JP2004311408A - Positive active material for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive electrode active material for a nonaqueous electrolyte secondary battery which has superior battery characteristics, in concrete, load characteristics, cycle characteristics, low-temperature characteristics and thermal stability even under far more severe using environments. <P>SOLUTION: This is the positive electrode active material for the nonaqueous electrolyte secondary battery which has at least a lithium transitional metal complex oxide having a layered structure. Abundance of zirconium on a surface of the lithium transitional metal complex oxide is 20% or more. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a positive electrode active material used for a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery. For example, it is suitably used for mobile phones, personal computers, and electric vehicles.

Non-aqueous electrolyte secondary batteries have the characteristics of higher operating voltage and higher energy density than conventional nickel-cadmium secondary batteries and the like, and are used in mobile electronic devices such as mobile phones, notebook computers, and digital cameras. It is widely used as a power source for equipment. As the positive electrode active material of the nonaqueous electrolyte secondary battery, a lithium transition metal composite oxide represented by LiCoO ₂ , LiNiO ₂ , and LiMn ₂ O ₄ can be mentioned. Among them, LiCoO ₂ is conventionally used for mobile electronic devices. Used, and sufficient battery characteristics were obtained.

However, at present, the usage environment of mobile devices is becoming more severe due to enhancement of functions such as various functions and use at high and low temperatures. Further, application to a power supply such as a battery for an electric vehicle is expected, and a conventional non-aqueous electrolyte secondary battery using LiCoO ₂ cannot provide sufficient battery characteristics, and further improvement is required. I have.

Patent Literature 1 describes a positive electrode made of Li _1-x CoO ₂ (0 ≦ x <1) to which zirconium (Zr) is added or a material obtained by substituting a part of cobalt with another transition metal. The surface of the LiCoO ₂ particles is stabilized by being covered with zirconium oxide (ZrO ₂ ) or a composite oxide of lithium and zirconium, Li ₂ ZrO _3. As a result, even at a high potential, the decomposition reaction of the electrolytic solution and the crystallization can occur. It is described that a positive electrode active material exhibiting excellent cycle characteristics and storage characteristics without breakage can be obtained.
However, this positive electrode active material cannot satisfy the load characteristics, low-temperature characteristics, and thermal stability required for recent nonaqueous electrolyte secondary batteries. There is also room for improvement in cycle characteristics.

JP-A-4-319260

  Therefore, an object of the present invention is to provide a positive electrode active material for a non-aqueous electrolyte secondary battery having excellent battery characteristics even in a more severe use environment, and a non-aqueous electrolyte secondary battery using the same. Specifically, it is to provide a positive electrode active material for a non-aqueous electrolyte secondary battery having excellent load characteristics, cycle characteristics, low-temperature characteristics, and thermal stability, and a non-aqueous electrolyte secondary battery using the same. .

  The present invention provides the following (1) to (6).

(1) A positive electrode active material for a nonaqueous electrolyte secondary battery having at least a layered structure lithium transition metal composite oxide,
A positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the proportion of zirconium 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 layered structure lithium transition metal composite oxide,
A positive electrode active material for a non-aqueous electrolyte secondary battery, which satisfies the following relational expression when a line analysis is performed on a surface of the lithium transition metal composite oxide along a line segment passing through a maximum peak portion of zirconium.
(Sum of the length of the portion where the peak value of zirconium is 4% or more when the maximum peak value is 100%) / (length of line segment) ≧ 0.2

  (3) The positive electrode active material for a non-aqueous electrolyte secondary battery according to the above (1) or (2), wherein the lithium transition metal composite oxide is a particle.

  (4) The lithium transition metal composite oxide is at least one selected from the group consisting of lithium cobaltate, lithium nickel cobaltate, lithium nickel cobalt aluminate and lithium nickel cobalt manganate having at least zirconium on its surface. The positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of the above (1) to (3).

(5) A positive electrode active material for a non-aqueous electrolyte secondary battery having at least a layered lithium transition metal composite oxide,
The non-aqueous electrolyte secondary oxide is at least one selected from the group consisting of lithium nickel cobaltate, lithium nickel cobalt aluminate and lithium nickel cobalt manganate, the lithium transition metal composite oxide having zirconium on at least its surface. Positive electrode active material for batteries.

(6) A structure in which a positive electrode active material layer using the positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of the above (1) to (5) is formed on at least one surface of a belt-shaped positive electrode current collector. Strip-shaped positive electrode,
By forming a negative electrode active material layer using lithium metal, a lithium alloy, a carbon material capable of inserting and extracting lithium ions or a compound capable of inserting and extracting lithium ions as an anode active material on at least one surface of the strip-shaped negative electrode current collector. A configured strip-shaped negative electrode,
A belt-shaped separator,
A spiral winding in which the strip-shaped positive electrode and the strip-shaped negative electrode are wound a plurality of times in a stacked state with the strip-shaped separator interposed therebetween, 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.

  As described below, the positive electrode active material for a nonaqueous electrolyte secondary battery of the present invention has a high potential, and is excellent in load characteristics, cycle characteristics, low-temperature characteristics, and thermal stability. Therefore, the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention is suitably used for a lithium ion secondary battery or the like.

  Hereinafter, the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention (hereinafter, also simply referred to as “the positive electrode active material of the present invention”) and the non-aqueous electrolyte secondary battery of the present invention will be described.

<Positive electrode active material for non-aqueous electrolyte secondary batteries>
The positive electrode active material of the first aspect of the present invention is a positive electrode active material for a nonaqueous electrolyte secondary battery having at least a layered structure lithium transition metal composite oxide, and the zirconium on the surface of the lithium transition metal composite oxide Is a positive electrode active material for a non-aqueous electrolyte secondary battery having an existing ratio of 20% or more.
The positive electrode active material of the second embodiment of the present invention is a positive electrode active material for a non-aqueous electrolyte secondary battery having at least a layered structure lithium transition metal composite oxide, wherein the lithium transition metal composite oxide is at least A positive electrode active material for a non-aqueous electrolyte secondary battery, which is at least one selected from the group consisting of lithium nickel cobaltate, lithium nickel cobalt aluminate, and lithium nickel cobalt manganate having zirconium on the surface.

The positive electrode active material of the first and second aspects of the present invention (hereinafter, also simply referred to as “the positive electrode active material of the present invention”) has 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 called an α-NaFeO ₂ type structure, in which lithium ions and transition metal ions occupy half of each of the six coordination sites in a solid matrix having a cubic densely packed oxygen arrangement regularly.
FIG. 5 is a schematic diagram showing a crystal structure of a layered lithium transition metal composite oxide. In FIG. 5, lithium occupies 3b site 3, oxygen occupies 6c site 2, and transition metal occupies 3a site 1.
The layered structure is not particularly limited, and examples thereof include a layered rock salt structure and a zigzag layered rock salt structure. Among them, 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, and nickel cobalt lithium aluminate are mentioned. Preferably, lithium cobaltate, lithium nickel cobaltate, nickel cobalt lithium aluminate and nickel cobalt lithium manganate are mentioned.
The lithium transition metal composite oxide suitably used in the present invention will be described later in detail.

The positive electrode active material of the present invention has zirconium on the surface of the lithium transition metal composite oxide.
The lithium transition metal composite oxide is usually a particle, but the form is not particularly limited, and may be, for example, a film. The particles may be primary particles or secondary particles, and these may be mixed.
The form of zirconium is not particularly limited, and can exist as a simple substance or a compound.
Hereinafter, the case where the lithium transition metal composite oxide is particles and zirconium is present as a zirconium compound will be described as an example. However, the present invention is not limited to these.

As the zirconium compound, zirconium oxide and lithium zirconate are preferable. More preferred zirconium compounds are ZrO ₂ and Li ₂ ZrO ₃ . More preferably Li ₂ ZrO _3.
The zirconium compound exerts the effects of the present invention regardless of the form of the zirconium compound present on the surface of the lithium transition metal composite oxide particles. For example, even when the zirconium compound is uniformly coated on the entire surface of the particles of the lithium transition metal composite oxide, the zirconium compound is uniformly coated on a part of the particle surface of the lithium transition metal composite oxide. Even if it is, the load characteristics, low-temperature characteristics, and thermal stability are improved. However, as described later, it is not preferable that the particles of the lithium transition metal composite oxide be completely covered with the thick layer of the zirconium compound because the discharge capacity may be reduced.

More preferably, the zirconium compound is uniformly coated on the entire surface of the lithium transition metal composite oxide particles. In this case, a positive electrode active material for a non-aqueous electrolyte secondary battery having not only improved load characteristics, low-temperature characteristics, cycle characteristics, and thermal stability but also improved high-load characteristics and low-temperature load characteristics can be obtained.
The zirconium compound only needs to be present at least on the surface of the particle. Therefore, the zirconium compound may be present inside the particles. In this case, the zirconium compound present inside the particles may be incorporated in the crystal structure of the lithium transition metal composite oxide. It is considered that the presence of the zirconium compound inside the particles stabilizes the crystal structure of the particles of the lithium transition metal composite oxide and further improves the cycle characteristics.

Whether or not the zirconium compound is present on the surface of the lithium transition metal composite oxide particles can be analyzed by various methods. For example, analysis can be performed by Auger Electron Spectroscopy (AES) or X-ray Photoelectron Spectroscopy (XPS).
Various methods can be used for the determination of the zirconium compound. For example, it can be quantified by inductively coupled high-frequency plasma (ICP: Inductively Coupled Plasma) spectroscopy or titration.

In the lithium transition metal composite oxide used for the positive electrode active material of the first embodiment of the present invention, the proportion of zirconium on the surface is 20% or more. In the lithium transition metal composite oxide used for the positive electrode active material according to the second aspect of the present invention, the proportion of zirconium on the surface is not particularly limited, but is preferably 20% or more.
In this case, since the zirconium is uniformly dispersed on the surface of the lithium transition metal composite oxide, that is, since the zirconium compound is not locally localized, the interface resistance decreases, thereby reducing the temperature at normal temperature and low temperature. Under the load, the discharge potential at the time of load increases, and the capacity retention rate at the time of load improves. That is, it is considered that the load characteristics and the low-temperature characteristics are improved.
It is also considered that local deposition of lithium on the negative electrode during charging can be suppressed. For this reason, it is considered that generation of gas during charging can be suppressed and dryout can be prevented, so that cycle characteristics are improved.
Further, it is considered that the presence of the zirconium compound uniformly on the surface suppresses the elimination of oxygen and improves the thermal stability.
Therefore, a positive electrode active material having not only cycle characteristics, low-temperature characteristics, and thermal stability but also excellent load characteristics and low-temperature load characteristics can be obtained.

In any of the first and second aspects of the present invention, the proportion of zirconium on the surface of the lithium transition metal composite oxide is preferably 40% or more, more preferably 60% or more, More preferably, it is at least 80%.
When the proportion of zirconium is large as described above, among the load characteristics, the load characteristics when a higher load is applied (high load characteristics) and the load characteristics at a low temperature (low temperature load characteristics) are more excellent. .

In the present invention, “the abundance ratio of zirconium on the surface of the lithium transition metal composite oxide” is determined as follows.
First, the presence state of zirconium on the surface of the lithium transition metal composite oxide particles is observed using an electron beam microanalyzer (EPMA) equipped with a wavelength dispersive X-ray spectrometer (WDX). Next, in the observation visual field, a portion having the largest amount of zirconium per unit area (a portion having a largest zirconium peak: a maximum peak portion) is selected, and a line segment passing through this portion (for example, a line segment having a length of 260 μm) is selected. Perform line analysis along. In the line analysis, when the peak value (maximum peak value) in the portion where the amount of zirconium per unit area is the largest is 100%, the total length of the portion where the peak is 4% or more is the length of the line segment. The quotient divided by the above is defined as “the proportion of zirconium present on the surface of the lithium transition metal composite oxide”. Note that by performing line analysis a plurality of times (for example, 10 times) on an arbitrary surface of the lithium transition metal composite oxide, the average value of “the abundance ratio of zirconium on the surface of the lithium transition metal composite oxide” can be used. preferable.
In the above method, a portion where the peak of zirconium is less than 4% has a large difference from a portion where the amount of zirconium is the largest, and therefore is not included in the abundance ratio in the present invention.

  The above-mentioned “ratio of zirconium on the surface of the lithium transition metal composite oxide” can indicate whether zirconium is present uniformly or unevenly on the surface of the lithium transition metal composite oxide. Specifically, it means that zirconium present on the surface of the lithium transition metal composite oxide is more uniformly dispersed as the abundance ratio increases.

  In the first aspect of the present invention, as described above, the proportion of zirconium on the surface of the lithium transition metal composite oxide is 20% or more. That is, the following relational expression is satisfied when a line analysis is performed on the surface of the lithium transition metal composite oxide along a line segment passing through the maximum peak portion of zirconium.

  (Sum of the length of the portion where the peak value of zirconium is 4% or more when the maximum peak value is 100%) / (length of line segment) ≧ 0.2

  In addition, when the maximum peak value of zirconium is 100%, it is not preferable that the ratio of the portion where the peak value of zirconium is 70% or more is 100%. In this case, the discharge capacity may be reduced. In this case, it is considered that the surface of the lithium transition metal composite oxide is covered with a thick layer of zirconium.

In the positive electrode active material of the present invention, the ratio of the zirconium compound present on the surface of the lithium transition metal composite oxide is preferably 0.01 to 2 mol% of zirconium based on the lithium transition metal composite oxide. When the content is 0.01 mol% or more, the zirconium compound can be present on the entire surface of the lithium transition metal composite oxide, which is preferable. When the content is 2 mol% or less, the discharge capacity increases, which is preferable. More preferably, it is 0.02 to 0.3 mol%, and still more preferably 0.04 to 0.25 mol%.
When the content is in the above range, it is possible to obtain a positive electrode active material for a non-aqueous electrolyte secondary battery having not only improved low-temperature characteristics, cycle characteristics, and thermal stability but also improved high-load characteristics and low-temperature load characteristics.

  Hereinafter, lithium transition metal composite oxides suitably used in the present invention will be exemplified. Note that any lithium transition metal composite oxide has zirconium on at least its surface, and when used in the first embodiment of the present invention, the proportion of zirconium on its surface is 20% or more.

(1) When the lithium transition metal composite oxide is at least one selected from the group consisting of lithium cobalt oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminate and lithium nickel cobalt manganate, the lithium transition metal composite oxide is lithium cobalt oxide or lithium nickel cobalt oxide; A positive electrode active material for a non-aqueous electrolyte secondary battery having further improved cycle characteristics and excellent load characteristics, low-temperature characteristics and thermal stability. 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 having improved load characteristics, low-temperature characteristics, output characteristics, cycle characteristics and thermal stability. Therefore, the non-aqueous electrolyte secondary battery using the 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 nickel cobalt 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 with improved 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, electric tools, and electric vehicles.

Lithium nickel cobaltate, lithium nickel cobalt aluminate and lithium nickel cobalt manganate have the same layered crystal structure as lithium cobalt oxide.
However, these have a problem in that a large amount of gas is generated and the potential at the time of discharge is low as compared with lithium cobalt oxide.
In the present invention, since zirconium is present on these surfaces, residual lithium in the raw material is reduced, and generation of gas during charging can be prevented.
In addition, the interface resistance is reduced, thereby increasing the discharge potential under normal temperature and low temperature under load, and improving the capacity retention rate under load. That is, it is considered that the load characteristics and the low-temperature characteristics are improved.
Further, it is considered that local precipitation of lithium on the negative electrode during charging can be suppressed. For this reason, it is considered that generation of gas during charging can be suppressed and dryout can be prevented, so that cycle characteristics are improved.
Further, it is considered that the presence of the zirconium compound on the surface suppresses the elimination of oxygen and improves the thermal stability.
Therefore, the lithium transition metal composite oxide having at least zirconium on its surface is at least one selected from the group consisting of lithium nickel cobaltate, lithium nickel cobalt aluminate and lithium nickel cobalt manganate, The second embodiment is useful.

(2) Lithium cobalt oxide containing at least one element selected from the group consisting of transition metals that are not the same as cobalt, elements of Groups 2, 13, and 14 of the periodic table, halogen elements, and sulfur. This further improves the load characteristics, low-temperature characteristics, cycle characteristics, and thermal stability.
Among them, lithium cobaltate is a compound represented by the general formula Li _x CoO _y (where 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 halogen elements, a represents a number satisfying 0.95 ≦ a ≦ 1.10. B represents 0 <b ≦ 0.10 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 Represents a lithium transition metal composite oxide.

(3) Nickel lithium cobaltate containing at least one element selected from the group consisting of transition metals not identical to nickel and cobalt, elements of Groups 2, 13 and 14 of the periodic table, halogen elements and sulfur; nickel Lithium nickel cobalt lithium aluminate containing at least one element selected from the group consisting of and a transition metal that is not the same as cobalt, a Group 2 element of the Periodic Table, elements of Groups 13 and 14 that are not the same as aluminum, a halogen element, and sulfur; Or nickel nickel lithium manganate containing at least one element selected from the group consisting of nickel, cobalt and transition metals not identical with cobalt, 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 improvements in output characteristics, cycle characteristics and thermal stability can be realized. Therefore, the non-aqueous electrolyte secondary battery using the positive electrode active material can be suitably used for electric tools, electric vehicles, mobile phones, notebook computers, and the like.

Among them, transition metals that are not the same as Co and Ni (transition metals that are not the same as Co, Ni and Mn when Z is Mn in the following formula), Group 2 and Group 13 of the periodic table (when Z is Al in the following formula, Al not identical to the group 13 elements) and group 14 elements of at least one element selected from the group consisting of halogen elements and S, the general formula _{Li k Ni m Co p Z (} 1-mp) 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 0. Represents a number that satisfies 1 ≦ p ≦ 0.9, m + p represents a number that satisfies m + p ≦ 1, and r represents a number that satisfies 1.8 ≦ r ≦ 2.2.) Oxides are preferred.

Preferred specific examples, the general formula _{Li k Ni m Co p Z (} 1-mp) O r ( where, Z is represents Al or Mn, k is a number satisfying 0.95 ≦ k ≦ 1.10 And 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, and r represents 1 .8 ≦ r ≦ 2.2.) Represents a lithium transition metal composite oxide.

(4) 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 causes a pillar effect, resulting in a crystal structure It is considered that the cycle characteristics are improved by stabilizing. It is considered that the cycle characteristics are improved by the 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. Further, by containing magnesium, in addition to these effects, thermal stability is further improved.

Among them, lithium cobaltate is a compound represented by the general formula Li _x CoO _y (where x represents a number satisfying 0.95 ≦ x ≦ 1.10, and y represents a number satisfying 1.8 ≦ y ≦ 2.2. )).

(5) It consists of lithium nickel cobaltate, 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. It is considered that the presence of at least one element selected from the group causes a pillar effect, and that the crystal structure is stabilized to improve cycle characteristics. It is also considered that the surface modification improves the cycle characteristics.
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. Further, by containing magnesium, the thermal stability is further improved in addition to these effects.

Among them, Ti, Al, V, Zr , Mg, Ca, comprises at least one element selected from the group consisting of Sr and S, the general formula _{Li k Ni m Co p Z (} 1-mp) O r ( Formula In the formula, 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 0.1 ≦ represents a number that satisfies p ≦ 0.9, m + p represents a number that satisfies m + p ≦ 1, and r represents a number that satisfies 1.8 ≦ r ≦ 2.2.) Is preferred.

Specific preferable examples, at least the general formula in _{Li a Co 1-b M b} O c X d S e ( wherein, M is Ti, Al, V, Zr, Mg, selected from the group consisting of Ca and Sr 1 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.) The lithium transition metal composite oxide represented is mentioned.

The specific surface area of the lithium transition metal composite oxide is preferably from 0.2 to ³ m ² / g.
If the specific surface area is too small, the particle size of the positive electrode active material becomes too large, and the battery characteristics deteriorate. If the specific surface area is too large, the reactivity of the oxidative decomposition reaction of the electrolytic solution occurring on or near the surface of the positive electrode active material increases, and the amount of generated gas increases. Within the above ranges, gas generation can be reduced without impairing the 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 diameter of 50 μm or more is preferably 10% by volume or less of all the particles. Within the above ranges, the coating properties and the slurry properties can be improved without impairing the improvements in the load characteristics, low-temperature characteristics, output characteristics, and thermal stability.

In a preferred embodiment of the present invention, at least a part of the surface of the lithium transition metal composite oxide is covered with a coating layer made of Al ₂ O ₃ and / or LiTiO ₂ powder.
It is considered that when the coating layer is made of Al ₂ O ₃ powder, the moving speed in the electric double layer can be reduced somewhat, and the moving speed of lithium ions in the crystal lattice can be kept in balance. Therefore, the voltage drop can be improved without impairing the improvement of the load characteristics and the high load characteristics.
When the coating layer is made of LiTiO ₂ powder, a unique phenomenon occurs when lithium ions are exchanged during charging and discharging, so that the load characteristics can be further improved without impairing the load characteristics and the high load characteristics. Can be done. LiTiO ₂ preferably belongs to the space group Fm3m.

In a preferred embodiment of the present invention, a sulfate group is provided on the surface of the lithium transition metal composite oxide.
It is considered that by having a sulfate group on the surface of the lithium transition metal composite oxide having a layered structure, the sulfate group easily conducts electrons. Therefore, the load characteristics can be further improved without impairing the low-temperature characteristics, output characteristics, cycle characteristics, and thermal stability.

<Method for producing positive electrode active material for non-aqueous electrolyte secondary battery>
The method for producing the positive electrode active material of the present invention is not particularly limited. Hereinafter, an example of the method for producing a positive electrode active material of the present invention will be described.

For example, when the lithium transition metal composite oxide used in the present invention is lithium cobalt oxide, first, an aqueous solution containing a predetermined composition ratio of cobalt ions and zirconium ions is dropped into pure water being stirred. Further, an alkaline solution is added dropwise so as to have a pH of 7 to 11, and cobalt and zirconium are precipitated to obtain a precipitate.
The aqueous solution is not particularly limited. For example, it can be obtained by dissolving each of water-soluble compounds (for example, salts) of cobalt and zirconium in water.

The cobalt compound is not particularly limited. Basically, any salt that can form an aqueous solution can be used. Examples include cobalt chloride, cobalt iodide, cobalt sulfate, cobalt bromate, and cobalt nitrate. Among _{them, CoSO 4 · 7H 2 O,} Co (NO 3) · 6H 2 O are preferable.

The zirconium compound is not particularly limited. Basically, any salt that can form an aqueous solution can be used. Examples include zirconium sulfate, zirconium nitrate, zirconium oxalate, and zirconium oxychloride. Among them, Zr (SO ₄ ) ₂ and ZrOCl ₂ are preferred.

  Examples of the alkaline solution include an aqueous solution of sodium hydroxide, an aqueous solution of sodium hydrogen carbonate, an aqueous solution of potassium hydroxide, and an aqueous solution of lithium hydroxide.

  Similarly to the above, when the lithium transition metal composite oxide used in the present invention is lithium nickelate, nickel and zirconium are precipitated to obtain a precipitate. In the case of lithium nickel cobaltate, nickel, cobalt and zirconium are precipitated to obtain a precipitate. In the case of nickel cobalt lithium aluminate, nickel, cobalt, aluminum and zirconium are precipitated to obtain a precipitate. In the case of nickel cobalt lithium manganate, nickel, cobalt, manganese and zirconium are precipitated to obtain a precipitate.

The nickel compound is not particularly limited. Basically, any salt that can form an aqueous solution can be used. Examples include nickel chloride, nickel bromide, nickel iodide, nickel sulfate, nickel nitrate, and nickel formate. Among _{them, NiSO 4 · 6H 2 O,} Ni (NO 3) 2 · 6H 2 O are preferable.

The aluminum compound is not particularly limited. Basically, any salt that can form an aqueous solution can be used. Examples include aluminum chloride, aluminum iodide, aluminum sulfate, and aluminum nitrate. Among them, Al ₂ (SO ₄ ) ₃ .xH ₂ O and Al (NO ₃ ) ₃ .9H ₂ O are preferable.

The manganese compound is not particularly limited. Basically, any salt that can form an aqueous solution can be used. For example, there are manganese chloride, manganese iodide, manganese sulfate, and manganese nitrate. Among _{them, MnSO 4 · 7H 2 O,} MnCl 2 · 4H 2 O are preferred.

  Next, the obtained precipitate is filtered, washed with water, heat-treated, mixed with a predetermined amount of a lithium compound, and dried at a temperature of 650 to 1200 ° C. in the air or in an atmosphere in which the oxygen partial pressure is controlled. By baking for up to 36 hours, the positive electrode active material of the present invention can be obtained.

The lithium compound is not particularly limited. Basically, any lithium compound can be used. Examples include lithium carbonate, lithium hydroxide, lithium fluoride, lithium chloride, lithium bromide, lithium iodide, lithium oxide, and lithium peroxide. Among them, 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.

  Here, when the precipitate is mixed with the lithium compound, a sulfur-containing compound, a compound containing a halogen element, a boron compound, and the like can be further added and mixed.

The sulfur-containing compound is not particularly limited. Examples include sulfide, sulfur iodide, hydrogen sulfide, sulfuric acid and its salts, and nitrogen sulfide. Among _{them, Li 2 SO 4, MnSO 4} · 7H 2 O, is _{(NH 4) 2 SO 4,} Al 2 (SO 4) 3 · xH 2 O, MgSO 4 preferred.

The compound containing a halogen element is not particularly limited. Examples include hydrogen fluoride, oxygen fluoride, hydrofluoric acid, hydrogen chloride, hydrochloric acid, chlorine oxide, chlorine fluoride oxide, bromine oxide, bromine fluorosulfate, hydrogen iodide, iodine oxide, and periodic acid. Among them, 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.

The boron compound is not particularly limited. For example, boride, boron oxide, and boron phosphate are mentioned. Among them, B ₂ O ₃ and H ₃ BO ₃ are preferable.

The firing temperature is preferably 650 ° C. or higher, more preferably 750 ° C. or higher. When the content is in the above range, the unreacted raw material does not remain in the obtained positive electrode active material, and the characteristics as the positive electrode active material are sufficiently exhibited.
The firing temperature is preferably 1200 ° C. or lower, more preferably 1100 ° C. or lower. Within the above range, it is difficult to generate by-products that cause problems such as a decrease in discharge capacity per unit weight, a decrease in cycle characteristics, and a decrease in operating voltage.
The firing time is preferably at least 1 hour, more preferably at least 6 hours. Within the above range, the diffusion reaction between the particles of the mixture proceeds sufficiently.
In addition, the firing time is preferably 36 hours or less, and more preferably 30 hours or less. Within the above range, the synthesis proceeds sufficiently.
Examples of the sintering atmosphere include air, oxygen gas, and a mixed gas of these with an inert gas such as nitrogen gas or argon gas.

  The lithium transition metal composite oxide obtained by the above calcination can be pulverized by a mortar, a ball mill, a vibration mill, a pin mill, a jet mill or the like. Thereby, a desired specific surface area and particle size distribution can be obtained.

  By using the above manufacturing method, it is possible to obtain the intended cathode active material of the present invention.

<Non-aqueous electrolyte secondary battery>
The non-aqueous electrolyte secondary battery of the present invention is a non-aqueous 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 nonaqueous electrolyte secondary batteries such as lithium ion secondary batteries and lithium ion polymer secondary batteries.

The nonaqueous electrolyte secondary battery may use the positive electrode active material of the present invention as at least a part of the positive electrode active material in a conventionally known nonaqueous electrolyte secondary battery, 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 for 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 positive electrode active material, lithium manganate can be used together with the positive electrode active material of the present invention. As a result, it is possible to obtain a nonaqueous electrolyte secondary battery having not only high potential, load characteristics and thermal stability but also excellent overcharge characteristics and safety.

As such a lithium manganate, the general formula is Li _a Mn _3-a O _{4 + f} (a represents a number satisfying 0.8 ≦ a ≦ 1.2, and f represents −0.5 ≦ f ≦ 0 .5 represents a number that satisfies .5). This lithium manganate is partially 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. May be substituted with at least one of the above.

  It is also preferable to use the following lithium transition metal composite oxide together with the positive electrode active material of the present invention as the positive electrode active material. That is, a lithium transition metal composite oxide having a first lithium manganate and a second lithium manganate, wherein the first lithium manganate is smaller than the second lithium manganate containing boron. It is also preferable to use a transition metal composite oxide. This makes it possible to obtain a nonaqueous electrolyte secondary battery which is excellent not only in high potential, load characteristics and thermal stability but also in overcharge characteristics and safety and can prevent dryout.

  As the negative electrode active material, at least one selected from the group consisting of metallic lithium, a lithium alloy, a carbon material capable of inserting and extracting lithium ions, and a compound capable of inserting and extracting lithium ions can be suitably used. Examples of the lithium alloy include a LiAl alloy, a LiSn alloy, and a LiPb alloy. Examples of the carbon material capable of inserting and extracting lithium ions include graphite and graphite. Examples of the compound capable of inserting and extracting lithium ions include oxides such as tin oxide and titanium oxide.

The electrolytic solution is not particularly limited as long as it is a compound that does not deteriorate or decompose at the operating voltage.
Examples of the solvent used for 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 are exemplified. These can be used alone or in combination 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 trifluoromethane.
The above-mentioned solvent and electrolyte are mixed to form an electrolyte. Here, a gelling agent or the like may be added and used as a gel. Further, it may be used after being absorbed by a hygroscopic polymer. Further, a solid electrolyte having inorganic or organic lithium ion conductivity may be used.

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

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

  The non-aqueous electrolyte secondary battery of the present invention can be obtained according to a standard method using the positive electrode active material of the present invention, the above-described negative electrode active material, electrolytic solution, separator and binder.

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 a powder of the positive electrode active material of the present invention with a carbon-based conductive agent such as acetylene black or graphite, a binder, and a solvent or a dispersion medium of the binder. The obtained positive electrode mixture is formed into a slurry or a kneaded material, which is applied or supported on a current collector such as an aluminum foil, and is pressed and rolled to form a positive electrode active material layer on the current collector.
FIG. 6 is a schematic cross-sectional view of the positive electrode. As shown in FIG. 6, the positive electrode 13 is formed by holding the positive electrode active material 5 on the current collector 12 with the binder 4.

It is considered that the positive electrode active material of the present invention is excellent in the mixing property with the conductive agent powder and the internal resistance of the battery is small. Therefore, the charge / discharge characteristics, particularly the load characteristics, are excellent.
In addition, the positive electrode active material of the present invention has excellent fluidity even when kneaded with a binder, easily entangles with a polymer of the binder, and has excellent binding properties.

As a preferred embodiment of the nonaqueous electrolyte secondary battery of the present invention, a positive electrode active material layer using the positive electrode active material of the present invention is formed on at least one surface (that is, either one surface or both surfaces) of the belt-shaped positive electrode current collector. And a negative electrode active material layer using as a negative electrode active material a metallic lithium, a lithium alloy, a carbon material capable of storing and releasing lithium ions or a compound capable of storing and releasing lithium ions. A band-shaped negative electrode formed by being formed on at least one surface of the body, and a band-shaped separator, and the band-shaped positive electrode and the band-shaped negative electrode are wound a plurality of times in a laminated state with the band-shaped separator interposed therebetween; A non-aqueous electrolyte secondary battery includes a spiral wound body in which the strip separator is interposed between a positive electrode and the strip negative electrode.
Such a nonaqueous electrolyte secondary battery has a simple manufacturing process and is less likely to crack the positive electrode active material layer and the negative electrode active material layer and to be separated from the strip separator. Also, the battery capacity is large and the energy density is high. In particular, the positive electrode active material of the present invention has excellent filling properties and is easily compatible with a binder. Therefore, a positive electrode having a high charge / discharge capacity, and excellent in binding property and surface smoothness can be prevented, so that cracking and peeling of the positive electrode active material layer can be prevented.
In addition, a positive electrode active material layer using the positive electrode active material of the present invention is formed on both sides of a belt-shaped positive electrode current collector, and a negative electrode active material layer using the above negative electrode active material is formed on both sides of a band-shaped negative electrode current collector. By doing so, a non-aqueous 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 non-aqueous electrolyte secondary battery of the present invention, a positive electrode, a negative electrode, a non-aqueous electrolyte secondary battery having a separator and a non-aqueous electrolyte, the following I 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 a negative electrode is exemplified. 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 for the positive electrode active material of the present invention, wherein the weight of the lithium manganate is A and the weight of the lithium transition metal composite oxide is B In this case, the positive electrode active material for a non-aqueous electrolyte secondary battery is mixed so as to satisfy the range of 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, carbon materials capable of inserting and extracting lithium ions, and compounds capable of inserting and extracting lithium ions.

In the positive electrode active material of the above I, it is preferable to mix them 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 load characteristics, low-temperature characteristics, output characteristics, and thermal stability but also overcharge characteristics and safety are remarkably improved.
In the positive electrode active material of the above I, part of lithium manganate is magnesium, aluminum, calcium, vanadium, titanium, chromium, manganese, iron, cobalt, nickel, copper, zinc, strontium, zirconium, niobium, molybdenum. , Boron and tin may be substituted.
As the negative electrode active capable of absorbing and releasing compound lithium ions used in the material of the II, the general formula _{Li a Ti b O 4 + c} (a consisting of spinel structure containing an alkali metal and / or alkaline earth metal 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 non-aqueous electrolyte secondary batteries represented by At this time, it is possible to obtain a non-aqueous electrolyte secondary battery in which not only load characteristics, low-temperature characteristics, output characteristics, and thermal stability but also cycle characteristics are significantly improved.

The shape of the nonaqueous electrolyte secondary battery of the present invention is not particularly limited, and may be a cylindrical type, a coin type, a square type, a laminate type, or the like.
FIG. 7 is a schematic sectional view of a cylindrical battery. As shown in FIG. 7, 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. 8 is a schematic partial sectional view of a coin-type battery. As shown in FIG. 8, in a coin-type battery 30, a positive electrode 13 in which a positive electrode active material layer is formed on a current collector 12 and a negative electrode 11 are stacked via a separator 14.
FIG. 9 is a schematic sectional perspective view of a prismatic battery. As shown in FIG. 9, in the prismatic 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 Are repeatedly laminated via the separator 14.

<Uses 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 personal computers, pen input personal computers, pocket personal computers, notebook type word processors, pocket word processors, e-book players, mobile phones, cordless handsets, electronic notebooks, calculators, LCD TVs, electric shavers, electric tools, electronic translators, automobiles Telephone, 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 devices.
In addition, lighting equipment, air conditioners, TVs, stereos, water heaters, refrigerators, microwave ovens, dishwashers, washing machines, dryers, game machines, toys, road conditioners, medical equipment, automobiles, electric vehicles, golf carts, It can also be used as a power source for electric carts, power storage systems, and the like.
Further, the application is not limited to civilian use, but may be for military use or space use.

  Hereinafter, the present invention will be described specifically with reference to examples. However, the present invention is not limited to these.

1. Preparation of positive electrode active material [Example 1]
An aqueous solution of cobalt sulfate and an aqueous solution of zirconium oxychloride were added dropwise to the stirred pure water so as to have a predetermined composition ratio. The aqueous solution of zirconium oxychloride was added dropwise so that the amount of zirconium was 0.2 mol% with respect to cobalt. Further, an aqueous solution of sodium hydroxide was added dropwise so as to have a pH of 7 to 7.5, and cobalt and zirconium were precipitated at 60 ° C. at a rotation speed of 650 rpm to obtain a precipitate. The obtained precipitate was filtered, washed with water, heat-treated, mixed with lithium carbonate, and fired at 995 ° C. for 7 hours in the air. Thus, a positive electrode active material was obtained.

[Example 2]
An aqueous solution of cobalt sulfate and an aqueous solution of zirconium oxychloride were added dropwise to the stirred pure water so as to have a predetermined composition ratio. The aqueous solution of zirconium oxychloride was dropped so that the amount of zirconium was 0.04 mol% with respect to cobalt. Further, an aqueous solution of sodium hydroxide was added dropwise so as to have a pH of 7 to 7.5, and cobalt and zirconium were precipitated at 60 ° C. at a rotation speed of 650 rpm to obtain a precipitate. The obtained precipitate was filtered, washed with water, heat-treated, mixed with lithium carbonate, and fired at 995 ° C. for 7 hours in the air. Thus, a positive electrode active material was obtained.

[Example 3]
An aqueous solution containing cobalt and nickel was dropped into stirred pure water so as to have a predetermined composition ratio. Further, an aqueous solution of sodium hydroxide was added dropwise so as to have a pH of 9, and cobalt and nickel were precipitated at 80 ° C. at a rotation speed of 650 rpm to obtain a precipitate. The obtained precipitate was filtered, washed with water, heat-treated, mixed with zirconium oxide and lithium hydroxide, and calcined at about 750 ° C. for about 10 hours in an atmosphere with a controlled oxygen partial pressure. Zirconium oxide was mixed with the precipitate at 0.03 mol% in terms of zirconium. Thus, a positive electrode active material was obtained.

[Comparative Example 1]
Lithium carbonate (Li ₂ CO ₃ ), cobalt trioxide (Co ₃ O ₄ ), and zirconium oxide (ZrO ₂ ) were used as compounds as raw materials. The raw material compound was weighed so as to have a predetermined composition ratio, and was dry-mixed to obtain a raw material mixed powder. The obtained raw material mixed powder was fired in an air atmosphere at 995 ° C. for 7 hours. Thus, a positive electrode active material was obtained.

[Comparative Example 2]
An aqueous solution of cobalt sulfate was dropped into the stirred pure water so as to have a predetermined composition ratio. Here, an aqueous sodium hydroxide solution was added dropwise so as to have a pH of 7, and cobalt was precipitated at 60 ° C. at a rotation speed of 650 rpm to obtain a precipitate. The obtained precipitate was filtered, washed with water, heat-treated, mixed with lithium carbonate, and fired at 1045 ° C. for 7 hours in the air. Thus, a positive electrode active material was obtained.

[Comparative Example 3]
An aqueous solution containing cobalt and nickel was dropped into stirred pure water so as to have a predetermined composition ratio. Further, an aqueous solution of sodium hydroxide was added dropwise so as to have a pH of 9, and cobalt and nickel were precipitated at 80 ° C. at a rotation speed of 650 rpm to obtain a precipitate. The obtained precipitate was filtered, washed with water, heat-treated, mixed with lithium hydroxide, and calcined at about 750 ° C. for about 10 hours in an atmosphere having a controlled oxygen partial pressure. Thus, a positive electrode active material was obtained.

2. Properties of Positive Electrode Active Material (1) Configuration of Positive Electrode Active Material The positive electrode active materials obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were subjected to ICP spectroscopy.
The positive electrode active material obtained in Example 1 was LiCoO ₂ in which 0.2 mol% of zirconium was present. XPS showed that Zr was present on the surface of the positive electrode active material obtained in Example 1. EPMA showed that Zr on the surface of the positive electrode active material obtained in Example 1 was uniformly present. The existence ratio of Zr on the particle surface was 98.3%.
The positive electrode active material obtained in Example 2 was LiCoO ₂ having 0.04 mol% of zirconium. XPS showed that Zr was present on the surface of the positive electrode active material obtained in Example 2. EPMA showed that Zr on the surface of the positive electrode active material obtained in Example 2 was uniformly present. The existence ratio of Zr on the particle surface was in the range of 20% or more.
The positive electrode active material obtained in Example 3 was LiNi _0.79 Co _0.21 O ₂ in which 0.03 mol% of zirconium was present based on the lithium nickel cobaltate composite oxide. XRD (X-ray diffraction) showed that Zr was present on the surface of the positive electrode active material obtained in Example 3.
The positive electrode active material obtained in Comparative Example 1 was LiCoO ₂ in which 0.2 mol% of zirconium was present. EPMA revealed that the segregation of Zr present on the surface of the positive electrode active material obtained in Comparative Example 1 was severe. The existence ratio of Zr on the particle surface was 12.8%.
The positive electrode active material obtained in Comparative Example 2 was LiCoO ₂ .
The positive electrode active material obtained in Comparative Example 3 was LiNi _0.79 Co _0.21 O ₂ .

FIG. 1 shows the result of line analysis of the lithium transition metal composite oxide of Example 1 at two points between 260 μm by EPMA. From FIG. 1, it can be seen that in the lithium transition metal composite oxide of Example 1, zirconium is uniformly dispersed on the surface of the particles and segregation is small.
FIG. 2 shows the results of line analysis of the lithium transition metal composite oxide of Comparative Example 1 at two points between 260 μm by EPMA. From FIG. 2, it can be seen that the lithium transition metal composite oxide of Comparative Example 1 has almost no zirconium on the surface of the particles, and segregates even if present.

(2) Specific Surface Area of Positive Electrode Active Material The specific surface area of the obtained positive electrode active material was determined by a constant pressure BET adsorption method using nitrogen gas.
The specific surface area of the positive electrode active material obtained in Example 1 was 0.55 m ² / g. The specific surface area of the positive electrode active material obtained in Comparative Example 1 was 0.47 m ² / g.

(3) Crystallinity An X-ray diffraction method was performed on the obtained positive electrode active material.
The X-ray diffraction method can be performed, for example, under the conditions of a tube current of 100 mA and a tube voltage of 40 kV. The crystallinity is calculated from the diffraction peak attributable to the (104) plane or (110) plane obtained by the X-ray diffraction method, according to Scherrer's formula represented by the following formula (1).

  D = Kλ / (βcosθ) (1)

In the above formula, D represents (104) crystallinity (Å) or (110) crystallinity (Å), and K is a Scherrer constant (K is a sintered Si for optical system adjustment (manufactured by Rigaku Denki Co., Ltd.) , (104) or (110) the diffraction peak due to the (110) plane is 1000 °), λ represents the wavelength of the X-ray source (1.540562 ° for CuKα1), and β is β = by (B denotes the width of the observation profile, y is calculated by ^{y = 0.9991-0.019505b-2.8205b 2 + 2.878b} 3 -1.0366b 4. here, b is unit Means the width of the constant profile), and θ represents the diffraction angle.

Here, an X-ray diffractometer was used, CuKα1 was used as an X-ray source, and the tube current was set to 100 mA and the tube voltage was set to 40 kV.
The crystallinity of the positive electrode active material obtained in Example 1 was 924 °. The crystallinity of the positive electrode active material obtained in Comparative Example 1 was 989 °.

3. Evaluation of positive electrode active material (1)
(1) Preparation of Lithium Ion Secondary Battery For each positive electrode active material obtained in Examples 1 and 2 and Comparative Example 1, a test secondary battery was prepared and evaluated as follows.
A paste was prepared by kneading 90 parts by weight of the powder of the positive electrode active material, 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 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.

(2) Load characteristics The initial discharge capacity was measured under the conditions of a discharge load of 0.2 C (1 C is a current load at which discharge is completed in one hour), a charge potential of 4.3 V, and a discharge potential of 2.75 V. After that, the load discharge capacity was measured under the conditions of a discharge load of 1 C, a charge potential of 4.3 V, and a discharge potential of 2.75 V. The load capacity retention ratio (%) at a discharge load of 1C was determined from the following equation.

  Load capacity maintenance rate (%) = (1 C discharge capacity) / (0.2 C discharge capacity) × 100

  Next, a high load discharge capacity was measured under the conditions of a discharge load of 2C, a charge potential of 4.3 V, and a discharge potential of 2.75 V. The load capacity maintenance ratio (%) at the time of the discharge load 2C was determined from the following equation.

  Load capacity maintenance ratio (%) = (2C discharge capacity) / (0.2C discharge capacity) × 100

(3) Average voltage The initial discharge capacity and the electric energy were measured under the conditions of a discharge load of 0.2 C, a charge potential of 4.3 V, and a discharge voltage of 2.75 V. The average voltage was determined from the following equation.

  Average voltage (V) = electric energy (mWh / g) / capacity (mAh / g)

  The results are shown in Table 1. FIG. 3 shows the relationship between the discharge capacity and the potential when the average voltage of the test secondary batteries using the positive electrode active materials of Example 1 and Comparative Example 1 was obtained. FIG. 4 shows the relationship between the discharge capacity and the potential when the average voltage of the test secondary battery using the positive electrode active material was obtained.

As is clear from Table 1, the positive electrode active materials of the present invention (Examples 1 and 2) have a high potential, and have excellent load characteristics and high load characteristics.
In addition, since the positive electrode active material of the present invention has low impedance and low-temperature impedance, it has excellent output characteristics and low-temperature output characteristics. Furthermore, it has excellent low-temperature load characteristics and excellent thermal stability.

  On the other hand, the positive electrode active material (Comparative Example 1) in which the ratio of zirconium is small on the surface of the lithium transition metal composite oxide obtained by dry-mixing and obtaining the raw material mixed powder is potential, load characteristics, and high load characteristics. , Low-temperature load characteristics, output characteristics, low-temperature output characteristics and thermal stability.

4. Evaluation of positive electrode active material (2)
For each of the positive electrode active materials obtained in Example 1 and Comparative Example 2, a laminated battery was prepared and evaluated as follows.
A positive electrode plate was obtained in the same manner as in the case of the test secondary battery. In addition, a carbon material was used as a negative electrode active material, and applied to a negative electrode current collector and dried in the same manner as in the case of the positive electrode plate to obtain a negative electrode plate. A porous polypropylene film was used for the separator. As the electrolytic solution, a solution in which LiPF ₆ was dissolved in a mixed solvent of ethylene carbonate / methyl ethyl carbonate = 3/7 (volume ratio) to a concentration of 1 mol / L was used. The positive electrode plate, the negative electrode plate, and the separator were formed into a thin sheet, laminated, stored in a battery case of a laminate film, and injected with an electrolytic solution into the battery case to obtain a laminate battery.

(1) Impedance The impedance measurement device (SI1287 and SI1260, both manufactured by SOLARTRON) was used.
The clips of the measuring device were attached to the lead wires provided on the positive and negative electrodes of the laminated battery, and the internal impedance at 0.1 Hz at an SOC of 60% and 0 ° C. was measured by an AC impedance method. It can be said that the smaller the impedance, the better the output characteristics.

(2) Thermal stability Using a laminated battery, charging and discharging were performed at a constant current, and the battery was adapted. Thereafter, charging was performed at a rate of 0.2 C with CC-CV charging, a termination voltage of 4.2 V, and a termination current of 0.02 mA. After the charging was completed, the positive electrode was taken out of the laminated battery, washed with a one-component solution contained in the electrolytic solution used for the laminated battery, dried, and the positive electrode active material was scraped off from the positive electrode. Ethylene carbonate used for the electrolyte and the positive electrode active material scraped from the positive electrode were put into an aluminum cell at a weight ratio of 0.40: 1.00, and the differential scanning calorimetry was measured at a rate of temperature increase of 5.0 ° C./min. .
Differential scanning calorimetry (DSC) is a method of measuring the difference between the energy input of a substance and a reference substance as a function of temperature while changing the temperature of the substance and the reference substance according to a program. In the low temperature part, the differential scanning calorific value did not change even when the temperature increased, but at a certain temperature or higher, the differential scanning calorific value greatly increased. 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 2.

  Table 2 shows that the positive electrode active material of the present invention (Example 1) has reduced impedance and excellent output characteristics. Further, it can be seen that the thermal stability is excellent.

5. Evaluation of positive electrode active material (3)
For each of the positive electrode active materials obtained in Example 3 and Comparative Example 3, a test secondary battery in which the negative electrode was made of lithium metal was produced in the same manner as described above, and the load characteristics were measured in the same manner as described above. evaluated.
For each of the positive electrode active materials obtained in Example 3 and Comparative Example 3, a test secondary battery in which the negative electrode was carbon was produced in the same manner as described above except that the negative electrode was carbon, and the same as above. The impedance was measured by the above method. The difference between the value of the impedance obtained in Comparative Example 3 and the value of the impedance obtained in Example 3 was divided by the value of the impedance obtained in Comparative Example 3 to determine the rate of decrease in impedance. It can be said that the larger the reduction rate, the better the output characteristics.
The results are shown in Table 3.

  Table 3 shows that the positive electrode active material of the present invention (Example 3) is excellent in load characteristics and output characteristics.

FIG. 3 is a diagram showing the results of line analysis of two points between 260 μm by EPMA for the lithium transition metal composite oxide of Example 1. FIG. 5 is a diagram showing the results of line analysis of two points between 260 μm by EPMA for the lithium transition metal composite oxide of Comparative Example 1. FIG. 2 is a diagram showing the relationship between discharge capacity and potential for the lithium transition metal composite oxide of Example 1 and the lithium transition metal composite oxide of Comparative Example 1. FIG. 3 is a diagram showing the relationship between discharge capacity and potential for the lithium transition metal composite oxide of Example 2 and the lithium transition metal composite oxide of Comparative Example 1. It is a schematic diagram which shows the crystal structure of the lithium transition metal composite oxide of a layer structure. It is a typical sectional view of a positive electrode. FIG. 3 is a schematic sectional view of a cylindrical battery. It is a typical fragmentary sectional view of a coin type battery. It is a typical sectional perspective view of a prismatic battery.

Explanation of reference numerals

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

Claims (6)

A positive electrode active material for a non-aqueous electrolyte secondary battery having at least a layered structure lithium transition metal composite oxide,
A positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the proportion of zirconium 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 having at least a layered structure lithium transition metal composite oxide,
A positive electrode active material for a non-aqueous electrolyte secondary battery, which satisfies the following relational expression when a line analysis is performed on a surface of the lithium transition metal composite oxide along a line segment passing through a maximum peak portion of zirconium.
(Sum of the length of the portion where the peak value of zirconium is 4% or more when the maximum peak value is 100%) / (length of line segment) ≧ 0.2   The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the lithium transition metal composite oxide is a particle.   The lithium transition metal composite oxide has at least zirconium on its surface and is at least one selected from the group consisting of lithium cobaltate, lithium nickel cobaltate, nickel cobalt lithium aluminate and nickel cobalt lithium manganate. Item 4. The positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of Items 1 to 3. A positive electrode active material for a non-aqueous electrolyte secondary battery having at least a layered structure lithium transition metal composite oxide,
The non-aqueous electrolyte secondary oxide is at least one selected from the group consisting of lithium nickel cobaltate, lithium nickel cobalt aluminate and lithium nickel cobalt manganate, the lithium transition metal composite oxide having zirconium on at least its surface. Positive electrode active material for batteries. A positive electrode active material layer using the positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 5, a band-shaped positive electrode formed by forming on at least one surface of a band-shaped positive electrode current collector,
By forming a negative electrode active material layer using lithium metal, a lithium alloy, a carbon material capable of inserting and extracting lithium ions or a compound capable of inserting and extracting lithium ions as an anode active material on at least one surface of the strip-shaped negative electrode current collector. A configured strip-shaped negative electrode,
A belt-shaped separator,
A spiral winding in which the strip-shaped positive electrode and the strip-shaped negative electrode are wound a plurality of times in a stacked state with the strip-shaped separator interposed therebetween, 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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