JPH09171829A - Positive electrode active material for lithium secondary battery, and lithium secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive electrode active material for lithium secondary battery which is inexpensive and excellent in resource property, and also excellent in cycle characteristic with high capacity by using a compound oxide of Li-Ni-Al-P system having specified composition for the active material. SOLUTION: This positive electrode active material for lithium secondary battery contains a composite oxide represented by the formula LiNiw Alx Py Ox (wherein 0.4<w<1.1, 0<x<0.6, 0<y<0.1, 1.8<=z<=2.2). This lithium secondary battery has a positive electrode using the above positive electrode material, a negative electrode and an electrolyte. The positive electrode active material in which Al and P having small ion radiuses are coexistent in addition to Li and Ni shows excellent resistance to collapse of crystal even under charge and discharge cycles.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive electrode active material for a lithium secondary battery, which is inexpensive, excellent in resource properties, high in capacity, and excellent in cycle characteristics, and a lithium secondary battery having a positive electrode using the same. .

[0002]

2. Description of the Related Art Conventionally, many materials have been studied as positive electrode active materials for lithium secondary batteries, and typical ones are reversibly intercalated and deintercalated with lithium ions. There are inorganic compounds that can be released. As such inorganic compounds, many chalcogen compounds such as oxides and sulfides have been studied, and among them, oxides having a high potential and capable of providing a battery with a high energy density are promising.

LiCoO ₂ is an example of a positive electrode active material using the above oxide. This positive electrode active material composed of LiCoO ₂ was prepared by Mizushima et al. (Mat. Res. Bull., V.
ol.15, pp.783-789), which is a 4V class, and is often used as a positive electrode active material of a lithium secondary battery used as a main power source of a portable device currently in practical use. . However, the positive electrode active material using LiCoO ₂ has a problem that Co is expensive and inferior in resource property.

[0004] By contrast, Ni is inexpensive as compared with Co, since blessed with natural resources, there is a proposal to use a LiNiO ₂ having the same chemical structure as LiCoO ₂ as a positive electrode active material. For example, Japanese Patent Publication No. 63-59507 discloses an example in which LiNiO ₂ is used as the positive electrode active material in addition to LiCoO ₂ .

Further, in JP-A-63-121258, has a layered structure, the general formula _{A x B y C z D w} O 2 [A alkali metal; B is a transition metal; C is Al, In or Sn; D is (a) an alkali metal other than A, (b) a transition metal other than B, (c) a Group IIa element or (d) Al, In, S
IIIb group, IVb group, Vb group, excluding n, carbon, nitrogen and oxygen,
VIb Group 2-6 element; 0.05 ≦ x ≦ 1.1
0; 0.85≤y≤1.00; 0.001≤z≤0.1
0; 0.001 ≦ w ≦ 0.10] is disclosed as a positive electrode, and a non-aqueous secondary battery is disclosed.

Of a positive electrode active material using Ni as a transition metal
As an example, in the former publication, Li_0.85Ni_1.15O_Two
In the latter publication, only Li_1.05Ni_0.96Sn_0.04
Sc _0.002O_TwoOnly shown respectively, but those
Has insufficient discharge capacity and cycle characteristics.

[0007] For example, the proceedings of the 35th battery discussion meeting (13th
(P. 5, 1994, Nagoya), a LiNiO ₂ -based positive electrode active material was used in the charging and discharging cycle characteristics of a battery.
The problem of being inferior to the O ₂ positive electrode active material has been clarified. As described above, the LiNiO ₂ -based positive electrode active material has not yet been put into practical use at present.

An object of the present invention is to provide a positive electrode active material for a lithium secondary battery which eliminates the above-mentioned drawbacks, is inexpensive and has excellent resource properties, and has a high capacity and excellent cycle characteristics. Another object of the present invention is to provide a lithium secondary battery that can be stably produced at low cost and has high capacity and excellent cycle characteristics.

[0009]

DISCLOSURE OF THE INVENTION The present inventors have replaced the conventionally proposed LiNiO ₂ -based oxide with L having a specific composition.
We obtained new knowledge that a positive electrode active material excellent in capacity and cycle characteristics can be obtained by using an i-Ni-Al-P-based composite oxide. The present invention has been made based on this finding and has the following gist.

That is, the positive electrode active material for lithium secondary batteries of the present invention
The material has the formula LiNi_wAl_xP_yO _z(However, 0.4
<W <1.1, 0 <x <0.6, 0 <y <0.1, 1.
Containing a complex oxide represented by 8 ≦ z ≦ 2.2)
It is. Further, the lithium secondary battery of the present invention is the positive electrode
It has a positive electrode using an active material, a negative electrode, and an electrolyte.
Things.

The conventionally proposed LiNiO ₂ has a layered structure, and is composed of a Li layer-O layer-Ni layer-O layer -...
It has a structure in which Li layers and Ni layers are alternately provided between O layers. When this material is used as the positive electrode active material, Li is extracted by charging and Li is inserted again by discharging. When Li is extracted by charging, oxygen (O
^2- ) Since the layers face each other, repulsive force is exerted, the crystal becomes unstable, and the probability of collapse increases, which is one of the causes of cycle deterioration. On the other hand, the positive electrode active material of the present invention in which Al and P having a small ionic radius coexist in addition to Li and Ni exhibit excellent resistance to crystal collapse even under a cycle of charge and discharge. . The reason is considered as follows.

The ionic radius of Al ³⁺ is 0.68Å,
It is slightly smaller than the ion radius of Ni ³⁺ of 0.74Å. From this, the presence of Al facilitates the formation of a structure in which Al is substituted for Ni. In addition, since Al is an element having a large bonding force, it is strongly bonded to surrounding oxygen, and oxygen is more strongly attracted to the Al side. As a result, O generated when Li ions are released by charging
Relax the repulsive force between ^2- and O ^2- . In addition, since the P ion has an ionic radius of 0.31Å, which is considerably smaller than Ni ions and oxygen ions (1.28Å), it is an interstitial ion that enters between ions (Ni ion, oxygen ion, etc.). Conceivable. The P ions prevent repulsion between O ²⁻ and O ²⁻ due to the Coulomb force of P ions and O ²⁻ with respect to the repulsive force between O ²⁻ and O ²⁻ after Li is released. Although the individual actions of Al and P are presumed to be as described above, the cycle characteristics are remarkably improved by introducing both of Al and P at the same time as compared with the case of introducing Al or P alone. The reason seems to be the synergistic effect of the above-mentioned actions of both elements.

[0013] To add further note, the fact that the conventionally proposed LiNiO ₂ -based complex oxide has a problem in the charge / discharge cycle characteristics is that the hexagonal crystal form before charging is caused by the loss of lithium during charging. The cause is considered to be the phase change to the unstable monoclinic form. On the other hand, the LiNi _w Al _x P _y O used in the present invention
_{In the z} composite oxide, the monoclinic form in which the phase change from the hexagonal form is frequent is stable, and as a result, the positive electrode active material of the present invention comprising the composite oxide has excellent cycle characteristics and a large capacity. . By the way, Sn and S with large ionic radius
It is considered that ions such as c and Mn have a smaller binding force than an element having a small ionic radius and that they do not penetrate into the positions between the ions, so that the above effect can hardly be expected.

[0014]

DETAILED DESCRIPTION OF THE INVENTION The above formula LiNi _w Al _x P _y O _z
In the complex oxide represented by, the range of w is 0.4 <
w <1.1, preferably 0.5 <w <1.0. w
If ≦ 0.4, the capacity becomes insufficient, while w ≧ 1.1.
If so, capacity and cycle characteristics become insufficient.

The range of x is 0 <x <0.6, preferably 0.1 <x <0.5. When x = 0, the cycle characteristics are inferior, while when x ≧ 0.6, the capacity and the cycle characteristics are insufficient.

The range of y is 0 <y <0.1, preferably 0.01 <y <0.09. When y = 0, the cycle characteristics are inferior, while when y ≧ 0.1, the capacity and the cycle characteristics are insufficient.

The range of z is 1.8 ≦ z ≦ 2.2, preferably 1.9 ≦ z ≦ 2.1. When z <1.8, oxygen vacancies increase, while when z> 2.2, the amount of side reaction substances increases. In either case, the capacity and cycle characteristics are inferior.

The complex oxide is, for example, a simple substance of each of lithium, nickel, aluminum and phosphorus, or an oxide, hydroxide, salt (carbonate, nitrate, etc.) thereof,
Alternatively, a compound such as an organic compound is mixed, and the obtained mixture is baked (heating temperature of about 600 to 900 ° C., preferably about 650 to 750 ° C.), solid phase method, sol-gel method,
It can be obtained by synthesizing by a method such as a CVD method, a PVD method, a thermal spraying method, or a thermal decomposition method.

The composite oxide obtained as described above is
Usually, it is pulverized with a mortar, a ball mill, a hammer mill, a jet mill or the like to prepare a particle size of about 0.1 to 20 μm and used as a positive electrode active material.

A positive electrode for a lithium secondary battery can be obtained as follows using the positive electrode active material of the present invention. For example, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, ethylene-propylene-diene-based polymer (EPD) may be added to the positive electrode active material as needed.
M) and other binders, and conductive agents such as acetylene black, Ketjen black, and graphite are added to form a positive electrode mixture, and this positive electrode mixture can be used in any of the doctor blade method, casting molding, compression molding, roll molding, etc. A positive electrode for a lithium secondary battery is formed by molding into a suitable shape and size.

The above positive electrode active material is preferably contained in 80 to 95 parts by weight in 100 parts by weight of the positive electrode mixture. In addition, the compounding amount of the binder is 1 to 100 parts by weight of the positive electrode mixture.
The amount of the conductive agent is preferably about 10 parts by weight, and the amount of the conductive agent is preferably about 3 to 15 parts by weight in 100 parts by weight of the positive electrode mixture. In addition, for example, when the doctor blade method is used, 100 parts by weight of the positive electrode mixture is usually added to N-methyl-2-pyrrolidone, propylene carbonate, dimethylformamide (DMF), dimethylsulfoxide (DMSO), A positive electrode paste is prepared by mixing about 30 to 100 parts by weight of a solvent such as xylene or cyclohexane.

FIG. 1 is a schematic sectional view showing an embodiment of the lithium secondary battery of the present invention. In the lithium secondary battery shown in the figure, a separator 3 is interposed between a positive electrode 1 and a negative electrode 2, and a positive electrode can 5 press-contacted to the outer surface of the positive electrode 1 and a negative electrode 2
The negative electrode cap 6 that comes into pressure contact with the outer surface of the is sealed with an insulator 7. Incidentally, 4a and 4b are current collectors.

As the positive electrode 1, a positive electrode using the positive electrode active material of the present invention is used.

As the negative electrode 2, a conventionally known negative electrode material for lithium secondary batteries can be used. For example, metallic lithium or its alloy, carbon material, Nb ₂ O ₃ , Fe ₂
Oxides such as O are used.

When a lithium alloy is used, this alloy contains lithium in an atomic ratio of 10% or more, preferably 10 to 50%.
It is desirable that it be contained. When the content of lithium is 10% or more, it is possible to suppress a decrease in capacity and battery voltage due to alloy formation.

Examples of the lithium alloy include Li
-X1-Te alloy (X1 is Ag, Zn, Ca, Al,
One or more selected from Mg and Sn) and the like are included, which are preferable in terms of the cycle characteristics of the negative electrode, charge / discharge capacity, energy density and the like. In addition, preferably L
i: X1: Te = 10 to 120: 1 to 20: 0.001
˜2, more preferably Li: X1: Te = 10 to 80:
It has a composition ratio (atomic ratio) of 5 to 20: 0.01 to 0.5.

In addition to the above, Li-Ag-M1-
M2-Te alloy [M1 is 3B, 4B of the long period type periodic table]
And one or more selected from Group 5B metals, M
2 is one or more selected from transition metals (excluding Ag)] is particularly preferable. In addition, in this invention, a transition metal shall include 3A-7A, 8, 1B, and 2B group of a long period type periodic table.

Various kinds of carbon materials can be used as the carbon material for the negative electrode 2. Above all, highly crystalline carbon materials are generally preferred. Highly crystalline carbon materials include, for example, pitch, coke, or organic substances such as naturally occurring or synthetic organic polymers at high temperatures, for example, 500 to 3000.
Examples include artificial carbon materials obtained by firing at ° C, and naturally occurring carbon materials. The artificial carbon materials include soft carbon that can be graphitized and hard carbon that cannot be graphitized. Any of them can be used in the present invention. Further, regarding the shape of the carbon material, it may be in the form of particles, fibers, scales, or other various shapes. From the crystal structure, the carbon hexagonal plane spacing (d ₀₀₂ ) is 3.34 to 3.40Å and c
Graphite having an axial crystallite size (L _C ) of 300 Å or more is preferable. Also, from the viewpoint of shape, the average aspect ratio is 2
10 to 10 fibrous or scale-like, average fiber diameter of 5 to 1
Graphite fibers of 5 μm are preferred.

In general, when pure lithium is used as the negative electrode, a high energy density negative electrode can be obtained, but on the other hand, dendrites called dendrites easily grow with repeated charge and discharge, which causes the negative electrode to short-circuit with the positive electrode. There is a problem in safety such as a fire, and a problem that the cycle life of the battery is significantly shortened. On the other hand, for example, Al, Bi, P
It is known that when a lithium alloy composed of an intermetallic compound of b, Sn, In, etc. and Li is used for the negative electrode, the lithium absorption rate in the negative electrode is increased, so that lithium is prevented from being deposited in a dendrite form. However, since the negative electrode becomes fragile, the problem that the negative electrode volume is expanded and contracted due to absorption and release of lithium, resulting in cracking of the negative electrode and eventually pulverization, and a negative electrode made of pure lithium Since the electrode potential is higher than that of, the electromotive force of the battery is low.

On the other hand, the above-mentioned Li-X1-T
According to the e-based alloy, the diffusion rate of lithium in the negative electrode is high, and lithium is smoothly absorbed and released during charge and discharge, so that the growth of dendrite is suppressed. Also, Li
The potential of the electrode made of the -X1-Te alloy is equal to the potential of the negative electrode made of pure lithium, and therefore the battery electromotive force is the same as that using the negative electrode made of pure lithium.

Further, the Li-Ag-M1-M2-T is used.
In the case of the e-based alloy, in addition to having the same advantages as the Li-X1-Te-based alloy, each alloy component of M1 and M2 acts as a Li diffusion promoter or a binder,
The growth of dendrite is more effectively suppressed, and the deterioration due to the expansion and contraction of the negative electrode due to the absorption and release of lithium is suppressed, and as a result, the cycle life is further improved.

In the above Li-Ag-M1-M2-Te system alloy, M1 is preferably Al, Si, In, S.
One or two or more selected from n, Bi and Pb, more preferably one or two or more selected from In, Sn, Bi and Pb, and M2 is preferably Zn, Fe,
One or more selected from Co, Ni, Mn, Mo, and W, and more preferably one or more selected from Zn, Fe, and Ni.

The Li-Ag-M1-M2-Te based alloy has a composition ratio based on atomic ratio, preferably Li: Ag:
M1: M2: Te = 10 to 120: 1 to 30: 1 to 10
0: 1 to 30: 0.001 to 2, more preferably Li:
Ag: M1: M2: Te = 10-80: 10-30: 1
It is 0 to 100: 1 to 20: 0.01 to 0.5.

In the above Li-Ag-M1-M2-Te system alloy, when the atomic ratio of Li is within the above range, the cycle characteristics become good, the diffusion rate of Li tends to be high, and the electromotive force tends to be high. It is preferable because it is shown. When the atomic ratio of Ag is within the above range, the cycle characteristics become good, and L
It is preferable because the diffusion speed of i is high and the electromotive force tends to be high. When the atomic ratio of M1 and M2 is within the above range, each alloy component of M1 and M2 has a sufficient L content.
The i diffusion promotion effect and the binder effect are exhibited, and the cycle life, charge / discharge capacity, electromotive force, and energy density of the battery are improved. If the atomic ratio of Te is within the above range, L
This is preferable because diffusion of i is promoted and cycle life is extended.

The above Li-X1-Te system alloy, Li-Ag
For lithium alloys such as -M1-M2-Te alloys, for example, a known appropriate alloying method such as a method of melting and reacting a predetermined ratio of each alloy component (melting method), a method of reacting by a vapor deposition method, or the like. Is obtained by

In the melting method, alloying can be performed by heating and melting the alloy components in an inert gas atmosphere.
It is preferable that the heating and melting be performed at a temperature equal to or higher than the melting point of the Li alloy, because the alloying reaction can be rapidly advanced.

The alloying method by vapor deposition is carried out by evaporating the alloy components and solidifying them on the surface of another metal. According to this vapor deposition method, a so-called non-equilibrium phase alloy of a high melting point metal and a low melting point metal that cannot be alloyed by the melting method can be manufactured. As the vapor deposition method, it is possible to adopt an appropriate method such as various sputtering methods such as ion beam sputtering, electron beam evaporation method, various ion plating methods, flash plasma evaporation method, pulse plasma evaporation method, and CVD method. However, in the case of producing the alloy of the non-equilibrium phase as described above, it is desirable to use a method of accelerating atoms or ions toward the substrate such as an ion plating method and a sputtering method to deposit.

The method for forming the negative electrode 2 is not particularly limited, and a usual method can be used. For example, the negative electrode material may be formed into a sheet shape, a tape shape, a thin film shape, a substrate shape (hereinafter collectively referred to as a sheet shape) by any method such as a doctor blade method, casting molding, compression molding, or roll molding. It can be performed by an appropriate method such as molding into a negative electrode form.

When a metal material such as lithium or its alloy is used as the negative electrode material, for example, a method of forming the negative electrode material into a sheet shape by a hot rolling method or a hot extrusion method, a hot dipping method for a current collector, or a A method of providing a negative electrode material layer by a low pressure plasma spraying method or the like can be used. The latter method of providing the negative electrode material layer on the current collector is advantageous when forming a sheet-shaped negative electrode, and the negative electrode material layer can be provided on one surface or both surfaces of the current collector.

The hot rolling method is a processing method in which a metal material is heated to make it easy to work, and the hot extrusion method is a hot rolling method. It is a processing method of extruding. Further, the hot dip plating method is a method of melting a metal in an inert gas and dipping a current collector in the metal for plating, and the low pressure plasma spraying method is under a low pressure inert gas atmosphere (preferably This is a method of spraying a metal on the current collector at about 10 to 100 Torr).

The sheet-shaped negative electrode is, for example, a collector sheet,
It can also be obtained by depositing the negative electrode material component by the above-described vapor deposition method. Also, a sheet-shaped negative electrode material is joined to the current collecting sheet by an appropriate method such as brazing, soldering, ultrasonic welding, or spot welding to form a laminate of the negative electrode material sheet and the current collecting sheet. can do.

The collector sheet is, for example, Ni or A.
A sheet-shaped current collector made of an appropriate conductor such as 1, Cu, Ag, and Fe. As a specific form, a sheet-shaped metal foil, a metal mesh, a metal porous body, etc. are exemplified.

In the present invention, since Li is contained in the positive electrode active material, for example, a carbon material containing no Li can be used as it is as the negative electrode 2. Further, a small amount of the negative electrode material (0.
If about 0.1 to 5 parts by weight of Li is contained, even if a part of Li reacts with the electrolyte or becomes inactive, it should be supplemented with Li contained in the negative electrode material. Is preferable because it can As described above, in order to make the negative electrode material contain Li, for example, the heated and melted lithium is applied onto the current collector to which the negative electrode material is pressure bonded to impregnate the negative electrode material with Li, or the negative electrode material is electrolyzed in an electrolytic solution. L as a negative electrode material chemically
i may be doped.

As the electrolyte used in the lithium secondary battery, an electrolytic solution in which salts are dissolved in an organic solvent or a solid electrolyte can be used. When the electrolyte is an electrolytic solution, the salts include LiClO ₄ , LiBF ₄ , LiPF ₄ , and LiP.
F ₆ , LiAsF ₃ , LiAsF ₆ , LiAlCl ₄ ,
_{Li (CF 2 SO 2) 2} , Li (CF 3 SO 2) , such as ₂ N can be used, such as ethylene carbonate, propylene carbonate, dimethyl sulfoxide, sulfolane, .gamma.-butyrolactone, 1,2-dimethoxyethane, N, N -
Dimethylformamide, tetrahydrofuran, 1,3-dioxolane, 2-methyltetrahydrofuran, diethyl ether, dimethyl carbonate, diethyl carbonate,
Ethyl methyl carbonate, methyl formate, methyl acetate,
It is dissolved in an organic solvent such as acetonitrile or a mixture thereof to prepare a concentration of about 0.1 to 3 mol / liter and used. If necessary, organic additives such as 2-methylfuran, thiophene, pyrrole, and crown ether may be dissolved in the electrolytic solution. This electrolytic solution is usually used by impregnating or filling a separator such as a porous polymer, a glass filter or a non-woven fabric.

When the electrolyte is a solid electrolyte, the above-mentioned salts are used by being mixed with a salt-electrolytic polymer such as polyethylene oxide, polyphosphazene, polyaziridine, polyethylene sulfide, polyvinyl alcohol and the like, their derivatives, mixtures and complexes. . This solid electrolyte is
It can also serve as a separator for the positive electrode 1 and the negative electrode 2.

Examples of the positive electrode can include stainless copper and aluminum. As the negative electrode cap,
For example, stainless copper, nickel, nickel-plated iron, etc. may be mentioned. Examples of the insulator include polypropylene and polyethylene.

Examples of the form of the lithium secondary battery of the present invention include a button type, a cylindrical type, a square type, a sheet type, and a paper type other than the coin type shown in FIG. It may be selected as appropriate.

The method for producing the above lithium secondary battery is not particularly limited and can be produced by a known method.

[0049]

EXAMPLES Examples of the present invention will now be described in more detail. It should be noted that the present invention is by no means limited to these examples.

Example 1 (Preparation of Positive Electrode Active Material) Lithium hydroxide monohydrate [LiO
H · H ₂ O], nickel hydroxide [Ni (OH) ₂ ], aluminum hydroxide [Al (OH) ₃ ] and lithium phosphate [Li ₃ PO ₄ ] in atomic ratios of Li: N
i: Al: P = 1: 0.99: 0.002: 0.005
Were weighed and sufficiently mixed in a mortar, and then this mixture was placed in an alumina crucible, and this was subjected to heat treatment in an electric furnace in an oxygen stream at 700 ° C. for 24 hours. The obtained substance is crushed in a mortar and classified with a sieve to obtain a particle size of 20.
A powdery positive electrode active material having a size of not more than μm was obtained.

Examples 2 to 14 Powdery positive electrode active materials were prepared in the same manner as in Example 1 except that the atomic ratio of Li, Ni, Al and P was changed as shown in Table 1.

Comparative Example 1 Lithium hydroxide monohydrate [LiOH.H ₂ O] and nickel hydroxide [Ni (OH) ₂ ] in atomic ratio L respectively.
A powdery positive electrode active material was produced in the same manner as in Example 1 except that the weight was adjusted to i: Ni = 1: 1.

Comparative Examples 2 to 4 Powdery positive electrode active materials were prepared in the same manner as in Example 1 except that the atomic ratio of Li, Ni, Al and P was changed as shown in Table 1.

Comparative Example 5 Lithium hydroxide monohydrate and Ni powder were mixed in the amounts shown in Table 1, heat-treated at 750 ° C. for 12 hours in an oxygen atmosphere, pulverized and mixed, and then the same. The heat treatment was performed under the conditions. Otherwise in the same manner as in Example 1, a powdery positive electrode active material was produced.

Comparative Example 6 Lithium carbonate and cobalt carbonate were mixed in the amounts shown in Table 2, heat treated in air at 900 ° C. for 20 hours, pulverized and mixed, and further heat treated under the same conditions. .
Otherwise in the same manner as in Example 1, a powdery positive electrode active material was produced.

Comparative Example 7 Lithium carbonate, nickel oxide, stannic oxide and scandium oxide were mixed in the amounts shown in Table 2 and mixed in air at 65
After firing at 0 ° C for 5 hours, at 850 ° C for 12 hours in air
Fired for hours. Otherwise in the same manner as in Example 1, a powdery positive electrode active material was produced.

Comparative Example 8 Except that lithium carbonate, aluminum oxide, cobalt oxide and scandium oxide were mixed in the amounts shown in Table 2,
A powdery positive electrode active material was produced in the same manner as in Comparative Example 7.

Comparative Example 9 A powdery positive electrode active material was prepared in the same manner as in Comparative Example 7 except that lithium carbonate, cobalt oxide, stannic oxide, scandium oxide and manganese dioxide were mixed in the amounts shown in Table 2. did.

The above Examples 1 to 14 and Comparative Example 1
The atomic ratio of O in the positive electrode active material obtained by
Was within the range of 1.8 to 2.2.

[Production of Positive Electrode] Using the positive electrode active materials obtained in Examples 1 to 14 and Comparative Examples 1 to 9, positive electrodes were produced as follows. Positive electrode active material 9
0 parts by weight, 7 parts by weight of acetylene black as a conductive agent,
3 parts by weight of polyvinylidene fluoride (PVDF) as a binder, N-methyl-2-pyrrolidone (NMP) as a solvent
A paste was prepared by mixing and stirring 97 parts by weight. This paste is then applied to a thickness of 20 with a doctor blade.
It was coated on a collector (aluminum sheet) having a thickness of μm, dried, and then rolled to obtain a sheet electrode having a thickness of 100 μm. Then, this sheet electrode was punched out into a disk shape having a diameter of 12 mm to obtain a positive electrode.

[Preparation of Test Battery] The above positive electrode and thickness 2
A separator made of a disc-shaped polypropylene microporous membrane having a diameter of 5 μm and a diameter of 16 mm and a negative electrode obtained by punching out a lithium sheet having a thickness of 0.3 mm into a disc shape having a diameter of 15 mm are superposed in this order and placed in a battery can. I loaded it. Then, an electrolyte obtained by dissolving 1 mol / liter of lithium perchlorate in propylene carbonate was injected into the battery can, and the battery can was sealed with an insulating gasket to obtain the one shown in FIG. A similar coin-type lithium secondary battery was produced.

[Evaluation Test 1] Using the test batteries prepared as described above using the positive electrode active materials obtained in Examples 1 to 14 and Comparative Examples 1 to 9, charge and discharge were carried out by the following method. I went. After charging to 4.2V with a constant current of 0.5mA and resting for 1 hour, 2.75 with a constant current of 0.5mA
It discharges to V and rests for 1 hour.
As a cycle, charging / discharging was repeated up to 100 cycles. In this charge and discharge, the initial discharge capacity and 100
The capacity retention rate after completion of the cycle (ratio of discharge capacity after completion of 100 cycles to initial discharge capacity) was examined. The results are shown in Tables 1 and 2. Further, in Tables 1 and 2, the initial discharge capacity is shown by the capacity per 1 g of the positive electrode active material.

[0063]

[Table 1]

[0064]

[Table 2]

Example 15 Using the positive electrode active material obtained in Example 1 above, a positive electrode was prepared as described above. Moreover, the negative electrode was produced as follows. A lithium secondary battery was manufactured in the same manner as the test battery described above except for the above. [Production of Negative Electrode] Li: Ag: In: Zn: Fe: Te in atomic ratio in a high-purity Ar atmosphere (dew point -60 ° C).
= 60: 15: 45: 38: 4: 1 was weighed and heated to 800 ° C., and this was melted and alloyed. This alloy was pulverized to prepare a negative electrode active material powder, and a negative electrode was prepared as follows. 92 parts by weight of the negative electrode active material, 5 parts by weight of acetylene black as a conductive agent, 3 parts by weight of an ethylene-propylene-diene polymer as a binder,
As a solvent, 97 parts by weight of xylene was mixed and stirred to prepare a paste. Next, this paste was coated on a current collector (Cu sheet) having a thickness of 10 μm with a doctor blade, dried and then rolled to obtain a sheet electrode having a thickness of 50 μm. Then, the sheet-shaped electrode was
It was punched out into a disk shape of mm to obtain a negative electrode.

Example 16 In Example 15, the atomic ratio of Li: Ag: Zn:
Fe: Si: Te = 60: 15: 70: 4: 9: 1 Weighed in a similar atmosphere (high-purity Ar atmosphere) and heated to 750 ° C. under the same conditions to perform alloying. A negative electrode and a lithium secondary battery were produced in the same manner as in Example 15.

Example 17 In Example 15, the atomic ratio of Li: Ag: Al:
Except that alloyed by heating what was weighed so as to be Si: Mn: Te = 60: 15: 20: 9: 4: 1 under the same atmosphere (high-purity Ar atmosphere) to 750 ° C. A negative electrode and a lithium secondary battery were produced in the same manner as in Example 15.

Examples 18 to 21 A negative electrode and a lithium secondary battery having the compositions shown in Table 3 were prepared in the same manner as in Example 15 above.

[Evaluation Test 2] The electromotive force of each of the test batteries obtained in Examples 15 to 21 was measured by the two-terminal method. Further, using the above-mentioned test battery, charging and discharging were performed in the same manner as in the evaluation test 1, and the initial discharge capacity and the capacity retention rate after 100 cycles were examined. Moreover, the energy density at the time of 50 cycles was measured. Table 3 shows the results.

[0070]

[Table 3]

Example 22 In the same manner as in Example 1, Li: Ni: Al: P = 1:
0.86: 0.10: 0.05 powdery positive electrode active material
It was made. 90 parts by weight of this positive electrode active material, black as a conductive agent
7 parts by weight of lead, polyvinylidene fluoride (PV
DF) 3 parts by weight, and N-methyl-2-pi as a solvent
Slurry by mixing and stirring 55 parts by weight of loridone (NMP)
And a 20 μm thick current collector (aluminum
Coated, dried and then rolled into a positive electrode
And On the other hand, graphite fiber (soft carbo manufactured by Mitsubishi Chemical
, Average fiber diameter: approx. 9 μm, d ₀₀₂: 3.43Å,
L_C: 20Å, average aspect ratio: 3-4) 90 weight
Parts, polyvinylidene fluoride (PVDF) 1 as a binder
0 parts by weight, and N-methyl-2-pyrrolide as a solvent
99 parts by weight of NMP (NMP) are mixed and stirred to form a slurry.
Then, coat this with a current collector (copper sheet) with a thickness of 10 μm.
After drying, it was rolled to obtain a negative electrode. above
25 μm thick polypropylene micropores for the positive and negative electrodes
It was rolled through the membrane and loaded into a battery can. Then
1 mol / liter of propylene carbonate in the battery can
Inject the electrolyte obtained by dissolving lithium perchlorate
After that, sealing was performed to manufacture an AA lithium secondary battery. this
The battery was charged with an initial current of 250 mA and reached 4.2V
Sometimes a low voltage of 4.2V (However, the current decreases with time.
Less) for a total of 5 hours. Then at 100 mA
When discharged to 2.75V, initial capacity is 420mA
It was h. A cycle in which the above charging / discharging is one cycle
Cycle test, discharge capacity at 100th cycle
Was 415 mAh. This is 98.8% of the initial capacity
It is.

Example 23 As a graphite fiber for the negative electrode, soft carbon (average fiber diameter: about 9 μm, d ₀₀₂ : 3.36Å, L _C : manufactured by Petka Co., Ltd.) was used.
An AA lithium secondary battery was produced by the same method and conditions as in Example 22 except that 500Å and average aspect ratio: 3 to 4) were used. When the battery performance was evaluated by the same method and conditions as in Example 22, the initial capacity was 500 mA.
and the discharge capacity at the 100th cycle is 522 mAh.
(104% of initial capacity).

[0073]

INDUSTRIAL APPLICABILITY The positive electrode active material for a lithium secondary battery of the present invention is inexpensive and excellent in resource property as compared with the positive electrode active material using LiCoO _2, etc., and by using it, high capacity can be obtained. A lithium secondary battery having excellent cycle characteristics can be obtained. That is, since the lithium secondary battery of the present invention has a positive electrode using the above positive electrode active material, it has high capacity and excellent cycle characteristics, and can be stably produced at low cost. .

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a lithium secondary battery of the present invention.

[Explanation of symbols]

 1 Positive electrode 2 Negative electrode 3 Separator 4a, 4b Current collector 5 Positive electrode can 6 Negative electrode cap 7 Insulator

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuyuki Tateishi 4-3 Ikejiri, Itami City, Hyogo Prefecture Mitsubishi Cable Industries Itami Works Co., Ltd.

Claims (8)

[Claims] 1. The formula LiNi _w Al _x P _y O _z (where
0.4 <w <1.1, 0 <x <0.6, 0 <y <0.
1, 1.8 ≦ z ≦ 2.2) A positive electrode active material for a lithium secondary battery containing a composite oxide. 2. A lithium secondary battery comprising a positive electrode using the positive electrode active material according to claim 1, a negative electrode, and an electrolyte. 3. The negative electrode is a Li—X1-Te-based alloy (X1
Is one or more selected from Ag, Zn, Ca, Al, Mg, and Sn), and the lithium secondary battery according to claim 2. 4. Li in a Li-X1-Te system alloy,
The atomic ratio of X1 and Te is Li: X1: Te = 10.
The lithium secondary battery according to claim 3, which is 120: 1 to 20: 0.001-2. 5. The negative electrode is Li-Ag-M1-M2-Te.
Alloys [M1 is 3B, 4B and 5B of the long periodic table]
The lithium secondary battery according to claim 2, wherein the lithium secondary battery is one or more selected from group metals, and M2 is one or more selected from transition metals (excluding Ag). 6. The atomic ratio of Li, Ag, M1, M2 and Te in the Li-Ag-M1-M2-Te based alloy is
Li: Ag: M1: M2: Te = 10 to 120: 1 to 3
The lithium secondary battery according to claim 5, which is 0: 1 to 100: 1 to 30: 0.001-2. 7. The lithium secondary battery according to claim 2, wherein the negative electrode is made of a carbon material. 8. The negative electrode is made of graphite having d _{002 of} 3.34 to 3.40 Å and L _{C of} 300 Å or more, and an average fiber diameter of 5 to 5.
The lithium secondary battery according to claim 2 or 7, which is made of graphite fibers having an average aspect ratio of 2 to 10 and having a thickness of 15 μm.