JP2005222956A - Nonaqueous electrolytic solution secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolytic solution secondary battery in which a positive electrode active material having at least a lithium transition metal complex oxide of spinel structure is used, and in which battery characteristics are superior especially in cycle characteristics, load characteristics, storage characteristics or the like, and swelling of the battery is little. <P>SOLUTION: This is the nonaqueous electrolytic solution secondary battery in which the positive electrode active material having at least the lithium transition metal complex oxide of spinel structure is used for the battery, and the lithium transition metal complex oxide exists in the form of a primary particle and a second particle which is the aggregate of the primary particle, and when two-dimensional coordinates are given to the respective particles in which cubic roots of light emission voltages caused by the transition metal and lithium are taken as coordinate components and they are expressed as points on a coordinate plane, and when a primary regression straight line passing through the origin is calculated, the absolute error deviation at the respective point against the primary regression straight line is 0.25 or less. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery. Specifically, the present invention relates to a non-aqueous electrolyte secondary battery having a spinel-structure lithium transition metal composite oxide that has excellent cycle charge / discharge characteristics (cycle characteristics), storage characteristics, load characteristics, and the like.

  Nonaqueous electrolyte secondary batteries such as lithium ion secondary batteries are widely used as power sources for mobile electronic devices typified by mobile phones and notebook computers. Recently, application to a large-capacity power source such as an electric vehicle battery is expected.

At present, mobile electronic devices such as mobile phones are provided with various functions, and accordingly, non-aqueous electrolyte secondary batteries serving as power sources are required to further improve load characteristics.
Moreover, when using a nonaqueous electrolyte secondary battery for an electric vehicle, the battery life of 5 years or more is requested | required and it is necessary to improve cycling characteristics. Furthermore, in that case, it is necessary to discharge a large current, and further improvement in load characteristics is required.

Non-aqueous 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. Examples of the positive electrode active material of the non-aqueous electrolyte secondary battery include lithium transition metal composite oxides typified by LiMn ₂ O ₄ , LiCoO ₂ and LiNiO ₂ .

Among these, LiMn ₂ O ₄ has a problem that gas is generated during charging and discharging and the battery swells. In addition, there has been a problem that cycle characteristics at a practical level cannot be obtained. Since these problems appear particularly remarkably at high temperatures, for example, applications such as mobile devices expected to be used at high temperatures could not be put to practical use.

One of the causes of the above problem is that manganese ions are eluted from the crystal structure of LiMn ₂ O ₄ into the electrolytic solution with charge and discharge. This will be specifically described below.
Manganese ions eluted in the electrolytic solution are deposited on the negative electrode surface, hindering insertion and desorption of lithium ions from the negative electrode material, leading to an increase in internal resistance. As a result, repeated charge / discharge causes a decrease in discharge capacity.
Further, elution of manganese ions from the LiMn ₂ O ₄ crystal constituting the positive electrode into the electrolytic solution is accompanied by alteration and deterioration of the positive electrode and the electrolytic solution. Such alteration and deterioration of each material constituting the battery causes a decrease in cycle characteristics.
Furthermore, there is a theory that manganese ions eluted in the electrolyte promote the decomposition reaction of the ester compound in the electrolyte. By the decomposition of the ester compound, gas such as CO ₂ is generated and the battery is swollen.
And it is known that this elution of manganese ions occurs not only when charging / discharging is performed, but also when it is left alone.

If the present inventor can suppress elution of manganese ions in a positive electrode active material using LiMn ₂ O ₄ , the discharge capacity can be improved, cycle characteristics can be improved, and battery swelling can be prevented. Thought.
Moreover, as a positive electrode active material, the thing which is excellent in a storage characteristic in which elution of manganese ion does not occur during the preservation | save of a nonaqueous electrolyte secondary battery is preferable.
Furthermore, the above is true not only for LiMn ₂ O ₄ using manganese as a transition metal, but also for spinel-structure lithium transition metal composite oxides using other transition metals (for example, titanium). It is.
Accordingly, an object of the present invention is a non-aqueous electrolyte secondary battery using a positive electrode active material having at least a lithium transition metal composite oxide having a spinel structure, and battery characteristics, in particular, cycle characteristics, load characteristics, storage characteristics And a non-aqueous electrolyte secondary battery with less swelling of the battery.

That is, the present invention provides the following (1) to (9).
(1) A non-aqueous electrolyte secondary battery using a positive electrode active material having at least a spinel-structure lithium transition metal composite oxide,
The lithium transition metal composite oxide exists in the form of particles composed of one or both of primary particles and secondary particles that are aggregates thereof,
Each particle is given a two-dimensional coordinate whose coordinate component is the cube root of the light emission voltage value caused by the transition metal and lithium in each particle, expressed as a point on the coordinate plane, and linear regression through the origin When finding a straight line
A nonaqueous electrolyte secondary battery in which an absolute deviation of an error at each point with respect to the primary regression line is 0.25 or less.

  In other words, it is a non-aqueous electrolyte secondary battery using a positive electrode active material having at least a spinel structure lithium transition metal composite oxide, wherein the lithium transition metal composite oxide is composed of lithium transition metal composite oxide particles. Lithium transition with respect to an approximate straight line when X and Y are linearly returned to a straight line passing through the origin, where the cube root of the light emission voltage caused by the transition metal is the X value and the cube root of the light emission voltage caused by the lithium is the Y value. This is a non-aqueous electrolyte secondary battery in which the absolute deviation of the error of the metal composite oxide particle group is 0.25 or less.

As a result of earnest research to achieve the above object, the present inventor has suppressed the elution of transition metal ions by reducing the variation in the composition ratio of particles of the lithium transition metal composite oxide having a spinel structure. As a result, it was found that cycle characteristics and storage characteristics were improved, and that battery swelling was suppressed.
The inventor further provides that the composition ratio variation among the particles of the lithium transition metal composite oxide is such that each particle has a coordinate component representing the third root of the light emission voltage value caused by the transition metal and lithium in each particle. And expressed as a point on the coordinate plane, and when a primary regression line passing through the origin is obtained, it can be expressed by an absolute deviation of the error of each point with respect to the primary regression line; and It has been found that when the absolute deviation of the error is 0.25 or less, elution of transition metal ions is suppressed to such an extent that the cycle characteristics, storage characteristics, and battery swelling become practical.
The inventor has completed the non-aqueous electrolyte secondary battery (1) based on these findings.

Further, according to the knowledge of the present inventor, the insertion and desorption of lithium ions in the whole positive electrode are averaged by reducing the variation in the composition ratio of each particle and increasing the uniformity of the composition ratio at the particle level. Therefore, it is considered that current density unevenness does not occur and load characteristics are improved.
Furthermore, according to the inventor's knowledge, by suppressing the variation in the composition ratio of each particle and improving the uniformity of the composition ratio at the particle level, the discharge potential at the time of loading is increased, and the capacity retention ratio at the time of loading is increased. Therefore, the output characteristics are also expected to improve.

(2) In the particle size distribution of the particles, when the particle sizes at which the volume accumulation frequency reaches 10%, 50% and 90% are D10, D50 and D90, respectively,
0.1 ≦ (D10 / D50) <1,
1 <(D90 / D50) ≦ 3 and 5 μm ≦ D50 ≦ 40 μm
The nonaqueous electrolyte secondary battery according to (1), wherein all of the above are satisfied.

  The inventor not only reduces the variation in the composition ratio of each particle, but also impairs the improvement of cycle characteristics, storage characteristics, load characteristics and output characteristics by controlling the size variation of each particle. Without increasing the suppression of battery swelling, the electrode plate density when applying the positive electrode active material to the positive electrode plate can be improved, thereby improving the charge / discharge capacity per unit volume of the battery. In addition, by satisfying a specific relational expression regarding the volume cumulative frequency of the particle size distribution, it is possible to achieve both improvement in cycle characteristics, storage characteristics, load characteristics and output characteristics, and improvement in electrode plate density. Based on these findings, the non-aqueous electrolyte secondary battery of (2) was completed.

  (3) The nonaqueous electrolyte secondary battery according to (1) or (2), wherein the standard deviation of the particle diameter is 0.4 or less in the particle size distribution of the particles.

  The present inventor can also achieve both improvement in cycle characteristics, storage characteristics, load characteristics and output characteristics and improvement in electrode plate density by setting the standard deviation of the particle diameter to 0.4 or less. As a result, the non-aqueous electrolyte secondary battery of (3) was completed.

  (4) The nonaqueous electrolyte secondary battery according to any one of (1) to (3), wherein the transition metal is manganese.

  When the transition metal is manganese, the non-aqueous electrolyte secondary battery of the present invention is particularly excellent in cycle characteristics, storage characteristics, and load characteristics. Therefore, the transition metal is particularly preferably used for applications such as mobile phones and electric tools. Can do. 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.

  (5) The non-aqueous electrolyte secondary battery according to (4), wherein the lithium transition metal composite oxide is a lithium manganese composite oxide having aluminum and / or magnesium and boron.

The present inventor can stabilize the crystal structure by using a lithium manganese composite oxide in which a part of manganese of lithium manganate is replaced with aluminum and / or magnesium, and can preserve storage characteristics, load characteristics, and output. It has been found that the cycle characteristics can be further improved and the swelling of the battery can be further suppressed without impairing the characteristics.
Further, the present inventor has found that since boron acts as a flux and crystallinity increases, the addition of boron further improves the cycle characteristics without impairing the storage characteristics, load characteristics and output characteristics. .
Based on these findings, the present inventor completed the nonaqueous electrolyte secondary battery of (5) above.

(6) The lithium transition metal composite oxide has the general formula Li _{1 + a} M _b Mn _2−ab B _c O _{4 + d} (M represents aluminum and / or magnesium, and a represents −0.2 ≦ a ≦ 0.2 represents a number satisfying 0.2, b represents a number satisfying 0 ≦ b ≦ 0.2, c represents a number satisfying 0 ≦ c ≦ 0.02, and d represents −0.5 ≦ d ≦ 0. The non-aqueous electrolyte secondary battery according to (4), which is represented by the following formula:

Furthermore, the present inventors have found the following.
That is, to suppress elution of manganese ions, it is effective to increase the Li / Mn molar ratio. However, as the Li / Mn molar ratio is increased, the charge / discharge capacity decreases. Moreover, if the variation in the composition ratio among the particles of the lithium manganese composite oxide is large, elution of manganese ions from particles having a small Li / Mn molar ratio occurs even if the Li / Mn molar ratio of the average composition is increased.
In the non-aqueous electrolyte secondary battery of (1) above, elution of transition metal ions is suppressed by reducing the variation in the composition ratio of each particle, but this reduces the charge / discharge capacity. In addition, the Li / Mn molar ratio can be adjusted within a range in which elution of manganese ions can be effectively suppressed.
Based on these findings, the present inventor has determined the preferred range of the Li / Mn molar ratio and completed the nonaqueous electrolyte secondary battery of (6) above. Therefore, the non-aqueous electrolyte secondary battery of the above (6) is excellent in cycle characteristics, load characteristics, storage characteristics and charge / discharge capacity, and has less battery swelling.

  (7) The non-aqueous electrolyte secondary battery according to any one of (1) to (6), wherein the lithium transition metal composite oxide has a (400) crystallite diameter of 600 to 1200 angstroms.

  (400) When the crystallite diameter is 600 to 1200 angstroms, more excellent cycle characteristics can be realized without impairing storage characteristics, load characteristics and output characteristics.

(8) The nonaqueous electrolyte secondary battery according to any one of (1) to (7), wherein the specific surface area is 0.2 to 1.2 m ² / g.

When the specific surface area is 0.2 to 1.2 m ² / g, the expansion coefficient of the battery can be further suppressed without impairing cycle characteristics, storage characteristics, load characteristics, and output characteristics.

  (9) The non-aqueous solution according to any one of (1) to (8), wherein in the particle size distribution of the particles, the proportion of particles having a volume-based particle size of 50 μm or more is 10% by volume or less of all particles. Electrolyte secondary battery.

  In the particle size distribution of the particles, if the ratio of particles having a volume-based particle diameter of 50 μm or more is 10% by volume or less of the total particles, smoothness is maintained without impairing cycle characteristics, storage characteristics, load characteristics and output characteristics. A positive electrode-coated surface that is superior to the above can be obtained.

  As will be described below, the nonaqueous electrolyte secondary battery of the present invention is excellent in battery characteristics such as cycle characteristics, load characteristics, and storage characteristics. As a result, a non-aqueous electrolyte secondary battery having excellent battery characteristics that could not be achieved in the past can be put into practical use, and can be applied to various fields.

  Hereinafter, the nonaqueous electrolyte secondary battery of the present invention will be described with reference to embodiments, examples, and FIGS. However, the present invention is not limited to this embodiment, examples, and FIGS.

(Positive electrode active material)
The positive electrode active material used in the present invention has at least a lithium transition metal composite oxide having a spinel structure (spinel 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. 4 is a schematic diagram showing a crystal structure of a spinel-structure lithium transition metal composite oxide. In FIG. 4, 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 and lithium titanium composite oxide. Among these, lithium manganese composite oxide is preferable.

  In the positive electrode active material used in the present invention, the lithium transition metal composite oxide is present in the form of particles composed of one or both of primary particles and secondary particles that are aggregates thereof. That is, the lithium transition metal composite oxide exists in the form of particles, and the particles may be composed only of primary particles, or may be composed only of secondary particles that are aggregates of primary particles. It may consist of both particles and secondary particles.

In the positive electrode active material used in the present invention, each particle is given a two-dimensional coordinate having a coordinate component corresponding to the third root of the light emission voltage value caused by the transition metal and lithium in each particle, on the coordinate plane. When the primary regression line passing through the origin is obtained, the absolute deviation of the error of each point with respect to the primary regression line is 0.25 or less. Details will be described below.
“Luminescence voltage value” was obtained by introducing lithium transition metal composite oxide particles into microwave plasma, decomposing the particles into atoms and exciting them, and detecting the emission spectrum emitted by the excited atoms as a voltage. Is the time value. In the present invention, the light emission voltage value resulting from the transition metal atom and the lithium atom is determined for each particle of the lithium transition metal composite oxide.

  Hereinafter, the method actually performed by the inventor will be described as an example. First, using a fine particle component analyzer (Particle Analyzer PT1000, manufactured by Yokogawa Electric Corp.), manganese and lithium for thousands to tens of thousands of particles of the positive electrode active material of Example 1 and Comparative Example 1 described later. Elemental analysis of was performed. For manganese, the detector channel of the above apparatus was set to 2, and the emission spectrum at an emission wavelength of 257.610 nm was measured at a high voltage power supply magnification of 1.00. For lithium, the detector channel of the above apparatus was set to 3, and the emission spectrum with an emission wavelength of 670.780 nm was measured at a high-voltage power factor of 0.75. In the present invention, the present invention is not limited to the above apparatus, and an apparatus for performing elemental analysis of each particle using a light emission voltage of each element using microwave plasma can be used.

For each particle, the cube root of the emission voltage value resulting from the obtained manganese atom is taken as the X value, the cube root of the emission voltage value resulting from the obtained lithium atom is taken as the Y value, and each particle is coordinated Two-dimensional coordinates (X, Y) as components are given and expressed as points on a coordinate plane. FIG. 1 is a scatter diagram representing the distribution of (X, Y) for Example 1, and FIG. 2 is a scatter diagram representing the distribution of (X, Y) for Comparative Example 1. Note that particles with Y = 0 and / or X = 0 were excluded because they were particles below the measurement limit. The ratio of the X value and the Y value at each point represents the ratio of the content of lithium and manganese in each particle of the lithium manganese composite oxide.
Next, a linear regression line (approximate line) passing through the origin represented by Y = aX (a is a constant) was obtained by the least square method and represented in FIG. 1 and FIG.

  Further, the absolute deviation of the error at each point with respect to the linear regression line was determined as follows. 1 and 2, the directional distance between each point and the intersection of the perpendicular drawn from each point and the approximate line (positive when the point is on the approximate line and negative when it is below) .) Is d, and H is the distance between the intersection and the intersection of the perpendicular drawn from the intersection and the X axis. At this time, the error e is expressed by the following formula (1).

  e = d / H (1)

FIG. 3 is an explanatory diagram of a specific method for obtaining the error of each point with respect to the linear regression line. In FIG. 3, the distances between the points A and B and the intersections of the perpendiculars drawn from the points A and B and the approximate line are d ₁ (> 0) and d ₂ (<0), respectively. Let H ₁ and H ₂ be the lengths of the perpendiculars drawn from the intersection with the perpendicular to the X axis, respectively. At this time, the errors e ₁ and e ₂ are represented by e ₁ = d ₁ / H ₁ (> 0) and e ₂ = d ₂ / H ₂ (<0), respectively.
Here, the absolute deviation E of the error is expressed by the following formula (2).

  E = 1 / n · Σ | e−e ′ | (2)

  In the above formula (2), n represents the number of particles measured, and e ′ represents an average value of errors. The absolute deviation E of the error varies in the range of 0 ≦ E ≦ 1.

In the positive electrode active material used in the present invention, the absolute deviation of the error described above is 0.25 or less, preferably 0.22 or less. If the absolute deviation of the error is in the above range, the cycle characteristics, load characteristics, storage characteristics, and charge / discharge capacity are excellent without excessively increasing the Li / Mn molar ratio, and battery swelling is suppressed. The
On the other hand, if the absolute deviation of the error is too large, the composition ratio of each lithium manganese composite oxide varies greatly, and manganese ions are likely to be eluted from particles having a small Li / Mn molar ratio. As a result, cycle characteristics and storage characteristics may be deteriorated, and the battery may swell.
In the present invention, the effects described above are realized by controlling the composition ratio of each particle by the absolute deviation of the error.

In the present invention, in the particle size distribution of the particles, when the particle sizes at which the volume accumulation frequency reaches 10%, 50%, and 90% are D10, D50, and D90, respectively,
0.1 ≦ (D10 / D50) <1,
1 <(D90 / D50) ≦ 3 and 5 μm ≦ D50 ≦ 40 μm
It is preferable to satisfy all of the following.
When D10, D50, and D90 satisfy the above relational expression, the electrode plate density is further reduced without impairing improvement of cycle characteristics, storage characteristics, load characteristics, and output characteristics, and without impairing suppression of battery swelling. Can be improved.

Further, D10, D50, and D90 are expressed by a more preferable relational expression according to the purpose and application. For example, in order to further improve the electrode plate density,
0.2 ≦ (D10 / D50) ≦ 0.9,
1.2 ≦ (D90 / D50) ≦ 2 and 7 μm ≦ D50 ≦ 30 μm
It is preferable to satisfy all of the following.

In addition, in order for the nonaqueous electrolyte secondary battery using the positive electrode active material used in the present invention to be suitably used for stationary use such as residential use and home use,
0.7 ≦ (D10 / D50) <1,
1 <(D90 / D50) ≦ 1.3 and 7 μm ≦ D50 ≦ 15 μm
It is preferable to satisfy all of the following. In this case, the cycle characteristics, storage characteristics, load characteristics and output characteristics are particularly excellent.

Furthermore, in order for the nonaqueous electrolyte secondary battery using the positive electrode active material used in the present invention to be suitably used for applications such as mobile phones, electric tools, electric vehicles,
0.2 ≦ (D10 / D50) ≦ 0.7,
1.3 ≦ (D90 / D50) ≦ 2 and 15 μm ≦ D50 ≦ 36 μm
It is preferable to satisfy all of the following. In this case, cycle characteristics, storage characteristics, load characteristics, and output characteristics are excellent, and the electrode plate density is also excellent.

  In the present invention, examples of the method for measuring the particle size distribution of the particles include a sieving method, an image analysis method, a sedimentation method, a laser diffraction scattering method, and an electrical detection method.

  In the particle size distribution of the particles, the positive electrode active material used in the present invention preferably has a standard deviation of the particle size of 0.4 or less, more preferably 0.36 or less, and 0.07 or more. Preferably there is. Within this range, the electrode plate density can be increased without impairing cycle characteristics, storage characteristics, load characteristics, and output characteristics.

  In the positive electrode active material used in the present invention, the transition metal is preferably manganese. When the transition metal is manganese, the non-aqueous electrolyte secondary battery using the positive electrode active material used in the present invention is particularly excellent in cycle characteristics, storage characteristics, and load characteristics. It can be particularly preferably used for the following applications. 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.

  In the positive electrode active material used in the present invention, the following (i) to (viii) may be mentioned 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 and boron.

Aspect (i) is excellent in cycle characteristics, load characteristics, storage characteristics and charge / discharge capacity, and has less battery swelling. The reason is described below.
When aluminum and / or magnesium are included, the crystal structure is stabilized, so that the storage characteristics, load characteristics and output characteristics are not impaired, the cycle characteristics are excellent, and the swelling of the battery is further suppressed. it can. Further, boron acts as a flux, promotes crystal growth, and further improves cycle characteristics and storage characteristics.

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 Represents a number satisfying ≦ 0.2, and d preferably represents a number satisfying −0.5 ≦ d ≦ 0.5. The same applies to the later-described embodiment (iii), embodiment (v) and embodiment (vii).
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) The lithium transition metal composite oxide has the general formula Li _{1 + a} M _b Mn _2−ab B _c O _{4 + d} (M represents aluminum and / or magnesium, and a represents −0.2 ≦ a ≦ 0. .2 represents a number satisfying 0 ≦ b ≦ 0.2, c represents a number satisfying 0 ≦ c ≦ 0.02, and d represents −0.5 ≦ d ≦ 0.5. Represents a number satisfying the above.)

Aspect (ii) is excellent in cycle characteristics, load characteristics, storage characteristics and charge / discharge capacity, and has less battery swelling.
In embodiment (ii), 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 (ii), b is preferably larger than 0, and more preferably 0.05 or more. When aluminum and / or magnesium are included, the crystal structure is stabilized, so that the storage characteristics, load characteristics and output characteristics are not impaired, 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 (ii), 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.

  (Iii) The aspect 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.

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

In the embodiment (iv), the lithium transition metal composite oxide comprises a cubic spinel-type lithium manganese composite oxide represented by Li _{1 + a} M _c Mn _{2 -ac} O ₄ and 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 (iv), a is preferably 0.02 or more, and preferably 0.08 or less. For the same reason as in the case of mode (ii).
In embodiment (iv), 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 (iii).
In embodiment (iv), e is preferably 0.001 or more, and preferably 0.01 or less. For the same reason as in the case of mode (ii).

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

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

In aspect (v), the reason for having elements other than sulfur is the same as in aspects (i) to (iv).
In aspect (v), by having each of the above elements, a positive electrode plate having high charge / discharge capacity and excellent binding and surface smoothness can be obtained due to the synergistic effect of each element.

(Vi) The lithium transition metal composite oxide has the general formula Li _{1 + a} M _b Mn _{2 -ab} X _c B _{d Se} O _{4 + f} (M represents aluminum and / or magnesium, X represents fluorine, chlorine, Represents at least one selected from the group consisting of bromine and iodine, a represents a number satisfying −0.2 ≦ a ≦ 0.2, b represents a number satisfying 0 <b ≦ 0.2, and c represents Represents a number satisfying 0 ≦ c ≦ 0.05, d represents a number satisfying 0 <d ≦ 0.02, e represents a number satisfying 0 ≦ e ≦ 0.1, and f represents −0.5 ≦ A number represented by f ≦ 0.5.)

In embodiment (vi), e is preferably greater than 0. For the same reason as in the case of mode (v).
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 (v).

  (Vii) 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 (vii), by having sodium and / or calcium, elution of manganese ions can be further suppressed by a synergistic effect with boron (preferably boron and sulfur), and an excellent cycle at a practical level. Characteristics can be realized.
In the aspect (vii), the reason for having an element other than sodium and / or calcium is the same as in the aspects (i) to (vi).

(Viii) The lithium transition metal composite oxide has the general formula Li _{1 + a} M _b Mn _2−ab X _{cB d Se} A _g O _{4 + f} (M represents aluminum and / or magnesium, X represents fluorine, Represents at least one selected from the group consisting of chlorine, bromine and iodine, A represents sodium and / or calcium, a represents a number satisfying −0.2 ≦ a ≦ 0.2, and b represents 0 <b Represents a number satisfying ≦ 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. The number to satisfy | fill, f represents the number which satisfy | fills -0.5 <= f <= 0.5, g represents the number which satisfy | fills 0.00004 <= g <= 0.015).

The reason why the embodiment (viii) is preferable is the same as that of the embodiment (vii).
In embodiment (viii), 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 (vii).

  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.

When the lithium transition metal composite oxide has magnesium, it is preferable that the presence ratio of magnesium on the surface of the particles is 20% or more. The proportion of magnesium present on the surface of the particles is more preferably 40% or more, still more preferably 60% or more, and even more preferably 80% or more.
When the proportion of magnesium present on the surface of the lithium transition metal composite oxide particles is in the above range, magnesium is uniformly present on the surface of the particle, so that the effect of suppressing elution of transition metal ions is excellent.
In the present invention, the presence state of magnesium on the surface of the particle is not particularly limited.

In the present invention, the “magnesium content on the surface of the lithium transition metal composite oxide particles” is determined as follows.
First, the presence state of magnesium on the particle surface of the particle group of the lithium transition metal composite oxide is observed by an electron beam microanalyzer (EPMA) equipped with a wavelength dispersive X-ray spectrometer (WDX). Next, in the observation field of view, select the portion with the largest amount of magnesium per unit area (the portion with the largest magnesium peak), and line along the line segment that passes through this portion (for example, the line segment with a length of 300 μm). Perform analysis. In line analysis, the quotient obtained by dividing the total length of the portion where the peak is 4% or more when the peak value in the portion having the largest amount of magnesium per unit area is 100% by the length of the line segment. Is “abundance ratio of magnesium on the surface of the lithium transition metal composite oxide particles”. In addition, it is preferable to use the average value of the “magnesium content ratio on the surface of the lithium transition metal composite oxide particles” by performing line analysis a plurality of times (for example, 10 times).
In the above method, the portion where the magnesium peak is less than 4% has a large difference from the portion where the amount of magnesium is the largest, so it is regarded as a portion where no magnesium exists.

  According to the above-mentioned “abundance ratio of magnesium on the surface of the lithium transition metal composite oxide particle”, it indicates whether the magnesium exists uniformly or unevenly on the surface of the lithium transition metal composite oxide particle. be able to.

  In the positive electrode active material used in the present invention, the lithium transition metal composite oxide preferably has a (400) crystallite diameter (crystallite diameter in the (400) vector direction) of 600 to 1200 angstroms. The (400) crystallite diameter is more preferably 700 angstroms or more, and more preferably 1100 angstroms or less.

Here, “crystallite” means the maximum aggregate that can be considered as a single crystal, and “crystallite diameter” means the size of the crystallite.
Therefore, the larger the crystallite diameter, the better the crystallinity and the less the distortion of the crystal structure. In the lithium transition metal composite oxide having a spinel structure as used in the present invention, the degree of regularity of unit cell arrangement can be shown by the following (400) crystallite diameter.

  The (400) crystallite diameter of the lithium transition metal composite oxide can be determined, for example, by an X-ray diffraction method. The X-ray diffraction method can be performed, for example, under conditions of a tube current of 100 mA and a tube voltage of 40 kV. From the diffraction peak derived from the (400) plane obtained by the X-ray diffraction method, the crystallite diameter is calculated by the Scherrer equation represented by the following equation (3).

  D = Kλ / (βcos θ) (3)

  In the above formula, D represents the crystallite size (Å), K represents the Scherrer constant (1.05 when β is calculated from the integral width), and λ represents the wavelength of the X-ray source (in the case of CuKα1). Represents 1.540562Å), β represents the width of the diffraction line spread depending on the crystallite size (radian), and θ represents the diffraction angle (degree).

In the positive electrode active material used in the present invention, the specific surface area is preferably 0.2 to 1.2 m ² / g. The specific surface area is more preferably 0.25 m ² / g or more, and more preferably 0.9 m ² / g or less. When the specific surface area is too small, the discharge capacity decreases. If the specific surface area is too large, the cycle characteristics are not excellent. The specific surface area can be measured by a nitrogen gas adsorption method.

In the positive electrode active material used in the present invention, in the particle size distribution of the particles, the proportion of particles having a volume-based particle size of 50 μm or more is preferably 10% by volume or less, and 7% by volume or less. More preferably.
By controlling the particle size distribution of the particles as described above, coarse particles composed of secondary aggregates can be prevented from being included, and thus a positive electrode coated surface with excellent smoothness can be obtained.

  The production method of the positive electrode active material used in 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 (for example, MnO ₂ , Mn ₂ O ₃ , Mn ₃ O ₄ ), hydroxide, nitrate, carbonate (MnCO ₃ ), chloride salt ( For example, MnCl ₂ ), manganese iodide, manganese sulfate, manganese nitrate (for example, MnSO ₄ ) can be mentioned. Of these, manganese metal, MnCO ₃ , MnSO ₄ , and MnCl ₂ are preferable.
Manganese compounds have a particle size distribution in which the particle size at which the volume cumulative frequency reaches 10%, 50% and 90% is d10, d50 and d90, respectively, d10 is 5 to 25 μm, d50 is 7 to 40 μm, It is preferable to use one having d90 of 10 to 60 μm. In order to obtain a manganese compound having such a particle size distribution, a rough mortar, ball mill, vibration mill, jet mill or the like can be used. Various classifiers can also be used.

The 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, perchloric acid Magnesium is mentioned. Of these, MgSO ₄ and Mg (NO ₃ ) ₂ are preferable.
Aluminum compound is not particularly limited, for _{example, Al 2 O 3, Al (} NO 3) 3, Al 2 (SO 4) 3, Al 2 (CO 3) 3, is Al (CH ₃ COO) ₃ and the like.

The boron compound is not particularly limited, and examples thereof include B ₂ O ₃ (melting point: 460 ° C.), H ₃ BO ₃ (decomposition temperature: 173 ° C.), lithium boron composite oxide, orthoboric acid, boron oxide, and boron phosphate. . Among these, H ₃ BO ₃ and B ₂ O ₃ are preferable.
The halogen compound is not particularly limited. For example, NH ₄ F, NH ₄ Cl, NH ₄ Br, NH ₄ I, LiF, LiCl, LiBr, LiI, MnF ₂ , MnCl ₂ , MnBr ₂ , MnI ₂ , 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 these, NH ₄ F, NH ₄ Cl, NH ₄ Br, NH ₄ I, LiF, LiCl, LiBr, LiI, MnF ₂ , MnCl ₂ , MnBr ₂ , and MnI ₂ are preferable.

The sulfur compound is not particularly limited, and examples thereof include Li ₂ SO ₄ , MnSO ₄ , (NH ₄ ) ₂ SO ₄ , Al ₂ (SO ₄ ) ₃ , MgSO ₄ , sulfide, sulfur iodide, hydrogen sulfide, and sulfuric acid. 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 COONa and the like.

The calcium compound is not particularly limited, and examples thereof include CaO, CaCO ₃ , Ca (OH) ₂ , CaCl ₂ , CaSO ₄ , Ca (NO ₃ ) ₂ , and Ca (CH ₃ COO) ₂ .
Moreover, you may use the compound containing 2 or more types of each element mentioned above.

Hereinafter, a suitable method for obtaining the raw material mixture will be described in detail by taking as an example a positive electrode active material which 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 the stirring pure water.
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.

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.
When firing in an atmosphere in which the oxygen concentration is controlled, generation of oxygen vacancies in the crystal structure can be suppressed, and there is almost no crystal distortion and a (400) crystallite diameter is large. Can be produced.

Among these, an oxidizing atmosphere having an oxygen concentration of 10% by volume or more is preferable. When firing in an oxidizing atmosphere having an oxygen concentration of 10% by volume or more, a powder having a (400) crystallite diameter of 600 angstroms or more is obtained.
In particular, an oxidizing atmosphere having an oxygen concentration of 18% by volume or more is preferable. When firing in an oxidizing atmosphere having an oxygen concentration of 18% by volume or more, sufficient oxygen is supplied into the crystal structure, and a powder having a (400) crystallite size of 600 to 1200 angstroms is obtained.

  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. Thus, the specific surface area can be set to the above-described preferred range by grinding after firing.

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

The non-aqueous electrolyte secondary battery of the present invention is a non-aqueous electrolyte secondary battery using the positive electrode active material described above. The nonaqueous electrolyte secondary battery of the present invention is suitably used as a nonaqueous electrolyte secondary battery such as a lithium ion secondary battery or a lithium ion polymer secondary battery.
The non-aqueous electrolyte secondary battery of the present invention may be configured, for example, in a conventionally known non-aqueous electrolyte secondary battery using the above-described positive electrode active material as at least a part of the positive electrode active material. The configuration is not particularly limited. 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 compound capable of occluding and releasing lithium ions include carbon materials such as graphite and graphite; and oxides such as tin oxide and titanium oxide.

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

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

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

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

  Using the above-described positive electrode active material and the above-described negative electrode active material, electrolytic solution, separator, and binder, a lithium ion secondary battery can be obtained according to a conventional method.

A preferred method for producing a positive electrode using the positive electrode active material described above will be described below.
A positive electrode mixture is prepared by mixing the above-described positive electrode active material powder with a carbon-based conductive agent such as acetylene black or graphite, a binder, and a solvent or dispersion medium of the binder. The obtained positive electrode mixture 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. 5 is a schematic cross-sectional view of the positive electrode. As shown in FIG. 5, the positive electrode 13 is obtained by holding the positive electrode active material 5 on the current collector 12 with the binder 4.

The positive electrode active material used in the present invention is considered to be excellent in mixing with the conductive agent powder and have a low internal resistance of the battery. Accordingly, the charge / discharge characteristics, particularly the discharge capacity, are excellent.
In addition, the positive electrode active material used in the present invention has excellent fluidity when kneaded with a binder, and is easily entangled with a polymer of the binder and has excellent binding properties.
Furthermore, since the positive electrode active material used in 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. 6 is a schematic cross-sectional view of a cylindrical battery. As shown in FIG. 6, 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. However, they are repeatedly laminated via the separator 14.
FIG. 7 is a schematic partial cross-sectional view of a coin-type battery. As shown in FIG. 7, 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. 8 is a schematic perspective view of a prismatic battery. As shown in FIG. 8, 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.

The use of the nonaqueous electrolyte secondary battery 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, 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 other devices.
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 also 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 with particle sizes (d10, d50, and d90) that reach 10%, 50%, and 90% in the particle size distribution of particles are 11 μm, 14 μm, and 18 μm, respectively, washed with water and dried And then mixed with orthoboric acid and lithium carbonate. The resulting mixture was calcined at about 800 ° C. for about 10 hours. The obtained fired product was pulverized to obtain a positive electrode active material.
The composition of the obtained positive electrode active material was Li _1.09 Mn _1.94 Mg _0.01 B _0.008 O ₄ . The sulfate group content was 0.5% by weight based on the total of the lithium transition metal composite oxide and the sulfate group. The Fe content was 7 ppm based on the total of the lithium transition metal composite oxide and Fe.

[Example 2]
A positive electrode active material was obtained in the same manner as in Example 1 except that the mixing ratio of manganese and magnesium carbonate, orthoboric acid, and lithium carbonate was changed.
The composition of the obtained positive electrode active material was Li _1.08 Mn _1.94 Mg _0.01 B _0.005 O ₄ . The sulfate group content was 0.4% by weight based on the total of the lithium transition metal composite oxide and the sulfate group. The Fe content was 2 ppm based on the total of the lithium transition metal composite oxide and Fe.

Example 3
A positive electrode active material was obtained in the same manner as in Example 1 except that the mixing ratio of manganese and magnesium carbonate, orthoboric acid, and lithium carbonate was changed.
The composition of the obtained positive electrode active material was Li _1.05 Mn _1.95 Mg _0.01 B _0.005 O ₄ . The sulfate group content was 0.4% by weight based on the total of the lithium transition metal composite oxide and the sulfate group. The Fe content was 2 ppm based on the total of the lithium transition metal composite oxide and Fe.

Example 4
A positive electrode active material was obtained in the same manner as in Example 1 except that the mixing ratio of manganese and magnesium carbonate, orthoboric acid, and lithium carbonate was changed.
The composition of the obtained positive electrode active material was Li _1.05 Mn _1.95 Mg _0.01 B _0.008 O ₄ .

Example 5
Manganese and magnesium carbonates having d10, d50 and d90 of 23 μm, 31 μm and 48 μm, respectively, were washed with water, dried and then mixed with orthoboric acid and lithium carbonate. The resulting mixture was calcined at about 800 ° C. for about 10 hours. The obtained fired product was pulverized to obtain a positive electrode active material.
The composition of the obtained positive electrode active material was Li _1.08 Mn _1.95 Mg _0.01 B _0.0002 O ₄ . The sulfate group content was 0.5% by weight based on the total of the lithium transition metal composite oxide and the sulfate group. The Fe content was 8 ppm based on the total of the lithium transition metal composite oxide and Fe.

Example 6
A positive electrode active material was obtained in the same manner as in Example 5 except that the mixing ratio of manganese and magnesium carbonate, orthoboric acid, and lithium carbonate was changed.
The composition of the obtained positive electrode active material was Li _1.08 Mn _1.95 Mg _0.01 B _0.003 O ₄ . The sulfate group content was 0.5% by weight based on the total of the lithium transition metal composite oxide and the sulfate group. The Fe content was 5 ppm with respect to the total of the lithium transition metal composite oxide and Fe.

Example 7
Manganese and magnesium carbonates having d10, d50 and d90 of 20 μm, 29 μm and 41 μm, respectively, were washed with water, dried and then mixed with orthoboric acid and lithium carbonate. The resulting mixture was calcined at about 800 ° C. for about 10 hours. The obtained fired product was pulverized to obtain a positive electrode active material.
The composition of the obtained positive electrode active material was Li _1.08 Mn _1.94 Mg _0.01 B _0.005 O ₄ .

Example 8
Manganese and magnesium carbonates having d10, d50, and d90 of 10 μm, 13 μm, and 18 μm, respectively, were washed with water, dried, and then mixed with orthoboric acid and lithium carbonate. The resulting mixture was calcined at about 800 ° C. for about 10 hours. The obtained fired product was pulverized to obtain a positive electrode active material.
The composition of the obtained positive electrode active material was Li _1.08 Mn _1.94 Mg _0.01 B _0.005 O ₄ . The sulfate group content was 0.4% by weight based on the total of the lithium transition metal composite oxide and the sulfate group. The Fe content was 5 ppm with respect to the total of the lithium transition metal composite oxide and Fe.

Example 9
Manganese carbonates having d10, d50 and d90 of 9 μm, 12 μm and 16 μm, respectively, were washed with water, dried and then mixed with orthoboric acid, lithium carbonate and aluminum hydroxide. The resulting mixture was calcined at about 800 ° C. for about 10 hours. The obtained fired product was pulverized to obtain a positive electrode active material.
The composition of the obtained positive electrode active material was Li _1.08 Mn _1.94 Al _0.04 B _0.005 O ₄ . The sulfate group content was 0.4% by weight based on the total of the lithium transition metal composite oxide and the sulfate group. The Fe content was 2 ppm based on the total of the lithium transition metal composite oxide and Fe.

Example 10
A positive electrode active material was obtained in the same manner as in Example 8, except that the mixing ratio of manganese and magnesium carbonate, orthoboric acid, and lithium carbonate was changed.
The composition of the obtained positive electrode active material was Li _1.07 Mn _1.94 Mg _0.04 B _0.005 O ₄ . The sulfate group content was 0.4% by weight based on the total of the lithium transition metal composite oxide and the sulfate group. The Fe content was 16 ppm based on the total of the lithium transition metal composite oxide and Fe.

[Comparative Example 1]
Manganese dioxide, lithium carbonate, magnesium carbonate, and orthoboric acid having d10, d50, and d90 of 0.4 μm, 9.6 μm, and 28.3 μm, respectively, were dry mixed to obtain a powder of a raw material mixture. The obtained raw material mixture was baked at 830 ° C. for 11 hours in the air atmosphere. The obtained fired product was pulverized to obtain a positive electrode active material.
The composition of the obtained positive electrode active material was Li _1.10 Mn _1.93 Mg _0.01 B _0.0083 O ₄ . The content of the sulfate group was 1.2% by weight with respect to the total of the lithium transition metal composite oxide and the sulfate group. The Fe content was 40 ppm based on the total of the lithium transition metal composite oxide and Fe.

  In the above-described examples and comparative examples, the composition of the positive electrode active material was determined by inductively coupled high-frequency plasma spectroscopy (ICP spectroscopy). The sulfate radical and Fe contents were determined by ICP spectroscopy.

2. Properties of positive electrode active material (1) Structure of positive electrode active material About the positive electrode active material obtained in Example 1 and Comparative Example 1, using EPMA equipped with WDX, a line segment having a length of 300 μm was formed by the method described above. A line analysis was performed along. The results are shown in FIG. 9 and FIG.
From FIG. 9, it can be seen that in the positive electrode active material obtained in Example 1, the presence state of magnesium present on the surface is uniform. The proportion of magnesium present on the surface of the lithium transition metal composite oxide particles was 84.5%.
FIG. 10 shows that in the positive electrode active material obtained in Comparative Example 1, the presence state of magnesium present on the surface is non-uniform (biased). The proportion of magnesium present on the surface of the lithium transition metal composite oxide particles was 2.0%.

(2) Absolute deviation of error Elemental analysis of the obtained positive electrode active material was performed using a particle analyzer “PT-1000” (manufactured by Yokogawa Electric Corporation) that performs elemental analysis based on the light emission voltage of each element. . From the above formulas (1) and (2), the absolute deviation of the error based on the light emission voltage caused by the transition metal and lithium was determined.

(3) Specific surface area and particle size distribution of positive electrode active material The specific surface area of the obtained positive electrode active material was measured by a constant pressure BET adsorption method using nitrogen gas.
Further, the particle size distribution of the obtained positive electrode active material is measured by a laser diffraction scattering method, and D10, D50, D90, the standard deviation of the particle diameter, and the ratio of the particles whose volume-based particle diameter is 50 μm or more are obtained. It was.

(4) (400) Crystallite diameter of positive electrode active material The obtained positive electrode active material was subjected to an X-ray diffraction method. The X-ray diffraction method was performed using an X-ray diffractometer (RINT2500V, manufactured by Rigaku Corporation), using CuKα1 as an X-ray source, a tube current of 100 mA, and a tube voltage of 40 kV. Based on the X-ray diffraction pattern obtained by the X-ray diffraction method, the (400) crystallite diameter of the positive electrode active material was determined from the Scherrer equation represented by the above equation (3).

(5) Mn dissolution test of positive electrode active material After the obtained positive electrode active material was dried at 110 ° C. for 15 hours, LiPF ₆ was dissolved in a mixed solvent of ethylene carbonate / diethyl carbonate = 3/7 at a concentration of 1 mol / L. The mixed electrolyte solution was mixed and stored at 85 ° C. for 48 days. After removing the positive electrode active material by filtering this, the elution amount of Mn (weight of the Mn element with respect to the weight of the electrolytic solution) was measured by ICP spectroscopy. It can be said that the smaller the amount of Mn eluted, the better the storage characteristics.

(6) Electrode Plate Density of Positive Electrode Active Material A paste is prepared by kneading 95 parts by weight of the positive electrode active material powder and a normal methylpyrrolidone solution of polyvinylidene fluoride (5 parts by weight as the amount of polyvinylidene fluoride). Was applied to an aluminum electrode plate and dried to obtain a positive electrode plate. After the positive electrode plate was cut into a predetermined size (5 cm ² ), the electrode plate was pressurized with a uniaxial press. The electrode plate density was calculated from the thickness and weight of the electrode plate after pressing.

The results are shown in Table 1. In the table, “-” indicates that the corresponding item is not measured.
As is clear from Table 1, the positive electrode active material used in the non-aqueous electrolyte secondary battery of the present invention has a lower elution amount of Mn and excellent storage characteristics than the positive electrode active material of Comparative Example 1. It was. Further, the positive electrode active material used in the non-aqueous electrolyte secondary battery of the present invention had an electrode plate density equivalent to that of the positive electrode active material of Comparative Example 1.

3. Evaluation of Positive Electrode Active Material Using each of the positive electrode active materials obtained above, a secondary battery for test in which the negative electrode is lithium metal, a secondary battery for test in which the negative electrode is carbon, and a cylindrical battery are manufactured. Evaluation was performed as described above.

A. Evaluation using a secondary battery for test in which the negative electrode is lithium metal A secondary battery for test in which the negative electrode is lithium metal was produced as follows.
A paste was prepared by kneading 90 parts by weight of a 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). Was applied to a positive electrode current collector and dried to obtain a positive electrode plate. Using the obtained positive electrode plate, a test secondary battery in which the negative electrode was lithium metal was produced.

(1) Initial discharge capacity Under the conditions of a charge potential of 4.3 V, a discharge potential of 2.85 V, and a discharge load of 0.2 C (where 1 C is a current load that completes the discharge in one hour. The same applies hereinafter) A test secondary battery in which the negative electrode was lithium metal was discharged. The discharge capacity at this time was set to 0.2 C initial discharge capacity.
In addition, the test secondary battery in which the negative electrode was lithium metal was discharged under the conditions of a charge potential of 4.3 V, a discharge potential of 3.0 V, and a discharge load of 0.24 C. The discharge capacity at this time was 0.24C initial discharge capacity.

(2) Evaluation of swelling at the end of discharge At the time of measuring the initial discharge capacity of 0.2C, the change in capacity during discharge from 3.3 V to 2.85 V was measured to evaluate the swelling at the end of discharge. It can be said that the smaller the swelling at the end of discharge, the better the cycle characteristics.

(3) Initial efficiency A secondary battery for testing in which the negative electrode was lithium metal was discharged under the conditions of a charging potential of 4.3 V, a discharging potential of 2.85 V, and a discharging load of 0.2 C. At this time, the value of the discharge capacity was the initial discharge capacity, and the value of the charge capacity was the initial charge capacity. The initial efficiency was determined by dividing the obtained initial discharge capacity value by the initial charge capacity.

(4) Load Discharge Capacity The test secondary battery in which the negative electrode was lithium metal was discharged under the conditions of a charge potential of 4.3 V, a discharge potential of 2.85 V, and a discharge load of 2.0 C. The discharge capacity at this time was defined as the load discharge capacity.

(5) Load efficiency (load capacity maintenance rate)
Using a test secondary battery in which the negative electrode is a lithium metal, the initial discharge capacity was measured under the conditions of a charge potential of 4.3 V, a discharge potential of 2.85 V, and a discharge load of 0.2 C, and then the charge potential of 4.3 V, The load discharge capacity was measured under the conditions of a discharge potential of 2.85 V and a discharge load of 2.0 C. The obtained load discharge capacity value was divided by the initial discharge capacity to determine the load efficiency at a discharge load of 2.0C.

  Further, using a test secondary battery in which the negative electrode is a lithium metal, the initial discharge capacity was measured under the conditions of a charge potential of 4.3 V, a discharge potential of 2.85 V, and a discharge load of 0.24 C. The load discharge capacity was measured under the conditions of 3 V, a discharge potential of 2.85 V, and a discharge load of 3.5 C. The obtained load discharge capacity value was divided by the initial discharge capacity to determine the load efficiency at a discharge load of 3.5C.

The results are shown in Table 2. In the table, “-” indicates that the corresponding item is not measured.
As is apparent from Table 2, the nonaqueous electrolyte secondary battery of the present invention is excellent in both initial discharge capacity and load discharge capacity, excellent in both initial efficiency and load efficiency, and in cycle characteristics. It was excellent.

B. Evaluation using test secondary battery in which negative electrode is carbon A positive electrode plate was obtained in the same manner as in the case of the test secondary battery in which the negative electrode was lithium metal. Using the obtained positive electrode plate, a test secondary battery in which the negative electrode was carbon was produced.

(1) Discharge capacity Under the conditions of a charge potential of 4.2 V, a discharge potential of 2.75 V, and a discharge load of 0.2 C, the charge / discharge of the test secondary battery in which the negative electrode is carbon was performed 43 cycles. The discharge capacity after 43 cycles was measured.

(2) End-of-discharge swelling At the time of measurement of the discharge capacity after 43 cycles, the change in capacity during discharge from 3.3 V to 2.85 V was measured to evaluate the end-of-discharge swelling. It can be said that the smaller the swelling at the end of discharge, the better the cycle characteristics.

(3) Elution amount of Mn After charging and discharging for 43 cycles, the secondary battery for test in which the negative electrode was carbon was disassembled, the negative electrode and the separator were taken out, Mn adhering to the negative electrode and the separator was dissolved and concentrated, and ICP The amount of Mn elution (weight of Mn element dissolved from the negative electrode and the separator) was measured by spectroscopic analysis. If the Mn elution amount is small, it can be said that the cycle characteristics and the storage characteristics are excellent.

(4) Discharge capacity maintenance ratio after 43 cycles Charging / discharging 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 1.0 C, and the discharge capacity after 43 cycles was measured. The obtained discharge capacity value after 43 cycles was divided by the discharge capacity value after 1 cycle to determine the discharge capacity retention rate after 43 cycles, and the cycle characteristics were evaluated.

The results are shown in Table 3. In the table, “-” indicates that the corresponding item is not measured.
As is apparent from Table 3, the nonaqueous electrolyte secondary battery of the present invention was excellent in cycle characteristics and storage characteristics.

C. Evaluation using cylindrical battery The cylindrical battery was produced as follows.
A positive electrode plate was obtained by the same method as in the case of the test secondary battery in which the negative electrode was lithium metal. 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 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. A positive electrode plate, a negative electrode plate, and a separator are formed into a thin sheet, wound and housed in a metal cylindrical battery case, and an electrolytic solution is injected into the battery case to obtain a lithium ion battery cylindrical battery. It was.

(1) Discharge capacity maintenance rate after 200 cycles 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 200 cycles was measured. The obtained discharge capacity value after 200 cycles was divided by the discharge capacity value after 1 cycle to obtain the discharge capacity retention rate after 200 cycles, and the cycle characteristics were evaluated.

(2) 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 200 cycles was measured. The obtained value of the discharge capacity after 200 cycles was divided by the value of the discharge capacity after 1 cycle to determine the high temperature discharge capacity retention rate, and the high temperature cycle characteristics were evaluated.

(3) Load efficiency (load capacity maintenance rate)
After measuring the initial discharge capacity under the conditions of a charging potential of 4.2 V, a discharging potential of 2.75 V, and a discharging load of 0.2 C, the charging potential of 4.2 V, the discharging potential of 2.75 V, and the discharging load of 2.0 C were The load discharge capacity was measured. The obtained load discharge capacity value was divided by the initial discharge capacity to determine the load efficiency at a discharge load of 2.0C.

(4) Average potential Initial discharge capacity and electric energy were measured under the conditions of a charge potential of 4.2 V, a discharge voltage of 2.75 V, and a discharge load of 0.2 C. The obtained electric energy value was divided by the initial discharge capacity to obtain an average potential.

The results are shown in Table 4. In the table, “-” indicates that the corresponding item is not measured.
As is apparent from Table 4, the non-aqueous electrolyte secondary battery of the present invention is excellent in both cycle characteristics and high-temperature cycle characteristics, has a high average potential under load, and is excellent in load capacity maintenance rate. It was.

FIG. 1 shows a positive electrode active material used in the present invention (Example 1), where the third root of the light emission voltage value attributable to the manganese atom of the lithium manganese composite oxide particle is taken as the X value, and the light emission voltage due to the lithium atom. It is a scatter diagram showing distribution of (X, Y) when the cube root of the value is a Y value. FIG. 2 shows that in the conventional positive electrode active material for a lithium ion secondary battery (Comparative Example 1), the third root of the light emission voltage value attributable to the manganese atom of the lithium manganese composite oxide particle is taken as the X value, It is a scatter diagram showing distribution of (X, Y) when the cube root of the light emission voltage value to be made is set to Y value. FIG. 3 is an explanatory diagram of a specific method for obtaining the error of each point with respect to the linear regression line. FIG. 4 is a schematic diagram showing a crystal structure of a spinel-structure lithium transition metal composite oxide. FIG. 5 is a schematic cross-sectional view of the positive electrode. FIG. 6 is a schematic cross-sectional view of a cylindrical battery. FIG. 7 is a schematic partial cross-sectional view of a coin-type battery. FIG. 8 is a schematic perspective view of a prismatic battery. It is a chart which shows the presence state of magnesium obtained by conducting line analysis by EPMA about the positive electrode active material obtained in Example 1. It is a chart which shows the presence state of magnesium obtained by carrying out line analysis by EPMA about the positive electrode active material obtained by the comparative example 1.

Explanation of symbols

DESCRIPTION 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 type battery

Claims (1)

A non-aqueous electrolyte secondary battery using a positive electrode active material having at least a spinel-structure lithium transition metal composite oxide,
The lithium transition metal composite oxide exists in the form of particles composed of one or both of primary particles and secondary particles that are aggregates thereof,
Each particle is given a two-dimensional coordinate whose coordinate component is the cube root of the light emission voltage value caused by the transition metal and lithium in each particle, expressed as a point on the coordinate plane, and linear regression through the origin When finding a straight line
A nonaqueous electrolyte secondary battery in which an absolute deviation of an error at each point with respect to the primary regression line is 0.25 or less.

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