JP5516926B2 - Monoclinic Lithium Manganese Composite Oxide with Regular Structure and Method for Producing the Same - Google Patents

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).

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 optimum chemical composition and manufacturing conditions of the positive electrode materials are required. 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

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. The material can have a discharge capacity equivalent to or higher than that, can be obtained by using an inexpensive raw material with less resource restrictions, and compared with a known low-cost positive electrode material. An object of the present invention is to provide a novel material that can exhibit better charge / discharge characteristics.

The present inventor has intensively studied to achieve the above-described object. As a result, in lithium manganese oxide (Li ₂ MnO ₃ ) or lithium manganese oxide in which Fe and / or Ti are dissolved in the lithium manganese oxide, transition metal ions composed of Mn, Fe and Ti are known. The present inventors have found that a novel composite oxide having a unique distribution state different from that of lithium manganese oxide has excellent performance capable of achieving the above-described object, and has completed the present invention.

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 (0 <x <1/3, 0 ≦ m ≦ 0.60, 0 ≦ n ≦ 0.60, 0 ≦ m + n
≦ 0.60), and a monolithic Li ₂ MnO ₃ type lamellar rock salt structure containing a crystalline phase comprising a lithium manganese based composite oxide,
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 center position is the transition metal occupancy at the hexagonal network configuration 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 , 0.20 ≦ m + n ≦ 0.60.
4). An aqueous solution containing a manganese compound and, if necessary, an aqueous solution containing a titanium compound and an iron compound is made alkaline to form a precipitate, and the obtained precipitate is hydrothermally treated with an oxidizing agent and a water-soluble lithium compound under alkaline conditions of pH 11 or higher. Then, the product after hydrothermal treatment is fired in the presence of a lithium compound, The method for producing a lithium manganese composite oxide according to Item 1 above.
5. Composition formula: Li _{1 + x} (Mn _1-mn Fe _m Ti _n ) _1-x O ₂ (0 <x <1/3, 0 ≦ m ≦ 0.60, 0 ≦ n ≦ 0.60, 0 ≦ m + n
≦ 0.60), a lithium manganese based composite oxide containing a monoclinic Li ₂ MnO ₃ type lamellar rock salt type crystal phase,
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 center position is the transition metal occupancy at the hexagonal network configuration position A positive electrode material for a lithium ion secondary battery comprising a larger lithium manganese composite oxide.
6). Composition formula: Li _{1 + x} (Mn _1-mn Fe _m Ti _n ) _1-x O ₂ (0 <x <1/3, 0 ≦ m ≦ 0.60, 0 ≦ n ≦ 0.60, 0 ≦ m + n
≦ 0.60), a lithium manganese based composite oxide containing a monoclinic Li ₂ MnO ₃ type lamellar rock salt type crystal phase,
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 center position is the transition metal occupancy at the hexagonal network configuration 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.

Lithium manganese composite oxide of the present invention, the composition _{formula: Li 1 + x (Mn 1} -mn Fe m Ti n) 1-x O 2 (0 <x <1/3, 0 ≦ m ≦ 0.60, 0 ≦ n ≦ 0.60, 0 ≦ m + n ≦ 0.60), which is based on a rock salt structure that is a general crystal structure of the oxide, and is a known substance, Li ₂ MnO ₃ (P. Strobel and B. Lanbert-Andron, Journal of Solid State Chemistry, 75, 90-98 (1988); hereinafter referred to as `` references '')

It contains a crystal phase of monoclinic Li ₂ MnO ₃ type layered rock salt structure with However, in the lithium manganese based composite oxide of the present invention, as will be described later, in the above monoclinic Li ₂ MnO ₃ type layered rock salt structure, transition metal ions composed of Mn, Fe and Ti are known substances ( It has a unique distribution state different from Li ₂ MnO ₃ ).

In addition, the crystal structure and cation distribution of the space group represented by LiCoO ₂ , LiNiO ₂ , LiNi _0.5 Mn _0.5 O ₂ etc.

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. In addition to the crystal phase, a mixed phase including a crystal phase having a cubic rock salt structure similar to α-LiFeO ₂ may be used.

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.

FIG. 1 and FIG. 2 are drawings schematically showing the crystal structure of the lithium manganese composite oxide of the present invention, taking Li ₂ MnO ₃ of the above-mentioned reference as an example, and FIG. 1 is characterized by a layered rock salt structure. FIG. 2 is a diagram showing a stacked state of a typical Li single layer and an Mn—Li layer, and FIG. 2 is a diagram showing an arrangement of Li and Mn in an Mn—Li layer obtained by rotating FIG. 1 by 90 °.

Hereinafter, composition formula: In the composite oxide of the present invention represented by _{Li 1 + x (Mn 1-} mn Fe m Ti n) 1-x O 2,
The cation distribution in the composite oxide of the present invention will be described by taking as an example the case of m = 0 and n = 0, that is, the case of containing only Mn as a transition metal.

First, in FIG. 1, two Li crystal layers having different crystallographic positions and Mn-Li layers are alternately stacked through oxide oxide single layers having two crystallographic positions. It can be seen that this is similar to the method of stacking the Li layer and the Co layer in the crystal structure of LiCoO ₂ having a typical hexagonal layered rock salt structure. LiCoO ₂ is different from the composite oxide of the present invention in that there is one kind of lattice point position in each layer.

  In FIG. 2, Mn 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.
Occupy 100% and there should be no Mn ions at the Li positions 2b, 4h, 2c. Actually, the Mn ions are not 100% at the 4g position. In the above reference, only 88% of the Mn occupies the 4g position, and the remaining 12% of the Mn ions are in the three Li positions (2b, 4h). , 2c position). 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). Those having a positive value (S> 0) are considered to be known substances like Li ₂ MnO ₃ .

On the other hand, space groups represented by LiCoO ₂ , LiNiO ₂ , LiNi _0.5 Mn _0.5 O ₂ etc.

In the hexagonal layered rock-salt structure having, since there is only one kind of lattice point position (either 3a position or 3b position), the degree of hexagonal network regular arrangement is 0% (S = 0).

On the other hand, the composite oxide of the present invention has a monoclinic Li ₂ MnO ₃ type layered rock salt structure crystalline phase, the 2b position in the hexagonal network regular structure in the transition metal-containing layer, that is, the hexagonal network center position. Transition metal (Mn, Fe, Ti) occupancy is larger than the transition metal occupancy at the 4g position, that is, at the hexagonal mesh configuration position, and the hexagonal network regularity (g _4g -g _2b ) is negative (S <0 ). The oxide having such a transition metal ion distribution is a novel compound that has not been reported so far. According to the composite oxide of the present invention, by having such a unique cation distribution, effects such as charge / discharge characteristics improvement, smoothing of the discharge curve, suppression of shape change during the cycle of the discharge curve, etc. are exhibited, It has excellent performance as a positive electrode material for a lithium ion battery.

Hereinafter, when the hexagonal mesh regular arrangement degree is 0 or 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), Describe.

The composite oxide of the present invention having a crystal phase of a monoclinic Li ₂ MnO ₃ type layered rock salt structure having the above reverse hexagonal network structure has, for example, the above specific composition formula using a hydrothermal method. It can be obtained by producing the oxide represented. In this case, in particular, in the above composition formula, Fe and Ti are considered to contribute to the stability of the transition metal ion distribution of the inverted hexagonal network structure. Therefore, in order to stably obtain a composite oxide having an inverted hexagonal network structure, the total amount of Fe ions and Ti ions is preferably about 0.2 ≦ m + n <0.6 in the composition formula.

Further, when the amount of Fe ions and Ti ions is small, for example, when the total amount of m + n is less than 0.2, it is difficult to form an inverted hexagonal network structure. In this case, it is preferable to use a permanganate such as potassium permanganate as the manganese compound that serves as the manganese source. Due to this, even if the precipitate formed is finer and the content of Fe ions and Ti ions is small, it has a crystal phase of a monoclinic Li ₂ MnO ₃ type layered rock salt structure with an inverted hexagonal network structure A complex oxide is easily formed.

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 desirably 60% or less of the amount of metal ions other than Li ions. When the amount of Fe ion solid solution is excessive, the abundance of the layered rock salt type crystal phase is remarkably lowered, which is not preferable in terms of battery characteristics. In the lithium manganese composite oxide of the present invention, the amount of Ti ions to be dissolved (n value: Ti / (Fe + Mn + Ti)) is preferably 60% or less of the amount of metal ions other than Li ions. Even when the amount of Ti ion solid solution is excessive, the abundance of the layered rock salt type crystal phase is remarkably reduced, which is not preferable in terms of battery characteristics. The total amount of Fe ions and Ti ions dissolved in the lithium manganese composite oxide of the present invention is in the range of about 0 ≦ m + n <0.6 in the composition formula.

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 0.05-0.30.

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

  Hereinafter, the manufacturing method using a hydrothermal reaction is shown as a manufacturing method of the complex oxide of this invention. By applying the hydrothermal method, which is a low-temperature synthesis method, the inverted hexagonal network structure is easily stabilized.

First, a mixed solution in which a metal compound that is a source of manganese ions and, if necessary, a metal compound that is a source of iron ions and titanium ions is dissolved in water, a water / alcohol mixture, or the like, is made alkaline to form a precipitate. Form. Subsequently, the target lithium manganese composite oxide can be obtained by adding an oxidizing agent and a water-soluble lithium compound thereto and performing hydrothermal treatment under alkaline conditions. Next, a lithium compound is added to the obtained lithium manganese composite oxide and fired. At this time, by adjusting the addition amount of the lithium compound and the firing conditions, the target lithium manganese-based composite oxide can be obtained by controlling the powder characteristics such as the particle size, the Li content, and the like. Hereinafter, this manufacturing method will be specifically described.

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 chloride, nitrate, sulfate, oxalate,
Examples thereof include water-soluble salts such as acetates and hydroxides. 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.

  In particular, as the manganese compound, it is preferable to use a permanganate such as potassium permanganate. Thereby, the complex oxide having the unique structure of the present invention is easily formed stably.

  The mixing ratio of the iron compound, manganese compound, and titanium compound in the mixed 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 mixed 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.

  In order to generate a precipitate (coprecipitate) from the mixed aqueous solution, 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, so that spinel ferrite is generated due to the generation of heat of neutralization during the reaction. Suppressed and homogeneous coprecipitate is likely to be 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.

  Next, the precipitate obtained by the above method is subjected to hydrothermal treatment under alkaline conditions together with an oxidizing agent and a water-soluble lithium compound. Hydrothermal treatment can be performed by heating an aqueous solution containing the precipitate, the oxidizing agent, and the water-soluble lithium compound under alkaline conditions. Heating is usually performed in a sealed container.

In the aqueous solution used for the hydrothermal reaction, the content of precipitates containing iron, manganese and titanium is water 1
It is preferable to set it as about 1-100g per liter, and it is more preferable to set it as about 10-80g.

  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 amount of the water-soluble lithium compound used 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.

  In the present invention, the Li content and powder characteristics can be controlled by firing the lithium manganese-based composite oxide obtained above together with a lithium compound.

  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. The usage-amount of a lithium compound should just be about 0.01-2 mol with respect to 1 mol of lithium manganese complex oxide obtained by the hydrothermal method.

  Usually, in order to improve the reactivity, it is preferable to add a lithium compound to the lithium manganese based composite oxide 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 1000 ° C, more preferably about 300 to 800 ° 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 addition, when the target composite oxide is an oxide with a small amount of Ti and / or Fe, for example, when m + n is less than 0.2 in the composition formula, the stability of the inverted hexagonal network structure is poor. For this reason, it may change to a hexagonal network structure in the above baking process. Therefore, it is preferable that such a complex oxide is not subjected to the above-described firing treatment or is subjected to a firing treatment at a temperature of about 500 ° C. or lower.

  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.

The lithium ion secondary battery using the lithium manganese composite oxide according to the present invention can be manufactured 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.

  Unlike the conventional positive electrode material, the lithium manganese composite oxide of the present invention has such a large capacity, and the discharge curve gradually decreases toward the end-of-discharge voltage (2.0 V or 1.5 V). This is because of the shape, and the capacity can be easily increased by lowering the discharge end voltage to about 2.0 V or about 1.5 V.

Further, the lithium manganese composite oxide of the present invention is 200 mAh / g or more at 30 ° C., 150 mAh / g at 0 ° C.
As described above, since it has a large discharge capacity of 100 mAh / g or more even at −20 ° C., it can exhibit excellent performance even in a low temperature environment. Furthermore, it has a discharge capacity of about 100 mAh / g or higher even at a high current density of 1275 mA / g (equivalent to 10 C), and is extremely useful as a positive electrode material for large-sized lithium ion secondary batteries not only for small-sized consumers but also for vehicles. is there.

  The lithium manganese composite oxide according to the present invention has the above-described excellent performance, and is extremely useful 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 40.40 g of iron (III) nitrate nonahydrate and 29.69 g of manganese (II) chloride tetrahydrate (total amount 0.25 mol, Fe: Mn molar ratio = 4: 6) 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, the metal salt aqueous solution was gradually dropped into the lithium hydroxide aqueous solution 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. 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 in order 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. Rietveld analysis results (program is
From RIETAN-2000, all peaks are monoclinic layered rock salt type Li ₂ MnO ₃ unit cells described in the above reference

It was possible to index only with a crystal phase having a (a = 4.9793 (9) Å, b = 8.6537 (12) Å, c = 5.0419 (6) Å, β = 109.252 (14) °).

The obtained transition metal occupancy (g _4g ) at the 4g position is 60.0 (6)%, whereas the transition metal occupancy (g _2b ) at the 2b position is 73.1 (9)%, The defined hexagonal mesh regularity S was -13.1 (9)%, which was a negative value. From this result, it can be seen that the lithium manganese composite oxide obtained in Example 1 has a so-called inverted hexagonal network structure.

According to chemical analysis (Table 1 below), Fe contained 40 mol% (m value) close to the charged amount (40 mol%), and x value calculated from Li / (Mn + Fe + Ti) value was 0.22 Therefore, in Example 1, it was confirmed that the lithium manganese composite oxide (Li _1.22 (Fe _0.40 Mn _0.60 ) _0.78 O ₂ ) having the target composition was obtained.

Example 2
Except for using 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), the same as in Example 1 Then, precipitation preparation, aging, hydrothermal treatment, and lithium hydroxide addition were performed. Next, the obtained powder was heated to 850 ° C. in the air over 1 hour and baked at that temperature for 1 minute. Then, in order to remove the excess lithium salt in the furnace, the fired product is washed with distilled water, filtered, dried in the atmosphere at 300 ° C. for 10 hours, and the target lithium manganese System complex oxide was obtained 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.

(A = 4.9493 (8) Å, b = 8.6124 (10) Å, c = 5.0283 (6) Å. Β = 109.111 (9) °)
Could index only. The resulting transition metal occupancy (g _4g ) at the 4g position is 60.4 (4)%, whereas the transition metal occupancy (g _2b ) at the 2b position is 74.1 (8)%, The defined hexagon mesh regularity S was -13.7 (8)%, which was a negative value. From this result, it can be seen that the lithium manganese composite oxide obtained in Example 2 also has an inverted hexagonal network structure.

According to chemical analysis (Table 1 below), Fe is 29 mol% (m value) close to the charged amount (30 mol%), and x value calculated from Li / (Mn + Fe) value is 0.26. Thus, in Example 2, it was confirmed that a lithium manganese composite oxide (Li _1.26 (Fe _0.29 Mn _0.71 ) _0.74 O ₂ ) having the target composition was obtained.

Comparative Example 1
Sample 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. Fabrication was performed, and the target lithium manganese composite oxide was obtained 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

(A = 4.9389 (13) Å, b = 8.5602 (17) Å, c = 5.0207 (8) Å. Β = 109.15 (2) °)
Could index only.

The obtained transition metal occupancy (g _4g ) at the 4g position is 64.5 (4)%, whereas the transition metal occupancy (g _2b ) at the 2b position is 60.6 (7)%, Since the defined hexagonal network regularity S is +3.9 (7)% and takes a positive value, the lithium manganese composite oxide obtained in Comparative Example 1 has a hexagonal network structure different from those in Examples 1 and 2. It can be seen that In the composite oxide of Comparative Example 1, it is considered that the reverse hexagonal network structure was not formed because Fe content was small and potassium chloride was used as the manganese source.

According to chemical analysis (Table 1 below), Fe contained 10 mol% (m value) close to the charged amount (10 mol%), and x value calculated from Li / (Mn + Fe) value was 0.29. Thus, in Comparative Example 1, it was confirmed that a lithium manganese composite oxide (Li _1.29 (Fe _0.10 Mn _0.90 ) _0.71 O ₂ ) having the target composition was obtained.

Charge / Discharge Test For each composite oxide 20 mg obtained in Example 1 and Comparative Example 1, acetylene black 5 mg
, PTFE powder 0.5 mg dry mixed as positive electrode material, Li metal as negative electrode material, 1M solution in which LiPF ₆ as supporting salt is dissolved in mixed solvent of ethylene carbonate and diethyl carbonate, and coin as electrolyte Type lithium battery was created. The charge / discharge characteristics of this lithium battery at 30 ° C (potential range 2.0-4.8V (first cycle), 2.0-4.6V (second cycle and later),
The current density was 42.5 mA / g).

FIG. 6 shows the charge / 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). In FIG. 6, the upward curve corresponds to the charge curve, and the downward curve corresponds to the discharge curve. FIG. 7 shows the charge / discharge cycle dependency of the discharge capacity of each battery. Table 2 below shows the initial charge / discharge data obtained in the above test and the discharge capacity after 20 cycles.

From FIG. 6 and Table 2, the positive electrode material obtained in Example 1 is superior in terms of discharge capacity, discharge average voltage, charge / discharge efficiency, and discharge energy density, although only the charge capacity is inferior to the sample of Comparative Example 1. Recognize. Further, it can be seen from FIG. 7 and Table 2 that the positive electrode of Example 1 has a larger discharge capacity after 8 cycles. From these results, the sample of Example 1 containing a monoclinic layered rock salt type crystal phase having an inverted hexagonal network structure has better charge / discharge characteristics than the sample of Comparative Example 1 having a hexagonal network structure. It is clear.

Further, 5 mg of each composite oxide obtained in Example 2 and Comparative Example 1 above was prepared by dry mixing acetylene black 5 mg and PTFE powder 0.5 mg as a positive electrode material, using Li metal as a negative electrode material, ethylene carbonate and diethyl 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 with carbonate as an electrolyte. The discharge rate characteristics of this lithium battery were examined at the start of charging at 30 ° C. The electric potential range is 2.0-4.6V, the current density during charging is fixed at 42.5mA / g (1 / 3C), and the current density during discharging is from 1 / 3C (42.5mA / g) to 5C (212.5mA / g) , 10C (425 mA / g), 30 C (1275 mA / g), and 60 C (2550 mA / g) in this order to obtain a discharge curve.

  The obtained discharge curve is shown in FIG. The solid line is Example 2, and the broken line is Comparative Example 1. The obtained discharge capacity is shown in Table 3.

From FIG. 8 and Table 3, it is clear that the positive electrode material obtained in Example 2 suppresses the voltage drop at the time of high current density discharge of 5 C or more and has a larger discharge capacity than that of Comparative Example 1. is there. From these results, the sample of Example 2 containing a monoclinic layered rock salt type crystal phase having an inverted hexagonal network structure is superior in discharge characteristics at a high current density than the sample of Comparative Example 1 having a hexagonal network structure. It is clear that

Example 3
Sample preparation was carried out in the same manner as in Example 1 except that 30.30 g of iron (III) nitrate nonahydrate and 27.66 g of potassium permanganate (total amount 0.25 mol, Fe: Mn molar ratio = 3: 7) were used. A lithium manganese composite oxide as a product was obtained 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.

And a crystalline phase (a = 4.961 (2) Å, b = 8.631 (3) Å, c = 5.0338 (17) Å, β = 109.24 (4) °) and α-LiFeO ₂

It was possible to index with a crystal phase (a = 4.0793 (4) Å) having a unit cell (cubic rock salt structure). The ratio of monoclinic layered rock salt type crystal phase and cubic rock salt type crystal phase was 61:39.

In the monoclinic layered rock salt type crystal phase, the obtained transition metal occupancy (g _4g ) at the 4g position is 68.4 (14)%, whereas the transition metal occupancy (g _2b ) at the 2b position is 87. Since the hexagonal network regularity S defined by the difference is -19 (2)%, which is a negative value, the lithium manganese composite oxide obtained in Example 3 is It can be seen that it has an inverted hexagonal network structure.

According to chemical analysis (Table 4 below), Fe contained 30 mol% (m value) close to the charged amount (30 mol%), and the x value calculated from the Li / (Mn + Fe) value was 0.23. Thus, it was confirmed in Example 3 that a lithium manganese composite oxide (Li _1.23 (Fe _0.30 Mn _0.70 ) _0.77 O ₂ ) having the target composition was obtained.

Comparative Example 2
Sample preparation was carried out in the same manner as in Example 1 except that 10.10 g of iron (III) nitrate nonahydrate and 35.56 g of potassium permanganate (total amount 0.25 mol, Fe: Mn molar ratio = 1: 9) were used. A lithium manganese composite oxide as a product was obtained 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.

(A = 4.9404 (13) Å, b = 8.5641 (15) Å, c = 5.0234 (8) Å, β = 109.22 (2) °)
Could index only. The obtained transition metal occupancy (g _4g ) at the 4g position was 66.6 (5)%, whereas the transition metal occupancy (g _2b ) at the 2b position was 54.1 (7)%, The defined hexagonal network regularity S is +12.5 (7)%, which is a positive value. Thus, it can be seen that the lithium manganese composite oxide obtained in Comparative Example 2 has a hexagonal network structure. By using potassium permanganate, the inverted hexagonal network structure can be easily stabilized, but it seems that the hexagonal network structure is obtained by high-temperature heat treatment.

According to chemical analysis (Table 4 below), 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 0.30. From this, it was confirmed that in Comparative Example 2, a lithium manganese composite oxide (Li _1.30 (Fe _0.10 Mn _0.90 ) _0.70 O ₂ ) having the target composition was obtained.

Charging / discharging test 5 mg of each composite oxide obtained in Example 3 and Comparative Example 2 above was obtained by dry mixing acetylene black 5 mg and PTFE powder 0.5 mg as a positive electrode material, and using Li metal 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 sodium carbonate and diethyl carbonate as an electrolyte. Charge and discharge characteristics of this lithium battery at 30 ° C (potential range 2.0-5.5V (capacity regulated charge of the first cycle, 500mAh / g), 2.0-4.8V (second cycle and later), current density 40mA / g) Considered at the beginning.

The charge / discharge characteristics of the lithium batteries using the positive electrode materials of Example 3 (solid line in the figure) and Comparative Example 2 (dashed line in the figure) are shown in the graph of FIG. In FIG. 11, the upward curve corresponds to the charging curve, and the downward curve corresponds to the discharge curve. FIG. 12 shows the charge / discharge cycle dependency of the discharge capacity of each battery. Table 5 below shows the initial charge / discharge data obtained in the above test and the discharge capacity after 20 cycles.

From FIG. 11 and Table 5, it can be seen that the positive electrode material obtained in Example 3 is superior to the sample of Comparative Example 2 in terms of discharge capacity, discharge average voltage, charge / discharge efficiency, and discharge energy density. Further, from FIG. 12 and Table 5, it can be seen that the discharge capacity of the positive electrode of Example 3 is larger up to 20 cycles. From these results, the sample of Example 3 containing a monoclinic layered rock salt type crystal phase having an inverted hexagonal network structure has better charge / discharge characteristics than the sample of Comparative Example 2 having a hexagonal network structure. It is clear.

FIG. 13 shows the charge / discharge curves of Example 3 and Comparative Example 2 at the 10th and 20th cycles, with the larger capacity corresponding to the 10th cycle and the smaller capacity corresponding to the 20th cycle. Corresponds to an upward curve and a discharge curve corresponds to a downward curve. It can be seen that the sample of Example 3 is less bent than the sample of Comparative Example 2 particularly in the region of 3 V or less during discharge, and the charge / discharge curve can be approximated by a linear line. This indicates that the capacity of each battery can be easily grasped from the battery voltage, which is required particularly in an assembled battery in which a plurality of batteries are connected, and is an important characteristic in practical use.

In order to clarify the above fact, a linear regression analysis of y = ax + b was performed on the charge / discharge curve in FIG. 13 to obtain the correlation coefficient r value, a, b value and its error. The results are shown in Table 6 below. From Table 6,
Since the sample of Example 3 has a correlation coefficient r closer to 1 and smaller errors in the a and b values, the linearity of the charge / discharge curve is better and the battery capacity can be easily confirmed from the battery voltage. Is clear.

Further, 5 mg of each composite oxide obtained in Example 3 and Comparative Example 2 above was dry mixed with 5 mg of acetylene black and 0.5 mg of PTFE powder as a positive electrode material, and Li metal was used as a negative electrode material. Ethylene carbonate and diethyl 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 with carbonate as an electrolyte. The discharge rate characteristics of this lithium battery were examined at the start of charging at 30 ° C. The electric potential range is 2.0-4.6V, the current density during charging is fixed at 42.5mA / g (1 / 3C), and the current density during discharging is from 1 / 3C (42.5mA / g) to 5C (212.5mA / g) , 10C (425 mA / g), 30 C (1275 mA / g), and 60 C (2550 mA / g) in this order to obtain a discharge curve. The obtained discharge curve is shown in FIG. The solid line is Example 3 and the broken line is Comparative Example 2. Table 7 shows the obtained discharge capacity.

  From FIG. 14 and Table 7, it is clear that the positive electrode material obtained in Example 3 suppresses the voltage drop at the time of high current density discharge of 5 C or more and has a larger discharge capacity than that of Comparative Example 2. is there. From these results, the sample of Example 3 containing a monoclinic layered rock salt type crystal phase having an inverted hexagonal network structure is superior in discharge characteristics at a high current density than the sample of Comparative Example 2 having a hexagonal network structure. It is clear that

Further, 5 mg of each composite oxide obtained in Example 3 and Comparative Example 2 above was dry mixed with 5 mg of acetylene black and 0.5 mg of PTFE powder as a positive electrode material, and Li metal was used as a negative electrode material. Ethylene carbonate and diethyl 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 with carbonate as an electrolyte. The low-temperature discharge characteristics of this lithium battery were examined at the start of charging at 30 ° C. The electric potential range is 2.0-4.6V, the current density during charging / discharging is fixed at 42.5mA / g (1 / 3C), and the environmental temperature during discharging is changed in the order of 30 ° C to 0 ° C and -20 ° C. A curve was acquired. The obtained discharge curve is shown in FIG. The solid line is Example 3 and the broken line is Comparative Example 2. Table 8 shows the obtained discharge capacity.

From FIG. 15 and Table 8, it is clear that the positive electrode material obtained in Example 3 has a lower voltage drop from 30 ° C. to −20 ° C. and a larger discharge capacity than that of Comparative Example 2. is there. From these results, the sample of Example 3 containing a monoclinic layered rock salt type crystal phase having an inverted hexagonal network structure is superior to the sample of Comparative Example 2 having a hexagonal network structure in low temperature discharge characteristics. It is clear.

  From the above results, the lithium manganese composite oxide containing Fe ions having an inverted hexagonal network structure has excellent charge / discharge initial characteristics and cycle characteristics at room temperature, linearity of charge / discharge curve shape, high current It is clear that the positive electrode material is excellent in density discharge characteristics and low temperature discharge characteristics.

Example 4
40.00 g of 30 wt% titanium sulfate aqueous solution and 39.58 g of manganese (II) chloride tetrahydrate (total amount 0.25 mol, Ti: Mn molar ratio = 2: 8) were added to 500 ml of distilled water and completely dissolved. 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, 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 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 650 ° C. in the air for 1 hour, fired at that temperature for 1 minute, then cooled to near room temperature in the furnace, and the calcined product was removed in order 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.

(A = 4.9517 (14) Å, b = 8.5668 (18) Å, c = 5.0294 (8) Å. Β = 109.17 (2) °)
Could index only.

The resulting transition metal occupancy (g _4g ) at the 4g position is 56.1 (4)%, whereas the transition metal occupancy (g _2b ) at the 2b position is 69.2 (6)%, The defined hexagonal network regularity S is −13.1 (6)%, which is a negative value. Thus, it can be understood that the lithium manganese composite oxide obtained in Example 4 has an inverted hexagonal network structure.

According to chemical analysis (Table 9 below), 20 mol% (n value) close to the charged amount (20 mol%) is included, and the x value calculated from the Li / (Mn + Ti) value is 0.32. From this, it was confirmed that in Example 4, a lithium manganese composite oxide (Li _1.32 (Ti _0.20 Mn _0.80 ) _0.68 O ₂ ) having the target composition was obtained.

Comparative Example 3
A sample was prepared in the same manner as in Example 4 except that 30.00 g of 30 wt% aqueous titanium sulfate solution and 44.53 g of manganese (II) chloride tetrahydrate (total amount: 0.25 mol, Ti: Mn molar ratio = 1: 9) were used. The target product, lithium manganese composite oxide, was obtained as a powdered 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.

(A = 4.9419 (10) Å, b = 8.5467 (13) Å, c = 5.0255 (6) Å. Β = 109.211 (14) °
) Was able to index.

The resulting transition metal occupancy (g _4g ) at the 4g position is 66.8 (4)%, whereas the transition metal occupancy (g _2b ) at the 2b position is 51.7 (6)%, The defined hexagonal network regularity S is +15.1 (6)%, which is a positive value, indicating that the lithium manganese composite oxide obtained in Comparative Example 3 has a hexagonal network structure. In the composite oxide of Comparative Example 3, it is considered that the reverse hexagonal network structure was not formed due to the low Ti content and the use of potassium chloride as the manganese source.

According to chemical analysis (Table 9 below), Ti is 10 mol% (n value) close to the charged amount (10 mol%), x value calculated from Li / (Mn + Ti) value is 0.33 Thus, in Comparative Example 3, it was confirmed that a lithium manganese composite oxide (Li _1.33 (Ti _0.10 Mn _0.90 ) _0.67 O ₂ ) having the target composition was obtained.

Charging / discharging test 5 mg of each composite oxide obtained in Example 4 and Comparative Example 3 above, dry mixture of 5 mg of acetylene black and 0.5 mg of PTFE powder was used 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 sodium carbonate and diethyl carbonate as an electrolyte. The charge / discharge characteristics of this lithium battery were examined at 30 ° C. (potential range 2.0-4.8 V (first cycle), 2.0-4.6 V (second cycle and later), current density 40.0 mA / g) at the start of charging.

  The charge / discharge characteristics of the lithium batteries using the positive electrode materials of Example 4 (solid line in the figure) and Comparative Example 3 (dashed line in the figure) are shown in the graph of FIG. In FIG. 18, the upward curve corresponds to the charging curve, and the downward curve corresponds to the discharge curve. FIG. 19 shows the charge / discharge cycle dependency of the discharge capacity of each battery. Table 10 below shows the initial charge / discharge data obtained in the above test and the discharge capacity after 20 cycles.

From FIG. 18 and Table 10, it can be seen that the positive electrode material obtained in Example 4 is superior in terms of discharge capacity and discharge energy density although charge / discharge efficiency and average discharge voltage are substantially the same. Further, FIG. 19 and Table 10 show that the positive electrode of Example 4 has a larger discharge capacity in each cycle. From these results, the sample of Example 4 containing a monoclinic layered rock salt type crystal phase having an inverted hexagonal network structure has better charge / discharge characteristics than the sample of Comparative Example 3 having a hexagonal network structure. It is clear.

  From the above results, it is clear that the lithium manganese-based composite oxide containing Ti ions having an inverted hexagonal network structure is a positive electrode material having excellent room temperature charge / discharge initial characteristics and cycle characteristics.

Example 5
Distillation of 40.00 g of 30 wt% titanium sulfate aqueous solution, 23.70 g of potassium permanganate and 20.20 g of iron (III) nitrate nonahydrate (total amount 0.25 mol, Fe: Ti: Mn molar ratio = 2: 2: 6) to 500 ml Added to water and completely dissolved. 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. Subsequently, the metal salt aqueous solution was gradually dropped into the lithium hydroxide aqueous solution over 2 to 3 hours to form a Fe-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 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 in order 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.

With crystal phase (a = 5.017 (5) Å, b = 8.526 (6) Å, c = 5.050 (4) Å, β = 109.64 (7) °) and cubic rock salt type α-LiFeO ₂ or Li ₂ TiO ₃ unit cell

It can be indexed as a two-phase mixture of crystalline phases having a (a = 4.0872 (2) Å). The relative proportions of both phases were 30% for the monoclinic phase and 70% for the cubic phase. The transition metal occupancy (g _4g ) at the 4g position in the obtained monoclinic layered rock salt structure is 92 (2)%, whereas the transition metal occupancy (g _2b ) at the 2b position is 100%. (If this value is a variable parameter, it will exceed 100% and will be physically meaningless, so it will be fixed to 100%.) The hexagonal mesh order degree S defined by the difference is -8 (2)%. Since it takes a negative value, it can be seen that the lithium manganese composite oxide obtained in Example 5 includes a crystal phase having an inverted hexagonal network structure.

According to chemical analysis (Table 11 below), Fe and Ti contained 21 mol% (m value) and 20 mol% (n value) close to the charged amount (20 mol%), respectively, Li / (Mn + Fe + Since the x value calculated from the (Ti) value is 0.26, in Example 5, the lithium manganese based composite oxide (Li _1.26 (Fe _0.21 Ti _0.20 Mn _0.59 ) _0.74 O ₂ ) having the target composition was obtained. Was confirmed.

Comparative Example 4
30wt% titanium sulfate aqueous solution 20.00g, manganese (II) chloride tetrahydrate 39.58g and iron (III) nitrate 9
Sample preparation was performed in the same manner as in Example 5 except that 10.10 g of hydrate (total amount: 0.25 mol, Fe: Ti: Mn molar ratio = 1: 1: 8) was used, and the target lithium manganese composite oxide Was obtained 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.

(A = 4.9526 (12) Å, b = 8.5846 (16) Å, c = 5.0300 (7) Å, β = 109.155 (17) °
) Was able to index. The obtained transition metal occupancy (g _4g ) at the 4g position is 63.3 (5)%, whereas the transition metal occupancy (g _2b ) at the 2b position is 64.0 (8)%, Since the defined hexagonal network regularity S is -0.7 (8)% and takes a value of almost zero, the lithium manganese composite oxide obtained in Comparative Example 4 has an existing hexagonal layered rock salt structure It turns out that it has the same ion distribution as a compound. In the composite oxide of Comparative Example 4, the Fe and Ti contents are less than 20 mol%, and it seems that no inverted hexagonal network structure was formed by using potassium chloride as the manganese source.

According to chemical analysis (Table 11 below), Fe and Ti are both contained 10 mol% (m value) and 8.5 mol% (n value) close to the charged amount (10 mol%), Li / (Mn + Since the x value calculated from the value of (Fe + Ti) is 0.31, in Comparative Example 4, a lithium manganese based composite oxide (Li _1.31 (Fe _0.10 Ti _0.085 Mn _0.815 ) _0.69 O ₂ ) of the target composition was obtained. I was able to confirm.

Charge / discharge test 20 mg of each composite oxide obtained in Example 5 and Comparative Example 4 above, dry mixture of 5 mg of acetylene black and 0.5 mg of PTFE powder was used 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 sodium carbonate and diethyl carbonate as an electrolyte. The charge / discharge characteristics of this lithium battery were studied at 30 ° C. (potential range 2.0-4.8 V (first cycle), 2.0-4.6 V (second cycle and later), current density 42.5 mA / g) at the start of charging.

  The charge / discharge characteristics of the lithium batteries using the positive electrode materials of Example 5 (solid line in the figure) and Comparative Example 4 (dashed line in the figure) are shown in the graph of FIG. In FIG. 22, the upward curve corresponds to the charging curve, and the downward curve corresponds to the discharge curve. FIG. 23 shows the charge / discharge cycle dependency of the discharge capacity of each battery. Table 12 below shows the initial charge / discharge data obtained in the above test and the discharge capacity after 20 cycles.

From FIG. 22 and Table 12, it can be seen that the positive electrode material obtained in Example 5 has substantially the same charge capacity and average discharge voltage, but is excellent in terms of discharge capacity, charge / discharge efficiency, and discharge energy density. Further, from FIG. 23 and Table 12, it can be seen that the positive electrode of Example 5 has a larger discharge capacity after the sixth cycle. From these results, the sample of Example 5 containing a monoclinic layered rock salt type crystal phase having an inverted hexagonal network structure has better charge / discharge characteristics than the sample of Comparative Example 4 having no such structure. Obviously.

Further, 5 mg of each composite oxide obtained in Example 5 above, 5 mg of acetylene black and 0.5 mg of PTFE powder were dry-mixed as a positive electrode material, using Li metal as a negative electrode material, mixing ethylene carbonate and diethyl carbonate A coin-type lithium battery was prepared using a 1M solution in which LiPF ₆ as a supporting salt was dissolved in a solvent as an electrolyte. The low-temperature discharge characteristics of this lithium battery were examined at the start of charging at 30 ° C. The electric potential range is 2.0-4.6V, the current density during charging / discharging is fixed at 42.5mA / g (1 / 3C), and the environmental temperature during discharging is changed in the order of 30 ° C to 0 ° C and -20 ° C. A curve was acquired. The obtained discharge curve is shown in FIG. Table 13 shows the discharge capacity obtained in Example 5.

From FIG. 24 and Table 13, the positive electrode material obtained in Example 3 has a capacity retention rate of 79% at 0 ° C. and 55% at −20 ° C., and the capacity decrease due to the temperature decrease is kept low. I understand that. From these results, it can be seen that the sample of Example 5 containing a monoclinic layered rock salt type crystal phase having an inverted hexagonal network structure has excellent low-temperature discharge characteristics.

  From the above results, the lithium-manganese composite oxide containing Fe and Ti ions having an inverted hexagonal network structure has not only excellent room temperature charge / discharge initial characteristics and cycle characteristics but also excellent low temperature discharge characteristics. It is clear that

Example 6
39.51 g (total amount 0.25 mol) of potassium permanganate was added to 800 ml of distilled water and completely dissolved. 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 an 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 and filtered to obtain a powdery product (lithium manganese composite oxide). The product was dried in the atmosphere 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.

(A = 4.9247 (11) Å, b = 8.5348 (13) Å, c = 5.0162 (6) Å. Β = 109.168 (18) °
) Was able to index.

The resulting transition metal occupancy (g _4g ) at the 4g position is 56.3 (4)%, whereas the transition metal occupancy (g _2b ) at the 2b position is 74.8 (6)%, The defined hexagonal network regularity S is -18.5 (6)%, which is a negative value. Thus, it can be understood that the lithium manganese composite oxide obtained in Example 6 has an inverted hexagonal network structure.

According to chemical analysis (Table 14 below), since the x value calculated from the Li / Mn value is 0.31, in Example 6, a lithium manganese composite oxide (Li _1.31 Mn _0.69 O ₂ ) having the target composition was obtained. I was able to confirm.

Comparative Example 5
Manganese (II) chloride tetrahydrate 49.48 g (total amount 0.25 mol) was added to 500 ml of distilled water and completely dissolved. 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, the metal salt aqueous solution was gradually dropped into the lithium hydroxide aqueous solution over 2 to 3 hours to form an 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 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, baked at that temperature for 20 hours, cooled to near room temperature in the furnace, and then baked 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.

It was possible to index only with a crystal phase having (a = 4.9239 (4) Å, b = 8.5287 (5) Å, c = 5.0160 (3) Å, β = 109.274 (3) °).

The resulting transition metal occupancy (g _4g ) at the 4g position was 83.3 (3)%, whereas the transition metal occupancy (g _2b ) at the 2b position was 26.0 (3)%, Since the defined hexagonal network regularity S is +57.3 (3)% and takes a positive value, the lithium manganese composite oxide obtained in Comparative Example 5 has a hexagonal network structure different from that in Example 6. I understand that.

As a result of chemical analysis (Table 14 below), the x value calculated from the Li / Mn value is 0.35. Therefore, in Comparative Example 5, a lithium manganese composite oxide (Li _1.35 Mn _0.65 O ₂ ) having the target composition was obtained. I was able to confirm.

Charge / discharge test 5 mg of each composite oxide obtained in Example 6 and Comparative Example 5 above, dry mixture of acetylene black 5 mg and PTFE powder 0.5 mg was used as a positive electrode material, Li metal was used as a negative electrode material, ethylene carbonate 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 sodium carbonate and diethyl carbonate as an electrolyte. The charge / discharge characteristics of this lithium battery were studied at 30 ° C. (potential range 2.0-5.5 (initial charge amount was 500 mAh / g capacity regulation), current density 40.0 mA / g) at the start of charge.

FIG. 27 is a graph showing charge / discharge characteristics of lithium batteries using the positive electrode materials of Example 6 (solid line in the figure) and Comparative Example 5 (dashed line in the figure). In FIG. 27, the upward curve corresponds to the charge curve, and the downward curve corresponds to the discharge curve. Table 15 below shows the initial charge / discharge data obtained in the above test.

From FIG. 27 and Table 15, the positive electrode material obtained in Example 6 is the same as that in Comparative Example 5 only in the discharge average voltage.
Although it is inferior to this sample, it is understood that the discharge capacity, charge / discharge efficiency, and discharge energy density are excellent. From these results, the sample of Example 6, which is a lithium manganese oxide containing a monoclinic layered rock salt type crystal phase having an inverted hexagonal network structure, has more charge / discharge characteristics than the sample of Comparative Example 5 having a hexagonal network structure. It is clear that it is excellent.

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 inverted hexagonal network structure of the present invention only exhibits excellent discharge characteristics at room temperature. In addition, since the charge / discharge curve has high linearity, it is easy to check the battery capacity.In addition, it has excellent discharge characteristics when discharged under large current densities and at temperatures as low as -20 ° C. As a positive electrode material for large-sized lithium ion secondary batteries not only for use 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 structure crystal phase of Li ₂ MnO ₃ as an example, among the crystal phases constituting the lithium manganese composite oxide of the present invention. The Li layer and the Mn-Li It shows the laminated state of the layers. FIG. ₂ is a drawing schematically showing a monoclinic layered rock-salt structure crystal phase as an example of Li ₂ MnO ₃ among the crystal phases constituting the lithium-manganese composite oxide of the present invention. It shows a cation array. 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 constituting the calculation curve is shown directly under the pattern in the form of a vertical bar. 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 constituting the calculation curve is shown directly under the pattern in the form of a vertical bar. 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 diffraction peak position constituting the calculation curve is shown directly under the pattern in the form of a vertical bar. It is a graph which shows the initial stage charging / discharging characteristic in 30 degreeC of the coin-type lithium battery which used the sample obtained in Example 1 and Comparative Example 1 as a positive electrode material, respectively. It is a graph which shows the cycle number dependence of the discharge capacity in 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. It is a graph which shows the current density dependence of the discharge curve in 30 degreeC of the coin-type lithium battery which each used the sample obtained in Example 2 and Comparative Example 1 as a positive electrode material. 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. The diffraction peak position of each phase (monoclinic phase and cubic phase) constituting the calculation curve is shown directly below the pattern in the form of a vertical bar. 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 diffraction peak position constituting the calculation curve is shown directly under the pattern in the form of a vertical bar. It is a graph which shows the initial stage charge / discharge characteristic in 30 degreeC of the coin-type lithium battery which used the sample obtained in Example 3 and Comparative Example 2 as a positive electrode material, respectively. It is a graph which shows the cycle number dependence of the discharge capacity in 30 degreeC of the coin-type lithium battery which each used the sample obtained in Example 3 and Comparative Example 2 as a positive electrode material. It is a graph which shows the charging / discharging characteristic of the 10th cycle and 30th cycle in 30 degreeC of the coin-type lithium battery which each used the sample obtained in Example 3 and Comparative Example 2 as a positive electrode material. It is a graph which shows the current density dependence of the discharge curve in 30 degreeC of the coin-type lithium battery which each used the sample obtained in Example 3 and Comparative Example 2 as a positive electrode material. It is a graph which shows the temperature dependence of the discharge curve of the coin-type lithium battery which used the sample obtained in Example 3 and Comparative Example 2 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 constituting the calculation curve is shown directly under the pattern in the form of a vertical bar. 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 diffraction peak position constituting the calculation curve is shown directly under the pattern in the form of a vertical bar. It is a graph which shows the initial stage charge / discharge characteristic in 30 degreeC of the coin-type lithium battery which used the sample obtained in Example 4 and Comparative Example 3 as a positive electrode material, respectively. It is a graph which shows the cycle number dependence of the discharge capacity in 30 degreeC of the coin-type lithium battery which each used the sample obtained in Example 4 and Comparative Example 3 as a positive electrode material. 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. The diffraction peak position of each phase (monoclinic phase and cubic phase) constituting the calculation curve is shown directly below the pattern in the form of a vertical bar. 5 is a drawing showing an X-ray diffraction pattern obtained in Comparative 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 constituting the calculation curve is shown directly under the pattern in the form of a vertical bar. It is a graph which shows the initial stage charge / discharge characteristic in 30 degreeC of the coin-type lithium battery which used the sample obtained in Example 5 and Comparative Example 4 as a positive electrode material, respectively. It is a graph which shows the cycle number dependence of the discharge capacity in 30 degreeC of the coin-type lithium battery which used the sample obtained in Example 5 and Comparative Example 4 as a positive electrode material, respectively. It is a graph which shows the temperature dependence of the discharge curve of the coin-type lithium battery which each used the sample obtained in Example 5 as a positive electrode material. 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 constituting the calculation curve is shown directly under the pattern in the form of a vertical bar. 6 is a drawing showing an X-ray diffraction pattern obtained in Comparative 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 constituting the calculation curve is shown directly under the pattern in the form of a vertical bar. It is a graph which shows the initial stage charge / discharge characteristic in 30 degreeC of the coin-type lithium battery which each used the sample obtained in Example 6 and Comparative Example 5 as a positive electrode material.

Claims (6)

Composition formula: Li _{1 + x} (Mn _1-mn Fe _m Ti _n ) _1-x O ₂ (0 <x <1/3, 0 ≦ m ≦ 0.60, 0 ≦ n ≦ 0.60, 0 ≦ m + n ≦ 0.60 And a monolithic Li ₂ MnO ₃ type layered rock salt type structure containing a crystalline phase comprising a lithium manganese-based composite oxide,
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 center position is the transition metal occupancy at the hexagonal network configuration 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 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 , 0.20 ≦ m + n ≦ 0.60. An aqueous solution containing a manganese compound and, if necessary, an aqueous solution containing a titanium compound and an iron compound is made alkaline to form a precipitate, and the obtained precipitate is hydrothermally treated with an oxidizing agent and a water-soluble lithium compound under alkaline conditions of pH 11 or higher. Then, the product after hydrothermal treatment is fired in the presence of a lithium compound, The method for producing a lithium manganese composite oxide according to claim 1.
Composition formula: Li _{1 + x} (Mn _1-mn Fe _m Ti _n ) _1-x O ₂ (0 <x <1/3, 0 ≦ m ≦ 0.60, 0 ≦ n ≦ 0.60, 0 ≦ m + n ≦ 0.60 And a monolithic Li ₂ MnO ₃ type layered rock salt type structure containing a crystalline phase comprising a lithium manganese-based composite oxide,
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 center position is the transition metal occupancy at the hexagonal network configuration 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 (0 <x <1/3, 0 ≦ m ≦ 0.60, 0 ≦ n ≦ 0.60, 0 ≦ m + n ≦ 0.60 And a monolithic Li ₂ MnO ₃ type layered rock salt type structure containing a crystalline phase comprising a lithium manganese-based composite oxide,
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 center position is the transition metal occupancy at the hexagonal network configuration 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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