JP2002321919A - Lithium manganese compound oxide and lithium secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium manganese compound oxide having a high active material capacity, its manufacturing method and a lithium secondary battery using the compound oxide. SOLUTION: The lithium manganese compound oxide is represented by Li1-x MnO2-δ (wherein, x denotes a lithium defective amount and satisfies 0<=x<0.6 and δ denotes an oxygen defective amount and satisfies 0<=δ<=0.2), and a space group of the crystal structure can be represented by R3m and when R3m is adopted, (104)/(003) face index intensity ratio y satisfies 0.168<=y<=0.238. The lithium manganese compound oxide is manufactured by mixing a lithium compound with a manganese compound, burning the mixture in an atmosphere of a low oxygen concentration and electrochemically treating the burnt material. A lithium secondary battery is accommodated with a positive electrode formed by a positive electrode material and a negative electrode containing a lithium group metal, a metal oxide, a metal nitride, a carbon material and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel lithium manganese composite oxide, and more particularly, to a lithium manganese composite oxide having a specific crystal structure and useful as a positive electrode active material of a lithium secondary battery. And a lithium secondary battery using the same.

[0002]

2. Description of the Related Art In recent years, measures against environmental problems
There is a strong demand for the development of an electric vehicle, which is a high-performance vehicle.
As a secondary battery that is a power source for such an electric vehicle,
Among various secondary batteries, high charge / discharge voltage and high charge / discharge capacity
Lithium secondary batteries are expected to have a large size. Note that
LiCoO as the positive electrode active material for future lithium secondary batteries
_TwoSystem-based materials, but stable in the operating environment
Rechargeable batteries for automobiles from the viewpoints of safety, price and reserves
Lithium manganese with spinel structure as positive electrode active material for
Complex oxide (LiMn_TwoO_Four) Is currently under consideration
(JP-A-11-171550 and JP-A-11-171550)
No. 1-73962).

[0003]

However, the above-mentioned spinel-structured lithium manganese composite oxide (Li
Mn ₂ O ₄ ) is LiCo having an active material capacity of about 100 mAh / g and an active material capacity of about 140 mAh / g.
O capacity is not sufficient for _two systems, Therefore, to improve the driving range of electric vehicles, a high capacity than the spinel structure lithium manganese composite oxide, inexpensive lithium manganese oxide than LiCoO ₂ system There is a demand for the development of a positive electrode active material. Lithium manganese composite oxides (orthogonal LiMnO ₂ , monoclinic LiMnO ₂ ) as candidates
Although it is conceivable, there is still nothing that can solve all of these problems.

Accordingly, the present invention has been made in view of such problems of the prior art, and an object of the present invention is to provide a novel lithium manganese composite oxide (rhombic hexagon) having a high capacity of an active material. Crystalline LiMnO ₂ ),
It is an object of the present invention to provide a method of manufacturing the same and a lithium secondary battery using the composite oxide.

[0005]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, have performed electrochemical treatment such as charging and discharging on a predetermined lithium manganese composite oxide to obtain a crystal structure thereof. It has been found that the above problems can be solved by controlling, and the present invention has been completed.

That is, the present invention for achieving the above object is configured as follows for each claim.

According to the first aspect of the present invention,

[0008]

Embedded image

(Where x represents the amount of lithium deficiency, and 0 ≦
x <0.6, δ indicates the amount of oxygen deficiency and satisfies 0 ≦ δ ≦ 0.2)

[0010]

[Outside 2]

A (104) / (003) plane index intensity ratio y is 0.168 ≦ y ≦ 0.238.

According to a second aspect of the present invention, in the lithium manganese composite oxide according to the first aspect, the lithium deficiency x is electrochemically controlled.

According to a third aspect of the present invention, in producing the lithium manganese composite oxide according to the first or second aspect, a lithium compound and a manganese compound are mixed, and the mixture is mixed with a low oxygen concentration. (More specifically, firing in an atmosphere having an oxygen concentration of 10 ppm to 1000 ppm), and then subjecting the obtained fired product to an electrochemical treatment. It is.

According to a fourth aspect of the present invention, there is provided the method for producing a lithium-manganese composite oxide according to the third aspect, wherein lithium and manganese are contained in the calcined product in an approximately equimolar ratio (more specifically, Mn of 1.0 mol). Is 0.8-1.
(A ratio of 1 mol).

According to a fifth aspect of the present invention, there is provided a positive electrode material for a lithium secondary battery, comprising the lithium manganese composite oxide according to the first or second aspect.

According to a sixth aspect of the present invention, there is provided a positive electrode formed of the positive electrode material for a lithium secondary battery according to the fifth aspect, and a positive electrode selected from the group consisting of a lithium-based metal, a metal oxide, a metal nitride, and a carbon material. A lithium secondary battery comprising a negative electrode containing at least one selected from the group consisting of:

[0017]

According to the first aspect of the present invention, a novel lithium manganese composite oxide is represented by the following formula:

[0018]

Embedded image

(Where x represents the amount of lithium deficiency, 0 ≦
x <0.6, δ indicates the amount of oxygen deficiency and satisfies 0 ≦ δ ≦ 0.2)

[0020]

[Outside 3]

Since the (104) / (003) plane index intensity ratio y satisfies 0.168 ≦ y ≦ 0.238, the crystal structure is controlled, so that the ratio is high. Active material capacity can be achieved. In addition, from the viewpoints of stability under use environment, price and reserves, L
It is more advantageous than iCoO ₂ system.

[0022] That is, the lithium-manganese composite oxide of the present invention, a high capacity than the spinel structure lithium manganese composite oxide (110mAh / g), LiCoO ₂
A novel Mn-containing lithium composite oxide that can achieve a high capacity (about 134 to 154 mAh / g) which is substantially the same as or higher than that of a LiCoO ₂ system (140 mAh / g) and is extremely cheaper than a LiCoO ₂ system or the like You can do it.

According to a second aspect of the present invention, in the lithium manganese composite oxide according to the first aspect, the amount x of lithium deficiency is electrochemically controlled. Therefore, the same function and effect as the first aspect can be obtained. In particular, the amount x of lithium deficiency can be adjusted as designed (as desired), and as a result, a higher active material capacity can be freely selected within the range defined in claim 1, which is advantageous. .

According to the third aspect of the present invention, in producing the lithium manganese composite oxide according to any one of the first and second aspects, a lithium compound and a manganese compound are mixed, and the mixture is mixed. Low oxygen concentration (more specifically, oxygen concentration is 1000 ppm or less, preferably 10 ppm
This is a method for producing a lithium manganese composite oxide, characterized by firing in an atmosphere having a low oxygen concentration (ppm to 1000 ppm) and then subjecting the obtained fired product to an electrochemical treatment. That is, the basic technology of each step and its applied technology (oxide mixing technology, oxide firing technology under low oxygen concentration, electrochemical treatment technology such as charge and discharge of oxide, etc.) itself have been developed. However, by combining them organically (and functionally) so as to achieve the effects and advantages described in claims 1 and 2, the number of manufacturing steps is small, and it is relatively easy to combine the already developed technologies. It can be manufactured (mass-produced), and can be manufactured at low cost using inexpensive oxide raw materials.
It is possible to obtain a lithium manganese composite oxide which is less expensive than an O ₂ -based oxide. Further, from the viewpoint of stability under the use environment, it is more advantageous than the LiCoO ₂ system.

According to a fourth aspect of the present invention, in the method for producing a lithium manganese composite oxide according to the third aspect, the calcined product contains lithium and manganese in an approximately equimolar ratio (more specifically, Mn1 Li is 0.1 to 1.0 mol.
(Molar ratio of 8 to 1.1 mol), and the same operation and effect as in claim 3 can be obtained. In particular, in addition to the constitutional requirements of claim 3, by allowing lithium and manganese to be contained in the fired product in an approximately equimolar ratio, the desired monoclinic crystal structure can be sintered before the electrochemical treatment. Things. Therefore, by controlling the amount of lithium deficiency x and the like by the subsequent electrochemical treatment of the sintered product, lithium having a rhombohedral hexagonal crystal structure having the function and effect shown in claims 1 to 2 as designed is obtained. A manganese composite oxide can be obtained. Therefore, the steps that affect the performance of the lithium manganese composite oxide of the present invention are not limited to the electrochemical treatment, and the composites that can be obtained if the desired fired product is not obtained by each of the steps leading to such steps. The performance of the oxide greatly influences the performance. From this, the production method of the present invention must organically combine the steps described in claim 3 so as to achieve the effects of the present invention. You can see that.

According to a fifth aspect of the invention, there is provided a positive electrode material for a lithium secondary battery, comprising the lithium manganese composite oxide according to the first or second aspect. Therefore, the high active material capacity of the lithium manganese composite oxide can have an effect directly linked to the increase in the capacity of the battery. In particular, the use of the lithium-manganese composite oxide as a positive electrode active material that greatly affects battery performance can achieve the above effects more remarkably.

According to a sixth aspect of the present invention, there is provided a novel lithium secondary battery comprising: a positive electrode formed of the positive electrode material for a lithium secondary battery according to the fifth aspect;
It is characterized by having a negative electrode containing at least one selected from the group consisting of metal oxides, metal nitrides and carbon materials, so that it is less expensive than LiCoO ₂ and discharge. High capacity of 130 mAh / g or more (this is higher than that of the spinel-structured lithium manganese composite oxide, and is about the same as or higher than that of the LiCoO ₂ system (for details, see Table 1 in Examples described later). Further, it is more advantageous than the LiCoO ₂ system from the viewpoint of stability under the use environment.

That is, in the lithium secondary battery of the present invention using the novel composite oxide according to claims 1 and 2 as a positive electrode material and a lithium ion conductive non-aqueous electrolyte,
It has excellent charge / discharge capacity and cycle characteristics, can be manufactured at low cost, is also excellent in environmental adaptability, exhibits high performance with small size and high capacity, and has an EV (electric vehicle) and an HEV (hybrid). It is very useful industrially as a battery for electric vehicles (hybrid vehicles).

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the lithium manganese composite compound of the present invention will be described in detail. In the present specification, “%” is a percentage by mass (% by mass) unless otherwise specified.
Is shown.

As described above, the lithium manganese composite oxide of the present invention has the following formula:

[0031]

Embedded image

(X in the formula indicates the amount of lithium deficiency, and 0 ≦
x <0.6, δ indicates the amount of oxygen deficiency and satisfies 0 ≦ δ ≦ 0.2)

[0033]

[Outside 4]

The (104) / (003) plane index intensity ratio y satisfies 0.168 ≦ y ≦ 0.238.

In the lithium manganese composite oxide of the present invention, the amount x of lithium deficiency in the above formula is 0 ≦ x <0.
6 is satisfied. Here, when x is 0 or more, the cycle characteristics of the battery using the lithium-manganese composite compound are not sharply reduced, which is preferable. When x is smaller than 0.6, Li _1-x M
Since the structure of nO _{2 -δ} can be stably maintained, a secondary battery having an effect intended by the present invention, typically, an active material capacity of 130 mAh / g or more is easily obtained, which is preferable.

The oxygen deficiency δ in the above formula is 0 ≦
It satisfies δ ≦ 0.2. Here, δ is 0 or more
Is better for a battery using the lithium manganese composite compound.
This is preferable because the cycle characteristics do not significantly decrease. on the other hand,
When δ is 0.2 or less, Li _1-xMnO_2-δThe structure of
The effect intended by the present invention, typically
Is a secondary battery having an active material capacity of 130 mAh / g or more.
It is preferable because a pond is easily obtained.

In the present invention, x = 0, δ =
It is fully possible to produce the lithium-manganese composite compound of the invention represented by 0.

In the present invention, the lithium content x is measured by ICP (inductively coupled high frequency plasma analysis) (for example, using an ICP device such as SPS-1700HVR manufactured by Seiko Instruments Inc.). Measurement) can be calculated.

The oxygen deficiency δ was calculated by calculating the valence of Mn and setting Li to +1 and oxygen to −2.
The valence of Mn can be measured by coulometry (for example, using a device such as GT-07 manufactured by Diamond Instruments Co., Ltd.). The coulometry is preferably performed in an inert gas atmosphere, for example, it is preferable to perform the measurement while purging with nitrogen gas or argon gas.

[0040]

[Outside 5]

Has

In this case, the plane index (10
4) and the diffraction peak intensity ratio y of (003) y (= (10
4) diffraction intensity / (003) diffraction peak intensity) satisfies the relationship of 0.168 ≦ y ≦ 0.238. The intensity ratio is considered to be related to the amount of Li (see Examples described later).

If the (104) / (003) plane index intensity ratio y is less than 0.168, a discharge capacity of 130 mAh / g or more may be obtained (see FIG. 2). In the electrochemical treatment of
Of 0.168 or more is easier to obtain. On the other hand, when the intensity ratio y is 0.238 or less, the discharge capacity 130 m
Ah / g is preferred because it is easily obtained.

The lithium deficiency x, peak intensity ratio y, etc. of the lithium manganese composite oxide of the present invention are determined by charging and discharging a predetermined lithium manganese composite oxide, as described in detail in the following production method. It can be controlled by applying a chemical treatment.

The crystal structure of the lithium manganese composite oxide of the present invention can be measured by using a commercially available device using known means such as X-ray crystal structure diffraction and powder X-ray diffraction. For example, MXP18 is used for X-ray crystal structure diffraction.
An XRD apparatus of VAHF (manufactured by Mac Science) can be used, and RIETAN94 can be used as a structure determination program. As a calculation method, a general Rietveld analysis can be used. Note that the above (104) / (0
03) Since the plane index intensity ratio y does not change depending on the target, Cu, Fe, Co, Cr,
Mo, Ag, etc. can be used. The crystal structure and the space group do not change depending on the target. However, the intensity of the peak changes.

Hereinafter, the method for producing the lithium manganese composite oxide of the present invention will be described in detail.

As described above, in the production method of the present invention, a predetermined lithium compound and a predetermined manganese compound are mixed, and the mixture is fired in an atmosphere having a low oxygen concentration to obtain a fired lithium manganese product. By subjecting this lithium manganese fired product to a predetermined electrochemical treatment, a lithium manganese composite oxide represented by the above formula can be obtained.

Here, the manganese compound which is the manganese source of the intended lithium manganese composite oxide includes:
There is no particular limitation, for example, electrolytic manganese dioxide, chemically synthesized manganese dioxide, dimanganese trioxide, γ
-MnOOH, manganese carbonate, manganese nitrate, manganese acetate and the like can be used. The choice of lithium manganese composite oxide in the present invention is that a cobalt compound as a cathode material of a lithium battery is dangerous in an overcharged state,
While there is an environmental problem, the manganese compound is safe even if overcharged and has no environmental problems.
In addition, manganese easily changes its valence, so that various structures exist and high discharge capacity can be expected. In fact, in the present invention, a lithium manganese composite oxide having a structure suitable as a cathode material having a high discharge capacity according to the present invention. Can be found.

At this time, the manganese compound powder preferably has an average particle size of 0.1 to 100 μm.
More preferably, the thickness is 0.1 to 20 μm. The average particle size of the manganese compound is preferably 100 μm or less, because the reaction between the manganese compound and the lithium compound is not significantly delayed and a uniform product is easily generated. on the other hand,
When the average particle diameter of the manganese compound is 0.1 μm or more, when the obtained lithium manganese composite oxide is used as a positive electrode material (positive electrode active material) of a lithium battery, the cycle characteristics of the battery are more improved, so that it is preferable.

On the other hand, the lithium compound serving as the lithium source is not particularly limited, and for example, lithium carbonate, lithium hydroxide, lithium nitrate, lithium oxide, lithium acetate and the like can be used. Among them, lithium carbonate and lithium hydroxide can be preferably used. That is, other lithium oxides and the like are preferable for synthesizing LiMnO ₂ , but are difficult to handle due to hygroscopicity, but these lithium carbonates and lithium hydroxides are preferable for synthesizing LiMnO _{2 and} are more stable and easy to handle. That's why. The average particle diameter of the lithium compound powder is preferably 0.1 to 100 μm, more preferably 0.1 to 30 μm, for the same reason as the above-mentioned average particle diameter of the manganese compound powder.

The method of mixing the above-mentioned lithium compound and the above-mentioned manganese compound is not particularly limited, and can be carried out by using various known techniques. For example, a method of dry-mixing or wet-mixing a lithium compound and a manganese compound can be used.

Examples of the atmosphere having a low oxygen concentration at the time of firing the above-mentioned mixture include a gas atmosphere containing almost no oxygen, such as nitrogen, argon or carbon dioxide, and a mixed gas thereof. The oxygen concentration in such an atmosphere is typically 1000 ppm or less,
It is preferable to control the concentration within a range of 1000 ppm. When the oxygen concentration in such an atmosphere is 1000 ppm or less, the valence of manganese becomes lower, and when the obtained lithium manganese composite oxide is used as a cathode material (cathode active material) of a lithium battery, a sufficient cycle of the battery is obtained. It is preferable because characteristics and high capacity can be obtained. Although the lower limit is not particularly limited, the oxygen concentration is 10 pp.
If it is less than m, it is difficult to obtain a layered structure of LiMnO ₂ , so it can be said that it is desirable to control it to 10 ppm or more.

Further, the firing temperature is typically 500 to 11
00 ° C, preferably in the range of 700 to 950 ° C. When the firing temperature is 1100 ° C. or lower, the product is less likely to be decomposed. On the other hand, when the firing temperature is 500 ° C. or higher, L
Since the structure of iMnO ₂ becomes stable, it becomes easy to perform an electrochemical treatment (for example, a charge / discharge treatment).

The firing time can be 1 to 48 hours, preferably 5 to 24 hours. Firing time 1
It is preferable that the calcination time is longer than 48 hours because the structure of LiMnO ₂ is easily formed, and the calcination time is 48 hours or shorter when the obtained lithium manganese composite oxide is used as a positive electrode material (positive electrode active material) of a lithium battery. This is preferable because the cycle characteristics of the battery are improved.

The firing method is not particularly limited, and single-stage firing or multi-stage firing at different temperatures as needed may be performed.

It is preferable that the calcined product after the calcining is adjusted to a certain particle size or less by pulverization. The average particle size of the fired product after pulverization is in the range of 0.1 to 100 μm, preferably 0.1 to 20 μm. When the average particle size of the fired product after the pulverization is 0.1 μm or more, the cycle characteristics of the battery do not deteriorate when the obtained lithium manganese composite oxide is used as a positive electrode material (positive electrode active material) of a lithium battery. Not preferred. On the other hand, when the average particle diameter of the fired product after pulverization is 100 μm or less, a battery having a high discharge capacity is obtained when the obtained lithium manganese composite oxide is used as a positive electrode material (positive electrode active material) of a lithium battery. Therefore, it is preferable.

As described above, in the production method of the present invention, the above-mentioned lithium compound and manganese compound are used as essential raw materials, and these are mixed by an appropriate mixing method to obtain a mixture. Depending on the amount of other additives, an appropriate amount can be added to the essential raw materials before firing.

Examples of such additives include carbon-containing compounds, preferably carbon powders such as carbon black and acetylene black, and organic substances such as citric acid. These additives may be used alone or in a combination of two or more. By adding these additives before firing, the oxygen concentration in the firing atmosphere can be efficiently reduced.

The amounts of these additives are not particularly limited as long as the effects of the present invention are not impaired as long as the effects of the individual additives can be sufficiently exhibited. Is typically 0.05 to 10% by mass, and preferably 0.1 to 2% by mass, based on the manganese compound. When the amount of the additive is 0.05% by mass or more based on the manganese compound, the effect is high, and
When the amount of the additive is 10% by mass or less based on the manganese compound, by-products are less likely to be generated, and the remaining carbon compound added is small. Does not reduce the purity.

In the production method of the present invention, the fired lithium manganese product has an almost equimolar ratio of lithium to manganese, specifically, 0.8 to 1.0 mol of Mn in the fired product. Preferably, it is contained at a ratio of 1.1 mol. By including these in substantially equimolar ratio, the electrochemical treatment of the post-treatment can be effectively performed, and the lithium manganese composite oxide represented by the above formula (hereinafter, this lithium manganese composite oxide) Is also simply referred to as a LiMn composite oxide.).

The electrochemical treatment in the production method of the present invention is carried out in order to appropriately control the lithium deficiency x and the peak intensity ratio y of the target LiMn composite oxide. It can be performed by conducting electricity to the manganese fired product.

A typical example is charge / discharge performed by adjusting the applied voltage under a constant current. In this case, the charge / discharge is affected by the size of the fired product, but is preferably 1 to 300 mA / g. It is desirable to employ a constant current of about 30 mA / g and a voltage of 2.0 to 4.2 V. The constant current is 1 mA /
g or more is preferable because the reaction proceeds easily by the charge / discharge treatment and the peak intensity ratio y changes to a desired region. On the other hand, when the constant current is 300 mA / g or less, a battery having a high discharge capacity can be obtained when the target LiMn composite oxide is used as a positive electrode material (positive electrode active material) of a lithium battery, which is preferable. Further, a voltage value of 2.0 V or more is preferable because overdischarge is less likely to occur. On the other hand, 4.2
It is preferable that V is as follows because overcharging hardly occurs.
It is preferable that the charging / discharging process is performed within the range of the current value and the voltage value. That is, at the time of charging, the current value (for example, under a constant current of about 30 mA / g) is 4.2.
The battery is charged up to V, and if it exceeds this, the battery is overcharged, so that the charge / discharge is switched by the voltage (preferably a fixed pause time of about 10 minutes is provided between the charge / discharge). It is sufficient to discharge to 2.0 V at the same current value. A discharge of up to 2.0 V is preferable because overdischarge does not easily occur and the LiMn composite oxide shown in the formula can be adjusted by charging and discharging. The temperature conditions during charging and discharging are not particularly limited, and it is preferable to perform the charging at a temperature from room temperature to about 60 ° C. as shown in Examples. Usually, it is preferable to carry out the reaction at room temperature, since a product having a high capacity and excellent cycle characteristics can be obtained, and it is economically advantageous.
The charge and discharge time depends on the current and voltage values.

The charge / discharge may be applied to the fired material itself. However, the fired material is molded using an appropriate binder (to be described in detail later), and a plate-like material or a sheet obtained by heat treatment is obtained. It may be applied to a rod-like object, and if such a plate-like object is used, connection at the time of charge / discharge processing can be easily performed. Specifically, as shown in Examples, a desired electrochemical treatment (charge / discharge treatment) may be performed after assembling a battery using these plate-like objects (positive electrodes).

The above-described LiMn composite oxide of the present invention comprises:
Although it can be used for applications such as lithium primary batteries,
Particularly, it is useful as a positive electrode active material of a lithium secondary battery.

The positive electrode material for a lithium secondary battery according to the present invention comprises:
It contains this LiMn composite oxide. Such a positive electrode material may be composed of only a LiMn composite oxide (including unavoidable impurities) as the positive electrode active material, or may include a LiNi composite oxide,
Other positive electrode active materials such as a LiCo composite oxide and a LiFe composite oxide may be included.

Other positive electrode active materials such as LiNi composite oxide, LiCo composite oxide and LiFe composite oxide are Li
The charge / discharge treatment similar to the Mn composite oxide need not be particularly performed.

The amount of each of these other positive electrode active materials is within a range that does not impair the effects of the present invention and is within a range in which the functions and effects of these other positive electrode active materials can be effectively exhibited. Each can be blended in an appropriate amount.

Further, the positive electrode material for a lithium secondary battery of the present invention contains various additives such as a binder (also referred to as a binder) and a conductive auxiliary agent in addition to a positive electrode active material such as a LiMn composite oxide. May be. The additives may be added in appropriate amounts within a range that does not impair the effects of the present invention, and within a range in which the effects of these additives can be effectively exhibited. In particular, it is preferable that the mixing ratio of the positive electrode active material and the binder is appropriately determined according to the shape of the electrode and the like.

The binder is not particularly limited, and various kinds of conventionally known binders used for a positive electrode material for a lithium secondary battery can be used.
For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and the like can be given.

The conductive auxiliary is not particularly limited, and various conventional conductive auxiliary used for a positive electrode material for a lithium secondary battery can be used. For example, carbon black, graphite, Acetylene black and the like can be mentioned.

Next, as described above, the lithium secondary battery of the present invention comprises a positive electrode (also referred to as a positive electrode body) formed of the above positive electrode material for a lithium secondary battery, a lithium-based metal, various metal oxides, and various metals. The battery is provided with a negative electrode (also referred to as a negative electrode body) containing a nitride, a carbon material, and the like, and has a high active material capacity, specifically, an active material capacity of 130 mAh / g or more.

Here, any positive electrode may be used as long as it is formed of the above-described positive electrode material. For example, the positive electrode material may be pressure-formed, heat-treated, and formed in close contact with an appropriate positive electrode current collector, or a suitable positive electrode current collector and the positive electrode material may be pressure-formed. In addition, it may be formed by further heat treatment, or may be formed by appropriately applying (coating) a paste containing the positive electrode material to an appropriate positive electrode current collector and drying. It should not be restricted.

As the positive electrode current collector, various known materials can be used. Specifically, stainless steel (SU)
S) and aluminum.

The paste containing the positive electrode material is obtained by mixing the above-mentioned positive electrode active material with a binder in an appropriate solvent and, if necessary, an additive such as a conductive auxiliary to form a paste. The positive electrode material is as described above.

As the solvent used for the positive electrode material-containing paste, various polar solvents that dissolve the binder can be used. Specific examples include dimethylformamide, dimethylacetamide, methylformamide, N-methylpyrrolidone, and the like.

The method of manufacturing a positive electrode material containing the LiMn composite oxide according to the present invention, a positive electrode formed of the positive electrode material, and a method of manufacturing a lithium secondary battery provided with the positive electrode material are not particularly limited. Instead, conventionally known techniques for manufacturing various lithium secondary batteries can be appropriately used. For example, a positive electrode active material containing a LiMn composite oxide, and if necessary, additives such as a binder and a conductive additive are added and mixed to form a positive electrode material, which is subjected to pressure molding and heat treatment, A positive electrode is brought into close contact with the positive electrode current collector (or 'the positive electrode current collector and the positive electrode material are pressure-formed,
Further heat treatment to form a positive electrode, a positive electrode material-containing paste obtained by dissolving a positive electrode material in a solvent is applied to a positive electrode current collector, and dried to obtain a positive electrode), a negative electrode, and, if necessary, an electrolytic solution. A lithium secondary battery can be assembled using a separator, a battery case, etc. The electrochemical treatment of the LiMn composite oxide may be performed before use in the above step, or as described in Examples. To
There is no particular limitation, for example, it may be performed after the above steps.

The negative electrode may be any one containing a negative electrode material used for a normal lithium secondary battery. For example, the negative electrode material and an appropriate negative electrode current collector are molded by pressure ( Further, the anode material may be formed by press-bonding, or may be formed by pressure-forming (heat-treating) the negative electrode material and closely contacting it with an appropriate positive electrode current collector. It is not particularly limited, and the paste may be formed by appropriately applying (coating) a paste containing the negative electrode material to an appropriate negative electrode current collector and drying the paste.

As the negative electrode material, any of the materials used in ordinary lithium secondary batteries can be used. For example, lithium-based metals, metal oxides, metal nitrides, carbon alloy wood alloys, fine particle multi-component alloys And a composite of an alloy and a conductive polymer. Preferably, it is at least one selected from the group consisting of lithium-based metals, metal oxides, metal nitrides, and carbon materials. Specific examples of such a positive electrode material include lithium-based metals such as metallic lithium and lithium alloy (such as a Li-Al alloy), and Sn-based metals.
Metal oxides such as SiO ₃ , metal nitrides such as LiCoN ₂ , and carbon materials such as coke, natural graphite, artificial graphite, and non-graphitizable carbon can be preferably used. In the present invention, carbon materials such as coke, natural graphite, artificial graphite, and non-graphitizable carbon can be suitably used. The reason why these carbon materials are preferably used is that, since the standard electrode potential is low, a high voltage can be obtained by combining with the LiMn composite oxide. The negative electrode material may contain other conventionally known additives in addition to the various negative electrode active materials described above.

For the negative electrode current collector, various known materials can be used, and specific examples include stainless steel and copper.

It is preferable that the lithium secondary battery of the present invention further comprises an electrolytic solution. As the electrolytic solution, those obtained by dissolving various lithium salts as an electrolyte in a non-aqueous solvent such as an organic solvent can be used.

In this case, as the electrolyte, for example, Li
ClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₆ , LiC
F ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ S
O ₂ ) ₂ , LiN (CF ₂ SO ₃ ) ₂ , LiBF ₄ , LiNH
₂ , LiF, LiCl, LiBr, LiI, LiCN,
Conventionally known various lithium salts such as LiClO ₄ , LiNO ₃ and C ₆ H ₅ COOLi are exemplified, but not limited to these. In addition, these electrolytes may be used alone or in combination of two or more.

Examples of the organic solvent include, but are not particularly limited to, carbonates, lactones, ethers and the like. Specific examples include ethylene carbonate, propylene carbonate, butylene carbonate, diethyl carbonate, dimethyl Carbonate, methyl ethyl carbonate, 1,2-dimethoxyethane,
1,2-diethoxyethane, tetrahydrofuran, 1,
3-dioxolane, γ-butyrolactone, γ-valerolactone, acetonitrile, diethyl ether, dimethylsulfoxide, methyl formate, 2-methyltetrahydrofuran, 3-methyl-1,3-oxazolidin-2-one, sulfolane, ethyl acetate, propionic acid Solvents such as methyl can be used alone or in combination of two or more.

The concentration of the electrolyte dissolved in these non-aqueous solvents and organic solvents is preferably 0.5 to 2.0 mol / liter.

Further, in the lithium secondary battery of the present invention, it is possible to use an electrolytic medium other than the above-mentioned electrolytic solution, for example, a solid or viscous material in which the above-mentioned electrolyte is uniformly dispersed in a polymer matrix. Alternatively, those impregnated with a non-aqueous solvent can be used. In this case, the polymer matrix is not particularly limited, and materials conventionally used for conventionally known lithium secondary batteries can be appropriately selected and used, for example, polyethylene oxide, polypropylene oxide, polyacrylonitrile, and polyfluoroethylene. And vinylidene chloride. These may be used alone or in combination of two or more. Alternatively, lithium halides such as lithium iodide and derivatives thereof, lithium nitride, oxyacid-based materials, sulfide-based materials, and the like can be used as the solid electrolyte.

Further, in the lithium secondary battery of the present invention, a separator for preventing short circuit between the positive electrode and the negative electrode can be provided.

The separator is not particularly limited, and may be appropriately selected from conventionally used materials for a lithium secondary battery.
Examples include porous sheets and nonwoven fabrics of a polymer material such as polyethylene, polypropylene, and cellulose.

Further, in the lithium secondary battery of the present invention, an appropriate housing (battery case) can be provided depending on the intended use.

[0088]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. In these examples and comparative examples,
Using the positive electrode, the negative electrode, and the nonaqueous electrolyte prepared as described below, a sealed nonaqueous battery cell was prepared and evaluated.

[Preparation of Positive Electrode Active Material] Lithium hydroxide monohydrate powder and manganese trioxide powder were weighed at a predetermined molar ratio, and these were mixed in a mortar. After heating at 900 ° C. for 24 hours and calcining, and then cooling, the calcined material is pulverized using a mortar, and the molar ratio of lithium to manganese contained in the calcined material is 1: 1. Of LiMn composite oxide (positive electrode active material) was obtained.

[Preparation of Battery and Measurement of Discharge Capacity] The obtained LiMn composite oxide (cathode active material) of each example, acetylene black as a conductive additive, and polytetrafluoroethylene (PTFE) powder as a binder were prepared. Were mixed at a mass ratio of 80: 16: 4 to obtain a positive electrode material. This mixture (positive electrode material) was 12 m in diameter at a pressure of ² t / cm ^2.
m was pressed into a disk shape. The obtained molded product is heated at 150 ° C.
For 16 hours, and a stainless steel (SUS) thin plate was used as a positive electrode current collector to form a positive electrode body.

On the other hand, a disc-shaped lithium metal having a diameter of 12 mm and a reticulated negative electrode current collector made of stainless steel were pressed to form a negative electrode body.

As the electrolytic solution, a solution in which LiPF ₆ was dissolved at a concentration of 1 mol / l in a mixed solvent of ethylene carbonate and diethyl carbonate at a volume ratio of 1: 1 was used. A polypropylene film was used as a separator.

The positive electrode body and the negative electrode body obtained in this manner are connected to leads, and a separator is interposed between them to make the elements face each other. The elements are sandwiched between two PTFE plates while being pressed by a spring. It is. Furthermore, the side of the element is also P
The cell was covered with a TEF plate and sealed to obtain a sealed nonaqueous solvent battery cell. The cell was prepared under an argon atmosphere.

[Lithium deficiency x and surface index intensity ratio y
Control] Using the sealed non-aqueous solvent battery cell obtained as described above, charging and discharging are performed at a constant current of 30 mA / g at 60 ° C. and a voltage of 4.2 to 2.0 V. Thereby, the amount x of lithium deficiency and the (104) / (003) plane index intensity ratio y in the positive electrode active material Li _1-x MnO _2-δ of the positive electrode material are controlled, and the LiMn composite oxide of each example is controlled. The composite oxide of the present invention was prepared.

Similarly, charge / discharge was performed using a sample in which the amount of lithium deficiency x and the (104) / (003) plane index intensity ratio y were controlled by charge / discharge. The capacity of the sealed nonaqueous solvent battery cell was used.

[Evaluation of peak intensity of X-ray diffraction pattern]
The LiMn composite oxide of each example, which had been subjected to the charge / discharge treatment as described above, was taken out of the cell and subjected to X-ray diffraction measurement. Cu is used as a target and 10 ° to 11 in 2θ (θ; diffraction angle).
The measurement was performed in the range of 0 °. FIG. 1 shows X-ray diffraction patterns of Examples 1 to 3 and Comparative Examples 1 and 2.

[0097]

[Outside 6]

The (104) / (003) plane index intensity ratio y was obtained by dividing the (104) plane index peak intensity maximum value from the diffraction pattern by the (003) plane index peak intensity maximum value. FIG. 2 shows Examples 1 to 3 and Comparative Examples 1 and 2.
Shows the relationship between the surface index intensity ratio y and the cell capacity in FIG.

Example 1 The above-mentioned charge / discharge treatment was performed using Li _1-x MnO _2-δ (x = 0), and the (104) / (003) plane index intensity ratio y was controlled to 0.168. The LiMn composite oxide of this example was obtained. The oxygen deficiency δ was 0.02. This composite oxide was evaluated as described above.

Example 2 The above-described charge / discharge treatment was performed using Li _1-x MnO _2-δ (x = 0.5), and the (104) / (003) plane index intensity ratio y was controlled to 0.186. Thus, a LiMn composite oxide of this example was obtained. The oxygen deficiency δ was 0.02. This composite oxide was evaluated as described above.

Example 3 The above-described charge / discharge treatment was performed using Li _1-x MnO _2-δ (x = 0.55), and the (104) / (003) plane index intensity ratio y was controlled to 0.238. Thus, a LiMn composite oxide of this example was obtained. The oxygen deficiency δ was 0.02. This composite oxide was evaluated as described above.

Comparative Example 1 The above-described charge / discharge treatment was performed using Li _1-x MnO _2-δ (x = 0.6), and the (104) / (003) plane index intensity ratio y was controlled to 0.414. Thus, a LiMn composite oxide of this example was obtained. The oxygen deficiency δ was 0.02. This composite oxide was evaluated as described above.

Comparative Example 2 The above-mentioned charge / discharge treatment was performed using Li _1-x MnO _2-δ (x = 0.7), and the (104) / (003) plane index intensity ratio y was controlled to 0.544. Thus, a LiMn composite oxide of this example was obtained. The oxygen deficiency δ was 0.02. This composite oxide was evaluated as described above.

Table 1 shows the (104) / (003) plane index intensity ratio y and the capacity (initial discharge capacity) of each cell prepared using each composite oxide. Shown in

[0105]

[Table 1]

[Brief description of the drawings]

FIG. 1 is an X-ray diffraction pattern of various lithium manganese composite oxides.

FIG. 2 is a graph showing a relationship between a surface index intensity ratio and a cell capacity.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G048 AA04 AB01 AB05 AC06 AD06 AE05 5H029 AJ03 AJ05 AK03 AL06 AL16 AL18 AM03 AM04 AM05 AM07 CJ02 CJ08 CJ11 CJ28 HJ02 HJ13 5H050 AA07 AA08 BA16 BA17 CA09 CB01 CB02 CB02 CB02 CB02 GA27 HA02 HA13

Claims (6)

[Claims] 1. The following formula: (X in the formula indicates the amount of lithium deficiency, 0 ≦ x <0.6,
δ indicates the amount of oxygen deficiency and satisfies 0 ≦ δ ≦ 0.2). (104) / (003) plane index intensity ratio y is 0.168 ≦
A lithium-manganese composite oxide, wherein y ≦ 0.238. 2. The lithium manganese composite oxide according to claim 1, wherein the lithium deficiency x is electrochemically controlled. 3. In producing the lithium manganese composite oxide according to claim 1 or 2, a lithium compound and a manganese compound are mixed, and the mixture is fired in an atmosphere having a low oxygen concentration. Next, a method for producing a lithium manganese composite oxide, comprising subjecting the obtained fired product to an electrochemical treatment. 4. The method for producing a lithium-manganese composite oxide according to claim 3, wherein lithium and manganese are contained in the fired product in an approximately equimolar ratio. 5. A positive electrode material for a lithium secondary battery, comprising the lithium manganese composite oxide according to claim 1 or 2. 6. A positive electrode formed of the positive electrode material for a lithium secondary battery according to claim 5, and at least one selected from the group consisting of a lithium-based metal, a metal oxide, a metal nitride, and a carbon material. A lithium secondary battery comprising a negative electrode containing: