JP2009117261A - Positive-electrode active material for lithium secondary battery, and positive electrode and lithium secondary battery using positive electrode active material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive-electrode active material for a lithium secondary battery that makes improvement in load characteristics such as rate-output characteristics compatible with high densification. <P>SOLUTION: The positive-electrode active material for a lithium secondary battery is made of a mixture of lithium-containing transition metal compound powder A (spherical secondary particles having surface roughness and internal opening voids) and lithium-containing transition metal compound powder B (primary particles having sizes fillable into the surface roughness part and internal opening voids of the powder A). In the mercury intrusion curve by the mercury intrusion method, the mercury intrusion volume is ≤0.75 cm<SP>3</SP>/g during pressure rising from 3.86 kPa to 413 MPa. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a positive electrode active material for a lithium secondary battery, a positive electrode for a lithium secondary battery using the positive electrode active material, and a lithium secondary battery including the positive electrode for a lithium secondary battery.

  Lithium secondary batteries are excellent in energy density and output density, and are effective in reducing the size and weight. Therefore, the demand for lithium secondary batteries as a power source for portable devices such as notebook computers, mobile phones, and handy video cameras has increased rapidly. ing. Lithium secondary batteries are also attracting attention as power sources for electric vehicles and power load leveling, and in recent years, demand for power sources for hybrid electric vehicles is rapidly expanding. In particular, in electric vehicle applications, it is necessary to be excellent in low cost, safety, life (particularly under high temperature) and load characteristics, and improvements in materials are desired.

  Among the materials constituting the lithium secondary battery, as the positive electrode active material, a substance having a function capable of desorbing and inserting lithium ions can be used. There are various types of these positive electrode active material materials, each having its own characteristics. In addition, a common problem for improving performance is to improve load characteristics, and improvements in materials are strongly desired.

  Usually, for the problem of improving load characteristics such as rate and output characteristics, the active material particles are made finer and the void volume and specific surface area are increased. As a result, the density of the electrode and the electrode density are reduced, and it is difficult to handle the powder and adjust the electrode.

  For example, as a result of intensive investigations aimed at improving load characteristics such as rate and output characteristics, the present inventors have made a lithium transition metal system in which load characteristics are dramatically improved by adopting a monodispersed form of fine primary particles. It has been found that a compound powder can be obtained, but it has been found that there are cases where the bulk density and the electrode density are lowered, and the problem that handling as a powder and electrode preparation becomes difficult may occur.

  Therefore, as a result of intensive investigations to solve the problem that handling as a powder and electrode preparation becomes difficult without lowering the improved load characteristic level, spherical secondary particles having surface irregularities and internal opening voids are obtained. It was found that it can be improved by forming a body. However, the gaps between the obtained active material particles are still large, and in order to improve the bulk density and the electrode density, a device for further reducing the gaps between the active material particles is required.

  Therefore, as a result of intensive studies to improve the load characteristics while reducing the voids between the active material particles, the surface of the spherical secondary particles formed by agglomeration of the primary particle crystals has irregularities, and the secondary particles By forming a mixture of lithium-containing transition metal compound powder having voids inside and lithium-containing transition metal compound powder consisting of fine particles smaller than the surface irregularities and the internal opening void size, the latter is the former surface irregularities The present invention was completed by finding that the inner opening gap was filled, thereby improving the bulk density and further improving the load characteristics. Therefore, the feature of the present invention is that the intergranular voids are formed by a mixture of spherical secondary particles having surface irregularities and internal opening voids, and primary particles having a size that can be filled in the surface irregularity portions and internal opening voids. Is to further increase the output while improving the bulk density.

  On the other hand, the following Patent Documents 1 to 15 have been disclosed as known documents relating to a mixture in which powder physical property parameters are defined for a positive electrode active material powder for a lithium secondary battery. However, none of these known documents is characterized by the particle morphology of the present invention.

Japanese Patent No. 3869605 Japanese Patent No. 3867030 Japanese Patent No. 3543437 Japanese Patent No. 2865355 Japanese Patent No. 3024636 JP 2006-278322 A JP 2006-228733 A JP 2006-156004 A Japanese Patent Laying-Open No. 2005-019149 WO2002-86993 JP 2004-022239 A JP 2003-229128 A JP 2002-110253 A JP 2003-173766 A JP 2002-270247 A

  An object of the present invention is to provide a positive electrode for a lithium secondary battery in which the bulk density and the electrode density are improved while improving load characteristics such as rate and output characteristics in use as a positive electrode active material for a lithium secondary battery. An object is to provide an active material, a positive electrode for a lithium secondary battery using the positive electrode active material, and a lithium secondary battery including the positive electrode for a lithium secondary battery.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that spherical secondary particles having surface irregularities and internal opening voids, and sizes capable of filling the surface irregularities and internal opening voids of such particles. The present invention has been completed by finding that the above problems can be solved by a positive electrode active material having a specific amount of mercury intrusion in a mercury intrusion curve.

That is, the present invention includes lithium-containing transition metal compound powder A (spherical secondary particles having surface irregularities and internal opening voids) and lithium-containing transition metal compound powder B (surface irregularities and internal openings of powder A). In the mercury intrusion curve by the mercury intrusion method, the intrusion amount of mercury at a pressure of 3.86 kPa to 413 MPa is 0.75 cm ³ / g or less. A positive electrode active material for a lithium secondary battery is provided (claim 1).

  Here, the positive electrode active material for a lithium secondary battery of the present invention has at least one peak having a peak top at a pore radius of 80 nm or more and less than 800 nm in a pore distribution curve by a mercury intrusion method. Preferred (claim 2).

  The positive electrode active material for a lithium secondary battery of the present invention is a mixture of lithium-containing transition metal compound powders A and B, and the mixing ratio of the powders A and B is 20: 1 to 1. : 20 is preferable (Claim 3).

Moreover, the positive electrode active material for a lithium secondary battery of the present invention preferably has a bulk density of 1.6 g / cm ³ or more and 2.4 g / cm ³ or less (claim 4).

  In addition, the positive electrode active material for a lithium secondary battery of the present invention is set to a refractive index of 1.24 using a laser diffraction / scattering particle size distribution measuring device, and the ultrasonic wave for 5 minutes with the particle size reference as the volume reference. It is preferable that the median diameter measured after dispersion (output: 30 W, frequency: 22.5 kHz) is 0.1 μm or more and 20 μm or less.

In addition, the positive electrode active material for a lithium secondary battery of the present invention preferably has a BET specific surface area of 0.5 m ² / g or more and 5 m ² / g or less (Claim 6).

Furthermore, the positive electrode active material for a lithium secondary battery of the present invention preferably has a volume resistivity of 1 × 10 ³ Ω · cm or more and 1 × 10 ⁶ Ω · cm or less when consolidated at a pressure of 40 MPa. (Claim 7).

  Moreover, the positive electrode active material for a lithium secondary battery of the present invention preferably has a C value of 0.01 wt% or more and 0.3 wt% or less when the carbon concentration is C (wt%). (Claim 8).

  Further, in the positive electrode active material for a lithium secondary battery of the present invention, the lithium-containing transition metal compound powder A is obtained by pulverizing a lithium compound and at least one or more transition metal compounds in a liquid medium. A slurry preparation step for obtaining a slurry in which particles are uniformly dispersed, a spray drying step for spray-drying the obtained slurry, a firing step for firing the obtained spray-dried powder, and a classification for classifying the obtained fired body Preferably, it is obtained by a production method including at least a process.

  Further, the positive electrode active material for a lithium secondary battery of the present invention is obtained by refracting the lithium compound and the transition metal compound in a liquid medium using a laser diffraction / scattering particle size distribution measuring device in the slurry preparation step. The rate is set to 1.24, the particle diameter reference is volume reference, and the mixture is pulverized until the median diameter measured after 5 minutes of ultrasonic dispersion (output 30 W, frequency 22.5 kHz) becomes 0.4 μm or less, and the above spray In the drying process, when the slurry viscosity during spray drying is V (cp), the slurry supply amount is S (L / min), and the gas supply amount is G (L / min), 50 cp ≦ V ≦ 4000 cp, 500 ≦ G / S ≦ 10000 is obtained by a production method in which spray drying is performed under the condition of ≦ 10000, and the spray-dried powder is fired at 700 ° C. or higher in an oxygen-containing gas atmosphere in the firing step. It was it is preferable to use a lithium-containing transition metal compound powder A (claim 10).

  Furthermore, in the positive electrode active material for a lithium secondary battery of the present invention, in the slurry preparation step, the boron-containing compound and the tungsten-containing compound are each added in a total amount of 0.00 to the total molar amount of the transition metal elements in the main component raw material. It is preferable to use the lithium-containing transition metal compound powder A that has been added at a rate of 01 mol% or more and less than 2 mol% and then baked at 900 ° C. or more.

  Furthermore, in the positive electrode active material for a lithium secondary battery of the present invention, the lithium-containing transition metal compound powder B contains a lithium compound, at least one transition metal compound, and grain growth and sintering during firing. A slurry preparation step for obtaining a slurry in which the additive to be crushed is pulverized in a liquid medium, and these are uniformly dispersed, a spray drying step for spray-drying the obtained slurry, and the obtained spray-dried powder. It is preferably obtained by a production method including at least a firing step for firing and a classification step for classifying the obtained fired body (claim 12).

  Furthermore, the positive electrode active material for a lithium secondary battery according to the present invention is a laser diffraction / scattering particle size distribution measurement in a liquid medium in the slurry preparation step, the lithium compound, the transition metal compound, and the additive. By means of an apparatus, the refractive index is set to 1.24, the particle diameter standard is the volume standard, and grinding is performed until the median diameter measured after 5 minutes of ultrasonic dispersion (output 30 W, frequency 22.5 kHz) is 0.4 μm or less. In the spray drying step, when the slurry viscosity during spray drying is V (cp), the slurry supply amount is S (L / min), and the gas supply amount is G (L / min), 50 cp ≦ V ≦ 4000 cp And spray drying under conditions of 500 ≦ G / S ≦ 10000, and in the firing step, the spray-dried powder is fired at 700 ° C. or higher in an oxygen-containing gas atmosphere. It is preferable that a lithium-containing transition metal composite oxide powder B obtained by the method (claim 13).

  Furthermore, the positive electrode active material for a lithium secondary battery of the present invention includes Mo, W, Nb, Ta and Re as additives for suppressing grain growth and sintering during firing in the lithium-containing transition metal compound powder B. It is preferable to use an oxide containing at least one element selected from the group consisting of (claim 14).

  Furthermore, the positive electrode active material for a lithium secondary battery of the present invention is a lithium nickel manganese cobalt based composite oxide in which the lithium transition metal compound powder A and / or B includes a crystal structure belonging to a layered structure. It is preferable that the main component is a product (claim 15).

Furthermore, in the positive electrode active material for a lithium secondary battery of the present invention, the lithium transition metal compound powder A and / or B is preferably represented by the following formula (1) (claim 16).
LiMO ₂ (1)
[In Formula (1), M is an element comprised from Li, Ni, and Mn or Li, Ni, Mn, and Co, Mn / Ni molar ratio is 0.1-5, Co / ( Mn + Ni + Co) molar ratio is 0 or more and 0.35 or less, and Li molar ratio in M is 0.001 or more and 0.2 or less. ]

Furthermore, in the positive electrode active material for a lithium secondary battery of the present invention, M in the above formula (1) is preferably one represented by the following formula (2) (claim 17).
Li _{z / (2 + z)} [(Ni _{(1 + y) / 2} Mn _{(1-y) / 2} ) _1-x Co _x ] _{2 / (2 + z)} (2)
[In the formula (2), 0.1 <x ≦ 0.35, −0.1 ≦ y ≦ 0.1,
(1-x) (0.02-0.98y) ≤z≤ (1-x) (0.20-0.88y). ]

In the positive electrode active material for a lithium secondary battery of the present invention, M in the above formula (1) is preferably one represented by the following formula (3) (claim 18).
Li _{z '/ (2 + z')} [(Ni _{(1 + y ') / 2} Mn _{(1-y') / 2} ) _{1-x '} Co _x' ] _{2 / (2 + z ')} (3)
[In formula (3), 0 ≦ x ′ ≦ 0.1, −0.1 ≦ y ′ ≦ 0.1,
(1-x ′) (0.05−0.98y ′) ≦ z ′ ≦ (1-x ′) (0.20−0.88y ′)
It is. ]

  Further, in the positive electrode active material for a lithium secondary battery of the present invention, the lithium transition metal composite oxide powder B which is a constituent material thereof is further selected from the group consisting of Mo, W, Nb, Ta and Re. Those containing one or more elements are preferred (claim 19).

  The positive electrode for a lithium secondary battery of the present invention has a positive electrode active material layer containing at least the positive electrode active material for a lithium secondary battery and a binder on the current collector (claim). 20).

  The lithium secondary battery of the present invention is a lithium secondary battery comprising a negative electrode capable of inserting and extracting lithium, a non-aqueous electrolyte containing a lithium salt, and a positive electrode capable of inserting and extracting lithium. Such a positive electrode for a lithium secondary battery of the present invention is used (claim 21).

  The positive electrode active material for a lithium secondary battery of the present invention, when used as a positive electrode for a lithium secondary battery, can achieve both improvement in load characteristics such as rate and output characteristics and higher density, and therefore, in the present invention. According to this, a lithium secondary battery having excellent performance can be provided.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. However, the description of the constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention is not limited to the gist of the present invention. It is not specified in the contents.

[Positive electrode active material for lithium secondary battery]
The positive electrode active material for a lithium secondary battery of the present invention (hereinafter sometimes referred to as “positive electrode active material”) is composed of a compound having a structure capable of desorbing and inserting Li ions, and at least specified. The two types of compounds (lithium-containing transition metal compound powder A and lithium-containing transition metal compound powder B) are mixed, and the mercury intrusion amount by the mercury intrusion method is 0.75 cm ³ / g or less. Features.

<Lithium-containing transition metal compound powder A>
The lithium-containing transition metal compound powder A in the present invention is characterized by having a spherical secondary particle form having surface irregularities and internal voids. Here, “having surface irregularities” means that primary particles having a non-constant size and shape are randomly aggregated to form spherical secondary particles, and the surface is not smooth and undulated. It refers to having a rich form. In addition, “having internal voids” means that there are not a few voids (including both open voids and closed voids) in the secondary particles, and that the void shape is complicated. Is one of the features. Such morphological features can be confirmed, for example, by a scanning electron microscope (SEM) of the surface or cross section, and the degree of voids present in the powder is measured, for example, by pore volume by mercury porosimetry. This can be confirmed.

<Lithium-containing transition metal compound powder B>
The lithium-containing transition metal compound powder B in the present invention is characterized by comprising primary particles having a size that can be filled in the surface irregularities of the secondary particles and the internal opening voids of the lithium-containing transition metal compound powder A. Such primary particles are preferably monodispersed and fine.

  The method for obtaining the lithium-containing transition metal compound powder B is not particularly limited as long as the morphological characteristics can be obtained. For example, the lithium compound, at least one kind of transition metal compound, and firing A slurry preparation step for obtaining a slurry in which an additive for suppressing grain growth and sintering at the time is pulverized in a liquid medium to uniformly disperse them, and a spray drying step for spray drying the obtained slurry; It can be obtained by a production method including at least a firing step of firing the obtained spray-dried powder and a classification step of classifying the obtained fired body.

<Mercury intrusion method>
The positive electrode active material for a lithium secondary battery of the present invention is a mixture of the lithium-containing transition metal compound powder A and the lithium-containing transition metal compound powder B, and has specific conditions in the measurement by mercury porosimetry. It is characterized by satisfying. Therefore, the mercury intrusion method will be briefly described below. The mercury intrusion method is a method for obtaining information such as specific surface area and pore size distribution from the relationship between pressure and the amount of mercury intruded into a pore of a sample such as porous particles while applying pressure. It is.

  Specifically, first, the container containing the sample is evacuated and filled with mercury. Mercury has a high surface tension, and as it is, mercury does not penetrate into the pores on the sample surface, but when pressure is applied to the mercury and the pressure is gradually increased, the pores increase in size from the smallest to the smallest. Gradually mercury enters the pores. If a change in the mercury liquid level (that is, the amount of mercury intruded into the pores) is detected while the pressure is continuously increased, a mercury intrusion curve representing the relationship between the pressure applied to the mercury and the amount of mercury intruded can be obtained. .

Here, assuming that the pore shape is cylindrical, the radius thereof is r, the surface tension of mercury is δ, and the contact angle is θ, the size in the direction of pushing mercury out of the pore is −2πrδ (cos θ (If θ> 90 °, this value is positive). Further, since the magnitude of the force in the direction of pushing mercury into the pores under the pressure P is represented by πr ² P, the following formulas (1) and (2) are derived from the balance of these forces. It will be.

−2πrδ (cos θ) = πr ² P (1)
Pr = -2δ (cos θ) (2)

In the case of mercury, values of surface tension δ = 480 dyn / cm and contact angle θ = 140 ° are generally used. When these values are used, the radius of the pore into which mercury is injected under the pressure P is expressed by the following formula (3).
r (nm) = (7.5 × 10 ⁸ ) / P (Pa) (3)

  That is, since there is a correlation between the pressure P applied to mercury and the radius r of the pore into which mercury enters, the size of the pore radius of the sample and its volume are calculated based on the obtained mercury intrusion curve. A pore distribution curve representing the relationship can be obtained. For example, when the pressure P is changed from 0.1 MPa to 100 MPa, the pores in the range from about 7500 nm to about 7.5 nm can be measured.

  Note that the approximate measurement limit of the pore radius by the mercury intrusion method is that the lower limit is about 2 nm or more and the upper limit is about 200 μm or less, and the pores in a relatively large range compared to the nitrogen adsorption method described later. It can be said that it is suitable for analysis of distribution.

  Measurement by the mercury intrusion method can be performed using an apparatus such as a mercury porosimeter. Specific examples of the mercury porosimeter include an autopore manufactured by Micromeritics, a pore master manufactured by Quantachrome, and the like.

The positive electrode active material for a lithium secondary battery according to the present invention has a mercury intrusion amount of 0.75 cm ³ / g or less at a pressure increase from a pressure of 3.86 kPa to 413 MPa in a mercury intrusion curve by a mercury intrusion method. Features. The mercury intrusion amount is essential to be 0.75 cm ³ / g or less, preferably 0.73 cm ³ / g or less, more preferably 0.70 cm ³ / g or less. The lower limit is not particularly limited, but is usually 0.1 cm ³ / g or more, preferably 0.2 cm ³ / g or more, more preferably 0.4 cm ³ / g or more, particularly preferably 0.5 cm ³ / g or more. . When the upper limit of this range is exceeded, the gap becomes excessive, and when the positive electrode active material of the present invention is used as the positive electrode material, the filling rate of the positive electrode active material into the positive electrode plate is lowered, and the battery capacity is restricted. There is a case. On the other hand, if the lower limit of this range is not reached, voids between the particles become excessively small. Therefore, when a battery is produced using the positive electrode active material of the present invention as a positive electrode material, lithium diffusion between particles is inhibited, and load characteristics are reduced. May decrease.

  In the positive electrode active material of the present invention, when a pore distribution curve is measured by a mercury intrusion method described later, it is usually preferable that a specific peak described below is present. In the present specification, the “pore distribution curve” means the total pore volume per unit weight (usually 1 g) of pores having a radius equal to or larger than the logarithm of the radius of the pores on the horizontal axis. Is the value obtained by differentiating the logarithm of the pore radius (Log Differential Intrusion (mL / g)) on the vertical axis, and the plotted points are usually connected. Represent as a graph. In particular, a pore distribution curve obtained by measuring the positive electrode active material of the present invention by mercury porosimetry is referred to as “a pore distribution curve in the present invention” as appropriate in the following description.

  In the present specification, “peak top” refers to the point at which the coordinate value of the vertical axis takes the largest value in each peak of the pore distribution curve.

<Peak possessed by pore distribution curve>
In the peak of the pore distribution curve in the present invention, the peak top has a pore radius of usually 80 nm or more, preferably 100 nm or more, more preferably 200 nm or more, most preferably 300 nm or more, and usually 800 nm or less, preferably It is desirable that it exists in the range of 700 nm or less, more preferably 600 nm or less, more preferably 500 nm or less, and most preferably 400 nm or less.

  When the upper limit of this range is exceeded, when a battery is produced using the positive electrode material of the present invention, lithium diffusion in the positive electrode material may be inhibited, or the conductive path may be insufficient, resulting in a decrease in load characteristics. . On the other hand, below the lower limit of this range, when a positive electrode is produced using the porous particles of the present invention, the necessary amount of conductive material and binder increases, and the positive electrode plate (positive electrode current collector) is increased. The filling rate of the active material is restricted, and the battery capacity may be restricted. In addition, with the formation of fine particles, the mechanical properties of the coating film at the time of coating become hard or brittle, and the coating film may be easily peeled off during the winding process during battery assembly.

Further, the pore volume of the peak of the pore distribution curve in the present invention are preferably usually 0.01 cm ³ / g or more, preferably 0.05 cm ³ / g or more, more preferably 0.08 cm ³ / g or more, most preferably 0.1 cm ³ / g or more and usually 0.5 cm ³ / g or less, preferably 0.4 cm ³ / g or less, more preferably 0.35 cm ³ / g or less, and most preferably 0 .3 cm ³ / g or less. When the upper limit of this range is exceeded, the gap becomes excessive, and when the positive electrode active material of the present invention is used as the positive electrode material, the filling rate of the positive electrode active material into the positive electrode plate becomes low and the battery capacity is limited. There is. On the other hand, if the lower limit of this range is exceeded, voids between particles become excessively small, so when a battery is produced using the positive electrode active material of the present invention as a positive electrode material, lithium diffusion between secondary particles is inhibited, Load characteristics may deteriorate.

  The pore distribution curve in the present invention may have a plurality of peaks in other ranges in addition to the peak appearing in the range of the pore radius described above.

In the pore distribution curve in the present invention, when a peak exists at a pore radius of 800 nm or more and 2000 nm, the upper limit thereof is preferably 1800 nm or less, particularly preferably 1500 nm or less, and the lower limit thereof is preferably 1000 nm or more, preferably It is 1200 nm or more. Further, the pore volume is preferably usually 0.5 cm ³ / g or less, preferably 0.4 cm ³ / g or less, more preferably 0.35 cm ³ / g or less, and most preferably 0.3 cm ³ / g or less. If the upper limit of the pore volume range is exceeded, voids between secondary particles become excessive, and when the positive electrode active material of the present invention is used as a positive electrode material, the filling rate of the positive electrode active material into the positive electrode plate becomes low. The battery capacity may be limited.

  The mercury intrusion amount of the positive electrode active material for the lithium secondary battery of the present invention is the smaller amount of mercury intrusion of the lithium-containing transition metal compound powder A or B before becoming the positive electrode active material (mixture) of the present invention. On the other hand, it is preferably 98% or less, more preferably 95% or less, particularly preferably 90% or less, usually 40% or more, preferably 50% or more, more preferably 60% or more, and particularly preferably 70% or more. is there. When the upper limit of this range is exceeded, the voids become excessive, and when the positive electrode active material of the present invention is used as the positive electrode material, the filling rate of the positive electrode active material into the positive electrode plate is lowered, and the battery capacity is restricted. On the other hand, if the lower limit of this range is not reached, voids between the particles become excessively small. Therefore, when a battery is produced using the positive electrode active material of the present invention as a positive electrode material, lithium diffusion between particles is inhibited, and load characteristics are reduced. May decrease.

  Moreover, the range of the mixing ratio of the lithium-containing transition metal compound powder A and the lithium-containing transition metal compound powder B is usually 20/1 or less, preferably 15/1 or less, in terms of weight ratio (A / B). Preferably it is 10/1 or less, most preferably 5/1 or less, usually 1/20 or more, preferably 1/15 or more, more preferably 1/10 or more, and most preferably 1/5 or more. If it deviates from this range, it may be difficult to obtain the effects of the present invention.

<Bulk density>
The bulk density of the positive electrode active material for a lithium secondary battery of the present invention is usually 1.6 g / cm ³ or more, preferably 1.7 g / cm ³ or more, more preferably 1.8 g / cm ³ or more, most preferably 1.9 g / cm ³ or more, usually 2.4 g / cm ³ or less, preferably 2.3 g / cm ³ or less, more preferably 2.1 g / cm ³ or less, and most preferably 2.0 g / cm ³ or less. is there. It is preferable for the bulk density to exceed this upper limit to improve the powder filling property and the electrode density, while the specific surface area may become too low, and the battery performance may deteriorate. When the bulk density is lower than this lower limit, the powder filling property and electrode preparation may be adversely affected.

In the present invention, the bulk density is 4 to 10 g of lithium transition metal compound powder in a 10 mL glass measuring cylinder and tapped 200 times with a stroke of about 20 mm (tap density) g / Obtained as cm ³ .

<Median diameter and 90% integrated diameter ( _D90 )>
The median diameter of the positive electrode active material for a lithium secondary battery of the present invention is usually 0.1 μm or more, preferably 0.3 μm or more, more preferably 0.5 μm or more, still more preferably 0.8 μm or more, and most preferably 1 μm. As described above, it is usually 20 μm or less, preferably 15 μm or less, more preferably 10 μm or less, still more preferably 9 μm or less, and most preferably 6 μm or less. When the median diameter is less than this lower limit, there may be a problem in applicability at the time of forming the positive electrode active material layer, and when the upper limit is exceeded, battery performance may be deteriorated.

Further, the 90% cumulative diameter (D ₉₀ ) of the secondary particles of the positive electrode active material for a lithium secondary battery of the present invention is usually 40 μm or less, preferably 30 μm or less, more preferably 20 μm or less, still more preferably 18 μm or less, most preferably It is preferably 12 μm or less, usually 0.5 μm or more, preferably 1 μm or more, more preferably 1.5 μm or more, and most preferably 2 μm or more. When the 90% cumulative diameter (D ₉₀ ) exceeds the above upper limit, battery performance may be deteriorated. When the 90% integrated diameter (D ₉₀ ) is less than the lower limit, there may be a problem in applicability when forming the positive electrode active material layer.

In the present invention, the median diameter and the 90% integrated diameter (D ₉₀ ) as the average particle diameter are set to a refractive index of 1.24 using a known laser diffraction / scattering particle size distribution measuring device, and the particle diameter standard is determined. Measured as a volume reference. In the present invention, a 0.1 wt% sodium hexametaphosphate aqueous solution was used as a dispersion medium used in the measurement, and measurement was performed after 5 minutes of ultrasonic dispersion (output 30 W, frequency 22.5 kHz).

<BET specific surface area>
The positive electrode active material for a lithium lithium secondary battery of the present invention has a BET specific surface area of usually 0.5 m ² / g or more, preferably 0.8 m ² / g or more, more preferably 1.0 m ² / g or more, Most preferably, it is 1.3 m ² / g or more, usually 5 m ² / g or less, preferably 4 m ² / g or less, more preferably 3 m ² / g or less, and most preferably 2.8 m ² / g or less. If the BET specific surface area is smaller than this range, the battery performance is likely to be lowered. If the BET specific surface area is larger, the bulk density is hardly increased, and a problem may occur in applicability at the time of forming the positive electrode active material.

  The BET specific surface area is measured by a known BET powder specific surface area measuring device. In the present invention, Okura Riken: AMS8000 type fully automatic powder specific surface area measurement device is used, nitrogen is used as the adsorption gas, helium is used as the carrier gas, and the measurement is performed by the BET one-point method by the continuous flow method. Is done. Specifically, the powder sample was heated and deaerated with a mixed gas at a temperature of 150 ° C., then cooled to liquid nitrogen temperature to adsorb the mixed gas, and then heated to room temperature with water to be adsorbed. Nitrogen gas was desorbed, the amount was detected by a heat conduction detector, and the specific surface area of the sample was calculated therefrom.

<Volume resistivity>
The volume resistivity value when the positive electrode active material for a lithium secondary battery of the present invention is compacted at a pressure of 40 MPa is preferably 1 × 10 ³ Ω · cm or more as a lower limit, and 5 × 10 ³ Ω · cm. The above is more preferable, and 1 × 10 ⁴ Ω · cm or more is even more preferable. The upper limit is preferably 1 × 10 ⁶ Ω · cm or less, more preferably 5 × 10 ⁵ Ω · cm or less, and still more preferably 1 × 10 ⁵ Ω · cm or less. If this volume resistivity exceeds this upper limit, the load characteristics as a battery may deteriorate. On the other hand, if the volume resistivity falls below this lower limit, the safety and the like when used as a battery may be reduced.

  In the present invention, the volume resistivity of the positive electrode active material for a lithium secondary battery is such that the four probe / ring electrode, the electrode spacing is 5.0 mm, the electrode radius is 1.0 mm, the sample radius is 12.5 mm, and the applied voltage limiter is Is the volume resistivity measured in a state where the lithium transition metal-based compound powder is compacted at a pressure of 40 MPa, with 90V. The volume resistivity is measured on a powder under a predetermined pressure by a powder probe unit using a powder resistance measurement device (Dia Instruments, Lorester GP powder resistance measurement system).

<Contained carbon concentration C>
The carbon concentration C (wt%) value of the positive electrode active material for a lithium secondary battery of the present invention is usually 0.01 wt% or more, preferably 0.015 wt% or more, more preferably 0.02 wt% or more. Most preferably 0.3% by weight or more, usually 0.25% by weight or less, preferably 0.2% by weight or less, more preferably 0.15% by weight or less, most preferably 0.1% by weight or less. is there. If the lower limit is not reached, battery performance may be reduced, and if the upper limit is exceeded, swelling due to gas generation when the battery is formed may increase or battery performance may be reduced.

  In the present invention, the carbon content C of the positive electrode active material for a lithium secondary battery is determined by measurement by an oxygen gas combustion (high-frequency heating furnace type) infrared absorption method, as shown in the following examples. In addition, the carbon component contained in the positive electrode active material for a lithium secondary battery obtained by the carbon analysis described later can be regarded as indicating information on the amount of carbonic acid compound, particularly lithium carbonate. This is due to the fact that the carbon amount determined by carbon analysis is assumed to be all derived from carbonate ions, and the carbonate ion concentration analyzed by ion chromatography generally agrees.

  On the other hand, when a composite treatment with conductive carbon is performed as a method for increasing the electron conductivity, a C amount exceeding the specified range may be detected, but such a treatment was performed. The C value in the case is not limited to the specified range.

  Here, the method for producing the lithium-containing transition metal compound powder A is not particularly limited as long as the morphological characteristics can be obtained. For example, the lithium compound and at least one or more kinds of transition metal compounds are used. Are prepared in a liquid medium, and a slurry preparation step for obtaining a slurry in which these are uniformly dispersed, a spray drying step for spray-drying the obtained slurry, and a firing step for firing the obtained spray-dried powder And a production method including at least a classification step of classifying the obtained fired body.

  Further, in producing the lithium-containing transition metal composite oxide powder A, in the slurry preparation step, the lithium compound and the transition metal compound are mixed in a liquid medium with a refractive index using a laser diffraction / scattering particle size distribution analyzer. Is set to 1.24, the particle size reference is volume reference, and the mixture is pulverized until the median diameter measured after 5 minutes of ultrasonic dispersion (output 30 W, frequency 22.5 kHz) is 0.4 μm or less, and spray drying step , When the slurry viscosity at spray drying is V (cp), the slurry supply amount is S (L / min), and the gas supply amount is G (L / min), 50 cp ≦ V ≦ 4000 cp, 500 ≦ G / S Spray drying is performed under the condition of ≦ 10000, and in the firing step, the spray-dried powder is fired at 700 ° C. or higher in an oxygen-containing gas atmosphere. Performance can express.

  Further, in producing the lithium-containing transition metal compound powder A, in the slurry preparation step, the boron-containing compound and the tungsten-containing compound are each 0.01 mol in total with respect to the total molar amount of the transition metal elements in the main component raw material. Particularly excellent performance can be exhibited by firing at 900 ° C. or higher after the combined addition at a ratio of% or more and less than 2 mol%. Here, the range of the addition amount is usually 0.01 mol or more and less than 2 mol%, preferably 0.1 mol% or more and 1.9 mol% or less, more preferably 0.5 mol% or more, It is 1.8 mol% or less, most preferably 1 mol% or more and 1.75 mol% or less. The range of the firing temperature is usually 900 ° C. or higher, preferably 950 ° C. or higher and 1200 ° C. or lower, more preferably 975 ° C. or higher and 1100 ° C. or lower, and most preferably 990 ° C. or higher and 1050 ° C. or lower.

  The method for producing the lithium-containing transition metal compound powder B is not particularly limited as long as the morphological characteristics can be obtained. For example, the lithium compound and at least one or more transition metal compounds , A slurry preparation step for obtaining a slurry in which the additives for suppressing grain growth and sintering during firing are pulverized in a liquid medium, and these are uniformly dispersed, and a spray drying step for spray drying the obtained slurry And a production method including at least a firing step of firing the obtained spray-dried powder and a classification step of classifying the obtained fired body.

  Further, in producing the lithium-containing transition metal compound powder B, in the slurry preparation step, the lithium compound, the transition metal compound, and the additive are mixed in a liquid medium with a laser diffraction / scattering type particle size distribution measuring device. Then, the refractive index is set to 1.24, the particle diameter standard is the volume standard, and the mixture is pulverized until the median diameter measured after 5 minutes of ultrasonic dispersion (output 30 W, frequency 22.5 kHz) is 0.4 μm or less. In the spray drying process, when the slurry viscosity during spray drying is V (cp), the slurry supply amount is S (L / min), and the gas supply amount is G (L / min), 50 cp ≦ V ≦ 4000 cp, 500 Spray drying is performed under the condition of ≦ G / S ≦ 10000, and the spray-dried powder is fired at 900 ° C. or higher in an oxygen-containing gas atmosphere in the firing step. More can be expressed particularly excellent performance.

<Additives that suppress grain growth and sintering during firing>
In the present invention, the “additive that suppresses grain growth and sintering during firing” refers to an active material that suppresses sintering between primary particles or secondary particles during positive electrode active material firing during high temperature firing. This refers to those that have the effect of suppressing the growth of particles and achieving high crystallization, and obtaining a fine powder property having a large number of voids.

  In the present invention, the specific compound added as an additive that suppresses grain growth and sintering during firing is not clear as to the mechanism that exerts the effect of suppressing grain growth and sintering during firing. Since compounds composed of metal elements that can be pentavalent or hexavalent have common effects, they are different from any of the cationic elements that constitute the lithium transition metal compounds. It is possible to stably take an expensive number state such as a valence, and as a result of being hardly dissolved by a solid-phase reaction, it is unevenly distributed on the surface or grain boundary of the lithium transition metal compound particles. Therefore, it is presumed that the mass transfer due to the contact between the positive electrode active material particles is inhibited, and the growth and sintering of the particles are suppressed.

  The type of additive is not particularly limited as long as it exhibits the above effects, but an element selected from the group consisting of Mo, W, Nb, Ta, and Re, which is stable in the high number state. The compound to contain is preferable and an oxide material is used normally.

Exemplary compounds as an _{additive, MoO, MoO 2, MoO 3} , MoO x, Mo 2 O 3, Mo 2 O 5, Li 2 MoO 4, WO, WO 2, WO 3, WO x, W 2 O 3 , W ₂ O ₅ , W ₁₈ O ₄₉ , W ₂₀ O ₅₈ , W ₂₄ O ₇₀ , W ₂₅ O ₇₃ , W ₄₀ O ₁₁₈ , Li ₂ WO ₄ , NbO, NbO ₂ , Nb ₂ O, Nb ₂ O ₅ , Nb ₄ O, Nb ₆ O, LiNbO ₃ , TaO, TaO ₂ , Ta ₂ O ₅ , LiTaO ₃ , ReO ₂ , ReO ₃ , Re ₂ O _{3 and the} like can be mentioned, preferably MoO ₃ , Li ₂ MoO ₄ , WO _{3, Li 2 WO 4, LiNbO} 3, Ta 2 O 5, LiTaO 3, ReO 3 , and more preferably include include _{WO 3, Li 2 WO 4,} ReO 3, most virtuous Properly it can be mentioned WO _3.

  The range of the amount of these additives is usually 0.01 mol% or more, preferably 0.03 mol% or more, more preferably 0, based on the total molar amount of transition metal elements constituting the main component raw material. 0.04 mol% or more, particularly preferably 0.05 mol% or more, usually less than 2 mol%, preferably 1.8 mol% or less, more preferably 1.5 mol% or less, particularly preferably 1.3 mol% or less. It is. If the lower limit is not reached, the above effect may not be obtained. If the upper limit is exceeded, battery performance may be reduced.

In addition, the lithium-containing transition metal compound powder A and / or B in the present invention is a compound having a structure capable of desorbing and inserting Li ions, such as sulfides, phosphate compounds, and lithium transitions. Examples include metal complex oxides. As the sulfide, a strong compound represented by a compound having a two-dimensional layered structure such as TiS ₂ or MoS ₂ or a general formula Me _x Mo ₆ S ₈ (Me is various transition metals such as Pb, Ag, and Cu). Examples include a chevrel compound having a three-dimensional skeleton structure. Examples of the phosphate compound include those belonging to the olivine structure, and are generally represented by LiMePO ₄ (Me is at least one or more transition metals). Specifically, for example, LiFePO ₄ , LiCoPO ₄ , LiNiPO _{4 4} and LiMnPO ₄ .

Examples of the lithium transition metal composite oxide include spinel structures capable of three-dimensional diffusion and those belonging to a layered structure capable of two-dimensional diffusion of lithium ions. Those having a spinel structure are generally represented as LiMe ₂ O ₄ (Me is at least one or more transition metals), specifically, for example, LiMn ₂ O ₄ , LiCoMnO ₄ , LiNi _0.5 Mn _{1. 5} O ₄ , CoLiVO _{4 and the} like. Those having a layered structure are generally expressed as LiMeO ₂ (Me is at least one or more transition metals). Specifically, for example, LiCoO ₂ , LiNiO ₂ , LiNi _1-x Co _x O ₂ , LiNi _{1 -x-y Co x Mn y O} 2, LiNi 0.5 Mn 0.5 O 2, Li 1.2 Cr 0.4 Mn 0.4 O 2, Li 1.2 Cr 0.4 Ti 0.4 O ₂ , LiMnO _{2 and the} like.

  The lithium-containing transition metal compound powder A and / or B in the present invention preferably includes a crystal structure belonging to an olivine structure, spinel structure, or layered structure from the viewpoint of lithium ion diffusion. Among these, those including a crystal structure belonging to a layered structure are particularly preferable.

Here, the layered structure will be described in more detail. As a typical crystal system having a layered structure, there are those belonging to the α-NaFeO ₂ type such as LiCoO ₂ and LiNiO ₂ , which are hexagonal and have a space group due to their symmetry.
Is attributed to Hereinafter, this may be referred to as a “layered R (−3) m structure”.

However, the layered LiMeO ₂ is not limited to the layered R (−3) m structure. In addition, LiMnO ₂ called so-called layered Mn is an orthorhombic and space-group Pm2m layered compound, and Li ₂ MnO ₃ called so-called 213 phase is Li [Li _1/3 Mn _{2 / 3} ] O ₂ , which is a monoclinic space group C2 / m structure, but is also a layered compound in which a Li layer, a [Li _1/3 Mn _2/3 ] layer and an oxygen layer are laminated.

<Lithium nickel manganese cobalt based composite oxide>
In addition, the lithium-containing transition metal compound powder A and / or B in the present invention is mainly composed of a lithium nickel manganese cobalt-based composite oxide including a crystal structure belonging to a layered structure. It is more preferable that the composition is represented by the following formula (I).
LiMO ₂ (I)

  In the formula (I), M is an element composed of Li, Ni and Mn, or Li, Ni, Mn and Co, and the Mn / Ni molar ratio is usually 0.1 or more, preferably 0.3 or more. More preferably 0.5 or more, particularly preferably 0.6 or more, still more preferably 0.7 or more, still more preferably 0.8 or more, most preferably 0.9 or more, usually 5 or less, preferably 4 or less. , More preferably 3 or less, particularly preferably 2.5 or less, and most preferably 1.5 or less. The Co / (Mn + Ni + Co) molar ratio is usually 0 or more, preferably 0.01 or more, more preferably 0.02 or more, still more preferably 0.03 or more, most preferably 0.05 or more, usually 0.35 or less, Preferably it is 0.345 or less, More preferably, it is 0.34 or less. The molar ratio of Li in M is usually 0.001 or more, preferably 0.01 or more, more preferably 0.02 or more, still more preferably 0.03 or more, most preferably 0.04 or more, usually 0.2 or less. , Preferably 0.19 or less, more preferably 0.18 or less, still more preferably 0.17 or less, and most preferably 0.15 or less.

  In the above composition formula (I), the atomic ratio of the oxygen amount is described as 2 for convenience, but there may be some non-stoichiometry. In the case of non-stoichiometry, the atomic ratio of oxygen is usually in the range of 2 ± 0.2, preferably in the range of 2 ± 0.15, more preferably in the range of 2 ± 0.12, and even more preferably 2 ± 0. It is in the range of 10, particularly preferably in the range of 2 ± 0.05.

<Preferred composition>
The lithium-containing transition metal compound powders A and / or B that are constituent elements of the present invention are particularly preferably those in which the atomic configuration in the M site in the composition formula (I) is represented by the following formula (II).
M = Li _{z / (2 + z)} {(Ni _{(1 + y) / 2} Mn _{(1-y) / 2} ) _1-x Co _x } _{2 / (2 + z)} (II)

And x, y, z in the above formula (II) usually satisfies the following relational expression.
0.1 <x ≦ 0.35,
−0.1 ≦ y ≦ 0.1,
(1-x) (0.02-0.98y) ≤z≤ (1-x) (0.20-0.88y)

  In the above formula (II), the value of x is usually larger than 0.1, preferably 0.15 or more, more preferably 0.2 or more, further preferably 0.25 or more, most preferably 0.30 or more, Usually 0.35 or less, preferably 0.345 or less, and most preferably 0.34 or less.

  The value of y is usually -0.1 or more, preferably -0.05 or more, more preferably -0.03 or more, most preferably -0.02 or more, usually 0.1 or less, preferably 0.05 or less. More preferably, it is 0.03 or less, and most preferably 0.02 or less.

  The value of z is usually (1-x) (0.02-0.98y) or more, preferably (1-x) (0.03-0.98y) or more, more preferably (1-x) (0 0.04-0.98y) or more, more preferably (1-x) (0.05-0.98y) or more, most preferably (1-x) (0.10-0.98y) or more, usually (1 -X) (0.20-0.88y) or less, preferably (1-x) (0.18-0.88y) or less, more preferably (1-x) (0.17-0.88y), Most preferably, it is (1-x) (0.16-0.88y) or less. When z is less than this lower limit, the conductivity is reduced, and when it exceeds the upper limit, the amount of substitution to transition metal sites is excessive and the battery capacity is lowered, leading to a decrease in performance of a lithium secondary battery using this. There is. On the other hand, if z is too large, the carbon dioxide absorbability of the active material powder increases, which may make it easier to absorb carbon dioxide in the atmosphere. As a result, it is estimated that the concentration of contained carbon increases.

In addition, the lithium-containing transition metal compound powder B which is a constituent element of the present invention is particularly preferably one in which the atomic configuration in the M site in the composition formula (I) is represented by the following formula (III).
M = Li _{z ′ / (2 + z ′)} {(Ni _{(1 + y ′) / 2} Mn _{(1-y ′) / 2} ) _{1-x ′} Co _{x ′} } _{2 / (2 + z ′)} ( III)
here,
0 ≦ x ′ ≦ 0.1,
−0.1 ≦ y ′ ≦ 0.1,
(1-x ′) (0.05−0.98y ′) ≦ z ′ ≦ (1-x ′) (0.20−0.88y ′)
Those within the range are preferred.

  In the above formula (III), the value of x ′ is usually 0 or more, preferably 0.01 or more, more preferably 0.02 or more, still more preferably 0.03 or more, most preferably 0.04 or more, usually 0. 1 or less, preferably 0.098 or less, more preferably 0.09 or less, further preferably 0.08 or less, more preferably 0.07 or less, and most preferably 0.05 or less. The value of y ′ is usually −0.1 or more, preferably −0.05 or more, more preferably −0.03 or more, most preferably −0.02 or more, usually 0.1 or less, preferably 0.05 or less. More preferably, it is 0.03 or less, and most preferably 0.02 or less.

  The value of z ′ is usually (1−x ′) (0.05−0.98y ′) or more, preferably (1−x ′) (0.06−0.98y ′) or more, more preferably (1− x ′) (0.07−0.98y ′) or more, more preferably (1−x ′) (0.08−0.98y ′) or more, most preferably (1−x ′) (0.10− 0.98y ') or more and usually (1-x') (0.20-0.88y ') or less, preferably (1-x') (0.18-0.88y ') or less, more preferably ( 1-x ') (0.17-0.88y'), most preferably (1-x ') (0.16-0.88y') or less. If the lower limit is not reached, the conductivity decreases, and if the upper limit is exceeded, the amount of substitution to the transition metal site becomes too large, resulting in a decrease in battery capacity. . On the other hand, if z ′ is too large, the carbon dioxide absorbability of the active material powder is increased, which may make it easier to absorb carbon dioxide in the atmosphere. As a result, it is estimated that the concentration of contained carbon increases.

  Here, when the x ′ value is in the range of 0 ≦ x ′ ≦ 0.1 and the amount of Co is small, the cost is reduced and the lithium secondary battery is designed to be charged at a high charging potential. As a result, the charge / discharge capacity, cycle characteristics, and safety are improved.

  In addition, foreign elements may be introduced into the lithium-containing transition metal compound powder A and / or B of the present invention. Different elements include B, Na, Mg, Al, Si, K, Ca, Ti, V, Cr, Fe, Mn, Co, Ni, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, and Mo. , Ru, Rh, Pd, Ag, In, Sn, Sb, Te, Ba, Ta, W, Re, Os, Ir, Pt, Au, Pb, Bi, La, Ce, Pr, Nd, Sm, Eu, Gd , Tb, Dy, Ho, Er, Tm, Yb, Lu, N, F, P, S, Cl, Br, and I are selected from one or more. These foreign elements may be incorporated into the crystal structure of the lithium-containing transition metal compound powder A and / or B, or may not be incorporated into the crystal structure of the lithium-containing transition metal compound powder A and / or B, It may be unevenly distributed as a simple substance or a compound on the particle surface, crystal grain boundary or the like.

  In addition, in the composition range of the above formulas (II) and (III), as the z and z ′ values are closer to the lower limit, which is a constant ratio, the rate characteristics and output characteristics of the battery tend to be lower, and vice versa. However, the closer the z and z ′ values are to the upper limit, the higher the rate characteristics and output characteristics of the battery, but there is a tendency for the capacity to decrease. In addition, the lower the y and y ′ values, that is, the smaller the manganese / nickel atomic ratio, the lower the charging voltage, the higher the capacity, the lower the cycle characteristics and safety of the battery set high charging voltage is seen, Conversely, as the y and y ′ values are closer to the upper limit, the cycle characteristics and safety of the battery set at a higher charge voltage are improved, while the discharge capacity, rate characteristics, and output characteristics tend to decrease. In addition, the closer the x and x ′ values are to the lower limit, the lower the load characteristics such as the rate characteristics and output characteristics of the battery, and conversely, the closer the x and x ′ values are to the upper limit, However, if this upper limit is exceeded, cycle characteristics and safety when set at a high charge voltage will be reduced, and raw material costs will be increased. It is an important component of the present invention that the composition parameters x, x ', y, y', z, and z 'are within a specified range.

  Here, the preferred composition of the lithium-containing transition metal compound powder A which is a constituent element of the present invention and the lithium nickel manganese cobalt-based composite oxide which is the composition of the lithium-containing transition metal compound powder B defined by the formula (III) The chemical meaning of the Li composition (z, z ′ and x, x ′) will be described in more detail below.

  As described above, the layered structure is not necessarily limited to the R (-3) m structure, but is preferably one that can be attributed to the R (-3) m structure from the viewpoint of electrochemical performance.

  To determine x, x ′, y, y ′, z, and z ′ of the composition formula of the lithium transition metal compound, each transition metal and Li are analyzed with an inductively coupled plasma emission spectrometer (ICP-AES). And it calculates by calculating | requiring the ratio of Li / Ni / Mn / Co.

  From a structural point of view, it is considered that Li related to z and z ′ is substituted for the same transition metal site. Here, Li related to z and z 'causes the average valence of Ni to be greater than 2 due to the principle of charge neutrality (trivalent Ni is generated). Since z and z 'increase the Ni average valence, they become indices of the Ni valence (the ratio of Ni (III)).

In addition, when calculating the Ni valence (m) accompanying the change of z and z ′ from the above composition formula, it is assumed that the Co valence is trivalent and the Mn valence is tetravalent.
It becomes.

  This calculation result means that the Ni valence is not determined only by z and z ', but is a function of x, x' and y, y '. If z, z '= 0 and y, y' = 0, the Ni valence remains divalent regardless of the values of x, x '. When z and z ′ are negative values, it means that the amount of Li contained in the active material is less than the stoichiometric amount, and those having a very large negative value are effective for the present invention. It may not be. On the other hand, even if the z and z ′ values are the same, the Ni valence becomes higher as the composition is richer in Ni (larger y value) and / or richer in Co (larger x value). In this case, the rate characteristic and the output characteristic are improved, but on the other hand, the capacity tends to decrease. From this, it can be said that it is more preferable to define the upper and lower limits of the z and z 'values as a function of x, x' and y, y '.

  The lithium-containing transition metal compound powder B, which is a constituent of the present invention, preferably further contains at least one element selected from Mo, W, Nb, Ta and Re. It is especially preferable that it contains.

<Average primary particle size>
The average primary particle diameter (average primary particle diameter) of the positive electrode active material for a lithium secondary battery of the present invention is not particularly limited, but the lower limit is preferably 0.01 μm or more, more preferably 0.05 μm or more. The upper limit is preferably 3 μm or less, more preferably 2.5 μm or less, still more preferably 2 μm or less, and most preferably 1.5 μm or less. is there. When the average primary particle diameter exceeds the above upper limit, it may adversely affect the powder filling property or the specific surface area may decrease, which increases the possibility that the battery performance such as rate characteristics and output characteristics will decrease. There is. On the other hand, if the lower limit is not reached, problems such as inferior reversibility of charge and discharge may occur due to undeveloped crystals.

<Reason why the positive electrode active material for a lithium secondary battery of the present invention brings about the above-mentioned effect>
The reason why the positive electrode active material for a lithium secondary battery of the present invention brings about the above-described effect is considered as follows.
In other words, when the specific mixture of the present invention is used, battery performance with improved balance between load characteristics and powder physical properties (fillability) can be exhibited as compared with the case where each single lithium transition metal composite oxide powder is used. . Particularly for low temperature resistance, by optimizing the mixing ratio, it is possible to obtain performance superior to the case where each is used alone. Also, the bulk density can be improved as compared with the case where each is used alone. By the way, as a reason why a mixture of specific active material powders provides superior characteristics than each single substance, and a reason why a mixture of specific active material powders exhibits characteristics superior to other mixtures, powder physical properties ( As a result of the difference in morphology) acting in a good direction, it is presumed that a synergistic effect was developed.

[Method for producing positive electrode active material for lithium secondary battery]
In the method for producing a positive electrode active material for a lithium secondary battery according to the present invention, a lithium compound and at least one transition metal compound are pulverized in a liquid medium to obtain a slurry in which these are uniformly dispersed. Lithium-containing produced by including a slurry preparation step, a spray drying step of spray drying the obtained slurry, a firing step of firing the obtained spray dried powder, and a classification step of classifying the obtained fired body The transition metal compound powder A, the lithium compound, at least one transition metal compound, and an additive that suppresses grain growth and sintering during firing are pulverized in a liquid medium, and these are uniformly dispersed. A slurry preparing step for obtaining the slurry, a spray drying step for spray drying the obtained slurry, a firing step for firing the obtained spray-dried powder, and a classification for classifying the obtained fired body It is suitably prepared by mixing the produced lithium-containing transition metal compound powder B contains degree.

  Below, the manufacturing method of the positive electrode active material material for lithium secondary batteries of this invention is demonstrated in detail taking a lithium nickel manganese cobalt type complex oxide as an example.

<Slurry preparation process>
Among the raw material compounds used for preparing the slurry in producing the lithium-containing transition metal composite oxide powders A and B by the method of the present invention, the lithium compounds include Li ₂ CO ₃ , LiNO ₃ , LiNO ₂ and LiOH. , LiOH.H ₂ O, LiH, LiF, LiCl, LiBr, LiI, CH ₃ OOLi, Li ₂ O, Li ₂ SO ₄ , dicarboxylic acid Li, Li citrate, fatty acid Li, alkyl lithium and the like. Among these lithium compounds, lithium compounds containing no nitrogen atom, sulfur atom, or halogen atom are preferable because they do not generate harmful substances such as SO _x and NO _x during the firing treatment. It is a compound that tends to form voids by generating cracked gas in the secondary particles of spray-dried powder due to generation of cracked gas, etc. Considering these points, Li ₂ CO ₃ , LiOH, among others LiOH.H ₂ O is preferable, and Li ₂ CO ₃ is particularly preferable because it is easy to handle and relatively inexpensive. These lithium compounds may be used individually by 1 type, and may use 2 or more types together.

Further, when nickel is included as a constituent element of the lithium-containing transition metal composite oxide powder A and / or B, the nickel compound used for the production thereof is Ni (OH) ₂ , NiO, NiOOH, NiCO ₃ , 2NiCO ₃・ 3Ni (OH) ₂ .4H ₂ O, NiC ₂ O ₄ .2H ₂ O, Ni (NO ₃ ) ₂ .6H ₂ O, NiSO ₄ , NiSO ₄ .6H ₂ O, fatty acid nickel, nickel halide, etc. It is done. Among these, Ni (OH) ₂ , NiO, NiOOH, NiCO ₃ , 2NiCO ₃ .3Ni (OH) ₂ .4H ₂ O, NiC are used in that no harmful substances such as SO _X and NO _X are generated during the firing process. Nickel compounds such as ₂ O ₄ .2H ₂ O are preferred. Furthermore, Ni (OH) ₂ , NiO, NiOOH, and NiCO ₃ are preferable from the viewpoint of being inexpensively available as industrial raw materials and high reactivity, and further, since a decomposition gas is generated during firing, etc. Ni (OH) ₂ , NiOOH, and NiCO ₃ are particularly preferable from the viewpoint of easily forming voids in the secondary particles of the dry powder. These nickel compounds may be used individually by 1 type, and may use 2 or more types together.

Further, when manganese is included as a constituent element of the lithium-containing transition metal composite oxide powder A and / or B, manganese compounds used for the production thereof include manganese oxidation such as Mn ₂ O ₃ , MnO ₂ , Mn ₃ O _4, etc. Products, manganese salts such as MnCO ₃ , Mn (NO ₃ ) ₂ , MnSO ₄ , manganese acetate, manganese dicarboxylate, manganese citrate, and fatty acid manganese, and halides such as oxyhydroxide and manganese chloride. Among these manganese compounds, MnO ₂ , Mn ₂ O ₃ , Mn ₃ O ₄ , and MnCO ₃ do not generate gases such as SO _X and NO _X during firing, and can be obtained at low cost as industrial raw materials. Therefore, it is preferable. These manganese compounds may be used individually by 1 type, and may use 2 or more types together.

Further, when nickel is included as a constituent element of the lithium-containing transition metal composite oxide powder A and / or B, as the cobalt compound used for the production, Co (OH) ₂ , CoOOH, CoO, Co ₂ O ₃ , Examples thereof include Co ₃ O ₄ , Co (OCOCH ₃ ) ₂ .4H ₂ O, CoCl ₂ , Co (NO ₃ ) ₂ .6H ₂ O, Co (SO ₄ ) ₂ .7H ₂ O, CoCO _{3 and the} like. Among them, Co (OH) ₂ , CoOOH, CoO, Co ₂ O ₃ , Co ₃ O ₄ , and CoCO ₃ are preferable, and more preferably, from the viewpoint that no harmful substances such as SO _X and NO _X are generated during the firing process. Co (OH) ₂ and CoOOH are industrially inexpensively available and highly reactive. In addition, Co (OH) ₂ , CoOOH, and CoCO ₃ are particularly preferable from the viewpoint of easily forming voids in the secondary particles of the spray-dried powder due to generation of decomposition gas during firing. These cobalt compounds may be used individually by 1 type, and may use 2 or more types together.

Further, the transition metal compound raw material is not limited to a single element compound, and a compound in which a plurality of elements are complexed such as a complex oxide or a complex hydroxide may be used. Examples of compounds include
_{(Ni 1-a-b Mn} a Co b) 3 O 4, include _{(Ni 1-a-b Mn} a Co b) (OH) 2 and the like.

  In addition to the above Li, Ni, Mn, and Co raw material compounds, other elements are used, or other elements are substituted to introduce the above-mentioned foreign elements, or secondary formed by spray drying described later. It is possible to use a compound group for the purpose of efficiently forming voids in the particles. In addition, the addition stage of the compound used for the purpose of efficiently forming the voids of the secondary particles used here can be selected either before or after mixing the raw materials depending on the property. It is. In particular, it is preferable to add a compound which is easily decomposed due to mechanical shear stress applied by the mixing step after the mixing step.

  Moreover, as an additive which suppresses the grain growth and sintering at the time of baking used for manufacture of lithium containing transition metal complex oxide powder B, as long as it expresses the target effect as mentioned above, Although there is no particular limitation on the type, a compound containing an element selected from elements such as Mo, W, Nb, Ta, and Re, which are stable in an expensive number state, is preferable, and an oxide material is usually used.

Specific examples of additives that suppress grain growth and sintering during firing include, for example, MoO, MoO ₂ , MoO ₃ , MoO _x , Mo ₂ O ₃ , Mo ₂ O ₅ , and Li ₂ MoO _{4. , WO, WO 2, WO 3} , WO x, W 2 O 3, W 2 O 5, W 18 O 49, W 20 O 58, W 24 O 70, W 25 O 73, W 40 O 118, Li 2 WO _{4, NbO, NbO 2, Nb} 2 O, Nb 2 O 5, Nb 4 O, Nb 6 O, LiNbO 3, TaO, TaO 2, Ta 2 O 5, LiTaO 3, ReO 2, ReO 3, Re 2 O 3 etc., and preferably _{MoO 3, Li 2 MoO 4,} WO 3, Li 2 WO 4, LiNbO 3, Ta 2 O 5, LiTaO 3, ReO 3 . particularly preferred _WO 3, L ₂ WO _4, ReO _3, and the like, most preferably include WO _3. These additives may be used individually by 1 type, and may use 2 or more types together.

  The method for mixing the raw materials is not particularly limited, and may be wet or dry. For example, a method using an apparatus such as a ball mill, a vibration mill, or a bead mill can be used. Wet mixing in which the raw material compound is mixed in a liquid medium such as water or alcohol is preferable because more uniform mixing is possible and the reactivity of the mixture can be increased in the firing step. The mixing time varies depending on the mixing method, but it is sufficient that the raw materials are uniformly mixed at the particle level. For example, a ball mill (wet or dry type) usually takes about 1 to 2 days, and a bead mill (wet continuous method) residence time. Is usually about 0.1 to 6 hours.

  In the raw material mixing stage, it is preferable that the raw material is pulverized in parallel. As the degree of pulverization, the particle diameter of the raw material particles after pulverization is an index, but the average particle diameter (median diameter) is usually 0.4 μm or less, preferably 0.3 μm or less, more preferably 0.25 μm or less, Most preferably, it is 0.2 μm or less. If the average particle size of the pulverized raw material particles is too large, the reactivity in the firing process is lowered, and the composition is difficult to homogenize. However, making particles smaller than necessary leads to an increase in the cost of pulverization, so that the average particle size is usually 0.01 μm or more, preferably 0.02 μm or more, more preferably 0.05 μm or more. That's fine. A means for realizing such a degree of pulverization is not particularly limited, but a wet pulverization method is preferable. Specific examples include dyno mill.

  In the present invention, the median diameter of the pulverized particles in the slurry was measured with a known laser diffraction / scattering type particle size distribution measuring apparatus with a refractive index of 1.24 and a particle diameter standard set as a volume standard. Is. In the present invention, a 0.1 wt% sodium hexametaphosphate aqueous solution was used as a dispersion medium used in the measurement, and measurement was performed after 5 minutes of ultrasonic dispersion (output 30 W, frequency 22.5 kHz).

<Spray drying process>
After the wet mixing, it is then usually subjected to a drying process. The drying method is not particularly limited, but spray drying is preferable from the viewpoints of uniformity of the generated particulate matter, powder fluidity, powder handling performance, and efficient production of dry particles. In this case, the spraying method is not particularly limited, and examples thereof include a method using a nozzle type atomizer (two-fluid nozzle, three-fluid nozzle, four-fluid nozzle), a rotating disk-shaped atomizer, and the like.

(Spray-dried powder)
In the method for producing the lithium-containing transition metal compound powder A of the present invention, the slurry obtained by wet pulverizing the raw material compound is spray-dried, whereby the method for producing the lithium-containing transition metal compound powder B includes the raw material. A slurry obtained by wet-grinding a compound and an additive is spray-dried to obtain a powder in which primary particles are aggregated to form secondary particles. The spray-dried powder formed by agglomerating primary particles to form secondary particles is a shape feature of the spray-dried powder of the present invention. Examples of the shape confirmation method include SEM observation and cross-sectional SEM observation.

  The median diameter of the powder obtained by spray drying, which is also the firing precursor of the lithium-containing transition metal composite oxide powders A and B in the present invention (here, a value measured without applying ultrasonic dispersion) is usually 15 μm or less. More preferably, it is 12 μm or less, more preferably 9 μm or less, and most preferably 7 μm or less. However, since it tends to be difficult to obtain a too small particle size, it is usually 3 μm or more, preferably 5 μm or more, more preferably 6 μm or more.

  In the case of producing a particulate material by the spray drying method, the particle size can be controlled by appropriately selecting the spray format, the pressurized gas flow supply rate, the slurry supply rate, the drying temperature, and the like.

  That is, for example, when producing lithium compounds, nickel compounds, manganese compounds, cobalt compounds, and lithium-containing transition metal compound powders B, additives that suppress grain growth and sintering during firing are dispersed in the liquid medium. In the production of lithium transition metal-based compound powders such as lithium nickel manganese cobalt-based composite oxide powders by spray-drying the obtained slurry, the slurry viscosity during spray-drying is expressed as V (cp ), When the slurry supply amount is S (L / min) and the gas supply amount is G (L / min), the slurry viscosity V is 50 cp ≦ V ≦ 4000 cp, and the gas-liquid ratio G / S is And spray drying under the condition of 500 ≦ G / S ≦ 10000.

  If the slurry viscosity V (cp) is too low, it may be difficult to obtain a powder formed by agglomerating primary particles to form secondary particles. If it is too high, the supply pump may fail or the nozzle may be blocked. There is a case. Therefore, the slurry viscosity V (cp) is usually 50 cp or more as a lower limit, preferably 100 cp or more, more preferably 300 cp or more, most preferably 500 cp, and the upper limit is usually 4000 cp or less, preferably 3500 cp or less. Is 3000 cp or less, most preferably 2500 cp or less.

  Further, when the gas-liquid ratio G / S is less than the lower limit, the secondary particle size is likely to be coarsened or the drying property is liable to be lowered, and when it exceeds the upper limit, the productivity may be lowered. Therefore, the gas-liquid ratio G / S is usually 500 or more as a lower limit, preferably 1000 or more, more preferably 1500 or more, most preferably 1800 or more, and the upper limit is usually 10,000 or less, preferably 9000 or less, Preferably it is 8000 or less, most preferably 7500 or less.

  The slurry supply amount S and the gas supply amount G are appropriately set according to the viscosity of the slurry used for spray drying, the specifications of the spray drying apparatus used, and the like.

  In the method of the present invention, the above-mentioned gas-liquid ratio G / S is satisfied by controlling the slurry supply amount and gas supply amount that meet the above-mentioned slurry viscosity V (cp) and that are suitable for the specifications of the spray drying apparatus to be used. Spray drying may be performed within a range, and other conditions are appropriately set according to the type of apparatus to be used, but it is preferable to select the following conditions.

  That is, spray drying of the slurry is usually 50 ° C. or higher, preferably 70 ° C. or higher, more preferably 120 ° C. or higher, most preferably 140 ° C. or higher, usually 300 ° C. or lower, preferably 250 ° C. or lower, most preferably 200 ° C. It is preferable to carry out at a temperature of ℃ or less. When this temperature is too high, the obtained granulated particles may have a lot of hollow structures, and the packing density of the powder may decrease. On the other hand, if it is too low, problems such as powder sticking and blockage due to moisture condensation at the powder outlet may occur.

<Baking process>
The fired precursor thus obtained is then fired. Here, the “firing precursor” in the present invention means a precursor of a lithium-containing transition metal compound such as a lithium nickel manganese cobalt based composite oxide before firing obtained by treating a spray-dried powder. For example, the above spray-dried powder may contain a compound that generates or sublimates decomposition gas during the above-described firing to form voids in the secondary particles, and serves as a firing precursor.

  This firing condition depends on the composition and the lithium compound raw material used, but as a tendency, if the firing temperature is too high, primary particles grow excessively, sintering between particles proceeds too much, and the specific surface area is small. Sometimes it becomes too much. On the other hand, if it is too low, heterogeneous phases are mixed, and the crystal structure does not develop and lattice strain increases. Moreover, the specific surface area may become too large. Accordingly, the firing temperature is usually 700 ° C. or higher, preferably 750 ° C. or higher, more preferably 800 ° C. or higher, further preferably 850 ° C. or higher, particularly preferably 900 ° C. or higher, and usually 1500 ° C. or lower, preferably 1300 ° C. Hereinafter, it is more preferably 1200 ° C. or less, particularly preferably 1200 ° C. or less. However, in the production of the lithium-containing transition metal compound powders A and B having the composition represented by the composition formulas (I), (II) and (III), 900 ° C. or higher is preferable, more preferably 925 ° C. or higher, still more preferably. Is 950 ° C. or higher, more preferably 975 ° C. or higher, most preferably 990 ° C. or higher, usually 1200 ° C. or lower, preferably 1175 ° C. or lower, more preferably 1150 ° C. or lower, and most preferably 1125 ° C. or lower.

  For firing, for example, a box furnace, a tubular furnace, a tunnel furnace, a rotary kiln or the like can be used. The firing process is usually divided into three parts: temperature increase, maximum temperature retention, and temperature decrease. The second maximum temperature holding portion is not necessarily limited to once, and may include two or more steps depending on the purpose, which means that aggregation is eliminated to the extent that secondary particles are not destroyed. The step of raising the temperature, maintaining the maximum temperature, and lowering the temperature may be repeated twice or more with the pulverization step or the pulverization step which means crushing to primary particles or even fine powder.

  In the temperature raising step, the temperature in the furnace is usually raised at a temperature raising rate of 1 ° C./min to 10 ° C./min. Even if this rate of temperature rise is too slow, it takes time and is industrially disadvantageous. However, if it is too fast, the furnace temperature does not follow the set temperature depending on the furnace. The rate of temperature rise is preferably 1.2 ° C./min or more, more preferably 1.5 ° C./min or more, preferably 7 ° C./min or less, more preferably 5 ° C./min or less.

  Although the holding time in the maximum temperature holding step varies depending on the temperature, it is usually 30 minutes or longer, preferably 1 hour or longer, more preferably 2 hours or longer, more preferably 3 hours or longer, most preferably within the above-mentioned temperature range. Is 5 hours or longer, usually 50 hours or shorter, preferably 25 hours or shorter, more preferably 20 hours or shorter, most preferably 15 hours or shorter. If the firing time is too short, it may be difficult to obtain a lithium transition metal compound powder having good crystallinity. On the other hand, if the firing time is too long, it may be disadvantageous because subsequent crushing becomes necessary or crushing becomes difficult.

  In the temperature lowering step, the temperature in the furnace is normally decreased at a temperature decreasing rate of 0.1 ° C./min to 10 ° C./min. If the temperature lowering rate is too slow, it takes time and is industrially disadvantageous, but if it is too fast, it tends to lack uniformity of the target product or accelerate deterioration of the container. The temperature lowering rate is preferably 1 ° C./min or more, more preferably 3 ° C./min or more, preferably 7 ° C./min or less, more preferably 5 ° C./min or less.

  Since the firing atmosphere has an appropriate oxygen partial pressure region depending on the composition of the lithium transition metal-based compound powder to be obtained, appropriate various gas atmospheres for satisfying the oxygen partial pressure region are used. Examples of the gas atmosphere include oxygen, air, nitrogen, argon, hydrogen, carbon dioxide, and a mixed gas thereof. An oxygen-containing gas atmosphere such as air can be used for the lithium nickel manganese cobalt based composite oxide powder specifically implemented in the present invention. The oxygen concentration is usually 1% by volume or higher, preferably 10% by volume or higher, more preferably 15% by volume or higher, and usually 100% by volume or lower, preferably 50% by volume or lower, more preferably 25% by volume or lower.

  In such a production method, in order to produce the lithium-containing transition metal composite oxide powder A of the present invention, when the production conditions are constant, for example, a lithium compound, a nickel compound, a manganese compound, and a cobalt compound And a slurry in which an additive that suppresses grain growth and sintering at the time of firing is dispersed in a liquid medium, the target Li / Ni / Mn / The molar ratio of Co can be controlled.

  Subsequently, the lithium-containing transition metal compound powder A thus obtained and the lithium-containing transition metal compound powder B are mixed at a weight ratio. In order to mix the lithium-containing transition metal compound powder A and the lithium-containing transition metal compound powder B, dry mixing or wet mixing may be used. For example, artificial hand shaking mixing and mortar mixing, mechanically blender, Redige mixer, mechano-fusion, etc. can be mentioned.

  The positive electrode active material for a lithium secondary battery thus obtained provides a positive electrode material for a lithium secondary battery having a high bulk density, excellent load characteristics such as rate and output, and a good performance balance.

[Positive electrode for lithium secondary battery]
The positive electrode for a lithium secondary battery of the present invention is obtained by forming a positive electrode active material layer containing a positive electrode active material for a lithium secondary battery of the present invention and a binder on a current collector.

  The positive electrode active material layer is usually formed by mixing a positive electrode material, a binder, and a conductive material and a thickener, which are used if necessary, in a dry form into a sheet shape, and then pressing the positive electrode current collector on the positive electrode current collector. Alternatively, these materials are dissolved or dispersed in a liquid medium to form a slurry, which is applied to the positive electrode current collector and dried.

  As the material for the positive electrode current collector, metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum, and carbon materials such as carbon cloth and carbon paper are usually used. Of these, metal materials are preferable, and aluminum is particularly preferable. As for the shape, in the case of a metal material, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, an expanded metal, a punch metal, a foam metal, etc., and in the case of a carbon material, a carbon plate, a carbon thin film, a carbon cylinder Etc. Among these, metal thin films are preferable because they are currently used in industrialized products. In addition, you may form a thin film suitably in mesh shape.

  When a thin film is used as the positive electrode current collector, its thickness is arbitrary, but it is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and usually 100 mm or less, preferably 1 mm or less, more preferably 50 μm or less. The range of is preferable. If it is thinner than the above range, the strength required for the current collector may be insufficient. On the other hand, if it is thicker than the above range, the handleability may be impaired.

  The binder used in the production of the positive electrode active material layer is not particularly limited, and in the case of a coating method, any material that is stable with respect to the liquid medium used during electrode production may be used. Specific examples include polyethylene, Resin polymers such as polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, nitrocellulose, SBR (styrene butadiene rubber), NBR (acrylonitrile butadiene rubber), fluorine rubber, isoprene rubber, butadiene rubber, ethylene・ Rubber polymers such as propylene rubber, styrene / butadiene / styrene block copolymers and hydrogenated products thereof, EPDM (ethylene / propylene / diene terpolymers), styrene / ethylene / butadiene / ethylene copolymers, Styrene / isoprene styrene bromide Such as thermoplastic elastomeric polymers such as copolymer and hydrogenated products thereof, syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer, etc. Fluorine polymers such as soft resin-like polymers, polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymers, ion conductivity of alkali metal ions (especially lithium ions) And a polymer composition having the same. In addition, these substances may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  The ratio of the binder in the positive electrode active material layer is usually 0.1% by weight or more, preferably 1% by weight or more, more preferably 5% by weight or more, and usually 80% by weight or less, preferably 60% by weight or less. More preferably, it is 40% by weight or less, and most preferably 10% by weight or less. If the proportion of the binder is too low, the positive electrode active material cannot be sufficiently retained and the positive electrode has insufficient mechanical strength, which may deteriorate battery performance such as cycle characteristics. It may lead to a decrease in capacity and conductivity.

  The positive electrode active material layer usually contains a conductive material in order to increase conductivity. There are no particular restrictions on the type, but specific examples include metal materials such as copper and nickel, graphite such as natural graphite and artificial graphite, carbon black such as acetylene black, and amorphous carbon such as needle coke. The carbon material etc. of this can be mentioned. In addition, these substances may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio. The proportion of the conductive material in the positive electrode active material layer is usually 0.01% by weight or more, preferably 0.1% by weight or more, more preferably 1% by weight or more, and usually 50% by weight or less, preferably 30%. % By weight or less, more preferably 20% by weight or less. If the proportion of the conductive material is too low, the conductivity may be insufficient, and conversely if it is too high, the battery capacity may be reduced.

  As a liquid medium for forming a slurry, it is possible to dissolve or disperse a lithium transition metal compound powder as a positive electrode material, a binder, and a conductive material and a thickener used as necessary. If it is a solvent, there is no restriction | limiting in particular in the kind, You may use either an aqueous solvent or an organic solvent. Examples of the aqueous solvent include water, alcohol and the like, and examples of the organic solvent include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N, N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran (THF), toluene, acetone, dimethyl ether, dimethylacetamide, hexamethylphosphamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, etc. Can be mentioned. In particular, when an aqueous solvent is used, a dispersant is added together with the thickener, and a slurry such as SBR is slurried. In addition, these solvents may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  The content of the lithium transition metal-based compound powder of the present invention as the positive electrode material in the positive electrode active material layer is usually 10% by weight or more, preferably 30% by weight or more, more preferably 50% by weight or more, and usually 99%. .9% by weight or less, preferably 99% by weight or less. If the proportion of the lithium transition metal compound powder in the positive electrode active material layer is too large, the strength of the positive electrode tends to be insufficient, and if it is too small, the capacity may be insufficient.

  The thickness of the positive electrode active material layer is usually about 10 to 200 μm.

The positive electrode active material layer obtained by coating and drying is preferably consolidated by a roller press or the like in order to increase the packing density of the positive electrode active material.
Thus, the positive electrode for a lithium secondary battery of the present invention can be prepared.

[Lithium secondary battery]
The lithium secondary battery of the present invention includes the above-described positive electrode for a lithium secondary battery of the present invention capable of occluding and releasing lithium, a negative electrode capable of occluding and releasing lithium, and a non-aqueous electrolyte using a lithium salt as an electrolytic salt, Is provided. Furthermore, a separator that holds a non-aqueous electrolyte may be provided between the positive electrode and the negative electrode. In order to effectively prevent a short circuit due to contact between the positive electrode and the negative electrode, it is desirable to interpose a separator in this way.

<Negative electrode>
The negative electrode is usually configured by forming a negative electrode active material layer on a negative electrode current collector, similarly to the positive electrode. As a material of the negative electrode current collector, a metal material such as copper, nickel, stainless steel, nickel-plated steel, or a carbon material such as carbon cloth or carbon paper is used. Among these, in the case of a metal material, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, etc., and in the case of a carbon material, a carbon plate, a carbon thin film, a carbon cylinder, etc. are mentioned. Among these, metal thin films are preferable because they are currently used in industrialized products. In addition, you may form a thin film suitably in mesh shape. When a metal thin film is used as the negative electrode current collector, the preferred thickness range is the same as the range described above for the positive electrode current collector.

  The negative electrode active material layer includes a negative electrode active material. The negative electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions, but it can usually occlude and release lithium from the viewpoint of high safety. A carbon material is used.

  Although there is no restriction | limiting in particular as a carbon material, The graphite (graphite), such as artificial graphite and natural graphite, and the thermal decomposition thing of organic substance on various thermal decomposition conditions are mentioned. Examples of pyrolysis products of organic matter include coal-based coke, petroleum-based coke, coal-based pitch carbide, petroleum-based pitch carbide, or carbide obtained by oxidizing these pitches, needle coke, pitch coke, phenol resin, crystalline cellulose, etc. And carbon materials obtained by partially graphitizing these, furnace black, acetylene black, pitch-based carbon fibers, and the like. Among them, graphite is preferable, and particularly preferable is artificial graphite, purified natural graphite, or graphite material containing pitch in these graphites manufactured by subjecting easy-graphite pitch obtained from various raw materials to high-temperature heat treatment. Therefore, those subjected to various surface treatments are mainly used. One of these carbon materials may be used alone, or two or more thereof may be used in combination.

When a graphite material is used as the negative electrode active material, the d value (interlayer distance: d ₀₀₂ ) of the lattice plane (002 plane) determined by X-ray diffraction by the Gakushin method is usually 0.335 nm or more, and usually 0.34 nm. Hereinafter, it is preferably 0.337 nm or less.

  Further, the ash content of the graphite material is usually 1% by weight or less, particularly 0.5% by weight or less, and particularly preferably 0.1% by weight or less, based on the weight of the graphite material.

  Furthermore, the crystallite size (Lc) of the graphite material determined by X-ray diffraction by the Gakushin method is usually 30 nm or more, preferably 50 nm or more, and more preferably 100 nm or more.

  Further, the median diameter of the graphite material determined by the laser diffraction / scattering method is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and particularly preferably 7 μm or more. Further, it is usually 100 μm or less, preferably 50 μm or less, more preferably 40 μm or less, and particularly preferably 30 μm or less.

Moreover, the BET specific surface area of the graphite material is usually 0.5 m ² / g or more, preferably 0.7 m ² / g or more, more preferably 1.0 m ² / g or more, and further preferably 1.5 m ² / g. or more, and usually 25.0 m ² / g or less, preferably 20.0 m ² / g, more preferably 15.0 m ² / g or less, still more preferably 10.0 m ² / g or less.

Further, when performing Raman spectroscopy using argon laser light for graphite material, and strength _{I A} of the peak _{P A} is detected in the range of 1580~1620cm ^-1, 135
Intensity ratio _I A / _{I B} of the intensity _{I B} of a peak _{P B} detected in the range of 0～1370Cm ^-1 is intended preferably 0 or more and 0.5 or less. Further, the half width of the peak _{P A} is preferably 26cm ^-1 or less, 25 cm ^-1 or less is more preferable.

In addition to the above-mentioned various carbon materials, it can also be used as a negative electrode active material of other materials capable of inserting and extracting lithium. Specific examples of negative electrode active materials other than carbon materials include metal oxides such as tin oxide and silicon oxide, nitrides such as Li _2.6 Co _0.4 N, lithium alloys such as lithium alone and lithium aluminum alloys, and the like. Can be mentioned. One of these materials other than the carbon material may be used alone, or two or more thereof may be used in combination. Moreover, you may use in combination with the above-mentioned carbon material.

  As in the case of the positive electrode active material layer, the negative electrode active material layer is usually prepared by slurrying the above-described negative electrode active material, a binder, and optionally a conductive material and a thickener in a liquid medium. It can manufacture by apply | coating to a negative electrode electrical power collector, and drying. As the liquid medium, the binder, the thickener, the conductive material, and the like that form the slurry, the same materials as those described above for the positive electrode active material layer can be used.

<Nonaqueous electrolyte>
As the non-aqueous electrolyte, for example, known organic electrolytes, polymer solid electrolytes, gel electrolytes, inorganic solid electrolytes, and the like can be used. Of these, organic electrolytes are preferable. The organic electrolytic solution is configured by dissolving a solute (electrolyte) in an organic solvent.

  Here, the type of the organic solvent is not particularly limited. For example, carbonates, ethers, ketones, sulfolane compounds, lactones, nitriles, chlorinated hydrocarbons, ethers, amines, esters, amides. A phosphoric acid ester compound or the like can be used.

  Typical examples include dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene carbonate, ethylene carbonate, vinylene carbonate, vinyl ethylene carbonate, tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 4-methyl- 2-pentanone, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methylsulfolane, acetonitrile, pro Examples include pionitrile, benzonitrile, butyronitrile, valeronitrile, 1,2-dichloroethane, dimethylformamide, dimethyl sulfoxide, trimethyl phosphate, and triethyl phosphate. Is, these compounds, hydrogen atoms may be partially substituted with a halogen atom. Moreover, these single or 2 or more types of mixed solvents can be used.

  The organic solvent described above preferably contains a high dielectric constant solvent in order to dissociate the electrolytic salt. Here, the high dielectric constant solvent means a compound having a relative dielectric constant of 20 or more at 25 ° C. Among the high dielectric constant solvents, it is preferable that ethylene carbonate, propylene carbonate, and compounds in which hydrogen atoms thereof are substituted with other elements such as halogen or alkyl groups are contained in the electrolytic solution. The proportion of the high dielectric constant solvent in the electrolyte is preferably 20% by weight or more, more preferably 25% by weight or more, and most preferably 30% by weight or more. If the content of the high dielectric constant solvent is less than the above range, desired battery characteristics may not be obtained.

In addition, in the organic electrolyte, a gas such as CO ₂ , N ₂ O, CO, SO ₂ , vinylene carbonate, polysulfide S _x ^2−, etc., which enables efficient charge / discharge of lithium ions on the negative electrode surface You may add the additive which forms a film in arbitrary ratios. Among these additives, vinylene carbonate is particularly preferable.

  Furthermore, the organic electrolyte solution may contain a compound that exhibits an effect of improving cycle life and output characteristics, such as lithium difluorophosphate, in an arbitrary ratio.

The type of the electrolytic salt is not particularly limited, and any conventionally known solute can be used. Specifically, for example, LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , LiBOB, LiCl, LiBr, CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, LiN (SO _{2 CF 3) 2, LiN (SO} 2 C 2 F 5) 2, LiC (SO 2 CF 3) 3, LiN (SO 3 CF 3) 2 and the like. Any one of these electrolytic salts may be used alone, or two or more thereof may be used in any combination and ratio.

  The lithium salt of the electrolytic salt is usually contained in the electrolytic solution so as to have a concentration of 0.5 mol / L to 1.5 mol / L. Even if the lithium salt concentration in the electrolytic solution is less than 0.5 mol / L or more than 1.5 mol / L, the electrical conductivity may be lowered, and the battery characteristics may be adversely affected. The lower limit of this concentration is preferably 0.75 mol / L or more, and the upper limit is preferably 1.25 mol / L or less.

Even when a polymer solid electrolyte is used, the type thereof is not particularly limited, and any known crystalline / amorphous inorganic substance can be used as the solid electrolyte. Examples of the crystalline inorganic solid electrolyte include LiI, Li ₃ N, Li _{1 + x} J _x Ti _2-x (PO ₄ ) ₃ (J = Al, Sc, Y, La), Li _0.5-3x RE _{0. .5 + x} TiO ₃ (RE = La, Pr, Nd, Sm) and the like. Examples of the amorphous inorganic solid electrolyte include oxide glasses such as 4.9LiI-34.1Li ₂ O-61B ₂ O ₅ and 33.3Li ₂ O-66.7SiO ₂ . Any one of these may be used alone, or two or more may be used in any combination and ratio.

<Separator>
When the above-described organic electrolyte is used as the electrolyte, a separator is interposed between the positive electrode and the negative electrode in order to prevent a short circuit between the electrodes. The material and shape of the separator are not particularly limited, but those that are stable with respect to the organic electrolyte used, have excellent liquid retention properties, and can reliably prevent short-circuiting between electrodes are preferable. Preferable examples include microporous films, sheets, nonwoven fabrics and the like made of various polymer materials. Specific examples of the polymer material include polyolefin polymers such as nylon, cellulose acetate, nitrocellulose, polysulfone, polyacrylonitrile, polyvinylidene fluoride, polypropylene, polyethylene, and polybutene. In particular, from the viewpoint of chemical and electrochemical stability, which is an important factor for separators, polyolefin polymers are preferable. From the viewpoint of self-occluding temperature, which is one of the purposes of use of separators in batteries, polyethylene is preferred. Is particularly desirable.

  When using a separator made of polyethylene, it is preferable to use ultra-high molecular weight polyethylene from the viewpoint of maintaining high-temperature shape, and the lower limit of the molecular weight is preferably 500,000, more preferably 1,000,000, and most preferably 1,500,000. On the other hand, the upper limit of the molecular weight is preferably 5 million, more preferably 4 million, and most preferably 3 million. This is because if the molecular weight is too large, the fluidity becomes too low, and the pores of the separator may not close when heated.

<Battery shape>
The lithium secondary battery of the present invention is produced by assembling the above-described positive electrode for a lithium secondary battery of the present invention, a negative electrode, an electrolyte, and a separator used as necessary into an appropriate shape. Furthermore, other components such as an outer case can be used as necessary.

  The shape of the lithium secondary battery of the present invention is not particularly limited, and can be appropriately selected from various commonly employed shapes according to the application. Examples of commonly used shapes include a cylinder type with a sheet electrode and separator spiral, an inside-out cylinder type with a combination of pellet electrode and separator, a coin type with a stack of pellet electrode and separator, etc. Can be mentioned. The method for assembling the battery is not particularly limited, and can be appropriately selected from various commonly used methods according to the shape of the target battery.

  The general embodiment of the lithium secondary battery of the present invention has been described above. However, the lithium secondary battery of the present invention is not limited to the above-described embodiment, and various modifications are possible as long as the gist thereof is not exceeded. Can be implemented.

  EXAMPLES The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples unless it exceeds the gist.

[Measurement method of physical properties]
The physical properties and the like of lithium transition metal-based compound powders produced in each Example and Comparative Example described below were measured as follows.

<Composition (Li / Ni / Mn / Co)>
It was determined by inductively coupled plasma optical emission spectrometry (ICP-AES) by the method described above.

<Quantification of additive element (W)>
It calculated | required by ICP-AES analysis by the method similar to a composition (Li / Ni / Mn / Co).

<Median diameter of secondary particles>
With the above-described method, that is, with a laser diffraction / scattering particle size distribution measuring apparatus, the refractive index is set to 1.24, the particle diameter reference is the volume reference, and ultrasonic dispersion for 5 minutes (output 30 W, frequency 22.5 kHz). ) Measured later.

<Bulk density>
That is, the powder packing density when 4 to 10 g of the sample powder was put in a 10 mL glass graduated cylinder and tapped 200 times with a stroke of about 20 mm was obtained by the method described above.

<Specific surface area>
The BET method was used in the above method.

<Contained carbon concentration C>
An EMIA-520 carbon sulfur analyzer manufactured by HORIBA, Ltd. was used. A sample of several tens to 100 mg was weighed into an air-baked magnetic crucible, a combustion aid was added, and carbon was extracted by combustion in a high-frequency heating furnace in an oxygen stream. CO ₂ in the combustion gas was quantified by non-dispersive infrared absorption spectrophotometry. For sensitivity calibration, 150-15 low alloy steel No. 1 (C guaranteed value: 0.469% by weight) manufactured by Japan Iron and Steel Federation was used.

<Volume resistivity>
Using a powder resistivity measuring device (Dia Instruments: Lorester GP powder low-efficiency measurement system PD-41), the sample weight is set to 2 to 3 g, and a powder probe unit (four probe / ring electrodes, electrode spacing 5) The volume resistivity [Ω · cm] of the powder under various pressures was measured at an applied voltage limiter of 90 V using an electrode radius of 1.0 mm, an electrode radius of 1.0 mm, and a sample radius of 12.5 mm. The rate values were compared.

<Median diameter of pulverized particles in slurry>
Using a known laser diffraction / scattering particle size distribution measuring device, the refractive index was set to 1.24, and the particle diameter standard was measured as the volume standard. Further, a 0.1 wt% aqueous solution of sodium hexametaphosphate was used as a dispersion medium, and measurement was performed after 5 minutes of ultrasonic dispersion (output 30 W, frequency 22.5 kHz).

[Production of cathode active material for lithium secondary battery (Examples and Comparative Examples)]
Example 1
First, for the purpose of obtaining lithium-containing transition metal compound powder A, synthesis was performed as described below.
Weigh Li ₂ CO ₃ , Ni (OH) ₂ , Mn ₃ O ₄ , and CoOOH so as to have a molar ratio of Li: Ni: Mn: Co = 1.08: 0.333: 0.333: 0.333. After mixing, pure water was added to prepare a slurry. While stirring this slurry, the solid content in the slurry was pulverized to a median diameter of 0.34 μm using a circulating medium agitation type wet pulverizer (DM45 type).

  Next, this slurry (solid content 20% by weight, viscosity 1550 cp) was spray dried using a four-fluid nozzle type spray dryer (Fujisaki Electric Co., Ltd .: MDP-105 type). At this time, air was used as the dry gas, the dry gas introduction amount G was 2100 L / min, and the slurry introduction amount S was 1800 mL / min (gas-liquid ratio G / S = 1167). The drying inlet temperature was 200 ° C.

  About 1800 g of particulate powder obtained by spray drying with a spray dryer is charged into an alumina square bowl and fired at 1007 ° C. for about 5 hours in an air atmosphere (temperature increase rate: about 1.3 ° C./min, temperature decrease rate) : About 3.2 ° C./min), followed by classification using a Puffer filter with a 45 μm mesh, and lithium-containing transition metal oxide powder A composed of spherical secondary particles having surface irregularities and internal opening voids (hereinafter referred to as “ A1 ”).

This lithium-containing transition metal oxide powder A has a composition of
Lithium nickel manganese cobalt composite oxide having a layered structure of Li (Li _0.023 Ni _0.327 Mn _0.324 Co _0.326 ) O ₂ (x = 0.334, y = 0.006, z = 0. 048).

Next, for the purpose of obtaining lithium-containing transition metal compound powder B, synthesis was performed as described below.
Li ₂ CO ₃ , Ni (OH) ₂ , Mn ₃ O ₄ , CoOOH, WO ₃ are mixed with Li: Ni: Mn: Co: W = 1.15: 0.475: 0.475: 0.05: 0. After weighing and mixing to a molar ratio of 015, pure water was added thereto to prepare a slurry. While stirring this slurry, the solid content in the slurry was pulverized to a median diameter of 0.27 μm using a circulating medium agitation type wet pulverizer.

Next, this slurry (solid content 15% by weight, viscosity 840 cp) was spray-dried using a two-fluid nozzle type spray dryer (Okawara Kako Co., Ltd .: LT-8 type). Air was used as the drying gas at this time, the drying gas introduction amount G was 45 L / min, and the slurry introduction amount S was 6 × 10 ⁻³ mL / min (gas-liquid ratio G / S = 7500). The drying inlet temperature was 150 ° C.

  About 120 g of particulate powder obtained by spray drying with a spray dryer is charged in an alumina square bowl and fired at 1050 ° C. for 2 hours in an air atmosphere (temperature increase rate: about 1.7 ° C./min, temperature decrease rate: About 3.3 ° C./min), and then classified using a 45 μm sieve, the lithium-containing transition metal oxide powder B having a size that can fill the surface irregularities and the internal opening voids of the powder A1 ( This was referred to as “B1”).

The lithium-containing transition metal oxide powder B1 has a composition of
Lithium nickel manganese cobalt composite oxide having a layered structure of Li (Li _0.072 Ni _0.442 Mn _0.441 Co _0.045 ) O ₂ (x ′ = 0.048, y ′ = 0.002, z ′ = 0.156). When the total molar ratio of (Ni, Mn, Co) was 1, the W molar ratio was 1.46 mol%.

  Next, the lithium-containing transition metal compound powders A1 and B1 were sufficiently mixed at a ratio of 5: 1 (weight ratio) to obtain a target mixed powder.

The mixed powder has a volume resistivity of 4.3 × 10 ⁴ Ω · cm, a carbon concentration C of 0.031 wt%, a median diameter of 5.1 μm, a 90% integrated diameter (D ₉₀ ) of 9.0 μm, The bulk density was 1.8 g / cm ³ and the BET specific surface area was 1.3 m ² / g.

Example 2
A mixed powder was produced in the same manner as in Example 1 except that the lithium-containing transition metal composite oxide powders A1 and B1 were mixed at a ratio of 1: 1 (weight ratio).

This mixed powder has a volume resistivity of 6.4 × 10 ⁴ Ω · cm, a carbon concentration C of 0.063 wt%, a median diameter of 1.9 μm, a 90% cumulative diameter (D ₉₀ ) of 9.9 μm, The bulk density was 1.9 g / cm ³ and the BET specific surface area was 2.0 m ² / g.

Example 3
A mixed powder was produced in the same manner as in Example 1 except that the lithium-containing transition metal composite oxide powders A1 and B1 were mixed at a ratio of 1: 5 (weight ratio).

This mixed powder has a volume resistivity of 7.2 × 10 ⁴ Ω · cm, a carbon concentration C of 0.084 wt%, a median diameter of 1.2 μm, a 90% cumulative diameter (D ₉₀ ) of 2.0 μm, The bulk density was 1.6 g / cm ³ and the BET specific surface area was 2.8 m ² / g.

Comparative Example 1
The lithium-containing transition metal compound powder B1 used in Examples 1 to 3 was evaluated without being mixed with the lithium-containing transition metal composite oxide powder A.

This unmixed powder has a volume resistivity of 7.4 × 10 ⁴ Ω · cm, a carbon concentration C of 0.106 wt%, a median diameter of 1.2 μm, and a 90% integrated diameter (D ₉₀ ) of 2.0 μm. The bulk density was 1.5 g / cm ³ and the BET specific surface area was 3.1 m ² / g.

Comparative Example 2
The lithium-containing transition metal composite oxide powder A1 used in Examples 1 to 3 was evaluated without being mixed with the lithium-containing transition metal composite oxide powder B.

This unmixed powder has a volume resistivity of 4.5 × 10 ⁴ Ω · cm, a carbon concentration C of 0.013% by weight, a median diameter of 8.2 μm, and a 90% integrated diameter (D ₉₀ ) of 12.8 μm. The bulk density was 1.5 g / cm ³ and the BET specific surface area was 0.9 m ² / g.

Comparative Example 3
First, for the purpose of obtaining lithium-containing transition metal compound powder A, synthesis was performed as described below.
Weigh Li ₂ CO ₃ , Ni (OH) ₂ , Mn ₃ O ₄ , and CoOOH so that the molar ratio is Li: Ni: Mn: Co = 1.05: 0.333: 0.333: 0.333. After mixing, pure water was added to prepare a slurry. While the slurry was stirred, the solid content in the slurry was pulverized to a median diameter of 0.33 μm using a circulating medium agitation type wet pulverizer (DM20 type).

  Next, this slurry (solid content 20% by weight, viscosity 2320 cp) was spray-dried using a four-fluid nozzle type spray dryer (manufactured by Fujisaki Electric Co., Ltd .: MDP-50 type). At this time, air was used as the dry gas, the dry gas introduction amount G was 1600 L / min, and the slurry introduction amount S was 780 mL / min (gas-liquid ratio G / S = 2051). The drying inlet temperature was 200 ° C. About 1800 g of particulate powder obtained by spray drying with a spray dryer is charged in an alumina square bowl and fired at 1000 ° C. for about 5 hours in an air atmosphere (temperature increase rate: about 1.3 ° C./min, temperature decrease rate) : About 3.4 ° C./min), followed by classification using a turbo screener with a 45 μm mesh, and a lithium-containing transition metal oxide powder A (which has a spherical secondary particle form having surface irregularities and internal opening voids) (Referred to as “A2”).

This lithium-containing transition metal oxide powder A2 has a composition of
_{Li (Li 0.024 Ni 0.320 Mn 0.325} Co 0.331) Lithium nickel manganese cobalt composite oxide having a layered structure of _{O 2 (x = 0.339, y} = -0.008, z = 0 0.050).

Next, for the purpose of obtaining lithium-containing transition metal compound powder B, synthesis was performed as described below.
Li ₂ CO ₃ , Ni (OH) ₂ , Mn ₃ O ₄ , CoOOH, WO ₃ are mixed with Li: Ni: Mn: Co: W = 1.12: 0.45: 0.45: 0.10: 0. After weighing and mixing to a molar ratio of 01, pure water was added thereto to prepare a slurry. While stirring this slurry, the solid content in the slurry was pulverized to a median diameter of 0.23 μm using a circulating medium agitation type wet pulverizer. Next, this slurry (solid content 16.5% by weight, viscosity 1650 cp) was spray-dried using a four-fluid nozzle type spray dryer (manufactured by Fujisaki Electric Co., Ltd .: MDP-50 type). At this time, air was used as the dry gas, the dry gas introduction amount G was 1600 L / min, and the slurry introduction amount S was 780 mL / min (gas-liquid ratio G / S = 2051). The drying inlet temperature was 200 ° C.

  About 370 g of particulate powder obtained by spray drying with a spray dryer is charged into an alumina square bowl and fired at 1000 ° C. for 2 hours in an air atmosphere (temperature increase rate: about 1.7 ° C./min, temperature decrease rate: After about 3.3 ° C./min), the powder is classified using a Puffer footer (manufactured by Tsukasa Kogyo Co., Ltd.) with a 45 μm mesh, and does not have a size that can fill the surface irregularities and internal openings of the powder A. A lithium-containing transition metal oxide powder (referred to as “B′2”) having a primary particle form was obtained.

This lithium-containing transition metal oxide powder B′2 has a composition of
_{Li (Li 0.053 Ni 0.425 Mn 0.427} Co 0.095) Lithium nickel manganese cobalt composite oxide having a layered structure of _{O 2 (x '= 0.100,} y' = - 0.002, z '= 0.111). When the total molar ratio of (Ni, Mn, Co) was 1, the W molar ratio was 1.0 mol%.

  Next, lithium-containing transition metal compound powders A2 and B′2 were sufficiently mixed at a ratio of 1: 1 (weight ratio) to obtain a mixed powder.

The mixed powder has a volume resistivity of 8.2 × 10 ⁴ Ω · cm, a carbon concentration C of 0.024% by weight, a median diameter of 3.2 μm, a 90% integrated diameter (D ₉₀ ) of 5.9 μm, The bulk density was 1.2 g / cm ³ and the BET specific surface area was 1.9 m ² / g.

Comparative Example 4
A mixed powder was prepared in the same manner as in Comparative Example 3 except that lithium-containing transition metal composite oxide powders A2 and B′2 were mixed at a ratio of 1: 5 (weight ratio).

The mixed powder has a volume resistivity of 6.8 × 10 ⁴ Ω · cm, a carbon concentration C of 0.029% by weight, a median diameter of 2.2 μm, a 90% cumulative diameter (D ₉₀ ) of 4.4 μm, The bulk density was 1.0 g / cm ³ and the BET specific surface area was 2.6 m ² / g.

Comparative Example 5
A mixed powder was produced in the same manner as in Comparative Example 3 except that the lithium-containing transition metal composite oxide powders A2 and B′2 were mixed at a ratio of 5: 1 (weight ratio).

The mixed powder has a volume resistivity of 6.8 × 10 ⁴ Ω · cm, a carbon concentration C of 0.029% by weight, a median diameter of 2.2 μm, a 90% cumulative diameter (D ₉₀ ) of 4.4 μm, The bulk density was 1.0 g / cm ³ and the BET specific surface area was 2.6 m ² / g.

Comparative Example 6
The lithium-containing transition metal composite oxide powder A2 used in Comparative Examples 3 to 5 was evaluated without being mixed with the lithium-containing transition metal composite oxide powder B.

This unmixed powder has a volume resistivity of 1.6 × 10 ⁵ Ω · cm, a carbon concentration C of 0.013% by weight, a median diameter of 5.6 μm, and a 90% integrated diameter (D ₉₀ ) of 10.1 μm. The bulk density was 1.5 g / cm ³ and the BET specific surface area was 1.0 m ² / g.

Comparative Example 7
The lithium-containing transition metal composite oxide powder B′2 used in Comparative Examples 3 to 5 was evaluated without being mixed with the lithium-containing transition metal composite oxide powder A. This unmixed powder has a volume resistivity of 6.3 × 10 ⁴ Ω · cm, a carbon concentration C of 0.031 wt%, a median diameter of 2.7 μm, and a 90% integrated diameter (D ₉₀ ) of 4.9 μm. The bulk density was 1.0 g / cm ³ and the BET specific surface area was 2.8 m ² / g.

Comparative Example 8
Li (OH) ₂ , NiO, Co (OH) ₂ , and AlOOH are weighed so as to have a molar ratio of Li: Ni: Co: Al = 1.05: 0.80: 0.15: 0.05, After mixing, pure water was added thereto to prepare a slurry. While the slurry was stirred, the solid content in the slurry was pulverized using a circulating medium stirring wet pulverizer.

  Next, this slurry was spray-dried using a four-fluid nozzle type spray dryer (manufactured by Fujisaki Electric Co., Ltd .: MDP-50 type). Particulate powder obtained by spray drying with a spray dryer is charged into an alumina square bowl, fired at 740 ° C. in an oxygen atmosphere, classified, and has some surface irregularities, but does not have internal opening voids. A lithium-containing transition metal oxide powder (referred to as “A′3”) composed of spherical secondary particles was obtained.

This lithium-containing transition metal oxide powder has the following composition:
It was a lithium nickel cobalt aluminum composite oxide having a layered structure of Li _1.040 Ni _0.798 Co _0.152 Al _0.049 O ₂ .

  Next, the lithium-containing transition metal compound powder A′3 and the same lithium-containing transition metal oxide powder B′2 as used in Comparative Examples 3 to 5 and 7 were mixed 1: 1 (weight ratio). The mixture was sufficiently mixed to obtain a mixed powder.

The mixed powder has a volume resistivity of 6.3 × 10 ² Ω · cm, a carbon concentration C of 0.067% by weight, a median diameter of 3.0 μm, a 90% cumulative diameter (D ₉₀ ) of 5.8 μm, The bulk density was 1.3 g / cm ³ and the BET specific surface area was 1.5 m ² / g.

Comparative Example 9
A mixed powder was produced in the same manner as in Comparative Example 8 except that lithium-containing transition metal compound powders A′3 and B′2 were mixed at a ratio of 1: 5 (weight ratio).

The mixed powder has a volume resistivity of 3.0 × 10 ⁴ Ω · cm, a carbon concentration C of 0.045% by weight, a median diameter of 2.1 μm, a 90% cumulative diameter (D ₉₀ ) of 4.1 μm, The bulk density was 1.0 g / cm ³ and the BET specific surface area was 2.5 m ² / g.

Comparative Example 10
A mixed powder was prepared in the same manner as in Comparative Example 8 except that lithium-containing transition metal compound powders A′3 and B′2 were mixed at a ratio of 5: 1 (weight ratio).

The mixed powder has a volume resistivity of 1.6 × 10 ² Ω · cm, a carbon concentration C of 0.076% by weight, a median diameter of 5.4 μm, a 90% cumulative diameter (D ₉₀ ) of 9.2 μm, The bulk density was 1.8 g / cm ³ and the BET specific surface area was 1.1 m ² / g.

Comparative Example 11
The lithium-containing transition metal compound powder A′3 used in Comparative Examples 8 to 10 was evaluated without being mixed with another lithium-containing transition metal composite oxide powder. This unmixed powder has a volume resistivity of 1.3 × 10 ² Ω · cm, a carbon concentration C of 0.089% by weight, a median diameter of 7.3 μm, and a 90% integrated diameter (D ₉₀ ) of 11.8 μm. The bulk density was 2.0 g / cm ³ and the BET specific surface area was 0.7 m ² / g.

Comparative Example 12
A lithium-containing transition metal oxide powder (referred to as “A′4”) composed of spherical secondary particles having surface irregularities but almost no internal opening voids was obtained. This lithium-containing transition metal oxide powder A′4 was a lithium manganese aluminum composite oxide having a spinel structure with a composition of Li (Li _0.03 Mn _1.85 Al _0.12 ) O ₄ .

  Next, the lithium-containing transition metal compound powder A′4 and the same lithium-containing transition metal compound powder B′2 used in Comparative Examples 3 to 5 and 7 to 10 were mixed at 1: 1 (weight ratio). ) To obtain a mixed powder.

The mixed powder has a volume resistivity of 3.0 × 10 ⁴ Ω · cm, a carbon concentration C of 0.025 wt%, a median diameter of 2.7 μm, a 90% cumulative diameter (D ₉₀ ) of 5.9 μm, The bulk density was 1.3 g / cm ³ and the BET specific surface area was 1.7 m ² / g.

Comparative Example 13
The lithium-containing transition metal compound powder A′4 used in Comparative Example 12 was evaluated without being mixed with another lithium-containing transition metal compound powder.

This unmixed powder has a volume resistivity of 1.3 × 10 ⁴ Ω · cm, a carbon concentration C of 0.001% by weight, a median diameter of 11.7 μm, and a 90% integrated diameter (D ₉₀ ) of 18.0 μm. The bulk density was 1.8 g / cm ³ and the BET specific surface area was 0.7 m ² / g.

Comparative Example 14
Lithium cobalt composite oxide powder (referred to as “B′3”) composed of plate-like primary particles and having a layered structure with a composition of Li _1.03 Co _1.00 O ₂ and used in Comparative Example 7 The lithium-containing fiber metal compound powder B′2 was sufficiently mixed at a ratio of 1: 1 (weight ratio) to obtain a mixed powder.

The mixed powder has a volume resistivity of 2.3 × 10 ⁴ Ω · cm, a carbon concentration C of 0.041% by weight, a median diameter of 2.6 μm, a 90% integrated diameter (D ₉₀ ) of 5.6 μm, The bulk density was 1.4 g / cm ³ and the BET specific surface area was 1.7 m ² / g.

Comparative Example 15
The lithium cobalt composite oxide powder B′3 used in Comparative Example 14 was evaluated without being mixed with another lithium-containing transition metal compound powder. This unmixed powder has a volume resistivity of 1.3 × 10 ⁴ Ω · cm, a carbon concentration C of 0.026 wt%, a median diameter of 11.6 μm, and a 90% integrated diameter (D ₉₀ ) of 16.9 μm. The bulk density was 2.6 g / cm ³ and the BET specific surface area was 0.7 m ² / g.

  Table 1 shows the powder property values of the positive electrode active material materials for lithium secondary batteries produced in the above Examples and Comparative Examples.

[Production and evaluation of batteries]
Using the lithium transition metal-based compound powders produced in Examples 1 to 3 and Comparative Examples 1 to 15 as positive electrode materials (positive electrode active materials), lithium secondary batteries were prepared and evaluated by the following methods. Went.

(1) Rate test:
A mortar obtained by weighing 75% by weight of each of the lithium transition metal compound powders produced in Examples 1 to 3 and Comparative Examples 1 to 15, 20% by weight of acetylene black, and 5% by weight of polytetrafluoroethylene powder. Were mixed thoroughly and made into a thin sheet, and punched out using a 9 mmφ punch. At this time, the total weight was adjusted to about 8 mg. This was pressure-bonded to an aluminum expanded metal to obtain a 9 mmφ positive electrode.

The positive electrode of 9 mmφ was used as a test electrode, a lithium metal plate was used as a counter electrode, and a solvent of EC (ethylene carbonate): DMC (dimethyl carbonate): EMC (ethyl methyl carbonate) = 3: 3: 4 (volume ratio) was mixed with LiPF _6. A coin cell was assembled using a 25 μm thick porous polyethylene film as a separator.

The obtained coin-type cell was subjected to a constant current constant voltage charge of 0.2 mA / cm ² at an upper limit voltage of 4.2 V and a constant current discharge test of 0.2 mA / cm ² at a lower limit voltage of 3.0 V for the first cycle. In the second cycle, a constant current constant voltage charge of 0.5 mA / cm ² at an upper limit voltage of 4.2 V and a constant current discharge test of 0.2 mA / cm ² at a lower limit voltage of 3.0 V were conducted. the cycle, constant current charge of 0.5 mA / cm ^2, was constant current discharge test of 11 mA / cm ^2.

As an acceptance criterion for the examples, the initial discharge capacity in the first cycle was set to 140 mAh / g or more, and the high rate discharge capacity at 11 mA / cm ² in the third cycle was set to 100 mAh / g or more.

(2) Low temperature load characteristic test and high temperature cycle test:
Each of the mixed powders produced in Examples 1 to 3 and Comparative Examples 1 to 15 was weighed in a ratio of 75% by weight, 20% by weight of acetylene black, and 5% by weight of polytetrafluoroethylene powder. A thin sheet was punched out using a 12 mmφ punch. At this time, the total weight was adjusted to about 18 mg. This was pressure-bonded to an aluminum expanded metal to obtain a 12 mmφ positive electrode.

  Using the results of charge and discharge in the first cycle in the rate test of (1), the initial charge capacity per unit weight of the positive electrode active material is Qs (C) [mAh / g], and the initial discharge capacity is Qs (D) [mAh / g].

As the negative electrode active material, graphite powder having an average particle diameter of 8 to 10 μm (d ₀₀₂ = 3.35 Å) and polyvinylidene fluoride as a binder were weighed in a weight ratio of 92.5: 7.5, This was mixed in an N-methylpyrrolidone solution to obtain a negative electrode mixture slurry. This slurry was applied to one side of a 20 μm thick copper foil, dried to evaporate the solvent, punched to 12 mmφ, and pressed at 0.5 ton / cm ² (49 MPa) to form a negative electrode. At this time, the amount of the negative electrode active material on the electrode was adjusted to be about 5 to 9 mg.

In addition, this negative electrode is used as a test electrode, a battery cell is assembled using lithium metal as a counter electrode, and the negative electrode is made to occlude lithium ions by a constant current-constant voltage method (cut current 0.05 mA) of 0.2 mA / cm ² -3 mV The initial storage capacity per unit weight of the negative electrode active material when the test was performed at the lower limit of 0 V was defined as Q _f [mAh / g].

The positive electrode and the negative electrode were combined, a test battery was assembled using a coin cell, and the battery performance was evaluated. That is, the above-described positive electrode prepared was placed on the positive electrode can of the coin cell, a porous polyethylene film having a thickness of 25 μm was placed thereon as a separator, pressed with a polypropylene gasket, and then EC ( Using an electrolytic solution in which LiPF ₆ was dissolved at a concentration of 1 mol / L in a solvent of ethylene carbonate): DMC (dimethyl carbonate): EMC (ethyl methyl carbonate) = 3: 3: 4 (volume ratio), this was added to the can. Then, the separator was sufficiently infiltrated, and then the negative electrode B described above was placed, the negative electrode can was placed and sealed, and a coin-type lithium secondary battery was produced. At this time, the balance between the weight of the positive electrode active material and the weight of the negative electrode active material was set so as to satisfy the following expression.
Positive electrode active material weight [g] / Negative electrode active material weight [g]
= (Q _f [mAh / g] /1.2) Qs (C) [mAh / g]

In order to measure the low-temperature load characteristics of the battery thus obtained, the hourly rate current value of the battery, that is, 1C was set as in the following equation, and the following tests were performed.
1C [mA] = Qs (D) × positive electrode active material weight [g] / hour [h]

First, a constant current 0.2C charge / discharge cycle and a constant current 1C charge / discharge cycle were performed at room temperature. The upper limit of charging was 4.1 V, and the lower limit voltage was 3.0 V. Next, when a coin cell adjusted to a charging depth of 40% is held in a low temperature atmosphere of −30 ° C. for 1 hour or longer by 1/3 C constant current charging / discharging and then discharged for 10 seconds at a constant current of 0.5 C [mA]. Assuming that the voltage after 10 seconds is V [mV] and the voltage before discharge is V ₀ [mV], the resistance value R [Ω] is calculated from the following equation as ΔV = V−V ₀ .
R [Ω] = ΔV [mV] /0.5C [mA]

Next, a constant current 0.2C charge / discharge cycle was conducted at a high temperature of 60 ° C., followed by a constant current 1C charge / discharge cycle 100. The upper limit of charging was 4.1 V, and the lower limit voltage was 3.0 V. At this time, the ratio of the discharge capacity Qh (100) at the 100th cycle of 1C charge / discharge at 60 ° C. was calculated as the high-temperature cycle capacity retention ratio P by the following formula, and the high-temperature characteristics of the batteries were compared with this value.
P [%] = {Qh (100) / Qh (1)} × 100

  Next, the resistance value R [Ω] after the high-temperature cycle test was calculated in the same manner as described above.

  Table 2 shows the low-temperature resistance values and 60 ° C. cycle maintenance rates of the batteries using the positive electrode active material materials for lithium secondary batteries of Examples 1 to 3 and Comparative Examples 1 to 15, respectively. The smaller the resistance value, the better the low temperature load characteristic, and the higher the maintenance ratio, the better the high temperature cycle characteristic. In addition, it set as the acceptance criterion of an Example that the low temperature resistance value before and behind a cycle is 430 ohms or less, and a 60 degreeC cycle maintenance factor is 80% or more.

  From Tables 1 and 2, according to the positive electrode active material of the lithium secondary battery of the present invention, lithium having high filling property (bulk density) and excellent capacity characteristics, cycle characteristics, and load characteristics (high rate performance, low temperature output performance). It can be seen that a secondary battery can be realized. In Comparative Examples 3, 4 and 9, the determination result of the battery performance is good, but the filling property (bulk density) is low and cannot be used.

In Example 1, it is the SEM image (photograph) (magnification x30,000) of the manufactured positive electrode active material material for lithium secondary batteries. In Example 2, it is a SEM image (photograph) (magnification x30,000) of the manufactured positive electrode active material for lithium secondary batteries. In Example 3, it is a SEM image (photograph) (magnification x30,000) of the manufactured positive electrode active material for lithium secondary batteries. In the comparative example 1, it is a SEM image (photograph) ((a): magnification x10,000, (b): magnification x30,000) of the manufactured positive electrode active material material for lithium secondary batteries. In the comparative example 2, it is a SEM image (photograph) ((a): magnification x10,000, (b): magnification x30,000) of the manufactured positive electrode active material material for lithium secondary batteries. In the comparative example 3, it is a SEM image (photograph) (magnification x30,000) of the manufactured positive electrode active material material for lithium secondary batteries. In the comparative example 4, it is a SEM image (photograph) (magnification x30,000) of the manufactured positive electrode active material material for lithium secondary batteries. In Comparative example 5, it is a SEM image (photograph) (magnification x30,000) of the manufactured positive electrode active material for lithium secondary batteries. In the comparative example 6, it is a SEM image (photograph) ((a): magnification x10,000, (b): magnification x30,000) of the manufactured positive electrode active material material for lithium secondary batteries. In the comparative example 7, it is a SEM image (photograph) ((a): magnification x10,000, (b): magnification x30,000) of the manufactured positive electrode active material material for lithium secondary batteries. In the comparative example 8, it is a SEM image (photograph) (magnification x30,000) of the manufactured positive electrode active material for lithium secondary batteries. In Comparative Example 9, it is an SEM image (photograph) (magnification × 30,000) of the manufactured positive electrode active material for a lithium secondary battery. In Comparative Example 10, it is a SEM image (photograph) (magnification × 30,000) of the manufactured positive electrode active material for a lithium secondary battery. In Comparative example 11, it is a SEM image (photograph) ((a): magnification x10,000, (b): magnification x50,000) of the manufactured positive electrode active material for lithium secondary batteries. In Comparative example 12, it is a SEM image (photograph) (magnification x30,000) of the cathode active material material for lithium secondary batteries manufactured. In the comparative example 13, it is a SEM image (photograph) ((a): magnification x10,000, (b): magnification x30,000) of the manufactured positive electrode active material material for lithium secondary batteries. In Comparative example 14, it is a SEM image (photograph) (magnification x30,000) of the manufactured positive electrode active material for lithium secondary batteries. In the comparative example 15, it is a SEM image (photograph) ((a): magnification x10,000, (b): magnification x30,000) of the manufactured positive electrode active material for lithium secondary batteries. In Example 1, it is a graph which shows the pore distribution curve of the positive electrode active material material for lithium secondary batteries manufactured. The horizontal axis is the pore radius (Pore Radius) (Å). For example, “1.E + 04” or the like indicates “10 ⁴ ” or the like. The vertical axis represents Log differential pore volume (mL / g) (Log Differential Intrusion (mL / g)). The same applies hereinafter. In Example 2, it is a graph which shows the pore distribution curve of the positive electrode active material material for lithium secondary batteries manufactured. In Example 3, it is a graph which shows the pore distribution curve of the positive electrode active material material for lithium secondary batteries manufactured. In Comparative example 1, it is a graph which shows the pore distribution curve of the positive electrode active material material for lithium secondary batteries manufactured. In Comparative example 2, it is a graph which shows the pore distribution curve of the positive electrode active material material for lithium secondary batteries manufactured. In Comparative example 3, it is a graph which shows the pore distribution curve of the positive electrode active material material for lithium secondary batteries manufactured. In the comparative example 4, it is a graph which shows the pore distribution curve of the positive electrode active material material for lithium secondary batteries manufactured. In the comparative example 5, it is a graph which shows the pore distribution curve of the positive electrode active material material for lithium secondary batteries manufactured. In Comparative example 6, it is a graph which shows the pore distribution curve of the positive electrode active material material for lithium secondary batteries manufactured. In Comparative example 7, it is a graph which shows the pore distribution curve of the positive electrode active material material for lithium secondary batteries manufactured. In Comparative example 8, it is a graph which shows the pore distribution curve of the positive electrode active material material for lithium secondary batteries manufactured. In Comparative example 9, it is a graph which shows the pore distribution curve of the positive electrode active material material for lithium secondary batteries manufactured. In Comparative example 10, it is a graph which shows the pore distribution curve of the positive electrode active material material for lithium secondary batteries manufactured. In Comparative example 11, it is a graph which shows the pore distribution curve of the positive electrode active material material for lithium secondary batteries manufactured. In Comparative example 12, it is a graph which shows the pore distribution curve of the positive electrode active material material for lithium secondary batteries manufactured. In Comparative Example 13, it is a graph showing the pore distribution curve of the manufactured positive electrode active material for lithium secondary battery. In Comparative example 14, it is a graph which shows the pore distribution curve of the positive electrode active material material for lithium secondary batteries manufactured. In Comparative Example 15, it is a graph showing the pore distribution curve of the manufactured positive electrode active material for lithium secondary battery.

Claims (21)

Lithium-containing transition metal compound powder A (spherical secondary particles having surface irregularities and internal opening voids) and lithium-containing transition metal compound powder B (size capable of filling the surface irregularities and internal opening voids of the powder A) And a mercury intrusion curve by a mercury intrusion method has a mercury intrusion amount of 0.75 cm ³ / g or less at a pressure increase from 3.86 kPa to 413 MPa. A positive electrode active material for a lithium secondary battery.   2. The positive electrode active material for a lithium secondary battery according to claim 1, which has at least one peak having a peak top at a pore radius of 80 nm or more and less than 800 nm in a pore distribution curve by a mercury intrusion method. material.   Lithium-containing transition metal compound powder A comprising spherical secondary particles having surface irregularities and internal opening voids, and lithium-containing transition metal compound powder comprising primary particles having a size capable of filling the surface irregularities and internal opening voids The positive electrode for a lithium secondary battery according to claim 1 or 2, wherein the mixture is a mixture with B, and the mixing ratio of the powders A and B is in the range of 20: 1 to 1:20. Active material. 4. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the bulk density is 1.6 g / cm ³ or more and 2.4 g / cm ³ or less. 5.   The median diameter measured after 5 minutes of ultrasonic dispersion (output 30 W, frequency 22.5 kHz) using a laser diffraction / scattering particle size distribution analyzer with a refractive index of 1.24 and a particle size standard as a volume standard. 5 is 0.1 μm or more and 20 μm or less, The positive electrode active material for a lithium secondary battery according to any one of claims 1 to 4. 6. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the BET specific surface area is 0.5 m ² / g or more and 5 m ² / g or less. The volume resistivity when consolidated at a pressure of 40 MPa is 1 × 10 ³ Ω · cm or more and 1 × 10 ⁶ Ω · cm or less. 7. Positive electrode active material for secondary batteries.   The lithium according to any one of claims 1 to 7, wherein the C value is 0.01 wt% or more and 0.3 wt% or less when the carbon concentration is C (wt%). Positive electrode active material for secondary batteries.   A slurry preparation step in which the lithium-containing transition metal compound powder A is obtained by pulverizing a lithium compound and at least one or more transition metal compounds in a liquid medium, and uniformly dispersing them, and the resulting slurry Characterized in that it is obtained by a production method comprising at least a spray-drying step for spray-drying, a firing step for firing the obtained spray-dried powder, and a classification step for classifying the obtained fired body. The positive electrode active material for a lithium secondary battery according to any one of claims 1 to 8.   In the slurry preparation step, the lithium compound and the transition metal compound are set in a liquid medium by a laser diffraction / scattering particle size distribution measuring device with a refractive index of 1.24, and a particle diameter reference is a volume reference. Grind until the median diameter measured after ultrasonic dispersion (output 30 W, frequency 22.5 kHz) for 5 minutes is 0.4 μm or less, and in the spray drying step, the slurry viscosity at the time of spray drying is V (cp), When the slurry supply amount is S (L / min) and the gas supply amount is G (L / min), spray drying is performed under the conditions of 50 cp ≦ V ≦ 4000 cp and 500 ≦ G / S ≦ 10000, and the firing step Use a lithium-containing transition metal compound powder A obtained by a production method in which the spray-dried powder is fired at 700 ° C. or higher in an oxygen-containing gas atmosphere. Positive electrode active material for lithium secondary battery according to claim 9, characterized.   In the slurry preparation step, after the boron-containing compound and the tungsten-containing compound are added in combination at a ratio of 0.01 mol% or more and less than 2 mol% in total with respect to the total molar amount of the transition metal elements in the main component raw materials, respectively. 11. The positive electrode active material for a lithium secondary battery according to claim 9, wherein the lithium-containing transition metal compound powder A fired at 900 ° C. or higher is used.   The lithium-containing transition metal compound powder B is pulverized in a liquid medium with a lithium compound, at least one transition metal compound, and an additive that suppresses grain growth and sintering during firing. A slurry preparation step for obtaining a uniformly dispersed slurry, a spray drying step for spray-drying the obtained slurry, a firing step for firing the obtained spray-dried powder, and a classification step for classifying the obtained fired body 9. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the positive electrode active material is obtained by a production method including at least:   In the slurry preparation step, the lithium compound, the transition metal compound, and the additive are set in a liquid medium with a refractive index of 1.24 using a laser diffraction / scattering particle size distribution analyzer, Is used as a volume reference and pulverized until the median diameter measured after ultrasonic dispersion for 5 minutes (output: 30 W, frequency: 22.5 kHz) is 0.4 μm or less. In the spray drying step, the slurry viscosity during spray drying is V (Cp) When the slurry supply amount is S (L / min) and the gas supply amount is G (L / min), spray drying is performed under the conditions of 50 cp ≦ V ≦ 4000 cp and 500 ≦ G / S ≦ 10000. In the firing step, the lithium-containing transition metal compound powder B obtained by the production method in which the spray-dried powder is fired at 700 ° C. or higher in an oxygen-containing gas atmosphere. Positive electrode active material for lithium secondary battery according to claim 12, characterized in that there.   14. The additive according to claim 12 or 13, wherein the additive is an oxide containing at least one element selected from the group consisting of Mo, W, Nb, Ta and Re. Positive electrode active material for lithium secondary battery.   The lithium-containing transition metal compound powder A and / or B is mainly composed of a lithium nickel manganese cobalt-based composite oxide including a crystal structure belonging to a layered structure. Item 15. The positive electrode active material for a lithium secondary battery according to any one of Items 1 to 14. The composition of the lithium nickel manganese cobalt based composite oxide is represented by the following formula (1), and the positive electrode active material for a lithium secondary battery according to claim 15.
LiMO ₂ (1)
[In Formula (1), M is an element comprised from Li, Ni, and Mn or Li, Ni, Mn, and Co, Mn / Ni molar ratio is 0.1-5, Co / ( Mn + Ni + Co) molar ratio is 0 or more and 0.35 or less, and Li molar ratio in M is 0.001 or more and 0.2 or less. ] The positive electrode active material for a lithium secondary battery according to claim 16, wherein M in the formula (1) is represented by the following formula (2).
Li _{z / (2 + z)} [(Ni _{(1 + y) / 2} Mn _{(1-y) / 2} ) _1-x Co _x ] _{2 / (2 + z)} (2)
[In the formula (2), 0.1 <x ≦ 0.35, −0.1 ≦ y ≦ 0.1,
(1-x) (0.02-0.98y) ≤z≤ (1-x) (0.20-0.88y). ] The positive electrode active material for a lithium secondary battery according to claim 16, wherein M in the formula (1) is represented by the following formula (3).
Li _{z '/ (2 + z')} [(Ni _{(1 + y ') / 2} Mn _{(1-y') / 2} ) _{1-x '} Co _x' ] _{2 / (2 + z ')} (3)
[In formula (3), 0 ≦ x ′ ≦ 0.1, −0.1 ≦ y ′ ≦ 0.1,
(1-x ′) (0.05−0.98y ′) ≦ z ′ ≦ (1-x ′) (0.20−0.88y ′). ]   The lithium-containing transition metal compound powder B further contains at least one element selected from the group consisting of Mo, W, Nb, Ta, and Re. 2. The positive electrode active material for a lithium secondary battery according to claim 1.   A lithium secondary battery comprising a positive electrode active material layer containing at least the positive electrode active material material for a lithium secondary battery according to any one of claims 1 to 19 and a binder on a current collector. Battery positive electrode.   21. A lithium secondary battery comprising a negative electrode capable of inserting and extracting lithium, a non-aqueous electrolyte containing a lithium salt, and a positive electrode capable of inserting and extracting lithium, wherein the lithium secondary battery according to claim 20 is used as the positive electrode. A lithium secondary battery using a positive electrode for a battery.