JPH10308218A - Positive electrode active material for lithium ion secondary battery, and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the positive electrode active material, which can improve the heat stability at the time of charging a lithium ion secondary battery and while which can improve the charging and discharging cycle characteristic, by forming the particle structure of the positive electrode active material of particles, which are formed by collecting single crystals having a fine crystal lattice as a unit, and forming shape of the crystal lattice and particles into the three-dimensional isotropic shape. SOLUTION: This positive electrode active material is expressed with a general formula LiMO2 , and M means at least one kind of heavy metal element to be selected among a group of Co, Ni, Fe, Mn, Cr. This active material has a spherical shape, in which shape of a crystal lattice is basically grown to an isotropic shape in a space, and since direction of distortion of the crystal due to a movement of Li with a charge and a discharge is evened in all directions of the space, collapse is restrained at the minimum. Collapse of the crystal structure to be generated at the time of separation Li ion is reduced by forming a large crystal lattice.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive electrode active material for a secondary battery, and more particularly to a positive electrode active material for a non-aqueous lithium ion secondary battery capable of improving cycle characteristics and thermal stability, and a method for producing the same. .

[0002]

2. Description of the Related Art In recent years, new cordless electronic devices such as a camera-integrated VTR, an audio / video device, a notebook personal computer, and a mobile phone have appeared one after another, and have rapidly spread widely in a short time. In order to reduce the size and weight of these devices, it is essential to improve the performance of secondary batteries as portable power supplies.

A non-aqueous lithium ion secondary battery has a high battery voltage, a high discharge capacity, and excellent cycle characteristics.
Recently, it has been actively studied to meet such applications.

The positive electrode active material of this battery is Li heavy metal salt L typified by lithium cobalt oxide (LiCoO 2).
iMO2 (M = Co, Ni, Fe, Mn, Cr, etc.) is used.

Conventionally, a non-aqueous secondary battery using LiMO2 as a positive electrode active material has had a problem of deterioration in cycle characteristics such that the battery discharge capacity is gradually reduced by repeatedly performing charge and discharge cycles. This is because LiMO
It was thought that the crystal of 2 collapsed. Especially,
By repeating charging and discharging, expansion and contraction of the fine particles constituting the positive electrode active material in the c-axis direction occur, and in the case of a polycrystal or the like, since there are many interfaces of crystallites, crystals collapse from there, and It has been considered that peeling of the positive electrode active material from the current collector causes deterioration of cycle characteristics. On the other hand, Japanese Unexamined Patent Publication No. 9-22693 discloses a method of improving the cycle characteristics by monocrystallizing a crystal and growing flat particles oriented in a direction perpendicular to the c-axis ((003) plane). Proposed.

In addition, it is disclosed in Japanese Patent Application Laid-Open No. H05-205580 that by limiting the peak intensity ratio between the (003) plane and the (104) plane of the X-ray diffraction line of LiCoO2 as a positive electrode active material to a specific range. JP-A-2585751, JP-A-9-2
No. 2692, JP-A-9-22693, and JP-A-8-55624.

Further, the positive electrode active material of a lithium ion secondary battery is stable in high-temperature air, but its thermal stability is reduced by being charged, and the organic solvent constituting the electrolyte of the secondary battery is poor. The potential problem is that it oxidatively decomposes and, in some cases, ignites.

[0008] A number of studies have been made on the characteristics of the positive electrode active material for lithium ion secondary batteries in order to improve the charge / discharge cycle characteristics. However, the thermal stability during charging has not been mentioned much. There was no. This is because it was common knowledge that if the thermal stability at the time of charging was improved, the charge-discharge cycle characteristics would be reduced.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and provides a positive electrode active material that improves the thermal stability during charging of a lithium ion secondary battery and achieves good charge / discharge cycle characteristics. The purpose is to do.

[0010]

Means for Solving the Problems The present inventors have made intensive studies on the particle shape and structure of the positive electrode active material, and found that the positive electrode active material is composed of particles in which fine single crystals called crystallites are aggregated. The inventors have found that the size or shape of the primary particles is closely related to the thermal stability and charge / discharge cycle characteristics of the lithium ion battery, and have completed the present invention.

That is, the positive electrode active material for a lithium ion secondary battery of the present invention is a positive electrode active material for a lithium ion secondary battery represented by the general formula LiMO 2, and the particle structure of the positive electrode active material is small crystallites. And the shape of the crystallites and the particles is three-dimensionally substantially isotropic. (However, M is Co, N
i, at least one heavy metal element selected from the group consisting of Fe, Mn, and Cr)

The term “crystallite” refers to the maximum set considered to be a single crystal, and is referred to as XRD (X-ray diffraction).
n) From the measurement, it can be calculated by using the following Scherrer equation. <Scherrer's formula> Crystallite size D (angstrom) = Kλ / (βsi
nθ) K: Scherrer's constant (when β is calculated from the integral width, K =
1.05) λ: wavelength of the used X-ray tube (CuKα1 = 1.40556)
2 angstrom β: width of spread of diffraction line due to crystallite size (rad)
ian) θ: diffraction angle 2θ / 2 (degree)

The term “particle” as used herein refers to the smallest particle that can be imaged by SEM. When the particle is formed of one single crystal, the crystallite diameter and the particle diameter are the same. When a single particle includes a plurality of single crystals, the sizes do not naturally match.

The three-dimensionally isotropic shape refers to a shape in which the particles have no orientation and grow isotropically in all directions of the space, and are typically spherical, but not necessarily spherical. The present invention is not limited thereto, and includes those having a substantially spherical shape. An ordinary crystalline substance has a particle shape that reflects its crystal structure. On the other hand, it can be said that the positive electrode active material useful in the present invention has a special shape having no such orientation.

In the case where the three-dimensional shape of crystallites constituting the primary particles of the positive electrode active material is expressed by a direction in which layers are superposed ((003) vector direction) and a direction perpendicular thereto ((110) vector direction), 110) The ratio of the crystallite diameter in the (003) direction to the crystallite diameter in the vector direction is 0.5
It is preferably in the range of 1.6. The direction in which the layers are stacked indicates that the basic lattice of LiMO2 as the positive electrode active material is hexagonal, and points in the c-axis direction. Therefore, the direction perpendicular to the direction refers to the a-axis direction.

The crystallite diameter of the crystallite of the positive electrode active material in the (003) vector direction is preferably in the range of 500 to 750 angstroms.

The crystallite diameter of the crystallite of the positive electrode active material in the (110) vector direction is preferably in the range of 450 to 1000 Å.

The average particle diameter of the positive electrode active material is obtained by measuring the specific surface area by an air permeation method and calculating the average value of the particle diameters of the primary particles. Specifically, the average particle diameter is determined by a Fischer subsieve sizer (FS. SS).

The ratio of the minor axis particle diameter to the major axis particle diameter of the particles by SEM observation is preferably in the range of 0.5 to 1.0. The ratio is calculated as follows. FIG.
As shown in (1), the center of each of 20 randomly extracted particle images is determined from the SEM photograph, the longest diameter passing through the center is determined, and this is defined as the long-axis particle diameter. Next, the diameter in the direction perpendicular to the major axis passing through the center is defined as the minor axis particle diameter. The average of the ratio of the minor axis particle diameter / major axis particle diameter of each of the obtained particles is calculated.

In the method for producing a positive electrode active material for a lithium ion secondary battery according to the present invention, the raw metal oxide and the lithium salt are mixed so that the Li / M ratio is in the range of 0.98 to 1.01. In the method for producing a positive electrode active material to be fired, the particle shape of the heavy metal oxide is composed of primary particles having a substantially three-dimensionally isotropic shape or secondary particles in which the primary particles are aggregated, and the central particle size is 0.1%. -10 μm. (Where M is at least one heavy metal element selected from the group consisting of Co, Ni, Fe, Mn, and Cr)

The center particle diameter of the raw material heavy metal oxide is a value measured by using a particle size distribution measuring device of an electric resistance method.
Here, it is the central particle diameter measured using Coulter Multisizer 2. This can be said to be a particle size that includes a knowledge of whether it is in a dispersed state or an aggregated state from the measurement principle.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION

<Particle Shape> In the present invention, the degree of growth of crystallites in the particles of the positive electrode active material affects battery characteristics, and the degree of growth in a specific vector direction has a correlation with individual characteristics. I found something. LiMO2, which is a positive electrode active material of a lithium ion secondary battery, originally has a layered structure. The crystal shape of the crystallite of the positive electrode active material of the present invention grows isotropically in the space as shown in FIG. 2A, and does not have c-axis orientation as in the comparative example. If this is expressed using the crystallite diameter according to Scherrer's formula, the range of 500 to 750 angstroms in the (003) vector direction,
(110) Range of 450-1000 Angstroms in vector direction, (105) 500-90 in vector direction
It can be said that it is in the range of 0 angstroms and in the range of 450 to 1000 angstroms in the (113) vector direction.

In the present invention, (105), (113)
Although the vector direction was also mentioned, this is a means for expressing whether or not the crystal is growing three-dimensionally. If the plane is not parallel or perpendicular to the layer (104)
Alternatively, other plane directions such as the (108) vector direction may be used. However, it is considered that if these crystallites are too large, the diffusion of Li ions is hindered, and if they are too small, they cause crystal collapse.

<Material for Heavy Metal Oxide> The positive electrode active material for a lithium ion secondary battery of the present invention is characterized by the particle shape as described above. In order to obtain such a particle structure, a heavy metal oxide raw material whose secondary particles are spherical and whose primary particles have a small crystallite diameter is selected as a raw material. As for the particle shape of the positive electrode active material, it is easy to take over the particle shape of the raw material as it is. For example, when the shape of the secondary particles of the heavy metal raw material is an octahedral structure, the obtained LiMO2 crystallites and particles are likely to have an octahedral structure, and when the shape of the heavy metal oxide is spherical, the obtained LiMO2 crystal Particles and particles tend to have a spherical structure. Further, when the secondary particles have a hexagonal plate-like structure, the obtained LiMO2 crystallites and particles tend to have a hexagonal plate-like structure. The present invention excludes a hexagonal plate-like structure. In particular, when the heavy metal element M is Co 3 O 4 where Co is Co, the crystallite size in the (222) vector direction is 100.
Preferably, it is in the range of ４００400 Å.

The heavy metal oxide has a primary particle size of 0.01
The diameter of the secondary particles is preferably in the range of 0.1 to 10.0 μm. For example, M
Is Co, cobalt carbonate CoCO3,
It can be obtained by thermally decomposing particles having a ratio of short axis particle diameter / long axis particle diameter in the range of 0.5 to 1.0.

The reason for selecting the ratio of the short axis particle diameter to the long axis particle diameter of the secondary particles of the heavy metal element oxide and the center particle diameter of the secondary particles of the heavy metal oxide in the above ranges is as described above. This is because the particle structure of M3O4 is directly reflected on the particle structure of LiMO2, so that the limitation of the parameters of the raw material particles is very important.

<Lithium raw material> As a result of various studies, as a raw material Li salt used in the lithium secondary battery in the present invention, Li2CO3 and Li2 (CO2
O) 2 or LiOH can be preferably used.

<Mixing of Heavy Metal Raw Material and Lithium> In the present invention, M3O4 and a lithium salt are mixed with a Li / M ratio of 0.98 to 0.98.
Mix so as to be in the range of 1.01. It is Li / M
If the ratio deviates from this range, the excess acts as a flux, causing abnormal growth of the particles, making it difficult to control the particle diameter and particle shape.

<Firing> The obtained mixed raw material is fired at 750 to 1100 ° C. in an air atmosphere. When an alkali metal salt, B, Bi, Pb, or the like is added as a flux, or when granulation is performed, the growth in the (110) vector direction is easily promoted, and the cycle characteristics are reduced. ) It is necessary to control the growth in the vector direction.

[0030]

The positive electrode active material of the lithium ion secondary battery is charged with Li, which is desorbed from the crystal, and LixMO2
(X <1.0), and the hexagonal LiM
O2 is transformed into a monoclinic system. Distortion of the crystal due to this transition is the largest cause of the decrease in thermal stability during charging of the positive electrode active material. This lowers the thermal stability by the following mechanism.

When the crystal collapses during charging, oxygen is released from the positive electrode active material. The positive electrode active material constitutes the battery in a state of being in contact with an electrolytic solution such as EC (ethylene carbonate). The free oxygen oxidizes and decomposes the electrolytic solution to cause an oxidation reaction, thereby generating heat and, in some cases, igniting. Could lead to serious problems.

<Thermal Stability> The thermal stability is improved in the present invention for the following reasons. LiMO2 of the positive electrode material of the present invention is basically a crystallite having a spherical shape with isotropic growth in space, and has a large crystallite diameter. By making the crystallite shape a spherical isotropic structure, the direction of crystal distortion due to the movement of Li due to charge and discharge becomes uniform in all spatial directions, so that the conventional crystal structure oriented in a certain direction In comparison, collapse can be minimized. In addition, by increasing the crystallite, it is possible to reduce the collapse of the crystal structure that occurs when Li ions are eliminated. For these reasons, the crystallite in the (003) vector direction is preferably 500 Å or more, and the crystallite in the (110) vector direction is preferably 450 Å or more.

The thermal stability of the positive electrode active material of the present invention was measured as follows. The charged lithium ion secondary battery is disassembled in a dry box, the positive electrode plate is taken out, and about 10 mg is cut out to be a measurement sample. The obtained measurement sample was subjected to Thermal Gravimetric A
Thermogravimetric analysis was performed using a analyzer (TGA). (Solid State Ionics vol.69, No.3 / 4 Page 265-27
0 (1994)) Basically, a method of measuring a limit temperature that causes a change in weight of a sample while increasing the temperature of the sample from the outside. This weight change is mainly based on the weight loss due to liberation of oxygen from the positive electrode active material. An increase in the oxygen concentration in the battery electrolyte causes abnormal heat generation. Therefore, the higher the limit temperature, the lower the problem of abnormal heat generation, which is preferable.

The relationship between the crystallite diameter and the critical temperature of the TGA apparatus was measured for a cathode active material having substantially spherical crystallites and plotted in FIG. Since the cathode active material of the present invention is substantially spherical, the crystallite diameter is the same regardless of the vector direction, but here, the (003) crystallite diameter in the vector direction is calculated by the above-mentioned Scherrer equation. Calculated using FIG. 2 shows that the thermal stability during charging of LiMO2 is linearly related to the thermal stability, and it can be understood that the larger the crystallite diameter, the higher the limit temperature, that is, the higher the thermal stability. This is because, as described above, when the crystallite diameter is large, the influence of crystal breakage due to detachment of Li during charging is reduced, and the free oxygen concentration is reduced.

<Charge / Discharge Cycle Characteristics> Regarding the charge / discharge cycle, the crystallite diameter in the (110) vector direction is 10
It is important that they do not grow too much above 00 Angstroms. This is because if the crystal grows too much in the (110) vector direction, as shown in FIG.
When inserting (discharging) i, only the direction parallel to the layer is L
This is because, since i-ions cannot be inserted, the surface into which Li ions can be inserted relatively decreases, and the diffusion of Li ions at the particle interface deteriorates. In particular, when discharging at a high current density, this tendency becomes remarkable.

FIG. 4 shows the crystallite diameter of the positive electrode active material of the present invention and 1
The relationship of the 00 cycle deterioration rate was plotted. Here, since the product of the present invention is spherical, the crystallite diameter is almost the same no matter which direction is evaluated. Here, however, the crystallite diameter is plotted with respect to the crystallite diameter in the (110) vector direction. As shown in FIG. 3, when the crystallite diameter is in the range of 500 to about 1000 angstroms, the cycle characteristics hardly change.
It is understood that the capacity retention ratio defined later decreases when the thickness exceeds Å.

The charge / discharge test of the lithium secondary battery is performed as follows. First, as a positive electrode, 70 parts by weight of LiMO2, 15 parts by weight of acetylene black, and 15 parts by weight of PTFT (polytetrafluoroethylene) were mixed with ethanol and kneaded to form a paste, which was then pressed on a SUS mesh and pressed. Dry to obtain a positive electrode plate. On the other hand, both electrodes are immersed in an electrolytic solution in which EC (ethylene carbonate), DEC (diethylene carbonate) and the electrolyte LiPCl4 are mixed, using Li metal as a negative electrode. The charging is set to a current load of 0.2 C (1 C is a current load at which charging or discharging is completed in one hour), and the charging upper limit voltage is set to 4.20 V. Discharge is set to 0.6C current load,
The lower limit voltage is set to 2.75 V, and charge / discharge for 100 cycles is performed. The capacity retention ratio is calculated by the (%) formula of (10th discharge capacity) / (1st discharge capacity) × 100.

As described above, in the prior art, in order to improve the cycle characteristics, the particles are made into a flat plate single crystal, and the expansion and contraction of the particles in the c-axis direction are made in a certain direction, thereby preventing the particles from collapsing and collecting. It is said to prevent peeling from the conductor. On the other hand, in the present invention, on the contrary, the crystal was formed into a shape close to a spherical shape without orientation. This increases the adhesion of the particles themselves to the current collector, prevents the positive electrode active material from peeling off from the current collector due to charge / discharge cycles, and further increases the surface on the particle interface where Li can be inserted. Thereby, the cycle characteristics are improved.

[0039]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention uses LiCo as a positive electrode active material.
O2 will be described, but the composition is not limited to this. The same applies to all possible compositions of LiMO2 (where M is at least one heavy metal element selected from the group consisting of Co, Ni, Fe, and Cr).

Example 1 <Preparation of Raw Materials> Cobalt tetroxide (Co 3 O 4) 3.000 kg Lithium carbonate (Li 2 CO 3) 1.380 kg Cobalt tetroxide was (222 2) The crystallite diameter in the vector direction is 200 angstroms, and the secondary particles are substantially spherical polycrystalline particles. Regarding the secondary particle size, C
The center particle size was 5.0 μm as measured using an Oulter Multisizer 2. L of the above raw materials
The charging ratio of i / Co is 1.00. These raw materials are charged into a ceramic pot and ball milled to obtain a mixed raw material of the positive electrode active material.

The obtained mixed raw material was heated at 900 ° C. in air for 10 hours.
After firing for a period of time and pulverizing, the desired LiCoO2 was synthesized.

The obtained LiCoO 2 was measured for powder X-ray diffraction using CuKα as a radiation source, and was calculated using Scherrer's formula. As a result, the crystallite diameter in the (003) vector direction was 60%.
The crystallite diameter in the 6 Å and (110) vector directions is 879 Å, and the other (11
5) The crystallite diameter in the vector direction was 795 angstroms, and the crystallite diameter in the (113) vector direction was 848 angstroms.

Regarding the particle size of the LiCoO 2 cathode active material, S. S. S. The average particle size was 4.0 μm as measured by using the formula (1), and the average of the ratio of the short axis particle diameter / the long axis particle diameter of each particle was 0.9. S
When preparing a measurement sample to be subjected to EM, if it is prepared by applying pressure, it will be difficult to distinguish it from the isotropically shaped particles of the present invention. Therefore, when preparing a SEM measurement sample,
The sample surface was prepared so as not to apply pressure to make it difficult to receive the shape of the particles.

<Cycle characteristics> The obtained positive electrode active material Li
A mixture of 70 parts by weight of CoO2, 15 parts by weight of acetylene black, and 15 parts by weight of PTFT (polytetrafluoroethylene) mixed with ethanol and kneaded into a paste was pressed on a SUS mesh, dried and dried to form a positive electrode. Get the board. On the other hand, both electrodes are immersed in an electrolytic solution in which EC (ethylene carbonate), DEC (diethylene carbonate) and the electrolyte LiPCl4 are mixed, using Li metal as a negative electrode. The charging is set to a current load of 0.2C (1C is a current load at which charging or discharging is completed in one hour),
The charging upper limit voltage is set to 4.20V. The discharge is set to a 0.6 C current load, the lower limit voltage is set to 2.75 V, and charge / discharge for 100 cycles is performed. The capacity retention ratio was 95.2% as a result of an expression of (100th discharge capacity) / (first discharge capacity) × 100.

<Thermal stability> The obtained positive electrode active material LiCO
2 was used to prepare a secondary battery under the same conditions as the cycle characteristics measurement, charging was performed under the conditions of a charging load of 0.2 C and a charging upper limit voltage of 4.20 V, and then the lithium ion secondary battery was placed in a dry box. The positive electrode plate is taken out, and about 10 mg thereof is cut out to obtain a measurement sample. As a result of performing thermogravimetric analysis on the obtained measurement sample using a TGA device,
At 8.0 ° C., a weight change due to oxygen release was observed, with a limiting temperature of 218.0 ° C.

Comparative Example 1 Cobalt tetroxide particles were SE
According to observation by M, the particles were hexagonal plate-like particles, and (222)
The crystallite diameter in the vector direction is 100 Å, C
LiCoO2 was synthesized by mixing and firing the raw materials under the same conditions as in Example 1 except that secondary particles having a center particle diameter of 6.2 μm measured using an Oulter Multisizer 2 were used.

When the obtained LiCoO 2 was calculated using Scherrer's formula in the same manner as in Example 1, (003)
The crystallite diameter in the vector direction is 649 angstroms, the crystallite diameter in the (110) vector direction is 1150 angstroms, the crystallite diameter in the (115) vector direction is 798 angstroms, and the crystallite diameter in the (113) vector direction is It was 868 angstroms.

Regarding the particle size of the LiCoO 2 cathode active material S. S. S. As a result, the average particle size was 3.5 μm.

Further, the ratio of the minor axis particle diameter to the major axis particle diameter of the LiCoO 2 particles observed by SEM was 0.3.

<Cycle Characteristics> A secondary battery was prepared in the same manner as in Example 1 except that the obtained positive electrode active material was used.
The charge and discharge were performed for 00 cycles. 85.0% capacity retention
Met.

<Thermal stability> The obtained positive electrode active material LiCO
As a result of performing thermogravimetric analysis using TGA and using TGA in the same manner as in Example 1, the limit temperature at which a weight change due to oxygen release was observed was 190.8 ° C.

[0052]

As described above, LiMO2 of the cathode material of the present invention is basically a sphere in which the crystallite shape is isotropically grown in space, and has a larger crystallite diameter. By making the crystallite shape a spherical isotropic structure, the direction of crystal distortion due to the movement of Li due to charge and discharge becomes uniform in all spatial directions, so that the conventional crystal structure oriented in a certain direction In comparison, collapse can be minimized. Further, by further increasing the crystallite to a specific range, the collapse of the crystal structure that occurs when Li ions are eliminated can be reduced. In these respects, the product of the present invention was able to significantly improve the thermal stability and cycle characteristics of the positive electrode active material as compared with the conventional product.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a method for evaluating a long axis particle diameter and a short axis particle diameter based on an SEM photograph.

FIG. 2 is an enlarged schematic diagram showing a comparison of the particle shapes of a positive electrode active material of (a) the present invention product and (b) a comparative product.

FIG. 3 is a characteristic diagram showing a relationship between a crystallite diameter and a limit temperature.

FIG. 4 is a characteristic diagram showing a relationship between a capacity retention ratio and a crystallite diameter.

[Explanation of symbols]

 1 ····· The surface into which Li ions can be inserted

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kenji Fujino 491-100 Kaminakacho Oka, Anan City, Tokushima Prefecture Inside Nichia Kakoh Kogyo Co., Ltd. Within Aka Chemical Industry Co., Ltd.

Claims (6)

[Claims] 1. A positive electrode active material for a lithium ion secondary battery represented by the general formula LiMO2, wherein the particle structure is composed of particles in which a crystallite is a unit and which is aggregated,
The positive electrode active material for a lithium ion secondary battery, wherein the shape of the crystallite and the particles is three-dimensional and substantially isotropic. (Where M is at least one heavy metal element selected from the group consisting of Co, Ni, Fe, Mn, and Cr) 2. A case in which the three-dimensional shape of crystallites constituting the primary particles of the positive electrode active material is expressed by a direction in which layers are superposed ((003) vector direction) and a direction perpendicular thereto ((110) vector direction). 2. The lithium ion secondary according to claim 1, wherein a ratio of a crystallite diameter in the (003) vector direction to a crystallite diameter in the (110) vector direction is in a range of 0.5 to 1.6. 3. Positive electrode active material for batteries. 3. The positive electrode active material for a lithium ion secondary battery according to claim 1, wherein a crystallite diameter in a (003) vector direction of a crystallite of the positive electrode active material is in a range of 500 to 750 Å. material. 4. The positive electrode active material for a lithium ion secondary battery according to claim 1, wherein the crystallite diameter of the crystallite of the positive electrode active material in the (110) vector direction is in a range of 450 to 1000 Å. material. 5. The particle has a substantially spherical shape, an average particle diameter of 0.1 to 10 μm, and a ratio of a short axis particle diameter to a long axis particle diameter of the particle measured by SEM is 0.5 to 10 μm.
The positive electrode material for a lithium ion secondary battery according to claim 1, wherein the positive electrode material has a range of 1.0. 6. A method for converting raw material heavy metal oxide and lithium salt into Li
In the method for producing a positive electrode active material, which is mixed and fired so that the / M ratio is in the range of 0.98 to 1.01, the particle shape of the heavy metal oxide is substantially three-dimensional. A method for producing a positive electrode active material for a lithium ion secondary battery, comprising secondary particles in which particles or primary particles are aggregated, and having a central particle size of 0.1 to 10 μm. (Where M is at least one heavy metal element selected from the group consisting of Co, Ni, Fe, Mn, and Cr)