JP2001297761A - Positive electrode activator for nonaqueous electrolyte secondary cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive electrode activator which enables to manufacture a nonaqueous electrolyte secondary cell with good cycle characteristics, durability, and large discharging capacity at high efficiency discharging. SOLUTION: The crystal system of a double oxide of lithium and cobalt, synthesized by granulating and burning the mixed powder of lithium compound and cobalt compound with molar ratio Li/Co ranging from 0.98 to 1.005, is hexagonal. At the X-ray diffraction pattern of powder method by CuKα-ray, diffraction strength of crystal face (003) I(003) and that of crystal face (104) I(104) are in the ratio of 2.0<=I(003)/I(104)<=4.0, or preferably 2.5<=I(003)/I(104)<=3.5. For the above double oxide of lithium and cobalt, dispersion of molar ratio Li/Co is made less than 0.04 or preferably less than 0.03.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a negative electrode comprising lithium,
The present invention relates to a positive electrode active material for a non-aqueous electrolyte secondary battery using a lithium alloy or carbon, and more particularly to an improvement in a positive electrode active material for the purpose of improving high-rate discharge characteristics.

[0002]

2. Description of the Related Art In recent years, with the spread of portable devices such as mobile phones and notebook computers, secondary batteries having a high energy density, small size, light weight and high capacity have been developed. As such a secondary battery, there is a lithium ion secondary battery using lithium, a lithium alloy or carbon as a negative electrode, and research and development have been actively conducted.

[0003] In particular, lithium cobalt double oxide (LiC
Lithium-ion secondary batteries using oO ₂ ) as a positive electrode active material are expected to be secondary batteries having a high energy density because a high voltage of 4 V class can be obtained, and their practical use is progressing.

Therefore, in a secondary battery using a lithium-cobalt double oxide, development for obtaining excellent cycle characteristics, high-rate charge / discharge characteristics, and storage characteristics (characteristics relating to self-discharge and reduction in discharge capacity due to storage) has been developed. Many have been performed so far, and many results have already been reported.

[0005] For example, in Japanese Patent Publication No. Sho 63-59507, discloses Li _x CoO ₂ having a layered crystal structure, in JP-A-62-90863, C in Li _x CoO ₂
Part of the element o is Al, In, Sn, W, Mn, Ta, T
Attempts have been made to improve storage characteristics by substituting with different metals such as i and Nb.

As disclosed in Japanese Patent Application Laid-Open No. 7-335200, Li _x V _y CoO ₂ (where x is 1.00 ≦ x
≦ 1.10, y is 0.01 ≦ y ≦ 0.04)
In the powder X-ray diffraction pattern, the (003) crystal plane diffraction intensity I (003) and the (104) crystal plane diffraction intensity I (1
It has been proposed that a secondary battery composed of a positive electrode active material having a ratio of 4 ≦ I (003) / I (104) ≦ 25 has excellent storage characteristics. I (003) /
I (104) is an index of the layered crystal structure, and a larger value indicates that the layered crystal structure is more highly developed.

In Japanese Patent Application Laid-Open No. Hei 5-258751, Li _x CoO _z (where 0 <x ≦ 1.3, 1.8 <z
In <2.2), in the X-ray diffraction intensity, 0.4 ≦ I (104) / I (003) ≦ 0.75 (When rewritten, about 1.33 ≦ I (003) / I (10
It has been proposed that a secondary battery having a large high-rate discharge capacity can be obtained with the positive electrode active material in the range of 4) ≦ 2.5).

However, in the inventions of JP-B-63-59507 and JP-A-62-90863, the discharge capacity of the secondary battery is not yet sufficient, and
If the X-ray diffraction intensity ratio is in the range of 4 ≦ I (003) / I (104) ≦ 25 as in JP-A-200, it is considered that the compound has a layered crystal structure and has excellent storage characteristics. However, it has been found that the number of coarse plate-like crystals of LiCoO ₂ increases, the cycle characteristics deteriorate, and the high-rate discharge capacity does not increase.

Further, as disclosed in Japanese Patent Application Laid-Open No. 5-258751, the X-ray diffraction intensity ratio is 0.4 ≦ I (104) / I (003) ≦ 0.75 (in the case of rewriting, about 1.33 ≦ I (003) / I (10
It has been found that when the content is in the range of 4) ≦ 2.5), particles having a layered crystal structure are reduced, storage characteristics are deteriorated, and the charge / discharge capacity itself is reduced.

[0010]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a positive electrode active material capable of producing a non-aqueous electrolyte secondary battery having excellent cycle characteristics, storage characteristics, and excellent discharge capacity when high-rate discharge is performed. To provide a substance.

[0011]

Means for Solving the Problems In order to solve this problem, the inventors examined the crystal morphology of various lithium-cobalt double oxides by using the powder X-ray diffraction method. Between the value of the ratio of the diffraction intensity of the lattice plane (the peak height of the diffraction line is defined as the diffraction intensity in this specification) and the cycle characteristics, storage characteristics, and high-rate discharge capacity. We found that a correlation exists.

That is, the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention comprises a lithium compound and a cobalt compound,
A lithium-cobalt double oxide synthesized by granulating and firing a mixed powder mixed in a Li / Co molar ratio of 0.98 to 1.005, and having a hexagonal type. In the powder X-ray diffraction pattern by CuKα ray,
(003) The diffraction intensity I (003) of the crystal plane and (10
4) The ratio of the crystal plane to the diffraction intensity I (104) is 2.0 ≦ I (003) / I (104) ≦ 4.0.

More preferably, 2.5 ≦ I (003) / I (104) ≦ 3.5.

As the lithium cobalt double oxide,
The variation width of the Li / Co molar ratio of each part of the mixed powder obtained by mixing the lithium compound and the cobalt compound is 0.04 or less, more preferably 0.03 or less.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The above specific lithium-cobalt double oxide in the present invention is, for example, a lithium salt such as lithium carbonate, a lithium compound such as lithium hydroxide or lithium oxide, a cobalt salt such as cobalt carbonate, a cobalt oxide or the like. A mixture comprising a cobalt compound such as cobalt oxyhydroxide and cobalt hydroxide is heated at 800 ° C. in air.
It is obtained by firing in a temperature range of about 1000 ° C.

However, in order to obtain an X-ray diffraction intensity ratio in the range of 2.0 ≦ I (003) / I (104) ≦ 4.0, the mixed state of the lithium compound and the cobalt compound must be changed. It is necessary to raise the level, and sampling is performed from various places in a state where both compounds are mixed, and Li and Co of each mixed powder are analyzed, and Li / Co
The variation width of the molar ratio needs to be 0.04 or less.

The variation width of the Li / Co molar ratio is 0.04
Is exceeded, there is a locally high Li portion in the mixed powder, and in that portion, even if fired under the same conditions, the crystal growth of the primary particles is accelerated, and as a result, the plate-shaped layered crystal structure which is coarsened It is estimated that a lithium-cobalt double oxide having

As is generally practiced, the lithium-cobalt double oxide of the present invention is formed from a conductive material such as acetylene black and carbon black and a binder such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PFV). Knead with the adhesive to form a positive electrode mixture.

As the negative electrode material, lithium, a lithium alloy, or a carbon material capable of inserting and extracting lithium is used. When a carbon material is used, it is kneaded with a binder such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PFV) to form a negative electrode mixture.

As the separator, a microporous thin film made of polyethylene or polypropylene having excellent ionic conductivity is used. As the electrolytic solution, a solution obtained by dissolving lithium perchlorate in a mixed solvent of propylene carbonate and dimethoxyethane is used. For example, various ones conventionally used for non-aqueous batteries can be used.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on embodiments.

(Example 1) The lithium / cobalt ratio was 1.
Lithium carbonate (Li ₂ CO ₃ ; purity 99)
%) And 7.261 kg of cobalt oxide (Co ₃ O ₄ ; Co content: 73.3% by weight) were premixed for 7 minutes with a V-type mixer and mixed for 10 minutes using a mixing granulator. Was done.

In the mixed state, sampling (n = 1)
0), and the variation width of the Li / Co molar ratio in each part of the mixed powder was 0.03.

312 g of a 4 wt% PVA (polyvinyl alcohol) aqueous solution is added, and the mixture is granulated for 15 minutes.
A 5 mm granulated product was produced. This granulated product is heated at 100 ° C. for 2 hours.
After drying for an hour, the temperature was further increased to 950 ° C. at a heating rate of 5 ° C./min at an oxygen flow rate of 3 liter / min using a magnesia setter and maintained for 15 hours. The lithium-cobalt double oxide calcined in this manner is crushed to a particle size of 4
The thickness was set to 0 μm or less.

Using an X-ray diffraction Cu tube, a voltage of 40 kV and 150 mA is applied, a sampling width is 0.02 °, and a scanning speed is 4.0 ° / mi.
n, divergence slit 1.00 °, scattering slit 1.00
°, the light receiving slit was measured as 0.3 mm. From the obtained diffraction pattern, the lithium-cobalt double oxide was a hexagonal crystal, and the peak intensities of the (003) plane and the (104) plane of LiCoO ₂ were determined, and the X-ray intensity ratio was determined. I (003) / I (104) = 2.8.

Raw material by powder X-ray diffraction using CuKα ray
For identification of the phase, JCPDS file number 16-42
7th LiCoO_TwoThe other phase is Li_TwoCO_ThreeAnd C
o_ThreeO _FourIs not recognized, except for the presence of traces of
Was.

Battery Evaluation Further, a battery was assembled using the obtained lithium cobaltate as an active material, and the charge / discharge capacity was measured.

FIG. 1 is a partially cutaway perspective view of a secondary battery incorporating a positive electrode active material according to an embodiment of the present invention.

The lithium cobaltate positive electrode active material,
Acetylene black and polytetrafluoroethylene resin (PTFE) were mixed at a weight ratio of 80: 15: 5 to prepare a mixture, and 50 mg was weighed out of the mixture,
It was press-molded at a pressure of 200 MPa into a disk having a diameter of 10 mmφ. The disc was placed in a vacuum dryer at 120 ° C.
And dried overnight to form a positive electrode 5.

The positive electrode 5 was heated at a dew point of -80 ° C. in an Ar atmosphere.
Was assembled into a 2032 type coin battery (also called a button type battery) in a controlled glove box. For the negative electrode 2, Li metal having a diameter of 16 mmφ and a thickness of 1 mm was used. For the electrolytic solution, ethylene carbonate (EC) using 1 M LiPF ₆ as a supporting salt, and 1,2-dimethoxyethane (DM)
The mixed solution of an equal amount of E) was used. As the separator 3, a 25 μm-thick polyethylene porous film was used. Although the electrolytic solution is not shown in the figure, the electrolytic solution exists in a void inside the battery.

The assembled 2032 type coin battery is
After assembling for about 10 hours, after the OCV was stabilized, the charge current density was 1.0 mA / cm ² and the cutoff voltage was 4.3.
After charging the battery to V, the battery was left for 2 hours, and the discharge current density was 1.
A discharge test was performed at 0 mA / cm ^{2 up} to 3.0 V. When this initial discharge capacity was measured, it was 147 mAh / g.
Met.

Further, the charge / discharge test was repeated under the same conditions as above, and the 100th discharge capacity was measured. The capacity retention rate was determined by the following equation.

Capacity retention rate (%) = 100th discharge capacity / initial discharge capacity × 100 The capacity retention rate was 83%.

Dependency on Discharge Current Density After assembling a 2032 type coin battery, the OCV was allowed to stand for about 10 hours and the cut-off was performed at a charge current density of 1.0 mA / cm ^2. 4.3V voltage
After charging the battery for 2 hours, the discharge current density was 1.0 m
A discharge test was performed at A / cm ^{2 up} to a cutoff voltage of 3.0 V, and a discharge capacity (1) was obtained.

After the discharge test was completed, the device was left for 2 hours, charged again at a charge current density of 1.0 mA / cm ² to a cutoff voltage of 4.3 V, and then left for 2 hours to increase the discharge current density to 8.0 mA / cm. cm ² and cutoff voltage of 3.0
A discharge test was performed up to V to determine a discharge capacity (8). The discharge current density dependency was determined by the following equation.

Discharge current density dependency = discharge capacity (8) / discharge capacity (1) × 100 The discharge current density dependency was 70%.

Table 2 shows the results.

Example 2 When the lithium / cobalt ratio was 1.
Lithium carbonate (Li ₂ CO ₃ ; purity 99)
%) And 7.261 kg of cobalt oxide (Co ₃ O ₄ ; Co content: 73.3% by weight) were premixed for 7 minutes with a V-type mixer and mixed for 15 minutes using a mixing granulator. Was done.

In the mixed state, sampling (n = 1)
0), and the variation width of the Li / Co molar ratio in each part of the mixed powder was 0.03.

[0040] A 4 wt% aqueous solution of PVA (polyvinyl alcohol) (3012 g) was added and granulated for 15 minutes.
A 5 mm granulated product was produced. This granulated product is heated at 100 ° C. for 2 hours.
After drying for an hour, the temperature was raised to 900 ° C. at a heating rate of 5 ° C./min at an oxygen flow rate of 3 liter / min using a magnesia setter and maintained for 18 hours. The lithium-cobalt double oxide calcined in this manner is crushed to a particle size of 4
The thickness was set to 0 μm or less.

X-ray Diffraction In the same manner as in Example 1, the obtained X-ray diffraction pattern showed that the lithium-cobalt double oxide was a hexagonal crystal.
When the peak intensities of the (003) plane and the (104) plane of LiCoO ₂ were determined and the X-ray intensity ratio was determined, I (003) / I (104) = 2.6.

As in Example 1, the produced phase was LiCoO
_No phases other than ₂ were recognized except for the traces of Li ₂ Co ₃ and Co ₃ O ₄ phases.

Battery Evaluation Further, as the battery evaluation, the initial discharge capacity, the capacity dependency ratio and the discharge current density dependency were measured in the same manner as in Example 1.

Table 2 shows the results.

Example 3 When the lithium / cobalt ratio was 1.
Lithium carbonate (Li ₂ CO ₃ ; purity 99)
%) And 7.261 kg of cobalt oxide (Co ₃ O ₄ ; Co content: 73.3% by weight) were premixed for 10 minutes with a V-type mixer and mixed for 10 minutes with a mixing granulator. Was done.

Sampling in mixed state (n = 5)
Was performed and the variation width of the Li / Co molar ratio of each part of the mixed powder was 0.026.

3012 g of a 4 wt% PVA (polyvinyl alcohol) aqueous solution was added, and the mixture was granulated for 15 minutes.
A 5 mm granulated product was produced. This granulated product is heated at 100 ° C. for 2 hours.
After drying for an hour, the temperature was further increased to 1000 ° C. at a heating rate of 5 ° C./min at an oxygen flow rate of 3 liter / min using a magnesia setter and maintained for 10 hours. The thus-calcined lithium-cobalt double oxide was pulverized to a particle size of 40 μm or less.

X-Ray Diffraction In the same manner as in Example 1, the obtained X-ray diffraction pattern showed that the lithium-cobalt double oxide was a hexagonal crystal.
When the peak intensities of the (003) plane and the (104) plane of LiCoO ₂ were determined and the X-ray intensity ratio was determined, I (003) / I (104) = 3.4.

As in Example 1, the produced phase was LiCoO
_No phases other than ₂ were recognized except for the traces of Li ₂ Co ₃ and Co ₃ O ₄ phases.

Battery Evaluation Further, as the battery evaluation, the initial discharge capacity, the capacity dependence and the discharge current density dependence were measured in the same manner as in Example 1.

The results are shown in Tables 1 and 2.

Example 4 The lithium / cobalt ratio was 1.
Lithium carbonate (Li ₂ CO ₃ ; purity 99)
%) And 8.261 kg of cobalt oxide (Co ₃ O ₄ ; Co content: 73.3% by weight) were mixed for 3 minutes by a high-speed mixing fine granulator.

Sampling in a mixed state (n = 5)
Was performed and the variation width of the Li / Co molar ratio of each part of the mixed powder was 0.022.

3012 g of a 4 wt% PVA (polyvinyl alcohol) aqueous solution was added and granulated for 15 minutes.
A 3 mm granulated product was produced. This granulated product is heated at 100 ° C. for 2 hours.
After drying for an hour, the temperature was further increased to 960 ° C. at a heating rate of 5 ° C./min at an oxygen flow rate of 3 liter / min using a magnesia setter and maintained for 13 hours. The lithium-cobalt double oxide calcined in this manner is crushed to a particle size of 4
The thickness was set to 0 μm or less.

X-Ray Diffraction In the same manner as in Example 1, the obtained X-ray diffraction pattern showed that the lithium-cobalt double oxide was a hexagonal crystal.
When the peak intensities of the (003) plane and the (104) plane of LiCoO ₂ were determined and the X-ray intensity ratio was determined, I (003) / I (104) = 3.0.

As in Example 1, the produced phase was LiCoO
_No phases other than ₂ were recognized except for the traces of Li ₂ Co ₃ and Co ₃ O ₄ phases.

Battery Evaluation Further, as the battery evaluation, the initial discharge capacity, the capacity dependency ratio and the discharge current density dependency were measured as in Example 1.

Tables 1 and 2 show the results.

Comparative Example 1 As in Example 1, lithium carbonate (L
3.788 kg of i ₂ CO ₃ ; purity: 99%; 8.261 k of cobalt oxide (Co ₃ O ₄ ; Co content: 73.3% by weight)
g was premixed for 7 minutes with a V-type mixer, and in this comparative example, mixing was performed for 3 minutes using a mixing granulator.

In the mixed state, sampling (n = 1)
0), and the variation range of the Li / Co molar ratio in each part of the mixed powder was 0.05.

3012 g of a 4 wt% PVA (polyvinyl alcohol) aqueous solution is added, and granulated for 15 minutes.
A 5 mm granulated product was produced. This granulated product is heated at 100 ° C. for 2 hours.
After drying for an hour, the temperature was further increased to 950 ° C. at a heating rate of 5 ° C./min at an oxygen flow rate of 3 liter / min using a magnesia setter and maintained for 15 hours. The lithium-cobalt double oxide calcined in this manner is crushed to a particle size of 4
The thickness was set to 0 μm or less.

X-ray Diffraction In the same manner as in Example 1, the obtained X-ray diffraction pattern showed that the lithium-cobalt double oxide was a hexagonal crystal.
When the peak intensities of the (003) plane and the (104) plane of LiCoO ₂ were determined and the X-ray intensity ratio was determined, I (003) / I (104) = 5.8.

As in Example 1, the produced phase was LiCoO
_No phases other than ₂ were recognized except for the traces of Li ₂ Co ₃ and Co ₃ O ₄ phases.

Battery evaluation Further, as the battery evaluation, the initial discharge capacity, the capacity dependency ratio and the discharge current density dependency were measured in the same manner as in Example 1.

Table 2 shows the results.

Comparative Example 2 As in Example 1, lithium carbonate (L) was used so that the lithium / cobalt ratio was 1.0.
3.788 kg of i ₂ CO ₃ ; purity: 99%; 8.261 k of cobalt oxide (Co ₃ O ₄ ; Co content: 73.3% by weight)
g was premixed for 7 minutes in a V-type mixer,
Mixing was performed for 3 minutes using a mixing granulator.

In the mixed state, sampling (n = 1)
0), and the variation range of the Li / Co molar ratio in each part of the mixed powder was 0.05.

[0068] A 3wt% PVA (polyvinyl alcohol) aqueous solution (3012g) was added, and the mixture was granulated for 15 minutes.
A 5 mm granulated product was produced. This granulated product is heated at 100 ° C for 2 hours.
After drying for an hour, the temperature was raised to 900 ° C. at a heating rate of 5 ° C./min at an oxygen flow rate of 3 liter / min using a magnesia setter and maintained for 18 hours. The lithium-cobalt double oxide calcined in this manner is crushed to a particle size of 4
The thickness was set to 0 μm or less.

X-ray Diffraction In the same manner as in Example 1, the obtained X-ray diffraction pattern showed that the lithium-cobalt double oxide was a hexagonal crystal.
When the peak intensities of the (003) plane and the (104) plane of LiCoO ₂ were determined and the X-ray intensity ratio was determined, I (003) / I (104) = 4.2.

As in Example 1, the produced phase was LiCoO
_No phases other than ₂ were recognized except for the traces of Li ₂ Co ₃ and Co ₃ O ₄ phases.

Battery Evaluation Further, as the battery evaluation, the initial discharge capacity, the capacity dependency ratio and the discharge current density dependency were measured in the same manner as in Example 1.

Table 2 shows the results.

(Comparative Example 3) As in Example 1, lithium carbonate (L
3.788 kg of i ₂ CO ₃ ; purity: 99%; 8.261 k of cobalt oxide (Co ₃ O ₄ ; Co content: 73.3% by weight)
g was premixed in a V-type mixer for 5 minutes.
Mixing was performed for 5 minutes using a mixing granulator.

Sampling in mixed state (n = 5)
Was performed, and the variation width of the Li / Co molar ratio of each part of the mixed powder was 0.071.

3012 g of a 4 wt% PVA (polyvinyl alcohol) aqueous solution was added, and the mixture was granulated for 15 minutes.
A 5 mm granulated product was produced. This granulated product is heated at 100 ° C for 2 hours.
After drying for an hour, the temperature was further increased to 1000 ° C. at a heating rate of 5 ° C./min at an oxygen flow rate of 3 liter / min using a magnesia setter and maintained for 10 hours. The thus-calcined lithium-cobalt double oxide was pulverized to a particle size of 40 μm or less.

X-ray Diffraction In the same manner as in Example 1, the obtained X-ray diffraction pattern showed that the lithium-cobalt double oxide was a hexagonal crystal.
The peak intensities of the (003) plane and the (104) plane of LiCoO ₂ were determined, and the X-ray intensity ratio was determined. As a result, I (003) / I (104) = 8.3.

As in Example 1, the produced phase was LiCoO
_No phases other than ₂ were recognized except for the traces of Li ₂ Co ₃ and Co ₃ O ₄ phases.

Battery Evaluation Further, as the battery evaluation, the initial discharge capacity, the capacity dependence and the discharge current density dependence were measured in the same manner as in Example 1.

The results are shown in Tables 1 and 2.

(Comparative Example 4) As in Example 1, lithium carbonate (L
3.788 kg of i ₂ CO ₃ ; purity: 99%; 8.261 k of cobalt oxide (Co ₃ O ₄ ; Co content: 73.3% by weight)
g was preliminarily mixed with a V-type mixer for 5 minutes, and mixed for 5 minutes using a mixing granulator.

Sampling (n = 1) in a mixed state
0), and the variation width of the Li / Co molar ratio in each part of the mixed powder was 0.07.

3012 g of a 4 wt% PVA (polyvinyl alcohol) aqueous solution was added, and the mixture was granulated for 15 minutes.
A 5 mm granulated product was produced. The granulated product was dried at 100 ° C. for 2 hours, and further heated to 900 ° C. at a heating rate of 5 ° C./min at an oxygen flow rate of 3 liter / min using a magnesia setter and held for 18 hours. The thus-calcined lithium-cobalt double oxide is crushed to determine the particle size,
It was 40 μm or less.

X-ray Diffraction In the same manner as in Example 1, the obtained X-ray diffraction pattern showed that the lithium-cobalt double oxide was a hexagonal crystal.
When the peak intensities of the (003) plane and the (104) plane of LiCoO ₂ were determined and the X-ray intensity ratio was determined, I (003) / I (104) = 1.8.

As in Example 1, the produced phase was LiCoO
_No phases other than ₂ were recognized except for the traces of Li ₂ Co ₃ and Co ₃ O ₄ phases.

Battery Evaluation Further, as the battery evaluation, the initial discharge capacity, the capacity dependency ratio and the discharge current density dependency were measured in the same manner as in Example 1.

Table 2 shows the results.

Reference Example As a reference example, as in Example 1, 3.788 kg of lithium carbonate (Li ₂ CO ₃ ; purity 99%) was used so that the lithium / cobalt ratio became 1.0.
Cobalt oxide (Co ₃ O ₄ ; Co content 73.3% by weight)
8.261 kg was premixed for 5 minutes with a V-type mixer.

Sampling in mixed state (n = 5)
Was performed, and the variation width of the Li / Co molar ratio of each part of the mixed powder was found to be as large as 0.118. Table 1 shows the results.
Shown in

[0089]

[Table 1]

[0090]

[Table 2]

As is apparent from Examples 1 to 4, in the present invention, the lithium-cobalt double oxide is prepared by increasing the mixture state of the lithium raw material and the cobalt raw material. In particular,
In a state where both raw materials are mixed, sampling is performed from various places, Li and Co of each mixed powder are analyzed, and Li / Co
By setting the variation width of the molar ratio to be equal to or less than 0.03, the X-ray diffraction intensity ratio falls within the range of 2.5 ≦ I (003) / I (104) ≦ 3.5.

When this is used as a positive electrode active material, it becomes possible to manufacture a nonaqueous electrolyte secondary battery having excellent cycle characteristics, storage characteristics, and excellent discharge capacity when high-rate discharge is performed.

On the other hand, as in Comparative Examples 1 to 3, Li / Co
When the variation ratio of the molar ratio exceeds 0.04, a portion with a large amount of Li is locally formed in the mixed powder, and in that portion, even if firing is performed under the same conditions, the crystal growth of the primary particles is accelerated, and as a result, As a result, a lithium-cobalt double oxide having a coarse plate-like layered crystal structure is easily formed. In this case, Comparative Examples 1 to 3 having an X-ray diffraction intensity ratio of 3.5 <I (003) / I (104) have a layered crystal structure and have excellent storage characteristics. However, it is estimated that the number of coarse plate-like crystals of LiCoO ₂ increases, the cycle characteristics deteriorate, and the high-rate discharge capacity does not increase.

Further, as in Comparative Example 4, the variation width of the Li / Co molar ratio exceeds 0.04, and the X-ray diffraction intensity ratio is I (003) / I (104) <2.0. In this case, it is considered that the growth of the primary particles is suppressed, the particles having a layered crystal structure are reduced, the storage characteristics are low, and the charge / discharge capacity itself is low.

Table 3 shows the results of 10-point sampling of the synthesized lithium-cobalt double oxide in Example 1 and Comparative Example 3. In both Example 1 and Comparative Example 3, the dispersion after the synthesis was about 1/10 compared to the powder in the mixed state.
Had become a variation.

[0096]

[Table 3]

[0097]

The lithium-cobalt double oxide according to the present invention is used as a positive electrode active material for a non-aqueous electrolyte secondary battery to provide a cycle characteristic, a storage characteristic, and a high rate discharge of the secondary battery. The capacity can be improved, and an excellent secondary battery can be manufactured.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a 2032 type coin battery used in an example.

[Explanation of symbols]

 Reference Signs List 1 negative electrode can 2 Li metal pellet 3 separator 4 gasket 5 positive electrode pellet 6 positive electrode can

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hayami Sogabe 3-5-3 Nishihara-cho, Niihama-shi, Ehime F-term in the Besshi Works of Sumitomo Metal Mining Co., Ltd. 4G048 AA04 AB01 AB05 AC06 AD06 AE05 5H029 AJ04 AJ05 AK03 AL07 AM03 AM04 AM05 AM07 BJ03 BJ16 CJ02 CJ06 CJ08 DJ16 DJ17 HJ13 5H050 AA07 AA09 BA17 CA08 CB08 DA02 EA24 FA17 FA19 GA02 GA10 HA13

Claims (2)

[Claims] 1. A method according to claim 1, wherein the lithium compound and the cobalt compound are
a lithium-cobalt double oxide synthesized by granulating, shaping, and firing a mixed powder mixed in a range of 0.98 to 1.005 at an i / Co molar ratio, having a hexagonal type; In the powder X-ray diffraction pattern by CuKα ray, (0
03) The ratio of the diffraction intensity I (003) of the crystal plane to the diffraction intensity I (104) of the (104) crystal plane is 2.0 ≦ I (003) / I (104) ≦ 4.0. A positive electrode active material for a non-aqueous electrolyte secondary battery, comprising: 2. The variation width of the Li / Co molar ratio of each part of a mixed powder obtained by mixing a lithium compound and a cobalt compound is as follows:
The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, which is 0.04 or less.