JP2002216759A - Lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery which has a stable crystal structure of an active material, and has high safety without burst ignition in nailing test, and has a long life. SOLUTION: In a lithium ion secondary battery equipped with a positive electrode 4 including an active material, an negative electrode 6, and a nonaqueous electrolyte, the active material includes a compound oxide having a composition which is expressed in the chemical formula: Lix(Nil-y-vCovMely) (O2-zXz). Here, Mel is at least one kind of element selected from a group of Cr, Hf and W, and X is at least one kind of halogen elements selected from a group of F, Cl, Br and I, and mole ratios x, y, z and v are given as 0.02<=x<=1.3, 0.005<=y<=0.3, 0.01<=z<=0.5, and 0.005<=v<=0.5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium ion secondary battery provided with a positive electrode active material containing a nickel oxide containing lithium.

[0002]

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

As such a secondary battery, a lithium ion secondary battery using a material capable of occluding and releasing lithium ions, such as a carbon material, as a negative electrode material has been developed and has been put to practical use as a power source for small electronic devices. The demand for this secondary battery is increasing because it is smaller and lighter than conventional lead storage batteries and nickel-cadmium batteries and has a high energy density.

As a positive electrode active material of this lithium ion secondary battery, a lithium-containing cobalt oxide (LiCoO ₂ ) having a high discharge potential and a high energy density has been put to practical use. However, cobalt, which is a raw material for this composite oxide, is scarce as a resource and is ubiquitous in countries where commercially available mineral deposits are scattered in a few countries. It is accompanied by supply anxiety.

[0005] Therefore, researches on positive electrode active materials other than lithium-containing cobalt oxides have been actively conducted in recent years. As an example, various compounds have been reported as composite oxides of lithium and manganese synthesized from various manganese raw materials and lithium raw materials. Specifically, a lithium manganese composite oxide represented by LiMn ₂ O ₄ having a spinel-type crystal structure has a potential of 3 V with respect to lithium due to 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 disadvantage that the capacity is significantly deteriorated when used in an environment at room temperature or higher. This is because manganese oxide and lithium manganese composite oxide are destabilized by high temperature, and Mn is eluted in the non-aqueous electrolyte. Particularly in recent years, large-sized lithium ion secondary batteries for electric vehicles or road leveling have been developed in various fields. In this large-sized lithium ion secondary battery, heat generation during use cannot be ignored as the battery becomes larger, and the inside of the battery tends to become relatively high even when the ambient environmental temperature is around room temperature. In addition, even a relatively small battery used for a small portable device or the like may be used in a high-temperature environment such as a cabin of a car in the middle of summer, and the temperature inside the battery may be relatively high. is there. From such a problem, it is very difficult to put a positive electrode active material using manganese as a raw material into practical use.

[0007] By the way, nickel composite oxides have been actively studied as post-cobalt composite oxides. 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. Therefore, it is a very promising cathode active material. However, since the crystal structure of LiNiO ₂ is unstable, the initial discharge capacity in the charge / discharge cycle test decreases significantly with the number of times of charge / discharge,
In a nail penetration test of a lithium ion secondary battery manufactured using LiNiO ₂ , there is a problem in safety leading to rupture and ignition.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a lithium ion secondary battery having a stable active material crystal structure, no bursting and firing even in a nail penetration test, high safety and a long life. It is something to offer.

[0009]

The first lithium ion secondary battery according to the present invention comprises a positive electrode containing an active material, a negative electrode,
In a lithium ion secondary battery including a nonaqueous electrolyte, the active material includes a composite oxide having a composition represented by the following chemical formula (1).

[0010] _{Li x (Ni 1-yv Co} v Me1 y) (O 2-z X z) (1) where said Me1 is, Cr, at least one element selected from the group consisting of Hf and W , The X is F, C
at least one halogen element selected from the group consisting of l, Br and I, wherein the molar ratios x, y, z and v are 0.0
2 ≦ x ≦ 1.3, 0.005 ≦ y ≦ 0.3, 0.01 ≦
z ≦ 0.5 and 0.005 ≦ v ≦ 0.5, respectively.

[0011] A second lithium ion secondary battery according to the present invention is a lithium ion secondary battery comprising a positive electrode containing an active material, a negative electrode, and a non-aqueous electrolyte.
It is characterized by containing a composite oxide having a composition represented by the following chemical formula (2).

[0012] _{Li x (Ni 1-yuv Co} v Me1 y Me2 u) (O 2-z X z) (2) where said Me1 is, Cr, at least one selected from the group consisting of Hf and W In the element, the Me2 is Ti,
At least one element selected from the group consisting of V, Zr, Nb, Mo and Ta, wherein X is F, Cl, B
at least one halogen element selected from the group consisting of r and I, wherein the molar ratios x, y, z, v and u are 0.02
≦ x ≦ 1.3, 0.005 ≦ y ≦ 0.3, 0.01 ≦ z
≤0.5, 0.005≤v≤0.5, and 0 <u≤0.3, respectively.

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

[0014] _{Li x (Ni 1-vst Co} v V s Me3 t) (O 2-z X z) (3) where the Me3 is, Cr, Zr, Nb, Mo , Hf, T
X is at least one kind of element selected from the group consisting of F, Cl, Br and I, and is at least one kind of element selected from the group consisting of a and W, and has a molar ratio of x, v, s, t and z are 0.02 ≦ x ≦ 1.3, 0.0
05 ≦ v ≦ 0.5, 0.005 ≦ s ≦ 0.3, 0 <t ≦
0.3 and 0.01 ≦ z ≦ 0.5, respectively.

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

Li _x (Ni _{1 -y} Me1 _y ) (O ₂ -z X _z ) (4) wherein Me 1 is at least one element selected from the group consisting of Cr, Hf and W; X is F, C
at least one halogen element selected from the group consisting of l, Br and I, wherein the molar ratios x, y and z are 0.02 ≦
x ≦ 1.3, 0.005 ≦ y ≦ 0.3, 0.01 ≦ z ≦
0.5 is indicated respectively.

A fifth lithium ion secondary battery according to the present invention is a lithium ion secondary battery comprising a positive electrode containing an active material, a negative electrode, and a non-aqueous electrolyte, wherein the active material comprises:
It is characterized by including a composite oxide having a composition represented by the following chemical formula (5).

Li _x (Ni _{1 -yu} Me _{1 y} Me _{2 u} ) (O ₂ -z X _z ) (5) wherein Me 1 is at least one element selected from the group consisting of Cr, Hf and W , The Me2 is Ti,
At least one element selected from the group consisting of V, Zr, Nb, Mo and Ta, wherein X is F, Cl, B
at least one halogen element selected from the group consisting of r and I, wherein the molar ratios x, y, u and z are 0.02 ≦ x
≦ 1.3, 0.005 ≦ y ≦ 0.3, 0 <u ≦ 0.3,
0.01 ≦ z ≦ 0.5, respectively.

A sixth lithium ion secondary battery according to the present invention is a lithium ion secondary battery including a positive electrode containing an active material, a negative electrode, and a non-aqueous electrolyte.
It is characterized by including a composite oxide having a composition represented by the following chemical formula (6).

Li _x (Ni _1-st V _s Me3 _t ) (O ₂ -z X _z ) (6) where Me 3 is Cr, Zr, Nb, Mo, Hf, T
X is at least one element selected from the group consisting of a and W, and X is at least one type of halogen element selected from the group consisting of F, Cl, Br and I, and has a molar ratio of x, s, t and z is 0.02 ≦ x ≦ 1.3, 0.005
≦ s ≦ 0.3, 0.005 ≦ t ≦ 0.3, 0.01 ≦ z
≤0.5 is indicated.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A lithium ion secondary battery according to the present invention includes 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 to be described later.
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 electrolyte) prepared by dissolving an electrolyte in a non-aqueous solvent, and a non-aqueous solvent and an electrolyte held in a polymer material Examples thereof include a polymer gel nonaqueous electrolyte, a solid polymer electrolyte mainly composed of an electrolyte, and an inorganic solid nonaqueous electrolyte having lithium ion conductivity. As the non-aqueous solvent and the electrolyte contained in each non-aqueous electrolyte, those described in a liquid non-aqueous electrolyte described later can be used.

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

Hereinafter, an example of the lithium ion secondary battery according to the present invention will be described.

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 a liquid non-aqueous electrolyte impregnated in at least the separator.

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

1) Positive electrode This positive electrode has a current collector and a positive electrode layer supported on the current collector and containing at least one of the first to sixth positive electrode active materials.

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

[0029] _{Li x (Ni 1-yv Co} v Me1 y) (O 2-z X z) (1) where said Me1 is, Cr, at least one element selected from the group consisting of Hf and W , The X is F, C
at least one halogen element selected from the group consisting of l, Br and I, wherein the molar ratios x, y, z and v are 0.0
2 ≦ x ≦ 1.3, 0.005 ≦ y ≦ 0.3, 0.01 ≦
z ≦ 0.5 and 0.005 ≦ v ≦ 0.5, respectively.

The molar ratio x of Li will be described. If the molar ratio x is less than 0.02, the crystal structure of the composite oxide becomes extremely unstable, so that the cycle characteristics of the secondary battery are deteriorated and the safety is reduced. On the other hand, when the molar ratio x is 1.
If it exceeds 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 Me1 will be described. If the molar ratio y is less than 0.005, it becomes difficult to improve the safety of the secondary battery. On the other hand, when the molar ratio y exceeds 0.3, the charge / discharge cycle characteristics and the discharge capacity are significantly reduced. A more preferable range of the molar ratio y is 0.01 ≦ y
≦ 0.25. Further, among the elements Me1, Cr is preferable.

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 charge / discharge cycle characteristics and safety of the secondary battery. On the other hand, when the molar ratio z exceeds 0.5, the discharge capacity is significantly reduced. A more preferred range of the molar ratio z is 0.1.
02 ≦ z ≦ 0.3. The halogen element X is represented by F
It is preferred that

The molar ratio v of Co will be described. When the molar ratio v is less than 0.005, it is difficult to improve the safety of the secondary battery. On the other hand, when the molar ratio y exceeds 0.5, the charge / discharge cycle characteristics and the discharge capacity are significantly reduced. A more preferred range of the molar ratio v is 0.01 ≦ v
≤ 0.35.

One of the preferable compositions of the composite oxide is that the halogen element X is F, and the molar ratios x, y, z and v are 0.05 ≦ x ≦ 1.2, 0.01 ≦ y ≦ 0.25,
It is represented by 0.02 ≦ z ≦ 0.3 and 0.01 ≦ v ≦ 0.35. A secondary battery provided with a positive electrode containing the composite oxide having such a composition can further improve safety and cycle life.

The composite oxide is produced, for example, by a solid phase method, a coprecipitation method or a hydrothermal synthesis method. When synthesized by a coprecipitation method or a hydrothermal synthesis method, the uniformity of the composition can be improved, and a layer containing a Li atom, a layer containing Ni, Co and Me1, and a layer containing a halogen atom and an oxygen atom such as F can be obtained. Can be arranged regularly, so that the charge / discharge capacity, cycle characteristics and safety can be further improved. In particular, when the composite oxide is synthesized by hydrothermal synthesis, the characteristics can be greatly improved as compared with the solid phase method.

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

[0037] _{Li x (Ni 1-yuv Co} v Me1 y Me2 u) (O 2-z X z) (2) where said Me1 is, Cr, at least one selected from the group consisting of Hf and W In the element, the Me2 is Ti,
At least one element selected from the group consisting of V, Zr, Nb, Mo and Ta, wherein X is F, Cl, B
at least one halogen element selected from the group consisting of r and I, wherein the molar ratios x, y, z, v and u are 0.02
≦ x ≦ 1.3, 0.005 ≦ y ≦ 0.3, 0.01 ≦ z
≤0.5, 0.005≤v≤0.5, and 0 <u≤0.3, respectively.

The reason why the molar ratio x of Li is set in the above range is for the same reason as described in the first positive electrode active material. A more preferred range of the molar ratio x is:
0.05 ≦ x ≦ 1.2.

The reason why the molar ratio y of the element Me1 is defined in the above range is for the same reason as described in the first positive electrode active material. A more preferable range of the molar ratio y is 0.01 ≦ y ≦ 0.25. Further, among the elements Me1, Cr is preferable.

The molar ratio u of the element Me2 will be described. When the molar ratio u exceeds 0.3, the charge / discharge cycle characteristics and the discharge capacity are significantly reduced. Further, the molar ratio u is 0.00
If the ratio is less than 5, it may be difficult to sufficiently improve the safety of the secondary battery.
It is desirable to be 005 or more and 0.3 or less. A more preferable range of the molar ratio u is 0.01 ≦ u ≦ 0.25. Further, among the elements Me2, Nb and Ta are preferable.

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

The reason why the molar ratio v of Co is defined in the above range is for the same reason as described in the first positive electrode active material. A more preferred range of the molar ratio v is
0.01 ≦ v ≦ 0.35.

One of the preferable compositions of the composite oxide is that the halogen element X is F and the molar ratio x, y, z, v
And u is 0.05 ≦ x ≦ 1.2, 0.01 ≦ y ≦ 0.2
5, 0.02 ≦ z ≦ 0.3, 0.01 ≦ v ≦ 0.35,
It is represented by 0.01 ≦ u ≦ 0.25. A secondary battery provided with a positive electrode containing a composite oxide having such a composition,
Safety and cycle life can be further improved.

The composite oxide is produced by, for example, a solid phase method, a coprecipitation method or a hydrothermal synthesis method. When synthesized by a coprecipitation method or a hydrothermal synthesis method, uniformity of the composition can be improved, and a Li layer, a layer containing Ni, Co, Me1, and Me2, and a halogen atom and an oxygen atom such as F can be formed. Since the layers including the layers can be regularly arranged, the charge / discharge capacity, cycle characteristics, and safety can be further improved. In particular, when the composite oxide is synthesized by hydrothermal synthesis, the characteristics can be greatly improved as compared with the solid phase method.

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

[0046] _{Li x (Ni 1-vst Co} v V s Me3 t) (O 2-z X z) (3) where the Me3 is, Cr, Zr, Nb, Mo , Hf, T
X is at least one kind of element selected from the group consisting of F, Cl, Br and I, and is at least one kind of element selected from the group consisting of a and W, and has a molar ratio of x, v, s, t and z are 0.02 ≦ x ≦ 1.3, 0.0
05 ≦ v ≦ 0.5, 0.005 ≦ s ≦ 0.3, 0 <t ≦
0.3 and 0.01 ≦ z ≦ 0.5, respectively.

The reason why the molar ratio x of Li is defined in the above range is for the same reason as described in the first positive electrode active material. A more preferred range of the molar ratio x is:
0.05 ≦ x ≦ 1.2.

The reason why the molar ratio v of Co is defined in the above range is for the same reason as described in the first positive electrode active material. A more preferred range of the molar ratio v is
0.01 ≦ v ≦ 0.35.

The molar ratio s of V will be described. Molar ratio s
Is less than 0.005, it is difficult to improve the safety of the secondary battery. On the other hand, when the molar ratio s exceeds 0.3, the charge / discharge cycle characteristics and the discharge capacity are significantly reduced. A more preferred range of the molar ratio s is 0.01 ≦ s ≦
0.25.

The molar ratio t of the element Me3 will be described. When the molar ratio t exceeds 0.3, the charge / discharge cycle characteristics and the discharge capacity are significantly reduced. Further, the molar ratio t is 0.00
If the ratio is less than 5, it may be difficult to sufficiently improve the safety of the secondary battery.
It is desirable to be 005 or more and 0.3 or less. A more preferred range of the molar ratio t is 0.01 ≦ t ≦ 0.25. Further, among the elements Me3, Nb and Ta are preferable.

The reason why the molar ratio z of the halogen element X is defined in the above range is for the same reason as described for the first positive electrode active material. A more preferable range of the molar ratio z is 0.02 ≦ z ≦ 0.3. 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 ratio x, v, s, t
And z are 0.05 ≦ x ≦ 1.2, 0.01 ≦ v ≦ 0.3
5, 0.01 ≦ s ≦ 0.25, 0.01 ≦ t ≦ 0.2
5, 0.02 ≦ z ≦ 0.3. A secondary battery provided with a positive electrode containing the composite oxide having such a composition can further improve safety and cycle life.

The composite oxide is prepared, for example, by a solid phase method, a coprecipitation method or a hydrothermal synthesis method. When synthesized by a coprecipitation method or a hydrothermal synthesis method, uniformity of the composition can be improved, and a Li layer, a layer containing Ni, Co, V, and Me3, and a halogen atom and an oxygen atom such as F are formed. Since the layers including the layers can be regularly arranged, the charge / discharge capacity, cycle characteristics, and safety can be further improved. In particular, when the composite oxide is synthesized by hydrothermal synthesis, the characteristics can be greatly improved as compared with the solid phase method.

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

Li _x (Ni _{1 -y} Me1 _y ) (O ₂ -z X _z ) (4) wherein Me 1 is at least one element selected from the group consisting of Cr, Hf and W; X is F, C
at least one halogen element selected from the group consisting of l, Br and I, wherein the molar ratios x, y and z are 0.02 ≦
x ≦ 1.3, 0.005 ≦ y ≦ 0.3, 0.01 ≦ z ≦
0.5 is indicated respectively.

The reason why the molar ratio x of Li is defined in the above range is for the same reason as described in the first positive electrode active material. A more preferred 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 described in the first positive electrode active material. A more preferable range of the molar ratio y is 0.01 ≦ y ≦ 0.25. Further, among the elements Me1, Cr is preferable.

The reason why the molar ratio z of the halogen element X is defined in the above range is for the same reason as described in the first positive electrode active material. A more preferable range of the molar ratio z is 0.02 ≦ z ≦ 0.3. 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, 0.01 ≦ y ≦ 0. .25,
0.02 ≦ z ≦ 0.3. A secondary battery provided with a positive electrode containing the composite oxide having such a composition can further improve safety and cycle life.

The composite oxide is produced by, for example, a solid phase method, a coprecipitation method or a hydrothermal synthesis method. When synthesized by a coprecipitation method or a hydrothermal synthesis method, uniformity of composition can be improved, and a Li layer, a layer containing Ni and Me1,
And a layer containing a halogen atom and an oxygen atom as described above can be regularly arranged, so that the charge / discharge capacity, cycle characteristics and safety can be further improved. In particular, when the composite oxide is synthesized by hydrothermal synthesis, the characteristics can be greatly improved as compared with the solid phase method.

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

Li _x (Ni _{1 -yu} Me _{1 y} Me _{2 u} ) (O ₂ -z X _z ) (5) where Me 1 is at least one element selected from the group consisting of Cr, Hf and W , The Me2 is Ti,
At least one element selected from the group consisting of V, Zr, Nb, Mo and Ta, wherein X is F, Cl, B
at least one halogen element selected from the group consisting of r and I, wherein the molar ratios x, y, u and z are 0.02 ≦ x
≦ 1.3, 0.005 ≦ y ≦ 0.3, 0 <u ≦ 0.3,
0.01 ≦ z ≦ 0.5, respectively.

The reason why the molar ratio x of Li is defined in the above range is for the same reason as described for the first positive electrode active material. A more preferred range of the molar ratio x is:
0.05 ≦ x ≦ 1.2.

The reason why the molar ratio y of the element Me1 is specified in the above range is for the same reason as described in the first positive electrode active material. A more preferable range of the molar ratio y is 0.01 ≦ y ≦ 0.25. Further, among the elements Me1, Cr is preferable.

The reason that the molar ratio u of the element Me2 is defined in the above range is for the same reason as described in the second positive electrode active material. The more preferable range of the molar ratio u is 0.005 ≦ u ≦ 0.3, and the more preferable range is 0.1.
01 ≦ u ≦ 0.25. Also, among the elements Me2,
Nb and Ta are preferred.

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

One of the preferred compositions of the composite oxide is that the halogen element X is F and the molar ratio x, y, u
And z are 0.05 ≦ x ≦ 1.2, 0.01 ≦ y ≦ 0.2
5, 0.01 ≦ u ≦ 0.25, 0.02 ≦ z ≦ 0.3. A secondary battery provided with a positive electrode containing the composite oxide having such a composition can further improve safety and cycle life.

The composite oxide is produced, for example, by a solid phase method, a coprecipitation method or a hydrothermal synthesis method. When synthesized by a coprecipitation method or a hydrothermal synthesis method, the uniformity of the composition can be improved, and a layer containing a Li atom, a layer containing Ni, Me1 and Me2, and a layer containing a halogen atom and an oxygen atom such as F can be obtained. Can be arranged regularly, so that the charge / discharge capacity, cycle characteristics and safety can be further improved. In particular, when the composite oxide is synthesized by hydrothermal synthesis, the characteristics can be greatly improved as compared with the solid phase method.

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

Li _x (Ni _1-st V _s Me3 _t ) (O ₂ -z X _z ) (6) where Me 3 is Cr, Zr, Nb, Mo, Hf, T
X is at least one element selected from the group consisting of a and W, and X is at least one type of halogen element selected from the group consisting of F, Cl, Br and I, and has a molar ratio of x, s, t and z is 0.02 ≦ x ≦ 1.3, 0.005
≦ s ≦ 0.3, 0.005 ≦ t ≦ 0.3, 0.01 ≦ z
≤0.5 is indicated.

The reason why the molar ratio x of Li is set in the above range is for the same reason as described for the first positive electrode active material. A more preferred range of the molar ratio x is:
0.05 ≦ x ≦ 1.2.

The molar ratio s of V will be described. Molar ratio s
Is less than 0.005, it is difficult to improve the safety of the secondary battery. On the other hand, when the molar ratio s exceeds 0.3, the charge / discharge cycle characteristics and the discharge capacity are significantly reduced. A more preferred range of the molar ratio s is 0.01 ≦ s ≦
0.25.

The molar ratio t of the element Me3 will be described. If the molar ratio t is less than 0.005, it becomes difficult to improve the safety of the secondary battery. On the other hand, when the molar ratio t is 0.3
If it exceeds, the charge / discharge cycle characteristics and the discharge capacity are significantly reduced. A more preferred range of the molar ratio t is 0.01
≦ t ≦ 0.25. Also, among the elements Me3, N
b and Ta are preferred.

The reason why the molar ratio z of the halogen element X is defined in the above range is for the same reason as described in the first positive electrode active material. A more preferable range of the molar ratio z is 0.02 ≦ z ≦ 0.3. 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 ratio x, s, t
And z are 0.05 ≦ x ≦ 1.2, 0.01 ≦ s ≦ 0.2
5, 0.01 ≦ t ≦ 0.25 and 0.02 ≦ z ≦ 0.3. A secondary battery provided with a positive electrode containing the composite oxide having such a composition can further improve safety and cycle life.

The composite oxide is produced by, for example, a solid phase method, a coprecipitation method or a hydrothermal synthesis method. When synthesized by a coprecipitation method or a hydrothermal synthesis method, the uniformity of the composition can be improved, and a layer containing Li atoms, a layer containing Ni, V and Me3, and a layer containing halogen atoms and oxygen atoms such as F can be obtained. Can be arranged regularly, so that the charge / discharge capacity, cycle characteristics and safety can be further improved. In particular, when the composite oxide is synthesized by hydrothermal synthesis, the characteristics can be greatly improved as compared with the solid phase method.

The first to sixth positive electrode active materials are listed in the order of excellent safety and cycle characteristics. First positive electrode active material> second positive electrode active material> third positive electrode active material Positive electrode active material> Sixth positive electrode active material> Fourth and fifth positive electrode active materials.

The positive electrode is manufactured by, for example, mixing at least one of the first to sixth positive electrode active materials, 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 an appropriate 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 ranges from 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 preferable. As the current collector, a conductive substrate having a porous structure or a non-porous conductive substrate can be used. Examples of the material constituting the current collector include aluminum, stainless steel, and nickel.

2) Separator As the separator, for example, a synthetic resin nonwoven 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 (undoping) lithium.

Examples of such a material include lithium metal, a Li-containing alloy capable of inserting and extracting lithium, a metal oxide capable of inserting and extracting lithium, and an oxide storing and releasing lithium. Metal sulfides, metal nitrides capable of storing and releasing lithium, chalcogen compounds capable of storing and releasing lithium, and carbon materials capable of storing and releasing lithium ions. it can. In particular, 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 occludes / releases lithium ions include coke, carbon fiber, pyrolytic gas phase carbon material, graphite, resin fired body, mesophase pitch-based carbon fiber, mesophase pitch spherical carbon, and the like. Can be. Carbon materials of the type described above 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 capacity of the negative electrode is increased although the battery voltage is reduced, 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. You.

In this case, examples of the binder include 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 to be within the range. Further, as the current collector, for example, a conductive substrate of aluminum, 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 and chain carbonates (eg, ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, etc.), cyclic ethers and chain ethers (eg, , 2−
Dimethoxyethane, 2-methyltetrahydrofuran, etc.), cyclic ester or chain ester (for example, γ-butyrolactone, γ-valerolactone, σ-valerolactone, methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, methyl propionate, propion) Ethylate, propyl propionate, etc.). The non-aqueous solvent includes one or two selected from the types described above.
Up to five types of mixed solvents can be used, but the present invention is not necessarily limited to these.

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

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

One 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. FIG. 2 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. 2.

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

The container 1 contains a non-aqueous electrolyte. A PTC element 7 having an opening in the center,
A safety valve 8 disposed on the TC element 7 and a hat-shaped positive terminal 9 disposed on the safety valve 8 are caulked and fixed to an upper opening of the container 1 via an insulating gasket 10. The positive electrode terminal 9 has a built-in safety mechanism serving as a gas vent hole (not shown). One end of a positive electrode lead 11 is connected to the positive electrode 4 and the other end is connected to the PTC element 7.
Connected to each other. The negative electrode 6 is connected to the container 1 as a negative terminal via a negative lead (not shown).

As shown in FIG. 2, an electrode group 22 is housed in a housing 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 one or both surfaces of a metal layer are covered with a resin layer such as a thermoplastic resin. 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. The laminate includes, from the lower side in FIG. 3, a separator 23, a positive electrode 26 including a positive electrode layer 24, a positive electrode current collector 25, and a 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 provided with the separator 2
3, positive electrode layer 24, positive electrode current collector 25, positive electrode 26 including positive electrode layer 24, separator 23, negative electrode layer 27, and negative electrode current collector 2
A negative electrode 29 provided with a negative electrode 8 is laminated in this order. A negative electrode current collector 28 is located at the outermost periphery of the electrode group 22. One end of the strip-shaped positive electrode lead 30 is
Is connected to the positive electrode current collector 25 of the
Has been extended from. On the other hand, the strip-shaped negative electrode lead 31
One end is connected to the negative electrode current collector 28 of the electrode group 22, and the other end extends from the storage container 21.

The lithium ion secondary battery according to the present invention described above comprises a positive electrode containing at least one of the above-described first to sixth positive electrode active materials, a negative electrode, and a nonaqueous electrolyte. Prepare. According to such a secondary battery, while maintaining excellent cycle characteristics, it is possible to suppress a rapid temperature rise when a large current flows instantaneously due to a short circuit state caused by a nail penetration test or the like. According to the present invention, although the mechanism of improving safety is not clear, when a composite oxide having the composition represented by the above-mentioned chemical formulas (1) and (2) is used, the mechanism described below is used. It is supposed to be.

That is, when a lithium ion secondary battery provided with a positive electrode containing LiNiO ₂ as an active material is short-circuited by, for example, a nail penetration test, and a large current is instantaneously applied, the secondary battery generates heat due to the large current. At the same time, LiN
Since the crystal structure of iO ₂ is broken and oxygen atoms constituting the crystal are released, it may explode or ignite. The composite oxide having the composition represented by the chemical formulas (1) and (2) according to the present invention contains at least one element Me1 selected from the group consisting of Cr, Hf and W. Since the element Me1 has a lower electronegativity than Ni, it is strongly linked to a halogen atom such as a fluorine atom or an oxygen atom. As a result, since the stability of the crystal structure of the composite oxide is improved, the DC resistance of the composite oxide is reduced, or the crystal structure of the composite oxide is changed when a large current flows instantaneously due to a short circuit or the like. Collapse is suppressed, and safety of the secondary battery can be improved. In addition, since the stability of the crystal structure of the composite oxide is improved, the charge / discharge cycle characteristics of the secondary battery are also improved.

[0100]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail.

(Examples 1 to 9 and Comparative Examples 1 to 6) <Preparation of Positive Electrode> Li hydroxide, fluoride, chloride and bromide, Ni (OH) ₂ , Co (O
H) _2, and oxides, hydroxides, carbonates, and nitrates of _{Me 1} were prepared, and these compounds were prepared using Li _1.1 (Ni _{1-yv
Co v Me1 y) (O 1.9} X 0.1) selected so that, after preparation, to prepare a mixed powder by mixing for 30 minutes in a Henschel mixer. This mixed powder was placed in an alumina sheath and fired. The calcination was carried out at 480 ° C. for 10 hours while flowing oxygen at 5 liter / min, and then at 700 ° C. for 20 hours to obtain a lithium-containing composite oxide having the composition shown in Table 1 below.

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

<Preparation of Negative Electrode> After carbonizing mesophase pitch carbon fiber from mesophase pitch as a raw material at 1000 ° C. in an argon atmosphere, the average fiber length was 30 μm.
After appropriately pulverizing so that 90 volume% is present in an average fiber diameter of 11 μm and a particle diameter of 1 to 80 μm, and particles having a particle diameter of 0.5 μm or less are reduced (5% or less), 3000 ° C. in an argon atmosphere To produce a carbonaceous material.

The polyvinylidene fluoride was converted to N-methyl-2-
The carbonaceous material and artificial graphite are added to the solution dissolved in pyrrolidone, and the mixture is stirred and mixed. The negative electrode mixture is composed of 86.5% by weight of carbonaceous material, 9.5% by weight of artificial graphite, and 4% by weight of polyvinylidene fluoride. An agent was prepared. This is copper foil (thickness 1
(5 μm), dried and then pressed under a roller press to produce a negative electrode. On this occasion,
The packing density and the electrode length were adjusted such that the ratio (capacity balance) of the designed capacity of the negative electrode to the designed capacity of the positive electrode after molding was 1.03 or more and 1.1 or less.

<Preparation of non-aqueous electrolyte (liquid non-aqueous electrolyte)>
Ethylene carbonate (EC) and methyl ethyl carbonate
(MEC) was mixed such that the volume ratio was 1: 2.
Lithium hexafluorophosphate (LiPF) ₆) To 1
By dissolving M, a non-aqueous electrolyte was prepared.

<Assembly of Battery> After welding a positive electrode lead made of aluminum and a negative electrode lead made of nickel to the positive electrode and the negative electrode, respectively, the positive electrode, a separator made of a porous film made of polyethylene and the negative electrode were respectively attached. The electrodes were stacked in this order, and spirally wound so that the negative electrode was located outside, to produce an electrode group.

This electrode group is housed in a bottomed cylindrical container,
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 arranged at the opening of the bottomed cylindrical container. Subsequently, 4 mL of a non-aqueous electrolyte was injected into the bottomed cylindrical container, and the electrode group was sufficiently impregnated with the non-aqueous electrolyte. After the positive electrode terminal was arranged on the safety valve, it was fixed by caulking. As described above, a cylindrical lithium ion secondary battery (18650 size) having a designed rated capacity of 1700 mAh was assembled.

The obtained secondary batteries of Examples 1 to 9 and Comparative Examples 1 to 6 were subjected to a nail penetration test. First, these secondary batteries were charged. Charging was performed at a current value corresponding to the designed rated capacity of each secondary battery of 0.2 C up to 4.2 V, and then maintained at a constant voltage of 4.2 V for a total of 8 hours.
After charging at 4.2 V, 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 using a thermocouple attached to the outer surface of the battery. Table 1 below shows the presence or absence of rupture / ignition in the nail penetration test and the battery temperature in the nail penetration test.

Further, the secondary batteries of Examples 1 to 9 and Comparative Examples 1 to 6 were subjected to a charge / discharge cycle test at room temperature.
The rate of decrease in discharge capacity after 100 cycles was determined, and the results are shown in Table 1 below. The charging in the charge / discharge cycle test was performed at a current value corresponding to the design rated capacity of 0.5 C up to 4.2 V, and then maintained at a constant voltage of 4.2 V for a total of 5 hours. Discharge was performed up to 2.7 V at the same current value. There was a 30-minute pause between charging and discharging.

[0110]

[Table 1]

As is clear from Table 1, the secondary batteries of Examples 1 to 9 containing the composite oxide having the composition represented by the above-mentioned chemical formula (1) as the positive electrode active material burst or fired in the nail penetration test. It can be seen that the temperature rise can be suppressed and the safety is excellent. In addition, it can be seen that the secondary batteries of Examples 1 to 9 have a smaller discharge capacity reduction rate after 100 cycles than Comparative Examples 1 to 6.

On the other hand, the molar ratio y of Me1 is 0.005.
It can be seen that the secondary batteries of Comparative Examples 1, 3, and 5, which are less than 1, lead to burst ignition by nail penetration test. On the other hand, the secondary batteries of Comparative Examples 2, 4, and 6 in which the molar ratio y of Me1 exceeds 0.3 are as follows:
Although it did not lead to explosion and ignition in the nail penetration test, it was 100
It can be seen that the capacity reduction rate after the cycle is large.

(Examples 10 to 59 and Comparative Examples 7 to 16)
Li hydroxide, fluoride, chloride, bromide as starting material
Object and Ni (OH)_TwoAnd Co (OH)_TwoAnd oxidation of Me1
Substances, hydroxides, carbonates, nitrates and oxides of Me2,
Prepare hydroxides, carbonates and nitrates, and combine these
The composition is Li _1.1(Ni_1-yvuCo_vMe1_yMe2_u) (O
_1.9X_0.1), And mix it, then add Henschelmi
A mixed powder was prepared by mixing with a mixer for 30 minutes. This
Was put in an alumina sheath and fired. Firing
At 480 ° C while flowing oxygen at 5 L / min.
After holding for 0 hours, the reaction was carried out at 700 ° C. for 20 hours.
~ Obtaining a lithium-containing composite oxide having the composition shown in Table 4
Was.

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

The obtained Examples 10 to 59 and Comparative Examples 7 to
A nail penetration test was performed on the 16 secondary batteries in the same manner as described in Example 1 above, and the presence or absence of rupture / ignition in the nail penetration test and the battery temperature in the nail penetration test were shown in Tables 2 to 4 below. Shown in

Examples 10 to 59 and Comparative Examples 7-1
The secondary battery of No. 6 was subjected to a charge / discharge cycle test in the same manner as described in Example 1 described above, and the rate of decrease in discharge capacity after 100 cycles was obtained.
To Table 4 below.

[0117]

[Table 2]

[0118]

[Table 3]

[0119]

[Table 4]

As is clear from Tables 2 to 4, the secondary batteries of Examples 10 to 59 containing the composite oxide having the composition represented by the chemical formula (2) as the positive electrode active material in the nail penetration test It can be seen that there is no rupture or ignition, temperature rise can be suppressed, and safety is excellent. Example 1
It can be seen that the secondary batteries Nos. 0 to 59 have smaller capacity reduction rates after 100 cycles than Comparative Examples 7 to 16. In particular,
Examples 10 to 5 in which the molar ratio u of Me2 is 0.005 or more
The secondary battery of No. 4 has a temperature rise of 70 ° C.
It can be kept within the range of 73 ° C.

On the other hand, Comparative Examples 7, 9, 11, and 1 in which the molar ratio y of Me1 and the molar ratio u of Me2 were less than 0.005.
It can be seen that the secondary batteries of Nos. 3 and 15 lead to explosion and ignition by nail penetration test. On the other hand, in the secondary batteries of Comparative Examples 8, 10, 12, 14, and 16 in which the molar ratio u of Me2 exceeds 0.3, although the burst ignition does not occur, the capacity after 100 cycles is significantly reduced. Understand.

(Examples 60 to 73 and Comparative Examples 17 to 3)
0) lithium hydroxide and fluoride as starting materials;
Ni (OH) ₂ , Co (OH) ₂ , oxides of vanadium, hydroxides, carbonates, nitrates and oxides of Me 3,
Hydroxides, hydrides carbonate, prepared and nitrates, the composition of these compounds is _{Li 1.1 (Ni 1-vst Co} v V s Me3 t) (O
_1.9 X _0.1 ), and after mixing, mixed with a Henschel mixer for 30 minutes to produce a mixed powder. This mixed powder was placed in an alumina sheath and fired. Calcination is performed at 480 ° C for 1 while flowing oxygen at 5 L / min.
After holding for 0 hours, the reaction was performed at 700 ° C. for 20 hours.
~ A lithium-containing composite oxide having the composition shown in Table 6 was obtained.

A cylindrical lithium ion secondary battery was manufactured in the same manner as in Example 1 except that this lithium-containing composite oxide was used as a positive electrode active material.

Examples 60 to 73 obtained and Comparative Example 17
For the secondary batteries of Nos. To 30, a nail penetration test was performed in the same manner as described in Example 1 above, and the presence or absence of rupture / ignition in the nail penetration test and the battery temperature in the nail penetration test were shown in Tables 5 to 5 below. 6 is shown.

Examples 60 to 73 and Comparative Examples 17 to
For the secondary battery of No. 30, a charge / discharge cycle test was performed in the same manner as described in Example 1 above, and the rate of decrease in the discharge capacity after 100 cycles was obtained. The results are shown in Tables 5 to 6 below. Show.

[0126]

[Table 5]

[0127]

[Table 6]

As is clear from Tables 5 and 6, the secondary batteries of Examples 60 to 73 containing the composite oxide having the composition represented by the above chemical formula (3) as a positive electrode active material were subjected to a nail penetration test. It can be seen that there is no rupture or ignition, temperature rise can be suppressed, and safety is excellent. Example 6
It can be seen that the secondary batteries of Nos. 0 to 73 have smaller capacity reduction rates after 100 cycles than those of Comparative Examples 17 to 30. In particular, Example 6 where the molar ratio t of Me3 is 0.005 or more.
In the secondary batteries of 1, 63, 65, 67, 69, 71, and 73, the temperature rise due to the nail penetration test can be suppressed within the range of 71 ° C to 73 ° C.

On the other hand, the molar ratio t of Me3 is 0.005.
Comparative Examples 17, 19, 21, 23, 25, 2
It can be seen that the secondary batteries of Nos. 7 and 29 lead to explosion and ignition by nail penetration test. On the other hand, the secondary batteries of Comparative Examples 18, 20, 22, 24, 26, 28, and 30 in which the molar ratio t of Me3 exceeds 0.3 did not lead to burst and ignition, but had a large capacity after 100 cycles. It turns out that it falls.

(Examples 74 to 82 and Comparative Examples 31 to 3)
6) hydroxides, fluorides, chlorides of Li as starting materials,
Oxides and hydroxides of bromide, Ni (OH) ₂ and Me1,
A carbonate and a nitrate are prepared, and these compounds are selected so that the composition becomes Li _1.1 (Ni _1-y Me1 _y ) (O _1.9 X _0.1 ). After blending, they are mixed with a Henschel mixer for 30 minutes. A mixed powder was prepared. This mixed powder was placed in an alumina sheath and fired. After sintering at 480 ° C. for 10 hours while flowing oxygen at 5 L / min, 700
C. for 20 hours to obtain a lithium-containing composite oxide having the composition shown in Table 7 below.

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

Examples 74 to 82 and Comparative Example 31
For the secondary batteries of Nos. 36 to 36, a nail penetration test was performed in the same manner as described in Example 1 above, and the presence or absence of rupture / ignition in the nail penetration test and the battery temperature in the nail penetration test are shown in Table 7 below. .

Examples 74 to 82 and Comparative Examples 31 to
A charge / discharge cycle test was performed on the secondary battery No. 36 in the same manner as described in Example 1 above, and the rate of decrease in the discharge capacity after 100 cycles was obtained. The results are shown in Table 7 below.

[0134]

[Table 7]

As is clear from Table 7, the secondary batteries of Examples 74 to 82 containing the composite oxide having the composition represented by the above-mentioned chemical formula (4) as a positive electrode active material burst or fired in a nail penetration test. It can be seen that the temperature rise can be suppressed and the safety is excellent. Examples 74 to 8
It can be seen that the secondary battery of No. 2 has a smaller capacity reduction rate after 100 cycles than Comparative Examples 31 to 36.

On the other hand, when the molar ratio y of Me1 is 0.005
It can be seen that the secondary batteries of Comparative Examples 31, 33, and 35, which are less than the above, lead to rupture and ignition by a nail penetration test. On the other hand, Me1
It can be seen that the secondary batteries of Comparative Examples 32, 34, and 36 in which the molar ratio y exceeds 0.3 did not cause burst ignition, but the capacity after 100 cycles was significantly reduced.

(Examples 83 to 132 and Comparative Examples 37 to 6)
6) hydroxides, fluorides, chlorides of Li as starting materials,
Oxides and hydroxides of bromide, Ni (OH) ₂ and Me1,
Prepare carbonates and nitrates and oxides, hydroxides, carbonates and nitrates of Me2, and prepare these compounds with a composition of Li
_1.1 (Ni _1-yu Me1 _y Me2 _u ) (O _1.9 X _0.1 ) was selected, mixed, and mixed with a Henschel mixer for 30 minutes to prepare a mixed powder. This mixed powder was placed in an alumina sheath and fired. After sintering at 480 ° C. for 10 hours while flowing oxygen at 5 liter / min,
The reaction was performed at 0 ° C. for 20 hours to obtain a lithium-containing composite oxide having a composition shown in Tables 8 to 11.

A cylindrical lithium ion secondary battery was manufactured in the same manner as in Example 1 except that this lithium-containing composite oxide was used as a positive electrode active material.

Examples 83 to 132 obtained and Comparative Example 3
For the secondary batteries of Nos. 7 to 66, a nail penetration test was performed in the same manner as described in Example 1 above, and the presence or absence of rupture / ignition in the nail penetration test and the battery temperature in the nail penetration test were shown in Tables 8 to 8 below. It is shown in Table 11.

Examples 83 to 132 and Comparative Example 37
A charge / discharge cycle test was performed on the secondary batteries of Nos. To 66 in the same manner as described in Example 1 above,
The rate of decrease in the discharge capacity after the cycle was determined, and the results are shown in Tables 8 to 11 below.

[0141]

[Table 8]

[0142]

[Table 9]

[0143]

[Table 10]

[0144]

[Table 11]

As is clear from Tables 8 to 11, the secondary batteries of Examples 83 to 132 containing the composite oxide having the composition represented by the chemical formula (5) as the positive electrode active material in the nail penetration test It can be seen that there is no rupture or ignition, temperature rise can be suppressed, and safety is excellent. Further, it can be seen that the secondary batteries of Examples 83 to 132 have smaller capacity reduction rates after 100 cycles than those of Comparative Examples 37 to 66. In particular, in the secondary batteries of Examples 83 to 85 and 87 to 128 in which the molar ratio u of Me2 is 0.005 or more, the temperature rise due to the nail penetration test can be suppressed to the order of 90 ° C.

On the other hand, Comparative Examples 37, 39, and 4 in which the molar ratio y of Me1 and the molar ratio u of Me2 are less than 0.005.
1,43,45,47,49,51,53,55,5
It can be seen that the secondary batteries of 7, 59, 61, 63 and 65 are ruptured and fired by the nail penetration test. On the other hand, Comparative Examples 38, 40, 42, 44, where the molar ratio u of Me2 exceeds 0.3,
46, 48, 50, 52, 54, 56, 58, 60, 6
It can be seen that the capacity of the 2, 64, 66 secondary batteries does not lead to burst ignition, but the capacity is significantly reduced after 100 cycles.

(Examples 133 to 139 and Comparative Examples 67 to 139)
80) Lithium hydroxide and fluoride as starting materials
And Ni (OH)_TwoAnd vanadium oxide, hydroxide
Substances, carbonates, nitrates and oxides and hydroxides of Me3,
Prepare carbonate and nitrate, and these compounds have the composition
Li_1.1(Ni_1-stV_sMe3 _t) (O_1.9X_0.1)
After mixing, mix with a Henschel mixer for 30 minutes.
Thus, a mixed powder was prepared. This mixed powder is alumina
It was put in a sheath and fired. Baking is 5 liter / min acid
After holding at 480 ° C for 10 hours while flowing the element,
Performed at 700 ° C. for 20 hours and have the composition shown in Table 12 below
Thus, a lithium-containing composite oxide was obtained.

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

The obtained secondary batteries of Examples 133 to 139 and Comparative Examples 67 to 80 were subjected to a nail piercing test in the same manner as described in Example 1 above, and the rupture and ignition of the batteries by the nail piercing test were performed. Table 12 below shows the presence / absence and the battery temperature obtained by the nail penetration test.

Examples 133 to 139 and Comparative Example 6
For the secondary batteries of Nos. 7 to 80, a charge / discharge cycle test was performed in the same manner as described in Example 1 described above.
The rate of decrease in the discharge capacity after 0 cycles was determined, and the results are shown in Table 12 below.

[0151]

[Table 12]

As is clear from Table 12, the secondary batteries of Examples 133 to 139 containing the composite oxide having the composition represented by the above-mentioned chemical formula (6) as a positive electrode active material burst or ignited in a nail penetration test. It can be seen that the temperature rise can be suppressed and the safety is excellent. Example 1
It can be seen that the secondary batteries of Nos. 33 to 139 have smaller capacity reduction rates after 100 cycles than those of Comparative Examples 67 to 80.

On the other hand, the molar ratio t of Me3 is 0.005.
Comparative Examples 67, 69, 71, 73, 75, 7
It can be seen that the secondary batteries of No. 7, 79 are ruptured and ignited by the nail penetration test. On the other hand, in the secondary batteries of Comparative Examples 68, 70, 72, 74, 76, 78, and 80 in which the molar ratio t of Me3 exceeds 0.3, the capacities after 100 cycles were greatly increased, although the burst batteries did not cause ignition. It turns out that it falls.

Example 140 <Preparation of Positive Electrode> 91% by weight of a lithium-containing composite oxide powder having the same composition as that described in Example 1 was added to 2.5% by weight of acetylene black, 3% by weight of graphite, 4% by weight of polyvinylidene fluoride (PVdF) and an N-methylpyrrolidone (NMP) solution were added and mixed to obtain a thickness of 15%.
The resultant was applied to a current collector of aluminum foil having a thickness of μm, dried, and pressed to produce a band-shaped positive electrode having an electrode density of 3.0 g / cm ³ .

<Preparation of Negative Electrode> 94% by weight of powder of mesophase pitch-based 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 A pyrrolidone (NMP) solution was added and mixed, applied to a copper foil having 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 produced.

<Preparation of Electrode Group> The positive electrode, thickness 16 μm
With a porosity of 50% and an air permeability of 200 seconds / 100 cm
After laminating in order of the separator made of the polyethylene porous film of No. ^3, the negative electrode, and the separator, they were spirally wound. This was hot-pressed at 90 ° C. to produce a flat electrode group having a width of 30 mm and a thickness of 3.0 mm. The obtained electrode group was housed in a 0.1 mm-thick laminated film pack composed of an aluminum foil having a thickness of 40 μm and polypropylene layers formed on both sides of the aluminum foil. Vacuum drying was performed for hours.

<Preparation of non-aqueous electrolyte (liquid non-aqueous electrolyte)>
1.5 mol / L 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 was completely sealed by heat sealing.
A thin lithium ion secondary battery having the structure shown in FIGS. 2 and 3 described above and having a width of 35 mm, a thickness of 3.2 mm, and a height of 65 mm was manufactured.

(Example 141) Example 140 was repeated except that a lithium-containing composite oxide having the same composition as that described in Example 10 was used as the positive electrode active material.
In the same manner as described above, a thin lithium ion secondary battery was manufactured.

Example 142 The procedure of Example 140 was repeated except that a lithium-containing composite oxide having the same composition as that described in Example 60 was used as the positive electrode active material.
In the same manner as described above, a thin lithium ion secondary battery was manufactured.

(Example 143) Example 140 was repeated except that a lithium-containing composite oxide having the same composition as that described in Example 74 was used as the positive electrode active material.
In the same manner as described above, a thin lithium ion secondary battery was manufactured.

(Example 144) Example 140 was repeated except that a lithium-containing composite oxide having the same composition as that described in Example 83 was used as the positive electrode active material.
In the same manner as described above, a thin lithium ion secondary battery was manufactured.

(Example 145) The same as in Example 14 except that a lithium-containing composite oxide having the same composition as that described in Example 133 was used as the positive electrode active material.
0, a thin lithium ion secondary battery was manufactured.

A nail penetration test was performed on the obtained secondary batteries of Examples 140 to 145. First, these secondary batteries were charged. After charging was performed up to 4.2 V at a current value corresponding to the design rated capacity of 0.2 C of each secondary battery,
The measurement was performed at a constant voltage of 4.2 V for a total of 8 hours. 4.2V
After charging, 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 using a thermocouple attached to the outer surface of the battery. Table 13 below shows the presence or absence of rupture / ignition in the nail penetration test and the battery temperature in the nail penetration test.

Further, the secondary batteries of Examples 140 to 145 were subjected to a charge / discharge cycle test at room temperature, and the rate of decrease in discharge capacity after 100 cycles was determined. The results are shown in Table 13 below. The charging in the charge / discharge cycle test was performed at a current value corresponding to the design rated capacity of 0.5 C up to 4.2 V, and then maintained at a constant voltage of 4.2 V for a total of 5 hours. Discharge was performed up to 2.7 V at the same current value. There was a 30-minute pause between charging and discharging.

[0166]

[Table 13]

As is clear from Table 13, Examples 140 to 145 each containing, as an active material, a lithium-containing composite oxide having a composition represented by the aforementioned chemical formulas (1) to (6).
It can be seen that the thin secondary battery of No. 1 does not rupture or ignite in a nail penetration test, can suppress a temperature rise, and is excellent in safety. Further, the thin secondary batteries of Examples 140 to 145 are:
It turns out that it has excellent cycle characteristics.

[0168]

As described above in detail, according to the present invention, a lithium ion secondary battery having improved charge / discharge cycle characteristics and safety can be provided.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view showing a cylindrical lithium ion secondary battery which is an example of a 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 sectional view showing a portion A in FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Container, 2 ... Insulator, 3 ... Electrode group, 4 ... Positive electrode, 5 ... Separator, 6 ... Negative electrode.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Koichi Kubo 1-term, Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa F-term in Toshiba R & D Center (reference) 4G048 AA04 AA06 AB05 AC06 AE05 5H029 AJ05 AJ12 AK03 AL02 AL04 AL06 AL07 AL08 AL12 BJ02 BJ14 HJ02 5H050 AA07 AA15 BA16 BA17 CA08 CB02 CB05 CB07 CB08 CB09 CB12 HA02

Claims (3)

[Claims] 1. A lithium ion secondary battery comprising a positive electrode containing an active material, a negative electrode, and a non-aqueous electrolyte, wherein the active material comprises a composite oxide having a composition represented by the following chemical formula (1). A lithium ion secondary battery comprising: _{Li x (Ni 1-yv Co} v Me1 y) (O 2-z X z) (1) where said Me1 is, Cr, at least one element selected from the group consisting of Hf and W, wherein X Is F, C
at least one halogen element selected from the group consisting of l, Br and I, wherein the molar ratios x, y, z and v are 0.0
2 ≦ x ≦ 1.3, 0.005 ≦ y ≦ 0.3, 0.01 ≦
z ≦ 0.5 and 0.005 ≦ v ≦ 0.5, respectively. 2. A lithium ion secondary battery comprising a positive electrode containing an active material, a negative electrode, and a non-aqueous electrolyte, wherein the active material comprises a composite oxide having a composition represented by the following chemical formula (2). A lithium ion secondary battery comprising: _{Li x (Ni 1-yuv Co} v Me1 y Me2 u) (O 2-z X z) (2) where said Me1 is, Cr, at least one element selected from the group consisting of Hf and W, The Me2 is Ti,
At least one element selected from the group consisting of V, Zr, Nb, Mo and Ta, wherein X is F, Cl, B
at least one halogen element selected from the group consisting of r and I, wherein the molar ratios x, y, z, v and u are 0.02
≦ x ≦ 1.3, 0.005 ≦ y ≦ 0.3, 0.01 ≦ z
≤0.5, 0.005≤v≤0.5, and 0 <u≤0.3, respectively. 3. A lithium ion secondary battery comprising a positive electrode containing an active material, a negative electrode, and a non-aqueous electrolyte, wherein the active material comprises a composite oxide having a composition represented by the following chemical formula (3). A lithium ion secondary battery comprising: _{Li x (Ni 1-vst Co} v V s Me3 t) (O 2-z X z) (3) where the Me3 is, Cr, Zr, Nb, Mo , Hf, T
X is at least one kind of element selected from the group consisting of F, Cl, Br and I, and is at least one kind of element selected from the group consisting of a and W, and has a molar ratio of x, v, s, t and z are 0.02 ≦ x ≦ 1.3, 0.0
05 ≦ v ≦ 0.5, 0.005 ≦ s ≦ 0.3, 0 <t ≦
0.3 and 0.01 ≦ z ≦ 0.5, respectively.