Method for manufacturing positive electrode active material for nonaqueous electrolyte secondary battery

Abstract

To provide an efficient manufacturing method to obtain a positive electrode active material including lithium transition metal oxide particles each consisting of a particle, or including secondary particles each formed by primary particles of which the number is reduced.SOLUTION: A method for manufacturing a positive electrode active material for a nonaqueous electrolyte secondary battery comprises the steps of: preparing nickel-containing composite oxide particles of which the ratio 1D90 / 1D10 of a 90%-particle diameter 1D90 to a 10%-particle diameter 1D10 in a volume-based cumulative particle-size distribution is 3 or less; obtaining a raw material mixture including the composite oxide particles and a lithium compound, of which the ratio of a total mole number of lithium to a total mole number of a metal element included in the composite oxide is 1-1.3; performing a thermal treatment on the first mixture to obtain a thermal treatment product; performing a dispersion treatment on the thermal treatment product in a dry manner to obtain a first dispersoid; and bringing the first dispersoid into contact with a liquid medium to obtain a second dispersoid.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a method for producing 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 for large power equipment such as electric vehicles are required to have high output characteristics and high durability at the same time. In order to obtain high output characteristics, it is effective to use a positive electrode active material having a structure of secondary particles in which many primary particles are aggregated, to make the inside of the secondary particles hollow to increase the BET, and to reduce the primary particle size of the aggregated secondary particles. However, in such positive electrode active materials, cracks may occur in the secondary particles due to pressure treatment when forming the electrode, expansion and contraction during charging and discharging, etc., and there is room for improvement in durability. In relation to the above-mentioned problems, a positive electrode active material containing lithium transition metal oxide particles in which the number of primary particles constituting a single particle or one secondary particle is reduced, and a method for producing the same have been proposed in which a lithium transition metal composite oxide in which secondary particles are aggregated is pulverized to adjust the particle size of the secondary particles, and the lithium transition metal composite oxide after particle size adjustment is heat-treated again (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2001-243949 A Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional methods for producing positive electrode active materials are cumbersome and inefficient because they require the lithium transition metal composite oxide, which is an agglomeration of secondary particles obtained by heat treatment, to be pulverized to adjust the particle size, and then the material is subjected to heat treatment again. An object of one embodiment of the present disclosure is to provide an efficient manufacturing method for obtaining a positive electrode active material containing lithium transition metal oxide particles that are composed of a single particle or in which the number of primary particles constituting one secondary particle is reduced. [Means for solving the problem]

[0005] Specific means for solving the above problems are as follows, and the present invention includes the following aspects. 90% particle size of cumulative particle size distribution based on volume 1 D 90 10% particle size 1 D 10 Ratio to 1 D 90 / 1 D 10 preparing composite oxide particles containing nickel, obtaining a raw material mixture containing the composite oxide particles and a lithium compound, in which the ratio of the total mole number of lithium to the total mole number of metal elements contained in the composite oxide is 1 or more and 1.3 or less; heat-treating the raw material mixture to obtain a heat-treated product; subjecting the heat-treated product to a dry dispersion treatment to obtain a first dispersion; and contacting the first dispersion with a liquid medium to obtain a second dispersion, The positive electrode active material has an average particle size based on observation with an electron microscope. 2 D SEM 50% particle size of cumulative particle size distribution based on volume for 2 D 50 Ratio of 2 D 50 / 2 D SEM is 1 or more and 4 or less, and the lithium transition metal composite oxide particles have a composition represented by the following formula (1): Li p Ni x Co y M 1 z O 2+α (1) (In formula (1), p, x, y, z, and α satisfy 1.0≦p≦1.3, 0.6≦x<0.95, 0≦y≦0.4, 0≦z≦0.5, x+y+z=1, and −0.1≦α≦0.1; M 1 represents at least one of Mn and Al. Effect of the Invention

[0006] An embodiment according to the present disclosure can provide an efficient manufacturing method for obtaining a positive electrode active material including lithium transition metal oxide particles that are composed of a single particle or in which the number of primary particles constituting one secondary particle is reduced. [Brief description of the drawings]

[0007] [Figure 1] FIG. 2 is a diagram showing an example of an SEM image of the lithium transition metal composite oxide particles according to Example 1. [Diagram 2] FIG. 4 is a diagram showing an example of an SEM image of the lithium transition metal composite oxide particles according to Example 2. [Diagram 3] FIG. 2 is a diagram showing an example of an SEM image of the lithium transition metal composite oxide particles according to Comparative Example 1. [Figure 4] FIG. 13 is a diagram showing an example of an SEM image of the lithium transition metal composite oxide particles according to Comparative Example 2. [Diagram 5] FIG. 11 is a diagram showing an example of an SEM image of the lithium transition metal composite oxide particles according to Example 4. [Figure 6] FIG. 11 is a diagram showing an example of an SEM image of the lithium transition metal composite oxide particles according to Example 5. [Figure 7] FIG. 13 is a diagram showing one example of an SEM image of the lithium transition metal composite oxide particles according to Example 6. [Figure 8] FIG. 11 is a diagram showing an example of an SEM image of the lithium transition metal composite oxide particles according to Comparative Example 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, the manufacturing method of the positive electrode active material for non-aqueous electrolyte secondary batteries according to the present disclosure will be described based on the embodiments. However, the embodiments shown below are intended to embody the technical idea of ​​the present invention, and do not limit the present invention to the following. In this specification, the content of each component in the composition means the total amount of the multiple substances present in the composition when multiple substances corresponding to each component are present in the composition, unless otherwise specified.

[0009] [Method of manufacturing positive electrode active material for non-aqueous electrolyte secondary battery] In one embodiment of the present disclosure, a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery is provided. 1 D 90 10% particle size 1 D 10 Ratio to 1 D 90 / 1 D 10 The method includes: preparing composite oxide particles (hereinafter also referred to as "first composite oxide particles") containing nickel, the ratio of the total number of moles of lithium to the total number of moles of metal elements contained in the composite oxide being 1 or more and 1.3 or less, heat-treating the raw material mixture to obtain a heat-treated product, dispersing the heat-treated product in a dry state to obtain a first dispersion, and contacting the first dispersion with a liquid medium to obtain a second dispersion. The positive electrode active material has an average particle size of 100 nm or less based on observation with an electron microscope. 2 D SEM 50% particle size of cumulative particle size distribution based on volume for 2 D 50 Ratio of 2 D 50 / 2 D SEM is 1 or more and 4 or less, and the lithium transition metal composite oxide particles have a composition represented by the following formula (1): Li p Ni x Co y M 1 z O 2+α (1) In formula (1), p, x, y, z, and α satisfy the following conditions: 1.0≦p≦1.3, 0.6≦x<0.95, 0≦y≦0.4, 0≦z≦0.5, x+y+z=1, and −0.1≦α≦0.1. 1 represents at least one of Mn and Al.

[0010] 1 D 90 / 1 D 10 First composite oxide particles having a uniform particle size of 3 or less are used as the raw material, which are heat-treated together with a lithium compound, and then, instead of being pulverized, a dry dispersion process and a contact process with a liquid medium are carried out, thereby efficiently producing lithium transition metal composite oxide particles which are particles consisting of a single particle or particles composed of a few primary particles (hereinafter, also referred to simply as "single particles"). In conventional methods for producing positive electrode active materials consisting of single particles, the particle size is adjusted by pulverization, but it is difficult to control the particle size distribution, and it is particularly difficult to obtain a sharp particle size distribution with uniform particle size.

[0011] As the proportion of Ni in the composition increases, so does the proportion of trivalent Ni, but because trivalent Ni is unstable to heat, it is prone to thermal reduction from trivalent to divalent (for example, LiNiO2→0.5Li2O+NiO+0.25O2) during heat treatment, which causes Li compounds to precipitate near the grain boundaries between the sintered primary particles. By contacting the precipitated Li compounds with a liquid medium, the sintering becomes easier to loosen, and by applying force in this state, the primary particles peel off, allowing single-particle lithium transition metal composite oxide particles to be obtained.

[0012] The first composite oxide particles used in the method for producing a positive electrode active material contain at least nickel, and preferably contain nickel and at least one element selected from the group consisting of cobalt, manganese and aluminum, and more preferably contain nickel, cobalt, and at least one of manganese and aluminum.

[0013] The first composite oxide particles are 1 D 90 / 1 D 10is 3 or less, and preferably 2 or less. The first composite oxide particles have a 50% particle size of the cumulative particle size distribution based on volume. 1 D 50 However, it is, for example, 12 μm or less, and preferably 6 μm or less, and, for example, 1 μm or more, and preferably 2 μm or more.

[0014] When the first composite oxide particles contain nickel, cobalt, and at least one of manganese and aluminum, the content ratio of nickel, cobalt, manganese, and aluminum, Ni / Co / (Mn+Al), on a molar basis, can be, for example, 6 / 2 / 2, 6 / 2 / (1.5 / 0.5), 8 / 1 / 1, 8 / 1 / (0.5 / 0.5), etc.

[0015] The first composite oxide particles may be prepared by appropriately selecting from commercially available products, or may be prepared by manufacturing a product having desired properties. When manufacturing the first composite oxide particles, for example, the first composite oxide particles can be manufactured by heat treating a composite hydroxide containing a desired metal element. The composite hydroxide can be obtained by a coprecipitation method in which a raw material compound soluble in a solvent is dissolved in the solvent, and a composite hydroxide with a desired composition is obtained by adjusting the temperature, adjusting the pH, adding a complexing agent, etc. For details of the method of obtaining a composite oxide by the coprecipitation method, JP 2003-292322 A, JP 2011-116580 A, etc. can be referred to.

[0016] The first composite oxide particles thus prepared are mixed with a lithium compound to prepare a raw material mixture. Examples of the lithium compound include lithium hydroxide, lithium carbonate, and lithium oxide.

[0017] The particle size of the lithium compound used is the 50% particle size D of the cumulative particle size distribution based on volume. 50 For example, the thickness is 0.1 μm or more and 100 μm or less, and preferably 2 μm or more and 20 μm or less. The ratio of the total number of moles of lithium to the total number of moles of metal elements constituting the first composite oxide particles in the raw material mixture is 1 or more and 1.3 or less, preferably 1 or more and 1.2 or less, and more preferably 1 or more and 1.1 or less.

[0018] The first composite oxide particles and the lithium compound can be mixed using, for example, a high-speed shear mixer.

[0019] The resulting raw material mixture is heat-treated to form a heat-treated product. The heat treatment of the raw material mixture is, for example, performed by raising the temperature from room temperature to a heat treatment temperature, performing heat treatment at the heat treatment temperature for a predetermined period of time, and then lowering the temperature to, for example, room temperature, thereby obtaining a heat-treated product. The heat treatment temperature is, for example, from 850° C. to 1100° C., preferably from 870° C. to 1050° C., and more preferably from 900° C. to 1020° C. The heat treatment time is, for example, from 1 hour to 30 hours, and preferably from 1 hour to 20 hours.

[0020] The heat treatment of the raw material mixture may be performed at least at one temperature for a predetermined time, or may be performed at a plurality of temperatures for a predetermined time each. When heat treatment is performed at a plurality of temperatures, the heat treatment may be performed at a first temperature and then at a second temperature higher than the first temperature to obtain a heat-treated product, or the heat treatment may be performed at the first temperature and then at a third temperature lower than the first temperature to obtain a heat-treated product, or the heat treatment may be performed at the first temperature and then at a second temperature higher than the first temperature and then at a third temperature lower than the second temperature to obtain a heat-treated product.

[0021] In one embodiment of the manufacturing method, the raw material mixture is heat-treated at a first temperature, and then at a second temperature higher than the first temperature to generate a heat-treated product. By heat-treating at the first temperature and then at the second temperature, the reaction between the lithium compound and the first composite oxide is sufficiently carried out at the first temperature, and the lithium compound remaining at the second temperature acts as a flux, so that particle growth can be carried out while suppressing sintering between particles. This makes it possible to obtain lithium transition metal composite oxide particles with few contact grain boundaries between particles and a narrow particle size distribution. In this case, the heat treatment at the second temperature may be followed by an additional heat treatment at a temperature higher than the second temperature.

[0022] Furthermore, by carrying out a heat treatment for a predetermined time at a third temperature during the temperature drop after the heat treatment at the first or second temperature, the effect of reducing the Ni disorder value described below tends to be obtained.

[0023] The first temperature is, for example, 700° C. or more and 950° C. or less, and preferably 750° C. or more and 900° C. or less. The second temperature is, for example, 850° C. or more and 1100° C. or less, and preferably 900° C. or more and 1020° C. or less. The difference between the first temperature and the second temperature is, for example, 30° C. or more, preferably 80° C. or more, and, for example, 250° C. or less, preferably 180° C. or less. The third temperature is, for example, 700° C. or more and 950° C. or less, and preferably 700° C. or more and 900° C. or less.

[0024] The heat treatment time at the first temperature is, for example, from 1 hour to 10 hours, and preferably from 3 hours to 10 hours. The heat treatment time at the second temperature is, for example, from 1 hour to 20 hours, and preferably from 5 hours to 15 hours. The heat treatment time at the first temperature and the heat treatment time at the second temperature may be the same or different. When they are different, for example, the heat treatment time at the second temperature can be longer than the heat treatment time at the first temperature. Specifically, for example, the heat treatment time at the second temperature can be 1.1 to 3 times, preferably 1.5 to 2.5 times, the heat treatment time at the first temperature. Here, the heat treatment at the first temperature and the heat treatment at the second temperature may be performed continuously or independently. When the heat treatment at the first temperature and the heat treatment at the second temperature are performed continuously, the temperature rise rate from the first temperature to the second temperature can be, for example, 5° C. / min.

[0025] The heat treatment time at the third temperature is, for example, from 1 hour to 20 hours, and preferably from 3 hours to 10 hours.

[0026] The heat treatment atmosphere may be air or oxygen atmosphere. The heat treatment atmosphere preferably contains oxygen. By containing oxygen in the heat treatment atmosphere, for example, the amount of residual lithium can be suppressed, and sintering between the lithium transition metal composite oxide particles can be more effectively suppressed. When the heat treatment atmosphere contains oxygen, the content of oxygen is preferably 15% by volume or more, more preferably 30% by volume or more, and even more preferably 80% by volume or more. 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, or the like.

[0027] The heat-treated product is subjected to a dry dispersion treatment to obtain a first dispersion. The dispersion treatment is not a pulverization treatment involving strong shearing force or impact, but rather dissociates the sintered primary particles, thereby obtaining lithium transition metal composite oxide particles with a narrow particle size distribution and uniform particle size. The dispersion treatment can be performed using, for example, a ball mill, a jet mill, or the like.

[0028] For example, when the dispersion treatment is performed using a ball mill, a resin media can be used. Examples of the material of the resin media include urethane resin and nylon resin. Generally, alumina, zirconia, and the like are used as the material of the media of a ball mill, and particles are pulverized by these media. In contrast, by using a resin media, the particles are not pulverized and the sintered primary particles are dissociated. The size of the resin media can be, for example, φ5 mm or more and 30 mm or less. For the body (shell), for example, a urethane resin or a nylon resin can be used. The time of the dispersion treatment is, for example, 3 minutes or more and 60 minutes or less, and preferably 10 minutes or more and 30 minutes or less. The conditions for the dispersion treatment using a ball mill are as follows: 2 D 50 / 2 D SEM In order to achieve the above, the first composite oxide particles as the raw material 1 D 90 / 1 D 10Depending on the above, the amount of media, the rotation or oscillation speed, the dispersion time, the specific gravity of the media, etc. may be adjusted.

[0029] For example, when the dispersion process is carried out using a jet mill, the primary particles are not pulverized, and the desired 2 D 50 / 2 D SEM The first composite oxide particles as the raw material are 1 D 90 / 1 D 10 The supply pressure, pulverization pressure, supply speed, etc. may be adjusted depending on the above. The supply pressure may be, for example, 0.1 MPa or more and 0.5 MPa or less, and the pulverization pressure may be, for example, 0.1 MPa or more and 0.6 MPa or less.

[0030] The first dispersion is brought into contact with a liquid medium to obtain a second dispersion. The liquid medium may be any liquid medium that dissolves the lithium compound, and may be, for example, a liquid medium containing water. By bringing the first dispersion into contact with the liquid medium, for example, the lithium compound present at the grain boundaries of the lithium transition metal composite oxide particles contained in the first dispersion is dissolved, 2 D 50 / 2 D SEM becomes smaller.

[0031] When the liquid medium contains water, the water content is, for example, 50% by volume or more, and preferably 70% by volume or more. The liquid medium may further contain a solvent other than water. Examples of the solvent other than water include alcohol, an alkaline solution, and an acidic solution. The liquid medium may contain a coating agent for the particles, and the coating treatment may be carried out simultaneously with the dispersion treatment.

[0032] The mass ratio of the liquid medium to the first dispersion during contact between the first dispersion and the liquid medium is, since dissociation of primary particles is likely to occur if the mass ratio is low, for example, 20 mass% or less, preferably 15 mass% or less, and for example, 2 mass% or more, preferably 5 mass% or more.

[0033] In contacting the first dispersion with the liquid medium, the mixture of the first dispersion and the liquid medium may be stirred as necessary. Stirring can be performed using, for example, a high-speed stirring mixer, a double cone, a kneader, or the like. The contact time between the first dispersion and the liquid medium is, for example, from 1 minute to 30 minutes, and preferably from 3 minutes to 15 minutes. The temperature at which the first dispersion comes into contact with the liquid medium is, for example, 0°C or higher and 100°C or lower, and preferably 10°C or higher and 40°C or lower.

[0034] It is preferable to carry out a drying process after the first dispersion is contacted with the liquid medium. This allows the lithium compound dissolved in the liquid medium to be inserted again near the surface of the lithium transition metal oxide particles, thereby suppressing the output decrease. After the drying process, a sieving process, a classification process, etc. may be further carried out. According to the above-described manufacturing method, a positive electrode active material containing single-particle lithium-lithium transition metal composite oxide particles can be efficiently manufactured.

[0035] The lithium transition metal composite oxide particles obtained by the above-mentioned production method have a composition represented by formula (1) and an average particle diameter based on observation with an electron microscope. 2 D SEM 50% particle size in cumulative particle size distribution based on volume 2 D 50 Ratio of 2 D 50 / 2 D SEM The particle size distribution is 1 or more and 4 or less. 2 D 90 10% particle size 2 D 10 Ratio to 2 D 90 / 2 D 10 It is preferable that the ratio is 4 or less.

[0036] 2 D 50 / 2 D SEMThe fact that the value is 1 or more and 4 or less means that the lithium transition metal composite oxide particle is a single particle or is composed of a small number of primary particles, and there are few contact grain boundaries between the primary particles. 2 D 90 / 2 D 10 A positive electrode active material containing lithium transition metal composite oxide particles having such characteristics can achieve both excellent output characteristics and excellent durability.

[0037] Compared to positive electrode active materials containing conventional single-particle lithium transition metal composite oxide particles with secondary particles consisting of a large number of aggregated primary particles, positive electrode active materials containing single-particle lithium transition metal composite oxide particles exhibit excellent durability because they suppress the decrease in capacity retention rate due to the disconnection of the lithium ion conductive path caused by grain boundary dissociation of the secondary particles during charge / discharge cycles, and the increase in the diffusion movement resistance of lithium ions. On the other hand, a three-dimensional grain boundary network like that of positive electrode active materials made of aggregated particles is hardly formed, making it impossible to design a high output that utilizes grain boundary conduction, and so the output characteristics tend to be insufficient. In order to improve the output characteristics, the particle size of the single particles ( 2 D SEM However, if the particle size is too small, the interactions between the powder particles increase, which tends to significantly worsen the plate packing, and the powder flowability decreases, which can significantly worsen handling. On the other hand, a certain particle size is necessary to obtain a practical energy density, but if the particle size is large, it is thought that the output deficiency tends to become more pronounced.

[0038] The lithium transition metal composite oxide particles of one embodiment according to the present disclosure have a more uniform particle size than conventional single particles. Therefore, even when charging and discharging are performed at a high current density, unevenness in the charge and discharge depth for each particle due to current concentration in some particles can be suppressed. It is therefore considered that local deterioration due to cycling can be suppressed while suppressing an increase in resistance due to current concentration.

[0039] Furthermore, because the particle size of the lithium transition metal composite oxide particles is uniform, the particles do not collapse even when pressed under high pressure when preparing an electrode, and it is believed that the gaps between the particles can be made uniform. When a battery is constructed, the gaps between the particles are filled with electrolyte to become a diffusion path for lithium ions, and it is believed that the uniform size of the diffusion path can suppress unevenness in charging and discharging for each particle. As a result, it is believed that even lithium transition metal composite oxide particles with few contact grain boundaries between primary particles can achieve excellent output characteristics while ensuring plate filling properties.

[0040] In addition, when synthesizing single particles, a high heat treatment temperature is generally required to grow the particles. In particular, in compositions with a high Ni ratio, high-temperature sintering may cause Ni elements to be mixed into the Li site, i.e., disorder. Disorder is preferable to suppress because it inhibits the diffusion of Li ions in the lithium transition metal composite oxide particles, becomes resistance, and has effects such as a decrease in charge / discharge capacity at practical current density and a decrease in output characteristics. By suppressing disorder, it is possible to achieve better capacity and output characteristics in single particles.

[0041] The lithium transition metal composite oxide particles that make up the positive electrode active material have an average particle size based on electron microscope observation. 2 D SEM From the viewpoints of output characteristics and plate packing, the thickness is preferably 1 μm or more, more preferably 1.5 μm or more, and is preferably 5.5 μm or less, and more preferably 3 μm or less.

[0042] Average particle size based on electron microscope observation 2 D SEM is obtained by observing using a scanning electron microscope (SEM) at magnifications of 1,000 to 10,000 times depending on the particle size, selecting 100 particles whose particle outlines can be confirmed, calculating the equivalent sphere diameter of the selected particles using image processing software, and then taking the arithmetic mean of the obtained equivalent sphere diameters.

[0043] The lithium transition metal composite oxide particles are 50% particle size in the cumulative particle size distribution based on volume. 2 D 50 Average particle size based on electron microscope observation 2 D SEM The ratio to 2 D 50 / 2 D SEM When the value is 1, it indicates a single particle, and the closer it is to 1, the fewer the number of primary particles it contains. 2 D 50 / 2 D SEM From the standpoint of durability, 2 D 50 / 2 D SEM is preferably 1 to 4, and from the viewpoint of output characteristics, is preferably 3 or less, and particularly preferably 2.5 or less.

[0044] In addition, the 50% particle size of the lithium transition metal composite oxide particles 2 D 50 is, for example, 1 μm or more, preferably 1.5 μm or more, and is, for example, 21 μm or less, preferably 8 μm or less, and more preferably 6 μm or less.

[0045] 50% particle size 2 D 50 is calculated as the particle size corresponding to the cumulative 50% from the small diameter side in the cumulative particle size distribution on a volume basis measured under wet conditions using a laser diffraction particle size distribution analyzer. Similarly, the 90% particle size 2 D 90 and 10% particle size 2 D 10 are calculated as the particle diameters corresponding to the cumulative 90% and 10% from the small diameter side, respectively.

[0046] The lithium transition metal composite oxide particles are 90% particle size in the cumulative particle size distribution based on volume. 2 D 90 10% particle size 2 D 10 Ratio to 2 D 90 / 2 D 10From the viewpoint of output characteristics, it is preferably 4 or less, more preferably 3 or less, and still more preferably 2.5 or less.

[0047] The lithium transition metal composite oxide constituting the lithium transition metal composite oxide particles has the composition represented by the above formula (1). Further, the lithium transition metal composite oxide preferably has a layered structure. Examples of the lithium transition metal composite oxide having the composition represented by the formula (1) and having a layered structure include lithium nickel composite oxide, lithium nickel cobalt manganese composite oxide, and the like.

[0048] In the formula (1), from the viewpoint of output, p preferably satisfies 1.0 ≦ p ≦ 1.1. From the viewpoint of cycle capacity retention rate, x preferably satisfies 0.6 ≦ x < 0.9. From the viewpoint of material cost, y preferably satisfies 0 < y ≦ 0.3, and from the viewpoint of output characteristics, z preferably satisfies 0 < z ≦ 0.3. Also, y:z is preferably from 1:2 to 5:1, and more preferably from 1:1 to 3:1.

[0049] The positive electrode active material may be doped with an element other than the elements constituting the lithium transition metal composite oxide in the lithium transition metal composite oxide particles obtained by the above production method. Examples of the doped element include B, Na, Mg, Si, P, S, K, Ca, Ti, V, Cr, Zn, Sr, Y, Zr, Nb, Mo, In, Sn, Ba, La, Ce, Nd, Sm, Eu, Gd, Ta, W, and Bi. Examples of the compound used for doping these elements include oxides, fluorides, and Li composite oxides containing these elements. The doping amount can be, for example, 0.005 mol% or more and 10 mol% or less with respect to the lithium transition metal composite oxide particles.

[0050] The positive electrode active material may have a core particle containing a lithium transition metal composite oxide obtained by the above-mentioned manufacturing method, and an attachment disposed on the surface of the core particle. The attachment may be disposed on at least a part of the surface area of ​​the core particle, and is preferably disposed on an area of ​​1% or more of the surface area of ​​the core particle. The composition of the attachment is appropriately selected depending on the purpose, and examples thereof include oxides and fluorides containing at least one selected from the group consisting of B, Na, Mg, Si, P, S, K, Ca, Ti, V, Cr, Zn, Sr, Y, Zr, Nb, Mo, In, Sn, Ba, La, Ce, Nd, Sm, Eu, Gd, Ta, W, and Bi, and Li composite oxides thereof. The content of the attachment may be, for example, 0.03% by mass or more and 10% by mass or less in the lithium transition metal composite oxide particles, and preferably 0.1% by mass or more and 2% by mass or less.

[0051] From the viewpoint of the initial efficiency of a non-aqueous electrolyte secondary battery, the lithium transition metal composite oxide preferably has a nickel element disorder of 5% or less, more preferably 3% or less, and even more preferably 2.5% or less, as determined by an X-ray diffraction method. Here, the disorder of the nickel element means a chemical disorder of the transition metal ion (nickel ion) that should occupy the original site. In a lithium transition metal composite oxide with a layered structure, a typical example is the replacement of a lithium ion that should occupy a site represented by 3b (3b site, the same applies below) and a transition metal ion that should occupy a 3a site when expressed in Wyckoff notation. The smaller the disorder of the nickel element, the better, since the initial efficiency is improved.

[0052] The positive electrode active material produced by the manufacturing method of one embodiment of the present disclosure can be used in the positive electrode of a nonaqueous electrolyte secondary battery to constitute a nonaqueous electrolyte secondary battery that can achieve both excellent output characteristics and excellent durability. The positive electrode active material can be included in a positive electrode active material layer disposed on a current collector to constitute a positive electrode. That is, the present invention encompasses an electrode for a nonaqueous electrolyte secondary battery that includes the positive electrode active material produced by the manufacturing method, and a nonaqueous electrolyte secondary battery that includes the electrode.

[0053] [Nonaqueous electrolyte secondary battery electrode] The electrode for a non-aqueous electrolyte secondary battery includes 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 produced by the above-mentioned production method. A non-aqueous electrolyte secondary battery including such an electrode can achieve high durability and high output characteristics.

[0054] Examples of the material of the current collector include aluminum, nickel, stainless steel, etc. 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 a drying process, a pressure process, etc. Examples of the conductive material include natural graphite, artificial graphite, acetylene black, etc. Examples of the binder include polyvinylidene fluoride, polytetrafluoroethylene, polyamide acrylic resin, etc.

[0055] [Non-aqueous electrolyte secondary battery] The non-aqueous electrolyte secondary battery comprises the above-mentioned electrode for non-aqueous electrolyte secondary battery. The non-aqueous electrolyte secondary battery comprises, in addition to the electrode for non-aqueous electrolyte secondary battery, a negative electrode for non-aqueous secondary battery, a non-aqueous electrolyte, a separator, etc. In the non-aqueous electrolyte secondary battery, the negative electrode, non-aqueous electrolyte, separator, etc., for example, those for non-aqueous electrolyte secondary batteries described in JP 2002-075367 A, JP 2011-146390 A, JP 2006-12433 A (the entire disclosures of which are incorporated herein by reference) can be appropriately used. EXAMPLES

[0056] Hereinafter, examples of the present invention will be described in detail.

[0057] First, the methods for measuring physical properties in the following Examples and Comparative Examples will be described. 1 D 10 and 2 D 10 , 1 D50 and 2 D 50 ,Line up 1 D 90 and 2 D 90 For the above, a laser diffraction particle size distribution analyzer (SALD-3100, manufactured by Shimadzu Corporation) was used to measure the cumulative particle size distribution on a volume basis, and the particle sizes were calculated corresponding to the cumulative size from the smallest diameter side. Average particle size based on electron microscope observation 1 D SEM and 2 D SEM In the study, 100 particles whose particle outlines could be confirmed were selected from images observed at 1,000 to 10,000 times magnification using a scanning electron microscope (SEM), and the spherical equivalent diameter of the selected particles was calculated using image processing software (ImageJ), and the arithmetic mean value of the obtained spherical equivalent diameters was obtained.

[0058] The disorder value of nickel element (Ni disorder amount) was determined by X-ray diffraction method according to the following procedure. The obtained lithium transition metal composite oxide particles were subjected to X-ray diffraction spectrum measurement using CuKα radiation (tube current 200 mA, tube voltage 45 kV). Based on the obtained X-ray diffraction spectrum, a composition model was created based on Li 1-d Ni d The lithium transition metal composite oxide was subjected to structural optimization by Rietveld analysis using Rietan2000 software, with MeO2 (Me being the transition metal other than nickel in the lithium transition metal composite oxide). The percentage of d calculated as a result of structural optimization was taken as the amount of Ni disorder.

[0059] Example 1 (Seed generation process) First, 10 kg of water was placed in the reaction tank and the ammonium ion concentration was adjusted to 1.8% by mass while stirring. The temperature inside the tank was set to 25°C, nitrogen gas was circulated, and the oxygen concentration in the space inside the reaction tank was maintained at 10% or less. A 25% by mass aqueous solution of sodium hydroxide was added to the water in the reaction tank to adjust the pH value of the solution in the tank to 13.5 or more. Next, a mixed aqueous solution of nickel sulfate, cobalt sulfate and manganese sulfate in a molar ratio of 6:2:2 was prepared. The mixed aqueous solution was added until the solute amount became 4 moles, and seeds were generated while controlling the pH value of the reaction solution to 12.0 or more with a sodium hydroxide solution.

[0060] (Crystallization process) After the seed generation step, the temperature in the tank was maintained at 25°C or higher until the end of the crystallization step. A mixed aqueous solution of 1200 moles of solute was prepared and, together with the aqueous ammonia solution, was simultaneously added over a period of 5 hours or more to the reaction tank while maintaining the ammonium ion concentration in the solution at 2000 ppm or higher so as to prevent new seed generation. During the reaction, the pH value in the reaction solution was controlled to be maintained at 10.5 to 12.0 with a sodium hydroxide solution. Sampling was carried out successively during the reaction, and the D of the composite hydroxide particles was measured. 50 The addition was stopped when the particle size reached approximately 4.7 μm. The product was then washed with water, filtered and dried to obtain composite hydroxide particles. The obtained hydroxide precursor was heat-treated at 300° C. for 20 hours in an air atmosphere to obtain a hydroxide having a composition ratio of Ni / Co / Mn=0.60 / 0.20 / 0.20. 1 D 10 = 4.0 μm, 1 D 50 = 4.7 μm, 1 D 90 = 6.2 μm, 1 D 90 / 1 D 10 = 1.6.

[0061] (synthesis process) The obtained first composite oxide particles and lithium hydroxide monohydrate were mixed so that Li / (Ni+Co+Mn)=1.06 to obtain a raw material mixture. The obtained raw material mixture was fired in an oxygen stream at 870°C for 7 hours, and then at 970°C for 7 hours to obtain a sintered body (heat-treated product). The obtained sintered body was crushed and dispersed for 10 minutes in a resin ball mill to obtain a powder. The powder was then added to a rotary blade-type high-speed stirring mixer and 10% by mass of water relative to the powder was stirred at 2000 rpm to dissolve the residual alkali at the grain boundaries, and the mixture was dried at 350°C and then sieved through a dry sieve to obtain a powder. From the above, the average particle size based on the electron microscope observation 2 D SEM is 3.7 μm, 2 D 10 = 3.4 μm, 2 D 50 = 5.4 μm, 2 D 90 =7.7μm, average particle size 2 D SEM for 2 D 50 Ratio of 2 D 50 / 2 D SEM is 1.5, and the ratio in the particle size distribution 2 D 90 / 2 D 10 is 2.3, Ni disorder amount is 1.5%, and the composition formula is Li 1.06 Ni 0.60 Co 0.20 Mn 0.20 A lithium transition metal composite oxide represented by O2 was obtained. The physical properties of the obtained lithium transition metal composite oxide particles are shown in Table 1, and an SEM image is shown in Figure 1.

[0062] Example 2 First composite oxide particles were obtained under the same conditions as in Example 1. The obtained first composite oxide particles and lithium hydroxide monohydrate were mixed so that Li / (Ni+Co+Mn)=1.17 to obtain a raw material mixture. The obtained raw material mixture was fired in air at 930°C for 10 hours to obtain a sintered body (heat-treated product). The obtained sintered body was crushed and dispersed in a resin ball mill for 10 minutes to obtain a powder. The powder was then added to a rotary blade-type high-speed stirring mixer and stirred at 2000 rpm to dissolve residual alkali at the grain boundaries, and the mixture was dried at 350°C and then sieved through a dry sieve to obtain a powder. From the above, the average particle size 2 D SEM is 3.2 μm, 2 D 10 = 3.6 μm, 2 D 50 = 6.1 μm, 2 D 90 =9.2μm, average particle size 2 D SEM for 2 D 50 Ratio of 2 D 50 / 2 D SEM is 1.9, and the ratio in particle size distribution 2 D 90 / 2 D 10 is 2.6, Ni disorder amount is 1.2%, and the composition formula is Li 1.17 Ni 0.60 Co 0.20 Mn 0.20 The 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 an SEM image is shown in Figure 2.

[0063] Example 3 First composite oxide particles were obtained under the same conditions as in Example 1. The obtained first composite oxide particles and lithium carbonate were mixed so that Li / (Ni+Co+Mn)=1.17 to obtain a raw material mixture. The obtained raw material mixture was fired in air at 930°C for 10 hours to obtain a sintered body (heat-treated product). The obtained sintered body was crushed and dispersed in a resin ball mill for 10 minutes to obtain a powder. The powder was then added to a rotary blade-type high-speed stirring mixer and stirred at 2000 rpm to dissolve residual alkali at the grain boundaries, and the mixture was dried at 350°C and then dry-sieved to obtain a powder. From the above, the average particle size 2 D SEM is 3.1 μm, 2 D 10 = 3.8 μm, 2 D 50 = 6.3 μm, 2 D 90 =9.6μm, average particle size 2 D SEM for 2 D 50 Ratio of 2 D 50 / 2 D SEM is 2.0, and the ratio D 90 2 / D 10 2 is 2.5, Ni disorder amount is 2.2%, and the composition formula is Li 1.17 Ni 0.60 Co 0.20 Mn 0.20 The 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.

[0064] Comparative Example 1 First composite oxide particles were obtained under the same conditions as in Example 1. The obtained first composite oxide particles were mixed with lithium hydroxide monohydrate so that Li / (Ni+Co+Mn)=1.17 to obtain a raw material mixture. The obtained raw material mixture was fired in air at 810°C for 10 hours to obtain a sintered body. The obtained sintered body was crushed, subjected to a dispersion treatment in a resin ball mill for 10 minutes, and then sieved through a dry sieve to obtain a powdered body. From the above, the average particle size 2 D SEM is 0.4 μm, 2 D 10 = 3.2 μm, 2 D 50 = 4.7 μm, 2 D 90 =7.5μm, average particle size 2 D SEM for 2 D 50 Ratio of 2 D 50 / 2 D SEM is 11.8, and the ratio in particle size distribution 2 D 90 / 2 D 10 is 2.3, Ni disorder amount is 1.0%, and the composition formula is Li 1.17 Ni 0.60 Co 0.20 Mn 0.20 The 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 an SEM image is shown in Figure 3.

[0065] Comparative Example 2 First composite oxide particles were obtained under the same conditions as in Example 1. The obtained first composite oxide particles were mixed with lithium hydroxide monohydrate so that Li / (Ni+Co+Mn)=1.17 to obtain a raw material mixture. The obtained raw material mixture was fired in air at 930°C for 10 hours to obtain a sintered body. The obtained sintered body was crushed, subjected to a dispersion treatment in a resin ball mill for 10 minutes, and then sieved through a dry sieve to obtain a powdered body. From the above, the average particle size 2 D SEM is 3.2 μm, 2 D 10 = 4.1 μm, 2 D 50 = 9.6 μm, 2 D 90 =23.4μm, average particle size 2 D SEM for 2 D 50 Ratio of 2 D 50 / 2 D SEM is 3.0, and in the particle size distribution 2 D 90 / 2 D 10 The ratio is 5.7, the Ni disorder amount is 1.3%, and the composition formula is Li 1.17 Ni 0.60 Co 0.20 Mn 0.20 The 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 an SEM image is shown in Figure 4.

[0066] Example 4 The same procedure was carried out under the same conditions as in Example 1, except that the mixing ratio of the nickel sulfate solution, the cobalt sulfate solution, and the manganese sulfate solution was changed to 8:1:1 in molar ratio to obtain a mixed aqueous solution having a composition ratio of Ni / Co / Mn=0.80 / 0.10 / 0.10, 1 D 10 = 3.4 μm, 1 D 50 = 4.6 μm, 1 D 90 = 6.1 μm, 1 D 90 / 1 D 10 The first composite oxide particles having a ratio of 1.8 and lithium hydroxide monohydrate were mixed so that Li / (Ni+Co+Mn)=1.04 to obtain a raw material mixture. The obtained raw material mixture was fired in an oxygen stream at 780°C for 5 hours, then at 1000°C for 10 hours, and then at 780°C for 5 hours to obtain a sintered body (heat-treated product). The obtained sintered body was crushed and dispersed in a resin ball mill for 10 minutes to obtain a powder. The powder was then added to a rotary blade-type high-speed stirring mixer and stirred at 2000 rpm to dissolve the residual alkali at the grain boundaries, and the mixture was dispersed. The powder was then dried at 350°C and sieved through a dry sieve to obtain a powder. From the above, the average particle size 2 D SEM is 3.1 μm, 2 D 10 = 3.7 μm, 2 D 50 = 7.1 μm, 2 D90 =12.0μm, average particle size 2 D SEM for 2 D 50 Ratio of 2 D 50 / 2 D SEM is 2.3, and the ratio in particle size distribution 2 D 90 / 2 D 10 is 3.2, Ni disorder amount is 1.7%, and the composition formula is Li 1.04 Ni 0.80 Co 0.10 Mn 0.10 The 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 an SEM image is shown in Figure 5.

[0067] Example 5 The first composite oxide particles were obtained under the same conditions as in Example 4. The obtained first composite oxide particles and lithium hydroxide monohydrate were mixed so that Li / (Ni+Co+Mn)=1.04 to obtain a raw material mixture. The obtained raw material mixture was fired in an oxygen stream at 780°C for 5 hours, and then fired at 950°C for 10 hours to obtain a sintered body (heat-treated product). The obtained sintered body was crushed and dispersed in a resin ball mill for 10 minutes to obtain a powder. The powder was then added to a rotary blade-type high-speed stirring mixer and stirred at 2000 rpm to dissolve the residual alkali at the grain boundaries, and the mixture was dried at 350°C and then sieved through a dry sieve to obtain a powder. From the above, the average particle size 2 D SEM is 2.5 μm, 2 D 10 = 3.0 μm, 2 D 50 = 5.3 μm, 2 D 90 =8.2μm, average particle size 2 D SEM for 2 D 50 Ratio of 2 D 50 / 2 D SEMis 2.1, and the ratio in particle size distribution 2 D 90 / 2 D 10 is 2.7, Ni disorder amount is 2.3%, and the composition formula is Li 1.04 Ni 0.80 Co 0.10 Mn 0.10 The 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 an SEM image is shown in Figure 6.

[0068] Example 6 The first composite oxide particles were obtained under the same conditions as in Example 4. The obtained first composite oxide particles and lithium hydroxide monohydrate were mixed so that Li / (Ni+Co+Mn)=1.04 to obtain a raw material mixture. The obtained raw material mixture was fired in an oxygen stream at 780°C for 5 hours, and then fired at 1000°C for 10 hours to obtain a sintered body (heat-treated product). The obtained sintered body was crushed and dispersed in a resin ball mill for 10 minutes to obtain a powder. The powder was then added to a rotary blade-type high-speed stirring mixer and stirred at 2000 rpm to dissolve the residual alkali at the grain boundaries, and the mixture was dried at 350°C and then dry-sieved to obtain a powder. From the above, the average particle size 2 D SEM is 3.0 μm, 2 D 10 = 3.7 μm, 2 D 50 = 6.6 μm, 2 D 90 =9.6μm, average particle size 2 D SEM for 2 D 50 Ratio of 2 D 50 / 2 D SEM is 2.2, and the ratio in particle size distribution 2 D 90 / 2 D 10 is 2.6, Ni disorder amount is 4.2%, and the composition formula is Li 1.04 Ni 0.80 Co0.10 Mn 0.10 The 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 an SEM image is shown in Figure 7.

[0069] Comparative Example 3 The mixed aqueous solution in Example 1 was changed to a mixed solution of nickel sulfate and cobalt sulfate in a molar ratio of 80:15, and the timing of the end of the introduction of the mixed solution in the crystallization process was adjusted to the D 50 The same conditions were used except that the thickness was changed when the thickness reached 4.6 μm. The composition ratio of Ni / Co was 0.80 / 0.15. 1 D 10 = 3.4 μm, 1 D 50 = 4.6 μm, 1 D 90 = 6.1 μm, 1 D 90 / 1 D 10 =1.8. The first composite oxide particles obtained were mixed with aluminum oxide so that the composition ratio of Ni / Co / Al was 0.80 / 0.15 / 0.05, and lithium hydroxide monohydrate was mixed so that Li / (Ni+Co+Al) was 1.04, to obtain a raw material mixture. The raw material mixture obtained was fired at 710°C for 5 hours in an oxygen stream to obtain a sintered body. The sintered body obtained was crushed, dispersed in a resin ball mill for 10 minutes, and sieved to obtain a powdered body. From the above, the average particle size 2 D SEM is 0.3 μm, 2 D 10 = 4.5 μm, 2 D 50 = 5.8 μm, 2 D 90 =7.4μm, average particle size 2 D SEM for 2 D 50 Ratio of 2 D 50 / 2 D SEM is 19.3, and the ratio in particle size distribution 2 D 90 / 2 D 10 is 1.6, Ni disorder amount is 1.0%, and the composition formula is Li 1.04 Ni 0.80 Co 0.15 Al 0.05 The 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 an SEM image is shown in Figure 8.

[0070] [Table 1]

[0071] The lithium transition metal oxide particles produced by the above-mentioned production method are composed of a single particle or a small number of primary particles, so that the lithium transition metal oxide obtained can be efficiently produced without being pulverized to adjust the particle size and then subjected to another heat treatment.

[0072] In the lithium transition metal oxide particles produced by the above-mentioned production method, compared with Comparative Examples 1 to 3, 2 D 50 / 2 D SEM and 2 D 90 / 2 D 10 Since the particle diameter is small, it is a single particle or is composed of a few primary particles, and the particle size is uniform. 2 D 50 / 2 D SEM and 2 D 90 / 2 D 10 Since the amount of the cations in the positive electrode active material is small, it is possible to configure a non-aqueous electrolyte secondary battery having excellent output characteristics and durability by applying the cations in the positive electrode active material to the non-aqueous electrolyte secondary battery. 2 D 50 / 2 D SEM and 2 D 90 / 2 D 10 Since the amount of Ni disorder is smaller than that of Example 6, by applying this to the positive electrode active material of a nonaqueous electrolyte secondary battery, a nonaqueous electrolyte secondary battery excellent in output characteristics and durability can be constructed.

Claims

1. 90% particle size of cumulative particle size distribution based on volume １ D ９０ 10% particle size １ D １０ Ratio to １ D ９０ / １ D １０ preparing composite oxide particles containing nickel, obtaining a raw material mixture containing the composite oxide particles and a lithium compound, in which the ratio of the total mole number of lithium to the total mole number of metal elements contained in the composite oxide is 1 or more and 1.3 or less; heat-treating the raw material mixture to obtain a heat-treated product; subjecting the heat-treated product to a dry dispersion treatment to obtain a first dispersion; and contacting the first dispersion with a liquid medium to obtain a second dispersion, The positive electrode active material has an average particle size based on observation with an electron microscope. ２ D ＳＥＭ 50% particle size of cumulative particle size distribution based on volume ２ D ５０ Ratio of ２ D ５０ / ２ D ＳＥＭ is 1 or more and 4 or less, and the lithium transition metal composite oxide particles have a composition represented by the following formula (1): Li ｐ Ni ｘ Co ｙ M １ ｚ O ２＋α (1) (In formula (1), p, x, y, z, and α satisfy 1.0≦p≦1.3, 0.6≦x<0.95, 0≦y≦0.4, 0≦z≦0.5, x+y+z=1, and −0.1≦α≦0.1; M １ represents at least one of Mn and Al.)

2. The method according to claim 1, wherein p in formula (1) satisfies 1.0≦p≦1.

1.

3. The lithium transition metal composite oxide particles have a particle size of 90% of a cumulative particle size distribution based on volume. ２ D ９０ 10% particle size ２ D １０ Ratio to ２ D ９０ / ２ D １０ The method according to claim 1 or 2, wherein

4. The method according to claim 1 , wherein the heat treatment of the raw material mixture includes a heat treatment at a first temperature and a heat treatment at a second temperature higher than the first temperature.

5. The method according to claim 4 , wherein the heat treatment of the raw material mixture further comprises, after the heat treatment at the second temperature, a heat treatment at a third temperature lower than the second temperature.

6. The method according to claim 1 , wherein the heat treatment of the raw material mixture is carried out in an atmosphere containing oxygen.

7. The method according to claim 1 , wherein the first dispersion is contacted with the liquid medium such that a mass ratio of the liquid medium to the first dispersion is 2 mass % or more and 20 mass % or less.

8. The lithium transition metal composite oxide particles have a particle size of 90% of a cumulative particle size distribution based on volume. ２ D ９０ 10% particle size ２ D １０ Ratio to ２ D ９０ / ２ D １０ The method according to any one of claims 1 to 7, wherein the ratio of the stoichiometric ratio to the total stoichiometric ratio is 4 or less.

9. The above ２ D ５０ The above ２ D ＳＥＭ Ratio to ２ D ５０ / ２ D ＳＥＭ The method according to any one of claims 1 to 8, wherein is 1 or more and 3 or less.

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