JP4626141B2 - Positive electrode active material for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery - Google Patents

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”), a positive electrode mixture for a non-aqueous electrolyte secondary battery (hereinafter simply referred to as “ And a non-aqueous electrolyte secondary battery. Specifically, the positive electrode active material having a layered lithium transition metal composite oxide, the positive electrode active material having a layered lithium transition metal composite oxide, and a positive electrode mixture having a conductive agent and the present invention, which have greatly improved battery characteristics The present invention relates to a non-aqueous electrolyte secondary battery using the positive electrode active material of the invention as a positive electrode active material.

Nonaqueous electrolyte secondary batteries are characterized by a higher operating voltage and higher energy density than conventional nickel cadmium secondary batteries, and are widely used as power sources for electronic devices. As the positive electrode active material of this non-aqueous electrolyte secondary battery, lithium transition metal composite oxides typified by LiCoO ₂ , LiNiO ₂ , LiMn ₂ O _{4 and the} like are used.

However, at present, mobile electronic devices represented by mobile phones, notebook computers, digital cameras, etc. are required characteristics due to high functionality such as various functions added and use at high and low temperatures. Has become even more severe. 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, titanium oxide and / or lithium titanate is coated on a part of the particle surface of lithium cobalt oxide particle powder, and the coating amount of the titanium oxide and / or lithium titanate is lithium cobalt oxide particle powder. A positive electrode active material for a non-aqueous electrolyte secondary battery, characterized in that it is 2.0 to 4.0 mol% as Ti with respect to cobalt therein. And by covering a part of lithium cobaltate particle surface with titanium oxide and / or lithium titanate, it is excellent in charge / discharge cycle characteristics under high temperature while maintaining the initial discharge capacity as a secondary battery. It is described.

  However, with this positive electrode active material, sufficient cycle characteristics and initial charge / discharge capacity could not be obtained. In addition, the load characteristics and average potential required for recent nonaqueous electrolyte secondary batteries could not be satisfied.

JP 2002-151078 A

  An object of the present invention is to provide a positive electrode active material for a non-aqueous electrolyte secondary battery, a positive electrode mixture 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. There is to do.

  The present invention provides the following (1) to (10).

(1) A positive electrode active material for a non-aqueous electrolyte secondary battery having at least a lithium transition metal composite oxide having a layered structure,
A positive electrode active material for a non-aqueous electrolyte secondary battery, wherein an existing ratio of titanium on the surface of the lithium transition metal composite oxide is 20% or more.

(2) A positive electrode active material for a non-aqueous electrolyte secondary battery having at least a lithium transition metal composite oxide having a layered structure,
A positive electrode active material for a non-aqueous electrolyte secondary battery, comprising a titanium compound having a surface ratio of 20% or more on the surface of the lithium transition metal composite oxide.

(3) A positive electrode active material for a non-aqueous electrolyte secondary battery having at least a lithium transition metal composite oxide having a layered structure,
A positive electrode active for a non-aqueous electrolyte secondary battery satisfying the following relational expression when line analysis is performed along a line segment passing through the maximum peak portion of titanium on an arbitrary surface of the lithium transition metal composite oxide: material.
(Total length of the portion where the peak value is 8% or more when the maximum peak value of titanium is 100%) / (length of line segment)> 0.2

  (4) The positive electrode active material for a nonaqueous electrolyte secondary battery according to (2), wherein the titanium compound is lithium titanate.

  (5) The positive electrode active material for a nonaqueous electrolyte secondary battery according to (2), wherein the titanium compound is lithium titanate belonging to the space group Fm3m.

  (6) Any of (1) to (4), wherein the lithium transition metal composite oxide is at least one selected from lithium cobaltate, lithium nickel cobaltate, nickel cobalt lithium aluminate and nickel cobalt lithium manganate A positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1.

(7) A positive electrode mixture for a non-aqueous electrolyte secondary battery having a positive electrode active material having a lithium transition metal composite oxide having a layered structure and a conductive agent,
The proportion of titanium present on the surface of the lithium transition metal composite oxide is 20% or more,
A positive electrode mixture for a nonaqueous electrolyte secondary battery, comprising titanium between the positive electrode active material and the conductive agent.

(8) A positive electrode mixture for a non-aqueous electrolyte secondary battery having a positive electrode active material having at least a layered lithium transition metal composite oxide and a conductive agent,
On the surface of the lithium transition metal composite oxide, a titanium compound having a surface presence ratio of 20% or more,
A positive electrode mixture for a non-aqueous electrolyte secondary battery having a titanium compound between the positive electrode active material and the conductive agent.

(9) Titanium on the surface of the lithium transition metal composite oxide, which is a positive electrode mixture for a non-aqueous electrolyte secondary battery having a positive electrode active material having a lithium transition metal composite oxide having a layered structure and a conductive agent When the line analysis is performed along the line segment that passes through the largest peak of, the following relational expression is satisfied,
A positive electrode mixture for a nonaqueous electrolyte secondary battery, comprising titanium between the positive electrode active material and the conductive agent.
(Total of the length of the portion where the peak is 8% or more when the peak value is 100%) / (Length of line segment)> 0.2

(10) A positive electrode active material layer using the positive electrode active material for a nonaqueous electrolyte secondary battery according to any one of (1) to (6) as a positive electrode active material is formed on at least one surface of a strip-shaped positive electrode current collector. A belt-like positive electrode constituted by
A negative electrode active material layer using one kind selected from 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 as a negative electrode active material, A strip-shaped negative electrode formed by forming on at least one side;
A strip separator,
A spiral-type winding in which the strip-shaped positive electrode and the strip-shaped negative electrode are wound a plurality of times in a state of being laminated via the strip-shaped separator, and the strip-shaped separator is interposed between the strip-shaped positive electrode and the strip-shaped negative electrode A non-aqueous electrolyte secondary battery comprising a body.

In the positive electrode active material described in (1), the proportion of titanium present on the surface of the lithium transition metal composite oxide being 20% or more means that there is little segregation of titanium present on the surface of the lithium transition metal composite oxide. Represents. That is, it represents that titanium is uniformly present on the surface of the lithium transition metal composite oxide.
It is considered that the interfacial resistance is further reduced by the uniform presence of titanium on the surface of the lithium transition metal composite oxide. Thereby, load characteristics and low temperature load characteristics are improved.
Further, it is considered that when the interface resistance is further reduced, no extra resistance is generated when electrons are exchanged, and the disappearance of the potential is suppressed. This increases the average potential.
Furthermore, since titanium is uniformly present on the surface of the lithium transition metal composite oxide, it is considered that when lithium ions move from the negative electrode to the positive electrode, it acts as a buffer and suppresses the collapse of the crystal structure. . This is considered to improve the cycle characteristics.
In addition, since the titanium is uniformly present on the surface of the lithium transition metal composite oxide, the charge of the lithium transition metal composite oxide from which lithium has been released can be kept stable, and oxygen desorption is suppressed. It is considered that the crystal structure during charging is kept stable. This improves the thermal stability.

In the positive electrode active material according to (2), the presence of a titanium compound having a surface ratio of 20% or more on the surface of the lithium transition metal composite oxide exists on the surface of the lithium transition metal composite oxide. This indicates that there is little segregation of the titanium compound. That is, the titanium compound is uniformly present on the surface of the lithium transition metal composite oxide.
It is considered that the interfacial resistance is further reduced by the uniform presence of titanium on the surface of the lithium transition metal composite oxide. Thereby, load characteristics and low temperature load characteristics are improved.
Further, it is considered that when the interface resistance is further reduced, no extra resistance is generated when electrons are exchanged, and the disappearance of the potential is suppressed. This increases the average potential.
Furthermore, since titanium is uniformly present on the surface of the lithium transition metal composite oxide, it is considered that when lithium ions move from the negative electrode to the positive electrode, it acts as a buffer and suppresses the collapse of the crystal structure. . This is considered to improve the cycle characteristics.
In addition, since the titanium is uniformly present on the surface of the lithium transition metal composite oxide, the charge of the lithium transition metal composite oxide from which lithium has been released can be kept stable, and oxygen desorption is suppressed. It is considered that the crystal structure during charging is kept stable. This improves the thermal stability.

In the positive electrode active material described in (3), the following relational expression is satisfied when line analysis is performed along a line segment passing through the maximum peak portion of titanium on an arbitrary surface of the lithium transition metal composite oxide. This indicates that there is little segregation of titanium present on the surface of the lithium transition metal composite oxide. That is, it represents that titanium is uniformly present on the surface of the lithium transition metal composite oxide.
(Total length of the portion where the peak value is 8% or more when the maximum peak value of titanium is 100%) / (length of line segment)> 0.2
It is considered that the interfacial resistance is further reduced by the uniform presence of titanium on the surface of the lithium transition metal composite oxide. Thereby, load characteristics and low temperature load characteristics are improved.
Further, it is considered that when the interface resistance is further reduced, no extra resistance is generated when electrons are exchanged, and the disappearance of the potential is suppressed. This increases the average potential.
Furthermore, since titanium is uniformly present on the surface of the lithium transition metal composite oxide, it is considered that when lithium ions move from the negative electrode to the positive electrode, it acts as a buffer and suppresses the collapse of the crystal structure. . This is considered to improve the cycle characteristics.
In addition, since the titanium is uniformly present on the surface of the lithium transition metal composite oxide, the charge of the lithium transition metal composite oxide from which lithium has been released can be kept stable, and oxygen desorption is suppressed. It is considered that the crystal structure during charging is kept stable. This improves the thermal stability.

  In the positive electrode active material according to (4), since the titanium compound is lithium titanate, lithium titanate itself plays a role as a positive electrode active material, so that a reduction in discharge capacity can be suppressed.

In the positive electrode active material described in (5), the cycle characteristics and the thermal stability can be further improved when the titanium compound is lithium titanate belonging to the space group Fm3m.
Lithium titanate belonging to Fm3m is a substance whose crystal structure is stable even when lithium is desorbed. Thereby, when lithium titanate itself plays a role as a positive electrode active material, cycle characteristics and thermal stability are improved.

In the positive electrode active material according to (6), when the lithium transition metal composite oxide is lithium cobaltate, the non-aqueous electrolyte secondary battery using the positive electrode active material of the present invention is a mobile phone, a laptop computer, or the like. It can be particularly preferably used for the following applications.
When the lithium transition metal composite oxide is lithium nickel cobalt oxide, the non-aqueous electrolyte secondary battery using the positive electrode active material of the present invention can be suitably used for applications such as mobile phones and laptop computers.
When the lithium transition metal composite oxide is nickel cobalt lithium aluminate, the nonaqueous electrolyte secondary battery using the positive electrode active material of the present invention is preferably used for applications such as electric vehicles, mobile phones, and notebook computers. be able to.
When the lithium transition metal composite oxide is nickel cobalt lithium manganate, the non-aqueous electrolyte secondary battery using the positive electrode active material of the present invention is suitably used for applications such as mobile phones, electric tools, and electric vehicles. be able to.

  In the positive electrode mixture described in (7), the load ratio, cycle characteristics, and thermal stability are the same for the same reason as in (1) because the proportion of titanium present on the surface of the lithium transition metal composite oxide is 20% or more. A positive electrode active material with improved can be obtained. By having titanium between the positive electrode active material and the conductive agent, it is considered that the interfacial resistance to the lithium insertion / release reaction of the lithium transition metal composite oxide is further reduced. Thereby, load characteristics, cycle characteristics and thermal stability are improved.

  In the positive electrode mixture described in (8), the lithium transition metal composite oxide has a titanium compound having a surface presence ratio of 20% or more on the surface of the lithium transition metal composite oxide. A positive electrode active material with improved load characteristics and thermal stability is obtained. By having titanium between the positive electrode active material and the conductive agent, it is considered that the interfacial resistance to the lithium insertion / release reaction of the lithium transition metal composite oxide is further reduced. Thereby, load characteristics, cycle characteristics and thermal stability are improved.

In the positive electrode mixture described in (9), the following relational expression is satisfied when line analysis is performed along a line segment passing through the maximum peak portion of titanium on an arbitrary surface of the lithium transition metal composite oxide. Thus, a positive electrode active material having improved cycle characteristics, load characteristics, and thermal stability can be obtained.
(Total length of the portion where the peak value is 8% or more when the maximum peak value of titanium is 100%) / (length of line segment)> 0.2
By having titanium between the positive electrode active material and the conductive agent, it is considered that the interfacial resistance to the lithium insertion / release reaction of the lithium transition metal composite oxide is further reduced. Thereby, load characteristics, cycle characteristics and thermal stability are improved.

  In the nonaqueous electrolyte secondary battery according to (10), a positive electrode active material layer using the positive electrode active material for a nonaqueous electrolyte secondary battery according to any one of (1) to (6) as a positive electrode active material. A belt-shaped positive electrode formed by forming on at least one surface of a belt-shaped positive electrode current collector, and one selected from metallic lithium, lithium alloy, a carbon material capable of occluding and releasing lithium ions, or a compound capable of occluding and releasing lithium ions. A negative electrode active material layer used as a negative electrode active material is formed on at least one surface of a strip-shaped negative electrode current collector, and includes a strip-shaped negative electrode and a strip-shaped separator, and the strip-shaped positive electrode and the strip-shaped negative electrode are stacked via the strip-shaped separator In this state, the coil is wound a plurality of times to form a spiral wound body in which a strip separator is interposed between the strip-shaped positive electrode and the strip-shaped negative electrode. It is possible to obtain a non-aqueous electrolyte secondary battery having excellent thermal stability.

  Hereinafter, the positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention will be described with reference to embodiments, examples, and FIGS. However, the present invention is not limited to this embodiment, examples, and FIGS.

  The positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention comprises at least a layered lithium transition metal composite oxide. 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 cobaltate, lithium nickelate, lithium chromate, lithium vanadate, lithium manganate, lithium nickel cobaltate, nickel cobalt lithium manganate, nickel cobalt lithium aluminate. Preferable examples include lithium cobaltate, lithium nickel cobaltate, nickel cobalt lithium aluminate and nickel cobalt lithium manganate.

In the positive electrode active material of the present invention, the form of the lithium transition metal composite oxide is not particularly limited. Examples of the form of the lithium transition metal composite oxide include particles and films.
In the present invention, the lithium transition metal composite oxide is preferably in the form of particles. Since titanium is uniformly dispersed in the lithium transition metal composite oxide, the battery characteristics can be further improved.
In the present invention, the lithium transition metal composite oxide may be present in the form of particles composed of one or both of primary particles and secondary particles that are aggregates thereof. That is, the lithium transition metal composite oxide exists in the form of particles, and the particles may be composed only of primary particles, or may be composed only of secondary particles that are aggregates of primary particles. It may consist of both particles and secondary particles.

  In the positive electrode active material of the present invention, it is preferable that the titanium content in the surface of the lithium transition metal composite oxide particles is 20% or more. When the titanium content on the surface of the particles is 20% or more, the cycle characteristics, load characteristics and thermal stability are improved for the same reason as the positive electrode active material described in (1).

  In the positive electrode active material of the present invention, it is preferable that the surface of the lithium transition metal composite oxide particles has a titanium compound having a surface presence ratio of 20% or more. When the ratio of the particle surface is 20% or more, the cycle characteristics, load characteristics and thermal stability are improved for the same reason as the positive electrode active material described in (2).

In the positive electrode active material of the present invention, the following relational expression is satisfied when line analysis is performed along a line segment passing through the maximum peak portion of titanium on an arbitrary surface of the lithium transition metal composite oxide particles. Is preferred.
(Total length of the portion where the peak value is 8% or more when the maximum peak value of titanium is 100%) / (length of line segment)> 0.2
By satisfying the above relational expression on any surface of the particles, cycle characteristics, load characteristics, and thermal stability are improved for the same reason as the positive electrode active material described in (3).

The positive electrode active material of the present invention is preferably a lithium transition metal composite oxide having titanium on at least the surface.
Titanium exhibits the effect of the present invention regardless of the form of titanium present on the surface of the lithium transition metal composite oxide. For example, even when titanium covers the entire surface of the lithium transition metal composite oxide, even when titanium covers a part of the surface of the lithium transition metal composite oxide, Characteristics, load characteristics and thermal stability can be improved.
The presence state of titanium on the surface of the lithium transition metal composite oxide is not particularly limited. It may exist in the state of a titanium compound.
As the titanium compound, titanium oxide and lithium titanate are preferable. More preferably, it is lithium titanate.
Whether titanium is present on the surface of the lithium transition metal composite oxide can be analyzed by various methods. For example, it can be analyzed by Auger Electron Spectroscopy (AES) or X-ray Photoelectron Spectroscopy (XPS).

In the positive electrode active material of the present invention, the titanium compound is preferably lithium titanate belonging to the space group Fm3m. Among various lithium titanates, when lithium titanate belonging to the space group Fm3m is used, load characteristics are further improved.
Among lithium titanates, the above effect cannot be obtained when reverse spinel type Li ₄ Ti ₅ O ₁₂ or ramsteride type Li ₂ Ti ₃ O ₇ is used. In addition, the above effects cannot be obtained when LiFeO ₂ or LiNiO ₂ having a crystal structure belonging to the space group Fm3m is used.
Moreover, in the positive electrode active material of the present invention, it is preferable that titanium exists in a trivalent state.
Usually, titanium is tetravalent, but load characteristics are further improved by making it trivalent and stable.

  Titanium is preferably fixed to the surface of the lithium transition metal composite oxide. In the present invention, fixing means that the lithium transition metal composite oxide and titanium are not liberated even when the positive electrode active material of the present invention is stirred with water or an organic solvent. If titanium is not fixed to the surface of the lithium transition metal composite oxide, titanium may be liberated from the surface of the lithium transition metal composite oxide during slurry preparation, which is not preferable.

  As described above, the lithium transition metal composite oxide is preferably present in the form of particles.

  In the present invention, more preferably, the titanium compound is uniformly coated on the entire surface of the lithium transition metal composite oxide particles. In this case, the positive electrode active material is further improved in cycle characteristics, load characteristics and thermal stability.

Moreover, the titanium compound should just exist on the surface of the particle | grains at least. Therefore, the titanium compound may be present inside the particles. In this case, the titanium compound present inside the particles may be incorporated into the crystal structure of the lithium transition metal composite oxide.
It is considered that the presence of the titanium compound in the particles stabilizes the crystal structure of the lithium transition metal composite oxide particles and further improves the cycle characteristics.
Moreover, it is thought that a pillar effect arises when titanium is dissolved. This further improves the thermal stability.

In the positive electrode active material of the present invention, the proportion of titanium present on the surface of the lithium transition metal composite oxide is preferably 0.01 mol% or more with respect to the lithium transition metal composite oxide, and 0.05 mol% or more. More preferably, it is 0.1 mol% or more, more preferably 3 mol% or less, still more preferably 2 mol% or less, and even more preferably 1 mol% or less. If the proportion of titanium present on the surface of the lithium transition metal composite oxide is too small, titanium cannot be present on the entire surface of the lithium transition metal composite oxide, which is not preferable. If the ratio of titanium present on the surface of the lithium transition metal composite oxide is too large, it is not preferable because it causes a reduction in discharge capacity.
In addition, various methods can be used for quantitative determination of titanium. For example, it can be quantified by inductively coupled plasma (ICP) spectroscopy or titration.
As described above, the lithium transition metal composite oxide is preferably present in the form of particles.

In the positive electrode active material of the present invention, the proportion of titanium present on the surface of the lithium transition metal composite oxide is preferably 40% or more, more preferably 50% or more, and further preferably 60% or more. preferable. In this case, titanium is uniformly dispersed on the surface of the lithium transition metal composite oxide, and a positive electrode active material with improved cycle characteristics, load characteristics, and thermal stability can be obtained.
As described above, the lithium transition metal composite oxide is preferably present in the form of particles.

In the present invention, the “ratio of titanium present on the surface of the lithium transition metal composite oxide” is determined as follows.
First, the presence state of titanium on the surface of the particles of the lithium transition metal composite oxide particles is observed with an electron beam microanalyzer (EPMA) equipped with a wavelength dispersive X-ray spectrometer (WDX). Next, in the observation field, select the part with the largest amount of titanium per unit area (the part where the titanium peak is large), and perform line analysis along the line segment that passes through this part (for example, the line segment with a length of 300 μm). I do. In the line analysis, the quotient obtained by dividing the total length of the portion where the peak is 8% or more when the peak value in the portion having the largest amount of titanium per unit area is 100% by the length of the line segment. Is the “abundance ratio of titanium on the surface of the lithium transition metal composite oxide”. In addition, it is preferable to use the average value of “abundance ratio of titanium on the surface of the lithium transition metal composite oxide” by performing line analysis a plurality of times (for example, 10 times).
In the above method, the portion where the titanium peak is less than 8% has a large difference from the portion where the amount of titanium is the largest, and therefore is regarded as a portion where no titanium exists.

  The above-described “ratio of titanium present on the surface of the lithium transition metal composite oxide” can indicate whether titanium is present uniformly or unevenly on the surface of the lithium transition metal composite oxide.

In the positive electrode active material of the present invention, the proportion of the titanium compound present on the surface of the lithium transition metal composite oxide is preferably 40% or more, more preferably 50% or more, and 60% or more. Further preferred. In this case, the titanium compound is uniformly dispersed on the surface of the lithium transition metal composite oxide, and a positive electrode active material with improved cycle characteristics, load characteristics, and thermal stability can be obtained.
As described above, the lithium transition metal composite oxide is preferably present in the form of particles.

  In the present invention, the “abundance ratio of the titanium compound on the surface of the lithium transition metal composite oxide” is obtained in the same manner as the “abundance ratio of titanium on the surface of the lithium transition metal composite oxide” described above.

In the positive electrode active material of the present invention, it is preferable that the following relational expression is satisfied when line analysis is performed along a line segment passing through the maximum peak portion of titanium on an arbitrary surface of the lithium transition metal composite oxide. .
(Total length of the portion where the peak value of titanium is 8% or more when the maximum peak value of titanium is 100%) / (length of line segment)> 0.4
Further, it is more preferable to satisfy the following relational expression.
(Total length of the portion where the peak value is 8% or more when the maximum peak value of titanium is 100%) / (length of line segment)> 0.5
Furthermore, it is more preferable to satisfy the following relational expression.
(Total length of the portion where the peak value of titanium is 8% or more when the maximum peak value of titanium is 100%) / (length of line segment)> 0.6

  In the positive electrode active material of the present invention, the following (i) to (iii) are mentioned as preferred embodiments of the lithium transition metal composite oxide.

  (I) An embodiment in which the lithium transition metal composite oxide is lithium cobalt oxide containing at least one element selected from the group consisting of titanium, aluminum, vanadium, zirconium, magnesium, calcium, strontium, and sulfur.

The presence of these elements is considered to cause a pillar effect and to improve 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 the aspect (i), 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 embodiment (i), 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 embodiment (i), 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 embodiment (i), 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.

(Ii) The lithium transition metal composite oxide is at least selected from the group consisting of Li _a Co _{1- b} MbO _{c Xd} S _e (M is Ti, Al, V, Zr, Mg, 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.) A mode represented by
Preferred for the same reason as in embodiment (i).

  (Iii) Lithium transition metal composite oxide, at least one element selected from the group consisting of titanium, aluminum, vanadium, zirconium, magnesium, calcium, strontium, and sulfur, lithium nickel cobalt oxide, nickel cobalt lithium aluminate And an embodiment that is lithium nickel cobalt manganate.

The presence of these elements is considered to cause a pillar effect and to improve 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 the embodiment (iii), it is considered that the cycle characteristics and the load characteristics are further improved because the passage of electrons is improved by the presence of sulfur.
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 embodiment (iii), 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 embodiment (iii), 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.

Embodiments in (iii), 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 embodiment (iii), 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 embodiment (iii), 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 positive electrode active material 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 nickel cobalt lithium aluminate and nickel cobalt lithium manganate. Moreover, the mixture of these and lithium cobaltate may be sufficient.

Nickel cobalt lithium, nickel cobalt lithium lithium and nickel cobalt lithium manganate have a layered crystal structure similar to lithium cobalt oxide. However, compared to lithium cobaltate, there are disadvantages that a large amount of gas is generated and the electric potential during discharge is lowered.
In the present invention, generation of gas is prevented by having titanium on the surface of at least one lithium transition metal composite oxide selected from the group consisting of lithium nickel cobaltate, nickel cobalt lithium aluminate and nickel cobalt lithium manganate. In addition, the discharge potential during loading can be increased. By having titanium on the surface of the lithium transition metal composite oxide, it is considered that residual lithium is reduced and gas generation can be prevented. Since titanium can reduce the interfacial resistance, it is considered that the discharge potential under load is increased by the uniform presence of titanium in the lithium transition metal composite oxide.
As described above, the lithium transition metal composite oxide is preferably present in the form of particles.

  In the positive electrode active material 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 positive electrode active material within this range, coating characteristics and slurry properties can be improved without impairing improvement in cycle characteristics and low temperature characteristics.

  Although the manufacturing method of the positive electrode active material of the present invention is not particularly limited, for example, it can be manufactured as in the following (1) and (2).

(1) Preparation of raw material mixture The compounds 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 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 and Al (NO ₃ ) 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.

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.
(I) Prepared from the cobalt compound and titanium compound described above. An aqueous solution containing cobalt ions and titanium ions having a predetermined composition ratio is dropped into pure water being stirred.
Next, a sodium hydroxide aqueous solution is dropped so as to have a pH of 7 to 11, and the mixture is stirred at 40 to 80 ° C. and a rotational speed of 500 to 1500 rpm to precipitate cobalt and titanium, thereby obtaining a salt of cobalt and titanium. 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.

(2) 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 650 ° C. or higher, more preferably 700 ° C. or higher, and further preferably 750 ° 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. Further, the firing temperature is preferably 1200 ° C. or less, more preferably 1100 ° C. or less, and further preferably 950 ° C. or less. 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.

  The positive electrode active material of the present invention can be obtained by the manufacturing method described above. The positive electrode active material of the present invention is suitably used for the positive electrode mixture of the present invention and the nonaqueous electrolyte secondary battery described later.

Next, the positive electrode mixture of the present invention will be described.
The positive electrode mixture of the present invention has at least a positive electrode active material having a lithium transition metal composite oxide having a layered structure and a conductive agent.
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 natural 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.
In the positive electrode mixture of the present invention, the presence state of titanium is not particularly limited. It may exist in the state of a titanium compound.

  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.
That is, the nonaqueous electrolyte secondary battery of the present invention is a nonaqueous electrolyte secondary battery using the positive electrode active material of the present invention. The non-aqueous electrolyte secondary battery of the present invention only needs to use the positive electrode active material of the present invention as at least a part of the positive electrode active material.
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 is not particularly limited as long as it is a compound that is not altered or decomposed by the operating voltage. The electrolyte includes an electrolytic solution.
Examples of the solvent for the electrolyte include dimethoxyethane, diethoxyethane, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl formate, γ-butyrolactone, 2-methyltetrahydrofuran, dimethyl sulfoxide, sulfolane, and the like. These organic solvents are mentioned. These can be used alone or in admixture of two or more.

Examples of the lithium salt of the electrolytic solution include lithium salts such as lithium perchlorate, lithium tetrafluoroborate, lithium hexafluorophosphate, and lithium trifluoromethanoate.
The above-described solvent and lithium salt 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 for the polymer which has liquid absorptivity.
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, a lithium ion secondary battery can be obtained according to a conventional method.
Thereby, the outstanding battery characteristic which was not able to be achieved conventionally is realizable.

  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. The following (i) to (vii) are mentioned as preferred embodiments of the lithium transition metal composite oxide.

(I) the general 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 (i) is excellent in cycle characteristics, high temperature cycle characteristics and load characteristics.
In embodiment (i), a is preferably greater than 0. It is considered that the cycle characteristics are improved by substituting a part of manganese with lithium.
In the embodiment (i), 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 embodiment (i), 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 embodiment (i), 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.

  (Ii) An embodiment 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.

(Iii) 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 embodiment (iii), it is considered that the cycle characteristics and the load characteristics are further improved since the passage of electrons is improved by the presence of sulfur.
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 (iii), the reason for containing elements other than sulfur is the same as in aspect (ii).
In the embodiment (iii), by containing each of the above elements, a positive electrode plate having a high charge / discharge capacity and excellent binding properties and surface smoothness can be obtained due to 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.
Further, 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.

  (Iv) An embodiment 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 embodiment (iv), 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 embodiment (iv), the reason for containing an element other than sodium and / or calcium is the same as in embodiment (ii) and (iii).

  (V) 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.

  (Vi) 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.

(Vii) The lithium transition metal composite oxide has a general formula of Li _{1 + a} M _b 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 (vii) is excellent in cycle characteristics, load characteristics, storage characteristics, and charge / discharge capacity, and has less battery swelling.
In embodiment (vii), a is preferably greater than 0. It is considered that the cycle characteristics are improved by substituting a part of manganese with lithium.
In the embodiment (vii), 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 embodiment (vii), 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. 4 is a schematic cross-sectional view of the positive electrode. As shown in FIG. 4, 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.
Furthermore, since the positive electrode active material of the present invention does not contain coarse particles and is spherical, the surface of the coating film surface of the produced positive electrode has excellent smoothness. For this reason, the coating film surface of a positive electrode plate is excellent in binding property, and becomes difficult to peel off. In addition, since the surface is smooth and lithium ions are uniformly introduced and exited on the surface of the coating film accompanying charging / discharging, the cycle characteristics are remarkably improved.

The shape of the lithium ion secondary battery is not particularly limited, and may be a cylindrical shape, a coin shape, a square shape, a laminate shape, or the like.
FIG. 5 is a schematic cross-sectional view of a cylindrical battery. As shown in FIG. 5, 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. 6 is a schematic partial cross-sectional view of a coin-type battery. As shown in FIG. 6, 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. 7 is a schematic perspective view of a prismatic battery. As shown in FIG. 7, 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.

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 and the following II is used as a negative electrode active material of the negative electrode Can do.
I: Lithium transition metal composite oxide used for the positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention, and a general formula Li _a Mn _3-a O _{4 + f} (a is 0.8 ≦ a ≦ 1.2 Wherein f represents a number satisfying −0.5 ≦ f ≦ 0.5.), The weight of the lithium transition metal composite oxide is A, and the cobalt acid A positive electrode active material for a non-aqueous electrolyte secondary battery, mixed so that lithium and / or the lithium nickelate weight is B, so that 0.2 ≦ B / (A + B) ≦ 0.8.
II: A negative electrode active material for a nonaqueous electrolyte secondary battery comprising at least one selected from the group consisting of metallic lithium, a lithium alloy and a compound capable of occluding and releasing lithium ions.

This nonaqueous electrolyte secondary battery not only has improved cycle characteristics, load characteristics and thermal stability, but also has excellent overcharge characteristics and safety. The positive electrode active material is preferably mixed so that 0.4 ≦ B / (A + B) ≦ 0.6. This is because if the range is 0.4 ≦ B / (A + B) ≦ 0.6, the overcharge characteristics and safety are significantly improved. As a compound capable of occluding and releasing lithium ions used for the negative electrode active material, a general formula having _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 represents a number satisfying 1.5, b represents a number satisfying 1.5 ≦ b ≦ 2.2, and c represents a number satisfying −0.5 ≦ c ≦ 0.5. A negative electrode active material for a water electrolyte secondary battery is preferred. At this time, a nonaqueous electrolyte secondary battery with improved cycle characteristics and output characteristics can be obtained.

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]
A cobalt sulfate aqueous solution and a titanium sulfate aqueous solution having a predetermined composition ratio were dropped into pure water being stirred. Titanium sulfate was dropped by 0.2 mol% with respect to cobalt. Sodium hydroxide was added dropwise so that the pH was 7 and cobalt and titanium were precipitated at 60 ° C. and a rotational speed of 650 rpm to obtain 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 composition ratio of the obtained positive electrode active material was 1.0 for Li, 0.998 for Co, and 0.002 for Ti.

[Comparative Example 1]
Lithium carbonate (Li ₂ CO ₃ ), cobalt trioxide (Co ₃ O ₄ ), and titanium oxide (TiO ₂ ) were used as the raw material compounds. The compound as the raw material was weighed so as to have a predetermined composition ratio, and dry-mixed to obtain a raw material mixed powder. Titanium oxide was mixed at 0.1 mol% with respect to cobalt. The obtained raw material mixed powder was fired at 950 ° C. for 7 hours in an air atmosphere. In this way, a positive electrode active material was obtained.
The composition ratio of the obtained positive electrode active material was 1.0 for Li, 0.999 for Co, and 0.001 for Ti.

[Comparative Example 2]
Lithium carbonate (Li ₂ CO ₃ ) and cobalt trioxide (Co ₃ O ₄ ) were used as raw materials. The compound as the raw material was weighed so as to have a predetermined composition ratio, and dry-mixed to obtain a raw material mixed powder. The obtained raw material mixed powder was fired at 995 ° C. for 7 hours in the air atmosphere. In this way, a positive electrode active material was obtained.
The composition ratio of the obtained positive electrode active material was 1.0 for Li and 1.0 for Co.

2. Properties of positive electrode active material (1) Structure of positive electrode active material The positive electrode active materials obtained in Example 1 and Comparative Example 1 were subjected to ICP spectroscopy.
The positive electrode active material obtained in Example 1 was lithium cobalt oxide in which 0.2 mol% of titanium was present. It was found by EPMA that titanium on the surface of the positive electrode active material obtained in Example 1 was present uniformly. The proportion of titanium present on the particle surface was 100%.
The positive electrode active material obtained in Comparative Example 1 was lithium cobalt oxide in which 0.1 mol% of titanium was present. It was found by EPMA that the segregation of titanium existing on the surface of the positive electrode active material obtained in Comparative Example 1 was severe. The proportion of titanium present on the particle surface was 7.1%.

FIG. 1 shows a chart showing the presence of titanium, which was obtained by performing line analysis by EPMA on the positive electrode active material obtained in Example 1. As can be seen from FIG. 1, the positive electrode active material of the present invention has less segregation because titanium is uniformly dispersed on the surface of the lithium transition metal composite oxide particles.
FIG. 2 shows a chart showing the presence state of magnesium obtained by line analysis by EPMA for the positive electrode active material obtained in Comparative Example 1. It can be seen from FIG. 2 that the positive electrode active material of Comparative Example 1 has almost no titanium on the surface of the lithium transition metal composite oxide particles and segregates even if it exists.

3. Evaluation of Positive Electrode Active Material For each positive electrode active material obtained in Example 1, Comparative Example 1 and Comparative Example 2, test secondary batteries were prepared and evaluated as follows.

The test secondary battery was produced as follows.
A paste was prepared by kneading 90 parts by weight of the positive electrode active material powder, 5 parts by weight of carbon powder to be a conductive agent, and a normal methylpyrrolidone solution of polyvinylidene fluoride (5 parts by weight as the amount of polyvinylidene fluoride). The obtained paste was applied to a positive electrode current collector to obtain a test secondary battery in which the negative electrode was lithium metal.

(1) 0.2C initial discharge capacity and 2.0C initial discharge capacity Charge potential 4.3V, discharge potential 2.85V, discharge load 0.2C (Note that 1C is a current load that completes the discharge in one hour. The initial discharge capacity of 0.2C was measured under the conditions of.
In addition, the 2.0 C initial discharge capacity was measured under the conditions of a charging potential of 4.3 V, a discharging potential of 2.85 V, and a discharging load of 2.0 C.

(2) Load capacity maintenance rate After measuring initial discharge capacity under the conditions of charge potential 4.3V, discharge potential 2.70V, discharge load 0.2C, charge potential 4.3V, discharge potential 2.70V, discharge load The load discharge capacity was measured under the condition of 2.0C. The obtained load discharge capacity value was divided by the initial discharge capacity value to obtain the load capacity retention rate, and the load characteristics were evaluated.

(3) Power The discharge capacity and average potential at a discharge load of 0.2 C were measured, and the product of these values was 0.2 C power.
The discharge capacity and average potential at a discharge load of 1.0 C were measured, and the product of these values was 1.0 C power.
The discharge capacity and average potential at a discharge load of 2.0 C were measured, and the product of these values was 2.0 C power.

(4) Thermal stability Charging / discharging with a constant current was performed using a secondary battery for testing. Thereafter, the battery was charged at a 0.2C rate with CC-CV charging, a final voltage of 4.3 V, and a final charge current of 0.02 mA. After the charging was completed, the positive electrode was taken out from the test secondary battery, washed with one component solution contained in the electrolytic solution used in the test secondary battery, and dried, and the positive electrode active material was scraped off from the positive electrode. An aluminum cell was charged with ethylene carbonate used for the electrolyte and the positive electrode active material scraped from the positive electrode in a weight ratio of 0.40: 1.0, and the differential scanning calorific value was measured at a heating rate of 4.5 ° C./min. .
Differential scanning calorimetry (DSC) is a method of measuring a difference in energy input as a function of temperature while changing the temperature of a material and a reference material according to a program. Although the differential scanning calorific value did not change even when the temperature rose in the low temperature part, the differential scanning calorific value greatly increased above a certain temperature. The temperature at this time was defined as the heat generation start temperature. The higher the heat generation start temperature, the better the thermal stability.

The results are shown in Table 1. In the table, “-” indicates that the corresponding item is not measured.
As is apparent from Table 1, the positive electrode active material of the present invention has a high discharge capacity, a large electric power, and excellent load characteristics and thermal stability.

FIG. 1 is a diagram showing the results of line analysis of the positive electrode active material obtained in Example 1 at two points between 300 μm by EPMA. FIG. 2 is a diagram showing the results of line analysis of the positive electrode active material obtained in Comparative Example 1 with respect to two points between 300 μm by EPMA. It is a figure which shows the lithium transition metal complex oxide of a layered structure. It is a binding schematic diagram of an active material. It is sectional drawing of a cylindrical battery. It is a figure which shows the structure of a coin-type battery. It is a figure which shows the structure of a square battery.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 3a site 2 6c site 3 3b site 4 Binder 5 Active material 11 Negative electrode 12 Current collector 13 Positive electrode 14 Separator 20 Cylindrical battery 30 Coin type battery 40 Square type battery

Claims (4)

A positive electrode active material for a non-aqueous electrolyte secondary battery having at least a layered lithium transition metal composite oxide,
The lithium transition metal composite oxide is obtained by mixing and baking a precipitate obtained by dropping an alkaline solution into an aqueous solution containing at least cobalt ions and titanium ions so as to have a pH of 7 to 11 with a lithium compound. Lithium transition metal composite oxide, and in the line analysis of the particles by an electron beam microanalyzer, the peak of the portion where the amount of titanium per unit area is the largest is 100%. The total length is a quotient obtained by dividing the total length by the length of a line segment passing through the above portion, and the “abundance ratio of titanium on the surface of the lithium transition metal composite oxide” is 20% or more. A positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the positive electrode active material is uniformly present on the surface of the transition metal composite oxide . 2. The nonaqueous electrolyte secondary battery according to claim 1 , wherein the lithium transition metal composite oxide is at least one selected from lithium cobaltate, lithium nickel cobaltate, nickel cobalt lithium aluminate, and nickel cobalt lithium manganate. Positive electrode active material. A positive electrode mixture for a non-aqueous electrolyte secondary battery having a positive electrode active material having at least a layered lithium transition metal composite oxide and a conductive agent,
The positive electrode active material is a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 or 2, and has titanium between the positive electrode active material and the conductive agent, for a non-aqueous electrolyte secondary battery. Positive electrode mixture. A strip-shaped positive electrode configured by forming a positive electrode active material layer using the positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 or 2 as a positive electrode active material on at least one surface of a strip-shaped positive electrode current collector;
A negative electrode active material layer using one kind selected from 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 as a negative electrode active material, A strip-shaped negative electrode formed by forming on at least one side;
A strip separator,
A spiral-type winding in which the strip-shaped positive electrode and the strip-shaped negative electrode are wound a plurality of times in a state of being laminated via the strip-shaped separator, and the strip-shaped separator is interposed between the strip-shaped positive electrode and the strip-shaped negative electrode A non-aqueous electrolyte secondary battery comprising a body.

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