JPH09129230A - Nonaqueous electrolytic battery and manufacture of positive active material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery with high capacity, high cycle characteristic, and excellent high rate discharge characteristic by specifying particle size, particle shape, and filling method of a specific positive active material. SOLUTION: The figure shows a longitudinal cross section of a cylindrical nonaqueous electrolyte battery. An electrode plate group 4, a positive plate 5, and a negative plate 6 are spirally wound through a separator 7 plural times, then housed in a battery case 1 made of a stainless steel plate resistant to an organic electrolyte. A positive aluminum lead 5a drawn out from the positive plate 5 is connected to a sealing plate 2, and a negative nickel lead 6a drawn out from the negative plate 6 is connected to the bottom of the battery case 1. The negative plate 6 is formed with paste prepared by mixing heat treated coke with a mixed solution. A positive active material of the positive plate 5 is prepared in such a way that a sodium hydroxide solution is added to nickel sulfate and cobalt sulfate to form a nickel cobalt complex oxide having specified particle size and shape of fine crystal particles, then the composite oxide is mixed with sodium hydroxide, then crushed with a ball mill to primary particles.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a non-aqueous electrolyte secondary battery and a method for producing a positive electrode active material thereof,
In particular, it relates to the improvement of battery characteristics.

[0002]

2. Description of the Related Art In recent years, portable electronic devices have become more portable.
Cordless use is rapidly progressing. At present, nickel-cadmium batteries or sealed small lead-acid batteries play a role as driving power sources for these electronic devices, but as they become more portable and cordless, they become the driving power sources. Higher energy density of secondary battery,
The demand for smaller and lighter is increasing.

Further, in recent years, it has attracted attention as a power source for portable telephones, and along with the rapid expansion of the market, there is a great demand for extending the call duration and improving the cycle life.

Under these circumstances, lithium composite transition metal oxides exhibiting a high charge / discharge voltage such as LiCoO ₂ (for example, JP-A-63-59507) and LiNiO ₂ aiming at higher capacity (for example, US Pat. No. 4,302,251).
At least one Japanese 63-299056 JP, LixMyNzO ₂ (where, M is selected Fe, Co, from among Ni: 8 No.), a composite oxide of a plurality of metal elements lithium (e.g. LiyNixCo1-xO ₂ And N is Ti, V, C
(At least one selected from r and Mn):
No. 3-267053) has been proposed as a positive electrode active material, and a non-aqueous electrolyte secondary battery utilizing insertion and removal of lithium ions has been proposed.

Regarding the physical properties of the positive electrode active material, for example, the average particle size (Japanese Patent Laid-Open No. 1-304664 and Japanese Laid-Open Patent Publication No. 6-264).
No. 243897, Japanese Patent Laid-Open No. 6-290783, Japanese Patent Laid-Open No. 7-114942)
(JP-A-267539, JP-A-7-37576)
An improved method for is proposed.

[0006]

However, in the non-aqueous electrolyte secondary battery using LiNiO ₂ as the positive electrode active material, which has been reported so far, the battery discharge capacity is gradually increased by repeating the charge / discharge cycle. It became clear that the problem of cycle deterioration, which decreased to zero, was found.

As a result of thorough investigations by the present inventors, it has been found that such characteristic deterioration is caused by the following.

Disassemble the cycle-degraded battery,
As a result of the line analysis, it was found that the crystal structure of the positive electrode active material was remarkably changed in the positive electrode plate which was repeatedly charged and discharged.

LiNiO ₂ is used as the battery is charged and discharged,
It has been reported that the lattice constant changes (S.Yama
da, M. Fujiwara and M. Kanda, J. Power Source, 54,
209 (1995)) It is known that expansion and contraction are large on both the a-axis and the c-axis.

By repeating the charge / discharge cycle in this manner, the active material expands and contracts, the crystal structure becomes amorphous, the particles become finer, and the active material falls off from the electrode plate.
It became clear that the cause was a decrease in the amount of active material that could be involved in charging and discharging.

In order to solve such problems, a lithium-containing composite metal oxide in which a part of Ni is replaced with another metal,
The change in crystal structure was relaxed, and good cycle characteristics were exhibited.

[0012] However, the active material obtained by substituting a part of Ni with another metal element as described above has improved cycle characteristics, while the discharge capacity becomes smaller, and the discharge voltage becomes lower, especially when a high current is passed. There was a problem that the discharge capacity was remarkably reduced during the rate discharge.

Further, as a result of studying finer particles of the active material in order to improve the high rate discharge characteristics, there was a problem that the filling property into the battery electrode plate was remarkably reduced and the battery capacity itself was reduced.

An object of the present invention is to solve the above-mentioned problems relating to the conventional positive electrode, to provide a better positive electrode active material, and to determine the particle size, particle shape and filling method of a specific positive electrode active material. Is to provide a non-aqueous electrolyte secondary battery having excellent charge / discharge characteristics.

[0015]

[Means for Solving the Problems] In order to solve such a problem, we have substituted a part of Ni of LiNiO ₂ with another metal element and made the size, shape, and polarity of particles of the positive electrode active material. Further investigation was conducted on the method of filling the active material in the plate configuration. As a result, by controlling these factors, it has been possible to realize a battery having a high capacity and excellent cycle characteristics and high rate discharge characteristics.

Specifically, the present invention relates to LiNi _x M _1-x O
₂ (M is one or more of Co, Mn, Cr, Fe, V, and Al, x: 1> x ≧ 0.5) is used as the positive electrode active material, and the positive electrode active material has a unidirectional diameter in SEM observation ( Feret
Fine crystal particles whose diameter is in the range of 0.1 to 2 μm and a large number of micro crystal particles
A mixture of secondary particles having a diameter of 2 to 20 μm is used as the positive electrode active material.

The secondary particles are preferably spherical or ellipsoidal, and the mixing ratio of the fine crystal particles to be mixed is preferably in the range of 5 to 50% by weight.

Such a spherical active material is S as a raw material.
The constant diameter (Feret diameter) in EM observation is 0.1 to
2 to 20 unidirectional diameter with a large number of 2 μm fine crystal grains
Ni _x M _1-x (OH) _{2 in} the range of μm (M is Co, M
Any one or more of n, Cr, Fe, V, Al, x: 1
> X ≧ 0.5) and a lithium salt (either lithium carbonate or lithium hydroxide) are mixed and the mixture is heat treated.

Further, fine crystal grains to be mixed is synthesized positive electrode active material LiNi _x M _{1 over} x O ₂ (M is Co, Mn, C
Any one or more of r, Fe, V, and Al, x: 1> x ≧ 0.
Raw material Ni _x M obtained by crushing 5) or crushing in advance
_1-x (OH) ₂ (M is Co, Mn, Cr, Fe, V, Al
It is also obtained by mixing at least one of the above, x: 1> x ≧ 0.5) with secondary particles, then mixing with a lithium salt (either lithium carbonate or lithium hydroxide), and subjecting this mixture to heat treatment. be able to.

As a method for measuring the particle diameter, a finite diameter (Ferret diameter) in SEM observation is adopted. This is the average diameter of particles in various directions in a SEM photograph read from a certain direction. It is a thing. (Reference: Basics of Powder Engineering p.285
(Edited by Nikkan Kogyo Shimbun))

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION When the positive electrode active material according to the present invention is used, by using the positive electrode active material in which fine crystal particles having a small unidirectional diameter of 0.1 to 2 μm in SEM observation are primary particles, Increasing the contact area between the positive electrode active material particles and the electrolytic solution to improve the decrease in the interfacial concentration of Li ions, which was the cause of the increase in polarization during high-rate discharge, and to mix the secondary particles and the microcrystalline particles. As a result, the space between the secondary particles is filled with microcrystalline particles, which makes it possible to improve the electrical conductivity between the particles and significantly improve the filling property of the active material in the electrode plate. Is.

FIG. 1 is a conceptual diagram of the positive electrode active material in the present invention.
It was shown to. When the method of the present invention is used to measure the positive electrode active material of the present invention using, for example, a laser particle size distribution meter, it can be seen that the particle size distribution has two peaks.

Needless to say, the particle on the larger particle size side of these two peaks is the particle size of the secondary particle, and the peak on the smaller particle size side is the particle size of the added fine crystalline particles.

Such an effect can be obtained by, for example, Japanese Patent Laid-Open No. 6-26.
It cannot be obtained simply by limiting the shape or particle size of the active material as in JP-A-7539, JP-A-1-304664, JP-A-6-243897 and JP-A-7-37576.

[0025]

Embodiment 1 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 shows a vertical sectional view of the cylindrical battery used in the first embodiment. In FIG. 2, reference numeral 1 is a battery case formed by processing an organic electrolytic solution resistant stainless steel plate, 2 is a sealing plate provided with a safety valve, and 3 is an insulating packing. Reference numeral 4 denotes an electrode plate group, in which the positive electrode plate 5 and the negative electrode plate 6 are spirally wound a plurality of times via the separator 7 and housed in the case. A positive electrode aluminum lead 5a is drawn out from the positive electrode plate 5 and connected to the sealing plate 2, and a negative electrode nickel lead 6a is drawn out from the negative electrode plate 6 and connected to the bottom of the battery case 1. Reference numeral 8 denotes an insulating ring provided on the upper and lower portions of the electrode plate group 4, respectively.

The negative electrode plate 6, the electrolytic solution and the like will be described in detail below. The negative electrode plate 6 was made into a paste by mixing 100 parts by weight of carbon powder obtained by heat-treating coke with a styrene-butadiene rubber-based binder and suspending it in an aqueous carboxymethylcellulose solution. Then paste this paste to a thickness of 0.0
0.2m thickness after coating on the surface of 15mm copper foil and drying
A negative electrode plate having m, a width of 37 mm and a length of 300 mm was prepared.

The method of synthesizing the positive electrode active material will be described in detail below. Using a nickel sulfate, cobalt sulfate, and sodium hydroxide solution, the nickel sulfate solution and the cobalt sulfate solution were introduced into the container at a constant flow rate, and the sodium hydroxide solution was added with sufficient stirring.

By varying the amount of sodium hydroxide added, nickel-cobalt composite hydroxides having various particle sizes were obtained.

The precipitate formed was washed with water and dried to obtain nickel-cobalt composite hydroxides having various particle sizes.

The chemical compositions of the obtained nickel-cobalt composite hydroxides were all Ni _0.85 Co _0.15 (OH) ₂ .

The nickel-cobalt composite hydroxide prepared by the method of this example was measured for its directional diameter from SEM photographs, and as a result, fine crystal particles (primary particles) in the range of 0.1 to 2 μm were obtained. Are spherical secondary particles composed of a large number of particles, and the unidirectional diameters of the secondary particles are 0.5, 2.0,
It was 5.0, 10, 20, 30 μm.

The nickel-cobalt composite hydroxide thus obtained was mixed with lithium hydroxide, and the mixture was heated in an oxidizing atmosphere to 70%.
LiNi _0.85 Co _0.15 O ₂ was synthesized by firing at 0 ° C. for 10 hours.

An SEM photograph of the obtained lithium composite nickel-cobalt oxide is shown in FIG. The synthesized lithium composite nickel-cobalt oxide has a unidirectional diameter of 0.51, 2 ,.
It was obtained as spherical secondary particles of 53, 5.04, 10.1, 20.7, 30.5 μm, and the shape of the nickel-cobalt composite hydroxide as the raw material was almost maintained, and lithium was It was confirmed that the nickel-cobalt composite hydroxide diffused inside without changing the shape and the reaction proceeded.

Each of the lithium composite nickel-cobalt oxides obtained by the above synthesis method was extracted in a weight ratio of 0, 5, 20, 50, 70, and 100%, and pulverized by a ball mill until it became primary particles. Then, it was mixed with the unground material.

A total of 36 kinds of positive electrode active materials were synthesized by the above method. Hereinafter, a method for manufacturing the positive electrode plate will be described.

The positive electrode plate is made of LiNi which is a positive electrode active material.
100 parts by weight of _0.85 Co _0.15 O ₂ powder is mixed with 3 parts by weight of acetylene black and 5 parts by weight of a fluororesin-based binder and suspended in an N-methylpyrrolidone solution to form a paste. This paste is applied to both sides of an aluminum foil having a thickness of 0.020 mm, and after drying, the thickness is 0.130 mm and the width is 35 m.
A positive electrode plate 5 having a length of m and a length of 270 mm was prepared.

Then, the positive electrode plate and the negative electrode plate are spirally wound with a separator interposed therebetween to have a diameter of 13.8 mm and a height of 50 m.
It was stored in the m battery case.

An electrolytic solution prepared by dissolving a mixed solvent of ethylene carbonate and ethyl methyl carbonate in an equal volume at a ratio of 1 mol / l of lithium hexafluorophosphate was injected into the electrode plate group 4, and then the battery was charged. It was sealed and used as a test battery.

In Table 1, the test battery numbers corresponding to the positive electrode active materials produced in Example 1 are shown.

[0041]

[Table 1]

[0042]

Example 2 As a second example, a nickel-manganese composite hydroxide was prepared in the same manner as in Example 1 except that nickel sulfate, manganese sulfate and sodium hydroxide solution were used as an aqueous salt solution for producing the nickel-manganese composite hydroxide. Was generated.

The obtained nickel-manganese composite hydroxide was measured for its unidirectional diameter from an SEM photograph, and as a result,
It is a spherical secondary particle composed of a large number of fine crystal particles in the range of 1 to 2 μm, and the unidirectional diameter of the secondary particle is 5.
It was 0 μm.

The obtained nickel-manganese composite hydroxide was mixed with lithium hydroxide and heated in an oxidizing atmosphere to 70%.
LiNi _0.85 Mn _0.15 O ₂ was synthesized by firing at 0 ° C. for 10 hours.

The synthesized lithium composite nickel-manganese oxide has a unidirectional diameter of 0.1 to 2 in SEM observation.
Spherical secondary particles each having a fixed diameter of 5.2 μm were obtained by aggregating a large number of fine crystal particles in the range of μm.

20% by weight of the lithium composite nickel-manganese oxide obtained by the above synthesis method was extracted, crushed by a ball mill until it became primary particles, and then mixed with an uncrushed material to obtain a positive electrode active material. A battery was prepared in the same manner as in Example 1. The battery in Example 2 was replaced with battery 3.
7 was set.

[0047]

Third Embodiment As a third embodiment, a nickel-chromium composite hydroxide is prepared in the same manner as in the first embodiment by using nickel sulfate, chromium sulfate and sodium hydroxide solution as an aqueous salt solution for producing the nickel-chromium composite hydroxide. Was generated.

The nickel-chromium composite hydroxide thus obtained was measured for its directional diameter from an SEM photograph, and as a result,
It is a spherical secondary particle composed of a large number of fine crystal particles in the range of 1 to 2 μm, and the unidirectional diameter of the secondary particle is 5.
It was 0 μm.

The nickel-chromium composite hydroxide thus obtained was mixed with lithium hydroxide, and the mixture was heated to 700 in an oxidizing atmosphere.
LiNi _0.85 Cr _0.15 O ₂ was synthesized by firing at 10 ° C. for 10 hours.

The synthesized lithium composite nickel-chromium oxide has a unidirectional diameter of 0.1 to 2 μm in SEM observation.
Spherical secondary particles each having a unidirectional diameter of 5.4 μm were obtained, in which a large number of fine crystal particles in the range of m were aggregated.

The lithium composite nickel-chromium oxide obtained by the above synthesis method was extracted in a weight ratio of 20% and pulverized by a ball mill until it became primary particles.
A battery was prepared in the same manner as in Example 1 by mixing with an unpulverized product to obtain a positive electrode active material. The battery in Example 3 was referred to as Battery 38.

[0052]

[Fourth Embodiment] As a fourth embodiment, nickel sulfate and iron sulfate as a salt aqueous solution for producing a nickel-iron composite hydroxide,
A nickel-iron composite hydroxide was produced in the same manner as in Example 1 using a sodium hydroxide solution.

The obtained nickel-iron composite hydroxide is S
As a result of measuring the unidirectional diameter from the EM photograph, 0.1-2
It is a spherical secondary particle composed of a large number of fine crystal particles in the range of μm, and the unidirectional diameter of the secondary particle is 5.0 μm.
Met.

The obtained nickel-iron composite hydroxide was mixed with lithium hydroxide and calcined in an oxidizing atmosphere at 700 ° C. for 10 hours to synthesize LiNi _0.85 Fe _0.15 O ₂ .

The synthesized lithium composite nickel-iron oxide is a sphere having a unidirectional diameter of 4.9 μm, which is a collection of a large number of fine crystal particles having a directional diameter in the range of 0.1 to 2 μm in SEM observation. Secondary particles were obtained.

20% by weight of the lithium composite nickel-iron oxide obtained by the above synthesis method was extracted, crushed by a ball mill until it became primary particles, and then mixed with an uncrushed material to obtain a positive electrode active material. A battery was prepared in the same manner as in Example 1. The battery in Example 4 was used as battery 39.

[0057]

Fifth Embodiment As a fifth embodiment, a nickel-vanadium composite hydroxide is used in the same manner as in the first embodiment by using nickel sulfate, vanadium sulfate and sodium hydroxide solution as an aqueous salt solution for producing a nickel-vanadium composite hydroxide. Was generated.

The nickel-vanadium composite hydroxide thus obtained was measured for its unidirectional diameter from an SEM photograph.
It was a spherical secondary particle composed of a large number of fine crystal particles in the range of 0.1 to 2 μm, and the unidirectional diameter of the secondary particle was 4.8 μm.

The nickel-vanadium composite hydroxide obtained was mixed with lithium hydroxide and the mixture was mixed in an oxidizing atmosphere to give 7
LiNi _0.85 V _0.15 O ₂ was synthesized by firing at 00 ° C. for 10 hours.

The synthesized lithium composite nickel-vanadium oxide has a unidirectional diameter of 0.1 to 0.1 in SEM observation.
Spherical secondary particles each having a unidirectional diameter of 5.5 μm were obtained by aggregating a large number of fine crystal particles in the range of 2 μm.

20% by weight of the lithium composite nickel-vanadium oxide obtained by the above synthesis method was extracted and crushed by a ball mill until it became primary particles, and then mixed with an uncrushed material to obtain a positive electrode active material. A battery was prepared in the same manner as in Example 1. The battery in Example 5 was replaced with battery 4.
It was set to 0.

[0062]

[Sixth Embodiment] As a sixth embodiment, a nickel-aluminum composite hydroxide is prepared in the same manner as in the first embodiment by using nickel sulfate, aluminum sulfate and sodium hydroxide solution as an aqueous salt solution for producing a nickel-aluminum composite hydroxide. Was generated.

The nickel-aluminum composite hydroxide thus obtained was measured for its unidirectional diameter from a SEM photograph.
It was a spherical secondary particle formed by aggregating a large number of fine crystal particles in the range of 0.1 to 2 μm, and the unidirectional diameter of the secondary particle was 4.3 μm.

The obtained nickel-aluminum composite hydroxide was mixed with lithium hydroxide and baked at 700 ° C. for 10 hours in an oxidizing atmosphere to obtain LiNi _0.85 Al _0.15 O ₂
Was synthesized.

The synthesized lithium composite nickel-aluminum oxide has a unidirectional diameter of 0.1 in SEM observation.
As a result, spherical secondary particles each having a unidirectional diameter of 4.4 μm and obtained by accumulating a large number of fine crystal particles in the range of up to 2 μm were obtained.

20% by weight of the lithium composite nickel-aluminum oxide obtained by the above synthesis method
A battery was prepared in the same manner as in Example 1 by extracting only the amount and pulverizing with a ball mill until it became primary particles, and then mixing with an unpulverized material to obtain a positive electrode active material. The battery in Example 6 was used as the battery 41.

[0067]

[Embodiment 7] As a seventh embodiment, nickel-cobalt-
A nickel-cobalt-manganese composite hydroxide was produced in the same manner as in Example 1 using nickel sulfate, cobalt sulfate, manganese sulfate and sodium hydroxide solution as an aqueous salt solution for producing the manganese composite hydroxide.

The nickel-cobalt-manganese composite hydroxide thus obtained was measured for its unidirectional diameter from an SEM photograph, and as a result, it was found to be spherical with a large number of fine crystal particles in the range of 0.1 to 2 μm. The particles were secondary particles, and the unidirectional diameter of the secondary particles was 5.7 μm.

The obtained nickel-cobalt-manganese composite hydroxide was mixed with lithium hydroxide and fired at 700 ° C. for 10 hours in an oxidizing atmosphere to obtain LiNi _0.85 Co.
_0.1 Mn _0.05 O ₂ was synthesized.

The synthesized lithium composite nickel-cobalt-manganese oxide has a directional diameter of 6.3 μm, each of which is a collection of many fine crystal particles having a directional diameter in the range of 0.1 to 2 μm in SEM observation. Spherical secondary particles of were obtained.

Each of the lithium composite nickel-cobalt-manganese oxides obtained by the above synthesis method was extracted in a weight ratio of 0, 5, 20, 50, 70, 100%, and pulverized with a ball mill until each became primary particles. After that, a non-pulverized material was mixed to obtain a positive electrode active material, and a battery was prepared in the same manner as in Example 1. The batteries in Example 7 were 42, 43, 44, 45, 46 and 47, respectively.

[0072]

[Embodiment 8] A nickel-cobalt composite hydroxide having a unidirectional diameter of 5.1 μm in SEM observation was produced in the same manner as in Embodiment 1, and the weight ratio of each nickel-cobalt composite hydroxide was 0, 5, 20, 5 respectively.
Only 0, 70 and 100% were extracted, crushed by a ball mill until each became primary particles, and then mixed with an uncrushed material.

The nickel-cobalt composite hydroxide thus obtained was mixed with lithium hydroxide, and the mixture was heated in an oxidizing atmosphere to 70%.
LiNi _0.85 Co _0.15 O ₂ was synthesized by firing at 0 ° C. for 10 hours.

The synthesized lithium composite nickel-cobalt oxide has a unidirectional diameter of 0.1 to 2 in SEM observation.
0.1-2 μm with spherical secondary particles with a unidirectional diameter of 6.04 μm formed by aggregating many fine crystal particles in the range of μm
Obtained as a mixture with minute crystal particles in the range of
The shape of the nickel-cobalt composite hydroxide, which is the raw material, is almost maintained, and lithium diffuses inside without changing the shape of the nickel-cobalt composite hydroxide during synthesis, and the reaction proceeds. It could be confirmed.

A battery was prepared in the same manner as in Example 1 except that the lithium composite nickel-cobalt oxide thus obtained was used as the positive electrode active material.

Four batteries were used in the above-mentioned Example 8.
8,49,50,51,52,53.

[0077]

Example 9 A nickel-cobalt composite hydroxide having a unidirectional diameter of 5.1 μm in SEM observation was produced in the same manner as in Example 1, mixed with lithium hydroxide, and heated at 700 ° C. in an oxidizing atmosphere at 10 ° C. LiNi _0.85 Co after firing for hours
_0.15 O ₂ was synthesized.

The synthesized lithium composite nickel-cobalt oxide has a unidirectional diameter of 0.1 to 2 in SEM observation.
Spherical secondary particles having a unidirectional diameter of 6.04 μm were obtained, in which a large number of fine crystal particles in the range of μm were aggregated.

The lithium composite nickel-cobalt oxide thus obtained was used as a positive electrode active material in the same manner as in Example 1 with 100 parts by weight of LiNi _0.85 Co _0.15 O ₂ powder.
3 parts by weight of acetylene black and 5 parts by weight of a fluorine resin binder are mixed and suspended in an N-methylpyrrolidone solution to form a paste. This paste has a thickness of 0.020 mm
The aluminum foil was coated on both sides so that the thickness after drying was 0.4 mm, and after drying, the thickness was reduced to 0.
Rolling was repeated until it became 130 mm.

It was confirmed that about 10% of the secondary particles of the obtained positive electrode active material of the electrode plate were crushed into primary particles by a roller press and filled in the voids between the secondary particles.

A battery was prepared in the same manner as in Example 1 except that the obtained positive electrode plate was used. The battery in Example 9 was used as the battery 54.

[0082]

[Comparative Example 1] As Comparative Example 1, a unidirectional diameter (Feret diamete
In the same manner as in Example 1, a lithium composite nickel-cobalt oxide was synthesized using as a raw material a nickel-cobalt composite hydroxide having a unidirectional diameter of 15 μm of secondary particles formed by aggregating a large number of fine crystal particles having r) of 5 μm. did. The chemical composition of the obtained compound was LiNi _0.85 Co _0.15 O ₂ .

The synthesized lithium composite nickel-cobalt oxide had a unidirectional diameter of 5.2 μm in SEM observation.
Was obtained as spherical secondary particles each having a unidirectional diameter of 17 μm and formed by aggregating a large number of fine crystal particles.

Each of the lithium composite nickel-cobalt oxides obtained by the above-mentioned synthesis method was mixed in a weight ratio of 2
Only 0% was extracted, crushed by a ball mill until each became primary particles, and then mixed with an uncrushed material.

A battery was prepared in the same manner as in Example 1 except that the active material obtained by the above method was used. The battery in Comparative Example 1 was designated as Battery 55.

[0086]

[Comparative Example 2] As Comparative Example 2, a lithium composite nickel-cobalt oxide was synthesized in the same manner as in Example 1 using a nickel-cobalt composite hydroxide having a lumpy particle shape as a raw material. Chemical composition of the obtained nickel-cobalt composite hydroxide was LiNi _0.85 Co _{0. 15} O _2.

The synthesized lithium composite nickel-cobalt oxide was obtained as agglomerated particles having a unidirectional diameter of 16 μm in SEM observation.

20% by weight was extracted, and each was crushed by a ball mill and then mixed with an uncrushed material.

A battery was prepared in the same manner as in Example 1 except that the lithium composite nickel-cobalt oxide obtained by the above-mentioned synthesis method obtained by the above method was used as the positive electrode active material.

The battery of Comparative Example 2 was used as battery 56.

[0091]

[Comparative Example 3] As Comparative Example 3, a unidirectional diameter (Feret diamete
A lithium composite nickel oxide was synthesized in the same manner as in Example 1 using spherical nickel hydroxide having a regular diameter of 15 μm of secondary particles formed by aggregating a large number of fine crystal particles having r) of 1 μm as the raw material. The chemical composition of the obtained lithium composite nickel oxide was LiNiO ₂ .

The synthesized lithium composite nickel oxide has a unidirectional diameter of 16 μm, which is a collection of a large number of fine crystal particles having a unidirectional diameter of 1.2 μm in SEM observation.
Obtained as spherical secondary particles of m.

20% by weight of each of the lithium composite nickel oxides obtained by the above synthesis method was extracted, pulverized with a ball mill to form primary particles, and then mixed with an unpulverized product.

A battery was prepared in the same manner as in Example 1 except that the active material obtained by the above method was used. The battery in Comparative Example 1 was designated as Battery 57.

Two batteries 1 to 57 thus prepared are used.
0 ℃, charge end voltage 4.2V, discharge end voltage 2.5V,
The charging / discharging was repeated at 500 mA to perform a cycle charging / discharging test.

Tables 2 to 6 show the cycle test results of the batteries of Examples and Comparative Examples of the present invention. In addition, 30 batteries each were assembled and tested, and the average values are shown in (Table 2) to (Table 6).

[0097]

[Table 2]

[0098]

[Table 3]

[0099]

[Table 4]

[0100]

[Table 5]

[0101]

[Table 6]

From the test results of Example 1 (Table 2), the case where the active material having the secondary particle diameter smaller than 2 μm was used (Battery 1
6), although the discharge capacity is slightly improved by adding the fine crystal particles obtained by pulverization, the discharge capacity is not more than 500 mAh or less, which is not preferable.

This is because the particle size of the secondary particles was as small as 2 μm or less and there was no difference from the added fine crystal particles, so that the effect of filling voids between particles was hardly obtained.

On the other hand, in the batteries 7 to 30 having the secondary particle diameter of 2 μm or more, by adding the fine crystalline particles obtained by pulverization, the voids between the secondary particles are filled with the active material, and the electron conduction is further increased. Since the route is secured, 500mA
A high discharge capacity of 550 mAh or more was obtained even in the high rate discharge of.

Further, since there are few voids between the particles, the conduction path is maintained to some extent even if the active material is miniaturized with the charge / discharge cycle, so that good cycle characteristics are obtained.

However, when the secondary particle size is as large as 30 μm (Batteries 31 to 36), a large discharge capacity is secured in the initial stage, but the secondary particles are destroyed with charge / discharge cycles, and the active material is removed from the electrode. It dropped out, and the discharge capacity was significantly reduced.

As described above, the particle diameter of the secondary particles is preferably 20 μm or less in the unidirectional diameter in SEM observation.

The same effect as shown in Example 1 is obtained by replacing a part of Ni with Mn, Cr, Fe, V and Al.
In the case of No. 6 (Batteries 37 to 41), it was obtained, and a high capacity and good cycle characteristics were obtained.

Even if a part of Ni is replaced with one or more kinds of metals (for example, Co and Mn in Example 7), the batteries 43, 44 and 45 within the scope of the present invention have high capacity and good cycle characteristics. realizable.

In this embodiment, only the combination of Co and Mn is shown, but Co, Mn, Cr, Fe, V, A
It was confirmed that the same characteristics could be obtained in any combination as long as the combination was 1. Further, the same effect was obtained by combining three or more kinds of metals.

Further, as shown in the batteries 49, 50 and 51 of Example 8, the effect of the present invention is to crush a part of the nickel hydroxide which is the raw material in advance and then mix it with the uncrushed material, The same effect can be obtained when a lithium composite oxide is synthesized by mixing with a lithium salt.

In the present invention, the ball mill is used as the method for pulverizing the secondary particles. However, the same effect can be obtained by using a generally applied pulverizer (for example, a pebble mill, a vibration mill, a jet mill, etc.). Needless to say.

Also, as shown in Example 9, even after the active material was formed on the current collector in advance and the secondary particles were crushed by rolling with a roller press, the same result as shown in the battery 54 was obtained. The effect was obtained.

On the other hand, in the case of the battery 55 shown in Comparative Example 1 having a large primary particle diameter of 5 μm, the effect of filling voids is hardly obtained even when mixed with the secondary particles, and thus the initial value is small. The discharge capacity is significantly reduced.

Therefore, the primary particle size is preferably 2 μm or less. Further, when the agglomerated particles were used, the filling property was low as they were, and when the agglomerated particles were further pulverized, the discharge capacity was extremely lowered like the battery 56 of Comparative Example 2. It was considered that this is because the crystal structure of the grain interface destroyed by pulverization was destroyed and the movement of lithium ions was hindered.

As described above, the positive electrode active material has a finite diameter (Feret diameter) of 2 to 2 formed by a large number of fine crystal particles.
The secondary particles are in the range of 0 μm, and are preferably spherical or ellipsoidal.

Further, in the case of LiNiO ₂ single phase not using a substitution metal, although the initial capacity was large like the battery 57 of Comparative Example 3, extreme cycle deterioration was observed.

It is considered that this is because the reversibility was lost because the crystal structure changed with charge and discharge.

Thus, as shown in the present invention, LiNi
_x M _1-x O ₂ (M is one or more of Co, Mn, Cr, Fe, V, and Al, x: 1> x ≧ 0.5) is used as a positive electrode active material, and the positive electrode active material is obtained by SEM observation. Direction diameter (Feret
Fine crystal particles whose diameter is in the range of 0.1 to 2 μm and a large number of micro crystal particles
A battery having such a high capacity and good cycle characteristics can be realized only when it is a mixture of secondary particles having a diameter of 2 to 20 μm.

In the present invention, the sulfate is used as the salt for adding the substituted metal, but the same effect can be obtained by using nitrate, chloride, acetate or the like.

Although sodium hydroxide was used as the alkali source for precipitating hydroxide, similar effects can be obtained by using lithium hydroxide or potassium hydroxide.

In the above examples, the evaluation was performed using a cylindrical battery, but the same effect can be obtained even if the battery shape is different, such as a prismatic battery.

Further, although a carbonaceous material was used for the negative electrode in the above examples, since the effect of the present invention works on the positive electrode plate, lithium metal, lithium alloy, Fe ₂
Similar effects can be obtained by using other negative electrode materials such as oxides of O ₃ , WO ₂ , WO _{3 and the} like.

Further, although lithium hexafluorophosphate was used as the electrolyte in the above examples, other lithium-containing salts such as lithium perchlorate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, and hexafluoride were used. Similar effects were obtained with lithium arsenate and the like.

Further, although a mixed solvent of ethylene carbonate and ethyl methyl carbonate was used in the above-mentioned examples, other non-aqueous solvents such as cyclic ester such as propylene carbonate, cyclic ether such as tetrahydrofuran, chain ether such as dimethoxyethane, etc. Similar effects were also obtained by using a non-aqueous solvent such as a chain ester such as methyl propionate or a mixed solvent of these multi-components.

[0126]

As is apparent from the above description, in the present invention, LiNi _x M _{1 -x} O ₂ (M is Co, Mn, Cr, F
One or more selected from e, V, and Al, x:
1> x ≧ 0.5) as the positive electrode active material, specify the particle size and particle shape of the fine crystal particles of this active material and the secondary particles in which a large number of them are aggregated, and use a positive electrode plate in which these are mixed As a result, it is possible to provide a non-aqueous electrolyte secondary battery having a high capacity and excellent cycle characteristics.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of the present invention.

FIG. 2 is a vertical sectional view of a cylindrical battery.

[Explanation of symbols]

 1 Battery Case 2 Sealing Plate 3 Insulating Packing 4 Electrode Plate Group 5 Positive Electrode Plate 5a Positive Electrode Lead 6 Negative Electrode Plate 6a Negative Lead 7 Separator 8 Insulating Ring

Claims (8)

[Claims] 1. A negative electrode plate and LiNi _x M _{1 -x} O ₂ (M is C
o, Mn, Cr, Fe, V, Al, one or more kinds, x: 1> x ≧ 0.5) as a positive electrode active material, and a separator between the negative electrode plate and the positive electrode plate. In the nonaqueous electrolyte battery, A non-aqueous electrolyte battery comprising a mixture with secondary particles having a (Feret diameter) in the range of 2 to 20 μm. 2. The non-aqueous electrolyte battery according to claim 1, wherein the secondary particles have a spherical shape or an elliptic spherical shape. 3. The non-aqueous electrolyte battery according to claim 1, wherein the mixing ratio of the fine crystal particles to the secondary particles is in the range of 5 to 50% by weight. 4. The non-aqueous electrolyte battery according to claim 1, wherein the fine crystal particles are pulverized secondary particles. 5. The positive electrode active material LiNi _x M _{1 -x} O ₂ (M is C
1 selected from o, Mn, Cr, Fe, V and Al
More than one kind, x: 1> x ≧ 0.5), and S
The constant diameter (Feret diameter) in EM observation is 0.1 to
It is a secondary particle made up of a large number of 2 μm microcrystalline particles,
N in which the unidirectional diameter of the secondary particles is in the range of 2 to 20 μm
i _x M _1-x (OH) ₂ (M is Co, Mn, Cr, Fe,
At least one selected from V and Al, x: 1
> X ≧ 0.5) is mixed with lithium carbonate or lithium hydroxide, and the mixture is heat-treated to obtain a positive electrode active material, which is a method for producing a positive electrode active material for a non-aqueous electrolyte battery. 6. The method for producing a positive electrode active material for a non-aqueous electrolyte battery according to claim 5, wherein the secondary particles have a spherical shape or an elliptic spherical shape. 7. The positive electrode active material LiNi _x M _{1 -x} O ₂ (M is C
1 selected from o, Mn, Cr, Fe, V and Al
It is more than one kind, and x: 1> x ≧ 0.5), and N
i _x M _1-x (OH) ₂ (M is Co, Mn, Cr, Fe,
At least one selected from V and Al, x: 1> x
≧ 0.5), and the unidirectional diameter (Feret
a part of the secondary particles having a diameter of 0.1 to 2 μm and having a unidirectional diameter in the range of 2 to 20 μm. A method for producing a positive electrode active material for a non-aqueous electrolyte battery, which comprises mixing the secondary particles, then mixing with lithium carbonate or lithium hydroxide, and heat-treating the mixture to obtain a positive electrode active material. 8. The positive electrode active material for a non-aqueous electrolyte battery according to claim 7, wherein the mixing ratio of the pulverized secondary particles to the unpulverized secondary particles is in the range of 5 to 50% by weight. Manufacturing method.