JPH07101728A - Lithium manganese oxide, method for producing the same, and use thereof - Google Patents

Abstract

(57) [Summary] [Object] To provide a new layered LiMnO ₂ having a fine and high surface area, which can be applied to various applications as a host compound, and a synthesis method thereof. In particular, until now, the synthesis was possible only in an oxygen-free atmosphere such as in a N ₂ stream, but by using the synthesis method of the present invention, the layered L layer can be formed without limiting the atmosphere.
It is also possible to synthesize iMnO ₂ . Furthermore, by using this layered LiMnO ₂ for the positive electrode, a 3V class lithium secondary battery with high output and high energy density that has never been provided is provided. [Structure] A layered LiMnO ₂ having a particle diameter of 5 μm or less and a BET specific surface area of 10 m ² / g or more, a method for producing the same, and a lithium secondary battery using the same.

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 oxide, a method for producing the same, and a lithium secondary battery using the same. More specifically, it comprises particles having a particle size of 5 μm or less and a BET specific surface area of 10 m. ^{The present} invention relates to a layered LiMnO ₂ of ² / g or more, a method for producing the same, and a lithium secondary battery using the same.

Layered LiMnO ₂ is a material that is expected to function as a lithium host compound because it has a migration path and an accommodation site for Li ions in its crystal structure.
Furthermore, since it also has an oxidation-reduction ability, it has attracted attention as a positive electrode material for lithium secondary batteries.

The lithium secondary battery is a new type secondary battery which is expected to be put into practical use as a battery having a high energy density.

[0004]

2. Description of the Related Art A layered structure of manganese oxide has a function as a host compound having redox ability because it can accommodate ions and molecules between layers and can change the valence of manganese atoms continuously and reversibly. It is a compound that has.

Examples of the layered manganese oxide include δ-type manganese dioxide and layered manganese hydroxide (Mn
Birnessite type compounds which are derivatives of (OH) ₂ ) and hydrated manganese oxide (α-MnOOH, β-MnOOH, γ
-MnOOH), but since all of these compounds have water molecules (H ₂ O) and hydroxyl groups (-OH) between layers, they are host compounds except for aqueous solutions in which H ⁺ ions (protons) participate. It does not function as a battery and cannot be applied to a non-aqueous system such as a lithium secondary battery in which protons are not involved.

Further, since these manganese oxides are easily dissolved in an aqueous solution and it is difficult to reversibly carry out a redox reaction, various manganese oxides have various physical properties as a host compound having a redox ability. It could not be applied to the purpose.

Therefore, recently, water molecules (H ₂
Synthesis of a compound having a layered structure which does not contain O) or a hydroxyl group (—OH) is being studied.

For example, S. BACH et al. Have proposed the synthesis of Birnessite that does not contain water between layers (Electrochim
ica Acta, Vol.36, No.10, pp.1595-1603, 1991).

This is potassium permanganate (KMnO).
₄ ) or sodium gel permanganate (NaMnO ₄ ) and fumaric acid (C ₄ O ₄ H ₄ ) are mixed and dried and calcined to form NaMnO ₂ or KMnO _2. Birnessite with a small amount of water between layers is synthesized by the method of removing Na or K by treating the compound with sulfuric acid.

However, the Birnessite obtained by this method
Still contains 0.6 mol of water per mol of Mn atoms.

Further, since it has intercalation water, when it is used for a positive electrode of a lithium secondary battery, under a condition of charging and discharging between 4.4 V and 2.0 V with a strong current value of 1 mA / cm ² , a theoretical discharge is obtained. Only about 30% of the capacity can be obtained, and it is not a material that exhibits a sufficient function.

On the other hand, for the purpose of conversion into a host compound having lithium as a guest, by complexing with a lithium compound, water molecules (H ₂ O) between the layers and a hydroxyl group (—O) are formed.
A method of removing H) and converting it into a compound having lithium between layers is being studied.

[0013] Otsuki et al. Formed a layered product by molding an equimolar mixture of γ-MnOOH and lithium hydroxide (LiOH.H ₂ O) into pellets and firing them in a N ₂ stream at a temperature of 450 ° C. for 15 hours. A method for synthesizing LiMnO ₂ has been proposed (Chemistry Express, Vol. 7, No. 3, pp. 193-196 (1
992)).

When the compound obtained by this method is used for the positive electrode of a lithium secondary battery and charged / discharged between 4.25 V and 2.0 V, it exceeds 60% of the theoretical discharge capacity.
Although a discharge capacity of mAh / g was obtained, it was a value at a low current density of 0.1 mA / cm ² , which is a relatively mild discharge condition.

LiMn ₂ O ₄ having a spinel structure has also been studied as one of layered lithium manganese oxides.

LiMn ₂ O ₄ having a spinel type crystal structure is a compound having a layered structure in which Mn layers and Li—Mn layers are alternately arranged between oxygen layers stacked in the (111) plane direction of the spinel crystal structure. .

This compound is expected to function as a lithium host compound because it has three-dimensionally developed lithium migration paths and accommodating sites, and also has redox ability. Therefore, this compound has a positive electrode for a lithium secondary battery. It is attracting attention as a material.

Since half of the theoretical discharge capacity of this compound functions as a 4V class positive electrode, it is mainly studied as a 4V class positive electrode material for lithium secondary batteries.

On the other hand, with the recent development of cordless equipment, there is a strong demand for the development of a small-sized, lightweight secondary battery having a high energy density.

As a secondary battery that can meet this demand,
A lithium secondary battery has been proposed which uses lithium or a substance capable of inserting and extracting lithium for the negative electrode.

As the positive electrode of the lithium secondary battery, molybdenum, vanadium, niobium, titanium, nickel, cobalt and other oxides and sulfides have been mainly studied. I haven't arrived.

Further, manganese oxide has been studied as a promising positive electrode material, but it has been applied only to a positive electrode for a lithium primary battery and has not been put into practical use as a positive electrode for a lithium secondary battery.

[0023]

DISCLOSURE OF THE INVENTION The object of the present invention is to provide a layered LiM having a fine and high surface area which has not been proposed so far.
It is to provide nO ₂ and a synthesis method thereof.

In particular, up to now, the synthesis was possible only in an oxygen-free atmosphere such as in a N ₂ stream, but by using the synthesis method of the present invention, the layered L layer can be formed without limiting the atmosphere.
It is also possible to synthesize iMnO ₂ .

Further, the use of this layered LiMnO ₂ for the positive electrode is to provide a 3V class lithium secondary battery having a high output and a high energy density which has never been obtained.

[0026]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that the minor axis diameter is 1 μm.
Needle-like hydrated manganese oxide (γ-MnOOH) having an equivalent diameter of m or less, major axis diameter of 5 μm or less, and height of 1 μm or less.
With a (Li / Mn) molar ratio of 1.0 or more, and (OH
^- / Mn) is a method of removing water after stirring in an alkaline aqueous solution containing lithium having a molar ratio of 1.0 or more,
Layered LiMnO ₂ having a fine and high specific surface area which has never been obtained can be synthesized. Furthermore, by using the synthesis method of the present invention, it is possible to synthesize layered LiMnO ₂ without limiting the atmosphere. Further, they have found that a 3V class lithium secondary battery having excellent output characteristics and cycle characteristics can be constructed by using this as a positive electrode, and completed the present study.

The equivalent diameter used herein by the present inventors means that one particle is allowed to stand still on a horizontal surface, and the shape of the particle is displayed by the lengths of axes in three directions orthogonal to each other. Heyw
It is based on the definition of ood (see Yasuo Arai, Material Chemistry of Powder, Baifukan).

[0028]

The present invention will be described in detail below.

The X-ray diffraction peak of the layered LiMnO ₂ of the present invention is different from the ordinary layered manganese dioxide Birnessite type peak, and is different from that of JCPDS (Joint Committee Powder Diffra
Corresponding to the X-ray diffraction peak of the layered LiMnO ₂ described in 35-749 of the Standards card. From this, the crystal structure of the layered LiMnO ₂ of the present invention is MnO ₆
Octahedral edge-sharing chains are arranged in parallel with the C-axis direction of the crystal axis, and further, the chains are condensed in the a-axis direction of the crystal axis so as to share the edge to form a double layer parallel to the (010) plane. And has a crystal structure containing lithium between the layers formed by oxygen atoms,
It is presumed to be a layered lithium manganese compound.

However, the layered LiMnO _{2 of the} present invention can be prepared by a known method (for example, 35-749 of the above JCPDS card).
The method described in. ) Obtained layered LiMn
Different from O _2, it is a novel layered LiMnO ₂ having a large BET specific surface area of 10 m ² / g or more.

The layered LiMnO _{2 of the} present invention has a minor axis diameter of 1
a needle-like hydrated manganese oxide having an equivalent diameter of not more than μm, a major axis diameter of not more than 5 μm and a height of not more than 1 μm, (Li / Mn)
After stirring in an alkaline aqueous solution containing lithium having a molar ratio of 1.0 or more and an (OH ⁻ / Mn) molar ratio of 1.0 or more, water is added at a temperature of less than 200 ° C. in an atmosphere containing oxygen. It is preferable to synthesize by a method of removing water and removing water at a temperature of 200 ° C. or higher in an oxygen-free atmosphere. However, it is of course possible to remove water at a temperature of less than 200 ° C. in an oxygen-free atmosphere.

By using the above method, layered LiMnO ₂ having a fine and high specific surface area which has never been obtained can be synthesized.

Although the reaction mechanism is not clear, it is considered as follows.

The acicular hydrated manganese oxide used in the present invention is
3 shows a crystal structure belonging to a monoclinic system (trigonal orthorhombic system) in which manganese is regularly arranged at hexacoordinate positions of hexagonal close packing of O and OH. This crystal structure has a crystal structure in which a hydroxyl group (-OH) is brought close to oxygen in a tetragonal lattice of rutile type manganese dioxide (β-MnO ₂ ) so as to form a pair, and a hydrogen bond is formed between oxygen and the hydroxyl group. Is formed.

The hydroxyl group of this compound has both basic and acidic characteristics, that is, a so-called amphoteric property. Therefore, the hydroxyl group functions as an acid in an alkaline solution and releases H in the form of H ⁺ ion. At this time, it is considered that Li ⁺ ions having a small ion size are accommodated in order to compensate the charge of the compound.

This reaction is considered to be an equilibrium reaction, and H of the hydroxyl group in the hydrated manganese oxide and Li ⁺ ions in the solution are gradually exchanged, so that the layered crystal structure is maintained and uniform. Ion exchange is thought to occur. Further, it is considered that this exchange reaction is promoted by the removal of water, and finally the exchange reaction proceeds completely.

However, when Li is compared with H, which does not need to take the size into consideration, its size is sufficiently large, so that although the layered structure is maintained, the atomic arrangement slightly changes. And the X-ray diffraction pattern is γ-MnOOH
It is considered that the type is changed to the layered LiMnO ₂ type.

Since this reaction proceeds even at a low temperature at which the redox reaction of Mn does not occur, layered LiMnO 2 is present even in the atmosphere.
_It is thought that ₂ can be synthesized.

The minor axis diameter is 1 μm or less and the major axis diameter is 5 μm.
By using acicular hydrated manganese oxide (γ-MnOOH) having an equivalent diameter of m or less and a height of 1 μm or less, the exchange reaction easily proceeds, and 5 μm which cannot be obtained by the conventional method. A layered LiMnO ₂ comprising the following particles and having a BET specific surface area of 10 m ² / g or more is obtained.

Further, in order to obtain a compound having a LiMnO ₂ composition, H of the hydroxyl group and Li ⁺ ions must be completely exchanged, so that the (Li / Mn) molar ratio is 1.0.
Above, an alkaline aqueous solution containing lithium having an (OH ⁻ / Mn) molar ratio of 1.0 or more is required.

The alkaline aqueous solution containing lithium used in the present invention is not particularly limited as long as the (Li / Mn) molar ratio is 1.0 or more and the (OH ⁻ / Mn) molar ratio is 1.0 or more.

Examples include an aqueous solution in which metallic lithium, lithium hydroxide and lithium oxide are dissolved, and an aqueous solution in which various lithium salts and quaternary ammonium hydroxide salt are dissolved.

Needle-like hydrated manganese oxide (γ-MnOOH) used in the present invention and having a corresponding minor axis diameter of 1 μm or less, major axis diameter of 5 μm or less and height of 1 μm or less is, for example,
The method reported by Owen Bricker:
Manganese hydroxide (Mn (OH) ₂ ) was replaced with hydrogen peroxide (H ₂ O
₂ ) Oxidation with (The AmericanMi
neralogist, vol. 50, p. 129
6 (1965)), and K. The method reported by Matsuki et al., That is, manganese sulphate (M
nSO ₄ ) and hydrogen peroxide in a mixed solution of ammonia water (N
H ₄ OH) addition method (Electrochimic
a Acta, vol. 31, p. 13 (198
6)).

In the synthesis of the layered LiMnO ₂ of the present invention, in the removal of water, in an atmosphere containing oxygen, 20
It is preferable to remove at a temperature lower than 0 ° C., and if it is desired to remove at a temperature of 200 ° C. or higher, it is essential to remove in an oxygen-free atmosphere. As this atmosphere, for example,
Examples thereof include a dry nitrogen atmosphere and a dry argon atmosphere.

When the treatment is carried out at a temperature of 200 ° C. or higher in an atmosphere containing oxygen, the layered LiMnO ₂ is used although details are unknown.
, The XRD diffraction intensity of the (010) plane showing the crystallinity in the layer direction was decreased, and a compound having an X-ray diffraction pattern showing a crystal structure similar to spinel type LiMn ₂ O ₄ was obtained.
MnO ₂ cannot be obtained.

However, in an atmosphere without oxygen, 20
It is of course possible to remove water at temperatures below 0 ° C.

The positive electrode of the lithium secondary battery of the present invention has 5
It is composed of particles of less than μm and has a BET specific surface area of 10 m ² /
It is essential to use layered LiMnO _{2 of} g or more.

By using layered LiMnO ₂ having particles of 5 μm or less and having a BET specific surface area of 10 m ² / g or more, the positive electrode reaction surface area can be increased and the strong discharge characteristics can be improved. Therefore, since the overvoltage of charge and discharge is lowered and the utilization factor is improved, it is possible to construct a secondary battery having a high energy density and excellent output characteristics as compared with the case of using the conventional layered LiMnO ₂ .

Further, as compared with the conventional layered LiMnO ₂ , since it has a fine and high specific surface area, it is easy to absorb the expansion and contraction of crystals due to the charge / discharge reaction, and the secondary battery has excellent cycle characteristics.

For the negative electrode used in the lithium secondary battery of the present invention, lithium or a substance capable of inserting and extracting lithium is used. For example, a lithium metal, a lithium / aluminum alloy, a lithium / tin alloy, a lithium / lead alloy, a carbon-based material that electrochemically absorbs and releases lithium ions, and the like are exemplified.

The electrolyte used in the lithium secondary battery of the present invention is not particularly limited, but for example, one obtained by dissolving a lithium salt in an organic solvent such as carbonates, sulfolanes, lactones and ethers, A lithium ion conductive solid electrolyte can be used.

Using the layered LiMnO _{2 of the} present invention, FIG.
The battery shown in was constructed.

In the figure, 1: lead wire for positive electrode, 2:
Positive electrode current collecting mesh, 3: positive electrode, 4: separator,
5: negative electrode, 6: negative electrode current collecting mesh, 7: negative electrode lead wire, 8: container.

[0054]

EXAMPLES Examples will be described below, but the present invention is not limited thereto.

The X-ray diffraction measurement, the particle structure observation and the surface area measurement in this example and the comparative example were carried out by the following methods.

X-ray diffraction measurement: Measurement model MXP3 irradiation X-ray Cu Kα ray measurement mode manufactured by Mac Science Co., Ltd. Step scan Scan condition 2θ 0.04 ° interval Measurement time 5 seconds Measurement range 2θ 5 ° to 75 ° Particle structure Observation: Measurement model JEOL JSM-
T220A Acceleration voltage 15KV Surface area measurement: Treated in a nitrogen gas stream (flow rate: 15 milliliters per minute) for 40 minutes at 250 ° C., and then using an automatic surface area measurement device (ASA-2000 type, manufactured by Shibata Scientific Instruments Co., Ltd.) It was measured.

Example 1 [Preparation of Layered LiMnO ₂ ] As Example 1, layered LiMnO ₂ was prepared.
MnO ₂ was prepared by the following method.

Commercially available minor axis diameter is 1 μm or less, major axis diameter is 5 μm
Needle-like hydrated manganese oxide powder (γ-MnOOH: manufactured by Tosoh Corporation, having an equivalent diameter of m or less and a thickness of 1 μm or less,
Hereinafter, abbreviated as needle-shaped hydrated manganese oxide manufactured by Tosoh Corporation) 5 g
2.4 g of lithium hydroxide monohydrate powder (LiOH
(H ₂ O) was added to 50 ml of dissolved water and stirred for 1 hour, and then left in an open air dryer maintained at 60 ° C. for 50 hours to remove water.

From the results of X-ray diffraction and chemical composition analysis of the obtained compound, it was found that this compound was layered LiMnO ₂ . In addition, as a result of particle structure and surface area measurement, 5
It was found to be composed of particles of less than μm and have a BET specific surface area of 14 m ² / g. An X-ray diffraction pattern is shown in FIG. 2, a chemical composition analysis result is shown in Table 1, and a photograph of the particle structure is shown in FIG.

[0060]

[Table 1]

[Battery Structure] Obtained Layered LiMn
O ₂ , carbon powder as a conductive agent and polytetrafluoroethylene powder as a binder were mixed in a weight ratio of 88: 7: 5. 75 mg of this mixture was molded into pellets of 8 mmφ at a pressure of ² ton / cm ² and then at 150 ° C. for 5 minutes.
A vacuum drying process was performed for a period of time. This is used for the positive electrode of 3 in FIG. 1, and for the negative electrode of 5 in FIG.
mm), a lithium piece cut out from the separator was used to impregnate a separator of 4 in FIG. 1 with a propylene carbonate solution in which lithium perchlorate was dissolved at a concentration of 1 mol / dm ³ was used as an electrolytic solution. Figure 1 of 0.5 cm ²
The battery shown in was constructed.

[Evaluation of Battery Characteristics] Using the battery prepared by the above method, charging / discharging was repeated at a constant current of 1.0 mA / cm ² and a battery voltage of 4.2V to 2.0V. The results are shown in Fig. 9. The discharge capacity at the 50th cycle was maintained at 90% of the discharge capacity at the 1st cycle.

Example 2 As Example 2, LiMnO ₂ was prepared in the same manner as in Example 1 except that water was removed at 150 ° C. for 2 hours.

From the results of X-ray diffraction and chemical composition analysis of the obtained compound, it was found that this compound was layered LiMnO ₂ . In addition, as a result of particle structure and surface area measurement, 5
It was found to be composed of particles of less than μm and to have a BET specific surface area of 17 m ² / g. An X-ray diffraction pattern is shown in FIG. 2, a chemical composition analysis result is shown in Table 1, and a grain structure photograph is shown in FIG. Next, a battery was formed in the same manner as in Example 1 except that this was used as the positive electrode in FIG. The results are shown in Fig. 9. The discharge capacity at the 50th cycle is 95% of the discharge capacity at the first cycle.
Was maintained.

Example 3 As Example 3, LiMn was prepared in the same manner as in Example 1 except that water was removed in N ₂ at a temperature of 450 ° C. for 15 hours.
O ₂ was created.

From the results of X-ray diffraction and chemical composition analysis of the obtained compound, it was found that this compound was layered LiMnO ₂ . In addition, as a result of particle structure and surface area measurement, 5
It was found to be composed of particles of less than μm and have a BET specific surface area of 10 m ² / g. An X-ray diffraction pattern is shown in FIG. 2, a chemical composition analysis result is shown in Table 1, and a photograph of the particle structure is shown in FIG. Next, a battery was formed in the same manner as in Example 1 except that this was used as the positive electrode in FIG. The results are shown in Fig. 9. The discharge capacity at the 50th cycle is 86% of the discharge capacity at the first cycle.
Was maintained.

Example 4 As Example 4, LiMnO ₂ was added in the same manner as in Example 1 except that 1.7 g of lithium oxide powder (Li ₂ O) was used in place of the lithium hydroxide monohydrate powder. Created.

From the results of X-ray diffraction and chemical composition analysis of the obtained compound, it was found that this compound was layered LiMnO ₂ . In addition, as a result of particle structure and surface area measurement, 5
It was found to be composed of particles of less than μm and have a BET specific surface area of 15 m ² / g. An X-ray diffraction pattern is shown in FIG. 2, a chemical composition analysis result is shown in Table 1, and a grain structure photograph is shown in FIG. Next, a battery was formed in the same manner as in Example 1 except that this was used as the positive electrode in FIG. The results are shown in Fig. 9. The discharge capacity at the 50th cycle is 95% of the discharge capacity at the first cycle.
Was maintained.

Example 5 As Example 5, 2.5 g of lithium chloride powder (LiC
1) was dissolved in 83.7 g of a 10% aqueous solution of tetraethylammonium hydroxide ((CH ₃ CH ₂ ) ₄ NOH), 5 g of Tohso needle-shaped hydrated manganese oxide powder was added thereto, and the mixture was stirred for 1 hour. Water was removed by leaving it under reduced pressure at 60 ° C. for 20 hours.

From the results of X-ray diffraction and chemical composition analysis of the obtained compound, it was found that this compound was layered LiMnO ₂ . In addition, as a result of particle structure and surface area measurement, 5
It was found to be composed of particles of less than μm and have a BET specific surface area of 14 m ² / g. 2 shows an X-ray diffraction pattern, Table 1 shows the results of chemical composition analysis, and FIG. 7 shows a photograph of the particle structure. Next, a battery was formed in the same manner as in Example 1 except that this was used as the positive electrode in FIG. The results are shown in Fig. 9. The discharge capacity at the 50th cycle is 85% of the discharge capacity at the first cycle.
Was maintained.

Comparative Example 1 As Comparative Example 1, layered LiMnO ₂ was prepared by the following method.

5 g of needle-shaped hydrated manganese oxide powder manufactured by Tosoh Corporation
And 2.4 g of lithium hydroxide monohydrate powder (LiOH
· H a ₂ O) and, after mixing in an agate mortar for 20 minutes, 2g of the powder mixture at a pressure of 1 ton / cm ² 25 mm
The pellet was molded into a pellet of φ and fired at a temperature of 450 ° C. for 15 hours in an N ₂ stream.

From the results of X-ray diffraction and chemical composition analysis of the obtained compound, it was found that this compound was layered LiMnO ₂ . In addition, as a result of particle structure and surface area measurement, 5
It is composed of particles of less than μm, but has a BET specific surface area of 8
It was found to be m ² / g. Fig. 8 shows the X-ray diffraction pattern, Table 1
The chemical composition analysis results are shown in.

Next, a battery similar to that of Example 1 was constructed except that this was used for the positive electrode of FIG. The results are shown in Fig. 9. The discharge capacity at the 50th cycle maintained only 65% of the discharge capacity at the 1st cycle.

Comparative Example 2 As Comparative Example 2, synthesis was performed in the same manner as in Example 4 except that the water removal temperature was 300 ° C.

From the result of X-ray diffraction of the obtained compound, it was found that this compound had a diffraction pattern similar to that of spinel type LiMn ₂ O ₄ . The X-ray diffraction diagram is shown in FIG.

Comparative Example 3 Example 1 was repeated except that 2.5 g of lithium chloride powder was used instead of lithium hydroxide monohydrate powder.
Synthesis was performed in the same manner as in.

From the result of X-ray diffraction of the obtained powder, it was found that this powder was a mixture of acicular hydrated manganese oxide and lithium chloride. The X-ray diffraction diagram is shown in FIG.

Comparative Example 4 JCPDS (Joint Committee Powder Diffraction Stan
The layered LiMnO ₂ was synthesized by the method described in Dards) card 35-749.

An X-ray diffraction pattern is shown in FIG.

The BET specific surface area of the obtained compound was 5 m.
It was ² / g.

[0082]

As described above, according to the present invention, it becomes possible to provide a layered LiMnO ₂ having a fine and high surface area, which can be applied to various applications as a new host compound which has never existed before, and a method for synthesizing the layered LiMnO ₂ .

In particular, until now, the synthesis was possible only in an oxygen-free atmosphere such as in a N ₂ stream, but by using the synthesis method of the present invention, the layered L layer can be formed without limiting the atmosphere.
It is also possible to synthesize iMnO ₂ .

Furthermore, by using this layered LiMnO ₂ for the positive electrode, it becomes possible to construct a 3V class lithium secondary battery having a high output and a high energy density which has never been obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional area showing an embodiment of a battery configured in Examples and Comparative Examples.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode lead wire 2 Positive electrode current collecting mesh 3 Positive electrode 4 Separator 5 Negative electrode 6 Negative electrode current collecting mesh 7 Negative electrode lead wire 8 Container

FIG. 2 is a LiMn prepared in Examples 1 to 5 and Comparative Example 4.
The X-ray diffraction pattern of O ₂ is shown.

FIG. 3 is a photograph showing a particle structure of LiMnO ₂ prepared in Example 1.

FIG. 4 is a photograph showing a particle structure of LiMnO ₂ prepared in Example 2.

5 is a photograph showing the particle structure of LiMnO ₂ prepared in Example 3. FIG.

FIG. 6 is a photograph showing the particle structure of LiMnO ₂ prepared in Example 4.

FIG. 7 is a photograph showing a particle structure of LiMnO ₂ prepared in Example 5.

FIG. 8 shows X-ray diffraction patterns of various powders produced in Comparative Examples 1 to 3.

FIG. 9 shows the results of characteristic evaluation of the batteries prepared in Examples 1 to 5 and Comparative Example 1.

Claims (5)

[Claims] 1. A layered LiMnO ₂ comprising particles of 5 μm or less and having a BET specific surface area of 10 m ² / g or more. _2. The method for producing a layered LiMnO _{2 according} to claim 1, wherein the acicular hydrated manganese oxide (corresponding to a minor axis diameter of 1 μm or less, a major axis diameter of 5 μm or less, and a thickness of 1 μm or less ( (γ-MnOOH) is stirred in an alkaline aqueous solution containing lithium having a (Li / Mn) molar ratio of 1.0 or more and an (OH ⁻ / Mn) molar ratio of 1.0 or more, and then water is removed. A method for producing a layered LiMnO _{2 comprising} : 3. A method of producing a layer LiMnO ₂ according to claim 2, in an atmosphere containing oxygen, the layered and removing water at a temperature below 200 ° C. LiMnO
_2. Manufacturing method. 4. A method of producing a layer LiMnO ₂ according to claim 2, in 200 ° C. or higher temperatures, layered and removing the water in absence of oxygen atmosphere LiMnO
_2. Manufacturing method. 5. The layered LiMnO according to claim 1.
A lithium secondary battery characterized by using ₂ as a positive electrode.