JP3232790B2 - Novel manganese oxide, its production method and its use - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates not relate to novel manganese oxide and a lithium secondary battery manufacturing method, and using this, more specifically, expressed by the general formula A _x Mn ₂ O ₄
That a manganese oxide (However, A is Zn, Mg,
If Ca is Co or A is Zn, 0 <x
<1, n = 0 , crystal structure is spinel type, A is
In the case of Mg, 0 <x <1, 0 ≦ n ≦ 20
And the crystal structure is a layered type, and X = 1, 0 ≦ n ≦ 2
0 and the crystal structure has a specific plane spacing
Type, if A is Ca, 0 <x <1,0 ≦ n ≦ 20 der
And the crystal structure is δ type, and X = 1, 0 ≦ n ≦ 20
And the crystal structure is amorphous, A is Co 0 <
X < 1, n = 0 , and the crystal structure is a lamellar type or spinel type
The present invention relates to a manganese oxide characterized by having both types of crystal structures, a method for producing the same, and a lithium secondary battery using at least one of these manganese oxides as a positive electrode.

[0002] A manganese oxide having a spinel type or layered type crystal structure is expected to function as a host compound because it has a path through which ions can move in the crystal structure. Further, a manganese atom is capable of continuously and reversibly changing its valence, and thus is a promising material having both a redox ability and a function as a host compound.

[0003] From such properties, manganese oxide is
This material is expected to be used as a battery active material, catalyst, adsorbent, and magnetic material.

[0004] A lithium secondary battery is a new type of secondary battery that is expected to be put to practical use as a battery with high output and high energy density.

[0005]

2. Description of the Related Art Manganese oxides are compounds having various compositions and crystalline forms. For example, manganese dioxide shows crystal forms such as α-type, β-type, γ-type, λ-type, and δ-type. In β-type manganese dioxide, MnO ₆ octahedra share a ridge to form a single chain connected three-dimensionally in the C-axis direction, and a (1 × 1) tunnel structure develops in the (110) direction. are doing. Similarly, in γ-type manganese dioxide, MnO ₆ octahedra forms a double chain, and the double chains share a ridge and are connected three-dimensionally in the C-axis direction.
It has a (1 × 2) tunnel structure along the 0) direction and α
Manganese dioxide also has a two-dimensionally developed tunnel structure such as (2 × 2) or (3 × 2). On the other hand, λ-type manganese dioxide has a tunnel structure in which (1 × 1) tunnels are connected three-dimensionally, and exhibits a crystal form belonging to a spinel-type crystal structure.

The spinel-type crystal structure has sites where cations enter octahedral and tetrahedral positions of close-packed oxygen, and these sites are three-dimensionally connected.

[0007] ZnMn ₂ O ₄ having a spinel crystal structure is a compound in which octahedral sites are occupied by Mn atoms and tetrahedral sites are occupied by Zn. If Zn can be removed from this compound while maintaining the spinel-type crystal structure, sites capable of accommodating cations are formed in the crystal structure, and the Mn atom can change continuously and reversibly. . Therefore, this compound becomes an effective material as a host compound.

In particular, when Zn can be completely removed, the above-mentioned λ-type manganese dioxide in which manganese atoms occupy two-thirds of the sites capable of accommodating cations and all the remaining one-third sites are empty And the amount of cations that can be accommodated from outside into the crystal structure is maximized.

However, up to now, Zn cannot be removed while maintaining the spinel-type crystal structure, so that ZnMn ₂ O ₄ is used as it is, for example, only as a raw material for ferrite. Therefore, application as a host compound was not achieved.

[0010] In addition, various studies have been made on the synthesis of λ-type manganese dioxide having a spinel structure, but the material has not been able to sufficiently exhibit its original function. For example, λ-type manganese dioxide having a spinel structure proposed so far has been synthesized by a method of treating a manganese spinel compound fired at a high temperature with an acid.

In Japanese Patent Application Laid-Open No. 55-100224, a powder of β-type manganese dioxide and Li ₂ CO ₃ is
i: Mn = 1: 2 (molar ratio), mixed in a solid phase, and calcined at 850 ° C. in air to obtain LiMn ₂ O _4. Synthesizes manganese dioxide with a structure.

However, according to the study of the present inventors, manganese dioxide having a spinel structure obtained by this method can be obtained by subjecting a precursor LiMn ₂ O ₄ to sulfuric acid treatment to obtain Li
Is removed, the resulting compound is a manganese oxide having a proton-type spinel crystal structure in which Li and proton have been ion-exchanged. Therefore, it is a compound that is limited to only a very limited field of application for its intended use as a host compound.

In Japanese Patent Application Laid-Open No. 62-270420, an aqueous solution of magnesium chloride and an aqueous solution of manganese chloride are mixed with Mg:
Mn = 1: 2 (molar ratio), ammonia was added to the mixture to form a mixed hydroxide of Mg and Mn, and the product was filtered and then calcined at 700 ° C. Manganese dioxide having a spinel structure is synthesized by treating MgMn ₂ O ₄ with nitric acid to remove Mg. However, for the same reason as in the case of LiMn ₂ O ₄ , there is a problem that the material is not a material that can sufficiently exhibit the original function of manganese dioxide having a spinel structure.

The δ-type manganese dioxide has a crystal form in which MnO ₆ octahedra shares a ridge and is connected two-dimensionally.
This shows a layered structure in which atoms are arranged.

[0015] The manganese oxide having a layered structure is present as Birnsite in nature.

Synthetic Birnsite is described in
Electroanal. Chem. Vol. 222.
p. 101-117 (1987), sodium birnessite obtained by subjecting manganese hydroxide produced by the neutralization of sodium hydroxide of an aqueous solution of Mn ²⁺ to aeration at a low temperature near 0 ° C.
It has been known. As described above, this oxide has a layered structure in which Mn atoms are arranged every other layer of hexagonal close-packed oxygen. A layer is formed by electrostatic repulsion between oxygen atoms of an empty layer with Mn atoms, and usually a +1 valent cation such as sodium enters between the layers, thereby counteracting the electrostatic repulsion and stabilizing the crystal structure. ing. At the time of cation insertion, some water molecules are also taken in as hydration water.

As described above, the manganese oxide having a layered structure can take in cations between layers generated by electrostatic repulsion between oxygen, and further has a layered structure. This material is considered to be capable of inserting and removing cations, and is expected to be applied as a host compound.

However, in the conventional method, as described above, it is necessary to synthesize at around 0 ° C., which is a disadvantageous process for industrialization. Therefore, a manganese oxide having a layer structure is practically used as a host compound. Had not yet been realized.

As an attempt to solve such a problem, U.S. Pat.
In SP-4, 520, 005, Bi and P
b and Pb inserted between layers at room temperature by allowing the ion of b to coexist with sodium ions in the solution.
It enables site synthesis. This patent is issued by Bir
The purpose of this application is to apply nessite to a positive electrode active material of an alkaline secondary battery, but there is a problem that the production cost is increased because expensive Bi or Pb is used.

From such a background, the layered manganese oxide is a material expected to be applied as a host compound, but has not been put to practical use.

The δ-type manganese dioxide has a layered structure, but is not a layered structure developed like the above-mentioned sodium Birnsitesite, but is considered to be an aggregate of microcrystals having a layered structure. δ-type manganese dioxide is
For example, it is manufactured by a known method such as a method obtained by calcining a precipitate obtained by mixing potassium permanganate and hydrochloric acid at 250 ° C. However, known stable δ-type manganese dioxide has an oxidation degree of Mn only in a narrow range of about 1.5 to 1.8. Therefore, the low degree of oxidation of Mn impairs the function expected from the crystal structure.

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

As a secondary battery that satisfies this demand, a lithium secondary battery using lithium or a substance capable of occluding and releasing lithium as a negative electrode has been proposed.

As the positive electrode of the lithium secondary battery, oxides and sulfides such as molybdenum, vanadium, niobium, titanium, nickel and cobalt have been mainly studied. Has not been reached. In addition, although manganese oxide has been studied as a promising positive electrode material, it has been applied only to a positive electrode for a lithium primary battery and has not been put to practical use as a positive electrode for a lithium secondary battery.

When manganese dioxide is used for the positive electrode of a lithium secondary battery, the crystal structure expands or contracts due to the penetration and release of lithium ions into the crystal structure by charge and discharge. In the case of manganese dioxide which has been used in conventional lithium primary batteries, the repetition of expansion and contraction of the crystal structure causes the crystal structure to collapse, resulting in a remarkable reduction in discharge capacity. Therefore, a manganese oxide that does not destroy the crystal structure even in the cycle of lithium ions entering and releasing into the crystal structure has been required.

From such a background, recently, a manganese oxide having a crystal structure, such as a spinel structure or a layered structure, having a site capable of accommodating lithium ions in a crystal structure, and the sites being connected in a tunnel shape, has been developed. Now being considered.

Various studies have been made on manganese oxides having a spinel-type crystal structure, and for example, LiMn ₂ O ₄ as described above has been proposed as a cathode material. However, according to the study of the present inventors, the manganese oxides having a spinel-type crystal structure proposed so far have a problem that both output and utilization are low and reversibility of charge and discharge is insufficient. I found something.

On the other hand, a study on a manganese oxide having a layered structure or a manganese oxide having a δ-type crystal structure, which is considered to facilitate the movement of lithium ions in the solid phase rather than the spinel-type crystal structure, has been made to date. There is no suitable material for the battery positive electrode material, so the situation is almost none.

[0029]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object the application of a host compound to a battery active material, a catalyst, an adsorbent, and a magnetic material. A novel manganese oxide exhibiting a new spinel type, layered type, amorphous type crystal structure which can be expected and a crystal structure having both spinel type and layered type, and a method for producing the same, and at least one of these oxides It is an object of the present invention to provide a lithium secondary battery having high output, high energy density, and good charge / discharge cycle reversibility, using as a positive electrode.

[0030]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above problems, and as a result, have found that a hydroxide of A (A is any one of Zn, Mg, Ca, and Co in molar ratio). )
Oxidizes an alkaline aqueous solution of a mixture containing two manganese hydroxides with respect to one, and oxidizes the resulting compound, so that it can be used as a host compound for battery active materials, catalysts, adsorbents, and magnetic materials. Possible general formula A _x Mn ₂ O
₄ · nH ₂ O (where A is any one of Zn, Mg, Ca, and Co. When A is Zn, 0 <X <1 and n =
When 0 and A are Mg and Ca, 0 ≦ X ≦ 1 and 0 ≦ n ≦
20, when A is Co, a novel manganese oxide exhibiting a crystal structure having a spinel type, a layer type, an amorphous type, or a combination of both spinel type and layer type can be represented by 0 <X ≦ 1 and n = 0) When at least one of these manganese oxides is used for the positive electrode, it has been found that a lithium secondary battery having high output, high energy density, and good charge / discharge cycle reversibility can be formed, and the present invention It was completed.

More specifically, Z of a spinel type crystal structure
By removing Zn from nMn ₂ O ₄ by an oxidation treatment, it was found that a manganese oxide having a spinel-type crystal structure represented by the general formula Zn _x Mn ₂ O ₄ (0 <X <1) can be produced. It has been found that when manganese oxide is used for the positive electrode, a lithium secondary battery having high output, high energy density, and good charge / discharge cycle reversibility can be formed.

In particular, when ZnMn ₂ O ₄ having a BET specific surface area of 10 m ² / g or more is used as a starting material, a BET specific surface area of 100 m ² / g cannot be obtained by the conventional method.
It has been found that manganese dioxide having the above spinel-type crystal structure can be synthesized, and that when this is used as a positive electrode, a lithium secondary battery having high output, high energy density, and good charge / discharge cycle reversibility can be constructed. I found it.

Further, the molar ratio of magnesium hydroxide is 1
By oxidizing a mixture containing two manganese hydroxides in an aqueous alkali solution at room temperature, an oxide composed of Mg and Mn, and having an Mg: Mn molar ratio of 1: 2, It has been found that a manganese oxide having a novel layer structure having a novel interplanar spacing not shown so far can be synthesized. The plane spacing can be easily obtained from the X-ray diffraction angle using Bragg's equation.

Further, by removing Mg by an oxidation treatment, the general formula Mg _x Mn ₂ O ₄ .nH ₂ O (0 <X <1,
0 ≦ n ≦ 20), and found that a manganese oxide having a layered structure represented by the following formula can be produced. When this is used for the positive electrode, it has a high output, a high energy density, and a good charge / discharge cycle reversibility. It has been found that a lithium secondary battery can be constructed.

An oxide composed of Ca and Mn is obtained by oxidizing a mixture containing 2 parts of manganese hydroxide with respect to 1 part of calcium hydroxide in a molar ratio, thereby obtaining an oxide comprising Ca and Mn. As an oxide having a molar ratio of 1: 2,
It has been found that a new manganese oxide having an amorphous crystal structure, which has not been shown, can be synthesized.

Further, by removing Ca by an oxidation treatment, the general formula Ca _x Mn ₂ O ₄ .nH ₂ O (0 <X <1,
0 ≦ n ≦ 20), and found that a manganese oxide having a δ-type crystal structure represented by the following formula can be produced. When this is used for the positive electrode, high output, high energy density, and cycle reversibility of charge and discharge are obtained. It has been found that a good lithium secondary battery can be constructed.

A mixture of Co and Mn is obtained by oxidizing a mixture of cobalt hydroxide and manganese hydroxide in a molar ratio of 1 in an alkaline aqueous solution. As an oxide having a molar ratio of 1: 2, it has been found that a new manganese oxide having a layered type and a spinel type crystal structure, which has not been shown, can be synthesized. Furthermore, they have found that a new manganese oxide composed of a layered type and a spinel type manganese dioxide represented by the general formula Co _x Mn ₂ O ₄ (0 <X <1) can be produced by removing Co by an oxidation treatment. It has been found that, when this is used for the positive electrode, a lithium secondary battery having high output, high energy density, and good charge / discharge cycle reversibility can be formed.

As described above, the present invention relates to a compound represented by the general formula A _x Mn ₂
O ₄ .nH ₂ O (where A is Zn, Mg, Ca, Co
When A is Zn, n is 0 <X <1.
= 0, when A is Mg or Ca, 0 ≦ X ≦ 1 and 0 ≦ n ≦
20, when A is Co, 0 <X ≦ 1 and n = 0), a novel manganese oxide having a spinel type, a layered type crystal structure and a crystal structure having both spinel type and layered type; The present invention relates to a method for producing the same and a lithium secondary battery using at least one of these manganese oxides as a positive electrode.

[0039]

Hereinafter, the present invention will be described in detail.

The general formula A _x Mn ₂ O ₄ .nH ₂ in the present invention
O (where A is any one of Zn, Mg, Ca and Co, and when A is Zn, 0 <X <1 and n = 0 and A is M
For g and Ca, 0 ≦ X ≦ 1 and 0 ≦ n ≦ 20, and A is C
In the case of o, manganese oxide, which can be represented by 0 <X ≦ 1 and n = 0), has an ion movement path and an accommodation site in the crystal structure, and is expected to function as a host compound. . Further, a manganese atom is capable of continuously and reversibly changing its valence, and thus is a promising material having both a redox ability and a function as a host compound.

In the present invention, the general formula Zn _x Mn ₂ O ₄ (0
The manganese oxide having a spinel crystal structure represented by <X <1) is obtained by removing Zn from the manganese oxide having a spinel crystal structure represented by ZnMn ₂ O ₄ by an oxidation treatment.

In particular, when ZnMn ₂ O ₄ having a BET specific surface area of 10 m ² / g or more is used, it belongs to a spinel type crystal structure having a BET specific surface area of 100 m ² / g or more, which has not been obtained so far. λ-type manganese dioxide is obtained.

The ZnMn ₂ O ₄ used in the raw material of the present invention is a manganese oxide having a usual spinel crystal structure, in which Mn atoms are inserted in the octahedral position of the closest packed oxygen and Zn atoms are inserted in the tetrahedral position. It has an embedded crystal structure.

In the method for producing a spinel-type crystal structure from which Zn has been removed, it is important that a mixed hydroxide of Mn and Zn in an aqueous alkaline solution is aerated and oxidized to oxidize the resulting ZnMn ₂ O ₄ .

Specifically, after adding an equivalent amount or more of an alkali solution to an aqueous solution in which a divalent Mn salt and a Zn salt are dissolved at a molar ratio of 2: 1, the resulting hydroxide is aerated. This is achieved by oxidizing ZnMn ₂ O ₄ obtained by an oxidizing method by a method capable of oxidizing Mn to +4 valence. In addition,
The ZnMn ₂ O ₄ obtained here may have improved crystallinity by heat treatment. The aeration oxidation is performed by blowing air and / or oxygen into the solution.

As a method of oxidizing Mn to a valence of +4, for example, there is a method of chemically or electrochemically oxidizing. Specifically, at least an oxidizing agent capable of oxidizing Mn to a valence of +4 is used. One or more types of dissolved Zn
Examples include a method of treating Mn ₂ O ₄ , a method of disposing a solution in which ZnMn ₂ O ₄ is suspended on the anode side of an electrolytic cell in which an anode chamber and a cathode chamber are separated, and oxidizing the solution on the anode electrode.

The oxidizing agent used herein is not particularly limited as long as it has a function of oxidizing Mn to a valence of +4, for example, sodium persulfate,
Persulfates such as potassium persulfate and ammonium persulfate,
Examples include hydrogen peroxide and chlorine.

Conventionally, a method of removing Zn by treating ZnMn ₂ O ₄ with a mineral acid or an organic acid has been studied.
In this method, the dissolution of Mn occurs in addition to the removal of Zn, the spinel-type crystal structure is not maintained, and γ-type manganese dioxide is obtained. Alternatively, even when Zn is partially removed, Z
A proton-type spinel-type crystal structure in which H ⁺ is introduced instead of n does not result in a compound that functions as a host compound as intended in the present invention.

On the other hand, as in the present invention, Mn is changed to +
When the treatment is performed by a method capable of oxidizing up to tetravalent, oxidation of Mn and removal of Zn proceed simultaneously, and a manganese oxide having a spinel crystal structure from which Zn is removed is obtained. In particular, BE
When ZnMn ₂ O ₄ having a T specific surface area of 10 m ² / g or more is used, λ-type manganese dioxide having a BET specific surface area of 100 m ² / g or more and belonging to a spinel crystal structure is obtained.

The general formula of the present invention, MgMn ₂ O ₄ .nH ₂ O (
The oxide represented by (0 ≦ n ≦ 20) and having a molar ratio of Mg: Mn of 1: 2 is an oxide having a crystal structure that has not been confirmed so far.

As the oxide having a molar ratio of Mg: Mn of 1: 2, only manganese oxide having a spinel-type crystal structure of MgMn ₂ O ₄ composition is known.

On the other hand, the oxide of the present invention does not have a spinel-type crystal structure, but has a sodium Binessite structure.
Similar to e, it is a manganese oxide having a layered structure with various interplanar spacings including 7.14 angstroms.
In the layered structure, Mn atoms are arranged every other side of the hexagonal close-packed oxygen.

The layered manganese oxide having a molar ratio of Mg: Mn of 1: 2 according to the present invention oxidizes a mixture containing 2 parts of manganese hydroxide with respect to 1 part of magnesium hydroxide in an aqueous alkali solution. It is important to synthesize by methods.

Although the details are unknown, an oxide having a Mg: Mn ratio of 1: 2 in a molar ratio of the layered structure can be synthesized by oxidizing the mixed hydroxide in an alkaline aqueous solution.

Since the Mg compound is an inexpensive material and can be synthesized at room temperature, a layered manganese oxide can be synthesized at low production cost.

The oxidation is performed by aeration oxidation. That is, manganese hydroxide is oxidized by blowing air and / or oxygen into the solution to obtain a manganese oxide having a layered structure complexed with Mg.

This general formula MgMn ₂ O ₄ .nH ₂ O (0
≦ n ≦ 20), a layered manganese oxide obtained by removing some or all of the Mg atoms between layers,
The general formula Mg _x Mn ₂ O ₄ .nH ₂ O (0 ≦ X <1,
It is a manganese oxide having a layered structure represented by 0 ≦ n ≦ 20).

The compound having the layer structure of the present invention and having the general formula Mg _x M
A manganese oxide represented by n ₂ O ₄ .nH ₂ O (0 ≦ x <1, 0 ≦ n ≦ 20) has a general formula of MgMn ₂ O ₄ .nH ₂ O
It is obtained by removing some or all of the Mg atoms between layers from a manganese oxide (0 ≦ n ≦ 20), and has a structure having an empty site for cations between layers.

MgMn ₂ O ₄ .nH ₂ O (0 ≦ n ≦ 20)
Of Mg from the general formula Zn _x Mn ₂ O ₄ (0 <X <
This is achieved by the same method as in the production of manganese oxide having a spinel-type crystal structure represented by 1). That is, it is achieved by performing an oxidation treatment using a method capable of oxidizing Mn to +4 valences.

Conventionally, a method of treating with a mineral acid has been proposed. However, in this method, a proton-type layered manganese oxide in which cations and protons between layers are exchanged becomes a material which can be used in a wide range of fields. It does not become.

The general formula of the present invention, CaMn ₂ O ₄ .nH ₂ O (
An oxide having a molar ratio of Ca: Mn of 1: 2 represented by (0 ≦ n ≦ 20) has an unidentified crystal structure.

As oxides having a Ca: Mn ratio of 1: 2 in molar ratio, only manganese oxides belonging to the spinel type crystal structure of CaMn ₂ O ₄ composition are known.

On the other hand, the oxide of the present invention has an extremely weak and broad X-ray near the X-ray diffraction position corresponding to the interplanar spacing of 4.8 Å and 3.1 Å instead of the spinel crystal structure. It is an oxide having an amorphous crystal structure having no diffraction peak except for the diffraction peak and showing no specific crystal symmetry. As described above, the plane spacing can be easily obtained from the position of the X-ray diffraction peak using Bragg's equation.

In order to obtain an amorphous manganese oxide having a molar ratio of Ca: Mn of 1: 2 according to the present invention, a mixture containing 2 parts of manganese hydroxide with respect to 1 part of calcium hydroxide by molar ratio is used. It is important to oxidize in an alkaline aqueous solution.

Although the details are unknown, by oxidizing the mixed hydroxide in an alkaline aqueous solution, Ca:
An amorphous oxide having a Mn molar ratio of 1: 2 can be synthesized.

The above general formula MgMn ₂ O ₄ .nH ₂ O (0
≦ n ≦ 20), as in the synthesis of the manganese oxide having a layered structure represented by the following formula: That is,
By blowing air and / or oxygen into the solution, the hydroxide is oxidized, and an amorphous manganese oxide complexed with Ca is obtained.

The general formula CaMn ₂ O ₄ .nH ₂ O (0 ≦ n ≦
An amorphous manganese oxide represented by the following formula (20) is obtained by removing some or all of the Ca atoms from the general formula C of the present invention.
This is a manganese oxide having a δ-type structure represented by a _x Mn ₂ O ₄ .nH ₂ O (0 ≦ X <1, 0 ≦ n ≦ 20).

CaMn ₂ O ₄ .nH ₂ O (0 ≦ n ≦ 20)
Can be removed from the amorphous manganese oxide by the same method as in the production of a manganese oxide having a spinel crystal structure represented by the general formula Zn _x Mn ₂ O ₄ (0 <X <1). You. That is, the oxidation is performed by a method capable of oxidizing Mn to a valence of +4.

Although the details are unknown, the crystal structure is reduced by removing some or all of the Ca atoms of the amorphous manganese oxide of the general formula CaMn ₂ O ₄ .nH ₂ O (0 ≦ n ≦ 20). It changes from an amorphous to an undeveloped layered structure, but to a δ-type structure with empty sites between the layers where cations enter.

In general, the δ-type structure is a layered structure having cations between layers, and it is considered that even when some or all of Ca is removed, empty sites for cations are similarly formed between layers.

Conventionally, a method of treating with a mineral acid has been used to remove cations. However, in order to sufficiently remove Ca, it is necessary to use a mineral acid having a high acid concentration. When an acid is used, the disproportionation reaction of Mn atoms is promoted, and the crystal structure changes from δ-type to γ-type, so that Ca is sufficiently removed while maintaining the δ-type crystal structure. I couldn't.

Furthermore, in the case of a mineral acid, the compound is not used as a host compound and its use range is limited because it becomes a proton-type layered manganese oxide in which cations and protons between layers are simply exchanged.

Co: Mn represented by the general formula CoMn ₂ O ₄
An oxide having a molar ratio of 1: 2 and having a layered type and a spinel type crystal structure has not been identified so far.

The only known composite oxide composed of Co and Mn is a manganese oxide having a spinel-type crystal structure of CoMn ₂ O ₄ composition.
In contrast, the manganese oxide of the present invention has not only a spinel crystal structure but also sodium
Manganese oxide similar to e and having a composite crystal structure with a layered structure having various plane spacings including 7.25 angstroms. A manganese oxide having a layered type and a spinel type crystal structure having a molar ratio of Co: Mn of 1: 2 according to the present invention is a mixture containing 2 parts of manganese hydroxide with respect to 1 part of cobalt hydroxide by molar ratio. It is important to produce by oxidizing in an aqueous alkaline solution.

Although the details are unknown, the mixed hydroxide is oxidized in an aqueous alkaline solution to show both a layered type and a spinel type crystal structure.
A composite oxide having a ratio of 1: 2 can be produced.

As for the oxidation method, the above-mentioned general formula MgM
As in the production of a manganese oxide having a layered structure of n ₂ O ₄ .nH ₂ O (0 ≦ n ≦ 20), it is carried out by aeration method. That is, by blowing air and / or oxygen into the solution, Co
And a manganese oxide showing both a layered type and a spinel type crystal structure, which are composited, is obtained.

The manganese oxide of the present invention represented by the general formula Co _x Mn ₂ O ₄ (0 ≦ X <1) and having both a layered structure and a spinel type crystal structure is represented by the general formula CoMn ₂ O ₄ It has both a layered and spinel type crystal structure and can move cations between a two-dimensional layer formed by electrostatic repulsion of oxygen and a three-dimensional tunnel formed by close-packed oxygen. It is obtained by removing some or all of Co atoms from a manganese oxide having a pathway and an accommodation site for cations.

The oxide having such a crystal structure has the following characteristic functions.

In general, when a cation is inserted into a layered structure formed by electrostatic repulsion of oxygen, as in a layered structure, the electrostatic repulsion of oxygen is suppressed by the charge of the cation and the interlayer distance is reduced. Conversely, when the cations are desorbed, the electrostatic repulsion of oxygen is increased and the interlayer distance is increased.

On the other hand, like a spinel type structure,
When a cation is inserted into a three-dimensional tunnel formed by the closest-packed oxygen, the bond distance of the closest-packed oxygen is extended depending on the size of the ion of the cation. Conversely, when the cation is desorbed, it returns to the original bond distance of the closest packed oxygen.

As described above, in the layered structure and the spinel type structure, the expansion and contraction of the crystal structure due to the insertion and desorption of cations are exactly reversed. Therefore, in a manganese oxide having both a layered structure and a spinel type crystal structure represented by the general formula Co _x Mn ₂ O ₄ (0 ≦ X <1) of the present invention in which both crystal structures coexist, cation insertion is performed. The expansion and shrinkage of the crystal due to elimination and elimination are extremely small, and it is considered that when used as a host compound, the compound exhibits a more stable and reversible function as compared with a single crystal structure.

The removal of Co from CoMn ₂ O ₄ is as follows.
This is achieved by a method similar to that for synthesizing a manganese oxide having a spinel crystal structure represented by the general formula Zn _x Mn ₂ O ₄ (0 <X <1). That is, it is achieved by performing an oxidation treatment using a method capable of oxidizing Mn to +4 valence.

Formula A _x Mn ₂ O ₄ .nH ₂ O (where A
Is any of Zn, Mg, Ca and Co, and A is Zn
Is 0 <X <1, n = 0, A is Mg, Ca, 0 ≦ X ≦ 1, 0 ≦ n ≦ 20, and A is Co, 0 <
By using at least one of the manganese oxides of the present invention represented by X ≦ 1 and n = 0) as a positive electrode of a lithium secondary battery, high output, high energy density, and good charge / discharge cycle reversibility are obtained. A lithium secondary battery can be provided.

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

The electrolyte used in the lithium secondary battery of the present invention is not particularly limited. Examples thereof include electrolytes in which a lithium salt is dissolved in an organic solvent such as carbonates, sulfolanes, lactones and ethers. Alternatively, a lithium ion conductive solid electrolyte can be used.

Formula A _x Mn ₂ O ₄ .nH ₂ O (where A
Is any of Zn, Mg, Ca and Co, and A is Zn
Is 0 <X <1, n = 0, A is Mg, Ca, 0 ≦ X ≦ 1, 0 ≦ n ≦ 20, and A is Co, 0 <
FIG. 1 shows a three-electrode cell using at least one of the manganese oxides of the present invention as a positive electrode, wherein X is represented by X ≦ 1 and n = 0).

Examples will be described below, but the present invention is not limited to these examples.

[0088]

In the examples and comparative examples of the present invention, X
The line diffraction pattern was measured under the following conditions.

Measurement model: Philips PW-1729 Irradiated X-ray: Cu Kα ray Measurement mode: Step scan Scan condition: 0.02 degrees per second (However, as 2θ) Measurement time: 3 seconds Measurement range: 5 ° to 70 as 2θ The surface area was measured by the following method in Examples of the present invention and Comparative Examples.

Surface area measurement: After treatment in a nitrogen gas stream (flow rate: 15 ml / min) for 40 minutes at 250 ° C., measurement was carried out with an automatic surface area measuring apparatus (ASA-2000, manufactured by Shibata Scientific Instruments Co., Ltd.). did.

Example 1 As Example 1, the general formula Zn _x Mn ₂ O ₄ (0 <X <1)
A manganese oxide having a spinel crystal structure represented by the following formula was prepared by the following method.

[Preparation of ZnMn ₂ O ₄ ] 0.52 mol /
After thoroughly blowing nitrogen gas into the aqueous solution containing the zinc sulfate manganese sulfate and 0.26 mol / dm ³ of dm ^3, per minute of sodium 2 liters hydroxide 2.67 mol / dm ³ in the l of solution 10 The solution was added at a rate of milliliters, and then the solution was blown with air at a rate of 25 milliliters per minute for three days. The obtained precipitate was washed with water, filtered, and then dried at 70 ° C. overnight. X-ray diffraction of the obtained compound indicated that the compound was ZnMn ₂ O ₄ . FIG. 2 shows an X-ray diffraction diagram. Further, it was found that the BET specific surface area was 42 m ² / g.

[Removal of Zn / Preparation of Zn _x Mn ₂ O ₄ ]
5 g of ZnMn ₂ O ₄ powder obtained by the above method was added to 250 ml of 0.042 mol / dm ³ aqueous solution of ammonium persulfate, stirred at 70 ° C. for 4 hours, washed with water, filtered, and dried at 70 ° C. for 24 hours. From X-ray diffraction and composition analysis of the obtained compound, this compound was found to have a spinel crystal structure of Z.
n _0.67 Mn ₂ O ₄ . FIG. 3 shows an X-ray diffraction pattern, and Table 1 shows the results of composition analysis.

[0094]

[Table 1]

[Construction of Battery] The obtained manganese oxide having a spinel-type crystal structure, carbon powder of a conductive material and polytetrafluoroethylene powder of a binder were mixed at a weight ratio of 88:
The mixture was mixed at a ratio of 7: 5. 75 mg of this mixture is 2t
It was formed into an 8 mmφ pellet at a pressure of on / cm ² . After drying the pellet at 250 ° C. for 2 hours, the pellet was used as a test electrode 2 and a lithium foil was used as a counter electrode 4.
Lithium foil A piece of lithium perforated from lithium foil was used as the reference electrode 3 and the electrolyte was 1 m of lithium perchlorate.
A three-electrode cell as shown in FIG. 1 was constructed using propylene carbonate dissolved at a concentration of ol / dm ³ .

The three-pole cell constructed as described above
Cyclic voltammetry in which oxidation and reduction were repeated at a potential scanning speed of 5 mV / sec with the electrode potential of the test electrode relative to the reference electrode ranging from 0.75 V to 5.0 V was performed. Table 2 shows the reduction capacity (equivalent to the discharge capacity), the peak current value, and the average output obtained from the cyclic voltammogram at the tenth cycle.

Example 2 Zn _x Mn _{2 was} prepared in the same manner as in Example 1 except that 0.084 mol / dm ³ of ammonium persulfate was used for the oxidation treatment.
O ₄ was created. From the X-ray diffraction and composition analysis of the obtained compound, this compound was found to have a Zn _0.33 M spinel crystal structure.
It was found to be n ₂ O ₄ . FIG. 4 shows an X-ray diffraction diagram,
Table 1 shows the results of the composition analysis.

Next, a three-electrode cell was constructed in the same manner as in Example 1 except that this manganese oxide was used as a test electrode, and cyclic voltammetry was performed in the same manner as in Example 1. Table 2 shows the results.

[0099]

[Table 2]

Example 3 Zn _x Mn ₂ O _{4 was} prepared in the same manner as in Example 1 except that 0.5 mol / dm ³ of ammonium persulfate was used for the oxidation treatment.
It was created. From X-ray diffraction and composition analysis of the obtained compound, this compound was found to have a spinel-type crystal structure of Zn _0.10 Mn _2.
O ₄ was found. FIG. 5 shows an X-ray diffraction pattern, and Table 1 shows the results of composition analysis.

Next, a three-electrode cell was constructed in the same manner as in Example 1 except that this manganese oxide was used as a test electrode, and cyclic voltammetry was performed in the same manner as in Example 1. Table 2 shows the results.

Example 4 The same treatment as in Example 1 was performed except that 1.0 mol / dm ³ of ammonium persulfate was used for the oxidation treatment. X-ray diffraction and composition analysis of the obtained compound indicated that the compound was manganese dioxide having a spinel-type crystal structure. FIG. 6 shows an X-ray diffraction pattern, and Table 1 shows the results of composition analysis. Further, the BET specific surface area was 152 m ² / g.

Next, a three-electrode cell was constructed in the same manner as in Example 1 except that this manganese oxide was used as a test electrode, and cyclic voltammetry was performed in the same manner as in Example 1. Table 2 shows the results.

Example 5 As Example 5, ZnMn ₂ was prepared in the same manner as in Example 1 except that an aqueous solution containing 0.52 mol / dm ³ of manganese nitrate and 0.26 mol / dm ³ of zinc nitrate was used. O ₄
It was created. X-ray diffraction of the obtained compound indicated that the compound was ZnMn ₂ O ₄ . FIG. 7 shows an X-ray diffraction diagram. Further, it was found that the BET specific surface area was 12 m ² / g.

Next, an oxidation treatment was performed in the same manner as in Example 1 except that an aqueous solution of 0.5 mol / dm ³ of ammonium persulfate was used. From X-ray diffraction and composition analysis of the obtained compound, this compound was found to have a spinel-type crystal structure of Zn.
_{It was found to be 0.10} Mn ₂ O ₄ . FIG. 8 shows an X-ray diffraction pattern, and Table 1 shows the results of composition analysis.

Next, a three-electrode cell was constructed in the same manner as in Example 1 except that this manganese oxide was used as a test electrode, and cyclic voltammetry was performed in the same manner as in Example 1. Table 2 shows the results.

Example 6 The same treatment as in Example 5 was performed except that 1.0 mol / dm ³ of ammonium persulfate was used for the oxidation treatment. X-ray diffraction and composition analysis of the obtained compound indicated that the compound was manganese dioxide having a spinel-type crystal structure. FIG. 9 shows an X-ray diffraction pattern, and Table 1 shows the results of composition analysis. The BET specific surface area was 113 m ² / g.

Next, a three-electrode cell was constructed in the same manner as in Example 1 except that this manganese oxide was used as a test electrode, and cyclic voltammetry was performed in the same manner as in Example 1. Table 2 shows the results.

Comparative Example 1 A 0.1 mol / dm ³ aqueous sulfuric acid solution of 250 was used for the oxidation treatment.
The same processing as in Example 1 was performed except that milliliters were used. X-ray diffraction and composition analysis of the obtained compound revealed that the compound was a manganese oxide having a γ-type crystal structure. FIG. 10 shows an X-ray diffraction pattern, and Table 1 shows the results of composition analysis.

Comparative Example 2 As Comparative Example 2, ZnMn ₂ O ₄ was prepared by the following method.

14. Manganese trioxide (Mn ₂ O ₃ ) powder
8 g and zinc oxide (ZnO) powder 8.1 g were sufficiently mixed in an agate mortar, and the mixed powder was fired at 850 ° C. for 20 hours using an open-air electric furnace. From the results of X-ray diffraction and composition analysis of the obtained compound, this compound was found to be ZnMn.
It was found to be ₂ O ₄ . FIG. 11 shows an X-ray diffraction diagram,
Table 1 shows the results of the composition analysis.

The BET specific surface area was 1 m ² / g.

Next, the same oxidation treatment as in Example 4 was performed.
Zn _x Mn ₂ O ₄ was prepared. From the results of X-ray diffraction and composition analysis of the obtained compound, it was found that this compound was Zn _0.9 Mn ₂ O ₄ having a spinel type crystal structure. X in FIG.
A line diffraction diagram is shown, and Table 1 shows the results of composition analysis.

The BET specific surface area was 27 m ² / g.

Next, a three-electrode cell was constructed in the same manner as in Example 1 except that this manganese oxide was used as a test electrode, and cyclic voltammetry was performed in the same manner as in Example 1. Table 2 shows the results.

Comparative Example 3 As Comparative Example 3, LiMn ₂ O ₄ was prepared as a manganese oxide having a spinel crystal structure by the following method.

14. Manganese trioxide (Mn ₂ O ₃ ) powder
8 g and 1.5 g of lithium oxide (Li ₂ O) powder were sufficiently mixed in an agate mortar, and the mixed powder was fired at 850 ° C. for 20 hours using an open-air electric furnace. From the results of X-ray diffraction and composition analysis, the obtained compound was identified as LiM
It was found to be n ₂ O ₄ (lithium manganese spinel).

Next, a three-electrode cell was constructed in the same manner as in Example 1 except that this LiMn ₂ O ₄ was used for the test electrode 2, and cyclic voltammetry was performed in the same manner as in Example 1. Table 2 shows the results.

Example 7 As Example 7, the general formula Mg _x Mn ₂ O ₄ .nH ₂ O (0 ≦
X ≦ 1, 0 ≦ n ≦ 20) A manganese oxide represented by the following method was synthesized.

[MgMn ₂ O ₄ .nH ₂ O (0 ≦ n ≦ 2
Preparation of 0)] Nitrogen gas is sufficiently blown into an aqueous solution containing 0.52 mol / dm ³ of manganese sulfate and 0.26 mol / dm ³ of magnesium sulfate, and 2.67 mol / dm ³ of water is added to 1 liter of this solution. 2 liters of sodium oxide were added at a rate of 10 milliliters per minute to obtain an alkaline aqueous solution of a mixture containing two manganese hydroxides per one magnesium hydroxide in a molar ratio.

Then, air was blown into the solution at a rate of 25 ml / min for 3 days. The obtained precipitate was washed with water, filtered, and then dried at 70 ° C. all day and night.

From the compositional analysis of the obtained compound, the compound contained Mg and Mn at a molar ratio of 1: 2,
oxidation degree of n has a degree of oxidation of X = 1.79 in MnO _x terms, it has been found that a manganese oxide represented by a composition formula _{MgMn 2 O 4 · 16H 2 O} .

The compound was subjected to X-ray diffraction measurement using Cu Kα radiation as an X-ray source.
It was found to be a layered manganese oxide with interplanar spacing of 51, 3.56, 5.00, 7.14 and 9.23 Å. FIG. 13 shows an X-ray diffraction diagram of this manganese oxide. Table 3 shows the X-ray diffraction pattern of this compound. For reference, the X-ray diffraction pattern of MgMn ₂ O ₄ described in the ASTM card is also shown.

[0124]

[Table 3]

As is evident from Table 3, the manganese oxide obtained in this example is a known spinel type MgMn ₂
It is a novel substance completely different from O ₄ .

[Removal of Mg / Mg _x Mn ₂ O ₄ .nH ₂ O (
0 ≦ X <1, 0 ≦ n ≦ 20)] Next, 0.5 mo
1 / dm ³ aqueous solution of ammonium persulfate in 250 ml,
In addition the resulting MgMn ₂ O ₄ · 16H ₂ O powder 5g, After stirring for 4 hours at 70 ° C., washed with water filtration, 70 ° C.
And dried all day and night. The results of composition analysis of the obtained compound, the compound was found to be _{Mg 0.08 Mn 2 O 4 · H} 2 O. From the evaluation of the valence of Mn, the degree of oxidation of Mn in this compound was 1.95 in terms of MnO _x .

[0127] Further, from the results of X-ray diffraction measurement, this compound was found to exhibit a layered structure that maintains the original MgMn ₂ O ₄ · 16H ₂ O crystal structure. FIG. 14 shows an X-ray diffraction diagram.

[Preparation of Battery] The obtained layered Mg
A three-pole cell was constructed in the same manner as in Example 1 except that _0.08 Mn ₂ O ₄ .H ₂ O was used for the test electrode 2, and cyclic voltammetry was performed in the same manner as in Example 1. Table 4 shows 10
The reduction capacity (equivalent to the discharge capacity), the peak current value, and the average output obtained from the cyclic voltammogram at the cycle are shown.

[0129]

[Table 4]

[0130] As Example 8 Example 8, using magnesium nitrate manganese nitrate and 0.26 mol / dm ³ of 0.52 mol / dm ^3, except that was blown oxygen instead of air, as in Example 7 Thus, a manganese oxide was synthesized.

From the compositional analysis of the obtained compound, this compound contained Mg and Mn in a molar ratio of 1: 2,
oxidation degree of n has a degree of oxidation of X = 1.79 in MnO _x terms, it has been found that a manganese oxide represented by a composition formula _{MgMn 2 O 4 · 14H 2 O} .

The compound was subjected to an X-ray diffraction measurement using Cu Kα ray as an X-ray source.
It was found to be a manganese oxide having a layered structure with plane spacings of 51, 3.56, 5.00, 7.14 and 9.23. FIG. 15 shows an X-ray diffraction diagram of this manganese oxide. Table 3 shows the X-ray diffraction pattern of this compound. As is clear from Table 3, the manganese oxide obtained in this example is a novel substance completely different from the known spinel-type MgMn ₂ O ₄ .

[0133] Then, except for using the powder 5g of this _{MgMn 2 O 4 · 14H 2 O} , was treated similarly to Example 7. The compound obtained by this treatment has a composition formula of Mg _0.06 Mn
_It was found that the manganese oxide was represented by ₂ O ₄ · 0.8H ₂ O and had a layered structure in which the degree of oxidation of Mn was X = 1.95 in terms of MnO _x . FIG. 16 shows an X-ray diffraction diagram.

The obtained layered structure of Mg _0.06 Mn ₂ O ₄ .H
A three-electrode cell was constructed in the same manner as in Example 1 except that ₂ O was used for the test electrode 2, and cyclic voltammetry was performed in the same manner as in Example 1. Table 4 shows the results.

Comparative Example 4 As Comparative Example 4, sodium Birne having a layered structure was used.
Ssite was synthesized by the following method. 0.52mol / d
After cooling the aqueous solution containing m ³ manganese nitrate to 0 ° C., nitrogen gas was sufficiently blown therein. While cooling, 2 liters of 2.67 mol / dm ³ sodium hydroxide were added to 1 liter of the solution at a rate of 10 ml / min, and then air was blown into the solution at a rate of 25 ml / min for 3 days. . The obtained precipitate was washed with water, filtered, and then dried at 70 ° C. all day and night. From the results of composition analysis and X-ray diffraction measurement of the obtained compound, the obtained compound shows a layered structure.
It was confirmed to be _{e (Na 4 Mn 14 O 27} · 9H 2 O). FIG. 17 shows an X-ray diffraction pattern.

Next, 5 g of this compound powder was added to 2 liters of an aqueous solution of nitric acid having a pH of 2, and the mixture was stirred at 70 ° C. for 16 hours, washed with water, filtered and dried at 70 ° C. overnight. From the results of the composition analysis and X-ray diffraction measurement of the obtained compound, the obtained compound shows a layered structure,
It was confirmed to be _{irnessite (Mn 7 O 13 · 5H} 2 O). FIG. 18 shows an X-ray diffraction pattern.

[0137] except for using the the Mn ₇ O ₁₃ · 5H ₂ O in the resulting layered structure test electrode 2, constitute the same three-electrode cell of Example 1, cyclic in the same manner as in Example 1 Voltammetry was performed. Table 4 shows the results.

Example 9 As Example 9, the general formula Ca _x Mn ₂ O ₄ .nH ₂ O (0 ≦
X ≦ 1, 0 ≦ n ≦ 20) A manganese oxide represented by the following method was synthesized.

[CaMn ₂ O ₄ .nH ₂ O (0 ≦ n ≦ 2
Preparation of 0)] After sufficiently blowing nitrogen gas into an aqueous solution containing 0.52 mol / dm ³ of manganese sulfate and 0.26 mol / dm ³ of calcium nitrate, 2.67 mol / dm ³ of water is added to 1 liter of this solution. 2 liters of sodium oxide was added at a rate of 10 milliliters per minute to obtain an alkaline aqueous solution of a mixture containing two manganese hydroxides per one calcium hydroxide in a molar ratio.

Then, air was blown into the solution at a rate of 25 ml / min for 3 days. The obtained precipitate was washed with water, filtered, and then dried at 70 ° C. all day and night.

From the compositional analysis of the obtained compound, this compound contained Ca and Mn in a molar ratio of 1: 2,
The degree of oxidation of n was found to be a manganese oxide represented by the composition formula CaMn ₂ O ₄ .3H ₂ O having an oxidation degree of X = 1.75 in terms of MnO _x . In addition, Kα of Cu is used for the X-ray source.
X-ray diffraction measurement of this compound using X-ray
Amorphous manganese having no diffraction peak except for a broad and extremely weak X-ray diffraction peak near the X-ray diffraction angle corresponding to the d value indicating the plane spacing being 4.8 angstroms and 3.1 angstroms. It was found to be an oxide. FIG. 19 shows an X-ray diffraction diagram of this manganese oxide. Table 5 shows the X-ray diffraction pattern of this compound. For reference, the CaTM described in the ASTM card was used.
The X-ray diffraction pattern of Mn ₂ O ₄ is also shown.

[0142]

[Table 5]

As is clear from Table 5, the manganese oxide obtained in this example was a known spinel type CaMn ₂
It is a novel substance completely different from O ₄ .

[Removal of Ca / Ca _x Mn ₂ O ₄ .nH ₂ O (
0 ≦ X <1, 0 ≦ n ≦ 20)] Next, 0.5 mo
5 g of the obtained powder of CaMn ₂ O ₄ .3H ₂ O was added to 250 ml of 1 / dm ³ aqueous solution of ammonium persulfate, stirred at 70 ° C. for 4 hours, washed with water and filtered.
Dry at 0 ° C overnight. When the composition of the obtained compound was analyzed, this compound was found to be Ca _0.19 Mn ₂ O ₄ .0.4H
It was found to be ₂ O. Also, from the valence evaluation of Mn,
X = 1 degree of oxidation of the Mn of the compound is in the MnO _x conversion.
80.

Further, from the result of X-ray diffraction measurement, it was found that this compound had a δ-type crystal structure. FIG. 20 shows an X-ray diffraction diagram.

[Preparation of Battery] C of the obtained δ-type crystal structure
a A three-electrode cell was constructed in the same manner as in Example 1 except that a _0.19 Mn ₂ O ₄ .0.4H ₂ O was used for the test electrode 2, and cyclic voltammetry was performed in the same manner as in Example 1. Table 6 shows the reduction capacity (equivalent to the discharge capacity), the peak current value, and the average output obtained from the cyclic voltammogram at the tenth cycle.

[0147] As Example 10 Example 10, using magnesium nitrate manganese nitrate and 0.26 mol / dm ³ of 0.52 mol / dm ^3, except that was blown oxygen instead of air, Example 9
A manganese oxide was synthesized in the same manner as described above.

From the compositional analysis of the obtained compound, this compound contained Ca and Mn in a molar ratio of 1: 2,
oxidation degree of n has a degree of oxidation of X = 1.75 in MnO _x terms, it has been found that a manganese oxide represented by a composition formula _{CaMn 2 O 4 · 2.3H 2 O} .

The compound was subjected to an X-ray diffraction measurement using Cu Kα ray as an X-ray source.
Amorphous manganese oxide that does not show any diffraction peak except for a broad and extremely weak X-ray diffraction peak near the X-ray diffraction angle corresponding to a value of 4.8 Å and 3.1 Å. I understand. FIG. 21 shows an X-ray diffraction diagram of this manganese oxide. Table 5 shows the X-ray diffraction pattern of this compound. As is clear from Table 5, the manganese oxide obtained in this example is a novel substance completely different from the known spinel-type CaMn ₂ O ₄ .

[0150] Then, except for using the powder 5g of this _{CaMn 2 O 4 · 2.3H 2 O} , was treated similarly to that in Example 9. The compound obtained by this treatment has a composition formula of Ca _0.10 Mn
_It was found that the manganese oxide was represented by ₂ O ₄ · 0.3 H ₂ O and had a δ-type crystal structure in which the degree of oxidation of Mn was X = 1.95 in terms of MnO _x . FIG. 22 shows an X-ray diffraction diagram.

The obtained Ca _0.10 Mn ₂ O ₄ having a δ-type crystal structure was obtained.
· 0.3H ₂ except that the manganese oxide represented by O is used to test electrode 2 constitute the same three-electrode cell of Example 1,
Cyclic voltammetry was performed in the same manner as in Example 1. Table 6 shows the results.

[0152]

[Table 6]

Comparative Example 5 As Comparative Example 5, a manganese oxide having a δ-type crystal structure was prepared by the following method. To 2 mol / dm ³ of aqueous potassium permanganate solution 1 liter by adding aqueous hydrochloric acid solution one liter of 1 mol / dm ^3, and stirred for 2 hours. Next, this solution was filtered and washed with water until the washing liquid became neutral to obtain a red-brown powder.

This powder was dried at 70 ° C. for 24 hours, and then heat-treated at 250 ° C. for 20 hours in an air atmosphere.

From the composition analysis and X-ray diffraction measurement of the obtained powder, it was found that the obtained compound was MnO _1.83 having a δ-type crystal structure. FIG. 23 shows the X-ray diffraction pattern.

Next, the same oxidizing treatment as in Example 9 was carried out except that 5 g of the obtained powder was used, whereby a normal manganese oxide having a γ-type crystal structure was obtained.

Example 11 As Example 11, a manganese oxide represented by Co _x Mn ₂ O ₄ (0 <X ≦ 0) was synthesized by the following method.

[Preparation of CoMn ₂ O ₄ ] 0.52 mol /
After thoroughly blowing nitrogen gas into the aqueous solution containing the dm ³ of cobalt sulfate of manganese sulfate and 0.26 mol / dm ^3,
To 1 liter of this solution, 2 liters of 2.67 mol / dm ³ sodium hydroxide were added at a rate of 10 ml / min, and an alkaline aqueous solution of a mixture containing 2 parts of manganese hydroxide with respect to 1 part of calcium hydroxide by mole ratio was added. Obtained.

Next, air was blown into the solution at a rate of 25 ml / min for 3 days. The obtained precipitate was washed with water, filtered, and then dried at 70 ° C. all day and night.

From the composition analysis of the obtained compound, it was found that this compound contains Co and Mn in a molar ratio of 1: 2, and is a manganese oxide represented by the composition formula CoMn ₂ O _4. Was.

X-ray diffraction of this compound showed that this compound showed both a layered type and a spinel type crystal structure. FIG. 24 shows an X-ray diffraction diagram of this manganese oxide. [Removal of Ca / Ca _x Mn ₂ O ₄ (0 <X <1)
Next, the obtained CoMn ₂ was added to 250 ml of an aqueous 0.5 mol / dm ³ ammonium persulfate solution.
After adding 5 g of O ₄ powder and stirring at 70 ° C. for 4 hours,
The mixture was washed with water, filtered, and dried at 70 ° C. overnight. When the composition of the obtained compound was analyzed, this compound was found to have Co _0.80 M
It was found to be n ₂ O ₄ . From the results of X-ray diffraction measurement, it was found that this compound showed both a layered structure and a λ-type crystal structure belonging to a spinel-type structure. FIG. 25 shows an X-ray diffraction diagram.

[Preparation of Battery] The procedure of Example 1 was repeated except that Co _0.80 Mn ₂ O ₄ showing both the obtained layered structure and the λ-type crystal structure belonging to the spinel structure was used for the test electrode 2. A three-electrode cell similar to that of Example 1 was constructed, and cyclic voltammetry was performed in the same manner as in Example 1. Table 7 shows 10
The reduction capacity (equivalent to the discharge capacity), the peak current value, and the average output obtained from the cyclic voltammogram at the cycle are shown.

Example 12 A manganese oxide was synthesized in the same manner as in Example 11, except that 0.52 mol / dm ³ of manganese nitrate and 0.26 mol / dm ³ of cobalt nitrate were used.

From the composition analysis of the obtained compound, it was found that this compound contains Co and Mn in a molar ratio of 1: 2, and is a manganese oxide represented by the composition formula CoMn ₂ O _4. Was.

From the result of X-ray diffraction measurement, it was found that this compound showed both a layered structure and a spinel type crystal structure. FIG. 26 shows an X-ray diffraction diagram.

Next, the same treatment as in Example 11 was performed except that 5 g of the obtained CoMn ₂ O ₄ powder was used. It was found that the compound obtained by this treatment was represented by the composition formula Co _0.70 Mn ₂ O ₄ . Also, from the results of the X-ray diffraction measurement,
This compound has a lamellar structure and a spinel type structure.
It was found that both types of crystal structure are shown. FIG.
FIG. 7 shows an X-ray diffraction diagram.

Co _0.70 M showing both the obtained layered structure and the λ type crystal structure belonging to the spinel type structure.
A three-electrode cell was constructed in the same manner as in Example 1 except that the manganese oxide represented by n ₂ O ₄ was used for the test electrode 2.
The cyclic voltammetry was performed in the same manner as described above.
Table 7 shows the results.

[0168]

[Table 7]

Comparative Example 6 As Comparative Example 6, CoMn ₂ O ₄ was prepared by the following method.

14. Manganese trioxide (Mn ₂ O ₃ ) powder
8g and basic cobalt carbonate (2CoCO ₃ / 3Co (O
H) ₂ ) After sufficiently mixing 10.3 g of the powder in an agate mortar, the mixed powder was heated to 900 ° C. in an open-air electric furnace.
For 20 hours. From the results of X-ray diffraction and composition analysis of the obtained compound, it was found that this compound was CoMn ₂ O ₄ having a spinel-type crystal structure.

[0171]

As described above, according to the present invention, a novel spinel type, layer type, and spinel type which can be expected to be applied to a battery active material, a catalyst, an adsorbent, and a magnetic material as a host compound which have not been hitherto existed. And a novel manganese oxide exhibiting a crystal structure having both a layer-type crystal structure and a layer-type crystal structure.

Further, by using at least one of these manganese oxides for the positive electrode, a lithium secondary battery having high output, high energy density, and good charge / discharge cycle reversibility can be constructed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a battery constituted by an example and a comparative example.

[Explanation of symbols]

 1: Test electrode holder 2: Test electrode 3: Reference electrode 4: Counter electrode 5: Container

FIG. 2 shows an X-ray diffraction diagram of ZnMn ₂ O ₄ prepared in Example 1.

FIG. 3 shows an X-ray diffraction diagram of Zn _0.67 Mn ₂ O ₄ prepared in Example 1.

4 shows an X-ray diffraction diagram of Zn _0.33 Mn ₂ O ₄ prepared in Example 2. FIG.

5 shows an X-ray diffraction diagram of Zn _0.10 Mn ₂ O ₄ prepared in Example 3. FIG.

6 shows an X-ray diffraction pattern of manganese dioxide having a spinel-type crystal structure prepared in Example 4. FIG.

FIG. 7 shows an X-ray diffraction diagram of ZnMn ₂ O ₄ prepared in Example 5.

8 shows an X-ray diffraction diagram of Zn _0.10 Mn ₂ O ₄ prepared in Example 5. FIG.

FIG. 9 shows an X-ray diffraction pattern of manganese dioxide having a spinel-type crystal structure prepared in Example 6.

10 shows an X-ray diffraction diagram of a manganese oxide having a γ-type crystal structure prepared in Comparative Example 1. FIG.

11 shows an X-ray diffraction diagram of ZnMn ₂ O ₄ produced in Comparative Example 2. FIG.

12 shows an X-ray diffraction diagram of Zn _0.90 Mn ₂ O ₄ produced in Comparative Example 2. FIG.

[13] MgMn prepared in Example 7 ₂ O ₄ · 16H ₂
1 shows an X-ray diffraction pattern of O.

[14] Mg _0.08 produced in Example 7 Mn ₂ O ₄ · H ₂
1 shows an X-ray diffraction pattern of O.

[15] MgMn prepared in Example 8 ₂ O ₄ · 14H ₂
1 shows an X-ray diffraction pattern of O.

FIG. 16 shows Mg _0.06 Mn ₂ O ₄ · 16 prepared in Example 8.
1 shows an X-ray diffraction pattern of H ₂ O.

FIG. 17 shows sodium Birnes prepared in Comparative Example 4.
2 shows an X-ray diffraction diagram of the site.

FIG. 18 shows a sodium-free Bir prepared in Comparative Example 4.
FIG. 2 shows an X-ray diffraction pattern of nessite.

[Figure 19] CaMn prepared in Example 9 ₂ O ₄ · 3H ₂ O
FIG.

FIG. 20 shows the _{results of} Ca _0.19 Mn ₂ O _{4 .0} .
4 shows an X-ray diffraction diagram of 4H ₂ O. FIG.

CaMn ₂ O ₄ · 2.3 to [21] prepared in Example 10
1 shows an X-ray diffraction pattern of H ₂ O.

FIG. 22 shows Ca _0.10 Mn ₂ O _4.
Shows the X-ray diffraction diagram of 0.3H ₂ O.

FIG. 23 shows MnO having a δ-type crystal structure prepared in Comparative Example 5.
The X-ray diffraction diagram of _1.83 is shown.

24 shows an X-ray diffraction diagram of CoMn ₂ O ₄ produced in Example 11. FIG.

FIG. 25 shows X of Co _0.80 Mn ₂ O ₄ prepared in Example 11.
FIG.

26 shows an X-ray diffraction diagram of CoMn ₂ O ₄ produced in Example 12. FIG.

FIG. 27 shows X of Co _0.70 Mn ₂ O ₄ produced in Example 12.
FIG.

 ──────────────────────────────────────────────────続 き Continuation of the front page (31) Priority claim number Japanese Patent Application No. 4-324467 (32) Priority date December 3, 1992 (1992.12.3) (33) Priority claim country Japan (JP) (31) Priority claim number Japanese Patent Application No. 4-324469 (32) Priority date December 3, 1992 (1992.12.3) (33) Priority claim country Japan (JP) (31) Priority claim number Japanese Patent Application No. 4-329411 (32) Priority date December 9, 1992 (1992.12.9) (33) Priority claiming country Japan (JP)

Claims (6)

(57) [Claims] 1. Manganese acid represented by the general formula A _x Mn ₂ O ₄
A product (although, A is a either Zn, Mg, Ca, of Co, if A is Zn, 0 <x <1, n = 0
, And the and crystal structure spinel, when A is Mg
Where 0 <x <1, 0 ≦ n ≦ 20 and the crystal structure
The structure is a layered mold, and X = 1, 0 ≦ n ≦ 20, and
Layered type with crystal structure having the following plane spacing, where A is Ca
In this case, 0 <x <1, 0 ≦ n ≦ 20 and the crystal structure is
δ type, X = 1, 0 ≦ n ≦ 20 , and a crystal structure
If concrete is amorphous, A is Co 0 <x <1, n = 0 der
The crystal structure is based on both the layered and spinel crystal structures.
Manganese oxide characterized by comprising. Interplanar spacing (angstrom) 9.23 ± 0.05 7.14 ± 0.05 5.00 ± 0.05 3.36 ± 0.05 2.51 ± 0.05 2.43 ± 0.05 2. The manganese oxide according to claim 1, wherein A is any one of Zn, Mg, Ca, and Co.
<X <1 is a manganese oxide. 3. A hydroxide of A in a molar ratio (A is Zn, M
3. A manganese oxide according to claim 2, wherein after oxidizing an alkaline aqueous solution of a mixture containing 2 manganese hydroxides per 1 of g, Ca and Co), oxidizing treatment is carried out to remove A. Manufacturing method. 4. Zn having a BET specific surface area of 10 m ² / g or more.
The Mn ₂ O ₄ was used as a starting material, and method for producing manganese oxide according to claim 3, characterized in that the removal of Zn by oxidation treatment. 5. Manganese produced by the method according to claim 4.
An oxide, from which Zn was completely removed, 100 m ² /
A manganese oxide having a spinel structure having a BET specific surface area of at least g. 6. A lithium secondary battery using at least one of the manganese oxides according to claim 1 and / or 2 as a positive electrode.