JP5263761B2 - Monoclinic lithium manganese composite oxide having cation ordered structure and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new material which exhibits excellent charge and discharge characteristics in comparison with a known inexpensive positive electrode material for a lithium ion battery, by using a raw material being little restricted in terms of natural resources and inexpensive. <P>SOLUTION: The new material is a lithium manganese-based compound oxide represented by composition formula: Li<SB>1+x</SB>(Mn<SB>1-m-n</SB>Fe<SB>m</SB>Ti<SB>n</SB>)<SB>1-x</SB>O<SB>2</SB>(wherein, 0&lt;x&lt;1/3; 0&le;m&le;0.60; 0&le;n&le;0.80; and 0&lt;m+n&le;0.80) and containing a crystal phase having a monoclinic Li<SB>2</SB>MnO<SB>3</SB>type layered rock-salt structure. In a hexagonal network ordered structure in a transition metal-containing layer of the crystal phase of the monoclinic Li<SB>2</SB>MnO<SB>3</SB>type layered rock-salt structure, the occupying ratio of a transition metal in the positions constituting hexagonal network lattice is higher than that of the occupying ratio of the transition metal in the hexagonal network central positions. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a lithium manganese composite oxide useful as a positive electrode material for a next-generation low-cost lithium ion secondary battery and a method for producing the same.

  Currently, in Japan, most of secondary batteries installed in portable devices such as mobile phones and notebook computers are lithium ion secondary batteries. In addition, lithium ion secondary batteries are expected to be put into practical use as large batteries for electric vehicles, power load leveling systems, and the like, and their importance is increasing.

Currently, in lithium ion secondary batteries, a lithium cobalt oxide (LiCoO ₂ ) material is mainly used as a positive electrode material, and a carbon material such as graphite is used as a negative electrode material.

In such a lithium ion secondary battery, the amount of lithium ions reversibly desorbed (equivalent to charging) and inserted (equivalent to discharging) in the positive electrode material determines the capacity of the battery, and the voltage at the time of desorption / insertion is the battery. LiCoO ₂ as a positive electrode material is an important battery constituent material related to battery performance. For this reason, the demand for lithium cobalt oxide is expected to increase further with the future expansion and enlargement of lithium ion secondary batteries.

However, since lithium cobalt oxide contains a large amount of rare metal cobalt, it is one of the causes of high material costs of lithium ion secondary batteries. Furthermore, considering that about 20% of cobalt resources are currently used in the battery industry, it is considered difficult to meet future demand growth with only the cathode material made of LiCoO ₂ .

Currently, lithium nickel oxide (LiNiO ₂ ) and lithium manganese oxide (LiMn ₂ O ₄ ) have been reported as cheaper and less resource-constrained positive electrode materials, and some have been put into practical use as alternative materials. Yes. However, lithium nickel oxide has the problem of reducing the safety of the battery during charging, and lithium manganese oxide elutes trivalent manganese into the electrolyte during charge and discharge at high temperatures (about 60 ° C). There is a problem that the battery performance is significantly deteriorated, and the substitution to these materials is not so advanced. Among the lithium manganese oxides, a positive electrode material called LiMnO ₂ has also been proposed, but this material also gradually changes from its original structure to the spinel crystal structure with charge and discharge, and the shape of the charge / discharge curve changes. Since it changes greatly with the progress of the charge / discharge cycle, it has not been put into practical use.

Further, lithium ferrite (LiFeO ₂ ) containing iron, which is more abundant in resources, less toxic, and cheaper than manganese and nickel, has been studied as a potential electrode material. However, since lithium ferrite obtained by a normal manufacturing method, that is, by mixing an iron source and a lithium source and firing at high temperature, hardly charges or discharges, it cannot be used as a positive electrode material for a lithium ion secondary battery.

On the other hand, LiFeO ₂ obtained by the ion exchange method has been reported to be chargeable / dischargeable (see Patent Documents 1 and 2 below), but the average discharge voltage of these materials is 2.5 V or less and the value of LiCoO ₂ Since it is significantly lower than (approximately 3.7V), it is difficult to replace LiCoO ₂ .

The present inventors have already described a layered rock salt type solid solution (Li _{1 + x} (Fe _y Mn ₁ ) composed of lithium manganese oxide (Li ₂ MnO ₃ ) and lithium ferrite, which are cheaper and resource-rich after iron. _-y ) _1-x O
₂ , (0 <x <1/3, 0 <y <1), hereinafter referred to as “iron-containing Li ₂ MnO ₃ ”, is an average discharge voltage close to 4 V, comparable to lithium cobalt oxide, in charge and discharge tests at room temperature (See Patent Documents 3 and 4 below).

Furthermore, the present inventors show that a lithium-iron-manganese composite oxide satisfying specific conditions exhibits a higher capacity (150 mAh / g) and stable charge / discharge cycle characteristics than LiMn ₂ O ₄ during a high-temperature cycle test. (See Patent Document 5 below). Furthermore, a solid solution lithium-iron-titanium-manganese or lithium-titanium-manganese composite oxide having a hexagonal layered rock salt structure obtained by adding titanium as an element other than iron is also a lithium-iron-manganese composite oxide. Similarly, it has been found that it has a discharge capacity exceeding 250 mAh / g and has excellent charge / discharge characteristics (see Patent Document 6 below).

As described above, various reports have been made on lithium manganese-based positive electrode materials that can replace lithium cobalt-based positive electrode materials. However, in order to further improve the charge / discharge characteristics, the chemical composition, crystal structure and manufacturing conditions of the positive electrode material Further optimization is desired.
Japanese Patent Laid-Open No. 10-120421 JP-A-8-295518 JP 2002-68748 A Japanese Patent Laid-Open No. 2002-121026 JP 2005-154256 A JP 2008-63211 A

  The present invention has been made in view of the current state of the prior art described above, and its main object is to maintain an average discharge voltage of 3 V or more in a long-term charge / discharge cycle and to provide a lithium cobalt oxide-based positive electrode material. Is a material having a discharge capacity equivalent to or higher than that, can be obtained by using raw materials with less resource restrictions and cheaper, and more excellent than known low-cost positive electrode materials. It is another object of the present invention to provide a novel material capable of exhibiting excellent charge / discharge characteristics.

The present inventor has intensively studied to achieve the above-described object. As a result, in the lithium manganese complex oxide in which Fe and / or Ti are dissolved in lithium manganese oxide (Li ₂ MnO ₃ ), the transition metal ion composed of Mn, Fe and Ti is converted into the known lithium manganese complex oxidation. A new monoclinic complex oxide having a unique distribution state different from that of a hexagonal layered rock salt structure has excellent performance capable of achieving the above-mentioned purpose, It discovered that it had a discharge cycle characteristic, and came to complete this invention here.

That is, the present invention provides the following lithium manganese composite oxide, a production method thereof, a lithium ion secondary battery positive electrode material and a lithium ion secondary battery comprising the lithium manganese composite oxide.
1. Composition formula: Li _{1 + x} (Mn _1-mn Fe _m Ti _n ) _1-x O ₂ (wherein the subscripts are as follows: 0 <x <1/3, 0 ≦ m ≦ 0.60, 0 ≦ n ≦ 0.80, 0 <m + n ≦ 0.80), and a lithium manganese based composite oxide containing a crystal phase having a monoclinic Li ₂ MnO ₃ type layered rock salt structure,
In the hexagonal network regular structure in the transition metal-containing layer of the crystal phase of the monoclinic Li ₂ MnO ₃ type layered rock salt structure, the transition metal occupancy at the hexagonal network lattice position is the transition metal occupancy at the hexagonal network center position. Lithium manganese complex oxide characterized by being larger.
2. Crystalline single phase of monoclinic Li ₂ MnO ₃ type layered rock-salt structure, or monoclinic Li ₂ MnO ₃ type layered rock-salt type structure crystalline phase and the cubic of crystalline phase mixed phase of the rock salt structure above Item 2. The lithium manganese composite oxide according to Item 1.
3. The lithium manganese-based composite oxide according to Item 1 or 2, wherein in the composition formula: Li _{1 + x} (Mn _1-mn Fe _m Ti _n ) _1-x O ₂ , 0.05 ≦ m + n ≦ 0.80.
4). At least one compound selected from the group consisting of a titanium compound and an iron compound and an aqueous solution containing a manganese compound are made alkaline to form a precipitate, and then the formed precipitate is fired in the presence of a lithium compound. The method for producing a lithium manganese composite oxide according to any one of Items 1 to 3.
5. At least one compound selected from the group consisting of a titanium compound and an iron compound and an aqueous solution containing a manganese compound are made alkaline to form a precipitate, and then the formed precipitate is combined with an oxidizing agent and a water-soluble lithium compound under alkaline conditions. 4. The method for producing a lithium manganese composite oxide according to any one of Items 1 to 3, wherein hydrothermal treatment is performed.
6). At least one compound selected from the group consisting of a titanium compound and an iron compound and an aqueous solution containing a manganese compound are made alkaline to form a precipitate, and then the formed precipitate is combined with an oxidizing agent and a water-soluble lithium compound under alkaline conditions. Item 4. The method for producing a lithium manganese composite oxide according to any one of Items 1 to 3, wherein after the hydrothermal treatment, firing is performed in the presence of a lithium compound.
7). Composition formula: Li _{1 + x} (Mn _1-mn Fe _m Ti _n ) _1-x O ₂ (wherein the subscripts are as follows: 0 <x <1/3, 0 ≦ m ≦ 0.60, 0 ≦ n ≦ 0.80, 0 <m + n ≦ 0.80), and a lithium manganese based composite oxide containing a crystal phase having a monoclinic Li ₂ MnO ₃ type layered rock salt structure,
In the hexagonal network regular structure in the transition metal-containing layer of the crystal phase of the monoclinic Li ₂ MnO ₃ type layered rock salt structure, the transition metal occupancy at the hexagonal network lattice position is the transition metal occupancy at the hexagonal network center position. A positive electrode material for a lithium ion secondary battery comprising a larger lithium manganese composite oxide.
8). Composition formula: Li _{1 + x} (Mn _1-mn Fe _m Ti _n ) _1-x O ₂ (wherein the subscripts are as follows: 0 <x <1/3, 0 ≦ m ≦ 0.60, 0 ≦ n ≦ 0.80, 0 <m + n ≦ 0.80), and a monoclinic Li ₂ MnO ₃ type layered rock salt structure containing a crystalline phase comprising a lithium manganese-based composite oxide, the monoclinic Li _{2 In} the hexagonal network regular structure in the transition metal-containing layer of the crystalline phase of the MnO ₃ type layered rock salt structure, the lithium manganese system in which the transition metal occupancy at the hexagonal network lattice position is larger than the transition metal occupancy at the hexagonal network center position A lithium ion secondary battery comprising a lithium ion secondary battery positive electrode material made of a composite oxide as a constituent element.

  Hereinafter, the lithium manganese composite oxide and the method for producing the same of the present invention will be specifically described.

Lithium manganese composite oxide of lithium manganese-based composite oxide present invention, the composition formula: Li _{1 + x} in _{(Mn 1-mn Fe m Ti} n) 1-x O 2 ( wherein each subscript as follows Yes: 0 <x <1/3, 0 ≦ m ≦ 0.60, 0 ≦ n ≦ 0.80, 0 <m + n ≦ 0.80), which is a general crystal structure of the oxide Li ₂ MnO ₃ (P. Strobel and B. Lanbert-Andron, Journal of Solid State Chemistry, 75, 90-98 (1988). The same space group as

を有する単斜晶Li₂MnO₃型層状岩塩型構造の結晶相を含むものである。但し、本発明のリ
チウムマンガン系複合酸化物は、上記した単斜晶Li₂MnO₃型層状岩塩型構造内において、Mn以外に、Feおよび／またはTiからなる遷移金属(以下、Mn、Fe及びTiからなる遷移金属をMと略記することがある)を含むという点で、公知物質（Li₂MnO₃）とは異なる。また、そ
の結晶構造および陽イオン分布は、LiCoO₂、LiNiO₂、LiNi_0.5Mn_0.5O₂や、特許文献６に記載されているLi_1+x(Mn_1-m-nFe_mTi_n)_1-xO₂ 等に代表される空間群

It contains a crystal phase of monoclinic Li ₂ MnO ₃ type layered rock salt structure with However, the lithium manganese-based composite oxide of the present invention has a transition metal composed of Fe and / or Ti in addition to Mn (hereinafter referred to as Mn, Fe, and Mn) in the above monoclinic Li ₂ MnO ₃ type layered rock salt structure. It differs from a known substance (Li ₂ MnO ₃ ) in that it contains a transition metal composed of Ti (may be abbreviated as M). The crystal structure and cation distribution are LiCoO ₂ , LiNiO ₂ , LiNi _0.5 Mn _0.5 O _2, and Li _{1 + x} (Mn _1-mn Fe _m Ti _n ) _1-x described in Patent Document 6. Space groups represented by O ₂ etc.

を有する六方晶層状岩塩型構造とも異なっている。

It is also different from the hexagonal layered rock-salt type structure.

The lithium manganese-based composite oxide of the present invention only needs to include a monoclinic Li ₂ MnO ₃ type layered rock salt structure crystal phase having the above-mentioned specific cation distribution, and other rock salts having different cation distributions. A mixed phase including a crystal phase of a mold structure (such as a cubic rock salt structure) may be used.

For example, it may be a single phase of monoclinic Li ₂ MnO ₃ type lamellar rock salt structure having the above-mentioned specific cation distribution, or such monoclinic Li ₂ MnO ₃ type lamellar rock salt type structure. Space group of cubic rock salt structure similar to α-LiFeO ₂ in addition to crystalline phase

の結晶相を含む混合相であってもよい。

It may be a mixed phase including the crystal phase of

In this case, the ratio of the crystal phase of the monoclinic Li ₂ MnO ₃ layered rock salt structure and the crystal phase of the cubic rock salt structure is usually the monoclinic Li ₂ MnO ₃ layered rock salt structure crystal phase: cubic The rock salt structure crystal phase (weight ratio) may be in the range of about 100: 0 to 10:90.

FIGS. 1 and 2 are diagrams schematically showing the crystal structure of the lithium manganese composite oxide of the present invention based on Li ₂ MnO ₃ of the above-mentioned reference, and FIG. 1 is characterized by a layered rock salt structure. FIG. 2 is a diagram showing a laminated state of a typical Li single layer and a transition metal-containing layer (M-Li layer). FIG. 2 shows the Li and M arrangement in the M-Li layer obtained by rotating FIG. FIG.

Hereinafter, in the composite oxide represented by the composition formula: Li _{1 + x} (Mn _1-mn Fe _m Ti _n ) _1-x O ₂ , Fe and / or
Alternatively, the cation distribution in the composite oxide of the present invention will be described using a case where Ti is included as an example.

First, in FIG. 1, a Lic composed of 2c and 4h positions having two different crystallographic positions, respectively, through an oxide ion single layer having two kinds of crystallographic positions (4i and 8j positions).
Layers and M-Li layers consisting of 2b and 4g positions are alternately stacked, similar to the way of stacking Li and Co layers in a typical LiCoO ₂ crystal structure with a hexagonal layered rock-salt structure It is. However, LiCoO ₂ is different from the composite oxide of the present invention in that there is one kind of crystallographic position in each layer.

In FIG. 2, M ions corresponding to the position of the lattice point 4g form a hexagonal mesh lattice, and Li ions occupy the center position (2b position) of the hexagonal mesh lattice.

In Li ₂ MnO ₃ which is a known substance, when Mn ions are in an ideal arrangement state, Mn is located at the 4 g position.
Occupies 100%, and there should be no Mn ions at the Li positions 2b, 4h, 2c, but in reality, the Mn ions are not 100% at the 4g position. It is reported that only 88% of Mn occupies the 4g position, and the remaining 12% of Mn ions are present in any of the three Li positions (2b, 4h, 2c positions). Even if all 12% Mn is present at the hexagonal mesh center position (2b position), the Mn occupancy at the 4g position (g _4g , 88%) is the Mn occupancy at the 2b position (g _2b , 12%). ) Will be higher than. This difference (g _4g −g _2b = 76%) is defined as the degree of hexagonal mesh regular arrangement (S).

In the present invention, in addition to Mn, the transition metal (M) including Fe and Ti, the occupation ratio (g _4g ) at the hexagonal network lattice constituting position (4g) of the hexagonal network regular structure in the transition metal-containing layer, The difference (g _4g −g _2b ) from the occupation ratio (g _2b ) of the hexagonal mesh center position (g _2b ) is defined as the hexagonal mesh regular arrangement degree (S). The composite oxide of the present invention is characterized in that the degree of hexagonal network regularity (S) is positive ((S> 0) for the transition metal (M). By having such a peculiar cation distribution, effects such as improvement of charge / discharge cycle characteristics are exhibited, and it has excellent performance as a positive electrode material for a lithium ion battery.

  The composite oxide of the present invention having such a peculiar cation distribution is positioned as an essentially stable structure as compared with a hexagonal layered rock salt type structure or a reverse hexagonal network structure described later, It can be produced by appropriately selecting an Mn source such as manganese (II) chloride or by selecting firing conditions according to the substitution ratio of Fe or Ti. Specific manufacturing conditions will be described in detail in the section of the manufacturing method described later.

On the other _{hand, LiCoO 2, LiNiO 2, LiNi} 0.5 Mn 0.5 O 2 or _{Li 1 + x (Mn 1-} mn Fe m Ti n) disclosed in Patent Document 6 space group represented by _1-x O _2, etc.

を有する六方晶層状岩塩型構造においては、Li層、M-Li層の各層に対して1種の結晶学的
位置(3a位置または3b位置のいずれか)しかないので、六角網目規則配列度は０％(S=0)と
なる。この構造は、Mnイオンに対して比較的多くのFeイオン及び／又はTiイオンを固溶させる方法、水熱処理を行う方法、低温で焼成する方法などによって安定化することができる。この構造は、2種の格子位置の区別がほとんどつかなくなることから、遷移金属イオ
ン不規則配列（ランダム）構造と考えられる。この結晶相は、最終的に安定な上記六角網目構造に至る前の準安定相と位置づけられる。

In the hexagonal layered rock-salt structure with, there is only one crystallographic position (either 3a position or 3b position) for each of the Li layer and the M-Li layer, so the hexagonal network regularity is 0% (S = 0). This structure can be stabilized by a method in which a relatively large amount of Fe ions and / or Ti ions are dissolved in Mn ions, a method of hydrothermal treatment, a method of firing at a low temperature, and the like. This structure is considered to be a transition metal ion disordered (random) structure because the two types of lattice positions can hardly be distinguished. This crystal phase is positioned as a metastable phase before finally reaching the stable hexagonal network structure.

In addition, when using, for example, potassium permanganate (VII) as the Mn source, or when firing at a relatively low temperature by increasing the substitution ratio of Fe or Ti, monoclinic Li ₂ MnO ₃ type layered rock salt In the crystal phase of the type structure, the transition metal (Mn, Fe, Ti) occupancy of the 2b position in the hexagonal network regular structure in the transition metal-containing layer, that is, the center position of the hexagonal network is the 4g position, that is, the hexagonal network structure It is larger than the transition metal occupancy at the position, and the hexagonal network regularity (g _4g −g _2b ) may be negative (S <0). Such a structure is called an inverted hexagonal network structure. This is a metastable phase with the above random structure, and many primary particles are relatively small, and excellent initial charge / discharge characteristics, discharge rate characteristics, and low-temperature discharge characteristics can be obtained. May be disadvantageous in terms of

Hereinafter, when the hexagonal mesh regular arrangement degree is a positive value (S> 0), it is described as a hexagonal network structure, and when the hexagonal mesh regular arrangement degree is a negative value (S <0), the reverse hexagonal network structure, the hexagonal mesh is described. When the degree of regular arrangement is zero (S = 0), it is described as a random structure.

The composite oxide of the present invention having a crystal phase of a monoclinic Li ₂ MnO ₃ type layered rock salt structure having a positive hexagonal network regularity (S> 0) forms, for example, a precipitation product described later. After that, it can be obtained by producing an oxide represented by the above specific composition formula using a method of firing this.

In this case, in the above composition formula, Fe and Ti contribute to the improvement of charge / discharge characteristics, but when dissolved in large quantities, higher temperature firing is required to ensure the stability of the transition metal ion distribution of the hexagonal network structure. . Therefore, in order to stably obtain the above complex oxide having a hexagonal network structure, the total amount of Fe ions and Ti ions, that is, m + n is in the range of about 0 <m + n ≦ 0.80 in the composition formula. It is appropriate to do.

When the amount of Fe ions and Ti ions is small, for example, even when the total amount of m + n is less than 0.05, a hexagonal network structure with a positive degree of hexagonal network regularity (S> 0) can be formed. However, there is a tendency that the effect of improving the initial charge / discharge characteristics associated with the precipitation becoming finer due to the solid solution of Fe ions and Ti ions is reduced. For this reason, in order to exhibit good initial charge / discharge characteristics, the total amount of m + n is desirably 0.05 or more.

  From the above, the preferable range of m + n is about 0.05 ≦ m + n ≦ 0.80.

In the lithium manganese composite oxide of the present invention, the amount of Fe ions to be dissolved (m value: Fe / (Fe + Mn + Ti)) is 60% or less of the amount of metal ions other than Li ions, that is, 0 ≦ m It is desirable that ≦ 0.60. When the amount of Fe ions in excess is excessive, the thermal stability of the sample is reduced, making high-temperature firing difficult, and as a result, the abundance of the monoclinic layered rock-salt crystal phase is significantly reduced. It is not preferable in terms of characteristics.

In the lithium manganese based composite oxide of the present invention, the amount of Ti ions to be dissolved (n value: Ti / (Fe + Mn + Ti)) is 80% or less of the amount of metal ions other than Li ions, that is, 0 It is desirable that ≦ n ≦ 0.80. Even when the amount of Ti ion solid solution is excessive, the abundance of the monoclinic layered rock salt type crystal phase is remarkably reduced, which is not preferable in terms of battery characteristics.

Further, in the lithium manganese composite oxide of the present invention, as long as the above-described crystal structure can be maintained, _{x of} Li _{1 + x} (Mn _1-mn Fe _m Ti _n ) _1-x O ₂ is a transition metal ion. Depending on the average valence, it can take values between 0 and 1/3. Preferably it is the range of 0.05-0.33.

  Further, the composite oxide of the present invention is a lithium hydroxide, lithium carbonate, titanium compound, iron compound, manganese compound (solid solution or hydration thereof) in a range that does not significantly affect the charge / discharge characteristics (up to about 10 mol%). An impurity phase such as a product).

Method for Producing Lithium Manganese Composite Oxide Hereinafter, as a method for producing the lithium manganese composite oxide of the present invention, a method of hydrothermal treatment after precipitation formation; a method of firing after precipitation formation; and a combination of these methods A method will be described.
(1) Formation of precipitate First, an aqueous solution containing at least one compound selected from the group consisting of a titanium compound and an iron compound and a manganese compound is prepared as a metal source compound constituting the composite oxide of the present invention. To do.

  As an iron compound, a manganese compound, and a titanium compound, if it is a component which can form the mixed aqueous solution containing these compounds, it can be used without limitation. Usually, a water-soluble compound may be used. Specific examples of such water-soluble compounds include water-soluble salts such as chlorides, nitrates, sulfates, oxalates and acetates, hydroxides and the like. These water-soluble compounds may be either anhydrides or hydrates. Further, even a water-insoluble compound such as an oxide can be used as an aqueous solution after being dissolved using an acid such as hydrochloric acid. Each of these raw material compounds may be used alone or in combination of two or more for each metal source.

The manganese compound can be used without particular limitation as long as it is a water-soluble compound. In particular, in order to stably form a hexagonal network composite oxide, a divalent Mn source, such as manganese (II) chloride, etc. Is preferably used. When using a permanganate such as potassium permanganate (VII) as the Mn source, it is easy to produce a fine precipitate, but it is difficult to stably form a hexagonal network composite oxide. It is necessary to devise such as shifting the firing conditions to the high temperature side.

  The mixing ratio of the iron compound, manganese compound, and titanium compound in the aqueous solution may be set to the same element ratio as each element ratio in the target composite oxide.

  The concentration of each compound in the aqueous solution is not particularly limited, and may be determined as appropriate so that a uniform mixed aqueous solution can be formed and a coprecipitate can be smoothly formed. Usually, the total concentration of the iron compound, manganese compound and titanium compound may be about 0.01 to 5 mol / l, preferably about 0.1 to 2 mol / l.

  As a solvent for the mixed aqueous solution, water may be used alone, or a water-alcohol mixed solvent containing a water-soluble alcohol such as methanol or ethanol may be used. By using a water-alcohol mixed solvent, a precipitate can be formed at a temperature lower than 0 ° C. The amount of alcohol used may be appropriately determined according to the target precipitation temperature, but it is usually appropriate to use about 50 parts by weight or less with respect to 100 parts by weight of water.

  Next, a precipitate (coprecipitate) is generated from the mixed aqueous solution. In order to generate a precipitate, the mixed aqueous solution may be made alkaline. Conditions for forming a good precipitate vary depending on the type and concentration of each compound contained in the mixed aqueous solution, and thus cannot be defined unconditionally. However, it is usually preferable to set the pH to about 8 or more, and to about pH 11 or more. More preferred.

  The method for making the mixed aqueous solution alkaline is not particularly limited, and usually an alkali or an aqueous solution containing an alkali may be added to the mixed aqueous solution. Moreover, a coprecipitate can be formed also by the method of adding this mixed aqueous solution to the aqueous solution containing an alkali.

Examples of the alkali used to make the mixed aqueous solution alkaline include alkali metal hydroxides such as potassium hydroxide, sodium hydroxide, and lithium hydroxide, ammonia, and the like. When these alkalis are used as an aqueous solution, for example, 0.1
It can be used as an aqueous solution having a concentration of about ˜20 mol / l, preferably about 0.3 to 10 mol / l.

  Further, the alkali may be dissolved in a water-alcohol mixed solvent containing a water-soluble alcohol, similarly to the mixed aqueous solution of the metal compound described above.

  During precipitation, the temperature of the mixed aqueous solution is set to about -50 ° C to + 15 ° C, preferably about -40 ° C to + 10 ° C. The generation of spinel ferrite, which is an accompanying impurity phase, is suppressed, and a homogeneous coprecipitate is easily formed.

After making the mixed aqueous solution alkaline, the reaction solution is further blown with air at about 0 to 150 ° C. (preferably about 10 to 100 ° C.) for about 1 to 7 days (preferably about 2 to 4 days). In addition, it is preferable to oxidize and age the precipitate.

  The precipitate can be purified by washing the resulting precipitate with distilled water or the like to remove excess alkali components, residual raw materials, and the like, followed by filtration.

Subsequently, the target lithium manganese composite oxide can be obtained by a method of subjecting the obtained precipitate to hydrothermal treatment or a method of firing with a lithium compound. Less than,
These methods will be described.

(2) Hydrothermal treatment The hydrothermal treatment can be performed by heating the aqueous solution containing the precipitate formed in the step (1), the oxidizing agent, and the water-soluble lithium compound under alkaline conditions. Heating is usually performed in a sealed container.

  Hydrothermal treatment is a reaction at a relatively low temperature, and in the case of a composition with a small value of m + n and good stability of the hexagonal network structure, for example, when 0 <m + n ≦ 0.20, hydrothermal treatment is performed. It is possible to obtain a target complex oxide having a hexagonal network structure. In the case of a composition in which the value of m + n exceeds 0.20, the stability of the hexagonal network structure is inferior. Therefore, it is difficult to obtain a target complex oxide having a hexagonal network structure by simply performing hydrothermal treatment. It may be necessary to stabilize the crystals by performing the treatment at a high temperature.

  When the desired lithium manganese composite oxide is obtained by hydrothermal treatment, the primary particles that are formed are refined, so in addition to excellent charge / discharge cycle characteristics due to the hexagonal network structure, charge / discharge such as initial capacity Characteristics can be improved.

In the aqueous solution used for the hydrothermal reaction, the content of the precipitate containing iron, manganese and titanium is preferably about 1 to 100 g per liter of water in terms of dry product, more preferably about 10 to 80 g. .

  As the water-soluble lithium compound, for example, water-soluble lithium salts such as lithium chloride, lithium acetate and lithium nitrate, lithium hydroxide and the like can be used. These water-soluble lithium compounds can be used singly or in combination of two or more, and any of anhydrides and hydrates may be used.

The use amount of the water-soluble lithium compound is preferably about Li / (Fe + Mn + Ti) = 1 to 10 as a molar ratio of lithium element to the total number of moles of Fe, Mn and Ti in the precipitation product, More preferably, it is about 3-7.

The concentration of the water-soluble lithium compound is preferably about 0.1 to 10 mol / l, 1 to 8 mol / l
More preferably, it is about.

  The oxidizing agent can be used without particular limitation as long as it decomposes during the hydrothermal reaction to generate oxygen, and specific examples include potassium chlorate, lithium chlorate, sodium chlorate, hydrogen peroxide water, and the like. Can do.

The concentration of the oxidizing agent is preferably about 0.1 to 10 mol / l, and more preferably about 0.5 to 5 mol / l.

  About pH of the aqueous solution at the time of performing a hydrothermal reaction, it is usually preferable to set it as about pH8 or more, and it is more preferable to set it as about pH11 or more.

  When the aqueous solution containing the precipitate, the oxidizing agent and the aqueous lithium compound is under alkaline conditions, it may be heated as it is, but when the pH value is low, for example, an alkali metal such as potassium hydroxide or sodium hydroxide. The pH value may be increased by adding hydroxide, ammonia or the like.

Hydrothermal reaction can be performed using a normal hydrothermal reaction apparatus (for example, a commercially available autoclave).

  Hydrothermal reaction conditions are not particularly limited, but may be usually about 100 to 300 ° C. and about 0.1 to 150 hours, preferably about 150 to 250 ° C. and about 1 to 100 hours.

After completion of the hydrothermal reaction, the reaction product is usually washed in order to remove the remaining lithium compound and the like. For example, water, water-alcohol, acetone or the like can be used for washing. Next, the product is filtered and dried, for example, at a temperature of 80 ° C. or higher (usually about 100 ° C.) to obtain a lithium manganese composite oxide.

(3) Firing treatment In the firing treatment step, the precipitate obtained in the step (1) may be fired together with the lithium compound. At this time, by adjusting the addition amount of the lithium compound, the firing conditions, the firing atmosphere, etc., it is possible to control the powder characteristics such as the particle size, the Li content, the monoclinic layered rock salt type crystal phase content, etc. Thus, a lithium manganese based composite oxide can be obtained.

  The lithium compound can be used without particular limitation as long as it contains a lithium element. Specific examples include lithium salts such as lithium chloride, lithium nitrate, and lithium acetate, lithium hydroxide, and hydrates thereof. it can. If the usage-amount of a lithium compound shall be about 0.01-3 mol with respect to 1 mol of preparation mole numbers of the lithium manganese type complex oxide obtained by the hydrothermal method or the precipitate obtained in the previous process. Good.

  In general, in order to improve the reactivity, it is preferable to add a lithium compound to the lithium manganese composite oxide or precipitate obtained by the hydrothermal method, pulverize and mix, and then fire. As for the degree of pulverization, it is sufficient that coarse particles are not included and the mixture has a uniform color tone.

  The lithium compound can be used in the form of a powder, an aqueous solution, or the like, but is preferably used in the form of an aqueous solution in order to ensure the uniformity of the reaction. In this case, the concentration of the aqueous solution is usually about 0.1 to 10 mol / l.

The firing atmosphere is not particularly limited, and any atmosphere such as the air, an oxidizing atmosphere, an inert atmosphere, or a reducing atmosphere can be selected. The firing temperature is preferably about 200 to 1500 ° C, and more preferably about 300 to 1200 ° C. The firing time is preferably about 0.1 to 100 hours including the time to reach the firing temperature, and more preferably about 0.5 to 60 hours.

In the present invention, in order to obtain a lithium manganese composite oxide having a hexagonal network structure, it is important to appropriately select firing conditions. When the target composite oxide is an oxide having a large amount of Ti and / or Fe, for example, when m + n exceeds 0.2 in the composition formula,
Since the hexagonal network structure is inferior in stability, it may be changed to an inverted hexagonal network structure in the above baking process. Therefore, it is preferable to stabilize the crystal of such a complex oxide by performing a baking treatment at a high temperature of 500 ° C. or higher. Moreover, it is preferable to lengthen baking time.

  When the solid solution amount of Ti and / or Fe is relatively small, the hexagonal network structure, which is a stable structure, is likely to be obtained. Therefore, even when firing at a relatively low temperature within the above firing temperature range, the purpose and A composite oxide having a hexagonal network structure can be obtained. However, high temperature firing also has the effect of reducing the crystal phase content of the cubic rock salt structure, and therefore the firing conditions may be determined according to the charge / discharge characteristics to be emphasized.

  In the present invention, the desired hexagonal network lithium-manganese composite oxide can be obtained by appropriately selecting the firing conditions according to the composition of the target composite oxide based on the above criteria. .

  Further, the lithium manganese composite oxide obtained by hydrothermal treatment in the step (2) may be fired together with the lithium compound according to the above-described conditions. In this case, by performing hydrothermal treatment, primary particles can be made finer, and charge / discharge characteristics can be further improved.

  After completion of the firing, the fired product is usually subjected to a water washing treatment, a solvent washing treatment or the like in order to remove excess lithium compound. Thereafter, filtration is performed, and for example, heat drying may be performed at a temperature of 80 ° C. or higher, preferably about 100 to 400 ° C.

Furthermore, if necessary, the heat-dried product is pulverized, a lithium compound is added, calcined, washed, and dried, and a series of operations are repeated. Stable charge / discharge characteristics, high capacity, etc. in the operating voltage region as a positive electrode material for a lithium ion secondary battery can be further improved.

Lithium ion secondary battery A lithium ion secondary battery using the lithium manganese composite oxide according to the present invention can be produced by a known method. That is, the novel composite oxide according to the present invention is used as the positive electrode material, the known metal lithium, carbon-based material (activated carbon, graphite), etc. are used as the negative electrode material, and the known ethylene carbonate and dimethyl are used as the electrolyte. A lithium ion secondary battery can be assembled according to a conventional method using a solution in which a lithium salt such as lithium perchlorate or LiPF ₆ is dissolved in a solvent such as carbonate, and using other known battery components. That's fine.

  The lithium manganese composite oxide of the present invention is a material obtained by using inexpensive raw materials and elements, and has a unique cation distribution different from known oxides. The composite oxide can maintain an average discharge voltage of 3 V or more, and has a discharge capacity (250 mAh / g or more) and a discharge weight energy density (700 mWh / g or more) equivalent to or higher than that of a lithium cobalt oxide-based positive electrode material. In addition, it is a substance useful as a positive electrode material with little change in curve shape during charge / discharge cycles.

  The reason why the lithium manganese composite oxide of the present invention has such a large capacity is that, unlike the conventional positive electrode material, the discharge curve gradually decreases toward the end-of-discharge voltage. In addition, the capacity can be easily increased by reducing the discharge end voltage to about 2.0 V or about 1.5 V.

  In addition, the lithium manganese based composite oxide of the present invention has not only excellent initial discharge capacity but also excellent charge / discharge cycle characteristics, so that it can be used not only for a small consumer but also for a large-sized lithium ion secondary vehicle. It is extremely useful as a positive electrode material for batteries.

  The lithium manganese composite oxide according to the present invention has the above-described excellent performance, and is a highly useful material as a positive electrode material for a lithium ion secondary battery having a high capacity, a long life, and a low cost. .

EXAMPLES Hereinafter, examples and comparative examples will be shown to further clarify the features of the present invention, but the present invention is not limited to the following examples.

Example 1
Add 20.20 g of iron (III) nitrate nonahydrate and 39.58 g of manganese (II) chloride tetrahydrate (total amount 0.25 mol, Fe: Mn molar ratio = 2: 8) to 500 ml of distilled water and dissolve completely. It was. An aqueous lithium hydroxide solution (a solution in which 50 g of lithium hydroxide monohydrate was dissolved in 500 ml of distilled water) was prepared in another beaker. This lithium hydroxide aqueous solution was put into a titanium beaker, 150 ml of ethanol was added and stirred, and then allowed to stand in a thermostatic bath, and the thermostatic bath was kept at −10 ° C. Next, while stirring this lithium hydroxide aqueous solution, the above metal salt aqueous solution was gradually dropped over 2 to 3 hours to form an Fe-Mn precipitate. After confirming that the reaction solution was completely alkaline (pH 11 or more), air was blown into the reaction solution containing the coprecipitate with stirring at room temperature for 12 hours or more to ripen the precipitate.

  The resulting precipitate was washed with distilled water and filtered, and the precipitated product was placed in a polytetrafluoroethylene beaker together with 50 g of lithium hydroxide monohydrate, 50 g of potassium chlorate, 309 g of potassium hydroxide and 600 ml of distilled water. And stirred well. The pH of this aqueous solution was 11 or more. Thereafter, it was placed in a hydrothermal reactor (autoclave) and hydrothermally treated at 220 ° C. for 8 hours.

  After the hydrothermal treatment is completed, the reaction furnace is cooled to near room temperature, the beaker containing the hydrothermal treatment reaction solution is taken out of the autoclave, and the generated precipitate is washed with distilled water to remove excess lithium hydroxide and the like. Salts were removed and filtered to obtain a powdery product (lithium manganese composite oxide).

The powder obtained by filtration was mixed with lithium hydroxide aqueous solution in which 5.25 g of lithium hydroxide monohydrate was dissolved in 100 ml of distilled water, stirred, dried overnight at 100 ° C, and pulverized to produce powder did.

The resulting powder was then heated to 650 ° C. in an oxygen stream over 1 hour, fired at that temperature for 20 hours, cooled to near room temperature in a furnace, and fired to remove excess lithium salt. The product was washed with distilled water, filtered, and dried in the air at 300 ° C. for 10 hours to obtain the target lithium manganese composite oxide as a powder product.

The X-ray diffraction pattern of this final product is shown in FIG. From the results of Rietveld analysis (the program uses RIETAN-2000), all peaks are unit cells of monoclinic layered rock salt type Li ₂ MnO ₃ described in the above references.

を有する結晶相（a=4.9420(12)Å, b=8.5643(14)Å、c=5.0265(7)Å。β=109.249(19)°
）のみで指数付けできた。

(A = 4.9420 (12) Å, b = 8.5643 (14) Å, c = 5.0265 (7) Å. Β = 109.249 (19) °
) Was able to index.

The obtained transition metal occupancy (g _4g ) at the 4g position was 62.5 (5)%, whereas the transition metal occupancy (g _2b ) at the 2b position was 54.1 (9)%, The defined hexagon mesh regularity S was +8.4 (9)%, a positive value. From this result, the lithium manganese composite oxide obtained in Example 1 is
It turns out that it has what is called a hexagonal network structure.

According to chemical analysis (Table 1 below), Fe contained 20 mol% (m value) close to the charged amount (20 mol%), and x value calculated from Li / (Mn + Fe) value is 0.26. Thus, in Example 1, it was confirmed that a lithium manganese composite oxide (Li _1.26 (Fe _0.20 Mn _0.80 ) _0.74 O ₂ ) having the target composition was obtained.

  The following 1 also shows the chemical analysis results of the samples obtained in Examples 2 to 6 and Comparative Examples 1 to 3 described later.

Comparative Example 1
Precipitation was carried out in the same manner as in Example 1 except that 30.30 g of iron (III) nitrate nonahydrate and 34.63 g of manganese (II) chloride tetrahydrate (total amount 0.25 mol, Fe: Mn molar ratio = 3: 7) were used. Preparation, hydrothermal treatment, washing treatment and the like were performed to obtain a powdery product (lithium manganese composite oxide).

The powder obtained by filtration was mixed with lithium hydroxide aqueous solution in which 5.25 g of lithium hydroxide monohydrate was dissolved in 100 ml of distilled water, stirred, dried overnight at 100 ° C, and pulverized to produce powder did. Next, the obtained powder was heated to 750 ° C. in the air over 1 hour, fired at that temperature for 1 minute, then cooled to near room temperature in the furnace, and the fired product was removed to remove excess lithium salt. Was washed with distilled water, filtered, and dried in the atmosphere at 300 ° C. for 10 hours to obtain the target lithium manganese composite oxide as a powdery product.

The X-ray diffraction pattern of this final product is shown in FIG. From the results of Rietveld analysis (the program uses RIETAN-2000), all peaks are monoclinic layered rock salt-type Li ₂ MnO ₃ unit cells described in the above reference

を有する結晶相（a=4.9738(9)Å, b=8.5840(13)Å、c=5.0341(7)Å。β=109.174(15)°）と立方晶岩塩型のα-LiFeO₂の単位胞

Unit cell of α-LiFeO ₂ with crystal phase (a = 4.9738 (9) Å, b = 8.5840 (13) Å, c = 5.0341 (7) Å. Β = 109.174 (15) °) and cubic rock salt type

を有する結晶相（a=4.084(4)Å）指数付けできた。両相の存在比は、単斜晶相94%、立方
晶相6%の割合であった。

The crystal phase with a (a = 4.084 (4) 指数) could be indexed. The abundance ratio of both phases was 94% monoclinic phase and 6% cubic phase.

The transition metal occupancy (g _4g ) at the 4g position in the obtained monoclinic phase is 60.1 (8)%, whereas 2b
The transition metal occupancy (g _2b ) at the position is 75.3 (12)%, and the hexagonal network regularity S defined by the difference is -15.2 (12)%, which is a negative value. It can be seen that the lithium manganese composite oxide obtained in 1 has an inverted hexagonal network structure different from those of Example 1 and composite oxides obtained in Example 2 and Example 3 described later. In the composite oxide of Comparative Example 1, it is considered that the hexagonal network structure was not formed because of the high Fe content and the relatively low temperature and short firing time.

According to chemical analysis (Table 1 above), Fe contained 30 mol% (m value) close to the charged amount (30 mol%), and x value calculated from Li / (Mn + Fe) value is 0.25. Thus, in Comparative Example 1, it was confirmed that a lithium manganese composite oxide (Li _1.25 (Fe _0.30 Mn _0.70 ) _0.75 O ₂ ) having the target composition was obtained.

Charge / Discharge Test 5 mg of each composite oxide obtained in Example 1 and Comparative Example 1 above was dry mixed with 5 mg of acetylene black and 0.5 mg of PTFE powder as the positive electrode material, and Li metal as the negative electrode material. A coin-type lithium battery was prepared using a 1M solution in which LiPF ₆ as a supporting salt was dissolved in a mixed solvent of dimethyl carbonate and dimethyl carbonate as an electrolyte. Charging / discharging characteristics of this lithium battery at 30 ° C (potential range 1.5-5.5V (charge capacity regulation 500mAh / g, 1st cycle), 1.5-4.8V (after 2nd cycle), current density 40mA / g), We examined at the start of charging.

FIG. 5 shows the discharge characteristics of the lithium batteries using the positive electrode materials of Example 1 (solid line in the figure) and Comparative Example 1 (dashed line in the figure) at the initial stage and after 20 cycles. Also, in Table 2 below,
The initial discharge data obtained in the above test and the discharge capacity after 20 cycles are shown. Table 2 also shows the measurement results of the charge / discharge characteristics of the samples obtained in Examples 2 to 6 and Comparative Examples 1 to 3 described later.

  From FIG. 5 and Table 2, the positive electrode material obtained in Example 1 is superior to the sample of Comparative Example 1 in terms of the initial and 20th cycle discharge capacity, initial charge / discharge efficiency, average discharge voltage, and discharge energy density. You can see that From these results, the sample of Example 1 containing a hexagonal network monoclinic layered rock salt type crystal phase was superior in charge / discharge characteristics to the sample of Comparative Example 1 having an inverted hexagonal network structure. It is clear that there is.

Example 2
Precipitation was performed in the same manner as in Example 1 except that 10.10 g of iron (III) nitrate nonahydrate and 44.53 g of manganese (II) chloride tetrahydrate (total amount 0.25 mol, Fe: Mn molar ratio = 1: 9) were used. Preparation and precipitation aging were performed.

  The resulting precipitate was washed with distilled water and filtered, and the precipitated product was placed in a polytetrafluoroethylene beaker together with 50 g of lithium hydroxide monohydrate, 50 g of potassium chlorate, 309 g of potassium hydroxide and 600 ml of distilled water. And stirred well. The pH of this aqueous solution was 11 or more. Thereafter, it was placed in a hydrothermal reactor (autoclave) and hydrothermally treated at 220 ° C. for 48 hours.

  After the hydrothermal treatment is completed, the reaction furnace is cooled to near room temperature, the beaker containing the hydrothermal treatment reaction solution is taken out of the autoclave, and the generated precipitate is washed with distilled water to remove excess lithium hydroxide and the like. Salts were removed and filtered to obtain a powdery product (lithium manganese composite oxide).

The powder obtained by filtration was mixed with lithium hydroxide aqueous solution in which 5.25 g of lithium hydroxide monohydrate was dissolved in 100 ml of distilled water, stirred, dried overnight at 100 ° C, and pulverized to produce powder did.

The resulting powder was then heated to 550 ° C. in an oxygen stream for 1 hour, fired at that temperature for 20 hours, cooled to near room temperature in a furnace, and fired to remove excess lithium salt. The product was washed with distilled water, filtered, and dried in the air at 300 ° C. for 10 hours to obtain the target lithium manganese composite oxide as a powder product.

The X-ray diffraction pattern of this final product is shown in FIG. From the results of Rietveld analysis (the program uses RIETAN-2000), all peaks are unit cells of monoclinic layered rock salt type Li ₂ MnO ₃ described in the above references.

を有する結晶相（a=4.9384(13)Å, b=8.5484(15)Å、c=5.0167(7)Å。β=109.17(2)°）
のみで指数付けできた。

(A = 4.9384 (13) Å, b = 8.5484 (15) Å, c = 5.0167 (7) Å. Β = 109.17 (2) °)
Could index only.

The obtained transition metal occupancy (g _4g ) at the 4g position is 72.0 (7)%, whereas the transition metal occupancy (g _2b ) at the 2b position is 42.5 (11)%, The defined hexagon mesh regularity S was +29.5 (11)%, a positive value. From this result, it can be seen that the lithium manganese composite oxide obtained in Example 2 has a hexagonal network structure.

Chemical analysis (Table 1 above) shows that Fe is included in 9.3 mol% (m value) close to the charged amount (10 mol%), and the x value calculated from the Li / (Mn + Fe) value is 0.29. it from the example 2, it was confirmed that the lithium-manganese-based composite oxide of the target composition _{(Li 1.29 (Fe 0. 093 Mn} 0.907) 0.71 O 2) was obtained.

Charge / discharge test 5 mg of each composite oxide obtained in Example 2 and Comparative Example 1 above was dry mixed with 5 mg of acetylene black and 0.5 mg of PTFE powder as the positive electrode material, and Li metal as the negative electrode material. A coin-type lithium battery was prepared using a 1M solution in which LiPF ₆ as a supporting salt was dissolved in a mixed solvent of dimethyl carbonate and dimethyl carbonate as an electrolyte. Charging / discharging characteristics of this lithium battery at 30 ° C (potential range 1.5-5.5V (charge capacity regulation 500mAh / g, 1st cycle), 1.5-4.8V (after 2nd cycle), current density 40mA / g), We examined at the start of charging.

The graph of FIG. 7 shows the discharge characteristics after initial and 20 cycles for the lithium batteries using the positive electrode materials of Example 2 (solid line in the figure) and Comparative Example 1 (dashed line in the figure). Table 2 shows the initial discharge data obtained in the above test and the discharge capacity after 20 cycles.

From FIG. 7 and Table 2, the positive electrode material obtained in Example 2 is superior to the sample of Comparative Example 1 in terms of the initial and 20th cycle discharge capacity, initial charge / discharge efficiency, average discharge voltage, and discharge energy density. I understand that. From these results, the sample of Example 2 containing a hexagonal network monoclinic layered rock salt type crystal phase is superior in charge / discharge characteristics to the sample of Comparative Example 1 having an inverted hexagonal network structure. It is clear that there is.

Example 3
In the same manner as in Example 2, the metal salt was weighed, the mixed aqueous solution was prepared, the precipitate was prepared, and the precipitate was aged.

  The resulting precipitate was washed with distilled water and filtered, and the precipitated product was placed in a polytetrafluoroethylene beaker together with 50 g of lithium hydroxide monohydrate, 50 g of potassium chlorate, 309 g of potassium hydroxide and 600 ml of distilled water. And stirred well. The pH of this aqueous solution was 11 or more. Thereafter, it was placed in a hydrothermal reactor (autoclave) and hydrothermally treated at 220 ° C. for 8 hours.

After the hydrothermal treatment is completed, the reaction furnace is cooled to near room temperature, the beaker containing the hydrothermal treatment reaction solution is taken out of the autoclave, and the generated precipitate is washed with distilled water to remove excess lithium hydroxide and the like. Salts were removed and filtered to obtain a powdery product (lithium manganese composite oxide).

The powder obtained by filtration was mixed with lithium hydroxide aqueous solution in which 5.25 g of lithium hydroxide monohydrate was dissolved in 100 ml of distilled water, stirred, dried overnight at 100 ° C, and pulverized to produce powder did.

The resulting powder was then heated to 1050 ° C. in an oxygen stream for 1 hour, fired at that temperature for 1 minute, cooled to near room temperature in the furnace, and fired to remove excess lithium salt. The product was washed with distilled water, filtered, and dried in the air at 300 ° C. for 10 hours to obtain the target lithium manganese composite oxide as a powder product.

The X-ray diffraction pattern of this final product is shown in FIG. From the results of Rietveld analysis (the program uses RIETAN-2000), all peaks are unit cells of monoclinic layered rock salt type Li ₂ MnO ₃ described in the above references.

を有する結晶相（a=4.9341(3)Å, b=8.5407(4)Å、c=5.0249(2)Å。β=109.290(3)°）のみで指数付けできた。

It was possible to index only with a crystal phase having (a = 4.9341 (3) Å, b = 8.5407 (4) Å, c = 5.0249 (2) Å, β = 109.290 (3) °).

The obtained transition metal occupancy (g _4g ) at the 4g position is 77.7 (4)%, whereas the transition metal occupancy (g _2b ) at the 2b position is 35.7 (5)%, The defined hexagonal mesh regularity S was +42.0 (5)%, a positive value. From this result, it can be seen that the lithium manganese composite oxide obtained in Example 3 has a hexagonal network structure.

According to chemical analysis (Table 1 above), Fe is contained in an amount of 10 mol% (m value) close to the charged amount (10 mol%), and the x value calculated from the Li / (Mn + Fe) value is 0.31. From this, it was confirmed that in Example 2, a lithium manganese composite oxide (Li _1.31 (Fe _{0. 10} Mn _0.90 ) _0.69 O ₂ ) having the target composition was obtained.

Charge / Discharge Test 5 mg of each composite oxide obtained in Example 3 and Comparative Example 1 above was dry mixed with 5 mg of acetylene black and 0.5 mg of PTFE powder as the positive electrode material, and Li metal as the negative electrode material. A coin-type lithium battery was prepared using a 1M solution in which LiPF ₆ as a supporting salt was dissolved in a mixed solvent of dimethyl carbonate and dimethyl carbonate as an electrolyte. Charging / discharging characteristics of this lithium battery at 30 ° C (potential range 1.5-5.5V (charge capacity regulation 500mAh / g, 1st cycle), 1.5-4.8V (after 2nd cycle), current density 40mA / g), We examined at the start of charging.

The graph of FIG. 9 shows the discharge characteristics at the initial stage and after 20 cycles for the lithium batteries using the positive electrode materials of Example 3 (solid line in the figure) and Comparative Example 1 (dashed line in the figure). Table 2 shows the initial discharge data obtained in the above test and the discharge capacity after 20 cycles.

From FIG. 9 and Table 2, the positive electrode material obtained in Example 2 is slightly inferior to the sample of Comparative Example 1 in terms of initial characteristics (initial discharge capacity, initial charge / discharge efficiency, discharge average voltage, discharge energy density). However, from the discharge curve after 20 cycles, it can be seen that the discharge capacity is almost the same as the initial discharge capacity, and that the voltage drop with the progress of the cycle is suppressed to be significantly lower than that of the sample of Comparative Example 1. From these results, the sample of Example 3 containing a monoclinic layered rock salt type crystal phase having a hexagonal network structure has better charge / discharge cycle characteristics than the sample of Comparative Example 1 having an inverted hexagonal network structure. It is clear that

Example 4
Using 20.00 g of 30% titanium sulfate (IV) aqueous solution and 44.53 g of manganese (II) chloride tetrahydrate (total amount 0.25 mol, Ti: Mn molar ratio = 1: 9), 500 ml of distilled water was added and dissolved, An aqueous salt solution was prepared. An aqueous lithium hydroxide solution (a solution in which 100 g of lithium hydroxide monohydrate was dissolved in 1000 ml of distilled water) was prepared in another beaker. This lithium hydroxide aqueous solution was put into a titanium beaker, 300 ml of ethanol was added and stirred, and then left in a constant temperature bath to keep the constant temperature chamber at -10 ° C. Next, the metal salt aqueous solution was gradually dropped into the lithium hydroxide aqueous solution over 2 to 3 hours to form a Ti-Mn precipitate. After confirming that the reaction solution was completely alkaline (pH 11 or more), air was blown into the reaction solution containing the coprecipitate with stirring at room temperature for 12 hours or more to ripen the precipitate.

  The resulting precipitate was washed with distilled water and filtered, and the precipitated product was placed in a polytetrafluoroethylene beaker together with 50 g of lithium hydroxide monohydrate, 50 g of potassium chlorate, 309 g of potassium hydroxide and 600 ml of distilled water. And stirred well. The pH of this aqueous solution was 11 or more. Thereafter, it was placed in a hydrothermal reactor (autoclave) and hydrothermally treated at 220 ° C. for 48 hours.

After the hydrothermal treatment is completed, the reaction furnace is cooled to near room temperature, the beaker containing the hydrothermal treatment reaction solution is taken out of the autoclave, and the generated precipitate is washed with distilled water to remove excess lithium hydroxide and the like. Salts were removed, filtered, and dried in air at 200 ° C. for 10 hours to obtain the target lithium manganese composite oxide as a powder product.

The X-ray diffraction pattern of this final product is shown in FIG. From the results of Rietveld analysis (the program uses RIETAN-2000), all peaks are unit cells of monoclinic layered rock salt type Li ₂ MnO ₃ described in the above references.

を有する結晶相（a=4.9415(11)Å, b=8.5489(14)Å、c=5.0294(6)Å。β=109.219(16)°
）のみで指数付けできた。

(A = 4.9415 (11) Å, b = 8.5489 (14) Å, c = 5.0294 (6) Å. Β = 109.219 (16) °
) Was able to index.

The obtained transition metal occupancy (g _4g ) at the 4g position is 74.4 (4)%, whereas the transition metal occupancy (g _2b ) at the 2b position is 39.9 (8)%, The defined hexagonal mesh regularity S was +34.5 (8)%, a positive value. From this result, it can be seen that the lithium manganese composite oxide obtained in Example 4 has a hexagonal network structure.

According to chemical analysis (Table 1 above), Ti is 10 mol% (n value) close to the charged amount (10 mol%), x value calculated from Li / (Mn + Ti) value is 0.29 From this, it was confirmed that in Example 4, a lithium manganese composite oxide (Li _1.29 (Ti _{0. 10} Mn _0.90 ) _0.71 O ₂ ) having the target composition was obtained.

Comparative Example 2
Precipitation preparation and precipitation as in Example 4 except that 80.00 g of 30% titanium sulfate (IV) aqueous solution and 23.70 g of potassium permanganate (VII) (total amount 0.25 mol, Ti: Mn molar ratio = 4: 6) were used. Aging treatment was performed.

The resulting precipitate was washed with distilled water and filtered, and the precipitated product was placed in a polytetrafluoroethylene beaker together with 50 g of lithium hydroxide monohydrate, 50 g of potassium chlorate, 309 g of potassium hydroxide and 600 ml of distilled water. And stirred well. The pH of this aqueous solution was 11 or more. Thereafter, it was placed in a hydrothermal reactor (autoclave) and hydrothermally treated at 220 ° C. for 8 hours.

  After the hydrothermal treatment is completed, the reaction furnace is cooled to near room temperature, the beaker containing the hydrothermal treatment reaction solution is taken out of the autoclave, and the generated precipitate is washed with distilled water to remove excess lithium hydroxide and the like. Salts were removed and filtered to obtain a powdery product (lithium manganese composite oxide).

The powder obtained by filtration was mixed with lithium hydroxide aqueous solution in which 5.25 g of lithium hydroxide monohydrate was dissolved in 100 ml of distilled water, stirred, dried overnight at 100 ° C, and pulverized to produce powder did.

Next, the obtained powder was heated to 750 ° C. in the air over 1 hour, fired at that temperature for 1 minute, then cooled to near room temperature in the furnace, and the fired product was removed to remove excess lithium salt. Was washed with distilled water, filtered, and dried in the atmosphere at 300 ° C. for 10 hours to obtain the target lithium manganese composite oxide as a powdery product.

The X-ray diffraction pattern of this final product is shown in FIG. From the results of Rietveld analysis (the program uses RIETAN-2000), all peaks are unit cells of monoclinic layered rock salt type Li ₂ MnO ₃ described in the above references.

を有する結晶相（a=4.9775(18)Å, b=8.621(3)Å、c=5.0436(12)Å。β=109.15(3)°）と立方晶岩塩型のLi₂TiO₃の単位胞

Unit cell of Li ₂ TiO ₃ with cubic phase (a = 4.9775 (18) Å, b = 8.621 (3) Å, c = 5.0436 (12) Å, β = 109.15 (3) °)

を有する結晶相（a=4.0912(5)Åの二相共存状態として指数付けできた。両相の存在比は
単斜晶相が64%、立方晶相が36%であった。

It was indexed as a two-phase coexistence state of a crystal phase (a = 4.0912 (5) Å). The abundance ratio of both phases was 64% for the monoclinic phase and 36% for the cubic phase.

The obtained transition metal occupancy (g _4g ) at the 4g position is 63.7 (12)%, whereas the transition metal occupancy (g _2b ) at the 2b position is 63.1 (18)%, The defined hexagonal mesh regularity S is +0.8 (18)%, and it is not a positive value but zero when the error range is included. From this result, it can be seen that the lithium manganese composite oxide obtained in Comparative Example 2 has a random structure disclosed in Patent Document 6.

According to chemical analysis (Table 1 above), Ti contained 42 mol% (n value) close to the charged amount (40 mol%), and x value calculated from Li / (Mn + Fe) value is 0.31. Thus, it was confirmed that in Comparative Example 2, a lithium manganese composite oxide (Li _1.31 (Ti _0.42 Mn _0.58 ) _0.69 O ₂ ) having the target composition was obtained.

Charge / discharge test 5 mg of each composite oxide obtained in Example 4 and Comparative Example 2 above, 5 mg of acetylene black and 0.5 mg of PTFE powder were dry-mixed as a positive electrode material, and Li metal was used as a negative electrode material. A coin-type lithium battery was prepared using a 1M solution in which LiPF ₆ as a supporting salt was dissolved in a mixed solvent of dimethyl carbonate and dimethyl carbonate as an electrolyte. Charging / discharging characteristics of this lithium battery at 30 ° C (potential range 1.5-5.5V (charge capacity regulation 500mAh / g, 1st cycle), 1.5-4.8V (after 2nd cycle), current density 40mA / g), We examined at the start of charging.

  The graph of FIG. 12 shows the discharge characteristics at the initial stage and after 20 cycles for the lithium batteries using the positive electrode materials of Example 4 (solid line in the figure) and Comparative Example 2 (dashed line in the figure). Table 2 shows the initial discharge data obtained in the above test and the discharge capacity after 20 cycles.

From FIG. 12 and Table 2, the positive electrode material obtained in Example 4 is only slightly lower in discharge average voltage than the sample of Comparative Example 2, but the initial and 20-cycle discharge capacity, initial charge / discharge efficiency, discharge energy. It can be seen that the density is excellent. Especially initial discharge energy density is 1000mWh / g
More than is obtained. From these results, the sample of Example 4 containing a monoclinic layered rock salt type crystal phase of hexagonal network structure is superior in charge / discharge characteristics than the sample of Comparative Example 2 having a random structure. Is clear.

Example 5
Precipitation was produced in the same manner as in Example 4 except that 100.00 g of 30% titanium sulfate (IV) aqueous solution and 24.74 g of manganese chloride (II) tetrahydrate (total amount: 0.25 mol, Ti: Mn molar ratio = 5: 5) were used. And precipitation aging was performed.

The obtained precipitate was washed with distilled water and filtered, and this precipitated product was put into 300 ml of distilled water in which 20.98 g of 0.50 mol of lithium hydroxide monohydrate was dissolved without hydrothermal treatment. Stir. After stirring, it was dried overnight at 100 ° C. and pulverized to produce a powder. Next, the obtained powder was heated to 950 ° C. in the air over 1 hour, fired at that temperature for 1 minute, then cooled to near room temperature in the furnace, and the calcined product was removed to remove excess lithium salt. After being pulverized, it was washed with distilled water, filtered, and dried in the atmosphere at 300 ° C. for 10 hours to obtain the target lithium manganese composite oxide as a powder product.

The X-ray diffraction pattern of this final product is shown in FIG. From the results of Rietveld analysis (the program uses RIETAN-2000), all peaks are unit cells of monoclinic layered rock salt type Li ₂ MnO ₃ described in the above references.

を有する結晶相（a=4.9927(10)Å, b=8.6454(12)Å、c=5.0542(6)Å。β=109.345(13)°
）のみで指数付けできた。

(A = 4.9927 (10) Å, b = 8.6454 (12) Å, c = 5.0542 (6) Å. Β = 109.345 (13) °
) Was able to index.

The obtained transition metal occupancy (g _4g ) at the 4g position is 69.8 (8)%, whereas the transition metal occupancy (g _2b ) at the 2b position is 50.2 (10)%, The defined hexagon mesh regularity S is +19.6 (10)%, which is a positive value. From this result, it can be seen that the lithium manganese composite oxide obtained in Example 5 has a hexagonal network structure.

According to chemical analysis (Table 1 above), Ti is included at 50 mol% (n value) close to the charged amount (50 mol%), and the x value calculated from the Li / (Mn + Ti) value is 0.31. since, in example 5, it was confirmed that the lithium-manganese-based composite oxide of the target composition _{(Li 1.31 (Ti 0. 50 Mn} 0.50) 0.69 O 2) was obtained.

Charge / discharge test 5 mg of each composite oxide obtained in Example 5 and Comparative Example 2 above, 5 mg of acetylene black and 0.5 mg of PTFE powder were dry-mixed as a positive electrode material, and Li metal was used as a negative electrode material. A coin-type lithium battery was prepared using a 1M solution in which LiPF ₆ as a supporting salt was dissolved in a mixed solvent of dimethyl carbonate and dimethyl carbonate as an electrolyte. The charge / discharge characteristics of this lithium battery at 30 ° C (potential range 1.5-5.5V (however, charge capacity regulation 500mAh / g, 1st cycle), 1.5-4.
8V (2nd cycle and later), current density 40mA / g), the start of charging was studied.

  FIG. 14 is a graph showing the discharge characteristics at the initial stage and after 20 cycles for the lithium batteries using the positive electrode materials of Example 5 (solid line in the figure) and Comparative Example 2 (dashed line in the figure). Table 2 shows the initial discharge data obtained in the above test and the discharge capacity after 20 cycles.

From FIG. 14 and Table 2, the positive electrode material obtained in Example 5 was only slightly lower in discharge average voltage than the sample of Comparative Example 2, but the initial and 20-cycle discharge capacity, initial charge / discharge efficiency, discharge energy. It can be seen that the density is excellent. In particular, from the discharge curve after 20 cycles, the effect of suppressing the voltage drop due to cycle deterioration is remarkable. From these results, the sample of Example 5 containing a monoclinic layered rock salt type crystal phase of hexagonal network structure has better charge / discharge characteristics than the sample of Comparative Example 2 having a random structure. Is clear.

Example 6
Iron (III) nitrate nonahydrate 5.05g and 30% titanium sulfate aqueous solution 10.00g, manganese (II) chloride tetrahydrate 44.53g (total amount 0.25mol, Fe: Ti: Mn molar ratio = 1: 1: 18) Precipitation preparation and precipitation ripening were performed in the same manner as in Example 1 except that was used.

  Thereafter, the hydrothermal treatment of the precipitate (220 ° C., 48 hours), firing after adding LiOH (550 ° C. in the air), post-treatment, and drying were performed in the same way as in Example 2 to obtain the target lithium manganese composite oxide. Obtained.

The X-ray diffraction pattern of this final product is shown in FIG. From the results of Rietveld analysis (the program uses RIETAN-2000), all peaks are unit cells of monoclinic layered rock salt type Li ₂ MnO ₃ described in the above references.

を有する結晶相（a=4.9419(9)Å, b=8.5517(11)Å、c=5.0261(6)Å。β=109.257(12)°）のみで指数付けできた。

It was possible to index only with a crystal phase having (a = 4.9419 (9) Å, b = 8.5517 (11) Å, c = 5.0261 (6) Å, β = 109.257 (12) °).

The resulting transition metal occupancy (g _4g ) at the 4g position is 78.7 (4)%, whereas the transition metal occupancy (g _2b ) at the 2b position is 32.5 (6)%, The defined hexagonal mesh regularity S was +46.2 (6)%, a positive value. From this result, it can be seen that the lithium manganese composite oxide obtained in Example 6 has a hexagonal network structure.

According to chemical analysis (Table 1 above), Fe and Ti are close to the charged amount (5 mol%), respectively 5.2 and 5.1.
In Example 6, since the x value calculated from the Li / (Mn + Fe + Ti) value is 0.32, the lithium manganese-based composite oxidation of the target composition is included. It was confirmed that the product (Li _1.32 (Fe _0.052 Ti _0.051 Mn _0.897 ) _0.68 O ₂ ) was obtained.

Comparative Example 3
Iron (III) nitrate nonahydrate 20.20g, 30% titanium sulfate aqueous solution 40.00g, manganese (II) chloride tetrahydrate 29.69g (total amount 0.25mol, Fe: Ti: Mn molar ratio = 2: 2: 6) Precipitation preparation and precipitation ripening were performed in the same manner as in Example 1 except that was used.

Thereafter, the precipitate was hydrothermally treated (220 ° C., 8 hours) in the same manner as in Example 1. The product was washed with distilled water, filtered, and 100 ml of distilled water in which 5.25 g of lithium hydroxide monohydrate was dissolved. Placed in and stirred well. After stirring, it was dried overnight at 100 ° C. and pulverized to produce a powder. Next, the obtained powder was heated to 650 ° C. in the air over 1 hour, fired at that temperature for 1 minute, then cooled to near room temperature in the furnace, and the fired product was removed to remove excess lithium salt. After being pulverized, it was washed with distilled water, filtered, and dried in the atmosphere at 300 ° C. for 10 hours to obtain the target lithium manganese composite oxide as a powder product.

The X-ray diffraction pattern of this final product is shown in FIG. From the results of Rietveld analysis (the program uses RIETAN-2000), all peaks are unit cells of monoclinic layered rock salt type Li ₂ MnO ₃ described in the above references.

を有する結晶相（a=4.972(2)Å, b=8.620(3)Å、c=5.0413(15)Å。β=109.10(4)°）と立方晶岩塩型のLi₂TiO₃の単位胞

Unit cell of Li ₂ TiO ₃ with cubic phase (a = 4.972 (2) Å, b = 8.620 (3) Å, c = 5.0413 (15) Å, β = 109.10 (4) °)

を有する結晶相（a=4.0916(5)Åの二相共存状態として指数付けできた。両相の存在比は
単斜晶相が60%、立方晶相が40%であった。

It was indexed as a two-phase coexistence state of a crystal phase with a = 4.0916 (5) Å. The abundance ratio of both phases was 60% for the monoclinic phase and 40% for the cubic phase.

The obtained transition metal occupancy (g _4g ) at the 4g position was 69.1 (15)%, whereas the transition metal occupancy (g _2b ) at the 2b position was 83.3 (19)%, The defined hexagon mesh regularity S was -14.2 (19)%, which was a negative value. From this result, it can be seen that the lithium manganese composite oxide obtained in Comparative Example 3 has an inverted hexagonal network structure.

According to chemical analysis (Table 1 above), Fe and Ti are 21 and 21 mol% (m and n values) close to the charged amount (20 mol%), respectively, and Li / (Mn + Fe + Ti) values Since the calculated x value was 0.25, in Comparative Example 3, it was confirmed that a lithium manganese-based composite oxide (Li _1.25 (Fe _0.21 Ti _0.21 Mn _0.58 ) _0.75 O ₂ ) having the target composition was obtained. .

Charging / discharging test 5 mg of each composite oxide obtained in Example 6 and Comparative Example 3 above, 5 mg of acetylene black and 0.5 mg of PTFE powder were dry-mixed as a positive electrode material, and Li metal was used as a negative electrode material. A coin-type lithium battery was prepared using a 1M solution in which LiPF ₆ as a supporting salt was dissolved in a mixed solvent of dimethyl carbonate and dimethyl carbonate as an electrolyte. Charging / discharging characteristics of this lithium battery at 30 ° C (potential range 1.5-5.5V (charge capacity regulation 500mAh / g, 1st cycle), 1.5-4.8V (after 2nd cycle), current density 40mA / g), We examined at the start of charging.

  The graph of FIG. 17 shows the discharge characteristics at the initial stage and after 20 cycles for the lithium batteries using the positive electrode materials of Example 6 (solid line in the figure) and Comparative Example 3 (dashed line in the figure). Table 2 shows the initial discharge data obtained in the above test and the discharge capacity after 20 cycles.

From FIG. 17 and Table 2, the positive electrode material obtained in Example 6 is superior to the sample of Comparative Example 3 in terms of discharge average voltage, initial and 20-cycle discharge capacity, initial charge and discharge efficiency, and discharge energy density. I understand that. From these results, the sample of Example 6 containing the hexagonal network monoclinic layered rock salt type crystal phase has better charge / discharge characteristics than the sample of Comparative Example 3 having an inverted hexagonal network structure. It is clear.

As is clear from the results of the above Examples and Comparative Examples, the lithium manganese composite oxide containing the monoclinic layered rock salt type crystal phase having the hexagonal network structure of the present invention exhibits excellent discharge characteristics at room temperature. As a positive electrode material for large-sized lithium ion secondary batteries not only for small-sized consumers but also for vehicles, it has been revealed that it has excellent performance.

FIG. 2 is a drawing schematically showing a monoclinic layered rock salt type crystal phase among the crystal phases constituting the lithium manganese composite oxide of the present invention, and a transition composed of a Li layer and Mn, Fe and / or Ti. 2 shows a stacked state of an M-Li layer containing a metal M. FIG. FIG. 2 is a drawing schematically showing a monoclinic layered rock salt type crystal phase among the crystal phases constituting the lithium manganese composite oxide of the present invention, and a transition metal M composed of Mn and Fe and / or Ti. It shows the cation arrangement in the included M-Li layer. 1 is a drawing showing an X-ray diffraction pattern obtained in Example 1. The + symbol is the measured value, and the solid line is the calculated curve. The residual is shown on the same scale below the pattern. Each diffraction peak position of the monoclinic phase constituting the calculation curve is shown in the form of a vertical bar immediately below the pattern. 6 is a drawing showing an X-ray diffraction pattern obtained in Comparative Example 1. The + symbol is the measured value, and the solid line is the calculated curve. The residual is shown on the same scale below the pattern. Each phase constituting the calculation curve (the upper part corresponds to the monoclinic phase and the lower part corresponds to the cubic phase) is shown directly below the pattern in the form of vertical bars. It is a graph which shows the discharge characteristic after the initial stage and 30 cycles at 30 degreeC of the coin-type lithium battery which each used the sample obtained in Example 1 and Comparative Example 1 as a positive electrode material. 2 is a drawing showing an X-ray diffraction pattern obtained in Example 2. The + symbol is the measured value, and the solid line is the calculated curve. The residual is shown on the same scale below the pattern. Each diffraction peak position of the monoclinic phase constituting the calculation curve is shown in the form of a vertical bar immediately below the pattern. It is a graph which shows the discharge characteristic after the initial stage and 30 cycles at 30 degreeC of the coin-type lithium battery which used the sample obtained in Example 2 and Comparative Example 1 as a positive electrode material, respectively. 2 is a drawing showing an X-ray diffraction pattern obtained in Example 3. The + symbol is the measured value, and the solid line is the calculated curve. The residual is shown on the same scale below the pattern. Each diffraction peak position of the monoclinic phase constituting the calculation curve is shown in the form of a vertical bar immediately below the pattern. It is a graph which shows the discharge characteristic after 30 cycles of the initial stage in 20 degreeC of the coin-type lithium battery which used the sample obtained in Example 3 and the comparative example 1 as a positive electrode material, respectively. 6 is a drawing showing an X-ray diffraction pattern obtained in Example 4. The + symbol is the measured value, and the solid line is the calculated curve. The residual is shown on the same scale below the pattern. Each diffraction peak position of the monoclinic phase constituting the calculation curve is shown in the form of a vertical bar immediately below the pattern. 6 is a drawing showing an X-ray diffraction pattern obtained in Comparative Example 2. The + symbol is the measured value, and the solid line is the calculated curve. The residual is shown on the same scale below the pattern. Each phase constituting the calculation curve (the upper part corresponds to the monoclinic phase and the lower part corresponds to the cubic phase) is shown directly below the pattern in the form of vertical bars. It is a graph which shows the discharge characteristic after 30 cycles of the initial stage in 20 degreeC of the coin-type lithium battery which used the sample obtained in Example 4 and Comparative Example 2 as a positive electrode material, respectively. 6 is a drawing showing an X-ray diffraction pattern obtained in Example 5. The + symbol is the measured value, and the solid line is the calculated curve. The residual is shown on the same scale below the pattern. Each diffraction peak position of the monoclinic phase constituting the calculation curve is shown in the form of a vertical bar immediately below the pattern. It is a graph which shows the discharge characteristic after 30 cycles of the initial stage in 30 degreeC of the coin-type lithium battery which used the sample obtained in Example 5 and the comparative example 2 as a positive electrode material, respectively. 6 is a drawing showing an X-ray diffraction pattern obtained in Example 6. The + symbol is the measured value, and the solid line is the calculated curve. The residual is shown on the same scale below the pattern. Each diffraction peak position of the monoclinic phase constituting the calculation curve is shown in the form of a vertical bar immediately below the pattern. 6 is a drawing showing an X-ray diffraction pattern obtained in Comparative Example 3. The + symbol is the measured value, and the solid line is the calculated curve. The residual is shown on the same scale below the pattern. Each phase constituting the calculation curve (the upper part corresponds to the monoclinic phase and the lower part corresponds to the cubic phase) is shown directly below the pattern in the form of vertical bars. It is a graph which shows the discharge characteristic after 30 cycles of the coin-type lithium battery which used the sample obtained in Example 6 and Comparative Example 3 as positive electrode materials, respectively, at 30 ° C.

Claims (8)

Composition formula: Li _{1 + x} (Mn _1-mn Fe _m Ti _n ) _1-x O ₂ (wherein the subscripts are as follows: 0 <x <1/3, 0 ≦ m ≦ 0.60, 0 ≦ n ≦ 0.80, 0 <m + n ≦ 0.80), and a lithium manganese based composite oxide containing a crystal phase having a monoclinic Li ₂ MnO ₃ type layered rock salt structure,
In the hexagonal network regular structure in the transition metal-containing layer of the crystal phase of the monoclinic Li ₂ MnO ₃ type layered rock salt structure, the transition metal occupancy at the hexagonal network lattice position is the transition metal occupancy at the hexagonal network center position. Lithium manganese complex oxide characterized by being larger. Crystalline single phase of monoclinic Li ₂ MnO ₃ type layered rock-salt structure, or monoclinic Li ₂ crystal phase of MnO ₃ type layered rock-salt structure and the cubic of crystalline phase mixed phase of the rock-salt type structure according Item 2. The lithium manganese composite oxide according to Item 1. 3. The lithium manganese based composite oxide according to claim 1, wherein in the composition formula: Li _{1 + x} (Mn _1-mn Fe _m Ti _n ) _1-x O ₂ , 0.05 ≦ m + n ≦ 0.80. At least one compound selected from the group consisting of a titanium compound and an iron compound and an aqueous solution containing a manganese compound are made alkaline to form a precipitate, and then the formed precipitate is fired in the presence of a lithium compound. The method for producing a lithium manganese composite oxide according to claim 1. At least one compound selected from the group consisting of a titanium compound and an iron compound and an aqueous solution containing a manganese compound are made alkaline to form a precipitate, and then the formed precipitate is combined with an oxidizing agent and a water-soluble lithium compound under alkaline conditions. The method for producing a lithium manganese composite oxide according to any one of claims 1 to 3, wherein hydrothermal treatment is performed. At least one compound selected from the group consisting of a titanium compound and an iron compound and an aqueous solution containing a manganese compound are made alkaline to form a precipitate, and then the formed precipitate is combined with an oxidizing agent and a water-soluble lithium compound under alkaline conditions. The method for producing a lithium manganese composite oxide according to any one of claims 1 to 3, wherein after the hydrothermal treatment, firing is performed in the presence of a lithium compound. Composition formula: Li _{1 + x} (Mn _1-mn Fe _m Ti _n ) _1-x O ₂ (wherein the subscripts are as follows: 0 <x <1/3, 0 ≦ m ≦ 0.60, 0 ≦ n ≦ 0.80, 0 <m + n ≦ 0.80), and a lithium manganese based composite oxide containing a crystal phase having a monoclinic Li ₂ MnO ₃ type layered rock salt structure,
In the hexagonal network regular structure in the transition metal-containing layer of the crystal phase of the monoclinic Li ₂ MnO ₃ type layered rock salt structure, the transition metal occupancy at the hexagonal network lattice position is the transition metal occupancy at the hexagonal network center position. A positive electrode material for a lithium ion secondary battery comprising a larger lithium manganese composite oxide. Composition formula: Li _{1 + x} (Mn _1-mn Fe _m Ti _n ) _1-x O ₂ (wherein the subscripts are as follows: 0 <x <1/3, 0 ≦ m ≦ 0.60, 0 ≦ n ≦ 0.80, 0 <m + n ≦ 0.80), and a lithium manganese based composite oxide containing a crystal phase having a monoclinic Li ₂ MnO ₃ type layered rock salt structure,
In the hexagonal network regular structure in the transition metal-containing layer of the crystal phase of the monoclinic Li ₂ MnO ₃ type layered rock salt structure, the transition metal occupancy at the hexagonal network lattice position is the transition metal occupancy at the hexagonal network center position. A lithium ion secondary battery comprising a lithium ion secondary battery positive electrode material made of a larger lithium manganese composite oxide as a constituent element.

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