JP3530174B2 - Positive electrode active material and lithium ion secondary battery - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a positive electrode active material containing lithium-containing nickel oxide, and a lithium ion secondary battery provided with this positive electrode active material.

[0002]

2. Description of the Related Art In recent years, as portable personal computers, mobile phones, and the like have become smaller and lighter, there has been a demand for smaller and lighter secondary batteries as the power source for these electronic devices. There is.

As such a secondary battery, a lithium ion secondary battery using a substance capable of inserting and extracting lithium ions such as a carbon material as a negative electrode material has been developed and put into practical use as a power source for small electronic devices. This secondary battery is smaller and lighter than conventional lead-acid batteries and nickel-cadmium batteries, and is characterized by having a high energy density, so that demand is increasing.

As a positive electrode active material of this lithium ion secondary battery, a lithium-containing cobalt oxide (LiCoO ₂ ) which has a high discharge potential and a high energy density has been put into practical use. However, since cobalt, which is a raw material of this complex oxide, is scarce in resources and is unevenly distributed in countries with few commercially available ore deposits, it is expensive and has large price fluctuations, and in the future. It is accompanied by supply insecurity.

Therefore, research on positive electrode active materials other than lithium-containing cobalt oxide has been actively conducted in recent years. As one example, various compounds have been reported as composite oxides of lithium and manganese synthesized from various manganese raw materials and lithium raw materials. Specifically, the lithium-manganese composite oxide represented by LiMn ₂ O ₄ having a spinel type crystal structure shows a potential of 3 V with respect to lithium by electrochemical oxidation and has a theoretical charge / discharge capacity of 148 mAh / g. Have.

However, a lithium ion secondary battery using a manganese oxide or a lithium manganese composite oxide as a positive electrode active material has a drawback that its capacity is significantly deteriorated when used in an environment of room temperature or higher. This is because the manganese oxide and the lithium-manganese composite oxide are destabilized by the high temperature and Mn is eluted in the non-aqueous electrolyte. In recent years, in particular, large-sized lithium ion secondary batteries for electric vehicles or load leveling have been developed in various fields. In this large-sized lithium-ion secondary battery, as the battery becomes larger, the heat generated during use cannot be ignored, and the inside of the battery tends to become relatively high even if the ambient environmental temperature is near room temperature. In addition, even a relatively small battery used for a small portable device may be used in a high temperature environment such as the interior of a car in the midsummer, and the battery may have a relatively high temperature inside. is there. Due to these problems, it is very difficult to put a positive electrode active material using manganese as a raw material into practical use.

By the way, studies on nickel composite oxides as post-cobalt composite oxides are being actively conducted. For example, a nickel composite oxide such as LiNiO ₂ has a theoretical capacity of 180 to 200 mAh / g, which is larger than that of a LiCoO _{2 based} active material or a LiMn ₂ O _{4 based} active material, and has an optimum discharge potential of about 3.6 V on average. Since it has, it is a very promising positive electrode active material. However, since the crystal structure of LiNiO ₂ is unstable, the problem that the initial discharge capacity greatly decreases with the number of charge and discharge in the charge and discharge cycle test,
In a nail penetration test of a lithium-ion secondary battery produced using LiNiO ₂ , there is a safety problem leading to rupture and ignition.

On the other hand, in claim 1 of JP-A-10-326621, a positive electrode using a lithium-containing metal composite oxide as an active material, a negative electrode using a metal composite oxide having an amorphous structure, and A secondary battery composed of a water electrolyte is disclosed. The active material of the positive electrode is Li _x Ni _1-y M
a nickel-containing lithium composite oxide represented by a composition of _y O _2-z X _a. However, the M is the second group, the first group of the periodic table.
At least one element selected from Group 3 and Group 14 elements and transition metal elements, X is a halogen element, and x, y, z and a are 0.2 <x ≦ 1.2,0. ≤ y ≤
0.5, 0 ≦ z ≦ 1, and 0 ≦ a ≦ 2z are shown.

Further, paragraph [0010] of the above-mentioned publication has the following description.

The content of the elements other than the elements (Li, Ni, Co and the other element M) in the composition formula contained as impurities in the positive electrode active material is 0.01 in terms of weight concentration of Fe.
% Or less (100 ppm or less), Cu 0.01% or less (100 ppm or less), Ca, Na and sulfate (SO
It is preferable that each of ₄ ) has a concentration of 0.05% or less (500 ppm or less). The water content in the active material is preferably 0.1% or less.

That is, in the above-mentioned publication, elements other than the elements in the composition formula, that is, Fe, Cu, Ca, Na and sulfate group are impurities, and therefore it is preferable that the elements are small.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to prevent a rupture and an ignition in a nail penetration test, and to improve a large current discharge characteristic (discharge rate characteristic). And a lithium ion secondary battery provided with this positive electrode active material.

[0013]

A first lithium ion secondary battery according to the present invention comprises a positive electrode containing an active material containing a composite oxide having a composition represented by the following chemical formula (1), and a negative electrode. , A non-aqueous electrolyte.

Li _x (Ni _1-y Me1 _y ) (O _2-z X _z ) + A (1) where Me 1 is B, Mg, Al, Sc, Ti, V, C
r, Mn, Co, Cu, Zn, Ga, Y, Zr, Nb,
Mo, Tc, Ru, Sn, La, Hf, Ta, W, R
e, at least one element selected from the group consisting of Pb and Bi, X is at least one halogen element selected from the group consisting of F, Cl, Br and I,
The molar ratios x, y and z are 0.02 ≦ x ≦ 1.
3, 0.005 ≦ y ≦ 0.5, 0.01 ≦ z ≦ 0.5, A contains at least one element selected from the group consisting of Na, K and S, and the composite oxide N in
The a content, K content, and S content are each 600 p
It is in the range of pm or more and 3000 ppm or less.

A second lithium ion secondary battery according to the present invention comprises a positive electrode containing an active material containing a complex oxide having a composition represented by the following chemical formula (2), a negative electrode, and a non-aqueous electrolyte. It is characterized by having.

Li _x (Ni _1-y Me1 _y ) (O _2-z X _z ) + A + bB (2) where Me 1 is B, Mg, Al, Sc, Ti, V, C
r, Mn, Co, Cu, Zn, Ga, Y, Zr, Nb,
Mo, Tc, Ru, Sn, La, Hf, Ta, W, R
e, at least one element selected from the group consisting of Pb and Bi, X is at least one halogen element selected from the group consisting of F, Cl, Br and I,
The molar ratios x, y and z are 0.02 ≦ x ≦ 1.
3, 0.005 ≦ y ≦ 0.5, 0.01 ≦ z ≦ 0.5, A contains at least one element selected from the group consisting of Na, K and S, and the composite oxide N in
The a content, K content, and S content are each 600 p
Within the range of pm or more and 3000 ppm or less, B is S
The composite oxide contains at least one element selected from the group consisting of i and Fe, and the content b of B in the composite oxide is in the range of 20 ppm to 500 ppm.

A third lithium ion secondary battery according to the present invention comprises a positive electrode containing an active material containing a composite oxide having a composition represented by the following chemical formula (3), a negative electrode, and a non-aqueous electrolyte. It is characterized by having.

Li _x (Ni _1-vs Co _v Me2 _s ) (O _2-z X _z ) + A (3) where Me 2 is B, Mg, Al, Sc, Ti, V, C
r, Mn, Cu, Zn, Ga, Y, Zr, Nb, Mo,
Tc, Ru, Sn, La, Hf, Ta, W, Re, Pb
And Bi at least one element selected from the group consisting of F, Cl, Br and I, and X is at least one halogen element selected from the group consisting of F, Cl, Br and I, and the molar ratios x, v, s and z are , 0.02 ≦ x ≦ 1.
3, 0.005 ≦ v ≦ 0.5, 0.005 ≦ s ≦ 0.
5, 0.01 ≦ z ≦ 0.5, A contains at least one element selected from the group consisting of Na, K and S, and Na content, K content in the composite oxide, S content is 600 ppm or more and 3000 ppm, respectively
It is within the following range.

A fourth lithium ion secondary battery according to the present invention comprises a positive electrode containing an active material containing a composite oxide having a composition represented by the following chemical formula (4), a negative electrode, and a non-aqueous electrolyte. It is characterized by having.

Li _x (Ni _1-vs Co _v Me2 _s ) (O _2-z X _z ) + A + bB (4) where Me 2 is B, Mg, Al, Sc, Ti, V, C
r, Mn, Cu, Zn, Ga, Y, Zr, Nb, Mo,
Tc, Ru, Sn, La, Hf, Ta, W, Re, Pb
And Bi at least one element selected from the group consisting of F, Cl, Br and I, and X is at least one halogen element selected from the group consisting of F, Cl, Br and I, and the molar ratios x, v, s and z are , 0.02 ≦ x ≦ 1.
3, 0.005 ≦ v ≦ 0.5, 0.005 ≦ s ≦ 0.
5, 0.01 ≦ z ≦ 0.5, A contains at least one element selected from the group consisting of Na, K and S, and Na content, K content in the composite oxide, S content is 600 ppm or more and 3000 ppm, respectively
Within the following range, B contains at least one element selected from the group consisting of Si and Fe, and the content b of B in the composite oxide is 20 ppm or more and 500 p.
It is within the range of pm or less.

The first positive electrode active material according to the present invention is characterized by containing a composite oxide having a composition represented by the following chemical formula (1).

Li _x (Ni _1-y Me1 _y ) (O _2-z X _z ) + A (1) where Me 1 is B, Mg, Al, Sc, Ti, V, C
r, Mn, Co, Cu, Zn, Ga, Y, Zr, Nb,
Mo, Tc, Ru, Sn, La, Hf, Ta, W, R
e, at least one element selected from the group consisting of Pb and Bi, X is at least one halogen element selected from the group consisting of F, Cl, Br and I,
The molar ratios x, y and z are 0.02 ≦ x ≦ 1.
3, 0.005 ≦ y ≦ 0.5, 0.01 ≦ z ≦ 0.5, A contains at least one element selected from the group consisting of Na, K and S, and the composite oxide N in
The a content, K content, and S content are each 600 p
It is in the range of pm or more and 3000 ppm or less.

The second positive electrode active material according to the present invention is characterized by containing a composite oxide having a composition represented by the following chemical formula (2).

Li _x (Ni _1-y Me1 _y ) (O _2-z X _z ) + A + bB (2) where Me 1 is B, Mg, Al, Sc, Ti, V, C
r, Mn, Co, Cu, Zn, Ga, Y, Zr, Nb,
Mo, Tc, Ru, Sn, La, Hf, Ta, W, R
e, at least one element selected from the group consisting of Pb and Bi, X is at least one halogen element selected from the group consisting of F, Cl, Br and I,
The molar ratios x, y and z are 0.02 ≦ x ≦ 1.
3, 0.005 ≦ y ≦ 0.5, 0.01 ≦ z ≦ 0.5, A contains at least one element selected from the group consisting of Na, K and S, and the composite oxide N in
The a content, K content, and S content are each 600 p
Within the range of pm or more and 3000 ppm or less, B is S
The composite oxide contains at least one element selected from the group consisting of i and Fe, and the content b of B in the composite oxide is in the range of 20 ppm to 500 ppm.

The third positive electrode active material according to the present invention is characterized by containing a composite oxide having a composition represented by the following chemical formula (3).

Li _x (Ni _1-vs Co _v Me2 _s ) (O _2-z X _z ) + A (3) where Me 2 is B, Mg, Al, Sc, Ti, V, C
r, Mn, Cu, Zn, Ga, Y, Zr, Nb, Mo,
Tc, Ru, Sn, La, Hf, Ta, W, Re, Pb
And Bi at least one element selected from the group consisting of F, Cl, Br and I, and X is at least one halogen element selected from the group consisting of F, Cl, Br and I, and the molar ratios x, v, s and z are , 0.02 ≦ x ≦ 1.
3, 0.005 ≦ v ≦ 0.5, 0.005 ≦ s ≦ 0.
5, 0.01 ≦ z ≦ 0.5, A contains at least one element selected from the group consisting of Na, K and S, and Na content, K content in the composite oxide, S content is 600 ppm or more and 3000 ppm, respectively
It is within the following range.

The fourth positive electrode active material according to the present invention is characterized by containing a composite oxide having a composition represented by the following chemical formula (4).

Li _x (Ni _1-vs Co _v Me2 _s ) (O _2-z X _z ) + A + bB (4) where Me 2 is B, Mg, Al, Sc, Ti, V, C
r, Mn, Cu, Zn, Ga, Y, Zr, Nb, Mo,
Tc, Ru, Sn, La, Hf, Ta, W, Re, Pb
And Bi at least one element selected from the group consisting of F, Cl, Br and I, and X is at least one halogen element selected from the group consisting of F, Cl, Br and I, and the molar ratios x, v, s and z are , 0.02 ≦ x ≦ 1.
3, 0.005 ≦ v ≦ 0.5, 0.005 ≦ s ≦ 0.
5, 0.01 ≦ z ≦ 0.5, A contains at least one element selected from the group consisting of Na, K and S, and Na content, K content in the composite oxide, S content is 600 ppm or more and 3000 ppm, respectively
Within the following range, B contains at least one element selected from the group consisting of Si and Fe, and the content b of B in the composite oxide is 20 ppm or more and 500 p.
It is within the range of pm or less.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION A lithium ion secondary battery according to the present invention comprises a positive electrode containing an active material, a negative electrode, and a non-aqueous electrolyte. The active material is a first positive electrode active material described below.
At least one of the sixth positive electrode active materials is included.

As the non-aqueous electrolyte, for example, a liquid non-aqueous electrolyte (non-aqueous electrolytic solution) prepared by dissolving the electrolyte in a non-aqueous solvent, or a polymer material holding the non-aqueous solvent and the electrolyte Examples thereof include a polymer gel non-aqueous electrolyte, a polymer solid electrolyte containing an electrolyte as a main component, and an inorganic solid non-aqueous electrolyte having lithium ion conductivity. As the non-aqueous solvent and the electrolyte contained in each non-aqueous electrolyte, those described in the liquid non-aqueous electrolyte described later can be used.

Examples of the polymer material contained in the gelled non-aqueous electrolyte include polyacrylonitrile, polyacrylate, polyvinylidene fluoride (PVdF), polyethylene oxide (PEO), acrylonitrile, acrylate, vinylidene fluoride or ethylene oxide. Examples thereof include a polymer contained as a monomer. Examples of the polymer material contained in the polymer solid electrolyte include polyacrylonitrile, polyvinylidene fluoride (PVdF), polyethylene oxide (PEO), or a polymer containing acrylonitrile, vinylidene fluoride or ethylene oxide as a monomer. Etc. can be mentioned. On the other hand, examples of the inorganic solid non-aqueous electrolyte include a ceramic material containing lithium. Specifically, Li ₃ N,
It can be mentioned _{Li 3 PO 4 -Li 2 S-} SiS glass.

An example of the lithium ion secondary battery according to the present invention will be described below.

This lithium-ion secondary battery comprises a positive electrode containing at least one of the first to sixth positive electrode active materials, a negative electrode, and a separator disposed between the positive electrode and the negative electrode. And at least a liquid non-aqueous electrolyte impregnated in the separator.

The positive electrode, separator, negative electrode and liquid non-aqueous electrolyte will be described in detail.

1) Positive Electrode This positive electrode includes a current collector and a positive electrode layer carried by the current collector and containing at least one of the first to sixth positive electrode active materials.

(First Positive Electrode Active Material) This first positive electrode active material contains a composite oxide having a composition represented by the following chemical formula (1).

Li _x (Ni _1-y Me1 _y ) (O _2-z X _z ) + A (1) where Me 1 is B, Mg, Al, Sc, Ti, V, C
r, Mn, Co, Cu, Zn, Ga, Y, Zr, Nb,
Mo, Tc, Ru, Sn, La, Hf, Ta, W, R
e, at least one element selected from the group consisting of Pb and Bi, X is at least one halogen element selected from the group consisting of F, Cl, Br and I,
The molar ratios x, y and z are 0.02 ≦ x ≦ 1.
3, 0.005 ≦ y ≦ 0.5 and 0.01 ≦ z ≦ 0.5 are shown.

The A contains at least one element selected from the group consisting of Na, K and S. For each element constituting the element A, the content in the complex oxide is 600 p
It is set within the range of pm or more and 3000 ppm or less.

The molar ratio x of lithium will be described. When the molar ratio x is less than 0.02, the crystal structure of the composite oxide becomes extremely unstable, which deteriorates the cycle characteristics of the secondary battery and lowers the safety. On the other hand, when the molar ratio x exceeds 1.3, the discharge capacity and safety of the secondary battery decrease. A more preferable range of the molar ratio x is 0.05 ≦
x ≦ 1.2.

The molar ratio y of the element Me1 will be described. When the molar ratio y is less than 0.005, it becomes difficult to improve the safety of the secondary battery. On the other hand, the molar ratio y is 0.5
When it exceeds, the discharge capacity is greatly reduced. A more preferable range of the molar ratio y is 0.01 ≦ y ≦ 0.35. In addition, among the elements Me1, Al, Ti, Mn, Nb, Ta
Is preferred.

The molar ratio z of the halogen element X will be described. When the molar ratio z is less than 0.01, it becomes difficult to improve the cycle characteristics and safety of the secondary battery.
On the other hand, when the molar ratio z exceeds 0.5, the discharge capacity is greatly reduced. A more preferable range of the molar ratio z is 0.02 ≦
z ≦ 0.3. Further, the halogen element X is preferably F.

One of the preferable compositions of the composite oxide is that the halogen element X is F and the molar ratios x, y and z are 0.05 ≦ x ≦ 1.2 and 0.01 ≦ y ≦ 0. 35, 0.
It is shown by 02 ≦ z ≦ 0.3.

The element A contained in the composite oxide will be described. By including the element A in the composite oxide, it is possible to prevent the battery temperature from rapidly rising when a large current flows through the secondary battery due to a short circuit or the like, and improve the safety of the secondary battery. can do.

When Na is contained in the composite oxide, Na
The content is in the range of 600 ppm or more and 3000 ppm or less. This is due to the following reasons.
When the Na content is less than 600 ppm, a high discharge capacity cannot be obtained when discharging with a large current (high rate). On the other hand, when the Na content exceeds 3000 ppm, the charge / discharge cycle characteristics deteriorate. Na content is 1000
More preferably, it is within the range of ˜2500 ppm.
By setting the Na content within the range of 1000 to 2500 ppm, it is possible to suppress the capacity decrease when the charge / discharge cycle of discharging at a high rate is repeated.

When K is contained in the composite oxide, the K content is in the range of 600 ppm or more and 3000 ppm or less. This is due to the following reasons. If the K content is less than 600 ppm, a high discharge capacity cannot be obtained when discharging with a large current (high rate). On the other hand, when the K content exceeds 3000 ppm, the charge / discharge cycle characteristics deteriorate. K content is 1000 to 2500
More preferably, it is within the ppm range. By setting the K content within the range of 1000 to 2500 ppm, it is possible to suppress the capacity decrease when the charge and discharge cycle in which the discharge is performed at a high rate is repeated.

When S is contained in the composite oxide, the S content is preferably in the range of 600 ppm or more and 3000 ppm or less. This is due to the following reasons. When the S content is less than 600 ppm, a high discharge capacity cannot be obtained when discharging with a large current (high rate). On the other hand, when the S content exceeds 3000 ppm, the charge / discharge cycle characteristics deteriorate. S content is 10
More preferably, it is within the range of 00 to 2500 ppm. By setting the S content within the range of 1000 to 2500 ppm, it is possible to suppress the capacity decrease when the charge / discharge cycle of discharging at a high rate is repeated.

The element A includes Ca in combination with at least one element selected from the group consisting of Na, K and S.
Is preferably included. The Ca content in the composite oxide is preferably within the range of 500 ppm or less. This is because if the Ca content exceeds 500 ppm, deterioration of charge / discharge cycle characteristics, high rate discharge characteristics (discharge rate characteristics) or high rate cycle characteristics may be promoted. The Ca content is more preferably in the range of 20 ppm or more and 500 ppm or less. By setting the Ca content within the range of 20 ppm or more and 500 ppm or less, the high rate discharge characteristic (discharge rate characteristic) or the high rate cycle characteristic can be significantly improved. A more preferable range of the Ca content is 50 ppm or more and 500 ppm or less.

The element A can sufficiently improve the safety even if added alone, but the safety can be further improved by adding a plurality of kinds of elements. As the element A, a combination of Na and S, a combination of Ca, Na and S, a combination of Na and Ca, and a combination of S and Ca are preferable.

Total content of element A in the composite oxide a
Is preferably in the range of 600 ppm or more and 7000 ppm or less. This is due to the following reasons. When the total content a of the element A is less than 600 ppm, it becomes difficult to improve the high rate discharge characteristics of the secondary battery. On the other hand, the total content a of element A is 7
If it exceeds 000 ppm, the charge / discharge cycle characteristics may deteriorate. A more preferable range of the total content a of the element A is 1000 to 5000 ppm.

In the complex oxide represented by the above chemical formula (1), it is preferable that at least part of the element A of at least one selected from the group consisting of Na, K, Ca and S is segregated. . In particular, it is desirable that at least a part of the element A is deposited at the triple points existing at the boundaries of the crystal grains of the composite oxide. By setting the crystal structure of the composite oxide to such a structure, both the safety and the cycle characteristics of the secondary battery can be further improved.

The composite oxide is prepared by, for example, a solid phase method, a coprecipitation method or a hydrothermal synthesis method. Above all, the powder of the compound of each element is heated at 450 to 550 ° C. in an oxygen gas stream.
At a temperature of 2 to 20 hours, then 630 to 730 ° C
It is desirable to obtain a composite oxide having a composition represented by the chemical formula (1) by firing at 2 to 50 hours. If the heat treatment temperature of the first step exceeds 550 ° C or if the heat treatment temperature of the second step becomes higher than 730 ° C, the element A is melted and adheres to the surface of the particles, which inhibits the occlusion / release of lithium. However, it becomes difficult to improve the safety and cycle characteristics of the secondary battery. Oxygen layer-Li layer-oxygen layer- (Ni + Me1) layer-
The oxygen layer-Li layer can be regularly arranged, and the element A can be deposited at the triple points existing at the boundaries of the crystal grains. As a result, the safety and charge / discharge cycle characteristics of the secondary battery can be further improved.

The lithium-ion secondary battery provided with the positive electrode containing the first positive electrode active material according to the present invention as described above has a battery temperature which is short-circuited when a large current flows as in a nail penetration test. Since it is possible to suppress the sudden rise, it is possible to prevent rupture and ignition in advance, and it is possible to improve safety. This is Na, K, Ca
It is supposed that at least one element A selected from the group consisting of S and S acts to reduce the DC resistance of the positive electrode active material and suppresses heat generation due to Joule heat when a large current flows. It Further, according to the secondary battery of the present invention, it is possible to realize high discharge capacity, excellent cycle characteristics, and excellent high rate discharge characteristics (discharge rate characteristics).

(Second Positive Electrode Active Material) This second positive electrode active material contains a composite oxide having a composition represented by the following chemical formula (2).

Li _x (Ni _1-y Me1 _y ) (O _2-z X _z ) + A + bB (2) where Me 1 is B, Mg, Al, Sc, Ti, V, C
r, Mn, Co, Cu, Zn, Ga, Y, Zr, Nb,
Mo, Tc, Ru, Sn, La, Hf, Ta, W, R
e, at least one element selected from the group consisting of Pb and Bi, X is at least one halogen element selected from the group consisting of F, Cl, Br and I,
The molar ratios x, y and z are 0.02 ≦ x ≦ 1.
3, 0.005 ≦ y ≦ 0.5 and 0.01 ≦ z ≦ 0.5 are shown.

The A includes at least one element selected from the group consisting of Na, K and S. For each element constituting the element A, the content in the composite oxide is 60
It is set within the range of 0 ppm or more and 3000 ppm or less.

The B essentially consists of at least one element selected from the group consisting of Si and Fe. The content b of B in the composite oxide is 20 ppm or more, 5
It is within the range of 00 ppm or less.

The reason for defining the molar ratio x of lithium within the above range is for the same reason as described for the above-mentioned first positive electrode active material. A more preferable range of the molar ratio x is 0.05 ≦ x ≦ 1.2.

The reason that the molar ratio y of the element Me1 is defined in the above range is for the same reason as explained in the above-mentioned first positive electrode active material. A more preferable range of the molar ratio y is 0.01 ≦ y ≦ 0.35. Further, as the more preferable element of the element Me1, the same element as described in the above-mentioned first positive electrode active material can be mentioned.

The reason that the molar ratio z of the halogen element X is defined in the above range is for the same reason as explained in the above-mentioned first positive electrode active material. A more preferable range of the molar ratio z is 0.02 ≦ z ≦ 0.3. Further, the halogen element X is preferably F.

When Na is contained in the composite oxide, the Na content is 600 ppm or more and 3000 pp for the same reason as described in the section of the first positive electrode active material.
It is desirable to be within the range of m or less. Further, the Na content is more preferably in the range of 1000 to 2500 ppm for the same reason as described in the section of the first positive electrode active material described above.

When K is contained in the composite oxide, the K content should be in the range of 600 ppm or more and 3000 ppm or less for the same reason as described in the section of the first positive electrode active material. Is desirable. Also, the K content is
For the same reason as described in the section of the first positive electrode active material described above, it is more preferable to set it within the range of 1000 to 2500 ppm.

When S is contained in the composite oxide, the S content should be in the range of 600 ppm or more and 3000 ppm or less for the same reason as described in the section of the first positive electrode active material. Is desirable. Further, the S content is
For the same reason as described in the section of the first positive electrode active material described above, it is more preferable to set it within the range of 1000 to 2500 ppm.

The element A includes Ca in combination with at least one element selected from the group consisting of Na, K and S.
Is preferably included. The Ca content in the composite oxide is preferably in the range of 500 ppm or less, more preferably in the range of 20 ppm or more, for the same reason as described above in the section of the first positive electrode active material.
Within the range of 500 ppm or less, a more preferable range is
It is in the range of 50 ppm or more and 500 ppm or less.

These elements A can sufficiently improve the safety even if added alone, but the safety can be further improved by adding a plurality of kinds of elements. As a preferable combination of the element A, the ones described in the above-mentioned first positive electrode active material can be mentioned.

Total content of element A in complex oxide a
Is preferably in the range of 600 ppm or more and 7000 ppm or less for the same reason as described for the above-mentioned first positive electrode active material. Total content of element A a
Is more preferably 1000 to 5000 ppm.

The element B contained in the composite oxide will be described. By including the element B in the composite oxide, it is possible to further suppress an increase in battery temperature when a large current flows through the secondary battery due to a short circuit or the like, and further improve the safety of the secondary battery. it can. The content b of element B
If it is less than 20 ppm, it may be difficult to sufficiently improve the safety of the secondary battery. On the other hand, if the content b of the element B exceeds 500 ppm, the charge / discharge cycle characteristics may be significantly deteriorated. A more preferable range of the content b of the element B is 20 ppm ≦ b ≦ 250 ppm. Further, by forming the element B from Si and Fe, it is possible to further improve the safety and charge / discharge cycle characteristics of the secondary battery.

In the complex oxide represented by the above chemical formula (2), at least a part of the element A consisting of at least one selected from the group consisting of Na, K, Ca and S, or the group consisting of Si and Fe. It is preferable that at least part of the element B consisting of at least one selected from the above is segregated. In particular, it is desirable that at least a part of at least one of the elements A and B is precipitated at the triple points existing at the boundaries of the crystal grains of the composite oxide. By setting the crystal structure of the composite oxide to such a structure, both the safety and the cycle characteristics of the secondary battery can be further improved.

The composite oxide is produced by, for example, a solid phase method, a coprecipitation method or a hydrothermal synthesis method. Above all, the powder of the compound of each element is heated at 450 to 550 ° C. in an oxygen gas stream.
At a temperature of 2 to 20 hours, then 630 to 730 ° C
It is desirable to obtain a composite oxide having a composition represented by the chemical formula (2) by firing at 2 to 50 hours. If the first-stage heat treatment temperature exceeds 550 ° C or the second-stage heat treatment temperature becomes higher than 730 ° C, the compound of the element A and the compound of the element B are melted and adhere to the surface of the particles. The occlusion and release of hydrogen are hindered, and it becomes difficult to improve the safety and cycle characteristics of the secondary battery. By performing a two-step heat treatment in which the firing temperature and the firing time are defined within the above ranges, the oxygen layer-Li layer-
The oxygen layer- (Ni + Me1) layer-oxygen layer-Li layer can be regularly arranged, and the elements A and B can be deposited at the triple points existing at the boundaries of the crystal grains.
As a result, the safety and charge / discharge cycle characteristics of the secondary battery can be further improved.

The lithium-ion secondary battery provided with the positive electrode containing the second positive electrode active material according to the present invention as described above has a battery temperature which is short-circuited when a large current flows as in a nail penetration test. Since it is possible to suppress the sudden rise, it is possible to prevent rupture and ignition in advance, and it is possible to improve safety. This is Na, K, Ca
And an element B consisting of at least one kind selected from the group consisting of S and S and an element B consisting of at least one kind selected from the group consisting of Si and Fe, each having a function of lowering the DC resistance of the positive electrode active material, Element A and element B
It is presumed that this is because the heat generation due to the Joule heat when a large current flows is sufficiently suppressed by the synergistic effect of. Further, according to the secondary battery of the present invention, a high discharge capacity,
It is possible to realize excellent cycle characteristics and excellent high rate discharge characteristics (discharge rate characteristics).

(Third Positive Electrode Active Material) This third positive electrode active material contains a composite oxide having a composition represented by the following chemical formula (3).

Li _x (Ni _1-vs Co _v Me2 _s ) (O _2-z X _z ) + A (3) where Me 2 is B, Mg, Al, Sc, Ti, V, C
r, Mn, Cu, Zn, Ga, Y, Zr, Nb, Mo,
Tc, Ru, Sn, La, Hf, Ta, W, Re, Pb
And Bi at least one element selected from the group consisting of F, Cl, Br and I, and X is at least one halogen element selected from the group consisting of F, Cl, Br and I, and the molar ratios x, v, s and z are , 0.02 ≦ x ≦ 1.
3, 0.005 ≦ v ≦ 0.5, 0.005 ≦ s ≦ 0.
5, 0.01 ≦ z ≦ 0.5 is shown.

The A contains at least one element selected from the group consisting of Na, K and S. For each element constituting the element A, the content in the composite oxide is 60
It is set within the range of 0 ppm or more and 3000 ppm or less.

The molar ratio x of lithium will be described. When the molar ratio x is less than 0.02, the crystal structure of the composite oxide becomes extremely unstable, which deteriorates the cycle characteristics of the secondary battery and lowers the safety. On the other hand, when the molar ratio x exceeds 1.3, the discharge capacity and safety of the secondary battery decrease. A more preferable range of the molar ratio x is 0.05 ≦
x ≦ 1.2.

The molar ratio v of Co will be described. By including Co in the composite oxide, it is possible to suppress gas ejection from the battery at the time of a short circuit such as a nail piercing test, and further suppress the temperature rise of the battery at the time of a short circuit. When the molar ratio v is less than 0.005, it becomes difficult to sufficiently improve the safety of the secondary battery. On the other hand, when the molar ratio v exceeds 0.5, the charge / discharge cycle characteristics and the discharge capacity are significantly reduced.

The molar ratio s of the element Me2 will be described. When the molar ratio s is less than 0.005, it becomes difficult to improve the safety of the secondary battery. On the other hand, the molar ratio s is 0.5
When it exceeds, the discharge capacity is greatly reduced. A more preferable range of the molar ratio s is 0.01 ≦ s ≦ 0.35. Among the elements Me2, Al, Ti, Mn, Nb, Ta
Is preferred.

The molar ratio z of the halogen element X will be described. When the molar ratio z is less than 0.01, it becomes difficult to improve the cycle characteristics and safety of the secondary battery.
On the other hand, when the molar ratio z exceeds 0.5, the discharge capacity is greatly reduced. A more preferable range of the molar ratio z is 0.02 ≦
z ≦ 0.3. Further, the halogen element X is preferably F.

One of the preferable compositions of the complex oxide is that the halogen element X is F, and the molar ratios x, v, s and z are 0.05 ≦ x ≦ 1.2 and 0.005 ≦ v ≦. 0.5,
0.01 ≦ s ≦ 0.35 and 0.02 ≦ z ≦ 0.3.

When Na is contained in the composite oxide, the Na content is 600 ppm or more and 3000 pp for the same reason as described in the section of the first positive electrode active material.
It is desirable to be within the range of m or less. Further, the Na content is more preferably in the range of 1000 to 2500 ppm for the same reason as described in the section of the first positive electrode active material described above.

When K is contained in the composite oxide, the K content should be in the range of 600 ppm or more and 3000 ppm or less for the same reason as described in the section of the first positive electrode active material. Is desirable. Also, the K content is
For the same reason as described in the section of the first positive electrode active material described above, it is more preferable to set it within the range of 1000 to 2500 ppm.

When S is contained in the composite oxide, the S content should be in the range of 600 ppm or more and 3000 ppm or less for the same reason as described in the section of the first positive electrode active material. Is desirable. Further, the S content is
For the same reason as described in the section of the first positive electrode active material described above, it is more preferable to set it within the range of 1000 to 2500 ppm.

The element A includes Ca in combination with at least one element selected from the group consisting of Na, K and S.
Is preferably included. The Ca content in the composite oxide is preferably in the range of 500 ppm or less, more preferably in the range of 20 ppm or more, for the same reason as described above in the section of the first positive electrode active material.
Within the range of 500 ppm or less, a more preferable range is
It is in the range of 50 ppm or more and 500 ppm or less.

These elements A can sufficiently improve the safety even if added alone, but the safety can be further improved by adding a plurality of kinds of elements. As the preferable combination of the element A, those described in the above-mentioned first positive electrode can be mentioned.

Total content of element A in the composite oxide a
Is preferably in the range of 600 ppm or more and 7000 ppm or less for the same reason as described for the above-mentioned first positive electrode active material. Total content of element A a
Is more preferably 1000 to 5000 ppm.

In the complex oxide represented by the above chemical formula (3), it is preferable that at least part of the element A consisting of at least one selected from the group consisting of Na, K, Ca and S is segregated. . In particular, it is desirable that at least a part of the element A is deposited at the triple points existing at the boundaries of the crystal grains of the composite oxide. By setting the crystal structure of the composite oxide to such a structure, both the safety and the cycle characteristics of the secondary battery can be further improved.

The complex oxide is produced by, for example, a solid phase method, a coprecipitation method or a hydrothermal synthesis method. Above all, the powder of the compound of each element is heated at 450 to 550 ° C. in an oxygen gas stream.
At a temperature of 2 to 20 hours, then 630 to 730 ° C
It is desirable to obtain a composite oxide having a composition represented by the chemical formula (3) by firing at 2 to 50 hours. According to such a method, the oxygen layer-Li layer-oxygen layer- (Ni + Co + Me2) layer-oxygen layer-Li layer can be regularly arranged, and the element A is present at the triple points existing at the boundaries of the crystal grains. It can be deposited. as a result,
The safety and charge / discharge cycle characteristics of the secondary battery can be further improved.

The lithium ion secondary battery provided with the positive electrode containing the third positive electrode active material according to the present invention as described above has a battery temperature which is short-circuited as in the nail piercing test and a large current flows. Since the rapid rise can be effectively suppressed, the risk of gas ejection and ignition can be further reduced, and the safety can be greatly improved. Further, according to the secondary battery of the present invention, it is possible to have a high discharge capacity and further improve the charge / discharge cycle characteristics and the high rate discharge characteristics (discharge rate characteristics).

(Fourth Positive Electrode Active Material) This fourth positive electrode active material contains a composite oxide having a composition represented by the following chemical formula (4).

Li _x (Ni _1-vs Co _v Me2 _s ) (O _2-z X _z ) + A + bB (4) where Me 2 is B, Mg, Al, Sc, Ti, V, C
r, Mn, Cu, Zn, Ga, Y, Zr, Nb, Mo,
Tc, Ru, Sn, La, Hf, Ta, W, Re, Pb
And Bi at least one element selected from the group consisting of F, Cl, Br and I, and X is at least one halogen element selected from the group consisting of F, Cl, Br and I, and the molar ratios x, v, s and z are , 0.02 ≦ x ≦ 1.
3, 0.005 ≦ v ≦ 0.5, 0.005 ≦ s ≦ 0.
5, 0.01 ≦ z ≦ 0.5 is shown.

The above A contains at least one element selected from the group consisting of Na, K and S. For each element constituting the element A, the content in the composite oxide is 60
It is set within the range of 0 ppm or more and 3000 ppm or less.

The B essentially consists of at least one element selected from the group consisting of Si and Fe. The content b of B in the composite oxide is 20 ppm or more, 5
It is within the range of 00 ppm or less.

The reason for limiting the molar ratio x of lithium to the above range is for the same reason as described for the above-mentioned third positive electrode active material. A more preferable range of the molar ratio x is 0.05 ≦ x ≦ 1.2.

The reason that the molar ratio v of Co is specified in the above range is for the same reason as explained in the above third positive electrode active material.

The reason why the molar ratio s of the element Me2 is defined in the above range is for the same reason as described for the above-mentioned third positive electrode active material. A more preferable range of the molar ratio s is 0.01 ≦ s ≦ 0.35. Further, among the more preferable elements of the element Me2, the same elements as those described in the above third positive electrode active material can be mentioned.

The reason for defining the molar ratio z of the halogen element X within the above range is for the same reason as described for the above-mentioned third positive electrode active material. A more preferable range of the molar ratio z is 0.02 ≦ z ≦ 0.3. Further, the halogen element X is preferably F.

When Na is contained in the composite oxide, the Na content is 600 ppm or more and 3000 pp for the same reason as described in the section of the first positive electrode active material.
It is desirable to be within the range of m or less. Further, the Na content is more preferably in the range of 1000 to 2500 ppm for the same reason as described in the section of the first positive electrode active material described above.

When K is contained in the composite oxide, the K content should be in the range of 600 ppm or more and 3000 ppm or less for the same reason as described in the section of the first positive electrode active material. Is desirable. Also, the K content is
For the same reason as described in the section of the first positive electrode active material described above, it is more preferable to set it within the range of 1000 to 2500 ppm.

When S is contained in the composite oxide, the S content should be in the range of 600 ppm or more and 3000 ppm or less for the same reason as described in the section of the first positive electrode active material. Is desirable. Further, the S content is
For the same reason as described in the section of the first positive electrode active material described above, it is more preferable to set it within the range of 1000 to 2500 ppm.

The element A includes Ca in combination with at least one element selected from the group consisting of Na, K and S.
Is preferably included. The Ca content in the composite oxide is preferably in the range of 500 ppm or less, more preferably in the range of 20 ppm or more, for the same reason as described above in the section of the first positive electrode active material.
Within the range of 500 ppm or less, a more preferable range is
It is in the range of 50 ppm or more and 500 ppm or less.

The safety of each of these elements A can be sufficiently improved by adding them alone, but the safety can be further improved by adding a plurality of kinds of elements. As the preferable combination of the element A, those described in the above-mentioned first positive electrode can be mentioned.

Total content of element A in the composite oxide a
Is preferably in the range of 600 ppm or more and 7000 ppm or less for the same reason as described for the above-mentioned first positive electrode active material. Total content of element A a
Is more preferably 1000 to 5000 ppm.

The content b of the element B in the composite oxide is defined in the above range for the same reason as described above for the first positive electrode active material. Content b of element B
Is more preferably 20 ppm ≦ b ≦ 250 ppm. Further, by forming the element B from Si and Fe,
It is possible to further improve the safety and charge / discharge cycle characteristics of the secondary battery.

In the complex oxide represented by the chemical formula (4), at least a part of the element A consisting of at least one selected from the group consisting of Na, K, Ca and S, or the group consisting of Si and Fe. It is preferable that at least part of the element B consisting of at least one selected from the above is segregated. In particular, it is desirable that at least a part of at least one of the elements A and B is precipitated at the triple points existing at the boundaries of the crystal grains of the composite oxide. By setting the crystal structure of the composite oxide to such a structure, both the safety and the cycle characteristics of the secondary battery can be further improved.

The complex oxide is produced by, for example, a solid phase method, a coprecipitation method or a hydrothermal synthesis method. Above all, the powder of the compound of each element is heated at 450 to 550 ° C. in an oxygen gas stream.
At a temperature of 2 to 20 hours, then 630 to 730 ° C
It is desirable to obtain a composite oxide having a composition represented by the chemical formula (4) by firing at 2 to 50 hours. According to such a method, the oxygen layer-Li layer-oxygen layer- (Ni + Co + Me2) layer-oxygen layer-Li layer can be regularly arranged, and the element A and the element A are present at the triple points existing at the boundaries of the crystal grains. The element B can be precipitated.
As a result, the safety and charge / discharge cycle characteristics of the secondary battery can be further improved.

The lithium-ion secondary battery provided with the positive electrode containing the fourth positive electrode active material according to the present invention as described above has a battery temperature which is short-circuited as in the nail penetration test and causes a large current to flow. Since the rapid rise can be effectively suppressed, the risk of gas ejection and ignition can be further reduced, and the safety can be greatly improved. Further, according to the secondary battery of the present invention, it is possible to have a high discharge capacity and further improve charge / discharge cycle characteristics and high rate discharge characteristics (discharge rate characteristics).

(Fifth Positive Electrode Active Material) This fifth positive electrode active material contains a composite oxide having a composition represented by the following chemical formula (5).

Li _x (Ni _1-vt Co _v Me3 _t ) (O _2-z X _z ) + A (5) where Me 3 is Ti, V, Cr, Zr, Nb, Mo,
At least one element selected from the group consisting of Hf, Ta and W, wherein X is at least one halogen element selected from the group consisting of F, Cl, Br and I,
The molar ratios x, v, t and z are 0.02 ≦ x ≦, respectively.
1.3, 0.005 ≦ v ≦ 0.5, 0.005 ≦ t ≦
0.5 and 0.01 ≦ z ≦ 0.5 are shown.

The A contains at least one element selected from the group consisting of Na, K and S. For each element constituting the element A, the content in the composite oxide is 60
It is set within the range of 0 ppm or more and 3000 ppm or less.

The molar ratio x of lithium will be described. When the molar ratio x is less than 0.02, the crystal structure of the composite oxide becomes extremely unstable, which deteriorates the cycle characteristics of the secondary battery and lowers the safety. On the other hand, when the molar ratio x exceeds 1.3, the discharge capacity and safety of the secondary battery decrease. A more preferable range of the molar ratio x is 0.05 ≦
x ≦ 1.2.

The molar ratio t of the element Me3 will be described. When the molar ratio t is less than 0.005, it becomes difficult to improve the safety of the secondary battery. On the other hand, the molar ratio t is 0.5
When it exceeds, the discharge capacity is greatly reduced. A more preferable range of the molar ratio t is 0.01 ≦ t ≦ 0.35. Further, among the element Me3, Ti, Nb, and Ta are preferable.

The molar ratio v of Co will be described. By including Co in the composite oxide, it is possible to suppress gas ejection from the battery at the time of a short circuit such as a nail piercing test, and further suppress the temperature rise of the battery at the time of a short circuit. When the molar ratio v is less than 0.005, it becomes difficult to sufficiently improve the safety of the secondary battery. On the other hand, when the molar ratio v exceeds 0.5, the charge / discharge cycle characteristics and the discharge capacity are significantly reduced.

The molar ratio z of the halogen element X will be described. When the molar ratio z is less than 0.01, it becomes difficult to improve the cycle characteristics and safety of the secondary battery.
On the other hand, when the molar ratio z exceeds 0.5, the discharge capacity is greatly reduced. A more preferable range of the molar ratio z is 0.02 ≦
z ≦ 0.3. Further, the halogen element X is preferably F.

One of the preferable compositions of the complex oxide is that the halogen element X is F, and the molar ratios x, v, t and z are 0.05 ≦ x ≦ 1.2 and 0.005 ≦ v ≦. 0.5,
0.01 ≦ t ≦ 0.35 and 0.02 ≦ z ≦ 0.3.

When Na is contained in the composite oxide, the Na content is 600 ppm or more and 3000 pp for the same reason as described in the section of the first positive electrode active material.
It is desirable to be within the range of m or less. Further, the Na content is more preferably in the range of 1000 to 2500 ppm for the same reason as described in the section of the first positive electrode active material described above.

When K is contained in the composite oxide, the K content should be in the range of 600 ppm or more and 3000 ppm or less for the same reason as described in the section of the first positive electrode active material. Is desirable. Also, the K content is
For the same reason as described in the section of the first positive electrode active material described above, it is more preferable to set it within the range of 1000 to 2500 ppm.

When S is contained in the composite oxide, the S content should be in the range of 600 ppm or more and 3000 ppm or less for the same reason as described in the section of the first positive electrode active material. Is desirable. Further, the S content is
For the same reason as described in the section of the first positive electrode active material described above, it is more preferable to set it within the range of 1000 to 2500 ppm.

The element A includes Ca in combination with at least one element selected from the group consisting of Na, K and S.
Is preferably included. The Ca content in the composite oxide is preferably in the range of 500 ppm or less, more preferably in the range of 20 ppm or more, for the same reason as described above in the section of the first positive electrode active material.
Within the range of 500 ppm or less, a more preferable range is
It is in the range of 50 ppm or more and 500 ppm or less.

The safety of the element A can be sufficiently improved by adding it alone, but the safety can be further improved by adding a plurality of kinds of elements. As the preferable combination of the element A, those described in the above-mentioned first positive electrode can be mentioned.

Total content of element A in the composite oxide a
Is preferably in the range of 600 ppm or more and 7000 ppm or less for the same reason as described for the above-mentioned first positive electrode active material. Total content of element A a
Is more preferably 1000 to 5000 ppm.

In the complex oxide represented by the chemical formula (5), at least a part of the element A consisting of at least one selected from the group consisting of Na, K, Ca and S is segregated. . In particular, it is desirable that at least a part of the element A is deposited at the triple points existing at the boundaries of the crystal grains of the composite oxide. By setting the crystal structure of the composite oxide to such a structure, both the safety and the cycle characteristics of the secondary battery can be further improved.

The composite oxide is produced by, for example, a solid phase method, a coprecipitation method or a hydrothermal synthesis method. Above all, the powder of the compound of each element is heated at 450 to 550 ° C. in an oxygen gas stream.
At a temperature of 2 to 20 hours, then 630 to 730 ° C
It is desirable to obtain a composite oxide having a composition represented by the chemical formula (5) by firing at 2 to 50 hours. According to such a method, the oxygen layer-Li layer-oxygen layer- (Ni + Co + Me3) layer-oxygen layer-Li layer can be regularly arranged, and the element A is present at the triple points existing at the boundaries of the crystal grains. It can be deposited. as a result,
The safety and charge / discharge cycle characteristics of the secondary battery can be further improved.

The lithium ion secondary battery provided with the positive electrode containing the fifth positive electrode active material according to the present invention as described above has a battery temperature which is short-circuited when a large current flows as in a nail penetration test. Since it is possible to suppress the sudden rise, it is possible to prevent rupture and ignition in advance, and it is possible to significantly improve safety. In addition, this secondary battery has a high discharge capacity, excellent charge and discharge cycle characteristics,
It is possible to realize excellent high rate discharge characteristics (discharge rate characteristics).

(Sixth Positive Electrode Active Material) This sixth positive electrode active material contains a composite oxide having a composition represented by the following chemical formula (6).

Li _x (Ni _1-vt Co _v Me3 _t ) (O _2-z X _z ) + A + bB (6) where Me3 is Ti, V, Cr, Zr, Nb, Mo,
At least one element selected from the group consisting of Hf, Ta and W, wherein X is at least one halogen element selected from the group consisting of F, Cl, Br and I,
The molar ratios x, v, t and z are 0.02 ≦ x ≦, respectively.
1.3, 0.005 ≦ v ≦ 0.5, 0.005 ≦ t ≦
0.5 and 0.01 ≦ z ≦ 0.5 are shown.

The above A contains at least one element selected from the group consisting of Na, K and S. For each element constituting the element A, the content in the composite oxide is 60
It is set within the range of 0 ppm or more and 3000 ppm or less.

The B essentially consists of at least one element selected from the group consisting of Si and Fe. The content b of B in the composite oxide is 20 ppm or more, 5
It is within the range of 00 ppm or less.

The reason for limiting the molar ratio x of lithium to the above range is for the same reason as described for the fifth positive electrode active material. A more preferable range of the molar ratio x is 0.05 ≦ x ≦ 1.2.

The reason that the molar ratio t of the element Me3 is defined in the above range is for the same reason as described in the above fifth positive electrode active material. A more preferable range of the molar ratio t is 0.01 ≦ t ≦ 0.35. Moreover, as the preferable element among the elements Me3, the same elements as those described in the above fifth positive electrode active material can be mentioned.

The reason that the molar ratio v of Co is defined in the above range is for the same reason as explained in the above fifth positive electrode active material.

The reason that the molar ratio z of the halogen element X is defined in the above range is for the same reason as described in the above fifth positive electrode active material. A more preferable range of the molar ratio z is 0.02 ≦ z ≦ 0.3. Further, the halogen element X is preferably F.

When Na is contained in the composite oxide, the Na content is 600 ppm or more and 3000 pp for the same reason as described in the section of the first positive electrode active material.
It is desirable to be within the range of m or less. Further, the Na content is more preferably in the range of 1000 to 2500 ppm for the same reason as described in the section of the first positive electrode active material described above.

When K is contained in the composite oxide, the K content should be in the range of 600 ppm or more and 3000 ppm or less for the same reason as described in the section of the first positive electrode active material. Is desirable. Also, the K content is
For the same reason as described in the section of the first positive electrode active material described above, it is more preferable to set it within the range of 1000 to 2500 ppm.

When S is contained in the composite oxide, the S content should be in the range of 600 ppm or more and 3000 ppm or less for the same reason as described in the section of the first positive electrode active material. Is desirable. Further, the S content is
For the same reason as described in the section of the first positive electrode active material described above, it is more preferable to set it within the range of 1000 to 2500 ppm.

The element A includes Ca in combination with at least one element selected from the group consisting of Na, K and S.
Is preferably included. The Ca content in the composite oxide is preferably in the range of 500 ppm or less, more preferably in the range of 20 ppm or more, for the same reason as described above in the section of the first positive electrode active material.
Within the range of 500 ppm or less, a more preferable range is
It is in the range of 50 ppm or more and 500 ppm or less.

The safety of the element A can be sufficiently improved by adding it alone, but the safety can be further improved by adding a plurality of kinds of elements. As the preferable combination of the element A, those described in the above-mentioned first positive electrode can be mentioned.

Total content of element A in the composite oxide a
Is preferably in the range of 600 ppm or more and 7000 ppm or less for the same reason as described for the above-mentioned first positive electrode active material. Total content of element A a
Is more preferably 1000 to 5000 ppm.

The content b of the element B in the composite oxide is defined in the above range for the same reason as explained in the above-mentioned first positive electrode active material. Content b of element B
Is more preferably 20 ppm ≦ b ≦ 250 ppm. Further, by forming the element B from Si and Fe,
It is possible to further improve the safety and charge / discharge cycle characteristics of the secondary battery.

In the complex oxide represented by the chemical formula (6), at least a part of the element A consisting of at least one selected from the group consisting of Na, K, Ca and S, or the group consisting of Si and Fe. It is preferable that at least part of the element B consisting of at least one selected from the above is segregated. In particular, it is desirable that at least a part of at least one of the elements A and B is precipitated at the triple points existing at the boundaries of the crystal grains of the composite oxide. By setting the crystal structure of the composite oxide to such a structure, both the safety and the cycle characteristics of the secondary battery can be further improved.

The composite oxide is produced, for example, by a solid phase method, a coprecipitation method or a hydrothermal synthesis method. Above all, the powder of the compound of each element is heated at 450 to 550 ° C. in an oxygen gas stream.
At a temperature of 2 to 20 hours, then 630 to 730 ° C
It is desirable to obtain a composite oxide having a composition represented by the chemical formula (6) by firing at 2 to 50 hours. According to such a method, the oxygen layer-Li layer-oxygen layer- (Ni + Co + Me3) layer-oxygen layer-Li layer can be regularly arranged, and the element A and the element A are present at the triple points existing at the boundaries of the crystal grains. The element B can be precipitated.
As a result, the safety and charge / discharge cycle characteristics of the secondary battery can be further improved.

The lithium-ion secondary battery provided with the positive electrode containing the sixth positive electrode active material according to the present invention as described above has a battery temperature which is short-circuited when a large current flows as in a nail penetration test. Since it is possible to suppress the sudden rise, it is possible to prevent rupture and ignition in advance, and it is possible to significantly improve safety. In addition, this secondary battery has a high discharge capacity, excellent charge and discharge cycle characteristics,
It is possible to realize excellent high rate discharge characteristics (discharge rate characteristics).

Of these first positive electrode active material to sixth positive electrode active material, the first to fourth positive electrode active materials are preferable because they can have excellent safety and cycle characteristics. . Particularly preferred are the third and fourth positive electrode active materials.

The positive electrode is prepared, for example, by mixing at least one of the first positive electrode active material to the sixth positive electrode active material, an electric conduction aid and a binder, and pressing the mixture on a current collector. Alternatively, the positive electrode active material, the electric conduction aid and the binder are suspended in a suitable solvent, and the suspension is applied to a current collector and dried.

Examples of the electric conduction aid include acetylene black, carbon black, graphite and the like.

Examples of the binder include polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVd).
F), ethylene-propylene-diene copolymer (EPD
M), styrene-butadiene rubber (SBR) and the like can be used.

The mixing ratio of the positive electrode active material, the electric conduction aid and the binder is in the range of 80 to 95% by weight of the positive electrode active material, 3 to 20% by weight of the electric conduction aid, and 2 to 7% by weight of the binder. Is preferred. As the current collector, a conductive substrate having a porous structure or a non-porous conductive substrate can be used. Examples of the material forming the current collector include aluminum, stainless steel, nickel and the like.

2) Separator As the separator, for example, a synthetic resin non-woven fabric,
A polyethylene porous film, a polypropylene porous film, or the like can be used.

3) Negative Electrode This negative electrode contains a material capable of occluding (doping) and releasing (dedoping) lithium.

Examples of such a material include lithium metal, a Li-containing alloy capable of occluding / releasing lithium, a metal oxide capable of occluding / releasing lithium, and a capability of occluding / releasing lithium. Examples include metal sulfides, metal nitrides capable of occluding and releasing lithium, chalcogen compounds capable of occluding and releasing lithium, and carbon materials capable of occluding and releasing lithium ions. it can. In particular, since the negative electrode containing the chalcogen compound or the carbon material has high safety and can improve the cycle life of the secondary battery,
desirable.

Examples of the carbon material that absorbs and releases lithium ions include coke, carbon fiber, pyrolytic vapor-phase carbonaceous material, graphite, resin fired body, mesophase pitch carbon fiber, mesophase pitch spherical carbon and the like. You can The above-mentioned types of carbon materials are desirable because they can increase the electrode capacity.

Examples of the chalcogen compound include titanium disulfide, molybdenum disulfide, niobium selenide, tin oxide and the like. When such a chalcogen compound is used for the negative electrode, the battery voltage decreases, but the capacity of the negative electrode increases, so that the capacity of the secondary battery is improved.

The negative electrode containing the carbon material is produced, for example, by kneading the carbon material and the binder in the presence of a solvent, applying the obtained suspension to a current collector, and drying. It

In this case, as the binder, for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), ethylene-propylene-diene copolymer (EP
DM), styrene-butadiene rubber (SBR) and the like can be used. Further, the mixing ratio of the carbon material and the binder is 90 to 98% by weight of the carbon material and 2 to 10% by weight of the binder.
It is preferable that it is within the range. Further, as the current collector, for example, a conductive substrate made of copper, stainless steel, nickel or the like can be used. The current collector may have a porous structure or a non-porous structure.

4) Liquid Non-Aqueous Electrolyte (Non-Aqueous Electrolyte) This liquid non-aqueous electrolyte is prepared by dissolving the electrolyte in a non-aqueous solvent.

Examples of the non-aqueous solvent include cyclic carbonates, chain carbonates (eg ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, etc.), cyclic ethers and chain ethers (eg 1 , 2-
Dimethoxyethane, 2-methyltetrahydrofuran, etc., cyclic ester and chain ester (eg, γ-butyrolactone, γ-valerolactone, σ-valerolactone, methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, methyl propionate, propione) Acid ethyl, propyl propionate, etc.) and the like. The non-aqueous solvent may be one or two selected from the above-mentioned types.
~ 5 kinds of mixed solvents can be used, but not limited thereto.

Examples of the electrolyte include lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (Li
PF ₆ ), lithium borofluoride (LiBF ₄ ), lithium hexafluoroarsenide (LiAsF ₆ ), lithium trifluoromethylsulfonylimide (LiCF ₃ SO ₃ ), lithium bistrifluoromethylsulfonylimide [LiN (CF ₃
SO ₂ ) ₂ ] and the like. As such an electrolyte, one kind or two to three kinds of lithium salts selected from these can be used, but the electrolyte is not limited thereto.

The amount of the electrolyte dissolved in the non-aqueous solvent is preferably within the range of 0.5 to 2 mol / L.

An example of the lithium ion secondary battery according to the present invention is shown in FIGS.

FIG. 1 is a partially cutaway perspective view showing a cylindrical lithium ion secondary battery which is an example of the lithium ion secondary battery according to the present invention, and FIG. 2 is an example of the lithium ion secondary battery according to the present invention. FIG. 3 is a cross-sectional view showing the thin lithium-ion secondary battery, and FIG. 3 is a cross-sectional view showing part A of FIG. 2.

As shown in FIG. 1, a bottomed cylindrical container 1 made of, for example, stainless steel has an insulator 2 arranged at the bottom. The electrode group 3 is housed in the container 1.
The electrode group 3 has a structure in which a band-shaped material in which a positive electrode 4, a separator 5 and a negative electrode 6 are laminated in this order is spirally wound.

The container 1 contains a non-aqueous electrolytic solution. The PTC element 7 having a hole at the center, the P
A safety valve 8 arranged on the TC element 7 and a hat-shaped positive electrode terminal 9 arranged on the safety valve 8 are caulked and fixed to an upper opening of the container 1 via an insulating gasket 10. Note that the positive electrode terminal 9 has a safety mechanism built therein to serve as a gas vent hole (not shown). One end of the positive electrode lead 11 is connected to the positive electrode 4 and the other end is connected to the PTC element 7.
Respectively connected to. The negative electrode 6 is connected to the container 1, which is a negative electrode terminal, via a negative electrode lead (not shown).

As shown in FIG. 2, an electrode group 22 is housed in a housing container 21 made of, for example, a film material. Examples of the film material include a metal film, a resin sheet such as a thermoplastic resin, and a sheet in which a resin layer such as a thermoplastic resin is coated on one side or both sides of the metal layer. The electrode group 22 has a structure in which a laminate including a positive electrode, a separator, and a negative electrode is wound into a flat shape. From the bottom of FIG. 3, the laminate includes a separator 23, a positive electrode layer 24, a positive electrode current collector 25, and a positive electrode 26 including the positive electrode layer 24, a separator 23, a negative electrode layer 27, a negative electrode current collector 28, and a negative electrode layer 27. Negative electrode 29 and separator 2 provided with
3, positive electrode layer 24, positive electrode current collector 25, and positive electrode 26 including positive electrode layer 24, separator 23, negative electrode layer 27, and negative electrode current collector 2
8 has a structure in which the negative electrode 29 having No. 8 is laminated in this order. A negative electrode current collector 28 is located on the outermost periphery of the electrode group 22. One end of the strip-shaped positive electrode lead 30 has the electrode group 22.
Connected to the positive electrode current collector 25 of which the other end is the storage container 21.
Has been extended from. On the other hand, the strip-shaped negative electrode lead 31 is
One end is connected to the negative electrode current collector 28 of the electrode group 22, and the other end is extended from the storage container 21.

[0161]

Embodiments of the present invention will now be described in detail with reference to the drawings.

Examples 1 to 26 As starting materials , LiOH.H ₂ O and Ni (OH)
₂ , oxides of element Me1, carbonates, nitrates, and NaO
A compound of each element including H, KOH, Ca (OH) ₂ , sodium sulfide (Na ₂ S.9H ₂ O) and a sulfuric acid compound (NiSO ₄ .6H ₂ O) as a sulfide compound is prepared, and these are prepared. From the compound powder of No. 1, the composition shown in Tables 1 and 2 below (Li _1.1 (Ni _0.88 Me1 _0.02 ) (O _1.9 X _0.1 ) + aA)
30% with a Henschel mixer after blending
A mixed powder was prepared by minute mixing. This mixed powder was put into an alumina sheath and fired. The firing was performed at 480 ° C. for 10 hours while flowing oxygen at 5 liters / minute, and then at 700 ° C. for 20 hours to obtain a positive electrode active material.

The composition analysis of the positive electrode active material was carried out by glow discharge mass spectrometry (GDMS).
etry). Here, with GDMS, in an Ar atmosphere of about 1 Torr, a voltage of several kV is applied to one electrode as a sample, the sample surface is sputtered by the formed glow discharge, and the generated sample ions are extracted from the aperture in the electrode. It is a method of accelerating and mass spectrometry. The content of each element constituting the composite oxide was determined by this glow discharge mass spectrometry, and the content of each element other than the element A was mol%.
By converting into, the desired chemical formula is obtained. The composition analysis of the positive electrode active materials obtained in the following examples is also performed by glow discharge mass spectrometry.

Polyvinylidene fluoride was added to N-methyl-2-
Lithium-containing composite oxide powder as a positive electrode active material, acetylene black as a conductive agent and artificial graphite were added to a solution dissolved in pyrrolidone and mixed with stirring to obtain 92.2% by weight of a positive electrode active material and 1.8 of acetylene black. weight%,
A positive electrode mixture containing 2.2% by weight of artificial graphite and 3.8% by weight of polyvinylidene fluoride was prepared. This positive electrode mixture was applied on both sides of an aluminum foil (thickness 20 μm), dried, and then pressure-molded using a roller press machine to produce a positive electrode.

<Preparation of Negative Electrode> Mesophase pitch carbon fibers made of mesophase pitch as a raw material were carbonized at 1000 ° C. in an argon atmosphere, and then the average fiber length was 30 μm.
After moderately pulverizing so that 90% by volume is present in an average fiber diameter of 11 μm and a particle size of 1 to 80 μm and the number of particles having a particle size of 0.5 μm or less is reduced (5% or less), 3000 ° C. in an argon atmosphere. A carbonaceous material was produced by graphitizing with.

Polyvinylidene fluoride was added to N-methyl-2-
The carbonaceous material and artificial graphite are added to a solution dissolved in pyrrolidone and mixed with stirring to form a negative electrode mixture having a mixture composition of 86.5% by weight carbonaceous material, 9.5% by weight artificial graphite, and 4% by weight polyvinylidene fluoride. The agent was prepared. Copper foil (thickness 1
5 μm) on both sides, dried and then pressure-molded with a roller press machine to prepare a negative electrode. On this occasion,
The filling density and the electrode length were adjusted so that the ratio (capacity balance) of the design capacity of the negative electrode to the design capacity of the positive electrode after molding was 1.03 or more and 1.1 or less.

<Preparation of Nonaqueous Electrolyte (Liquid Nonaqueous Electrolyte)>
Ethylene carbonate (EC) and methyl ethyl carbonate
(MEC) was mixed in a volume ratio of 1: 2
Lithium hexafluorophosphate (LiPF ₆) 1
A non-aqueous electrolyte was prepared by dissolving M.

<Assembly of Battery> After the positive electrode lead made of aluminum and the negative electrode lead made of nickel were welded to the positive electrode and the negative electrode, respectively, the positive electrode, the separator made of the polyethylene porous film and the negative electrode were respectively formed. The electrodes were laminated in order and spirally wound so that the negative electrode was located on the outside to prepare an electrode group.

This electrode group was housed in a cylindrical container with a bottom,
The negative electrode lead was welded to the bottom of the bottomed cylindrical container, and the positive electrode lead was welded to a safety valve disposed in the opening of the bottomed cylindrical container. Subsequently, 4 mL of a non-aqueous electrolytic solution was injected into the bottomed cylindrical container to sufficiently impregnate the electrode group with the non-aqueous electrolytic solution. Then, after arranging the positive electrode terminal on the safety valve, it was caulked and fixed. As described above, a cylindrical lithium ion secondary battery (18650 size) having a designed rated capacity of 1600 mAh was assembled.

Comparative Examples 1-9 As starting materials , LiOH.H ₂ O and Ni (OH)
₂ , oxides of element Me1, carbonates, nitrates, and NaO
A compound of each element including H, KOH, Ca (OH) ₂ , sodium sulfide (Na ₂ S.9H ₂ O) and a sulfuric acid compound (NiSO ₄ .6H ₂ O) as a sulfide compound is prepared, and these are prepared. A compound powder was selected from the compound powder of No. 1 so as to have the composition shown in Table 3 below, and after mixing, mixed powder was prepared by mixing with a Henschel mixer for 30 minutes. This mixed powder was put into an alumina sheath and fired. The firing was performed at 480 ° C. for 10 hours while flowing oxygen at 5 liters / minute, and then at 700 ° C. for 20 hours to obtain a positive electrode active material.

A cylindrical lithium ion secondary battery was manufactured in the same manner as described in Example 1 except that such a positive electrode active material was used.

<Nail Penetration Test> A nail penetration test was conducted on the obtained secondary batteries of Examples 1-26 and Comparative Examples 1-9. First, these secondary batteries were charged. Charging is
After carrying out up to 4.2V at a current value equivalent to 0.2C of the design rated capacity of each secondary battery, it was held at a constant voltage of 4.2V,
It went for a total of 8 hours. After charging to 4.2V, safety was examined by a nail penetration test. The nail used in the test had a diameter of 2 mm and a nail speed of 135 mm / s. The temperature rise of the battery in the nail penetration test was measured by a thermocouple attached to the outer surface of the battery. Tables 1 to 3 below show the presence or absence of rupture and ignition in the nail penetration test and the battery temperature in the nail penetration test.

<Initial Capacity and Charge / Discharge Cycle Life> With respect to the secondary batteries of Examples 1 to 26 and Comparative Examples 1 to 9, a charge / discharge cycle test was conducted at room temperature, and the discharge capacity at the first cycle (initial discharge capacity). And the reduction rate of the discharge capacity after 300 cycles was obtained, and the results are shown in Tables 1 to 3 below. Charging in the charge / discharge cycle test was performed for 5 hours in total by maintaining a constant voltage of 4.2V after performing up to 4.2V at a current value corresponding to the design rated capacity of 0.5C. Discharge is the same current value 2.
It went to 7V. A 30-minute rest time was provided for discharging and charging.

<High-rate discharge characteristic (discharge rate characteristic)
> With respect to the secondary batteries of Examples 1 to 26 and Comparative Examples 1 to 9, 4.2 V at a current corresponding to the design rated capacity of 0.5 C
After charging up to 4 hours, the battery was charged at a constant voltage of 4.2 V for a total of 5 hours. After 30 minutes, the battery was discharged to 2.7V with a current value corresponding to 5C. The discharge capacity at the time of 5C discharge is compared with the initial discharge capacity measured under the above-mentioned conditions, and the ratio (%) of the reduced capacity at the time of 5C discharge to the initial discharge capacity is determined by the high rate discharge characteristic (discharge rate characteristic).
And shown in Tables 1 to 3 below.

<Charge / Discharge Cycle Characteristics under High Current Discharge (High Rate Discharge) Conditions> Examples 1 to 26 and Comparative Examples 1 to 9
The secondary battery of No. 2 was charged up to 4.2 V at a current corresponding to the designed rated capacity of 0.5 C, and then held at a constant voltage of 4.2 V for a total of 5 hours of charging. Thirty
After a minute, the battery was discharged to 2.7 V with a current value corresponding to 5C.
The discharge capacity after repeating this charging / discharging 100 times was measured, and the ratio of the reduced capacity at the time of discharging after 100 cycles to the initial discharge capacity is shown as the high rate cycle characteristics in Tables 1 to 3 below.

[0176]

[Table 1]

[0177]

[Table 2]

[0178]

[Table 3]

As is clear from Tables 1 to 3, the secondary batteries of Examples 1 to 26 containing the composite oxide having the composition represented by the chemical formula (1) as the positive electrode active material were tested in the nail penetration test. There are no bursts and ignitions, the discharge capacity decrease rate after 300 cycles, the discharge capacity decrease rate during 5C discharge, and the discharge capacity decrease rate during a high rate cycle with a discharge rate of 5C are shown in Comparative Examples 1 to 9. It can be seen that it is smaller than that.

In particular, the secondary batteries of Examples 4 to 15 containing the positive electrode active material containing Na, K or S and having the content of each element within the range of 1000 to 2500 ppm are Compared with Nos. 16 to 18, the reduction rate of the discharge capacity during the high rate cycle could be reduced. Also, C
The secondary battery of Example 23 including the positive electrode active material containing a in an amount of 500 ppm or less was able to improve the high rate discharge characteristics and the high rate cycle characteristics as compared with Example 16.

On the other hand, containing Na, K or S,
The secondary batteries of Comparative Examples 1, 3 and 5 each including a positive electrode active material having a content of each element of 500 ppm, and Ca of 200 ppm
The secondary battery of Comparative Example 7 including the positive electrode active material contained contained 3
The discharge capacity decrease rate after 00 cycles, the discharge capacity decrease rate during 5C discharge, and the discharge capacity decrease rate during the high rate cycle with a discharge rate of 5C were all larger than those in Examples 1 to 26.

The lithium-containing composite oxide used in the secondary battery of Example 1 was observed by a transmission electron microscope. As a result, as shown in FIG. It was possible to confirm that Na metal was deposited in the hatched region).

Examples 27 to 49 As starting materials , LiOH.H ₂ O and Ni (OH)
₂ , oxides of element Me1, carbonates, nitrates, and NaO
H, KOH, Ca (OH) ₂ , sodium sulfide (Na ₂ S · 9H ₂ O) and sulfuric acid compound (NiSO ₄ · 6H ₂ O) as sulfide compounds, Si oxides, sulfides, and alkoxides , Compounds of each element including Fe oxides, sulfides, and alkoxides are prepared, and compositions of these compound powders are shown in Tables 4 to 5 below (Li _1.1 (Ni
_0.88 Me1 _0.02 ) (O _1.9 X _0.1 ) + aA + bB), and after mixing, mixed with a Henschel mixer for 30 minutes to prepare a mixed powder. This mixed powder was put into an alumina sheath and fired. The firing was carried out by holding 5 liters / minute of oxygen while keeping it at 480 ° C. for 10 hours,
It carried out at 700 degreeC for 20 hours, and obtained the positive electrode active material.

A cylindrical lithium ion secondary battery was manufactured in the same manner as described in Example 1 except that such a positive electrode active material was used.

Regarding the obtained secondary batteries of Examples 27 to 49, in the same manner as described in Example 1 above, the presence or absence of rupture or ignition in the nail penetration test, the battery temperature in the nail penetration test, and 1 Cycle discharge capacity (initial discharge capacity)
And the discharge capacity decrease rate after 300 cycles, the discharge capacity decrease rate during 5C discharge, and the discharge capacity decrease rate during a high rate cycle with a discharge rate of 5C, and the results are shown in Tables 4 to 5 below. .

[0186]

[Table 4]

[0187]

[Table 5]

As is clear from Tables 4 to 5, the secondary batteries of Examples 27 to 49 containing the composite oxide having the composition represented by the chemical formula (2) described above as the positive electrode active material were subjected to the nail penetration test. Comparative Examples 1 to 9 show the discharge rate reduction rate after 300 cycles without bursting and ignition, the discharge rate reduction rate during 5C discharge, and the discharge rate reduction rate during a high rate cycle with a discharge rate of 5C. You can see that it can be made smaller than that. Furthermore, the secondary batteries of Examples 27 to 49 were able to lower the battery temperature in the nail penetration test as compared to Examples 1 to 26.

In particular, the secondary batteries of Examples 30 to 38 containing the positive electrode active material containing Na, K or S and having the content of each element within the range of 1000 to 2500 ppm were evaluated as those of Examples 27 to 29, As compared with Nos. 39 to 41, the discharge capacity decrease rate during the high rate cycle could be reduced. In addition, the secondary batteries of Examples 42 to 46 including the positive electrode active material containing Ca in an amount of 500 ppm or less can improve the high rate discharge characteristics and the high rate cycle characteristics as compared with the secondary cells without Ca. It was

(Examples 50 to 69 and Comparative Example 10)
To 13) as a starting material, and _{LiOH · H 2 O, Ni (} OH)
₂ , Co (OH) ₂ , oxides, carbonates of element Me2,
Nitrate, NaOH, KOH, Ca (OH)
₂ and sodium sulfide as a sulfide compound (Na ₂ S.9H
And a ₂ O) and sulfuric acid compounds (NiSO ₄ · 6H ₂ O)
Compounds of each element were prepared, and the compositions of these compound powders are shown in Tables 6 to 7 below (Li _1.1 (Ni _0.70 Co _0.18 M
e2 _0.02 ) (O _1.9 X _0.1 ) + aA),
After mixing, mixed powder was prepared by mixing for 30 minutes with a Henschel mixer. This mixed powder was put into an alumina sheath and fired. Firing was performed by holding oxygen at a flow rate of 5 liters / minute for 10 hours at 480 ° C, and then at 700 ° C for 2 hours.
The operation was performed for 0 hours to obtain a positive electrode active material.

A cylindrical lithium ion secondary battery was manufactured in the same manner as described in Example 1 above, except that such a positive electrode active material was used.

Obtained Examples 50 to 69 and Comparative Example 10
For the secondary batteries of Nos. 13 to 13, in the same manner as described in Example 1 above, the presence or absence of rupture / ignition in the nail piercing test, the battery temperature in the nail piercing test, the discharge capacity at the first cycle (initial discharge capacity) ), The rate of decrease in discharge capacity after 300 cycles, the rate of decrease in discharge capacity during 5C discharge, and the rate of decrease in discharge capacity during high rate cycle with a discharge rate of 5C, and the results are shown in Tables 6 to 7 below. Show.

[0193]

[Table 6]

[0194]

[Table 7]

As is apparent from Tables 6 to 7, the secondary batteries of Examples 50 to 69 containing the composite oxide having the composition represented by the above chemical formula (3) as the positive electrode active material were subjected to the nail penetration test. Comparative Examples 1 to 13 show no rupture and ignition, a discharge capacity decrease rate after 300 cycles, a discharge capacity decrease rate during 5C discharge, and a discharge capacity decrease rate during a high rate cycle with a discharge rate of 5C. You can see that it can be made smaller than that.

In particular, Examples 51 to 53, 56, 58, and 60 containing a positive electrode active material containing Na, K, or S and containing each element in the range of 1000 to 2500 ppm.
The secondary battery has a content of each element of 1000 to 2500 p.
Example 50, 54, 57, 59, 61, 6 out of pm
Compared with No. 3, the rate of decrease in discharge capacity during the high rate cycle with a discharge rate of 5C could be reduced. Also,
The secondary battery of Example 64 including the positive electrode active material containing Ca in an amount of 500 ppm or less is the same as that of Example 53 in which Ca is not added.
It was possible to improve the high-rate discharge characteristics and high-rate cycle characteristics as compared with.

[0197] (Example 70 Example 89) starting material, and _{LiOH · H 2 O, Ni (} OH)
₂ , Co (OH) ₂ , oxides, carbonates of element Me2,
Nitrate, NaOH, KOH, Ca (OH)
₂ and sodium sulfide as a sulfide compound (Na ₂ S.9H
₂ O) and sulfuric acid compounds (NiSO ₄ .6H ₂ O), Si
Oxides, sulfides, alkoxides, and Fe oxides,
Compounds of each element including sulfides and alkoxides were prepared, and the compositions of these compound powders are shown in Tables 8 to 9 below (Li _1.1 (Ni _0.70 Co _0.18 Me2 _0.02 ) (O
_1.9 X _0.1 ) + aA + bB), and after mixing, mixed with a Henschel mixer for 30 minutes to prepare a mixed powder. This mixed powder was put into an alumina sheath and fired. The firing was performed at 480 ° C. for 10 hours while flowing oxygen at 5 liters / minute, and then at 700 ° C. for 20 hours to obtain a positive electrode active material.

A cylindrical lithium ion secondary battery was manufactured in the same manner as described in Example 1 above, except that such a positive electrode active material was used.

Regarding the obtained secondary batteries of Examples 70 to 89, in the same manner as described in Example 1 above, the presence or absence of rupture / ignition in the nail penetration test, the battery temperature in the nail penetration test, and 1 Cycle discharge capacity (initial discharge capacity)
And the discharge capacity decrease rate after 300 cycles, the discharge capacity decrease rate during 5C discharge, and the discharge capacity decrease rate during a high rate cycle with a discharge rate of 5C, and the results are shown in Tables 8 to 9 below. .

[0200]

[Table 8]

[0201]

[Table 9]

As is apparent from Tables 8 to 9, the secondary batteries of Examples 70 to 89 containing the composite oxide having the composition represented by the chemical formula (4) as the positive electrode active material were subjected to the nail penetration test. Comparative Examples 1 to 13 show no rupture and ignition, a discharge capacity decrease rate after 300 cycles, a discharge capacity decrease rate during 5C discharge, and a discharge capacity decrease rate during a high rate cycle with a discharge rate of 5C. You can see that it can be made smaller than that.

In particular, Examples 71, 72, 74, 76, 79 having a positive electrode active material containing Na, K or S and having the content of each element within the range of 1000 to 2500 ppm.
~ 81 secondary battery, the content of each element is 1000 ~ 25
Examples 70, 73, 77, 78, 8 deviating from 00 ppm
Compared with 3,85, the rate of decrease in discharge capacity during the high rate cycle with a discharge rate of 5C could be reduced.
Further, the secondary batteries of Examples 75, 82, 84, 86, 87 including the positive electrode active material containing Ca in an amount of 500 ppm or less can significantly improve both the high rate discharge characteristics and the high rate cycle characteristics. It was

[0204] (Example 90 Example 105) starting material and _{LiOH · H 2 O, Ni (} OH)
₂ , Co (OH) ₂ and oxides and carbonates of the element Me3,
Nitrate, NaOH, KOH, Ca (OH)
₂ and sodium sulfide as a sulfide compound (Na ₂ S.9H
And a ₂ O) and sulfuric acid compounds (NiSO ₄ · 6H ₂ O)
Compounds of each element were prepared, and the compositions of these compound powders are shown in Tables 10 to 11 below (Li _1.1 (Ni _0.70 Co
_0.18 Me3 _0.02 ) (O _1.9 X _0.1 ) + aA), and after mixing, mixed powder was prepared by mixing with a Henschel mixer for 30 minutes. This mixed powder was put into an alumina sheath and fired. Firing was performed by holding oxygen at a flow rate of 5 liters / minute at 480 ° C. for 10 hours and then 700
The positive electrode active material was obtained at 20 ° C. for 20 hours.

A cylindrical lithium ion secondary battery was manufactured in the same manner as described in Example 1 except that such a positive electrode active material was used.

Regarding the obtained secondary batteries of Examples 90 to 105, in the same manner as described in Example 1 above, the presence or absence of rupture / ignition in the nail penetration test, the battery temperature in the nail penetration test, and 1 Cycle discharge capacity (initial discharge capacity)
The discharge capacity decrease rate after 300 cycles, the discharge capacity decrease rate during 5C discharge, and the discharge capacity decrease rate during a high rate cycle with a discharge rate of 5C were obtained, and the results are shown in Tables 10 to 11 below. .

[0207]

[Table 10]

[0208]

[Table 11]

As is clear from Tables 10 to 11, the secondary batteries of Examples 90 to 105 containing the composite oxide having the composition represented by the chemical formula (5) as the positive electrode active material were subjected to the nail penetration test. No rupture or ignition, and 3
It can be seen that the discharge capacity decrease rate after 00 cycles, the discharge capacity decrease rate during 5C discharge, and the discharge capacity decrease rate during the high rate cycle with a discharge rate of 5C can be made smaller than in Comparative Examples 1 to 13.

In particular, the secondary batteries of Examples 91 to 93 and 95 which include the positive electrode active material containing Na, K or S, and the content of each element is within the range of 1000 to 2500 ppm, contain the respective elements. As compared with Examples 96 to 98 in which the amount deviates from 1000 to 2500 ppm, the reduction rate of the discharge capacity during the high rate cycle with the discharge rate of 5 C could be reduced. In addition, Examples 90, 94, 99, 10 provided with a positive electrode active material containing Ca in an amount of 500 ppm or less.
In the secondary batteries of Nos. 0, 103, and 105, both the capacity reduction rate during high rate discharge and the discharge capacity reduction rate during high rate cycle could be within 10%.

Examples 106 to 120 As starting materials , LiOH.H ₂ O and Ni (OH)
₂ , Co (OH) ₂ and oxides and carbonates of the element Me3,
Nitrate, NaOH, KOH, Ca (OH)
₂ and sodium sulfide as a sulfide compound (Na ₂ S.9H
₂ O) and sulfuric acid compounds (NiSO ₄ .6H ₂ O), Si
Oxides, sulfides, alkoxides, and Fe oxides,
Compounds of each element including sulfides and alkoxides are prepared, and the compositions of these compound powders are shown in Tables 12 to 13 below.
(Li _1.1 (Ni _0.70 Co _0.18 Me3 _0.02 ) (O _1.9
X _0.1 ) + aA + bB), and after mixing,
Mixed powder was prepared by mixing for 30 minutes with a Henschel mixer. This mixed powder was put into an alumina sheath and fired. The firing was performed at 480 ° C. for 10 hours while flowing oxygen at 5 liters / minute, and then at 700 ° C. for 20 hours to obtain a positive electrode active material.

A cylindrical lithium ion secondary battery was manufactured in the same manner as described in Example 1 except that such a positive electrode active material was used.

Regarding the obtained secondary batteries of Examples 106 to 120, in the same manner as described in Example 1 above, the presence or absence of rupture / ignition in the nail penetration test, the battery temperature in the nail penetration test, and 1 Discharge capacity at the cycle (initial discharge capacity), decrease rate of discharge capacity after 300 cycles, and 5C
The discharge capacity decrease rate during discharge and the discharge capacity decrease rate during a high rate cycle with a discharge rate of 5 C were determined, and the results are shown in Tables 12 to 13 below.

[0214]

[Table 12]

[0215]

[Table 13]

As is clear from Tables 12 to 13, the secondary batteries of Examples 106 to 120 containing the composite oxide having the composition represented by the chemical formula (6) as the positive electrode active material were subjected to the nail penetration test. No rupture or ignition, and
It can be seen that the discharge capacity decrease rate after 300 cycles, the discharge capacity decrease rate during 5C discharge, and the discharge capacity decrease rate during the high rate cycle with a discharge rate of 5C can be made smaller than those in Comparative Examples 1 to 13.

In particular, Examples 107, 108, 113, 11 having a positive electrode active material containing Na, K or S and having the content of each element within the range of 1000 to 2500 ppm.
In the secondary battery of No. 4, the content of each element is 1000 to 2500.
As compared with Examples 109, 111, and 112 that are out of ppm, the rate of decrease in discharge capacity during the high-rate cycle at a discharge rate of 5C could be reduced. Also, Ca is 50
The secondary batteries of Examples 106, 110, 115, 116 to 118 including the positive electrode active material contained in an amount of 0 ppm or less were able to make the capacity decrease rate during high rate discharge and high rate cycle within 10%. .

Example 121 <Production of Positive Electrode> Lithium-containing composite oxide powder 9 having the same composition as that described in Example 1 described above.
2.5% by weight of acetylene black, 3% by weight of graphite, 4% by weight of polyvinylidene fluoride (PVdF) and 1% by weight of N-methylpyrrolidone (NMP) solution were added and mixed to collect a 15 μm thick aluminum foil. The electrode density is 3.0 g /
A band-shaped positive electrode having a size of cm ³ was produced.

<Production of Negative Electrode> 94% by weight of powder of mesophase pitch carbon fiber (average particle diameter 25 μm, average fiber length 30 μm) heat-treated at 3000 ° C., 6% by weight of polyvinylidene fluoride (PVdF), and N-methyl Pyrrolidone (NMP) solution was added and mixed, applied to a copper foil with a thickness of 12 μm, dried and pressed to obtain an electrode density of 1.4.
A strip-shaped negative electrode of g / cm ³ was prepared.

<Production of Electrode Group> The positive electrode, thickness 16 μm
With a porosity of 50%, an air permeability of 200 seconds / 100 cm
^The separator made of the polyethylene porous film of ^3, the negative electrode, and the separator were laminated in this order, and then spirally wound. This was hot-pressed at 90 ° C. to prepare a flat electrode group having a width of 30 mm and a thickness of 3.0 mm. The obtained electrode group was stored in a laminate film pack having a thickness of 0.1 mm, which was composed of an aluminum foil having a thickness of 40 μm and a polypropylene layer formed on both surfaces of the aluminum foil, and was stored at 80 ° C. for 24 hours. It was vacuum dried for an hour.

<Preparation of non-aqueous electrolyte (liquid non-aqueous electrolyte)>
1.5 mol / L of lithium tetrafluoroborate (LiBF ₄ ) as an electrolyte in a mixed solvent (volume ratio 24: 75: 1) of ethylene carbonate (EC), γ-butyrolactone (BL) and vinylene carbonate (VC). A non-aqueous electrolyte was prepared by dissolving.

After injecting the non-aqueous electrolyte into the laminate film pack containing the electrode group, the laminate film pack is completely sealed by heat sealing,
A thin lithium ion secondary battery having the structure shown in FIGS. 2 and 3 and having a width of 35 mm, a thickness of 3.2 mm and a height of 65 mm was manufactured.

(Example 122) The above-mentioned Example 121 except that a lithium-containing composite oxide having the same composition as that described in Example 27 was used as the positive electrode active material.
A thin lithium-ion secondary battery was manufactured in the same manner as described above.

Example 123 The above-described Example 121 was repeated except that a lithium-containing composite oxide having the same composition as that described in Example 50 was used as the positive electrode active material.
A thin lithium-ion secondary battery was manufactured in the same manner as described above.

(Example 124) The above-mentioned Example 121 except that a lithium-containing composite oxide having the same composition as that described in the above-mentioned Example 70 was used as the positive electrode active material.
A thin lithium-ion secondary battery was manufactured in the same manner as described above.

(Example 125) The above-mentioned Example 121 except that a lithium-containing composite oxide having the same composition as that described in the above-mentioned Example 90 was used as the positive electrode active material.
A thin lithium-ion secondary battery was manufactured in the same manner as described above.

(Example 126) Example 126 described above except that a lithium-containing composite oxide having the same composition as that described in Example 106 was used as the positive electrode active material.
A thin lithium-ion secondary battery was manufactured in the same manner as described in 1.

<Nail Pricking Test> Obtained Examples 121 to 1
A nail penetration test was performed on 26 secondary batteries. First,
These secondary batteries were charged. Charging is 4.2V at a current value equivalent to 0.2C of the rated design capacity of each secondary battery.
After that, the voltage was maintained at a constant voltage of 4.2 V, and the operation was performed for a total of 8 hours. After charging to 4.2V, safety was examined by a nail penetration test. The nail used for the test has a diameter of 2 mm and a nail speed of 135 m.
It was m / s. The temperature rise of the battery in the nail penetration test was measured by a thermocouple attached to the outer surface of the battery. Table 14 below shows the presence or absence of rupture / ignition in the nail penetration test and the battery temperature in the nail penetration test.

<Discharge Capacity Reduction Rate after 300 Cycles> The secondary batteries of Examples 121 to 126 were subjected to a charge / discharge cycle test at room temperature to obtain the discharge capacity reduction rate after 300 cycles, and the results are shown below. It shows in Table 14. Charging in the charge / discharge cycle test was performed for 5 hours in total by maintaining a constant voltage of 4.2V after performing up to 4.2V at a current value corresponding to the design rated capacity of 0.5C. Discharge is the same current value 2.
It went to 7V. A 30-minute rest time was provided for discharging and charging.

<High-rate discharge characteristic (discharge rate characteristic)
> Regarding the secondary batteries of Examples 121 to 126, after charging up to 4.2V with a current corresponding to the designed rated capacity of 0.5C, the battery is held at a constant voltage of 4.2V, so that a total of 5 hours of charging is performed. went. After 30 minutes, the battery was discharged to 2.7V with a current value corresponding to 0.5C. The discharge capacity at this time is defined as the initial discharge capacity. Next, the battery was charged to 4.2 V with a current corresponding to the designed rated capacity of 0.5 C, and then held at a constant voltage of 4.2 V, whereby charging was performed for a total of 5 hours. Three
After 0 minutes, the battery was discharged to 2.7V with a current value corresponding to 5C. The discharge capacity at the time of 5C discharge is compared with the initial discharge capacity, and the ratio (%) of the reduced capacity at the time of 5C discharge to the initial discharge capacity is defined as a high rate discharge characteristic (discharge rate characteristic) and shown in Table 14 below.

<Charge / Discharge Cycle Characteristics under High-Current Discharge (High Rate Discharge) Conditions> The secondary batteries of Examples 121 to 126 were charged to 4.2 V with a current corresponding to the designed rated capacity of 0.5 C, and Charging was performed for a total of 5 hours by holding the battery at a constant voltage of 4.2V. 30 minutes later, 5
It was discharged to 2.7 V with a current value corresponding to C. After repeating this charging and discharging 100 times, the discharge capacity was measured and
The ratio of the reduced capacity at the time of discharge after the cycle to the initial discharge capacity is shown in Table 14 below as high rate cycle characteristics.

[0232]

[Table 14]

As is clear from Table 14, Examples 121 to 126 containing the lithium-containing composite oxide having the composition represented by the above chemical formulas (1) to (6) as an active material.
It can be seen that the thin secondary battery of No. 1 does not burst or ignite in the nail penetration test, can suppress the temperature rise, and is excellent in safety. Further, the thin secondary batteries of Examples 121 to 126 are
It can be seen that the charge / discharge cycle characteristics, the discharge rate characteristics, and the high rate cycle characteristics are excellent.

Since the lithium ion secondary battery shown in the above embodiment uses an organic solvent as an electrolytic solution, it is necessary to suppress rupture and ignition. In order to suppress the rupture and the ignition, it is preferable that the temperature rise of the battery is 150 ° C. or lower, preferably 110 ° C. or lower, though it depends on the kind of the organic solvent used in the electrolytic solution. If it exceeds 110 ° C, there is a possibility of rupture and ignition, and in the case of Examples 1-126, the battery temperature is 110 ° C or lower, and rupture and ignition have not occurred. On the other hand, in Comparative Examples 2, 4, 6, 8 to 12, the battery temperature rapidly increased to 400 ° C. or higher, leading to rupture and ignition.

In the above-mentioned embodiments, the examples applied to the cylindrical lithium ion secondary battery and the thin lithium ion secondary battery have been described. The lithium ion secondary battery according to the present invention has a cylindrical shape and The shape is not limited to a thin shape, but may be a rectangular shape, a button shape, etc. in addition to a cylindrical shape and a thin shape. A laminate film can be used as the exterior material instead of the metal can.

[0236]

As described in detail above, according to the present invention, a positive electrode active material capable of preventing rupture and ignition in a nail penetration test and improving high rate discharge characteristics (discharge rate characteristics). And, a lithium ion secondary battery including this positive electrode active material can be provided.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view showing a cylindrical lithium ion secondary battery as an example of the lithium ion secondary battery according to the present invention.

FIG. 2 is a cross-sectional view showing a thin lithium-ion secondary battery which is an example of the lithium-ion secondary battery according to the present invention.

FIG. 3 is a cross-sectional view showing a portion A of FIG.

FIG. 4 is a schematic diagram showing a crystal structure of a lithium-containing composite oxide contained in the lithium-ion secondary battery of Example 1.

[Explanation of symbols]

1 ... container, 2 ... insulator, 3 ... electrode group, 4 ... Positive electrode, 5 ... Separator, 6 ... Negative electrode.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hideo Iwasaki, 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa, Toshiba Research and Development Center, Inc. (72) Koichi Kubo, Komu-shi Toshiba-cho, Kawasaki-shi, Kanagawa No. 1 Toshiba Research & Development Center Co., Ltd. (56) Reference JP-A-11-345615 (JP, A) JP-A-2000-21402 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) ) H01M 4/58

Claims (10)

(57) [Claims] 1. A positive electrode active material comprising a composite oxide having a composition represented by the following chemical formula (1). Li _x (Ni _1-y Me1 _y ) (O _2-z X _z ) + A (1) where Me 1 is B, Mg, Al, Sc, Ti, V, C
r, Mn, Co, Cu, Zn, Ga, Y, Zr, Nb,
Mo, Tc, Ru, Sn, La, Hf, Ta, W, R
e, at least one element selected from the group consisting of Pb and Bi, X is at least one halogen element selected from the group consisting of F, Cl, Br and I,
The molar ratios x, y and z are 0.02 ≦ x ≦ 1.
3, 0.005 ≦ y ≦ 0.5, 0.01 ≦ z ≦ 0.5, A contains at least one element selected from the group consisting of Na, K and S, and the composite oxide N in
The a content, K content, and S content are each 600 p
It is in the range of pm or more and 3000 ppm or less. 2. A positive electrode active material containing a composite oxide having a composition represented by the following chemical formula (2). Li _x (Ni _1-y Me1 _y ) (O _2-z X _z ) + A + bB (2) where Me 1 is B, Mg, Al, Sc, Ti, V, C
r, Mn, Co, Cu, Zn, Ga, Y, Zr, Nb,
Mo, Tc, Ru, Sn, La, Hf, Ta, W, R
e, at least one element selected from the group consisting of Pb and Bi, X is at least one halogen element selected from the group consisting of F, Cl, Br and I,
The molar ratios x, y and z are 0.02 ≦ x ≦ 1.
3, 0.005 ≦ y ≦ 0.5, 0.01 ≦ z ≦ 0.5, A contains at least one element selected from the group consisting of Na, K and S, and the composite oxide N in
The a content, K content, and S content are each 600 p
Within the range of pm or more and 3000 ppm or less, B is S
The composite oxide contains at least one element selected from the group consisting of i and Fe, and the content b of B in the composite oxide is in the range of 20 ppm to 500 ppm. 3. A positive electrode active material containing a composite oxide having a composition represented by the following chemical formula (3). Li _x (Ni _1-vs Co _v Me2 _s ) (O _2-z X _z ) + A (3) where Me 2 is B, Mg, Al, Sc, Ti, V, C
r, Mn, Cu, Zn, Ga, Y, Zr, Nb, Mo,
Tc, Ru, Sn, La, Hf, Ta, W, Re, Pb
And Bi at least one element selected from the group consisting of F, Cl, Br and I, and X is at least one halogen element selected from the group consisting of F, Cl, Br and I, and the molar ratios x, v, s and z are , 0.02 ≦ x ≦ 1.
3, 0.005 ≦ v ≦ 0.5, 0.005 ≦ s ≦ 0.
5, 0.01 ≦ z ≦ 0.5, A contains at least one element selected from the group consisting of Na, K and S, and Na content, K content in the composite oxide, S content is 600 ppm or more and 3000 ppm, respectively
It is within the following range. 4. A positive electrode active material comprising a composite oxide having a composition represented by the following chemical formula (4). Li _x (Ni _1-vs Co _v Me2 _s ) (O _2-z X _z ) + A + bB (4) where Me 2 is B, Mg, Al, Sc, Ti, V, C
r, Mn, Cu, Zn, Ga, Y, Zr, Nb, Mo,
Tc, Ru, Sn, La, Hf, Ta, W, Re, Pb
And Bi at least one element selected from the group consisting of F, Cl, Br and I, and X is at least one halogen element selected from the group consisting of F, Cl, Br and I, and the molar ratios x, v, s and z are , 0.02 ≦ x ≦ 1.
3, 0.005 ≦ v ≦ 0.5, 0.005 ≦ s ≦ 0.
5, 0.01 ≦ z ≦ 0.5, A contains at least one element selected from the group consisting of Na, K and S, and Na content, K content in the composite oxide, S content is 600 ppm or more and 3000 ppm, respectively
Within the following range, B contains at least one element selected from the group consisting of Si and Fe, and the content b of B in the composite oxide is 20 ppm or more and 500 p.
It is within the range of pm or less. 5. The positive electrode active material according to claim 2, wherein the content b of B in the composite oxide is in the range of 20 ppm or more and 250 ppm or less. 6. The positive electrode according to claim 1, wherein the element A further contains Ca, and the Ca content in the composite oxide is within a range of 500 ppm or less. Active material. 7. The element A is Ca, Na and S, or Na
7. The positive electrode active material according to claim 6, wherein the cathode active material contains Ca and S or S and Ca. 8. The Na content, K content, and S content in the composite oxide are 1000 ppm or more and 25, respectively.
The positive electrode active material according to any one of claims 1 to 7, which is in a range of 00 ppm or less. 9. The positive electrode according to claim 1, wherein at least a part of the element A is deposited at a triple point existing at a boundary between crystal grains of the composite oxide. Active material. 10. A lithium ion secondary battery comprising a positive electrode containing the positive electrode active material according to claim 1, a negative electrode, and a non-aqueous electrolyte.