JP2003068299A - Positive electrode active material for use in lithium secondary battery and lithium secondary battery using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive electrode active material for use in a lithium secondary battery that can produce the lithium secondary battery having high discharge capacity and superior cycle performance, and to provide the lithium secondary battery having high discharge capacity and superior cycle performance. SOLUTION: This positive electrode active material for use in the lithium secondary battery contains a Li-Mn-Ni composite oxide characterized in that a mean diameter of primary particles of the Li-Mn-Ni composite oxide is 2.0 μm or less and N2 -BET specific surface area is 0.4 m<2> /g or more. Then, the positive electrode active material for use in the lithium secondary battery contains a Li-Mn-Ni-Co composite oxide characterized in that a mean diameter of primary particles of the Li-Mn-Ni-Co composite oxide is 3.0 μm or less and N2 -BET specific surface area is 0.2 m<2> /g or more.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a positive electrode active material for a lithium secondary battery, which has a high discharge capacity and is capable of producing a lithium secondary battery having excellent cycle performance, and a high discharge capacity. The present invention relates to a lithium secondary battery having excellent performance.

[0002]

2. Description of the Related Art Non-aqueous electrolyte secondary batteries such as lithium secondary batteries exhibit high energy density and high voltage, and are widely used as power sources for small portable terminals, mobile communication devices and the like. The positive electrode active material for lithium secondary batteries includes
It is required that the crystal structure is stable and the electrochemical working capacity is large even by repeated insertion and desorption of lithium.

At present, as an operating voltage near 4 V, lithium cobalt oxide (LiCo) having a layered structure is used.
O ₂ ), lithium nickel oxide (LiNiO ₂ ), or lithium manganese oxide having a spinel structure (LiMn
A composite oxide of lithium and a transition metal, which has a basic structure of O ₂ , LiMn ₂ O _4, etc., is known. Among these positive electrode active materials having an α-NaFeO ₂ structure that can be expected to have a high energy density, lithium cobalt composite oxides represented by LiCoO _{2 and the} like are widely used in consumer lithium ion batteries and the like. Is a rare metal,
There was a problem that the price was high. In addition, LiNiO ₂
The lithium nickel composite oxide represented by
Since it has a higher energy density than O ₂ or LiMn ₂ O ₄ , many studies have been made for its practical use. However, LiNiO ₂ has a problem in that the charge / discharge performance is poor because the crystal structure changes with charge / discharge.

The cause of this is Kanno, R .; Kubo, H .; Kawamot
o, Y.; Kamiyama, T .; Izumi, F .; Takeda, Y .; Takano, M.
Phase Relationship and Lithium Deintercalation in
Lithium Nickel Oxides. J. Solid Sate Chem. 110 (2),
According to 1994, 216-225., In the process of oxidizing Ni (II) salt used as a raw material into Ni (III) in an oxygen atmosphere at 600 ° C. or higher, Li is desorbed in the form of Li ₂ O or the like. It is said that. That is, Ni is added to such a defective site.
Alternatively, it is believed that Li diffuses irregularly, which impedes Li migration and causes a capacity decrease.

As a means for solving this, LiNiO ₂
A technique for substituting the Ni site of Ni with a different element has been widely disclosed. For example, U.S. Pat. No. 5,626,635 (1997) discloses a technique relating to a Li-Mn-Ni-O element system. U.S. Pat. No. 604009
No. 0 (2000) and Japanese Patent Application Laid-Open No. 8-213015 disclose techniques relating to the Li-Mn-Ni-Co-O element system. All of these active materials show high initial discharge performance, but their capacity is greatly reduced by repeated charging / discharging, and they have not been put into practical use.

Further, in Japanese Patent Application Laid-Open No. 8-171910, in order to surely replace a part of Ni with Mn, 800 ° C.
It has been pointed out that when synthesized at the above high temperature, Ni and Mn enter into the site where Li should enter in the crystal, and the crystal structure is disturbed, and the cycle reversibility and the discharge capacity are reduced. Therefore, in this publication, LiNi _1- αMnα
The value of α represented by O ₂ is set to 0.05 to 0.30, and 60
The problem is solved by firing at 0 ° C to 800 ° C. However, even with this method, LiNiO ₂
However, there is still a problem that the discharge capacity is deteriorated due to the repeated charging and discharging due to the above characteristics.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to provide a lithium secondary battery having a high discharge capacity and excellent cycle performance. A positive electrode active material for a secondary battery, and a lithium secondary battery having a high discharge capacity and excellent cycle performance.

[0008]

Means for Solving the Problems As a result of intensive studies, the present inventors have made a lithium secondary containing a complex oxide in which the average diameter of primary particles and the N ₂ -BET specific surface area are within a specific range. It has been found that a lithium secondary battery having a high discharge capacity and excellent cycle performance can be obtained by using a positive electrode active material for a battery, and the present invention has been completed. That is, the technical configuration and operational effects of the present invention are as follows.
However, the action mechanism includes estimation, and the correctness of the action mechanism does not limit the present invention.

The positive electrode active material for a lithium secondary battery according to claim 1 is at least lithium (Li) and manganese (M
Li-Mn having n) and nickel (Ni) as constituent elements
A positive electrode active material for a lithium secondary battery, which contains a —Ni composite oxide, wherein the average diameter of primary particles of the Li—Mn—Ni composite oxide is 2.0 μm or less, and N ₂ —
The BET specific surface area is 0.4 m ² / g or more. With such a configuration, a positive electrode active material for a lithium secondary battery, which has a high discharge capacity and is capable of producing a lithium secondary battery having excellent cycle performance, can be obtained.

The positive electrode active material for a lithium secondary battery according to claim 2 is at least lithium (Li) and manganese (M
n), nickel (Ni), and cobalt (Co) as constituent elements, which is a positive electrode active material for a lithium secondary battery containing a Li-Mn-Ni-Co composite oxide, said Li-M
The average diameter of the primary particles of the n-Ni-Co composite oxide is 3.
Is 0 μm or less, and the N ₂ -BET specific surface area is 0.
It is characterized by being 2 m ² / g or more. With such a configuration, a positive electrode active material for a lithium secondary battery, which has a high discharge capacity and is capable of producing a lithium secondary battery having excellent cycle performance, can be obtained.

The positive electrode active material for a lithium secondary battery according to claim 3 is the Li-Mn-Ni composite oxide or the L-Mn-Ni composite oxide.
The i-Mn-Ni-Co composite oxide is α-NaFeO _2.
Which has a crystal structure, a composition formula Li _x Mn _a Ni _b C
o _c O ₂ (However, a, b, and c are in the ternary phase diagram
(A, b, c) is point A (0.5, 0.5, 0) and point B
(0.45, 0.55, 0) and point C (0.25, 0.3
5, 0.4) and a point D (0.3, 0.3, 0.4) are vertices within a quadrangle ABCD, 0.95 ≦ x / (a + b + c). ) ≦ 1.30)). In particular, it can be used as a positive electrode active material for a lithium secondary battery, which has a high discharge capacity and is capable of producing a lithium secondary battery having excellent cycle performance.

A lithium secondary battery according to a fourth aspect is a positive electrode containing the positive electrode active material for a lithium secondary battery according to the present invention, a negative electrode containing a negative electrode material capable of inserting and extracting lithium ions, and a non-aqueous electrolyte. Since it has, it is possible to obtain a lithium secondary battery having a high discharge capacity and excellent cycle performance.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be illustrated below, but the present invention is not limited to the following embodiments. A lithium secondary battery (hereinafter, also simply referred to as “battery”) according to the present invention includes a positive electrode containing a positive electrode active material for a lithium secondary battery (hereinafter also simply referred to as “positive electrode active material”) and a lithium ion storage material. It has a negative electrode containing a releasable negative electrode material and a non-aqueous electrolyte containing an electrolyte salt in a non-aqueous solvent. Generally, a separator is provided between the positive electrode and the negative electrode.

First, in the present invention, the first positive electrode active material constituting the positive electrode is L containing at least lithium (Li), manganese (Mn) and nickel (Ni) as constituent elements.
A positive electrode active material for a lithium secondary battery containing an i-Mn-Ni composite oxide, wherein the average diameter of primary particles of the Li-Mn-Ni composite oxide is 2.0 μm or less, and N _{It is} required that the _2- BET specific surface area (hereinafter, also simply referred to as specific surface area) is 0.4 m ² / g or more. When the average diameter of the primary particles of the Li-Mn-Ni-Co composite oxide exceeds 2.0 μm, the discharge characteristics (discharge capacity)
And battery characteristics such as cycle characteristics deteriorate. When the average diameter is 2.0 μm or less, the electrolyte can be widely contacted with the electrolyte, and as a result, high battery characteristics can be achieved. It is considered that the electrolytic solution hardly penetrates into the gap, and the diffusion or electron conduction of Li is rate-controlled inside the solid particles.

Preferably, the average diameter is 2.0 μm or less, more preferably 1.5 μm or less, most preferably 1.0 μm or less, and 0.2 μm or more, the thermal stability of the active material during charging. Is preferable, and the density can be increased, which is preferable. Moreover, the specific surface area is 0.4 m ^2.
If it is less than / g, it becomes difficult for the powder of the positive electrode active material to come into contact with the electrolytic solution, and the battery performance such as cycle performance is deteriorated. Preferably, the specific surface area is 0.4 m ² / g or more, more preferably 0.6 m ² / g or more and 4.0
It is preferably m ² / g or less from the viewpoint of high thermal stability of the active material during charging and high density.

In the present invention, the second positive electrode active material constituting the positive electrode is Li-Mn containing at least lithium (Li), manganese (Mn), nickel (Ni) and cobalt (Co) as constituent elements. A positive electrode active material for a lithium secondary battery containing a —Ni—Co composite oxide, wherein the average diameter of primary particles of the Li—Mn—Ni—Co composite oxide is 3.0 μm or less, and The requirement is that the N ₂ -BET specific surface area is 0.2 m ² / g or more.
When the average diameter of the primary particles of the Li-Mn-Ni-Co composite oxide exceeds 3.0 μm, the battery characteristics such as discharge characteristics (discharge capacity) and cycle characteristics deteriorate. When the average diameter is 3.0 μm or less, the electrolyte can be widely contacted with the electrolyte, and as a result, high battery characteristics can be achieved. It is considered that the electrolytic solution hardly penetrates into the gap, and the diffusion or electron conduction of Li is rate-controlled inside the solid particles.

Preferably, the average diameter is 3.0 μm or less, more preferably 1.5 μm or less, most preferably 1.0 μm or less, and 0.5 μm or more, the thermal stability of the active material during charging. Is preferable, and the density can be increased, which is preferable. Moreover, the specific surface area is 0.2 m ^2.
If it is less than / g, the density of the particles becomes high, and it becomes difficult for the powder of the positive electrode active material to come into contact with the electrolytic solution, and the battery performance such as cycle performance deteriorates. Preferably,
The specific surface area is 0.2 m ² / g or more, more preferably 0.
It is preferably 5 m ² / g or more and 1.5 m ² / g or less from the viewpoint that the thermal stability of the active material during charging is high and the density can be increased.

The composite oxides constituting the first and second positive electrode active materials of the present invention may have any size of the primary particles within the range described above. Since the size and shape of the aggregated secondary particles often affect the battery characteristics, the diameter of the secondary particles is 5 μm to 30 μm.
m is preferable, and more preferably 8 μm to 12 μm.
m. Further, the particle size distribution of these secondary particles can be appropriately designed, but it is possible to provide higher battery performance, for example, by changing the particle ratio of the primary particles and the secondary particles. Become.

Constituting the first and second positive electrode active materials of the present invention
The complex oxide is α-NaFeO. ₂Have a crystal structure
Together with the composition formula Li_xMn_aNi_bCo_cO₂(However,
a, b, c are (a, b, c) on the ternary phase diagram
Point A (0.5, 0.5, 0) and point B (0.45, 0.
55,0) and the point C (0.25,0.35,0.4) and the point
Square A with D (0.3, 0.3, 0.4) as vertices
It is a value within the range that exists inside the BCD, and is 0.9.
5 ≦ x / (a + b + c) ≦ 1.30)
It is preferably a complex oxide, which makes it
Lithium secondary with high discharge capacity and excellent cycle performance
Batteries can be made. In the above composition formula, a, b and
And the values of c are the transitions of each contained in the mixture before heat treatment.
It can be set arbitrarily by setting the mixing ratio of the metal transfer compound.
Can be set.

In the above composition formula, when a is out of the above range, that is, when the amount of Mn is out of the range, there is a tendency that the problem that the discharge capacity is lowered occurs. In the above composition formula, when b is out of the above range, that is, N
If the amount of i deviates, there is a tendency that the thermal stability of the active material during charging is poor, or the cycle performance is also poor. Further, in the above composition formula, when c is out of the above range, that is, when the amount of Co is out, there is a tendency that the thermal stability of the active material during charging is deteriorated. Further, in the above composition formula, “x / (a + b) which defines the amount of Li with respect to transition metals other than Li
+ C) ”deviates from the above range, there is a tendency that a problem occurs that discharge capacity and cycle performance are adversely affected.

The method for producing the positive electrode active material of the present invention is not particularly limited as long as the composite oxide constituting the positive electrode active material has the above-mentioned particle size and specific surface area, but is not particularly limited. A preferable manufacturing method will be described in detail below.

The first and second positive electrode active materials according to the present invention are described as "at least Li component, Mn component and Ni component, respectively.
Li-Mn-Ni composite oxide precursor containing components ",
It is preferable to obtain the "Li-Mn-Ni-Co composite oxide precursor containing at least a Li component, a Mn component, a Ni component and a Co component" by firing at 900 ° C or higher. The firing temperature is particularly preferably 900 ° C to 1100 ° C,
0 ° C to 1050 ° C is particularly preferable.

If the firing temperature is lower than 900 ° C., the cycle performance tends to be deteriorated. On the other hand, when the firing temperature is higher than 1100 ° C., there are problems in production such as difficulty in obtaining a complex oxide having a target composition due to volatilization of Li, and a problem that battery performance is deteriorated due to high density of particles. Cheap. This is above 1100 ° C,
This is due to the fact that the primary particle growth rate increases and the crystal particles of the complex oxide become too large.
It is considered that the cause may be that the amount of Li deficiency locally increases and the structure becomes unstable. When the firing temperature is 950 ° C. or higher, a lithium secondary battery having particularly high discharge capacity and excellent cycle performance can be manufactured.

The firing of the Li-Mn-Ni-Co composite oxide precursor causes a chemical change to the α-NaFeO ₂ crystal structure, and this phase transition is completed at 700 ° C., but still higher. By performing the heat treatment at a high temperature of ℃ or more, the battery performance can be significantly improved.

The firing time is preferably 3 hours to 50 hours. When the firing time exceeds 50 hours, there is no problem in battery performance, but the battery performance tends to be substantially inferior due to volatilization of Li. If the firing time is less than 3 hours, the crystal development will be poor and the battery characteristics will tend to be poor.

The preferable ranges of the firing temperature and the firing time have been described above, but the average diameter and N ₂ -BET specific surface area of the primary particles of the obtained composite oxide should be within the ranges specified in the present invention. It is selected appropriately.

As the Li-Mn-Ni composite oxide precursor, "Li compound, Mn compound and Ni compound are pulverized.
A mixture obtained by mixing (physically mixing) "or" Mn
A mixture obtained by mixing an Mn—Ni coprecipitate obtained by coprecipitating (chemically mixing) a compound and an Ni compound with a Li compound ”and the like. Also, L
Examples of the i-Mn-Ni-Co composite oxide precursor include "L
a mixture obtained by pulverizing and mixing (physically mixing) an i compound, a Mn compound, a Ni compound and a Co compound ",
"Mn-Ni-Co coprecipitate obtained by coprecipitating (chemically mixing) Mn compound, Ni compound and Co compound,
A mixture obtained by mixing with a Li compound "and the like can be mentioned.

Li compounds include lithium hydroxide and lithium carbonate, and Mn compounds include manganese oxide and
Manganese carbonate, manganese sulfate, manganese nitrate, etc.
Examples of the compound include nickel hydroxide, nickel carbonate, nickel sulfate and nickel nitrate, and examples of the Co compound include cobalt hydroxide, cobalt carbonate, cobalt oxide, cobalt sulfate and cobalt nitrate.

The Mn-Ni coprecipitate is preferably prepared by uniformly mixing Mn and Ni.
The —Ni—Co coprecipitate is preferably prepared by uniformly mixing Mn, Ni, and Co. Mn-N
As an example of the preparation of the i coprecipitate, the acidic aqueous solution of Ni and Mn can be preferably prepared by precipitating with sodium hydroxide. The Mn-Ni-Co coprecipitate can be preferably prepared by precipitating an acidic aqueous solution of Ni, Mn, and Co with sodium hydroxide. On this occasion,
By making an excess amount of ammonium ions coexist with respect to the metal in the reaction system, it becomes possible to produce precursor particles having a spherical morphology. In this case, if the valence of the element varies, an oxidizing agent or a reducing agent may be appropriately present. When the coprecipitate is precipitated in the presence of a hydroxide, its form is mainly hydroxide, but Mn and the like may be in the form of oxide.

The method for producing a positive electrode active material according to the present invention uses, for example, the above-mentioned production method so that the composite oxide constituting the positive electrode active material has the particle size and the specific surface area described above. Although not limited thereto, for example, Mn-Ni coprecipitate or Mn-Ni-C can be obtained by passing Mn, Ni, and Co through hydroxide.
o Prepare a coprecipitate, and use Mn-Ni coprecipitate or Mn-N
A preferred method is a method of mixing and heat treating an i-Co coprecipitate and a Li compound. The Mn-Ni coprecipitate and the Mn-Ni-Co coprecipitate may be produced by a batch method or a continuous precipitation method.

In the case of this method, according to the particle size distribution of the Mn-Ni coprecipitate and the Mn-Ni-Co coprecipitate,
Although the optimum primary particle diameter for battery characteristics is different, the effect of the present invention can be obtained as long as it is within the range of the primary particles specified in the present invention. That is, when a coprecipitate is produced in a state where the crystal nucleation rate exceeds the growth rate, for example, as in the batch coprecipitation method, the average distribution diameter of the powder after heat treatment increases. There is a tendency. In that case, the powder has a high primary particle ratio. In that case, even if the primary particle diameter is close to the upper limit defined by the present invention, the isolated primary particles come into wide contact with the electrolytic solution, and as a result, high charge / discharge characteristics are exhibited. On the other hand, as in the case of a continuous precipitation method in which a raw material liquid (for example, an aqueous solution of a Mn compound, a Ni compound, and a Co compound) is continuously added and a coprecipitate is collected, the nucleus growth rate of crystals is increased. When the coprecipitate produced under the condition of exceeding the speed is heat-treated, the powder tends to form uniform spherical secondary particles in which a large number of primary particles are aggregated. In such a case, it is particularly preferable that the primary particle size is much smaller than the upper limit value specified in the present invention.

The non-aqueous electrolyte that constitutes the lithium secondary battery of the present invention is usually one in which an electrolyte salt is contained in a non-aqueous solvent, and those generally proposed for use in lithium batteries can be used. Is. Examples of the non-aqueous solvent include cyclic ester carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, chloroethylene carbonate and vinylene carbonate; cyclic esters such as γ-butyrolactone and γ-valerolactone; dimethyl carbonate, diethyl carbonate and ethyl. Chain carbonates such as methyl carbonate; methyl formate,
Chain esters such as methyl acetate and methyl butyrate; tetrahydrofuran or its derivatives; 1,3-dioxane, 1,
4-dioxane, 1,2-dimethoxyethane, 1,4-
Ethers such as dibutoxyethane and methyl diglyme;
Examples thereof include, but are not limited to, nitriles such as acetonitrile and benzonitrile; dioxolane or a derivative thereof; ethylene sulfide, sulfolane, sultone or a derivative thereof alone or a mixture of two or more thereof.

As the electrolyte salt, for example, LiCl
O_Four, LiBF_Four, LiAsF₆, LiPF₆, LiSC
N, LiBr, LiI, Li₂SO_Four, Li₂B_TenC
l_Ten, NaClO_Four, NaI, NaSCN, NaBr,
KClO_Four, KSCN, Lithium (Li), Natriu
Inorganic ion containing one of sodium (Na) or potassium (K)
Salt, LiCF₃SO₃, LiN (CF₃SO₂)₂, LiN
(C₂F_FiveSO₂)₂, LiN (CF₃SO₂) (C_FourF₉SO
₂), LiC (CF₃SO₂)₃, LiC (C₂F_FiveS
O₂)₃, (CH₃)_FourNBF_Four, (CH₃)_FourNBr, (C₂
H_Five)_FourNClO_Four, (C₂H_Five)_FourNI, (C₃H₇)_FourNB
r, (n-C_FourH₉)_FourNClO_Four, (N-C_FourH₉)_FourN
I, (C ₂H_Five)_FourN-maleate, (C₂H_Five)_FourN-
benzoate, (C₂H_Five)_FourN-phtalat
e, lithium stearyl sulfonate, octyl sulfone
Lithium acid, lithium dodecylbenzene sulfonate, etc.
Organic ionic salts, etc. are listed, and these ionic compounds are
Can be used alone or in combination of two or more
is there.

Furthermore, LiBF ₄ and LiN (C ₂ F ₅ S
By mixing with a lithium salt having a perfluoroalkyl group such as O ₂ ) ₂ and using it, the viscosity of the electrolyte can be further lowered, so that the low temperature characteristics can be further enhanced, which is more desirable.

The concentration of the electrolyte salt in the non-aqueous electrolyte is preferably 0.1 mol / l to 5 mol / l in order to surely obtain a non-aqueous electrolyte battery having high battery characteristics.
More preferably, 0.5 mol / l to 2.5 mol /
It is l.

The positive electrode of the lithium secondary battery of the present invention comprises an electrode containing the above-mentioned specific complex oxide, and the negative electrode comprises a carbonaceous material, particularly graphite having a high degree of graphitization with good initial charging efficiency. The electrodes used are preferably used.

As the positive electrode active material which is the main constituent of the positive electrode, in addition to the above-described composite oxide of the present invention, other lithium-containing transition metal oxides, lithium-containing phosphates, lithium-containing sulfates, etc. are mixed. It is preferable to use it because high energy density and high safety can be obtained. Examples of the other lithium-containing transition metal oxides include the general formulas Li _x MX ₂ and Li _x MN _y X ₂ (M and N are metals from Group I to VIII, and X is a chalcogen compound such as oxygen or sulfur.). And, for example, Li _y Co _1-x M _x O ₂ , Li
_y Mn _2-X M _X O ₄ (M is a group I to VIII metal (for example,
Li, Ca, Cr, Ni, Fe, one or more elements of Co) and the like. Regarding the x value showing the substitution amount of the different element of the lithium-containing transition metal oxide, it is effective up to the maximum substitution amount, but preferably 0 ≦ x from the viewpoint of discharge capacity.
≦ 1. As for the y value indicating the amount of lithium, the maximum amount that can reversibly use lithium is effective, and preferably 0 ≦ y ≦ 2 in terms of discharge capacity. ), But is not limited thereto.

Further, the positive electrode active material composed of the composite oxide according to the present invention may be further mixed with other positive electrode active material, and the other positive electrode active materials include CuO, Cu ₂ O, Ag ₂
Group I metal compounds such as O, CuS, CuSO ₄ , TiS ₂ , S
Group IV metal compounds such as iO ₂ and SnO, V ₂ O ₅ , V ₆ O ₁₂ ,
Group V metal compounds such as VO _x , Nb ₂ O ₅ , Bi ₂ O ₃ , and Sb ₂ O ₃ , CrO ₃ , Cr ₂ O ₃ , MoO ₃ , MoS ₂ , WO ₃ ,
VI group metal compounds such as SeO ₂ and VI such as MnO ₂ and Mn ₂ O ₃
Group I metal compounds, Fe ₂ O ₃ , FeO, Fe ₃ O ₄ , Ni ₂ O
Metal compounds represented by Group VIII metal compounds such as ₃ , NiO, CoO ₃ , and CoO, such as lithium-cobalt complex oxides and lithium-manganese complex oxides, and further disulfides, polypyrroles, polyanilines, poly Examples include conductive polymer compounds such as paraphenylene, polyacetylene, and polyacene-based materials, and carbonaceous materials having a pseudo-graphite structure, but are not limited thereto.

When other oxides are used in combination with the specific composite oxide according to the present invention as the positive electrode active material, the use ratio of the other oxides is limited as long as the effect of the present invention is not impaired. Although not required, the other components are preferably 1% by weight to 50% by weight, and more preferably 5% by weight to 30% by weight in the whole positive electrode active material.

In the positive electrode, the composite oxide is kneaded with a conductive agent and a binder, and further, if necessary, a filler to form a positive electrode mixture, and then the positive electrode mixture is used as a collector such as a foil or a lath plate. 2. Apply or press-bond to the surface at a temperature of 50 to 250 ° C for 2
It is produced by heat treatment for about an hour.

As the negative electrode material, any material having a form capable of depositing or occluding lithium ions may be selected. For example, lithium metal, lithium alloys (lithium-aluminum, lithium-lead, lithium-tin, lithium-aluminum-tin, lithium-gallium, and lithium metal-containing alloys such as wood alloys),
In addition to lithium composite oxide (lithium-titanium) and silicon oxide, carbon materials (for example, graphite, hard carbon,
Low temperature calcined carbon, amorphous carbon, etc.) and the like. Among these, graphite has an operating potential extremely close to that of metallic lithium and can realize charge / discharge at a high operating voltage. In addition, when a lithium salt is used as the electrolyte salt, self-discharge can be reduced and irreversible capacity during charge / discharge can be reduced, which is preferable as a negative electrode material. For example, artificial graphite and natural graphite are preferable. In particular, graphite whose negative electrode material particle surface is modified with amorphous carbon etc.
It is desirable because it generates less gas during charging.

The analysis results of X-ray diffraction of graphite which can be preferably used are shown below: Lattice plane spacing (d ₀₀₂ ) 0.333 to 0.350 nm Crystallite size La in the a-axis direction La 20 nm or more c Axial crystallite size Lc 20 nm or more True density 2.00 to 2.25 g / cm ^{3 In} addition to graphite, metal oxides such as tin oxide and silicon oxide, phosphorus, boron, and amorphous carbon are added. It is also possible to carry out reforming. In particular, by modifying the surface of graphite by the above method, it is possible to suppress decomposition of the electrolyte and enhance the battery characteristics, which is desirable. In addition, graphite may be used in combination with lithium metal, lithium-aluminum, lithium-lead, lithium-tin, lithium-aluminum-tin, lithium-gallium, and lithium metal-containing alloys such as wood alloys, and may be used in advance for electrical Graphite in which lithium is inserted by being chemically reduced can also be used as the negative electrode material.

The average particle size of the composite oxide constituting the positive electrode active material is as described above, but the powder of the negative electrode material preferably has an average particle size of 100 μm or less. A crusher or a classifier is used to obtain the powder in a predetermined shape. For example, a mortar, a ball mill, a sand mill, a vibrating ball mill, a planetary ball mill, a jet mill, a counter jet mill, a swirling airflow type jet mill, a sieve and the like are used. Wet grinding in which water or an organic solvent such as hexane coexists may be used during grinding. The classification method is not particularly limited, and a sieve or a wind classifier,
Both dry type and wet type are used as necessary.

The positive electrode active material and the negative electrode material, which are the main constituents of the positive electrode and the negative electrode, have been described above in detail. The positive electrode and the negative electrode, in addition to the main constituents, have a conductive agent, a binder and a thickening agent. Agents, fillers and the like may be contained as other constituent components.

The conductive agent is not limited as long as it is an electron conductive material that does not adversely affect the battery performance, but usually,
Natural graphite (scaly graphite, flake graphite, earth graphite, etc.), artificial graphite, carbon black, acetylene black, Ketjen black, carbon whiskers, carbon fiber, metal (copper, nickel, aluminum, silver, gold, etc.) powder, A conductive material such as a metal fiber or a conductive ceramic material may be contained as one kind or a mixture thereof.

Of these, acetylene black is preferable as the conductive agent from the viewpoint of electron conductivity and coatability. The amount of the conductive agent added is preferably 0.1% by weight to 50% by weight, more preferably 0.5% by weight to 30% by weight, based on the total weight of the positive electrode or the negative electrode. In particular, it is desirable to grind acetylene black into ultrafine particles of 0.1 to 0.5 μm and use it because the required carbon amount can be reduced. These mixing methods are physical mixing, and ideally, they are homogeneous mixing. Therefore, a powder mixer such as a V-type mixer, an S-type mixer, a grinder, a ball mill, and a planetary ball mill can be mixed in a dry or wet manner.

The binder is usually thermoplastic resin such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM. , A polymer having rubber elasticity such as styrene-butadiene rubber (SBR) and fluororubber can be used as one kind or as a mixture of two or more kinds. The amount of the binder added is preferably 1 to 50% by weight, and particularly preferably 2 to 30% by weight, based on the total weight of the positive electrode or the negative electrode.

As the thickener, polysaccharides such as carboxymethyl cellulose, methyl cellulose and the like can be usually used as one kind or as a mixture of two or more kinds. In addition, it is desirable that the thickening agent having a functional group that reacts with lithium such as a polysaccharide is deactivated by, for example, methylating. The addition amount of the thickener is preferably 0.5 to 10% by weight based on the total weight of the positive electrode or the negative electrode,
In particular, 1 to 2% by weight is preferable.

As the filler, any material may be used as long as it does not adversely affect the battery performance. Usually, olefin polymers such as polypropylene and polyethylene, amorphous silica, alumina, zeolite, glass, carbon and the like are used. The amount of the filler added is preferably 30% by weight or less based on the total weight of the positive electrode or the negative electrode.

For the positive electrode and the negative electrode, the active material, the conductive agent, and the binder are mixed with an organic solvent such as N-methylpyrrolidone and toluene, and the resulting mixed liquid is used as a current collector described in detail below. It is suitably prepared by applying it on the surface and drying it. Regarding the coating method, for example, roller coating such as an applicator roll, screen coating, doctor blade method, spin coating, it is desirable to apply to any shape using a means such as bar coater, but is not limited to these It is not something that will be done.

Any current collector may be used as long as it is an electron conductor that does not adversely affect the constructed battery. For example, as the positive electrode current collector, in addition to aluminum, titanium, stainless steel, nickel, baked carbon, conductive polymer, conductive glass, etc., aluminum may be used for the purpose of improving adhesiveness, conductivity and oxidation resistance. It is possible to use a material such as copper or copper whose surface is treated with carbon, nickel, titanium, silver or the like. As the current collector for the negative electrode, copper, nickel,
Iron, stainless steel, titanium, aluminum, calcined carbon,
In addition to conductive polymers, conductive glass, Al-Cd alloys, etc., those whose surface is treated with carbon, nickel, titanium, silver, etc. for the purpose of adhesion, conductivity, and reduction resistance are used. be able to. It is also possible to oxidize the surface of these materials.

With respect to the shape of the current collector, in addition to a foil shape, a film shape, a sheet shape, a net shape, a punched or expanded material, a lath body, a porous body, a foam body, a fiber group forming body, or the like is used. To be There is no particular limitation on the thickness, but 1
Those having a thickness of up to 500 μm are used. Among these current collectors, the positive electrode is an aluminum foil having excellent oxidation resistance, and the negative electrode is a reduction resistance, and also has excellent electrical conductivity, and an inexpensive copper foil, nickel foil, iron foil, and It is preferable to use alloy foils containing some of them. Further, it is preferable that the foil has a rough surface with a surface roughness of 0.2 μmRa or more, and thereby the adhesion between the positive electrode active material or the negative electrode material and the current collector becomes excellent. Therefore, it is preferable to use the electrolytic foil because it has such a rough surface. In particular, an electrolytic foil that has been treated with a hook is most preferable. Further, when the foil is coated on both sides, it is desirable that the surface roughness of the foil is the same or almost the same.

As the separator, it is preferable to use a porous film or a non-woven fabric having excellent rate characteristics, either alone or in combination. Examples of the material forming the separator for the non-aqueous electrolyte battery include polyolefin resins represented by polyethylene, polypropylene, etc., polyester resins represented by polyethylene terephthalate, polybutylene terephthalate, etc., polyvinylidene fluoride, and vinylidene fluoride-hexa. Fluoropropylene copolymer, vinylidene fluoride-perfluorovinyl ether copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-fluoroethylene copolymer, fluorine Vinylidene fluoride-hexafluoroacetone copolymer, vinylidene fluoride-ethylene copolymer, vinylidene fluoride-propylene copolymer, vinylidene fluoride-trifluoropropylene copolymer, vinylidene fluoride - tetrafluoroethylene - hexafluoropropylene copolymer, vinylidene fluoride - ethylene - can be mentioned tetrafluoroethylene copolymer.

The porosity of the separator is 98 from the viewpoint of strength.
Volume% or less is preferable. From the viewpoint of charge / discharge characteristics, the porosity is preferably 20% by volume or more.

As the separator, for example, a polymer gel composed of a polymer such as acrylonitrile, ethylene oxide, propylene oxide, methyl methacrylate, vinyl acetate, vinylpyrrolidone, polyvinylidene fluoride and an electrolyte may be used.

It is preferable to use the non-aqueous electrolyte of the present invention in a gel state as described above in terms of the effect of preventing liquid leakage.

Further, it is desirable that the separator is used in combination with the above-mentioned porous membrane, non-woven fabric or the like and the polymer gel because the liquid retaining property of the electrolyte is improved. That is, by forming a film in which the surface of the polyethylene microporous membrane and the wall surface of the micropores are coated with a hydrophilic solvent polymer having a thickness of several μm or less, and holding an electrolyte in the micropores of the film, the hydrophilic solvent polymer is formed. Gels.

Examples of the solvent-philic polymer include polyvinylidene fluoride, a polymer obtained by crosslinking an acrylate monomer having an ethylene oxide group or an ester group, an epoxy monomer, a monomer having an isocyanate group, and the like. The monomer is used in combination with a radical initiator for heating, ultraviolet rays (UV), electron beam (EB), etc.
It is possible to carry out the cross-linking reaction using actinic rays or the like.

For the purpose of controlling strength and physical properties, the above-mentioned solvent-philic polymer may be blended with a physical property adjusting agent within a range not interfering with the formation of a crosslinked product. Examples of the physical property modifier include inorganic fillers {metal oxides such as silicon oxide, titanium oxide, aluminum oxide, magnesium oxide, zirconium oxide, zinc oxide and iron oxide, metal carbonates such as calcium carbonate and magnesium carbonate}. , Polymers {polyvinylidene fluoride, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc.} and the like. The addition amount of the physical property adjusting agent is usually 50% by weight or less, preferably 20% by weight or less with respect to the crosslinkable monomer.

Illustrative examples of the acrylate monomer include bifunctional or higher functional unsaturated monomers.
More specific examples include bifunctional (meth) acrylates {ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, adipic acid / dineopentyl glycol ester di (meth) acrylate, polyethylene glycol having a degree of polymerization of 2 or more. Di (meth) acrylate, polypropylene glycol di (meth) acrylate having a degree of polymerization of 2 or more, polyoxyethylene / polyoxypropylene copolymer di (meth) acrylate, butanediol di (meth) acrylate, hexamethylene glycol di (meth) ) Acrylate etc.} trifunctional (meth)
Acrylate {Trimethylolpropane tri (meth) acrylate, glycerin tri (meth) acrylate, tri (meth) acrylate of ethylene oxide adduct of glycerin, tri (meth) acrylate of propylene oxide adduct of glycerin, ethylene oxide of glycerin, propylene oxide addition Object tri (meth) acrylate, etc.}, tetrafunctional or higher polyfunctional (meth) acrylate {pentaerythritol tetra (meth) acrylate,
And diglycerin hexa (meth) acrylate}. These monomers can be used alone or in combination.

A monofunctional monomer may be added to the acrylate monomer for the purpose of adjusting physical properties and the like. Examples of the monofunctional monomers include unsaturated carboxylic acids {acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, vinylbenzoic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, methylenemalonic acid, Aconitic acid, etc., unsaturated sulfonic acid {styrene sulfonic acid, acrylamido-2-methylpropane sulfonic acid, etc.} or salts thereof (Li salt, Na salt, K salt, ammonium salt,
Tetraalkylammonium salt, etc.), or these unsaturated carboxylic acids are partially esterified with a C1-C18 aliphatic or alicyclic alcohol, alkylene (C2-C4) glycol, polyalkylene (C2-C4) glycol, etc. (Methyl maleate, monohydroxyethyl maleate, etc.) and those partially amidated with ammonia, primary or secondary amine (maleic acid monoamide,
(N-methylmaleic acid monoamide, N, N-diethylmaleic acid monoamide, etc.), (meth) acrylic acid ester [C1-C18 aliphatic (methyl, ethyl, propyl, butyl, 2-ethylhexyl, stearyl, etc.) alcohol and ( Ester with (meth) acrylic acid, or alkylene (C2-C4) glycol (ethylene glycol,
Ester of (meth) acrylic acid with propylene glycol, 1,4-butanediol) and polyalkylene (C2-C4) glycol (polyethylene glycol, polypropylene glycol)]; (meth) acrylamide or N-substituted (meth) acrylamide [(Meth) acrylamide, N-methyl (meth) acrylamide, N-
Methylol (meth) acrylamide etc.]; vinyl ester or allyl ester [vinyl acetate, allyl acetate etc.];
Vinyl ether or allyl ether [butyl vinyl ether, dodecyl allyl ether, etc.]; unsaturated nitrile compound [(meth) acrylonitrile, crotonnitrile, etc.]; unsaturated alcohol [(meth) allyl alcohol, etc.]; unsaturated amine [(meth) allylamine, Dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, etc .; Heterocycle-containing monomers [N-vinylpyrrolidone, vinylpyridine, etc.]; Olefinic aliphatic hydrocarbons [ethylene, propylene, butylene, isobutylene, pentene, (C6-C50) α-olefin and the like]; olefin-based alicyclic hydrocarbon [cyclopentene, cyclohexene, cycloheptene, norbornene and the like]; olefin-based aromatic hydrocarbon [styrene, α-
Methylstyrene, stilbene, etc.]; unsaturated imides [maleimide, etc.]; halogen-containing monomers [vinyl chloride, vinylidene chloride, vinylidene fluoride, hexafluoropropylene, etc.] and the like.

Examples of the epoxy monomer include glycidyl ethers {bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, brominated bisphenol A diglycidyl ether, phenol novolac glycidyl ether, cresol novolac glycidyl ether, etc.}, glycidyl esters { Hexahydrophthalic acid glycidyl ester, dimer acid glycidyl ester, etc.}, glycidyl amines {triglycidyl isocyanurate, tetraglycidyl diaminophenylmethane, etc.}, linear aliphatic epoxides {epoxidized polybutadiene, epoxidized soybean oil, etc.},
Alicyclic epoxides {3,4 epoxy-6 methylcyclohexyl methyl carboxylate, 3,4 epoxy cyclohexyl methyl carboxylate, etc.} and the like can be mentioned. These epoxy resins can be used alone or after curing by adding a curing agent.

Examples of the curing agent include aliphatic polyamines {diethylenetriamine, triethylenetetramine, 3,9- (3-aminopropyl) -2,4,8,1.
0-tetrooxaspiro [5,5] undecane etc.}, aromatic polyamines {metaxylenediamine, diaminophenylmethane etc.}, polyamides {dimer acid polyamide etc.}, acid anhydrides {phthalic anhydride, tetrahydromethyl anhydride Phthalic acid, hexahydrophthalic anhydride, trimellitic anhydride, methylnadic acid anhydride}, phenols {phenol novolac, etc.}, polymercaptans {polysulfide, etc.}, tertiary amines {tris (dimethylaminomethyl) phenol, 2-ethyl -4-methylimidazole, etc., Lewis acid complex {boron trifluoride / ethylamine complex, etc.} and the like.

Examples of the above-mentioned monomer having an isocyanate group include toluene diisocyanate, diphenylmethane diisocyanate, 1,6-hexamethylene diisocyanate, and 2,2,4 (2,2,4) -trimethyl-hexahexane. Methylene diisocyanate, p-phenylene diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, 3,3′-dimethyldiphenyl 4,4′-diisocyanate, dianisidine diisocyanate, m-xylene diisocyanate Nato, trimethyl xylene diisocyanate, isophorone diisocyanate, 1,5-naphthalene diisocyanate, trans
Examples include -1,4-cyclohexyl diisocyanate and lysine diisocyanate.

In crosslinking the monomer having an isocyanate group, polyols and polyamines [bifunctional compounds {water, ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, etc.] trifunctional compounds {glycerin, trimethylolpropane , 1,2,6-hexanetriol, triethanolamine and the like}, tetrafunctional compounds {pentaerythritol, ethylenediamine, tolylenediamine, diphenylmethanediamine, tetramethylolcyclohexane,
Methyl glucoside etc.}, 5-functional compound {2,2,6,6
-Tetrakis (hydroxymethyl) cyclohexanol, diethylenetriamine, etc., 6-functional compounds {sorbitol, mannitol, dulcitol, etc.}, 8-functional compounds {sucrose, etc.}, and polyether polyols {propylene oxide and / or the polyol or polyamine. Ethylene oxide adduct}, polyester polyol [polyol and polybasic acid {adipic acid, o, m, p-phthalic acid, succinic acid, azelaic acid,
A compound having active hydrogen such as a condensate with sebacic acid or ricinoleic acid, a polycaprolactone polyol {poly ε-caprolactone etc.}, a polycondensate of hydroxycarboxylic acid etc.] can be used in combination.

A catalyst may be used in combination in the crosslinking reaction. Examples of the catalyst include organotin compounds, trialkylphosphines, amines [monoamines {N, N-dimethylcyclohexylamine, triethylamine, etc.], cyclic monoamines {pyridine, N
-Methylmorpholine, etc.}, diamines {N, N, N ',
N'-tetramethylethylenediamine, N, N, N ',
N'-tetramethyl 1,3-butanediamine etc., triamines {N, N, N ', N'-pentamethyldiethylenetriamine etc.}, hexamines {N, N, N'N'-
Tetra (3-dimethylaminopropyl) -methanediamine etc., cyclic polyamines {diazabicyclooctane (DABCO), N, N'-dimethylpiperazine, 1,
2-dimethylimidazole, 1,8-diazabicyclo (5,4,0) undecene-7 (DBU), etc., and salts thereof.

In the lithium secondary battery according to the present invention, the electrolyte is injected before or after the lithium secondary battery separator, the positive electrode and the negative electrode are laminated, and finally,
It is preferably manufactured by sealing with an exterior material. Further, in a lithium secondary battery in which a positive electrode and a negative electrode are wound around a power generation element laminated via a lithium secondary battery separator, an electrolyte is injected into the power generation element before and after the winding. Is preferred. As the injection method, it is possible to inject at normal pressure, but a vacuum impregnation method or a pressure impregnation method can also be used.

Examples of the material for the outer casing of the lithium secondary battery include nickel-plated iron, stainless steel, aluminum, and a metal resin composite film. For example, a metal-resin composite film having a structure in which a metal foil is sandwiched between resin films is preferable. Specific examples of the metal foil are not limited as long as they are pinhole-free foils such as aluminum, iron, nickel, copper, stainless steel, titanium, gold, and silver, but are preferably lightweight and inexpensive aluminum foil. As the resin film on the outside of the battery, a resin film having excellent puncture strength such as polyethylene terephthalate film or nylon film,
As the resin film on the inner side of the battery, a film that can be heat-sealed and has solvent resistance, such as a polyethylene film or a nylon film, is preferable.

The structure of the lithium secondary battery is not particularly limited, and a coin battery or button battery having a positive electrode, a negative electrode and a single-layer or multi-layer separator, and
Examples thereof include a cylindrical battery having a positive electrode, a negative electrode, and a roll-shaped separator, a prismatic battery, a flat battery, and the like.

[0070]

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited thereto.

(Example 1) Li _1.0 Mn _0.33 Ni _0.33
Preparation of Co _0.33 O ₂ The reaction tank used in this example is a cylindrical one equipped with an overflow pipe for discharging the reaction crystallization product slurry to the outside of the system at a constant constant flow rate, and has a volume of 15 L. is there.
13 L of water was put into this reaction tank, and a 32% sodium hydroxide aqueous solution was further added so that pH = 11.6. 7
The mixture was stirred at 1350 rpm using a stirrer equipped with a 0 mmφ paddle type stirring blade, and the temperature of the solution in the reaction tank was kept at 50 ° C. by a heater. A 1.7 mol / L nickel sulfate aqueous solution, a 1.1 mol / L manganese sulfate aqueous solution, and a 4 wt% hydrazine aqueous solution were used in a volume ratio of 11: 1.
The mixture was mixed at a ratio of 7: 0.36 (L), and 4.92 kg of crystals of cobalt sulfate hexahydrate were dissolved in this mixed solution to obtain Ni / Mn /
The raw material solution was Co = 3/3/3 (molar ratio). 13 mL / min of this raw material solution and 6 mol / L ammonium sulfate aqueous solution were continuously added dropwise to the reaction tank at a flow rate of 0.9 mL / min. In addition, the pH of the solution in the reaction tank is 11.3
A 32% aqueous sodium hydroxide solution was intermittently added so that the above was constant. Further, the temperature of the solution in the reaction tank was intermittently controlled by a heater so as to be constant at 50 ° C. 120 hours after starting the feeding of the raw material solution, N which is a reaction crystallization product (coprecipitate) was continuously fed through the overflow pipe for 24 hours.
A slurry of i-Mn-Co composite oxide was collected. The collected slurry was washed with water and filtered. 20 at 100 ℃
After drying for an hour, a dry powder of Ni-Mn-Co composite oxide was obtained.

The obtained Ni-Mn-Co composite oxide powder and lithium hydroxide monohydrate powder were mixed with Li / (Ni + Mn + C).
o) = 1.02, weighed and mixed well.
Fill this into an alumina mortar and use an electric furnace to
Under oxygen gas flow, the temperature was raised to 1000 ° C. at 100 ° C./hour, held at 1000 ° C. for 15 hours, cooled to 600 ° C. at 100 ° C./hour, and then allowed to cool. As a result of X-ray diffraction analysis, the Li-Ni-Mn-Co composite oxide was α-
It was found to be a single phase having a NaFeO ₂ structure. The ICP emission analysis, the composition of the Li-Ni-Mn-Co composite _{oxide, Li 1.0 Mn 0.33 Ni 0.33 Co} 0.33
It was asked for O ₂ . The morphology was observed with a scanning electron microscope (SEM). A photograph at a magnification of 5,000 is shown in FIG. 1, and secondary particles formed by aggregating rectangular uniform primary particles are recognized. When an average of primary particle diameters was calculated by approximating spherical particles of arbitrary 100 particles to 1.1 μm.
Was asked. As a result of BET specific surface area measurement by N ₂ adsorption, it was determined to be 0.6 m ² / g.

(Example 2) Mn-Ni as in Example 1
-Co composite oxide powder and the LiOH · H ₂ O Li: M
n: Ni: Co = 3.06: 1: 1: was mixed to be a first element ratio, distribution of oxygen gas, except that the heat treatment at 950 ° C. 15 hours, likewise Li _1. Example 1 ₀ Mn _0.33 N
A positive electrode active material having a composition represented by i _0.33 Co _0.33 O ₂ was produced. The average diameter of the primary particles calculated by SEM analysis was determined to be 0.92 μm. As a result of BET specific surface area measurement by N ₂ adsorption, it was determined to be 0.65 m ² / g.

(Example 3) As in Example 1, Mn-Ni was used.
-Co composite oxide powder and LiOH / H₂O and Li: M
The element ratio is n: Ni: Co = 3.06: 1: 1: 1.
And mix under oxygen gas flow at 1050 ° C for 15 hours
Li as in Example 1 except that heat treatment was performed. _1.0Mn_0.33
Ni_0.33Co_0.33O₂Create a positive electrode active material with the composition shown in
Made Average diameter of primary particles calculated by SEM analysis
Was determined to be 1.38 μm. N₂BET ratio due to adsorption
Surface area measurement result is 1.1m²Was determined to be / g.

(Example 4) Mn-Ni was prepared in the same manner as in Example 1.
-Co composite oxide powder and the LiOH · H ₂ O Li: M
n: Ni: Co = 3.06: 1: 1: was mixed to be a first element ratio, distribution of oxygen gas, except that the heat treatment at 900 ° C. 15 hours, likewise Li _1. Example 1 ₀ Mn _0.33 N
A positive electrode active material having a composition represented by i _0.33 Co _0.33 O ₂ was produced. The average diameter of the primary particles calculated by SEM analysis was determined to be 0.76 μm. BET by N ₂ adsorption
As a result of measuring the specific surface area, it was determined to be 0.7 m ² / g.

(Example 5) Mn-Ni was prepared in the same manner as in Example 1.
-Co composite oxide powder and the LiOH · H ₂ O Li: M
n: Ni: Co = 3.06: 1: 1: was mixed to be a first element ratio, distribution of oxygen gas, except that the heat treatment at 850 ° C. 15 hours, likewise Li _1. Example 1 ₀ Mn _0.33 N
A positive electrode active material having a composition represented by i _0.33 Co _0.33 O ₂ was produced. As shown in the SEM photograph at 5,000 magnification (FIG. 2), the particle development was somewhat incomplete compared to FIG.
As a result of extracting 100 points of arbitrary primary particles and calculating the average particle diameter of the primary particles, it was determined to be 0.64 μm. As a result of BET specific surface area measurement by N ₂ adsorption, 0.75 m ² / g was obtained.

(Comparative Example 1) Mn-Ni as in Example 1
-Co precursor and LiOH / H₂O and Li: Mn: N
i: Co = 3.30: 1: 1: 1 mixed to have an element ratio
Heat treatment at 1100 ° C for 15 hours under flowing oxygen gas
Li as in Example 1 except that_1.0Mn_0.33Ni
_0.33Co_0.33O₂A positive electrode active material having the composition shown in
It was The average diameter of the primary particles calculated by SEM analysis is
It was determined to be 3.2 μm. N ₂BET specific surface by adsorption
Product measurement result, 0.1m²Was determined to be / g.

(Comparative Example 2) As in Example 1, Mn-Ni was used.
-Co precursor and LiOH · H ₂ O and Li: Mn: N
Li _1.0 Mn _0.33 Ni as in Example 1 except that the elements were mixed at an element ratio of i: Co = 3.15: 1: 1: 1 and heat-treated at 1050 ° C. for 45 hours under the flow of oxygen gas.
A positive electrode active material having a composition represented by _0.33 Co _0.33 O ₂ was produced. As shown in the SEM photograph at 5,000 magnification (FIG. 3), angular irregular-shaped primary particles were observed. Any 1
As a result of extracting 100 points of the secondary particles and calculating the average particle diameter of the primary particles, it was found to be 2.6 μm. BE by N ₂ adsorption
As a result of T specific surface area measurement, it was determined to be 0.1 m ² / g.

(Regarding the ternary phase diagram of LiNi _0.33 Mn _0.33 Co _0.33 O ₂ ) LiN used as the positive electrode active material
i _0.33 Mn _0.33 Co _0.33 O ₂ has a composition formula of Li _x Mn _a Ni _b.
In Co _c O ₂ , (a, b, c) = (0.33, 0.
33, 0.33), so that (a, b, c) is point A (0.5, 0.5, 0), as shown in the ternary state diagram of FIG.
And point B (0.45, 0.55, 0) and point C (0.25,
0.35,0.4) and point D (0.3,0.3,0.4)
It can be seen that they exist inside the quadrangle ABCD with and as vertices.

(Preparation of Lithium Secondary Battery) Li _1.0 Mn _0.33 Ni synthesized as described above, which is a positive electrode active material.
_0.33 Co _{0.3 3} and O _2, acetylene black and the binder as a conductive agent poly (vinylidene fluoride) (PVdF)
Were mixed at a weight ratio of 85: 10: 5, N-methyl-2-pyrrolidone (NMP) was added and sufficiently kneaded to obtain a positive electrode paste. The positive electrode paste is applied to one surface of an aluminum foil current collector having a thickness of 20 μm, naturally dried at room temperature of about 25 ° C., then applied to the other surface in the same manner, and dried at 130 ° C. for 12 hours under reduced pressure. After that, press working, 1 cm ²
It was cut into a disk shape and used as a positive electrode.

Artificial graphite as the negative electrode material (average particle size 6 μm
m, plane spacing (d ₀₀₂ ) 0.33 by X-ray diffraction method
7 nm, crystallite size in the c-axis direction (Lc) 55 nm)
And polyvinylidene fluoride (PVdF) in a weight ratio of 95:
Mix in a ratio of 5 and mix with N-methyl-2-pyrrolidone (NM
P) was added and sufficiently kneaded to obtain a negative electrode paste. next,
The thickness of the negative electrode paste is 1 μm on a copper foil current collector having a thickness of 15 μm.
It is applied on one surface of a 2 μm electrolytic copper foil, naturally dried at room temperature of about 25 ° C., and then applied on the other surface in the same manner, and the pressure is reduced.
After drying at 0 ° C. for 12 hours, it was pressed and cut into a 1 cm ² disk shape to obtain a negative electrode. LiPF ₆ which is a fluorine-containing electrolyte salt is added to a mixed solvent in which ethylene carbonate and diethyl carbonate are mixed at a volume ratio of 1: 1.
It was dissolved at a concentration of mol / l to prepare a non-aqueous electrolyte.
The water content in the electrolyte was less than 20 ppm.

Using the above-mentioned members, the coin type lithium secondary batteries of Examples 1 to 5 and Comparative Examples 1 and 2 had a dew point of -5.
It was produced in a dry atmosphere at 0 ° C. or lower. The positive electrode was used by pressure bonding to a positive electrode can with a positive electrode collector. The negative electrode was used by pressure bonding to a negative electrode can with a negative electrode current collector. More specifically, as shown in the cross-sectional view of FIG. 4, the coin-type lithium secondary battery is a coin-type lithium secondary battery after the positive electrode 1 and the negative electrode 2 are housed in the coin battery case 4 via the separator 3. It is configured to be covered by a lid 5, and a resin packing 8 is inserted between the coin battery battery case 4 and the coin battery lid 5. Here, the positive electrode 1 is housed so as to be pressure-bonded to the positive electrode current collector 6 provided inside the coin battery battery case 4. Further, the negative electrode 2 is housed so as to be pressure bonded to the negative electrode current collector 7 provided inside the coin battery lid 5. As the separator 3, a polypropylene microporous film was used. Using the positive electrode 1, the negative electrode 2, the separator 3 and the non-aqueous electrolyte,
A coin-type lithium battery having a diameter of 20 mm and a thickness of 1.6 mm was produced.

(Battery Characteristic Test) Examples 1 to 5 and Comparative Example 1
6 coin-type lithium secondary batteries of Nos. 2 to 6 were prepared, and initial charge and discharge were performed for 10 cycles. The charging condition at this time was a current of 0.1 ItA (10 hour rate), a constant current of 4.2 V and a constant voltage, and the discharging condition was a current of 0.1 ItA (1
(0 hour rate), and the final voltage was constant current discharge of 3.0V.
The average value of the discharge capacities at the 10th cycle was defined as the discharge capacity.
Then, a cycle test was performed. The charging conditions of the cycle test were 1.0 ItA (1 hour rate) and 4.2 V constant current constant voltage charging, and the discharging conditions were current 1.0 ItA (1 hour rate) and final voltage of 3.0 V constant. A current discharge was used. The cycle performance was evaluated by the average value of the discharge capacities of 6 batteries after 30 cycles. Table 1 shows the results of the battery characteristic test.

[0084]

[Table 1]

As shown in Table 1, the batteries using the positive electrode active materials of Examples 1 to 3 in which the average diameter and the specific surface area of the primary particles of the composite oxide were within the ranges specified in the present invention, were extremely It showed good battery performance. That is, the discharge capacity is 160
It was extremely high at mAh / g or more, and, surprisingly, it was confirmed that even after 30 cycles of repeated charging and discharging, the discharge capacity did not decrease at all, which was an incredible good cycle performance.

In the batteries using the positive electrode active materials of Examples 4 and 5, although the average diameter and the specific surface area of the primary particles were within the ranges specified in the present invention, the heat treatment temperature at the time of manufacturing the positive electrode active material was high. Was less than 950 ° C., the battery performance was superior to that of the comparative battery, but it was found that the cycle performance was particularly inferior to that of Examples 1 to 3. It is highly possible that there was some defect in the crystal structure, the crystal structure changed due to repeated charging and discharging, and the movement of Li was hindered. From the results of the above examples, the average diameter of the primary particles was 3.0 when the composite oxide as the positive electrode active material was prepared.
It has been found that in the present invention, a powder having a BET specific surface area of 0.2 m ² / g or more and a powder property of not more than μm is particularly preferable in the present invention.

The batteries of Comparative Examples 1 and 2 in which the average diameter and the specific surface area of the primary particles of the composite oxide were out of the ranges specified in the present invention, both the discharge capacity and the cycle performance were significantly reduced. As a result of crushing these particles and decreasing the average particle size by increasing the amount of primary particles,
Although the cell performance was slightly improved, it still showed a low value. From this result, the primary particle size grows and the voids in the secondary particles decrease, and the electrolytic solution cannot contact with the primary particles. In addition, the primary particles grow so as to exceed the effective diffusion distance of Li. It is presumed that the decrease in conductivity resulted from this.

In the present embodiment, a method for producing a precipitate by a continuous method was used for producing a Ni--Mn--Co coprecipitate. However, as described in the above effect, nucleation is performed in a batch format, for example. It has been confirmed that the same effect can be expected even in the case of being produced under the condition that exceeds the nucleus growth. Further, in this embodiment, Mn: Ni: Co = 1: 1: 1.
Although only the Li _1.0 Mn _0.33 Ni _0.33 Co _0.33 O ₂ composition of the above is exemplified, it has been confirmed that the similar effect is exhibited in other compositions. Moreover, although the laminated button type battery is exemplified, the effect of the present invention is not limited to the battery shape, and for example, when the wound electrode is used as the power generating element or when the battery shape is made cylindrical. But you get exactly the same results.

[0089]

According to the positive electrode active material for a lithium secondary battery of the first aspect, Li containing at least lithium (Li), manganese (Mn), and nickel (Ni) as constituent elements.
A lithium secondary battery positive electrode active material containing a —Mn—Ni composite oxide, wherein the average diameter of primary particles of the Li—Mn—Ni composite oxide is 2.0 μm or less, and
Since the N ₂ -BET specific surface area is 0.4 m ² / g or more,
It is possible to provide a positive electrode active material for a lithium secondary battery, which has a high discharge capacity and is capable of producing a lithium secondary battery having excellent cycle performance.

According to the positive electrode active material for a lithium secondary battery of the second aspect, Li-Mn- containing at least lithium (Li), manganese (Mn), nickel (Ni) and cobalt (Co) as constituent elements. A positive electrode active material for a lithium secondary battery, comprising a Ni-Co composite oxide, wherein the Li
Since the average diameter of the primary particles of the —Mn—Ni—Co composite oxide is 3.0 μm or less and the N ₂ —BET specific surface area is 0.2 m ² / g or more, it has a high discharge capacity. ,
It is possible to provide a positive electrode active material for a lithium secondary battery capable of producing a lithium secondary battery having excellent cycle performance.

Positive electrode active material for lithium secondary battery according to claim 3
According to the substance, the Li-Mn-Ni composite oxide or
The Li-Mn-Ni-Co composite oxide is α-NaF.
eO ₂It has a crystal structure and a composition formula Li_xMn_aN
i_bCo_cO₂(However, a, b, and c are in the ternary diagram.
And (a, b, c) is point A (0.5, 0.5, 0)
Point B (0.45, 0.55, 0) and point C (0.25,
0.35,0.4) and point D (0.3,0.3,0.4)
It exists inside a square ABCD with and as vertices.
It is a value in the range of 0.95 ≦ x / (a + b + c) ≦ 1.
30), it has a particularly high discharge capacity.
It is possible to produce a lithium secondary battery with excellent cycle performance.
A positive electrode active material for a lithium secondary battery can be provided.

According to the lithium secondary battery of the fourth aspect, a positive electrode containing the positive electrode active material for a lithium secondary battery of the present invention, a negative electrode containing a negative electrode material capable of inserting and extracting lithium ions, Since it has an aqueous electrolyte, it is possible to provide a lithium secondary battery having a high discharge capacity and excellent cycle performance.

[Brief description of drawings]

FIG. 1 is a scanning electron microscope (SEM) photograph of a composite oxide that is a positive electrode active material of Example 1 (× 500).
0).

FIG. 2 is a scanning electron microscope (SEM) photograph of the composite oxide that is the positive electrode active material of Example 5 (× 500).
0).

FIG. 3 is a scanning electron microscope (SEM) photograph of a composite oxide that is a positive electrode active material of Comparative Example 2 (× 500).
0).

FIG. 4 is a cross-sectional view of a coin battery of an example.

FIG. 5 is a ternary phase diagram illustrating a positive electrode active material of an example.

[Explanation of symbols]

1 positive electrode 2 Negative electrode 3 separator 4 coin battery case 5 coin battery lid 6 Positive electrode current collector 7 Negative electrode current collector 8 resin packing

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[Submission date] August 24, 2001 (2001.8.2)
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   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroshi Yufu             2-32 Kosobe-cho, Takatsuki City, Osaka Prefecture Stock             Ceremony company Yuasa Corporation (72) Inventor Masahiko Oshiya             2-32 Kosobe-cho, Takatsuki City, Osaka Prefecture Stock             Ceremony company Yuasa Corporation F-term (reference) 4G048 AA04 AB05 AC06 AD04 AD06                       AE05                 5H029 AJ03 AJ05 AK02 AK03 AK05                       AK16 AK18 AL02 AL03 AL06                       AL07 AL08 AL12 AM02 AM03                       AM04 AM05 AM07 BJ03 DJ16                       DJ17 HJ02 HJ05 HJ07                 5H050 AA07 AA08 BA16 BA17 CA02                       CA08 CA09 CA11 CA23 CA25                       CA26 CA29 CB02 CB03 CB07                       CB08 CB09 CB12 FA17 FA19                       HA02 HA05 HA07

Claims (4)

[Claims] 1. Li-containing at least lithium (Li), manganese (Mn), and nickel (Ni) as constituent elements.
A positive electrode active material for a lithium secondary battery, comprising an Mn-Ni composite oxide, wherein the primary particles of the Li-Mn-Ni composite oxide have an average diameter of 2.0 μm or less, and N
_A positive electrode active material for a lithium secondary battery, which has a _2- BET specific surface area of 0.4 m ² / g or more. 2. A positive electrode for a lithium secondary battery containing a Li—Mn—Ni—Co composite oxide containing at least lithium (Li), manganese (Mn), nickel (Ni) and cobalt (Co) as constituent elements. An active material, said Li
-Mn-Ni-Co composite oxide primary particles having an average diameter of 3.0 µm or less, and N ₂ -BET specific surface area of 0.2 m ² / g or more, lithium secondary. Positive electrode active material for batteries. 3. The Li—Mn—Ni composite oxide or the Li—Mn—Ni—Co composite oxide is α-NaF.
eO ₂ having a crystal structure and a composition formula of Li _x Mn _a N
i _b Co _c O ₂ (where a, b and c are points (a, b, c) at point A (0.5, 0.5, 0) and point B (0. 45, 0.55, 0) and point C (0.25,
0.35,0.4) and point D (0.3,0.3,0.4)
And 0.92 ≦ x / (a + b + c) ≦ 1.
It is a compound oxide represented by 30). The positive electrode active material for a lithium secondary battery according to claim 1, wherein 4. A positive electrode containing the positive electrode active material for a lithium secondary battery according to claim 1, and a negative electrode containing a negative electrode material capable of inserting and extracting lithium ions.
A lithium secondary battery having a non-aqueous electrolyte.