JP2001015110A - Positive electrode for battery and nonaqueous electrolyte secondary battery using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid use of a rare element and to improve cycle characteristics and conservative characteristics at a high temperature. SOLUTION: This positive electrode for a battery and the nonaqueous electrolyte secondary battery contain a transition metal composite oxide as a positive electrode active material. The transition metal composite oxide has a maximum diffraction peak by a X-ray diffraction using CuKα-ray in 10 deg.<2θ<20 deg. as a single peak and does not have a peak with intensity of not less than 1/10 of the maximum diffraction peak in 20 deg.<2θ<25 deg.. Alternatively, in the range of discharge depth of 50-90%, the relationship of a minimum value I1 of X-ray diffraction intensity of at least one or more X-ray diffraction peak to X-ray diffraction intensity I0 at 100% of discharge depth satisfies I1/I0>0.5. Alternatively, in the range of discharge depth of 50-90%, differential scanning calorimetry does not exhibit a heat absorption-heat radiation peak of not less than 10 J/g in the range of 20-80 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a positive electrode for a battery and a non-aqueous electrolyte secondary battery using the same, and more particularly to an improvement in a positive electrode active material.

[0002]

2. Description of the Related Art In recent years, with the remarkable progress of various electronic devices, a secondary battery which can be used for a long time and which can be repeatedly charged as an economically usable power source has been developed.

[0003] Typical secondary batteries include a lead storage battery, an alkaline storage battery, and a non-aqueous electrolyte secondary battery (so-called lithium secondary battery).

[0004] Among them, lithium secondary batteries have advantages such as high output and high energy density, and are expected to be used in various applications.

The lithium ion secondary battery is composed of a positive electrode and a negative electrode into which lithium ions can be reversibly inserted and removed, and a non-aqueous electrolyte or a solid electrolyte.

In general, as the negative electrode active material, lithium metal, a lithium alloy, a conductive polymer doped with lithium, and a layered compound (such as a carbon material and a metal oxide) are used.

As an electrolytic solution, a solution in which a lithium salt is dissolved in an aprotic non-aqueous solvent such as propylene carbonate is used.

[0008]

On the other hand, as for the positive electrode active material, LiCoO having a potential of Li4V has been hitherto considered from the viewpoint that a high energy density and a high voltage can be obtained.
₂ is widely used.

[0009] LiCoO ₂ is an ideal material in various aspects, but its constituent element Co is unevenly distributed as a resource on the earth and is rare. Therefore, there is a problem that it is difficult to provide a stable supply, and it is desired to develop a cathode material that is easily available and lower in cost.

At this time, considering the actual battery, it is desirable to improve not only the battery capacity but also the storage characteristics, the cycle characteristics, the storage characteristics at high temperatures, the cycle characteristics, etc. in order to achieve higher performance. It is.

The present invention has been proposed in view of such a conventional situation, is easily available, has a capacity, a high-temperature storage property,
An object of the present invention is to develop a positive electrode active material excellent in high-temperature cycle characteristics and the like, thereby providing a high-performance positive electrode for a battery and a nonaqueous electrolyte secondary battery.

[0012]

In order to achieve the above-mentioned object, a positive electrode for a battery according to the present invention comprises a transition metal composite oxide as a positive electrode active material, and the transition metal composite oxide comprises Cu
The maximum diffraction peak in X-ray diffraction using Kα ray is 10 ° <
Exists as a single peak at 2θ <20 ° and 20 ° <
It is characterized in that there is no peak having an intensity of 1/10 or more of the maximum diffraction peak at 2θ <25 °.

[0013] Further, the transition metal composite oxide contains a transition metal composite oxide as a positive electrode active material.
Within the scope of 90%, the minimum value I ₁ of the X-ray diffraction intensity of at least one or more X-ray diffraction peak discharge depth 100
%, And the relationship of I ₁ / I ₀ > 0.5 is satisfied with respect to the X-ray diffraction intensity I _{0 in} %.

Further, a transition metal composite oxide is contained as a positive electrode active material, and the transition metal composite oxide has a discharge depth of 50%.
% To 90% by differential scanning calorimetry.
It is characterized by not showing an endothermic-radiative peak of 10 J / g or more in the range of ° C to 80 ° C.

On the other hand, the nonaqueous electrolyte secondary battery of the present invention has a positive electrode containing a transition metal composite oxide as a positive electrode active material, a negative electrode containing a carbonaceous material or a lithium-based metal as a negative electrode active material, and a separator. In the transition metal composite oxide, the maximum diffraction peak in X-ray diffraction using CuKα ray exists as a single peak at 10 ° <2θ <20 °,
And 1/10 of the maximum diffraction peak at 20 ° <2θ <25 °
It is characterized in that there is no peak of the above intensity.

Also, the battery includes a positive electrode containing a transition metal composite oxide as a positive electrode active material, a negative electrode containing a carbonaceous material or a lithium-based metal as a negative electrode active material, and a separator. , Discharge depth 50% to 90
% In the range of at least 1 or more with respect to the X-ray diffraction intensity I ₀ of the minimum value I ₁ of the X-ray diffraction intensity of X-ray diffraction peak at a depth of discharge 100% I ₁ / I _0> 0.7 the relationship Is satisfied.

Further, the cathode has a positive electrode containing a transition metal composite oxide as a positive electrode active material, a negative electrode containing a carbonaceous material or a lithium-based metal as a negative electrode active material, and a separator. , Discharge depth 50% to 90
% In the range of 20 ° C to 80 ° C by differential scanning calorimetry.
It does not show an endothermic-radiative peak of 10 J / g or more in the range of ° C.

The modified positive electrode active material defined by the above conditions is excellent in storage stability at high temperatures and cycle characteristics. Therefore, a positive electrode for a battery and a non-aqueous electrolyte secondary battery using the same are excellent. Demonstrate performance.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a positive electrode for a battery and a non-aqueous electrolyte secondary battery to which the present invention is applied will be described in detail.

In a lithium secondary battery, it is desired to convert Co into another element for the above-mentioned reason, and as one of them, lithium-containing manganese oxide has been studied.

In particular, lithium-containing manganese oxides mainly having a spinel structure are very promising from the viewpoint of an easy synthesis method and battery capacity.

However, the lithium-containing manganese oxide has an oxygen defect or a cation defect depending on conditions at the time of synthesis. When the composition of a lithium-containing manganese oxide having few defects is expressed as Li _x Mn ₂ O ₄ , x is around 0.75, but in this case, storage deterioration is more remarkable than other compositions. .

This is because it has a superlattice structure near this composition, and it is considered that this superlattice structure adds instability to the crystal.

The present inventors have proposed LiM which has no instability.
As a result of intensive search for n ₂ O ₄ , introduction of cation defects and Mn
By substituting a part of the compound with another element, a target material was obtained, and it was concluded that this material could be used as an active material having excellent high-temperature storage characteristics and cycle characteristics.

The present invention has defined LiMn ₂ O ₄ having no instability from various viewpoints.
Focuses on the fact that the superlattice structure is involved in the instability, and defines a diffraction peak that appears in X-ray diffraction using CuKα radiation.

That is, as the first condition, the maximum diffraction peak exists as a single peak at 10 ° <2θ <20 °, and 1/20 of the maximum diffraction peak at 20 ° <2θ <25 °.
That is, there is no peak having an intensity of 10 or more. The temperature at which the presence or absence of this superlattice is discussed is room temperature.
It means a value obtained by X-ray diffraction measurement at least at 40 ° C. or less.

The same applies to the following description, but the depth of discharge is defined assuming that the discharge capacity obtained in the voltage range of 4.5 V to 3.0 V is Q ₁ and the discharge amount at any point in the discharge process is Q. , Q / Q ₁ .

The measurement conditions were as follows: CuKα ray was used as the characteristic X-ray, and the X-ray intensity was 12 kW (current 300 mA, voltage 40
kV), the set slit width is 0.5, 0.5, 0.15 for DR, RS, and SS, respectively, and the sample surface and X-ray detector (N
The distance between aI scintillation counters) is 185
mm, the scanning range is 5 ° <2θ <80 in 2θ of θ-2θ method.
°, the number of measurement steps is 0.02 ° / step.

Second, focusing on the fact that the instability appears as a broadening of the X-ray diffraction peak, the change in the X-ray diffraction intensity depending on the discharge depth and the half width of the X-ray diffraction peak are defined.

Specifically, the second condition is that the minimum value I ₁ of the X-ray diffraction intensity of at least one or more X-ray diffraction peaks within the range of 50% to 90% of the depth of discharge is 100% of the depth of discharge. I ₁ / I _0> 0 to X-ray diffraction intensity I ₀ at.
5 is satisfied. More preferably, I ₁
/ I ₀ > 0.7. Here, the X-ray diffraction intensity refers to the maximum value of the number of counts per unit time at a certain diffraction peak of interest.

Further, in addition to the above conditions, a discharge depth of 50
% Within the range of 90% to 90%, the maximum value FWHM ₁ of the half width of at least one or more X-ray diffraction peaks is 10 discharge depths.
It is preferable that the relationship of FWHM ₁ / FWHM ₀ <1.3 is satisfied with respect to the half-value width FWHM ₀ of the X-ray diffraction peak at 0%. Here, the half-value width is the width of a peak at a half of the maximum value of the count number per unit time in a certain diffraction peak of interest.

Here, the temperature at which the broadening of the X-ray diffraction peak is discussed is room temperature, which means a value obtained by X-ray diffraction measurement at least at 40 ° C. or less.

The measurement was performed using a Rigaku RINT 2500 rotating anti-cathode. The characteristic X-ray was CuKα.
Wire, current 100mA, voltage 40kV, goniometer vertical standard (radius 185mm), counter monochromator used, no filter used, set slit width DR, RS,
The SS is 1, 1, 1.5 mm, respectively, the counting device is a scintillation counter, the measuring method is a reflection method (continuous scanning), the scanning range is 10 ° <2θ <80 °, and the scanning speed is 4 ° / min.

Third, focusing on the fact that the instability appears due to instability of the crystal structure, specifies the appearance of a peak in a DSC curve by differential scanning calorimetry.

Therefore, the third condition is that the depth of discharge is in the range of 50% to 90% (or when the composition during charging and discharging is Li _x Mn ₂ O ₄ , 0.5 <x <0. 9) within the range of 20 ° C to 80 ° C by differential scanning calorimetry.
Does not exhibit an endothermic-radiative peak with a calorific value of 10 J / g or more.

The measuring conditions are that the temperature rising speed and the temperature falling speed are both 10 ° C./min.

In the battery positive electrode or the nonaqueous electrolyte secondary battery of the present invention, a transition metal composite oxide satisfying any of the above conditions, for example, a lithium-containing manganese oxide having a spinel structure is used as a positive electrode active material.

The positive electrode for a battery is produced, for example, by applying a positive electrode mixture containing the above-mentioned positive electrode active material and a binder on a positive electrode current collector and drying. A metal foil such as an aluminum foil is used as the positive electrode current collector.

At this time, as the binder for the positive electrode mixture, a known binder usually used for a positive electrode mixture for a battery can be used. Further, a known additive such as a conductive agent can be added to the positive electrode mixture.

On the other hand, in the case of a non-aqueous electrolyte secondary battery, it is preferable to use lithium, a lithium alloy, or a material capable of doping or undoping lithium as a negative electrode material. As a material that can dope and dedope lithium,
For example, a non-graphitizable carbon-based material having a (002) plane spacing of 0.37 nm or more, or a (002) plane spacing of 0.03
A carbon material such as a graphite material having a size of 40 nm or less can be used. Specifically, carbon materials such as pyrolytic carbons, cokes, graphites, glassy carbon fibers, organic polymer compound fired bodies, carbon fibers, and activated carbon can be used. Examples of the coke include pitch coke, needle coke, and petroleum coke. Also,
The organic polymer compound fired body is obtained by firing a phenol resin, a furan resin, or the like at an appropriate temperature and carbonizing the resin.

In addition to the above-mentioned carbon materials, as a material capable of doping and undoping lithium, a polymer such as polyacetylene and polypyrrole and an oxide such as SnO ₂ can be used. Further, as the lithium alloy, a lithium-aluminum alloy or the like can be used.

The negative electrode is produced by applying a negative electrode mixture containing the above-mentioned negative electrode active material and a binder on a current collector and drying the mixture. For the current collector, for example, a metal foil such as a copper foil is used.

At this time, as the binder for the negative electrode mixture, a known binder usually used for a negative electrode mixture of a lithium ion battery can be used. In addition, a known additive or the like can be added to the negative electrode mixture.

As the electrolyte, a known electrolyte usually used for an electrolyte of this type of battery can be used. Specifically, LiPF ₆ , LiBF ₄ , LiAs
F ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiN (SO ₂ C
F ₃ ) ₂ , LiC (SO ₂ CF ₃ ) ₃ , LiAlCl ₄ , Li
A lithium salt such as SiF ₆ can be used. Among them, LiPF ₆ and LiBF ₄ are particularly desirable from the viewpoint of oxidation stability and the like.

Such an electrolyte is contained in a non-aqueous solvent at a concentration of 0.1%.
Preferably, it is dissolved at a concentration of from mol / l to 5.0 mol / l. More preferably, 0.5 mol / l
３3.0 mol / l.

As the non-aqueous solvent, various non-aqueous solvents conventionally used for non-aqueous electrolytes can be used. For example, propylene carbonate, ethylene carbonate, butylene carbonate, vinylene carbonate, γ-butyl lactone, sulfolane, 1,2-dimethoxyethane, 1,2-diethoxyethane, 2-methyltetrahydrofuran, 3-methyl-1,3-dioxolane , Methyl propionate, methyl butyrate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate and the like can be used. In particular, it is preferable to use cyclic carbonates such as propylene carbonate and vinylene carbonate, and chain carbonates such as dimethyl carbonate, diethyl carbonate and dipropyl carbonate from the viewpoint of voltage stability. These non-aqueous solvents may be used alone or in combination of two or more.

Other structures of the nonaqueous electrolyte secondary battery, for example, a separator, a battery can, and the like can be the same as the conventional lithium ion nonaqueous electrolyte secondary battery.

For example, a polymer film such as polypropylene is used as the separator. In this case, the separator must be as thin as possible from the viewpoint of lithium ion conductivity and energy density. Considering this, a separator having a thickness of 50 μm or less is practical.

In the above description, a lithium-ion non-aqueous electrolyte secondary battery using a non-aqueous electrolyte obtained by dissolving an electrolyte in a non-aqueous solvent has been described as an example. The present invention is not limited thereto, and is also applicable to a solid electrolyte battery using a polymer solid electrolyte in which an electrolyte is dispersed in a matrix polymer.

As the matrix polymer in which the electrolyte is dispersed, various polymers used for forming a normal polymer solid electrolyte can be used.

Specific examples of the matrix polymer include ether polymers such as polyethylene oxide and crosslinked polyethylene oxide, ester polymers such as polymethacrylate and acrylate polymers, polyvinylidene fluoride, vinylidene fluoride and hexadecane. Fluoropolymers such as copolymers with fluoropropylene alone,
Alternatively, they can be used in combination. Among the,
It is desirable to use a fluorine-based polymer such as polyvinylidene fluoride or a copolymer of vinylidene fluoride and hexafluoropropylene.

Further, such a solid polymer electrolyte may contain a plasticizer and be in a gel form. When the solid polymer electrolyte is in a gel state, the electrolyte is 0.1 m in the plasticizer.
ol / l to 3.0 mol / l, more preferably 0.5 mol / l
1 to 2.0 mol / l.

The shape of the battery of the present invention, such as a cylindrical type, a square type, a coin type, and a button type, is not particularly limited, and the dimensions can be set arbitrarily.

[0054]

EXAMPLES Specific examples to which the present invention is applied will be described below based on experimental results.

<Experiment 1> In this experiment, the difference in battery performance depending on the presence or absence of the superlattice structure was examined.

In this experiment, the production of the positive electrode was carried out under the following conditions.

That is, 80% by weight of dried lithium-containing manganese oxide synthesized as an active material, 15% by weight of graphite (average particle size: 5 μm to 20 μm: KS-15, manufactured by Lonza Co.) as a conductive agent, Polyvinylidene fluoride PVDF (manufactured by Aldrich, trade name # 1300) as a binder is dimethylformamide DMF
The mixture was kneaded to form a paste, pelletized together with an aluminum mesh serving as a current collector, and dried at 100 ° C. for 1 hour (in a stream of dry argon).

For charging, a coin cell (2) was prepared by arranging lithium metal as a counter electrode on a pellet carrying 60 mg of the active material.
025) and propylene carbonate PC + dimethyl carbonate DMC (1: 1) / 1
Performed using MLiPF ₆ . When the lithium-containing manganese oxide as the positive electrode active material was expressed as Li _x Mn ₂ O ₄ , lithium was electrochemically extracted up to x = 0.75.

The determination of the superlattice was made by using X-ray diffraction. When measuring X-ray diffraction, CuK was used as the characteristic X-ray.
X-ray intensity was set to 12 kW (current 300 mA, voltage 40 kV) using α-rays, and the set slit width was DR, RS, SS
Were set to 0.5, 0.5, and 0.15, respectively. The distance between the sample surface and the X-ray detector (NaI scintillation counter) was 185 mm. Scan range is θ
In the 2θ method, 2θ was set to 5 ° <2θ <80 °, and the number of measurement steps was set to 0.02 ° / step.

In addition, the physical property values as an index of the high-temperature storage characteristics were calculated as follows.

First, the quantity of electricity (mAh) required to charge LiMn ₂ O ₄ until the composition becomes Li _0.75 Mn ₂ O ₄ was set as Q _pre .

Next, the battery was left to stand at 55 ° C. for 24 hours while being charged, and then quickly cooled to room temperature, and then cooled to 3.0 V.
_Was measured until the value reached.

The charging and discharging were performed at a current density of 1 mA / cm ² . Both charging and discharging were performed at normal temperature (23 ° C.).

Let S1 be the storage characteristic value, and S1 = Q _aft / Q
_pre The storage characteristic value S1 always takes a value of 1 or less and a value of 0 or more, and it can be considered that the closer to 1, the better the characteristic.

Example 1 Li ₂ CO ₃ (> 99.9%) and MnCO ₃ (> 99.9)
%) Was weighed so that Li / Mn = 0.51, mixed, and baked at 750 ° C. in the air for 12 hours. When X-ray diffraction measurement was performed on this product, the maximum diffraction peak was present as a single peak at 10 ° <2θ <20 °, and 1/20 of the maximum diffraction peak at 20 ° <2θ <25 °.
No peaks with an intensity of 10 or more were present.

Example 2 Li ₂ CO ₃ (> 99.9%) and MnCO ₃ (> 99.9)
%) Was weighed so that Li / Mn = 0.52, mixed, and then baked at 750 ° C. in the air for 12 hours. When X-ray diffraction measurement was performed on this product, the maximum diffraction peak was present as a single peak at 10 ° <2θ <20 °, and 1/20 of the maximum diffraction peak at 20 ° <2θ <25 °.
No peaks with an intensity of 10 or more were present.

Example 3 Li ₂ CO ₃ (> 99.9%) and MnCO ₃ (> 99.9)
%) Was weighed so that Li / Mn = 0.50, mixed, and baked at 850 ° C. in the air for 12 hours. When X-ray diffraction measurement was performed on this product, the maximum diffraction peak was present as a single peak at 10 ° <2θ <20 °, and 1/20 of the maximum diffraction peak at 20 ° <2θ <25 °.
No peaks with an intensity of 10 or more were present.

Example 4 Li ₂ CO ₃ (> 99.9%) and MnCO ₃ (> 99.9)
%) Was weighed so that Li / Mn = 0.50, mixed, baked at 750 ° C. in the air for 12 hours, and further processed at 500 ° C. for 2 hours under a nitrogen stream. When X-ray diffraction measurement was performed on this product, the maximum diffraction peak was present as a single peak at 10 ° <2θ <20 °, and 1/20 of the maximum diffraction peak at 20 ° <2θ <25 °.
No peaks with an intensity of 10 or more were present.

Comparative Example 1 Li ₂ CO ₃ (> 99.9%) and MnCO ₃ (> 99.9)
%) Was weighed so that Li / Mn = 0.50, mixed, and then baked at 750 ° C. in the air for 12 hours. When the X-ray diffraction measurement was performed on this product, the above conditions were not satisfied.

A coin cell was manufactured using the products obtained in each of the examples and comparative examples, and the high-temperature storage characteristic value S1 was calculated in accordance with the above evaluation method. Table 1 shows the results.

[0071]

[Table 1]

As is clear from Table 1, Li / Mn
Is generated at an atomic content ratio not equal to 0.50, or at a high temperature of 850 ° C., and further under conditions such as heat treatment in an environment where the oxygen partial pressure is lower than in the atmosphere, and the maximum diffraction peak is 10 ° <2θ.
Present as a single peak at <20 ° and 20 ° <2θ
A battery using a lithium-containing manganese oxide having a feature that a peak having an intensity of 1/10 or more of the maximum diffraction peak does not exist at <25 ° has excellent high-temperature storage stability.

<Experiment 2> In this experiment, the difference in battery performance due to the difference in crystal structure was examined.

The production of the positive electrode was performed in the same manner as in Experiment 1 described above.

For charging, a coin cell (2) was prepared by arranging lithium metal as a counter electrode on a pellet carrying 60 mg of the active material.
025) and propylene carbonate PC + dimethyl carbonate DMC (1: 1) / 1
Performed using MLiPF ₆ . After the battery was charged at a constant current up to 4.5 V, the voltage was kept at 4.5 V, and the charge was terminated when the current became 0.01 mA / cm ² or less. Thereafter, discharging was performed, and when the voltage dropped to 3.0 V, the discharging was terminated.

Both charging and discharging are performed at normal temperature (23 ° C.).
And at a high temperature (60 ° C.).

The physical property values used as indices of the cycle characteristics (normal temperature, high temperature) were calculated as follows.

First, the quantity of electricity (mAh) required to initially charge to 4.5 V is set as Qc. After that, 3.0V
Discharge until then and charge again. This process is 30
The discharge amount Qd after the repetition is measured.

The cycle characteristic value (capacity maintenance ratio) is set as S2, and S2 is S2 = Qd / Qc. S2 always takes a value of 1 or less and a value of 0 or more, and it can be considered that the closer to 1, the better the characteristics.

The difference in the crystal structure of the lithium-containing manganese oxide was determined from the dependence of the X-ray diffraction pattern on the depth of discharge. The depth of discharge dependence of the X-ray diffraction pattern was measured under the following conditions.

That is, using the coin cell described above, 4.
After charging to 5 V, 0.1 m corresponding to a predetermined amount of electricity
After a low-speed discharge of A / cm ² , the positive electrode active material was taken out, washed with dimethyl carbonate, and the X-ray diffraction pattern was measured.

For the measurement, a Rigaku RINT 2500 rotating counter cathode was used. The measurement conditions are as follows. That is, the characteristic X-ray is CuKα ray, current 100 mA, voltage 40
kV, goniometer vertical type standard (radius 185 mm), counter monochromator used, no filter used, set slit width DR, RS, SS 1 °, 1 °, respectively
1.5 mm, counter scintillation counter, measurement method is reflection method (continuous scan), scan range is 10 ° <2
θ <80 °, and the scan speed is 4 ° / min.

The present process can be carried out more simply by a chemical synthesis method as described below.

That is, first, 15 g of the synthesized sample was
The solution is added to 500 ml of a solution of Cl: H ₂ O = 1: 33 and stirred at room temperature for 5 hours. The precipitate obtained is thoroughly washed with distilled water and dried in vacuo at room temperature. This process allows Li
Is extracted to obtain Li _0.15 Mn ₂ O ₄ .

1 g of this powder and a predetermined amount of LiI
1 x acetonitrile for 24 hours and the precipitate is washed well with acrylonitrile to give any x value of Li _x M
n ₂ O ₄ (0.15 <x <1.0) is obtained.

Here, the x value corresponds to the depth of discharge. The dependence of the X-ray diffraction pattern on the depth of discharge of the sample thus produced was almost the same as that of the sample obtained by the coin cell.

Example 5 Li ₂ CO ₃ (> 99.9%) and MnCO ₃ (> 99.9)
%) And the final composition of the product is Li (Li _0.02 Mn _1.98 ) O
₄ and were weighed so as to, after mixing, in the air at 750 ° C., 1
The firing was performed for 2 hours.

Example 6 Li ₂ CO ₃ (> 99.9%) and MnCO ₃ (> 99.9)
%) When the final composition of the product is Li (Li _0.05 Mn _1.95 ) O
₄ and were weighed so as to, after mixing, in the air at 750 ° C., 1
The firing was performed for 2 hours.

Example 7 Li ₂ CO ₃ (> 99.9%) and MnCO ₃ (> 99.9)
%) Was weighed so that Li / Mn = 0.50, mixed, and baked at 650 ° C. in the air for 12 hours. At this time, since the firing temperature is low, defects are introduced into the cation sites.

Example 8 Li ₂ CO ₃ (> 99.9%) and MnCO ₃ (> 99.9)
%) And CoCO ₃ with a final composition of Li (Mn _1.95
Co _0.05 ) O ₄ , weighed and mixed, then 750 ° C
For 12 hours in the atmosphere.

Example 9 Li ₂ CO ₃ (> 99.9%) and MnCO ₃ (> 99.9)
%), The final composition of the product CrCO ₃ is Li (Mn _1.95
Cr _0.05 ) O ₄ , weighed and mixed, 750 ° C
For 12 hours in the atmosphere.

Comparative Example 2 Li ₂ CO ₃ (> 99.9%) and MnCO ₃ (> 99.9)
%) Was weighed so that Li / Mn = 0.50, mixed, and then baked at 750 ° C. in the air for 12 hours.

With respect to a coin-type battery using the samples prepared in the above Examples and Comparative Examples as a positive electrode active material, the dependence of the X-ray diffraction pattern on the depth of discharge was measured, and the peak intensities I ₀ and I ₁ , the half width FWHM ₁ And FWHM ₀ were measured. The measurement results are shown in FIGS.

The cycle characteristics at room temperature (23 ° C.) and the cycle characteristics at high temperature (60 ° C.) were measured for the coin batteries using the samples prepared in the above Examples and Comparative Examples as the positive electrode active material. The results are shown in FIGS.

Lithium-containing manganese oxide having a cation deficiency synthesized at 700 ° C. or lower, or lithium-containing manganese oxide in which Mn is substituted by an appropriate other element has predetermined characteristics in the dependence of the X-ray diffraction pattern on the depth of discharge. It is clear that the battery using this has good cycle characteristics, especially at high temperatures, and it can be said that the battery has a great practical advantage.

<Experiment 3> In this experiment, the relationship between the DSC curve and the battery characteristics was examined.

The production of the positive electrode was carried out in the same manner as in Experiment 1 described above. Further, the phase identification of the synthesized sample was performed by using the X-ray diffraction method. The measurement conditions are as follows.

Apparatus Rigaku RINT 2500 rotation counter electrode X-ray CuKα ray, current 100 mA, voltage 40 kV Goniometer Vertical standard, radius 185 mm Counter monochromator Use filter Not used Slit Diverging slit (DS) 1 ° Scattering slit (RS) 1 ° Receiving slit (SS) 1.5mm counter Scintillation counter Measuring method Straight irradiation method, continuous scan Scanning range 10 ° <2θ <100 ° Scan speed 4 ° / min The cycle characteristics are evaluated by the constant current method and 4.2V.
The charge / discharge test was repeatedly performed in the potential range of up to 3.0 V.
The charge and discharge current densities were fixed at 1 mA / cm ² .
In addition, both charging and discharging were performed at normal temperature (23 ° C.).

Also, it is possible to use the above-mentioned coin cell for 4.5V.
After charging to 0.1 mA / c corresponding to a predetermined amount of electricity
After performing a low-speed discharge of m ² , the positive electrode active material was washed with dimethyl carbonate, and a change in crystal structure was examined.

The determination of the change in crystal structure was made by differential scanning calorimetry (DSC). The measurement conditions are as follows.

Apparatus Shinku-Rio ULVAC Differential Scann
ing Calorimeter 7000 Heating speed 10 ° C / min Cooling speed 10 ° C / min Measurement temperature range -100 ° C to 150 ° C Weight of measurement sample 25mg Example 10 Li ₂ CO ₃ (> 99.9%) and MnCO
₃ (> 99.9%) was weighed so that the final composition of the product was Li (Li _0.02 Mn _1.98 ) O ₄ , mixed, and then calcined at 750 ° C. in the air for 12 hours.

Example 11 Li ₂ CO ₃ (> 99.9%) and MnCO ₃ (> 99.9)
%) When the final composition of the product is Li (Li _0.05 Mn _1.95 ) O
₄ and were weighed so as to, after mixing, in the air at 750 ° C., 1
The firing was performed for 2 hours.

Example 12 Li ₂ CO ₃ (> 99.9%) and MnCO ₃ (> 99.9)
%) Was weighed so that Li: Mn = 1: 2, mixed, and baked at 650 ° C. in the air for 12 hours. At this time, since the firing temperature was low, defects were introduced into the cation sites.

Example 13 Li ₂ CO ₃ (> 99.9%) and MnCO ₃ (> 99.9)
%) And CoCO ₃ with a final composition of Li (Mn _1.95
Co _0.05 ) O ₄ , weighed and mixed, then 750 ° C
For 12 hours in the atmosphere.

Example 14 Li ₂ CO ₃ (> 99.9%) and MnCO ₃ (> 99.9)
%), The final composition of the product CrCO ₃ is Li (Mn _1.95
Cr _0.05 ) O ₄ , weighed and mixed, 750 ° C
For 12 hours in the atmosphere.

Comparative Example 3 Li ₂ CO ₃ (> 99.9%) and MnCO ₃ (> 99.9)
%) Was weighed so that Li: Mn = 1: 2, mixed, and then baked at 750 ° C. in the air for 12 hours.

The samples prepared in the above Examples and Comparative Examples were used as the positive electrode active material, and the DSC curves at a discharge depth of 50% or more and 90% or less were measured under the above conditions. FIG. 5 shows the results.

In the sample of the comparative example, an endothermic peak and an exothermic peak are observed at around 50 ° C. On the other hand, in the samples of the examples, no endothermic peak or heat release peak of 10 J / g or more was observed at all.

The cycle characteristics at room temperature (23 ° C.) of the coin type batteries using the samples prepared in the above Examples and Comparative Examples as the positive electrode active material were measured under the above conditions. FIG. 6 shows the results.

The lithium-containing manganese oxide having a cation defect or the lithium-containing manganese oxide obtained by substituting Mn with an appropriate other element has a feature that it does not have an endothermic peak and an exothermic peak in a DSC curve. It is clear that the used battery has good cycle characteristics, and it can be said that the practical advantage is large.

[0111]

As is clear from the above description, according to the present invention, a positive electrode for a battery and a non-aqueous electrolyte secondary battery having excellent performance in terms of capacity, high-temperature storage stability, high-temperature cycle characteristics and the like are provided. It is possible to provide.

Furthermore, according to the present invention, Co, which is a rare element, is not required as a constituent element of the positive electrode active material, and its synthesis is easy. Therefore, from the viewpoint of the global environment and the production cost, it is very difficult. Is advantageous.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing the relationship between the depth of discharge and I ₁ / I ₀ in Examples 5 to 9 and Comparative Example 2.

FIG. 2 is a characteristic diagram showing a relationship between a discharge depth and FWHM ₁ / FWHM ₀ in Examples 5 to 9 and Comparative Example 2.

FIG. 3 is a characteristic diagram showing cycle characteristics at 23 ° C. in Examples 5 to 9 and Comparative Example 2.

FIG. 4 is a characteristic diagram showing cycle characteristics at 60 ° C. in Examples 5 to 9 and Comparative Example 2.

FIG. 5 shows DSC in Examples 10 to 14 and Comparative Example 3.
It is a characteristic view showing a curve.

FIG. 6 is a characteristic diagram showing cycle characteristics in Examples 10 to 14 and Comparative Example 3.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kiyoshi Yamaura 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Takuya Endo 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation F-term (reference)

Claims (20)

[Claims] 1. A transition metal composite oxide as a positive electrode active material, wherein the transition metal composite oxide has a single peak at 10 ° <2θ <20 ° in X-ray diffraction using CuKα ray. And a peak having an intensity of 1/10 or more of the maximum diffraction peak does not exist at 20 ° <2θ <25 °. 2. The positive electrode for a battery according to claim 1, wherein the transition metal composite oxide has a spinel structure. 3. The positive electrode for a battery according to claim 1, wherein the transition metal composite oxide is a manganese oxide containing lithium. 4. A positive electrode including a transition metal composite oxide as a positive electrode active material, a negative electrode including a carbonaceous material or a lithium-based metal as a negative electrode active material, and a separator. , The maximum diffraction peak in X-ray diffraction using CuKα ray exists as a single peak at 10 ° <2θ <20 °, and has an intensity of 1/10 or more of the maximum diffraction peak at 20 ° <2θ <25 °. A non-aqueous electrolyte secondary battery characterized by having no peak. 5. The non-aqueous electrolyte secondary battery according to claim 4, wherein the transition metal composite oxide has a spinel structure. 6. The non-aqueous electrolyte secondary battery according to claim 4, wherein the transition metal composite oxide is a lithium-containing manganese oxide. 7. A transition metal composite oxide as a positive electrode active material, wherein the transition metal composite oxide has an X-ray diffraction intensity of at least one or more X-ray diffraction peaks within a discharge depth range of 50% to 90%. Wherein the minimum value I ₁ of the above satisfies the relationship of I ₁ / I ₀ > 0.5 with respect to the X-ray diffraction intensity I ₀ at a depth of discharge of 100%. 8. The transition metal composite oxide has a discharge depth of 5
Within the range of 0% to 90%, at least one X
The maximum value FWHM ₁ of the half width of the X-ray diffraction peak is 1
8. The positive electrode for a battery according to claim 7, wherein a relationship of FWHM ₁ / FWHM ₀ <1.3 is satisfied with respect to a half width FWHM ₀ of the X-ray diffraction peak at 00%. 9. The positive electrode for a battery according to claim 7, wherein the transition metal composite oxide has a spinel structure. 10. The positive electrode for a battery according to claim 7, wherein the transition metal composite oxide is a manganese oxide containing lithium. 11. A positive electrode including a transition metal composite oxide as a positive electrode active material, a negative electrode including a carbonaceous material or a lithium-based metal as a negative electrode active material, and a separator. , within the scope of the discharge depth 50% to 90%, the minimum value I ₁ of the X-ray diffraction intensity of at least one or more X-ray diffraction peak with respect to X-ray diffraction intensity I ₀ at 100% depth of discharge I ₁ / I A non-aqueous electrolyte secondary battery characterized by satisfying a relationship of ₀ > 0.7. 12. The transition metal composite oxide has a maximum FWHM _{1 of} at least one or more X-ray diffraction peaks at 50% to 90% in a discharge depth of 50% to 90%. 12. The non-aqueous electrolyte secondary battery according to claim 11, wherein a relationship of FWHM ₁ / FWHM ₀ <1.3 is satisfied with respect to a half width FWHM ₀ of a line diffraction peak. 13. The non-aqueous electrolyte secondary battery according to claim 11, wherein the transition metal composite oxide has a spinel structure. 14. The transition metal composite oxide is a lithium-containing manganese oxide.
The non-aqueous electrolyte secondary battery according to the above. 15. A transition metal composite oxide as a positive electrode active material, wherein the transition metal composite oxide is in a range of 20 ° C. to 80 ° C. by differential scanning calorimetry within a discharge depth range of 50% to 90%. A positive electrode for a battery, which does not exhibit an endothermic-radiative peak of 10 J / g or more. 16. The positive electrode for a battery according to claim 15, wherein the transition metal composite oxide has a spinel structure. 17. The method according to claim 15, wherein the transition metal composite oxide is a lithium-containing manganese oxide.
The positive electrode for a battery according to the above. 18. A positive electrode including a transition metal composite oxide as a positive electrode active material, a negative electrode including a carbonaceous material or a lithium-based metal as a negative electrode active material, and a separator. A non-aqueous electrolyte secondary battery which does not exhibit an endothermic-radiative peak of 10 J / g or more in a range of 20 ° C. to 80 ° C. by differential scanning calorimetry within a range of a discharge depth of 50% to 90%. 19. The non-aqueous electrolyte secondary battery according to claim 18, wherein the transition metal composite oxide has a spinel structure. 20. The method according to claim 18, wherein the transition metal composite oxide is a lithium-containing manganese oxide.
The non-aqueous electrolyte secondary battery according to the above.