JP2002068746A - Method of producing lithium manganate, lithium manganate, positive electrode for lithium ion secondary battery using the same as positive-electrode active substance, and lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode material for lithium ion secondary battery, particularly lithium manganate having spinel structure usable as the positive- electrode active substance, to provide a novel method capable of easily produc ing the lithium manganate at a low cost, to provide a positive electrode excel lent in charging/discharging capacities and charging/discharging cycle properties, and to provide a lithium ion secondary battery. SOLUTION: Lithium manganate is obtained by bringing a manganese halide, a lithium compound, at least one selected from the group consisting of a nickel compound, a cobalt compound, a manganese compound, a chromium compound, a magnesium compound, a chromium compound and an aluminum compound, and an oxidant into contact and reacting with each other in a liquid phase not more than 100 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing lithium manganate having a spinel structure suitable for an electrode material of a lithium ion secondary battery, lithium manganate obtained by the method, and a lithium ion secondary battery using the same. The present invention relates to a battery positive electrode and a lithium ion secondary battery.

[0002]

2. Description of the Related Art In recent years, with advances in electronic technology, miniaturization of electronic devices such as personal computers and mobile phones has been rapidly advancing. Accordingly, these power supplies also need to be miniaturized, and lithium secondary batteries have been actively developed recently. On the other hand, electric vehicles are attracting attention due to environmental problems, and some of them are being put to practical use. In order to further generalize this electric vehicle, a battery having a large capacity and excellent cycle characteristics is indispensable as a power source, and the use of a lithium ion secondary battery is being studied for such a large battery. .

As a positive electrode active material for a lithium battery, manganese dioxide has been put into practical use for a primary battery, and vanadium oxide and a lithium cobalt compound have been put into practical use for a secondary battery. In addition, lithium manganese oxides such as lithium manganate are being actively developed because the manganese compound as a raw material is less expensive and less toxic than the above-mentioned cobalt compound.

[0004] Among these lithium manganates, lithium manganate having a spinel structure has a three-dimensional structure. Therefore, when this is used as a positive electrode material of a lithium ion secondary battery and charged and discharged, the lithium manganate has a crystal structure. Without destruction,
It is possible to stably dope and dedope lithium ions in the crystal lattice. Also, since the discharge voltage is high and stable, it is very promising as a positive electrode active material for secondary batteries. It is being actively researched. However, the theoretical capacity is as small as 148 mAh / g, and the charge / discharge cycle characteristics are also low. Therefore, it has been an important issue how to synthesize a spinel-type lithium manganate having a low degree of impurities and a high degree of single phase in which lithium and manganese are uniformly dispersed.

As a characteristic required for lithium manganate having a spinel structure as a positive electrode active material for a lithium ion secondary battery, in the case of a liquid conductive electrolyte, it is preferable that the electrolyte has the largest possible electrode surface. Specifically, those having the characteristics of high specific surface area, low crystallinity (low density), high pore volume, and high manganese oxidation number are desirable.

On the other hand, in the case of a solid electrolyte, the pores are rather harmful because they do not penetrate into the pores. Therefore, in this case, as the characteristics required for the lithium manganate, those having the characteristics of high specific surface area, high density, low pore volume, and minimum particle size are desirable.

[0007] Conventionally, lithium manganate having a spinel structure includes lithium compounds such as lithium hydroxide, lithium nitrate, lithium oxide, lithium carbonate and lithium acetate, manganese oxide, manganese carbonate and γ-MnO 2.
Manufactured by using a manganese compound such as OH as a raw material, by a solid phase reaction, a solid phase sintering method, a melt impregnation method, a hydrothermal method, an electrodeposition method, and a chelate method.

However, in the solid-phase method and the solid-phase sintering method,
Since the reaction is performed at a high temperature, sintering occurs and the specific surface area decreases. Therefore, charging and discharging cannot be performed at a high current density. That is, since the solid-phase reaction is a batch reaction, the reaction is slow and the reaction is non-uniform, and the composition of the obtained lithium manganate compound is also non-uniform. Further, the obtained particles have a large particle size, which is unsuitable for an electrode material. In particular, the charge / discharge cycle characteristics are significantly deteriorated. Furthermore,
In the case of a solid-phase reaction, which is a diffusion reaction, if the reaction is to be carried out uniformly, it is necessary to make the particles of the raw material solid finer (submicron). In addition, lithium hydroxide was usually 100 microns or more, and it was difficult to obtain a uniform mixture, and a uniform reaction was not possible.

Further, in the synthesis by the hydrothermal method, the temperature of 100 ° C.
Since the reaction is performed at a high temperature of 300 ° C. and a high pressure of 300 atm, a reaction apparatus that can withstand this is required, and there has been a problem that energy costs and equipment costs are increased. Further, in the melt impregnation method, pulverization is necessary to obtain a porous manganese raw material, and when pulverized, impurities such as iron may be mixed, which is a problem in that a high-purity product is obtained.

[0010] Further, in order to synthesize more uniform lithium manganate, synthesis of lithium manganate having a spinel structure by a liquid phase reaction has been attempted. For example, in Japanese Patent Application Laid-Open No. Hei 2-183963, after a divalent manganese salt and a lithium salt are reacted in an aqueous alkaline solution to obtain a lithium-containing manganese hydroxide, the manganese hydroxide is oxidized and washed with water. And a method of producing a manganese oxide having a spinel structure by heat treatment at 800 to 900 ° C. However, in this method, the lithium component is reduced by washing with water after the oxidation treatment, the lithium content of the resulting product is reduced, and it is difficult to obtain lithium manganate having a desired Li / Mn molar ratio. In addition, although it is a liquid phase reaction, after a manganese hydroxide is generated by the liquid phase reaction, lithium manganate must be obtained by heat treatment.

As described above, in the prior art, lithium manganate having a spinel structure useful as a positive electrode active material for a lithium ion secondary battery cannot be obtained, and a low-cost and simple synthesis method has not been found. .

Further, when lithium manganate is used as a positive electrode active material for a lithium ion secondary battery, other lithium, nickel, magnesium or aluminum other metals such as nickel, magnesium or aluminum are used to improve the battery characteristics, especially the cycle characteristics of the battery. A metal-substituted one may be used. However, even in such a method for producing a metal-substituted lithium manganate, a useful method as a positive electrode active material for a lithium ion secondary battery cannot be obtained by a conventional method, and a low-cost and simple synthesis method has been found. Absent.

On the other hand, regarding a lithium ion secondary battery using lithium manganate, see, for example,
No. 9662 discloses a LiMn ₂ O having a spinel structure.
A non-aqueous secondary battery using lithium manganate represented by ₄ as a positive electrode active material, a lithium alloy as a negative electrode active material, and a non-aqueous electrolyte containing lithium ions is disclosed.
Japanese Patent Application Laid-Open No. 10-50316 discloses an organic electrolyte secondary battery including, as an anode active material, a cathode containing lithium and LiMn ₂ O ₄ synthesized from lithium carbonate and manganese dioxide.

The prior art of the lithium ion secondary battery using lithium manganate as a positive electrode active material is more effective than a battery using manganese dioxide, titanium, molybdenum or niobium chalcogenide which has been used as a positive electrode active material. The charge / discharge capacity and cycle characteristics have been improved.

However, in recent years, with the demand for higher voltage and higher energy of the secondary battery, a secondary battery having a larger charge / discharge capacity and excellent charge / discharge cycle characteristics has been developed. However, these prior arts have not satisfied these requirements, and further improvements have been desired.

[0016]

SUMMARY OF THE INVENTION The present invention relates to an electrode material for a lithium ion secondary battery, in particular, lithium manganate having a spinel structure with a small amount of impurities useful as a positive electrode active material and a high degree of single phase, And a novel production method which enables the lithium manganate to be produced easily at a low cost. Further, by using the lithium manganate, a charge / discharge capacity for a high voltage / high energy lithium ion secondary battery is provided. It is an object of the present invention to provide a positive electrode for a lithium ion secondary battery having excellent charge and discharge cycle characteristics and a lithium ion secondary battery.

[0017]

The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have found that manganese halide, lithium compound, nickel compound, cobalt compound, magnesium compound, chromium compound, At least one compound selected from aluminum compounds and an oxidizing agent at a high temperature such as a solid phase reaction or a hydrothermal method,
Without high pressure, by liquid phase reaction at normal temperature,
They have found that metal-substituted lithium manganate having a spinel structure can be obtained, and that this metal-substituted lithium manganate having a spinel structure is suitable for an electrode material for a lithium ion secondary battery, particularly, its positive electrode active material. And completed the present invention.

That is, the present invention provides a manganese halide,
Lithium compound, nickel compound, cobalt compound,
Provided is a method for producing lithium manganate having a spinel structure, characterized by contacting and reacting at least one compound selected from a magnesium compound, a chromium compound, and an aluminum compound with an oxidizing agent in a liquid phase at 100 ° C. or lower. .

The present invention also relates to a manganese halide and a lithium compound, at least one compound selected from a nickel compound, a cobalt compound, a magnesium compound, a chromium compound, and an aluminum compound, and an oxidizing agent.
Lithium manganate having a spinel structure obtained by contacting and reacting in a liquid phase of 00 ° C. or lower,
The lithium manganate formula _{Li x Me y Mn 1-y} O
_z (where, Me represents one or more of Ni, Co, Mg, Cr, and Al, x is a real number satisfying 0 <x ≦ 0.8, y is a real number satisfying 0 <y ≦ 0.5, and z is a real number satisfying 0 <y ≦ 0.5. 1.8 ≦ z ≦ 2.4.) And the average particle diameter is 1 to 50 μm.
m, and a specific surface area of 10 to 150 m ² / g.

Further, the present invention provides a positive electrode for a lithium ion secondary battery, wherein the above-mentioned lithium manganate is used as a positive electrode active material.

Further, the present invention provides a lithium ion secondary battery using a positive electrode comprising the above-mentioned lithium manganate as a positive electrode active material.

[0022]

DETAILED DESCRIPTION OF THE INVENTION The manganese halide used in the production of the lithium manganate of the present invention is specifically manganese (II) dichloride and manganese (III) trichloride,
Contains anhydride or hydrate. Of these, manganese (II) dichloride is preferred because it is stable. The purity is preferably higher to obtain higher purity lithium manganate. Specifically, the purity is 99% by weight or more, preferably 99.9% by weight or more. And other metal components such as Na are preferably 0.1% by weight or less.

When a halide is used as a manganese compound in the solid phase method or the solid phase sintering method, a halogen component remains in lithium manganate, and it is difficult to remove the halogen component.
The use of manganese halide as a raw material has heretofore been avoided since it has an undesirable effect on its characteristics when used as a battery material. However, in the present invention,
By using manganese halide as an aqueous solution and reacting it with a lithium compound in the liquid phase, only lithium manganate is produced as a solid, and unnecessary halides are not mixed, making it possible to produce high-purity lithium manganate. is there. Manganese halides such as manganese chloride are cheaper than conventionally used manganese compounds, and it has become possible to produce lithium manganate at lower cost. For this reason, manganese chloride is preferred as the manganese halide.

Next, the lithium compounds used in the present invention include, specifically, lithium hydroxide, lithium chloride, lithium iodide, lithium bromide, lithium nitrate, lithium nitrite, lithium sulfate, and lithium hydrogen sulfate. , Lithium carbonate, lithium bicarbonate, lithium acetate, lithium oxide, lithium peroxide, lithium chlorate, and other lithium salts. Of these, lithium hydroxide, lithium chloride and lithium nitrate are particularly preferably used.

Further, in the present invention, it is desirable to use lithium hydroxide and lithium chloride in combination as a raw material as a lithium source. In the method for producing lithium manganate in the present invention, as will be described later, the manganese halide and the lithium compound are brought into contact in a liquid phase and allowed to react with each other. It is preferably used as an alkali source as well as a raw material as a lithium source. Further, as another alkali source of lithium hydroxide, a hydroxide such as sodium hydroxide or potassium hydroxide can be used.

As for the lithium compound, similarly to the manganese halide, a higher lithium compound is preferable in order to obtain higher purity lithium manganate.
It is preferable that the purity is 99% by weight or more, preferably 99.9% by weight or more, and in particular, other metal components such as Fe, Ni, and Na are each 0.1% by weight or less as impurities.

The nickel compound, cobalt compound, magnesium compound, chromium compound or aluminum compound (hereinafter sometimes referred to as “substituted metal compound”) used in the present invention is preferably a water-soluble compound. Nickel, cobalt chloride, magnesium chloride, chromium chloride, aluminum chloride, nickel nitrate, cobalt nitrate, magnesium nitrate, chromium nitrate, aluminum nitrate and their hydrates (hydrated salts), nickel sulfate, cobalt sulfate, magnesium sulfate, chromium sulfate , Aluminum sulfate, nickel perchlorate, cobalt perchlorate, magnesium perchlorate, chromium perchlorate, aluminum perchlorate, nickel fluoride, cobalt fluoride, nickel bromide, cobalt bromide, magnesium bromide, odor Chromium bromide, aluminum bromide , Mention may be made of nickel iodide, cobalt iodide, magnesium iodide, chromium, aluminum iodide, nickel acetate, cobalt acetate, magnesium acetate, chromium acetate, diacetate aluminum hydroxide, chromium oxide and the like. Of these, chlorides or nitrates are preferred. Specifically, nickel chloride, cobalt chloride, magnesium chloride, chromium chloride, aluminum chloride, nickel nitrate, cobalt nitrate, magnesium nitrate, chromium nitrate, aluminum nitrate and hydration thereof (Hydrated salt), and magnesium chloride and its hydrate are particularly preferred.

In the production of the lithium manganate of the present invention, in addition to the above-mentioned manganese halide, lithium compound and substituted metal compound, manganese is oxidized to a desired valence, and the manganese is not fired at a high temperature. It is desirable to use an oxidizing agent because lithium oxide can be produced. Specific examples of the oxidizing agent include oxidizing agents such as hydrogen peroxide, potassium permanganate, and chloric acid. Among them, particularly, hydrogen peroxide is preferably used without any impurity element mixed into the product after the reaction. Can be

As described above, the present invention is characterized in that the above-mentioned components are used as raw materials to contact and react in a liquid phase at a temperature of 100 ° C. or lower. It means that manganese oxide, lithium compound, substituted metal compound, and oxidizing agent are brought into contact with each other in the state of an aqueous solution and allowed to react with each other. In addition, the reaction of the present invention is performed by preparing an aqueous solution of these compounds and performing the reaction in a liquid phase, but may include a water-soluble organic solvent such as alcohol. Thus, the present invention is a method for producing lithium manganate having a spinel structure by a so-called gel-sol method or a direct synthesis method.

The reaction temperature is 100 ° C. or lower, preferably 20 to 100 ° C., more preferably 50 to 95 ° C. The reaction temperature is arbitrarily set in order to influence the composition of lithium manganate to be obtained as a target. For example, when obtaining a lithium manganate having a Li / Mn atomic ratio of less than 0.5, the reaction temperature is preferably less than 70 ° C., preferably Is not less than 30 ° C. and less than 60 ° C., and in order to obtain lithium manganate having an Li / Mn atomic ratio of 0.5 or more, the reaction temperature is 60 to 100 ° C., preferably 80 ° C. to 95 ° C.
It is as follows.

At this time, an aqueous solution of a manganese halide, a lithium compound and a substituted metal compound is brought into contact at room temperature,
Thereafter, the reaction may be carried out by raising the temperature. However, in the case of continuous production, it is preferable that the reaction be carried out beforehand by heating to the reaction temperature in advance. The reaction time is usually 1 minute or more, preferably 1 minute to 15 minutes, after each raw material is brought into contact and a predetermined reaction temperature is reached.
Time.

The contact method and reaction method are not particularly limited, but the following methods can be employed. 1) A mixed aqueous solution of a lithium compound, a manganese halide and a substituted metal compound is prepared at room temperature, and then heated to react.

2) A mixed aqueous solution of a manganese halide and a substituted metal compound at a normal temperature is dropped and brought into contact with a lithium compound aqueous solution at a normal temperature, and then the temperature is raised to cause a reaction.

3) A mixed aqueous solution of a manganese halide and a substituted metal compound at room temperature is dropped and brought into contact with the preheated aqueous solution of a lithium compound, and then the temperature is raised to cause a reaction.

4) A premixed aqueous solution of a manganese halide and a substituted metal compound is dropped into a preheated aqueous solution of a lithium compound, brought into contact, and then reacted.

5) A mixed aqueous solution of a lithium compound and a substituted metal compound at room temperature is dropped into a manganese halide aqueous solution at room temperature, brought into contact with the mixture, and then heated to react.

6) A mixed aqueous solution of a manganese halide, a lithium compound and a substituted metal compound at room temperature is dropped into an aqueous solution of a lithium compound at room temperature, brought into contact, and then heated to react.

7) A mixed aqueous solution of manganese halide, lithium compound and substituted metal compound at room temperature is dropped into the preheated aqueous solution of lithium compound, brought into contact with the mixture, and then heated to react.

8) A mixed aqueous solution of a preheated manganese halide, a lithium compound and a substituted metal compound is dropped into the preheated aqueous lithium compound solution, brought into contact, and then heated to react.

An oxidizing agent such as hydrogen peroxide is added at any stage of the above-mentioned contact and reaction. For example, it is added to a mixed aqueous solution containing a manganese halide and a substituted metal compound before contacting with a lithium compound. Alternatively, it is added to the aqueous solution of the lithium compound before the contact, or after the contact of the aqueous solution of the lithium compound with the manganese halide and the substituted metal compound. Among them, it is preferable that the manganese valence is adjusted in advance by adding to a mixed aqueous solution containing a manganese halide and a substituted metal compound before contact with a lithium compound, which is a preferable method.

The amount ratio of each of the above-mentioned raw materials is arbitrary as long as lithium manganate having a desired composition ratio can be obtained, but preferably, the lithium compound is 0.3 to 0.7 mol, more preferably 0.4 to 0.4 mol per mol of manganese halide. 0.6 mole,
The substituted metal compound is 0.01 to 0.5 mol, more preferably 0.06 mol.
~ 0.2 mol, oxidizing agent such as hydrogen peroxide, 0.3 ~ 2 mol,
More preferably, it is 0.6 to 1.5 mol. When lithium hydroxide and lithium chloride are used in combination as the lithium compound, 1 to 10 mol, preferably 3 to 7 mol of lithium hydroxide, 0.3 to 0.7 mol of lithium chloride, and 1 to 10 mol of manganese halide, Preferably it is 0.4 to 0.6 mol.

Further, each of the above-mentioned raw materials is brought into contact with an aqueous solution, and the concentration of each aqueous solution at that time is not particularly limited. Preferably, the aqueous solution of manganese halide is 0.1 to 2 mol / l.
More preferably, 0.8 to 1.2 mol / l, the aqueous lithium compound solution is 0.05 to 1 mol / l, more preferably 0.4 to 0.6 mol / l, and the substituted metal compound is 0.01 to 0.6 mol / l, more preferably 0.04 to 0.25 mol / l. l. When lithium hydroxide and lithium chloride are used in combination as the lithium compound, the aqueous solution of lithium hydroxide is 1 to 5 mol / l, preferably 3 to 3.5 mol / l, and lithium chloride is 1 mol of manganese halide. 0.3 to 0.7 mol / l, preferably
0.4 to 0.6 mol / l.

Further, the pH of the liquid phase at the time of contacting and reacting in the liquid phase as described above is usually 7 or more, preferably 13 or more. Adjust according to the density. Further, it is desirable to maintain the pH at 13 or more during the reaction. For this purpose, the pH of the reaction system is controlled by appropriately replenishing an aqueous solution of lithium hydroxide during the reaction.

As described above, each raw material is contact-reacted in a liquid phase to obtain lithium manganate having a spinel structure.
The obtained lithium manganate is separated from the liquid phase if necessary and dried. When the obtained lithium manganate is separated from the liquid phase, it is desirable to wash the obtained lithium manganate with pure water or alcohol to remove halogen and other free unreacted components remaining in the liquid phase. . As the separation means, a commonly used method such as decantation, filtration, or centrifugation can be adopted. The drying is performed while heating by vacuum drying or the like.

In the present invention, a metal-substituted lithium manganate having a spinel structure can be directly produced by reacting a manganese halide, a lithium compound and a substituted metal compound in a liquid phase as described above. As an invention, in order to further improve the crystallinity of lithium manganate, the thus obtained lithium manganate is subjected to a heat treatment. The temperature at this time is usually 4
The temperature is from 00 to 1000C, preferably from 400 to 800C, more preferably from 500 to 750C, and the heat treatment time is usually from 1 to 30 hours, preferably from 2 to 10 hours, more preferably from 4 to 8 hours. The heat treatment is usually performed in the atmosphere, but may be performed in an inert atmosphere such as argon or nitrogen or an oxygen atmosphere.

As described above, in the present invention, as a first step, lithium manganate having a spinel structure or a composite oxide or a mixture of lithium manganate having a spinel structure and manganese oxide is formed by a liquid phase reaction, As a second step, this is further separated and subjected to a heat treatment or a baking treatment, thereby making it possible to produce lithium manganate having a more uniform and highly crystalline spinel structure. In addition, in the conventional method for producing lithium manganate by the solid phase method, since firing at a high temperature,
There is a problem that sintering occurs, the specific surface area decreases, and as a result, characteristics as a positive electrode material deteriorate. However, in the present invention, since lithium manganate has already been generated by the liquid phase reaction,
The baking treatment as a step does not need to be performed at a high temperature as in the conventional solid phase method, and can be performed at a relatively low temperature.

The chemical formula Li _x M produced in the present invention
e _y Mn _1-y O _z (where x is 0 <x ≦ 0.80, y is 0 <y
≦ 0.5 and z indicate 1.8 ≦ z ≦ 2.4. In the chemical formula of lithium manganate having a spinel structure represented by
Is preferably 0.40 ≦ x ≦ 0.65, particularly preferably 0.50 ≦
x ≦ 0.62, more preferably a real number of 0.55 ≦ x ≦ 0.60, y is preferably a real number of 0 <y ≦ 0.3, particularly preferably 0.05 ≦ y ≦ 0.2, and z is preferably 1.9 ≦ z
A real number of ≦ 2.2, particularly preferably z = 2.0.

As a specific composition, Li _0.50 Me _0.10
Mn _0.90 O ₂ , Li _0.58 Me _0.20 Mn _0.80 O ₂ , Li
_0.60 Me _0.05 Mn _0.95 O ₂ .

The lithium manganate produced in the present invention may be a simple compound, a manganese composite oxide containing lithium manganate having a spinel structure and an oxide of manganese such as manganese oxide, or the lithium manganate. And a mixture of manganese oxide. In the case of the manganese composite oxide or the mixture, the other component of lithium manganate having a spinel structure is mainly manganese (III) oxide, and in some cases, may include lithium manganate having a perovskite structure. Its composition is usually 5% lithium manganate having a spinel structure.
0 to 100% by weight, preferably 80 to 100% by weight, manganese (III) oxide is 0 to 50% by weight, preferably 0 to 50% by weight.
-20% by weight.

The lithium manganate obtained as described above is a single oxide of lithium manganate having a spinel structure or a composite oxide or a mixture with manganese oxide, and has an average particle diameter of 1 to 50 μm before heat treatment. Preferably 1 to 30 μm, specific surface area is 10 to 150 m ² / g,
Preferably 30 to 130 m ² / g, BET diameter 0.01
加熱 0.2 μm, and the average particle size after heat treatment is 1-5
0 μm, preferably 5 to 50 μm, having a specific surface area of 5 to
50m ² / g, preferably, 5~30m ² / g, BET
The diameter is 0.08 to 0.3 μm.

Next, the present invention relates to a positive electrode for a lithium ion battery comprising the above-mentioned lithium manganate, wherein the positive electrode for a lithium battery comprises an electrode mixture such as a conductive agent or a binder arbitrarily added to the lithium manganate of the present invention. Can be manufactured. Specifically, graphite, carbon black, acetylene black, ketjen black, carbon fiber and copper,
Conductive materials such as metal powders such as nickel, aluminum, and silver, metal fibers, and polyphenylene derivatives can be used. As the binder, a polysaccharide, a thermoplastic resin, a polymer having rubber elasticity, or the like can be used. Specific examples include starch, polyvinyl alcohol, regenerated cellulose, polyvinyl chloride, polyvinylidene fluoride, polyethylene, polypropylene, ethylene-propylene rubber, and polytetrafluoroethylene. Further, in addition to the above, fillers such as polypropylene and polyethylene can be added.

The lithium ion secondary battery of the present invention comprises a positive electrode and a negative electrode composed of the above-mentioned lithium manganate, and a non-aqueous electrolyte containing lithium ions.

The negative electrode is, for example, lithium metal, a lithium alloy, a conductive polymer obtained by doping lithium ions into polyacetylene or polypyrrole, or a metal chalcogenide such as TiS ₂ , MoS ₂ or NbSe _3. Examples include an ion-doped compound, an inorganic compound such as WO ₂ , MoO ₂ , Fe ₂ O ₃ , and TiS ₂ , and graphite. Of these, a substance containing lithium is preferable, and a lithium alloy is particularly preferable. Specifically, it is an alloy of lithium and at least one metal such as aluminum, zinc, tin, lead, bismuth, cadmium, silver, and tellurium. Among them, an alloy of lithium and aluminum, or an alloy of lithium, silver, and tellurium Alloys are preferably used.

When a lithium alloy is used as the negative electrode active material, the lithium content in the alloy depends on the other metals to be combined, but is 10 to 95% by atom, preferably 4 to 95%.
0 to 70%. The lithium alloy can be obtained by a known method, and examples thereof include a method of melting and alloying, an electrolytic deposition method in an electrolytic solution, and a hot-dip plating method. When a lithium alloy is formed by these methods, a diffusion barrier layer of nickel, cobalt, iron or the like or a wetting promoting material layer of silver, copper, zinc, magnesium or the like is formed on the surface of the base material as necessary.

The non-aqueous electrolyte containing lithium ions constituting the lithium ion secondary battery is composed of a solvent and a lithium salt, and the solvent may be propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, or the like. Organic solvents such as methyl formate, methyl acetate, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolan, formamide, dimethylformamide, dioxolan, acetonitrile, nitromethane, and ethyl monoglyme. Can be. Lithium salts include LiPF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , L
iN (CF ₃ SO ₂ ) ₂ , LiBF _{4 and the} like can be given. The lithium salt is dissolved in the solvent to form a non-aqueous electrolyte, and the positive electrode and the negative electrode are combined to form a lithium ion secondary battery of the present invention.

As described above, the feature of the present invention is that a manganese halide, a lithium compound, and at least one compound selected from a nickel compound, a cobalt compound, a magnesium compound, a chromium compound and an aluminum compound are mixed at a temperature of 100 ° C. or less. The present invention is to produce lithium manganate having a spinel structure by a so-called gel-sol method or a direct method in which the phases are brought into contact with each other and reacted in the presence of an oxidizing agent. This makes it possible to produce a metal-substituted lithium manganate having a spinel structure more simply and at lower cost than the conventional method. In addition, in the production method of the present invention, since the raw material is made into a uniform solution and the liquid phase is contacted and reacted, the spinel structure is more suitable for the electrode material of the lithium ion secondary battery which is more uniform and has higher purity than the conventional solid phase method. Can be obtained. Furthermore, by using this lithium manganate as a positive electrode active material, a lithium ion secondary battery having excellent charge / discharge capacity and excellent charge / discharge cycle characteristics can be obtained as compared with a conventional lithium ion secondary battery.

[0057]

Next, the present invention will be described in more detail with reference to examples, but this is merely an example and does not limit the present invention. Further, X-ray diffraction measurement (Table 1), average particle diameter measurement, and specific surface area measurement of lithium manganate used in Examples and Comparative Examples were performed by the following methods. (X-ray diffraction measurement)

[0058]

[Table 1] ─────────────────────────────────── Diffractometer RAD-1C (manufactured by Rigaku Corporation) ) X-ray tube Cu tube voltage / tube current 40 kV, 30 mA slit DS-SS: 1 degree, RS: 0.15 mm Monochromator Graphite Measurement interval 0.002 degree Counting method Constant clock method ───────── ──────────────────────────

(Measurement of Average Particle Size) The average particle size was measured using a laser diffraction type particle size analyzer (LA-700 manufactured by Horiba, Ltd.).

(Measurement of specific surface area) It was measured by the BET method.

Example 1 In a 2 l flask equipped with a stirrer, 2.375 mol / l
0.8 l of an aqueous solution of lithium hydroxide was injected and heated to 91 ° C. On the other hand, in a 1 liter flask, 0.36 mol of manganese dichloride, 0.04 mol of magnesium chloride, 0.
0.8 l of a mixed aqueous solution containing 2 mol of lithium chloride and 0.24 mol of hydrogen peroxide was prepared. Next, while stirring, the mixed aqueous solution was sent using a tube pump, and the mixed solution was dropped from a funnel into a heated aqueous lithium hydroxide solution over 60 minutes. 1 hour after dropping,
The reaction was performed at 91 ° C. and cooled to room temperature. Thereafter, the operation of centrifuging the obtained suspension containing the solid product and removing the supernatant was repeated three times for washing. The obtained solid was dried at 120 ° C. for 24 hours to obtain magnesium-substituted lithium manganate. When the obtained magnesium-substituted lithium manganate was analyzed by X-ray diffraction, a lithium manganate peak having a spinel structure appeared, and there was no peak of impurities such as manganese oxide (see FIG. 1). When the composition was analyzed, the Li / (Mn + Mg) atomic ratio was 0.59. Further, the average particle diameter was 8.9 μm, the specific surface area was 101 m ² / g, and the BET diameter was 13.8 nm.

Example 2 The spinel-structured magnesium-substituted lithium manganate obtained in Example 1 was subjected to a heat treatment at 700 ° C. for 5.5 hours. The results of analysis of the obtained magnesium-substituted lithium manganate having a spinel structure are also shown in Table 2. When the obtained magnesium-substituted lithium manganate was analyzed by X-ray diffraction, a lithium manganate peak having a spinel structure appeared, and there was no peak of impurities such as manganese oxide.

Example 3 The procedure of Example 1 was repeated except that the concentration of the aqueous lithium hydroxide solution injected into the 2 l flask was 2.5 mol / l and the amount of hydrogen peroxide added to the mixed aqueous solution was 0.22 mol. The same experiment was conducted to obtain magnesium-substituted lithium manganate. When the obtained magnesium-substituted lithium manganate was analyzed by X-ray diffraction, a lithium manganate peak having a spinel structure appeared, and there was no peak of impurities such as manganese oxide. The results of the analysis are also shown in Table 2.

Example 4 The spinel-structured magnesium-substituted lithium manganate obtained in Example 3 was heat-treated at 700 ° C. for 5.5 hours. The results of analysis of the obtained magnesium-substituted lithium manganate having a spinel structure are also shown in Table 2. When the obtained magnesium-substituted lithium manganate was analyzed by X-ray diffraction, a lithium manganate peak having a spinel structure appeared, and there was no peak of impurities such as manganese oxide.

Example 5 The procedure of Example 1 was repeated except that the concentration of the aqueous lithium hydroxide solution injected into the 2 l flask was 2.5 mol / l and the amount of hydrogen peroxide added to the mixed aqueous solution was 0.23 mol. The same experiment was conducted to obtain magnesium-substituted lithium manganate. Table 2 shows the results of the analysis. When the obtained magnesium-substituted lithium manganate was analyzed by X-ray diffraction, a lithium manganate peak having a spinel structure appeared, and there was no peak of impurities such as manganese oxide.

Example 6 The spinel-structured magnesium-substituted lithium manganate obtained in Example 5 was heat-treated at 700 ° C. for 5.5 hours. The results of analysis of the obtained magnesium-substituted lithium manganate having a spinel structure are also shown in Table 2. When the obtained magnesium-substituted lithium manganate was analyzed by X-ray diffraction, a lithium manganate peak having a spinel structure appeared, and there was no peak of impurities such as manganese oxide.

Comparative Example 1 An experiment was conducted in the same manner as in Example 1 except that manganese nitrate was used instead of manganese dichloride. When the obtained solid was analyzed by X-ray diffraction, the peak appeared was mainly manganese oxide, and the peak of magnesium-substituted lithium manganate having a spinel structure did not appear.

Comparative Example 2 An experiment was conducted in the same manner as in Example 1 except that no hydrogen peroxide was used. When the obtained solid was analyzed by X-ray diffraction, the peak appeared was mainly manganese oxide, and the peak of magnesium-substituted lithium manganate having a spinel structure did not appear.

[0069]

[Table 2]

[0070]

As described above, according to the present invention, a manganese halide, a lithium compound, at least one compound selected from a nickel compound, a cobalt compound, a magnesium compound, a chromium compound, and an aluminum compound, Lithium manganate having a spinel structure suitable for an electrode material of a lithium ion secondary battery can be produced by contacting and reacting the agents in a liquid phase of 100 ° C. or lower. This method is capable of producing lithium manganate having a spinel structure at a simpler and lower cost than conventional methods, and the production method of the present invention makes the raw material a uniform solution, contacts in the liquid phase, Because of the reaction, lithium manganate having a spinel structure which is more uniform and higher in purity than the conventional solid phase method can be obtained. Further, by using the lithium manganate obtained by the above method as an active material of a positive electrode for a lithium ion secondary battery, a lithium ion secondary battery having excellent charge / discharge capacity and excellent charge / discharge cycle characteristics can be obtained. Can be.

[Brief description of the drawings]

FIG. 1 is an X-ray diffraction spectrum of lithium manganate obtained in Example 1.

Continued on the front page F-term (reference) 4G048 AA04 AB02 AC06 AD03 AD06 AE05 5H029 AJ03 AJ05 AJ14 AK03 AL02 AL04 AL07 AL12 AL16 AM02 AM03 AM04 AM05 AM07 CJ02 CJ14 CJ28 DJ16 DJ17 HJ02 HJ05 HJ07 HJ14 5H050 AA17 GA08 GA27 HA02 HA05 HA07 HA14

Claims (11)

[Claims] A manganese halide, a lithium compound, at least one compound selected from a nickel compound, a cobalt compound, a magnesium compound, a chromium compound and an aluminum compound, are contacted with an oxidizing agent in a liquid phase at 100 ° C. or lower to react. A method for producing lithium manganate having a spinel structure. 2. The method according to claim 1, wherein the lithium manganate has a chemical formula Li _x
Me _y Mn _1-y O _z (where Me is Ni, Co, Mg,
One or more of Cr and Al, and x is 0
<X ≦ 0.8 real number, y is 0 <y ≦ 0.5 real number, z is 1.8
≤z ≤2.4. The method for producing lithium manganate according to claim 1, wherein 3. The method for producing lithium manganate according to claim 1, wherein the manganese halide is manganese chloride. 4. The method according to claim 1, wherein the lithium compound is lithium hydroxide,
At least one selected from lithium chloride, lithium iodide, lithium bromide, lithium nitrate, lithium nitrite, lithium sulfate, lithium hydrogen sulfate, lithium carbonate, lithium hydrogen carbonate, lithium acetate, lithium oxide, lithium peroxide and lithium chlorate The method for producing lithium manganate according to claim 1, which is a seed. 5. The method for producing lithium manganate according to claim 1, wherein the lithium compound is lithium hydroxide and lithium chloride. 6. The nickel compound, a cobalt compound,
The method for producing lithium manganate according to claim 1, wherein at least one compound selected from a magnesium compound, a chromium compound, and an aluminum compound is chloride or hydroxide. 7. The method according to claim 1, wherein the oxidizing agent is hydrogen peroxide.
3. The method for producing lithium manganate according to item 1. 8. A manganese halide, a lithium compound, at least one compound selected from a nickel compound, a cobalt compound, a magnesium compound, a chromium compound, and an aluminum compound, and an oxidizing agent in a liquid phase at 100 ° C. or lower. A method for producing lithium manganate having a spinel structure, comprising reacting to form a solid, and then subjecting the solid to a heat treatment. 9. A manganese halide and a lithium compound, at least one compound selected from a nickel compound, a cobalt compound, a magnesium compound, a chromium compound, and an aluminum compound, are contacted with an oxidizing agent in a liquid phase at 100 ° C. or lower to react. A lithium manganate having a spinel structure, which is obtained by the chemical formula Li _x Me _y Mn _1-y O _z (wherein:
Me represents one or more of Ni, Co, Mg, Cr and Al, x is a real number satisfying 0 <x ≦ 0.8, and y is 0 <
A real number satisfying y ≦ 0.5, z indicates a real number satisfying 1.8 ≦ z ≦ 2.4. )
And an average particle diameter of 1 to 50 μm and a specific surface area of 10 to 150 m ² / g. 10. A positive electrode for a lithium ion secondary battery, comprising the lithium manganate according to claim 9 as a positive electrode active material. 11. A lithium ion secondary battery using a positive electrode comprising the lithium manganate according to claim 9 as a positive electrode active material.