JP2019139889A - Positive electrode active material for nonaqueous electrolyte secondary battery, method for manufacturing the same, and nonaqueous electrolyte secondary battery - Google Patents

Abstract

To provide a positive electrode active material for a nonaqueous electrolyte secondary battery, which enables the achievement of a high output as well as a high capacity when being used for a positive electrode active material of a battery.SOLUTION: Provided is a positive electrode active material for a nonaqueous electrolyte secondary battery, which comprises: lithium nickel complex oxide powder including primary particles of a lithium nickel complex oxide containing Li, Ni, Co and an additive element M (where the additive element M represents at least one element selected from Mn, V, Mg, Nb, Ti and Al), and secondary particles resulting from agglomeration of the primary particles; and a LiWMo compound arranged on the surface of the secondary particles of the lithium nickel complex oxide powder and the surface of the primary particles and containing Li, W and Mo.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a positive electrode active material for a non-aqueous electrolyte secondary battery, a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, 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 is composed of a negative electrode, a positive electrode, an electrolyte, and the like, and a material capable of desorbing 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 oxide has been attracting attention as a material that has good cycle characteristics, low resistance, and high output. In recent years, as a performance required for the positive electrode active material, reduction of resistance necessary for high output is 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 discloses that one or more elements selected from Mo, W, Nb, Ta, and Re are represented by a predetermined composition formula in an amount of 0.1 to the total molar amount of Mn, Ni, and Co. A lithium transition metal-based compound powder for a lithium secondary battery positive electrode material, which is contained in a proportion of 1 mol% or more and 5 mol% or less, has been proposed. 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 Patent Document 1, when the lithium transition metal-based compound powder for a lithium secondary battery positive electrode material is used as a lithium secondary battery positive electrode material, cost reduction, high safety, high load characteristics, powder handling It is said that it is possible to achieve both improvement in performance.

  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 being composed of primary particles and aggregates thereof. A group consisting of one or both of certain secondary particles, wherein the aspect ratio of the primary particles is within a predetermined range, and at least the surface of the particles is composed of molybdenum, vanadium, tungsten, boron and fluorine A positive electrode active material for a non-aqueous electrolyte secondary battery having a compound comprising at least one selected from

  According to the positive electrode active material for a non-aqueous electrolyte secondary battery, the conductivity is improved by having a compound having at least one selected from the group consisting of molybdenum, vanadium, tungsten, boron and fluorine on the surface of the particles. It is supposed to be considered. Further, it is said that the initial characteristics are improved without impairing the improvement of thermal stability, load characteristics and output characteristics.

  Furthermore, Patent Document 3 relates to a battery that can be reversibly charged and discharged a plurality of times consisting of a negative electrode, a positive electrode, and a non-aqueous electrolyte containing a lithium salt. Ti, Al, Sn, Proposal of a positive electrode active material coated with a metal containing at least one selected from Bi, Cu, Si, Ga, W, Zr, B, and Mo, or an intermetallic compound obtained by a combination of these, and / or an oxide Has been.

  According to such a battery, safety can be ensured by absorbing oxygen gas that causes ignition and explosion, and therefore, a low temperature of 1.5 to 2.5 ° C. is particularly important among safety tests that have been considered difficult. It is said that the effect can be demonstrated by overcharge that ignites with voltage, overcharge at low temperature, crushing, nailing, throwing away in fire.

In Patent Document 4, _a tungstic acid compound is deposited on a composite oxide particle having an average composition represented by Li _a Ni _x Co _y Al _z O ₂ and heat treatment is performed. A positive electrode active material of 0.15% by weight or less has been proposed.

  According to such a positive electrode active material, gas generation due to decomposition of a nonaqueous electrolytic solution or the like can be suppressed. Alternatively, it is said that gas generation from itself in the positive electrode active material can be suppressed.

Patent Document 5, the general formula _{Li z Ni 1-x-y} Co x M y O 2 ( however, 0.10 ≦ x ≦ 0.35,0 ≦ y ≦ 0.35,0.97 ≦ z ≦ 1 .20, M is composed of primary particles represented by (at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al) and secondary particles formed by aggregation of the primary particles. A lithium metal composite oxide,
A non-aqueous electrolyte 2 having fine particles containing lithium tungstate represented by any one of Li ₂ WO ₄ , Li ₄ WO ₅ , and Li ₆ W ₂ O _{9 on} the surface of the lithium metal composite oxide. A positive electrode active material for secondary batteries has been proposed.

  According to the positive electrode active material for a non-aqueous electrolyte secondary battery disclosed in Patent Document 5, the positive electrode active material for a non-aqueous electrolyte secondary battery that can achieve high capacity and high output when used as a positive electrode material for a battery. Is supposed to be obtained.

JP 2009-289726 A JP-A-2005-251716 Japanese Patent Laid-Open No. 11-16666 JP 2010-40383 A JP 2013-125732 A

  In the above-mentioned Patent Literature 1 to Patent Literature 4, when it is used as a positive electrode material of a battery, it has not been recognized and studied about high output with high capacity.

  In addition, according to the positive electrode active material for a non-aqueous electrolyte secondary battery disclosed in Patent Document 5, when used as a positive electrode material of a battery, although it can have high capacity and high output, in recent years it has further increased. High capacity is required.

  Therefore, in view of the problems of the above-described conventional technology, one aspect of the present invention is to provide a positive electrode active material for a non-aqueous electrolyte secondary battery that can provide a high output with a high capacity when used as a positive electrode material for a battery. Objective.

In order to solve the above problems, according to one aspect of the present invention,
Primary particles of lithium nickel composite oxide containing Li, Ni, Co, and additive element M (wherein additive element M is at least one element selected from Mn, V, Mg, Nb, Ti, and Al), and Lithium nickel composite oxide powder having secondary particles composed of aggregated primary particles;
A positive electrode active for a non-aqueous electrolyte secondary battery, which is disposed on the surface of the secondary particle of the lithium nickel composite oxide powder and a LiWMo compound containing Li, W, and Mo, which is disposed on the surface of the primary particle. Provide material.

  According to one embodiment of the present invention, when used as a positive electrode material for a battery, a positive electrode active material for a non-aqueous electrolyte secondary battery that provides high capacity and high output can be provided.

The schematic explanatory drawing of the coin-type battery used for battery evaluation by the Example and the comparative example. Schematic explanatory drawing of the equivalent circuit used for the measurement example and analysis of impedance evaluation. The cross-sectional SEM image of the positive electrode active material produced in the Example.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments, and the following embodiments are not departed from the scope of the present invention. Various modifications and substitutions can be made.
[Positive electrode active material for non-aqueous electrolyte secondary battery]
One structural example of the positive electrode active material for a non-aqueous electrolyte secondary battery of the present embodiment will be described.

  The positive electrode active material for a non-aqueous electrolyte secondary battery of the present embodiment (hereinafter also simply referred to as “positive electrode active material”) has a lithium nickel composite oxide powder and a LiWMo compound.

  The lithium nickel composite oxide powder is composed of primary particles of lithium nickel composite oxide containing Li (lithium), Ni (nickel), Co (cobalt), and an additive element M, and the primary particles are aggregated. Secondary particles. The additive element M can be at least one element selected from Mn (manganese), V (vanadium), Mg (magnesium), Nb (niobium), Ti (titanium), and Al (aluminum).

  Moreover, a LiWMo compound is arrange | positioned at the surface of the secondary particle of lithium nickel complex oxide powder, and the surface of a primary particle, and can contain Li, W (tungsten), and Mo (molybdenum).

  The positive electrode active material of the present embodiment uses, as a base material, lithium nickel composite oxide powder composed of primary particles and secondary particles formed by aggregation of the primary particles, thereby obtaining a high charge / discharge capacity. be able to.

The composition of the lithium nickel composite oxide of lithium nickel composite oxide of the powder is not particularly limited, for example, the general _{formula: Li z Ni 1-x-} y Co x M y O 2 ( however, 0.03 ≦ x ≦ 0.35 0.01 ≦ y ≦ 0.35, 0.95 ≦ z ≦ 1.20). The additive element M in the general formula is preferably at least one element selected from Mn, V, Mg, Nb, Ti and Al.

  In addition, the positive electrode active material of this embodiment contains lithium nickel composite oxide powder and a LiWMo compound described later. For this reason, when composition analysis of the positive electrode active material is performed, it may be difficult to define the composition of the lithium nickel composite oxide contained in the lithium nickel composite oxide powder. In such a case, the composition of the lithium nickel composite oxide contained in the raw material lithium nickel composite oxide powder used when preparing the positive electrode active material of the present embodiment is used as the positive electrode active material of the present embodiment. The composition of the lithium nickel composite oxide contained in the lithium nickel composite oxide powder.

  The positive electrode active material of the present embodiment further has a LiWMo compound on the secondary particle surface and the primary particle surface of the lithium nickel composite oxide powder. The primary particle surface specifically means the surface of the primary particle existing inside the secondary particle. Hereinafter, the secondary particle surface of the lithium nickel composite oxide powder and the primary particle surface existing inside the secondary particle may be collectively referred to as a particle surface.

  The positive electrode active material of the present embodiment can be a positive electrode active material having improved output characteristics while maintaining charge / discharge capacity by arranging the LiWMo compound on the particle surface of the lithium nickel composite oxide powder as described above. it can. That is, the positive electrode active material of the present embodiment has the above-described configuration, so that when used as a positive electrode material for a battery, it can be a positive electrode active material that can obtain a high output with a high capacity.

The composition of the LiWMo compound is not particularly limited, but is preferably a compound containing Li, W, and Mo, and more preferably an oxide containing Li, W, and Mo. As the LiWMo compound, for example, a compound represented by the general formula: Li ₂ W _1-b Mo _b O ₄ or Li ₄ W _1-b Mo _b O ₅ (where 0.1 ≦ b ≦ 0.5) is suitable. Can be used.

  In general, when the surface of the base material of the positive electrode active material is completely covered with a different compound, the movement (intercalation) of lithium ions is greatly limited, and as a result, the lithium nickel composite oxide has It was thought that the advantage of high capacity would be erased.

  In the positive electrode active material of this embodiment, a LiWMo compound is formed on the particle surface of the lithium nickel composite oxide powder. According to the study of the inventors of the present invention, the LiWMo compound has a lithium ion conductivity (lithium The ion conductivity is high, and there is an effect of promoting the movement of lithium ions. For this reason, by forming the above compound on the particle surface of the lithium nickel composite oxide powder, a Li conduction path is formed at the interface with the electrolytic solution, so that the reaction resistance of the positive electrode active material (hereinafter referred to as positive electrode resistance). The output characteristics are improved.

  That is, 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. Further, since the voltage applied to the load side is increased, the insertion and extraction of lithium at the positive electrode is sufficiently performed, so that the battery capacity is also improved.

  Here, when only the secondary particle surface of the lithium nickel composite oxide powder is coated with the layered product of the LiWMo compound, the specific surface area of the positive electrode active material becomes small regardless of the coating thickness. For this reason, even if the LiWMo compound as the coating has a high lithium ion conductivity, the contact area between the positive electrode active material and the electrolytic solution is reduced, thereby reducing the charge / discharge capacity and increasing the positive electrode resistance. There is also a risk of inviting. However, in the positive electrode active material of the present embodiment, the LiWMo compound is disposed not only on the surface of the secondary particles but also on the surface of the primary particles existing inside thereof. For this reason, in the positive electrode active material of the present embodiment, the specific surface area becomes large, the contact area between the positive electrode active material and the electrolyte solution is sufficient, the lithium ion conductivity can be effectively improved, and the positive electrode of the battery When used as a material, the positive electrode resistance can be reduced with high capacity, and high output can be achieved.

  The form of a LiWMo compound is not specifically limited, For example, at least one part can be made into a particulate form. Further, at least a part of the film can be formed into a film. The LiWMo compound may be a mixture of particles and films.

  When the LiWMo compound is in the form of particles, the particle diameter is preferably 1 nm or more and 500 nm or less. This is because when the LiWMo compound is in the form of particles and the particle diameter is 1 nm or more, it can have a particularly high lithium ion conductivity. Further, when the LiWMo compound is in the form of particles and the particle diameter is 500 nm or less, the formation of the coating with the particles can be made particularly uniform, and the effect of reducing the positive electrode resistance, that is, the effect of increasing the output is particularly sufficient. This is because it can be demonstrated.

  Further, when the LiWMo compound is in the form of a film, the film thickness is preferably 1 nm or more and 10 nm or less. This is because when the LiWMo compound is in the form of a film and the film thickness is 1 nm or more, it can have a particularly high lithium ion conductivity. In addition, when the LiWMo compound is in the form of a film and the film thickness is 10 nm or less, the contact area between the positive electrode active material and the electrolytic solution can be made particularly high. Because it can.

  In addition, as described above, the contact between the lithium nickel composite oxide powder and the electrolytic solution also occurs on the primary particle surface, so it is important that the LiWMo compound is arranged on the primary particle surface of the lithium nickel composite oxide powder. It is.

  The secondary particle surface of the lithium nickel composite oxide powder and the primary particle surface (and the particle surface) existing in the secondary particle surface are electrolyzed through the primary particle surface exposed on the outer surface of the secondary particle and the outside of the secondary particle. The primary particle surface exposed to the surface vicinity of the secondary particle which can permeate | transmit a liquid, and the space | gap inside is included. Furthermore, even if it is a grain boundary between primary particles, if the primary particle bond is incomplete and the electrolyte solution can permeate, it is included in the particle surface.

  The contact between the lithium nickel composite oxide powder and the electrolytic solution is not only the outer surface of the secondary particles formed by aggregation of the primary particles, but also the vicinity of the surface of the secondary particles and the internal voids, and the incompleteness. Since it also occurs at the grain boundaries, it is preferable to form a LiWMo compound on the surface of the primary particles to promote the movement of lithium ions.

  Therefore, the positive electrode resistance of the lithium nickel composite oxide can be further reduced by forming the LiWMo compound on the entire particle surface.

  The property of the particle surface of such a lithium nickel composite oxide powder can be judged by observing with a field emission scanning electron microscope, for example. About the positive electrode active material of this embodiment, it is preferable that the LiWMo compound of 1 or more types of shapes selected from the particle form and the film form is formed in the surface of the primary particle of lithium nickel complex oxide powder.

  In the positive electrode active material of the present embodiment, the total number of atoms of W and Mo contained is not particularly limited, but is 0.05 atomic% or more with respect to the total number of atoms of Ni, Co, and additive element M contained. It is preferable that it is 1.0 atomic% or less. In particular, the total number of atoms of W and Mo contained in the positive electrode active material of the present embodiment is 0. 0 relative to the total number of atoms of Ni, Co, and additive element M contained in the positive electrode active material of the present embodiment. It is more preferably 10 atomic% or more and 0.50 atomic% or less, and further preferably 0.15 atomic% or more and 0.30 atomic% or less. By setting the total number of W and Mo atoms contained in the positive electrode active material within the above range, particularly high charge / discharge capacity and output characteristics can be exhibited.

  In addition, W and Mo which the positive electrode active material of this embodiment contains are derived from the LiWMo compound which the positive electrode active material of this embodiment contains, Ni, Co, and the additive element M are the positive electrode active materials of this embodiment. This is derived from the lithium nickel composite oxide contained.

  The LiWMo compound disposed on the particle surface of the lithium nickel composite oxide powder is, for example, as described later, LiWMo compound powder added to a wash cake obtained by washing and solid-liquid separation of the fired powder of the lithium nickel composite oxide, It can be formed by heat treatment. This is because the LiWMo compound powder is dissolved in the water retained by the lithium nickel composite oxide cleaning cake and dispersed on the particle surface of the lithium nickel composite oxide powder, and the LiWM compound is formed on the particle surface by evaporating the water. It is thought to form.

  And when the total number of atoms of W and Mo contained in the LiWMo compound is 0.05 atomic% or more with respect to the total number of atoms of Ni, Co and additive element M contained in the lithium nickel composite oxide powder, The particle surface of the lithium nickel composite oxide powder can be sufficiently covered with the LiWMo compound. For this reason, the output characteristics of the positive electrode active material obtained can be particularly improved, which is preferable.

  Further, the total number of atoms of W and Mo contained in the LiWMo compound should be 1.0 atomic% or less with respect to the total number of atoms of Ni, Co and additive element M contained in the lithium nickel composite oxide powder. Thus, the specific surface area of the positive electrode active material can be particularly increased. For this reason, the contact area between the positive electrode active material and the electrolytic solution can be increased, the charge / discharge capacity can be further increased, and the positive electrode resistance can be suppressed. That is, particularly high capacity and high output can be achieved.

  The degree of dispersion of the LiWMo compound disposed on the particle surface of the lithium nickel composite oxide powder is not particularly limited. However, when LiWMo compounds are formed non-uniformly between the secondary particles of the lithium nickel composite oxide, the movement of lithium ions between the secondary particles becomes non-uniform, which places a load on specific secondary particles. It tends to cause deterioration of cycle characteristics.

  For this reason, it is preferable that the LiWMo compound is uniformly formed between the secondary particles of the lithium nickel composite oxide.

Up to this point, the effect of improving the output characteristics by arranging the LiWMo compound on the surface of the lithium nickel composite oxide powder has been described, but the effect is not limited to the case where the lithium nickel composite oxide powder is used as the base material. For example, powders such as lithium cobalt complex oxide, lithium manganese complex oxide, lithium nickel cobalt manganese complex oxide and the like, and not only the positive electrode active material listed in the present embodiment but also lithium It is applicable also to the positive electrode active material for secondary batteries.
[Method for producing positive electrode active material for non-aqueous electrolyte secondary battery]
The manufacturing method of the positive electrode active material for nonaqueous electrolyte secondary batteries of this embodiment can have the following processes.

Lithium nickel composite oxide primary particles containing Li, Ni, Co, and additive element M, and lithium nickel composite oxide powder having secondary particles formed by aggregation of the primary particles are washed with water, and solid-liquid separation is performed. The washing process to make a washing cake by doing.
A mixing step of mixing a cleaning cake and a powder of LiWMo compound containing Li, W, and Mo to prepare a mixture.
A heat treatment step having a first heat treatment step for heat-treating the mixture at a heat treatment temperature of 60 ° C. or more and 80 ° C. or less and a second heat treatment step for performing a heat treatment at a heat treatment temperature of 100 ° C. or more and 200 ° C. or less.
The additive element M can be at least one element selected from Mn, V, Mg, Nb, Ti, and Al.

  Hereafter, the manufacturing method of the positive electrode active material for nonaqueous electrolyte secondary batteries of this embodiment is demonstrated in detail for every process.

However, since the positive electrode active material described above can be manufactured by the method for manufacturing the positive electrode active material of the present embodiment, the description of some of the matters already described is omitted.
(1) Water washing step In the water washing step, lithium nickel composite oxide powder having primary particles and secondary particles constituted by aggregation of primary particles is mixed with water to form a slurry, which is washed with water, filtered, etc. A washing cake can be obtained by solid-liquid separation by the above. The cleaning cake can include moisture and the cleaned lithium nickel composite oxide powder.

Although the composition of the lithium nickel composite oxide of lithium nickel composite oxide powder subjected to the water washing step contains is not particularly limited, the lithium nickel composite oxide is represented by the general _{formula: Li z Ni 1-x-} y Co x M y O ₂ is preferable. In the above general formula, x, y, and z preferably satisfy 0.03 ≦ x ≦ 0.35, 0.01 ≦ y ≦ 0.35, and 0.95 ≦ z ≦ 1.20. Further, the additive element M can be at least one element selected from Mn, V, Mg, Nb, Ti and Al. Moreover, lithium nickel complex oxide powder can also be comprised from the lithium nickel complex oxide represented by the said general formula. However, this does not exclude the inclusion of inevitable components in the manufacturing process and the like.

  The manufacturing method of the lithium nickel composite oxide powder to be subjected to the water washing step is not particularly limited, and a product prepared by a known method may be used.

  In general, an unreacted lithium compound is present on the particle surface of the lithium nickel composite oxide powder. In particular, in a lithium nickel composite oxide powder obtained by firing nickel composite hydroxide particles or a mixture of nickel composite oxide particles and lithium compound particles, an unreacted lithium compound tends to remain on the particle surface.

  Therefore, an unreacted lithium compound such as lithium hydroxide or lithium carbonate that may deteriorate the battery characteristics from the lithium nickel composite oxide powder by performing a water washing step to wash the lithium nickel composite oxide powder with water. And other impurity elements are preferably removed.

  In the washing step, when the slurry is formed by mixing lithium nickel composite oxide powder and water, the slurry concentration is preferably 500 g / L or more and 1500 g / L or less, and more preferably 750 g / L or more and 1000 g / L or less. It is more preferable. Here, the slurry concentration “g / L” means the mass “g” of the lithium nickel composite oxide powder mixed with 1 L of water.

  By making the slurry concentration 500 g / L or more, it becomes possible to selectively remove the unreacted lithium compound on the particle surface of the lithium nickel composite oxide powder. For this reason, when washing with water, lithium is prevented from being extracted from the crystal of the lithium nickel composite oxide powder, and the positive electrode active material prepared using the lithium nickel composite oxide after washing with water is used as the positive electrode material. When a battery is used, battery characteristics can be improved.

  In addition, when the slurry concentration is 1500 g / L or less, unreacted lithium compounds, impurity elements, and the like attached to the particle surfaces of the lithium nickel composite oxide powder can be particularly reduced and removed. For this reason, when the positive electrode active material powder prepared using the lithium nickel composite oxide powder after washing with water is used as a positive electrode material, the battery characteristics can be improved, which is preferable.

  Although the temperature at the time of water washing, ie, the water washing temperature, is not particularly limited, it is preferably 10 ° C. or higher and 40 ° C. or lower, and more preferably 20 ° C. or higher and 30 ° C. or lower. By setting the washing temperature to 10 ° C. or higher, it is possible to particularly reduce and remove unreacted lithium compounds and the like on the particle surfaces of the lithium nickel composite oxide powder. For this reason, when the positive electrode active material prepared using the lithium nickel composite oxide powder after washing with water is used as a positive electrode material, battery characteristics can be improved, which is preferable.

  Moreover, it becomes possible to selectively remove the unreacted lithium compound on the particle surface of the lithium nickel composite oxide powder by setting the washing temperature to 40 ° C. or lower. Therefore, when washing with water, lithium is prevented from being extracted from the crystal of the lithium nickel composite oxide powder, and the positive electrode active material prepared using the lithium nickel composite oxide powder after washing with water is used as the positive electrode material. Battery characteristics can be improved.

  The washing time is not particularly limited, but is preferably about 5 minutes to 60 minutes. This is because, by setting the washing time to 5 minutes or more, unreacted lithium compounds and impurity elements on the particle surface of the lithium nickel composite oxide powder can be particularly reduced and removed, which is preferable.

  Further, even if the washing time is longer than 60 minutes, the washing effect is not greatly changed, and the productivity can be increased by setting the washing time to 60 minutes or less.

  The water used to form the slurry is not particularly limited, but in order to prevent deterioration of battery characteristics due to adhesion of impurities to the lithium nickel composite oxide powder, water having an electric conductivity of less than 10 μS / cm is preferable. Water of 1 μS / cm or less is more preferable.

  In the water washing step, a lithium nickel composite oxide powder and water are mixed to form a slurry, followed by solid-liquid separation, whereby a washed cake of the lithium nickel composite oxide powder can be obtained. The method of solid-liquid separation is not particularly limited, and is carried out by a commonly used apparatus or method. For example, one or more kinds of solid-liquid separation means selected from a suction filter such as a Nutsche (Buchner funnel), a centrifuge, a filter press and the like can be preferably used.

  The cake containing the washed lithium nickel composite oxide powder obtained by solid-liquid separation in the water washing step, that is, the moisture content of the washed cake is not particularly limited, but is 2.0% by mass or more and 10.0% by mass or less. It is preferable that the content be 3.0% by mass or more and 8.0% by mass or less.

  By setting the moisture content to 2.0% by mass or more, the amount of moisture necessary for dissolving the LiWMo compound powder in the mixing step and the like described later can be made more sufficient. For this reason, the LiWMo compound penetrates with moisture to the voids and incomplete grain boundaries between the primary particles communicating with the outside of the secondary particles of the particles contained in the lithium nickel composite oxide powder in the mixing step and the like. A LiWMo compound can be dispersed on the particle surface.

In addition, by setting the moisture content of the washing cake to 10.0% by mass or less, the viscosity of the washing cake is reduced to increase the viscosity, facilitating mixing of the LiWMo compound powder, and reducing the drying time. Productivity can be further improved. Moreover, the elution of lithium from the lithium nickel composite oxide powder is suppressed by setting the moisture content of the cleaning cake to 10.0% by mass or less, and the positive electrode active material obtained by the method for producing the positive electrode active material of the present embodiment The battery characteristic at the time of using for a positive electrode material of a battery can be improved.
(2) Mixing step The mixing step is performed by mixing the washing cake obtained in the water washing step with the LiWMo compound powder containing Li, W, and Mo, and the lithium nickel composite oxide powder and the LiWMo compound powder. (Hereinafter simply referred to as a mixture).

Although the composition of LiWMo compound contained in the powder mixing process to subjecting LiWMo compound is not particularly limited, for example, LiWMo compounds have the general _{formula: Li 2 W 1-b Mo} b O 4 or _{Li 4 W 1-b Mo b} O 5 (However, it is preferable that 0.1 ≦ b ≦ 0.5). In addition, although the powder of LiWMo can also be comprised from the LiWMo compound represented by the said general formula, even in this case, it does not exclude that an unavoidable component by a manufacturing process etc. is contained.

  The particle size of the LiWMo compound powder mixed with the cleaning slurry of the lithium nickel composite oxide powder is not particularly limited. However, the volume average particle size obtained by measuring the particle size distribution using a laser scattering particle size distribution meter after the ultrasonic wave dispersion treatment of the LiWMo compound powder in isopropyl alcohol (IPA) for 30 seconds is 20 μm or less. Preferably there is. By setting the volume average particle size to 20 μm or less, the LiWMo compound can be more reliably dissolved in the heat treatment step described later, and the LiWMo compound can be sufficiently formed on the particle surface of the lithium nickel composite oxide powder. For this reason, when the obtained positive electrode active material is used as a positive electrode material of a battery, the positive electrode resistance can be particularly reduced, which is preferable.

  In addition, the said volume average particle diameter should just be larger than 0, for example, and the lower limit is not specifically limited.

  In the mixing step, the ratio of mixing the LiWMo compound powder and the cleaning cake is not particularly limited. In the mixing step, for example, the total number of atoms of W and Mo contained in the LiWMo compound powder is the Ni, Co, and additive elements contained in the washing cake, more specifically, the lithium nickel composite oxide powder in the washing cake. It is preferable to mix so that it may become 0.05 atomic% or more and 1.0 atomic% or less with respect to the sum total of the number of atoms of M, and it is more preferable to set it as 0.10 mass% or more and 0.50 atomic% or less. More preferably, the mixing is performed so that the amount is 0.15% by mass or more and 0.30% by mass or less.

  That is, the total number of atoms of W and Mo contained in the mixture prepared in the mixing step is 0.05 to the total number of atoms of Ni, Co and additive element M contained in the lithium nickel composite oxide powder. It is preferable to set it as atomic% or more and 1.0 atomic% or less, More preferably, it is set as 0.10 atomic% or more and 0.50 atomic% or less, It is set as 0.15 atomic% or more and 0.30 atomic% or less. Further preferred. Thereby, both a particularly high charge / discharge capacity and output characteristics can be achieved.

  In the mixing step, the temperature at which the washing cake and the LiWMo compound powder are mixed is not particularly limited, but the mixing is preferably performed at a temperature of 50 ° C. or lower. By controlling the temperature to 50 ° C. or lower, drying of the mixture during mixing can be suppressed, the LiWMo compound powder can be sufficiently dissolved in the moisture of the washing cake, and the lithium nickel composite oxide powder is particularly uniformly dispersed on the particle surface. Because it can. Although the lower limit of the temperature of a mixture is not specifically limited, For example, it can be 20 degreeC or more. During the mixing step, it is preferable that at least the mixture of the washing cake and the LiWMo compound powder satisfy the above temperature, and it is more preferable that the temperature of the mixture and the ambient temperature of the mixture satisfy the above temperature. .

When mixing the cleaning cake of the lithium nickel composite oxide powder and the powder of the LiWMo 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, or the like so that the shape of the lithium nickel composite oxide particles is not destroyed.
(3) Heat treatment step The heat treatment step is a step of heat treating the mixture.

  The heat treatment process can be performed in two stages. That is, the heat treatment process can include a first heat treatment step and a second heat treatment step in which the heat treatment is performed at a temperature higher than the heat treatment temperature of the first heat treatment step. Specifically, the heat treatment step includes a first heat treatment step for performing heat treatment on the mixture at a heat treatment temperature of 60 ° C. or more and 80 ° C. or less, and a second heat treatment step for performing heat treatment at a heat treatment temperature of 100 ° C. or more and 200 ° C. or less. Can have.

  In the first heat treatment step, the LiWMo compound can be dispersed on the particle surface of the lithium nickel composite oxide powder. In the second heat treatment step, a LiWMo compound can be formed on the particle surface of the lithium nickel composite oxide powder.

  The heat treatment temperature in the first heat treatment step is preferably 60 ° C. or higher and 80 ° C. or lower as described above. This is because, by setting the first heat treatment temperature to 60 ° C. or higher, the LiWMo compound is more reliably connected to the voids between the primary particles and incomplete grain boundaries that communicate with the outside of the secondary particles of the lithium nickel composite oxide powder. It is because it can fully penetrate. On the other hand, by setting the first heat treatment temperature to 80 ° C. or less, it is possible to suppress the rapid evaporation of moisture, and between the primary particles where the LiWMo compound communicates with the outside of the secondary particles of the lithium nickel composite oxide powder. It is possible to sufficiently penetrate even voids and imperfect grain boundaries.

  The heat treatment time of the first heat treatment step is not particularly limited, but is preferably 0.5 hours or more and 2 hours or less in order to sufficiently infiltrate the LiWMo compound.

  In the second heat treatment step, heat treatment at a temperature higher than the heat treatment temperature of the first heat treatment step can sufficiently evaporate the water in the mixture and form a LiWMo compound on the particle surface of the lithium nickel composite oxide powder. . The heat treatment temperature in the second heat treatment step is preferably 100 ° C. or higher and 200 ° C. or lower.

  By setting the heat treatment temperature in the second heat treatment step to 100 ° C. or higher, moisture in the mixture can be sufficiently evaporated, and a LiWMo compound can be sufficiently formed on the particle surface of the lithium nickel composite oxide powder. Further, by setting the heat treatment temperature of the second heat treatment step to 200 ° C. or less, the particles of the lithium nickel composite oxide powder form necking through the LiWMo compound, and the specific surface area of the lithium nickel composite oxide powder is increased. It can suppress that it falls large. For this reason, when it is set as the battery which used the obtained positive electrode active material for positive electrode material, a battery characteristic can be improved especially.

  The heat treatment time of the second heat treatment step is not particularly limited, but is preferably 5 hours or more and 15 hours or less in order to sufficiently evaporate water and form a LiWMo compound on the primary particle surface.

  The atmosphere in the heat treatment step is preferably decarboxylated air, an inert gas, or a vacuum atmosphere in order to avoid a reaction between moisture or carbonic acid in the atmosphere and lithium on the surface of the lithium nickel composite oxide powder.

  The manufacturing method of the positive electrode active material of this embodiment can also have arbitrary processes in addition.

  For example, it may further include a LiWMo compound powder preparation step of preparing a LiWMo compound powder to be subjected to the mixing step described above.

  In this case, the LiWMo compound powder preparation process can have the following steps.

A starting material having lithium hydroxide (LiOH), tungsten oxide (WO ₃ ), and molybdenum oxide (MoO ₃ ), water having a mass ratio of 0.1 to 1 when the total mass of the starting material is 1. A slurry forming step in which a slurry is added by wet mixing to form a slurry.
A drying step of drying the slurry at a temperature of 100 ° C. or higher and 200 ° C. or lower to obtain a dried product.

  A crushing step for crushing dry matter.

  Each step will be described.

  In the slurry forming step, lithium hydroxide, tungsten oxide, molybdenum oxide, and water can be mixed to form a slurry.

  The reaction of the LiWMo compound is promoted by adding and mixing water to the starting material having lithium hydroxide, tungsten oxide and molybdenum oxide. However, at this time, when the total mass of the starting material is 1, water is preferably added so that the mass ratio is 0.1 or more and 1 or less. This is because the reaction of the LiWMo compound can be sufficiently promoted by setting the amount of water added to the starting material to be 0.1 or more. Moreover, it is because the drying time in a drying step can be suppressed and productivity can be improved by making the addition amount of water with respect to a starting material into 1 or less by mass ratio.

  Note that the mixing ratio of lithium hydroxide, tungsten oxide, and molybdenum oxide contained in the starting material is not particularly limited. For example, each raw material can be weighed and mixed so that the amount ratio (molar ratio) of each metal component contained in the starting raw material, that is, Li, W, and Mo, is the same as the target LiWMo compound. The starting material can also be composed of lithium hydroxide, tungsten oxide, and molybdenum oxide.

  In the drying step, the obtained slurry can be dried. The drying temperature is preferably 100 ° C. or more and 200 ° C. or less as described above. By setting the drying temperature to 100 ° C. or higher, the water contained in the slurry can be sufficiently removed, and the LiWMo compound can be prevented from being altered.

  Moreover, it can suppress that the primary particle | grains of the LiWMo compound obtained raise | generate strong necking by making drying temperature into 200 degrees C or less. For this reason, at the time of crushing at the crushing step which is the next step, it is possible to sufficiently crush, and it is possible to suppress the occurrence of contamination due to wear of the crusher, that is, contamination of impurities. Furthermore, when the drying temperature is set to 200 ° C. or lower, the dispersibility of the LiWMo compound powder can be improved when the obtained LiWMo compound powder is mixed with the lithium nickel composite oxide powder.

  Although the drying method in a drying step is not specifically limited, For example, various dryers, such as a stationary dryer, a vibration dryer, a drum dryer, and a spray dryer, can be used according to the slurry density | concentration of the slurry provided to a drying step.

In the crushing step, the obtained LiWMo compound can be crushed. The crusher used in the crushing step is not particularly limited, but in order to reduce contamination from the crusher, the contact portion of the crusher with the LiWMo compound is coated with tungsten carbide or Teflon (registered trademark). It is preferable to use the applied member.
[Nonaqueous electrolyte secondary battery]
Next, a configuration example of the non-aqueous electrolyte secondary battery of the present embodiment will be described.

  The non-aqueous electrolyte secondary battery of this embodiment can have a configuration including a positive electrode including the positive electrode active material for a non-aqueous electrolyte secondary battery described above.

  This will be specifically described below.

  The non-aqueous electrolyte secondary battery of the present embodiment (hereinafter also simply referred to as “secondary battery”) includes a positive electrode, a negative electrode, a non-aqueous electrolyte, and the like, and has the same configuration as a general non-aqueous electrolyte secondary battery. Consists of elements. 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. Further, the use of the nonaqueous electrolyte secondary battery of the present embodiment is not particularly limited.

Below, the structural member which the secondary battery of this embodiment contains is demonstrated.
(1) Positive electrode The secondary battery of this embodiment can be equipped with the positive electrode containing the positive electrode active material as stated above.

  Specifically, the positive electrode active material described above is used, and for example, the positive electrode of the secondary battery of this embodiment is manufactured 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 may be an important factor for determining the performance of the non-aqueous electrolyte secondary battery, and is preferably within a predetermined range. 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 not less than 60 parts by mass and not more than 95 parts by mass in the same manner as the positive electrode of a general non-aqueous electrolyte secondary battery. The conductive material content is preferably 1 part by mass or more and 20 parts by mass or less, and the binder content is preferably 1 part by mass or more and 20 parts by mass or less.

  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 material, 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.

In addition, the manufacturing method of a positive electrode is not limited to the said method, For example, after press-molding positive mix and positive electrode paste, it can also manufacture by drying in a vacuum atmosphere.
(2) Negative electrode The negative electrode composite material in which the negative electrode is made of metal lithium, lithium alloy, or the like, or a negative electrode active material capable of occluding and desorbing lithium ions, mixed with a binder, and added with a suitable solvent to form a paste. 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.
(3) 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.
(4) 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.
(5) Battery shape and configuration The shape of the non-aqueous electrolyte secondary battery according to the present embodiment, which includes the positive electrode, the negative electrode, the separator, and the non-aqueous electrolyte described above, can be various, such as a cylindrical type and a laminated type. It can be.

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. A secondary battery is completed by connecting between the positive electrode terminal and between the negative electrode current collector and the negative electrode terminal communicating with the outside using a current collecting lead or the like and sealing the battery case.
(6) Characteristics The secondary battery using the above-described positive electrode active material has high capacity and high output.

  The secondary battery of the present embodiment using the above-described positive electrode active material has a high initial discharge capacity of 165 mAh / g or more and low when, for example, the above-described positive electrode active material is used for the positive electrode of a 2032 type coin-type battery. A positive 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.

  The application of the secondary battery of this embodiment is not particularly limited, and can be used for various applications. However, since the secondary battery of the present embodiment has a high capacity and a high output, the power source of a small portable electronic device such as a notebook personal computer or a mobile phone terminal that always requires a high capacity or a high output is available. It can be suitably used for a required power source for an electric vehicle.

  In addition, the secondary battery of the present embodiment has excellent safety, and can be reduced in size and increased in output. Therefore, the secondary battery can be suitably used as a power source for an electric vehicle that is restricted by a mounting space. The secondary battery of this embodiment is used not only as a power source for electric vehicles driven purely by electric energy but also as a power source for so-called hybrid vehicles used in combination with combustion engines such as gasoline engines and diesel engines. Can do.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.
(Evaluation method)
Here, the positive electrode active material manufactured by the following example and the comparative example, and the evaluation method of a secondary battery are demonstrated first.
(Battery manufacture and evaluation)
A 2032 type coin-type battery 11 (hereinafter referred to as “coin-type battery”) shown in FIG. 1 was manufactured using the positive electrode active material manufactured in each example and comparative example, and the battery characteristics were evaluated.

  As shown in FIG. 1, the coin-type battery 11 includes a case 12 and an electrode 13 accommodated in the case 12.

  The case 12 has a positive electrode can 12a that is hollow and open at one end, and a negative electrode can 12b that is disposed in the opening of the positive electrode can 12a. And if the negative electrode can 12b is arrange | positioned in the opening part of the positive electrode can 12a, it is comprised so that the space which accommodates the electrode 13 may be formed between the negative electrode can 12b and the positive electrode can 12a.

  The electrode 13 includes a positive electrode 13a, a separator 13c, and a negative electrode 13b, which are stacked in this order. The positive electrode 13a contacts the inner surface of the positive electrode can 12a via the current collector 14, and the negative electrode 13b is negative. The case 12 is accommodated in the case 12 so as to be in contact with the inner surface of the can 12b via the current collector 14. A current collector 14 is also disposed between the positive electrode 13a and the separator 13c.

  The case 12 includes a gasket 12c, and relative movement is fixed by the gasket 12c so as to maintain a non-contact state between the positive electrode can 12a and the negative electrode can 12b. Further, the gasket 12c also has a function of sealing the gap between the positive electrode can 12a and the negative electrode can 12b to block the inside and outside of the case 12 in an airtight and liquid tight manner.

  The coin-type battery 11 shown in FIG. 1 was manufactured as follows.

  First, 52.5 mg of the positive electrode active material prepared in each Example and Comparative Example, 15 mg of acetylene black, and 7.5 mg of polytetrafluoroethylene resin (PTFE) were mixed and pressed to a diameter of 11 mm and a thickness of 100 μm at a pressure of 100 MPa. The positive electrode 13a was produced by molding. The produced positive electrode 13a was dried in a vacuum dryer at 120 ° C. for 12 hours.

  Using the positive electrode 13a, the negative electrode 13b, the separator 13c, and the electrolytic solution, the coin-type battery 11 described above was produced in a glove box in an Ar atmosphere in which the dew point was controlled at −80 ° C.

As the negative electrode 13b, 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. Further, a polyethylene porous film having a film thickness of 25 μm was used for the separator 13c. 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 the positive electrode resistance ratio showing the performance of the manufactured coin battery 11 were evaluated as follows.

The initial discharge capacity is left for about 24 hours after the coin-type battery 11 is manufactured, and 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.

  The positive electrode resistance was evaluated as follows.

  When the coin-type battery 11 is charged at a charging potential of 4.1 V and the frequency dependence of the battery reaction is measured by an AC impedance method using a frequency response analyzer and a potentiogalvanostat (Solartron, 1255B), FIG. The Nyquist plot shown in A) is obtained. Since this Nyquist plot is represented as the sum of the characteristic curves indicating the solution resistance, the negative electrode resistance and its capacity, and the positive resistance and its capacity, the equivalent circuit shown in FIG. 2B is used based on this Nyquist plot. Fitting calculation was performed to calculate the positive electrode resistance value.

  In addition, the positive electrode resistance of the positive electrode active material of Example 1 is set to 100, and the positive electrode resistances of other examples and comparative examples are shown as the ratio of the positive electrode active material of Example 1 to the positive electrode resistance, that is, the positive electrode resistance ratio.

Hereinafter, this example and a comparative example will be described in detail. In this example and comparative example, each sample of a reagent grade manufactured by Wako Pure Chemical Industries, Ltd. was used for the production of the positive electrode active material and the secondary battery.
[Example 1]
(1) Preparation of positive electrode active material Li _1.020 Ni _0.91 Co _0.06 Al _0.03 obtained by a known technique in which nickel composite oxide containing Ni as a main component and lithium hydroxide are mixed and fired A powder of lithium nickel composite oxide represented by O ₂ was prepared as a base material.

  To 150 g of the base material, 200 mL of pure water having an electrical conductivity of 1 μS / cm at 25 ° C. was added to form a slurry, which was then washed with water for 15 minutes. During the water washing step, the temperature of the slurry is kept at a water temperature of 25 ° C., and the slurry concentration becomes 750 g / L. After washing with water, the product was filtered using a Nutsche to obtain a washed cake by solid-liquid separation (water washing step). The moisture content of the washed cake was 6.2% by mass.

Next, W and Mo contained in the LiWMo compound powder with respect to the total number of Ni, Co and Al atoms contained in the washing cake, specifically, the lithium nickel composite oxide powder in the washing cake. LiWMo compound powder was added to the washed cake so that the amount was 0.15 atomic%. Specifically, 0.58 g of Li ₂ W _0.9 Mo _0.1 O ₄ powder having a volume average particle diameter of 17.8 μm was added as a LiWMo compound powder.

The LiWMo compound powder was prepared by the following procedure. First, 7.18 g of lithium hydroxide (LiOH) and 31 of tungsten oxide (WO ₃ ) were adjusted so that the molar ratio of Li, W, and Mo was Li: W: Mo = 2: 0.9: 0.1. .30 g and 2.16 g of molybdenum oxide (MoO ₃ ) were prepared and mixed. To this mixture, 12.2 ml of pure water having an electric conductivity of 1 μS / cm (the mass of pure water is 0.3 with respect to the total mass of lithium hydroxide, tungsten oxide and molybdenum oxide) is added and stirred while stirring. To form a LiWMo compound. The slurry containing this LiWMo compound was statically dried in a stationary dryer heated to 120 ° C. for 3 hours, cooled in the furnace and taken out of the dryer, and then crushed.

  Also in Examples 2 to 6 below, LiWMo compound powders were prepared in the same manner except that the mixing ratio of lithium hydroxide, tungsten oxide, and molybdenum oxide was changed in accordance with the composition of the target LiWMo compound. .

  Also in the following Examples 2 to 7 and Comparative Example 2, the amount of W and Mo contained in the LiWMo compound powder is 0 with respect to the total number of Ni, Co and Al atoms contained in the washing cake. The powder of LiWMo compound is added to the washing cake so as to be 15 atomic%.

  The volume average particle size of the LiWMo compound powder is determined by measuring the particle size distribution using a laser scattering particle size distribution meter after subjecting the LiWMo compound powder to ultrasonic dispersion treatment for 30 seconds in isopropyl alcohol (IPA). This corresponds to the particle size at an integrated value of 50% in the particle size distribution.

  Then, using a shaker mixer device (TURBULA Type T2C manufactured by Willy et Bacofen (WAB)), while maintaining the temperature of the mixture at 30 ° C., the washing cake and the LiWMo compound powder are sufficiently mixed, and the mixed powder Was obtained (mixing step).

  Subsequently, the obtained mixed powder was subjected to a heat treatment step including the following first heat treatment step and second heat treatment step.

  The obtained mixed powder was put in an aluminum bag, purged with nitrogen gas, laminated, put in a dryer heated to 70 ° C. for about 1 hour, and subjected to heat treatment (first heat treatment step). After heating, the mixed powder was taken out from the aluminum bag, replaced with a SUS container, left to dry using a vacuum dryer heated to 190 ° C. for 10 hours, and then cooled in the furnace (second heat treatment step).

  About the mixed powder which finished the 2nd heat treatment step, it crushed by passing through a sieve with an opening of 38 μm (crushing step). Thereby, the positive electrode active material which has a LiWMo compound on the primary particle surface was obtained.

When the W and Mo contents of the obtained positive electrode active material were analyzed by the ICP method, it was confirmed that the W and Mo contents were 0.15 atomic% with respect to the total number of Ni, Co and Al atoms. It was. In Table 1, the W and Mo contents with respect to the total number of Ni, Co and Al atoms of the obtained positive electrode active material are shown as W and Mo content ratios.
[Battery evaluation]
The battery characteristics of the coin-type battery 11 shown in FIG. 1 having a positive electrode produced using the obtained positive electrode active material were evaluated. The results are shown in Table 1.

Hereinafter, about an Example and a comparative example, only the substance and conditions which changed with Example 1 are shown.
[Example 2]
In the mixing step, a positive electrode active material was obtained and the battery characteristics were evaluated in the same manner as in Example 1 except that 0.54 g of Li ₂ W _0.7 Mo _0.3 O ₄ powder was added as the LiWMo compound powder. It was. The results are shown in Table 1.
[Example 3]
In the mixing step, a positive electrode active material was obtained and the battery characteristics were evaluated in the same manner as in Example 1 except that 0.50 g of Li ₂ W _0.5 Mo _0.5 O ₄ powder was added as the LiWMo compound powder. It was. The results are shown in Table 1.
[Example 4]
In the mixing step, a positive electrode active material was obtained and the battery characteristics were evaluated in the same manner as in Example 1 except that 0.65 g of Li ₄ W _0.9 Mo _0.1 O ₅ powder was added as the LiWMo compound powder. It was. The results are shown in Table 1.
[Example 5]
In the mixing step, a positive electrode active material was obtained and the battery characteristics were evaluated in the same manner as in Example 1 except that 0.61 g of Li ₄ W _0.7 Mo _0.3 O ₅ powder was added as the LiWMo compound powder. It was. The results are shown in Table 1.
[Example 6]
In the mixing step, a positive electrode active material was obtained and the battery characteristics were evaluated in the same manner as in Example 1, except that 0.57 g of Li ₄ W _0.5 Mo _0.5 O ₅ powder was added as the LiWMo compound powder. It was. The results are shown in Table 1.
[Example 7]
As LiWMo compound powder, Li ₂ W _0.9 Mo _0.1 O obtained by using lithium hydroxide, tungsten oxide, and molybdenum oxide as starting materials, dry-mixing the starting materials, and firing at 700 ° C. _A positive electrode active material was obtained and battery characteristics were evaluated in the same manner as in Example 1 except that 0.58 g of ₄ powders was added. The results are shown in Table 1.
[Comparative Example 1]
Except that the LiWMo compound powder was not added, a positive electrode active material was obtained and the battery characteristics were evaluated in the same manner as in Example 1. The results are shown in Table 1.
[Comparative Example 2]
150 g of lithium nickel composite oxide powder represented by Li _1.020 Ni _0.91 Co _0.06 Al _0.03 O ₂ prepared in Example 1, and the volume prepared as LiWMo compound powder in Example 1 average particle size was dry mixed with 0.58g of _Li 2 _W 0.9 _Mo 0.1 _{O 4} of 17.8. And it heat-processed at 720 degreeC in oxygen atmosphere for 1 hour, while obtaining the positive electrode active material, the battery characteristic was evaluated. The results are shown in Table 1.

[Evaluation]
As is clear from Table 1, the positive electrode active materials of Examples 1 to 7 have a higher initial discharge capacity and higher positive electrode resistance when used as the positive electrode material of the secondary battery than Comparative Examples 1 and 2. It was confirmed that high output can be obtained with high capacity.

  In Examples 1 to 6, in which the volume average particle size of the LiWMo compound powder used when producing the positive electrode active material was 20 μm or less, the initial discharge capacity was particularly high, and it was confirmed that the positive electrode resistance could be suppressed. This is because the volume average particle size of the LiWMo compound was sufficiently small as 20 μm or less, and therefore, when the mixing step was carried out, it could be sufficiently dissolved in the washing cake, particularly on the particle surface of the lithium nickel composite oxide powder. It is thought that it was possible to disperse uniformly.

  FIG. 3 shows an example of a cross-sectional SEM observation result of the positive electrode active material obtained in Example 1. Observation and analysis using SEM / EDS revealed that the obtained positive electrode active material was a secondary particle of lithium nickel composite oxide powder containing primary particles and secondary particles formed by agglomeration of primary particles. It was also confirmed that the LiWMo compound 31 was formed on the surface of the primary particles existing inside the secondary particles.

  In other examples 2 to 7, similarly, secondary particles and secondary particles of lithium nickel composite oxide powder including secondary particles formed by aggregation of primary particles and primary particles. It was also confirmed that a LiWMo compound was formed on the surface of the primary particles existing inside the.

  On the other hand, in Comparative Example 1, since the LiWMo compound related to the surface of the lithium nickel composite oxide particles is not formed, the positive electrode resistance is very high and it is difficult to meet the demand for higher output. Was confirmed.

  Moreover, in the comparative example 2, cation mixing is advancing by dry-mixing and baking lithium nickel complex oxide powder and LiWMo compound powder. Furthermore, since the LiWMo compound does not penetrate to the surface of the primary particles present in the secondary particles of the lithium nickel composite oxide powder, it is considered that the effect of improving battery characteristics was not sufficient.

  31 LiWMo compound

Claims (12)

Primary particles of lithium nickel composite oxide containing Li, Ni, Co, and additive element M (wherein additive element M is at least one element selected from Mn, V, Mg, Nb, Ti, and Al), and Lithium nickel composite oxide powder having secondary particles composed of aggregated primary particles;
A positive electrode active for a non-aqueous electrolyte secondary battery, which is disposed on the surface of the secondary particle of the lithium nickel composite oxide powder and a LiWMo compound containing Li, W, and Mo, which is disposed on the surface of the primary particle. material.   The total number of atoms of W and Mo contained is 0.05 atomic% or more and 1.0 atomic% or less with respect to the total number of atoms of Ni, Co, and additive element M contained. Positive electrode active material for non-aqueous electrolyte secondary battery.   3. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein at least a part of the LiWMo compound is in the form of particles, and the particle diameter thereof is 1 nm or more and 500 nm or less.   The positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein at least a part of the LiWMo compound is in the form of a film, and the film thickness thereof is 1 nm or more and 10 nm or less. Primary particles of lithium nickel composite oxide containing Li, Ni, Co, and additive element M (wherein additive element M is at least one element selected from Mn, V, Mg, Nb, Ti, and Al), and Washing with water a lithium nickel composite oxide powder having secondary particles constituted by agglomeration of primary particles, and solid-liquid separation to form a washing cake;
A mixing step of preparing the mixture by mixing the washing cake and a powder of LiWMo compound containing Li, W, and Mo;
A first heat treatment step in which heat treatment is performed on the mixture at a heat treatment temperature of 60 ° C. or higher and 80 ° C. or lower; and a second heat treatment step in which heat treatment is performed at a heat treatment temperature of 100 ° C. or higher and 200 ° C. or lower. A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery. The lithium nickel composite oxide represented by the general _{formula: Li z Ni 1-x-} y Co x M y O 2 ( however, 0.03 ≦ x ≦ 0.35,0.01 ≦ y ≦ 0.35,0. 95 ≦ z ≦ 1.20, wherein M is at least one element selected from Mn, V, Mg, Nb, Ti, and Al). The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 5 Manufacturing method. LiWMo compound has the general _{formula: Li 2 W 1-b Mo} b O 4 or _{Li 4 W 1-b Mo b} O 5 ( however, 0.1 ≦ b ≦ 0.5) according to claim 5 or represented by 6 The manufacturing method of the positive electrode active material for nonaqueous electrolyte secondary batteries as described in any one of.   In the mixing step, the total number of W and Mo atoms contained in the LiWMo compound powder is 0.05 atomic% or more to the total number of Ni, Co and M atoms contained in the cleaning cake. It is 0.0 atomic% or less, The manufacturing method of the positive electrode active material for nonaqueous electrolyte secondary batteries of any one of Claims 5-7.   The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 5 to 8, wherein a moisture content of the washing cake is 2.0 mass% or more and 10.0 mass% or less. .   The LiWMo compound powder obtained by subjecting the LiWMo compound powder to ultrasonic dispersion treatment for 30 seconds in isopropyl alcohol (IPA) and then measuring the particle size distribution using a laser scattering particle size distribution meter. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 5 to 9, wherein the volume average particle size is 20 µm or less. A LiWMo compound powder preparation step of preparing the LiWMo compound powder;
The LiWMo compound powder preparation step includes:
The starting material having lithium hydroxide (LiOH), tungsten oxide (WO ₃ ), and molybdenum oxide (MoO ₃ ) has a mass ratio of 0.1 or more and 1 or less when the total mass of the starting material is 1. A slurry forming step of adding water and wet mixing to form a slurry;
Drying the slurry at a temperature of 100 ° C. or higher and 200 ° C. or lower to obtain a dried product;
The manufacturing method of the positive electrode active material for non-aqueous electrolyte secondary batteries of any one of Claims 5-10 which has a crushing step which crushes the said dried material.   The non-aqueous electrolyte secondary battery provided with the positive electrode containing the positive electrode active material for non-aqueous electrolyte secondary batteries of any one of Claims 1-4.