JP5343347B2 - Positive electrode active material for lithium secondary battery, method for producing the same, positive electrode for lithium secondary battery and lithium secondary battery using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive-electrode active material for a lithium secondary battery that has small voids among active-material particles and high bulk density, achieves cost reduction, high safety, and high load characteristics when used as a positive-electrode material for a lithium secondary battery while achieving improvement in powder handleability due to improvement in bulk density, and consequently achieves an inexpensive lithium secondary battery which has excellent handleability, high safety, and excellent performance. <P>SOLUTION: The positive-electrode active material for a lithium secondary battery has mother particles made of a lithium-nickel-manganese-cobalt based composite oxide, in which primary particle crystals are aggregated so as to form spherical secondary particles and which have voids on each surface and in each inside of the secondary particles, and conductive fine powder filled into some voids in the mother particles. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

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

  Lithium secondary batteries are excellent in energy density and output density, and are effective in reducing the size and weight. Therefore, the demand for power supplies for portable devices such as notebook computers, mobile phones, and handy video cameras is growing 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.
Furthermore, there is a demand for a material with a good performance balance that is excellent in low cost, safety, and life (particularly under high temperatures).

  Currently, lithium manganese composite oxides having a spinel structure, layered lithium nickel composite oxides, layered lithium cobalt composite oxides, and the like have been put into practical use as positive electrode active material materials for lithium secondary batteries. All of the lithium secondary batteries using these lithium-containing composite oxides have advantages and disadvantages in terms of characteristics. That is, a lithium manganese composite oxide having a spinel structure is inexpensive and relatively easy to synthesize, and is excellent in safety when used as a battery, but has a low capacity and inferior high-temperature characteristics (cycle and storage). Layered lithium-nickel composite oxides have high capacity and excellent high-temperature characteristics, but are difficult to synthesize, have inferior safety when used as batteries, and have drawbacks such as requiring careful storage. Layered lithium cobalt-based composite oxides are widely used as power sources for portable devices because they are easy to synthesize and have an excellent balance of battery performance. However, they are not sufficient in safety and costly. It is a drawback.

  Under these circumstances, lithium nickel manganese cobalt-based composite oxides having a layered structure have been overcome as disadvantages of these positive electrode active material materials as possible candidates for active material materials that can overcome or be reduced as much as possible and are excellent in battery performance balance. Proposed. Particularly, in recent years, demands for lowering costs, higher voltages, and increasing safety demands are promising as positive electrode active material materials that can meet any of the demands.

  However, the degree of cost reduction, higher voltage, and safety will vary depending on the composition ratio. Therefore, for further cost reduction, use with a higher upper limit voltage, and higher safety requirements. Therefore, it is necessary to select and use one having a limited composition range such as a manganese / nickel atomic ratio of approximately 1 or more, or a reduction in the cobalt ratio. However, a lithium secondary battery using a lithium nickel manganese cobalt composite oxide having such a composition range as a positive electrode material deteriorates load characteristics such as rate and output characteristics and low-temperature output characteristics. An improvement was needed.

  Therefore, in order to solve the problem of improving load characteristics such as rate and output characteristics, the present inventors suppressed grain growth and sintering while maintaining sufficiently high crystallinity at the stage of firing the active material. As a result of earnest examination, considering that it is important to obtain fine particles, especially in layered lithium nickel manganese cobalt based composite oxide, after adding a compound containing an element such as W, firing at a certain temperature or more, We found that lithium transition metal compound powder consisting of fine particles with suppressed grain growth and sintering can be obtained, and as a lithium secondary battery positive electrode material, in addition to low cost, high voltage resistance and high safety The load characteristics such as rate and output characteristics can be improved. However, in this case, physical property changes such as a decrease in bulk density and an increase in specific surface area occur, so that new problems have been faced in that handling as a powder and in this case, electrode preparation becomes difficult.

  Therefore, as a result of intensive investigations aimed at improving the bulk density and optimizing the specific surface area, a compound containing an element such as W and a compound containing an element such as B were added together, It has been found that by firing at a temperature, lithium-containing transition metal compound powders that are easy to handle and electrode preparation can be obtained without impairing the above-described improvement effect. However, even in this method, the gaps between the obtained active material particles are still large, and in order to further improve the bulk density, a device for further reducing the gaps between the active material particles is necessary.

  Conventionally, the following Patent Documents 1 to 4 are disclosed as known documents in which a post-treatment for applying a compressive shear stress as indicated by the present invention is performed on a positive electrode active material powder for a lithium secondary battery. .

  Patent Document 1 (Japanese Patent Laid-Open No. 9-92265) includes a blending step of blending a powdered metal oxide and a powdered carbon material constituting an active material body, and the metal oxide and the carbon material. It is disclosed to perform a treatment comprising a coating step of applying a compressive shear stress to cover the surface of the metal oxide with 15% or more of the apparent surface of the metal oxide with the carbon material. However, the production method of the powdered metal oxide constituting the active material body is based on the liquid phase method, and one of the features of the present invention is that the primary particle crystals aggregate to form spherical secondary particles. The lithium transition metal compound powder having voids on the surface and inside of the secondary particles cannot be obtained, resulting in solid secondary particles. Accordingly, the blended carbon material is only coated on the surface of the secondary particles constituting the active material main body even when compressive shear stress is applied, and there is a problem that a good conductive path cannot be secured across the secondary particles. there were.

  In Patent Document 2 (Japanese Patent Laid-Open No. 2003-137554), compressive shear stress is applied to a lithium manganese composite oxide obtained by a production method characterized by spray drying a slurry obtained by wet pulverization and mixing. It is disclosed that the bulk density is improved by adding an additional post-treatment. However, the manufacturing method of the lithium transition metal-based compound powder constituting the active material main body uses lithium hydroxide as a lithium compound raw material, and there are differences such as different ratios of lithium raw materials. Secondary particles with few voids, in which primary particle crystals are aggregated to form spherical secondary particles, and it is difficult to obtain a powder having voids on and inside the secondary particles. It becomes. Therefore, the blended carbon material only covers the vicinity of the surface of the secondary particles constituting the active material body even when compressive shear stress is applied, and provides a good conductive path across the secondary particles as in the present invention. There was a problem that it could not be secured. In addition, since the oxide used as the active material main body is a lithium manganese aluminum composite oxide having a spinel structure, there is also a problem that battery performance with an excellent performance balance cannot be exhibited.

Patent Document 3 (Japanese Patent Application Laid-Open No. 2004-103546) uses positive electrode active material particles obtained by subjecting a mixture of a lithium / nickel composite oxide, activated carbon and carbon black to a compressive shear stress, thereby reducing the temperature. It is disclosed that the output under the atmosphere and the cycle life can be compatible at a high level. However, a lithium nickel manganese cobalt based composite oxide powder, which is one of the features of the present invention, is formed by agglomerating primary particle crystals to form spherical secondary particles and having voids on the surface and inside of the secondary particles. There is no provision of the manufacturing method necessary to obtain, and since the specific surface area of the layered lithium nickel cobalt aluminum composite oxide used in the examples is as low as 0.5 to 0.7 m ² / g, there are few voids. The probability that secondary particles are obtained is high. Therefore, the blended carbon material only covers the vicinity of the surface of the secondary particles constituting the active material body even when compressive shear stress is applied, and provides a good conductive path across the secondary particles as in the present invention. There was a problem that it could not be secured. In addition, in the examples, since the oxide used as the active material main body is a layered lithium nickel cobalt aluminum composite oxide, there is also a problem that the battery performance excellent in performance balance cannot be exhibited.

  In Patent Document 4 (Japanese Patent Laid-Open No. 2006-73482), a lithium compound is attached to the surface of lithium nickel manganese cobalt oxide particles using a mechano-fusion method, so that power can be stably output at a high output over a long period of time. It is disclosed to provide a positive electrode material capable of supplying However, since the manufacturing method of the lithium nickel manganese cobalt composite oxide constituting the active material main body is a manufacturing method in which spherical secondary particles cannot be formed, even if mechanofusion treatment is performed, the form as in the present invention is obtained. There was a problem that it was not possible. Furthermore, there was a difference that the substance to be attached was not a conductive carbon material.

Patent Document 5 (Japanese Patent Laid-Open No. 2007-173134) discloses an electrode material for a lithium ion battery comprising an electrode active material and a conductive material, and the surface of the electrode active material is covered with the conductive material. It is disclosed that a lithium battery electrode having a high discharge capacity at a high speed charge / discharge rate and having a sufficient charge / discharge rate performance can be formed by using the electrode material for a lithium ion battery characterized by the above. However, since such a technique is already known (for example, Patent Document 6: JP-A-9-92265), the surface is an electrode active material coated with a conductive material. There was a problem that a good conductive path could not be secured across the secondary particles. In addition, since the compound used as the active material main body is LiFePO ₄ having an olivine structure, there is a problem in that the battery performance excellent in performance balance cannot be exhibited.
JP-A-9-92265 JP 2003-137554 A JP 2004-103546 A JP 2006-73482 A JP 2007-173134 A JP-A-9-92265

  The present invention has a small gap between the active material particles, a high bulk density, and when used as a positive electrode material for a lithium secondary battery, it achieves a reduction in cost, a higher safety and a higher load characteristic, and an improvement in the bulk density. Providing a positive electrode active material for a lithium secondary battery that can improve the powder handleability, and thus can realize a lithium secondary battery that is inexpensive, excellent in handleability, high in safety, and excellent in performance. The purpose is to do.

  As a result of intensive studies to reduce the gaps between the active material particles, the present inventor has formed primary secondary crystals to form spherical secondary particles, and lithium nickel having voids on the surface and inside of the secondary particles. By filling fine particles smaller than the void size with respect to the manganese cobalt based composite oxide powder, the bulk density is drastically improved. Furthermore, by using conductive fine particles as the void filling fine particles, the output characteristics are also improved. Thus, the present inventors have found that a positive electrode active material powder for a lithium secondary battery that is easy to handle and prepare an electrode can be obtained without impairing the above-described improvement effect.

The positive electrode active material for a lithium secondary battery of the present invention comprises a lithium nickel manganese composite oxide in which primary particle crystals are aggregated to form spherical secondary particles, and there are voids in the surface and inside of the secondary particles. A positive electrode active material for a lithium secondary battery having a mother particle and a conductive fine powder filled in a part of a void of the mother particle , wherein the average primary particle diameter of the conductive fine powder is 50 nm or less Yes, the pore distribution curve by the mercury intrusion method has at least one main peak having a peak top at a pore radius of 300 nm or more and 1000 nm or less, and a peak top at a pore radius of 1 nm or more and less than 80 nm In the pore distribution curve by the mercury intrusion method, the pore volume related to the main peak having a peak top at a pore radius of 300 nm or more and 1000 nm or less There 0.1 cm ³ / g or more, 0.5 cm ³ / g or less and a pore radius of 1nm or more, the pore volume of the sub-peak with a peak top present at less than 80nm is 0.01 cm ³ / g or more, 0 .2 cm ³ / g or less, and in the mercury intrusion curve by the mercury intrusion method, the amount of mercury intrusion when the pressure is increased from 3.86 kPa to 413 MPa is 0.3 cm ³ / g or more and 0.8 cm ³ / g or less. Yes, when the carbon concentration is C (% by weight), the C value is 1% by weight or more and 10% by weight or less (claim 1).
That is, 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 primary particle crystals are aggregated to form spherical secondary particles, and there are voids on the surface and inside of the secondary particles. After the addition of conductive fine powder to the product powder, post-processing is applied to apply compressive shear stress to reduce the voids between primary particles and improve the bulk density while further increasing the output. It is possible.

Further, in the positive electrode active material for a lithium secondary battery of the present invention, in the mercury intrusion curve by this mercury intrusion method, the amount of mercury intrusion when the pressure is increased from 3.86 kPa to 413 MPa is equal to the amount of mercury intrusion of the mother particles. It is preferable to reduce to 80% or less (Claim 2 ).

The positive electrode active material for a lithium secondary battery of the present invention preferably has a volume resistivity of 0.01 Ω · cm or more and 1 × 10 ³ Ω · cm or less when consolidated at a pressure of 40 MPa (claims) Item 3 ).

The positive electrode active material for a lithium secondary battery of the present invention preferably has a BET specific surface area of 5 m ² / g or more and 100 m ² / g or less (claim 4 ).

The positive electrode active material for a lithium secondary battery of the present invention preferably has a bulk density of 1.5 g / cm ³ or more and 2.4 g / cm ³ or less (claim 5 ).

In addition, the positive electrode active material for a lithium secondary battery of the present invention has a refractive index set to 1.24 by a laser diffraction / scattering type particle size distribution measuring device, and the particle size reference is a volume reference. The median diameter measured without sonic dispersion is 3 μm or more and 30 μm or less, and the median diameter measured after 5 minutes of ultrasonic dispersion (output 30 W, frequency 22.5 kHz) is 0.5 μm or more and 10 μm or less. It is preferable that it is present (claim 6 ).

The positive electrode active material for lithium secondary battery of the present invention, the main component composition of the mother particle is represented by the following composition formula (I) is preferably (claim 7).
LiMO ₂ (I)
(However, in the above 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 0.8 or more and 5 or less, (The Co / (Mn + Ni + Co) molar ratio is 0 or more and 0.35 or less, and the Li molar ratio in M is 0.001 or more and 0.2 or less.)

Further, in the positive electrode active material for a lithium secondary battery of the present invention, it is preferable that M in the composition formula (I) is represented by the following formula (II) (claim 8 ).
M = Li _{z / (2 + z)} {(Ni _{(1 + y) / 2} Mn _{(1-y) / 2} ) _1-x Co _x } _{2 / (2 + z)} (II)
(However, in the above formula (II),
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 base particle is a total of B and W with respect to the total molar amount of the transition metal elements in the main component raw material. .01 mol% or more, after adding together in a ratio of less than 2 mol%, it is preferable that calcined at 900 ° C. or higher (claim 9).

The method for producing a positive electrode active material for a lithium secondary battery of the present invention is a method for producing such a positive electrode active material for a lithium secondary battery of the present invention, comprising lithium carbonate, a manganese compound, a nickel compound, and Each of the metal compounds of the cobalt compound used as necessary is pulverized in a liquid medium, a slurry adjusting step for obtaining a slurry in which these are uniformly dispersed, a spray drying step for spray drying the obtained slurry, A firing step of firing the obtained spray-dried body, a classification step of classifying the obtained fired powder, and a process of adding compressive shear stress after adding conductive fine powder to the obtained classified powder And a post-treatment step (claim 10 ).

In the method for producing a positive electrode active material for a lithium secondary battery according to the present invention, in the slurry adjustment step, the lithium carbonate and the metal compound are mixed in a liquid medium with a laser diffraction / scattering type particle size distribution measuring device. In the spray drying process, the particle size is set to 1.24, and 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. 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 ≦ it is preferred to carry out the spray drying under conditions such that a 10000 (claim 11).

The method for producing a positive electrode active material for a lithium secondary battery of the present invention includes a nickel compound, a manganese compound, a cobalt compound, a boron compound, and a tungsten compound as the metal compound, and the spray drying in the firing step. the body, an oxygen-containing gas atmosphere, it is preferably baked at 900 ° C. or higher (claim 12).

The positive electrode for a lithium secondary battery of the present invention has a positive electrode active material layer containing the active material for a lithium secondary battery positive electrode of the present invention and a binder on a current collector (claim). 13 ).

The positive electrode for a lithium secondary battery of the present invention has a density of a positive electrode active material layer after repeating pressurization for 1 minute at a pressure of 760 MPa five times (hereinafter sometimes referred to as “density after five presses”). Is preferably 3.0 g / cm ³ or more (claim 14 ).

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 15 ).

  When used as a positive electrode material for a lithium secondary battery, the positive electrode active material for a lithium secondary battery of the present invention achieves low cost, high safety and high load characteristics, and powder handling properties by improving bulk density. Improvements can be made. For this reason, according to the present invention, a lithium secondary battery that is inexpensive, excellent in handleability, high in safety, and excellent in performance is 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. The content of is not specified.

[Positive electrode active material for lithium secondary battery]
The positive electrode active material for a lithium secondary battery according to the present invention comprises a lithium nickel manganese composite oxide (this is a secondary oxide formed by agglomeration of primary particle crystals to form spherical secondary particles having voids on the surface and inside of the secondary particles). The composite oxide may further contain cobalt.Hereinafter, this may be referred to as “lithium nickel manganese (cobalt) -based composite oxide”) and one of the voids of the base particle. It has the conductive fine powder with which the part was filled.
Examples of methods for confirming the structural characteristics of the positive electrode active material for a lithium secondary battery of the present invention include SEM (scanning electron microscope) observation, cross-sectional SEM observation, and pore distribution measurement by mercury porosimetry. Can be mentioned.

<SEM>
The positive electrode active material for a lithium secondary battery of the present invention is a surface of a mother particle composed of spherical secondary particles in which primary particles of lithium nickel manganese (cobalt) composite oxide as a main component are aggregated in SEM observation. In addition, a part of the void existing inside is filled with conductive fine powder.

In the present invention, the spherical secondary particles are formed by aggregation of primary particle crystals as shown in SEM photographs (FIGS. 5 to 7) of Example 1 or Comparative Examples 1 and 2 shown later. The average value of the ratio [L _b / L _a ] of the small diameter [L _b (μm)] at the midpoint in the direction perpendicular to the maximum diameter direction [L _a (μm)] of the secondary particle It means 0.7 or more.

<Cross-section SEM>
The positive electrode active material for a lithium secondary battery according to the present invention is a matrix comprising spherical secondary particles in which primary particles of lithium nickel manganese (cobalt) composite oxide as a main component are randomly aggregated in cross-sectional SEM observation. Part of the voids present on the surface and inside of the particles, particularly the open voids, are filled with the conductive fine powder.

<Pore characteristics by mercury intrusion method>
The positive electrode active material for a lithium secondary battery of the present invention preferably satisfies a specific condition in measurement by mercury porosimetry.

The mercury intrusion method employed in the evaluation of the positive electrode active material for a lithium secondary battery of the present invention will be 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 shape of the pore is cylindrical, the radius is r, the surface tension of mercury is δ, and the contact angle is θ, the size in the direction of extruding mercury from the pore is −2πrδ (cos θ). (If θ> 90 °, this value is positive). Moreover, 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 (cosθ) = 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).

  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.

In the positive electrode active material for a lithium secondary battery of the present invention, when a pore distribution curve is measured by the above mercury intrusion method, a specific main peak described below usually appears.
In the present specification, the “pore distribution curve” refers to the total pore volume per unit weight (usually 1 g) of pores having a radius equal to or larger than the radius of the pores on the horizontal axis, The value obtained by differentiating the logarithm of the pore radius is plotted on the vertical axis, and is usually expressed as a graph connecting the plotted points. In particular, the pore distribution curve obtained by measuring the lithium transition metal-based compound powder of the present invention by mercury porosimetry is referred to as “the pore distribution curve according to the present invention” as appropriate in the following description.

In this specification, “main peak” refers to the largest peak among the peaks of the pore distribution curve, and “sub peak” refers to peaks other than the main peak of the pore distribution curve.
Further, in this specification, “peak top” refers to a point where the coordinate value of the vertical axis takes the largest value in each peak of the pore distribution curve.

(Main peak)
The main peak of the pore distribution curve according to the present invention has a peak top whose pore radius is usually 300 nm or more, preferably 400 nm or more, most preferably 500 nm or more, and usually 1000 nm or less, preferably 900 nm or less. It is preferably 800 nm or less, more preferably 700 nm or less, and most preferably 650 nm or less. When the upper limit of this range is exceeded, when a battery is produced using the active material of the present invention as a positive electrode material, lithium diffusion in the positive electrode material is hindered, or a conductive path is insufficient, and load characteristics may be deteriorated. There is sex. On the other hand, below the lower limit of this range, when a positive electrode is produced using the active material of the present invention, the required 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 there is a possibility that the coating film is likely to be peeled off during the winding process during battery assembly.

In addition, the pore volume of the main peak included in the pore distribution curve according to the present invention is suitably usually 0.1 cm ³ / g or more, preferably 0.15 cm ³ / g or more, more preferably 0.2 cm ^3. / g or more, most preferably 0.25 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 voids become excessive, and when the active material of the present invention is used as the positive electrode material, the positive electrode active material filling rate into the positive electrode plate is lowered, and the battery capacity may be restricted. There is sex. 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 active material of the present invention as a positive electrode material, lithium diffusion between secondary particles is inhibited, Load characteristics may be degraded.

(Sub peak)
The pore distribution curve according to the present invention may have a plurality of sub-peaks in addition to the above-mentioned main peak, and in particular, the sub-peak has a peak top within a pore radius range of 1 nm or more and less than 80 nm. It is preferable.

In addition, the pore volume of the above-mentioned sub-peak included in the pore distribution curve according to the present invention is suitably usually 0.01 cm ³ / g or more, preferably 0.02 cm ³ / g or more, more preferably 0.03 cm. ³ / g or more, most preferably 0.04 cm ³ / g or more and usually 0.2 cm ³ / g or less, preferably 0.15 cm ³ / g or less, more preferably 0.10 cm ³ / g or less, and most preferably Is 0.08 cm ³ / g or less. When the upper limit of this range is exceeded, voids between secondary particles become excessive, and when the 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 is lowered, and the battery capacity is reduced. There is a possibility of being constrained. On the other hand, if the lower limit of this range is not reached, voids between the secondary particles become excessively small, so that when a battery is produced using the active material of the present invention as the positive electrode material, lithium diffusion between the secondary particles is inhibited. As a result, the load characteristics may deteriorate.

(Mercury injection amount)
The positive electrode active material for a lithium secondary battery of the present invention has a mercury intrusion amount of 0.3 cm ³ / g or more, 0.8 cm at a pressure increase from 3.86 kPa to 413 MPa in a mercury intrusion curve by a mercury intrusion method. It is preferable that it is ³ / g or less.
The amount of mercury intrusion is usually 0.3 cm ³ / g or more, preferably 0.4 cm ³ / g or more, most preferably 0.5 cm ³ / g or more, usually 0.8 cm ³ / g or less, preferably 0.7 cm. ³ / g or less, more preferably 0.65 cm ³ / g or less, and most preferably not more than 0.6 cm ³ / g. When the upper limit of this range is exceeded, the voids become excessive, and when the 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 particles become excessively small. Therefore, when a battery is produced using the active material of the present invention as a positive electrode material, lithium diffusion between particles is inhibited, and load characteristics are reduced. Decreases.

Further, the positive electrode active material for a lithium secondary battery of the present invention is a mercury intrusion amount of lithium nickel manganese (cobalt) -based composite oxide secondary particle powder, that is, mother particles, before being filled with conductive fine powder. It is preferable that the mercury intrusion amount is 80% or less.
The mercury intrusion amount of the positive electrode active material for the lithium secondary battery of the present invention is usually 80% or less, preferably 75% or less, most preferably 80% or less with respect to the mercury intrusion amount of the mother particles before the conductive fine powder is filled. It is preferably 70% or less, usually 40% or more, preferably 50% or more, more preferably 55% or more, and most preferably 60% or more. When the upper limit of this range is exceeded, the voids become excessive, and when the 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 particles become excessively small. Therefore, when a battery is produced using the active material of the present invention as a positive electrode material, lithium diffusion between particles is inhibited, and load characteristics are reduced. Decreases.

<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 1 wt% or more, preferably 1.5 wt% or more, more preferably 2 wt% or more, most preferably It is 2.5% by weight or more, usually 10% by weight or less, preferably 8% by weight or less, more preferably 6% by weight or less, and most preferably 4% by weight or less. If the lower limit is not reached, battery performance may be reduced. If the upper limit is exceeded, swelling due to gas generation when the battery is produced 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 using an oxygen gas combustion (high-frequency heating furnace type) infrared absorption method, as shown in the Examples section below. .
In addition, the carbon component contained in the positive electrode active material material for lithium secondary batteries of Example 1 and Comparative Example 3 obtained by the carbon analysis described below is mainly used as a technique for increasing the electronic conductivity and bulk density of the mother particles. It is derived from the conductive fine powder filled in the gap. On the other hand, it is considered that the carbon component contained in the positive electrode active material for lithium secondary batteries of Comparative Examples 1 and 2 is derived from the lithium carbonate contained in the mother particles.

<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 0.01 Ω · cm or more, more preferably 0.1 Ω · cm or more as a lower limit. 1 Ω · cm or more is more preferable, and 5 Ω · cm or more is most preferable. The upper limit is preferably 1 × 10 ³ Ω · cm or less, more preferably 1 × 10 ² Ω · cm or less, further preferably 5 × 10 ¹ Ω · cm or less, and most preferably 1 × 10 ¹ Ω · cm or less. . If this volume resistivity exceeds this upper limit, the load characteristics when used as a battery may be reduced. On the other hand, if the volume resistivity falls below this lower limit, the safety when used as a battery may be reduced.

  In the present invention, the positive electrode active material for the lithium secondary battery has a volume resistivity of four probe / ring electrodes, an electrode interval of 5.0 mm, an electrode radius of 1.0 mm, a sample radius of 12.5 mm, and an applied voltage limiter. Is a volume resistivity measured in a state where the active material is compacted at a pressure of 40 MPa, with 90V. The volume resistivity can be measured, for example, by using a powder resistance measuring device (for example, Lorester GP powder resistance measuring system manufactured by Dia Instruments Co., Ltd.) with a powder probe unit on a powder under a predetermined pressure. It can be carried out.

<BET specific surface area>
Positive electrode active material for lithium secondary battery of the present invention may also, BET specific surface area is usually ^{5 m} 2 / g or more, preferably ^{10 m} 2 / g or more, more preferably ^{20 m} 2 / g or more, and most preferably ^{30 m} 2 / g or more and usually 100 m ² / g or less, preferably 80 m ² / g or less, more preferably 60 m ² / g or less, and most preferably 40 m ² / g or less. If the BET specific surface area is smaller than this range, the battery performance is likely to be lowered, and if it is larger, the bulk density is difficult to increase, and there is a possibility that a problem is likely to occur in the coating property at the time of forming the positive electrode active material.

  The BET specific surface area can be measured by a known BET type powder specific surface area measuring device. In the present invention, an OMS Riken: AMS8000 type automatic powder specific surface area measuring device was used, nitrogen was used as an adsorption gas, and helium was used as a carrier gas. 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.

<The bulk density>
The bulk density of the positive electrode active material for a lithium secondary battery of the present invention is usually 1.5 g / cc or more, preferably 1.55 g / cc or more, more preferably 1.6 g / cc or more, and most preferably 1.7 g / cc. cc or more, usually 2.4 g / cc or less, preferably 2.2 g / cc or less, more preferably 2.0 g / cc or less, and most preferably 1.9 g / cc or less. If the bulk density is lower than this lower limit, there is a possibility of adversely affecting the powder filling property and electrode preparation, and the fact that the bulk density exceeds the upper limit is preferable for improving the powder filling property and the electrode density, while the specific surface area. May become too low, and battery performance may be reduced.
In the present invention, the bulk density was determined as the powder packing density (tap density) g / cc when 5 to 10 g of the active material was placed in a 10 ml glass graduated cylinder and tapped 200 times with a stroke of about 20 mm. .

<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 3 μm or more, preferably 5 μm or more, more preferably 7 μm or more, even more preferably when measured without performing ultrasonic dispersion in an aqueous medium. It is 10 μm or more, most preferably 12 μm or more, and usually 30 μm or less, preferably 25 μm or less, more preferably 23 μm or less, still more preferably 20 μm or less, and most preferably 18 μm or less. The median diameter when measured after ultrasonic dispersion for 5 minutes is usually 0.5 μm or more, preferably 0.8 μm or more, more preferably 1 μm or more, still more preferably 1.2 μm or more, and most preferably 1. 4 μm or more, usually 10 μm or less, preferably 8 μm or less, more preferably 5 μm or less, still more preferably 3 μm or less, and most preferably 2 μm or less. If the lower limit is not reached, there may be a problem in applicability at the time of forming the positive electrode active material layer, and if the upper limit is exceeded, battery performance may be lowered.

In addition, the 90% cumulative diameter (D ₉₀ ) of the positive electrode active material for a lithium secondary battery of the present invention is usually 60 μm or less, preferably 55 μm or less, when measured without performing ultrasonic dispersion in an aqueous medium. Preferably it is 50 μm or less, most preferably 45 μm or less, usually 5 μm or more, preferably 10 μm or more, more preferably 12 μm or more, and most preferably 15 μm or more. The 90% integrated diameter (D ₉₀ ) measured after ultrasonic dispersion for 5 minutes is usually 20 μm or less, preferably 15 μm or less, more preferably 10 μm or less, most preferably 8 μm or less, and usually 1.5 μm. Above, preferably 2 μm or more, more preferably 2.5 μm or more, and most preferably 3 μm or more. If the upper limit is exceeded, battery performance may be reduced, and if the lower limit is not reached, 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 in an aqueous medium as a volume reference. In the present invention, a 0.1% by weight sodium hexametaphosphate aqueous solution was used as a dispersion medium used in the measurement, and measurement was performed after 0 minutes and 5 minutes of ultrasonic dispersion (output 30 W, frequency 22.5 kHz).

<Average primary particle size>
The 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 0.1 μm or more, more preferably 0.2 μm or more, and further preferably 0.3 μm. As described above, most preferably 0.5 μm or more, and the upper limit is preferably 2 μm or less, more preferably 1.5 μm or less, further preferably 1 μm or less, and most preferably 0.9 μm or less. If the average primary particle size exceeds the above upper limit, it may adversely affect the powder filling property or the specific surface area will decrease, which may increase the possibility that the battery performance such as rate characteristics and output characteristics will decrease. There is sex. If the lower limit is not reached, there is a possibility that problems such as inferior reversibility of charge / discharge due to the undeveloped crystals.

  In addition, the average primary particle diameter in this invention is an average diameter observed with the scanning electron microscope (SEM), and the average particle diameter of about 10-30 primary particles using a SEM image of 30,000 times. It can be obtained as a value.

<Crystal structure>
The mother particles of the positive electrode active material for a lithium secondary battery of the present invention are formed by agglomerating primary particle crystals of lithium nickel manganese (cobalt) -based composite oxide to form spherical secondary particles, and the surface of the secondary particles and The lithium nickel manganese (cobalt) -based composite oxide constituting the mother particle is characterized by having voids inside, and the lithium nickel manganese (cobalt) -based structure including a crystal structure belonging to a layered structure Those containing a composite oxide as the main component are preferred.

（以下「層状Ｒ（−３）ｍ構造」と表記することがある。）に帰属される。 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.

(Hereinafter referred to as “layered R (−3) m structure”).

However, the layered LiMeO ₂ is not limited to the layered R (−3) m structure. In addition to this, 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, is also a layered compound in which a Li layer, a [Li _1/3 Mn _2/3 ] layer, and an oxygen layer are stacked.

<composition>
Moreover, it is preferable that the main component of the base particle of the positive electrode active material for a lithium secondary battery of the present invention is a lithium nickel manganese (cobalt) -based composite oxide represented by the following composition formula (I).
LiMO ₂ (I)
However, M is an element comprised from Li, Ni, and Mn, or Li, Ni, Mn, and Co, Mn / Ni molar ratio is 0.8 or more, Preferably it is 0.82 or more, More preferably, it is 0. .85 or more, more preferably 0.88 or more, most preferably 0.9 or more, usually 5 or less, preferably 4 or less, more preferably 3 or less, still more preferably 2.5 or less, most preferably 1.5 or less. It is. 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 Is 0.20 or less, more preferably 0.15 or less, still more preferably 0.10 or less, and most preferably 0.099 or less. The molar ratio of Li in M is 0.001 or more, preferably 0.01 or more, more preferably 0.02 or more, further preferably 0.03 or more, most preferably 0.05 or more, usually 0.2 or less, preferably Is 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 ± 0.10. And particularly preferably in the range of 2 ± 0.05.

  Further, foreign elements may be introduced into the lithium nickel manganese (cobalt) -based composite oxide. The different elements include B, Na, Mg, Al, Si, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, Ru, Rh, and 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, and those in which B and W are introduced are particularly preferable. These foreign elements may be incorporated into the crystal structure of the lithium nickel manganese cobalt-based composite oxide, or may not be incorporated into the crystal structure of the lithium nickel manganese (cobalt) -based composite oxide. It may be unevenly distributed as a single substance or a compound at a grain boundary or the like.

<Preferred composition>
In the lithium nickel manganese (cobalt) -based composite oxide constituting the base particle of the positive electrode active material for a lithium secondary battery of the present invention, the atomic configuration in the M site in the composition formula (I) is represented by the following formula (II). Those shown are particularly preferred.
M = Li _{z / (2 + z)} {(Ni _{(1 + y) / 2} Mn _{(1-y) / 2} ) _1-x Co _x } _{2 / (2 + z)} (II)
(However, in the above formula (II),
0 ≦ x ≦ 0.1,
−0.1 ≦ y ≦ 0.1,
(1-x) (0.05-0.98y) ≤z≤ (1-x) (0.20-0.88y)
It is. )

  In the above formula (II), 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. Hereinafter, it is preferably 0.099 or less, and most preferably 0.098 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, 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. If z is below this lower limit, the conductivity will decrease, and if it exceeds the upper limit, the amount of substitution to transition metal sites will increase so much that the battery capacity will decrease, leading to a decrease in the performance of lithium secondary batteries using this. There is sex. On the other hand, if z is too large, the carbon dioxide absorbability of the active material powder increases, so that it becomes easy to absorb carbon dioxide in the atmosphere. As a result, it is estimated that the concentration of contained carbon increases.

  In the composition range of the above formula (II), the closer the z value is to the lower limit that is a constant ratio, the lower the rate characteristics and output characteristics as a battery, and the lower the z value is to the upper limit, Although the rate characteristics and output characteristics of the battery are improved, there is a tendency for the capacity to decrease. In addition, the lower the y value, that is, the smaller the manganese / nickel atomic ratio, the higher the capacity is obtained at a lower charging voltage. However, the cycle characteristics and safety of batteries set at a higher charging voltage tend to be reduced. As the value is 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 value is to the lower limit, the lower the load characteristics such as rate characteristics and output characteristics when the battery is used. Conversely, the closer the x value is to the upper limit, the rate characteristics when the battery is used. However, if this upper limit is exceeded, the cycle characteristics and safety when set at a high charge voltage are reduced, and the raw material cost is increased. Setting the composition parameters x, y, and z within a specified range is an important component of the present invention.

  Here, the chemical meaning of the Li composition (z and x) in the lithium nickel manganese (cobalt) -based composite oxide, which is a preferred composition of the mother particles according to the present invention, 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.
In order to obtain x, y, z of the composition formula of the lithium nickel manganese (cobalt) -based composite oxide, each transition metal and Li are analyzed with an inductively coupled plasma emission spectrometer (ICP-AES), and Li / It is calculated by obtaining the ratio of Ni / Mn / Co.

  From a structural point of view, it is considered that Li related to z is substituted for the same transition metal site. Here, due to Li related to z, the average valence of Ni becomes larger than divalent (trivalent Ni is generated) by the principle of charge neutrality. Since z raises the Ni average valence, it becomes an index of the Ni valence (the ratio of Ni (III)).

となる。この計算結果は、Ｎｉ価数はｚのみで決まるのではなく、ｘ及びｙの関数となっていることを意味している。ｚ＝０かつｙ＝０であれば、ｘの値に関係なくＮｉ価数は２価のままである。ｚが負の値になる場合は、活物質中に含まれるＬｉ量が化学量論量より不足していることを意味し、あまり大きな負の値を有するものは本発明の効果が出ない可能性がある。一方、同じｚ値であっても、Ｎｉリッチ（ｙ値が大きい）及び／又はＣｏリッチ（ｘ値が大きい）な組成ほどＮｉ価数は高くなるということを意味し、電池に用いた場合、レート特性や出力特性が高くなるが、反面、容量低下しやすくなる結果となる。このことから、ｚ値の上限と下限はｘ及びｙの関数として規定するのがより好ましいと言える。 From the above composition formula, when calculating the Ni valence (m) accompanying the change of z, 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 but is a function of x and y. If z = 0 and y = 0, the Ni valence remains divalent regardless of the value of x. When z is a negative value, 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 may not have the effect of the present invention. There is sex. On the other hand, even if the z value is the same, it means that the Ni valence becomes higher as the composition is rich in Ni (large y value) and / or rich in Co (large x value). The rate characteristics and output characteristics 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 value as a function of x and y.

  In addition, when the x value is in the range of 0 ≦ x ≦ 0.1 and the amount of Co is small, in addition to reducing the cost, it was used as a lithium secondary battery designed to be charged at a high charging potential. In some cases, charge / discharge capacity, cycle characteristics, and safety are improved.

  In the present invention, the mother particles contain a boron-containing compound and a tungsten-containing compound in a total of B and W with respect to the total molar amount of the transition metal elements in the lithium nickel manganese (cobalt) composite oxide raw material as the main component. It is preferable that it is fired after the combined addition at a ratio of 0.01 mol% or more and less than 2 mol%.

  In addition, the mother particles according to the present invention are preferably those obtained by firing at a high temperature in an oxygen-containing gas atmosphere in order to increase the crystallinity of the positive electrode active material. In particular, the lower limit of the firing temperature is usually 900 ° C. or higher, preferably 920 ° C. or higher, more preferably 940 ° C. or higher, even more preferably, in the lithium nickel manganese cobalt-based composite oxide having the composition represented by the composition formula (I). Is 950 ° C. or higher, most preferably 975 ° C. or higher, and the upper limit is 1200 ° C. or lower, preferably 1175 ° C. or lower, more preferably 1150 ° C. or lower, and most preferably 1125 ° C. or lower. If the firing temperature is too low, heterogeneous phases are mixed, and the lattice distortion increases without developing a crystal structure. Moreover, the specific surface area becomes too large. Conversely, if the firing temperature is too high, the primary particles grow excessively, sintering between the particles proceeds too much, and the specific surface area becomes too small.

The boron-containing compound used as a raw material for the mother particles is not particularly limited in type, but usually boric acid, oxo acid salts, oxides, hydroxides, and the like are used. These may be used alone or in combination of two or more. Among these compounds, boric acid and oxides are preferable, and boric acid is particularly preferable because it can be obtained as an industrial raw material at low cost. More specifically, BO, B ₂ O ₂ , B ₂ O ₃ , B ₄ O ₅ , B ₆ O, B ₇ O, B ₁₃ O ₂ , LiBO ₂ , LiB ₅ O ₈ , Li ₂ B ₄ O ₇ , HBO ₂ , H ₃ BO ₃ , B (OH) ₃ , B (OH) ₄ , and the like. From the viewpoint of being relatively inexpensive and easily available as industrial raw materials, B ₂ O ₃ , H ₃ BO are preferable. ₃ is particularly preferable, and H ₃ BO ₃ is particularly preferable.

In addition, the tungsten-containing compound is not particularly limited in its type, but an oxide is usually used. Exemplary compounds include 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 and the} like, and from the viewpoint of being relatively easily available as an industrial raw material or including lithium, WO ₃ and Li ₂ WO ₄ are preferable, and WO ₃ is particularly preferable.

  The range of the total addition amount of the boron-containing compound and the tungsten-containing compound is usually 0.01 mol% or more and 2 mol% in terms of the total molar amount of B and W with respect to the total molar amount of the transition metal elements constituting the main component. Less than, preferably 0.03 mol% to 1.8 mol%, more preferably 0.04 mol% to 1.6 mol%, particularly preferably 0.05 mol% to 1.5 mol%. . If the total molar amount of B and W is less than this lower limit, the above effects may not be obtained, and if the upper limit is exceeded, battery performance may be deteriorated.

  In order to sufficiently obtain the effect of using B and W together, the molar ratio of B and W is usually B: W = 10: 1 to 1:20, preferably 5: 1 to 1:15, More preferably, it is 2: 1 to 1:10, and particularly preferably 1: 1 to 1: 6. Even if there is more B and less W than this range, conversely, even if there is less B or more W, the effect of using B and W together cannot be sufficiently obtained.

<Conductive fine powder>
As the conductive fine powder filled in the voids of the base particle of the positive electrode active material for lithium secondary battery of the present invention, preferably, when the positive electrode active material layer of the lithium secondary battery is formed, its conductivity is Conductive materials used for enhancing, for example, metal materials such as copper and nickel, graphite such as natural graphite and artificial graphite, carbon black such as acetylene black and ketjen black, amorphous carbon such as needle coke, etc. Fine powders such as carbon materials can be used. These conductive fine powders may be used alone or in combination of two or more in any combination and ratio.
Among these, ketjen black, acetylene black, etc. are particularly easy because they are easily filled in the gap, the filled fine powder easily forms a conductive path, and the electrolyte is easily retained in the filled gap. Carbon black is preferred.

The conductive fine powder is preferably of a size that can penetrate into the voids of the mother particles when compressive shear stress is applied to the mother particles in a post-treatment step described later. The primary particle diameter is preferably 500 nm or less, more preferably 100 nm or less, particularly 50 nm or less, and the BET specific surface area is 30 m ² / g or more, more preferably 200 m ² / g or more, and particularly preferably 500 m ² / g or more. When the average particle size of the conductive fine powder is larger than the above upper limit and the BET specific surface area is smaller than the lower limit, the conductive fine powder is too large to smoothly enter the voids of the mother particle, A positive electrode active material for a lithium secondary battery cannot be obtained. Since the lower limit of the average particle size and the upper limit of the BET specific surface area are 1 nm and 5000 m ² / g, the average particle size is 5 nm or more, particularly 10 nm or more, and the BET specific surface area is 3000 m ² / g or less, particularly 2000 m. ² / g or less is preferable.

<Reason why the positive electrode active material for a lithium secondary battery of the present invention provides 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 effects is considered as follows.
That is, the positive electrode active material for a lithium secondary battery according to the present invention is formed by agglomerating primary particle crystals to form spherical secondary particles, and a part of the voids of the mother particles having voids on the surface and inside of the secondary particles. In addition, since the conductive fine powder is filled, conductivity and bulk density are improved by the filled conductive fine powder, and the crystalline secondary particles maintain a spherical shape, and mercury intrusion is achieved. Since the amount of mercury intrusion at the time of pressurization in the curve is large and the pore volume between crystal particles is large, it is possible to increase the contact area between the surface of the positive electrode active material and the electrolyte when a battery is produced using this As a result of the surface condition that improves load characteristics (especially low-temperature output characteristics), the crystallinity is highly developed, and the existence ratio of heterogeneous phases is extremely low. Excellent property balance It is estimated that achieved the powder handling characteristics.

[Method for producing positive electrode active material for lithium secondary battery]
The method for producing the positive electrode active material for a lithium secondary battery of the present invention is not particularly limited, and lithium carbonate and manganese compounds, nickel compounds, and cobalt compounds used as necessary Are prepared in a liquid medium, a slurry adjusting step for obtaining a slurry in which these are uniformly dispersed, a spray drying step for spray drying the obtained slurry, and the obtained spray dried product in an oxygen-containing gas atmosphere. After the firing step of firing with, a classification step of classifying the obtained fired powder, and after adding a conductive fine powder such as ketjen black to the obtained classified powder, and after applying a treatment to apply compressive shear stress It is suitably manufactured by the method for manufacturing a positive electrode active material for a lithium secondary battery of the present invention including a treatment step.
However, the method for producing the positive electrode active material for a lithium secondary battery of the present invention is not limited to this method.
Here, the steps from the firing step to the classification step are steps for producing the mother particles according to the present invention, and the post-treatment step is a step for filling the voids of the mother particles with conductive fine powder.

  Below, the manufacturing method of the positive electrode active material material for lithium secondary batteries of this invention is demonstrated in detail.

<Slurry preparation process>
Among the raw material compounds used for preparing the slurry, lithium carbonate (Li ₂ CO ₃ ) is used as the lithium compound in the production of the positive electrode active material for a lithium secondary battery by the method of the present invention. You may use together with the above lithium compound. Among the lithium compounds used in combination, a lithium compound containing no nitrogen atom, sulfur atom or halogen atom is preferable because it does not generate harmful substances such as SO _x and NO _x during the firing treatment. It is a compound that tends to form voids in the secondary particles of the spray-dried powder due to generation of cracking gas at times, and taking these points into consideration, LiOH and LiOH.H ₂ O are preferred.

The nickel compounds include 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 and the like. Among this, _SO x during the firing process, in that not generate toxic substances such as _{NO X, Ni (OH) 2} , NiO, NiOOH, NiCO 3, 2NiCO 3 · 3Ni (OH) 2 · 4H 2 O, NiC Nickel compounds such as ₂ O ₄ .2H ₂ O are preferred. Further, from the viewpoint that it can be obtained as an industrial raw material at a low cost and from the viewpoint of high reactivity, Ni (OH) ₂ , NiO, NiOOH, NiCO ₃ , further generating a decomposition gas during firing, etc. Ni (OH) ₂ , NiOOH, and NiCO ₃ are particularly preferable from the viewpoint that voids are easily formed in the secondary particles. These nickel compounds may be used individually by 1 type, and may use 2 or more types together.

As manganese compounds, manganese oxides such as Mn ₂ O ₃ , MnO ₂ , Mn ₃ O ₄ , MnCO ₃ , Mn (NO ₃ ) ₂ , MnSO ₄ , manganese acetate, manganese dicarboxylate, manganese citrate, manganese fatty acid And manganese salts such as oxyhydroxide, manganese chloride and the like. 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. Furthermore, these manganese compounds may be used individually by 1 type, and may use 2 or more types together.

Cobalt compounds include Co (OH) ₂ , CoOOH, CoO, Co ₂ O ₃ , 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 preferable in 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 that voids are easily formed 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.

  In addition to the above Li, Ni, Mn, and Co raw material compounds, other elements are substituted to introduce the above-mentioned foreign elements, and voids in secondary particles formed by spray drying described later are efficiently formed. It is possible to use a group of compounds intended to be used. 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 that is easily decomposed due to mechanical shear stress applied by the mixing step after the mixing step.

In the present invention, as described above, it is preferable to add a boron-containing compound and a tungsten-containing compound in combination at a predetermined ratio.
As described above, the boron-containing compound includes BO, B ₂ O ₂ , B ₂ O ₃ , B ₄ O ₅ , B ₆ O, B ₇ O, B ₁₃ O ₂ , LiBO ₂ , LiB ₅ O ₈ , Li ₂ B ₄ O ₇ , HBO ₂ , H ₃ BO ₃ , B (OH) ₃ , B (OH) ₄ , and the like. From the viewpoint of being relatively inexpensive and easily available as an industrial raw material, preferably B ₂ O ₃ and H ₃ BO ₃ , particularly preferably H ₃ BO ₃ . These may be used alone or in combination of two or more.

As the tungsten-containing _{compounds, 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 and the} like are mentioned. From the viewpoint of being relatively easily available as an industrial raw material or including lithium, WO ₃ and Li ₂ WO ₄ are preferred, and WO ₃ is particularly preferred. Can be mentioned. These may be used alone or in combination of two or more.

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) usually takes about 1 to 2 days, and a bead mill (wet continuous method) has a 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 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. It ’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). The median diameter of the spray-dried body described later is the same as that except that the measurement was performed after ultrasonic dispersion for 0, 1, 3, and 5 minutes, respectively.

<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 flowability, 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-type atomizer, and the like.

(Spray-dried powder)
In the method for producing a positive electrode active material for a lithium secondary battery according to the present invention, primary particles are aggregated to form secondary particles by spray drying a slurry obtained by wet pulverizing a raw material compound. Obtain powder. The spray-dried powder formed by agglomerating primary particles to form secondary particles is a shape characteristic of the mother particles according to 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 a calcined precursor of the mother particles according to the present invention (here, a value measured without applying ultrasonic dispersion) is usually 20 μm or less, more preferably 15 μm or less, and still more preferably 10 μm or less, 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 4 μm or more, more preferably 5 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, a lithium compound, a nickel compound, a manganese compound, and a slurry in which a cobalt compound and a boron compound and a tungsten compound are dispersed in a liquid medium are spray-dried, and the obtained powder is fired to obtain lithium nickel manganese cobalt In producing the composite oxide powder, 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), the slurry viscosity Spray drying is performed under conditions where V is 50 cp ≦ V ≦ 4000 cp and the gas-liquid ratio G / S is 500 ≦ G / S ≦ 10000.

  If the slurry viscosity V (cp) is too low, the primary particles may aggregate to make it difficult to obtain a powder formed of secondary particles. If the slurry viscosity is too high, the supply pump may fail or the nozzle may be blocked. There is a fear. 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 lower than the lower limit, the secondary particle size is coarsened or the drying property is liable to be lowered. When the upper limit is exceeded, 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, more preferably 200 ° C. It is preferable to carry out the reaction at a temperature of ℃ or less, most preferably 180 ℃ or less. If this temperature is too high, the resulting granulated particles may have a lot of hollow structures, which may reduce the packing density of the powder. 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.

In addition, the spray-dried powder according to the present invention is characterized in that the cohesive force between primary particles is moderately weak, and this can be confirmed by examining the change in median diameter accompanying ultrasonic dispersion. After applying the median diameter of the spray-dried particles measured before applying ultrasonic dispersion (ultrasonic 0 minutes) and applying ultrasonic dispersion “Ultra Sonic” (output 30 W, frequency 22.5 kHz) for 5 minutes. The upper limit of the difference ΔD _{50 in} the median diameter of the spray-dried particles when measured with the above is usually 5 μm or less, preferably 4.5 μm or less, more preferably 4 μm or less, still more preferably 3.5 μm or less, most preferably 3 μm or less. The lower limit is usually 1 μm or more, preferably 1.5 μm or more, more preferably 2 μm or more, and most preferably 2.5 μm or more. Lithium nickel manganese (cobalt) composite oxide base particles obtained by firing spray-dried particles having a median diameter difference before and after this ultrasonic dispersion smaller than the above values have few voids between the particles and load characteristics are low. Not improved. On the other hand, the lithium nickel manganese (cobalt) composite oxide base particles obtained by firing spray-dried particles having a median diameter difference before and after ultrasonic dispersion larger than the above values have too many voids between the particles. In addition, there is a possibility that secondary particles are easily disintegrated, the bulk density is lowered, and the coating properties are deteriorated.

In addition, when the powder obtained by spray drying has a small specific surface area, the reactivity with the lithium compound is reduced during the firing reaction with the lithium compound in the next step. The specific surface area is preferably as high as possible by means such as pulverizing the starting material. On the other hand, if the specific surface area is excessively increased, not only is it industrially disadvantageous, but the positive electrode active material for a lithium secondary battery of the present invention may not be obtained. Accordingly, the spray-dried particles thus obtained have a BET specific surface area of usually 10 m ² / g or more, preferably 20 m ² / g or more, more preferably 30 m ² / g or more, and most preferably 50 m ² / g or more. Usually, it is preferably 100 m ² / g or less, preferably 80 m ² / g or less, more preferably 70 m ² / g or less, and most preferably 65 m ² / g or less.

<Baking process>
The spray-dried powder as the calcined precursor thus obtained is then calcined.
Here, in the present invention, the “firing precursor” means a precursor of 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 the particles proceeds too much, and the specific surface area becomes small. Pass. On the other hand, if it is too low, heterogeneous phases are mixed, and the lattice distortion increases without developing the crystal structure. Moreover, the specific surface area becomes too large. The firing temperature is usually 700 ° C. or higher. However, in the composition represented by the general formulas (I) and (II), 900 ° C. or higher is preferable, more preferably 920 ° C. or higher, further preferably 940 ° C. or higher, and further Preferably it is 950 degreeC or more, Most preferably, it is 975 degreeC or more, Usually, 1200 degreeC or less, Preferably it is 1175 degreeC or less, More preferably, it is 1150 degreeC or less, Most preferably, it is 1125 degreeC or less.

  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 one time, and may include two or more stages depending on the purpose, which means that aggregation is eliminated to the extent that secondary particles are not destroyed. The temperature raising, maximum temperature holding, and temperature lowering steps may be repeated twice or more with a crushing step or a crushing step meaning 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 1.5 ° C./min or more, more preferably 2 ° C./min or more, further preferably 3 ° C./min or more, preferably 7 ° C./min or less, more preferably 5 ° C./min or less. More preferably, it is 4 ° C./min or less.

  The holding time in the maximum temperature holding step varies depending on the temperature, but 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 more, 50 hours or less, preferably 25 hours or less, more preferably 20 hours or less, still more preferably 15 hours or less, and most preferably 10 hours or less. If the firing time is too short, it becomes difficult to obtain a lithium nickel manganese cobalt based composite oxide powder with good crystallinity, and it is not practical to be too long. If the firing time is too long, it will be disadvantageous because it will be necessary to crush afterwards or it will be difficult to crush.

  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 it is too slow, it takes time and is industrially disadvantageous. However, if it is too fast, the uniformity of the target product tends to be lacking or the deterioration of the container tends to be accelerated. 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. Usually, the atmosphere has an oxygen concentration of 1% by volume or more, preferably 10% by volume or more, more preferably 15% by volume or more, and 100% by volume or less, preferably 50% by volume or less, more preferably 25% by volume or less.

  In such a manufacturing method, in order to manufacture the positive electrode active material for a lithium secondary battery of the present invention, the lithium compound, the nickel compound, the manganese compound, the cobalt compound, and the boron compound are used when the manufacturing conditions are constant. When preparing a slurry in which a tungsten compound and a tungsten compound are dispersed in a liquid medium, the target molar ratio can be controlled by adjusting the mixing ratio of each compound.

<Classification process>
The fired powder obtained by firing is then classified in order to crush it, adjust it to a particle size distribution preferable for electrode preparation, or remove coarse foreign matters and the like. The classification method is not particularly limited as long as the object can be achieved, and examples thereof include sieve classification (vibrating sieve, centrifugal sieve), and pneumatic classification. Specific examples of the apparatus include Dalton's “Ultrasonic Vibrating Sieve”, Tsukasa Industries '“Powder Footer”, Turbo Industries' “Turbo Screener”, Hosokawa Micron's “Turboplex”, and the like. However, it is not limited to these.

<Post-processing process>
From the lithium nickel manganese (cobalt) -based composite oxide base particles, the primary powder crystals are aggregated to form spherical secondary particles, and the secondary particle surface and inside have voids in the classified powder obtained by classification. Become. In order to fill a part of the voids of the base particles with the conductive fine powder, a post-treatment is applied to the classified powder to apply a compressive shear stress.

  Here, the post-treatment for applying compressive shear stress is to compress the powder particles by applying compression and shear stress to the composite oxide powder base particles, and to compress a part of the surface of the powder base particles by the load stress. This is a process that develops so-called mechanofusion, which has the effect of re-fusing fine particles generated by cutting to the particle surface. Specifically, for example, a cylindrical rotating drum and a central axis in the drum A fixed first arm having a hemispherical pressure shearing head in contact with the inner peripheral surface of the drum at the front end, and fixed to the central axis at a predetermined angle in front of the rotating drum, and an inner peripheral surface of the drum at the front end The processing is performed using a processing apparatus configured with a second arm provided with an acute-angled nail in contact with the arm.

In addition, in the post-processing to apply the compressive shear stress, the above-mentioned conductive fine powder is allowed to coexist so that the effect of increasing the bulk density and improving the electrical conductivity by this post-processing can be expressed more remarkably. Become.
In the post-treatment applying this compressive shear stress, when the conductive fine powder coexists and the conductive fine powder is filled in the voids of the lithium nickel manganese (cobalt) composite oxide mother particles, the amount of the conductive fine powder to coexist Is a positive electrode active material for a lithium secondary battery according to the present invention, preferably an amount capable of obtaining a positive electrode active material for a lithium secondary battery that satisfies the physical properties such as the amount of mercury intrusion and bulk density described above. Although there is no particular limitation, it is usually in a total of 100 parts by weight of lithium nickel manganese (cobalt) based composite oxide base particles (classified powder) and conductive fine powder subjected to post-treatment applying compressive shear stress. The conductive fine powder is preferably 0.1 parts by weight or more, particularly 1 part by weight or more and 10 parts by weight or less, particularly 5 parts by weight or less. If the amount of conductive fine powder is excessively larger than this range, the bulk density and battery capacity may be decreased or the electrode preparation may be adversely affected. If the amount is too small, the effects of the present invention will be sufficiently exerted. There is a risk that it will not be possible.

  In this post-treatment, the surface of the lithium nickel manganese (cobalt) -based composite oxide mother particles is 50% or more, more preferably 80% or more of the entire surface by coexisting the conductive fine powder. As a positive electrode active material material for secondary batteries, it is covered with fine powder and filled with voids between primary particles of the active material, and the tap density can easily satisfy the range described above. The conductivity of the positive electrode can be improved.

  In the present invention, any processing system used for this post-treatment may be used as long as it can achieve the morphological characteristics of the present invention. Specifically, for example, “Mechano-Fusion System” manufactured by Hosokawa Micron Corporation, Nara Machinery Co., Ltd. However, it is not limited to these.

In addition, primary particle crystals aggregate to form spherical secondary particles, and a part of the voids of the lithium nickel manganese (cobalt) -based composite oxide mother particles having voids on the surface and inside of the secondary particles are electrically conductive fine particles. As another method for obtaining the positive electrode active material of the present invention, which is filled with a powder, a conductive fine powder is applied to lithium nickel manganese (cobalt) based composite oxide base particles by a pressure impregnation action. A method such as a filling method or a method of filling lithium nickel manganese (cobalt) -based composite oxide base particles with conductive fine powder by centrifugal force may be used.
Further, in the step of forming the positive electrode, the lithium nickel manganese (cobalt) -based composite oxide mother particles may be filled with conductive fine powder by the above method.

  According to the positive electrode active material for a lithium secondary battery thus obtained, a positive electrode material for a lithium secondary battery with high filling properties, excellent low-temperature output characteristics, and good performance balance is provided.

[Positive electrode for lithium secondary battery]
The positive electrode for a lithium secondary battery of the present invention is formed by forming a positive electrode active material layer containing a positive electrode active material material of 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 Copolymer and its hydrogenated thermoplastic elastomeric polymer, syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer, etc. Fluorine polymers such as soft resinous 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 ratios.

  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. Battery capacity and conductivity may be reduced.

  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. And carbon materials. In addition, these substances may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

  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. The ratio of the conductive material does not include the conductive fine powder filled in the voids of the base particles of the positive electrode active material for a lithium secondary battery of the present invention.

  The liquid medium for forming the slurry is to dissolve or disperse the lithium nickel manganese cobalt composite oxide powder, which is the positive electrode material, the binder, and the conductive material and thickener used as necessary. As long as the solvent can be used, the type is not particularly limited, and either an aqueous solvent or an organic solvent may be used. Examples of the aqueous solvent include water and alcohol. 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. be able to. 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 ratio of the positive electrode active material for a lithium secondary battery of the present invention as the positive electrode material in the positive electrode active material layer is usually 75% by weight or more, preferably 80% by weight or more, more preferably 85% by weight or more, Usually, it is 98 weight% or less, Preferably it is 95 weight% or less, More preferably, it is 90 weight% or less. If the proportion of the positive electrode active material material for lithium secondary batteries of the present invention 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 adjusted.

Although the electrode density of the positive electrode for lithium secondary batteries of this invention is not specifically limited, The density which can be used with an actual battery is preferable, and the range of 2.0-3.7 g / cm < ³ > is preferable.

On the other hand, for the purpose of comparing the electrode plate characteristics of the positive electrode for a lithium secondary battery in the present invention, the density that can be reached when pressurized at a specific pressure is measured. At this time, an index of the ease of pressing the positive electrode plate can be obtained by comparing the measured density.
The positive electrode for a lithium secondary battery of the present invention is pressurized at a pressure of 760 MPa for 1 minute, and the density of the positive electrode active material layer after the pressurization is repeated 5 times (the density after 5 times pressing) is usually 3.0 g. / Cm ³ or more is preferable. A high density after the fifth press indicates that a positive electrode that is easily pressed and has a high packing density can be formed. The upper limit of the density after the 5th press is not particularly limited, but is preferably 3.7 g / cm ³ or less.
Note that the number of pressurizations in the density measurement after pressing five times may be more than five, and after one or more pressurizations, the battery is disassembled after being configured as a battery and repeated charging and discharging. You may pressurize 5 times with respect to the taken-out positive electrode.

[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. Further, a separator for holding a nonaqueous 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, 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, which is 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) 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 or less, preferably 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.

  Further, 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 particularly preferably 100 nm or more.

  The median diameter of the graphite material determined by the laser diffraction / scattering method is usually 1 μm or more, especially 3 μm or more, more preferably 5 μm or more, especially 7 μm or more, and usually 100 μm or less, especially 50 μm or less, more preferably 40 μm or less, especially 40 μm or less. It is preferable that it is 30 micrometers 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, it is detected in the range of 1350 ^-1 that intensity ratio _I a / _{I B} of the intensity _{I B} of a peak _{P B} is what is preferably 0 to 0.5. 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, and lithium alloys such as lithium alone and lithium aluminum alloys. 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. Among them, 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, propionitrile Benzonitrile, butyronitrile, valeronitrile, 1,2-dichloroethane, dimethylformamide, dimethyl sulfoxide, trimethyl phosphate, triethyl phosphate, etc. Et 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, and SO ₂ , vinylene carbonate, polysulfide S _x ^{2−, and the} like that enables efficient charge and 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, an additive that exhibits an effect of improving cycle life and output characteristics, such as lithium difluorophosphate, may be added to the organic electrolyte at an arbitrary ratio.

The type of the electrolytic salt is not particularly limited, and any conventionally known solute can be used. Specific examples include 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. Further, an additive that forms a good film that enables efficient charge and discharge of lithium ions on the negative electrode surface, such as gas such as CO ₂ , N ₂ O, CO, and SO ₂ , and polysulfide S _x ^2- , at an arbitrary ratio May be added.

  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 it 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 is preferably 0.75 mol / L or more and the upper limit is 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 manufactured 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 in a spiral shape, a cylinder type with an inside-out structure combining a pellet electrode and a separator, and a coin type with stacked pellet electrodes and a separator. 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.

  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 as long as the gist of the present invention is not exceeded.

[Method for measuring physical properties]
The physical properties and the like of lithium nickel manganese cobalt composite oxide powders produced in each of Examples and Comparative Examples described below were measured as follows.

<Composition (Li / Ni / Mn / Co)>
It was determined by ICP-AES analysis.

<Quantification of additive elements (B, W)>
It was determined by ICP-AES analysis.

<Secondary particle morphology>
It confirmed by the SEM image of 10,000 times.

<Secondary particle cross section>
It confirmed by the cross-sectional SEM image of 15,000 times.

<Median diameter of secondary particles>
Ultrasonic dispersion was measured after 0 and 5 minutes.

<Average primary particle size>
It calculated | required from the SEM image of 30,000 times.

<Measurement of various physical properties by mercury intrusion method>
As a measuring device by the mercury intrusion method, Autopore III9420 manufactured by Micromeritics was used. Moreover, as measurement conditions of the mercury intrusion method, measurement was performed while increasing the pressure from 3.86 kPa to 413 MPa at room temperature. The mercury surface tension value was 480 dyn / cm, and the contact angle value was 141.3 °.

<Bulk density>
4 to 10 g of the sample powder was put into a 10 ml glass graduated cylinder, and the powder packing density when tapped 200 times with a stroke of about 20 mm was obtained.

<Specific surface area>
Obtained by BET 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).

<Median Diameter as Average Particle Diameter of Raw Material Li ₂ CO ₃ Powder>
Using a known laser diffraction / scattering particle size distribution measuring apparatus (LA-920, manufactured by Horiba, Ltd.), the refractive index was set to 1.24, and the particle diameter standard was measured as a volume standard. Further, ethyl alcohol was used as a dispersion medium, and measurement was performed after ultrasonic dispersion for 5 minutes (output 30 W, frequency 22.5 kHz).

<Physical properties of particulate powder obtained by spray drying>
The form was confirmed by confirmation through SEM observation and cross-sectional SEM observation. The median diameter and 90% cumulative 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 (LA-920, manufactured by Horiba, Ltd.) The particle diameter standard was measured using the volume standard. Further, a 0.1 wt% sodium hexametaphosphate aqueous solution was used as a dispersion medium, and measurement was performed after 0 minutes, 1 minute, 3 minutes, and 5 minutes of ultrasonic dispersion (output 30 W, frequency 22.5 kHz). The specific surface area was determined by the BET method.

[Production of cathode active material for lithium secondary battery (Examples and Comparative Examples)]
(Comparative Example 1)
Li ₂ CO ₃ , Ni (OH) ₂ , Mn ₃ O ₄ , CoOOH, H ₃ BO ₃ , WO ₃ are replaced with Li: Ni: Mn: Co: B: W = 1.12: 0.45: 0.45. : Weighed so that the molar ratio was 0.10: 0.0025: 0.01, mixed, and then added pure water to prepare a slurry. While stirring this slurry, the solid content in the slurry was pulverized to a median diameter of 0.25 μm using a circulating medium agitation type wet pulverizer.

Next, this slurry (solid content 15.7 wt%, viscosity 1600 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) : About 3.3 ° C./min.), And then classified using a Puffer footer (manufactured by Tsukasa Kogyo Co., Ltd.) having a pore size of 45 μm to obtain a lithium nickel manganese cobalt composite oxide powder. The obtained lithium nickel manganese cobalt composite oxide powder has a form in which primary particle crystals are aggregated to form spherical secondary particles having voids on the surface and inside of the secondary particles, and the composition is Li (Li _0.051 Ni _0.429 Mn _0.425 Co _0.0.095) lithium nickel manganese cobalt composite oxide having a layered structure of _{O 2 (x = 0.100, y} = 0.004, z = 0.108 In addition, when the total molar ratio of (Ni, Mn, Co) was 1, the molar ratio of B was 0.17 mol%, and the molar ratio of W was 1.0 mol%.

The median diameter of this lithium nickel manganese cobalt composite oxide powder is 7.3 μm (ultrasonic 0 min), 1.9 μm (ultrasonic 5 min), and 90% cumulative diameter (D ₉₀ ) is 11.5 μm (ultrasonic 0). Min), 3.6 μm (ultrasonic wave 5 min), bulk density 1.2 g / cm ³ , BET specific surface area 1.4 m ² / g, volume resistivity 3.7 × 10 ⁶ Ω · cm, carbon content The concentration C was 0.028% by weight.

(Comparative Example 2)
Ni (OH) ₂ , Mn ₃ O ₄ , CoOOH, WO ₃ are weighed so as to have a molar ratio of Ni: Mn: Co: W = 0.45: 0.45: 0.10: 0.01, After mixing, pure water was added thereto to prepare a slurry. While the slurry was stirred, the solid content in the slurry was pulverized to a median diameter of 0.21 μm using a circulating medium agitation type wet pulverizer (Shinmaru Enterprises Co., Ltd .: Dino Mill KDLA type).

Next, this slurry (solid content 13 wt%, viscosity 1640 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 L / min (gas-liquid ratio G / S = 7500). The drying inlet temperature was 150 ° C. Li ₂ CO ₃ powder with a median diameter of 9 μm is added to the particulate powder obtained by spray drying with a spray dryer so that the Li / (Ni + Mn + Co) molar ratio is 1.12. Mixed. About 15 g of this mixed powder is charged into an alumina crucible, fired at 1000 ° C. for 6 hours under an air flow of 1 L / min (temperature raising / lowering rate 3.33 ° C./min.), And then classified using a 45 μm sieve. And lithium nickel manganese cobalt composite oxide powder was obtained. The obtained lithium nickel manganese cobalt composite oxide powder has a form in which primary particle crystals agglomerate to form spherical secondary particles, and there are slight voids on the surface and inside of the secondary particles, and the composition is Li Lithium nickel manganese cobalt composite oxide having a layered structure of (Li _0.062 Ni _0.421 Mn _0.424 Co _0.093 ) O ₂ (x = 0.099, y = −0.003, z = 0. 133), and when the total molar ratio of (Ni, Mn, Co) is 1, the W molar ratio was 1.03 mol%.

The average primary particle diameter of this lithium nickel manganese cobalt composite oxide powder is 0.3 μm, the median diameter is 5.4 μm (ultrasonic 0 min), 5.0 μm (ultrasonic 5 min), 90% cumulative diameter (D ₉₀ ) is 8.0 μm (ultrasonic 0 min), 7.5 μm (ultrasonic 5 min), bulk density is 1.7 g / cc, BET specific surface area is 1.7 m ² / g, and volume resistivity is 9.7. × 10 ⁴ Ω · cm, and the carbon concentration C was 0.037% by weight.

(Comparative Example 3)
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) : About 3.3 ° C./min.), And then classified using a Puffer footer (manufactured by Tsukasa Kogyo Co., Ltd.) having a pore size of 45 μm to obtain a lithium nickel manganese cobalt composite oxide powder. The lithium nickel manganese cobalt composite oxide powder, the composition is _{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), and when the total molar ratio of (Ni, Mn, Co) is 1, the W-containing molar ratio is 1.0 mol%. Met. The volume resistivity is 6.3 × 10 ⁴ Ω · cm, the carbon concentration C is 0.031 wt%, the median diameter is 2.7 μm, the 90% cumulative diameter (D ₉₀ ) is 4.9 μm, and the bulk density is 1. 0.0 g / cc and the BET specific surface area was 2.8 m ² / g.
The lithium nickel manganese cobalt composite oxide powder is a form in which primary particles are aggregated to form irregular secondary particles or monodispersed, and primary particles are aggregated to form spherical secondary particles. It was not formed in a form having voids on the surface and inside of the secondary particles.

To this lithium nickel manganese cobalt composite oxide powder, Ketjen Black (“EC600JD” manufactured by Mitsubishi Chemical Corporation, average primary particle size 34.0 nm, BET specific surface area 1270 m ² / g) as a conductive fine powder is obtained. Manganese cobalt composite oxide powder: Ketjen black = 97: 3 (weight ratio) was added and compression sheared using a Hosokawa Micron mechanofusion system “AM-20FS” at a rotation speed of 2000 rpm for 20 minutes. Post-treatment was applied by applying stress. The median diameter of the lithium nickel manganese cobalt composite oxide powder obtained after the post-treatment is 5.4 μm (ultrasonic 0 min), 1.5 μm (ultrasonic 5 min), and 90% integrated diameter (D ₉₀ ) is 8. 4 μm (ultrasonic 0 min), 2.5 μm (ultrasonic 5 min), bulk density 1.1 g / cc, BET specific surface area 35.3 m ² / g, volume resistivity 2.2 × 10 ¹ Ω · cm and the carbon content C were 2.62% by weight.

Example 1
The lithium nickel manganese cobalt composite oxide powder produced in Comparative Example 1 was mixed with ketjen black (“EC600JD” manufactured by Mitsubishi Chemical Corporation), an average primary particle size of 34.0 nm, a BET specific surface area of 1270 m as a conductive fine powder. ² / g) was added at a ratio of lithium nickel manganese cobalt composite oxide powder: Ketjen black = 97: 3 (weight ratio), and the rotation speed was adjusted using a mechanofusion system “AM-20FS” manufactured by Hosokawa Micron. The post-treatment was performed by applying compressive shear stress at 2000 rpm for 20 minutes. The median diameter of the lithium nickel manganese cobalt composite oxide powder obtained after the post-treatment is 15.7 μm (ultrasonic 0 min), 1.4 μm (ultrasonic 5 min), and 90% cumulative diameter (D ₉₀ ) is 44. 3 μm (ultrasonic 0 min), 3.2 μm (ultrasonic 5 min), bulk density 1.7 g / cc, BET specific surface area 34.0 m ² / g, volume resistivity 9.1 Ω · cm, carbon content Concentration C was 2.91% by weight.

  Tables 1 and 2 show physical property values and compositions of the positive electrode active material materials for lithium secondary batteries manufactured in the above Examples and Comparative Examples. Table 3 shows the powder property values of the spray-dried body, which is a firing precursor.

  Moreover, the pore distribution curve of the positive electrode active material material for lithium secondary batteries manufactured by Example 1 and Comparative Examples 1-3 is shown in FIGS. 1-4, respectively, and SEM image (photograph) (magnification x10,000) ) Are shown in FIGS. Moreover, the cross-sectional SEM image (photograph) (magnification x15,000) of the positive electrode active material material for lithium secondary batteries manufactured in Example 1 and Comparative Example 1 is shown in FIGS.

[Production and evaluation of batteries]
Using the positive electrode active material for lithium secondary batteries produced in Example 1 and Comparative Examples 1 to 3 described above, lithium secondary batteries were produced and evaluated by the following methods.

[Production of positive electrode]
A mortar obtained by weighing 75% by weight of each of the positive electrode active material materials for lithium secondary batteries produced in Example 1 and Comparative Examples 1 to 3, 20% by weight of acetylene black, and 5% by weight of polytetrafluoroethylene powder. Were mixed thoroughly and made into thin sheets, and punched using 9 mmφ and 12 mmφ punches, respectively. At this time, the total weight was adjusted to about 8 mg for 9 mmφ and about 18 mg for 12 mmφ, respectively. This was pressure-bonded to an aluminum expanded metal to obtain positive electrodes of 9 mmφ and 12 mmφ.

A 9 mmφ positive electrode was used as a test electrode, a lithium metal plate as a counter electrode, and 1 mol of LiPF ₆ in a solvent of EC (ethylene carbonate): DMC (dimethyl carbonate): EMC (ethyl methyl carbonate) = 3: 3: 4 (volume ratio). A coin-type cell was assembled using a 25 μm-thick porous polyethylene film as a separator using an electrolytic solution dissolved at / L.

The obtained coin-type cell was subjected to a constant current / constant voltage charge of 0.2 mA / cm ² , that is, a reaction for releasing lithium ions from the positive electrode at an upper limit of 4.2 V. Subsequently, the initial charge capacity per unit weight of the positive electrode active material when a constant current discharge of 0.2 mA / cm ² , that is, a reaction of occluding lithium ions in the positive electrode was performed at a lower limit of 3.0 V was Qs (C) [mAh / g], and the initial discharge capacity was Qs (D) [mAh / g].

[Production of negative electrode]
Graphite powder having an average particle size of 8 to 10 μm (d ₀₀₂ = 3.35 Å) was used as the negative electrode active material, and polyvinylidene fluoride was used as the binder, and these were weighed at a weight ratio of 92.5: 7.5. Were 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 about 7 mg.

A test in which a negative electrode is used as a test electrode, a battery cell is assembled using lithium metal as a counter electrode, and lithium ions are occluded in the negative electrode by a constant current-constant voltage method (cut current 0.05 mA) of 0.2 mA / cm ² -3 mV. The initial occlusion capacity per unit weight of the negative electrode active material when performing at a lower limit of 0 V was Q _f [mAh / g].

[Production of battery for performance test]
The above-mentioned 12 mmφ positive electrode and 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 is placed on the positive electrode can of the coin cell, a porous polyethylene film having a thickness of 25 μm is placed thereon as a separator, pressed with a polypropylene gasket, and then EC ( An electrolytic solution in which LiPF ₆ was dissolved at a rate of 1 mol / L in a solvent of ethylene carbonate): DMC (dimethyl carbonate): EMC (ethyl methyl carbonate) = 3: 3: 4 (volume ratio) was added to the can. After fully infiltrating the separator, the above-described negative electrode was placed, a 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]

[Battery characteristics test]
In order to measure the low temperature load characteristics of the battery thus obtained, the 1 hour rate current value of the battery, that is, 1C, was set as shown 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.
Next, the resistance value R [Ω] after the high-temperature cycle test was calculated in the same manner as described above.

  Table 4 shows the resistance values before and after cycling of the batteries using the positive electrode active material for lithium secondary batteries of Example 1 and Comparative Examples 1 to 3, respectively. The smaller the resistance value before the cycle, the better the output characteristics, and the smaller the resistance value after the cycle, the better the output life characteristics. In addition, as an acceptance criterion for the examples, it was set that both the resistance values before and after the cycle test were 350Ω or less.

[Measurement of density of positive electrode active material layer]
Using the positive electrode active material for lithium secondary battery produced in Example 1 and Comparative Examples 1 to 3 described above, a positive electrode for lithium secondary battery was produced by the following method, and density measurement before and after pressing was performed.
Moreover, the characteristic evaluation by a laminate type battery was performed by the following method using the positive electrode.

[Production of positive electrode]
85% by weight of each of the lithium transition metal-based compound powders prepared in Example 1 and Comparative Examples 1 to 3, 10% by weight of acetylene black, 5% by weight of polyvinylidene fluoride, and a necessary amount of N-methylpyrrolidone (NMP). The mixture was dispersed and mixed to obtain a positive electrode mixture slurry. This slurry was applied to one side of an aluminum foil having a thickness of 14 μm, dried, and the solvent was evaporated to obtain a positive electrode. This positive electrode punched with a 9 mmφ punch was used as a positive electrode for press density measurement. At this time, the weight of the positive electrode mixture on the electrode was about 5.5 mg. Table 5 shows the density of the positive electrode (before pressing).
Similarly, what was slit to 3 cm × 4 cm was used as a positive electrode for laminate type battery evaluation. At this time, the weight of the positive electrode mixture on the electrode was about 102 mg.

[Density measurement after 5 times pressing]
The obtained positive electrode (positive electrode for press density measurement) was pressed on the electrode at a pressure of 760 MPa for 1 minute using a 20 t hand press (manufactured by RIKEN), and this was repeated 5 times. By measuring the film thickness, the density after pressing five times was calculated. Table 5 shows the density of the positive electrode after the fifth press.

[Production and evaluation of laminated battery]
Using the 3 cm × 4 cm positive electrode (positive electrode for battery evaluation), a lithium secondary battery was prepared and evaluated by the following method.

[Production of positive electrode]
The 3 cm × 4 cm positive electrode described above was pressed to a density of 2.6 g / cm ³ to obtain a positive electrode for laminate type battery evaluation.

The aforementioned 9 mmφ positive electrode for coin-type battery evaluation was used as a test electrode, a lithium metal plate as a counter electrode, EC (ethylene carbonate): DMC (dimethyl carbonate): EMC (ethyl methyl carbonate) = 3: 3: 4 (capacity ratio) The coin-type cell was assembled using a porous polyethylene film having a thickness of 25 μm as a separator, using an electrolytic solution in which LiPF ₆ was dissolved at 1 mol / L in the solvent (1).

The obtained coin-type cell was subjected to a constant current / constant voltage charge of 0.2 mA / cm ² , that is, a reaction of releasing lithium ions from the positive electrode at an upper limit of 4.3V. Subsequently, the initial charge capacity per unit weight of the positive electrode active material when a constant current discharge of 0.2 mA / cm ² , that is, a reaction of occluding lithium ions in the positive electrode at a lower limit of 3.0 V is Q _s2 (C) [mAh / G], and the initial discharge capacity was Q _s2 (D) [mAh / g].

[Production of negative electrode]
Graphite powder (d ₀₀₂ = 3.35 μ) having an average particle diameter of 8 to 10 μm is used as the negative electrode active material, and carboxymethyl cellulose and styrene-butadiene copolymer are used as binders, respectively, and these are weighed at a ratio of 98: 1: 1 by weight This was mixed in water to obtain a negative electrode mixture slurry. This slurry is applied to one side of a 10 μm thick copper foil, dried and evaporated to a solvent, then pressed to a density of 1.45 g / cm ³ and slit to 3 cm × 4 cm Was used as the negative electrode. At this time, the amount of the negative electrode active material on the electrode was adjusted to about 52 mg.

This negative electrode was used as a test electrode, a coin-type battery cell was assembled using lithium metal as a counter electrode, and lithium ions were occluded in the negative electrode 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 _f2 [mAh / g].

[Production of battery for performance test]
The 12 cm ² positive electrode and negative electrode were combined, a laminate type cell was used to assemble a test battery, and the battery performance was evaluated. That is, a tab is attached to the prepared positive electrode and negative electrode, a porous polyethylene film having a thickness of 25 μm is sandwiched between them and placed in a laminate cell, and then EC (ethylene carbonate): An electrolyte solution in which LiPF ₆ was dissolved at 1 mol / L was added to a solvent of DMC (dimethyl carbonate): EMC (ethyl methyl carbonate) = 3: 3: 4 (volume ratio) and vacuum impregnated, and then the laminate cell was sealed. A laminate 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 _f2 [mAh / g] /1.3) Q _s2 (C) [mAh / g]

[Battery characteristics test]
In order to measure the low temperature load characteristics of the battery thus obtained, the 1 hour rate current value of the battery, that is, 1C, was set as shown in the following equation, and the following tests were performed.
1C [mA] = Q _s2 (D) × weight of positive electrode active material [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 4.2V, and the lower limit voltage was 3.0V. Next, after holding the coin cell adjusted to a charge depth of 40% by a 1/3 C constant current charge / discharge in a low temperature atmosphere of −30 ° C. for 1 hour or more, the battery was discharged at a constant current of 1 C [mA] for 10 seconds. When the voltage after 2 seconds was V [mV] and the voltage before discharge was V ₀ [mV], the resistance value R [Ω] was calculated from the following equation as ΔV = V−V ₀ .
R [Ω] = ΔV [mV] /0.5C [mA]

  Next, a constant current 0.2 C charge / discharge cycle was conducted at a high temperature of 60 ° C., followed by a constant current 2 C charge / discharge cycle 500. The upper limit of charging was 4.2V, and the lower limit voltage was 3.0V.

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

  Table 6 shows the low-temperature resistance values before and after the cycle of the laminate type batteries using the positive electrode active material materials for lithium secondary batteries of Example 1 and Comparative Examples 1 to 3, respectively. The smaller the resistance value, the better the low temperature load characteristics, and the higher the maintenance ratio, the better the high temperature cycle characteristics. In addition, it set that the low-temperature resistance value before and behind a cycle test was 100 ohms or less as an acceptance criterion of an Example.

From the above results, the following can be understood.
-The positive electrode active material material for lithium secondary batteries of this invention is easy to be pressed, and can form a positive electrode active material layer with a high packing density.
The positive electrode active material for a lithium secondary battery of the present invention is formed by agglomerating primary particle crystals to form spherical secondary particles, and is electrically conductive to the voids of the mother particles in a form having voids on the surface and inside of the secondary particles. By filling the fine powder, excellent effects such as improvement of load characteristics can be obtained.
In order to produce such a positive electrode active material for a lithium secondary battery, the primary particles aggregate primary particle crystals to form spherical secondary particles, and there are voids on the surface and inside of the secondary particles. As in Comparative Example 3, primary particle crystals are aggregated to form spherical secondary particles, and conductive to mother particles that are not in a form having voids on the surface and inside of the secondary particles. Even if compressive shear stress is applied in the presence of the conductive fine powder, the positive electrode active material for a lithium secondary battery of the present invention cannot be produced.

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. 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 Example 1, it is a SEM image (photograph) (magnification x10,000) of the manufactured positive electrode active material for lithium secondary batteries. In Comparative example 1, it is a SEM image (photograph) (magnification x10,000) of the manufactured positive electrode active material for lithium secondary batteries. In Comparative example 2, it is a SEM image (photograph) (magnification x10,000) of the manufactured positive electrode active material for lithium secondary batteries. In Comparative example 3, it is a SEM image (photograph) (magnification x10,000) of the manufactured positive electrode active material for lithium secondary batteries. In Example 1, it is a cross-sectional SEM image (photograph) (magnification x15,000) of the manufactured positive electrode active material material for lithium secondary batteries. In Comparative example 1, it is a cross-sectional SEM image (photograph) (magnification x15,000) of the cathode active material material for lithium secondary batteries manufactured.

Claims (15)

Primary particle crystals agglomerate to form spherical secondary particles, and a mother particle composed of a lithium nickel manganese composite oxide having voids in and on the surface of the secondary particles and a part of the voids of the mother particles are filled. A positive electrode active material for a lithium secondary battery having a conductive fine powder ,
The average primary particle diameter of the conductive fine powder is 50 nm or less,
A sub-peak in which the pore distribution curve by the mercury intrusion method has at least one main peak having a peak top at a pore radius of 300 nm or more and 1000 nm or less, and a peak top at a pore radius of 1 nm or more and less than 80 nm. Have
In the pore distribution curve by the mercury intrusion method, the pore volume related to the main peak having a peak top at a pore radius of 300 nm or more and 1000 nm or less is 0.1 cm ³ / g or more and 0.5 cm ³ / g or less, And the pore capacity | capacitance which concerns on the subpeak in which a peak top exists in pore radius 1 nm or more and less than 80 nm is 0.01 cm < ³ > / g or more and 0.2 cm < ³ > / g or less,
In the mercury intrusion curve according to the mercury intrusion method, the amount of mercury intrusion when the pressure is increased from 3.86 kPa to 413 MPa is 0.3 cm ³ / g or more and 0.8 cm ³ / g or less,
A positive electrode active material for a lithium secondary battery , wherein the C value is 1% by weight or more and 10% by weight or less when the carbon content is C (% by weight) . 2. The lithium according to claim 1 , wherein a mercury intrusion amount at a pressure of 3.86 kPa to 413 MPa in a mercury intrusion curve by a mercury intrusion method is 80% or less of the mercury intrusion amount of the mother particle. Positive electrode active material for secondary batteries. Volume resistivity when compacted at a pressure of 40MPa is 0.01 Ohm · cm or more, first positive electrode active material for a lithium secondary battery according to claim 1 or 2, wherein the × or less 10 ³ Ω · cm material. BET specific surface area of ^{5 m} 2 / g or more, the positive electrode active material for lithium secondary battery according to any one of claims 1 to 3, equal to or less than 100 m ² / g. Bulk density of 1.5 g / cm ³ or more, 2.4 g / cm ³ positive electrode active material for lithium secondary battery according to any one of claims 1 to 4, characterized in that less. Using a laser diffraction / scattering particle size distribution measuring device, the refractive index is set to 1.24, the particle diameter reference is the volume reference, and the median diameter measured without ultrasonic dispersion in an aqueous medium is 3 μm or more and 30 μm. or less, ultrasonic dispersion (output 30 W, frequency 22.5 kHz) for 5 minutes measured median diameter is 0.5μm or more after any one of claims 1 to 5, characterized in that at 10μm or less The positive electrode active material for lithium secondary batteries described in 1. The positive electrode active material for a lithium secondary battery according to any one of claims 1 to 6 , wherein the main component composition of the mother particles is represented by the following composition formula (I).
LiMO ₂ (I)
(However, in the above 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 0.8 or more and 5 or less, (The Co / (Mn + Ni + Co) molar ratio is 0 or more and 0.35 or less, and the 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 7 , wherein M 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)
(However, in the above formula (II),
0 ≦ x ≦ 0.1
−0.1 ≦ y ≦ 0.1,
(1-x) (0.05-0.98y) ≤z≤ (1-x) (0.20-0.88y)
It is. ) Addition of boron-containing compound and tungsten-containing compound in a proportion of 0.01 mol% or more and less than 2 mol% in total of B and W with respect to the total molar amount of transition metal elements in the main component raw material After that, the positive electrode active material for a lithium secondary battery according to claim 7 or 8 , which is fired at 900 ° C or higher. A slurry adjusting step for obtaining a slurry in which lithium carbonate and each metal compound of a manganese compound, a nickel compound, and a cobalt compound used as needed are pulverized in a liquid medium and uniformly dispersed therein, and obtained. A spray drying step for spray drying the slurry, a firing step for firing the obtained spray dried body, a classification step for classifying the obtained fired powder, and a conductive fine powder was added to the obtained classified powder. The manufacturing method of the positive electrode active material material for lithium secondary batteries of any one of Claim 1 thru | or 9 including the post-processing process which performs the process which adds a compression shearing stress afterwards. In the slurry adjusting step, the lithium carbonate and the 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 the particle size reference is set as a volume reference for 5 minutes. Is pulverized until the median diameter measured after ultrasonic dispersion (output 30 W, frequency 22.5 kHz) is 0.4 μm or less. In the spray drying process, the slurry viscosity during spray drying is V (cp), and the slurry supply amount is S (L / min), when the gas supply amount was set to G (L / min), according to claim, characterized in that performing spray drying under the conditions to be 50cp ≦ V ≦ 4000cp, 500 ≦ G / S ≦ 10000 10 The manufacturing method of the positive electrode active material material for lithium secondary batteries as described in any one of. The metal compound includes a nickel compound, a manganese compound, a cobalt compound, a boron compound, and a tungsten compound, and in the firing step, the spray-dried body is fired at 900 ° C. or higher in an oxygen-containing gas atmosphere. The manufacturing method of the positive electrode active material material for lithium secondary batteries of Claim 11 . A lithium secondary battery comprising a positive electrode active material layer containing the active material for a lithium secondary battery positive electrode according to any one of claims 1 to 9 and a binder on a current collector. Positive electrode. 14. The positive electrode for a lithium secondary battery according to claim 13 , wherein the density of the positive electrode active material layer after repeating the pressurization for 5 minutes at a pressure of 760 MPa is 3.0 g / cm ³ or more. 15. 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 13 or 14 is used as a positive electrode. A lithium secondary battery using a positive electrode for a secondary battery.

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