JP2017117766A - Positive electrode active material for nonaqueous electrolyte secondary battery and method for producing the same, and nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive electrode active material for a nonaqueous electrolyte secondary battery and others, by which a high capacity and a high output can be achieved, and the amount of using tungsten is reduced.SOLUTION: A method for producing a positive electrode active material for a nonaqueous electrolyte secondary battery comprises: the step of mixing first lithium nickel composite oxide particles including a lithium tungstate, and second lithium nickel composite oxide particles including no lithium tungstate. The first lithium nickel composite oxide particles have a composition expressed by LiNiCoMO, and include core materials consisting of secondary particles which primary particles agglomerate into, and the lithium tungstate existing in at least part of the surface of the primary particles located on the surface of and in each first lithium nickel composite oxide particle. The second lithium nickel composite oxide particles have a composition expressed by LiNiCoMO, and include secondary particles which primary particles agglomerate into.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a positive electrode active material for a non-aqueous electrolyte secondary battery, a method for producing the same, and a non-aqueous electrolyte secondary battery.

  In recent years, with the widespread use of portable electronic devices such as mobile phones and laptop computers, development of small and lightweight secondary batteries having high energy density is strongly desired. In addition, development of a high output secondary battery is strongly desired as a battery for electric vehicles including hybrid vehicles.

  As a secondary battery satisfying such a requirement, there is a non-aqueous electrolyte secondary battery represented by a lithium ion secondary battery. This lithium ion secondary battery includes a negative electrode, a positive electrode, an electrolyte, and the like, and a material capable of detaching and inserting lithium is used as an active material for the negative electrode and the positive electrode.

  Such non-aqueous electrolyte secondary batteries are currently being actively researched and developed. Among them, lithium ion secondary batteries using a layered or spinel-type lithium nickel composite oxide as a positive electrode material are among others. Since a high voltage of 4V class can be obtained, practical use is progressing as a battery having a high energy density.

The materials mainly proposed so far include lithium cobalt composite oxide (LiCoO ₂ ), which is relatively easy to synthesize, lithium nickel composite oxide (LiNiO ₂ ) using nickel, which is cheaper than cobalt, and lithium nickel. Examples thereof include cobalt manganese composite oxide (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ) and lithium manganese composite oxide (LiMn ₂ O ₄ ) using manganese. Among these, lithium nickel composite oxides are attracting attention as a material that has good cycle characteristics and can provide high output with low resistance. In recent years, reduction of resistance necessary for high output has been regarded as important.

  Addition of foreign elements is used as a method for realizing the low resistance, and transition metals capable of taking high numbers such as W, Mo, Nb, Ta, Re, etc. are particularly useful. For example, Patent Document 1 contains one or more elements selected from Mo, W, Nb, Ta, and Re in an amount of 0.1 to 5 mol% with respect to the total molar amount of Mn, Ni, and Co. Lithium transition metal compound powders for lithium secondary battery cathode materials have been proposed. Further, the atomic ratio of the total of Mo, W, Nb, Ta, and Re to the total of Li and the metal elements other than Mo, W, Nb, Ta, and Re in the surface portion of the primary particle is the atomic ratio of the entire primary particle. It is considered to be preferably 5 times or more. According to this proposal, it is said that it is possible to achieve both low cost and high safety of lithium transition metal-based compound powder for lithium secondary battery positive electrode material, high load characteristics, and improved powder handleability. .

  However, the lithium transition metal compound powder is obtained by pulverizing raw materials in a liquid medium, spray-drying a slurry in which these are uniformly dispersed, and firing the resulting spray-dried body. Therefore, a part of different elements such as Mo, W, Nb, Ta, and Re is replaced with Ni arranged in a layer, and there is a problem that battery characteristics such as battery capacity and cycle characteristics are deteriorated. It was.

  Patent Document 2 discloses a positive electrode active material for a non-aqueous electrolyte secondary battery having at least a layered lithium transition metal composite oxide, the lithium transition metal composite oxide comprising primary particles and aggregates thereof. A non-aqueous electrolyte having a compound which is present in the form of a particle composed of one or both of secondary particles, and which has at least one selected from the group consisting of molybdenum, vanadium, tungsten, boron and fluorine on at least the surface of the particle A positive electrode active material for a secondary battery has been proposed. By this proposal, it is said that a positive electrode active material for a non-aqueous electrolyte secondary battery having excellent battery characteristics even under even more severe usage environment can be obtained, and in particular, molybdenum, vanadium, tungsten, boron and fluorine are used on the particle surface. By having a compound having at least one selected from the group, the initial characteristics are improved without impairing the improvement of thermal stability, load characteristics and output characteristics.

  However, the effect of at least one additive element selected from the group consisting of molybdenum, vanadium, tungsten, boron and fluorine is considered to be an improvement in initial characteristics, that is, initial discharge capacity and initial efficiency, and refers to output characteristics. It is not a thing. Further, according to the manufacturing method disclosed in Patent Document 2, since the additive element is mixed with the hydroxide that has been heat-treated at the same time as the lithium compound and baked, nickel and a part of the additive element are disposed in layers There was a problem that the battery characteristics were degraded due to the replacement.

  Further, Patent Document 3 discloses a metal including at least one selected from Ti, Al, Sn, Bi, Cu, Si, Ga, W, Zr, B, and Mo around the positive electrode active material and / or a plurality of these. A positive electrode active material coated with an intermetallic compound and / or oxide obtained by a combination has been proposed. Such a coating can absorb oxygen gas and ensure safety, but no output characteristics are disclosed. Further, the disclosed manufacturing method is a method of coating using a planetary ball mill, and such a coating method causes physical damage to the positive electrode active material, resulting in deterioration of battery characteristics.

  In Patent Document 4, a composite oxide particle mainly composed of lithium nickelate is subjected to heat treatment by adhering a tungstic acid compound, and the content of carbonate ions is 0.15% by weight or less. A positive electrode active material has been proposed. According to this proposal, there is a tungstic acid compound or a decomposition product of the tungstic acid compound on the surface of the positive electrode active material, and the oxidation activity on the surface of the composite oxide particles in a charged state is suppressed. Although gas generation can be suppressed, the output characteristics are not disclosed at all.

  Furthermore, the production method disclosed in Patent Document 4 preferably includes a composite oxide particle heated to a temperature equal to or higher than the boiling point of a solution in which an adherent component is dissolved, a tungstic acid compound, a sulfuric acid compound, a nitric acid compound, a boric acid compound, or phosphorus. A solution in which an acid compound is dissolved in a solvent as an adhering component is applied, and the solvent is removed in a short time, so that the tungsten compound is not sufficiently dispersed on the surface of the composite oxide particles and is not uniformly applied. There is a problem.

Improvements have also been made with regard to higher output of lithium nickel composite oxide. For example, Patent Document 5 discloses a lithium nickel composite oxide composed of primary particles and secondary particles formed by agglomeration of the primary particles, and Li ₂ WO ₄ , A positive electrode active material for a non-aqueous electrolyte secondary battery having fine particles containing lithium tungstate represented by either Li ₄ WO ₅ or Li ₆ W ₂ O ₉ has been proposed, and high output is obtained with high capacity. ing.

JP 2009-289726 A JP 2005-251716 A Japanese Patent Laid-Open No. 11-16566 JP 2010-40383 A JP 2013-171785 A

  In Patent Document 5, although higher output is maintained while maintaining high capacity, further increase in capacity is required. Further, since tungsten is a rare element and expensive, it is necessary to reduce its use amount. Furthermore, since tungsten is added in the middle of the manufacturing process, after the addition of the tungsten compound, the manufacturing line is contaminated with tungsten, so it is necessary to perform line cleaning when manufacturing a wide variety of products, increasing man-hours and operating. Reduction is cited as an issue.

  In view of the problems, the present invention provides a high output with a high capacity when used as a positive electrode active material in a non-aqueous electrolyte secondary battery, and for a non-aqueous electrolyte secondary battery in which the amount of tungsten used is suppressed. An object is to provide a positive electrode active material. It is another object of the present invention to provide a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery that is easy to manufacture, has high productivity, and is suitable for production of various products.

In the first aspect of the present invention, a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery includes first lithium nickel composite oxide particles containing lithium tungstate and second lithium not containing lithium tungstate. The first lithium nickel composite oxide particles have a composition of Li _z1 Ni _1-x1-y1 Co _x1 M ¹ _y1 O ₂ (where 0 ≦ x1 ≦). 0.35,0 ≦ y1 ≦ 0.35,0.95 ≦ z1 ≦ 1.15, M 1 is represented by at least one element) selected Mn, V, Mg, Mo, Nb, Ti and Al A core material composed of secondary particle particles in which a plurality of primary particles are aggregated with each other, lithium tungstate present on at least a part of the surface of the second composite oxide particle and the surface of the primary particle located inside, It is al structure, the second lithium nickel complex oxide particles, the composition is _{Li z2 Ni 1-x2-y2} Co x2 M 2 y2 O 2 ( however, 0 ≦ x2 ≦ 0.35,0 ≦ y2 ≦ 0.35 0.95 ≦ z2 ≦ 1.15, and M ² is at least one element selected from Mn, V, Mg, Mo, Nb, Ti, and Al), and secondary particles in which a plurality of primary particles are aggregated with each other. Composed of particles.

  The second lithium nickel composite oxide particles may be washed with water before mixing. Moreover, 500 g / L or more and 2500 g / L or less of the slurry density | concentration in the case of water washing may be sufficient. Further, the first lithium nickel composite oxide particles and the second lithium nickel composite oxide particles are contained in lithium compounds other than lithium tungstate existing on both surfaces and the surfaces of primary particles located inside. The amount of lithium may be 0.05% by mass or less based on the total amount of the positive electrode active material. Further, the first lithium nickel composite oxide particles and the second lithium nickel composite oxide particles are contained so that the content of the first lithium nickel composite oxide contained in the positive electrode active material is 10% by mass or more based on the total amount of the positive electrode active material. Lithium nickel composite oxide particles may be mixed. Further, the amount of tungsten contained in the first lithium nickel composite oxide particles is 0.03 atomic percent or more and 2.5 atomic percent or less with respect to the total number of Ni, Co, and M atoms contained in the positive electrode active material. So that the first lithium nickel composite oxide particles and the second lithium nickel composite oxide particles may be mixed.

Further, before mixing, the composition is Li _z3 Ni _1-x3-y3 Co _x3 M ¹ _y3 O ₂ (however, 0.03 ≦ x3 ≦ 0.35, 0.01 ≦ y3 ≦ 0.35, 0.95 ≦ z3 ≦ 1.20, M ¹ is represented by Mn, V, Mg, Mo, Nb, Ti, and Al), and secondary particles formed by aggregation of a plurality of primary particles And adjusting a tungsten mixture containing a base material made of, a water content of 2% by mass or more based on the total amount of the base material, and a tungsten compound or a lithium compound not containing a tungsten compound and tungsten. Heat treating the tungsten mixture to form lithium tungstate on the surface of the base material and the surface of the primary particles inside to obtain first lithium nickel composite oxide particles, Gobutsu is for tungsten the total amount to be contained, moisture and tungsten compounds, or water, tungsten compound and a lithium compound, the molar ratio of lithium total amount may be 5 or less contained in the. Further, the first lithium nickel composite oxide particles are present on the surface and the surface of the primary particles inside, and the amount of lithium contained in the lithium compound other than lithium tungstate is the first lithium nickel composite oxide particles. 0.05 mass% or less may be sufficient with respect to this. Further, before the heat treatment, the base material and water may be mixed to form a slurry, and the base material may be washed with water, and the water-washed base material may be subjected to solid-liquid separation. The slurry concentration of the base material in water washing may be 500 g / L or more and 2500 g / L or less. When the base material washed with water is subjected to solid-liquid separation, the moisture content of the obtained washed cake may be controlled to be 3.0% by mass or more and 15.0% by mass or less. The tungsten compound may include at least one of tungsten oxide (WO ₃ ), tungstic acid (WO ₃ .H ₂ O), Li ₂ WO ₄ , Li ₄ WO ₅ and Li ₆ W ₂ O _9. . Further, the temperature of the heat treatment in the heat treatment may be 100 ° C. or more and 600 ° C. or less. Further, the amount of tungsten contained in the tungsten compound may be 0.05 to 3.0 atomic% with respect to the total number of Ni, Co, and M atoms contained in the base material.

In the second aspect of the present invention, the positive electrode active material for a non-aqueous electrolyte secondary battery includes first lithium nickel composite oxide particles containing lithium tungstate and second lithium nickel composite oxide containing no lithium tungstate. The composition of the first lithium nickel composite oxide particles is Li _z1 Ni _1-x1-y1 Co _x1 M ¹ _y1 O ₂ (where 0 ≦ x1 ≦ 0.35, 0 ≦ y1 ≦ 0.35, 0.95 ≦ z1 ≦ 1.15, M ¹ is represented by at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al), and a plurality of primary particles are aggregated together A core material composed of the secondary particle particles, and lithium tungstate present on at least a part of the surface of the second composite oxide particle and the surface of the primary particle located inside, the second lithium oxide Nickel composite oxide particles, the composition is _{Li z2 Ni 1-x2-y2} Co x2 M 2 y2 O 2 ( however, 0 ≦ x2 ≦ 0.35,0 ≦ y2 ≦ 0.35,0.95 ≦ z2 ≦ 1 .15, M ² is represented by at least one element selected from Mn, V, Mg, Mo, Nb, Ti, and Al, and is composed of secondary particles in which a plurality of primary particles are aggregated with each other.

  Further, the amount of lithium contained in the lithium compound other than lithium tungstate present on the surfaces of the first lithium nickel composite oxide particles and the second lithium nickel composite oxide particles and the surfaces of the primary particles located inside. However, 0.05 mass% or less may be sufficient with respect to the whole quantity of a positive electrode active material. Further, the amount of the first lithium nickel composite oxide particles contained in the positive electrode active material may be 10% by mass or more based on the total amount of the positive electrode active material. Further, the amount of tungsten contained in the lithium tungstate may be 0.03 atomic percent or more and 2.5 atomic percent or less with respect to the total number of Ni, Co, and M atoms contained in the positive electrode active material. Further, even if the amount of tungsten contained in lithium tungstate is 0.05 atomic% or more and 3.0 atomic% or less with respect to the total number of Ni, Co, and M atoms contained in the tungsten-coated composite oxide particles. Good. Further, lithium tungstate may be present on the surface of the first lithium nickel composite oxide particles and the surface of the primary particles inside as fine particles having a particle diameter of 1 nm to 500 nm. Further, lithium tungstate may be present on the surface of the first lithium nickel composite oxide particles and the surface of the primary particles inside as a film having a thickness of 1 nm to 200 nm. Further, lithium tungstate is present on the surface of the first lithium nickel composite oxide particles and the surface of the primary particles inside as both forms of fine particles having a particle diameter of 1 nm to 500 nm and a coating having a film thickness of 1 nm to 200 nm. Also good.

  In the 3rd aspect of this invention, a non-aqueous electrolyte secondary battery has a positive electrode containing the positive electrode active material for non-aqueous electrolyte secondary batteries.

  ADVANTAGE OF THE INVENTION According to this invention, when it uses for the positive electrode material of a secondary battery, high output is obtained with high capacity | capacitance, and the positive electrode active material for nonaqueous electrolyte secondary batteries with which the usage-amount of tungsten was suppressed is obtained. Furthermore, the manufacturing method is easy and highly productive, and is suitable for production on an industrial scale, and its industrial value is extremely large.

FIG. 1A is a schematic diagram illustrating an example of a positive electrode active material according to the embodiment, and FIG. 1B is a diagram illustrating an example of a manufacturing method thereof. FIG. 2 is a schematic diagram showing an example of the first lithium nickel composite oxide. FIG. 3 is a cross-sectional SEM photograph (observation magnification of 10,000 times) showing an example of the first lithium nickel composite oxide. (The circled portion indicates lithium tungstate.) FIG. 4 is a diagram illustrating an example of a method for producing the first lithium-nickel composite oxide. FIG. 5 is a diagram illustrating an example of a method for producing a tungsten mixture. FIG. 6 is a schematic explanatory diagram of an impedance evaluation measurement example and an equivalent circuit used for analysis. FIG. 7 is a schematic cross-sectional view of a coin-type battery used for battery evaluation.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Further, in the drawings, in order to make each configuration easy to understand, a part of the structure is emphasized or a part of the structure is simplified, and an actual structure, shape, scale, or the like may be different. Hereinafter, this embodiment will be described.

1. FIG. 1A shows a positive electrode active material for a non-aqueous electrolyte secondary battery of the present embodiment (hereinafter sometimes simply referred to as “positive electrode active material”). FIG. 1B is a diagram illustrating an example of a method for producing the positive electrode active material 10 of the present embodiment. Hereinafter, first, the positive electrode active material 10 will be described, and then a method for producing the positive electrode active material 10 and a nonaqueous electrolyte secondary battery using the positive electrode active material 10 (hereinafter sometimes simply referred to as “secondary battery”). explain.

(1) Positive electrode active material for non-aqueous electrolyte secondary battery As shown in FIG. 1A, the positive electrode active material 10 includes first lithium nickel composite oxide particles containing lithium tungstate (hereinafter referred to as “first composite”). 1) and a second lithium nickel composite oxide particle 2 that does not contain lithium tungstate (hereinafter sometimes referred to as “second composite oxide particle”). .

  The first composite oxide particles 1 include a core material 5 composed of secondary particle particles 4 in which a plurality of primary particles 3 are aggregated with each other, and primary particles located on the surface and inside of the first composite oxide particle 1 (core material). 3 (3a and 3b) and lithium tungstate 6 (6a and 6b) present on at least a part of the surface. The first composite oxide particle 1 has lithium tungstate 6 on the surface of the primary particle 3, so that when the positive electrode active material 10 is used for a secondary battery, the first composite oxide particle 1 has a high output and a high charge / discharge capacity ( Hereinafter, it may be referred to as “battery capacity”).

  In general, when the surface of the lithium nickel composite oxide particles is completely covered with a different compound, the movement (intercalation) of lithium ions is greatly limited, resulting in the high capacity of the lithium nickel composite oxide. The advantages may be erased.

  On the other hand, the first composite oxide particles 1 used in the present embodiment have lithium tungstate (hereinafter, lithium tungstate is referred to as “LWO compound”) on the surface and the surface of the primary particles 3 (3a and 3b) inside. There is 6). The LWO compound 6 has high lithium ion conductivity and has an effect of promoting the movement of lithium ions. For this reason, when the positive electrode active material 10 is used for a secondary battery, the primary particle 3 (3a and 3b) is obtained by having the LWO compound 6 on the surface of the primary particle 3 (3a and 3b) of the first composite oxide particle 1. Li conduction path can be formed at the interface between the electrode and the electrolyte, and the reaction resistance of the positive electrode (hereinafter sometimes referred to as “positive electrode resistance”) can be reduced. By reducing the positive electrode resistance, the voltage lost in the battery is reduced, and the voltage actually applied to the load side becomes relatively high, so that a high output can be obtained. Moreover, since the voltage applied to the load side is increased, lithium is sufficiently inserted and extracted from the positive electrode, so that the battery capacity can be improved.

  In addition, when only the secondary particle surface of the lithium nickel composite oxide particles is coated with a layered material as in the prior art, the specific surface area decreases regardless of the coating thickness, so the coating is high. Even if it has lithium ion conductivity, the contact area with the electrolyte is reduced. Moreover, when forming a layered material only on the surface of a secondary particle, it tends to result in the formation of a compound (layered material) being concentrated on the surface of a specific secondary particle. Therefore, although the layered material as the coating has high lithium ion conductivity, the effects of improving the charge / discharge capacity and reducing the reaction resistance can be obtained, but the effects are not sufficient and there is room for improvement.

  On the other hand, when the positive electrode active material 10 is used for a secondary battery, the contact between the first composite oxide particle 1 and the electrolytic solution occurs on the surface of the primary particle 3. Here, the surface of the primary particle 3 refers to a surface portion of the primary particle 3 that can be contacted with the electrolyte, for example, the surface of the primary particle (for example, the primary particle 3a) exposed on the outer surface of the secondary particle, The surface of the primary particle (for example, primary particle 3b) exposed to the space | gap near the surface of the secondary particle which can penetrate electrolyte solution through the secondary particle 4 exterior, and an inside is included. Furthermore, the surface of the primary particle 3 includes, for example, a grain boundary between the primary particles in which the primary particles are incompletely bonded and the electrolyte solution can permeate.

  As described above, when the positive electrode active material 10 is used in a secondary battery, the contact between the first composite oxide particles 1 and the electrolytic solution is only on the outer surface of the secondary particles 4 formed by aggregation of the primary particles 3. Not only in the vicinity of the surface of the secondary particles but also in the internal voids and incomplete grain boundaries. Therefore, by forming the LWO compound 6 also on the surfaces of the primary particles 3 (3a, 3b), the movement of lithium ions can be further promoted. Since the first composite oxide particle 1 has the LWO compound 6 not only on the surface of the primary particle 3 a located on the surface of the secondary particle 4 but also on the surface of the primary particle 3 b located inside the secondary particle 4, lithium The reaction resistance of the nickel composite oxide particles can be further reduced.

  FIG. 2 is a schematic diagram showing an example of the first composite oxide particle 1, and FIG. 3 is a cross-sectional SEM photograph (observation magnification 10,000 times) showing an example of the first composite oxide particle 1. The form of the LWO compound 6 contained in the first composite oxide particle 1 is not particularly limited as long as it exists on the surface of the primary particle 3 (3a, 3b). The LWO compound 6 may be present on the surface of the primary particle 3 (3a, 3b) in the form of fine particles 6a, 6b having a particle diameter of 1 nm to 500 nm, for example, as shown in FIG. 2 (a). In such a form, since the contact area with the electrolytic solution is sufficient and lithium ion conduction can be improved effectively, the charge / discharge capacity can be improved and the positive electrode resistance can be reduced more effectively. .

  When the particle diameters of the LWO compounds (fine particles) 6a and 6b are less than 1 nm, the fine particles 6a and 6b may not have sufficient lithium ion conductivity. Moreover, when the particle diameter of the LWO compounds (fine particles) 6a and 6b exceeds 500 nm, the formation of the fine particles (LWO compound 6) on the surfaces of the primary particles 3 (3a and 3b) becomes non-uniform, and the effect of reducing reaction resistance is achieved. You may not get enough. The particle diameters of the LWO compounds (fine particles) 6a and 6b are preferably 1 nm or more and 300 nm or less from the viewpoint that the fine particles of the LWO compound 6 are uniformly distributed on the surfaces of the primary particles 3 (3a and 3b) to obtain a higher effect. More preferably, it is 5 nm or more and 200 nm or less.

  The LWO compound 6 does not have to be completely formed on the entire surface of the primary particles, and may be in a scattered state. Even in the state where the LWO compound 6 is scattered, if LWO is formed on the outer surface of the lithium nickel composite oxide particle and the surface of the primary particle exposed inside, the effect of reducing the reaction resistance can be obtained. The LWO compounds (fine particles) 6a and 6b do not have to exist as fine particles having a particle diameter of 1 nm or more and 500 nm or less. Preferably, the number of LWO compounds (fine particles) 6a and 6b formed on the primary particle surface is 50. % Or more is formed in a particle diameter range of 1 nm or more and 500 nm or less, a high effect can be obtained.

  For example, as shown in FIG. 2B, the LWO compound 6 may exist in a form in which the surfaces of the primary particles 3a and 3b are covered with thin films (coating films) 6c and 6d formed from the LWO compound. When such coatings 6c and 6d are formed, it is possible to form a Li conduction path at the interface with the electrolyte while suppressing a decrease in specific surface area, thereby improving higher charge / discharge capacity and reducing reaction resistance. The effect is obtained.

  When coating the primary particle surface with the coatings 6c and 6d, it is preferable that the coating is present on the primary particle surface of the lithium metal composite oxide as a coating having a thickness of 1 nm to 200 nm. In order to obtain a higher effect, the film thickness is more preferably 1 nm or more and 150 nm or less, and further preferably 1 nm or more and 100 nm or less. If the thickness of the thin films 6c and 6d is less than 1 nm, the coating may not have sufficient lithium ion conductivity. On the other hand, when the film thickness of the thin films 6c and 6d exceeds 200 nm, the lithium ion conductivity is lowered, and an effect higher than the reaction resistance reduction effect may not be obtained.

  The coatings 6c and 6d may be formed by at least a part of the primary particles 3a and 3b, and may be partially formed on the surfaces of the primary particles 3a and 3b, for example. Moreover, the film thickness range of all the coating films 6c and 6d may not be 1 nm or more and 200 nm or less. For example, the coatings 6c and 6d can achieve a high effect as long as the coatings 6c and 6d having a film thickness in the above range are formed on at least a part of the primary particle surface.

  For example, as shown in FIG. 2C, the LWO compound 6 may exist on the surface of the primary particles in a mixture of both the form of the fine particles 6a and 6b and the form of the coatings 6c and 6d. Also in this case, a high effect on the battery characteristics can be obtained.

The properties of the primary particle surface 3 (3a, 3b) of the first composite oxide particle 1 can be judged by observing with a field emission scanning electron microscope or a transmission electron microscope, for example. In the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention, for example, as shown in FIG. 3, it was confirmed that lithium tungstate was formed on the primary particle surface of the first composite oxide particle 1. Yes.

The LWO compound 6 is not limited to a compound in which W and Li are in the form of lithium tungstate, but includes a compound containing W and Li. The LWO compound 6 includes, for example, Li ₂ WO ₄ , Li ₄ WO ₅ , Li ₆ WO ₆ , Li ₂ W ₄ O ₁₃ , Li ₂ W ₂ O ₇ , Li ₆ W ₂ O ₉ , Li ₂ W ₂ O ₇ , _{Li 2 W 5 O 16, Li} 9 W 19 O 55, Li 3 W 10 O 30, is preferably at least one form selected from Li ₁₈ W _{5 O 15} or a hydrate thereof. In the case of such lithium tungstate, the lithium ion conductivity is further increased, and the effect of reducing the reaction resistance is further increased.

  The amount of tungsten contained in the LWO compound 6 may be 0.05 atomic% or more and 3.0 atomic% or less with respect to the total number of Ni, Co, and M atoms contained in the first composite oxide particle 1. Preferably, it is more preferably 0.05 atomic percent or more and 2.0 atomic percent or less, and further preferably 0.08 atomic percent or more and 1.0 atomic percent or less. When the amount of tungsten is in the above range, both higher charge / discharge capacity and output characteristics can be achieved. The amount of tungsten can be measured by IPC emission spectroscopic analysis (ICP method).

  When the amount of tungsten is less than 0.05 atomic%, the effect of improving the output characteristics may not be sufficiently obtained. On the other hand, when the amount of tungsten exceeds 3.0 atomic%, the amount of the above-described compound formed becomes too large, lithium conduction between the lithium nickel composite oxide and the electrolytic solution may be hindered, and the charge / discharge capacity may be reduced.

As shown in FIG. 1 (A), the second composite oxide particles 2, the composition is _{Li z2 Ni 1-x2-y2} Co x2 M 2 y2 O 2 ( however, 0 ≦ x2 ≦ 0.35,0 ≦ y2 ≦ 0.35, 0.95 ≦ z2 ≦ 1.15, M ² is represented by at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al), and a plurality of primary particles 7 Is composed of secondary particles 8 aggregated with each other and does not contain lithium tungstate. As shown in FIG. 1B, the positive electrode active material 10 can be obtained, for example, by mixing the first composite oxide particles 1 and the second composite oxide particles 2. When the first composite oxide particles 1 and the second composite oxide particles 2 are mixed, when the positive electrode active material 10 is used for the positive electrode of the secondary battery, a high output is obtained and the battery capacity is improved. be able to.

  In general, if the battery characteristics are non-uniform among the composite oxide particles constituting the positive electrode active material, it is considered that specific particles are loaded, and the cycle characteristics are deteriorated and the reaction resistance is likely to increase. Moreover, it is thought that it is disadvantageous for the improvement of a battery characteristic that content of the lithium nickel composite oxide particle containing tungsten like the 1st composite oxide particle 1 decreases.

  However, as a result of investigation by the present inventors, when the first composite oxide particle 1 containing the LWO compound and the composite oxide 2 not containing the LWO compound are mixed, 1) the first composite oxide particle 1 containing tungsten Compared with the case where it is used alone as the positive electrode active material, the battery characteristics such as the output characteristics and the battery capacity are not deteriorated or are very small even when they are deteriorated. 2) The primary particles 7 have no LWO compound. It has become clear that the battery characteristics can be improved as compared with the case of the two composite oxide particles 2 alone.

  Such an improvement in battery characteristics is possible by mixing the first composite oxide particles 1, but in order to make this effect more satisfactory, the first composite oxide mixed in the positive electrode active material 10 is used. The lower limit of the amount of the product particles is preferably 10% by mass or more, and more preferably 20% by mass or more with respect to the positive electrode active material 10.

  On the other hand, the upper limit of the amount of the first composite oxide particles 1 is preferably 70% by mass or less and more preferably 60% by mass or less with respect to the positive electrode active material 10 from the viewpoint of suppressing the amount of tungsten used. Preferably, it is 50 mass% or less. When the content of the first composite oxide particles 1 in the positive electrode active material 10 increases, the battery characteristics approach those when the first composite oxide particles 1 are used alone. The amount of the single composite oxide particle 1 is preferably as small as possible in the range where the battery characteristics can be improved.

  The amount of tungsten contained in the first composite oxide particle 1 (lithium tungstate) is 0.03 atomic percent or more and 2.5 atomic percent or less with respect to the total number of Ni, Co, and M atoms contained in the positive electrode active material 10. It is preferably 0.05 atomic% or more and 1.5 atomic% or less, more preferably 0.05 atomic% or more and 1.0 atomic% or less. The amount of tungsten is an indicator of the amount of lithium tungstate 6 because the positive electrode active material 10 has improved battery characteristics with lithium tungstate 6. When the amount of tungsten is in the above range, sufficient battery characteristics can be obtained when the positive electrode active material 10 is used in a battery.

  In the positive electrode active material 10, the amount of lithium contained in the lithium compound other than lithium tungstate present on the primary particle surfaces of the first composite oxide particles 1 and the second composite oxide particles 2 (hereinafter “excess lithium amount”). Is preferably 0.05% by mass or less, and more preferably 0.03% by mass or less, based on the total amount of the positive electrode active material 10. By limiting the surplus lithium amount to the above range, higher charge / discharge capacity and output characteristics can be obtained and cycle characteristics can be improved.

  The lithium compound is a compound containing lithium other than lithium tungstate present on the surfaces of the primary particles 3 and 7. Examples of the lithium compound include lithium hydroxide and lithium carbonate. These lithium compounds have poor lithium conductivity and may inhibit the migration of lithium ions from the lithium nickel composite oxide material (including the first composite oxide particles 1 and the second composite oxide particles 2). The amount of lithium contained in these lithium compounds can represent the abundance as an excess amount of lithium.

  By reducing the amount of excess lithium in the positive electrode active material 10, the lithium ion migration promotion effect by the lithium tungstate 6 is enhanced, and the load on the lithium-nickel composite oxide during charge / discharge is reduced to further improve the output characteristics. In addition, the cycle characteristics can be further improved. Moreover, the lithium ion between lithium nickel composite oxide particles (including the first composite oxide particles 1 and the second composite oxide particles 2) is controlled by controlling the amount of excess lithium in the positive electrode active material 10 within the above range. Therefore, the above-described effect can be enhanced by suppressing the load on the specific lithium nickel composite oxide particles.

  Moreover, the lower limit of the amount of excess lithium is not particularly limited, but is preferably 0.01% by mass or more from the viewpoint of suppressing deterioration of battery characteristics. An excessively small amount of excess lithium indicates that lithium is excessively extracted from the crystal of the lithium nickel composite oxide particles, and battery characteristics are liable to deteriorate. The amount of excess lithium is the compound state of lithium that elutes from the neutralization point that appears when hydrochloric acid is added while measuring the pH of the filtrate after adding pure water to the positive electrode active material and stirring for a certain period of time. Can be calculated by analyzing.

The positive electrode active material 10 has a sulfate (sulfate group) content of preferably 0.05% by mass or less, more preferably 0.025% by mass or less, and further preferably 0.020% by mass or less. If the content of sulfate groups in the positive electrode active material 10 exceeds 0.05% by mass, the negative electrode material must be used in the battery by an amount corresponding to the irreversible capacity of the positive electrode active material when the battery is constructed. As a result, the capacity per unit weight and volume as a whole of the battery is reduced, and excess lithium accumulated in the negative electrode as an irreversible capacity becomes a problem from the viewpoint of safety, which is not preferable. Moreover, the minimum of sulfate content in the positive electrode active material 10 is although it does not specifically limit, For example, it is 0.001 mass% or more. The sulfate group content can be determined by converting the measured S (sulfur element) amount into the sulfate group (SO ₄ ) amount by IPC emission spectroscopic analysis (ICP method).

  Further, the total amount of lithium in the positive electrode active material 10 (including the first composite oxide particles 1 and the second composite oxide particles 2) is the sum of the number of atoms of Ni, Co, and M (Me) in the positive electrode active material. The ratio of Li to the number of atoms (Li / Me) is preferably in the range of 0.95 to 1.20, more preferably in the range of 0.97 to 1.15. If Li / Me is less than 0.95, the reaction resistance of the positive electrode in the non-aqueous electrolyte secondary battery using the obtained positive electrode active material increases, and the output of the battery decreases. On the other hand, if Li / Me exceeds 1.20, the initial discharge capacity of the positive electrode active material decreases and the reaction resistance of the positive electrode also increases. Li / Me can be measured by IPC emission spectroscopic analysis (ICP method).

The lithium nickel composite oxide particles as the core material 5 of the first composite oxide particles 1 have a composition of Li _z1 Ni _1-x1-y1 Co _x1 M ¹ _y1 O ₂ (where 0 ≦ x1 ≦ 0.35, 0 ≦ y1 ≦ 0.35, 0.95 ≦ z1 ≦ 1.15, and M ¹ is represented by at least one element selected from Mn, V, Mg, Mo, Nb, Ti, and Al. Li / Me in the core material 5 is more preferably 0.95 or more and 1.15 or less, and further preferably 0.95 or more and 1.10 or less.

  The positive electrode active material 10 improves the output characteristics and cycle characteristics by forming lithium tungstate 6a, 6b on the surfaces of the primary particles 3a, 3b of the first composite oxide particles 1. In addition, powder characteristics, such as a particle size as a positive electrode active material and a tap density, should just be in the range of the positive electrode active material used normally.

  In addition, the effect by providing lithium tungstate on the primary particle surface of lithium nickel composite oxide particles is, for example, lithium cobalt based composite oxide, lithium manganese based composite oxide, lithium nickel cobalt manganese based composite oxide, etc. The present invention can be applied not only to powders, but also to positive electrode active materials for lithium secondary batteries that are generally used as well as the positive electrode active materials listed in the present invention.

(2) Method for Producing Positive Electrode Active Material for Nonaqueous Electrolyte Secondary Battery As shown in FIG. 1 (B), the method for producing positive electrode active material 10 is the first lithium nickel containing lithium tungstate (LWO compound) 6 Mixing the composite oxide particles (first composite oxide particles) 1 and the second lithium nickel composite oxide particles (second composite oxide particles) 2 that do not include the LWO compound 6. FIG. 4 is a diagram illustrating an example of a method for producing the first composite oxide particles 1. When describing the method for producing the first composite oxide particles 1, FIG. 5 is appropriately referred to. The following description is an example of a manufacturing method and does not limit the manufacturing method.

The first composite oxide particle 1 has a composition of Li _z1 Ni _1-x1-y1 Co _x1 M ¹ _y1 O ₂ (where 0 ≦ x1 ≦ 0.35, 0 ≦ y1 ≦ 0.35, 0.95 ≦ z1). ≦ 1.15, M ¹ is represented by at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al), and a core material composed of secondary particles in which a plurality of primary particles are aggregated with each other 5 and the LWO compound 6 present on at least a part of the surface of the first composite oxide particle 1 (core material) and the surface of the primary particle 3 located inside. The manufacturing method of the 1st composite oxide particle 1 should just be what can make lithium tungstate exist on the surface, and can use a conventionally well-known manufacturing method. Hereinafter, an example of a method for producing the first composite oxide particle 1 will be described with reference to FIGS. 4 and 5.

As shown in FIG. 4 (A), the first composite oxide particle 1 is manufactured as follows. First, the composition is Li _z3 Ni _1-x3-y3 Co _x3 M ¹ _y3 O ₂ (where 0.00 ≦ x3 ≦ 0). Table with at least one element) selected .35,0.00 ≦ y3 ≦ 0.35,0.95 ≦ z3 ≦ 1.20, M 1 is Mn, V, Mg, Mo, Nb, Ti and Al A tungsten-coated base material (hereinafter, also simply referred to as “base material”) composed of secondary particles formed by agglomerating a plurality of primary particles, and 2% by weight or more of water with respect to the total amount of the base material, A tungsten mixture containing a tungsten compound is prepared. From the viewpoint of higher capacity and higher safety, 0.01 ≦ x3 ≦ 0.10, 0.01 ≦ y3 ≦ 0.05, and 0.97 ≦ z3 ≦ 1.05 are preferable.

  The tungsten mixture contains 2% by mass or more of moisture with respect to the total amount of the base material. As a result, tungsten in the tungsten compound penetrates into the voids between the primary particles communicating with the outside of the secondary particles (base material) and the grain boundaries between the incomplete primary particles together with moisture, and the primary particle surface is sufficient. An amount of tungsten can be dispersed. The upper limit of the amount of moisture is not particularly limited, but is, for example, 20% by mass or less. If the amount of water is excessively large, the efficiency of the heat treatment in the subsequent process will decrease, or the elution of lithium from the lithium metal composite oxide particles (base material) will increase, resulting in an increased Li molar ratio in the tungsten mixture. In some cases, battery characteristics when the obtained positive electrode active material is used for a positive electrode of a battery may deteriorate.

The amount of water with respect to the total amount of the base material is preferably 2% by mass or more and 20% by mass or less, more preferably 3% by mass or more and 15% by mass or less, and further preferably 3% by mass or more and 10% by mass or less. When the amount of water is in the above range, the pH rises due to the lithium content eluted in the water, and the effect of suppressing excessive lithium elution is exhibited. The amount of water in the tungsten mixture can be easily controlled within the above range by washing the base material with water and solid-liquid separation, as will be described later. Note that the molar ratio of Ni, Co and M ¹ in the base material powder is maintained up to the first composite oxide particle 1 (core material 5).

  The tungsten compound is a compound containing tungsten (W), and preferably has water solubility enough to dissolve in moisture contained in the tungsten mixture. When the tungsten compound is water-soluble, tungsten (W) can be sufficiently penetrated to the primary particle surface inside the secondary particles (base material). The tungsten compound may be in a solid state or an aqueous solution, for example. When the tungsten compound is in the state of an aqueous solution, the tungsten compound (aqueous solution) may be an amount that can penetrate to the surface of the primary particles inside the secondary particles (base material), and even if a part of the aqueous solution contains a solid state. Good. Further, the tungsten compound may be a compound that can be dissolved in water by heating during heat treatment even if it is difficult to dissolve in water at room temperature. In addition, the tungsten compound may be a compound that can be dissolved in an alkaline state because moisture in the tungsten mixture becomes alkaline due to lithium contained in the base material.

The tungsten compound is not particularly limited as long as it is a compound that can be dissolved in water, and examples thereof include tungsten oxide, tungstic acid, lithium tungstate, ammonium tungstate, and sodium tungstate. Among these, tungsten oxide, tungstic acid, lithium tungstate, and ammonium tungstate are more preferable from the viewpoint that impurities are unlikely to be mixed. Tungsten oxide (WO ₃ ), tungstic acid (WO ₃ .H ₂ O), Lithium tungstate (Li ₂ WO ₄ , Li ₄ WO ₅ , Li ₆ W ₂ O ₉ ) is more preferable. One type of tungsten compound may be used, or two or more types may be used in combination.

  The molar ratio of the total amount of lithium (Li) contained in the water and the tungsten compound or the water, the tungsten compound and the lithium compound with respect to the amount of tungsten (W) contained in the tungsten mixture (hereinafter referred to as “Li molar ratio”). ) Is preferably 5.0 or less, more preferably less than 4.5, and even more preferably 4.0 or less. When the upper limit of the Li molar ratio is in the above range, the excess lithium amount of the first composite oxide particles can be suppressed to improve the output characteristics and improve the cycle characteristics.

  On the other hand, the lower limit of the Li molar ratio is preferably 0.5 or more, more preferably 1.0 or more, and further preferably 1.5 or more. Lithium calculated as the Li molar ratio in the tungsten mixture forms tungsten (W) derived from the tungsten compound and lithium tungstate during the subsequent heat treatment. At least a part of the lithium can be lithium derived from the base material. When the lower limit of the Li molar ratio is less than 0.5, when the Li molar ratio is less than 0.5, too much lithium is extracted from the base material to form lithium tungstate, and the first composite oxide particles Battery characteristics may deteriorate.

  The amount of tungsten contained in the tungsten mixture is preferably 0.05 atomic percent or more and 3.0 atomic percent or less, more preferably 0.8 atomic percent or less with respect to the total number of Ni, Co and M atoms contained in the base material. It is from 05 atomic% to 2.0 atomic%, more preferably from 0.08 atomic% to 1.0 atomic%. When the amount of tungsten is in the above range, the amount of tungsten contained in the lithium tungstate in the first composite oxide particle 1 can be set to a preferable range, and when the positive electrode active material 1 is used for a secondary battery, High charge / discharge capacity and output characteristics can be achieved at a higher level.

  When adjusting the above tungsten mixture, it is only necessary to supply and mix the water together with the tungsten compound so that the water content of the tungsten mixture is 2% by mass or more, and supply the tungsten compound aqueous solution or the tungsten compound and water individually. May be.

Incidentally, the lithium source to form a lithium tungstate, for example, lithium derived from the tungsten compound lithium tungstate or the like, or, the base material _{(Li z3 Ni 1-x3-} y3 Co x3 M 1 y3 O 2 or excess lithium) Lithium derived from As shown in FIG. 4B, the tungsten mixture may contain a lithium compound not containing tungsten in addition to the base material, moisture, and tungsten compound. This lithium compound can be used as a lithium source for forming lithium tungstate. Examples of the lithium compound not containing tungsten include water-soluble compounds such as lithium hydroxide.

  FIG. 5 is a diagram illustrating an example of a method for adjusting the tungsten mixture obtained in the manufacturing process of the first composite oxide particles 1. As shown in FIG. 5, the lithium nickel composite oxide particles as the base material may be washed with water before preparing the tungsten mixture. The washing with water can be performed by mixing a base material and water to form a slurry. When the base material is washed with water, it is possible to remove excess unreacted lithium compounds and sulfate elements such as sulfate radicals that deteriorate the battery characteristics. Examples of the unreacted lithium compound include lithium hydroxide and lithium carbonate.

  When the base material is washed with water, the amount of lithium present in the water in the tungsten mixture is reduced, and the upper limit of the Li molar ratio can be easily controlled. Usually, a lithium composite metal oxide obtained by firing a metal composite hydroxide or a metal composite oxide and a lithium compound has an unreacted lithium compound on the surface of secondary particles or primary particles. . Lithium (Li) derived from an unreacted lithium compound contained in the base material is eluted in the added water when adjusting the tungsten mixture. When the amount of lithium eluting in moisture becomes too large, it may be difficult to control the upper limit of the Li molar ratio within the above range.

  The base material washed with water may be subjected to solid-liquid separation after washing in order to adjust the amount of water. When the base material is subjected to solid-liquid separation, the amount of water contained in the tungsten mixture can be easily adjusted.

  Washing conditions by slurrying the base material are not particularly limited as long as unreacted lithium compounds can be sufficiently reduced. The amount of unreacted lithium compound contained in the base material after washing with water is, for example, 0.08% by mass or less, preferably 0.05% by mass or less, based on the total amount of the base material. The amount of unreacted lithium compound contained in the base material can be measured by the same method as the amount of excess lithium in the positive electrode active material 1.

  The water washing by slurrying is performed, for example, by mixing the base material powder and water and stirring them. The density | concentration of the base material powder contained in a slurry is 200 g or more and 5000 g or less with respect to 1 L of water, for example. When the density | concentration of a base material powder is made into this range, an unreacted lithium compound can be reduced more fully, suppressing the deterioration by the elution of lithium from a base material.

  The washing time can be, for example, about 5 minutes to 60 minutes. When the washing time is within this range, the amount of unreacted lithium compound contained in the base material can be sufficiently reduced. The washing temperature can be in the range of 10 ° C. or more and 40 ° C. or less. When the washing temperature is within this range, the amount of unreacted lithium compound contained in the base material can be sufficiently reduced.

  When washing the base material with water, the procedure for adding the tungsten compound is not particularly limited as long as the above tungsten mixture is obtained. For example, as shown in FIG. 5A, after mixing the base material and the tungsten compound and adjusting the tungsten mixture, the tungsten mixture (including the base material) can be washed with water. In this case, since the tungsten compound is washed away by washing with water, the amount of tungsten in the tungsten mixture may be insufficient. For this reason, for example, as shown in FIGS. 5B and 5C, a tungsten compound is obtained by adding a tungsten compound in the step of washing the base material with water or in at least one step after the solid-liquid separation step. Is preferred.

  When the tungsten compound is added in the water washing step, the tungsten compound may be added in advance to the water mixed with the base material (powder) to form an aqueous solution or suspension. After mixing the base material and water into a slurry, A tungsten compound may be added.

As shown in FIG. 5B, when a tungsten compound is added at the time of washing the base material with water, it is preferable to use a compound that completely dissolves in the slurry at the time of washing with water or a compound that does not contain lithium. Examples of the tungsten compound dissolved in the slurry and containing lithium include lithium tungstate (Li ₂ WO ₄ , Li ₄ WO ₅ , Li ₆ W ₂ O ₉ ). Examples of the tungsten compound not containing lithium include , Tungsten oxide (WO ₃ ), and tungstic acid (WO ₃ .H ₂ O). By using these tungsten compounds, the amount of lithium in the tungsten mixture can be easily controlled without being affected by the amount of lithium contained in the solid tungsten compound in the tungsten mixture.

  As shown in FIG. 5C, when the tungsten compound is added after solid-liquid separation, there is no lithium or tungsten removed together with water during the solid-liquid separation, and all the tungsten compound remains in the mixture. The molar ratio can be easily controlled. In this case, the tungsten compound may be in an aqueous solution state or a powder state.

  When the tungsten compound is added during the water washing step, the tungsten compound may be in an aqueous solution state or a powder state. By adding the tungsten compound to the slurry and stirring, a uniform mixture is obtained.

  If a tungsten compound is used in the form of an aqueous solution or a water-soluble compound, most of the tungsten compound dissolved in the slurry in the solid-liquid separation step after washing with water is removed together with the liquid components of the slurry. However, the tungsten dissolved in the water in the tungsten mixture can make the amount of tungsten in the tungsten mixture sufficient. The amount of tungsten in the tungsten mixture becomes stable along with the amount of water depending on the water washing conditions and the solid-liquid separation conditions. Therefore, these conditions can be determined along with the type and amount of the tungsten compound by preliminary tests. The total amount of lithium contained in the tungsten compound and moisture relative to tungsten in the tungsten mixture (hereinafter referred to as the total amount of lithium) can be determined by a preliminary test in the same manner as the amount of tungsten.

  In addition, the amount of tungsten in the mixture when the tungsten compound is added in the water washing step can be obtained by ICP emission spectroscopy. Further, the amount of lithium contained in the water constituting the mixture can be determined from the analysis value of lithium and the amount of water by ICP emission spectroscopy in the liquid component separated into solid and liquid after washing with water.

  The amount of lithium contained in the solid tungsten compound constituting the tungsten mixture is determined by adding the tungsten compound to an aqueous lithium hydroxide solution having the same concentration as the liquid component after washing and stirring under the same conditions as in washing. The amount remaining as a solid content in the tungsten mixture can be calculated from the ratio of the tungsten compound remaining as follows, and obtained from the tungsten compound remaining as the solid content.

  Moreover, the amount of tungsten in the mixture when the tungsten compound is added after the solid-liquid separation step can be determined from the amount of the tungsten compound to be added.

  On the other hand, the total amount of lithium in the tungsten mixture is the amount of lithium in the water obtained from the analysis value of lithium by ICP emission spectroscopy and the amount of water in the liquid component separated into solid and liquid after washing, and the tungsten compound or tungsten compound to be added. It can be calculated as the sum of the lithium amounts obtained from the lithium compound.

  When the tungsten compound is added as an aqueous solution after the solid-liquid separation step, it is necessary to adjust the aqueous solution so that the water content preferably does not exceed 20% by mass, as described above, and the tungsten concentration is set to 0.1%. It is preferable to set it to 05 mol / L or more and 2 mol / L or less. When the tungsten concentration is within the above range, a necessary amount of tungsten can be added while suppressing moisture in the tungsten mixture. If the amount of water exceeds 20% by mass, the liquid may be adjusted again by solid-liquid separation, but the amount of tungsten and lithium in the removed liquid component should be determined to confirm the Li molar ratio of the mixture. Is required.

  In order to make the amount of water contained in the tungsten mixture 2% by mass or more, it is preferable to perform the mixing after the solid-liquid separation at a temperature of 50 ° C. or less. If the temperature exceeds 50 ° C., the moisture content may be less than 2% by mass due to drying during mixing.

  The mixing with the tungsten compound is not limited as long as it is a device capable of mixing uniformly, and a general mixer can be used. For example, the mixture may be sufficiently mixed with the tungsten compound using a shaker mixer, a Laedige mixer, a Julia mixer, a V blender, or the like so that the shape of the lithium metal composite oxide particles is not destroyed.

The component composition of the first composite oxide particles 1 is composed of composite oxide particles as a base material, tungsten that is added and increased in the adjustment step, and a lithium content that is added as necessary. Therefore, the base material is, from the viewpoint of high capacity and low reaction resistance, composition formula _{Li z Ni 1-x-y} Co x M y O 2 ( however, 0 <x ≦ 0.35,0 ≦ y ≦ 0.35, 0.95 ≦ z ≦ 1.20, and M is a lithium metal composite oxide represented by at least one element selected from Mn, V, Mg, Mo, Nb, Ti, and Al) It is preferable.

  On the other hand, when the base material is washed with water, Li / Me (corresponding to z in the general formula) in the base material decreases due to lithium elution at the time of water washing. As the material, a base material in which Li / Me is adjusted can be used. The decrease amount of Li / Me due to general water washing conditions is about 0.03 to 0.08. In addition, even when a small amount of water is supplied in the mixing step, lithium elutes though a small amount. Therefore, when washing with water, z indicating Li / Me of the base material before washing is preferably 0.95 ≦ z ≦ 1.20, more preferably 0.97 ≦ z ≦ 1.15. preferable.

  In addition, increasing the contact area with the electrolytic solution is advantageous for improving the output characteristics, so that the primary particles and secondary particles formed by aggregation of the primary particles are formed. It is preferable to use a lithium metal composite oxide powder having voids and grain boundaries that can be penetrated.

  Moreover, when mixing a base material and a tungsten compound or a tungsten compound and a lithium compound, a general mixer can be used. For example, the mixture may be sufficiently mixed using a shaker mixer, a Laedige mixer, a Julia mixer, a V blender, an air blender or the like so that the shape of the tungsten-coated base material is not destroyed. In addition, since excess Li contained in a base material adsorbs carbon dioxide to form lithium carbonate and causes gas generation, the mixed atmosphere is preferably performed at a carbon dioxide concentration of 0 to 100 ppm.

  Next, as shown in FIG. 4, the tungsten mixture obtained as described above is heat-treated. By performing the heat treatment, lithium and tungsten contained in the water of the tungsten mixture react to form lithium tungstate (LWO compound) on the primary particle surface of the base material (core material), and the first composite oxide particles 1 Is obtained.

  The heat treatment conditions are not particularly limited as long as the LWO compound 6 is formed on the primary particle surface of the base material (core material). The heat treatment condition is, for example, from the viewpoint of preventing deterioration of electrical characteristics when the positive electrode active material 10 is used in a secondary battery, avoiding reaction with moisture and carbonic acid in the atmosphere, and oxidizing properties such as an oxygen atmosphere. It can be performed in an atmosphere or a vacuum atmosphere.

  The heat treatment temperature is preferably 100 ° C. or more and 600 ° C. or less from the viewpoint of preventing deterioration of electrical characteristics when the positive electrode active material 10 is used in a secondary battery. When the heat treatment temperature is less than 100 ° C., the evaporation of moisture is not sufficient, and the LWO compound 6 may not be sufficiently formed. On the other hand, when the heat treatment temperature exceeds 600 ° C., primary particles of the lithium metal composite oxide are sintered and some tungsten is dissolved in the layered structure of the lithium metal composite oxide. The discharge capacity may decrease.

  On the other hand, when the tungsten compound contained in the tungsten mixture remains as a solid substance without being dissolved in moisture, especially when the tungsten compound is added as a powder after the solid-liquid separation step, the solid substance is sufficiently dissolved. During the process, the rate of temperature rise is preferably 0.8 to 1.2 ° C./min until, for example, 90 ° C. is exceeded. Even in the step of preparing the tungsten mixture, the tungsten compound powder is dissolved in the moisture contained in the mixture. By setting the temperature increase rate, the solid tungsten compound is sufficiently dissolved during the temperature increase. It can penetrate to the surface of the primary particle inside the secondary particle. In addition, when dissolving a solid tungsten compound, it is preferable to heat-process in the sealed container so that a water | moisture content may not volatilize, while melt | dissolving is fully performed.

  Although the heat treatment time is not particularly limited, it is preferably 3 hours or more and 20 hours or less, preferably 5 hours or more and 15 hours or less, from the viewpoint of sufficiently evaporating moisture in the tungsten mixture to form the LWO compound 6. It is more preferable.

  The heat treatment includes performing a first heat treatment in which a lithium compound and a tungsten compound existing on the primary particle surface of the base material are reacted to dissolve the tungsten compound and disperse tungsten on the primary particle surface, and after the first heat treatment, It is preferable to include performing a second heat treatment for forming a lithium tungstate compound on the primary particle surface of the lithium nickel composite oxide particles by performing a heat treatment at a temperature higher than the temperature of the first heat treatment.

  In the first heat treatment, by heating the tungsten mixture containing the tungsten compound, not only the lithium eluted in the mixture but also the lithium compound remaining on the primary particle surface of the base material reacts with the tungsten compound. Dissolve. Thereby, the excess lithium in the tungsten covering complex oxide particle obtained can be reduced significantly, and a battery characteristic can be improved. Furthermore, it has the effect of extracting lithium that is excessive in the base material, and the extracted lithium reacts with the tungsten compound to contribute to the improvement of crystallinity when it becomes tungsten-coated composite oxide particles. The battery characteristics can be made higher. By the first heat treatment, tungsten is sufficiently dissolved in the water in the tungsten mixture, penetrates to the voids between the primary particles inside the base material and the incomplete grain boundary, and disperses tungsten on the surface of the primary particles. Can be made.

  The heat treatment temperature in the first heat treatment is preferably 60 to 80 ° C. When the heat treatment temperature is within this range, the reaction proceeds sufficiently and moisture can remain until tungsten penetrates, allowing the lithium compound and the tungsten compound to react with each other and sufficiently disperse tungsten on the surface of the primary particles. it can. When the first heat treatment temperature is less than 60 ° C., the reaction between the lithium compound and the tungsten compound present on the primary particle surface of the base material may not sufficiently occur, and the required amount of lithium tungstate may not be synthesized. On the other hand, when the first heat treatment temperature is higher than 80 ° C., the evaporation of moisture is too early, and the reaction between the lithium compound and the tungsten compound existing on the surface of the primary particles and the penetration of tungsten may not sufficiently proceed. .

  The heating time in the first heat treatment is not particularly limited, but is preferably 0.5 to 2 hours in order to allow the lithium compound and the tungsten compound to react and sufficiently infiltrate tungsten.

In the second heat treatment, heat treatment is performed at a temperature higher than the heat treatment temperature of the first heat treatment, thereby sufficiently evaporating water in the mixture and forming a lithium tungstate compound on the primary particle surface of the lithium nickel composite oxide particles. Is.
The heat treatment temperature of the second heat treatment is preferably 100 ° C. or higher and 200 ° C. or lower. When the second heat treatment temperature is less than 100 ° C., the evaporation of moisture is not sufficient, and the lithium tungstate compound may not be sufficiently formed. On the other hand, if the second heat treatment temperature exceeds 200 ° C., the lithium nickel composite oxide particles may form necking through the lithium tungstate, or the specific surface area of the lithium nickel composite oxide particles may greatly decrease. In some cases, battery characteristics may deteriorate.

  The heat treatment time of the second heat treatment is not particularly limited, but is preferably 1 to 15 hours, and preferably 5 to 12 hours, in order to sufficiently evaporate moisture and form a lithium tungstate compound.

  The atmosphere in the heat treatment (including the first heat treatment and the second heat treatment) is decarboxylated air, inert gas, or vacuum in order to avoid reaction of moisture in the atmosphere and carbonic acid with lithium on the surface of the lithium nickel composite oxide particles. An atmosphere is preferable.

  Next, as shown in FIG. 1B, the positive electrode active material 10 is obtained by mixing the first composite oxide particles 1 and the second composite oxide 2 obtained by the above method. The manufacturing method of the 2nd composite oxide 2 is not specifically limited, The manufacturing method of a conventionally well-known lithium nickel composite oxide particle can be used.

  The second composite oxide particles 2 are preferably washed with water before mixing. As the water washing conditions, the same conditions as those for washing the base material of the first composite oxide particles 1 described above can be used. When the second composite oxide particles are washed with water, excess unreacted lithium compounds such as lithium hydroxide and lithium carbonate, sulfate groups, and other impurity elements that deteriorate the battery characteristics can be removed.

  The mixing ratio of the first composite oxide particles 1 and the second composite oxide particles 2 is such that the amount of the first composite oxide particles 1 is 10% by mass or more with respect to the positive electrode active material 10. It is preferable to mix with the composite oxide particles 2. In addition, the first composite oxide particle 1 has a tungsten content of 0.03 to 2.5 atomic% with respect to the total number of Ni, Co and M atoms contained in the positive electrode active material 10. It is preferable to mix one composite oxide particle 1 and second composite oxide particle 2. Thereby, it is possible to achieve both higher charge / discharge capacity and output characteristics.

  When mixing the first composite oxide particles 1 and the second composite oxide particles 2, a general mixer can be used. For example, the mixture may be sufficiently mixed using a shaker mixer, a Laedige mixer, a Julia mixer, a V blender, an air blender or the like so that the shape of the tungsten-coated base material is not destroyed.

2. Non-aqueous electrolyte secondary battery The non-aqueous electrolyte secondary battery according to the present embodiment includes a positive electrode, a negative electrode, a non-aqueous electrolyte solution, and the like, and includes the same components as those of a general non-aqueous electrolyte secondary battery. The embodiment described below is merely an example, and the nonaqueous electrolyte secondary battery of the present invention can be variously modified based on the knowledge of those skilled in the art based on the embodiment described in the present specification. It can be implemented in an improved form. Moreover, the use of the nonaqueous electrolyte secondary battery of the present invention is not particularly limited.

(A) Positive electrode Using the positive electrode active material for a non-aqueous electrolyte secondary battery described above, for example, a positive electrode of a non-aqueous electrolyte secondary battery is produced as follows.
First, a powdered positive electrode active material, a conductive material, and a binder are mixed, and, if necessary, a target solvent such as activated carbon and viscosity adjustment is added and kneaded to prepare a positive electrode mixture paste.
Each mixing ratio in the positive electrode mixture paste is also an important factor for determining the performance of the non-aqueous electrolyte secondary battery. When the total mass of the solid content of the positive electrode mixture excluding the solvent is 100 parts by mass, the content of the positive electrode active material is 60 to 95 parts by mass in the same manner as the positive electrode of a general non-aqueous electrolyte secondary battery, and the conductive material The content of is preferably 1 to 20 parts by mass, and the content of the binder is preferably 1 to 20 parts by mass.

  The obtained positive electrode mixture paste is applied to the surface of a current collector made of, for example, an aluminum foil and dried to disperse the solvent. If necessary, pressurization may be performed by a roll press or the like to increase the electrode density. In this way, a sheet-like positive electrode can be produced. The sheet-like positive electrode can be cut into an appropriate size or the like according to the target battery and used for battery production. However, the method for manufacturing the positive electrode is not limited to the illustrated one, and other methods may be used.

  In producing the positive electrode, as the conductive agent, for example, graphite (natural graphite, artificial graphite, expanded graphite, etc.), carbon black materials such as acetylene black, ketjen black (registered trademark), and the like can be used.

  The binder plays a role of anchoring the active material particles. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), fluorine rubber, ethylene propylene diene rubber, styrene butadiene, cellulosic resin, polyacrylic. An acid or the like can be used.

  If necessary, a positive electrode active material, a conductive material, and activated carbon are dispersed, and a solvent that dissolves the binder is added to the positive electrode mixture. Specifically, an organic solvent such as N-methyl-2-pyrrolidone can be used as the solvent. Activated carbon can be added to the positive electrode mixture in order to increase the electric double layer capacity.

(B) Negative electrode A negative electrode mixture in which a negative electrode active material capable of occluding and desorbing lithium ions is mixed with a binder and an appropriate solvent is added to the negative electrode for the negative electrode. Is applied to the surface of a metal foil current collector such as copper, dried, and compressed to increase the electrode density as necessary.

  As the negative electrode active material, for example, natural graphite, artificial graphite, a fired organic compound such as phenol resin, or a powdery carbon material such as coke can be used. In this case, as the negative electrode binder, a fluorine-containing resin such as PVDF can be used as in the case of the positive electrode, and as a solvent for dispersing these active materials and the binder, N-methyl-2-pyrrolidone or the like can be used. Organic solvents can be used.

(C) Separator A separator is interposed between the positive electrode and the negative electrode.
The separator separates the positive electrode and the negative electrode and retains the electrolyte, and a thin film such as polyethylene or polypropylene and a film having many minute holes can be used.

(D) Non-aqueous electrolyte The non-aqueous electrolyte is obtained by dissolving a lithium salt as a supporting salt in an organic solvent.
Examples of the organic solvent used include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and trifluoropropylene carbonate, chain carbonates such as diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, and dipropyl carbonate, and tetrahydrofuran, A single compound selected from ether compounds such as 2-methyltetrahydrofuran and dimethoxyethane, sulfur compounds such as ethyl methyl sulfone and butane sultone, phosphorus compounds such as triethyl phosphate and trioctyl phosphate, or a mixture of two or more. Can be used.
As the supporting salt, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , and complex salts thereof can be used.
Furthermore, the non-aqueous electrolyte solution may contain a radical scavenger, a surfactant, a flame retardant, and the like.

(E) Battery shape and configuration As described above, the shape of the nonaqueous electrolyte secondary battery of the present invention composed of the positive electrode, the negative electrode, the separator, and the nonaqueous electrolyte solution described above is various, such as a cylindrical type and a laminated type. can do.
In any case, the positive electrode and the negative electrode are laminated through a separator to form an electrode body, and the obtained electrode body is impregnated with a non-aqueous electrolyte and communicated with the positive electrode current collector and the outside. Connect between the positive electrode terminal and between the negative electrode current collector and the negative electrode terminal leading to the outside using a current collecting lead, etc., and seal the battery case to complete the non-aqueous electrolyte secondary battery. .

(F) Characteristics The nonaqueous electrolyte secondary battery using the positive electrode active material of the present invention has a high capacity and a high output.
In particular, the non-aqueous electrolyte secondary battery using the positive electrode active material according to the present invention obtained in a more preferable form has a high initial discharge capacity of 165 mAh / g or more and low when used for the positive electrode of a 2032 type coin battery, for example. A positive electrode resistance is obtained, and a high capacity and a high output are obtained. Moreover, it can be said that it has high thermal stability and is excellent in safety.
In addition, if the measuring method of the positive electrode resistance in this invention is illustrated, it will become as follows.
When the frequency dependence of the battery reaction is measured by a general AC impedance method as an electrochemical evaluation method, the Nyquist diagram based on the solution resistance, the negative electrode resistance and the negative electrode capacity, and the positive electrode resistance and the positive electrode capacity is shown in FIG. Is obtained as follows.

The battery reaction at the electrode consists of a resistance component accompanying the charge transfer and a capacity component due to the electric double layer. When these are expressed as an electric circuit, it becomes a parallel circuit of resistance and capacity. It is represented by an equivalent circuit in which circuits are connected in series.
Fitting calculation is performed on the Nyquist diagram measured using this equivalent circuit, and each resistance component and capacitance component can be estimated.

  The positive electrode resistance is equal to the diameter of the semicircle on the low frequency side of the obtained Nyquist diagram. From the above, the positive electrode resistance can be estimated by performing AC impedance measurement on the manufactured positive electrode and performing fitting calculation on the obtained Nyquist diagram with an equivalent circuit.

  Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

About the secondary battery which has a positive electrode using the positive electrode active material obtained by this invention, the performance (initial stage discharge capacity, positive electrode resistance, cycling characteristics) was measured.
Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

(Battery manufacture and evaluation)
For the evaluation of the positive electrode active material, a 2032 type coin battery CBA (hereinafter referred to as a coin type battery) shown in FIG. 7 was used. As shown in FIG. 6, the coin-type battery CBA includes an electrode EL and a case CA that accommodates the electrode EL therein. The electrode EL is composed of a positive electrode PE, a separator SE1, and a negative electrode NE, which are stacked so as to be arranged in this order. The positive electrode PE contacts the inner surface of the positive electrode can PC, and the negative electrode NE contacts the inner surface of the negative electrode can NC. Thus, it is accommodated in the case CA.

  The case CA has a positive electrode can PC that is hollow and open at one end, and a negative electrode can NC that is disposed in the opening of the positive electrode can PC, and the negative electrode can NC is disposed in the opening of the positive electrode can PC. A space for accommodating the electrode EL is formed between the negative electrode can NC and the positive electrode can PC. The case CA includes a gasket GA, and relative movement is fixed by the gasket GA so as to maintain a non-contact state between the positive electrode can PC and the negative electrode can NC. Further, the gasket GA also has a function of sealing the gap between the positive electrode can PC and the negative electrode can NC so as to block the inside and outside of the case CA in an airtight and liquidtight manner.

The coin-type battery CBA was manufactured as follows.
First, 52.5 mg of a positive electrode active material for a non-aqueous electrolyte secondary battery, 15 mg of acetylene black, and 7.5 mg of polytetrafluoroethylene resin (PTFE) are mixed and press-molded to a diameter of 11 mm and a thickness of 100 μm at a pressure of 100 MPa. A positive electrode PE was prepared. The produced positive electrode PE was dried at 120 ° C. for 12 hours in a vacuum dryer. Using this positive electrode PE, the negative electrode NE, the separator SE1, and the electrolytic solution, a coin-type battery CBA was produced in a glove box in an Ar atmosphere in which the dew point was controlled at −80 ° C.
As the negative electrode NE, a negative electrode sheet in which graphite powder with an average particle diameter of about 20 μm punched into a disk shape with a diameter of 14 mm and polyvinylidene fluoride were applied to a copper foil was used. As the separator SE1, a polyethylene porous film having a film thickness of 25 μm was used. As the electrolytic solution, an equivalent mixed solution (manufactured by Toyama Pharmaceutical Co., Ltd.) of ethylene carbonate (EC) and diethyl carbonate (DEC) using 1M LiClO ₄ as a supporting electrolyte was used.

The initial discharge capacity and positive electrode resistance showing the performance of the manufactured coin-type battery CBA were evaluated as follows. The initial discharge capacity is left for about 24 hours after the coin-type battery CBA is manufactured. After the open circuit voltage OCV (Open Circuit Voltage) is stabilized, the current density with respect to the positive electrode is set to 0.1 mA / cm ² and the cut-off voltage 4 The capacity when the battery was charged to 3 V, discharged after a pause of 1 hour to a cutoff voltage of 3.0 V was defined as the initial discharge capacity.

  When the positive electrode resistance is measured by the AC impedance method using a frequency response analyzer and a potentiogalvanostat (manufactured by Solartron, 1255B) after charging a coin-type battery CBA at a charging potential of 4.1 V, the Nyquist plot shown in FIG. can get. Since this Nyquist plot is expressed as the sum of the characteristic curve indicating the solution resistance, the negative electrode resistance and its capacity, and the positive electrode resistance and its capacity, the fitting calculation is performed using an equivalent circuit based on this Nyquist plot, and the positive resistance The value of was calculated. The positive electrode resistance was calculated as a relative value with Comparative Example 1 as “1.00”.

  In this example, each of the reagent special grades manufactured by Wako Pure Chemical Industries, Ltd. was used for producing the composite hydroxide, the positive electrode active material, and the secondary battery.

Example 1
[Production of positive electrode active material]
(Production of first composite oxide particles)
Lithium-nickel composite oxidation represented by Li _1.020 Ni _0.91 Co _0.06 Al _0.03 O ₂ obtained by a known technique in which an oxide containing Ni as a main component and lithium hydroxide are mixed and fired A powder of physical particles was used as a base material. 500 mL of pure water at 25 ° C. was added to 500 g of the base material to form a slurry, which was then stirred for 15 minutes and washed with water. The slurry after washing with water was filtered using a Nutsche to separate into solid and liquid. The moisture content of the obtained washed cake was 8.5% by mass.
3.58 g of tungsten oxide (WO ₃ ) is added to the washing cake so that the amount of W is 0.30 atomic% with respect to the total number of Ni, Co and Al atoms contained in the base material, and the shaker mixer device The mixture was sufficiently mixed using a TURBULA Type T2C manufactured by Willy et Bacofen (WAB) to obtain a tungsten mixture.
The obtained tungsten mixture was put in an aluminum bag, purged with nitrogen gas, laminated, and placed in a dryer heated to 80 ° C. for about 1 hour. After heating, it was taken out from the aluminum bag, replaced with a SUS container, left to dry (heat treatment) for 10 hours using a vacuum dryer heated to 190 ° C., and then cooled in the furnace.
Lithium nickel composite oxide particles (first composite oxide) having a lithium tungstate compound on the primary particle surface of the core material (base material) are pulverized by crushing the obtained tungsten mixture after drying through a sieve having an opening of 38 μm. Product particles). It was confirmed that the obtained first composite oxide particles had a surplus lithium amount (amount of Li contained in a lithium compound other than lithium tungstate) of 0.05% by mass or less.
(Production of second composite oxide particles)
Lithium-nickel composite oxidation represented by Li _1.020 Ni _0.91 Co _0.06 Al _0.03 O ₂ obtained by a known technique in which an oxide containing Ni as a main component and lithium hydroxide are mixed and fired 667 mL of 25 ° C. pure water was added to 500 g of the product particle powder to form a slurry, washed with water for 15 minutes, solid-liquid separated, and dried to obtain second composite oxide particles. It was confirmed that the obtained second composite oxide particles had an excess lithium amount of 0.05% by mass or less.
(Mixing of first composite oxide particles and second composite oxide particles)
To 300 g of the obtained lithium nickel composite oxide particles (first composite oxide particles), 300 g of lithium nickel composite oxide (second composite oxide particles) not containing a lithium tungstate compound is added, and a shaker mixer device (Willie ・The mixture was sufficiently mixed using TURBULA Type T2C manufactured by D. Bakkofen (WAB) to obtain a positive electrode active material. When the tungsten content of the obtained positive electrode active material was analyzed by the ICP method, it was confirmed that the tungsten content was 0.15 atomic% with respect to the total number of Ni, Co and Al atoms. Moreover, it was confirmed that the sulfate radical content of the obtained positive electrode active material is 0.05 mass% or less.

[Surplus lithium analysis]
The excess lithium of the obtained positive electrode active material was evaluated by titrating Li eluted from the positive electrode active material. After adding 10 ml of pure water to 1 g of the obtained positive electrode active material and stirring for 1 minute, the compound state of lithium eluted from the neutralization point that appears by adding hydrochloric acid while measuring the pH of the filtered filtrate is analyzed. Then, the excess lithium amount was evaluated. The surplus lithium amount was 0.02 mass% with respect to the total amount of the positive electrode active material.

[Battery evaluation]
The battery characteristics of the coin-type battery CBA having a positive electrode produced using the obtained positive electrode active material were evaluated. For the positive electrode resistance, a relative value in which Comparative Example 1 was “1.00” was used as an evaluation value. The initial discharge capacity was 213.1 mAh / g.
Hereinafter, about an Example and a comparative example, only the substance and conditions changed with the comparative example 1 are shown. Tables 1 and 2 show the initial discharge capacities and positive electrode resistance evaluation values of the examples and comparative examples.

(Example 2)
4. Tungsten oxide (WO ₃ ) is added to the cleaning cake so that the W amount is 0.45 atomic% with respect to the total number of Ni, Co and Al atoms contained in the lithium nickel composite oxide (base material). Except for the addition of 37 g, the mixture was sufficiently mixed in the same manner as in Example 1 using a shaker mixer apparatus (TURBULA Type T2C manufactured by Willy et Bacofen (WAB)) to obtain a tungsten mixture.
The obtained mixture was put in an aluminum bag, purged with nitrogen gas, laminated, and placed in a dryer heated to 80 ° C. for about 1 hour. After heating, it was taken out from the aluminum bag, replaced with a SUS container, left to dry for 10 hours using a vacuum dryer heated to 190 ° C., and then cooled in the furnace.
Lithium nickel composite oxide (first composite oxide) having a lithium tungstate compound on the primary particle surface of the core material (base material) by pulverizing the obtained tungsten mixture after drying through a sieve having an opening of 38 μm Got. To 300 g of the obtained composite oxide (first composite oxide), 600 g of lithium nickel composite oxide (second composite oxide particles) not containing the lithium tungstate compound obtained in the same manner as in Example 1 was added, and a shaker mixer was added. A positive electrode active material was obtained by sufficiently mixing using an apparatus (TURBULA Type T2C manufactured by Willy et Bacofen (WAB)).
When the tungsten content of the obtained positive electrode active material was analyzed by the ICP method, it was confirmed that the tungsten content was 0.15 atomic% with respect to the total number of Ni, Co and Al atoms.

(Example 3)
8. Tungsten oxide (WO ₃ ) is added to the washing cake so that the W amount becomes 0.75 atomic% with respect to the total number of Ni, Co and Al atoms contained in the lithium nickel composite oxide (base material). Except for adding 98 g, the mixture was sufficiently mixed in the same manner as in Example 1 using a shaker mixer apparatus (TURBULA Type T2C manufactured by Willy et Bacofen (WAB)) to obtain a tungsten mixture.
The obtained tungsten mixture was put in an aluminum bag, purged with nitrogen gas, laminated, and placed in a dryer heated to 80 ° C. for about 1 hour. After heating, it was taken out from the aluminum bag, replaced with a SUS container, left to dry for 10 hours using a vacuum dryer heated to 190 ° C., and then cooled in the furnace.
Lithium nickel composite having the lithium tungstate compound obtained in the same manner as in Example 1 on the surface of the primary particles of the core material (base material) by pulverizing the obtained tungsten mixture after drying through a sieve having an opening of 38 μm. An oxide (first composite oxide) was obtained.
To 300 g of the obtained composite oxide (first composite oxide), 1200 g of lithium nickel composite oxide (second composite oxide particles) that does not contain a lithium tungstate compound is added, and a shaker mixer device (Willy et Bacofen (WAB) is added. ) TURBULA Type T2C manufactured by KK) and mixed well to obtain a positive electrode active material.
When the tungsten content of the obtained positive electrode active material was analyzed by the ICP method, it was confirmed that the tungsten content was 0.15 atomic% with respect to the total number of Ni, Co and Al atoms.

Example 4
To 500 g of the base material, 667 mL of 25 ° C. pure water was added to form a slurry, which was washed with water for 15 minutes. After washing with water, solid-liquid separation was performed by filtration using a Nutsche. The moisture content of the washed cake was 8.5% by mass.
Lithium tungstate (LWO: Li ₂ WO) was added to the washing cake so that the amount of W was 0.30 atomic% with respect to the total number of Ni, Co and Al atoms contained in the lithium nickel composite oxide (base material). ₄ ) was added and mixed thoroughly using a shaker mixer apparatus (TURBULA Type T2C manufactured by Willy et Bacofen (WAB)) to obtain a tungsten mixture.
The obtained tungsten mixture was put in an aluminum bag, purged with nitrogen gas, laminated, and placed in a dryer heated to 80 ° C. for about 1 hour. After heating, it was taken out from the aluminum bag, replaced with a SUS container, left to dry for 10 hours using a vacuum dryer heated to 190 ° C., and then cooled in the furnace.
Lithium nickel composite oxide (first composite oxide) having a lithium tungstate compound on the primary particle surface of the core material (base material) by pulverizing the obtained tungsten mixture after drying through a sieve having an opening of 38 μm Got.
To 300 g of the obtained composite oxide (first composite oxide), 300 g of lithium nickel composite oxide (second composite oxide particles) containing no lithium tungstate compound obtained in the same manner as in Example 1 was added, and a shaker mixer was added. Mixing was sufficiently performed using an apparatus (TURBULA Type T2C manufactured by Willy et Bacofen (WAB)) to obtain a mixed positive electrode active material.
When the tungsten content of the obtained positive electrode active material was analyzed by the ICP method, it was confirmed that the tungsten content was 0.15 atomic% with respect to the total number of Ni, Co and Al atoms.

(Example 5)
To 500 g of the base material, 667 mL of 25 ° C. pure water was added to form a slurry, which was washed with water for 15 minutes. After washing with water, solid-liquid separation was performed by filtration using a Nutsche. The moisture content of the washed cake was 8.5% by mass.
Lithium tungstate (LWO: Li ₂ WO) was added to the cleaning cake so that the W amount was 0.45 atomic% with respect to the total number of Ni, Co and Al atoms contained in the lithium nickel composite oxide (base material). ₄ ) was added and sufficiently mixed using a shaker mixer apparatus (TURBULA Type T2C manufactured by Willy et Bacofen (WAB)) to obtain a tungsten mixture.
The obtained tungsten mixture was put in an aluminum bag, purged with nitrogen gas, laminated, and placed in a dryer heated to 80 ° C. for about 1 hour. After heating, it was taken out from the aluminum bag, replaced with a SUS container, left to dry for 10 hours using a vacuum dryer heated to 190 ° C., and then cooled in the furnace.
Lithium nickel composite oxide having lithium tungstate compound (first composite oxide) on the primary particle surface of the core material (base material) by pulverizing the obtained tungsten mixture after drying through a sieve having an opening of 38 μm Got.
To 300 g of the obtained composite oxide (first composite oxide), 600 g of lithium nickel composite oxide (second composite oxide) not containing a lithium tungstate compound obtained in the same manner as in Example 1 was added, and a shaker mixer device was added. (Will & Bakkofen (WAB) manufactured TURBULA Type T2C) was sufficiently mixed to obtain a positive electrode active material.
When the tungsten content of the obtained positive electrode active material was analyzed by the ICP method, it was confirmed that the tungsten content was 0.15 atomic% with respect to the total number of Ni, Co and Al atoms.

(Example 6)
To 500 g of the base material, 667 mL of 25 ° C. pure water was added to form a slurry, which was washed with water for 15 minutes. After washing with water, solid-liquid separation was performed by filtration using a Nutsche. The moisture content of the washed cake was 8.5% by mass.
Lithium tungstate (LWO: Li ₂ WO) was added to the cleaning cake so that the W amount was 0.75 atomic% with respect to the total number of Ni, Co and Al atoms contained in the lithium nickel composite oxide (base material). ₄ ) was added and the mixture was sufficiently mixed using a shaker mixer apparatus (TURBULA Type T2C manufactured by Willy et Bacofen (WAB)) to obtain a tungsten mixture.
The obtained tungsten mixture was put in an aluminum bag, purged with nitrogen gas, laminated, and placed in a dryer heated to 80 ° C. for about 1 hour. After heating, it was taken out from the aluminum bag, replaced with a SUS container, left to dry for 10 hours using a vacuum dryer heated to 190 ° C., and then cooled in the furnace.
Lithium nickel composite oxide having lithium tungstate compound (first composite oxide) on the primary particle surface of the core material (base material) by pulverizing the obtained tungsten mixture after drying through a sieve having an opening of 38 μm Got.
To 300 g of the obtained composite oxide (first composite oxide), 1200 g of lithium nickel composite oxide (second composite oxide) not containing the lithium tungstate compound obtained in the same manner as in Example 1 was added, and a shaker mixer device was added. (Will & Bacofen (WAB) TURBULA Type T2C) was sufficiently mixed to obtain a mixed positive electrode active material.
When the tungsten content of the obtained positive electrode active material was analyzed by the ICP method, it was confirmed that the tungsten content was 0.15 atomic% with respect to the total number of Ni, Co and Al atoms.

(Comparative Example 1)
Except that 500 mL of pure water at 25 ° C. was added to 500 g of lithium nickel composite oxide particles having the same composition as the base material to make a slurry, and no tungsten compound was added to the washed cake after solid-liquid separation. Obtained composite oxide particles (corresponding to the second composite oxide) in the same manner as in the first composite oxide of Example 1, and this was used as the positive electrode active material.

(Comparative Example 2)
Except that 667 mL of 25 ° C. pure water was added to a lithium nickel composite oxide particle having the same composition as 500 g of the base material to form a slurry, and no tungsten compound was added to the washed cake after solid-liquid separation. In the same manner as in the first composite oxide of Example 1, composite oxide particles (corresponding to the second composite oxide) were obtained, and this was used as the positive electrode active material.

(Comparative Example 3)
The first composite oxide of Example 1 except that 667 mL of 25 ° C. pure water was added to a 500 g base material to form a slurry, and the tungsten compound was not added to the washed cake after solid-liquid separation. Similarly, composite oxide particles (corresponding to the second composite oxide) were obtained. To the obtained composite oxide particles (corresponding to the second composite oxide), 2.0 g of lithium tungstate (LWO: Li ₂ WO ₄ ) powder was added, and shaker mixer apparatus (Willie & Bacofen (WAB)) A positive electrode active material was obtained by thoroughly mixing using TURBULA Type T2C).
When the tungsten content of the obtained positive electrode active material was analyzed by the ICP method, it was confirmed that the tungsten content was 0.15 atomic% with respect to the total number of Ni, Co and Al atoms.

[Evaluation]
As is clear from Tables 1 and 2, since the positive electrode active materials of the examples were manufactured according to the present invention, the initial discharge capacity was high and the positive electrode resistance was low. Excellent battery characteristics. FIG. 3 shows an example of a cross-sectional SEM observation result of the positive electrode active material obtained in the example of the present invention. The obtained positive electrode active material is a secondary material composed of aggregated primary particles and primary particles. It was confirmed that lithium tungstate was formed on the primary particle surface. Fine particles containing lithium tungstate are circled in FIG.

  On the other hand, in Comparative Example 1 and Comparative Example 2, since the fine particles containing lithium tungstate are not formed on the primary particle surfaces, the positive electrode resistance is significantly high, and it is difficult to meet the demand for higher output. Further, in Comparative Example 3, although there is an effect of reducing resistance by adding lithium tungstate, since a lithium tungstate compound is not formed on the primary particle surface of the lithium nickel composite oxide, a battery having a low initial discharge capacity It has become.

  The non-aqueous electrolyte secondary battery using the positive electrode active material of the present invention is suitably used as a power source for small portable electronic devices (such as notebook personal computers and mobile phone terminals) that always require a high capacity, and has a high output. It can also be suitably used for required electric vehicle batteries. Further, the nonaqueous electrolyte secondary battery of the present invention has excellent safety, and can be reduced in size and increased in output. it can. The non-aqueous electrolyte secondary battery using the positive electrode active material of the present invention is not only a power source for an electric vehicle driven purely by electric energy but also a so-called hybrid vehicle used in combination with a combustion engine such as a gasoline engine or a diesel engine. It can also be used as a power source.

DESCRIPTION OF SYMBOLS 1 ... 1st lithium nickel complex oxide 2 ... 2nd lithium nickel complex oxide 3, 3a, 3b ... Primary particle (1st lithium nickel complex oxide)
4 ... Secondary particles (first lithium nickel composite oxide)
5 ... Core material 6, 6a, 6b ... Lithium tungstate 7 ... Primary particles (second lithium nickel composite oxide)
8 ... Secondary particles (second lithium nickel composite oxide)
DESCRIPTION OF SYMBOLS 10 ... Positive electrode active material CBA ... Coin type battery CA ... Case PC ... Positive electrode can NC ... Negative electrode can GA ... Gasket EL ... Electrode PE ... Positive electrode NE ... Negative electrode SE1 ... Separator

Claims (23)

Mixing first lithium nickel composite oxide particles containing lithium tungstate and second lithium nickel composite oxide particles not containing lithium tungstate,
The composition of the first lithium nickel composite oxide particles is Li _z1 Ni _1-x1-y1 Co _x1 M ¹ _y1 O ₂ (where 0 ≦ x1 ≦ 0.35, 0 ≦ y1 ≦ 0.35,. 95 ≦ z1 ≦ 1.15, M ¹ is represented by Mn, V, Mg, Mo, Nb, Ti, and Al, and secondary particles having a plurality of primary particles aggregated with each other. A core material, and lithium tungstate present on at least a part of the surface of the first lithium nickel composite oxide particles and the surface of the primary particles located inside,
The second lithium nickel complex oxide particles, the composition is _{Li z2 Ni 1-x2-y2} Co x2 M 2 y2 O 2 ( however, 0 ≦ x2 ≦ 0.35,0 ≦ y2 ≦ 0.35,0. 95 ≦ z2 ≦ 1.15, M ² is represented by at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al), and is composed of secondary particles in which a plurality of primary particles are aggregated with each other To be
The manufacturing method of the positive electrode active material for non-aqueous electrolyte secondary batteries characterized by the above-mentioned.   The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the second lithium nickel composite oxide particles are washed with water before the mixing.   The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 2, wherein the slurry concentration in the water washing is 500 g / L or more and 2500 g / L or less.   The first lithium nickel composite oxide particles and the second lithium nickel composite oxide particles are contained in lithium compounds other than lithium tungstate present on both surfaces and the surfaces of primary particles located inside. The amount of lithium is 0.05% by mass or less based on the total amount of the positive electrode active material. The positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, Production method.   The first lithium nickel composite oxide particles and the first lithium nickel composite oxide particles so that the content of the first lithium nickel composite oxide particles contained in the positive electrode active material is 10% by mass or more based on the total amount of the positive electrode active material. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein the second lithium nickel composite oxide particles are mixed.   The amount of tungsten contained in the first lithium nickel composite oxide particles is 0.03 atomic percent or more and 2.5 atomic percent or less with respect to the total number of Ni, Co, and M atoms contained in the positive electrode active material. The first composite oxide particles and the second lithium nickel composite oxide particles are mixed so as to satisfy the following conditions. A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery. Before mixing,
The composition is Li _z3 Ni _1-x3-y3 Co _x3 M ¹ _y3 O ₂ (where 0.00 ≦ x3 ≦ 0.35, 0.00 ≦ y3 ≦ 0.35, 0.95 ≦ z3 ≦ 1.20, M ¹ is represented by at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al), and a base material composed of secondary particles formed by aggregation of a plurality of primary particles;
2% by mass or more of moisture based on the total amount of the base material
A tungsten compound or a lithium compound containing no tungsten compound and tungsten;
Adjusting the tungsten mixture containing, and heat-treating the obtained tungsten mixture to form lithium tungstate on the surface of the base material and the surface of the primary particles therein, and the first lithium nickel composite oxide Obtaining physical particles,
In the tungsten mixture, the molar ratio of the total amount of lithium contained in the moisture and the tungsten compound or the moisture, the tungsten compound and the lithium compound with respect to the total amount of tungsten contained is 5 or less.
The manufacturing method of the positive electrode active material for non-aqueous electrolyte secondary batteries as described in any one of Claims 1-5 characterized by the above-mentioned.   The first lithium-nickel composite oxide particles are present on the surface of the primary particles inside and the amount of lithium contained in the lithium compound other than lithium tungstate. The manufacturing method of the positive electrode active material for nonaqueous electrolyte secondary batteries of Claim 7 characterized by being 0.05 mass% or less with respect to this.   Before the heat treatment, the base material and water are mixed to form a slurry, the base material is washed with water, and the water-washed base material is solid-liquid separated. The manufacturing method of the positive electrode active material for non-aqueous electrolyte secondary batteries of Claim 7 or 8.   The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 9, wherein a slurry concentration of the base material in water washing is 500 g / L or more and 2500 g / L or less.   The moisture content of the resulting washed cake is controlled to be 3.0% by mass or more and 15.0% by mass or less when the base material washed with water is subjected to solid-liquid separation. A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery. The tungsten compound includes at least one of tungsten oxide (WO ₃ ), tungstic acid (WO ₃ .H ₂ O), Li ₂ WO ₄ , Li ₄ WO ₅ and Li ₆ W ₂ O _9. The manufacturing method of the positive electrode active material for nonaqueous electrolyte secondary batteries as described in any one of Claims 7-11.   The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 7 to 12, wherein the temperature of the heat treatment in the heat treatment is 100 ° C or higher and 600 ° C or lower.   The amount of tungsten contained in the tungsten compound is 0.05 atomic% or more and 3.0 atomic% or less with respect to the total number of Ni, Co, and M atoms contained in the base material. Item 14. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of Items 7 to 13. First lithium nickel composite oxide particles containing lithium tungstate, and second lithium nickel composite oxide particles not containing lithium tungstate,
The composition of the first lithium nickel composite oxide particles is Li _z1 Ni _1-x1-y1 Co _x1 M ¹ _y1 O ₂ (where 0 ≦ x1 ≦ 0.35, 0 ≦ y1 ≦ 0.35,. 95 ≦ z1 ≦ 1.15, M ¹ is represented by Mn, V, Mg, Mo, Nb, Ti, and Al, and secondary particles having a plurality of primary particles aggregated with each other. A core material, and lithium tungstate present on at least a part of the surface of the first lithium nickel composite oxide particles and the surface of the primary particles located inside,
The second lithium nickel complex oxide particles, the composition is _{Li z2 Ni 1-x2-y2} Co x2 M 2 y2 O 2 ( however, 0 ≦ x2 ≦ 0.35,0 ≦ y2 ≦ 0.35,0. 95 ≦ z2 ≦ 1.15, M ² is represented by at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al), and is composed of secondary particles in which a plurality of primary particles are aggregated with each other To be
A positive electrode active material for a non-aqueous electrolyte secondary battery.   The amount of lithium contained in the lithium compound other than lithium tungstate present on the surfaces of the first lithium nickel composite oxide particles and the second composite oxide particles and the surfaces of the primary particles located inside thereof, The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 15, wherein the content is 0.05% by mass or less based on the total amount of the positive electrode active material.   17. The non-aqueous system according to claim 15, wherein the amount of the first lithium nickel composite oxide particles contained in the positive electrode active material is 10% by mass or more based on the total amount of the positive electrode active material. Positive electrode active material for electrolyte secondary battery.   The amount of tungsten contained in the lithium tungstate is 0.03 atomic percent or more and 2.5 atomic percent or less with respect to the total number of Ni, Co, and M atoms contained in the positive electrode active material. Item 18. The positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of Items 15 to 17.   The amount of tungsten contained in the lithium tungstate is 0.05 atomic percent or more and 3.0 atomic percent or less with respect to the total number of Ni, Co, and M atoms contained in the first composite oxide particles. The positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 15 to 18.   The lithium tungstate is present on the surface of the first lithium-nickel composite oxide particle and the surface of the primary particle inside as fine particles having a particle diameter of 1 nm or more and 500 nm or less. The positive electrode active material for non-aqueous electrolyte secondary batteries according to one item.   The lithium gustenate is present on the surface of the first lithium-nickel composite oxide particle and the surface of the primary particle inside as a film having a film thickness of 1 nm to 200 nm. The positive electrode active material for non-aqueous electrolyte secondary batteries according to one item.   The lithium tungstate is present on the surface of the first lithium-nickel composite oxide particles and the surface of the primary particles inside as both forms of fine particles having a particle diameter of 1 nm to 500 nm and a coating having a film thickness of 1 nm to 200 nm. The positive electrode active material for a nonaqueous electrolyte secondary battery according to any one of claims 15 to 19. A non-aqueous electrolyte secondary battery comprising a positive electrode containing the positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 15 to 22.