JP5872279B2 - Spinel-type lithium-manganese composite oxide - Google Patents

Description

  The present invention relates to a lithium-manganese composite oxide that can be used as a positive electrode active material having excellent cycle characteristics, and a lithium ion secondary battery using the same as a positive electrode active material.

Examples of the positive electrode active material for a lithium ion battery include lithium cobaltate, lithium nickelate, and lithium manganate.
Among these, lithium cobaltate has the problem that the raw material cobalt is expensive and the effective storage amount is only about 50% of the theoretical amount. In addition, lithium nickelate is attracting attention because it is inexpensive and has an effective storage amount of about 1.4 times that of lithium cobaltate, but it is difficult to synthesize and has a problem with safety.
In contrast, lithium manganate is superior in that the effective amount of electricity stored is slightly inferior to lithium cobaltate, but the raw material manganese is inexpensive, and the storage stability and safety are equivalent to lithium cobaltate.

A positive electrode for a lithium ion battery is a positive electrode active material as described above, and is mixed with an organic solvent together with a carbon-based conductive agent such as graphite and a binder to obtain a paste mixture. It is manufactured by applying a uniform thickness on an aluminum foil of ˜20 μm and drying, and then compressing with a press to increase the density of the mixture and make the thickness of the electrode uniform.
This positive electrode is loaded into a battery container together with a negative electrode, a separator, etc. to form a battery. In order to improve battery performance such as charge capacity or discharge capacity, as much positive electrode active material as possible should be contained in a constant volume battery. Filling is preferred. For this purpose, the battery performance is improved by increasing the amount of the positive electrode active material in the mixture, but the amount of the positive electrode active material that can be blended in the mixture also has an upper limit. Therefore, it is preferable to increase the packing density by using as fine a fine-particle positive electrode active material as possible and increase the weight of the positive electrode active material filled per unit volume because a battery having a high discharge capacity can be obtained. That is, as the positive electrode active material, the discharge capacity per unit weight and the discharge capacity per unit volume (discharge capacity per unit weight × packing density of the particulate positive electrode active material) are also important factors.

However, the fine particles of lithium manganate conventionally used as the positive electrode active material have a small packing density when compared with the fine particles of lithium cobaltate having the same particle diameter. Therefore, although the discharge capacity per weight can be expected to be about 80% of lithium cobalt oxide, there is a problem that the discharge capacity per volume is low and is about 50 to 60%. Furthermore, in a battery using conventional lithium manganate as a positive electrode active material, there is a problem of deterioration in cycle characteristics in that the discharge capacity gradually decreases as charging and discharging are repeated.
In order to improve the performance of such lithium manganate, lithium-manganese composite oxides in which a third component such as boron (B) is added to lithium manganate have been proposed (see Patent Documents 1 to 5). ).

JP-A-4-237970 Japanese Patent Laid-Open No. 5-290846 JP-A-8-195200 Japanese Patent No. 38879983 Japanese Patent No. 4214564

  However, the discharge capacity per volume of the battery using the lithium-manganese composite oxide described in Patent Documents 1 to 5 as the positive electrode active material is not sufficiently high. In addition, the present inventor has a problem that the battery using the lithium-manganese composite oxide described in Patent Documents 1 to 5 has a low cycle characteristic when used at a temperature higher than room temperature. I found.

  The present invention solves the problems of the conventional lithium-manganese composite oxide as described above. That is, an object of the present invention is to provide a lithium-manganese composite oxide having a high discharge capacity per volume of a secondary battery obtained by using it as a positive electrode active material and excellent cycle characteristics when used at a high temperature. Another object of the present invention is to provide a lithium ion secondary battery using such a lithium-manganese composite oxide as a positive electrode active material. Furthermore, it aims at providing the manufacturing method of such a lithium manganese composite oxide.

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 (9).
(1) A spinel type lithium / manganese composite oxide represented by the following formula (I) obtained by firing a precursor,
In a DSC curve obtained by differential scanning calorimetry of the precursor, there is a peak in the range of 370 to 470 ° C., and the area of the peak is 30 mJ / mg or more, spinel type lithium manganese Complex oxide.
Formula (I): Li _{(x + y)} Mn _(2-ypq) M ¹ _p M ² _q O _(4-a)
However, in formula (I), 1.0 ≦ x <1.2, 0 <y ≦ 0.2, 1.0 <x + y ≦ 1.2, 0 ≦ p ≦ 1.0, 0 <q ≦ 1. 0, 0 ≦ a ≦ 1.0, M ¹ : at least one element selected from the group consisting of Ni, Co, Mg, Fe, Al and Cr, M ² : B, P, Pb, Sb and At least one element selected from the group consisting of V.
(2) The spinel-type lithium / manganese composite oxide according to (1) above, wherein the primary particle diameter is 0.1 to 5.0 μm.
(3) The spinel-type lithium-manganese composite oxide according to (1) or (2), wherein the secondary particle diameter is 2 to 30 μm.
(4) The spinel-type lithium / manganese composite oxide according to any one of (1) to (3), wherein the BET specific surface area is 0.1 to 2.0 m ² / g.
(5) The spinel type lithium-manganese composite oxide according to any one of (1) to (4), wherein the tap density is 1.5 to 2.5 g / ml.
(6) The spinel type lithium-manganese composite oxide according to any one of (1) to (5), wherein lithium hydroxide is used as a lithium source contained in the precursor.
(7) A positive electrode for a lithium ion secondary battery comprising the spinel type lithium / manganese composite oxide according to any one of (1) to (6) as a positive electrode active material.
(8) A lithium ion secondary battery comprising the positive electrode for a lithium ion secondary battery according to (7) above, a negative electrode, and an electrolytic solution.
(9) Lithium hydroxide, manganese compound, M ¹ so that the number of atoms is Li: Mn: M ¹ : M ² = (x + y) :( 2-ypq): p: q. The slurry containing the compound containing M ² and the compound containing M ² is dried to obtain a precursor, and then the precursor is fired at a temperature of 650 to 900 ° C., and any one of the above (1) to (6) A method for producing a spinel type lithium / manganese composite oxide, comprising obtaining the spinel type lithium / manganese composite oxide according to claim 1.

  According to the present invention, it is possible to provide a lithium-manganese composite oxide having a high discharge capacity per volume of a secondary battery obtained by using it as a positive electrode active material and excellent cycle characteristics when used at a high temperature. it can. In addition, a lithium ion secondary battery using such a lithium-manganese composite oxide as a positive electrode active material can be provided. Furthermore, the manufacturing method of such a lithium manganese composite oxide can be provided.

It is a figure which shows the differential scanning calorimetry result (DSC curve) in an Example. It is a figure which shows the differential scanning calorimetry result (DSC curve) in a comparative example.

The present invention will be described.
The present invention relates to a spinel-type lithium / manganese composite oxide represented by the following formula (I) obtained by firing a precursor, and a DSC curve obtained by differential scanning calorimetry of the precursor is 370 A spinel-type lithium-manganese composite oxide having a peak in a range of ˜470 ° C. and an area of the peak of 30 mJ / mg or more.
Formula (I): Li _{(x + y)} Mn _(2-ypq) M ¹ _p M ² _q O _(4-a)
However, in formula (I), 1.0 ≦ x <1.2, 0 <y ≦ 0.2, 1.0 <x + y ≦ 1.2, 0 ≦ p ≦ 1.0, 0 <q ≦ 1. 0, 0 ≦ a ≦ 1.0, M ¹ : at least one element selected from the group consisting of Ni, Co, Mg, Fe, Al and Cr, M ² : B, P, Pb, Sb and At least one element selected from the group consisting of V.
Such a spinel-type lithium / manganese composite oxide is hereinafter also referred to as “the composite oxide of the present invention”.

<Composite oxide of the present invention>
The composite oxide of the present invention is a spinel type lithium-manganese composite oxide represented by the formula (I). When the precursor is subjected to differential scanning calorimetry using a differential scanning calorimeter, a characteristic DSC curve is obtained. It is obtained.
Such a lithium-manganese composite oxide has a high tap density, and in addition, the initial discharge capacity of a secondary battery using this as a positive electrode active material is increased, and the high-temperature cycle characteristics of the secondary battery are particularly excellent. The inventor found out. When the tap density (g / ml) and the initial discharge capacity (mAh / g) are high, the discharge capacity per volume (mAh / ml), which is the product of these, becomes high. For example, when a secondary battery is used as a battery for an electric vehicle, it is important how much electricity can be stored in a limited space. Therefore, it is preferable that the discharge capacity per unit volume be higher. The secondary battery using the composite oxide of the present invention as the positive electrode active material has a high discharge capacity per unit volume and excellent high temperature cycle characteristics.

Further, in the composite oxide of the present invention, the precursor is calcined at a temperature of 650 to 900 ° C. in an atmosphere containing oxygen, whereby the spinel type lithium-manganese composite oxide represented by the formula (I) is obtained. When the differential scanning calorimeter is measured using a differential scanning calorimeter, there is a peak in the range of 370 to 470 ° C. of the obtained DSC curve, and the peak area is 30 mJ / mg or more. Is defined as
Specifically, the precursor includes a lithium compound, a manganese compound, a compound containing M ¹ and a compound containing M ² , and the atomic ratio of atoms contained in the precursor is Li: Mn: M ¹ : M. ² = (x + y) :( 2-ypq): p: q ratio. The precursor is preferably obtained by drying a slurry obtained by mixing a lithium compound, a manganese compound, a compound containing M ¹ and a compound containing M ² . The lithium compound is preferably lithium hydroxide. The precursor may not include “a compound containing M ¹ ” as described later. When p = 0, it means that “compound containing M ¹ ” is not included. In this case, the composite oxide of the present invention is Li _{(x + y)} Mn _(2-yq) M ² _q O _(4- It is expressed by the formula of _a) .

A DSC curve obtained by differential scanning calorimetry of such a precursor will be described.
In the present invention, the DSC curve is a graph in which the precursor is subjected to differential scanning calorimetry using a differential scanning calorimeter, and the results are plotted with the heat flow (Heat flow / mW) on the vertical axis and the temperature (° C.) on the horizontal axis. It means the curve shown above, specifically a curve as shown in FIG. FIG. 1 is a DSC curve in an embodiment of the present invention. Here, the differential scanning calorimetry is performed by filling a 50 mL platinum container with 20 mg of a sample and performing a heating rate of 10 ° C./min under air flow (30 mL / min).
When the differential scanning calorimetry of the precursor in the composite oxide of the present invention is performed, as shown in FIG. 1, a mountain-shaped peak indicating an exothermic reaction appears in the range of 370 to 470 ° C. Moreover, the area of this peak is 30 mJ / mg or more.
On the other hand, for example, in the case of a comparative example not included in the scope of the present invention, as shown in FIG. 2, even if a peak does not appear within the range of 370 to 470 ° C. in the DSC curve, The peak area is small and less than 30 mJ / mg.

Here, how to obtain the peak area will be described.
In the present invention, the area of the peak appearing in the range of 370 to 470 ° C. of the DSC curve obtained by differential scanning calorimetry of the precursor is obtained by connecting the point at 370 ° C. and the point at 470 ° C. on the DSC curve. The area surrounded by the straight line and the DSC curve is defined as the peak area. However, when the portion surrounded by the straight line and the DSC curve also exists below the straight line, the area of the lower portion of the straight line is not included, and only the upper portion is set as the peak area. Therefore, for example, when the DSC curve is valley-shaped and the point at 370 ° C. and the point at 470 ° C. on the DSC curve are connected by a straight line, the portion surrounded by the straight line and the DSC curve is the straight line. If it does not exist on the upper side of the line (when it exists only on the lower side of the straight line), the peak area becomes zero.

  The area of this peak is preferably 33 mJ / mg or more, and more preferably 36 mJ / mg or more. Further, the area of this peak is preferably 100 mJ / mg or less, more preferably 60 mJ / mg or less, and further preferably 50 mJ / mg or less.

Next, the composition of the composite oxide of the present invention will be described.
The composite oxide of the present invention is a spinel type lithium-manganese composite oxide represented by the formula (I): Li _{(x + y)} Mn _(2-ypq) M ¹ _p M ² _q O _(4-a) is there.

  In the composite oxide of the present invention, a part of Mn is substituted with Li. The theoretical value of the number of atoms (composition ratio) of Li in the composition formula of the lithium-manganese composite oxide having a spinel structure used as the positive electrode active material of the lithium ion battery is 1, but in the composite oxide of the present invention, Excess Li is contained. Therefore, by reducing the amount of Mn by an amount corresponding to a part or all of this excess Li, a structure is obtained in which at least a part of Li is substituted with Mn. That is, in the formula (I), the total amount of Li (x + y) is in the range of 1.0 <(x + y) ≦ 1.2, preferably 1.05 ≦ (x + y) ≦ 1.15. Here, x is in the range of 1.0 ≦ x <1.2, preferably 1.0 ≦ x ≦ 1.1, and more preferably x = 1.0. Further, the amount of Li substituted for Mn (y) is in the range of 0 <y ≦ 0.2, preferably 0.05 ≦ y ≦ 0.15. When the substitution amount (y) of Li increases, the charge / discharge capacity of the battery slightly decreases, but the cycle characteristics tend to improve. However, even if y is greater than 0.2 (ie, x + y is 1.2), the cycle characteristics tend not to be greatly improved. Further, when the total amount of Li (x + y) is 1.0 or less, a heterogeneous phase that is an impurity is generated, and the charge / discharge performance of the battery tends to be reduced.

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 3.2 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.

In the formula (I), the element M ¹ is at least one element selected from the group consisting of Ni, Co, Mg, Fe, Al, and Cr. Of these, a particularly preferred element is Al.

Further, p which is the substitution amount of M ¹ is 0 ≦ p ≦ 1, preferably 0.02 ≦ p ≦ 0.2. This is because when used as a positive electrode active material, a certain discharge capacity can be secured and high-temperature cycle characteristics can be maintained. If the amount of M ¹ substitution is excessive, the high-temperature cycle characteristics of the battery when used as the positive electrode active material are improved, but the discharge capacity of the battery may be reduced.
Note that p may be 0. In this case, the composite oxide of the present invention does not contain M ¹ . That is, the composite oxide of the present invention may have a composition represented by Li _{(x + y)} Mn _(2-yq) M ² _q O _(4-a) .

In the formula (I), the element M ² is at least one selected from the group consisting of B, P, Pb, Sb and V. Among these, particularly preferred elements are B and / or V. These elements M ² are considered to constitute a structure in which a part of Mn is substituted in the finally obtained lithium / manganese composite oxide.

Moreover, q which is the amount of M ² is 0 <q ≦ 1.0, preferably 0.0005 ≦ q ≦ 0.1, and more preferably 0.005 ≦ q ≦ 0.05. When q is in such a range, the obtained lithium / manganese composite oxide tends to grow easily. If q is too low, crystal growth tends to be weakened. Conversely, if q is too high, the discharge capacity of the battery when used as a positive electrode active material tends to decrease.

In the composite oxide of the present invention, these elements M ² are added to promote the formation and growth of spinel crystals. That is, it is considered that the oxide of the element M ² acts as a flux in the process of forming the spinel crystal, thereby promoting the generation and growth of the crystal, and further promoting the growth of the primary particles that are aggregates of crystallites. As a result, it is considered that a very dense lithium / manganese composite oxide having a small specific surface area can be obtained. 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 5000 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.

The composite oxide of the present invention preferably has a primary particle size of 0.1 to 5.0 μm, more preferably 0.2 to 4.5 μm, and 0.3 to 4.0 μm. More preferably,
Here, the primary particle diameter means the median diameter of the primary particles (aggregates of crystallites) described above.
The median diameter of the primary particle size was determined by taking a photograph of the composite oxide of the present invention at a magnification of 300,000 times using a scanning electron microscope, and arbitrarily selecting 100 pieces from the obtained photographs. The equivalent particle diameter is measured to determine the particle size distribution, and the average particle diameter (median diameter) is calculated from the particle size distribution.

The composite oxide of the present invention preferably has a secondary particle diameter of 2 to 30 μm, more preferably 11 to 20 μm, and still more preferably 14 to 17 μm.
Here, the secondary particles are obtained by sintering the primary particles as described above.
Further, the secondary particle diameter means the median diameter of the secondary particles.
Moreover, the secondary particle diameter shall mean the value measured by 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%, the particle size distribution is measured using a laser diffraction / scattering type particle size distribution measuring apparatus. The median diameter obtained from the particle size distribution measured in this way is defined as the secondary particle diameter in the composite oxide of the present invention.

Composite oxides of the present invention is preferably a BET specific surface area is of 0.1~2.0m ² / g, and more preferably of the 0.2~1.0m ² / g.
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 used are a mixed gas of nitrogen, air, and helium, and the powder sample is degassed by heating with the mixed gas at a temperature of 450 ° C. or lower, and then cooled with liquid nitrogen. Then, 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 is calculated as a specific surface area of the sample. 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”.

The composite oxide of the present invention has a high tap density. Specifically, the tap density of the composite oxide of the present invention is preferably 1.5 g to 2.5 g / ml. Further, it is preferably 1.8 g / ml or more, more preferably 1.9 g / ml or more, and further preferably 2.0 g / ml or more.
In addition, in this invention, 10 g of complex oxides of this invention are put into a 20 ml glass measuring cylinder, the volume after tapping 300 times is measured, and tap density is taken as the calculated value.

The initial discharge capacity of the secondary battery using the composite oxide of the present invention as the positive electrode active material is 90 mAh / g or more, preferably 100 mAh / g or more, more preferably 103 mAh / g or more, and even more preferably 105 mAh / g or more.
The capacity density, which is the product of the tap density (g / ml) and the initial discharge capacity (mAh / g), is 195 mAh / ml or more, preferably 200 mAh / ml or more, more preferably 205 mAh / ml or more, Preferably it may be 210 mAh / ml or more.
In the present invention, the initial discharge capacity (mAh / g) of the secondary battery is measured as follows.
First, a mixture of 75% by mass of the composite oxide of the present invention, 20% by mass of acetylene black, and 5% by mass of polytetrafluoroethylene powder was thoroughly mixed in a mortar. A sheet having a thickness of 0.1 mm is punched out using a 16 mmφ punch, and this is further vacuum dried at 110 ° C. to obtain a positive electrode.
Next, LiPF ₆ is added to a non-aqueous solvent obtained by mixing ethylene carbonate and diethyl carbonate so as to have a volume ratio of 1: 1 to obtain a non-aqueous electrolyte having a LiPF ₆ concentration of 1 mol / L. .
Next, the obtained positive electrode (test electrode) was placed in a stainless steel container, and further laminated with a polypropylene nonwoven fabric (lithium battery separator) and a metal lithium foil (counter electrode) having a thickness of 0.2 μm as a negative electrode. The non-aqueous electrolyte is sufficiently impregnated and then sealed with an upper part made of stainless steel to obtain a semi-open lithium battery.
The lithium battery thus obtained was subjected to constant current charging of 0.5 mA / cm ² (that is, a reaction for releasing lithium ions from the positive electrode) at an upper limit of 4.3 V, and 0.5 mA / cm ² ( An initial discharge capacity (mAh / g) per unit mass of the positive electrode active material when a constant current discharge (equivalent to 0.1 C) (that is, a reaction for occluding lithium ions in the positive electrode) is performed at a lower limit of 3.0 V is measured.
In the present invention, the value obtained by measuring in this way is defined as the initial discharge capacity.

Further, the cycle capacity maintenance rate at a high temperature of the secondary battery using the composite oxide of the present invention as the positive electrode active material is 88.0% or more, preferably 90.0% or more, more preferably 92.0% or more. Can be.
In the present invention, the cycle capacity retention rate (%) at a high temperature of the secondary battery is measured as follows.
A method similar to the above-described measurement of the initial discharge capacity, except that a sheet having a thickness of 0.1 mm is punched out with a 10 mmφ punch and vacuum-dried at 110 ° C. to form a positive electrode. A semi-open lithium battery is obtained.
Then, the obtained lithium battery was placed in a constant temperature bath of 55 ° C., and constant current charging at ^2.5 mA / cm ² was repeated at an upper limit of 4.3 V and a lower limit of 3.0 V, and the discharge capacity at the first cycle (initial discharge) The ratio (%) of the discharge capacity at the 100th cycle to the capacity) is defined as the cycle capacity maintenance rate at a high temperature.

The fine particles of the composite oxide of the present invention as described above have a tap density (g / ml) higher than that of the conventional lithium / manganese composite oxide when filled in a container having a constant volume. Therefore, when used as a positive electrode active material, the weight of the positive electrode active material that can be filled in a battery of a constant volume increases, and the discharge capacity per unit volume (mAh / ml) is larger than that of a conventional positive electrode active material. can do.
In addition, since the crystals are sufficiently grown, when this is used as the positive electrode active material, the amount of Mn dissolved in the electrolyte when it comes into contact with the electrolyte is smaller than that of the conventional lithium-manganese composite oxide. Even at high temperatures. As a result, it is considered that cycle characteristics at high temperatures can be improved.

  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.

<Method for producing composite oxide of the present invention>
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 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.
Moreover, as a preferable production method, for example, a precursor is prepared by preparing a slurry in which a lithium compound, a manganese compound, a compound containing M ¹ and a compound containing M ² are mixed in a solvent at a predetermined ratio, and drying the slurry. The method of baking this precursor at 650-900 degreeC after obtaining is mentioned.
This preferred production method (the preferred production method of the present invention) will be specifically described below.

In the preferred production method of the present invention, first, the atomic ratio of lithium, manganese, M ¹ and M ² represented by the above formula (I) (Li: Mn: M ¹ : M ² = (x + y) :( 2-y -Pq): A lithium source, a manganese source, a raw material containing M ^1, and a raw material containing M ² are charged into a solvent so that p: q).

  Here, 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. Further, it is more preferable to use lithium hydroxide as the lithium source because the initial discharge capacity per unit volume (mAh / ml) becomes higher and the high-temperature cycle characteristics tend to be improved.

  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 / or manganese carbonate. This is because it can be obtained at low cost as an industrial raw material.

As the raw material containing M ¹ , a compound containing at least one element selected from the group consisting of Ni, Co, Mg, Fe, Al, and Cr can be used. For example, basic nickel carbonate, basic cobalt carbonate, magnesia, hematite, alumina, chromium oxide, or the like can be used. Among these, alumina (Al ₂ O ₃ ) can be preferably used.

As the raw material containing M ² , a compound containing at least one element selected from the group consisting of B, P, Pb, Sb and V can be used. 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. The reason is that it can be obtained at low cost as an industrial raw material. As the raw material containing M ^2, or the like can be used _{P 2 O 5, PbO, Sb} 2 O 3 and V ₂ O _5.
When M ² is B, the sinterability at the time of sintering at 650 to 900 ° C. increases, the particle diameter grows, the tap surface density increases, and the specific surface area that causes Mn elution and side reactions decreases. The inventor presumes it.

The solvent into which these raw materials are added is not particularly limited, and 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, it is preferable that the solid content concentration of the slurry obtained by putting each said raw material into a solvent is 20-35 mass%, and it is more preferable that it is 30-35 mass%. This is because the solid content in the slurry becomes more uniform.

In the preferred production method of the present invention, each of the lithium source, the manganese source, the raw material containing M ¹ and the raw material containing M ² is previously dry pulverized (for example, pulverization using an air-flow impact crusher such as a ball mill or a jet mill). Or, it can be wet pulverized and then mixed in a solvent to obtain a slurry. After the raw materials are charged into the solvent as described above, the average particle size of the solids contained in the obtained slurry is It is preferable to grind and mix until it becomes 0.50 μm or less.
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. It is preferable to pulverize and mix all the raw materials (lithium source, manganese source, raw material containing M ¹ and raw material containing M ² ) at the same time in a solvent because they can be mixed more uniformly.
In addition, 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 0.20 μm or more, and more preferably 0.30 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 size is preferably 0.40 μm or less.
In addition, the average particle diameter here was adjusted so that it might become 40 to 60% transmittance | permeability by adding sodium hexametaphosphate aqueous solution to a slurry in room temperature air | atmosphere, making it disperse | distribute by ultrasonic dispersion and stirring. Thereafter, the particle size distribution 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 preferred production method of the present invention, 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, the slurry is caused to flow into the atomizer rotating at high speed, thereby causing the slurry component droplets to be discharged from the slit of the atomizer, and then sprayed using an appropriate drying gas temperature or air flow rate. A method for quickly drying the droplets is mentioned. At this time, the slurry flow rate is preferably 2 kg / h or more, more preferably 3 kg / h or more, and the atomizer rotational speed is preferably 30,000 rpm or more, more preferably 36,000 rpm. A treatment such as an appropriate temperature and air blowing is performed so as to quickly dry the dispersed droplets, but it is preferable to introduce a 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, it is preferable that the inlet temperature of the hot air for drying of a spray dryer is 190-210 degreeC, and outlet temperature is 110-120 degreeC.

In the preferred production method of the present invention, the precursor thus obtained is fired at 650 to 900 ° C.
By firing the precursor in an oxygen-containing atmosphere at such a temperature, the solid-phase reaction in the precursor can be advanced, and the composite oxide of the present invention can be obtained.
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 700 ° C. or higher, more preferably 750 ° C. or higher, and further preferably 800 or higher.
In addition, when the said precursor contains boron, when this baked at 650-900 degreeC, this inventor found out that there exists a tendency for a high temperature cycling characteristic to improve. The inventor presumes that this is due to a decrease in specific surface area due to the promotion of sintering of primary particles. When the specific surface area decreases, the inventor presumes that side reactions such as elution of Mn in the active material and expected decomposition of the organic solvent are suppressed, contributing to improvement of cycle characteristics at high temperatures.
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 time for firing the precursor at the firing temperature as described above is preferably 0.1 to 8 hours, more preferably 0.5 to 7 hours, and more preferably 0.5 to 4 hours, More preferably, it is 1-2h.

  According to such a preferred production method of the present invention, as described above, the composite oxide of the present invention, which can obtain a secondary battery having a high initial discharge capacity density per unit volume and excellent cycle characteristics at high temperatures, is compared. Can be manufactured easily.

<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 a positive electrode active material for a non-aqueous electrolyte secondary battery containing 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.

<Positive electrode of the present invention and manufacturing method thereof>
The positive electrode of the present invention may be in the same mode as, for example, a conventionally known positive electrode, as long as the positive electrode active material of the present invention is used. 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 non-aqueous electrolyte are the main battery components, and these components 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 non-aqueous electrolyte, an organic 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 non-aqueous electrolyte is a polymer electrolyte, it includes a matrix polymer compound that is gelled with a plasticizer (non-aqueous electrolyte). Examples of the matrix polymer compound include ethers such as polyethylene oxide and cross-linked products thereof. Fluorine-based resins such as vinyl resins, polymethacrylate resins, polyacrylate resins, polyvinylidene fluoride and vinylidene fluoride-hexafluoropropylene copolymers 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 production of 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 and comparative examples 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, MnO ₂ (average particle size: 25 μm) as a manganese source, Al ₂ O ₃ (average particle size: 30 μm) as an aluminum source, and H ₃ BO ₃ as a boron source were prepared. Then, after weighing each raw material so that the composition of the lithium-manganese composite oxide having a spinel structure finally obtained is Li _1.07 Mn _1.82 Al _0.10 B _0.01 O _4, and mixing these raw materials, Pure water was added so that the solid content concentration was 33.3 mass% to prepare a slurry.

Next, while stirring this slurry, it was pulverized using a wet pulverizer (manufactured by Ashizawa Finetech Co., Ltd .: Star Mill Lab Star LMZ-06) until the average particle size of the solid content in the slurry became 0.37 μm. . The grinding chamber capacity was 600 ml, and the grinding time was 1 hour.
Here, 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, dispersed by ultrasonic dispersion and stirring, adjusted to have a transmittance of 40 to 60%, and then the particle size using the above apparatus. It was determined by measuring the distribution.

Next, the slurry after pulverization was spray-dried using a disk-type spray dryer (Okawara Kako Co., Ltd .: L-8 type spray dryer). Here, air was used as the drying gas. Further, the cyclone differential pressure was adjusted to 0.7 kPa, and the drying gas inlet temperature was adjusted to 200 ° C. The slurry flow rate was 3 kg / h, and the atomizer speed was 36,000 rpm.
By performing such spray drying, a particulate precursor was obtained.

  And the obtained precursor was baked in the air at 850 degreeC for 6 hours, and the lithium manganese composite oxide of the target composition was obtained.

Next, differential scanning calorimetry (DSC) was performed on the precursor using a differential scanning calorimeter (manufactured by SII Nanotechnology: DSC6100). Here, 20 mg of a sample was filled in a 50 mL platinum container, and the heating rate was set to 10 ° C./min under air circulation (30 mL / min). And the peak area which appears in 370-470 degreeC in the obtained DSC curve was read, and the emitted-heat amount (mJ / mg) was calculated | required.
The results are shown in Table 1.

Moreover, about the obtained lithium manganese composite oxide, 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 results are shown in Table 1.

Further, 10 g of the obtained lithium-manganese composite oxide was sampled, put into a 20 ml graduated cylinder, tapped 300 times, then measured for volume (V), and tap density (g / ml) = 10 / V. The tap density was determined from the formula.
The results are shown in Table 1.

Further, powder X-ray diffraction was measured for the obtained lithium / manganese composite oxide. The obtained lithium-manganese composite oxide was found to have a cubic spinel structure.
For the X-ray diffraction measurement, a sample horizontal multi-purpose X-ray diffractometer (“UltimaIV” manufactured by Rigaku Corporation was used. Measurement conditions and the like are as follows.
TARGET: Cu
VOLTAGE & CURRENT: 40 kV, 40 mA
DETECTOR: DteX / Ultra
SLITS: DS 1/2 deg.
SAMPLING: 0.01 deg.
STEP SCAN: 2deg / min

  Next, a lithium ion secondary battery was produced using the lithium / manganese composite oxide obtained by the above method as a positive electrode active material.

First, a particulate lithium-manganese composite oxide, acetylene black as a conductive material, and polytetrafluoroethylene powder as a binder are mixed in a mass ratio of 75: 20: 5 and kneaded in a mortar to form a composite for a positive electrode. An agent was prepared. Then, this mixture was made into a sheet having a thickness of 0.1 mm with a stretch roller, and after being punched to 16 mmφ, vacuum drying was performed at 110 ° C. to prepare a test positive electrode.
Next, LiPF ₆ is added to a non-aqueous solvent obtained by mixing ethylene carbonate and diethyl carbonate so as to have a volume ratio of 1: 1 to obtain a non-aqueous electrolyte having a LiPF ₆ concentration of 1 mol / l. It was.
Next, the obtained test positive electrode was placed in a stainless steel container, and further laminated with a polypropylene non-woven fabric as a separator and a metal lithium foil (thickness 0.2 μm) as a negative electrode, and then sufficiently impregnated with the above non-aqueous electrolyte. After that, it was sealed with a stainless upper part to obtain a semi-open lithium battery.
And the charge / discharge test, the rate test, and the cycle test were done about the created test battery. Each is specifically shown below.

<Charge / discharge test>
The initial discharge capacity was measured under the conditions of a constant current of 0.5 mA / cm ² , a potential regulation of up to a charging potential of 4.3 V, and a discharging potential of 3.0 V. Further, the discharge capacity in the range of 3.0 to 3.2 V was read from the initial discharge curve obtained here, and the capacity of 3.2 V or less was obtained.
The results are shown in Table 1.

<Rate test>
After measuring the initial discharge capacity under the same conditions as described above, charging / discharging was performed at a current density of 10 mA / cm ² to measure the discharge capacity. And the capacity | capacitance maintenance factor was calculated | required by following Formula.
Capacity retention rate (%) = (discharge capacity at 10 mA / cm ² ) / (discharge capacity at 0.5 mA / cm ² ) × 100
The measurement results are shown in Table 1.

<High temperature cycle test>
Similar to the measurement of the initial discharge capacity in the above charge / discharge test except that the test battery was placed in a constant temperature bath at 55 ° C. and the current density was 2.5 mA / cm ³ , the discharge potential was up to 4.3V. The charge / discharge test was conducted 100 times under the condition of potential regulation up to 3.0 V, and the capacity retention rate was obtained by the following equation.
Capacity retention rate (%) = (100th discharge capacity / first discharge capacity) × 100
The measurement results are shown in Table 1.

<Mn dissolution test>
About the obtained lithium manganese composite oxide, the Mn elution amount in electrolyte solution was measured.
First, LiPF ₆ was added to a nonaqueous solvent obtained by mixing ethylene carbonate and diethyl carbonate at a volume ratio of 1: 1 to obtain an electrolytic solution having a LiPF ₆ concentration of 1 mol / l.
Next, 10 ml of this electrolytic solution and 1 g of lithium-manganese composite oxide powder were sealed in a plastic container, and then stored in a constant temperature bath at 55 ° C. for 7 days. The electrolyte solution after storage was filtered, the amount of Mn in the filtrate was measured with an atomic absorption spectrophotometer (manufactured by Seiko Instruments: SAS 7500A), and the Mn elution amount in the electrolyte solution was determined by the following equation.
Mn elution amount (%) = (Mn mass in electrolyte) / (Mass of lithium / manganese composite oxide powder (: 1 g)) × 100
The measurement results are shown in Table 1.

<Example 2>
LiOH · H ₂ O as a lithium source, MnO ₂ as a manganese source, and H ₃ BO ₃ as a boron source are prepared, and the composition of the lithium / manganese composite oxide having a spinel structure in which each raw material is finally obtained is Li _1.10 Mn _1.89 B _0.01 O ₄ was all measured in the same manner as in Example 1 except that it was weighed to be Mn _1.89 B _0.01 O ₄ .
The measurement results are shown in Table 1.

<Comparative Example 1>
Except that Li ₂ CO ₃ was used as the lithium source, the same measurement was performed using the same composition, the same operation, and the same method as in Example 1.
The measurement results are shown in Table 1.

<Comparative Example 2>
MnO ₂ pulverized so as to have an average particle size of 10 μm as a manganese source, LiOH · H ₂ O as a lithium source, and H ₃ BO ₃ as a boron source were prepared. And it weighed so that it might become Li _1.10 Mn _1.89 B _0.01 O _{4 of the} same composition as Example 2, and these raw materials were used for the agitator blade | wing 400rpm using the high speed mixer (Fukae Kogyo KK: FS.GS.10J type). The mixture was mixed for 10 minutes under the condition of chopper blade 2000 rpm. What is obtained after such mixing is referred to as a precursor in Comparative Example 2.
The obtained precursor was calcined in the air at 850 ° C. for 6 hours in the same manner as in Example 1 to obtain a lithium / manganese composite oxide. Analysis of the lithium / manganese composite oxide was carried out in the same manner as in Example 1.
The measurement results are shown in Table 1.
In addition, the average particle diameter of the manganese source was calculated | required using the laser diffraction / scattering type particle size distribution measuring apparatus (Horiba, Ltd .: LA-950v2) similarly to the average particle diameter of the solid content in the slurry in Example 1.

<Comparative Example 3>
A spray-dried powder having an average particle size of 10 μm obtained by slurry preparation and spray-drying of MnO ₂ under the same conditions as in Example 1 was prepared as a manganese source. LiOH.H ₂ O was used as the lithium source, and H ₃ BO ₃ was used as the boron source. These raw materials are weighed so as to be Li _1.10 Mn _1.89 B _0.01 O _4, and are used for 10 minutes under the conditions of agitator blade 400 pm and chopper blade 2000 rpm using a high speed mixer (Fukae Kogyo Co., Ltd .: FS.GS.10J type). Mixed. What is obtained after such mixing is used as a precursor in Comparative Example 3.
The obtained precursor was calcined in the air at 850 ° C. for 6 hours in the same manner as in Example 1 to obtain a lithium / manganese composite oxide. Analysis of the lithium / manganese composite oxide was carried out in the same manner as in Example 1.
The measurement results are shown in Table 1.

In Examples 1 and 2, the initial discharge capacity was 200 mAh / ml or more, and the capacity retention rate in the high-temperature cycle test was 92% or more. On the other hand, in Comparative Examples 1 to 3, the initial discharge capacity and the capacity retention rate in the high-temperature cycle test were low.
In Examples 1 and 2, the specific surface area (BET specific surface area) was smaller than that of the comparative example. The present inventors presume that this is a result of promoting the generation and growth of crystals and further promoting the growth of primary particles that are aggregates of crystallites. The lithium-manganese composite oxide obtained in Examples 1 and 2 within the scope of the present invention has a small specific surface area and is extremely dense.
In Examples 1 and 2, the capacity of 3.2 V or less was lower than that of the comparative example. In the case of the example, the present inventor presumes that the amount of oxygen defects is small (that is, a in Formula (I) is small).
Further, in Examples 1 and 2, the capacity retention rate in the rate test was higher than that of the comparative example, which was 98% or more.
In Examples 1 and 2, the Mn elution amount in the Mn elution test was smaller than that of the comparative example, which was 0.6% or less.

Claims (7)

A compound containing lithium hydroxide, a manganese compound, and M ¹ so that the number of atoms is Li: Mn: M ¹ : M ² = (x + y) :( 2-ypq): p: q. and each raw material of the compound containing M ² was put into a solvent, having an average particle diameter of the solids to give the following become to wet milling the slurry obtained was spray-dried precursor 0.50 .mu.m, the The precursor is calcined at a temperature of 650 to 900 ° C. for 0.1 to 8 hours in an oxygen-containing atmosphere ,
In a DSC curve obtained when 20 mg of the precursor is filled in a 50 mL platinum container and differential scanning calorimetry is performed under the condition of a heating rate of 10 ° C./min under an air flow rate of 30 mL / min, When there is a peak in the range of 370 to 470 ° C., the point at 370 ° C. and the point at 470 ° C. on the DSC curve are connected by a straight line, and the area surrounded by the straight line and the DSC curve is taken as the peak area And a spinel type lithium / manganese composite oxide represented by the following formula (I) having a peak area of 30 mJ / mg or more .
Formula (I): Li _{(x + y)} Mn _(2-ypq) M ¹ _p M ² _q O _(4-a)
However, in formula (I), 1.0 ≦ x <1.2, 0 <y ≦ 0.2, 1.0 <x + y ≦ 1.2, 0 ≦ p ≦ 1.0, 0 <q ≦ 1. 0, 0 ≦ a ≦ 1.0, M ¹ : at least one element selected from the group consisting of Ni, Co, Mg, Fe, Al and Cr, M ² : B, P, Pb, Sb and At least one element selected from the group consisting of V. The method for producing a spinel type lithium / manganese composite oxide according to claim 1, wherein the spinel type lithium / manganese composite oxide having a primary particle size of 0.1 to 5.0 μm is obtained . Secondary particle diameter obtain the spinel-type lithium-manganese composite oxide is 2 to 30 m, the manufacturing method of the spinel-type lithium-manganese composite oxide according to claim 1 or 2. The method for producing a spinel type lithium / manganese composite oxide according to any one of claims 1 to 3 , wherein the spinel type lithium / manganese composite oxide having a BET specific surface area of 0.1 to 2.0 m ² / g is obtained. . 5. The method for producing a spinel type lithium / manganese composite oxide according to claim 1 , wherein the spinel type lithium / manganese composite oxide having a tap density of 1.5 to 2.5 g / ml is obtained . After obtaining a spinel-type lithium-manganese composite oxide by the method according to any one of claims 1 to 5, and the step of using the resulting spinel-type lithium-manganese composite oxide as the positive electrode active material, a lithium-ion A method for producing a positive electrode for a secondary battery . After obtaining the positive electrode for lithium ion secondary batteries by the manufacturing method of Claim 6 , a lithium ion secondary battery is comprised using the obtained positive electrode for lithium ion secondary batteries, a negative electrode, and electrolyte solution. The manufacturing method of a lithium ion secondary battery provided with a process.