Positive electrode active material for non-aqueous electrolyte secondary battery and method for producing same

Abstract

To provide a method for manufacturing a cathode active material for a non-aqueous electrolyte secondary battery with which output characteristics during formation of a cathode are improved and fluidity as powder is improved.SOLUTION: A method for manufacturing a cathode active material for a non-aqueous electrolyte secondary battery includes: preparing a composition including a liquid medium and a first lithium transition metal composite oxide having 1D50, a 50% particle size in the volume cumulative particle size distribution, of 0.1 μm or more and less than 3.2 μm; and granulating the composition to obtain a second lithium transition metal composite oxide having 2D50, a 50% particle size in the volume cumulative particle size distribution, larger than 1D50. The second lithium transition metal composite oxide has different volume cumulative particle size distributions before and after ultrasonic treatment in the liquid medium. The ratio of 3D90, a 90% particle size in the volume cumulative particle size distribution measured after the ultrasonic treatment, to 2D90, a 90% particle size in the volume cumulative particle size distribution measured before the ultrasonic treatment (3D90 / 2D90), is 0.53 or less. The first lithium transition metal composite oxide has a composition represented by the formulas (1), (3) or (4). (1) LipCoxM1yO2. (3) LipFexM3yM4zPO4. (4) LipMnxM5yO4.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a positive electrode active material for a non-aqueous electrolyte secondary battery and a method for producing the same. [Background technology]

[0002] High output power is required for positive electrode active materials for non-aqueous electrolyte secondary batteries used in large power equipment such as electric vehicles. A positive electrode active material having a secondary particle structure in which many primary particles aggregate is considered effective for achieving high output power. For example, Patent Document 1 describes a positive electrode active material containing secondary particles composed of primary particles of two types of positive electrode active materials with different compositions, which is said to provide high output power over a wide range of states of charge (SOC). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-130272 Summary of the Invention [Problem to be solved by the invention]

[0004] One method for achieving high output characteristics is to reduce the particle size of the positive electrode active material and increase the specific surface area. However, reducing the particle size of the positive electrode active material reduces the flowability of the positive electrode active material as a powder, which tends to reduce productivity. One aspect of the present disclosure aims to provide a positive electrode active material for a non-aqueous electrolyte secondary battery that improves output characteristics during positive electrode formation and improves the flowability of the powder, and a method for producing the same. [Means for solving the problem]

[0005] The first aspect is the 50% particle size in the volume cumulative particle size distribution. 1 D 50a composition including a first lithium transition metal composite oxide having a particle size of 0.1 μm or more and less than 3.2 μm and a liquid medium; and granulating the composition to form a granule having a particle size of 50% in a volume cumulative particle size distribution. 2 D 50 but 1 D 50 and obtaining a second lithium transition metal composite oxide having a volume cumulative particle size distribution that differs before and after ultrasonic treatment in a liquid medium, and having a particle size of 90% or more in the volume cumulative particle size distribution measured before ultrasonic treatment. 2 D 90 is the 90% particle size in the volume cumulative particle size distribution measured after ultrasonic treatment 3 D 90 The ratio ( 3 D 90 / 2 D 90 ) is less than or equal to 0.53.

[0006] The second aspect includes a lithium transition metal composite oxide whose volume cumulative particle size distribution changes after ultrasonic treatment in a liquid medium, and the lithium transition metal composite oxide has a 90% particle size in the volume cumulative particle size distribution measured before the ultrasonic treatment. 2 D 90 is the 90% particle size in the volume cumulative particle size distribution measured after ultrasonic treatment 3 D 90 The ratio ( 3 D 90 / 2 D 90 ) is 0.53 or less. [Effects of the Invention]

[0007] According to one aspect of the present disclosure, it is possible to provide a positive electrode active material for a non-aqueous electrolyte secondary battery that has improved output characteristics when forming a positive electrode and improved flowability as a powder, and a method for producing the same. DETAILED DESCRIPTION OF THE INVENTION

[0008] In this specification, the term "process" refers not only to an independent process, but also to a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved. Furthermore, the content of each component in a composition refers to the total amount of the multiple substances present in the composition, unless otherwise specified, when multiple substances corresponding to each component are present in the composition. Hereinafter, embodiments of the present invention will be described in detail. However, the embodiments described below are intended to exemplify the positive electrode active material for a non-aqueous electrolyte secondary battery and the method for producing the same, in order to embody the technical concept of the present invention. The present invention is not limited to the positive electrode active material for a non-aqueous electrolyte secondary battery and the method for producing the same shown below.

[0009] Method for producing positive electrode active material for non-aqueous electrolyte secondary battery The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery is to 1 D 50 a preparation step of preparing a composition including a first lithium transition metal composite oxide having a particle size of 0.1 μm or more and less than 3.2 μm and a liquid medium; and granulating the prepared composition to obtain a granule having a particle size of 50% in a volume cumulative particle size distribution. 2 D 50 but 1 D 50 and a granulation step of obtaining a second lithium transition metal composite oxide having a particle size larger than 90% in the volume cumulative particle size distribution measured before and after the ultrasonic treatment in a liquid medium. 2 D 90 is the 90% particle size in the volume cumulative particle size distribution measured after ultrasonic treatment 3 D 90 The ratio ( 3 D 90 / 2 D 90 ) is less than or equal to 0.53.

[0010] Relatively small particle size (50% particle size in the volume cumulative particle size distribution) 1 D 50By granulating a composition containing primary particles (first lithium transition metal composite oxide) containing a lithium transition metal composite oxide having a particle size of 0.1 μm or more and less than 3.2 μm and a liquid medium, a relatively large particle size (50% particle size in the volume cumulative particle size distribution) in which the primary particles are aggregated is obtained. 2 D 50 The above 1 D 50 Secondary particles (second lithium transition metal composite oxide) having a particle size larger than that of the secondary particles are formed. The large particle size of the secondary particles improves the flowability of the powder, and therefore the productivity of the positive electrode active material containing the secondary particles is improved. Here, productivity means, for example, that clogging of a sieve is suppressed. Furthermore, the secondary particles formed by granulation have a volume cumulative particle size distribution that differs before and after ultrasonic treatment in a liquid medium, and the particle size is the 90% particle size in the volume cumulative particle size distribution measured before ultrasonic treatment. 2 D 90 is the 90% particle size in the volume cumulative particle size distribution measured after ultrasonic treatment 3 D 90 The ratio ( 3 D 90 / 2 D 90 ) is 0.53 or less, it is believed that primary particles are regenerated when ultrasonically treated in a liquid medium. Generally, an electrode active material layer is formed from a liquid electrode composition containing a positive electrode active material. When an electrode composition is prepared using a positive electrode active material containing granulated secondary particles, primary particles are regenerated in the electrode composition. Therefore, the positive electrode active material layer formed from the electrode composition contains primary particles of the positive electrode active material. It is believed that primary particles of the positive electrode active material have a relatively large specific surface area due to their particle size, and can achieve high output characteristics in batteries.

[0011] In the preparation process, the particle size is 50% in the volume cumulative particle size distribution. 1 D 50 A composition containing a first lithium transition metal composite oxide having a particle size of 0.1 μm or more and less than 3.2 μm and a liquid medium is prepared. 1 D 50From the viewpoint of output characteristics when a battery is constructed, the particle size is preferably 0.12 μm or more and 2.5 μm or less, and more preferably 0.13 μm or more and 2 μm or less. The 50% particle size is determined as the particle size corresponding to 50% of the cumulative volume from the small particle size side in the cumulative volume particle size distribution.

[0012] The first lithium transition metal composite oxide has a particle size of 90% in the volume cumulative particle size distribution. 1 D 90 From the viewpoint of output characteristics when constituting a battery, for example, the particle size is 0.13 μm or more and 5 μm or less, and preferably 0.15 μm or more and 3 μm or less. The 90% particle size is determined as the particle size corresponding to 90% of the cumulative volume from the small particle size side in the cumulative volume particle size distribution.

[0013] 50% particle size of the first lithium transition metal composite oxide 1 D 50 and 90% particle size 1 D 90 can be controlled by appropriately selecting the particle size of the composite oxide used as the raw material and the heat treatment conditions when producing the first lithium transition metal composite oxide. 1 D 50 However, the lithium transition metal composite oxide having a particle size of 3.2 μm or more may be pulverized to have a desired particle size distribution. The pulverization may be, for example, wet pulverization in a liquid medium using a ball mill or the like, or dry pulverization using a jet mill or the like.

[0014] The first lithium transition metal composite oxide may be, for example, any of a lithium transition metal composite oxide having a layered structure, a lithium transition metal composite oxide having an olivine structure, and a lithium transition metal composite oxide having a spinel structure.

[0015] As the lithium transition metal composite oxide having a layered structure, the lithium transition metal composite oxide containing cobalt may be lithium cobalt oxide. Lithium cobalt oxide contains a metal element M in addition to lithium and cobalt. 1 The metal element M may contain at least one of the following: 1Examples of the element include nickel (Ni), manganese (Mn), aluminum (Al), magnesium (Mg), calcium (Ca), titanium (Ti), zirconium (Zr), niobium (Nb), thallium (Ta), chromium (Cr), molybdenum (Mo), iron (Fe), copper (Cu), silicon (Si), tin (Sn), bismuth (Bi), gallium (Ga), yttrium (Y), samarium (Sm), erbium (Er), cerium (Ce), neodymium (Nd), lanthanum (La), cadmium (Cd), and lutetium (Lu), and the element may be at least one selected from the group consisting of these elements.

[0016] In the cobalt-containing lithium transition metal composite oxide having a layered structure, the ratio of the number of moles of cobalt to the total number of moles of metals other than lithium may be, for example, 1 or less.

[0017] The layered structure of the lithium transition metal composite oxide containing cobalt is 1 When lithium is included, the metal element M is the total number of moles of metals other than lithium. 1 The ratio of the number of moles of may be, for example, 0.1 or less.

[0018] In the lithium transition metal composite oxide containing cobalt having a layered structure, the ratio of the number of moles of lithium to the total number of moles of metals other than lithium may be, for example, 0.9 or more and 1.2 or less.

[0019] The cobalt-containing lithium transition metal composite oxide having a layered structure may have a composition represented by the following formula (1), for example. Li p Co x M 1 y O2(1) In formula (1), 0.9≦p≦1.2, 0 <x≦1、0≦y≦0.1、x+y≦1である。M 1is at least one selected from the group consisting of Ni, Mn, Al, Mg, Ca, Ti, Zr, Nb, Ta, Cr, Mo, Fe, Cu, Si, Sn, Bi, Ga, Y, Sm, Er, Ce, Nd, La, Cd, and Lu.

[0020] As a lithium transition metal composite oxide having a layered structure, the lithium transition metal composite oxide containing nickel contains at least lithium (Li) and nickel (Ni). The lithium transition metal composite oxide containing nickel may contain at least one selected from the group consisting of cobalt (Co), manganese (Mn) and aluminum (Al) in addition to lithium and nickel. The lithium transition metal composite oxide containing nickel may contain at least one selected from the group consisting of lithium, nickel, cobalt, manganese and aluminum in addition to the metal element M. 2 The metal element M 2 Examples of the metal include zirconium (Zr), titanium (Ti), magnesium (Mg), tantalum (Ta), niobium (Nb), and molybdenum (Mo), and the metal may be at least one selected from the group consisting of these.

[0021] In the nickel-containing lithium transition metal composite oxide having a layered structure, the ratio of the number of moles of nickel to the total number of moles of metals other than lithium may be, for example, 0.3 or more and less than 1.

[0022] When the nickel-containing lithium transition metal composite oxide having a layered structure contains cobalt, the ratio of the number of moles of cobalt to the total number of moles of metals other than lithium may be, for example, 0.7 or less.

[0023] When the layered lithium transition metal composite oxide containing nickel contains manganese, the ratio of the number of moles of manganese to the total number of moles of metals other than lithium may be, for example, 0.7 or less.

[0024] When the layered nickel-containing lithium transition metal composite oxide contains aluminum, the ratio of the number of moles of aluminum to the total number of moles of metals other than lithium may be, for example, 0.7 or less.

[0025] The layered structure of the lithium transition metal composite oxide containing nickel is 2 When lithium is included, the metal element M is the total number of moles of metals other than lithium. 2 The ratio of the number of moles of may be, for example, 0.02 or less.

[0026] In the lithium transition metal composite oxide containing nickel having a layered structure, the ratio of the number of moles of lithium to the total number of moles of metals other than lithium may be, for example, 1.0 or more and 1.5 or less.

[0027] The lithium transition metal composite oxide containing nickel and having a layered structure may have a composition represented by the following formula (2), for example. Li p Ni x Co y Mn z Al w M 2 u O2(2) In formula (2), 1.0≦p≦1.5, 0.3≦x<1, 0≦y≦0.7, 0≦z≦0.7, 0≦w≦0.7, 0≦u≦0.02, and x+y+z+w+u≦1. M 2 is at least one selected from the group consisting of Zr, Ti, Mg, Ta, Nb and Mo.

[0028] As a lithium transition metal composite oxide having an olivine structure, the iron-containing lithium transition metal composite oxide contains at least lithium (Li), iron (Fe), and phosphorus (P). The iron-containing lithium transition metal composite oxide contains the metal element M in addition to lithium, iron, and phosphorus. 3 The metal element M 3Examples of the metal element include cobalt (Co), manganese (Mn), and nickel (Ni), and at least one selected from the group consisting of these may be used. The lithium transition metal composite oxide containing iron contains lithium, iron, phosphorus, and the metal element M. 3 In addition to the metal element M 4 The metal element M 4 Examples of the metals include molybdenum (Mo), magnesium (Mg), zirconium (Zr), titanium (Ti), aluminum (Al), cerium (Ce), and chromium (Cr), and may be at least one selected from the group consisting of these metals.

[0029] In the iron-containing lithium transition metal composite oxide having an olivine structure, the ratio of the number of moles of iron to the total number of moles of metals other than lithium may be, for example, greater than 0 and may be 1 or less.

[0030] The lithium transition metal composite oxide containing iron having an olivine structure is 3 When lithium is included, the metal element M is the total number of moles of metals other than lithium. 3 The ratio of the number of moles of may be, for example, less than 1.

[0031] The lithium transition metal composite oxide containing iron having an olivine structure is 4 When lithium is included, the metal element M is the total number of moles of metals other than lithium. 4 The ratio of the number of moles of may be, for example, 0.3 or less.

[0032] In the iron-containing lithium transition metal composite oxide having an olivine structure, the ratio of the number of moles of lithium to the total number of moles of metals other than lithium may be, for example, 0.9 or more and 1.3 or less.

[0033] The iron-containing lithium transition metal composite oxide having an olivine structure may have a composition represented by the following formula (3), for example. Li p Fe x M 3 y M4 z PO4(3) In formula (3), 0.9≦p≦1.3, 0 <x≦1、0≦y<1、0≦z≦0.3、x+y+z≦1である。M 3 is at least one selected from the group consisting of Co, Mn and Ni. 4 is at least one selected from the group consisting of Mo, Mg, Zr, Ti, Al, Ce and Cr.

[0034] As a lithium transition metal composite oxide having a spinel structure, a manganese-containing lithium transition metal composite oxide contains at least lithium (Li) and manganese (Mn). The manganese-containing lithium transition metal composite oxide contains a metal element M in addition to lithium and manganese. 5 The metal element M 5 Examples of the metals include aluminum (Al), magnesium (Mg), silicon (Si), titanium (Ti), chromium (Cr), iron (Fe), cobalt (Co), copper (Cu), zinc (Zn), and gallium (Ga), and the metal may be at least one selected from the group consisting of these.

[0035] In the manganese-containing lithium transition metal composite oxide having a spinel structure, the ratio of the number of moles of Mn to the total number of moles of metals other than lithium may be, for example, more than 0 and may be 2 or less.

[0036] The lithium transition metal composite oxide containing manganese having a spinel structure is 5 When lithium is included, the metal element M is the total number of moles of metals other than lithium. 5 The ratio of the number of moles of may be, for example, 0.2 or less.

[0037] In the lithium transition metal composite oxide having a spinel structure and containing manganese, the ratio of the number of moles of lithium to the total number of moles of metals other than lithium may be, for example, 1 or more and 1.4 or less.

[0038] The lithium transition metal composite oxide having a spinel structure may have a composition represented by the following formula (4), for example. Li p Mn x M 5 y O4(4) In formula (4), 1≦p≦1.4, 0 <x≦2、0≦y≦0.2、x+y≦2である。M 5 is at least one selected from the group consisting of Al, Mg, Si, Ti, Cr, Fe, Co, Cu, Zn and Ga.

[0039] As a lithium transition metal composite oxide having a spinel structure, the lithium transition metal composite oxide containing nickel and manganese contains at least lithium (Li), nickel (Ni), and manganese (Mn). The lithium transition metal composite oxide containing nickel and manganese contains the metal element M in addition to lithium, nickel, and manganese. 6 The metal element M 6 Examples of the metals include aluminum (Al), magnesium (Mg), silicon (Si), titanium (Ti), chromium (Cr), iron (Fe), cobalt (Co), copper (Cu), zinc (Zn), and gallium (Ga), and the metal may be at least one selected from the group consisting of these.

[0040] In the lithium transition metal composite oxide containing nickel and manganese and having a spinel structure, the ratio of the number of moles of nickel to the total number of moles of metals other than lithium may be, for example, 0.3 or more and 0.6 or less.

[0041] In the lithium transition metal composite oxide containing nickel and manganese and having a spinel structure, the ratio of the number of moles of manganese to the total number of moles of metals other than lithium may be, for example, 1.2 or more and 1.7 or less.

[0042] A lithium transition metal composite oxide containing nickel and manganese having a spinel structure is 6When lithium is included, the metal element M is the total number of moles of metals other than lithium. 6 The ratio of the number of moles of may be, for example, 0.2 or less.

[0043] In the lithium transition metal composite oxide containing nickel and manganese and having a spinel structure, the ratio of the number of moles of lithium to the total number of moles of metals other than lithium may be, for example, 1 or more and 1.4 or less.

[0044] The lithium transition metal composite oxide containing nickel and manganese and having a spinel structure may have a composition represented by the following formula (5), for example. Li p Ni x Mn y M 6 z O4(5) In formula (5), 1≦p≦1.4, 0.3≦x≦0.6, 1.2≦y≦1.7, 0≦z≦0.2, and x+y+z≦2. M 6 is at least one selected from the group consisting of Al, Mg, Si, Ti, Cr, Fe, Co, Cu, Zn and Ga.

[0045] The liquid medium contained in the composition is preferably water from the viewpoint of the binding ability between particles of the second lithium transition metal composite oxide, and may further contain a water-soluble organic solvent such as alcohol or acetone in addition to water. The composition may be configured as a fluid slurry. The solids concentration of the first lithium transition metal composite oxide in the composition may be, for example, 5% by mass or more and 30% by mass or less, and preferably 10% by mass or more and 20% by mass or less.

[0046] In addition to the first lithium transition metal composite oxide and the liquid medium, the composition may contain other components depending on the binding ability of the second lithium transition metal composite oxide particles. Examples of other components include a binder and a dispersant. When the composition contains other components, the content thereof may be, for example, 10% by mass or less, preferably 5% by mass or less, and more preferably 1% by mass or less. The lower limit of the content may be, for example, 0.01% by mass or more.

[0047] The composition can be prepared by mixing the first lithium transition metal composite oxide with a liquid medium. For example, the composition can be prepared by mixing using a mixer equipped with a stirring blade. The composition obtained by mixing may be subjected to a dispersion treatment. The dispersion treatment can be performed wet using, for example, a ball mill.

[0048] In the granulation step, the composition to be prepared is granulated to obtain a particle having a particle size of 50% in the volume cumulative particle size distribution. 2 D 50 but 1 D 50 The second lithium transition metal composite oxide obtained has a volume cumulative particle size distribution that differs before and after ultrasonic treatment in a liquid medium, and has a 90% particle size in the volume cumulative particle size distribution measured before ultrasonic treatment. 2 D 90 is the 90% particle size in the volume cumulative particle size distribution measured after ultrasonic treatment 3 D 90 The ratio ( 3 D 90 / 2 D 90 ) is less than or equal to 0.53.

[0049] In the granulation step, the prepared composition is dried to remove at least a part of the liquid medium, and the 50% particle size in the volume cumulative particle size distribution is obtained. 2 D 50 but 1 D 50 The second lithium transition metal composite oxide having a particle size larger than that of the first lithium transition metal composite oxide is obtained as a dried product. Methods for drying the composition include spray drying and fluidized bed drying. Spray drying is preferred because it is easy to adjust the particle size of the second lithium transition metal composite oxide.

[0050] 50% particle size of the second lithium transition metal composite oxide 2 D 50From the viewpoint of flowability as a powder, the particle size may be, for example, 2 μm or more, preferably 2.3 μm or more, and more preferably 2.5 μm or more. 2 D 50 may be, for example, 50 μm or less, preferably 30 μm or less, and more preferably 15 μm or less. The 50% particle size is determined as the particle size corresponding to 50% of the cumulative volume from the small particle size side in the cumulative volume particle size distribution.

[0051] The second lithium transition metal composite oxide has a particle size of 90% in the volume cumulative particle size distribution. 2 D 90 From the viewpoint of flowability as a powder, the particle size is sufficient to be larger than 3.6 μm, preferably 5 μm or larger, and more preferably 6 μm or larger. 2 D 50 may be, for example, 55 μm or less, preferably 35 μm or less, and more preferably 25 μm or less. The 90% particle size is determined as the particle size corresponding to 90% of the cumulative volume from the small particle size side in the cumulative volume particle size distribution.

[0052] The ratio of the 50% particle size of the second lithium transition metal composite oxide to the 50% particle size of the first lithium transition metal composite oxide ( 2 D 50 / 1 D 50 ) is, for example, greater than 1, preferably 1.5 or greater, from the viewpoint of powder flowability. 2 D 50 / 1 D 50 ) may be, for example, 500 or less, and preferably 300 or less.

[0053] The ratio of the 90% particle size of the second lithium transition metal composite oxide to the 90% particle size of the first lithium transition metal composite oxide ( 2 D 90 / 1 D 90 ) is, for example, greater than 1, preferably 1.5 or greater, from the viewpoint of powder flowability. 2 D 90 / 1D 90 ) may be, for example, 500 or less, and preferably 300 or less.

[0054] The second lithium transition metal composite oxide has a different volume cumulative particle size distribution before and after ultrasonic treatment in a liquid medium. The second lithium transition metal composite oxide is formed as granules (secondary particles) of the first lithium transition metal composite oxide, which are primary particles. Because the granules have low physical strength, application of appropriate energy causes at least a portion of them to collapse and regenerate the primary particles. Therefore, by irradiating the second lithium transition metal composite oxide with ultrasonic waves in a liquid medium, at least a portion of the primary particles constituting the granules are regenerated, resulting in a change in particle size distribution. For example, if the 50% particle size in the volume cumulative particle size distribution of the second lithium transition metal composite oxide constituting the positive electrode active material is 2 D 50 and 90% particle size 2 D 90 are the 50% particle sizes measured after ultrasonic treatment of the second lithium transition metal composite oxide in a liquid medium, respectively. 3 D 50 and 90% particle size 3 D 90 Here, the ultrasonic treatment conditions in this specification are that 0.05 g of the second lithium transition metal composite oxide is dispersed in 200 ml of water containing 0.05 mass % of sodium hexametaphosphate, and ultrasonicated for 20 seconds at 20°C using an ultrasonic irradiation device with a frequency of 40 kHz and an output of 110 W.

[0055] The second lithium transition metal composite oxide has a 50% particle size measured after ultrasonic treatment in a liquid medium. 3 D 50 However, from the viewpoint of output characteristics when a battery is constructed, the particle size is, for example, 0.1 μm or more and less than 3.2 μm, and preferably 0.11 μm or more and 2.5 μm or less. The 50% particle size is determined as the particle size corresponding to 50% of the cumulative volume from the small particle size side in the cumulative volume particle size distribution.

[0056] The second lithium transition metal composite oxide has a 90% particle size measured after ultrasonic treatment in a liquid medium. 3 D 90 From the viewpoint of output characteristics when constituting a battery, the particle size is, for example, 0.1 μm or more and 5 μm or less, and preferably 0.15 μm or more and 3 μm or less. The 90% particle size is determined as the particle size corresponding to 90% of the cumulative volume from the small particle size side in the cumulative volume particle size distribution.

[0057] The second lithium transition metal composite oxide has the following properties in terms of output characteristics when used to construct a battery: 2 D 90 against 3 D 90 The ratio ( 3 D 90 / 2 D 90 ) may be, for example, greater than 0 and equal to or less than 0.53, preferably equal to or less than 0.5, and more preferably equal to or less than 0.3.

[0058] The second lithium transition metal composite oxide has the following properties in terms of output characteristics when used to construct a battery: 2 D 50 against 3 D 50 The ratio ( 3 D 50 / 2 D 50 ) may be, for example, greater than 0 and equal to or less than 0.53, preferably equal to or less than 0.5, and more preferably equal to or less than 0.3.

[0059] The first lithium transition metal composite oxide has a particle size of 50% in the volume cumulative particle size distribution. 1 D 50 is the 50% particle size measured after ultrasonic treatment of the second lithium transition metal composite oxide in a liquid medium, relative to 3 D 50 The ratio ( 3 D 50 / 1 D 50 ) is, for example, 0.8 or more and 1.5 or less, preferably 0.95 or more and 1.1 or less, from the viewpoint of output characteristics when a battery is constructed.

[0060] The first lithium transition metal composite oxide has a particle size of 90% in the volume cumulative particle size distribution. 1 D 90 90% particle size measured after ultrasonic treatment in a liquid medium of the second lithium transition metal composite oxide, 3 D 90 The ratio ( 3 D 90 / 1 D 90 ) is, for example, 0.8 or more and 2 or less, preferably 0.95 or more and 1.5 or less, from the viewpoint of output characteristics when a battery is constructed.

[0061] The second lithium transition metal composite oxide is formed, for example, by spray-drying the composition. The conditions, apparatus, etc. for spray-drying may be selected as appropriate. For example, the composition is dispersed in a drying chamber of a spraying device equipped with one or more nozzles for introducing the composition and one or more nozzles for an air flow, and at least a portion of the liquid medium is removed from the composition to obtain the desired dried product. The conditions, such as the flow rate of each nozzle, the flow rate ratio between each nozzle, and the temperature of the drying chamber, may be selected as follows: 1 D 50 Greater than 2 D 50 and the particle size is 90% in the volume cumulative particle size distribution measured before ultrasonic treatment in a liquid medium. 2 D 90 is the 90% particle size in the volume cumulative particle size distribution measured after ultrasonic treatment 3 D 90 The ratio ( 3 D 90 / 2 D 90 ) should be adjusted to 0.53 or less.

[0062] Specific conditions for spray drying include, for example, the ratio of the amount of gas supplied to the amount of composition supplied being, for example, 500 to 4000, and preferably 800 to 2000. The drying temperature may be, for example, 100°C to 170°C, and preferably 130°C to 160°C.

[0063] The second lithium transition metal composite oxide obtained by spray drying is preferably not subjected to an additional heat treatment. Here, the additional heat treatment means that the second lithium transition metal composite oxide is heated to, for example, 250°C or higher, preferably 300°C or higher. The additional heat treatment may improve the adhesive strength between the primary particles and suppress the collapse of the secondary particles.

[0064] Positive electrode active material for non-aqueous electrolyte secondary batteries The positive electrode active material for a non-aqueous electrolyte secondary battery contains a lithium transition metal composite oxide whose volume cumulative particle size distribution changes after ultrasonic treatment in a liquid medium. The lithium transition metal composite oxide has a 90% particle size in the volume cumulative particle size distribution measured before the ultrasonic treatment. 2 D 90 is the 90% particle size in the volume cumulative particle size distribution measured after ultrasonic treatment 3 D 90 The ratio ( 3 D 90 / 2 D 90 ) is less than or equal to 0.53.

[0065] By configuring the positive electrode active material including a lithium transition metal composite oxide whose volume cumulative particle size distribution changes after ultrasonic treatment in a liquid medium, the positive electrode active material has excellent fluidity as a powder. In addition, the volume cumulative particle size distribution changes after ultrasonic treatment, and the ratio ( 3 D 90 / 2 D 90 ) is 0.53 or less, high output characteristics can be achieved when a non-aqueous electrolyte secondary battery is constructed.

[0066] The lithium transition metal composite oxide constituting the positive electrode active material may be, for example, the second lithium transition metal composite oxide produced by the production method described above. Details of the second lithium transition metal composite oxide are as described above.

[0067] Non-aqueous 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 including the positive electrode active material for a non-aqueous electrolyte secondary battery manufactured by the manufacturing method described above. A non-aqueous electrolyte secondary battery including such an electrode can achieve high initial efficiency and high durability.

[0068] 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 composition 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 treatment. Examples of conductive materials include natural graphite, artificial graphite, and acetylene black. Examples of binders include polyvinylidene fluoride, polytetrafluoroethylene, and polyamide acrylic resin.

[0069] Nonaqueous electrolyte secondary battery The nonaqueous electrolyte secondary battery includes the above-mentioned electrode for a nonaqueous electrolyte secondary battery as a positive electrode. The nonaqueous electrolyte secondary battery is configured to include, in addition to the electrode for a nonaqueous electrolyte secondary battery, a negative electrode for a nonaqueous electrolyte secondary battery, a nonaqueous electrolyte, a separator, etc. For the negative electrode, nonaqueous electrolyte, separator, etc. of the nonaqueous electrolyte secondary battery, those for nonaqueous 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 used as appropriate. [Example]

[0070] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0071] First, the methods for measuring physical properties in the following Examples and Comparative Examples will be described. 1 D 50 , 2 D 50 and 3 D 50 and, 1 D 90 ,2 D 90 and 3 D 90 The cumulative particle size distribution on a volume basis was measured using a laser diffraction particle size distribution measuring device (MASTER SIZER), and the 50% and 90% particle sizes corresponding to the cumulative 50% and 90% from the smallest diameter side were determined. 1 D 50 and 1 D 90 The measurements were carried out on the prepared lithium transition metal composite oxide after ultrasonic treatment (frequency: 40 kHz, output: 110 W, 20°C, 20 seconds, 0.05 mass % of sodium hexametaphosphate dispersant added to 200 mL of pure water). 3 D 50 and 3 D 90 Regarding 2 D 50 The lithium transition metal composite oxides for which the above-mentioned properties were measured were subjected to ultrasonic treatment (frequency: 40 kHz, output: 110 W, 20°C, 20 seconds, 0.05% by mass of sodium hexametaphosphate dispersant added to 200 mL of pure water) and then subjected to measurement.

[0072] Example 1 Precursor preparation An aqueous solution of cobalt sulfate was added dropwise to pure water while stirring at 60°C and 650 rpm. At the same time, a 7.9 mol / L aqueous solution of sodium hydroxide was added dropwise to adjust the pH to 8.0. After the addition of the aqueous solution of cobalt sulfate was completed, the aqueous solution of sodium hydroxide alone was added dropwise until the pH reached 9.4 or higher and 9.8 or lower, yielding a precipitate containing cobalt. The resulting precipitate was filtered, washed with water, and then heat-treated at 330°C for 17 hours to yield a composite oxide containing cobalt.

[0073] Preparation of lithium transition metal composite oxides Lithium carbonate was weighed so that the molar ratio of lithium to cobalt in the cobalt-containing composite oxide was 1.01, and the cobalt-containing composite oxide and lithium carbonate were dry-mixed to obtain a lithium mixture. The obtained lithium mixture was heat-treated in air at 700°C for 5 hours, and then continuously heat-treated at 800°C for 5 hours to obtain a sintered body.

[0074] Distributed Processing The obtained sintered body was put into pure water to prepare a slurry with a slurry concentration of 20 mass %. The obtained slurry was dispersed in a ball mill (φ0.65 mm, zirconium oxide pellets) for 150 minutes to obtain a dispersion slurry. The physical properties ( 1 D 50 , 1 D 90 ) are shown in Table 1.

[0075] spray drying The obtained dispersion slurry containing the lithium transition metal composite oxide was introduced into a spray nozzle at a flow rate of 16 mL / min and air at a flow rate of 30 L / min, and spray drying was carried out at a drying temperature of 250°C to obtain a positive electrode active material of Example 1 containing a second lithium transition metal composite oxide. The physical properties ( 2 D 50 , 2 D 90 , 3 D 50 , 3 D 90 ) are shown in Table 1.

[0076] Comparative Example 1 A dispersion slurry containing a first lithium transition metal composite oxide was obtained in the same manner as in Example 1. The obtained dispersion slurry was filtered using a Buchner funnel (filter paper: ADVANTEC qualitative filter paper, 5C, 285 mm), and the obtained filtrate was left to dry at a drying temperature of 150°C, thereby obtaining a positive electrode active material containing the lithium transition metal composite oxide of Comparative Example 1. The physical properties ( 2 D 50 , 2 D90 , 3 D 50 , 3 D 90 ) are shown in Table 1.

[0077] Comparative Example 2 A sintered body was obtained in the same manner as in Example 1, except that the heat treatment conditions for the lithium mixture were changed to heat treatment in an air atmosphere at 700°C for 5 hours, followed by a subsequent heat treatment at 880°C for 5 hours. The obtained sintered body was dispersed for 15 minutes in a dry vibration mill (Chuo Kakoki, B-2 type, UX-Φ25Fe core), and the obtained dispersion was then poured into pure water to prepare a dispersion slurry with a slurry concentration of 20 mass%. The physical properties ( 1 D 50 , 1 D 90 ) are shown in Table 1.

[0078] The dispersion slurry obtained above was dried in the same manner as in Comparative Example 1 to obtain a positive electrode active material containing a lithium transition metal composite oxide of Comparative Example 2. The physical properties of the lithium transition metal composite oxide of Comparative Example 2 ( 2 D 50 , 2 D 90 , 3 D 50 , 3 D 90 ) are shown in Table 1.

[0079] Comparative Example 3 After spray drying in the same manner as in Example 1, the cathode active material containing the lithium transition metal composite oxide of Comparative Example 3 was obtained by further heat treatment at 400°C in the atmosphere. 2 D 50 , 2 D 90 , 3 D 50 , 3 D 90 ) are shown in Table 1.

[0080] Sieving speed 300 g of the lithium transition metal composite oxides obtained in Example 1 and Comparative Examples 1 to 3 were sieved for 60 seconds using a sieve with a diameter of 30 cm and 70 μm openings (Gyrosifter, 60 Hz), and the passing amount per unit area (kg / h m) was measured. 2 The results are shown in Table 1.

[0081] (Preparation of positive electrode) 11.6 g of the lithium transition metal composite oxide obtained in Example 1 and Comparative Examples 1 to 3 was mixed with 1.5 g (0.12 g of PVDF) of a solution of polyvinylidene fluoride (hereinafter referred to as PVDF) dissolved in N-methyl-2-pyrrolidone (hereinafter referred to as NMP), followed by further mixing with 1.2 g (0.24 g of AB) of acetylene black (hereinafter referred to as AB) solution to obtain a positive electrode composition. The positive electrode composition was mixed with NMP to a concentration of 58 mass % to prepare an NMP slurry. The obtained NMP slurry was applied to aluminum foil as a current collector and dried to obtain a dried product. The dried product was compression-molded using a roll press and then cut to a predetermined size to produce a positive electrode.

[0082] (Preparation of negative electrode) Graphite material was used as the negative electrode active material. 97.5 parts by mass of the negative electrode active material, 1.5 parts by mass of carboxymethyl cellulose (CMC), and 1.0 part by mass of styrene-butadiene rubber (SBR) were dispersed in water and kneaded to prepare a negative electrode paste. This paste was applied to a copper foil current collector, dried, and then compression-molded using a roll press. After drying, the paste was cut to a specified size to fabricate a negative electrode.

[0083] [Preparation of non-aqueous electrolyte] Ethyl carbonate and methyl ethyl carbonate were mixed in a volume ratio of 3:7 to obtain a mixed solvent. The resulting mixed solvent was added with lithium hexafluorophosphate to a concentration of 1.0 mol. %, to obtain a non-aqueous electrolyte solution.

[0084] [Assembly of non-aqueous electrolyte secondary batteries] Attach lead electrodes to the positive and negative electrode current collectors, respectively, and then vacuum dry at 120°C. Next, a separator made of porous polyethylene was placed between the positive electrode and the negative electrode, These were stored in a bag-shaped laminate pack. After storing, they were vacuum dried at 60°C and adsorbed to each component. After vacuum drying, the non-aqueous electrolyte solution was poured into the laminate pack and sealed. A laminate-type non-aqueous electrolyte secondary battery was obtained as a battery for evaluation. The obtained battery for evaluation was used to evaluate the following battery characteristics.

[0085] [Average voltage] After constant current / constant voltage charging at a charge rate of 0.2C with a full charge voltage of 4.45V, the battery was discharged at a constant current of 2C with a discharge voltage of 2.0V. The time average of the battery voltage during constant current discharge at a discharge rate of 2C was taken as the average voltage. The results are shown in Table 1.

[0086] [Table 1]

[0087] As shown in Table 1, a positive electrode active material with excellent sieving speed was obtained by forming granulated secondary particles in Example 1. Furthermore, in Example 1, the primary particles were regenerated when the granulated secondary particles were used to prepare an electrode, which increased the average voltage, thereby enabling the production of a positive electrode active material with excellent output characteristics.

Claims

1. The particle size is 50% in the volume cumulative particle size distribution. １ D ５０ preparing a composition including a first lithium transition metal composite oxide having a particle size of 0.1 μm or more and less than 3.2 μm, and a liquid medium; The composition is granulated to obtain a particle having a particle size of 50% in the volume cumulative particle size distribution. ２ D ５０ The above １ D ５０ and obtaining a second lithium transition metal composite oxide having a molecular weight greater than the second lithium transition metal composite oxide has a volume cumulative particle size distribution that differs before and after ultrasonic treatment in a liquid medium; The particle size is 90% in the volume cumulative particle size distribution measured before ultrasonic treatment. ２ D ９０ is the 90% particle size in the volume cumulative particle size distribution measured after ultrasonic treatment ３ D ９０ The ratio ( ３ D ９０ / ２ D ９０ ) is 0.53 or less, The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the first lithium transition metal composite oxide has a composition represented by the following formula (3) or (4): Li ｐ Fe ｘ M ３ ｙ M ４ ｚ 2O ４ (3) (In formula (3), 0.9≦p≦1.3, 0<x≦1, 0≦y<1, 0≦z≦0.3, and x+y+z≦1. M ３ is at least one selected from the group consisting of Co, Mn, and Ni. ４ is at least one selected from the group consisting of Mo, Mg, Zr, Ti, Al, Ce, and Cr. Li ｐ Mn ｘ M ５ ｙ O ４ (4) (In formula (4), 1≦p≦1.4, 0<x≦2, 0≦y≦0.2, and x+y≦2. M ５ is at least one selected from the group consisting of Al, Mg, Si, Ti, Cr, Fe, Co, Cu, Zn, and Ga.

2. 2. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the granulation is carried out by spray-drying the composition to remove at least a part of the liquid medium.

3. The second lithium transition metal composite oxide is ２ D ９０ 3. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the particle size is greater than 3.6 μm.

4. The second lithium transition metal composite oxide has a particle size of 50% in a volume cumulative particle size distribution measured after ultrasonic treatment. ３ D ５０ The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the particle size is less than 3.2 µm.

5. The aforementioned １ D ５０ is a 50% particle size in a volume cumulative particle size distribution measured after ultrasonic treatment of the second lithium transition metal composite oxide. ３ D ５０ The ratio ( ３ D ５０ / １ D ５０ 5. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the value of (a) is 0.8 or more and 2 or less.

6. a lithium transition metal composite oxide whose volume cumulative particle size distribution changes after ultrasonic treatment in a liquid medium; The lithium transition metal composite oxide has a particle size of 90% in the volume cumulative particle size distribution measured before ultrasonic treatment. ２ D ９０ is the 90% particle size in the volume cumulative particle size distribution measured after ultrasonic treatment ３ D ９０ The ratio ( ３ D ９０ / ２ D ９０ ) is 0.53 or less, The lithium transition metal composite oxide has a composition represented by the following formula (3) or (4): Li ｐ Fe ｘ M ３ ｙ M ４ ｚ 2O ４ (3) (In formula (3), 0.9≦p≦1.3, 0<x≦1, 0≦y<1, 0≦z≦0.3, and x+y+z≦1. M ３ is at least one selected from the group consisting of Co, Mn, and Ni. ４ is at least one selected from the group consisting of Mo, Mg, Zr, Ti, Al, Ce, and Cr. Li ｐ Mn ｘ M ５ ｙ O ４ (4) (In formula (4), 1≦p≦1.4, 0<x≦2, 0≦y≦0.2, and x+y≦2. M ５ is at least one selected from the group consisting of Al, Mg, Si, Ti, Cr, Fe, Co, Cu, Zn, and Ga.

7. The lithium transition metal composite oxide is ２ D ９０ The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 6, wherein the particle size is greater than 3.6 μm.

8. The lithium transition metal composite oxide has a particle size of 50% of the cumulative particle size distribution measured after ultrasonic treatment. ３ D ５０ 8. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 6, wherein the particle size is less than 3.2 μm.

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