JP2000012031A - Positive electrode active material for nonaqueous electrolyte secondary battery, method for producing the same, and nonaqueous electrolyte secondary battery using the above positive electrode active material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive electrode active material which can provide high capacity and excellent cycle characteristics to a non-aqueous electrolyte secondary battery by using manganese, which is abundant and inexpensive as a constituent element, as a constituent element. A general formula _{Li x Mn y O 4-z} (x + y =
When 3.00, 1.00 ≦ x ≦ 1.05, 0 <z ≦
0.15, where x is a value at the time of assembling the battery), and constitutes a positive electrode active material for a nonaqueous electrolyte secondary battery with a spherical or elliptical spinel-type lithium manganese oxide.
The above spinel-type lithium manganese oxide has a mixing ratio of manganese dioxide and lithium salt in a molar ratio of Li and Mn of L.
i / Mn ≦ 0.50, and can be manufactured by firing at 780 to 820 ° C. while supplying a mixed gas of an inert gas and an oxygen gas at a flow rate of 1 liter / minute or more per 100 g of the raw material mixture. , Its Fe content is 200
ppm or less, the average particle diameter is preferably 1 to 45 μm, and the specific surface area is preferably 0.5 to ³ m ² / g.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cathode active material for a non-aqueous electrolyte secondary battery, a method for producing the same, and a non-aqueous electrolyte secondary battery using the cathode active material. Positive electrode active material for a non-aqueous electrolyte secondary battery capable of providing a non-aqueous electrolyte secondary battery having excellent cycle characteristics, a method for producing the same, and the above-described positive electrode active material, high capacity, and cycle characteristics The present invention relates to a non-aqueous electrolyte secondary battery having excellent characteristics.

[0002]

2. Description of the Related Art In recent years, with the development of portable electronic devices such as mobile phones and notebook computers and the practical use of electric vehicles, secondary batteries of small size, light weight and high capacity have been required. Was. At present, a lithium ion secondary battery using LiCoO ₂ as a positive electrode active material and a carbon-based material as a negative electrode active material has been commercialized as a high capacity secondary battery that meets this demand. LiCoO ₂ used as a positive electrode active material of this lithium ion secondary battery
Is widely used as a suitable positive electrode active material because it is easy to manufacture and easy to handle.

[0003] However, LiCoO ₂ is produced from a rare metal, cobalt (Co), as a raw material.
It is expected that resource shortages will become serious in the future. In addition, since the price of cobalt itself is high and the price fluctuates greatly, it is desired to develop a cathode material that is inexpensive and has a stable supply.

[0004] Therefore, research has been conducted on lithium ion secondary batteries using lithium manganese oxide having a spinel structure, lithium nickelate, lithium titanate or the like as a positive electrode active material instead of LiCoO ₂ . Among these lithium-containing composite oxides, a lithium manganese oxide having a spinel structure using manganese as a constituent element, whose component element is inexpensive and whose supply is stable, is LiCoO 2.
It is attracting attention as a positive electrode active material that replaces ₂ .

The lithium manganese oxide having the spinel structure includes Li ₂ Mn ₄ O ₉ , Li ₄ Mn ₅ O ₁₂ and Li
Mn ₂ O _{4 and the} like, among which LiMn ₂ O ₄ can be charged and discharged in the 4V region with respect to the lithium potential, have been actively studied (Japanese Patent Laid-Open No. 6-76824).
JP, JP-A-7-73883, JP-A-7-23
0802, JP-A-7-245106, etc.).

[0006]

By the way, LiCoO
The theoretical discharge capacity of No. ₂ is 274 mAh / g, but when deep charge / discharge is performed, LiCoO ₂ causes a phase change and affects the cycle life, so that the practical discharge capacity of an actual lithium ion secondary battery is 125 ~ 140mAh /
g. In contrast, although the theoretical discharge capacity of LiMn ₂ O ₄ is 148 mAh / g, the LiMn ₂
O ₄ also undergoes a phase change during charge and discharge similarly to LiCoO _2, and when a carbon-based material is used as the negative electrode active material, the irreversible capacity of the carbon-based material is large, so that a battery is actually used. Discharge capacity can be 90-105mA
h / g. As is clear from this, L
When iMn ₂ O ₄ is used as the positive electrode active material, L
The battery capacity cannot be increased as compared with the case where iCoO ₂ is used as a positive electrode active material.

In addition, the true density of LiCoO ₂ is 4.9 or less.
Whereas it is 5.1 g / cm ^3, the true density of LiMn ₂ O ₄ is 4.0~4.2g / cm ^3, considering the filling property as a positive electrode active material, resulting in disadvantages in volume surface Will be. Furthermore, in a lithium ion secondary battery using LiMn ₂ O ₄ as a positive electrode active material, Li
Since the structure of Mn ₂ O ₄ itself is unstable, there is also a problem that cycle characteristics are shorter than that of a LiCoO ₂ battery.

Further, in a lithium ion secondary battery, since a non-aqueous electrolyte using an organic solvent is used as an electrolyte solvent, the conductivity of ions in the electrolyte is low, so that a large current flows from the battery. When a heavy load is applied to take out the battery, the discharge voltage drops more than during low-load discharge, and the battery capacity cannot be sufficiently taken out. When the temperature is low, the discharge voltage is greatly reduced as compared with the discharge characteristics at room temperature.

SUMMARY OF THE INVENTION It is a first object of the present invention to provide a positive electrode active material for a non-aqueous electrolyte secondary battery which is structurally stable and has a high capacity in view of the above-mentioned conventional circumstances. A second object of the present invention is to provide a non-aqueous electrolyte secondary battery having a high capacity and excellent cycle characteristics using the above-mentioned positive electrode active material. In addition, the present invention provides a non-aqueous electrolyte secondary battery that has improved utilization of the positive electrode active material, has excellent load characteristics, and has excellent discharge characteristics at low temperatures, in accordance with the recent use environment of secondary batteries. The third purpose is to provide

[0010]

The present inventors have SUMMARY OF THE INVENTION As a result of intensive research to solve the above problems, as a positive electrode active material for a nonaqueous electrolyte secondary battery, the general formula Li _x Mn _y O
_4-z (where x + y = 3.00, 1.00 ≦ x ≦ 1.
05, 0 <z ≦ 0.15, where x is a value at the time of battery assembly and is a value that changes in the range of 0 <x ≦ 1.05 upon charging and discharging). It has been found that when a spinel-type lithium manganese oxide is used, a nonaqueous electrolyte secondary battery having a discharge capacity closer to the theoretical discharge capacity, a high capacity, and excellent cycle characteristics can be obtained. Further, the present inventors have found that the above-mentioned general formula Li _x M _y O _4-z
The mixture ratio of manganese dioxide and lithium salt is Li / Mn ≦ 0.50 in terms of the molar ratio of Li and Mn, and the mixed gas of inert gas and oxygen gas is a raw material mixture. It has also been found that it can be manufactured by firing at 780 to 820 ° C. while supplying at a flow rate of 1 liter / min or more per 100 g. Furthermore, the present inventors have found that a non-aqueous electrolyte secondary battery having excellent load characteristics can be obtained by setting the Fe content in the spinel-type lithium manganese oxide to 200 ppm or less. Furthermore, the present inventors set the specific surface area of the spinel-type lithium manganese oxide in the range of 0.5 to 3 m ² / g, and set the average particle diameter to 1 to 45 μm, so that the discharge characteristics at low temperature can be improved. It has also been found that an excellent nonaqueous electrolyte secondary battery can be obtained.

Hereinafter, the present invention will be described more specifically. First, the characteristics of the spinel-type lithium manganese oxide as a positive electrode active material for a nonaqueous electrolyte secondary battery will be described. In the spinel-type lithium manganese oxide, the content ratio of its constituent elements Li, Mn, and O is described. However, has a significant effect on the electrochemical capacity.

As is apparent from the composition ratio of the conventional LiMn ₂ O ₄ , the average valence of Mn is 3.5, and trivalent Mn and tetravalent Mn are usually mixed in equal amounts. I have. However, it is clarified that only trivalent Mn actually participates in charge and discharge, and the discharge capacity increases as the trivalent Mn in the composition of LiMn ₂ O ₄ increases. Therefore, in order to increase trivalent Mn, LiMn ₂
It is conceivable to use a lithium manganese oxide in which the amount of oxygen in the crystal structure of O ₄ is reduced.

However, when the amount of trivalent Mn increases, Li
The structure of Mn ₂ O ₄ changes from a cubic spinel structure to a tetragonal LiMnO ₂ . This tetragonal LiM
nO ₂ has a lithium potential and can be charged and discharged in a 3 V region, but cannot be used when a high potential of around 4 V is required. The oxygen content in LiMn ₂ O ₄ is LiM
It is important for determining the valence of Mn in n ₂ O _{4. When} the oxygen content is high, tetravalent Mn increases, and when the oxygen content is low, trivalent Mn increases. Due to the Jahn-Teller effect, the trivalent Mn is liable to undergo a phase change when a valence change occurs, destabilizing the structure of LiMn ₂ O ₄ during charging and discharging, and causing spinel as Li ions enter and exit. Destruction of the phase is likely to occur.

In addition, LiMn ₂ O ₄ is used in the crystal structure.
By doping and undoping, the Li amount is 0 to 1.
In the range of 00, the charge and discharge can be performed electrochemically. However, if the amount of Li in the crystal structure is small, the amount of Li that can be used for charge and discharge is reduced, so that the electrochemical capacity is reduced. For this reason, it is desirable that the Li content be as high as possible. However, excess Li exceeding the stoichiometric composition enters the 16d site to be occupied by Mn in LiMn ₂ O ₄ , and the Li entering the 16d site of Mn is charged and discharged. Will no longer be involved.
Furthermore, when Li enters the 16d site of Mn, LiMn
Tetravalent Mn in ₂ O ₄ increases, and the charge / discharge capacity decreases. Therefore, when the amount of Li is x and the amount of Mn is y, x + y =
When the lithium manganese oxide is represented as 3.00,
The Li content is preferably 1.00, but the oxygen content is O
_{When 4-z} (0 <z ≦ 0.15), the Li content is 1.0
Even when it is 0 or more, a large amount of trivalent Mn can be contained. On the other hand, if the Li amount is too large, a large amount of the impurity phase is generated. Therefore, the Li amount is preferably from 1.00 to 1.05, more preferably from 1.01 to 1.03.

Further, if the oxygen content represented by O ₄ -Z in the above general formula becomes too large, tetravalent Mn increases as described above, and the charge / discharge capacity becomes small. Less than 3.85 or more,
It is more preferably 3.98 or less and 3.88 or more.

The spinel-type lithium manganese oxide of the present invention has a crystal structure in which Li (lithium) is doped.
The charge / discharge cycle is performed by undoping. The compositions at the time of battery assembly and charge / discharge cycle are as follows. The composition at the time of battery assembly _{Li x Mn y O 4-z} (x + y = 3.00,1.00 <x ≦ 1.05,0 <z
≦ 0.15) during charging and discharging composition _{Li x 'Mn y O 4-} z (0 <x' ≦ 1.05,1.95 / 4.00 <y / (4
−z) ≦ 2.00 / 3.85) At the time of charging and discharging, the amount of lithium is 0 <x ′ ≦ 1.05.
And the ratio of the amount of manganese to the amount of oxygen is 1.95 /
4.00 <y / (4-z) ≦ 2.00 / 3.85.

The present invention has been made based on the above findings, while maintaining a spinel structure with respect to lithium manganese oxide.
The trivalent Mn is contained as much as possible to increase the discharge capacity and to sufficiently cope with a high potential of 4V class. That is, the present invention relates to the general formula Li _x Mn
_y O _4-z (where x + y = 3.00, 1.00 ≦ x ≦
1.05, 0 <z ≦ 0.15, where x is a value at the time of assembling the battery and changes during charging and discharging in a range of 0 <x ≦ 1.05). The present invention relates to a positive electrode active material for a non-aqueous electrolyte secondary battery composed of manganese oxide, and the spinel-type lithium manganese oxide of the present invention has a higher oxygen content in the crystal structure than a conventional lithium manganese oxide. Even in the case where it is suppressed and contains a large amount of trivalent Mn, it is characterized by a long cycle life and excellent cycle characteristics.

[0018]

Spinel-type lithium manganese oxide of the present invention DETAILED DESCRIPTION OF THE INVENTION generally as described above formulas Li _x Mn _y O _4-z
(When x + y = 3.00, 1.00 ≦ x ≦ 1.0
5, 0 <z ≦ 0.15, where x is a value at the time of assembling the battery and is a value that changes in the range of 0 <x ≦ 1.05 upon charging and discharging). In describing the lithium manganese oxide in detail, regarding the conventional LiMn ₂ O ₄ , if its shape and raw materials are mentioned, electrolytic synthetic manganese dioxide is generally used as the raw material for producing LiMn ₂ O _4. I have. However, LiMn ₂ O ₄ produced using this conventional electrolytically synthesized manganese dioxide has an angular shape as shown in the electron micrograph of FIG. 2 (in FIG. 2, the whitish portion is LiMn). ₂ O ₄ particles).

In a non-aqueous electrolyte secondary battery, it is necessary to increase the mixture density of the positive electrode mixture to increase the capacity. In the case of LiMn ₂ O ₄ having the angular shape as described above, the angular Therefore, there is a problem that the mixture density cannot be increased and the packing density is reduced.

The spinel-type lithium manganese oxide of the present invention can meet such a demand, and as shown in FIG. 1 (in FIG. 1, the whitish portion is the spinel-type lithium manganese oxide of the present invention). Lithium manganese oxide particles), which are spherical or elliptical, so that the electrochemical reaction in the active material particles is considered to proceed uniformly, thereby allowing a large discharge capacity to be expected. Furthermore, when this spinel-type lithium manganese oxide is used as the positive electrode active material, the packing density of the positive electrode mixture can be increased, and a high capacity nonaqueous electrolyte secondary battery can be obtained. In the present invention, in expressing the shape of the spinel-type lithium manganese oxide, the shape is expressed as spherical or elliptical, but this is all from almost spherical to almost elliptical (that is, almost spherical). (Including intermediate shapes up to an almost elliptical shape), which means that any shape included therein may be used.

As will be described in detail later, the spinel-type lithium manganese oxide of the present invention has an average particle diameter of 1 to 45 μm in order to increase the charge / discharge efficiency.
m is preferable, and in particular, the average particle diameter is preferably 1 to 25 μm. The specific surface area is preferably 0.5 to ³ m ² / g, particularly preferably 1 to 3 m ² / g in order to increase the effective reaction area.
² / g is preferred.

Further, the present inventors have set the content of Fe contained in the spinel-type lithium manganese oxide to 200 ppm.
By using the following, it has been found that when the spinel-type lithium manganese oxide is used as a positive electrode active material, the charge / discharge capacity and the cycle characteristics are improved and the load characteristics can be improved.

That is, transition metals other than manganese are mixed during the production process of the chemically synthesized manganese dioxide which is a raw material of the lithium manganese oxide of the present invention. In particular, the mixing of the Fe component is remarkable. It has been found that the synthesis of lithium manganese oxide using a small amount of chemically synthesized manganese dioxide as a raw material can further improve the charge / discharge capacity of the product and obtain a nonaqueous electrolyte secondary battery with excellent load characteristics. Was. Although the reason for this is not always clear at present, the present inventors have considered that when manganese dioxide containing Fe is used, iron oxide or Fe which does not contribute to the charge / discharge reaction in the production process of lithium manganese oxide is considered. Containing lithium oxide is produced,
This is considered to be the cause of the deterioration of the load characteristics. Therefore, by using manganese dioxide having a small Fe content, the generation of those impurities is suppressed, and the Fe content in the lithium manganese oxide is reduced to 200 ppm.
By doing so, it is considered that the efficiency of diffusion in the solid phase of lithium ions to be doped and dedoped in the charge / discharge reaction can be increased, and not only the charge / discharge capacity can be improved, but also the load characteristics can be improved.

Further, in order to synthesize one equivalent of lithium manganese oxide as a product, two equivalents of manganese dioxide as a raw material are required. Therefore, Fe component, which is an impurity in manganese dioxide, is contained in lithium manganese oxide. Since the content is concentrated to about twice the content, the concentration of the Fe component in the manganese dioxide is considered to greatly affect the load characteristics of the spinel-type lithium manganese oxide.

According to the study of the present inventors, the Fe content in the lithium manganese oxide is 200 ppm or less, more preferably 100 ppm or less, and further preferably 50 pp or less.
It was found that when the lithium manganese oxide was used as a positive electrode active material, a non-aqueous electrolyte secondary battery having high charge / discharge capacity and excellent load characteristics was obtained when the lithium manganese oxide was used as a positive electrode active material.

The present inventors have found that the average particle diameter of the spinel-type lithium manganese oxide is preferably from 1 to 45 μm, more preferably from 1 to 25 μm, in order to enhance the charging and discharging efficiency. Preferably, the specific surface area is 0.5 to 3 to increase the effective reaction area.
m ² / g is preferred, and particularly preferably 1 to ³ m ² / g,
By the general formula Li _x Mn _y O such an average particle size and specific surface area of spherical or ellipsoidal shape of the spinel-type lithium manganese oxide represented by the _4-z of the present invention, the progress of the electrochemical reaction It has become advantageous, and it has been found that not only the charge / discharge capacity and cycle characteristics but also the discharge characteristics at low temperatures can be improved.

The spinel type lithium manganese oxide of the present invention has an average particle diameter of 1 to 45 μm and a specific surface area of 0.5 to 3 μm.
The reason why not only the excellent charge / discharge capacity and cycle characteristics but also the low-temperature discharge characteristics can be improved by adjusting the ratio to m ² / g is not necessarily clear at present, but is considered as follows. That is, the positive electrode of the nonaqueous electrolyte secondary battery of the present invention is a paste in which the spinel-type lithium manganese oxide is dispersed in a solvent together with a binder or the like to form a paste, which is coated on a substrate serving as a current collector and dried. The spinel-type lithium manganese oxide had an average particle diameter of 1 μm or more and a specific surface area of 3 m ² /
g or less, the agglomeration of the spinel-type lithium manganese oxide particles in the positive electrode mixture paste can be suppressed, and the wettability of the spinel-type lithium manganese oxide particles to the solvent is improved. The amount of solvent to be used can be reduced. Although the solvent remaining in the active material-containing layer after paste drying (that is, the positive electrode mixture layer) affects the load characteristics, the spinel-type lithium manganese oxide of the present invention requires the use of a small amount of solvent as described above. Since it is possible to reduce the residual solvent in the positive electrode mixture, it is possible to lower the drying temperature of the paste applied on the substrate, which contributes to the battery characteristics during the positive electrode manufacturing process, The distribution of the spinel-type lithium manganese oxide, binder, electron conduction aid, etc. in the positive electrode mixture after paste drying becomes uniform, improving the load characteristics. It is considered that the discharge characteristics of the semiconductor device are also improved.

On the other hand, the average particle diameter of the spinel type lithium manganese oxide is 45 μm or less, and the specific surface area is 0.5 m ² /
g or more, the progress of the electrochemical reaction on the particle surface of the spinel-type lithium manganese oxide is smoothed, and fine lithium manganese oxide is obtained. And the effect of the spherical or elliptical particle shape of the present invention can be more remarkably exhibited. Incidentally, the average particle diameter referred to in the present invention is determined by an electron micrograph (magnification: 50).
0 times), the particle size of each particle in the photograph was measured, and the value determined by the average value of the particle sizes of 50 particles was used. The specific surface area was defined by degassing 1 g of a sample at 120 ° C for 20 hours. After the measurement environment of the sample was reduced to 10 mTorr or less, the pores of 1 to 100 ° of the sample were measured by a nitrogen adsorption method (Autosorb 1, manufactured by Yuasa Ionics, Inc.), and the measured values were measured with an adsorbent. Means the value obtained from

Next, the method for producing the spinel-type lithium manganese oxide of the present invention will be described. As the manganese source, chemically synthesized manganese dioxide is used, and it is preferable to use spherical or elliptical ones.
By using this spherical or elliptical chemically synthesized manganese dioxide, the resulting spinel-type lithium manganese oxide can be spherical or elliptical. In order to produce a spinel-type lithium manganese oxide having the above average particle diameter and specific surface area, the average particle diameter of manganese dioxide is preferably from 1 to 45 μm, and particularly preferably from 1 to 25 μm. Further, the Fe content in the obtained spinel-type lithium manganese oxide was adjusted to 20.
In order to reduce the content to 0 ppm or less, it is preferable to use a chemically synthesized manganese dioxide having a small Fe content and appropriately select a temperature, an atmosphere, a gas flow rate, and the like within the range of the production conditions of the present invention described later.

The above-mentioned chemically synthesized manganese dioxide having a low Fe content can be obtained from the step of dissolving manganese as an ion in an aqueous solution in the process of producing manganese dioxide, by adding calcium carbonate or the like or by sulfurization. When the components are precipitated as salts, they can be produced by adjusting the pH and the amount of addition in the solution. Also, in the process of precipitating manganese ions with ammonium carbonate or the like and extracting them as manganese carbonate,
In the above-described process, when the adjustment of the pH and the amount of the solution in the solution is not sufficiently performed, the Fe component may precipitate at the same time. By adjustment, manganese dioxide having a small Fe content can be produced.

As the lithium source, various lithium salts can be used, for example, lithium hydroxide monohydrate, lithium nitrate, lithium carbonate, lithium acetate, lithium bromide, lithium chloride, lithium citrate, and fluoride. Lithium, lithium iodide, lithium lactate, lithium oxalate, lithium phosphate, lithium pyruvate, lithium sulfate, lithium oxide and the like, among them,
Lithium hydroxide monohydrate is preferred in that no gas such as carbon oxide, nitrogen oxide, and sulfur oxide, which adversely affects the environment, is generated.

In the production of the spinel-type lithium manganese oxide of the present invention, the charging ratio of manganese dioxide to lithium salt is Li / Mn ≦ 0.
5, particularly preferably 0.45 ≦ Li / Mn ≦ 0.49. The reason that the mixture molar ratio of Li and Mn is preferably set to 0.5 or less is that, when the mixture molar ratio of Li / Mn is larger than 0.5, a reaction intermediate product and the like easily remain, This is because the intermediate product may hinder the charge / discharge reaction in the battery system and reduce the charge / discharge capacity of the nonaqueous electrolyte secondary battery.

In the production of the spinel-type lithium manganese oxide of the present invention, it is preferable that the above-mentioned manganese dioxide and lithium salt are mixed and pelletized and fired. In other words, since the reaction proceeds by solid-phase diffusion of the raw material in order to carry out the reaction in a solid-phase reaction, the pelletization improves the contact between the lithium salt particles of the raw material and the manganese dioxide particles, thereby increasing the reaction. Progresses easily. The size of the pellet is 5 to 15 m
m is preferred.

It is preferable to raise the temperature of the spinel-type lithium manganese oxide of the present invention to 780 to 820 ° C. and hold the temperature for 24 to 36 hours. By firing at 780 to 820 ° C., the crystallinity of the generated lithium manganese oxide is improved, and a spinel-type manganese structure is easily formed. The firing temperature is 780 ° C
When the temperature is lower, the discharge capacity is reduced due to the decrease in crystallinity of the spinel-type lithium manganese oxide and the generation of impurities, and when the firing temperature is higher than 820 ° C., the charge capacity and discharge capacity of the spinel-type lithium manganese oxide , That is, the irreversible capacity becomes large, so that the discharge capacity becomes small.

As the heat treatment for the above-mentioned firing,
It is preferable to preheat from room temperature to 250 to 500 ° C., which is the melting point of the lithium salt, and then raise the temperature to 780 to 820 ° C., rather than raising the temperature to 780 to 820 ° C. at once. This is because the reaction between the lithium salt and manganese dioxide occurs stepwise, and the spinel-type lithium manganese oxide is generated via the intermediate product. This is for preheating as a reaction. When the temperature is raised to 780 to 820 ° C. at a stretch, the lithium salt and manganese dioxide partially react to the final stage, and the spinel-type lithium manganese oxide generated thereby is not reacted. It may interfere with the reaction of the product. It is also effective to carry out heating stepwise in order to shorten the firing time for obtaining the desired spinel-type lithium manganese oxide. The time for the preheating is not particularly limited, but is usually preferably 12 to 30 hours, and it is preferable to raise the temperature from room temperature to around the melting point of the lithium salt, and further maintain the temperature to perform heating.

The heat treatment including the above-mentioned baking and preheating is preferably performed in a mixed atmosphere of an inert gas such as argon, helium, or nitrogen and an oxygen gas. The mixing ratio of these gases is preferably in the range of 5/5 to 9/1 by volume ratio of inert gas / oxygen gas,
It is more preferable to set it in the range of 8/2 to 9/1. As described above, the volume ratio of inert gas / oxygen gas is 5/5 to 9
By setting the ratio to / 1, the progress of the reaction is facilitated, and a spinel-type lithium manganese oxide containing no impurities can be easily obtained.

The flow rate of the mixed gas of the inert gas and the oxygen gas is preferably 1 liter / min or more per 100 g of the starting material mixture, and more preferably 1 to 5 liter / min per 100 g of the starting material mixture. When the gas flow rate is small, that is, when the gas flow rate is low, a difference occurs in reactivity to the spinel structure, and Mn ₂ O ₃ or Li ₂ MnO
There is a possibility that impurities such as ₃ may remain.

In order to produce a positive electrode for a non-aqueous electrolyte secondary battery using the spinel-type lithium manganese oxide of the present invention as a positive electrode active material, for example, the lithium manganese oxide described above, if necessary, for example, phosphorus An electron conduction aid such as flaky graphite and acetylene black and a binder such as polytetrafluoroethylene and polyvinylidene fluoride may be added and mixed, and the resulting positive electrode mixture may be formed by an appropriate means.

As the active material of the negative electrode facing the positive electrode, lithium or a lithium-containing compound is used. As the lithium-containing compound, there are a lithium alloy and others. Examples of the lithium alloy include lithium-aluminum, lithium-lead, lithium-indium, lithium-gallium, lithium-indium-gallium, and the like. Examples of the lithium-containing compound other than the lithium alloy include tin oxide, silicon oxide, nickel-silicon alloy, magnesium-silicon alloy, carbon material having a turbostratic structure, graphite, tungsten oxide, and lithium iron composite oxide. Things. Some of these exemplified lithium-containing compounds do not contain lithium at the time of manufacture, but when they act as a negative electrode active material, they contain lithium. Of these, graphite is particularly preferred because of its high capacity density.

The negative electrode is mixed with the above-mentioned negative electrode active material, if necessary, by adding the same binder and electron conduction auxiliary as in the case of the above-mentioned positive electrode active material, and then molding the obtained negative electrode mixture by an appropriate means. It is produced by doing.

As the means for forming the positive electrode and the negative electrode, a positive electrode mixture and a negative electrode mixture can be molded under pressure, or the positive electrode mixture and the negative electrode mixture can be formed into a paste or slurry by using water or another suitable solvent. Various means can be adopted, such as applying or impregnating each paint on a substrate also serving as a current collector, drying and forming a coating film on the substrate, but as a coating film on the latter substrate. Forming is suitable.

As a method of applying the coating material to the substrate, various coating methods such as an extrusion coater, a reverse roller, a doctor blade and the like can be adopted. Further, as a base of an electrode such as a positive electrode and a negative electrode, for example, a mesh of metal such as aluminum, stainless steel, titanium, and copper, punched metal, expanded metal, foam metal, and foil are used.

The ratio of the amount of the active material between the positive electrode and the negative electrode depends on the type of the negative electrode active material, but is preferably 1.5 to 3.5 (weight ratio). .

In the non-aqueous electrolyte secondary battery using the spinel-type lithium manganese oxide of the present invention as a positive electrode active material, an organic solvent-based non-aqueous electrolyte in which an electrolyte is dissolved in an organic solvent is used as the electrolyte. Can be The solvent of the electrolytic solution is not particularly limited, but it is particularly suitable to use a chain ester as a main solvent. As such a chain ester, for example, dimethyl carbonate (D
MC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethyl acetate (EA), and organic solvents having a chain COO-bond such as methyl propionate (MP). The fact that the chain ester is the main solvent of the electrolytic solution means that these chain esters occupy more than 50% by volume of the total electrolyte solvent, and in particular, the chain ester is a total solvent. It is preferable that 65% by volume or more in the electrolyte solution solvent, especially the chain ester accounts for 70% by volume or more in the total electrolyte solution solvent, and that the chain ester accounts for 75% by volume or more in the total electrolyte solution solvent. Is preferred.

It is preferable that the chain ester be used as the main solvent as the solvent of the electrolyte because the chain ester exceeds 50% by volume in the total solvent of the electrolyte, so that the battery characteristics, especially the low-temperature characteristics, are obtained. Is improved.

However, as the solvent for the electrolytic solution, an ester having a high induction ratio (an ester having an induction ratio of 30 or more) is used for the chain ester in order to improve the battery capacity as compared with the case of using only the chain ester. It is preferable to use a mixture. The amount of the ester having such a high dielectric constant in the total electrolyte solvent is preferably at least 10% by volume, particularly preferably at least 20% by volume. That is, when the amount of the ester having a high dielectric constant is 10% by volume or more in the total electrolyte solvent, the improvement in capacity is clearly exhibited, and when the amount of the ester having a high dielectric constant becomes 20% by volume or more in the total electrolyte solution. The improvement in capacity is more clearly expressed. However, if the volume of the ester having a high dielectric constant in the total electrolyte solvent is too large, the discharge characteristics of the battery tend to decrease. As described above, the content is preferably 10% by volume or more, more preferably 20% by volume or more, preferably 40% by volume or less, more preferably 30% by volume or less, and still more preferably 25% by volume or less.

Examples of the ester having a high dielectric constant include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and γ.
-Butyrolactone (γ-BL), ethylene glycol sulphite (EGS), etc., and particularly those having a cyclic structure such as ethylene carbonate and propylene carbonate are preferable, and cyclic carbonates are particularly preferable. Specifically, ethylene carbonate (EC ) Is most preferred.

Examples of the solvent that can be used in combination with the ester having a high dielectric constant include 1,2-dimethoxyethane (1,2-DME), 1,3-dioxolan (1,3-DO), and tetrahydrofuran. (THF), 2
-Methyl-tetrahydrofuran (2-Me-THF),
Diethyl ether (DEE) and the like. In addition, an amine imide-based organic solvent, a sulfur-containing or fluorine-containing organic solvent, and the like can also be used.

As the electrolyte of the electrolytic solution, for example, Li
ClO ₄ , LiPF ₆ , LiBF ₄ , LiAsF ₆ , L
iSbF ₆ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ ,
LiCF ₃ CO ₂ , Li ₂ C ₂ F ₄ (SO ₃ ) ₂ , Li
N (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , L
iCnF _{2n + 1} SO ₃ (n ≧ 2) or the like is used alone or in combination of two or more. In particular, LiPF ₆ and LiC ₄ F
₉ SO _{3 and the} like are preferable because of good charge / discharge characteristics.
The concentration of the electrolyte in the electrolyte is not particularly limited, but is 0.3 to 1.7 mol / l, particularly 0.4 to 1.7 mol / l.
About 1.5 mol / l is preferable.

As the separator, a separator having sufficient strength and capable of holding a large amount of electrolyte is preferred. From such a viewpoint, polypropylene and polyethylene having a thickness of 10 to 50 μm and a porosity of 30 to 70% are used. And a microporous film or nonwoven fabric made of a copolymer of propylene and ethylene.

[0051]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below. However, the present invention is not limited to only these examples.

Example 1 A chemically synthesized manganese dioxide having a spherical shape (the content of Fe in the manganese dioxide was 21 ppm) was previously classified to 45 μm or less. Further, granular lithium hydroxide monohydrate as a lithium source was ground by a planetary ball mill until it became fine powder. Next, 19.23 g of the above-mentioned chemically synthesized manganese dioxide and 4.36 g of lithium hydroxide monohydrate were mixed, and further sufficiently pulverized and mixed in a planetary ball mill. The mixture was compression-molded into pellets using a press machine, and the pellets were placed in an alumina boat and fired in a tubular electric furnace. The molar ratio Li / Mn between the amount of Mn in the chemically synthesized manganese dioxide and the amount of Li in lithium hydroxide monohydrate was 0.47.

The firing atmosphere is argon gas / oxygen gas =
8/2 (volume ratio) of the mixed gas was mixed with the raw material mixture (ie,
The mixture was supplied at a flow rate of 1.0 liter / minute per 100 g of a mixture of a chemically synthesized manganese dioxide as a starting material and lithium hydroxide / monohydrate. In the firing, first, the temperature is raised to 470 ° C. at a temperature rising temperature of 200 ° C./h, and
Hold for a pre-heating time and then at 100 ° C / h for 8 hours.
This was performed by raising the temperature to 00 ° C. and maintaining the temperature at 800 ° C. for 36 hours. Thereafter, the product was naturally cooled, and after the temperature of the fired product was reduced to 80 ° C. or lower, the fired product was taken out of the tubular electric furnace and sufficiently pulverized and mixed in a mortar.

After the fired product was sufficiently pulverized and mixed as described above, it was compression-molded again into pellets, and the pellets were fired in the same manner as described above. That is, the temperature was raised to 800 ° C. at a temperature rising rate of 200 ° C./h, and firing was performed at a temperature of 800 ° C. for 36 hours. Thereafter, the temperature was allowed to cool to room temperature by natural cooling, and after the temperature was lowered, the pellet was sufficiently pulverized in an agate mortar, and the pulverized powder was classified to obtain a spherical or oval powder of 45 μm or less. FIG. 1 shows an electron micrograph of the lithium manganese oxide particle structure at a magnification of 1510. As shown in FIG. 1, the obtained lithium manganese oxide was spherical or elliptical.

When the obtained lithium manganese oxide was analyzed by X-ray diffraction, a diffraction line specific to LiMn ₂ O ₄ having a spinel structure was observed and no peak due to impurities was observed. It was confirmed that the obtained lithium manganese oxide was a lithium manganese oxide having a spinel structure. Further, the composition of Li, Mn, and O of the obtained lithium manganese oxide was measured by an atomic absorption spectrometer. The sample was prepared as follows. To 0.25 g of the produced lithium manganese oxide, 10 ml of ion-exchanged water and 110 ml of 12N hydrochloric acid were added, and the mixture was heated until the lithium manganese oxide was completely dissolved.
Thereafter, the mixture was allowed to cool to room temperature, ion-exchanged water was added to make the total amount 100 ml, and a sample for analysis was prepared. The analysis of each element was performed by the standard addition method. According to the analysis result, the composition of the manufactured lithium manganese oxide was Li _1.01 Mn _1.99 O _3.88.
Turned out to be. Further, when the Fe content in the lithium manganese oxide was measured by an atomic absorption spectrometer in the same manner as in the composition analysis of Li, Mn, and O described above, the Fe content was 40 ppm.

The average particle diameter of the obtained spinel-type lithium manganese oxide was determined by taking an electron micrograph (magnification: 500 times) of the product and measuring the particle diameter of each particle in the photograph. It was determined by calculating the average value of the particle diameters of 50 particles. As a result, the average particle size was 25 μm. Furthermore, the specific surface area of the obtained spinel-type lithium manganese oxide was measured by using Yuasa Ionics' Auto Souv 1 and the sample was subjected to degassing at 120 ° C. for 20 hours with the measurement range of the sample pores being 1 to 100 °. After confirming that the environmental vacuum degree was 10 mTorr or less, the specific surface area was 1.0 m ² / g when measured using nitrogen gas as a probe gas.

A model cell was prepared using the spinel-type lithium manganese oxide produced by the above method. First,
1.6 g of the spinel-type lithium manganese oxide, 0.3 g of acetylene black and 0.1 g of polytetrafluoroethylene were weighed out and mixed well in a mortar. These mixtures were thoroughly ground in a mortar until they became gummy, and the gummy mixture was pressed into a 500 μm mesh sieve to form a powder. 40m of this powder
g, and compression molded with a press machine together with a platinum net having a diameter of 10 mm to produce a pellet-shaped electrode.

The pellet-shaped electrode prepared as described above was used as a working electrode, and a lithium foil was used as a counter electrode and a reference electrode.
A non-aqueous solution in which PF ₆ was dissolved at a concentration of 1.0 mol / l in a mixed solvent of ethylene carbonate and ethyl methyl carbonate at a volume ratio of 1: 3 was used as an electrolyte to prepare a model cell, and to evaluate a positive electrode active material. Was done.

Further, a battery for evaluating cycle characteristics was manufactured as described below. 250 g of N-methyl-2-pyrrolidone was added to 20 g of polyvinylidene fluoride as a binder, and the mixture was heated to 60 ° C. to dissolve the polyvinylidene fluoride in N-methyl-2-pyrrolidone to prepare a binder solution. To this binder solution, 450 g of the above lithium manganese oxide was added as a positive electrode active material, and 5 g of carbon black and 25 g of graphite were further added as electron conduction aids, followed by stirring to prepare a slurry-like coating.

This paint was uniformly applied on both sides of an aluminum foil having a thickness of 20 μm, dried, compression molded by a roller press machine, and then cut to obtain an average thickness of 190 μm.
A 483 mm x 54 mm strip-shaped positive electrode having a diameter of 483 mm was produced.

A binder solution similar to the above was prepared, and graphite 180 was used as the negative electrode active material in the binder solution.
g was added and stirred to prepare a slurry-like coating. This paint is uniformly applied to both sides of a copper foil having a thickness of 18 μm, dried, compression-molded by a roller press machine, and then cut to give an average thickness of 140 μm and 522 mm × 56 mm.
Was produced.

Next, a separator made of a microporous polyethylene film having a thickness of 25 μm is arranged between the strip-shaped positive electrode and the strip-shaped negative electrode, and is spirally wound to form a spiral electrode body. Of the positive electrode lead body and the negative electrode lead body were welded.

After that, 1.0 mol / l was placed in the battery case.
An electrolytic solution composed of LiPF ₆ / EC + EMC (1 + 3) [that is, a non-solvent obtained by dissolving 1.0 mol / l of LiPF _{6 in} a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) having a volume ratio of 1: 3. Water electrolyte] was injected 4.0 cc.

Then, the opening of the battery case was sealed in a conventional manner to produce a cylindrical non-aqueous electrolyte secondary battery having the structure shown in FIG.

The battery shown in FIG. 3 will be described briefly. 1 is the positive electrode and 2 is the negative electrode. However, FIG. 3 does not show a metal foil or the like as a substrate used in manufacturing the positive electrode 1 or the negative electrode 2 in order to avoid complication, and the positive electrode 1 and the negative electrode 2
And is accommodated in a battery case 4 made of stainless steel, together with an electrolytic solution having the above composition, as a spiral electrode body.

The battery case 4 also serves as a negative electrode terminal, and an insulator 5 is provided at the bottom thereof, and an insulator 6 is also provided on the spiral electrode body. And battery case 4
The opening 8 is provided with a sealing body 8 through an annular insulating packing 7.
Are arranged, and the inside of the battery is sealed by tightening the open end of the battery case 4 inward. However, an irreversible vent mechanism for discharging the gas generated inside the battery to the outside of the battery when the pressure has risen to a certain pressure and preventing the battery from bursting under high pressure is incorporated in the sealing body 8. Have been.

Example 2 Using the same chemically synthesized manganese dioxide as in Example 1, the ratio of the amount of Mn in the chemically synthesized manganese dioxide to the amount of Li in lithium hydroxide monohydrate was expressed by a molar ratio. A lithium manganese oxide was manufactured in the same manner as in Example 1 except that the raw materials were mixed so as to be 0.50, and a model cell and a battery were manufactured. When the manufactured lithium manganese oxide was observed with an electron microscope in the same manner as in Example 1, the shape was spherical or elliptical. Further, when the lithium manganese oxide was confirmed by X-ray diffraction analysis, it was confirmed that the lithium manganese oxide was a lithium manganese oxide having a spinel structure. The composition of Li, Mn, and O was measured by an atomic absorption spectrometer in the same manner as in Example 1. As a result, the composition of the produced lithium manganese oxide was Li _1.03 Mn _1.97 O _3.94 . Further, when the Fe content in this spinel-type lithium manganese oxide was measured by an atomic absorption spectrometer in the same manner as in Example 1, the Fe content was 48 ppm. When the average particle diameter and the specific surface area were measured in the same manner as in Example 1, the average particle diameter was 19 μm and the specific surface area was 1.
It was 1 m ² / g.

Example 3 A lithium manganese oxide was manufactured in the same manner as in Example 1 except that the firing temperature was changed from 800 ° C. to 780 ° C., and a model cell and a battery were manufactured. When the manufactured lithium manganese oxide was observed with an electron microscope in the same manner as in Example 1, the shape was spherical or elliptical. Further, when the lithium manganese oxide was confirmed by X-ray diffraction analysis, it was confirmed that the lithium manganese oxide was a lithium manganese oxide having a spinel structure. In addition, as in Example 1, Li, M
When the composition of n and O was measured by an atomic absorption spectrometer, the composition of the produced lithium manganese oxide was Li _1.02 Mn.
_1.98 O _3.98 . Further, when the Fe content in this spinel-type lithium manganese oxide was measured by an atomic absorption spectrometer in the same manner as in Example 1, the Fe content was 43 pp.
m. Further, when the average particle diameter and the specific surface area were measured in the same manner as in Example 1, the average particle diameter was 23 μm,
The specific surface area was 1.0 m ² / g.

Example 4 A lithium manganese oxide was manufactured in the same manner as in Example 1 except that the firing temperature was changed from 800 ° C. to 820 ° C., and a model cell and a battery were manufactured. When the manufactured lithium manganese oxide was observed with an electron microscope in the same manner as in Example 1, the shape was spherical or elliptical. Further, when the lithium manganese oxide was confirmed by X-ray diffraction analysis, it was confirmed that the lithium manganese oxide was a lithium manganese oxide having a spinel structure. In addition, as in Example 1, Li, M
When the composition of n and O was measured by an atomic absorption spectrometer, the composition of the produced lithium manganese oxide was Li _1.01 Mn.
_1.99 O _3.94 . Further, when the Fe content in this spinel-type lithium manganese oxide was measured by an atomic absorption spectrometer in the same manner as in Example 1, the Fe content was 35 pp.
m. When the average particle diameter and the specific surface area were measured in the same manner as in Example 1, the average particle diameter was 16 μm.
The specific surface area was 1.2 m ² / g.

Example 5 The Fe content of the raw material chemically synthesized manganese dioxide was 98 p
A lithium manganese oxide was produced in the same manner as in Example 1, except that chemically synthesized manganese dioxide having a particle size of pm was used, and the classification of the lithium manganese oxide as a product was 63 μm or less, to prepare a model cell and a battery. . When the shape of the manufactured lithium manganese oxide was observed with an electron microscope in the same manner as in Example 1, the shape was spherical or elliptical. Further, when the above lithium manganese oxide was confirmed by X-ray diffraction analysis, it was confirmed that the lithium manganese oxide was a lithium manganese oxide having a spinel structure. The composition of Li, Mn, and O was measured by an atomic absorption spectrometer in the same manner as in Example 1. The composition of the produced lithium manganese oxide was Li _1.01 Mn _1.99 O _3.92 , as in Example 1. . Further, when the Fe content in the spinel-type lithium manganese oxide was measured by an atomic absorption spectrometer in the same manner as in Example 1, the Fe content was 195 ppm.
When the average particle diameter and the specific surface area were measured in the same manner as in Example 1, the average particle diameter was 32 μm and the specific surface area was 0.6 m ² / g.

Example 6 The classification of the product lithium manganese oxide was 32 μm or less, and the mixed gas was 1.
A lithium manganese oxide was produced in the same manner as in Example 1 except that the supply was controlled at a flow rate of 5 liter / min to produce a model cell and a battery. When the manufactured lithium manganese oxide was observed with an electron microscope in the same manner as in Example 1,
The shape was spherical or oval. Further, when the lithium manganese oxide was confirmed by X-ray diffraction analysis, it was confirmed that the lithium manganese oxide was a lithium manganese oxide having a spinel structure. In addition, Li, Mn,
When the composition of O was measured by an atomic absorption spectrometer, the composition of the produced lithium manganese oxide was Li _1.02 Mn _1.98.
O was _3.90 . Further, when the Fe content in this spinel-type lithium manganese oxide was measured by an atomic absorption spectrometer in the same manner as in Example 1, the Fe content was 49 ppm. When the average particle diameter and the specific surface area were measured in the same manner as in Example 1, the average particle diameter was 8 μm and the specific surface area was 2.3 m ² / g.

Comparative Example 1 A model cell and a battery were produced in the same manner as in Example 1, except that commercially available LiMn ₂ O ₄ (average particle diameter 31 μm, specific surface area 0.8 m ² / g) was used as a positive electrode active material. . When the commercially available LiMn ₂ O ₄ was observed with an electron microscope in the same manner as in Example 1, the shape was angular as shown in FIG. 2 (electron micrograph at 1500 × magnification).
In addition, Fe in the spinel-type lithium manganese oxide
When the content was measured with an atomic absorption spectrometer in the same manner as in Example 1, the Fe content was 600 ppm.

Comparative Example 2 The Fe content in the raw material chemically synthesized manganese dioxide was 512.
ppm of chemically synthesized manganese dioxide, and the amount of Mn in the chemically synthesized manganese dioxide and lithium hydroxide.
The lithium manganese oxide was mixed in the same manner as in Example 1 except that the raw materials were mixed so that the ratio with respect to the amount of Li in the monohydrate was 0.525, and the product was not classified. The product was manufactured, and a model cell and a battery were produced. When the manufactured lithium manganese oxide was confirmed by X-ray diffraction analysis, it was confirmed that the lithium manganese oxide had a spinel structure. Further, as in the first embodiment, L
When the composition of i, Mn, and O was measured by an atomic absorption spectrometer, the composition of the produced lithium manganese oxide was Li
_1.09 Mn _1.91 O _3.98 . Further, when the Fe content in this spinel-type lithium manganese oxide was measured by an atomic absorption spectrometer in the same manner as in Example 1, the Fe content was 957 ppm. When the average particle diameter and the specific surface area were measured in the same manner as in Example 1, the average particle diameter was 5
At 4 μm, the specific surface area was 0.1 m ² / g.

Comparative Example 3 The Fe content of the raw material chemically synthesized manganese dioxide was 329.
ppm of chemically synthesized manganese dioxide, and the amount of Mn in the chemically synthesized manganese dioxide and lithium hydroxide.
Except for mixing the raw materials so that the ratio with the amount of Li in the monohydrate was 0.525 in molar ratio, and changing the firing temperature to 850 ° C., and not classifying the product, Example 1
In the same manner as in the above, a lithium manganese oxide was produced, and a model cell and a battery were produced. When the manufactured lithium manganese oxide was confirmed by X-ray diffraction analysis, it was confirmed that the lithium manganese oxide had a spinel structure. The composition of Li, Mn, and O was measured by an atomic absorption spectrometer in the same manner as in Example 1. As a result, the composition of the produced lithium manganese oxide was Li _1.08 Mn _1.92 O _3.96 . Further, when the Fe content in this spinel-type lithium manganese oxide was measured by an atomic absorption spectrometer in the same manner as in Example 1, the Fe content was 643 ppm. When the average particle size and the specific surface area were measured in the same manner as in Example 1, the average particle size was 62 μm, and the specific surface area was 0.2 μm.
It was 1 m ² / g.

Comparative Example 4 The Fe content in the raw material chemically synthesized manganese dioxide was 481.
ppm of chemically synthesized manganese dioxide, and the amount of Mn in the chemically synthesized manganese dioxide and lithium hydroxide.
Except that the raw materials were mixed so that the ratio to the Li amount in the monohydrate was 0.525 in molar ratio, and the firing temperature was changed to 750 ° C., and the product was not classified, Example 1
In the same manner as in the above, a lithium manganese oxide was produced, and a model cell and a battery were produced. When the manufactured lithium manganese oxide was confirmed by X-ray diffraction analysis, it was confirmed that the lithium manganese oxide had a spinel structure. The composition of Li, Mn, and O was measured by an atomic absorption spectrometer in the same manner as in Example 1. As a result, the composition of the produced lithium manganese oxide was Li _1.08 Mn _1.92 O _3.93 . Further, when the Fe content in the spinel-type lithium manganese oxide was measured by an atomic absorption spectrometer in the same manner as in Example 1, the Fe content was 918 ppm. When the average particle diameter and the specific surface area were measured in the same manner as in Example 1, the average particle diameter was 60 μm, and the specific surface area was 0.5 μm.
It was 1 m ² / g.

Comparative Example 5 A lithium manganese oxide was produced in the same manner as in Example 1, except that the flow rate of the mixed gas of argon gas and oxygen gas was changed to 0.1 liter / min per 100 g of the raw material mixture. When the produced lithium manganese oxide was confirmed by X-ray diffraction analysis, the obtained lithium manganese oxide was a mixture of LiMn ₂ O ₄ and Li ₂ MnO _3, and Mn ₂ O ₃ as a reaction intermediate product. Was generated, and a lithium manganese oxide having only a spinel structure was not obtained.

Comparative Example 6 A lithium manganese oxide was produced in the same manner as in Example 1 except that the flow rate of the mixed gas of argon gas and oxygen gas was changed to 0.6 L / min per 100 g of the raw material mixture. When the produced lithium manganese oxide was confirmed by X-ray diffraction analysis, the obtained lithium manganese oxide was a mixture of LiMn ₂ O ₄ and Li ₂ MnO _3, and Mn ₂ O ₃ as a reaction intermediate product. Was generated, and a lithium manganese oxide having only a spinel structure was not obtained.

COMPARATIVE EXAMPLE 7 As a raw material of Mn, electrolytically synthesized manganese dioxide classified in advance to 45 μm (Fe of this electrolytically synthesized manganese dioxide
The raw material was mixed such that the molar ratio of the Mn amount of this electrolytically synthesized manganese dioxide to the Li amount in lithium hydroxide monohydrate was 0.525. Was carried out, the calcination temperature was 750 ° C., and the classification of the product was not carried out, lithium manganese oxide was produced in the same manner as in Example 1, and a model cell and a battery were produced. When the manufactured lithium manganese oxide was confirmed by X-ray diffraction analysis, it was confirmed that the lithium manganese oxide had a spinel structure. Further, when observed with an electron microscope in the same manner as in Example 1, the shape was the same angular shape as in Comparative Example 1. The composition of Li, Mn, and O was measured by an atomic absorption spectrometer in the same manner as in Example 1. As a result, the composition of the produced lithium manganese oxide was Li _1.10 Mn _1.90 O _3.92 . Further, when the Fe content in this spinel-type lithium manganese oxide was measured with an atomic absorption spectrometer in the same manner as in Example 1, the Fe content was 413 ppm. When the average particle diameter and the specific surface area were measured in the same manner as in Example 1, the average particle diameter was 37 μm and the specific surface area was 0.5 m ² / g.

The discharge capacity and load characteristics of each model cell produced as described above were examined, and the cycle characteristics and low temperature discharge characteristics of the battery were examined. Table 1 shows the results.
Shown in The discharge capacity of each model cell was 4.3 Vvs. After charging to Li / Li ⁺ ,
^{2. At} a current density of 0.5 mA / cm ^{2 in} an environment of 20 ° C.
0Vvs. The discharge capacity at the time of discharging to Li / Li ⁺ was measured, and the result was shown in terms of the discharge capacity per weight of the positive electrode active material. The load characteristics were 3.0 V vs. 3.0 at a current density of 4.0 mA / cm ² . 3.0 Vv at discharge capacity when discharging to Li / Li ⁺ and current density of 0.5 mA / cm ²
s. Ratio to discharge capacity when discharging to Li / Li ⁺ [(discharge capacity at current density of 4.0 mA / cm ² ) /
(Discharge capacity at a current density of 0.5 mA / cm ² ) × 10
0].

The cycle characteristics were as follows: charge at a constant current of 1 A up to 4.2 V in an environment of 20 ° C., and then perform charging by a constant voltage method so that the total charging time was 2.5 hours. After that, 3.0 V at a constant current of 1 A under an environment of 20 ° C.
In the cycle test when the battery was discharged to the maximum, the ratio of the discharge capacity at the 500th cycle to the discharge capacity at the first cycle [(5
The discharge capacity at the 00th cycle) / (the discharge capacity at the 1st cycle) × 100] was obtained as the capacity retention, and the capacity retention at the 500th cycle was evaluated.

Further, the discharge characteristics at low temperature are as follows: discharge capacity when discharged to 3.0 V at a constant current of 0.2 A in an environment of -20 ° C .; and discharge capacity of 0.2 A in an environment of 20 ° C. Ratio to discharge capacity when discharging to 3.0 V with current [(-2
(Discharge capacity at 0 ° C.) / (Discharge capacity at 20 ° C.) × 10
0]. When measuring the discharge characteristics at the low temperature, the charging conditions are set to 20 at any temperature.
After charging to 4.2V at a constant current of 1A in an environment of ° C,
The battery was charged by a constant voltage method so that the total charging time was 2.5 hours. Then, after leaving the battery at a predetermined discharge temperature for 4 hours, a discharge test was started.

[0082]

[Table 1]

As shown in Table 1, Examples 1 to 6 had larger discharge capacities and higher capacities than Comparative Examples 1 to 7.
In addition, the capacity retention at the 500th cycle was large, and the cycle characteristics were excellent. As described above, as can be seen from the large discharge capacity of Examples 1 to 6, Examples 1 to 6
Since the spinel-type lithium manganese oxide used in No. 6 was spherical or elliptical particles, it is considered that the filling property in producing the positive electrode was also good. Further, Examples 1 to
No. 6 had a large discharge capacity and excellent load characteristics. This is considered to be because in Examples 1 to 6, the spinel-type lithium manganese oxide having an Fe content of 200 ppm or less was used as the positive electrode active material. Further, Examples 1 to 6 also had excellent discharge characteristics at low temperatures. This is because, in Examples 1 to 6, a spinel-type lithium manganese oxide having an average particle diameter in a range of 1 to 45 μm and a specific surface area in a range of 0.5 to ³ m ² / g was used as a positive electrode active material. It is considered to be due to the use as

[0084] By contrast, composition formula Li _x Mn _y
O _4-z (where x + y = 3.00, 1.00 ≦ x ≦
1.05, 0 <z ≦ 0.15, where x is a value at the time of assembling the battery and changes during charge and discharge in the range of 0 <x ≦ 1.05). Comparative Examples 1 to 7 using the material as a positive electrode active material had smaller discharge capacities and poor cycle characteristics than Examples 1 to 6. Further, when the production conditions of the present invention were not satisfied as in Comparative Examples 2 to 7, a lithium manganese oxide having a large discharge capacity and excellent cycle characteristics as in the present invention could not be produced. . Further, when the Fe content is 2
In Comparative Examples 2 to 4 in which more than 00 ppm of spinel-type lithium manganese oxide was used as the positive electrode active material, the load characteristics were poor, and particularly in Comparative Examples 5 and 6, a lithium manganese oxide having only a spinel structure could not be obtained. Was. Further, in Comparative Examples 1 to 7, the average particle diameter was out of the range of 1 to 45 µm, and the specific surface area was out of the range of 0.5 to ³ m ² / g.

[0085]

As described in the foregoing case, in the present invention, which was the general formula _{Li x Mn y O 4-z} (x + y = 3.00,
1.00 ≦ x ≦ 1.05, 0 <z ≦ 0.15, provided that
x is a value when the battery is assembled, and 0 <x ≦ 1.
The positive electrode active material is composed of a spherical or elliptical spinel-type lithium manganese oxide represented by the following formula: A positive electrode active material for a non-aqueous electrolyte secondary battery capable of imparting a high capacity and excellent cycle characteristics to an aqueous electrolyte secondary battery could be provided. In the present invention, the Fe content in the spinel-type lithium manganese oxide is set to 200 ppm or less, and the discharge capacity is reduced by using the spinel-type lithium manganese oxide having the Fe content of 200 ppm or less as the positive electrode active material. A large non-aqueous electrolyte secondary battery having excellent load characteristics could be provided. Furthermore, in the present invention, the average particle diameter of the spinel-type lithium manganese oxide is 1
４５45 μm, and the specific surface area is 0.5-3 m ² /
By using the positive electrode active material within the range of g,
A non-aqueous electrolyte secondary battery having excellent low-temperature discharge characteristics can be provided.

Since the spinel-type lithium manganese oxide of the present invention is spherical or elliptical particles, it has a good filling property for producing a positive electrode, and uses manganese which is abundant and inexpensive as a constituent element. Therefore, it is suitable for mass production and its industrial significance is great.

[Brief description of the drawings]

FIG. 1 is an electron micrograph (magnification: 1510) showing the particle structure of a spinel-type lithium manganese oxide of the present invention.

FIG. 2: Magnification 1 showing the particle structure of commercially available LiMn ₂ O ₄
It is a 500 times electron microscope photograph.

FIG. 3 is a partial cross-sectional perspective view schematically illustrating an example of a non-aqueous electrolyte secondary battery.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 4 Battery case 5 Insulator 6 Insulator 7 Insulation packing 8 Sealing body

Continued on the front page F-term (reference) 4G048 AA04 AB05 AC06 AD04 AD06 AE05 5H003 AA00 AA01 AA02 AA04 AA08 BA01 BA03 BB05 BC01 BC06 BD01 BD02 BD03 BD04 BD05 5H014 AA02 BB01 BB06 EE10 HH00 HH01 HH06 AJ01 A02A03 AL03 AL07 AL12 AM01 AM02 AM03 AM04 AM05 AM07 CJ02 CJ08 CJ28 DJ16 DJ17 HJ01 HJ05 HJ07 HJ14

Claims (5)

[Claims] 1. A general formula _{Li x Mn y O 4-z} (x + y =
When 3.00, 1.00 ≦ x ≦ 1.05, 0 <z ≦
0.15, where x is a value at the time of assembling the battery and is a value that changes in the range of 0 <x ≦ 1.05 upon charging and discharging.) A positive electrode active material for a non-aqueous electrolyte secondary battery comprising: 2. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the Fe content in the spinel type lithium manganese oxide is 200 ppm or less. 3. The spinel-type lithium manganese oxide has an average particle diameter of 1 to 45 μm and a specific surface area of 0.5 to ³ m ^2.
The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein 4. A mixture ratio of manganese dioxide and lithium salt is defined as Li / Mn ≦ 0.50 by a molar ratio of Li and Mn, and a mixed gas of an inert gas and an oxygen gas is used as 100 g of a raw material mixture.
Per liter / minute or more,
By firing at ~ 820 ° C, the general formula Li _x Mn
_y O _4-z (where x + y = 3.00, 1.00 ≦ x ≦
1.05, 0 <z ≦ 0.15, where x is a value at the time of assembling the battery and changes during charge and discharge in the range of 0 <x ≦ 1.05). A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, comprising producing a cathode active material for a non-aqueous electrolyte secondary battery comprising a spinel-type lithium manganese oxide in the form of a spiral. 5. A non-aqueous electrolyte secondary battery using the positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1.