JP2002003220A - Anode material for lithium ion secondary battery, anode and battery using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anode-activating material which contains lithium and manganese compound oxide and is used for a lithium ion secondary battery with a superior recycle characteristic. SOLUTION: The anode material for a lithium ion secondary battery has a character that the material contains (a) lithium and manganese compound oxide that has a spinel structure of lithium manganese oxide in which one part of manganese site is substituted by other elements and the substituted element are distributed so that the standard deviation σ against the average of the substituted elements included in each primary crystal lattice is under 50% and (b) the compound oxide with lithium and at least a transition metal other than (a).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a positive electrode material for a lithium ion secondary battery. Specifically, the present invention relates to a positive electrode material containing a lithium manganese composite oxide.

[0002]

2. Description of the Related Art A lithium ion secondary battery, which functions as a battery by having a positive electrode and a negative electrode occlude and release lithium ions from each other, has a high voltage and a high energy density, and is used for mobile phones, portable personal computers, video cameras, It can be suitably used for applications such as electric vehicles. As a positive electrode active material for a lithium ion secondary battery, a lithium-cobalt composite oxide having a layered structure that has already been put into practical use is 4
A V-class high voltage can be obtained, and a high energy density is obtained. However, since the raw material cobalt is scarce in terms of resources and expensive, considering the possibility that demand will expand significantly in the future, there is concern about the supply of raw materials, and the price may rise further. is expected. As a positive electrode active material instead of lithium cobalt oxide, it has been considered to use a spinel-type lithium manganese composite oxide made of inexpensive manganese as a positive electrode material. However, lithium manganese composite oxide is inferior in cycle characteristics to the lithium cobalt composite oxide,
That is, there is a problem in that the capacity is significantly deteriorated when charge and discharge are repeatedly performed at a temperature of 50 to 60 ° C. In this regard, in order to (1) improve the crystallinity of the lithium-manganese composite oxide, or (2) replace some of the manganese sites with other elements in order to stabilize the crystal structure,
Although it has been found that capacity deterioration is suppressed, sufficient improvement in cycle characteristics has not been achieved by such improvement alone.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a positive electrode active material for a lithium ion secondary battery containing a lithium manganese composite oxide and having excellent cycle characteristics. It is intended for.

[0004]

The present inventors have found that, when a part of the Mn site of the spinel-type lithium manganese composite oxide is replaced by another element, the distribution state of the content of the replacement element between the primary crystal grains is reduced. Finding that it affects the cycle characteristics,
Proposal of using a spinel-type lithium manganese composite oxide having a distribution state as uniform as possible as a positive electrode active material
However, it has been found that the cycle characteristics are further improved by combining the spinel-type lithium manganese composite oxide with another lithium transition metal composite oxide, and the present invention has been achieved. That is, the gist of the present invention is that (a) a spinel-type lithium manganese oxide in which a part of a Mn site is substituted with another element, and a standard deviation σ of the average value of the substituted element content of each primary crystal particle is A lithium ion comprising: a lithium manganese composite oxide in which substitution atoms are distributed so as to be 50% or less; and (b) at least one lithium transition metal composite oxide other than (a). It exists in the positive electrode material for secondary batteries. The present invention also resides in a positive electrode for a lithium ion secondary battery and a battery using the material.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. According to the study of the present inventors, in the spinel-type lithium manganese composite oxide in which a part of the Mn site is replaced by another element, the content of the replacement element (other element) between the primary crystal particles is uniformly distributed. When the average content of the substitution element is the same, even when the content distribution between the primary particles is non-uniform, the effect of suppressing the amount of Mn eluted into the electrolytic solution is large,
As a result, there is an effect that the cycle characteristics are improved. As the spinel-type lithium manganese composite oxide (a) of the present invention, a composite oxide represented by the following general formula (1) is preferable.

[0006]

## STR2 ## _{Li 1 + X Mn 2-XY} M Y O 4 + z (1)

(However, 0 <X <0.5, 0 <Y <0.
5, -0.1 ≦ Z ≦ 0.1, and M represents a substitution element. ) Other elements that replace part of the Mn site include B, S
n, Al, Ti, V, Cr, Fe, Co, Ni, Cu,
One or more elements selected from Zn, Mg, and Ga are mentioned, and Al is preferable. Note that a part of the Mn site may be replaced by lithium together with the other elements. The present invention requires that the substitution elements are distributed such that the standard deviation σ thereof relative to the average value of the substitution element contents of the primary crystal particles of the spinel-type lithium manganese composite oxide is 50% or less.

The method for obtaining the average content of the substitution element in the lithium manganese composite oxide substituted with another element and the content of the substitution element for each primary particle are not particularly limited. For example, the average content is determined by dissolving a complex oxide sample with a small amount (about 0.5 to 5 g) of an acid and performing atomic absorption analysis, IC
It can be measured by P (inductively coupled plasma) analysis or the like. However, this analysis method cannot simultaneously measure the substitution element content of each primary particle. On the other hand, the substitution element content for each primary particle can be measured by, for example, Auger electron spectroscopy (AES). AES is
This is a method in which specific primary particles are spot-irradiated with an electron beam by observation with an electron microscope, and emitted electrons due to the Auger effect are detected by energy analysis of scattered electrons. AES is preferable because the beam diameter of the electron beam can be reduced to 100 nm or less, and local composition analysis becomes possible. Therefore, it is possible to determine the respective replacement element contents for several to several tens of primary particles selected from a plurality of secondary particles. The average content can be determined by averaging the measured values. Then, among the n primary particles, the i-th substitution element content is Xi, and the average substitution element content of the n primary particles is Xav. , The variation (sum of squares of deviation) S and the standard deviation σ are calculated according to the following equations.

[0009]

(Equation 1)

In the lithium manganese composite oxide (A) of the present invention, the standard deviation σ obtained as described above is not more than 50%, preferably not more than 30%, relative to the average value of the content of the substituted element. Need.

The method for producing a lithium manganese composite oxide having a specific standard deviation σ of the present invention is not particularly limited, and the composition of the produced composite oxide becomes as uniform as possible according to a known production method. A lithium compound, a manganese compound, and a substitution element compound can be pulverized, mixed, and fired so that the content distribution of the substitution element between the primary particles is within the above range. As the lithium compound as a raw material, for example, a mixture of one or more selected from lithium hydroxide, lithium carbonate, lithium nitrate, lithium oxide and the like, or a hydrate thereof is used. Examples of the manganese compound include MnO ₂ , Mn ₂ O ₃ , Mn ₃
One or a mixture of two or more of manganese oxides such as O ₄ and MnO, carbonates such as MnCO ₃ , and MnOOH are used. As a compound of another element that partially replaces the Mn site, an oxide, a hydroxide, an organic acid salt, a chloride, a nitrate, a sulfate, or the like or a hydrate thereof containing the aforementioned element is used. For example, when the substitution element is Al,
Al ₂ O ₃ , AlOOH, Al (OH) ₃ , Al (CH ₃ C
_{OO) 3, AlCl 3, Al} (NO 3) 3 · 9H 2 O, Al 2
(SO ₄ ) _{3 and the} like, preferably Al ₂ O ₃ , AlO
OH and Al (OH) ₃ .

These starting compounds are used in proportions corresponding to the desired composition of Li, Mn and the substitution element in the resulting composite oxide. In order to produce the lithium-manganese composite oxide of (a), first, raw material compounds are mixed. When the raw material is a compound that does not melt at the reaction temperature, the particle size of the raw material compound is reduced to 1 by a means such as pulverization in order to increase the reactivity.
It is preferable to set the thickness to 0 μm or less. The order of pulverization and mixing is not particularly limited, and pulverization and mixing can be performed in any order. The method of pulverization and mixing is not particularly limited as long as uniform mixing is possible, and a dry method or a wet method may be used, and examples thereof include a mixing method using an apparatus such as a ball mill, a vibration mill, and a bead mill. The wet mixing is preferable from the viewpoint that the uniformity of the substitution element content distribution among the primary particles of the obtained composite oxide is good. When the mixture is wet, the mixture may be granulated to, for example, 1 to 100 μm by a means such as spray drying when drying the mixture.

[0013] The raw material mixture is then calcined. The firing temperature is usually 500 ° C. or higher, preferably 550 ° C. or higher, and is usually 1000 ° C. or lower, particularly preferably 950 ° C. or lower. If the temperature is too low, a long reaction time is required to obtain a lithium-manganese composite oxide having good crystallinity, which is not preferable. On the other hand, if the temperature is too high, a phase other than the intended lithium manganese composite oxide is generated, or a lithium manganese composite oxide having many defects is generated, and the capacity of the secondary battery is reduced or It is not preferable because the crystal structure is degraded due to charge and discharge. When the temperature is raised from room temperature to the above-mentioned reaction temperature, in order to perform the reaction more uniformly, for example, the temperature is gradually raised at a temperature of 5 ° C. or less per minute, or the temperature is temporarily stopped on the way. It is preferable to include a holding time at a constant temperature.

The firing time is usually from 1 hour to 100 hours. If the time is too short, a lithium manganese composite oxide having good crystallinity cannot be obtained, and an excessively long reaction time is not practical. In order to obtain a lithium manganese composite oxide having few crystal defects, it is preferable to cool slowly to a certain temperature after the above reaction, and at a cooling rate of 5 ° C./min or less up to 800 ° C., preferably 600 ° C. Slow cooling is preferred. The heating device used for firing is not particularly limited as long as the above-described temperature and atmosphere can be achieved.
For example, a box furnace, a tubular furnace, a tunnel furnace, a rotary kiln and the like can be used. The lithium manganese oxide thus produced is composed of secondary particles having a particle diameter of 1 to 100 μm in which primary particles having a particle diameter of 0.1 to 3 μm are aggregated, and has a specific surface area of 0.1 to 5 m due to nitrogen adsorption. ² /
g is preferable. The size of the primary particles can be controlled by the degree of pulverization of the raw material, the firing temperature, the firing time, and the like. The particle size of the secondary particles depends on the grinding conditions of the raw material,
When spray drying is performed, it can be controlled by spray drying conditions, pulverization after firing, classification conditions, and the like. The specific surface area can be controlled by the particle size of the primary particles and the particle size of the secondary particles, and is reduced by increasing the particle size of the primary particles and / or the particle size of the secondary particles.

The transition metal contained in the lithium transition metal composite oxide (b), which is a component of the cathode material of the present invention, includes nickel, cobalt, manganese, iridium and the like, and is preferably nickel or cobalt. Particularly preferred is nickel. Specific examples of the lithium transition metal composite oxide (b) include LiNiO ₂ , LiCo
O ₂ , LiMnO ₂ , Li ₂ IrO _{3 and the} like can be mentioned, preferably LiNiO ₂ and LiCoO ₂ , and particularly preferably LiNiO ₂ . Further, a compound in which a part of the transition metal of these compounds is substituted by another element may be used, and the compound may have a non-stoichiometric oxygen content. From the viewpoint of stabilizing the crystal structure of the composite oxide (b), it is preferable that a part of the transition metal is substituted with another element. As other elements to be substituted, Al, Ti, V, Cr, Fe, Co, M
n, Ni, Cu, Zn, Mg, Ga, Zr, etc., preferably Al, Cr, Fe, Co, Ni, Mg,
Ga, more preferably Al. In addition, two or more kinds of other elements may be substituted.

The substitution ratio of the substitution element is usually at least 5 mol%, preferably at least 10 mol%, and usually at most 60 mol%, preferably at least 40 mol%, of the transition metal.
It is as follows. If the substitution ratio is too small, the cycle characteristics may decrease, and if it is too large, the capacity may decrease. The average particle size and specific surface area of the composite oxide of (b) are as follows:
Usually, there is no particular problem as long as the average particle diameter or specific surface area of the active material used for the positive electrode does not greatly deviate, but from the viewpoint of improving the contact efficiency with the composite oxide of (a), the average particle diameter is ( It is preferable that the average particle size of the composite oxide of a) is smaller than that of the composite oxide and that the specific surface area is larger than that of (a).
A preferred specific surface area of the composite oxide (b) is 2 m ² / g.
It is more preferably at least 3 m ² / g, particularly preferably at least 5 m ² / g. Making the specific surface area too large is also difficult in production, and is usually 100 m ² / g or less, preferably 30 m ² / g or less. Here, the specific surface area refers to a specific surface area measured by a BET method using nitrogen as an adsorbed species. Particles having a large specific surface area can be obtained by a method of controlling the firing conditions and the like during the production of the composite oxide, but also by controlling the particle size by grinding the formed particles with a jet mill or a dry ball mill or the like. Obtainable.

The form of the composite of the composite oxide (a) and the composite oxide (b) is not particularly limited, and may be a physical mixture, and a film of one particle is coated on the surface of one particle. It may be formed. LiNi which is a preferable oxide of (b)
The layered compound of O ₂ can be produced by various conventionally known methods. For example, it can be produced by mixing starting materials containing lithium, nickel, and a substitution element, and then heating and firing the mixture in an oxygen atmosphere. In the above manufacturing method, the raw material containing the substitution element was not used, and N
After preparing a lithium nickel oxide in which the i-site is not substituted and reacting it with an aqueous solution, a molten salt, or a vapor of a compound containing the substitution element, the substitution element is added to the lithium nickel composite oxide particles as necessary. The Ni site may be replaced by a replacement element by performing heat treatment again to diffuse the Ni.

Lithium compound used as raw material, substitution source
The elemental compounds include those described in the production method of (a).
Similar compounds may be mentioned. Nis used as raw materials
Oxides such as NiO, NiCO _Three,
Ni (NO_Three)_Two, NiSO_Four, Nickel acetate, dicarbo
Nickel phosphate, nickel citrate, fatty acid nickel, etc.
Nickel salts, nickel hydroxide, halides, etc.
And preferably NiO, NiCO_Three, Dicarboxylic acid
Nickel, nickel citrate and nickel hydroxide. This
These starting compounds are mixed in the same manner as in the production of (a).
If so, it is fired. Firing of layered lithium nickel oxide
Is, for example, a temperature of 600 to 1000 ° C. in an oxygen atmosphere.
Done in a range. In addition, Japanese Patent Application Laid-Open No. 9-320598
As described in the section, the firing atmosphere excludes carbon dioxide gas.
The removed atmosphere can also be suitably used. In the cathode material
The ratio of the composite oxide of (a) to the composite oxide of (b) is heavy.
(A) :( b) = 30: 70-99: 1 in a quantitative ratio,
More preferably, it is in the range of 50:50 to 95: 5.
If the amount of the composite oxide (b) deviates from the above range and increases,
There is fear of a decrease in totality.
Is difficult to obtain.

A secondary battery can be prepared using the positive electrode material containing the composite oxide of (a) and (b).
An example of a secondary battery is a secondary battery including a positive electrode, a negative electrode, an electrolyte, and a separator.An electrolyte is present between the positive electrode and the negative electrode, and the separator is provided so that the positive electrode and the negative electrode do not contact each other. Placed between. For the positive electrode, a predetermined amount of a conductive material, a binder, and a solvent for uniformly dispersing these components are mixed with the mixture of the above ratios (a) and (b), and then applied to a current collector. It is manufactured by As the conductive material used here, natural graphite, artificial graphite, acetylene black, etc., as the binder polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl acetate, polymethyl methacrylate, polyethylene, nitrocellulose, etc. are dispersed Examples of the solvent for use include N-methylpyrrolidone, tetrahydrofuran, dimethylformamide, and the like, but are not limited thereto. Examples of the material of the current collector include aluminum and stainless steel. After coating on the current collector, it is dried and compacted usually by a roller press or the like. On the other hand, as the negative electrode, a material obtained by applying a carbon-based material, for example, natural graphite, pyrolytic carbon, or the like on a current collector such as Cu, a lithium metal foil, a lithium-aluminum alloy, or the like can be used.

The electrolyte is a non-aqueous electrolyte. Specifically, the electrolyte is LiCLO ₄ , LiAsF ₆ , Li
PF ₆ , LiBF ₄ , LiBr, LiCF ₃ SO _{3 and the} like. Examples of the solvent constituting the electrolyte include tetrahydrofuran, 1,4-dioxane, dimethylformamide,
Acetonitrile, benzonitrile, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate,
Examples include butylene carbonate, but are not limited thereto. These solvents may be used alone or in combination of two or more.

Examples of the separator include a non-woven fabric filter such as a polymer such as Teflon (registered trademark), polyethylene, polypropylene, and polyester, or a non-woven fabric filter such as a glass fiber, or a composite non-woven fabric filter including a glass fiber and a polymer fiber. By using such a positive electrode material of the present invention, a secondary battery having a high capacity retention rate after a high-temperature charge / discharge cycle can be obtained, as is clear from the examples.

[0022]

EXAMPLES The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the following examples unless it exceeds the gist. Example 1 Mn ₂ O ₃ , AlOOH, and LiOH were each composed of Li: Mn: Al = 1.04: 1.8 in the final spinel-type lithium manganate composition.
It was weighed so as to be 4: 0.12 (molar ratio), and pure water was added thereto to prepare a slurry having a solid concentration of 30 wt%. While stirring the slurry, the average particle diameter of the solid content in the slurry was 0.5 μm using a circulating medium stirring wet pulverizer.
Then, the mixture was pulverized, spray dried using a two-fluid nozzle spray type spray dryer, and further baked at 900 ° C. for 10 hours in an air atmosphere. As a result, substantially spherical granulated particles having an average particle diameter of about 8 μm were obtained. X-ray diffraction measurement confirmed that the particles had a cubic spinel-type lithium manganate structure. The particle size distribution was measured using a laser diffraction / scattering particle size distribution analyzer (HORI
BA910 made by BA). When 1 g of the spinel-type lithium manganate powder thus obtained was dissolved in an acid and analyzed for composition by atomic absorption spectrometry, Li: Mn: Al
The composition ratio was 1.04: 1.85: 0.11 (molar ratio).

Next, as a result of observation by a scanning electron microscope (SEM), it was found that the particle diameter of the primary particles constituting the positive electrode active material granulated particles was 0.2 to 1.0 μm. The Al content in the primary particles was measured by Auger electron spectroscopy. First, for a total of four granulated particles, for each granulated particle, three primary particles constituting the granulated particle are selected.
r Electron spectroscopy was performed (Measuring device: MICROLAB3 manufactured by VG)
10-F). As the information, the signal strength values for Al and Mn are obtained, and the signal strength value of Al / the signal strength value of Mn is represented by A
Table 1 shows the scale of the 1 content. The standard deviation of these measurements from the average was 24.5%.

As the lithium transition metal composite oxide, a commercially available layered lithium nickel oxide having a composition of Li _1.05 Ni _0.80 Co _0.15 Al _0.05 O ₂ was used. The spinel-type lithium manganese oxide / layered lithium nickel oxide was mixed at a weight ratio of 3/1. The obtained mixed active material powder was mixed with acetylene black powder and polytetrafluoroethylene powder at a weight ratio of 75: 20: 5, kneaded in a mortar to form a sheet, and punched with a 12 mmφ punch to obtain 17.0. mg disk-shaped positive electrode mixture sheet was prepared. This positive electrode mixture sheet was pressure-bonded to a 16 mmφ aluminum mesh using a hand press to form a positive electrode. In addition, as the negative electrode agent, fine graphite powder was prepared by mixing polyvinylidene fluoride and N-
It was mixed with methyl-2-pyrrolidone to form a coating solution, and this coating solution was applied on a Cu sheet, dried, and punched into a disk shape with a 12 mmφ punch to obtain a negative electrode.

The net weight of the negative electrode active material in the negative electrode is 4.80 mg.
Met. The electrode prepared in this way was CR2032 type (diameter 20 mm x thickness 3.
2mm) coin battery. At that time, as the electrolytic solution, a 0.75M-LiPF ₆ ethylene carbonate (EC): diethyl carbonate (DEC) = 3: 7 composition was used. Four of these batteries were produced, one of which was charged to 4.2 V, and stored in a constant temperature bath at 50 ° C. for 7 days while being charged. After the storage was completed, the battery was disassembled to collect the electrolytic solution, and the amount of Mn contained in the electrolytic solution was measured to be 0.38 μmol / 5 ml. On the other hand, for the remaining three batteries, 3.0 to 4.2 V in a 50 ° C. constant temperature bath.
A 1C charge / discharge cycle test in the range of was carried out. This 3
Discharge capacity at 1C-1 cycle of battery test and 50
The average value of the capacity retention rate at the end of the cycle (discharge capacity at the 50th cycle / discharge capacity at the first cycle) was 95 mAh / g in the initial discharge capacity and 93% in the capacity retention rate.

Example 2 The layered lithium nickel oxide of Li _1.05 Ni _0.80 Co _0.15 Al _0.05 O ₂ used in Example 1 was used as a lithium transition metal composite oxide in a gas impingement pulverizer (Jet mill manufactured by Seishin Enterprise). ), And pulverized using an average particle diameter of 0.5 μm,
The particles had a specific surface area of 6.9 m ² . The layered lithium nickel oxide and the spinel-type lithium manganese composite oxide prepared in Example 1 were mixed so that the weight ratio of lithium manganese oxide / lithium nickel oxide was 3/1.

Using the mixed active material powder thus obtained as a positive electrode active material, a positive electrode was prepared in the same manner as in Example 1. In addition, as a negative electrode agent, a fine graphite powder was mixed with polyvinylidene fluoride and N-methyl-2-pyrrolidone to form a coating liquid, and a negative electrode was prepared in the same manner as in Example 1. The net weight of the negative electrode active material in the negative electrode was 4.80 mg. The electrode thus produced was connected to a CR2032 type (diameter) in the same manner as in Example 1 through a polyethylene separator.
Assembled into a coin battery of 20mm x 3.2mm thickness). Four of these batteries were manufactured, and 4.2 V was applied to one of the batteries.
The battery was kept in a constant temperature bath at 50 ° C. for 7 days. After storage is completed, disassemble the battery and collect the electrolyte,
When the amount of Mn contained in the electrolytic solution was measured, it was found that the amount of Mn was 0.1
13 μmol / 5 ml. On the other hand, with respect to the remaining three batteries, 1 in a range of 3.0 to 4.2 V was stored in a 50 ° C. thermostat.
C charge / discharge cycle test was performed. The average value of the discharge capacity in the 1C-1 cycle and the capacity retention rate after the 50th cycle (discharge capacity in the 50th cycle / discharge capacity in the first cycle) of the three battery tests was 95 mAh in the initial discharge capacity. / g,
The capacity retention was 96%.

Comparative Example 1 Mn ₂ O ₃ , AlOOH, and Li ₂ CO ₃ powders were prepared by mixing each of the final compositions in spinel-type lithium manganate at a ratio of Li: Mn: Al = 1.0.
The weight was weighed so as to be 4: 1.84: 0.12 (molar ratio) and dry-mixed by a ball mill. After mixing the powder, finally 90
It was baked at 0 ° C. for 10 hours. The product powder, by X-ray diffraction,
It had a cubic spinel-type lithium manganate structure. Also, from the results of particle size distribution measurement and SEM observation,
The primary particles of about 1.0 μm aggregated, and the average particle diameter of the aggregate was 10 μm. Further, 1 g of the thus obtained lithium manganese oxide powder was dissolved in an acid, and the composition was analyzed by an atomic absorption method. As a result, Li: Mn: Al = 1.04:
The composition ratio was 1.85: 0.11 (molR). Next, regarding the Al content in the primary particles of the powder, a total of four aggregated particles were selected in the same manner as in Example 1, and three primary particles constituting each aggregated particle were selected. A total of 12 primary particles were measured by Auger electron spectroscopy.
The results are shown in Table 1. The standard deviation for these measurements was 102.7%.

As the lithium transition metal composite oxide, a commercially available layered lithium nickel oxide having the composition Li _1.05 Ni _0.80 Co _0.15 Al _0.05 O ₂ was used, and the lithium manganese composite oxide / lithium nickel oxide = 3/1 by weight ratio. And mixed. Using the obtained mixture, four CR2032 type coin batteries were assembled in the same procedure as in Example 1, and one of the batteries was charged to 4.2 V, and placed in a 50 ° C. constant temperature bath with the charged state. Stored for 7 days. After saving,
The battery was disassembled to recover the electrolytic solution, and the amount of Mn contained in the electrolytic solution was measured to be 0.63 μmol.
On the other hand, for the remaining three batteries,
A 1C charge / discharge cycle test in the range of 3.0 to 402 V was performed. The average values of the initial discharge capacity in the first cycle and the capacity retention rate after 50 cycles (discharge capacity in the 50th cycle / discharge capacity in the first cycle) of the three battery tests were 94 mAh / initial discharge capacity. Although no significant difference was found between g and Example 1, the capacity retention ratio was 90%.

Comparative Example 2 The same lithium manganese composite oxide as in Comparative Example 1 and the lithium nickel oxide pulverized by the same jet mill as in Example 2 were mixed in a weight ratio of lithium manganese composite oxide / lithium nickel oxide = 3 / 1 was mixed. Using the obtained mixture, four CR2032 type coin batteries were assembled in the same procedure as in Example 1, and one of the batteries was charged to 4.2 V, and placed in a 50 ° C. constant temperature bath with the charged state. Stored for 7 days. After the storage was completed, the battery was disassembled to recover the electrolytic solution, and the amount of Mn contained in the electrolytic solution was measured to be 0.25 μmol / 5 ml. On the other hand, the remaining three batteries were subjected to a 1C charge / discharge cycle test in a range of 3.0 to 402 V in a constant temperature bath at 50 ° C. The initial discharge capacity in the first cycle of the three battery tests and the capacity retention rate after 50 cycles (discharge capacity in 50th cycle / 1
The average value of the discharge capacity at the cycle is
Although 94 mAh / g was not significantly different from Example 2, the capacity retention rate was 93%.

Comparative Example 3 The same lithium manganese composite oxide as in Example 1 was used alone as a positive electrode active material without mixing with a lithium transition metal composite oxide, and a CR2032 type coin battery was manufactured in the same procedure as in Example 1. 3. Assembling four batteries, one of which is 4.
The battery was charged to 2 V, and stored in a constant temperature bath at 50 ° C. for 7 days while being charged. After the storage was completed, the battery was disassembled to recover the electrolytic solution, and the amount of Mn contained in the electrolytic solution was measured to be 0.90 μmol / 5 ml. On the other hand, the remaining three batteries were stored in a 50 ° C.
C charge / discharge cycle test was performed. The average values of the initial discharge capacity in the first cycle and the capacity retention rate after 50 cycles (discharge capacity in the 50th cycle / discharge capacity in the first cycle) of the three battery tests were 95 mAh / initial discharge capacity.
g, and the capacity retention was 89%.

COMPARATIVE EXAMPLE 4 The same lithium manganese composite oxide as in Comparative Example 1 was used alone as a positive electrode active material without mixing with a lithium transition metal composite oxide, and a CR2032 type coin battery was produced in the same procedure as in Example 1. 3. Assembling four batteries, one of which is 4.
The battery was charged to 2 V, and stored in a constant temperature bath at 50 ° C. for 7 days while being charged. After the storage was completed, the battery was disassembled to recover the electrolytic solution, and the amount of Mn contained in the electrolytic solution was measured to be 1.60 μmol / 5 ml. On the other hand, with respect to the remaining three batteries, a 1C charge / discharge cycle test in a range of 3.0 to 4.2 V was performed in a thermostat at 50 ° C. The average values of the initial discharge capacity in the first cycle and the capacity retention rate after 50 cycles (discharge capacity in the 50th cycle / discharge capacity in the first cycle) of the three battery tests were 94% in the initial discharge capacity.
mAh / g and the capacity retention rate were 81%.

[0033]

[Table 1]

[0034]

As is apparent from the examples, the use of the positive electrode material containing the spinel-type lithium manganese composite oxide and the other lithium transition metal composite oxide according to the present invention in which the distribution of the substitution element is controlled is achieved. Thus, a lithium ion secondary battery having excellent cycle characteristics can be obtained.

Continued on the front page (72) Inventor Yuko Ishida 1000 Kamoshita-cho, Aoba-ku, Yokohama-shi, Kanagawa Prefecture Inside Mitsubishi Chemical Research Laboratory (72) Inventor Akira Utsunomiya 1000 Kamoshida-cho, Aoba-ku, Yokohama-shi, Kanagawa Prefecture Mitsubishi Chemical Corporation Inside Yokohama Research Laboratory (72) Koji Shima 1000 Kamoshitacho, Aoba-ku, Yokohama-shi, Kanagawa Prefecture Mitsubishi Chemical Corporation Yokohama Research Laboratory F-term (reference) 4G048 AA04 AB05 AC06 AD04 AD06 AE05 5H029 AJ05 AK03 AL07 AM03 AM04 AM05 AM07 DJ16 DJ17 HJ01 HJ02 HJ07 5H050 AA07 BA17 CA09 CB08 EA10 EA24 FA17 FA19 HA01 HA02 HA07

Claims (14)

[Claims] 1. (a) A spinel-type lithium manganese oxide in which a part of an Mn site is substituted with another element, and a standard deviation σ of the average value of the substituted element content of each primary crystal particle is 50%. A lithium manganese composite oxide containing a lithium manganese composite oxide in which the substitution elements are distributed as follows, and (b) at least one lithium transition metal composite oxide other than (a). Cathode material for battery. Wherein (a) is represented by the following general formula (1) ## STR1 ## _{Li 1 + X Mn 2-XY} M Y O 4 + z (1) ( where, 0 <X <0.5,0 < Y <0.5, -0.1 ≦
Z ≦ 0.1, M represents a substitution element. The positive electrode material for a lithium ion secondary battery according to claim 1, wherein the positive electrode material is selected from lithium manganese composite oxides represented by the following formula: 3. The method according to claim 1, wherein the substitution element is B, Sn, Al, Ti,
V, Cr, Fe, Co, Ni, Cu, Zn, Mg, Ga
The positive electrode material for a lithium ion secondary battery according to claim 1, wherein the positive electrode material is at least one element selected from the group consisting of: 4. The positive electrode material for a lithium ion secondary battery according to claim 3, wherein the substitution element is Al. 5. The positive electrode material for a lithium ion secondary battery according to claim 1, wherein the transition metal of the lithium transition metal composite oxide of (b) is Ni and / or Co. . 6. The lithium transition metal composite oxide (b) is selected from a lithium nickel composite oxide having a layered structure or a lithium nickel composite oxide in which nickel sites are partially substituted with cobalt. The positive electrode material for a lithium ion secondary battery according to claim 5. 7. The positive electrode for a lithium ion secondary battery according to claim 1, wherein the lithium transition metal composite oxide of (b) is a particle having a specific surface area of 2 m ² / g or more. material. 8. The weight ratio of the lithium manganese composite oxide of (a) to the lithium transition metal composite oxide of (b) is in the range of 30:70 to 99: 1. The positive electrode material for a lithium ion secondary battery according to claim 1. 9. The weight ratio of the lithium manganese composite oxide of (a) to the lithium transition metal composite oxide of (b) is in the range of 50:50 to 95: 5. The positive electrode material for a lithium ion secondary battery according to claim 8. 10. A positive electrode for a lithium ion secondary battery, wherein an active material layer containing the positive electrode material for a lithium secondary battery according to claim 1 is formed on a current collector. 11. A lithium ion secondary battery comprising the positive electrode material for a lithium secondary battery according to claim 1 in a positive electrode. 12. A lithium secondary battery comprising: a positive electrode using the positive electrode material for a lithium ion secondary battery according to claim 1; a negative electrode; and an electrolyte obtained by dissolving a lithium salt in a solvent. battery. 13. The lithium ion secondary battery according to claim 11, wherein the negative electrode contains a carbon material. 14. The lithium ion secondary battery according to claim 12, wherein the lithium salt is LiPF ₆ .