JP4954440B2 - Cathode active material for non-aqueous electrolyte secondary battery, cathode 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 nonaqueous electrolyte secondary battery such as a lithium ion secondary battery (hereinafter also simply referred to as “positive electrode active material”), a positive electrode for a nonaqueous electrolyte secondary battery (hereinafter simply referred to as “positive electrode”). And a non-aqueous electrolyte secondary battery. Specifically, the present invention relates to a lithium transition metal composite oxide having a spinel structure in which battery characteristics are greatly improved.

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.
In particular, LiMn ₂ O ₄ is easily available as a raw material at low cost because manganese, which is a constituent element, is present in a large amount as a resource. In addition, there is a feature that the load on the environment is small. Furthermore, even if all the Li ions in the crystal are desorbed by the deintercalation reaction, the crystal structure exists stably. For this reason, compared with LiCoO ₂ and LiNiO ₂ , the nonaqueous electrolyte secondary battery using LiMn ₂ O ₄ is excellent in thermal stability in a fully charged state.

Non-aqueous electrolyte secondary batteries using LiMn ₂ O ₄ having the advantages as described above have been used for mobile electronic devices such as mobile phones, notebook computers, digital cameras, etc. Battery characteristics sufficient for these applications were exhibited.
However, at present, the required characteristics of mobile electronic devices are becoming more severe due to high functionality such as various functions added and use at high and low temperatures. In addition, application to power sources such as batteries for electric vehicles is expected.
Therefore, conventional non-aqueous electrolyte secondary batteries cannot obtain sufficient battery characteristics, and further improvements are required.

  Patent Document 1 describes that positive electrode active material particles having an average particle size of 5 μm or more and 30 μm or less and a particle size distribution width with respect to the average particle size of ± 20% or less are used for the positive electrode. It is described that the discharge capacity and cycle characteristics can be improved by the positive electrode active material particles.

  However, with this positive electrode active material particle, a sufficient discharge capacity could not be obtained in a more severe use environment. Moreover, with this positive electrode active material particle, the high temperature characteristics could not be improved, and dryout could not be prevented.

Japanese Patent Laid-Open No. 10-162826

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

  The present invention provides the following (1) to (7).

(1) 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 lithium transition metal composite oxide is at least
It consists of primary particles, the first lithium transition metal composite oxide having a primary particle diameter of 0.1 to 5 μm, and secondary particles that are aggregates of primary particles. Having a second lithium transition metal composite oxide of 1-5 μm,
The positive active material for a non-aqueous electrolyte secondary battery, wherein the first lithium transition metal composite oxide is smaller than the second lithium transition metal composite oxide.

  (2) The positive electrode active material for a non-aqueous electrolyte secondary battery according to (1), wherein the median diameter of secondary particles of the second lithium transition metal composite oxide is 10 to 40 μm.

(3) 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 lithium transition metal composite oxide is a volume-based particle size distribution curve,
A first lithium transition metal composite oxide having a particle diameter of 0.1 to 10 μm and a second lithium transition metal composite oxide having a particle diameter of 10 to 100 μm, the first lithium transition metal composite oxide The integrated value of the relative particle amount of the oxide is 5 to 35%,
The second lithium transition metal composite oxide is a positive electrode active material for a non-aqueous electrolyte secondary battery, comprising secondary particles.

  (4) The positive electrode active material for a nonaqueous electrolyte secondary battery according to (3), wherein a primary particle diameter of the first lithium transition metal composite oxide is 0.1 to 5 μm.

  (5) The positive electrode active material for a nonaqueous electrolyte secondary battery according to (3) or (4), wherein the median diameter of the second lithium transition metal composite oxide is 10 to 40 μm.

(6) A positive electrode for a non-aqueous electrolyte secondary battery having at least a positive electrode active material having a lithium transition metal composite oxide having a spinel structure, a conductive agent, and a binder,
The positive electrode active material is a positive electrode for a nonaqueous electrolyte secondary battery, which is the positive electrode active material for a nonaqueous electrolyte secondary battery according to any one of (1) to (5).

(7) 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 (5) 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:
Constructed by forming a negative electrode active material layer using a metallic lithium, lithium alloy, 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 on at least one surface of a strip-shaped negative electrode current collector A strip-shaped negative electrode,
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.

The improvement of the electrode plate density is greatly related to the improvement of the charge / discharge capacity per unit volume. If the electrode plate density is improved, the charge / discharge capacity per unit volume is also improved. The electrode plate density can be improved by increasing the pressing pressure.
However, when the press pressure is increased, the particles of the lithium transition metal composite oxide are broken, fine powder is generated, the transition metal is eluted, and dry-out of the electrolyte solution is caused. Dryout is the largest cause of battery characteristic degradation.
In order to prevent this dry-out, it is preferable to increase the particle size, but the large-particle lithium transition metal composite oxide has a low electrode plate density.
Therefore, there is a trade-off between improving the electrode plate density and preventing dryout.
Moreover, high temperature characteristics deteriorate due to generation of fine powder of lithium transition metal composite oxide particles due to increase in press pressure and elution of transition metal.

In the positive electrode active material according to (1), the lithium transition metal composite oxide is composed of primary particles, and the primary lithium transition metal composite oxide having a primary particle diameter of 0.1 to 5 μm and primary particles And a secondary lithium transition metal composite oxide having a primary particle diameter of 0.1 to 5 μm. The first lithium transition metal composite oxide is smaller than the second lithium transition metal composite oxide.
By setting it as such a structure, even if it raises a press pressure and improves an electrode plate density, generation | occurrence | production of a fine powder can be prevented and dry out can be prevented. Thereby, while improving an electrode plate density, dryout can be prevented. Moreover, since generation | occurrence | production of the fine powder of lithium transition metal complex oxide particle can be prevented, a high temperature characteristic is also improved.

  In the positive electrode active material according to (2), the secondary particles of the second lithium transition metal composite oxide have a median diameter of 10 to 40 μm. The plate density can be improved. Therefore, the charge / discharge capacity per unit volume is further improved.

In the positive electrode active material according to (3), the lithium transition metal composite oxide has a first lithium transition metal composite oxide having a particle size of 0.1 to 10 μm and a particle size in a volume-based particle size distribution curve. The integrated value of the relative particle amount of the first lithium transition metal composite oxide is 5 to 35%. The second lithium transition metal composite oxide is composed of secondary particles.
By setting it as such a structure, even if it raises a press pressure and improves an electrode plate density, generation | occurrence | production of a fine powder can be prevented and dry out can be prevented. Thereby, while improving an electrode plate density, dryout can be prevented. Moreover, since generation | occurrence | production of the fine powder of lithium transition metal complex oxide particle can be prevented, a high temperature characteristic is also improved.

  In the positive electrode active material according to (4), when the primary particle diameter of the first lithium transition metal composite oxide is 0.1 to 5 μm, the generation of fine powder can be suppressed, the high temperature characteristics are improved, and the dryness is improved. Out can also be suppressed.

  In the positive electrode active material according to (5), when the median diameter of the second lithium transition metal composite oxide is 10 to 40 μm, the secondary particles become an aggregate, and the electrode plate density is further improved. be able to. Therefore, the charge / discharge capacity per unit volume is further improved.

  In the positive electrode according to (6), when the positive electrode active material is the positive electrode active material according to any one of (1) to (5), the electrode plate density and the high temperature characteristics are improved, and the dryout is suppressed. A positive electrode can be obtained.

  The nonaqueous electrolyte secondary battery according to (7) includes 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 (5) as a positive electrode active material. A strip-shaped positive electrode configured by forming on at least one surface of a strip-shaped positive electrode current collector, a 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 were used as a negative electrode active material. A negative electrode active material layer 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. A spiral wound body in which a strip separator is interposed between the strip-shaped positive electrode and the strip-shaped negative electrode is formed. By comprising in this way, the non-aqueous electrolyte secondary battery which can improve an electrode plate density and a high temperature characteristic and can prevent a dry-out can be obtained.

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

The positive electrode active material of the present invention includes at least a lithium transition metal composite oxide having a spinel structure (spinel-type crystal structure). The “spinel structure” is one of the typical crystal structure types found in double oxide AB ₂ O ₄ type compounds (A and B are metal elements).
FIG. 1 is a schematic diagram showing a crystal structure of a spinel-structure lithium transition metal composite oxide. In FIG. 1, lithium atom 1 occupies a tetrahedral site of 8a site, oxygen atom 2 occupies 32e site, and transition metal atom 3 (and possibly an excess of lithium atoms) occupies an octahedral site of 16d site. Occupy.

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

  In the present invention, the lithium transition metal composite oxide exists in the form of particles composed of both primary particles and secondary particles that are aggregates thereof. Here, the primary particles refer to particles grown reflecting the crystal form of the lithium transition metal composite oxide. The secondary particles are particles formed by aggregation or sintering of the primary particles.

  In the positive electrode active material of the present invention, the lithium transition metal composite oxide is composed of at least primary particles whose primary particle diameter is 0.1 to 5 μm, and the primary particles. It consists of secondary particles that are aggregates, and has a second lithium transition metal composite oxide having a primary particle diameter of 0.1 to 5 μm.

In the positive electrode active material of the present invention, the first lithium transition metal composite oxide is smaller than the second lithium transition metal composite oxide.
Here, “small” in the present invention means that the particle diameter or specific surface area diameter is small. The particle diameter includes a primary particle diameter and a secondary particle diameter. The particle diameter includes the median diameter. Preferably, the median diameter is small.

The method for measuring the specific surface area diameter is not particularly limited. For example, it can be measured using a Fischer sub-sieve sizer (FSSS) by the air permeation method. The median diameter means a particle diameter at which the volume cumulative frequency of the particle size distribution reaches 50%.
The method for measuring the median diameter is not particularly limited. For example, the particle size distribution is measured by a laser diffraction scattering method, and an integrated distribution using the logarithm of the volume-based particle diameter is obtained. % Particle size.
The measuring method of a primary particle diameter is not specifically limited. For example, it can be measured using an image analysis method (microscope method).

The primary particle diameter of the first lithium transition metal composite oxide is preferably 0.1 μm or more, more preferably 0.5 μm or more, and preferably 5 μm or less, and 3 μm or less. Is more preferable.
If the primary particle size is too large, the lithium ion diffusibility in the particles is lowered, so the potential is lowered and the cycle characteristics are deteriorated. When the primary particle size is too small, the filling property is lowered.
The primary particle diameter of the second lithium transition metal composite oxide is preferably 0.1 μm or more, more preferably 0.5 μm or more, and preferably 5 μm or less, and 3 μm or less. Is more preferable.
If the primary particle size is too large, the lithium ion diffusibility in the particles is lowered, so the potential is lowered and the cycle characteristics are deteriorated. When the primary particle size is too small, the filling property is lowered.

In the positive electrode active material of the present invention, the median diameter of the secondary particles of the second lithium transition metal composite oxide is preferably 10 to 40 μm.
The method for measuring the median diameter is not particularly limited. For example, the particle size distribution is measured by a laser diffraction scattering method, and an integrated distribution using the logarithm of the volume-based particle diameter is obtained. % Particle size.

The median diameter of the secondary particles of the second lithium transition metal composite oxide is more preferably 10 μm or more, further preferably 15 μm or more, more preferably 40 μm or less, and 35 μm or less. More preferably.
If the median diameter of the secondary particles is too large, the potential is lowered due to a decrease in lithium ion diffusibility, and the cycle characteristics are deteriorated. When the median diameter of lithium ions is too small, the filling property is lowered.

In the positive electrode active material of the present invention, the lithium transition metal composite oxide includes a first lithium transition metal composite oxide having a particle size of 0.1 to 10 μm and a particle size of 10 to 100 μm in a volume-based particle size distribution curve. And the integrated value of the relative particle amount of the first lithium transition metal composite oxide is 5 to 35%, and the second lithium transition metal composite oxide. The object consists of secondary particles.
Here, in the present invention, “particle size” refers to the particle size of the volume-based particle size distribution curve, and “relative particle amount” refers to the relative particle amount of the volume-based particle size distribution curve.
In the present invention, the first lithium transition metal composite oxide is a small particle, and the second lithium transition metal composite oxide is a large particle.

In the positive electrode active material of the present invention, the first lithium transition metal composite oxide preferably has a particle size of 10 μm or less. If the particle diameter of the first lithium transition metal composite oxide is too large, the space between the large particles cannot be filled with the small particles, so the electrode plate density is not improved.
In the positive electrode active material of the present invention, the particle diameter of the second lithium transition metal composite oxide is preferably 70 μm or less. When the particle diameter of the second lithium transition metal composite oxide is too large, the potential is lowered due to the decrease in lithium ion diffusibility, and the cycle characteristics are deteriorated.

In the positive electrode active material of the present invention, the integrated value of the relative particle amount of the first lithium transition metal composite oxide is preferably 20% or more, and preferably 30% or less.
When the integrated value of the relative particle amount of the first lithium transition metal composite oxide is too large, the ratio of small particles is large, the specific surface area is increased, and manganese elution is increased, so that the cycle characteristics are deteriorated. When the integrated value of the relative particle amount of the first lithium transition metal composite oxide is too small, the ratio of large particles is large and the filling property is lowered.

In the positive electrode active material of the present invention, the primary particle diameter of the first lithium transition metal composite oxide is preferably 0.1 μm or more, more preferably 0.5 μm or more, and 5 μm or less. Is preferable, and it is more preferable that it is 3 micrometers or less.
If the primary particle size is too large, the lithium ion diffusibility in the particles is lowered, so the potential is lowered and the cycle characteristics are deteriorated. When the primary particle size is too small, the filling property is lowered.
The primary particle diameter of the second lithium transition metal composite oxide is preferably 0.1 μm or more, more preferably 0.5 μm or more, and preferably 5 μm or less, and 3 μm or less. Is more preferable.
If the primary particle size is too large, the lithium ion diffusibility in the particles is lowered, so the potential is lowered and the cycle characteristics are deteriorated. When the primary particle size is too small, the filling property is lowered.

In the positive electrode active material of the present invention, the median diameter of the second lithium transition metal composite oxide is preferably 10 to 40 μm.
The median diameter of the large particles is more preferably 10 μm or more, more preferably 15 μm or more, further preferably 40 μm or less, and more preferably 35 μm or less.
The method for measuring the median diameter is not particularly limited. For example, the particle size distribution is measured by a laser diffraction scattering method, and an integrated distribution using the logarithm of the volume-based particle diameter is obtained. % Particle size.

  In the positive electrode active material of the present invention, the transition metal is preferably manganese. When the transition metal is manganese, the nonaqueous electrolyte secondary battery using the positive electrode active material of the present invention has excellent cycle characteristics, high temperature cycle characteristics, and load characteristics. It can be particularly preferably used. Moreover, since it becomes the thing excellent also in the output characteristic, it can use especially suitably also for the use of an electric vehicle.

The positive electrode active material of the present invention is preferably a lithium manganese composite oxide, and when the composition ratio of Li, Mn and O of the lithium manganese composite oxide is represented by the general formula Li _{1 + a} Mn _2−a O _{4 + d} , It is preferable that a represents a number satisfying −0.2 ≦ a ≦ 0.2, and d represents a number satisfying −0.5 ≦ d ≦ 0.5.
a is preferably larger than 0, and is preferably 0.15 or less. It is considered that the cycle characteristics are further improved by substituting a part of manganese with lithium.

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

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

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

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

  (Ii) 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.

(Iii) a lithium transition metal composite oxide is represented by the general formula _{Li 1 + a M b Mn 2} -a-b B c O 4 + d (M represents aluminum and / or magnesium, a is -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 (iii) is excellent in cycle characteristics, load characteristics, storage characteristics and charge / discharge capacity, and has less battery swelling.
In embodiment (iii), 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 (iii), b is preferably larger than 0, and 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 (iii), 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.

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

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

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

In embodiment (v), h is preferably greater than 0. For the same reason as in the case of the embodiment (iv).
Further, h is more preferably 0.001 or more, further preferably 0.005 or more, more preferably 0.05 or less, and further preferably 0.03 or less. In this range, it is considered that the impedance is reduced by increasing the mobility of lithium ions. If h is too large, the battery characteristics hardly change, which is not preferable.
About another point, it is the same as that of the case of aspect (iv).

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

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

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

In the embodiment (vii), the lithium-transition metal composite _oxide, and cubic spinel-type lithium manganese complex oxide represented by _{Li 1 + a M c Mn 2} -a-c O 4, Li b X d B e O f It is preferable to be comprised with the impurity phase which consists of 1 or more types of compounds represented by these.
In the embodiment (vii), a is preferably 0.02 or more and preferably 0.08 or less. For the same reason as in the case of (iii).
In embodiment (vii), X is preferably fluorine and / or chlorine. d is preferably 0.01 or more, and preferably 0.03 or less. For the same reason as in the case of the embodiment (vi).
In embodiment (vii), e is preferably 0.001 or more, and preferably 0.01 or less. For the same reason as in the case of (iii).

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

In the embodiment (viii), 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 0.3% 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 of electron movement. 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 (vii), the reason for containing elements other than sulfur is the same as in aspects (i) to (vi).
In the embodiment (vii), a positive electrode plate having a high charge / discharge capacity and excellent in binding property and surface smoothness can be obtained due to the synergistic effect of each element by containing each element. .

The lithium transition metal composite oxide may have a sulfate group at least on the surface of the particle.
The presence of the sulfate radical on the surface of the lithium transition metal composite oxide particle makes the electron transfer resistance around the particle extremely small, and as a result, the ease of passing electrons is improved, and the cycle characteristics and load characteristics are improved. It is thought to improve.
In addition, when the positive electrode active material of the present invention is used to form a high voltage battery (for example, a battery using LiMn _1.5 Ni _0.5 O ₄ as a lithium transition metal composite oxide), there is a problem in the conventional high voltage battery. The decomposition of the electrolyte during charging was suppressed, and as a result, the cycle characteristics were improved. The decomposition reaction of the electrolytic solution is thought to occur as a catalyst at the interface between the lithium transition metal composite oxide particles and the electrolytic solution, but the sulfate radical has no function of decomposing the electrolytic solution. Thus, it is considered that the entire surface or part of the surface of the lithium transition metal composite oxide particles reduces the contact area between the electrolytic solution and the catalyst and suppresses the reaction.

  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, the cycle characteristics, load characteristics and thermal stability 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 X-ray diffraction and XPS (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.

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

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

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

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

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

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

  (Xii) The lithium transition metal composite oxide is a particle, and the concentration of boron present on the surface of the particle is greater than the concentration of boron present inside the particle, and the concentration of magnesium present on the surface of the particle is The concentration of magnesium present in the interior of the particle is greater than the concentration of titanium present in the interior of the particle, and the concentration of magnesium present in the interior of the particle is greater than the concentration of boron present in the interior of the particle. An embodiment that is greater than the concentration of boron present.

The concentration of boron present on the surface of lithium transition metal composite oxide particles (hereinafter also simply referred to as “particles”) is greater than the concentration of boron present inside the particles, so that the primary particles of the particles can be effectively obtained. Diameter can be grown. Thereby, the packing property of particle | grains can be improved and an electrode plate density can be improved. Therefore, the charge / discharge capacity per unit volume of the battery is improved.
The concentration of magnesium present on the surface of the particles is greater than the concentration of magnesium present inside the particles, limiting the decrease in charge / discharge capacity to a practical level, and elution of transition metal ions into the electrolyte. It is thought that it can be suppressed. Thereby, the high temperature cycle characteristics are improved.
Since the concentration of titanium existing inside the particles is larger than the concentration of boron existing inside the particles, the lattice constant of the lithium transition metal composite oxide can be increased without impairing the growth of the primary particle diameter. . Thereby, load characteristics and cycle characteristics are improved.
Suppressing elution of transition metal ions into the electrolyte without impairing the growth of the primary particle size because the concentration of magnesium present inside the particles is greater than the concentration of boron present inside the particles. Can do. Thereby, the improvement of an electrode plate density and the improvement of a high temperature cycling characteristic can be aimed at.

  (Xiii) The aspect in which the lithium transition metal composite oxide is a lithium transition metal composite oxide having particles, boron at least on the surface of the particles, and magnesium and titanium.

By having boron on the surface of the particles, the primary particle diameter can be effectively grown.
In addition, by containing magnesium and titanium, it is possible to suppress the elution of transition metal ions into the electrolyte without impairing the growth of the primary particle diameter, and to increase the lattice constant of the lithium transition metal composite oxide. Can do.
Thereby, an electrode plate density can be improved and a high temperature cycling characteristic, a load characteristic, and cycling characteristics can be improved.

  (Xiv) The lithium transition metal composite oxide is a particle, and the concentration of zirconium and / or cerium present on the surface of the particle is greater than the concentration of zirconium and / or cerium present inside the particle, An embodiment in which the concentration of magnesium present on the surface is greater than the concentration of magnesium present within the particles and the concentration of zirconium and / or cerium present within the particles is less than the concentration of magnesium present within the particles.

In the embodiment (xiv), zirconium and / or cerium are considered to have a catalytic action on the lithium insertion / elimination reaction. This catalytic action occurs even when zirconium and / or cerium is uniformly present in the lithium transition metal composite oxide, but the effect is particularly great when zirconium and / or cerium is present on the surface. Therefore, when the concentration of zirconium and / or cerium existing on the surface of the lithium transition metal composite oxide is larger than the concentration of zirconium and / or cerium existing inside the lithium transition metal composite oxide, the catalytic action is achieved. And cycle characteristics and load characteristics are improved.
Moreover, since the concentration of magnesium present on the surface of the lithium transition metal composite oxide is larger than the concentration of magnesium present inside the lithium transition metal composite oxide, the decrease in charge / discharge capacity is suppressed to a practical level range, It is considered that the elution of transition metal ions into the electrolyte can be suppressed. Thereby, the high-temperature cycle characteristics are improved without impairing the improvement of the cycle characteristics and the load characteristics.
Decreasing the crystallinity of the lithium transition metal composite oxide when the concentration of zirconium and / or cerium present in the lithium transition metal composite oxide is smaller than the concentration of magnesium present in the lithium transition metal composite oxide It is thought that can be effectively suppressed. Thereby, the high temperature characteristics are improved without impairing the improvement of the cycle characteristics and the load characteristics.

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

  The production method of the positive electrode active material of the present invention is not particularly limited, and can be produced, for example, 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 powdery compounds as they are to obtain a raw material mixture; mixing in a slurry form using water and / or an organic solvent, and then drying to obtain a raw material mixture Method: A method in which an aqueous solution of the above-mentioned compound is mixed and precipitated, and the resulting precipitate is dried to obtain a raw material mixture; a method in which these are used in combination.

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

The manganese compound is not particularly limited. For example, manganese metal, oxide (eg, MnO ₂ , Mn ₂ O ₃ , Mn ₃ O ₄ ), hydroxide, nitrate, carbonate (MnCO ₃ ), chloride salt, Examples thereof include manganese iodide, manganese sulfate, and manganese nitrate. Among these, manganese metal, MnCO ₃ , MnSO ₄ , and MnCl ₂ are preferable.
In the present invention, the manganese compound comprises a first manganese compound having a particle size of 0.1 to 10 μm and a second manganese compound having a particle size of 10 to 100 μm in a volume-based particle size distribution curve. The integrated value of the relative particle amount of one manganese compound is 5 to 35%, and the second manganese compound is composed of secondary particles. In order to obtain such a manganese compound, a rough mortar, a ball mill, a vibration mill, a jet mill or the like can be used. Various classifiers can also be used.

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

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

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

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

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

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

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

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

Calcium compound is not particularly limited, for _{example, CaO, CaCO 3, Ca (} OH) 2, CaCl 2, CaSO 4, Ca (NO 3) 2, Ca (CH 3 COO) 2 and the like.
Moreover, you may use the compound containing 2 or more types of each element mentioned above.

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

  Next, the aqueous solution is filtered to collect a precipitate. The collected precipitate is washed with water and heat-treated, and then mixed with the above-described lithium compound and boron 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, and more preferably 700 ° C. or higher. If the firing temperature is too low, unreacted raw materials may remain in the positive electrode active material, and the original characteristics of the positive electrode active material may not be utilized. The firing temperature is preferably 1100 ° C. or lower, and more preferably 950 ° C. or lower. If the firing temperature is too high, the particle size of the positive electrode active material may become too large, and the battery characteristics may deteriorate. Further, by-products such as Li ₂ MnO ₃ and LiMnO ₂ are likely to be generated, which may lead to a decrease in discharge capacity per unit weight, a decrease in cycle characteristics, and a decrease in operating voltage.
In general, the firing time is preferably 1 to 24 hours, and more preferably 6 to 12 hours. When the firing time is too short, the diffusion reaction between the raw material particles does not proceed. If the firing time is too long, firing after the diffusion reaction is almost completed is wasted, and coarse particles may be formed by sintering.

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

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

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

  The positive electrode active material of the present invention can be obtained by the manufacturing method described above. The positive electrode active material of this invention is used suitably for the positive electrode of this invention mentioned later.

Next, the positive electrode of the present invention will be described.
The positive electrode of the present invention includes at least a positive electrode active material having a lithium transition metal composite oxide having a spinel structure, a conductive agent, and a binder.
The positive electrode active material used for the positive electrode of the present invention is the positive electrode active material of the present invention described above.

In the positive electrode 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 of the present invention, the binder is not particularly limited, and examples thereof include polyvinylidene fluoride, polytetrafluoroethylene, and polyamide acrylic resin.

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

(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.

(3) Preparation of positive electrode The obtained positive electrode mixture is apply | coated to the aluminum foil which is a collector. This is dried and then press-rolled to produce a positive electrode.

The positive electrode active material and the positive electrode of the present invention are suitably used for non-aqueous 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, 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 electrolyte solution 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.

  As the positive electrode active material, lithium cobaltate and / or lithium nickelate can be used together with the positive electrode active material of the present invention. As a result, a nonaqueous electrolyte secondary battery having a high charge / discharge capacity and excellent cycle characteristics, load characteristics and output characteristics can be obtained.

Lithium cobaltate represented by the general formula Li _{1 + x} CoO ₂ (x represents a number satisfying −0.5 ≦ x ≦ 0.5) is preferable. The lithium cobaltate is at least a part selected from the group consisting of magnesium, aluminum, calcium, vanadium, titanium, chromium, manganese, iron, cobalt, nickel, copper, zinc, strontium, zirconium, niobium, molybdenum and tin. It may be substituted with one kind.

Lithium nickelate represented by the general formula Li _{1 + x} NiO ₂ (x represents a number satisfying −0.5 ≦ x ≦ 0.5) is preferable. The lithium nickelate is at least a part selected from the group consisting of magnesium, aluminum, calcium, vanadium, titanium, chromium, manganese, iron, cobalt, nickel, copper, zinc, strontium, zirconium, niobium, molybdenum and tin. It may be substituted with one kind.

  The lithium cobaltate and / or lithium nickelate 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. The following (i)-(iii) are mentioned as a suitable aspect of this lithium transition metal complex oxide.

(I) the lithium transition metal composite oxide has a general formula Li _v Co _1-x M ¹ _w M ² _x O _y S _z (M ¹ represents Al or Ti, M ² represents Mg and / or Ba, v represents a number satisfying 0.95 ≦ v ≦ 1.05, w satisfies 0 <w ≦ 0.10 when 0 or M ¹ is Al, and 0 <w ≦ 0 when M ¹ is Ti. .05 represents a number satisfying 0 <x ≦ 0.10, y represents a number satisfying 1 ≦ y ≦ 2.5, and z satisfying 0 <z ≦ 0.015 The aspect represented by this.

  By combining the positive electrode active material having this lithium transition metal composite oxide and the positive electrode active material of the present invention, a battery having not only excellent high-temperature cycle characteristics, load characteristics and cycle characteristics but also high capacity and safety can be obtained. Obtainable.

(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) 1 represents at least one selected from halogen elements, a represents a number satisfying 0.95 ≦ a ≦ 1.05, b represents a number satisfying 0 <b ≦ 0.10, c represents a number satisfying 1 ≦ c ≦ 2.5, d represents a number satisfying 0 <d ≦ 0.1, and e represents a number satisfying 0 <e ≦ 0.015). Aspect.

  By combining the positive electrode active material having this lithium transition metal composite oxide and the positive electrode active material of the present invention, a battery having not only excellent high-temperature cycle characteristics, load characteristics and cycle characteristics but also high capacity and safety can be obtained. Obtainable.

  (Iii) The lithium transition metal composite oxide is at least one selected from the group consisting of lithium cobaltate, lithium nickel cobaltate, nickel cobalt lithium aluminate, and nickel cobalt lithium manganate, and is a particle. A mode in which the abundance ratio of zirconium on the surface is 20% or more.

  By combining the positive electrode active material having this lithium transition metal composite oxide and the positive electrode active material of the present invention, not only is it excellent in high temperature cycle characteristics, load characteristics and cycle characteristics, but also low temperature characteristics, high capacity and safety are excellent. A battery can be obtained.

In this positive electrode active material, the proportion of zirconium present on the surface of the particles is 20% or more. Details will be described below.
In the present invention, the “ratio of zirconium present on the surface of the lithium transition metal composite oxide particles” is determined as follows.
First, the presence state of zirconium 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 of view, select the part with the largest amount of zirconium per unit area (the part where the zirconium 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 line analysis, the quotient obtained by dividing the total length of the portions where the peak is 4% or more when the peak value in the portion having the largest amount of zirconium per unit area is 100% by the length of the line segment. Is the “ratio of zirconium present on the surface of the lithium transition metal composite oxide particles”. In addition, it is preferable to use the average value of “the zirconium abundance ratio on the surface of the lithium transition metal composite oxide particles” by performing the line analysis a plurality of times (for example, 10 times).
In the above method, the portion where the peak of zirconium is less than 4% has a large difference from the portion where the amount of zirconium is the largest, and therefore is regarded as a portion where zirconium does not exist.

  According to the above-mentioned “ratio of zirconium present on the surface of the lithium transition metal composite oxide particles”, it indicates whether zirconium is present uniformly or unevenly on the surface of the lithium transition metal composite oxide particles. be able to.

A preferred method for producing a positive electrode using the positive electrode mixture of the present invention will be described below.
The positive electrode material mixture of the present invention is made into a slurry or a kneaded product, applied to or supported on a current collector such as an aluminum foil, and press-rolled to form a positive electrode active material layer on the current collector.
FIG. 2 is a schematic cross-sectional view of the positive electrode. As shown in FIG. 2, the positive electrode 13 is obtained 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 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. 3 is a schematic cross-sectional view of a cylindrical battery. As shown in FIG. 3, 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. 4 is a schematic partial cross-sectional view of a coin-type battery. As shown in FIG. 4, 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. 5 is a schematic perspective view of a prismatic battery. As shown in FIG. 5, 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 nonaqueous electrolyte secondary battery according to the present invention, and a general formula of Li _{1 + x} CoO ₂ (x satisfies −0.5 ≦ x ≦ 0.5) Lithium cobaltate represented by lithium cobaltate and / or general formula Li _{1 + x} NiO ₂ (x represents a number satisfying −0.5 ≦ x ≦ 0.5). When the weight of the lithium transition metal composite oxide is A and the weight of the lithium cobaltate and / or the lithium nickelate is B, the range is 0.2 ≦ B / (A + B) ≦ 0.8. A positive electrode active material for a non-aqueous electrolyte secondary battery to be mixed.
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 non-aqueous electrolyte secondary battery has a high electrode plate density and is excellent not only in cycle characteristics and high-temperature cycle characteristics but also in load characteristics and output characteristics.
The positive electrode active material is preferably mixed so that 0.4 ≦ B / (A + B) ≦ 0.6. If it is in the range of 0.4 ≦ B / (A + B) ≦ 0.6, not only the electrode plate density, the prevention of dryout and the improvement of overcharge characteristics, but also the improvement of cycle charge / discharge characteristics, load characteristics and output characteristics can be achieved. Because it is remarkable.
As a compound capable of occluding and releasing lithium ions, a general formula consisting of a spinel structure containing an alkali metal and / or an alkaline earth metal is Li _a Ti _b O _{4 + c} (a is a number satisfying 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.) For non-aqueous electrolyte secondary batteries A negative electrode active material can be used. At this time, a non-aqueous electrolyte secondary battery with greatly improved cycle characteristics can be obtained.

The use of the nonaqueous electrolyte secondary battery using the positive electrode active material and the positive electrode mixture 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]
Manganese and magnesium carbonates were washed with water, dried, and then mixed with orthoboric acid, lithium fluoride and lithium carbonate. The manganese compound is composed of a first manganese compound having a particle top peak of 6 μm and a manganese compound having a particle diameter of 10 to 100 μm in a volume-based particle size distribution curve. The peak top of the particle diameter is composed of a second manganese compound with 19 μm, the integrated value of the relative amount of the first manganese compound is 10%, and the second manganese compound is composed of secondary particles Was used. The resulting mixture was calcined at about 800 ° C. for about 10 hours. The positive electrode active material was obtained by pulverization.
The primary particle diameter of the first lithium transition metal composite oxide of the obtained positive electrode active material was 2 μm. The primary particle diameter of the second lithium transition metal composite oxide was 1 μm.
The composition ratio of the obtained positive electrode active material was 1.03 for Li, 1.89 for Mn, 0.05 for Mg, 0.005 for B, and 0.015 for F.

[Example 2]
Manganese and magnesium carbonates were washed with water, dried, and then mixed with orthoboric acid, lithium fluoride and lithium carbonate. The manganese compound is composed of a first manganese compound having a particle top peak of 6 μm and a manganese compound having a particle diameter of 10 to 100 μm in a volume-based particle size distribution curve. The peak top of the particle diameter is composed of a second manganese compound having a particle size of 28 μm, the integrated value of the relative amount of the first manganese compound is 28%, and the second manganese compound is composed of secondary particles. Was used. The resulting mixture was calcined at about 800 ° C. for about 10 hours. The positive electrode active material was obtained by pulverization.
The primary particle diameter of the first lithium transition metal composite oxide of the obtained positive electrode active material was 2 μm. The primary particle diameter of the second lithium transition metal composite oxide was 1 μm.
The composition ratio of the obtained positive electrode active material was 1.03 for Li, 1.89 for Mn, 0.05 for Mg, 0.005 for B, and 0.015 for F.

[Comparative Example 1]
Manganese and magnesium carbonates were washed with water, dried, and then mixed with orthoboric acid and lithium carbonate. The manganese compound used was composed of a manganese compound having a particle diameter peak top of 18 μm and a secondary particle of a manganese compound having a particle diameter of 10 to 100 μm in a volume-based particle size distribution curve. The resulting mixture was calcined at about 800 ° C. for about 10 hours. The positive electrode active material was obtained by pulverization.
The primary particle diameter of the lithium transition metal composite oxide of the obtained positive electrode active material was 1 μm.
The composition ratio of the obtained positive electrode active material was 1.03 for Li, 1.89 for Mn, 0.05 for Mg, and 0.005 for B.

[Comparative Example 2]
Manganese and magnesium carbonates were washed with water, dried, and then mixed with orthoboric acid and lithium carbonate. The manganese compound was composed of a manganese compound having a particle diameter peak top of 32 μm and a secondary particle in a volume-based particle size distribution curve having a particle diameter of 10 to 100 μm. The resulting mixture was calcined at about 800 ° C. for about 10 hours. The positive electrode active material was obtained by pulverization.
The primary particle diameter of the lithium transition metal composite oxide of the obtained positive electrode active material was 1 μm.
The composition ratio of the obtained positive electrode active material was 1.03 for Li, 1.89 for Mn, 0.05 for Mg, and 0.005 for B.

[Comparative Example 3]
Manganese and magnesium carbonates were washed with water, dried, and then mixed with orthoboric acid and lithium carbonate. The manganese compound is composed of a first manganese compound having a peak size of 9 μm and a manganese compound having a particle size of 10 to 100 μm in a volume-based particle size distribution curve. The peak top of the particle diameter is composed of a second manganese compound having a particle size of 15 μm, the integrated value of the relative particle amount of the first manganese compound is 58%, and the second manganese compound is composed of secondary particles. Was used. The resulting mixture was calcined at about 800 ° C. for about 10 hours. The positive electrode active material was obtained by pulverization.
The primary particle diameter of the first lithium transition metal composite oxide of the obtained positive electrode active material was 3 μm. The primary particle diameter of the second lithium transition metal composite oxide was 3 μm.
The composition ratio of the obtained positive electrode active material was 1.03 for Li, 1.89 for Mn, 0.05 for Mg, and 0.005 for B.

Properties of positive electrode active material (1) The ratio of the particle size of the volume-based particle size distribution curve to 15 μm or less The particle size distribution of the obtained positive electrode active material was measured by a laser diffraction scattering method. An integrated distribution using the logarithm of the volume-based particle diameter was obtained, and the proportion of the lithium transition metal composite oxide having a particle diameter of 15 μm or less was measured.

(2) Median diameter The particle size distribution of the obtained positive electrode active material was measured by a laser diffraction scattering method. An integrated distribution using the logarithm of the volume-based particle diameter was obtained, and the particle diameter when occupying 50% of the entire lithium transition metal composite oxide powder, that is, the particle diameter of 50% oversize was measured.

(3) Electrode plate density 3 g of the obtained positive electrode active material was put into a cylindrical mold having a diameter of 20 mm and pressed twice at 160 MPa for 30 seconds. The thickness of the molded pellet was measured. The press density was calculated from the thickness of the pellet after pressing and the weight of the positive electrode active material. It can be said that the higher the press density, the higher the electrode plate density.

3. Evaluation of Positive Electrode Active Material A cylindrical battery was produced using each positive electrode active material obtained above and evaluated as follows.

The cylindrical 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 of polyvinylidene fluoride). The obtained paste was applied to a positive electrode current collector and dried to obtain a positive electrode plate. Further, a carbon material was used as the negative electrode active material, and was applied to the 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 propylene film was used as the separator. As the electrolyte, a solution in which LiPF6 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. A positive electrode plate, a negative electrode plate, and a separator are formed into a thin sheet, wound and accommodated in a metal cylindrical battery case, and an electrolyte is injected into the battery case to form a cylindrical battery of a lithium ion secondary battery. Obtained.

(1) High-temperature discharge capacity retention rate At 60 ° C., charge / discharge was repeated under the conditions of a charge potential of 4.2 V, a discharge potential of 2.75 V, and a discharge load of 2 C, and the discharge capacity after 100 cycles was measured. The obtained discharge capacity value after 100 cycles was divided by the discharge capacity value after 1 cycle to determine the high-temperature discharge capacity retention rate, and the cycle characteristics were evaluated.

The results are shown in Table 1.
As is apparent from Table 1, it can be seen that the positive electrode active material of the present invention can achieve both improvement in electrode plate density and improvement in high-temperature cycle characteristics.

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

FIG. 1 is a schematic diagram showing a crystal structure of a spinel-structure lithium transition metal composite oxide. FIG. 2 is a schematic cross-sectional view of the positive electrode. FIG. 3 is a schematic cross-sectional view of a cylindrical battery. FIG. 4 is a schematic partial cross-sectional view of a coin-type battery. FIG. 5 is a schematic perspective sectional view of a prismatic battery.

Explanation of symbols

1 8a site 2 32e site 3 16d site 4 binder 5 positive electrode active material 11 negative electrode 12 current collector 13 positive electrode 14 separator 20 cylindrical battery 30 coin-type battery 40 square battery

Claims (3)

A positive electrode active material for a non-aqueous electrolyte secondary battery having at least a spinel-structured lithium manganese composite oxide,
The lithium manganese composite oxide is
A lithium compound;
In the volume-based particle size distribution curve, the first manganese compound having a particle size of 0.1 to 10 μm and the second manganese compound having a particle size of 10 to 100 μm, and relative to the first manganese compound A manganese compound in which the integrated value of the particle amount is 5 to 35% and the second manganese compound is composed of secondary particles;
Obtained by mixing and firing raw materials containing
In the volume-based particle size distribution curve, the first lithium manganese composite oxide having a particle size of 0.1 to 10 μm and the second lithium manganese composite oxide having a particle size of 10 to 100 μm, the first The integrated value of the relative particle amount of the lithium manganese composite oxide is 5 to 35%, and the second lithium transition metal composite oxide is composed of secondary particles. The positive electrode active for a non-aqueous electrolyte secondary battery material. A positive electrode for a non-aqueous electrolyte secondary battery having at least a positive electrode active material having a lithium transition metal composite oxide having a spinel structure, a conductive agent, and a binder,
The positive electrode for a nonaqueous electrolyte secondary battery, wherein the positive electrode active material is the positive electrode active material for a nonaqueous electrolyte secondary battery according to claim 1. A band-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 as a positive electrode active material on at least one surface of a band-shaped positive electrode current collector;
Constructed by forming a negative electrode active material layer using a metallic lithium, lithium alloy, 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 on at least one surface of a strip-shaped negative electrode current collector A strip-shaped negative electrode,
A strip separator,
A spiral type winding in which the belt-like positive electrode and the belt-like negative electrode are wound a plurality of times in a state of being laminated via the belt-like separator, and the belt-like separator is interposed between the belt-like positive electrode and the belt-like negative electrode A non-aqueous electrolyte secondary battery comprising a body.

Images