions and, if necessary, metal element M may be used. 1 A solution containing ions of metal element M 2 A solution containing ions and the metal element M 3 A liquid medium containing seed crystals is prepared by adjusting the pH of a mixed solution, which is a mixture of solutions containing ions, to a range of 11 to 13. The mixed solution contains nickel salts and the metal element M. 1 Salt, metal element M 2 Salts and metal elements M 3 It can be prepared by dissolving the salt in water in the desired proportion. Metal element M 1 Salt, metal element M 2 Salts and metal elements M 3Examples of the salt include sulfates, nitrates, hydrochlorides, etc. The temperature in the tank in the seed generation step can be, for example, from 20°C to 80°C. The atmosphere in the seed generation step can be a low-oxidizing atmosphere, and for example, the oxygen concentration can be maintained at 10% by volume or less.

[0028] In the crystallization step, the generated seed crystals are grown to obtain a precipitate containing nickel. The growth of the seed crystals can be carried out, for example, by adding a solution containing nickel ions to a liquid medium containing the seed crystals while maintaining its pH at, for example, from 7 to 12.5, preferably from 7.5 to 12. The addition time of the solution containing nickel ions is, for example, from 1 hour to 24 hours, preferably from 3 hours to 18 hours. The temperature in the tank in the crystallization step can be, for example, from 20°C to 80°C. The atmosphere in the crystallization step is the same as that in the seed generation step. The pH adjustment in the seed generation step and the crystallization step can be carried out using acidic aqueous solutions such as sulfuric acid aqueous solution and nitric acid aqueous solution, and alkaline aqueous solutions such as sodium hydroxide aqueous solution and ammonia water.

[0029] The precipitate containing nickel in the crystallization step contains nickel, metal element M 1 , metal element M 2 and metal element M 3 may be contained in a desired ratio. The precipitate containing nickel, metal element M 1 , metal element M 2 and metal element M 3 contained in a desired ratio can be prepared by adding a mixed solution containing nickel ions and, if necessary, ions of metal element M 1 , ions of metal element M 2 and ions of metal element M 3 instead of the solution containing nickel ions in the crystallization step. Also, in parallel with the addition of the solution containing nickel ions, if necessary, a solution containing ions of metal element M 1 , a solution containing ions of metal element M 2 and a solution containing ions of metal element M 3 can be added respectively.

[0030] In the oxidation step of obtaining an oxide containing nickel, a precipitate containing nickel obtained in the crystallization step is heat-treated to obtain an oxide containing nickel. The upper limit of the heat treatment temperature in the step of obtaining an oxide containing nickel is, for example, 500 °C or lower, preferably 350 °C or lower. Also, the lower limit of the heat treatment temperature is, for example, 100 °C or higher, preferably 200 °C or higher. The heat treatment time is, for example, from 0.5 hours to 48 hours, preferably from 5 hours to 24 hours. The heat treatment atmosphere may be in air or an atmosphere containing oxygen. The heat treatment can be carried out using, for example, a box furnace, a rotary kiln furnace, a pusher furnace, a roller hearth kiln furnace, etc.

[0031] In the oxidation step, instead of the precipitate containing nickel, nickel, metal element M 1 , metal element M 2 and metal element M 3 are used to obtain a composite oxide (hereinafter also referred to as "composite oxide") containing nickel, metal element M 1 , metal element M 2 and metal element M 3 by using a precipitate containing them in a desired ratio.

[0032] The average particle size of the oxide or composite oxide containing nickel is, for example, 2 μm or more and 30 μm or less, preferably 3 μm or more and 25 μm or less. The average particle size of the composite oxide is the volume average particle size, which is the value at which the volume integration value from the small particle size side in the volume-based particle size distribution obtained by the laser scattering method becomes 50%.

[0033] [[ID=2t]]In the synthesis step, a lithium mixture obtained by mixing an oxide containing nickel, a lithium compound, and at least one of a titanium compound and a zirconium compound is heat-treated to obtain a heat-treated product. The obtained heat-treated product has a layered structure and contains a lithium transition metal composite oxide containing nickel and at least one of titanium and zirconium.

[0034] Examples of lithium compounds to be mixed with nickel-containing oxides include lithium hydroxide, lithium carbonate, and lithium oxide. The particle size of the lithium compound used in the mixture is preferably 2 μm to 20 μm, with a 50% average particle size of 0.1 μm to 100 μm, based on the cumulative particle size distribution by volume.

[0035] Examples of titanium compounds to be mixed with nickel-containing oxides include titanium hydroxide and titanium oxide. The particle size of the titanium compound used in the mixture is, for example, 0.1 μm to 100 μm, with a preferred size of 2 μm to 20 μm, based on the 50% average particle size of the cumulative particle size distribution by volume.

[0036] Examples of zirconium compounds to be mixed with nickel-containing oxides include zirconium hydroxide, zirconium oxide, and zirconium oxychloride. The particle size of the zirconium compound used in the mixture is, for example, 0.1 μm to 100 μm, with a preferred size of 2 μm to 20 μm, based on the 50% average particle size of the cumulative particle size distribution by volume.

[0037] In a lithium mixture, the ratio of the total number of moles of lithium to the total number of moles of other metal elements is, for example, between 0.95 and 1.5, and the ratio of the total number of moles of titanium and zirconium to the total number of moles of other metal elements is greater than 0 and less than or equal to 0.025. Mixing can be carried out using, for example, a high-speed shear mixer.

[0038] The lithium mixture contains at least one metallic element M selected from the group consisting of cobalt, manganese, and aluminum. 2 It may further include: Metal element M 2 Lithium mixtures containing the metal element M 2 The elemental form of a metal or metallic element M 2 It can be obtained by further mixing compounds containing the metal element M. 2Compounds containing this element include oxides, hydroxides, chlorides, nitrides, carbonates, sulfates, nitrates, acetates, oxalates, etc. The mixture contains the metal element M. 2 If it includes, the metal element M relative to the total number of moles of metals other than lithium. 2 The ratio of the number of moles is, for example, greater than 0 and less than or equal to 0.75.

[0039] Lithium mixtures contain the metallic element M 3 It may further contain: Metal element M 3 Examples include boron (B), sodium (Na), magnesium (Mg), silicon (Si), phosphorus (P), sulfur (S), potassium (K), calcium (Ca), vanadium (V), chromium (Cr), zinc (Zn), strontium (Sr), yttrium (Y), niobium (Nb), molybdenum (Mo), indium (In), tin (Sn), barium (Ba), lanthanum (La), cerium (Ce), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), etc., and it may be at least one selected from the group consisting of these elements. Metal element M 3 Lithium compounds containing the metal element M 3 The elemental form of a metal or metallic element M 3 A mixture can be obtained by further mixing compounds containing the metal element M. 3 Compounds containing this element include oxides, hydroxides, chlorides, nitrides, carbonates, sulfates, nitrates, acetates, oxalates, etc. The mixture contains the metal element M. 3 If it includes, the metal element M relative to the total number of moles of metals other than lithium. 3 The ratio of the number of moles is, for example, greater than 0 and less than or equal to 0.1.

[0040] In the synthesis process, a composite oxide obtained in the oxidation process may be used instead of a nickel-containing oxide. A mixture is obtained by mixing the composite oxide with a lithium compound and, if necessary, at least one of a titanium compound and a zirconium compound.

[0041] The heat treatment temperature for the lithium mixture is, for example, 550°C to 1100°C, but preferably 600°C to 1080°C, and more preferably 700°C to 1070°C. The heat treatment of the mixture may be carried out at a single temperature or at multiple temperatures. When heat treatment is carried out at multiple temperatures, for example, it is desirable to hold the first temperature for a predetermined time, then further increase the temperature, and hold the second temperature for a predetermined time. The first temperature is, for example, 800°C to 900°C, and the second temperature is, for example, 900°C to 1000°C.

[0042] When heat treatment is performed at a single temperature, the heat treatment time is, for example, 1 hour or more and 20 hours or less, preferably 5 hours or more and 10 hours or less. When heat treatment is performed at multiple temperatures, the heat treatment time at the first temperature is, for example, 1 hour or more and 20 hours or less, and the heat treatment time at the second temperature is, for example, 1 hour or more and 20 hours or less. The heat treatment time at the first temperature and the heat treatment time at the second temperature may be the same or different. If the heat treatment time at the first temperature and the heat treatment time at the second temperature are different, for example, the heat treatment time at the first temperature can be made longer than the heat treatment time at the second temperature. Here, the heat treatment at the first temperature and the heat treatment at the second temperature may be performed consecutively or independently. When the heat treatment at the first temperature and the heat treatment at the second temperature are performed consecutively, the heating rate from the first temperature to the second temperature can be, for example, 5°C / min.

[0043] The heat treatment atmosphere may be in the open air or an oxygen-containing atmosphere. The heat treatment can be carried out using, for example, a box furnace, rotary kiln, pusher furnace, roller hearth kiln, etc.

[0044] Dispersion treatment is performed on the heat-treated material as needed. Rather than pulverization treatment involving strong shear force or impact, dispersion treatment dissociates the sintered primary particles, resulting in lithium transition metal composite oxide particles with a narrow particle size distribution and uniform particle size. Dispersion treatment may be performed dry or wet, but dry treatment is preferred. Dispersion treatment can be performed using, for example, a ball mill or jet mill. The conditions for dispersion treatment are, for example, the D of the lithium transition metal composite oxide particles after dispersion treatment. 50 / D SEM This can be set to a desired range, for example, between 1 and 4.

[0045] For example, when performing dispersion processing with a ball mill, resin media can be used. Examples of resin media materials include urethane resin and nylon resin. Generally, alumina and zirconia are used as media materials in ball mills, and particles are pulverized by these media. In contrast, using resin media allows for the dissociation of sintered primary particles without pulverization. The size of the resin media can be, for example, φ5mm to 30mm. For the shell, for example, urethane resin or nylon resin can be used. The dispersion processing time is, for example, 3 to 60 minutes, with 10 to 30 minutes being preferable. The conditions for dispersion processing using a ball mill are as follows: 50 / D SEM To achieve this, the amount of media, rotation or amplitude speed, dispersion time, media specific gravity, etc., should be adjusted.

[0046] For example, when dispersion processing is performed with a jet mill, the primary particles are not pulverized, and the desired D 50 / D SEM To achieve this, the supply pressure, grinding pressure, etc., should be adjusted. The supply pressure can be, for example, 0.1 to 0.5 MPa, and the grinding pressure can be, for example, 0.1 to 0.6 MPa. By the above preparation method, single-particle lithium transition metal composite oxides can be efficiently produced.

[0047] Positive electrode for non-aqueous electrolyte secondary batteries The positive electrode for a non-aqueous electrolyte secondary battery comprises a current collector and a positive electrode active material layer disposed on the current collector and containing a positive electrode active material for a non-aqueous electrolyte secondary battery manufactured by the aforementioned manufacturing method. A non-aqueous electrolyte secondary battery equipped with such a positive electrode can achieve high initial efficiency and high durability.

[0048] Examples of materials for the current collector include aluminum, nickel, and stainless steel. The positive electrode active material layer can be formed by applying a positive electrode mixture, obtained by mixing the above-mentioned positive electrode active material, conductive material, binder, etc., with a solvent, onto the current collector, and then performing drying, pressurizing, etc. Examples of conductive materials include natural graphite, artificial graphite, and acetylene black. Examples of binders include polyvinylidene fluoride, polytetrafluoroethylene, and polyamide acrylic resin.

[0049] Nonaqueous electrolyte secondary battery A non-aqueous electrolyte secondary battery comprises a positive electrode for a non-aqueous electrolyte secondary battery. In addition to the positive electrode for a non-aqueous electrolyte secondary battery, the non-aqueous electrolyte secondary battery is configured to include a negative electrode for a non-aqueous electrolyte secondary battery, a non-aqueous electrolyte, a separator, etc. For the negative electrode, non-aqueous electrolyte, separator, etc. in the non-aqueous electrolyte secondary battery, for example, those described in Japanese Patent Publication No. 2002-075367, Japanese Patent Publication No. 2011-146390, Japanese Patent Publication No. 2006-12433 (the entire disclosures of these are incorporated herein by reference), etc., can be used as appropriate. [Examples]

[0050] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0051] First, the methods for measuring physical properties in the following examples and comparative examples will be explained. For D50, D10, and D90, the cumulative particle size distribution based on volume was measured using a laser diffraction particle size distribution analyzer (SALD-3100, Shimadzu Corporation), and the particle size corresponding to 50% of the volume accumulation from the smallest diameter side was determined. In addition, the average particle size D was determined based on electron microscope observation. SEM For this purpose, using a scanning electron microscope (SEM), 100 particles whose outlines could be confirmed were selected from images observed at magnifications ranging from 1,000x to 10,000x. The spherical equivalent diameter was calculated for the selected particles using image processing software (ImageJ), and the arithmetic mean of the obtained spherical equivalent diameters was used to determine the value.

[0052] (Example 1) (Seed generation process) First, 10 kg of water was added to the reaction vessel and stirred while an ammonium aqueous solution was added to adjust the ammonium ion concentration to 1.8% by mass. The vessel temperature was set to 25°C, and nitrogen gas was circulated to maintain the oxygen concentration in the reaction vessel space at 10% by volume or less. A 25% by mass sodium hydroxide aqueous solution was added to the water in the reaction vessel to adjust the pH value of the solution to 13.5 or higher. Next, nickel sulfate solution, cobalt sulfate solution, and manganese sulfate solution were mixed to prepare a mixed aqueous solution with a molar ratio of 55:20:25. This mixed aqueous solution was added until the solute amounted to 4 moles, and seed generation was carried out while controlling the pH value of the reaction solution to 12.0 or higher with sodium hydroxide aqueous solution.

[0053] (Crystallization process) After the seed generation step, the temperature inside the tank was maintained at 25°C or higher until the end of the crystallization step. Also, solute 12 Prepare a 00 mole mixed aqueous solution, and together with the ammonia aqueous solution, add the ammonium ions in the solution. While maintaining a concentration of 2000 ppm or higher, ensure that no new species are generated in the reaction vessel. The ingredients were added simultaneously over a period of time. During the reaction, the pH of the reaction solution was measured using a sodium hydroxide solution. The temperature was controlled to be maintained between 10.5 and 12.0. Sequential sampling was performed during the reaction, and composite samples were taken. Hydroxide particles D 50The addition was stopped when the particle size reached approximately 4.5 μm. Next, the product was washed with water, filtered, and dried to obtain composite hydroxide particles. The obtained hydroxide precursor was heat-treated at 300°C for 20 hours under an atmospheric environment, resulting in a composition ratio of Ni / Co / Mn = 0.55 / 0.20 / 0.25, and D 10 =3.8μm, D 50 =4.6μm, D 90 = 5.7 μm, D 90 / D 10 A composite oxide with a value of =1.5 was obtained.

[0054] (synthesis process) The obtained composite oxide, lithium carbonate, and titanium oxide were mixed so that Li / (Ni+Co+Mn) = 1.08 and Ti was 0.1 mol% relative to Ni+Co+Mn to obtain a raw material mixture. The obtained raw material mixture was fired in air at 850°C for 9.5 hours, then fired at 950°C for 6 hours to obtain a sintered body. The obtained sintered body was crushed and dispersed in a resin ball mill for 15 minutes, and then passed through a dry sieve to obtain a powder. Based on the above, the average particle size D was obtained from electron microscope observation. SEM It is 2.1 μm, D 10 =2.8μm, D 50 =4.7μm, D 90 =7.5μm, average particle size D SEM D 50 Ratio D 50 / D SEM The ratio D in the particle size distribution is 2.2. 90 / D 10 It is 2.7, and the empirical formula is Li 1.08 Ni 0.55 Co 0.20 Mn 0.25 Ti 0.001 Lithium transition metal composite oxide particles represented by O2 were obtained. The physical properties of the obtained lithium transition metal composite oxide particles are shown in Table 1, and the SEM image is shown in Figure 1.

[0055] (Example 2) The synthesis process was carried out in the same manner as in Example 1, except that the composite oxide, lithium carbonate, and titanium oxide were mixed in a ratio of Li / (Ni+Co+Mn) = 1.08 and Ti was present at 0.5 mol% relative to Ni+Co+Mn. The physical properties of the obtained lithium transition metal composite oxide particles are shown in Table 1, and the SEM images are shown in Figure 2.

[0056] (Example 3) The synthesis process was carried out in the same manner as in Example 1, except that the composite oxide, lithium carbonate, and titanium oxide were mixed in such a way that Li / (Ni+Co+Mn) = 1.08 and Ti was present at 1 mol% relative to Ni+Co+Mn. The physical properties of the obtained lithium transition metal composite oxide particles are shown in Table 1, and the SEM images are shown in Figure 3.

[0057] (Comparative Example 1) The procedure was the same as in Example 1, except that titanium oxide was not used in the synthesis process. The physical properties of the obtained lithium transition metal composite oxide particles are shown in Table 1, and the SEM images are shown in Figure 4.

[0058] (Comparative Example 2) The raw material mixture obtained in the synthesis process was fired in air at 850°C for 9.5 hours to obtain a sintered body. The procedure was the same as in Comparative Example 1, except that the obtained sintered body was crushed, dispersed in a resin ball mill for 10 minutes, and then sieved through a dry sieve to obtain a powder. The physical properties of the obtained lithium transition metal composite oxide particles are shown in Table 1, and the SEM image is shown in Figure 5.

[0059] (Comparative Example 3) The synthesis process was carried out in the same manner as in Comparative Example 2, except that the composite oxide, lithium carbonate, and titanium oxide were mixed in a ratio of Li / (Ni+Co+Mn) = 1.08 and Ti was present at 0.5 mol% relative to Ni+Co+Mn. The physical properties of the obtained lithium transition metal composite oxide particles are shown in Table 1, and the SEM images are shown in Figure 6.

[0060] (Comparative Example 4) The synthesis process was carried out in the same manner as in Comparative Example 2, except that the composite oxide, lithium carbonate, and titanium oxide were mixed in such a way that Li / (Ni+Co+Mn) = 1.08 and Ti was present at 1 mol% relative to Ni+Co+Mn. The physical properties of the obtained lithium transition metal composite oxide particles are shown in Table 1, and the SEM images are shown in Figure 7.

[0061] [Table 1]

[0062] (Example 4) The synthesis process was carried out in the same manner as in Example 1, except that zirconium oxide was used instead of titanium oxide in the synthesis process, and the composite oxide, lithium carbonate, and zirconium oxide were mixed so that Li / (Ni+Co+Mn) = 1.08 and Zr was 0.5 mol% relative to Ni+Co+Mn. The physical properties of the obtained lithium transition metal composite oxide particles are shown in Table 2, and the SEM image is shown in Figure 8.

[0063] (Example 5) The synthesis process was carried out in the same manner as in Example 1, except that the composite oxide, lithium carbonate, and zirconium oxide were mixed in such a way that Li / (Ni+Co+Mn) = 1.08 and Zr was present at 1 mol% relative to Ni+Co+Mn. The physical properties of the obtained lithium transition metal composite oxide particles are shown in Table 2, and the SEM images are shown in Figure 9.

[0064] (Example 6) The synthesis process was carried out in the same manner as in Example 1, except that the composite oxide, lithium carbonate, and zirconium oxide were mixed in such a way that Li / (Ni+Co+Mn) = 1.08 and Zr was present at 2 mol% relative to Ni+Co+Mn. The physical properties of the obtained lithium transition metal composite oxide particles are shown in Table 2, and the SEM images are shown in Figure 10.

[0065] (Comparative Example 5) The procedure was the same as in Example 4, except that zirconium oxide was not used in the synthesis process. The physical properties of the obtained lithium transition metal composite oxide particles are shown in Table 2, and the SEM images are shown in Figure 11.

[0066] (Comparative Example 6) The raw material mixture obtained in the synthesis process was fired in air at 850°C for 9.5 hours to obtain a sintered body. The procedure was the same as in Comparative Example 5, except that the obtained sintered body was crushed, dispersed in a resin ball mill for 10 minutes, and then sieved through a dry sieve to obtain a powder. The physical properties of the obtained lithium transition metal composite oxide particles are shown in Table 2, and the SEM image is shown in Figure 12.

[0067] (Comparative Example 7) The synthesis process was carried out in the same manner as in Comparative Example 6, except that the composite oxide, lithium carbonate, and zirconium oxide were mixed in a ratio of Li / (Ni+Co+Mn) = 1.08 and Zr was present at 0.5 mol% relative to Ni+Co+Mn. The physical properties of the obtained lithium transition metal composite oxide particles are shown in Table 2, and the SEM images are shown in Figure 13.

[0068] (Comparative Example 8) The synthesis process was carried out in the same manner as in Comparative Example 6, except that the composite oxide, lithium carbonate, and zirconium oxide were mixed in such a way that Li / (Ni+Co+Mn) = 1.08 and Zr was present at 1 mol% relative to Ni+Co+Mn. The physical properties of the obtained lithium transition metal composite oxide particles are shown in Table 2, and the SEM images are shown in Figure 14.

[0069] [Table 2]

[0070] Fabrication of evaluation batteries Using the positive electrode active material obtained above, an evaluation battery was fabricated according to the following procedure.

[0071] Fabrication of the positive electrode A positive electrode mixture was prepared by dispersing 92 parts by mass of positive electrode active material, 3 parts by mass of acetylene black, and 5 parts by mass of polyvinylidene fluoride (PVDF) in N-methyl-2-pyrrolidone (NMP). The obtained positive electrode mixture was applied to aluminum foil to be used as a current collector, dried, compressed and molded using a roll press, and then cut to a predetermined size to produce a positive electrode.

[0072] Fabrication of the negative electrode A negative electrode slurry was prepared by dispersing and dissolving 97.5 parts by mass of artificial graphite, 1.5 parts by mass of carboxymethylcellulose (CMC), and 1.0 part by mass of styrene-butadiene rubber (SBR) in pure water. The obtained negative electrode slurry was applied to a current collector made of copper foil, dried, compressed and molded using a roll press, and then cut to a predetermined size to produce a negative electrode.

[0073] Fabrication of evaluation batteries After attaching lead electrodes to the positive and negative electrode current collectors, a separator was placed between the positive and negative electrodes, and these were then placed in a laminated pouch. Next, this was vacuum-dried at 65°C to remove moisture adsorbed on each component. After that, an electrolyte was injected into the laminated pouch under an argon atmosphere and sealed to produce an evaluation battery. The electrolyte used was a mixture of ethylene carbonate (EC) and methyl ethyl carbonate (MEC) in a volume ratio of 3:7, with lithium hexafluoride phosphate (LiPF6) dissolved in it to a concentration of 1 mol / L. The evaluation battery thus obtained was placed in a constant temperature bath at 25°C and aged with a weak current, after which the following evaluations were performed. The evaluation results are shown in Table 3 or Table 4. The evaluation results using the positive electrode active materials obtained in Examples 1 to 3 and Comparative Examples 1 to 4 are shown in Table 3, and the evaluation results using the positive electrode active materials obtained in Examples 4 to 6 and Comparative Examples 5 to 8 are shown in Table 4.

[0074] (Room temperature DC internal resistance measurement) The evaluation batteries, after aging, were placed in an environment of 25°C, and their DC internal resistance was measured. After constant current charging up to 50% charge depth at a full charge voltage of 4.2V, a specific current i A pulse discharge was performed for 10 seconds, and the voltage V at the 10-second mark was measured. The horizontal axis represents current i, and the vertical axis represents Take the voltage V and plot the intersection points, then measure the slope of the line connecting the intersection points as the DC internal resistance (DC-IR). ) was set. Note that the currents i = 0.03A, 0.05A, 0.08A, 0.105A and 0. The current was set to 13A. A low DC-IR indicates good output characteristics.

[0075] (Low temperature DC internal resistance measurement) The evaluation batteries, after aging, were placed in an environment of -25°C, and their DC internal resistance was measured. After constant current charging up to 50% charge depth at a full charge voltage of 4.2V, a specific current i A pulse discharge was performed for 10 seconds, and the voltage V at the 10-second mark was measured. The horizontal axis represents current i, and the vertical axis represents Take the voltage V and plot the intersection points, then measure the slope of the line connecting the intersection points as the DC internal resistance (DC-IR). ) was set. Note that the currents i = 0.03A, 0.05A, 0.08A, 0.105A and 0. The current was set to 13A. A low DC-IR indicates good output characteristics.

[0076] (Calculation of resistance increase rate) aging The obtained evaluation battery underwent one charge-discharge cycle consisting of constant voltage / constant current charging at a charging voltage of 4.3V (counter electrode C) and a charging current of 0.1C, and constant voltage / constant current discharging at a discharge voltage of 2.75V (counter electrode C) and a discharge current of 0.2C. Subsequently, the charging current was changed to 0.2C and the charge-discharge cycle was performed twice to allow the non-aqueous electrolyte to permeate the positive and negative electrodes.

[0077] Measurement of AC impedance After aging, the battery was charged to 100% state of charge (SOC) using constant voltage and constant current charging at a charging voltage of 4.3V and a charging current of 0.2C. Resistance measurements were performed using the AC impedance method in the range of 1MHz to 0.1Hz using impedance measuring devices (1470E and 1455A, both manufactured by SOLARTRON), and a Nyquist plot was obtained. Following the above resistance measurements, the battery was discharged at a constant voltage and constant current of 2.75V and a discharge current of 0.2C. Next, the evaluation battery underwent 200 charge-discharge cycles at a constant temperature of 45°C, with each cycle consisting of constant voltage and constant current charging at a charging voltage of 4.3V and a charging current of 1C, and constant voltage and constant current discharge at a discharge voltage of 2.75V and a discharge current of 1C. After 200 charge-discharge cycles, the battery was charged to 100% SOC using constant voltage and constant current charging at a charging voltage of 4.3V and a charging current of 0.2C, and resistance measurements were performed similarly using the impedance measuring devices described above, to obtain a Nyquist plot.

[0078] Based on the obtained Nyquist plot, the equivalent circuit model shown in Figure 15 was constructed, and fitting calculations were performed. The resistance with the higher peak frequency of the measured impedance arc component was considered to be the resistance originating from the negative electrode, and the resistance with the lower peak frequency was considered to be the resistance originating from the positive electrode. The resistance value originating from the positive electrode before the cycle was R(p), and the resistance value originating from the positive electrode after the cycle was R(a), and the resistance increase rate was calculated as R(a) / R(p) × 100 (%).

[0079] [Table 3]

[0080] Table 3 shows that the positive electrode active materials in Examples 1 to 3 have a ratio of D 50 / D SEMA battery comprising a positive electrode active material in which the number of particles is between 1 and 4 (single particle) and the ratio of the number of moles of titanium to the total number of moles of metals other than lithium (hereinafter referred to as the ratio of the number of moles of titanium) is 0.025 or less was found to have superior room temperature power characteristics, low temperature power characteristics, and resistance increase rate compared to Comparative Example 1 (single particle) which does not contain titanium. Furthermore, it was found that Example 2, in which the ratio of the number of moles of titanium is 0.005, and Example 3, in which the ratio of the number of moles of titanium is 0.01, showed higher relative room temperature power characteristic improvement rates, relative low temperature power characteristic improvement rates, and relative resistance increase improvement rates compared to Example 1, in which the ratio of the number of moles of titanium is 0.001. Note that the relative room temperature power characteristic improvement rates, relative low temperature power characteristic improvement rates, and relative resistance increase improvement rates for Examples 1 to 3 in Table 3 are obtained by dividing the value of each characteristic in each example by the value of each characteristic in Comparative Example 1 and multiplying by 100.

[0081] Table 3 shows that Comparative Examples 3 and 4 (aggregated particles), in which the ratio of the number of moles of titanium to the total number of moles of metals other than lithium was 0.025 or less, did not show much improvement in room temperature power characteristics, low temperature power characteristics, or resistance increase rate compared to Comparative Example 2 (aggregated particles) which did not contain titanium. Furthermore, in Comparative Examples 3 and 4, the relative improvement rate of room temperature power characteristics, relative improvement rate of low temperature power characteristics, and relative resistance increase rate did not show much improvement. From these findings, it can be concluded that the effect of having a ratio of the number of moles of titanium of 0.025 or less is not significant in relation to ratio D 50 / D SEM It was confirmed that this is due to the effect of the positive electrode active material having a ratio of 1 to 4 (single particle). Note that the relative room temperature power characteristic improvement rate, relative low temperature power characteristic improvement rate, and relative resistance increase improvement rate in Comparative Examples 3 and 4 in Table 3 are obtained by dividing the value of each characteristic in each example by the value of each characteristic in Comparative Example 2 and multiplying by 100.

[0082] [Table 4]

[0083] Table 4 shows that the positive electrode active materials in Examples 4 to 6 have ratio D 50 / D SEMA battery comprising a positive electrode active material in which the number of moles of zirconium is between 1 and 4 (single particle) and the ratio of the number of moles of zirconium to the total number of moles of metals other than lithium (hereinafter referred to as the ratio of molars of zirconium) is 0.025 or less was found to have superior room temperature power characteristics, low temperature power characteristics, and resistance increase rate compared to Comparative Example 5 (single particle) which does not contain zirconium. Furthermore, it was found that Example 5, in which the ratio of molars of zirconium is 0.01, and Example 6, in which the ratio of molars of zirconium is 0.02, showed higher relative room temperature power characteristic improvement rates, relative low temperature power characteristic improvement rates, and relative resistance increase improvement rates compared to Example 4, in which the ratio of molars of zirconium is 0.005. Note that the relative room temperature power characteristic improvement rates, relative low temperature power characteristic improvement rates, and relative resistance increase improvement rates for Examples 4 to 6 in Table 4 are obtained by dividing the value of each characteristic in each example by the value of each characteristic in Comparative Example 5 and multiplying by 100.

[0084] Table 4 shows that Comparative Examples 7 and 8 (aggregated particles), in which the ratio of the number of moles of zirconium to the total number of moles of metals other than lithium was 0.025 or less, did not show much improvement in room temperature power characteristics, low temperature power characteristics, or resistance increase rate compared to Comparative Example 6 (aggregated particles) which did not contain zirconium. Furthermore, in Comparative Examples 7 and 8, the relative improvement rate of room temperature power characteristics, relative improvement rate of low temperature power characteristics, and relative resistance increase rate did not show much improvement. From these findings, it can be concluded that the effect of having a ratio of the number of moles of zirconium of 0.025 or less is not significant in relation to ratio D 50 / D SEM It was confirmed that this is due to the effect of the positive electrode active material having a ratio of 1 to 4 (single particle). Note that the relative room temperature power characteristic improvement rate, relative low temperature power characteristic improvement rate, and relative resistance increase improvement rate in Comparative Examples 7 and 8 in Table 4 are calculated by dividing the value of each characteristic in each example by the value of each characteristic in Comparative Example 6 and multiplying by 100.

Claims

1. A single positive electrode active material contained in the positive electrode of a non-aqueous electrolyte secondary battery, Lithium, nickel, and at least one metallic element M of titanium and zirconium １ and at least one metallic element M selected from the group consisting of cobalt, manganese, and aluminum. ２ It contains a lithium transition metal composite oxide having a layered structure including the following: The lithium transition metal composite oxide has a ratio D ５０ of the average particle size D ＳＥＭ based on electron microscope observation to the 50% particle size D ５０ in the cumulative particle size distribution by volume basis of 1 or more and 4 or less, and a ratio D ＳＥＭ / D ９０ of the 90% particle size D １０ to the 10% particle size D ９０ in the cumulative particle size distribution by volume basis of 1.2 or more and 3.9 or less, and a ratio of the number of moles of nickel to the total number of moles of metals other than lithium of 0.3 or more and less than 1, and a ratio of the number of moles of the metal element M １０ to the total number of moles of metals other than lithium of 0.025 or less, the metal element M １ contains cobalt, and the ratio of the number of moles of M ２ to the total number of moles of metals other than lithium is 0.05 or more and 0.5 or less, and is a positive electrode active material for a non-aqueous electrolyte secondary battery having such a composition.​​

2. The lithium transition metal composite oxide has a ratio of M of the metal element to the total number of moles of metals other than lithium. １ The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, having a composition in which the ratio of the number of moles of is 0.0001 or more and 0.022 or less.

3. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the lithium transition metal composite oxide has a composition represented by the following formula (1). Li ｐ Ni ｗ M １ ｘ M ２ ｙ M ３ ｚ O ２＋α (1) (In equation (1), p, w, x, y, z, and α satisfy 0.95 ≤ p ≤ 1.5, 0.3 ≤ w < 1, 0 < x ≤ 0.025, 0 ≤ y ≤ 0.75, 0 ≤ z ≤ 0.1, w + x + y + z ≤ 1, -0.1 ≤ α ≤ 0.1, M １ This represents at least one of Ti and Zr, and M ２ This represents at least one selected from Co, Mn, and Al, and M ３ This represents at least one element selected from the group consisting of B, Na, Mg, Si, P, S, K, Ca, V, Cr, Zn, Sr, Y, Nb, Mo, In, Sn, Ba, La, Ce, Nd, Sm, Eu, and Gd.

4. A positive electrode for a non-aqueous electrolyte secondary battery, comprising a current collector and a positive electrode active material layer disposed on the current collector and containing the positive electrode active material for a non-aqueous electrolyte secondary battery described in any one of claims 1 to 3.

5. A positive electrode for a non-aqueous electrolyte secondary battery comprising a single positive electrode active material, The positive electrode active material includes a lithium transition metal composite oxide having a layered structure comprising lithium, nickel, at least one metal element M1 from titanium and zirconium, and at least one metal element M2 selected from the group consisting of cobalt, manganese, and aluminum. The lithium transition metal composite oxide has a composition in which the ratio D50 / D10 of the 50% particle size D50 to the average particle size D10 based on electron microscopy observation in the cumulative particle size distribution based on volume is 1 or more and 4 or less, the ratio D90 / D10 of the 90% particle size D90 to the 10% particle size D10 in the cumulative particle size distribution based on volume is 1.2 or more and 3.9 or less, the ratio of the number of moles of nickel to the total number of moles of metals other than lithium is 0.3 or more and less than 1, the ratio of the number of moles of metal element M1 to the total number of moles of metals other than lithium is 0.025 or less, and metal element M2 contains cobalt, with the ratio of the number of moles of M2 to the total number of moles of metals other than lithium being 0.05 or more and 0.5 or less, and is a positive electrode for a non-aqueous electrolyte secondary battery.

6. A non-aqueous electrolyte secondary battery comprising a positive electrode for a non-aqueous electrolyte secondary battery according to claim 4 or 5.

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