Method for producing positive electrode active material for non-aqueous electrolyte secondary battery

Abstract

To provide an efficient manufacturing method for obtaining a positive electrode active material containing lithium transition metal oxide particles composed of single particles or reduced in the number of primary particles constituting one secondary particle.SOLUTION: In the manufacturing method of the positive electrode active material for the nonaqueous electrolyte secondary battery, composite oxide particles containing nickel as a main component and a lithium compound are heat-treated and dry-dispersed at a high temperature, and a particle size and a composition are controlled in a specific range. Is satisfied.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 nonaqueous electrolyte secondary batteries used in large power equipment such as electric vehicles are required to have both high output power and high durability. To achieve high output power, it is effective to use a positive electrode active material having a secondary particle structure in which many primary particles are aggregated, to form hollow structures within the secondary particles to increase the BET ratio, or to reduce the primary particle size of the aggregated secondary particles. However, such positive electrode active materials can suffer from cracks in the secondary particles due to pressure treatment during electrode formation and expansion and contraction during charge and discharge, leaving 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] Japanese Patent Application Laid-Open No. 2001-243949 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional methods for producing positive electrode active materials are complicated 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, wherein the value of the surface roughness of the composite oxide particles is 3 or less; obtaining a raw material mixture containing the composite oxide particles and a lithium compound, wherein the ratio of the total moles of lithium to the total moles 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 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; M 1 represents at least one of Mn and Al. [Effects of the Invention]

[0006] One embodiment of the present disclosure can 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. [Brief explanation 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. [Figure 2] FIG. 10 is a diagram showing an example of an SEM image of the lithium transition metal composite oxide particles according to Example 2. [Figure 3] FIG. 2 is a diagram showing an example of an SEM image of lithium transition metal composite oxide particles according to Comparative Example 1. [Figure 4] FIG. 10 is a diagram showing an example of an SEM image of the lithium transition metal composite oxide particles according to Example 4. [Figure 5] FIG. 10 is a diagram showing an example of an SEM image of the lithium transition metal composite oxide particles according to Example 5. [Figure 6] FIG. 10 is a diagram showing an example of an SEM image of the lithium transition metal composite oxide particles according to Example 6. [Figure 7] 10 is a diagram showing an example of an SEM image of lithium transition metal composite oxide particles according to Comparative Example 2. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to the present disclosure will be described based on embodiments. However, the embodiments shown below are intended to embody the technical concept of the present invention and are not intended to limit the present invention to the following. In this specification, the content of each component in a 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 for producing 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 and having an average particle size of 3 or less, obtaining a raw material mixture containing the first composite oxide particles and a lithium compound, wherein the ratio of the total moles of lithium to the total moles 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, dry-dispersing the heat-treated product to obtain a first dispersion, and contacting the first dispersion with a liquid medium to obtain a second dispersion. 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 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; and M 1 represents at least one of Mn and Al.

[0010] 1 D 90 / 1 D 10 Using first composite oxide particles having a uniform particle size of 3 or less as a raw material, these are heat-treated with a lithium compound, and then, instead of pulverization, dry dispersion treatment and contact treatment with a liquid medium are carried out, thereby efficiently producing lithium transition metal composite oxide particles that are single particles or particles composed of a few primary particles (hereinafter, collectively referred to as "single particles"). In conventional methods for producing positive electrode active materials consisting of single particles, particle size adjustment is carried out by pulverization, but it is difficult to control the particle size distribution, and it has been particularly difficult to obtain a sharp particle size distribution with uniform particle sizes.

[0011] As the proportion of Ni in the composition increases, so does the proportion of trivalent Ni, but because trivalent Ni is thermally unstable, thermal reduction from trivalent to divalent (for example, LiNiO2 → 0.5Li2O + NiO + 0.25O2) occurs easily during heat treatment, causing Li compounds to precipitate near the grain boundaries between the sintered primary particles. When the precipitated Li compounds come into contact with a liquid medium, the sintering becomes easier to loosen, and when force is applied in this state, the primary particles peel off, yielding single-particle lithium transition metal composite oxide particles.

[0012] The first composite oxide particles used in the method for producing a positive electrode active material contain at least nickel, preferably nickel and at least one element selected from the group consisting of cobalt, manganese, and aluminum, and more preferably 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 particle size of 50% of the cumulative particle size distribution on a volume basis. 1 D 50 However, it is, for example, 12 μm or less, preferably 6 μm or less, and for example, 1 μm or more, 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), can be, for example, 6 / 2 / 2, 6 / 2 / (1.5 / 0.5), 8 / 1 / 1, 8 / 1 / (0.5 / 0.5), etc. on a molar basis.

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

[0016] The prepared first composite oxide particles are mixed with a lithium compound to prepare a raw material mixture, such as lithium hydroxide, lithium carbonate, or lithium oxide.

[0017] The particle size of the lithium compound used is 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 carried out, for example, by raising the temperature from room temperature to a heat treatment temperature, continuing the heat treatment at the heat treatment temperature for a predetermined time, and then lowering the temperature to, for example, room temperature, thereby obtaining a heat-treated product. The heat treatment temperature is, for example, 850° C. to 1100° C., preferably 870° C. to 1050° C., and more preferably 900° C. to 1020° C. The heat treatment time is, for example, 1 hour to 30 hours, and preferably 1 hour to 20 hours.

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

[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 produce a heat-treated product. By heat-treating at the first temperature and then at the second temperature, the lithium compound and the first composite oxide are sufficiently reacted at the first temperature, and the remaining lithium compound acts as a flux at the second temperature, allowing particle growth while suppressing sintering between particles. This allows lithium transition metal composite oxide particles with few interparticle contact boundaries and a narrow particle size distribution to be obtained. In this case, the heat-treatment at the second temperature may further include an additional heat treatment at a temperature higher than the second temperature.

[0022] Furthermore, by performing heat treatment at the third temperature for a predetermined time during the temperature drop after 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 higher and 950° C. or lower, and preferably 750° C. or higher and 900° C. or lower. The second temperature is, for example, 850° C. or higher and 1100° C. or lower, and preferably 900° C. or higher and 1020° C. or lower. The difference between the first temperature and the second temperature is, for example, 30° C. or higher, preferably 80° C. or higher, and, for example, 250° C. or lower, preferably 180° C. or lower. The third temperature is, for example, 700°C or higher and 950°C or lower, and preferably 700°C or higher and 900°C or lower.

[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, and 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 consecutively or independently. When the heat treatment at the first temperature and the heat treatment at the second temperature are performed consecutively, 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, 1 hour or more and 20 hours or less, and preferably 3 hours or more and 10 hours or less.

[0026] The heat treatment atmosphere may be air or an oxygen atmosphere. The heat treatment atmosphere preferably contains oxygen. By including oxygen in the heat treatment atmosphere, for example, the amount of residual lithium can be reduced, and sintering between lithium transition metal composite oxide particles can be more effectively suppressed. When the heat treatment atmosphere contains oxygen, the oxygen content 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 then subjected to a dry dispersion process to obtain a first dispersion. The dispersion process dissociates the sintered primary particles, rather than using a pulverization process involving strong shear forces or impacts, thereby obtaining lithium transition metal composite oxide particles with a narrow particle size distribution and uniform particle size. The dispersion process can be carried out using, for example, a ball mill or a jet mill.

[0028] For example, when dispersion treatment is performed using a ball mill, resin media can be used. Examples of resin media materials include urethane resin and nylon resin. Generally, alumina, zirconia, etc. are used as media materials for ball mills, and particles are pulverized by these media. In contrast, by using resin media, sintered primary particles are dissociated without pulverizing the particles. The size of the resin media can be, for example, φ5 mm or more and 30 mm or less. Furthermore, for example, urethane resin or nylon resin can be used as the body (shell). The dispersion treatment time 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 The first composite oxide particles used as raw materials are 1 D 90 / 1 D 10The amount of media, rotation or vibration speed, dispersion time, media specific gravity, etc. may be adjusted depending on the above.

[0029] For example, when dispersion is performed using a jet mill, the primary particles are not pulverized, and the desired 2 D 50 / 2 D SEM The first composite oxide particles used as raw materials are 1 D 90 / 1 D 10 The supply pressure, grinding pressure, supply speed, etc. can be adjusted depending on the above. The supply pressure can be, for example, from 0.1 MPa to 0.5 MPa, and the grinding pressure can be, for example, from 0.1 MPa to 0.6 MPa.

[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 for example, a liquid medium containing water can be used. 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 eluted, 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, 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, alkaline solution, and acidic solution. The liquid medium may also contain a coating agent for the particles, and the coating treatment can be carried out simultaneously with the dispersion treatment.

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

[0033] When the first dispersion is brought into contact with the liquid medium, the mixture of the first dispersion and the liquid medium may be stirred, if necessary. Stirring can be carried out using, for example, a high-speed stirring mixer, a double cone mixer, 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] After the first dispersion is brought into contact with the liquid medium, it is preferable to carry out a drying treatment directly. This allows the lithium compound dissolved in the liquid medium to be re-inserted near the surface of the lithium transition metal oxide particles, thereby suppressing a decrease in output. After the drying treatment, further treatments such as sieving and classification may be carried out. By 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 production method have a composition represented by formula (1) and an average particle size based on observation with an electron microscope. 2 D SEM 50% particle size in the cumulative particle size distribution based on volume 2 D 50 Ratio of 2 D 50 / 2 D SEM The value is 1 or more and 4 or less. Also, the 90% particle size in the cumulative particle size distribution based on the volume 2 D 90 10% particle size 2 D 10 Ratio to 2 D 90 / 2 D 10 is preferably 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 value of 4 or less means that the cumulative particle size distribution of the lithium transition metal composite oxide particles on a volume basis is narrow and the particle sizes are uniform. A positive electrode active material containing lithium transition metal composite oxide particles with such characteristics can achieve both excellent output characteristics and excellent durability.

[0037] Compared to positive electrode active materials containing lithium transition metal composite oxide particles of conventional single particles, which have secondary particles consisting of a large number of agglomerated primary particles, positive electrode active materials containing single particles of 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 the grain boundary dissociation of the secondary particles during charge / discharge cycles, and the increase in the diffusion and migration resistance of lithium ions. On the other hand, since a three-dimensional grain boundary network like that of a positive electrode active material made of agglomerated particles is hardly formed, it is not possible to design a high output power using grain boundary conduction, and output characteristics tend to be insufficient. In order to improve 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 packing of the electrode plate, and the reduced powder flowability can significantly worsen handling. On the other hand, a certain particle size is necessary to obtain a particularly practical energy density, but if the particle size is increased, it is thought that the power shortage will tend 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. This prevents unevenness in charge / discharge depth among particles due to current concentration on some particles even when charging / discharging at a high current density. This is thought to prevent local degradation due to cycling while also suppressing an increase in resistance due to current concentration.

[0039] Furthermore, the uniform particle size of the lithium transition metal composite oxide particles with few grain boundaries prevents the particles from collapsing even when pressed under high pressure during electrode fabrication, which is thought to enable the voids between the particles to be homogenized. Furthermore, when a battery is constructed, the voids between the particles are filled with electrolyte, forming paths for lithium ions to diffuse. The uniform size of these diffusion paths is thought to reduce unevenness in charge and discharge behavior among particles. This suggests that even lithium transition metal composite oxide particles with few contact boundaries between primary particles can achieve excellent output characteristics while ensuring electrode plate packing.

[0040] Furthermore, 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 can cause Ni elements to become mixed into the Li site, a phenomenon known as disorder. Disorder inhibits the diffusion of Li ions in the lithium transition metal composite oxide particles, creating resistance and resulting in reduced charge / discharge capacity and output characteristics at practical current densities, so it is preferable to suppress this disorder. By suppressing disorder, better capacity and output characteristics can be achieved 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 is, for example, 1 μm or more and 7 μm or less, and from the viewpoint of output characteristics and electrode plate packing, it is preferably 1 μm or more, more preferably 1.5 μm or more, and is preferably 5.5 μm or less, 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 ranging from 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 value 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 perspective of durability, 2 D 50 / 2 D SEM is preferably 1 or more and 4 or less, 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, 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 smallest diameter side in the cumulative particle size distribution on a volume basis measured under wet conditions using a laser diffraction particle size distribution analyzer. 2 D 90 and 10% particle size 2 D 10 are calculated as the particle diameters corresponding to 90% and 10% cumulatively 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 perspective of output characteristics, it is preferably 4 or less, more preferably 3 or less, and even 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 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 a layered structure include lithium nickel composite oxide, lithium nickel cobalt manganese composite oxide, and the like.

[0048] In the formula (1), from the perspective of output, p preferably satisfies 1.0 ≦ p ≦ 1.1. From the perspective of cycle capacity retention rate, x preferably satisfies 0.6 ≦ x < 0.9. From the perspective of material cost, y preferably satisfies 0 < y ≦ 0.3, and from the perspective 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 containing these elements, and Li composite oxides thereof. 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 also include core particles containing a lithium transition metal composite oxide obtained by the above-described manufacturing method, and an attachment disposed on the surface of the core particles. The attachment may be disposed on at least a portion of the surface of the core particles, preferably occupying at least 1% of the surface area of ​​the core particles. The composition of the attachment may be appropriately selected depending on the intended purpose, and examples thereof include oxides and fluorides containing at least one element 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, as well as Li composite oxides thereof. The content of the attachment may be, for example, 0.03% by mass to 10% by mass, preferably 0.1% by mass to 2% by mass, in the lithium transition metal composite oxide particles.

[0051] From the viewpoint of initial efficiency in non-aqueous electrolyte secondary batteries, lithium transition metal composite oxides preferably have a nickel disorder of 5% or less, more preferably 3% or less, and even more preferably 2.5% or less, as determined by X-ray diffraction. Here, the disorder of nickel refers to a chemical disorder in the transition metal ions (nickel ions) that should occupy their original sites. In lithium transition metal composite oxides with a layered structure, this is typically the interchange of lithium ions that should occupy the site represented by 3b in Wyckoff notation (3b site, hereinafter the same) with transition metal ions that should occupy the 3a site. The smaller the disorder of nickel, the better, as this improves initial efficiency.

[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 form 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 form 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-described production method. A non-aqueous electrolyte secondary battery including such an electrode can achieve high durability and high output characteristics.

[0054] 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, a conductive material, a binder, and the like with a solvent onto the current collector, followed by drying and pressure treatments. Examples of conductive materials include natural graphite, artificial graphite, and acetylene black. Examples of binders include polyvinylidene fluoride, polytetrafluoroethylene, and polyamide acrylic resin.

[0055] [Non-aqueous electrolyte secondary battery] The non-aqueous electrolyte secondary battery includes the above-mentioned electrodes for a non-aqueous electrolyte secondary battery. The non-aqueous electrolyte secondary battery is configured to include, in addition to the electrodes for a non-aqueous electrolyte secondary battery, a negative electrode for a non-aqueous secondary battery, a non-aqueous electrolyte, a separator, etc. For the negative electrode, non-aqueous electrolyte, separator, etc. of the non-aqueous electrolyte secondary battery, those for non-aqueous electrolyte secondary batteries described in, for example, JP 2002-075367 A, JP 2011-146390 A, JP 2006-12433 A (the disclosures of which are incorporated herein by reference in their entirety) can be appropriately used. [Example]

[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 volume-based cumulative particle size distribution, and the particle sizes were determined 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 image observed at 1000 to 10,000 times magnification using a scanning electron microscope (SEM), 100 particles whose particle outlines could be confirmed were selected, and the spherical equivalent diameter of the selected particles was calculated using image processing software (ImageJ), and the particle diameter was determined as the arithmetic mean of the obtained spherical equivalent diameters.

[0058] The disorder value of the nickel element (Ni disorder amount) was determined by the X-ray diffraction method according to the following procedure. The obtained lithium transition metal composite oxide particles were subjected to X-ray diffraction spectroscopy using CuKα radiation (tube current 200 mA, tube voltage 45 kV). Based on the obtained X-ray diffraction spectrum, a composition model was established. 1-d Ni d Structural optimization was performed on the lithium transition metal composite oxide using Rietveld analysis with 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 a reaction tank and stirred until the ammonium ion concentration was adjusted to 1.8% by mass. The temperature inside the tank was set to 25°C, and nitrogen gas was circulated to maintain the oxygen concentration in the reaction tank space 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 higher. Next, a mixed aqueous solution of nickel sulfate solution, cobalt sulfate solution, and manganese sulfate solution in a molar ratio of 6:2:2 was prepared. The mixed aqueous solution was added until the solute amount reached 4 moles, and seeds were generated while controlling the pH value of the reaction solution to 12.0 or higher with a sodium hydroxide solution.

[0060] (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. A mixed aqueous solution of 1200 moles of solute was also prepared, and was simultaneously added to the reaction tank over a period of 5 hours or more, together with the aqueous ammonia solution, while maintaining the ammonium ion concentration in the solution at 2000 ppm or higher, to prevent new seed generation. During the reaction, the pH value of the reaction solution was controlled to be maintained at 10.5 to 12.0 using a sodium hydroxide solution. Sampling was carried out sequentially 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 precursor 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 resulting 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 resulting 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 resulting 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 10% by mass of water relative to the powder, and stirred at 2000 rpm to dissolve residual alkali at the grain boundaries, resulting in a dispersion treatment. The mixture was then dried at 350°C and dry-sieved to obtain a powder. From the above, the average particle size based on 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 against 2 D 50 Ratio of 2 D 50 / 2 D SEM is 1.5, and the ratio in particle size distribution 2 D 90 / 2 D 10 is 2.3, the 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 subjected to a dispersion treatment 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 residual alkali at the grain boundaries, thereby performing a dispersion treatment. 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 3.2 μm, 2 D 10 = 3.6 μm, 2 D 50 = 6.1 μm, 2 D 90 =9.2μm, average particle size 2 D SEM against 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, the Ni disorder amount is 1.2%, and the composition formula is Li 1.17 Ni 0.60 Co 0.20 Mn 0.20 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 subjected to a dispersion treatment 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 residual alkali at the grain boundaries, thereby performing a dispersion treatment. 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 against 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, the 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 dry-sieved to obtain a powder 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 against 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, the Ni disorder amount is 1.0%, and the composition formula is: Li 1.17 Ni 0.60 Co 0.20 Mn 0.20 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] Example 4 The same conditions were used 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. The mixed aqueous solution had 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 10First composite oxide particles with a ratio of 1.8 and lithium hydroxide monohydrate were mixed to obtain a raw material mixture such that Li / (Ni+Co+Mn)=1.04. The resulting 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 resulting sintered body was crushed and dispersed in a resin ball mill for 10 minutes to obtain a powder. The powder was then placed in a rotary blade high-speed agitator mixer, and 10% by mass of water was added to the powder and stirred at 2000 rpm to dissolve residual alkali from the grain boundaries, resulting in a dispersion treatment. The powder was then dried at 350°C and sieved 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 D 90 =12.0μm, average particle size 2 D SEM against 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, the Ni disorder amount is 1.7%, and the composition formula is Li 1.04 Ni 0.80 Co 0.10 Mn 0.10 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 5 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 at 950°C for 10 hours to obtain a sintered body (heat-treated product). The obtained sintered body was crushed and subjected to a dispersion treatment 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 stirred at 2000 rpm to dissolve residual alkali at the grain boundaries, thereby performing a dispersion treatment. The powder was then dried at 350°C and then dry-sieved 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 against 2 D 50 Ratio of 2 D 50 / 2 D SEM is 2.1, and the ratio in particle size distribution 2 D 90 / 2 D 10 is 2.7, the Ni disorder amount is 2.3%, and the composition formula is: Li 1.04 Ni 0.80 Co 0.10 Mn 0.10 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 6 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 at 1000°C for 10 hours to obtain a sintered body (heat-treated product). The obtained sintered body was crushed and subjected to a dispersion treatment 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 stirred at 2000 rpm to dissolve residual alkali at the grain boundaries, thereby performing a dispersion treatment. The powder was then 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 against 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, the Ni disorder amount is 4.2%, and the composition formula is: Li 1.04 Ni 0.80 Co 0.10 Mn 0.10 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] (Comparative Example 2) The mixed aqueous solution in Example 1 was changed to a mixed solution of nickel sulfate solution and cobalt sulfate solution in a molar ratio of 80:15, and the timing of finishing the addition of the mixed solution in the crystallization step was adjusted to the D 50The 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 resulting first composite oxide particles were mixed with aluminum oxide to give a composition ratio of Ni / Co / Al = 0.80 / 0.15 / 0.05, and with lithium hydroxide monohydrate to give a Li / (Ni + Co + Al) = 1.04, to give a raw material mixture. The resulting raw material mixture was fired in an oxygen stream at 710°C for 5 hours to give a sintered body. The resulting sintered body was crushed, dispersed in a resin ball mill for 10 minutes, and dry sieved to give a powder. 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 against 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, the Ni disorder amount is 1.0%, and the composition formula is: Li 1.04 Ni 0.80 Co 0.15 Al 0.05 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] [Table 1]

[0070] The lithium transition metal oxide particles produced by the above-described production method are composed of a single particle or a small number of primary particles, and therefore can be produced efficiently without pulverizing the obtained lithium transition metal oxide to adjust the particle size and then subjecting it to another heat treatment.

[0071] 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 small number of primary particles, and the particle size is uniform. 2 D 50 / 2 D SEM and 2 D 90 / 2 D 10 Since the value of the positive electrode active material is small, by applying the positive electrode active material to a non-aqueous electrolyte secondary battery, a non-aqueous electrolyte secondary battery having excellent output characteristics and durability can be constructed. 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. preparing composite oxide particles containing nickel; obtaining a raw material mixture containing the composite oxide particles and a lithium compound; heat-treating the raw material mixture at a first temperature and then at a second temperature higher than the first temperature to obtain a heat-treated product; The heat-treated product is obtained by heating the mixture of the composite oxide particles and the lithium compound to 850°C. ℃ or more and 1100 ℃ or less, and subjecting the heat-treated product to a dry dispersion treatment to obtain a first 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 between 1 and 4, The composition of the positive electrode active material is such that, relative to the total number of moles of metals other than lithium, hand, The ratio of the mole number of nickel is 0.6 or more and less than 0.95, The ratio of the number of moles of cobalt is 0.4 or less, the ratio of the total number of moles of manganese and aluminum is 0.5 or less; The ratio of the number of moles of lithium is 1.0 or more and 1.3 or less, The production method, wherein the ratio of the number of moles of oxygen atoms is 1.9 or more and 2.1 or less.

2. 90% particle size of cumulative particle size distribution based on volume of positive electrode active material ２ D ９０ 10% particle size ２ D １０ Ratio to ２ D ９０ / ２ D １０ 2. The method according to claim 1, wherein the value of β is 4 or less.

3. 3. 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 third temperature lower than the first temperature.

4. The method according to claim 3 , 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.

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

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

7. The lithium transition metal composite oxide particles have a particle size of 90% of the cumulative particle size distribution on a volume basis. 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 6, wherein the value of β is 4 or less.

8. The aforementioned 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 7, wherein is 1 or more and 3 or less.

Images