JP2006012426A - Positive electrode active material for nonaqueous electrolyte secondary battery and nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive electrode active material for a nonaqueous electrolyte secondary battery having high battery characteristics, especially excellent high-temperature characteristics and to provide the nonaqueous electrolyte secondary battery. <P>SOLUTION: The positive electrode active material for the nonaqueous electrolyte secondary battery comprises a powder main part and powder having a covering layer covering at least one part of the powder main part, the powder main part has a lithium transition metal composite oxide having layer structure, and the covering layer has a manganese oxide in at least one part of the lithium transition metal composite oxide having spinel structure. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a positive electrode active material for a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery (hereinafter also simply referred to as “positive electrode active material”) and a non-aqueous electrolyte secondary battery. More specifically, the present invention relates to a positive electrode active material having a lithium transition metal composite oxide having a layered structure and a non-aqueous electrolyte secondary battery with greatly improved battery characteristics.

Non-aqueous electrolyte secondary batteries are characterized by higher operating voltage and higher energy density compared to conventional nickel cadmium secondary batteries, etc. Mobile electronics such as mobile phones, notebook computers, digital cameras, etc. Widely used as a power source for equipment. Examples of the positive electrode active material of the non-aqueous electrolyte secondary battery include lithium transition metal composite oxides typified by LiCoO ₂ , LiNiO ₂ , and LiMn ₂ O _4. Among them, LiCoO ₂ has been conventionally used for mobile electronic devices. It was used, and sufficient battery characteristics were obtained.

At present, however, mobile electronic devices have a more severe usage environment due to higher functionality such as the addition of various functions and use at high and low temperatures. In addition, application to power sources such as batteries for electric vehicles is expected, and conventional non-aqueous electrolyte secondary batteries using LiCoO ₂ cannot obtain sufficient battery characteristics, and further improvements are required. Yes.

In Patent Document 1, in a non-aqueous electrolyte secondary battery using a lithium-containing composite oxide that occludes and releases lithium ions as a positive electrode active material, the lithium-containing composite oxide has a lithium cobalt oxide particle surface with lithium spinel manganate. Alternatively, a non-aqueous electrolyte secondary battery characterized by being coated with spinel lithium titanate is described. And it is described that a non-aqueous electrolyte secondary battery with higher safety that can function sufficiently even at abnormal heat generation such as an internal short circuit or at a high temperature exceeding 60 ° C. can be obtained.
However, this positive electrode active material could not satisfy the overcharge characteristics and load characteristics required for recent nonaqueous electrolyte secondary batteries. There is also room for improvement in high temperature characteristics and safety.

JP 2000-164214 A

  An object of the present invention is to provide a positive electrode active material for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery having excellent battery characteristics even in a more severe use environment.

  The present invention provides the following (1) to (4).

(1) A positive electrode active material for a nonaqueous electrolyte secondary battery comprising a powder having a powder body and a coating layer covering at least a part of the surface of the powder body,
The powder body has a layered structure lithium transition metal composite oxide,
The coating layer is a positive electrode active material for a non-aqueous electrolyte secondary battery, in which manganese oxide is included in at least part of the spinel structure lithium transition metal composite oxide.

(2) A positive electrode active material for a nonaqueous electrolyte secondary battery comprising a powder having a powder body and a coating layer covering at least a part of the surface of the powder body,
The powder body has a layered structure lithium nickel composite oxide,
The coating layer is a positive electrode active material for a non-aqueous electrolyte secondary battery, comprising a spinel structure lithium manganese composite oxide.

(3) A positive electrode active material comprising a powder having a powder body and a coating layer covering at least a part of the surface of the powder body,
The powder body has a layered structure lithium transition metal composite oxide,
The coating layer is formed by forming a positive electrode active material layer using a positive electrode active material having manganese oxide in at least a part of a spinel structure lithium transition metal composite oxide on at least one surface of a strip-shaped positive electrode current collector. A belt-shaped positive electrode configured;
Metallic lithium,
Lithium alloy,
A strip-shaped negative electrode configured by forming a negative electrode active material layer using, as a negative electrode active material, one selected from compounds capable of occluding and releasing lithium ions on at least one surface of a strip-shaped negative electrode current collector;
A strip separator,
A non-aqueous electrolyte secondary battery in which the strip separator is interposed between the strip positive electrode and the strip negative electrode.

(4) A positive electrode active material comprising a powder body and a powder having a coating layer covering at least a part of the surface of the powder body,
The powder body has a layered structure lithium nickel composite oxide,
The coating layer comprises a strip-shaped positive electrode formed by forming a positive electrode active material layer using a positive electrode active material on at least one surface of a strip-shaped positive electrode current collector, comprising a spinel structure lithium manganese composite oxide;
Metallic lithium,
Lithium alloy,
A strip-shaped negative electrode configured by forming a negative electrode active material layer using, as a negative electrode active material, one selected from compounds capable of occluding and releasing lithium ions on at least one surface of a strip-shaped negative electrode current collector;
A strip separator,
A non-aqueous electrolyte secondary battery in which the strip separator is interposed between the strip positive electrode and the strip negative electrode.

The positive electrode active material for a non-aqueous electrolyte secondary battery according to (1) comprises a powder having a powder body and a coating layer covering at least a part of the surface of the powder body, and the powder body has a layered structure lithium transition It has a metal composite oxide, and the coating layer has manganese oxide in at least a part of the spinel structure lithium transition metal composite oxide.
When the transition metal is eluted from the positive electrode active material, the eluted transition metal is deposited on the negative electrode and captures lithium, so that the battery characteristics are significantly deteriorated. Moreover, the elution of transition metals is more likely to occur at higher temperatures.
In the present invention, since the spinel structure lithium transition metal composite oxide has high crystal structure stability, it is considered that elution of the transition metal in the powder body is suppressed by using this as a coating layer. Since the elution of the transition metal in the powder body is suppressed even at a high temperature, the high temperature characteristics are improved.
In the lithium transition metal composite oxide having a layered structure, the crystal lattice expands by charging and contracts by discharging. On the contrary, in the lithium transition metal composite oxide having a spinel structure, the crystal lattice contracts by charging and expands by discharging. Therefore, it is considered that the expansion and contraction of the crystal lattice is offset at the particle level by using a layered lithium transition metal composite oxide as the powder body and a spinel structure lithium transition metal composite oxide as the coating layer. Improved characteristics.
Further, in the present invention, since manganese oxide is contained in at least a part of the spinel structure lithium transition metal composite oxide, the adhesion between the powder body and the coating layer is improved, and the effect of the present invention is further improved. .

The positive electrode active material for a non-aqueous electrolyte secondary battery according to (2) comprises a powder having a powder body and a coating layer covering at least a part of the surface of the powder body, the powder body having a layered structure lithium nickel It has a composite oxide, and the coating layer has a spinel structure lithium manganese composite oxide.
When nickel is eluted from the positive electrode active material, the eluted nickel is deposited on the negative electrode and captures lithium, so that the battery characteristics are remarkably deteriorated. Also, elution of nickel is more likely to occur at higher temperatures.
In the present invention, since the spinel structure lithium transition metal composite oxide has high crystal structure stability, it is considered that elution of nickel in the powder body is suppressed by using this as a coating layer. Since elution of nickel in the powder body is suppressed even at high temperatures, the high temperature characteristics are improved.
In the lithium nickel composite oxide having a layered structure, the crystal lattice expands by charging and contracts by discharging. On the contrary, in the lithium transition metal composite oxide having a spinel structure, the crystal lattice contracts by charging and expands by discharging. Therefore, it is considered that the expansion and contraction of the crystal lattice is offset at the particle level by using the layered lithium nickel composite oxide as the powder body and the spinel lithium transition metal composite oxide as the coating layer. Will improve.

The non-aqueous electrolyte secondary battery according to (3) is a positive electrode active material comprising a powder body and a coating layer that covers at least a part of the surface of the powder body, wherein the powder body has a layered structure A positive electrode active material layer using a positive electrode active material, comprising a lithium transition metal composite oxide and having a manganese oxide in at least part of the spinel structure lithium transition metal composite oxide. A negative electrode active material layer formed by forming at least one side of the body as a negative electrode active material and a negative electrode active material layer selected from metal lithium, a lithium alloy, and a compound capable of occluding and releasing lithium ions. A strip-shaped negative electrode configured by being formed on at least one surface of the current collector and a strip-shaped separator are provided, and the strip-shaped separator is interposed between the strip-shaped positive electrode and the strip-shaped negative electrode. By adopting such a configuration, a nonaqueous electrolyte secondary battery excellent in high temperature characteristics, cycle characteristics and the like can be obtained.

The nonaqueous electrolyte secondary battery according to (4) is a positive electrode active material comprising a powder body and a coating layer covering at least a part of the surface of the powder body, wherein the powder body has a layered structure By forming a positive electrode active material layer using a positive electrode active material having a lithium nickel composite oxide and having a spinel structure lithium manganese composite oxide on at least one surface of a strip-shaped positive electrode current collector A negative electrode active material layer using as a negative electrode active material a negative electrode active material selected from a configured belt-like positive electrode and metallic lithium, a lithium alloy, or a compound capable of occluding and releasing lithium ions is formed on at least one surface of the belt-like negative electrode current collector. The strip-shaped negative electrode comprised by this and the strip-shaped separator are comprised, and the said strip-shaped separator interposes between a strip-shaped positive electrode and a strip-shaped negative electrode. By adopting such a configuration, a nonaqueous electrolyte secondary battery excellent in high temperature characteristics, cycle characteristics and the like can be obtained.

  Hereinafter, the positive electrode active material for a nonaqueous electrolyte secondary battery and the nonaqueous electrolyte secondary battery according to the present invention will be specifically described. However, the present invention is not limited to this embodiment.

<Positive electrode active material for non-aqueous electrolyte secondary battery>
The positive electrode active material of the present invention comprises a powder having a powder body and a coating layer that covers at least a part of the surface of the powder body.
In the positive electrode active material of the present invention, the powder is usually particles, but the form is not particularly limited. The particles may be primary particles, secondary particles, or a mixture of these.

In the positive electrode active material according to the first aspect of the present invention, the powder body is composed of at least a lithium transition metal composite oxide having a layered structure. The layered structure means that the crystal structure of the lithium transition metal composite oxide is layered.
The layered structure is not particularly limited, and examples thereof include a layered rock salt structure and a zigzag layered rock salt structure. Among these, a layered rock salt structure is preferable.

  The lithium transition metal composite oxide having a layered structure is not particularly limited. For example, lithium cobalt composite oxides such as lithium cobaltate, lithium nickel composite oxides such as lithium nickelate, lithium nickel cobalt composite oxides such as nickel cobalt lithium, nickel cobalt lithium manganate, nickel cobalt lithium lithium aluminate, chromium Lithium acid, lithium vanadate, and lithium manganate. Preferable examples include lithium cobaltate, lithium nickel cobaltate, nickel cobalt lithium aluminate and nickel cobalt lithium manganate.

When the composition ratio of Li, Co, and O of lithium cobaltate is represented by the general formula Li _x CoO _y , x represents a number satisfying 0.95 ≦ x ≦ 1.10, and y is 1.8 ≦ y ≦ It is preferable to represent a number satisfying 2.2.
Li of lithium nickel cobaltate, Ni, when represents a composition ratio of Co and O in the general formula _{Li k Ni m Co p O r} , k represents a number satisfying 0.95 ≦ k ≦ 1.10, m Represents a number satisfying 0.1 ≦ m ≦ 0.9, p represents a number satisfying 0.1 ≦ p ≦ 0.9, and r represents a number satisfying 1.8 ≦ r ≦ 2.2. Is preferred.
Nickel cobalt aluminate lithium Li, Ni, Co, when represents a composition ratio of Al and O in the general formula _{Li k Ni m Co p Al (} 1-m-p) O r, k is 0.95 ≦ k ≦ 1.10, m represents a number satisfying 0.1 ≦ m ≦ 0.9, p represents a number satisfying 0.1 ≦ p ≦ 0.9, and m + p represents m + p ≦ 1. It is preferable to represent a number that satisfies, and r represents a number that satisfies 1.8 ≦ r ≦ 2.2.
When the composition ratio of Li, Ni, Co, Mn, and O of lithium nickel cobalt manganate is expressed by the general formula Li _k Ni _m Co _p Mn _(1-mp) O _r , k is 0.95 ≦ k ≦ 1.10, m represents a number satisfying 0.1 ≦ m ≦ 0.9, p represents a number satisfying 0.1 ≦ p ≦ 0.9, and m + p represents m + p ≦ 1. It is preferable to represent a number that satisfies, and r represents a number that satisfies 1.8 ≦ r ≦ 2.2.

In the positive electrode active material according to the first aspect of the present invention, the coating layer is composed of a lithium transition metal composite oxide having a spinel structure having manganese oxide at least partially. The spinel structure is one of typical crystal structure types found in double oxide AB ₂ O ₄ type compounds (A and B are metal elements).
In the spinel structure, lithium atoms occupy 8a site tetrahedral sites, oxygen atoms occupy 32e sites, and transition metal atoms (and possibly excess lithium atoms) occupy 16d site octahedron sites. Yes.

  Examples of the spinel structure lithium transition metal composite oxide include lithium manganese composite oxide, lithium titanium composite oxide, lithium / manganese / nickel composite oxide, and lithium / manganese / cobalt composite oxide. Among these, lithium manganese composite oxide is preferable.

When the composition ratio of Li, Mn and O of the lithium manganese composite oxide is represented by the general formula Li _{1 + a} Mn _2−a O _{4 + d} , a represents a number satisfying −0.2 ≦ a ≦ 0.2, d Preferably represents a number satisfying −0.5 ≦ d ≦ 0.5.

The manganese oxide which the spinel structure lithium transition metal complex oxide of a coating layer has in at least one part is not specifically limited.
Examples thereof include MnO, Mn ₃ O ₄ , Mn ₂ O ₃ , MnO ₂ , MnO ₃ , and Mn ₂ O ₇ . Mn ₃ O ₄ and Mn ₂ O ₃ are preferable. This is because they exist stably.
The spinel structure lithium transition metal composite oxide of the coating layer of the present invention may have a lithium manganese composite oxide in a part thereof. Examples of the lithium manganese composite oxide include Li ₂ MnO ₃ .

  In the positive electrode active material according to the second aspect of the present invention, the powder body is made of at least a layered lithium nickel composite oxide.

The lithium nickel composite oxide having a layered structure is not particularly limited. For example, lithium nickel cobalt composite oxides such as lithium nickelate, lithium nickel cobaltate, nickel cobalt lithium manganate, nickel cobalt lithium aluminate and the like. Preferable examples include lithium cobaltate, lithium nickel cobaltate, nickel cobalt lithium aluminate and nickel cobalt lithium manganate.
It is preferable that nickel cobalt lithium aluminate and nickel cobalt lithium manganate are represented by the general formula described above.

In the positive electrode active material according to the second aspect of the present invention, the coating layer is composed of a lithium manganese composite oxide having a spinel structure. The spinel structure is one of typical crystal structure types found in double oxide AB ₂ O ₄ type compounds (A and B are metal elements).
The lithium manganese composite oxide is preferably represented by the general formula described above.

  Hereinafter, lithium transition metal composite oxides suitably used for the powder body of the present invention will be exemplified.

(1) When at least one lithium transition metal composite oxide selected from the group consisting of lithium cobaltate, lithium nickel cobaltate, nickel cobalt lithium aluminate, and nickel cobalt lithium manganate is lithium cobaltate or nickel cobaltate, Cycle characteristics are further improved, and a positive electrode active material for a non-aqueous electrolyte secondary battery having excellent load characteristics, low temperature characteristics and thermal stability is obtained. Therefore, the nonaqueous electrolyte secondary battery using this positive electrode active material can be suitably used for applications such as mobile phones and notebook computers.
When the lithium transition metal composite oxide is nickel cobalt lithium aluminate, it becomes a positive electrode active material for a non-aqueous electrolyte secondary battery with further improved load characteristics, low temperature characteristics, output characteristics, cycle characteristics, and thermal stability. Therefore, the nonaqueous electrolyte secondary battery using this positive electrode active material can be suitably used for applications such as electric vehicles, mobile phones, and notebook computers.
When the lithium transition metal composite oxide is nickel cobalt lithium manganate, the load characteristics, low temperature characteristics, output characteristics and cycle characteristics are further improved, and the positive electrode active material for a non-aqueous electrolyte secondary battery is further improved in thermal stability. . Therefore, the nonaqueous electrolyte secondary battery using this positive electrode active material can be suitably used for applications such as mobile phones, electric tools, and electric vehicles.

Nickel cobalt lithium, nickel cobalt lithium lithium and nickel cobalt lithium manganate have a layered crystal structure similar to lithium cobalt oxide.
However, these methods have a problem that a large amount of gas is generated and a potential at the time of discharge is lower than that of lithium cobaltate.
In the present invention, it is considered that gas generation at the time of charging can be prevented by using these as a powder body and having a lithium manganese composite oxide having a spinel structure in the coating layer.
In addition, the interface resistance is reduced, thereby increasing the discharge potential under load at normal temperature and low temperature, and improving the capacity retention rate under load. That is, it is considered that load characteristics and low temperature characteristics are improved.
Further, it is considered that lithium can be prevented from locally depositing on the negative electrode during charging. For this reason, it is considered that the generation of gas during charging can be suppressed and dry-out can be prevented, so that the cycle characteristics are improved.
Furthermore, it is thought that by having a spinel-structured lithium manganese composite oxide in the coating layer, desorption of oxygen is suppressed and thermal stability is improved.
Accordingly, the powder body has at least one selected from the group consisting of lithium nickel cobaltate, nickel cobalt lithium aluminate and nickel cobalt lithium manganate, and the coating layer has a spinel-structure lithium manganese composite oxide. The embodiment is useful.

(2) transition metal that is not the same as cobalt, lithium cobalt oxide containing at least one element selected from the group consisting of Group 2, Group 13 and Group 14 elements of the periodic table, halogen element and sulfur Thus, load characteristics, low temperature characteristics, cycle characteristics and thermal stability are further improved.
Among them, lithium cobaltate is represented by the general formula Li _x CoO _y (wherein x represents a number satisfying 0.95 ≦ x ≦ 1.10 and y represents a number satisfying 1.8 ≦ y ≦ 2.2). .).
Preferred specific examples of the general formula is in _{Li a Co 1-b M b} O c X d S e ( wherein, M is a Group 2 of the transition metal and the periodic table is not identical to the cobalt, the Group 13 and 14 elements of the X represents at least one selected from the group consisting of halogen elements, a represents a number satisfying 0.95 ≦ a ≦ 1.10, and b represents 0 <b ≦ 0.10. C represents a number satisfying 1.8 ≦ c ≦ 2.2, d represents a number satisfying 0 ≦ d ≦ 0.10, and e represents a number satisfying 0 ≦ e ≦ 0.015. Lithium transition metal composite oxide represented by the following formula.

(3) nickel cobalt oxide lithium containing at least one element selected from the group consisting of transition metals that are not identical to nickel and cobalt, elements of groups 2, 13 and 14 of the periodic table, halogen elements and sulfur; nickel And nickel cobalt lithium aluminate containing at least one element selected from the group consisting of transition metals not identical to cobalt, group 2 of the periodic table, group 13 and group 14 elements not identical to aluminum, halogen elements and sulfur; Or a nickel cobalt lithium manganate containing at least one element selected from the group consisting of transition metals not identical to nickel, cobalt and manganese, elements of Groups 2, 13 and 14 of the periodic table, halogen elements and sulfur By including these elements, load characteristics, low temperature characteristics, Further improvement of output characteristics, cycle characteristics and thermal stability can be realized. Therefore, the nonaqueous electrolyte secondary battery using this positive electrode active material can be suitably used for applications such as electric tools, electric vehicles, mobile phones, and notebook computers.

Among them, transition metals that are not identical to Co and Ni (when Z is Mn in the following formula, transition metals that are not identical to Co, Ni, and Mn), Groups 2 and 13 of the periodic table (when Z is Al in the formula below) The general formula is Li _k Ni _m Co _p Z _(1-mp) containing at least one element selected from the group consisting of Group 13 elements not identical to Al) and Group 14 elements, halogen elements and S O _r (wherein Z represents Al or Mn, k represents a number satisfying 0.95 ≦ k ≦ 1.10, m represents a number satisfying 0.1 ≦ m ≦ 0.9, and p represents A number satisfying 0.1 ≦ p ≦ 0.9, m + p representing a number satisfying m + p ≦ 1, and r representing a number satisfying 1.8 ≦ r ≦ 2.2. Metal composite oxides are preferred.

As a preferable specific example, the general formula is Li _k Ni _m Co _p Z _(1-mp) O _r (wherein Z represents Al or Mn, and k satisfies 0.95 ≦ k ≦ 1.10. M represents a number satisfying 0.1 ≦ m ≦ 0.9, p represents a number satisfying 0.1 ≦ p ≦ 0.9, m + p represents a number satisfying m + p ≦ 1, r Represents a number satisfying 1.8 ≦ r ≦ 2.2).

(4) Lithium cobaltate containing at least one element selected from the group consisting of titanium, aluminum, vanadium, zirconium, magnesium, calcium, strontium, and sulfur. It is considered that the cycle characteristics are improved by stabilizing. Moreover, it is thought that cycling characteristics improve by surface modification.
More preferably, it contains at least one element selected from the group consisting of titanium, aluminum, zirconium and magnesium. By including at least one element selected from the group consisting of titanium, aluminum, zirconium and magnesium, the cycle characteristics are further improved. In addition to these effects, the thermal stability is further improved by including magnesium.

In the aspect (4), since the passage of electrons is improved by the presence of sulfur, it is considered that the cycle characteristics and the load characteristics are further improved.
The sulfur content is preferably 0.03 to 0.7% by weight based on the total of the lithium transition metal composite oxide and sulfur. If it is less than 0.03% by weight, it may be difficult to reduce the resistance to movement of electrons. If it is more than 0.7% by weight, gas generation may occur due to moisture adsorption.

In the aspect (4), sulfur may be present in any form. For example, it may exist in the form of sulfate radicals.
The sulfate radical includes sulfate ions, a group of atoms obtained by removing the electrons from sulfate ions, and a sulfo group. It is preferably based on at least one selected from the group consisting of alkali metal sulfates, alkaline earth metal sulfates, organic sulfates and organic sulfonic acids and salts thereof.
Among them, it is preferable to use at least one selected from the group consisting of alkali metal sulfates and alkaline earth metal sulfates, and more preferable to use alkali metal sulfates. This is because these are chemically stable because they are composed of strong acid strong base bonds.

In the aspect (4), the sulfate radical is preferably present on the surface of the lithium transition metal composite oxide particles. By having sulfate radicals on the surface of the particles, it is considered that the sulfate radicals can easily pass electrons. Therefore, load characteristics are further improved.
Even when the sulfate radical covers the entire particle surface of the lithium transition metal composite oxide, or even when the sulfate radical covers a part of the particle surface of the lithium transition metal composite oxide. Further, load characteristics are improved.

In the aspect (4), when the composition ratio of Li, Co, and O of lithium cobaltate is represented by the general formula Li _x CoO _y , x represents a number satisfying 0.95 ≦ x ≦ 1.10. Preferably represents a number satisfying 1.8 ≦ y ≦ 2.2.

(5) at least a lithium-transition metal composite oxide is represented by the general formula _{Li a Co 1-b M b} O c X d S e (M is Ti, Al, V, Zr, Mg, selected from the group consisting of Ca and Sr X represents at least one element selected from halogen elements, a represents a number satisfying 0.95 ≦ a ≦ 1.10, and b represents a number satisfying 0 ≦ b ≦ 0.10. C represents a number satisfying 1.8 ≦ c ≦ 2.2, d represents a number satisfying 0 ≦ d ≦ 0.10, and e represents a number satisfying 0 ≦ e ≦ 0.015.) An embodiment represented by
It is preferable for the same reason as in the aspect (4).

(6) It consists of nickel cobalt lithium, nickel cobalt lithium aluminate and lithium nickel cobalt manganate containing at least one element selected from the group consisting of titanium, aluminum, vanadium, zirconium, magnesium, calcium, strontium and sulfur. At least one selected from the group It is considered that the presence of these elements causes a pillar effect and improves the cycle characteristics by stabilizing the crystal structure. Moreover, it is thought that cycling characteristics improve by surface modification.
More preferably, it contains at least one element selected from the group consisting of titanium, aluminum, zirconium and magnesium. By including at least one element selected from the group consisting of titanium, aluminum, zirconium and magnesium, the cycle characteristics are further improved. In addition to these effects, the thermal stability is further improved by including magnesium.

In aspect (6), since the passage of electrons is improved by the presence of sulfur, it is considered that the cycle characteristics and load characteristics are further improved.
The sulfur content is preferably 0.03 to 0.7% by weight based on the total of the lithium transition metal composite oxide and sulfur. If it is less than 0.03% by weight, it may be difficult to reduce the resistance to movement of electrons. If it is more than 0.7% by weight, gas generation may occur due to moisture adsorption.

In the aspect (6), sulfur may be present in any form. For example, it may exist in the form of sulfate radicals.
The sulfate radical includes sulfate ions, a group of atoms obtained by removing the electrons from sulfate ions, and a sulfo group. It is preferably based on at least one selected from the group consisting of alkali metal sulfates, alkaline earth metal sulfates, organic sulfates and organic sulfonic acids and salts thereof.
Among them, it is preferable to use at least one selected from the group consisting of alkali metal sulfates and alkaline earth metal sulfates, and more preferable to use alkali metal sulfates. This is because these are chemically stable because they are composed of strong acid strong base bonds.

In the aspect (6), the sulfate group is preferably present on the surface of the lithium transition metal composite oxide particles. By having sulfate radicals on the surface of the particles, it is considered that the sulfate radicals can easily pass electrons. Therefore, load characteristics are further improved.
Even when the sulfate radical covers the entire particle surface of the lithium transition metal composite oxide, or even when the sulfate radical covers a part of the particle surface of the lithium transition metal composite oxide. Further, load characteristics are improved.

In the embodiment (6), when expressed Li of lithium nickel cobaltate, Ni, a composition ratio of Co and O in the general formula _{Li k Ni m Co p O r} , k is 0.95 ≦ k ≦ 1.10 M represents a number satisfying 0.1 ≦ m ≦ 0.9, p represents a number satisfying 0.1 ≦ p ≦ 0.9, and r represents 1.8 ≦ r ≦ 2. It is preferable to represent a number satisfying 2.

In the aspect (6), when the composition ratio of Li, Ni, Co, Al, and O of nickel cobalt lithium aluminate is represented by the general formula Li _k Ni _m Co _p Al _(1-mp) O _r , k represents a number satisfying 0.95 ≦ k ≦ 1.10, m represents a number satisfying 0.1 ≦ m ≦ 0.9, and p represents a number satisfying 0.1 ≦ p ≦ 0.9. , M + p represents a number satisfying m + p ≦ 1, and r preferably represents a number satisfying 1.8 ≦ r ≦ 2.2.

In the aspect (6), when the composition ratio of Li, Ni, Co, Mn and O of lithium nickel cobalt manganate is represented by the general formula Li _k Ni _m Co _p Mn _(1-mp) O _r , k represents a number satisfying 0.95 ≦ k ≦ 1.10, m represents a number satisfying 0.1 ≦ m ≦ 0.9, and p represents a number satisfying 0.1 ≦ p ≦ 0.9. , M + p represents a number satisfying m + p ≦ 1, and r preferably represents a number satisfying 1.8 ≦ r ≦ 2.2.

  In the powder body of the present invention, the lithium transition metal composite oxide may be a mixture of lithium nickel cobaltate and nickel cobalt lithium aluminate, or a mixture of lithium nickel cobaltate and nickel cobalt lithium manganate. It may be a mixture of lithium cobalt aluminate and lithium nickel cobalt manganate. Moreover, the mixture of these and lithium cobaltate may be sufficient.

  In the powder body of the present invention, the proportion of particles having a volume-based particle diameter of 50 μm or more of the lithium transition metal composite oxide is preferably 10% by volume or less of the total particles. By being a powder body within this range, it is possible to improve the coating characteristics and slurry properties without impairing the improvement of the cycle characteristics and thermal stability of the high charge potential.

The specific surface area of the lithium transition metal composite oxide is preferably 0.2 to ³ m ² / g.
If the specific surface area is too small, the particle size of the powder body becomes too large and the battery characteristics deteriorate. When the specific surface area is too large, the oxidative decomposition reaction of the electrolytic solution occurring at or near the surface of the powder body increases, and the amount of gas generated increases. Within the above range, gas generation can be reduced without impairing improvements in low temperature characteristics, output characteristics and thermal stability, and more excellent cycle characteristics and load characteristics can be obtained.
The specific surface area can be measured by a nitrogen gas adsorption method.

  In the lithium transition metal composite oxide, the proportion of particles having a volume-based particle size of 50 μm or more is preferably 10% by volume or less of the total particles. Within the above range, the coating characteristics and slurry properties can be improved without impairing the improvement of load characteristics, low temperature characteristics, output characteristics and thermal stability.

  Hereinafter, lithium transition metal composite oxides suitably used for the coating layer of the present invention will be exemplified.

  (1) An embodiment in which the lithium transition metal composite oxide is a lithium manganese composite oxide having aluminum and / or magnesium.

  When aluminum and / or magnesium are contained, the crystal structure is stabilized, so that the storage characteristics, load characteristics, and output characteristics are not impaired, and the cycle characteristics are excellent, and the swelling of the battery is further suppressed. it can.

In the aspect (1), when the composition ratio of Li, Mn and O of the lithium manganese composite oxide is represented by the general formula Li _{1 + a} Mn _2−a O _{4 + d} , a is −0.2 ≦ a ≦ 0.2. It is preferable that d represents a number satisfying −0.5 ≦ d ≦ 0.5. The same applies to modes (2), (4), (6), (8), and (10) described later.
a is preferably larger than 0, and is preferably 0.15 or less. It is considered that the crystal structure is further stabilized and the cycle characteristics are further improved by the synergistic effect of lithium in excess of the stoichiometric ratio and aluminum and / or magnesium.

  (2) An embodiment in which the lithium transition metal composite oxide is a lithium manganese composite oxide having aluminum and / or magnesium and boron.

  Boron acts as a flux, promotes crystal growth, and further improves cycle characteristics and storage characteristics.

(3) The lithium transition metal composite oxide has a general formula of Li _{1 + a Mb} Mn _2- abB _c O _{4 + d} (M represents aluminum and / or magnesium, and a represents −0.2 ≦ a ≦ 0.2. B represents a number satisfying 0 ≦ b ≦ 0.2, c represents a number satisfying 0 ≦ c ≦ 0.02, and d satisfied −0.5 ≦ d ≦ 0.5. A mode represented by a number).

Aspect (3) is excellent in cycle characteristics, load characteristics, storage characteristics and charge / discharge capacity, and has less battery swelling.
In aspect (3), a is preferably larger than 0. It is considered that the cycle characteristics are improved by substituting a part of manganese with lithium.
In the aspect (3), b is preferably larger than 0, more preferably 0.05 or more. When aluminum and / or magnesium is contained, the crystal structure is stabilized, so that the storage characteristics, load characteristics, and output characteristics are not impaired, and the cycle characteristics are excellent, and the swelling of the battery is further suppressed. it can. b is preferably 0.15 or less. When b is too large, the discharge capacity decreases.
In the aspect (3), c is preferably larger than 0, and more preferably 0.001 or more. Boron acts as a flux, promotes crystal growth, and further improves cycle characteristics and storage characteristics. c is preferably 0.01 or less. If c is too large, the cycle characteristics deteriorate.

  (4) The aspect in which the lithium transition metal composite oxide is a lithium manganese composite oxide having aluminum and / or magnesium, boron, and at least one selected from the group consisting of titanium, zirconium and hafnium.

By having at least one selected from the group consisting of titanium, zirconium, and hafnium, the lattice constant of the unit cell of the lithium manganese composite oxide particle increases, the mobility of lithium ions in the particle increases, and the impedance decreases. I think it can be done. For this reason, it is considered that the output characteristics are further improved without impairing storage characteristics, load characteristics and cycle characteristics and without impairing suppression of battery swelling.
In aspect (4), the reason for having an element other than at least one element selected from the group consisting of titanium, zirconium and hafnium is the same as in aspects (1) to (3).

(5) the group of lithium transition metal composite oxide is represented by the general formula _{Li 1 + a M b Mn 2} -a-b D h B c O 4 + d (M represents aluminum and / or magnesium, D is composed of titanium, zirconium and hafnium A represents a number satisfying −0.2 ≦ a ≦ 0.2, b represents a number satisfying 0 ≦ b ≦ 0.2, and c represents 0 ≦ c ≦ 0. 02 represents a number satisfying 02, d represents a number satisfying −0.5 ≦ d ≦ 0.5, and h represents a number satisfying 0 ≦ h ≦ 0.1.

In aspect (5), h is preferably greater than 0. For the same reason as in the case of the aspect (4).
Further, h is preferably 0.01 or more, more preferably 0.03 or more, more preferably 0.08 or less, and further preferably 0.05 or less. In this range, it is considered that the impedance is reduced by increasing the mobility of lithium ions. If h is too large, the battery characteristics hardly change, which is not preferable.
About another point, it is the same as that of the case of aspect (4).

  (6) An embodiment in which the lithium transition metal composite oxide is a lithium manganese composite oxide having aluminum and / or magnesium, at least one selected from the group consisting of fluorine, chlorine, bromine and iodine, and boron.

  The halogen element has the effect of making the lithium manganese composite oxide powder spherical and uniform in size. As a result, a positive electrode coated surface having excellent surface smoothness, low internal resistance and excellent binding properties can be formed without impairing cycle characteristics, storage characteristics, load characteristics, and output characteristics. As the halogen element, fluorine and / or chlorine is preferable.

(7) the lithium-transition metal composite oxide represented by the general formula _{Li 1 + a M c Mn 2} -a-c O 4 · Li b X d B e O f (M is aluminum and / or magnesium, X is fluorine, chlorine, bromine And at least one selected from the group consisting of iodine, a represents a number satisfying 0 <a ≦ 0.1, b represents a number satisfying 0 ≦ b ≦ 0.1, and c represents 0 <c ≦ 0.1. Represents a number satisfying 0.2, d represents a number satisfying 0 <d ≦ 0.05, e represents a number satisfying 0 <e ≦ 0.02, and f satisfies 0 ≦ f <0.1. A mode represented by a number).

In the aspect (7), the lithium transition metal composite oxide includes a cubic spinel-type lithium manganese composite oxide represented by Li _{1 + a} M _c Mn _2-ac- O ₄ , and Li _{b Xd} B _e O _f. It is preferable to be comprised with the impurity phase which consists of 1 or more types of compounds represented by these.
In the aspect (7), a is preferably 0.02 or more, and preferably 0.08 or less. For the same reason as in the case of the aspect (3).
In embodiment (7), X is preferably fluorine and / or chlorine. d is preferably 0.01 or more, and preferably 0.03 or less. For the same reason as in the case of the aspect (6).
In the aspect (7), e is preferably 0.001 or more, and is preferably 0.01 or less. For the same reason as in the case of the aspect (3).

  (8) The lithium transition metal composite oxide is a lithium manganese composite oxide having at least one selected from the group consisting of aluminum and / or magnesium, fluorine, chlorine, bromine and iodine, boron and sulfur. Aspect.

In aspect (8), since the passage of electrons is improved by the presence of sulfur, it is considered that the cycle characteristics and load characteristics are further improved.
The sulfur content is preferably 0.03 to 0.3% by weight based on the total of the lithium transition metal composite oxide and sulfur. If it is less than 0.03% by weight, it may be difficult to reduce the resistance to movement of electrons. If it exceeds 0.3% by weight, the battery may swell due to moisture adsorption.

Sulfur may be present in any form. For example, it may exist in the form of sulfate radicals.
The sulfate radical includes sulfate ions, a group of atoms obtained by removing the charge from sulfate ions, and sulfo groups. It is preferably based on at least one selected from the group consisting of alkali metal sulfates, alkaline earth metal sulfates, organic sulfates and organic sulfonic acids and salts thereof.
Among them, it is preferable to use at least one selected from the group consisting of alkali metal sulfates and alkaline earth metal sulfates, and more preferable to use alkali metal sulfates. This is because these are chemically stable because they are composed of strong acid strong base bonds.

In aspect (8), the reason for containing elements other than sulfur is the same as in aspects (1) to (7).
In aspect (8), the positive electrode plate which has high charging / discharging capacity | capacitance and is excellent in binding property and surface smoothness can be obtained by the synergistic effect of each element by containing each said element. .

The lithium transition metal composite oxide may have a sulfate group at least on the surface of the particle.
The presence of the sulfate radical on the surface of the lithium transition metal composite oxide particle makes the electron transfer resistance around the particle extremely small, and as a result, the ease of passing electrons is improved, and the cycle characteristics and load characteristics are improved. It is thought to improve.
In addition, when the positive electrode active material of the present invention is used to form a high voltage battery (for example, a battery using LiMn _1.5 Ni _0.5 O ₄ as a lithium transition metal composite oxide), there is a problem in the conventional high voltage battery. Thus, the decomposition of the electrolyte during charging is suppressed, and as a result, the cycle characteristics are improved. The electrolyte decomposition reaction is thought to occur as a catalyst at the interface between the lithium transition metal composite oxide particles and the electrolyte, but the lithium transition is caused by sulfate radicals that do not function to decompose the electrolyte. By covering all or part of the surface of the metal composite oxide particles, it is considered that the contact area between the electrolyte and the catalyst is reduced, and the above reaction is suppressed.

  In the present invention, the sulfate group exhibits the effect of the present invention regardless of the form of the sulfate group present on the surface of the lithium transition metal composite oxide particles. For example, even when the sulfate radical covers the entire particle surface of the lithium transition metal composite oxide, the sulfate radical covers a part of the particle surface of the lithium transition metal composite oxide. However, cycle characteristics and load characteristics are improved.

Moreover, the sulfate radical should just exist in the surface of particle | grains at least. Therefore, a part of the sulfate radical may exist inside the particle.
Whether or not the sulfate radical is present on the surface of the lithium transition metal composite oxide particles can be analyzed by various methods. For example, it can be analyzed by Auger electron spectroscopy or X-ray photoelectron spectroscopy.
Moreover, various methods can be used for the determination of sulfate radicals. For example, it can be quantified by ICP emission spectrometry or titration.

(9) the lithium-transition metal composite oxide represented by the general formula _{Li 1 + a M b Mn 2} -a-b D h X c B d S e O 4 + f (M represents aluminum and / or magnesium, D is titanium, zirconium, and Represents at least one selected from the group consisting of hafnium, X represents at least one selected from the group consisting of fluorine, chlorine, bromine and iodine, and a represents a number satisfying −0.2 ≦ a ≦ 0.2. B represents a number satisfying 0 <b ≦ 0.2, c represents a number satisfying 0 ≦ c ≦ 0.05, d represents a number satisfying 0 <d ≦ 0.02, and e represents 0 ≦ e ≦ 0.1, f represents a number satisfying −0.5 ≦ f ≦ 0.5, and h represents a number satisfying 0 ≦ h ≦ 0.1. Aspect.

In aspect (9), e is preferably greater than 0. For the same reason as in the case of the aspect (8).
Further, e is more preferably 0.0017 or more, and is preferably 0.02 or less. If e is too small, the electron transfer resistance may be low. If e is too large, the battery may swell due to moisture adsorption.
About another point, it is the same as that of the case of aspect (8).

  (10) The lithium transition metal composite oxide has at least one selected from the group consisting of aluminum and / or magnesium, fluorine, chlorine, bromine and iodine, boron, sulfur, sodium and / or calcium. The aspect which is lithium manganese complex oxide.

In the aspect (10), by containing sodium and / or calcium, elution of manganese ions can be further suppressed by a synergistic effect with boron (preferably boron and sulfur), and the practical level is excellent. Cycle characteristics can be realized.
In aspect (10), the reason for containing elements other than sodium and / or calcium is the same as in aspects (1) to (9).

(11) lithium transition metal composite oxide is represented by the general formula _{Li 1 + a M b Mn 2} -a-b D h X c B d S e A g O 4 + f (M represents aluminum and / or magnesium, D is titanium, Represents at least one selected from the group consisting of zirconium and hafnium, X represents at least one selected from the group consisting of fluorine, chlorine, bromine and iodine, A represents sodium and / or calcium, and a represents −0 .2 ≦ a ≦ 0.2, b represents a number satisfying 0 <b ≦ 0.2, c represents a number satisfying 0 ≦ c ≦ 0.05, and d represents 0 <d ≦ Represents a number satisfying 0.02, e represents a number satisfying 0 ≦ e ≦ 0.1, f represents a number satisfying −0.5 ≦ f ≦ 0.5, and g represents 0.00004 ≦ g ≦ Represents a number satisfying 0.015, h is 0 ≦ h Embodiments represented by represents.) A number satisfying 0.1.

The reason why the aspect (11) is preferable is the same as that in the aspect (10).
In the aspect (11), e is preferably 0.0017 or more, and preferably 0.02 or less. If e is too small, the electron transfer resistance may be low. If e is too large, the battery may swell due to moisture adsorption.
About another point, it is the same as that of the case of aspect (10).

  The lithium transition metal composite oxide of the coating layer of the present invention preferably has an iron content of 25 ppm or less, more preferably 20 ppm or less, and even more preferably 18 ppm or less. If the iron content is too high, it may cause an internal short circuit of the battery.

The median particle size of the lithium transition metal composite oxide in the coating layer is preferably 0.05 μm or more, more preferably 0.1 μm or more, more preferably 0.2 μm or more, and 50 μm. Or less, more preferably 30 μm or less, and even more preferably 20 μm or less. If the median particle size is too large, the powder body may not be coated.
The median particle size means a particle size at which the volume cumulative frequency of the particle size distribution of the secondary particles reaches 50%. The method for measuring the median particle size is not particularly limited. For example, the particle size distribution is measured by a laser diffraction scattering method, an integrated distribution using the logarithm of the volume-based particle diameter is obtained, and the particle diameter when occupying 50% of the entire lithium transition metal composite oxide powder, ie, oversize 50 % Particle size.

In the positive electrode active material of the present invention, when the weight part of the powder main body is 100, the weight part of the lithium transition metal composite oxide of the coating layer is mixed so that it is in the range of 0.5 or more and 250 or less. It is preferable to do this.
When the weight part of the powder body is 100, the weight part of the lithium transition metal composite oxide of the coating layer is preferably 1 or more, more preferably 3 or more, and 100 or less. Is more preferably 40 or less, and particularly preferably 30 or less. If it is too large, the capacity of the positive electrode active material is reduced, and if it is too small, the effect of the present invention cannot be obtained, which is not preferable.

<Method for producing positive electrode active material for non-aqueous electrolyte secondary battery>
Although the manufacturing method of the positive electrode active material of this invention is not specifically limited, For example, it can manufacture as follows.

(1) Production of powder body (i) Production of raw material mixture Compounds described below are mixed so that each constituent element has a predetermined composition ratio to obtain a raw material mixture. The compound used for the raw material mixture is selected according to the elements constituting the target composition.
The mixing method is not particularly limited, for example, a method of mixing in a slurry form using water and / or an organic solvent, and then drying to obtain a raw material mixture; A method of drying the resulting precipitate to obtain a raw material mixture; a method of using these together.

Below, the compound used for a raw material mixture is illustrated.
Lithium compound is not particularly limited, for _{example, Li 2 CO 3, LiOH,} LiOH · H 2 O, Li 2 O, LiCl, LiNO 3, Li 2 SO 4, LiHCO 3, Li (CH 3 COO), fluoride Examples include lithium, lithium bromide, lithium iodide, and lithium peroxide. Among these, Li ₂ CO ₃ , LiOH, LiOH · H ₂ O, Li ₂ O, LiCl, LiNO ₃ , Li ₂ SO ₄ , LiHCO ₃ , and Li (CH ₃ COO) are preferable.

The cobalt compound is not particularly limited, and examples thereof include cobalt oxide, cobalt hydroxide, cobalt carbonate, cobalt chloride, cobalt iodide, cobalt sulfate, cobalt bromate, and cobalt nitrate. Among these, CoSO ₄ · 7H ₂ O and Co (NO ₃ ) ₂ · 6H ₂ O are preferable.

The nickel compound is not particularly limited, and examples thereof include nickel oxide, nickel hydroxide, nickel carbonate, nickel chloride, nickel bromide, nickel iodide, nickel sulfate, nickel nitrate, and nickel formate. Among these, NiSO ₄ · 6H ₂ O and Ni (NO ₃ ) ₂ · 6H ₂ O are preferable.

The aluminum compound is not particularly limited, and examples thereof include aluminum oxide, aluminum hydroxide, aluminum carbonate, aluminum chloride, aluminum iodide, aluminum sulfate, and aluminum nitrate. Among these, Al ₂ (SO ₄ ) ₃ , Al (NO ₃ ) ₃ , Al ₂ O ₃ , and Al (OH) ₃ are preferable.

The manganese compound is not particularly limited, and examples thereof include manganese oxide, manganese hydroxide, manganese carbonate, manganese chloride, manganese iodide, manganese sulfate, and manganese nitrate. Among these, MnSO ₄ and MnCl ₂ are preferable.

The vanadium compound is not particularly limited, and examples thereof include vanadium oxide, vanadium hydroxide, vanadium chloride, and vanadium sulfate. Among these, V ₂ O ₅ and VCl ₂ are preferable.

The strontium compound is not particularly limited, and examples thereof include strontium oxide, strontium hydroxide, strontium chloride, and strontium sulfate. Of these, SrO and Sr (OH) ₂ are preferable.

The calcium compound is not particularly limited, and examples thereof include calcium oxide, calcium carbonate, calcium hydroxide, calcium chloride, and calcium nitrate. Of these, CaO and CaCO ₃ are preferable.

Although a sulfur containing compound is not specifically limited, For example, sulfide, sulfur iodide, hydrogen sulfide, a sulfuric acid, its salt, and nitrogen sulfide are mentioned. Among these, Li ₂ SO ₄ , MnSO ₄ , (NH ₄ ) ₂ SO ₄ , Al ₂ (SO ₄ ) ₃ , and MgSO ₄ are preferable.

The compound containing a halogen element is not particularly limited. For example, hydrogen fluoride, oxygen fluoride, hydrofluoric acid, hydrogen chloride, hydrochloric acid, chlorine oxide, fluorinated chlorine oxide, bromine oxide, bromine fluorosulfate, hydrogen iodide , Iodine oxide, and periodic acid. Among these, NH ₄ F, NH ₄ Cl, NH ₄ Br, NH ₄ I, LiF, LiCl, LiBr, LiI, MnF ₂ , MnCl ₂ , MnBr ₂ , and MnI ₂ are preferable.

Magnesium compound is not particularly limited, for _{example, MgO, MgCO 3, Mg (} OH) 2, MgCl 2, MgSO 4, Mg (NO 3) 2, Mg (CH 3 COO) 2, magnesium iodide, perchlorate Examples include magnesium. Among these, MgSO ₄ and Mg (NO ₃ ) ₂ are preferable.

The titanium compound is not particularly limited. Examples thereof include titanium fluoride, titanium chloride, titanium bromide, titanium iodide, titanium oxide, titanium sulfide, and titanium sulfate. Of these, TiO, TiO ₂ , Ti ₂ O ₃ , TiCl ₂ , and Ti (SO ₄ ) ₂ are preferable.

The zirconium compound is not particularly limited. Examples thereof include zirconium fluoride, zirconium chloride, zirconium bromide, zirconium iodide, zirconium oxide, zirconium sulfide, zirconium carbonate and the like. Of these, ZrF ₂ , ZrCl, ZrCl ₂ , ZrBr ₂ , ZrI ₂ , ZrO, ZrO ₂ , ZrS ₂ , Zr (OH) _{3 and the} like are preferable.
Moreover, you may use the compound containing 2 or more types of each element mentioned above.

Below, the suitable method of obtaining a raw material mixture is demonstrated concretely.
(A) Prepared from the cobalt compound, zirconium compound and magnesium compound described above. An aqueous solution containing cobalt ions, zirconium ions and magnesium ions having a predetermined composition ratio is dropped into pure water being stirred. Next, an aqueous sodium hydroxide solution is added dropwise so that the pH is 7 to 11, and the mixture is stirred and reacted at 40 to 80 ° C. and at a rotational speed of 500 to 1500 rpm. After finishing the dropping of the aqueous solution containing cobalt ions, zirconium ions and magnesium ions of a predetermined composition ratio, only the aqueous sodium hydroxide solution was dropped until the pH reached 9 to 10, and the precipitates of cobalt, zirconium and magnesium were added. obtain. Instead of the sodium hydroxide aqueous solution, an alkaline solution such as an ammonium hydrogen carbonate aqueous solution, a sodium hydrogen carbonate aqueous solution, a potassium hydroxide aqueous solution, or a lithium hydroxide aqueous solution can also be used.

  Next, the aqueous solution is filtered to collect a precipitate. The collected precipitate is washed with water and heat-treated, and then mixed with the above-described lithium compound to obtain a raw material mixture.

  (B) Prepared from the cobalt compound, nickel compound, manganese compound and zirconium compound described above. An aqueous solution containing cobalt ions, nickel ions, manganese ions and zirconium ions having a predetermined composition ratio is dropped into pure water being stirred. A sodium hydroxide aqueous solution is dripped here so that it may become pH 8-11, and it is made to react by stirring at 40-80 degreeC and rotation speed 500-1500 rpm. After finishing the dropping of the aqueous solution containing cobalt ions, nickel ions, manganese ions and zirconium ions having a predetermined composition ratio, only the aqueous sodium hydroxide solution was dropped until the pH reached 9 to 10, and cobalt, nickel, manganese and A zirconium precipitate is obtained. Instead of the sodium hydroxide aqueous solution, an alkaline solution such as an ammonium hydrogen carbonate aqueous solution, a sodium hydrogen carbonate aqueous solution, a potassium hydroxide aqueous solution, or a lithium hydroxide aqueous solution can also be used.

  Next, the aqueous solution is filtered to collect a precipitate. The collected precipitate is washed with water and heat-treated, and then mixed with the above-described lithium compound to obtain a raw material mixture.

  (C) Prepared from the cobalt compound, nickel compound, aluminum compound and zirconium compound described above. An aqueous solution containing cobalt ions, nickel ions, aluminum ions and zirconium ions having a predetermined composition ratio is dropped into pure water being stirred. A sodium hydroxide aqueous solution is dripped here so that it may become pH 8-11, and it is made to react by stirring at 40-80 degreeC and rotation speed 500-1500 rpm. After dropwise addition of an aqueous solution containing cobalt ions, nickel ions, aluminum ions and zirconium ions of a predetermined composition ratio, only sodium hydroxide aqueous solution is continuously dropped until the pH reaches 9 to 10, and precipitates of cobalt, nickel, manganese and zirconium Get. Instead of the sodium hydroxide aqueous solution, an alkaline solution such as an ammonium hydrogen carbonate aqueous solution, a sodium hydrogen carbonate aqueous solution, a potassium hydroxide aqueous solution, or a lithium hydroxide aqueous solution can also be used.

  Next, the aqueous solution is filtered to collect a precipitate. The collected precipitate is washed with water and heat-treated, and then mixed with the above-described lithium compound to obtain a raw material mixture.

(Ii) Firing and grinding of raw material mixture Next, the raw material mixture is fired. The firing temperature, time, atmosphere, and the like are not particularly limited, and can be appropriately determined according to the purpose.
The firing temperature is preferably 400 ° C. or higher, more preferably 700 ° C. or higher, and further preferably 850 ° C. or higher. If the firing temperature is too low, unreacted raw materials may remain in the positive electrode active material, and the original characteristics of the positive electrode active material may not be utilized. The firing temperature is preferably 1200 ° C or lower, more preferably 1150 ° C or lower, and further preferably 1100 ° C or lower. If the firing temperature is too high, by-products are likely to be generated, resulting in a decrease in discharge capacity per unit weight, a decrease in cycle characteristics, and a decrease in operating voltage.
The firing time is preferably 1 hour or longer, and more preferably 6 hours or longer. Within the above range, the diffusion reaction between the particles of the mixture proceeds sufficiently.
The firing time is preferably 36 hours or less, and more preferably 30 hours or less. When it is within the above range, the synthesis proceeds sufficiently.

  Examples of the firing atmosphere include air, oxygen gas, a mixed gas of these with an inert gas such as nitrogen gas and argon gas, an atmosphere in which the oxygen concentration (oxygen partial pressure) is controlled, and a weak oxidizing atmosphere.

  After firing, if desired, the powder may be pulverized using a rough mortar, ball mill, vibration mill, pin mill, jet mill or the like to obtain a powder having a desired particle size.

  By using the above production method, the intended powder body of the present invention can be obtained.

(2) Preparation of coating layer (i) Preparation of raw material mixture The above-described powder body and a compound described later are mixed so that each constituent element has a predetermined composition ratio to obtain a raw material mixture. The compound used for the raw material mixture is selected according to the elements constituting the target composition.
The mixing method is not particularly limited, for example, a method of mixing powdery compounds as they are to obtain a raw material mixture; mixing in a slurry form using water and / or an organic solvent, and then drying to obtain a raw material mixture Method: A method in which an aqueous solution of the above-mentioned compound is mixed and precipitated, and the resulting precipitate is dried to obtain a raw material mixture; a method in which these are used in combination.

Below, the compound used for a raw material mixture is illustrated.
Lithium compound is not particularly limited, for _{example, Li 2 CO 3, LiOH,} LiOH · H 2 O, Li 2 O, LiCl, LiNO 3, Li 2 SO 4, LiHCO 3, Li (CH 3 COO), fluoride Examples include lithium, lithium bromide, lithium iodide, and lithium peroxide. Among these, Li ₂ CO ₃ , LiOH, LiOH · H ₂ O, Li ₂ O, LiCl, LiNO ₃ , Li ₂ SO ₄ , LiHCO ₃ , and Li (CH ₃ COO) are preferable.

The manganese compound is not particularly limited. For example, manganese metal, oxide (eg, MnO ₂ , Mn ₂ O ₃ , Mn ₃ O ₄ ), hydroxide, nitrate, carbonate (MnCO ₃ ), chloride salt, Examples thereof include manganese iodide, manganese sulfate, and manganese nitrate. Among these, manganese metal, MnCO ₃ , MnSO ₄ , and MnCl ₂ are preferable.

Magnesium compound is not particularly limited, for _{example, MgO, MgCO 3, Mg (} OH) 2, MgCl 2, MgSO 4, Mg (NO 3) 2, Mg (CH 3 COO) 2, magnesium iodide, perchlorate Examples include magnesium. Among these, MgSO ₄ and Mg (NO ₃ ) ₂ are preferable.

The titanium compound is not particularly limited. Examples thereof include titanium fluoride, titanium chloride, titanium bromide, titanium iodide, titanium oxide, titanium sulfide, and titanium sulfate. Of these, TiO, TiO ₂ , Ti ₂ O ₃ , TiCl ₂ , and Ti (SO ₄ ) ₂ are preferable.

The boron compound is not particularly limited. For example, B ₂ O ₃ (melting point: 460 ° C.), H ₃ BO ₃ (decomposition temperature: 173 ° C.), lithium boron composite oxide, orthoboric acid, boron oxide, boron phosphate, etc. are used. It is done. Among these, H ₃ BO ₃ and B ₂ O ₃ are preferable.

The cerium compound is not particularly limited. Examples thereof include cerium fluoride, cerium chloride, cerium bromide, cerium iodide, cerium oxide, cerium sulfide, and cerium carbonate. Among them _{CeF 2, CeCl 2, CeBr 2} , CeI 2, CeO, CeO 2, CeS 2 and the like are preferable.

The zirconium compound is not particularly limited. Examples thereof include zirconium fluoride, zirconium chloride, zirconium bromide, zirconium iodide, zirconium oxide, zirconium sulfide, zirconium carbonate and the like. Of these, ZrF ₂ , ZrCl, ZrCl ₂ , ZrBr ₂ , ZrI ₂ , ZrO, ZrO ₂ , ZrS ₂ , Zr (OH) _{3 and the} like are preferable.

The hafnium compound is not particularly limited. Examples thereof include hafnium fluoride, hafnium chloride, hafnium bromide, hafnium iodide, hafnium oxide, and hafnium carbonate. Among these, HfF ₄ , HfCl ₂ , HfBr ₂ , HfO ₂ , Hf (OH) ₄ , Hf ₂ S and the like are preferable.

The sulfur compound is not particularly limited. For example, Li ₂ SO ₄ , MnSO ₄ , (NH ₄ ) ₂ SO ₄ , Al ₂ (SO ₄ ) ₃ , MgSO ₄ , sulfide, sulfur iodide, hydrogen sulfide, sulfuric acid and The salt and nitrogen sulfide are mentioned. Among these, Li ₂ SO ₄ , MnSO ₄ , (NH ₄ ) ₂ SO ₄ , Al ₂ (SO ₄ ) ₃ , and MgSO ₄ are preferable.

Sodium compound is not particularly limited, for _{example, Na 2 CO 3, NaOH,} Na 2 O, NaCl, NaNO 3, Na 2 SO 4, NaHCO 3, CH 3 CONa the like.

Calcium compound is not particularly limited, for _{example, CaO, CaCO 3, Ca (} OH) 2, CaCl 2, CaSO 4, Ca (NO 3) 2, Ca (CH 3 COO) 2 and the like.

The niobium compound is not particularly limited, and examples thereof include niobium oxide, niobium chloride, niobium oxide sulfate, and niobium fluoride. Among these, NbO ₂ and Nb ₂ O ₅ are preferable.
Moreover, you may use the compound containing 2 or more types of each element mentioned above.

Hereinafter, a preferred method for obtaining the raw material mixture will be specifically described by taking as an example a positive electrode active material in which the lithium transition metal composite oxide of the coating layer is a lithium manganese composite oxide having magnesium, zirconium and boron. .
The lithium cobaltate of the powder body is stirred in pure water. An aqueous solution containing manganese ions and magnesium ions having a predetermined composition ratio prepared from the above-described manganese compound and magnesium compound is dropped into the stirring solution.
Next, an aqueous ammonium hydrogen carbonate solution is added dropwise to precipitate manganese and magnesium to obtain manganese and magnesium salts, and a coating layer is formed on lithium cobalt oxide. In place of the ammonium hydrogen carbonate aqueous solution, an alkali solution such as a sodium hydroxide aqueous solution, a sodium hydrogen carbonate aqueous solution, a potassium hydroxide aqueous solution, or a lithium hydroxide aqueous solution can also be used.

  Next, the aqueous solution is filtered to collect a precipitate. The collected precipitate is washed with water and heat-treated, and then mixed with the above-described lithium compound, zirconium compound and boron compound to obtain a raw material mixture.

(Ii) Firing and grinding of raw material mixture Next, the raw material mixture is fired. The firing temperature, time, atmosphere, and the like are not particularly limited, and can be appropriately determined according to the purpose.
The firing temperature is preferably 400 ° C. or higher, and more preferably 700 ° C. or higher. If the firing temperature is too low, unreacted raw materials remain, and the original characteristics of the lithium transition metal composite oxide used for the coating layer may not be utilized. The firing temperature is preferably 1100 ° C. or lower, and more preferably 950 ° C. or lower. If the firing temperature is too high, the particle size may become too large and the battery characteristics may deteriorate. Moreover, since the lithium transition metal composite oxide coated on the powder body increases, the capacity may decrease.
In general, the firing time is preferably 1 to 24 hours, and more preferably 6 to 12 hours. When the firing time is too short, the diffusion reaction between the raw material particles does not proceed. If the firing time is too long, firing after the diffusion reaction is almost completed is wasted, and coarse particles may be formed by sintering.

  The firing may be divided into a plurality of firing steps. For example, a 1st baking process can be performed at 350-550 degreeC for 1 to 24 hours, and a 2nd baking process can be performed at 650-1000 degreeC for 1 to 24 hours.

  Examples of the firing atmosphere include air, oxygen gas, a mixed gas of these with an inert gas such as nitrogen gas and argon gas, an atmosphere in which the oxygen concentration (oxygen partial pressure) is controlled, and a weak oxidizing atmosphere. Among these, an atmosphere in which the oxygen concentration is controlled is preferable.

  After firing, if desired, the powder may be pulverized using a rough mortar, ball mill, vibration mill, pin mill, jet mill or the like to obtain a powder having a desired particle size.

  The positive electrode active material of the present invention can be obtained by the manufacturing method described above.

Hereinafter, a specific method for producing the positive electrode active material of the present invention will be described.
An aqueous solution containing cobalt ions, nickel ions and zirconium ions having a predetermined composition ratio is dropped into pure water being stirred. Here, a sodium hydroxide aqueous solution is dropped so that pH = 9, and cobalt, nickel and zirconium are precipitated at 80 ° C. and at a rotational speed of 650 rpm to obtain a precipitate of cobalt, nickel and zirconium. The resulting precipitate is filtered, washed with water, heat-treated, mixed with aluminum oxide and lithium hydroxide monohydrate, and calcined at about 750 ° C. for about 10 hours in an air atmosphere. This is pulverized to obtain a powder body.
The composition ratio of the obtained powder main body is Li: Ni: Co: Al: Zr = 1.04: 0.7: 0.2: 0.1: 0.01.
The resulting powder body is stirred in pure water. An aqueous solution containing manganese ions and magnesium ions having a predetermined composition ratio, prepared from manganese sulfate and magnesium sulfate, is dropped into the stirring solution.
Next, an aqueous ammonium hydrogen carbonate solution is added dropwise to precipitate manganese and magnesium to obtain a salt of manganese and magnesium to form a coating layer on the powder body. This is filtered, washed with water, heat-treated, mixed with lithium carbonate, and fired at about 700 ° C. for about 10 hours in an air atmosphere. This is pulverized to obtain the positive electrode active material of the present invention.
It can be seen by X-ray diffraction (XRD) that the coating layer is lithium manganate to which magnesium having a spinel structure is added.

<Positive electrode mixture>
Next, the positive electrode mixture will be described.
The positive electrode mixture includes a positive electrode active material and a conductive agent that are made of a powder having a powder body and a coating layer that covers at least a part of the surface of the powder body.
The positive electrode active material used for the positive electrode mixture of the present invention is the above-described positive electrode active material of the present invention.

In the positive electrode mixture of the present invention, the conductive agent is not particularly limited, and examples thereof include carbon materials such as graphite such as Tennobu graphite and artificial graphite, carbon black such as acetylene black, and amorphous carbon such as needle coast. .
Acetylene black and / or artificial graphite are preferable. Since these are excellent in conductivity, cycle characteristics and load characteristics are further improved.

In the positive electrode mixture of the present invention, “between” means between the conductive agent in contact with the lithium transition metal composite oxide.
In the present invention, the positive electrode mixture is not only a paste-like material composed of a positive electrode active material, a conductive agent, a binder, and a solvent for the binder, but also after being applied to the positive electrode current collector and then dried. This includes a state after the solvent is skipped.

  By using the positive electrode active material of the present invention described above, the positive electrode mixture of the present invention improves the coating properties to the current collector without impairing the effect of each positive electrode active material. Thereby, battery characteristics are improved, and a positive electrode mixture with improved coating characteristics is obtained.

  Although the manufacturing method of the positive electrode mixture of the present invention is not particularly limited, for example, it can be manufactured as follows.

(1) Production of positive electrode active material A positive electrode active material can be obtained by the method for producing a positive electrode active material of the present invention described above.

(2) Preparation of positive electrode mixture The positive electrode active material powder is mixed with a carbon-based conductive agent such as acetylene black and graphite, a binder, and a binder solvent or dispersion medium. To prepare.

  The positive electrode active material and the positive electrode mixture of the present invention are suitably used for nonaqueous electrolyte secondary batteries such as lithium ion secondary batteries and lithium ion polymer secondary batteries.

<Nonaqueous electrolyte secondary battery>
The nonaqueous electrolyte secondary battery of the present invention is a nonaqueous electrolyte secondary battery using the above-described positive electrode active material of the present invention. The positive electrode active material of the present invention is suitably used for non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries and lithium ion polymer secondary batteries.

The non-aqueous electrolyte secondary battery may be a known non-aqueous electrolyte secondary battery using the positive electrode active material of the present invention as at least a part of the positive electrode active material, and other configurations are not particularly limited. For example, an electrolytic solution is used for a lithium ion secondary battery, and a solid electrolyte (polymer electrolyte) is used for a lithium ion polymer secondary battery. Examples of the solid electrolyte used in the lithium ion polymer secondary battery include a solid electrolyte described later.
Hereinafter, a lithium ion secondary battery will be described as an example.

  As the negative electrode active material, metallic lithium, a lithium alloy, a carbon material capable of occluding and releasing lithium ions, or a compound capable of occluding and releasing lithium ions can be used. Examples of the lithium alloy include a LiAl alloy, a LiSn alloy, and a LiPb alloy. Examples of the carbon material capable of occluding and releasing lithium ions include carbon materials such as graphite and graphite. Examples of the compound capable of occluding and releasing lithium ions include oxides such as tin oxide and titanium oxide.

The electrolyte solution is not particularly limited as long as it is a compound that does not change or decompose with the operating voltage. The electrolyte includes an electrolytic solution.
Examples of the solvent used in the electrolytic solution include dimethoxyethane, diethoxyethane, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl formate, γ-butyrolactone, 2-methyltetrahydrofuran, dimethyl sulfoxide, Organic solvents such as sulfolane can be mentioned. These can be used alone or in admixture of two or more.

Examples of the electrolyte used for the electrolytic solution include lithium salts such as lithium perchlorate, lithium tetrafluoroborate, lithium hexafluorophosphate, and lithium trifluoromethanoate.
The above-described solvent and electrolyte are mixed to obtain an electrolytic solution. Here, a gelling agent or the like may be added and used as a gel. Moreover, you may make it absorb and use a hygroscopic polymer.
Further, a solid electrolyte having conductivity of inorganic or organic lithium ions may be used.

  Examples of the separator include a porous film made of polyethylene or polypropylene.

  Examples of the binder include polyvinylidene fluoride, polytetrafluoroethylene, polyamide acrylic resin, and the like.

Using the positive electrode active material of the present invention and the above-described negative electrode active material, electrolyte, separator, and binder, the nonaqueous electrolyte secondary battery of the present invention can be obtained according to a conventional method.

  By using lithium manganate as the positive electrode active material together with the positive electrode active material of the present invention, not only the cycle characteristics, load characteristics and thermal stability are improved, but also the non-aqueous electrolyte having excellent overcharge characteristics and safety. A secondary battery can be obtained.

Represented by the general formula Li _a Mn _3−a O _{4 + f} (a represents a number satisfying 0.8 ≦ a ≦ 1.2, and f represents a number satisfying −0.5 ≦ f ≦ 0.5). Lithium manganate is preferred. The lithium manganate is selected from the group consisting of magnesium, aluminum, calcium, vanadium, titanium, chromium, manganese, iron, cobalt, nickel, copper, zinc, strontium, zirconium, niobium, molybdenum, boron and tin. It may be substituted with at least one selected from the above.

  The lithium manganate used together with the positive electrode active material of the present invention is a positive electrode active material for a non-aqueous electrolyte secondary battery having at least a lithium transition metal composite oxide having a spinel structure. As preferred embodiments of the lithium transition metal composite oxide, the following (1) to (7) may be mentioned.

(1) In formula _{Li 1 + a Mg b Ti c} Mn 2-a-b-c B d O 4 + e (a represents a number satisfying -0.2 ≦ a ≦ 0.2, b is 0.005 ≦ b ≦ 0.10 represents a number satisfying 0.10, c represents a number satisfying 0.005 ≦ c ≦ 0.05, d represents a number satisfying 0.002 ≦ d ≦ 0.02, and e represents −0.5 ≦ e represents a number satisfying e ≦ 0.5.)

Aspect (1) is excellent in cycle characteristics, high temperature cycle characteristics and load characteristics.
In aspect (1), a is preferably larger than 0. It is considered that the cycle characteristics are improved by substituting a part of manganese with lithium.
In the aspect (1), b is preferably 0.01 or more, more preferably 0.02 or more, and preferably 0.08 or less, and 0.07 or less. More preferred. If b is too large, + 3-valent manganese ions decrease, and the charge / discharge capacity decreases. If b is too small, elution of transition metal ions increases and gas generation occurs, so that the high temperature characteristics deteriorate.
In the aspect (1), c is preferably 0.01 or more, more preferably 0.02 or more, and preferably 0.08 or less, and 0.07 or less. More preferred. When c is too large, the charge / discharge efficiency decreases. If c is too small, sufficient load characteristics and cycle characteristics cannot be obtained.
In the aspect (1), d is preferably 0.003 or more, and is preferably 0.008 or less. If d is too large, the initial capacity decreases. In addition, the elution of transition metal ions increases, causing gas generation, resulting in deterioration of high temperature characteristics. If d is too small, the primary particle size does not grow, and the particle packing property is not improved.

  (2) The aspect in which the lithium transition metal composite oxide is a lithium manganese composite oxide having at least one selected from the group consisting of titanium, zirconium and hafnium.

  By having at least one selected from the group consisting of titanium, zirconium, and hafnium, the lattice constant of the unit cell of the lithium manganese composite oxide particle increases, the mobility of lithium ions in the particle increases, and the impedance decreases. I think it can be done. For this reason, it is thought that output characteristics improve, without impairing improvement of cycling characteristics and high temperature cycling characteristics.

(3) The aspect in which the lithium transition metal composite oxide is a lithium manganese composite oxide having at least one selected from the group consisting of titanium, zirconium and hafnium and sulfur.

In the aspect (3), the easiness of passing electrons is improved by the presence of sulfur, so that it is considered that the cycle characteristics and the load characteristics are further improved.
The sulfur content is preferably 0.03 to 0.3% by weight based on the total of the lithium transition metal composite oxide and sulfur. If it is less than 0.03% by weight, it may be difficult to reduce the resistance to movement of electrons. If it exceeds 0.3% by weight, the battery may swell due to moisture adsorption.

Sulfur may be present in any form. For example, it may exist in the form of sulfate radicals.
The sulfate radical includes sulfate ions, a group of atoms obtained by removing the charge from sulfate ions, and sulfo groups. It is preferably based on at least one selected from the group consisting of alkali metal sulfates, alkaline earth metal sulfates, organic sulfates and organic sulfonic acids and salts thereof.
Among them, it is preferable to use at least one selected from the group consisting of alkali metal sulfates and alkaline earth metal sulfates, and more preferable to use alkali metal sulfates. This is because these are chemically stable because they are composed of strong acid strong base bonds.

In aspect (3), the reason for containing elements other than sulfur is the same as in aspect (ii).
In aspect (3), the positive electrode plate which has high charging / discharging capacity | capacitance, and is excellent in binding property and surface smoothness can be obtained by containing each said element by the synergistic effect of each element. .

The lithium transition metal composite oxide may have a sulfate group at least on the surface of the particle.
The presence of the sulfate radical on the surface of the lithium transition metal composite oxide particle makes the electron transfer resistance around the particle extremely small, and as a result, the ease of passing electrons is improved, and the cycle characteristics and load characteristics are improved. It is thought to improve.
In addition, when the positive electrode active material of the present invention is used to form a high voltage battery (for example, a battery using LiMn _1.5 Ni _0.5 O ₄ as a lithium transition metal composite oxide), there is a problem in the conventional high voltage battery. Thus, the decomposition of the electrolyte during charging is suppressed, and as a result, the cycle characteristics are improved. The electrolyte decomposition reaction is thought to occur as a catalyst at the interface between the lithium transition metal composite oxide particles and the electrolyte, but the lithium transition is caused by sulfate radicals that do not function to decompose the electrolyte. By covering all or part of the surface of the metal composite oxide particles, it is considered that the contact area between the electrolyte and the catalyst is reduced, and the above reaction is suppressed.

  In the present invention, the sulfate group exhibits the effect of the present invention regardless of the form of the sulfate group present on the surface of the lithium transition metal composite oxide particles. For example, even when the sulfate radical covers the entire particle surface of the lithium transition metal composite oxide, the sulfate radical covers a part of the particle surface of the lithium transition metal composite oxide. However, cycle characteristics and load characteristics are improved.

Moreover, the sulfate radical should just exist in the surface of particle | grains at least. Therefore, a part of the sulfate radical may exist inside the particle.
Whether or not the sulfate radical is present on the surface of the lithium transition metal composite oxide particles can be analyzed by various methods. For example, it can be analyzed by Auger electron spectroscopy or X-ray photoelectron spectroscopy.
Moreover, various methods can be used for the determination of sulfate radicals. For example, it can be quantified by ICP emission spectrometry or titration.

  (4) The aspect in which the lithium transition metal composite oxide is a lithium manganese composite oxide having at least one selected from the group consisting of titanium, zirconium and hafnium, sulfur, sodium and / or calcium.

In the aspect (4), by containing sodium and / or calcium, elution of manganese ions can be further suppressed by a synergistic effect with boron (preferably boron and sulfur), and the practical level is excellent. Cycle characteristics can be realized.
In aspect (4), the reason for containing elements other than sodium and / or calcium is the same as in aspects (2) and (3).

  (5) An embodiment in which the lithium transition metal composite oxide is a lithium manganese composite oxide having aluminum and / or magnesium.

  When aluminum and / or magnesium are contained, the crystal structure is stabilized, so that the storage characteristics, load characteristics, and output characteristics are not impaired, and the cycle characteristics are excellent, and the swelling of the battery is further suppressed. it can.

  (6) The aspect in which the lithium transition metal composite oxide is a lithium manganese composite oxide having aluminum and / or magnesium and boron.

  Boron acts as a flux, promotes crystal growth, and further improves cycle characteristics and storage characteristics.

(7) The lithium transition metal composite oxide has a general formula of Li _{1 + a Mb} Mn _2- abB _c O _{4 + d} (M represents aluminum and / or magnesium, and a represents −0.2 ≦ a ≦ 0.2. B represents a number satisfying 0 ≦ b ≦ 0.2, c represents a number satisfying 0 ≦ c ≦ 0.02, and d satisfied −0.5 ≦ d ≦ 0.5. A mode represented by a number).

Aspect (7) is excellent in cycle characteristics, load characteristics, storage characteristics and charge / discharge capacity, and has less battery swelling.
In aspect (7), a is preferably larger than 0. It is considered that the cycle characteristics are improved by substituting a part of manganese with lithium.
In the aspect (7), b is preferably larger than 0, more preferably 0.05 or more. When aluminum and / or magnesium is contained, the crystal structure is stabilized, so that the storage characteristics, load characteristics, and output characteristics are not impaired, and the cycle characteristics are excellent, and the swelling of the battery is further suppressed. it can. b is preferably 0.15 or less. When b is too large, the discharge capacity decreases.
In the aspect (7), c is preferably larger than 0, and more preferably 0.001 or more. Boron acts as a flux, promotes crystal growth, and further improves cycle characteristics and storage characteristics. c is preferably 0.01 or less. If c is too large, the cycle characteristics deteriorate.

  The production method of the lithium manganate used together with the positive electrode active material of the present invention is not particularly limited, and can be produced, for example, as follows.

A compound is mixed so that each constituent element has a predetermined composition ratio to obtain a raw material mixture. The compound used for the raw material mixture is selected according to the elements constituting the target composition.
The mixing method is not particularly limited, for example, a method of mixing powdery compounds as they are to obtain a raw material mixture; mixing in a slurry form using water and / or an organic solvent, and then drying to obtain a raw material mixture Method: A method in which an aqueous solution of the above-mentioned compound is mixed and precipitated, and the resulting precipitate is dried to obtain a raw material mixture; a method in which these are used in combination.
Next, the raw material mixture is fired to obtain lithium manganate. The firing temperature, time, atmosphere, and the like are not particularly limited, and can be appropriately determined according to the purpose.
After firing, if desired, the powder may be pulverized using a rough mortar, ball mill, vibration mill, pin mill, jet mill or the like to obtain a powder having a desired particle size.

A preferred method for producing a positive electrode using the positive electrode active material of the present invention will be described below.
A positive electrode mixture is prepared by mixing the positive electrode active material powder of the present invention with a carbon-based conductive agent such as acetylene black and graphite, a binder, and a binder solvent or dispersion medium. The obtained positive electrode mixture is made into a slurry or a kneaded product, applied to or supported on a band-shaped current collector such as an aluminum foil, and press-rolled to form a positive electrode active material layer on the band-shaped current collector.
FIG. 1 is a schematic cross-sectional view of a positive electrode. As shown in FIG. 1, the positive electrode 13 is obtained by holding the positive electrode active material 5 on the strip-shaped current collector 12 with the binder 4.

It is considered that the positive electrode active material of the present invention is excellent in mixing with the conductive agent powder and has a low internal resistance of the battery. Accordingly, the charge / discharge characteristics, particularly the discharge capacity, are excellent.
In addition, the positive electrode mixture of the present invention has excellent fluidity when kneaded with the binder, and is easily entangled with the binder polymer and has excellent binding properties.

As a preferred embodiment of the nonaqueous electrolyte secondary battery of the present invention, a strip-shaped positive electrode formed by forming a positive electrode active material layer using the positive electrode active material of the present invention on both surfaces of a strip-shaped positive electrode current collector, and metallic lithium A negative electrode active material layer using one selected from a lithium alloy, a carbon material capable of occluding and releasing lithium ions, or a compound capable of occluding and releasing lithium ions as a negative electrode active material is formed on both sides of a strip-shaped negative electrode current collector Examples include a non-aqueous electrolyte secondary battery that includes a strip-shaped negative electrode and a strip-shaped separator, and the strip-shaped separator is interposed between the strip-shaped positive electrode and the strip-shaped negative electrode.
A positive electrode active material layer using the positive electrode active material of the present invention is formed on both surfaces of a strip-shaped positive electrode current collector, and a negative electrode active material layer using the negative electrode active material is formed on both surfaces of the strip-shaped negative electrode current collector. Thus, a nonaqueous electrolyte secondary battery having a higher charge / discharge capacity can be obtained without impairing the battery characteristics of the present invention.

  Further, as another preferred embodiment of the nonaqueous electrolyte secondary battery of the present invention, a nonaqueous electrolyte secondary battery having a positive electrode, a negative electrode, a separator and a nonaqueous electrolyte, wherein the following I is used as a positive electrode active material of the positive electrode, A non-aqueous electrolyte secondary battery using the following II as a negative electrode active material of the negative electrode can be mentioned. This non-aqueous electrolyte secondary battery is excellent not only in load characteristics, low temperature characteristics, output characteristics and thermal stability, but also in overcharge characteristics and safety.

I: general formula _{Li a Mn 3-a O 4} + f (a is a number satisfying 0.8 ≦ a ≦ 1.2, f is a number satisfying -0.5 ≦ f ≦ 0.5.) And the lithium transition metal composite oxide used in the positive electrode active material of the present invention, the weight of the lithium manganate is A, and the weight of the lithium transition metal composite oxide is B. In some cases, the positive electrode active material for a non-aqueous electrolyte secondary battery is mixed so that 0.2 ≦ B / (A + B) ≦ 0.8.
II: A negative electrode active material comprising at least one selected from the group consisting of metallic lithium, lithium alloys, a carbon material capable of occluding and releasing lithium ions, and a compound capable of occluding and releasing lithium ions.

In the positive electrode active material of I described above, it is preferable to mix so that 0.4 ≦ B / (A + B) ≦ 0.6. This is because, in the range of 0.4 ≦ B / (A + B) ≦ 0.6, not only the load characteristics, the low temperature characteristics, the output characteristics, and the thermal stability, but also the overcharge characteristics and safety are remarkably improved.
In the positive electrode active material of I, a part of lithium manganate is magnesium, aluminum, calcium, vanadium, titanium, chromium, manganese, iron, cobalt, nickel, copper, zinc, strontium, zirconium, niobium, molybdenum. , May be substituted with at least one selected from the group consisting of boron and tin.
As a compound capable of occluding and releasing lithium ions used for the negative electrode active material of II, a general formula consisting of a spinel structure containing an alkali metal and / or an alkaline earth metal is Li _a Ti _b O _{4 + c} (a is 0.8). ≦ a ≦ 1.5, b represents a number satisfying 1.5 ≦ b ≦ 2.2, and c represents a number satisfying −0.5 ≦ c ≦ 0.5. The negative electrode active material for a non-aqueous electrolyte secondary battery is preferred. At this time, it is possible to obtain a nonaqueous electrolyte secondary battery in which not only load characteristics, low temperature characteristics, output characteristics and thermal stability but also cycle characteristics are greatly improved.

The shape of the nonaqueous electrolyte secondary battery of the present invention is not particularly limited, and may be a cylindrical shape, a coin shape, a square shape, a laminate shape, or the like.
FIG. 2 is a schematic cross-sectional view of a cylindrical battery. As shown in FIG. 2, in the cylindrical battery 20, the positive electrode 13 in which the positive electrode active material layer is formed on the current collector 12, and the negative electrode 11 in which the negative electrode active material layer is formed on the current collector 12. Are repeatedly laminated via the separator 14.
FIG. 3 is a schematic partial cross-sectional view of a coin-type battery. As shown in FIG. 3, in the coin-type battery 30, the positive electrode 13 in which the positive electrode active material layer is formed on the current collector 12 and the negative electrode 11 are stacked via the separator 14.
FIG. 4 is a schematic perspective view of a prismatic battery. As shown in FIG. 4, in the square battery 40, the positive electrode 13 in which the positive electrode active material layer is formed on the current collector 12, and the negative electrode 11 in which the negative electrode active material layer is formed on the current collector 12. However, they are repeatedly laminated via the separator 14.

<Applications of non-aqueous electrolyte secondary batteries>
The use of the nonaqueous electrolyte secondary battery using the positive electrode active material of the present invention is not particularly limited. For example, notebook computers, pen input computers, pocket computers, notebook word processors, pocket word processors, electronic book players, mobile phones, cordless phones, electronic notebooks, calculators, LCD TVs, electric shavers, electric tools, electronic translators, car phones , Portable printer, transceiver, pager, handy terminal, portable copy, voice input device, memory card, backup power supply, tape recorder, radio, headphone stereo, handy cleaner, portable compact disc (CD) player, video movie, navigation system, etc. It can be used as a power source for equipment.
Also, lighting equipment, air conditioner, TV, stereo, water heater, refrigerator, oven microwave, dishwasher, washing machine, dryer, game machine, toy, road conditioner, medical equipment, automobile, electric car, golf cart, It can be used as a power source for electric carts, power storage systems and the like.
Furthermore, the application is not limited to consumer use, and may be used for military use or space.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

1. Preparation of positive electrode active material [Example 1]
An aqueous cobalt sulfate solution and an aqueous zirconium oxychloride solution were dropped into the stirring pure water so as to have a predetermined composition ratio. The zirconium oxychloride aqueous solution was added dropwise so that zirconium was 0.2 mol% with respect to cobalt. Furthermore, sodium hydroxide aqueous solution was dripped so that it might become pH 7-7.5, and it was made to react at 60 degreeC and rotation speed 650rpm. After finishing the dropping of the cobalt sulfate aqueous solution and the zirconium oxychloride aqueous solution, only the sodium hydroxide aqueous solution was continuously dropped until the pH reached 9.4 to 9.6 to precipitate cobalt and zirconium, thereby obtaining a precipitate. The obtained precipitate was filtered, washed with water, heat-treated, mixed with lithium carbonate, and calcined at 995 ° C. for 7 hours in the air. In this way, a powder body was obtained.
The obtained powder body was LiCoO ₂ in which 0.2 mol% of zirconium was present.
The obtained powder body was stirred in pure water. An aqueous solution containing manganese ions having a predetermined composition ratio prepared from manganese sulfate was dropped into the stirring solution. This aqueous solution was added dropwise so that manganese was 50 mol% with respect to the powder body.
Next, an aqueous sodium hydroxide solution was added dropwise to precipitate manganese to obtain a manganese salt, and a coating layer was formed on the powder body. This was filtered, washed with water, heat-treated, mixed with lithium carbonate, and fired at about 500 ° C. for about 10 hours in an air atmosphere. This was pulverized to obtain the positive electrode active material of the present invention.
It was found by X-ray diffraction (XRD) that the coating layer was spinel lithium manganate having manganese oxide.

[Example 2]
A positive electrode active material of the present invention was obtained in the same manner as in Example 1 except that the coating layer was formed by baking at about 700 ° C.
It was found by X-ray diffraction (XRD) that the coating layer was spinel lithium manganate having manganese oxide.

Example 3
In the formation of the coating layer, the same method as in Example 1 except that an aqueous solution containing manganese ions having a predetermined composition ratio prepared from manganese sulfate is dropped so that manganese is 200 mol% with respect to the powder body. Thus, the positive electrode active material of the present invention was obtained.
It was found by X-ray diffraction (XRD) that the coating layer was spinel lithium manganate having manganese oxide.

Example 4
A positive electrode active material of the present invention was obtained in the same manner as in Example 3 except that the coating layer was fired at about 700 ° C.
It was found by X-ray diffraction (XRD) that the coating layer was spinel lithium manganate having manganese oxide.

Example 5
The powder body was formed in the same manner as in Example 1.
The obtained powder body was stirred in pure water. An aqueous solution containing manganese ions having a predetermined composition ratio prepared from manganese sulfate was dropped into the stirring solution. This aqueous solution was added dropwise so that manganese was 20 mol% with respect to the powder body.
Next, an aqueous sodium hydroxide solution was added dropwise to precipitate manganese to obtain a manganese salt, and a coating layer was formed on the powder body. This was filtered, washed with water, heat-treated and then fired at about 600 ° C. for about 10 hours. This was pulverized to obtain the positive electrode active material of the present invention.
It was found by X-ray diffraction (XRD) that the coating layer was spinel lithium manganate having manganese oxide.

Example 6
A positive electrode active material of the present invention was obtained in the same manner as in Example 5 except that the coating layer was formed by baking at about 950 ° C.
It was found by X-ray diffraction (XRD) that the coating layer was spinel lithium manganate having manganese oxide.

[Comparative Example 1]
An aqueous cobalt sulfate solution and an aqueous zirconium oxychloride solution were dropped into the stirring pure water so as to have a predetermined composition ratio. The zirconium oxychloride aqueous solution was added dropwise so that zirconium was 0.2 mol% with respect to cobalt. Furthermore, sodium hydroxide aqueous solution was dripped so that it might become pH 7-7.5, and it was made to react at 60 degreeC and rotation speed 650rpm. After finishing the dropping of the cobalt sulfate aqueous solution and the zirconium oxychloride aqueous solution, only the sodium hydroxide aqueous solution was continuously dropped until the pH reached 9.4 to 9.6 to precipitate cobalt and zirconium, thereby obtaining a precipitate. The obtained precipitate was filtered, washed with water, heat-treated, mixed with lithium carbonate, and calcined at 995 ° C. for 7 hours in the air. In this way, a positive electrode active material was obtained.
The obtained positive electrode active material was LiCoO ₂ in which 0.2 mol% of zirconium was present.

2. Properties of Positive Electrode Active Material (1) Co Elution Amount of Positive Electrode Active Material After the obtained positive electrode active material was dried at 110 ° C. for 15 hours, 1 mol / liter of LiPF ₆ was added to a mixed solvent of ethylene carbonate / diethyl carbonate = 3/7. The electrolyte solution dissolved at a concentration of L was mixed with the ratio of the positive electrode active material and the electrolyte solution at a weight ratio of 1: 5, and stored at 85 ° C. for 48 hours. After removing the positive electrode active material by filtering this, the elution amount of Mn (weight of the Mn element with respect to the weight of the electrolytic solution) was measured by ICP spectroscopy. It can be said that the smaller the Co elution amount, the better the high temperature characteristics.

  The results are shown in Table 1.

  From Table 1, it can be seen that the positive electrode active material of the present invention has a small amount of Co elution and is excellent in high temperature characteristics.

The positive electrode active material for a nonaqueous electrolyte secondary battery of the present invention can be used for a positive electrode mixture for a nonaqueous electrolyte secondary battery and a nonaqueous electrolyte secondary battery.
The nonaqueous electrolyte secondary battery of the present invention can be used as a power source for mobile devices such as mobile phones, notebook computers, digital cameras, and batteries for electric vehicles.

FIG. 1 is a schematic cross-sectional view of a positive electrode. FIG. 2 is a schematic cross-sectional view of a cylindrical battery. FIG. 3 is a schematic partial cross-sectional view of a coin-type battery. FIG. 4 is a schematic perspective sectional view of a prismatic battery.

Explanation of symbols

4 Binder 5 Active Material 6 Zirconium 11 Negative Electrode 12 Current Collector 13 Positive Electrode 14 Separator 20 Cylindrical Battery 30 Coin Battery 40 Square Battery

Claims (4)

A positive electrode active material for a non-aqueous electrolyte secondary battery comprising a powder body and a powder having a coating layer covering at least a part of the surface of the powder body,
The powder body has a layered structure lithium transition metal composite oxide,
The coating layer is a positive electrode active material for a non-aqueous electrolyte secondary battery, in which manganese oxide is included in at least part of the spinel structure lithium transition metal composite oxide. A positive electrode active material for a non-aqueous electrolyte secondary battery comprising a powder body and a powder having a coating layer covering at least a part of the surface of the powder body,
The powder body has a layered structure lithium nickel composite oxide,
The coating layer is a positive electrode active material for a non-aqueous electrolyte secondary battery, comprising a spinel structure lithium manganese composite oxide. A positive electrode active material comprising a powder body and a powder having a coating layer covering at least a part of the surface of the powder body,
The powder body has a layered structure lithium transition metal composite oxide,
The coating layer is formed by forming a positive electrode active material layer using a positive electrode active material having manganese oxide in at least a part of a spinel structure lithium transition metal composite oxide on at least one surface of a strip-shaped positive electrode current collector. A belt-shaped positive electrode configured;
Metallic lithium,
Lithium alloy,
A strip-shaped negative electrode configured by forming a negative electrode active material layer using, as a negative electrode active material, one selected from compounds capable of occluding and releasing lithium ions on at least one surface of a strip-shaped negative electrode current collector;
A strip separator,
A non-aqueous electrolyte secondary battery in which the strip separator is interposed between the strip positive electrode and the strip negative electrode. A positive electrode active material comprising a powder body and a powder having a coating layer covering at least a part of the surface of the powder body,
The powder body has a layered structure lithium nickel composite oxide,
The coating layer comprises a strip-shaped positive electrode formed by forming a positive electrode active material layer using a positive electrode active material on at least one surface of a strip-shaped positive electrode current collector, comprising a spinel structure lithium manganese composite oxide;
Metallic lithium,
Lithium alloy,
A strip-shaped negative electrode configured by forming a negative electrode active material layer using, as a negative electrode active material, one selected from compounds capable of occluding and releasing lithium ions on at least one surface of a strip-shaped negative electrode current collector;
A strip separator,
A non-aqueous electrolyte secondary battery in which the strip separator is interposed between the strip positive electrode and the strip negative electrode.