JP6022326B2 - Lithium composite oxide and method for producing the same, and positive electrode active material for secondary battery including the lithium composite oxide, positive electrode for secondary battery including the same, and lithium ion secondary battery using the same as positive electrode - Google Patents

Description

  The present invention relates to a lithium composite oxide and a method for producing the same, a positive electrode active material for a secondary battery including the lithium composite oxide, a positive electrode for a secondary battery including the lithium active material, and a lithium ion secondary battery using the positive electrode. .

  Lithium batteries have a high energy density compared to other batteries, are light and can be used for a long time, and are power sources for portable devices such as mobile phones, PHS and small computers, power storage power sources, electric vehicles Development is underway for use as a power source for automobiles.

Such a lithium battery includes a positive electrode made of a positive electrode active material containing a lithium-containing composite oxide, a negative electrode made of a material capable of occluding and releasing lithium such as carbon, and a separator containing a non-aqueous electrolyte. Alternatively, a solid electrolyte is provided as a main component.
Among these constituent elements, those studied as positive electrode active materials include lithium cobalt composite oxide (LiCoO ₂ ), lithium nickel composite oxide (LiNiO ₂ ), lithium manganese composite oxide (LiMn ₂ O _4). ) Etc. In particular, a battery using a lithium cobalt composite oxide as a positive electrode has been developed to obtain excellent initial capacity characteristics and cycle characteristics, and has already been put into practical use.
However, since cobalt is a rare resource, a lithium ion secondary battery using a lithium cobalt composite oxide for the positive electrode is expensive. Therefore, an alternative material that is cheaper than cobalt and can realize a high energy density has been demanded, and several proposals have already been made.

  For example, in Patent Document 1, a material containing an element having an effect of accelerating sintering of a raw material of a lithium transition metal compound, the main component of which is a lithium transition metal compound represented by a specific formula, is fired. In the pore distribution curve, a lithium transition for a lithium secondary battery positive electrode material, having a main peak peak top at a pore radius of 800 nm to 6000 nm and a sub peak peak top at a pore radius of 80 nm to 800 nm Metal compound powders are described.

  For example, Patent Document 2 includes a lithium composite oxide having a composition represented by a specific formula, and 3.5 V to 4 in a charge / discharge curve from 3.5 V to 5.2 V in terms of a metal lithium negative electrode or metal lithium negative electrode. A positive electrode active material for a lithium secondary battery is described which does not show a potential inflection or a potential plateau in the region of .5V.

  For example, Patent Document 3 describes a positive electrode active material represented by a specific composition formula and characterized in that the reaction in the charge / discharge region is a two-phase reaction.

For example, Patent Document 4 discloses a lithium manganese nickel composite oxide having a spinel structure represented by a specific formula, a lattice constant of a cubic unit cell of 8.17 to 8.18 Å, and a specific surface area of 0.2. -1.0 m < ² > / g, tap density is 1.52 g / cm < ³ > or more, and the region exceeding 4.5 V in the discharge curve is 120 mAh / g or more, and the potential region is from 3.5 to 4.5 V A positive electrode active material for a non-aqueous electrolyte secondary battery is described, which is characterized by eliminating the shelf.

JP 2012-15105 A JP 2001-148249 A JP 2003-323893 A JP 2004-303710 A

However, a lithium ion secondary battery having high energy density and excellent cycle characteristics and rate characteristics has not been proposed.
For example, the lithium secondary battery described in Patent Document 1 does not have excellent rate characteristics. Moreover, the lithium secondary battery described in Patent Document 2 or Patent Document 3 does not have excellent cycle characteristics.

  The present invention solves the problems of the conventional lithium composite oxide as described above. That is, when using it as a positive electrode active material, a lithium composite oxide that can provide a lithium ion secondary battery that has a 5V-class operating voltage and is excellent in cycle characteristics and rate characteristics is provided, and a method for producing the same. For the purpose. Moreover, it aims at providing the positive electrode active material containing such a lithium complex oxide. Moreover, it aims at providing the positive electrode for lithium ion secondary batteries containing this positive electrode active material. Furthermore, it aims at providing the lithium ion secondary battery using this positive electrode.

The inventor has intensively studied to solve the above-mentioned problems, and has completed the present invention.
The present invention includes the following (1) to (11).
(1) A composition containing Ni and Mn and represented by the following formula (I), an average secondary particle diameter of 3 to 29 μm, a crystal structure of a spinel type, and at least a part of space A lithium composite oxide, wherein the group is P4 ₃ 32.
Formula (I): Li _{(1 + x)} (Ni, Mn, M ¹ ) _(2-xp) M ² _p O _(4-a)
In the formula (I), M ¹ is at least one element selected from the group consisting of Co, Fe, Cr and Cu, and M ² is selected from B, P, Pb, Sb, Si, Ti, Mg, Al and V. At least one element selected from the group consisting of 0 ≦ x ≦ 0.2, 0 ≦ p ≦ 1.0, and 0 ≦ a ≦ 1.0.
(2) The lithium composite oxide according to (1), wherein the formula (I) is represented by the following formula (I-1).
Formula (I-1): Li _{(1 + x)} Ni _{0.5-0.25x-0.25p} (Mn _1.5-y M ¹ _y ) _-0.75x-0.75p M ² _p O _(4-a)
In Formula (I-1), 0 ≦ y <0.5.
(3) The lithium composite oxide according to (1) or (2), wherein the average primary particle size is 0.05 to 10 μm.
(4) Precursor adjustment in which a lithium source, a nickel source, a manganese source, a raw material containing M ¹ and a raw material containing M ² are pulverized and mixed in a solvent, and the resulting slurry is dried to obtain a precursor. Process,
A firing step of firing the precursor at a firing temperature within a range of 600 to 1200 ° C. to obtain a fired body;
A method for producing a lithium composite oxide, wherein the lithium composite oxide according to any one of (1) to (3) is obtained.
(5) The method for producing a lithium composite oxide according to (4), wherein a firing temperature in the firing step is 750 to 950 ° C.
(6) The precursor preparation step is a step of pulverizing and mixing a raw material containing a lithium source, a nickel source, a manganese source and M ¹ in a solvent, and drying the resulting slurry to obtain the precursor. And
The method for producing a lithium composite oxide according to (4) or (5) above, wherein a lithium composite oxide represented by the following formula (I-2) is obtained.
Formula (I-2): Li _{(1 + x)} (Ni, Mn, M ¹ ) _(2-x) O _(4-a)
(7) Any of the above (4) to (6), further comprising a cleaning step of cleaning the fired body and then heating at a heating temperature within a range of 100 to 750 ° C. to obtain a cleaned fired body. The manufacturing method of lithium composite oxide as described in any one of.
(8) A lithium composite oxide obtained by the production method according to any one of (4) to (7) above.
(9) A positive electrode active material comprising the lithium composite oxide according to (1), (2), (3) or (8).
(10) A positive electrode for a lithium ion secondary battery comprising the positive electrode active material according to (9) above.
(11) A lithium ion secondary battery comprising the positive electrode for a lithium ion secondary battery as described in (10) above, a negative electrode, and an electrolytic solution, and having a 5V class operating voltage.

  According to the present invention, when it is used as a positive electrode active material, a lithium composite oxide capable of providing a lithium ion secondary battery having an operating voltage of 5 V class and excellent in cycle characteristics and rate characteristics, and a method for producing the same Can be provided. Moreover, the positive electrode active material containing such a lithium composite oxide can be provided. Moreover, the positive electrode for lithium ion secondary batteries containing this positive electrode active material can be provided. Furthermore, a lithium ion secondary battery using this positive electrode can be provided.

It is an enlarged photograph for demonstrating the secondary particle and primary particle in the complex oxide of this invention. It is another enlarged photograph for demonstrating the secondary particle and primary particle in the complex oxide of this invention. 2 is a charge / discharge curve obtained in Example 1. FIG. 2 is a charge / discharge curve obtained in Example 2. FIG. 3 is a charge / discharge curve obtained in Example 3. FIG. It is the charging / discharging curve obtained in Example 4.

The present invention will be described.
The present invention includes a composition containing Ni and Mn and represented by the following formula (I), an average secondary particle diameter of 3 to 29 μm, a crystal structure of a spinel type, and at least a part of It is a lithium composite oxide whose space group is P4 ₃ 32.
Formula (I): Li _{(1 + x)} (Ni, Mn, M ¹ ) _(2-xp) M ² _p O _(4-a)
In the formula (I), M ¹ is at least one element selected from the group consisting of Co, Fe, Cr and Cu, and M ² is selected from B, P, Pb, Sb, Si, Ti, Mg, Al and V. At least one element selected from the group consisting of 0 ≦ x ≦ 0.2, 0 ≦ p ≦ 1.0, and 0 ≦ a ≦ 1.0.
Hereinafter, such a lithium composite oxide is also referred to as “the composite oxide of the present invention”.

  The inventor has intensively studied, and when the composite oxide of the present invention as described above is used as at least a part of the positive electrode active material, a lithium ion secondary having a 5 V class operating voltage and excellent cycle characteristics and rate characteristics. It has been found that a battery can be obtained.

<Composite oxide of the present invention>
The composition of the composite oxide of the present invention will be described.
The composite oxide of the present invention has a composition represented by the formula (I): Li _{(1 + x)} (Ni, Mn, M ¹ ) _(2-xp) M ² _p O _(4-a) .
Here, the composite oxide of the present invention necessarily contains Ni and Mn, but may not contain M ¹ and / or M ² . Therefore, the composite oxide of the present invention is
Li _{(1 + x)} (Ni, Mn) _(2-xp) M ² _p O _(4-a) ,
Li _{(1 + x)} (Ni, Mn, M ¹ ) _(2-x) O _(4-a) ,
In some cases, a composition represented by Li _{(1 + x)} (Ni, Mn) _(2-x) O _(4-a) or the like may be provided.

The composite oxide of the present invention preferably has a composition represented by the formula (I-1) as a subordinate concept of the above formula (I).
Formula (I-1): Li _{(1 + x)} Ni _{0.5-0.25x-0.25p} (Mn _1.5-y M ¹ _y ) _-0.75x-0.75p M ² _p O _(4-a)
In formula (I-1), M ¹ and M ² mean the same elements as in formula (I). The ranges of x, p and a are the same as in the case of formula (I).

In the composition represented by formula (I-1), when Li is excessively present (when x> 0), 75% of the excess Li atoms (percentage of the number of atoms) are substituted with Mn and / or M ^1, and the balance Means that 25% (percentage of atoms) of Ni substitutes Ni. Further, when M ² is contained, it means that 75% (percentage of the number of atoms) of M ² atoms is replaced with Mn and / or M ^1, and the remaining 25% (percentage of the number of atoms) is replaced with Ni. . Formula (I-1) means that Mn and M ¹ are substituted. In such a case, the inventor has found that a lithium ion secondary battery with higher operating voltage, excellent cycle characteristics and rate characteristics, and higher energy density can be obtained. In addition, that energy density is excellent means that initial stage charge / discharge capacity is high.
Preferable examples of the compound corresponding to the formula (I-1) include LiNi _0.5 (Mn _1.5-y Co _y ) O ₄ and LiNi _0.4975 (Mn _1.4925-y Co _y ) B _0.01 O ₄ .
Hereinafter, the description of the formula (I) also applies to the formula (I-1).

In the formula (I-1), y means the amount of substitution between Mn and M ¹ . When M ¹ means a plurality of kinds of elements, it means the total substitution amount.
In the formula (I-1), y is 0 ≦ y <0.5, preferably 0 ≦ y ≦ 0.2, and y = 0 (that is, the composite oxide of the present invention has M ¹ More preferably).

When y = 0, the composite oxide of the present invention is represented by the formula (I-1-1) as a subordinate concept of the formula (I-1).
Formula (I-1-1): Li _{(1 + x)} Ni _{0.5-0.25x-0.25p} Mn _{1.5-0.75x-0.75p} M ² _p O _(4-a)
In formula (I-1-1), M ² means the same element as in formula (I). The ranges of x, p and a are the same as in the case of formula (I).
Preferable examples of the compound corresponding to the formula (I-1-1) include LiNi _0.5 Mn _1.5 O ₄ and LiNi _0.4975 Mn _1.4925 B _0.01 O ₄ .
Hereinafter, the description of the formula (I) also applies to the formula (I-1-1).

X in the formula (I) will be described.
x means the amount of Li substituting with at least a part selected from the group consisting of Ni, Mn and M ¹ .
In the formula (I), x is in the range of 0 ≦ x ≦ 0.2, but is preferably in the range of x ≦ 0.15. Further, 0.05 ≦ x may be satisfied.
That is, in the composite oxide of the present invention, at least a part selected from the group consisting of Ni, Mn and M ¹ may be substituted with Li. The theoretical value of the number of Li atoms (composition ratio) in the composition formula of the spinel structure lithium composite oxide used as the positive electrode active material of the lithium ion battery is 1, but the composite oxide of the present invention has an excess of the theoretical value. Li may be contained, and by reducing the amount of at least a part selected from the group consisting of Ni, Mn and M ^{1 by} an amount commensurate with this excess Li, Li is reduced from Ni, Mn and M ^1. You may take the structure substituted with at least one part selected from the group which consists of.

Further, as shown in the formula (I-1), 75% (percentage of the number of atoms) of Li atoms present in excess replaces Mn and / or M ^1, and the remaining 25% (percentage of the number of atoms). Replacement with Ni is preferred. In such a case, the inventor has found that a lithium ion secondary battery with higher operating voltage, excellent cycle characteristics and rate characteristics, and higher energy density can be obtained.

  When the substitution amount (x) of Li increases, the charge / discharge capacity of the battery slightly decreases, but the cycle characteristics tend to improve. However, even if x is greater than 0.2, the cycle characteristics tend to be difficult to improve. Moreover, when the total amount of Li (1 + x) is less than 1.0, a heterogeneous phase that is an impurity is generated, and the charge / discharge performance of the battery tends to decrease.

M ¹ in the formula (I) will be described.
In the formula (I), M ¹ is at least one element selected from the group consisting of Co, Fe, Cr and Cu.
As described above, the composite oxide of the present invention may not contain M ¹ , but when M ¹ is contained, a preferable element as M ¹ is Co. In addition, as described above, M ¹ is preferably present by substituting Mn.

When the composite oxide of the present invention comprises M ^1, which a lithium ion secondary battery obtained by using as the positive electrode active material, easy to ensure a constant discharge capacity tends to maintain the cycle property. However, if the amount of M ¹ is too large, the discharge capacity of the lithium ion secondary battery may be reduced.
When the composite oxide of the present invention contains Co as M ¹ , the composition of the composite oxide of the present invention is, for example, LiNi _0.5 (Mn _1.5-y Co _y ) O ₄ , LiNi _0.4975 (Mn _1.4925-y Co _y ). _{Expressed as} B _0.01 O ₄ .

M ² in the formula (I) will be described.
In the formula (I), M ² is at least one element selected from the group consisting of B, P, Pb, Sb, Si, Ti, Mg, Al and V.
As described above, the composite oxide of the present invention may not contain M ² , but when M ² is contained, B is a preferable element as M ² .
Further, as shown in formula (I-1), 75% of M ² (percentage number of atoms) is substituted with Mn and / or M ^1, 25% of the remainder (percentage number of atoms) is substituted for Ni It is preferable. In such a case, the inventor has found that a lithium ion secondary battery with higher operating voltage, excellent cycle characteristics and rate characteristics, and higher energy density can be obtained.

In the formula (I), p means a substitution amount of M ² and at least one selected from the group consisting of Ni, Mn and M ¹ . When M ² means a plurality of kinds of elements, it means the total substitution amount.
P which is the substitution amount (atomic ratio) of M ² is 0 ≦ p ≦ 1.0. Further, p is preferably 0.0005 or more, and more preferably 0.005 or more. Further, p is more preferably 0.05 or less. When p is in such a range, the particles constituting the obtained lithium composite oxide tend to grow easily. If p is too low, crystal growth tends to be weakened. Conversely, if p is too high, the discharge capacity of the battery when used as a positive electrode active material tends to decrease.
When the composite oxide of the present invention contains B as M ² , the composition of the composite oxide of the present invention is, for example, LiNi _0.4975 Mn _1.4925 B _0.01 O ₄ , LiNi _0.4975 (Mn _1.4925-y Co _y ) B _0.01 O _4. It is expressed.

In the formula (I), a represents the amount of O (oxygen) deficiency.
In the formula (I), a satisfies 0 ≦ a ≦ 1.0 and is preferably a = 0.
When the amount of oxygen deficiency is small (that is, when a is small), the capacity of 4.5 V or less in the charge / discharge test tends to be small. When the amount of oxygen vacancies is small, the crystal structure is stabilized and the cycle characteristics tend to be improved.

Next, the particle diameter will be described.
The composite oxide of the present invention preferably contains secondary particles as a constituent element, and more preferably an aggregate of secondary particles.
Here, it is an aggregate of crystallites (single crystal part), and the smallest particle unit that can be visually recognized by SEM observation at a magnification of 10,000 times behaves as a single particle in handling, in which primary particles are sintered and primary particles are sintered. Particles are defined as secondary particles.

  FIG. 1 is an enlarged photograph obtained by observing one embodiment of the composite oxide of the present invention using an SEM. FIG. 1 (a) is 200 times, FIG. 1 (b) is 1000 times, and FIG. Is a photograph obtained by enlarging 5000 times, and FIG. FIG. 1 (a) is generally considered to indicate an aspect of secondary particles in the composite oxide of the present invention. From FIG. 1 (b) and FIG. 1 (c), it is understood that the composite oxide of the present invention is a secondary particle in which primary particles are aggregated. From FIG. 1 (d), primary particles in the composite oxide of the present invention can be observed.

  FIG. 2 is an enlarged photograph obtained by observing another embodiment of the composite oxide of the present invention using an SEM. FIG. 2 (a) is 200 times, FIG. 2 (b) is 1000 times, FIG. c) is a photograph obtained by magnifying to 5,000 times, and FIG. 2 (a) and 2 (b) are generally considered to indicate the aspect of the secondary particles in the composite oxide of the present invention. From FIG. 2C, it is understood that the composite oxide of the present invention is a secondary particle in which primary particles are aggregated. From FIG. 2 (d), primary particles in the composite oxide of the present invention can be observed.

The composite oxide of the present invention has an average secondary particle size (average secondary particle size) of 3 to 29 μm, preferably 4 to 25 μm, more preferably 6 to 15 μm, and more preferably 8 to More preferably, it is 10 μm. Lithium having an average secondary particle size in such a range, a specific composition as described above, and a crystal structure as described below further increases the operating voltage and has better cycle characteristics and rate characteristics. The inventor has found that an ion secondary battery can be obtained.
Here, the secondary particles are obtained by sintering the primary particles as described above.
Moreover, an average secondary particle diameter shall mean the median diameter of a secondary particle.

Moreover, an average secondary particle diameter shall mean the value measured with the following method.
First, the composite oxide of the present invention is added to an aqueous sodium hexametaphosphate solution at room temperature in the atmosphere, and is dispersed by ultrasonic dispersion and stirring to form a slurry. Next, after adjusting this slurry to have a transmittance of 80 to 90%, an integrated particle size distribution (volume basis) is measured using a laser diffraction / scattering particle size distribution measuring device. The median diameter obtained from the particle size distribution measured in this way is defined as the average secondary particle diameter in the composite oxide of the present invention.

The composite oxide of the present invention preferably has an average primary particle size (average primary particle size) of 0.05 to 10 μm, more preferably 0.05 to 7 μm, and 0.1 to 4 μm. More preferably it is.
Here, the average primary particle diameter means the median diameter of the primary particles (aggregates of crystallites) described above.
The average primary particle size was photographed with a scanning electron microscope (SEM) at a magnification of 10000 times using a scanning electron microscope (SEM), 500 pieces were arbitrarily selected from the obtained photographs, and calipers were used. Each projected area equivalent circle diameter is measured to determine an integrated particle size distribution (volume basis), and an average particle diameter (median diameter) is calculated therefrom to obtain a calculated value.

Composite oxides of the present invention is preferably has a BET specific surface area of 0.1 to 10 m ² / g, more preferably 0.4~8m ² / g, is 0.5~6m ² / g More preferably.
If the specific surface area is too low, the dissolution amount of Mn is reduced, but the contact between the positive electrode active material and the conductive agent and the contact between the positive electrode active material and the electrolytic solution in the positive electrode are insufficient, and the rate characteristics may be deteriorated. On the other hand, if it is too high, the tap density decreases, the discharge capacity per volume decreases, and the cycle characteristics may deteriorate due to an increase in the dissolved amount of Mn.

The BET specific surface area is a value obtained by BET one-point measurement by a continuous flow method. Specifically, both the adsorption gas and the carrier gas to be used are a mixed gas of nitrogen, air and helium. The sample is degassed by heating with the mixed gas at a temperature of 450 ° C. or lower, and then cooled with liquid nitrogen. The mixed gas is adsorbed, the adsorbed nitrogen gas is desorbed by returning to room temperature, detected by a thermal conductivity detector, the amount is obtained as a desorption peak, and the specific surface area of the sample is calculated. Such a BET specific surface area can be measured using a known BET powder specific surface area measuring device.
In the present invention, the simple description of “specific surface area” means “BET specific surface area”.

Next, the crystal structure will be described.
The crystal structure of the composite oxide of the present invention is a spinel, and at least a portion of the space group P4 ₃ 32.

In the crystal structure of the composite oxide of the present invention, at least a part of the space groups is preferably P4 ₃ 32 and all the space groups are preferably P4 ₃ 32. Crystal structure is a spinel, and at least a portion of the space group P4 ₃ 32, with an average secondary particle diameter in a specific range as described above, further lithium complex comprising a specific composition as described above The inventors have found that when an oxide is used, a lithium ion secondary battery having higher operating voltage and better cycle characteristics and rate characteristics can be obtained.

  In addition, it can confirm that a crystal structure is a spinel type by using the complex oxide of this invention for a powder X-ray-diffraction measurement.

The crystal structure of the composite oxide of the present invention may include a portion which is another space group because at least a part of the space group is P4 ₃ 32. For example, the composite oxide of the present invention may include a portion where the space group of the crystal structure is P4 ₃ 32 and a portion where Fd-3m.
Whether or not the space group contains P4 ₃ 32 in part of the crystal structure of the composite oxide of the present invention is measured by the following method.
A small sample is sampled on a slide glass and pressed with a spatula or the like to the extent that it does not fall even if tilted, and a measurement sample is prepared. Then, the created measurement sample is measured using a Raman spectroscope (for example, a micro laser Raman spectroscope: Lab RAM ARAMIS manufactured by HORIBA). The measurement conditions here are laser wavelength: 532 nm, D2 filter, 50 × lens, measurement time: 10 seconds, number of integrations: 20 times, measurement range: 100 to 1000 cm ⁻¹ . Further, as the determination of the crystal structure, in the case of Fd-3m only, in the region of Raman shift ^{100~1000cm -1, 155~165cm -1, 390~410cm -1} , 490~510cm -1, 580~610cm -1 , 630～650Cm to indicate five peaks having a peak top in the vicinity of ^{-1, 155~165cm -1} in the case including a portion ^{_{P4 3 32, 215~225cm -1, 235~245cm}} -1, 320 ^{~330cm -1, 370~390cm -1, 390~410cm -1} , 490~510cm -1, 510~535cm -1, 585~600cm -1, 605~620cm -1, 630~650cm -1 to 11 pieces of Shows the peak. Based on this difference, it is determined whether the space group of the crystal structure includes a part of P4 ₃ 32 or not.

In addition, when the composite oxide of the present invention includes a portion in which the space group of the crystal structure is P4 ₃ 32 and a portion that is Fd-3m, the mass ratio thereof is a portion that is P4 ₃ 32: Fd-3m The portion is preferably 1:99 to 99: 1, more preferably 50:50 to 99: 1, more preferably 70:30 to 99: 1, and 80:20 to 99. More preferably, the ratio is 1. These ratios can be determined by performing Raman analysis or electron diffraction analysis.

  In the present invention,

Is denoted as “space group Fd-3m” or simply Fd-3m.

  A lithium ion secondary battery using the composite oxide of the present invention as described above as at least a part of the positive electrode active material has a high operating voltage and excellent cycle characteristics and rate characteristics. These operating voltages, cycle characteristics, and rate characteristics will be described below.

The operating voltage will be described.
A lithium ion secondary battery using the composite oxide of the present invention as a positive electrode active material has a high operating voltage and a 5V class. Specifically, in a charge / discharge curve (capacity-voltage curve) obtained by conducting the following initial charge / discharge capacity test, both the charge voltage and the discharge voltage appear at 4.5 V or more. In such a case, it means that a 5V class operating voltage is provided.

The initial charge / discharge capacity test is as follows.
The composite oxide of the present invention is weighed in a proportion of 85% by mass, acetylene black is 7.5% by mass, and polyvinylidene fluoride is 7.5% by mass and dispersed in normal methylpyrrolidone to obtain a mixture. Then, the obtained mixture is applied on an Al foil so as to have a thickness of about 0.1 mm, vacuum-dried at about 110 ° C., and then punched out using a 14 mmφ punch to produce a positive electrode.
The obtained positive electrode was used as a test electrode, and this test electrode and a lithium metal foil (thickness 0.2 μm) were stacked and arranged in a coin-type battery case via a separator (trade name: Cell Guard). An electrolyte solution in which 1 mol / L LiPF ₆ is dissolved in a mixed solvent of 1: 1 ethylene carbonate and dimethyl carbonate is injected to prepare a test coin cell.
The initial charge / discharge capacity of the test coin cell thus created is measured. Specifically, the charge end voltage is set to 4.9 V, and constant current / constant voltage charging is performed at a current density of 0.14 mA / cm ² (equivalent to 0.2 C) (after the voltage reaches 4.9 V, 4. The positive electrode active material unit mass when a constant current discharge is performed at a current density of 0.14 mA / cm ² (equivalent to 0.2 C) with a discharge end voltage of 3.5 V. Per unit initial charge capacity (mAh / g) and initial discharge capacity (mAh / g) are measured. The charging is terminated when 10 hours have elapsed from the start of charging or when the current reaches 0.05C.
A charge / discharge curve (capacitance-voltage curve) is obtained by such a method.

Further, the initial charge capacity of a lithium ion secondary battery using the composite oxide of the present invention as the positive electrode active material may exceed the theoretical capacity of 147 mAh / g when evaluated by the above test method. This may be due to the decomposition of the electrolyte or the separator. Therefore, it is preferably 170 mAh / g or less, more preferably 165 mAh / g or less, and still more preferably 160 mAh / g or less.
The initial discharge capacity of a lithium ion secondary battery using the composite oxide of the present invention as the positive electrode active material can be 130 mAh / g or more. Further, it may be preferably 133 mAh / g or more, more preferably 135 mAh / g or more, and still more preferably 138 mAh / g or more.
Here, the initial charge capacity and the initial discharge capacity are determined by the initial charge / discharge capacity test.

The cycle characteristics will be described.
A lithium ion secondary battery using the composite oxide of the present invention as a positive electrode active material is excellent in cycle characteristics. Specifically, the cycle capacity maintenance rate obtained by conducting the following cycle characteristic test is high, and specifically, the cycle capacity maintenance rate can be 90% or more. Further, it may be preferably 91% or more, more preferably 93% or more, and still more preferably 94% or more.

The cycle characteristic test is as follows.
A test coin cell created by the same method as that for measuring the initial charge / discharge capacity is placed in a thermostatic chamber at room temperature (about 30 ° C.), and the charge potential 4 is measured in the same manner as the measurement of the initial charge / discharge capacity. The cycle of constant current / constant voltage charging and constant current discharging of 0.7 mA / cm ² (equivalent to 1 C) is performed 100 times under the condition of potential regulation up to. Obtained by the following equation.
Cycle capacity retention rate (%) = (100th discharge capacity / first discharge capacity) × 100

The rate characteristics will be described.
A lithium ion secondary battery using the composite oxide of the present invention as a positive electrode active material is excellent in rate characteristics. Specifically, the rate capacity maintenance rate obtained by performing the following rate characteristic test is high, and specifically, the rate capacity maintenance rate can be 70% or more. Further, it may be preferably 73% or more, more preferably 75% or more, and further preferably 80% or more.

The rate characteristic test is as follows.
The measurement of the initial charge and discharge capacity described above was performed at a constant current discharge of 0.14 mA / cm ^2, which was a constant current discharge of 7 mA / cm ^2, the other for were the same as the initial charge and discharge capacity of the test To measure the discharge capacity. Then, as in the following equation, to measure the discharge capacity when to the discharge capacity in the case of performing constant current discharge test at 0.14 mA / cm ^2, was constant current discharge test at 7 mA / cm ^2, The capacity maintenance rate is obtained by the following formula.
Rate capacity retention rate (%) = discharge capacity × 100 in the case of performing constant current discharge test at /0.14MA/cm ² (discharge capacity in the case of performing constant current discharge test at 7 mA / cm ²⁾

<Method for producing composite oxide of the present invention>
Next, the method for producing the composite oxide of the present invention will be described.
The method for producing the composite oxide of the present invention is not particularly limited. For example, the composite oxide of the present invention can be obtained by mixing a lithium source, a nickel source, a manganese source, a raw material containing the element M ¹ and a raw material containing the element M ² at a predetermined ratio and firing at a high temperature.

As described above, the method for producing the composite oxide of the present invention is not limited, but a lithium source, a nickel source, a manganese source, a raw material containing M ¹ and a raw material containing M ² are pulverized and mixed in a solvent and obtained. A precursor adjusting step for obtaining a precursor by drying the resulting slurry, and a firing step for firing the precursor at a firing temperature within a range of 600 to 1200 ° C. to obtain a fired body. It is preferable to manufacture by a manufacturing method.
Hereinafter, such a production method is also referred to as a production method of the present invention.
Hereinafter, the production method of the present invention will be described in detail.

<Precursor adjustment step>
The precursor adjustment process in the manufacturing method of this invention is demonstrated.
In the precursor preparation step, first, a lithium source, a nickel source, a manganese source, a raw material containing M ¹ and a raw material containing M ² are contained in a solvent.

As the lithium source, an inorganic or organic compound containing a lithium atom (that is, a lithium compound) can be used. For example, lithium hydroxide, lithium carbonate, lithium nitrate, or lithium acetate can be used. Among these, it is preferable to use lithium hydroxide and / or lithium carbonate. This is because generation of harmful gases can be suppressed.
Moreover, it is preferable that it is a solid raw material.

As the nickel source, an inorganic or organic compound containing nickel atoms (that is, a nickel compound) can be used. For example, nickel oxide, nickel hydroxide, nickel carbonate, nickel carbonate hydrate, or nickel oxyhydroxide can be used. Among these, it is preferable to use at least one selected from the group consisting of nickel oxide and nickel hydroxide as the nickel source. The reason is that it can be obtained at low cost as an industrial raw material.
Moreover, it is preferable that it is a solid raw material.

As the manganese source, an inorganic or organic compound containing a manganese atom (that is, a manganese compound) can be used. For example, manganese oxide, manganese carbonate, manganese carbonate hydrate, manganese hydroxide, manganese oxyhydroxide can be used. Among these, it is preferable to use manganese oxide, and it is more preferable to use MnO ₂ (electrolytic manganese dioxide · EMD) and / or Mn ₃ O ₄ . This is because a lithium ion secondary battery that can be obtained as an industrial raw material at low cost and has a higher cycle capacity retention rate tends to be obtained.
Moreover, it is preferable that it is a solid raw material.

As the raw material containing M ¹ , a compound containing at least one element selected from the group consisting of Co, Fe, Cr and Cu can be used. For example, cobalt oxide, iron oxide, chromium oxide, copper oxide, or the like can be used. Among these, a compound containing Co is preferably used, and cobalt oxide can be more preferably used. This is because it can be obtained as an industrial raw material, and replacement with Mn in the crystal structure is relatively easy to occur, and a lithium ion secondary battery having a higher cycle capacity maintenance rate tends to be obtained.
Moreover, it is preferable that it is a solid raw material.

As a raw material containing M ² , a compound containing at least one element selected from the group consisting of B, P, Pb, Sb, Si, Ti, Mg, Al and V can be used. The element M ² is preferably B and / or V.
For example, when M ² is B, boric acid (H ₃ BO ₃ ) or diboric acid triborate (B ₂ O ₃ ) can be used as a raw material containing boron, and boric acid (H ₃ BO ₃ ). Is preferably used. This is because it can be obtained at low cost as an industrial raw material. When M ² is B, the sinterability at the time of sintering at 600 to 1200 ° C. increases, the particle diameter grows, and contributes to the improvement of the capacity retention rate of the obtained lithium ion secondary battery, The inventor estimates.
As a raw material containing M ² , P ₂ O ₅ , PbO, Sb ₂ O ₃ , SiO ₂ , TiO ₂ , MgO, Al ₂ O ₃ and V ₂ O ₅ can be used.
Moreover, it is preferable that it is a solid raw material.

In the precursor adjusting step, it is preferable to ^first contain a raw material containing a lithium source, a nickel source, a manganese source and M ¹ in a solvent. That is, it is preferable not to use a raw material containing M ² . In this case, the lithium composite oxide represented by the following formula (I-2) is obtained by the production method of the present invention.
Formula (I-2): Li _{(1 + x)} (Ni, Mn, M ¹ ) _(2-x) O _(4-a)

In the precursor adjustment step, the lithium source, nickel source, manganese source, raw material containing M ¹ and raw material containing M ² have an atomic number of Li: (Ni + Mn + M ¹ ): M ² = (1 + x): (2-xp): It is made to contain in a solvent so that it may become a ratio of p.
Here, the ranges of x and p are as described above in the description of the composite oxide of the present invention.

The solvent containing these raw materials is not particularly limited. For example, a conventionally known solvent such as water (pure water or the like), ethanol, acetone, or the like can be used, but water is preferably used.
Moreover, said each raw material is contained so that the solid content concentration in a solvent may become preferably 5-40 mass%, More preferably, it is 10-35 mass%, More preferably, it is 15-25 mass%. This is because the raw material in the solvent tends to be more uniformly dispersed.

In the precursor adjustment step, a lithium source, a nickel source, a manganese source, a raw material containing M ¹ and a raw material containing M ² are pulverized and mixed in a state of being contained in the solvent.
The method of pulverization and mixing is not particularly limited, but a wet pulverization method using a wet pulverizer using a bead mill or the like is preferable.
Further, this pulverization is preferably carried out until a slurry having an average particle size of 0.50 μm or less is obtained. When pulverized and mixed so that the average particle size is 0.50 μm or less, the solid content tends to be uniform in the slurry. The average particle size is preferably 0.10 μm or more, and more preferably 0.15 μm or more. This is because if the particle size is too small by pulverization, handling in the subsequent steps will be worsened. The average particle diameter is preferably 0.40 μm or less, and more preferably 0.30 μm or less.

  Here, the average particle size of the solid content in the slurry is determined by adding a sodium hexametaphosphate aqueous solution to the slurry at room temperature in the atmosphere, and dispersing the slurry by ultrasonic dispersion and stirring. The slurry has a transmittance of 30 to 60%. The integrated particle size distribution (volume basis) is measured using a laser diffraction / scattering particle size distribution measuring device, and the median diameter obtained from the particle size distribution is meant.

  In the precursor adjustment step, the slurry obtained as described above is dried to obtain a precursor. The slurry can be dried by a drying method using a band dryer or a shelf dryer, but is preferably spray drying. Spray drying is drying after spraying the slurry and making it into a mist or mist. By spray-drying under desired conditions, the particle size of the resulting precursor can be adjusted within a desired range.

The method of spray drying is not particularly limited. For example, by allowing slurry to flow into a two-fluid nozzle, the slurry component droplets are ejected from the nozzle tip, and the droplets are scattered by adjusting to an appropriate drying gas temperature and air flow rate. For example, a method of quickly drying the lysate. At this time, the slurry flow rate is preferably 0.5 to 700 kg / h, more preferably 1 to 600 kg / h, and still more preferably 3 to 550 kg / h.
The pulverized air pressure is preferably 0.05 to 0.5 MPa, more preferably 0.05 to 0.4 MPa, and still more preferably 0.1 to 0.4 MPa.
A treatment such as an appropriate temperature and air blowing is performed so as to quickly dry the scattered droplets, but it is preferable to introduce the dry gas in a downward flow from the upper part of the drying tower to the lower part.
Spray drying is preferably performed using a spray dryer. Moreover, the inlet temperature of the hot air for drying of a spray dryer becomes like this. Preferably it is 60-500 degreeC, More preferably, it is 150-450 degreeC, More preferably, it is 200-400 degreeC, Outlet temperature is preferably 80-250 degreeC, More preferably, it is 100- 200 degreeC, More preferably, you may be 100-160 degreeC.

  A precursor can be obtained by such a precursor adjustment step.

<Baking process>
Next, the firing step in the production method of the present invention will be described.
In the firing step, the precursor obtained by the precursor adjustment step as described above is fired at a firing temperature in the range of 600 to 1200 ° C.
Here, the firing method is not particularly limited as long as it is performed in an oxygen-containing atmosphere, and examples thereof include conventionally known methods such as a firing method using a tunnel furnace, a muffle furnace, a rotary kiln, and the like.

The firing temperature is preferably 650 ° C. or higher, more preferably 700 ° C. or higher, more preferably 750 ° C. or higher, and further preferably 770 ° C. or higher.
The firing temperature is preferably 890 ° C. or lower, more preferably 870 ° C. or lower, and further preferably 850 ° C. or lower. When the firing temperature is too high, oxygen is released from the crystal structure, and the battery performance tends to deteriorate.
The firing temperature is preferably 750 to 950 ° C.

More preferably, the firing temperature is 750 to 950 ° C., and the precursor does not contain M ² . In such a case, the present inventor has found that the operating voltage of the lithium ion secondary battery obtained using the composite oxide of the present invention becomes higher, and the cycle characteristics and rate characteristics become more excellent. The reason for this is not clear at this stage, but the present inventor estimates that the crystallinity is high and the average primary particle size is small.

When the precursor does not contain M ² as described above, the lithium composite oxide represented by the above formula (I-2) is obtained by the production method of the present invention.

  The time for firing the precursor at the firing temperature as described above is preferably 0.1 to 30 hours, more preferably 0.1 to 8 hours, more preferably 0.5 to 7 hours, More preferably, it is 0.5-4h, and it is further more preferable that it is 1.5-2.5h.

<Washing process>
Next, the cleaning process will be described.
The production method of the present invention preferably further includes a cleaning step described below.
The washing step is a step of washing the fired body and then heating at a heating temperature within a range of 100 to 750 ° C. to obtain a washed fired body. The present inventor has found that the operating voltage of the lithium ion secondary battery obtained using the composite oxide of the present invention is higher, and the cycle characteristics and rate characteristics are also superior.

  The cleaning of the fired body is preferably performed by immersing the fired body in water. Moreover, it is preferable to wash using hot water of about 60 ° C. For example, a sufficient amount of warm water of about 40 to 80 ° C. (for example, 2 to 3 times the mass of the fired body) is stored in a container, the fired body is added thereto, and the fired body is stirred for several hours. Can be washed. Further, for example, a sufficient amount of warm water of about 40 to 80 ° C. (for example, 5 to 10 times the mass of the fired body) can be washed over the fired body.

  After washing the fired body, it is preferable to dry it by holding it in an atmosphere of about 90 to 150 ° C. (preferably 110 to 130 ° C.) for about 1 to 10 hours (preferably 3 to 6 hours).

  Washing in this manner, and preferably heating after further drying.

  Here, the heating method is not particularly limited as long as it is performed in an oxygen-containing atmosphere. For example, a conventionally known method such as a heating method using a tunnel furnace, a muffle furnace, a rotary kiln, or the like can be given.

The heating temperature is preferably 100 ° C. or higher, more preferably 110 ° C. or higher, and further preferably 120 ° C. or higher.
The heating temperature is preferably 750 ° C. or less, more preferably 550 ° C. or less, and further preferably 400 ° C. or less.

  Moreover, it is preferable that the time heated at such a heating temperature is 0.5 to 10 h, more preferably 1 to 5 h, and further preferably 2 to 4.

  The composite oxide of the present invention can be obtained by such a production method of the present invention.

<Positive electrode active material of the present invention>
The positive electrode active material of the present invention will be described.
The positive electrode active material of the present invention is preferably a positive electrode active material for a non-aqueous electrolyte secondary battery using the composite oxide of the present invention, including the composite oxide of the present invention.
The positive electrode active material of the present invention preferably contains 80% by mass or more of the composite oxide of the present invention, more preferably 90% by mass or more, and substantially 100% by mass, that is, from the composite oxide of the present invention. More preferably, it becomes substantially.
In addition to the composite oxide of the present invention, the positive electrode active material of the present invention includes LTO (Li ₄ Ti ₅ O ₁₂ ), LMO (LiMn ₂ O ₄ ), LNO (LiNiO ₂ ), NMC (LiNi _1/3 Mn _{1). / 3} Co _1/3 O ₂ ), NCA (Li [NiAlCo] O ₂ ), a solid electrolyte described later, and other oxides not containing lithium. Moreover, what apply | coated the material represented to these to the surface of the complex oxide of this invention can also be used as a positive electrode active material of this invention.

<Positive electrode of the present invention and manufacturing method thereof>
The positive electrode of the present invention contains the positive electrode active material of the present invention. As long as the positive electrode of this invention uses the positive electrode active material of this invention, others may be the same aspects as a conventionally well-known positive electrode, for example. For example, what formed the layer which consists of what added the conductive support agent, the binder, etc. and mixed with the positive electrode active material of this invention as needed on a collector is mentioned. Specifically, an ink (slurry) is prepared by kneading a conductive additive, a binder, and an organic solvent such as N-methylpyrrolidone with the positive electrode active material of the present invention, and this ink is applied to the aluminum foil of the current collector. After applying and drying, it can be obtained by applying to a roller press. By applying to a roller press, the contact between the positive electrode active material and the current collector can be improved and the density of the positive electrode active material can be increased. Moreover, after fully mixing a conductive support agent and a binder with the positive electrode active material of this invention, it shape | molds in a sheet form with a roller press, and can obtain a positive electrode.
Here, examples of the conductive assistant include graphite (natural graphite, artificial graphite, expanded graphite, etc.), carbon black materials such as acetylene black and ketjen black.
Examples of the binder include polyvinylidene fluoride, polytetrafluoroethylene, ethylene propylene diene rubber, fluorine rubber, styrene butadiene, cellulose resin, and polyacrylic acid.
Further, the current collector is not limited, and for example, a conventionally known net shape, sheet shape, or film shape can be used.

<Secondary battery of the present invention>
The secondary battery of the present invention will be described.
The secondary battery of the present invention may have the same configuration as a normal lithium ion secondary battery except that the positive electrode of the present invention is used as a positive electrode, and may be a cylindrical type, a square type, a coin type, a button type, or the like. It's okay. That is, the positive electrode, the negative electrode, and the electrolytic solution (non-aqueous electrolyte or the like) are the main battery constituent elements, and these elements are enclosed in, for example, a battery can. Each of the positive electrode and the negative electrode acts as a lithium ion carrier, and the lithium ions are occluded in the negative electrode during charging and detached from the negative electrode during discharging.

A negative electrode is not specifically limited, For example, the aspect similar to a conventionally well-known negative electrode may be sufficient. For example, as the negative electrode active material, a lithium alloy represented by lithium or lithium-aluminum can be used, and graphite, pyrolytic carbons, cokes, glassy carbons, a fired body of an organic polymer compound, Carbon-based materials that can reversibly occlude and release lithium ions such as mesocarbon microbeads, carbon fibers, and activated carbon can also be used. For example, the same current collector as that of the positive electrode can be used.
When the negative electrode active material is lithium or a lithium alloy, the negative electrode can be used as it is, or can be manufactured by pressure bonding to a current collector. In addition, when the negative electrode active material is a carbon-based material (graphite, carbon black, etc.) capable of occluding and releasing lithium ions, a binder similar to that for the positive electrode is added to the negative electrode active material and mixed as necessary. Then, paste it into a paste using a solvent, apply the obtained negative electrode mixture-containing paste to a negative electrode current collector made of copper foil, etc., dry it to form a negative electrode mixture layer, and press-mold as necessary It can manufacture by passing through a process.

  As the electrolyte, for example, an organic electrolyte that is a non-aqueous electrolyte, a polymer electrolyte, a solid electrolyte, or the like can be used. Here, the organic electrolyte is a lithium salt added to a non-aqueous solvent, and the polymer electrolyte is a lithium salt added to a polymer compound.

Here, as the lithium salt, for example, LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiSCN, LiBr, LiI, Li ₂ SO ₄ , Li ₂ B ₁₀ Cl ₁₀ , Examples thereof include LiN (SO ₂ CF ₃ ) ₂ and LiN (SO ₂ C ₂ F ₅ ) ₂ . Among these, LiBF ₄ (lithium tetrafluoroborate) is less reactive with moisture present in the electrolyte, so it has better safety, cycle characteristics, rate characteristics (high rate discharge characteristics), initial characteristics, etc. It is easy to obtain an excellent lithium battery.
The concentration of the lithium salt in the organic electrolyte is preferably 0.1 to 3.0 mol / l, more preferably 0.2 to 2.0 mol / l. This is because the ionic conductivity of the non-aqueous electrolyte is increased, lithium salts are hardly precipitated in the non-aqueous electrolyte, and a lithium battery having high-performance battery performance can be obtained.

  As the non-aqueous solvent of the organic electrolyte, for example, a conventionally known one can be used, and a mixed solvent of ethylene carbonate, γ-butyrolactone, propylene carbonate and vinylene carbonate can be preferably used. Since ethylene carbonate, γ-butyrolactone and propylene carbonate have a high dielectric constant, they can reliably cause ionic conduction. Further, by containing vinylene carbonate in a non-aqueous solvent, ethylene carbonate, γ -Since the film | membrane derived from vinylene carbonate which can suppress reliably decomposition | disassembly of butyrolactone and propylene carbonate can be formed on a negative electrode, it can fully charge.

  The organic electrolyte may contain another organic solvent in addition to the lithium salt and the non-aqueous solvent.

When the electrolyte (non-aqueous electrolyte) is a polymer electrolyte, it contains a matrix polymer compound that is gelled with a plasticizer (non-aqueous electrolyte). Examples of the matrix polymer compound include polyethylene oxide and its crosslinked product. Fluorine resins such as ether resins, polymethacrylate resins, polyacrylate resins, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, etc. can be used alone or in combination.
Among these, from the viewpoint of oxidation-reduction stability, it is preferable to use a fluorine-based resin such as polyvinylidene fluoride or vinylidene fluoride-hexafluoropropylene copolymer.

The method for producing the polymer electrolyte is not particularly limited, and examples thereof include a method in which a polymer compound constituting a matrix, a lithium salt, and a solvent are mixed and heated to melt and dissolve. In addition, after dissolving a polymer compound, a lithium salt, and a solvent in an organic solvent for mixing, the organic solvent for mixing is evaporated, a polymerizable monomer, a lithium salt, and a solvent are mixed, and ultraviolet rays, electron beams, or molecules are mixed. Examples include a method of polymerizing a polymerizable monomer by irradiating a line and the like to obtain a polymer.
10-90 mass% is preferable and, as for the ratio of the solvent in a polymer electrolyte, 30-80 mass% is more preferable. With such a ratio, the electrical conductivity is high, the mechanical strength is strong, and the film is easily formed.

Solid electrolytes include, for example, oxide-based quenching glasses containing lithium ions, glass-based solid electrolytes such as sulfide-based oxysulfide-based superionic conductive glasses, and high concentrations of Li salts dissolved and dispersed in polymers such as polyethers. Examples include molecular solid electrolytes.
The polymer solid electrolyte may be in the form of a gel containing a solvent component.

The secondary battery of the present invention preferably has a separator that prevents direct contact between the positive electrode and the negative electrode.
A separator is not specifically limited, For example, a conventionally well-known thing can be used, for example, a woven fabric, a nonwoven fabric, a synthetic resin microporous film, etc. are mentioned. A synthetic resin microporous membrane is preferred, and among them, a polyolefin microporous membrane is preferred in terms of thickness, membrane strength, and membrane resistance. Specifically, it is a microporous membrane made of polyethylene and polypropylene, or a microporous membrane that combines these.
In the case where an organic electrolyte or a polymer electrolyte is used as the nonaqueous electrolyte, a separator is usually used. However, in the case of a solid electrolyte, the solid electrolyte may be used without using the separator.

  The manufacturing method of the secondary battery of this invention is not specifically limited, For example, it can manufacture by a conventionally well-known method. For example, it can be manufactured by injecting a non-aqueous electrolyte before or after laminating the positive electrode of the present invention and the negative electrode via a lithium battery separator, and finally sealing with an exterior material. . Examples of the exterior material include a metal-resin composite film having a configuration in which nickel-plated iron, stainless steel, aluminum, and metal foil are sandwiched between resin films.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples.

<Example 1>
LiOH.H ₂ O as a lithium source (manufactured by Kanto Chemical Co., LiOH purity: 57.8% by mass), NiO as a nickel source (manufactured by Kanto Chemical Co., nickel purity: 77.1% by mass, average particle size: 9.4 μm) ), Electrolytic manganese dioxide (γ-MnO ₂ , manufactured by Kanto Chemical Co., Inc., manganese purity: 60.78% by mass, average particle size: 28.0 μm) as a manganese source, and H ₃ BO ₃ (manufactured by Kanto Chemical Co., Ltd.) (Purity: 99.9% by mass) was prepared. And each raw material was weighed so that the molar ratio of Li: Ni: Mn: B would be 1.0000: 0.4975: 1.4925: 0.0100.

  Next, the above-mentioned weighed raw materials were mixed, and pure water was added thereto so that the solid content concentration was 33.3% by mass, and then a wet pulverizer (manufactured by Ashizawa Finetech Co., Ltd .: Star Mill Lab Star LMZ-). 06) to obtain a slurry. Here, it grind | pulverized until the average particle diameter (median diameter) of solid content in a slurry became 0.40 micrometer or less. In the pulverization, a 600 ml vessel was used.

  In addition, the average particle diameter (median diameter) of the solid content in the slurry was determined using a laser diffraction / scattering particle size distribution analyzer (Horiba, Ltd .: LA-950v2). Specifically, an aqueous sodium hexametaphosphate solution is added to the slurry at room temperature in the atmosphere, and the mixture is dispersed by ultrasonic dispersion and stirring, adjusted to have a transmittance of 87.5 to 88.5%, and then integrated particle size distribution. It was determined by measuring (volume basis).

Next, after adding pure water to the pulverized slurry and adjusting the solid content concentration to 20% by mass, spray drying is performed using a nozzle type spray dryer (Okawara Kakoki Co., Ltd .: L-8 type spray dryer). It was. Here, air was used as the drying gas. Moreover, it adjusted so that cyclone differential pressure might be set to 0.7-0.8 kPa, and the inlet temperature of the dry gas was adjusted to 220 degreeC. The slurry flow rate was 3 kg / h, and the atomization air pressure was 0.1 MPa.
By performing such spray drying, a particulate precursor was obtained.

  Next, the obtained precursor was fired in air at 850 ° C. for 6 hours, and further fired in air at 700 ° C. for 20 hours to obtain a fired body.

  The obtained fired body is designated as composite oxide [1].

About the obtained complex oxide [1], the average secondary particle diameter (median diameter) was determined using a laser diffraction / scattering particle size distribution analyzer (Horiba, Ltd .: LA-950v2). The measuring method is as described above.
The measurement results are shown in Table 1.

About the obtained complex oxide [1], the average primary particle diameter was measured using a scanning electron microscope (SEM). The measuring method is as described above.
The measurement results are shown in Table 1.

The obtained composite oxide [1] was subjected to powder X-ray diffraction measurement using Cu—Kα rays and Si as an internal standard. For powder X-ray diffraction measurement, a sample horizontal multipurpose X-ray diffractometer ("UltimaIV" manufactured by Rigaku Corporation) was used.
As a result, it was confirmed that the composite oxide [1] was a spinel type.
Table 1 shows the lattice constants determined by powder X-ray diffraction measurement.

About the obtained complex oxide [1], the BET specific surface area was measured using the fully automatic BET specific surface area measuring apparatus (The product made by Mountech: Macsorb HM model-1220). The measurement conditions are as described above.
The measurement results are shown in Table 1.

The obtained complex oxide [1] was subjected to Raman spectroscopic measurement. The specific contents are as described above.
As a result, it was found that the complex oxide [1] was a mixture of a portion having a space group of P4 ₃ 32 and a portion having Fd-3m. Moreover, it was thought that the part whose space group is P4 ₃ 32 is about 90 mass%.

<Measurement of initial charge / discharge capacity>
The composite oxide [1] was weighed in a proportion of 85 mass%, acetylene black was 7.5 mass%, and polyvinylidene fluoride was 7.5 mass%, and dispersed in normal methylpyrrolidone to obtain a mixture. Then, the obtained mixture was applied on an Al foil so as to have a thickness of about 0.1 mm, vacuum-dried at about 110 ° C., and then punched using a 14 mmφ punch to produce a positive electrode.
The obtained positive electrode was used as a test electrode, and this test electrode and a lithium metal foil (thickness 0.2 μm) were stacked and arranged in a coin-type battery case via a separator (trade name: Cell Guard). An electrolytic solution in which 1 mol / L LiPF ₆ was dissolved in a mixed solvent of 1: 1 ethylene carbonate and dimethyl carbonate was injected to prepare a test coin cell.
The initial charge / discharge capacity of the test coin cell thus prepared was measured. Specifically, the charge end voltage is set to 4.9 V, and constant current / constant voltage charging is performed at a current density of 0.14 mA / cm ² (equivalent to 0.2 C) (after the voltage reaches 4.9 V, 4. The positive electrode active material unit mass when a constant current discharge is performed at a current density of 0.14 mA / cm ² (equivalent to 0.2 C) with a discharge end voltage of 3.5 V. Per unit initial charge capacity (mAh / g) and initial discharge capacity (mAh / g) are measured. The charging was terminated when 10 hours passed from the start of charging or when the current reached 0.05C.
The measurement results are shown in Table 1.
Moreover, the obtained charging / discharging curve (capacitance-voltage curve) is shown in FIG.

<4V capacity>
From the charge / discharge curve obtained by the above charge / discharge capacity measurement, the discharge capacity in the range of 3.5 to 4.5V was read and set to 4V capacity.
The measurement results are shown in Table 1.

<Rate characteristics>
The measurement of the initial charge and discharge capacity described above was performed at a constant current discharge of 0.14 mA / cm ^2, which was a constant current discharge of 7 mA / cm ^2, the other for were the same as the initial charge and discharge capacity of the test The discharge capacity was measured. Then, as in the following equation, to measure the discharge capacity when to the discharge capacity in the case of performing constant current discharge test at 0.14 mA / cm ^2, was constant current discharge test at 7 mA / cm ^2, The capacity retention rate was determined by the following formula.
Rate capacity retention rate (%) = discharge capacity × 100 in the case of performing constant current discharge test at /0.14MA/cm ² (discharge capacity in the case of performing constant current discharge test at 7 mA / cm ²⁾
The measurement results are shown in Table 1.

<Measurement of 100 cycle capacity maintenance ratio>
A test coin cell created by the same method as that for measuring the initial charge / discharge capacity is placed in a thermostatic chamber at room temperature (about 30 ° C.), and the charge potential 4 is measured in the same manner as the measurement of the initial charge / discharge capacity. The cycle of constant current / constant voltage charging and constant current discharging of 0.7 mA / cm ² (equivalent to 1 C) is performed 100 times under the condition of potential regulation up to. Obtained by the formula.
Cycle capacity retention rate (%) = (100th discharge capacity / first discharge capacity) × 100
The measurement results are shown in Table 1.

<Example 2>
A fired body was obtained in the same manner as in Example 1. The obtained fired body was added to pure water, heated to 60 ° C., stirred and held for 1 hour, washed, and then filtered. Here, the mass ratio of the fired body to pure water was set to 1: 2.5.
And operation which wash | cleans the wet cake obtained by filtering again by the same method was performed repeatedly until the electrical conductivity of a filtrate became 150 mS / m or less.
Thereafter, the wet cake was dried at 120 ° C. for 0.5 hour to obtain a dried product.

  Next, the obtained dried body was heated in air at 400 ° C. for 2 hours to obtain a washed fired body.

  The washed fired body obtained here is referred to as composite oxide [2].

For the obtained composite oxide [2], the secondary particle diameter, primary particle diameter, lattice constant, BET specific surface area, space group were obtained in the same manner as in Example 1 for the composite oxide [1]. The initial charge / discharge capacity, 4V capacity, rate capacity maintenance rate and cycle capacity maintenance rate were measured.
The measurement results are shown in Table 1.
Moreover, the obtained charging / discharging curve (capacitance-voltage curve) is shown in FIG.
Note that the composite oxide [2] was confirmed to be a spinel type by powder X-ray diffraction measurement.
Moreover, it turned out that complex oxide [2] is a mixture of the part whose space group is P4 ₃ 32, and the part which is Fd-3m. Moreover, it was thought that the part whose space group is P4 ₃ 32 is about 90 mass%.

<Example 3>
In Example 1, a lithium source (LiOH.H ₂ O), a nickel source (NiO), a manganese source (electrolytic manganese dioxide), and a boron source (H ₃ BO ₃ ) were used. In Example 3, a boron source was used. First, the lithium source, the nickel source, and the manganese source were weighed so that the molar ratio of Li: Ni: Mn was 1.0: 0.5: 1.5.
All the subsequent operations were performed in the same manner as in Example 1, and the same measurement was performed.

  Let the fired body obtained here be a composite oxide [3].

For the obtained composite oxide [3], the secondary particle size, primary particle size, lattice constant, BET specific surface area, space group in the same manner as in Example 1 for the composite oxide [1]. The initial charge / discharge capacity, 4V capacity, rate capacity maintenance rate and cycle capacity maintenance rate were measured.
The measurement results are shown in Table 1.
Moreover, the obtained charging / discharging curve (capacitance-voltage curve) is shown in FIG.
Note that the composite oxide [3] was confirmed to be a spinel type by powder X-ray diffraction measurement.
The composite oxide [3] was found to be a mixture of the subspace group is P4 ₃ 32, a portion that is Fd-3m. Moreover, it was thought that the part whose space group is P4 ₃ 32 is about 90 mass%.

<Example 4>
In Example 2, a lithium source (LiOH.H ₂ O), a nickel source (NiO), a manganese source (electrolytic manganese dioxide), and a boron source (H ₃ BO ₃ ) were used. In Example 4, a boron source was used. First, the lithium source, the nickel source, and the manganese source were weighed so that the molar ratio of Li: Ni: Mn was 1.0: 0.5: 1.5.
The subsequent operations were the same as in Example 2 and the same measurement was performed.

  The washed fired body obtained here is referred to as composite oxide [4].

For the obtained composite oxide [4], the secondary particle diameter, primary particle diameter, lattice constant, BET specific surface area, space group in the same manner as in Example 1 for the composite oxide [1]. The initial charge / discharge capacity, 4V capacity, rate capacity maintenance rate and cycle capacity maintenance rate were measured.
The measurement results are shown in Table 1.
Moreover, the obtained charging / discharging curve (capacitance-voltage curve) is shown in FIG.
Note that the composite oxide [4] was confirmed to be a spinel type by powder X-ray diffraction measurement.
The composite oxide [4] was found to be a mixture of the subspace group is P4 ₃ 32, a portion that is Fd-3m. Moreover, it was thought that the part whose space group is P4 ₃ 32 is about 90 mass%.

<Comparative Example 1>
NiSO ₄ .6H ₂ O (manufactured by Kanto Chemical Co., Inc., nickel purity: 22.3% by mass) was prepared as a nickel source, and dissolved in pure water to dissolve 20% by mass of NiSO ₄ .6H ₂ O. An aqueous nickel sulfate solution was prepared.
Next, MnSO ₄ · 5H ₂ O (manufactured by Kanto Chemical Co., Inc., manganese purity: 22.8 wt%) as the manganese source is prepared, by dissolving it in pure water, MnSO ₄ · 5H ₂ O 20 mass % Aqueous manganese sulfate solution was prepared.
Next, ammonium sulfate (NH ₄ ) ₂ SO ₄ (manufactured by Kanto Chemical Co., Inc., reagent purity 99.9%) was prepared and dissolved in pure water to 40 mass% to prepare an aqueous ammonium sulfate solution.

  Next, the nickel sulfate aqueous solution and the manganese sulfate aqueous solution prepared as described above are mixed so that the molar ratio of nickel to manganese is 1: 3, and then 10% by volume with respect to the obtained solution. Thus, an aqueous ammonium sulfate solution was added to obtain a mixed solution.

Next, a pure water having the same volume as the obtained mixed solution is put in a reaction vessel and kept at 50 ° C., and a 30% by mass aqueous sodium hydroxide solution is added so that the pH is between 11.5 and 12.0. The alkali solution adjusted to was obtained. Then, the mixed solution was added to the obtained alkaline solution at a flow rate of 10 cm ³ / min. Here, when adding the mixed solution to the alkaline solution, the pH was adjusted to 11.0 to 11.5 by appropriately adding a 30% by mass aqueous sodium hydroxide solution.
After the total amount of the mixed solution is added to the alkaline solution, it is left to stand for 1 hour in a state kept at 50 ° C., and then aged to form a solution containing a nickel manganese composite (hereinafter referred to as “composite solution [1]”). Obtained.

Next, the composite solution [1] was separated by filtration to obtain a wet cake. The obtained wet cake was added to pure water, heated to 50 ° C., stirred and held for 1 hour, washed, and then filtered.
And operation which wash | cleans the wet cake obtained by filtering again by the same method was performed repeatedly until the electrical conductivity of a filtrate became 100 mS / m or less.

Next, pure water is added to the washed wet cake so as to have a solid content concentration of 15 wt% to form a slurry, and LiOH · H ₂ O (produced by Kanto Chemical Co., LiOH purity: 57.8) is used as a lithium source there. (Mass%) was added to obtain a lithium nickel manganese mixed slurry. Here, the lithium source was added so that the ratio of the molar amount of lithium to the total molar amount of nickel and manganese was 1: 2.

Next, the obtained lithium nickel manganese mixed slurry was spray-dried in the same manner as in Example 1, and the obtained precursor was fired to obtain a fired body.
Let the obtained baked body be complex oxide [11].

For the obtained composite oxide [11], the secondary particle diameter, primary particle diameter, lattice constant, BET specific surface area, space group were obtained in the same manner as in Example 1 for the composite oxide [1]. The initial charge / discharge capacity, 4V capacity, rate capacity maintenance rate and cycle capacity maintenance rate were measured.
The measurement results are shown in Table 1.
The composite oxide [11] was confirmed to be a spinel type by powder X-ray diffraction measurement.
In addition, it was found that the complex oxide [11] has a space group of Fd-3m.

Claims (4)

A precursor preparation step in which a lithium source, a nickel source, a manganese source, a raw material containing M ¹ and a raw material containing M ² are pulverized and mixed in a solvent, and the resulting slurry is dried to obtain a precursor;
A firing step of firing the precursor at a firing temperature within a range of 750 to 950 ° C. to obtain a fired body;
The fired body is washed in warm water at 40 to 80 ° C., dried at 90 to 150 ° C. for 1 to 10 hours, and heated at a heating temperature within a range of 550 ° C. or less to obtain the washed fired body. A cleaning process to obtain;
With
It has a composition represented by the following formula (I) including Ni and Mn, an average secondary particle diameter of 3 to 29 μm, a crystal structure is a spinel type, and at least a part of the space group is P4. _A method for producing a lithium composite oxide, wherein a lithium composite oxide of 32 is obtained.
Formula (I): Li _{(1 + x)} (Ni, Mn, M ¹ ) _(2-xp) M ² _p O _(4-a)
In the formula (I), M ¹ is at least one element selected from the group consisting of Co, Fe, Cr and Cu, and M ² is selected from B, P, Pb, Sb, Si, Ti, Mg, Al and V. At least one element selected from the group consisting of 0 ≦ x ≦ 0.2, 0 ≦ p ≦ 1.0, and 0 ≦ a ≦ 1.0.   A method for producing a positive electrode active material, wherein a lithium composite oxide is obtained by the production method according to claim 1 and then a positive electrode active material is obtained using the lithium composite oxide.   The manufacturing method of the positive electrode for lithium ion secondary batteries which obtains the positive electrode for lithium ion secondary batteries using it after obtaining a positive electrode active material with the manufacturing method of Claim 2.   Lithium ion which obtains a lithium ion secondary battery using the positive electrode for lithium ion secondary batteries, a negative electrode, and electrolyte solution after obtaining the positive electrode for lithium ion secondary batteries by the manufacturing method of Claim 3 A method for manufacturing a secondary battery.