JP4937405B1 - Method for producing lithium composite metal oxide - Google Patents

Abstract

Provided is a method capable of stably producing a lithium composite metal oxide that can be used as a positive electrode active material of a nonaqueous electrolyte secondary battery even in a firing atmosphere containing carbon dioxide at a higher concentration than air.
A lithium compound, Ni metal or a compound thereof, and a metal or a compound thereof composed of one or more transition metal elements selected from the group consisting of Mn, Co, Ti, Cr and Fe are obtained. A method for producing a lithium composite metal oxide, comprising firing the raw material mixture at 630 ° C. or higher in an atmosphere having a carbon dioxide concentration of 1% by volume to 15% by volume. The non-aqueous electrolyte secondary battery using the lithium composite metal oxide obtained by the manufacturing method as a positive electrode active material is a non-aqueous electrolyte secondary battery used for the positive electrode active material manufactured in an air atmosphere not containing carbon dioxide. Comparing charge / discharge characteristics.
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Description

  The present invention relates to a method for producing a lithium composite metal oxide.

  Lithium composite metal oxide is used as a positive electrode active material in nonaqueous electrolyte secondary batteries such as lithium secondary batteries. Lithium secondary batteries have already been put into practical use as power sources for mobile phones, notebook computers, etc., and are also being applied to medium and large applications such as automobile applications and power storage applications.

  As a positive electrode active material of a lithium secondary battery, a composite oxide of lithium and a cobalt-based oxide has been used until now. It is considered to use transition metal oxides other than cobalt. For example, Patent Document 1 discloses a method for producing a lithium-nickel composite oxide in which a nickel compound and a lithium compound are mixed and heat-treated at 600 ° C. for 20 hours in an air atmosphere.

Lithium hydroxide is mainly used as a lithium raw material in the lithium composite metal oxide. However, lithium hydroxide tends to react with carbon dioxide in the air to become lithium carbonate (Li ₂ CO ₃ ). Since lithium carbonate has low reactivity with the transition metal raw material, the composition of the lithium composite metal oxide to be produced may be nonuniform.

  In order to avoid the reaction between lithium hydroxide and carbon dioxide in the atmosphere, in the conventional lithium composite metal oxide, pure oxygen not containing carbon dioxide or synthetic air is used, or carbon dioxide gas is reduced to 0.1%. Firing is performed in an air atmosphere of about 01% by volume or less (see, for example, Patent Document 2).

Japanese Patent Laid-Open No. 5-290851 JP 2000-58053 A

  As described above, in the conventional method for producing a lithium composite metal oxide, in order to sufficiently react the lithium raw material, pure oxygen or synthetic air that does not contain carbon dioxide or a special atmosphere is used by using a firing furnace that can control the atmosphere. It is necessary to install a large amount of equipment and use air from which carbon dioxide has been removed.

On the other hand, when producing a large amount of lithium composite metal oxides, which are rapidly increasing in demand as positive electrode active materials for non-aqueous electrolyte secondary batteries, lithium composite metal oxides are used from the viewpoint of improving the mass productivity of lithium composite metal oxides and reducing costs. As a firing furnace for obtaining an oxide, it is desired to use a versatile gas furnace using a flame of combustion gas such as propane as a heat source. However, since such a gas furnace burns and heats a hydrocarbon gas such as propane, a high-concentration CO ₂ (usually 10 to 15% by volume, even if CO ₂ removal means is provided in the furnace). About 5 to 10% by volume). Therefore, when baking is performed using such a gas furnace at a conventional temperature condition, the lithium compound (for example, lithium hydroxide) and carbon dioxide easily react as described above to produce lithium carbonate with low reactivity. End up. As a result, an insufficiently reacted lithium composite metal oxide was synthesized, and even when a nonaqueous electrolyte secondary battery was produced using the lithium composite metal oxide as a positive electrode active material, sufficient battery performance could not be obtained. It was.

  Under such circumstances, the object of the present invention is to stably provide a lithium composite metal oxide that can be used as a positive electrode active material of a nonaqueous electrolyte secondary battery even in a firing atmosphere containing carbon dioxide at a concentration higher than the concentration of carbon dioxide in the air. It is to provide a method that can be manufactured.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the following inventions meet the above object, and have reached the present invention.

That is, the present invention relates to the following inventions.
<1> It was obtained by mixing a lithium compound, Ni metal or a compound thereof, and a metal consisting of one or more transition metal elements selected from the group consisting of Mn, Co, Ti, Cr and Fe or a compound thereof. A method for producing a lithium composite metal oxide, comprising firing a raw material mixture at 630 ° C. or higher in an atmosphere having a carbon dioxide concentration of 1% by volume to 15% by volume.
<2> The method for producing a lithium composite metal oxide according to <1>, wherein an oxygen concentration in the baking is 1% by volume or more and 50% by volume or less.
<3> The method for producing a lithium composite metal oxide according to <1> or <2>, wherein the firing time at 630 ° C. or more is 0.5 hours or more and 24 hours or less.
<4> The method for producing a lithium composite metal oxide according to any one of <1> to <3>, further including a step of holding at a temperature lower than the firing temperature by 30 ° C or higher and at a temperature of 600 ° C or higher .
<5> The method for producing a lithium composite metal oxide according to any one of <1> to <4>, wherein the transition metal element is Mn and / or Fe.
<6> The method for producing a lithium composite metal oxide according to any one of <1> to <5>, wherein firing is performed in a gas furnace using a flame of combustion gas as a heat source.
<7> The raw material mixture is selected from the group consisting of carbonates, sulfates and chlorides of one or more elements selected from the group consisting of Na, K, Rb, Cs, Ca, Mg, Sr and Ba The method for producing a lithium composite metal oxide according to any one of <1> to <6>, further comprising a reaction accelerator composed of at least one kind of compound.
<8> The method for producing a lithium composite metal oxide according to claim 7, wherein the transition metal elements are Mn and Fe, and the reaction accelerator is a carbonate.

  According to the present invention, it is possible to stably produce a lithium composite metal oxide that can be used as a positive electrode active material of a nonaqueous electrolyte secondary battery even in a firing atmosphere containing carbon dioxide at a concentration higher than the concentration of carbon dioxide in the air. it can. Therefore, since an inexpensive gas firing furnace using a flame of combustion gas such as propane as a heat source can be used for manufacturing, the positive electrode active material for a non-aqueous electrolyte secondary battery can be manufactured at low cost and in a large amount.

  The present invention is obtained by mixing a lithium compound, Ni metal or a compound thereof, and a metal or a compound thereof composed of one or more transition metal elements selected from the group consisting of Mn, Co, Ti, Cr and Fe. The raw material mixture is calcined at 630 ° C. or higher in an atmosphere having a carbon dioxide concentration of 1% by volume to 15% by volume (hereinafter referred to as “the manufacturing method of the present invention”). It is.

One of the features of the production method of the present invention is that the firing temperature is 630 ° C. or higher. By setting the calcination temperature to 630 ° C. or higher, the reactivity can be improved, and even at a high carbon dioxide concentration of 1% by volume or more and 15% by volume or less, a metal oxide containing no by-product lithium, such as NiO , MnO ₂ , Mn ₃ O _{4 and the} like are suppressed, and a desired lithium composite metal oxide can be obtained. The firing temperature is preferably 650 ° C. or higher, more preferably 750 ° C. or higher, and further preferably 830 ° C. or higher from the viewpoint of increasing the reactivity while suppressing the production of by-products.
The reason why the formation of the metal oxide not containing lithium, which is a byproduct, is suppressed by firing in a temperature range of 630 ° C. or higher is not completely clear at present, but lithium carbonate is generated in the temperature raising step. In this case, it is speculated that by baking in a temperature range of 630 ° C. or higher, low-reactivity lithium carbonate is thermally decomposed and can react uniformly with other raw materials containing transition metals such as Ni, Mn, and Fe. Is done.

Hereinafter, the production method of the present invention will be described in more detail.
Examples of the lithium compound include one or more anhydrides and / or one or more hydrates selected from the group consisting of lithium hydroxide, lithium oxide, lithium chloride, lithium nitrate, lithium sulfate, and lithium carbonate. it can.
Among these, lithium hydroxide or lithium carbonate, which is low in cost and does not generate corrosive gas during heating, is preferably used. Lithium sulfate can be preferably used because it acts as an oxidant during the reaction during firing and has a reaction promoting effect.

Ni metal or a compound thereof (hereinafter sometimes referred to as “Ni compound”) includes Ni metal alone, oxide, hydroxide, oxyhydroxide, carbonate, sulfate, nitrate, acetate, halogen Compound, ammonium salt, oxalate, alkoxide and the like.
In addition, as a metal comprising one or more transition metal elements selected from the group consisting of Mn, Co, Ti, Cr, and Fe or a compound thereof (hereinafter sometimes referred to as “other transition metal compound”), Examples include simple metals, oxides, hydroxides, oxyhydroxides, carbonates, sulfates, nitrates, acetates, halides, ammonium salts, oxalates, and alkoxides of each element. Here, from the viewpoint of obtaining a high-capacity positive electrode active material, the transition metal element in the other transition metal compound is preferably Mn and / or Fe.

A raw material mixture obtained by mixing a lithium compound, a Ni compound, and other transition metal compounds (hereinafter sometimes referred to simply as “raw material mixture”) is dry mixing, wet mixing, liquid phase mixing, or a combination thereof. Any mixing method may be used, and the mixing order is not particularly limited. In addition, the raw material lithium compound, Ni compound and other transition metal compounds are not only physically mixed, but also a reaction product obtained by reacting a part of these raw materials after mixing. The remaining raw materials may be mixed.
Here, from the viewpoint of enhancing the reactivity during firing and synthesizing a more uniform lithium composite metal oxide, first, a Ni transition compound is mixed with another transition metal compound to synthesize a composite transition metal compound. A method of mixing the composite transition metal compound and the lithium compound is preferable. The mixing of the composite transition metal compound and the lithium compound may be any of dry mixing, wet mixing, and liquid phase mixing, but is preferably liquid phase mixing.

  The composite transition metal compound obtained from the above-described Ni compound and other transition metal compounds is not particularly limited, but the coprecipitate slurry obtained by contacting (liquid phase mixing) an aqueous solution containing each element and an alkali is solidified. A composite metal hydroxide produced by drying after liquid separation is preferable.

  Hereinafter, as a typical production method of the composite transition metal compound, an example of producing a composite metal hydroxide containing Ni, Mn, and Fe from a Ni compound and a transition metal compound containing Mn and Fe will be described. Will be described in detail.

  As the aqueous solution containing Ni, Mn and Fe, among the above raw material compounds, those which can be dissolved in water to become an aqueous solution can be suitably used. When the metal simple substance or compound is difficult to dissolve in water, an aqueous solution in which the respective elements are dissolved in an aqueous solution containing hydrochloric acid, sulfuric acid, nitric acid, acetic acid or the like can be used. Among these, an aqueous solution obtained by using each chloride and dissolving Ni chloride, Mn chloride and Fe chloride in water is preferable. The Fe chloride is preferably a divalent Fe chloride.

Examples of the alkali include LiOH (lithium hydroxide), NaOH (sodium hydroxide), KOH (potassium hydroxide), Li ₂ CO ₃ (lithium carbonate), Na ₂ CO ₃ (sodium carbonate), K ₂ CO ₃ (potassium carbonate). ) And (NH ₄ ) ₂ CO ₃ (ammonium carbonate). One or more anhydrides and / or one or more hydrates selected from the group consisting of the above-mentioned alkali aqueous solutions can be used. preferable. Aqueous ammonia can also be mentioned as an alkaline aqueous solution. The density | concentration of the alkali in aqueous alkali solution is about 0.5-10M normally, Preferably it is about 1-8M. From the viewpoint of production cost, it is preferable to use NaOH or KOH as the alkali to be used. Two or more of the alkalis described above may be used in combination.

  The water used as the solvent for the aqueous solution containing Ni, Mn and Fe and the aqueous alkaline solution is preferably pure water and / or ion-exchanged water. In addition, an organic solvent other than water, such as alcohol, a pH adjuster, or the like may be included as long as the effects of the present invention are not impaired.

A coprecipitate slurry containing a composite metal hydroxide containing Ni, Mn and Fe is obtained by bringing an aqueous solution containing Ni, Mn and Fe into contact with an alkali (liquid phase mixing). The “coprecipitate slurry” is mostly a slurry composed of a coprecipitate composed of a composite metal hydroxide containing Mn, Ni and Fe and water, and remains in the process of preparing the coprecipitate. The raw material, a by-product salt (for example, KCl) additive, an organic solvent, or the like may be included, but it may be removed by washing with pure water or an organic solvent.
As a method of contact (liquid phase mixing), an aqueous solution containing Ni, Mn and Fe is added and mixed, an aqueous solution containing Ni, Mn and Fe is added to the aqueous alkaline solution and mixed. A method of adding an aqueous solution containing Ni, Mn, Fe and an aqueous alkaline solution to water and mixing them can be mentioned. In mixing these, it is preferable to involve stirring. Further, among the above contact (liquid phase mixing) methods, the method of adding and mixing an aqueous solution containing Ni, Mn and Fe to an alkaline aqueous solution is preferably used because it is easy to keep the pH within a certain range. it can. In this case, as the aqueous solution containing Ni, Mn and Fe is added to and mixed with the alkaline aqueous solution, the pH of the mixed solution tends to decrease, but this pH is 9 or more, preferably 10 or more. It is preferable to add an aqueous solution containing Ni, Mn and Fe while adjusting so as to be. In addition, when one or both of an aqueous solution containing Ni, Mn and Fe and an alkaline aqueous solution are kept in contact at a temperature of 40 to 80 ° C. (liquid phase mixing), a more uniform composition can be obtained. A precipitate can be obtained, which is preferable.

  In the sense of obtaining a non-aqueous electrolyte secondary battery with higher capacity, in the aqueous solution containing Ni, Mn and Fe, the amount (mol) of Mn is 0.1 or more with respect to the total amount (mol) of Ni, Mn and Fe. It is preferable to set it to 0.7 or less.

  Further, in the sense of obtaining a non-aqueous electrolyte secondary battery with higher capacity, in an aqueous solution containing Ni, Mn and Fe, the amount (mol) of Fe with respect to the total amount (mol) of Ni, Mn and Fe is set to 0.01. It is preferable to set it to 0.5 or less.

Next, the coprecipitate slurry is solid-liquid separated and dried to dry a composite metal hydroxide containing Mn, Ni, and Fe (hereinafter, sometimes simply referred to as “dry matter”). Get.
Drying is usually performed by heat treatment, but may be performed by air drying, vacuum drying, or the like. As the drying atmosphere, air, oxygen, nitrogen, argon, or a mixed gas thereof can be used, but an air atmosphere is preferable. When drying is performed by heat treatment, it is usually performed at 50 to 300 ° C, preferably about 100 to 200 ° C.

The BET specific surface area of the dried product is usually about 10 m ² / g or more and 100 m ² / g or less. The BET specific surface area of the dried product can be adjusted by the drying temperature. The BET specific surface area of the dried product is preferably 20 m ² / g or more, and more preferably 30 m ² / g or more, in order to promote the reactivity during firing described later. Further, in the viewpoint of operability, BET specific surface area of the dried product is preferably 90m ² / g or less, and more preferably less 85 m ² / g. The dried product is usually composed of a mixture of primary particles having a particle diameter of 0.001 μm or more and 0.1 μm or less and secondary particles having a particle diameter of 1 μm or more and 100 μm or less formed by aggregation of the primary particles. The particle diameters of the primary particles and the secondary particles can be measured by observing with a scanning electron microscope (hereinafter sometimes referred to as SEM). The particle size of the secondary particles is preferably 1 μm or more and 50 μm or less, and more preferably 1 μm or more and 30 μm or less.

Subsequently, in order to produce a raw material mixture, the dried product of the composite metal hydroxide and the lithium compound are mixed.
The dry product and the lithium compound may be mixed by either dry mixing or wet mixing, but from the viewpoint of simplicity, dry mixing is preferable. Examples of the mixing device include stirring and mixing, a V-type mixer, a W-type mixer, a ribbon mixer, a drum mixer, a ball mill, and the like.

Hereinafter, the firing step in the production method of the present invention will be described.
A raw material mixture obtained by mixing the above-described lithium compound, Ni compound and other transition metal compound is fired at 630 ° C. or higher in an atmosphere having a carbon dioxide concentration of 1% by volume to 15% by volume.
Here, the firing at 630 ° C. or higher is only required to be held at 630 ° C. or higher, and does not need to be a constant holding temperature, but from the viewpoint of homogenizing the lithium composite metal oxide that is a fired product. The firing temperature should be a constant temperature. From the viewpoint of promoting the reaction, the firing temperature is preferably 650 ° C. or higher, more preferably 750 ° C. or higher, and further preferably 830 ° C. or higher. The upper limit temperature is not particularly limited, but is usually 1100 ° C. or lower, preferably 1000 ° C. or lower because sintering is facilitated when fired at a high temperature.

  The holding time at a temperature of 630 ° C. or higher is preferably 0.5 hours or longer and 24 hours or shorter. By firing within this time range, over-firing can be prevented, and a lithium composite metal oxide serving as a positive electrode active material for a non-aqueous electrolyte secondary battery that stably maintains high performance can be obtained. . If the holding time is shorter than 0.5 hours, the reaction between the lithium compound and the transition metal composite compound may be insufficient, and if it exceeds 24 hours, grain growth of the lithium composite metal oxide occurs, and the performance May decrease. In addition, from the viewpoint of suppressing grain growth due to over-baking, the holding time is more preferably 12 hours or less, and further preferably 8 hours or less.

  Here, the carbon dioxide concentration is preferably 1 to 10% by volume. As described above, in the present invention, it is possible to produce a lithium composite metal oxide that can be used as a positive electrode active material for a non-aqueous electrolyte secondary battery even when the carbon dioxide concentration is in the range of 1 to 15% by volume. However, by setting the carbon dioxide concentration to 1 to 10% by volume, the production of by-products can be reduced, and a lithium composite metal oxide with higher uniformity can be obtained.

  The firing furnace used for the production of the lithium composite metal oxide can be temperature-controlled and can control the carbon dioxide concentration in the internal atmosphere to 1 to 15% by volume. A gas furnace using a flame as a heat source can be mentioned.

Here, from the viewpoint of the productivity of the lithium composite metal oxide, it is preferable to use a gas furnace as the firing furnace. Since the gas furnace has a carbon dioxide concentration of 5 to 10% by volume under normal operating conditions, it can be suitably used in the production method of the present invention.
Examples of the type of gas furnace include a batch type and a continuous type. Examples of the continuous gas furnace include a belt furnace, a rotary kiln, a roller hearth kiln, and the like. A cart furnace that moves and fires a cart in which firing containers are stacked in multiple stages is preferable from the viewpoint of productivity.
Examples of gas species used as fuel gas in the gas furnace include hydrogen, methane, ethane, propane, butane, acetylene, and the like, and mixtures of these gases. Further, liquefied petroleum gas (LPG) which is mainly composed of hydrocarbons such as butane and propane, can be easily liquefied by compression, and has excellent portability can also be used. Among these gas types, liquefied petroleum gas (LPG) is preferable because it has a large amount of heat during combustion and is relatively inexpensive.

In firing in a gas furnace, the firing temperature may be maintained at 630 ° C. or higher, and does not need to be a constant retention temperature, but from the viewpoint of homogenizing the lithium composite metal oxide that is a fired product. The firing temperature should be a constant temperature. From the viewpoint of promoting the reaction, the firing temperature is preferably 650 ° C. or higher, more preferably 750 ° C. or higher, and further preferably 830 ° C. or higher. The upper limit temperature is not particularly limited, but is usually 1100 ° C. or lower, preferably 1000 ° C. or lower because sintering is facilitated when fired at a high temperature.
The holding time is preferably 0.5 hours or more and 24 hours or less. By firing within this time range, over-firing can be prevented, and a lithium composite metal oxide serving as a positive electrode active material for a non-aqueous electrolyte secondary battery that stably maintains high performance can be obtained. . If the holding time is shorter than 0.5 hours, the reaction between the lithium compound and the transition metal composite compound may be insufficient, and if it exceeds 24 hours, grain growth of the lithium composite metal oxide occurs, and the performance May decrease. In addition, from the viewpoint of suppressing grain growth due to over-baking, the holding time is more preferably 12 hours or less, and even more preferably 8 hours or less.

The gas components other than carbon dioxide in the atmosphere of the firing furnace are not particularly limited as long as they react with the raw materials and products of the present invention and do not generate by-products.
On the other hand, when synthesizing a lithium composite metal oxide, in order to obtain a lithium composite metal oxide with few oxygen vacancies and high crystallinity, it is desirable to contain 1 to 50% by volume of oxygen as an atmospheric gas. Is used. When the atmospheric gas contains 1 to 50% by volume of oxygen, the reaction proceeds sufficiently and a lithium composite metal oxide with high crystallinity can be obtained.
In addition, since the moisture (water vapor) in the air reacts with the lithium composite metal oxide and its raw material, it is desirable that the atmospheric gas be dehydrated.

From the viewpoint of further improving the crystallinity and uniformity of the lithium composite metal oxide, in the production method of the present invention, in addition to the step of firing at 630 ° C. or higher in the above-described atmosphere of carbon dioxide concentration of 1 to 15% by volume. In addition, it is preferable to include a step of holding at a temperature lower than the firing temperature by 30 ° C. or more and 600 ° C. or more. Moreover, it is better that the holding temperature in this holding step is constant.
The step of holding at a temperature range of 30 ° C. or higher and 600 ° C. or higher than the baking temperature may be provided before or after the step of baking at 630 ° C. or higher. It is preferable that both are provided.

  In the present invention, the atmospheric gas at a temperature lower than 600 ° C. is not limited to an atmospheric gas containing 1 to 15% by volume of carbon dioxide, and may be an oxidizing gas containing oxygen in air, an inert gas such as nitrogen or argon. Specifically, the case where the heating by the flame is stopped and the air is circulated in the case of the gas furnace can be mentioned.

During the firing, the raw material mixture may contain a reaction accelerator.
Specific examples of the reaction accelerator include chlorides such as NaCl, KCl, RbCl, CsCl, CaCl ₂ , MgCl ₂ , SrCl ₂ , BaCl ₂ and NH ₄ Cl, Na ₂ CO ₃ , K ₂ CO ₃ , Rb _2. Carbonates such as CO ₃ , Cs ₂ CO ₃ , CaCO ₃ , MgCO ₃ , SrCO ₃ and BaCO ₃ ; sulfates such as K ₂ SO ₄ and Na ₂ SO ₄ ; fluorides such as NaF, KF and NH ₄ F; Is mentioned. Among these, preferably, a chloride, carbonate or sulfate of one or more elements selected from the group consisting of Na, K, Rb, Cs, Ca, Mg, Sr and Ba can be mentioned. More preferably, it is a salt. Moreover, when the transition metal element of the other transition metal compound contained in the said raw material mixture is Mn and Fe, it is preferable that especially a reaction accelerator is carbonate.
Preferable examples of the reaction accelerator include NaCl, KCl, Na ₂ CO ₃ , K ₂ CO ₃ , Na ₂ SO ₄ , K ₂ SO ₄ , and Na ₂ CO ₃ , K ₂ CO ₃ , Na ₂ SO _4. , K ₂ SO ₄ is more preferable, and K ₂ CO ₃ is particularly preferable. Two or more reaction accelerators can be used in combination.
When the raw material mixture contains a reaction accelerator, it may be possible to improve the reactivity during firing of the raw material mixture and to adjust the BET specific surface area of the obtained lithium composite metal oxide.
The method of adding the reaction accelerator to the raw material mixture is not particularly limited, but when the composite transition metal compound is synthesized by liquid phase mixing as described above when producing the raw material mixture, the dried product and the lithium compound And may be added and mixed at the time of mixing.
In addition, when by-product salts (for example, KCl, K ₂ SO ₄ ) generated during liquid phase mixing remain in the composite transition metal compound, these by-product salts may be used as a reaction accelerator. In addition, a shortage of the reaction accelerator may be added at the time of mixing the dried product and the lithium compound.
Further, the reaction accelerator may remain in the lithium composite metal oxide, or may be removed by washing, evaporation or the like.
In addition, the mixing ratio of the raw material mixture and the reaction accelerator is preferably 0.1 part by weight or more and 100 parts by weight or less, more preferably 1.0 part by weight or more and 40 parts by weight or less with respect to 100 parts by weight of the raw material mixture.

  Further, after the firing, the obtained lithium composite metal oxide may be pulverized using a ball mill, a jet mill or the like. It may be possible to adjust the BET specific surface area of the lithium composite metal oxide by grinding. Moreover, you may repeat a grinding | pulverization and baking twice or more. Further, the lithium composite metal oxide can be washed or classified as necessary.

  The lithium composite metal oxide obtained by the production method of the present invention becomes a positive electrode active material useful for a nonaqueous electrolyte secondary battery having excellent charge / discharge characteristics.

  The lithium composite metal oxide of the present invention is usually composed of primary particles having an average particle diameter of 0.05 μm or more and 1 μm or less, and an average of 0.1 μm or more and 100 μm or less formed by agglomeration of primary particles and primary particles. It consists of a mixture with secondary particles of particle size. The average particle diameter of primary particles and secondary particles can be measured by observing with SEM. In order to further enhance the effect of the present invention, the size of the secondary particles is preferably 0.1 μm or more and 50 μm or less, and more preferably 0.1 μm or more and 10 μm or less.

In order to further enhance the effects of the present invention, the lithium composite metal oxide of the present invention preferably has an α-NaFeO ₂ type crystal structure, that is, a crystal structure belonging to the R-3m space group. The crystal structure can be identified for a lithium composite metal oxide from a powder X-ray diffraction pattern obtained by powder X-ray diffraction measurement using CuKα as a radiation source.

As the composition of Li in the lithium composite metal oxide of the present invention, the amount (mol) of Li is usually 0.5 or more and 1 with respect to the total amount (mol) of transition metal elements M such as Ni, Mn, and Fe. It is preferably 0.5 or more and 1.5 or less and 1.5 or less, more preferably 1.0 or more and 1.4 or less in the sense of further increasing the capacity retention rate. When expressed as the following formula (A), y is usually 0.5 or more and 1.5 or less, preferably 0.95 or more and 1.5 or less, more preferably 1.0 or more and 1.4 or less. is there.
Li _y (Ni _1-x M _x ) O ₂ (A)
(Here, M represents one or more transition metal elements selected from the group consisting of Mn, Co, Ti, Cr and Fe, and represents 0 <x <1.)

  In addition, a part of Li, Ni, Mn, and Fe in the lithium composite metal oxide of the present invention may be substituted with other elements within a range not impairing the effects of the present invention. Here, as other elements, B, Al, Ga, In, Si, Ge, Sn, Mg, Sc, Y, Zr, Hf, Nb, Ta, Mo, W, Tc, Ru, Rh, Ir, Pd, Examples of the element include Cu, Ag, and Zn.

  In addition, a compound different from the lithium composite metal oxide may be attached to the surface of the particles constituting the lithium composite metal oxide of the present invention as long as the effects of the present invention are not impaired. As the compound, a compound containing at least one element selected from the group consisting of B, Al, Ga, In, Si, Ge, Sn, Mg and a transition metal element, preferably B, Al, Mg, Ga, A compound containing one or more elements selected from the group consisting of In and Sn, more preferably an Al compound, and specific examples of the compound include oxides, hydroxides, and oxywater of the elements. Examples thereof include oxides, carbonates, nitrates, and organic acid salts, and oxides, hydroxides, and oxyhydroxides are preferable. Moreover, you may use these compounds in mixture. Among these compounds, a particularly preferred compound is alumina. Moreover, you may heat after adhesion.

  The positive electrode active material for a non-aqueous electrolyte secondary battery comprising the lithium composite metal oxide of the present invention is suitable for a non-aqueous electrolyte secondary battery. In the present invention, the positive electrode active material for a non-aqueous electrolyte secondary battery may be composed of the lithium composite metal oxide of the present invention as a main component.

  Using the positive electrode active material for nonaqueous electrolyte secondary batteries, for example, a positive electrode for nonaqueous electrolyte secondary batteries can be produced as follows.

  The positive electrode for a non-aqueous electrolyte secondary battery is manufactured by supporting a positive electrode mixture containing a positive electrode active material, a conductive material and a binder on a positive electrode current collector. A carbonaceous material can be used as the conductive material, and examples of the carbonaceous material include graphite powder, carbon black (for example, acetylene black), and fibrous carbon material. Carbon black (for example, acetylene black) is fine and has a large surface area. Therefore, adding a small amount to the positive electrode mixture can increase the conductivity inside the positive electrode and improve the charge / discharge efficiency and rate characteristics. If it is too large, the binding property between the positive electrode mixture and the positive electrode current collector by the binder is lowered, which causes an increase in internal resistance. Usually, the ratio of the conductive material in the positive electrode mixture is 5 parts by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the positive electrode active material. In the case where a fibrous carbon material such as graphitized carbon fiber or carbon nanotube is used as the conductive material, this ratio can be lowered.

  As the binder, a thermoplastic resin can be used. Specifically, polyvinylidene fluoride (hereinafter sometimes referred to as PVdF), polytetrafluoroethylene (hereinafter sometimes referred to as PTFE), and four fluorine. Fluoropolymers such as fluorinated ethylene / hexafluoropropylene / vinylidene fluoride copolymers, propylene hexafluoride / vinylidene fluoride copolymers, tetrafluoroethylene / perfluorovinyl ether copolymers, polyethylene, polypropylene, etc. Polyolefin resin and the like. Moreover, you may mix and use these 2 or more types. Further, by using a fluororesin and a polyolefin resin as a binder, the ratio of the fluororesin to the positive electrode mixture is 1 to 10% by weight, and the ratio of the polyolefin resin is 0.1 to 2% by weight, A positive electrode mixture excellent in binding property with the positive electrode current collector can be obtained.

  As the positive electrode current collector, Al, Ni, stainless steel or the like can be used, but Al is preferable in that it is easily processed into a thin film and is inexpensive. As a method of supporting the positive electrode mixture on the positive electrode current collector, there is a method of pressure molding, or a method of pasting using an organic solvent or the like, applying onto the positive electrode current collector, drying and pressing to fix the positive electrode current collector. Can be mentioned. In the case of forming a paste, a slurry composed of a positive electrode active material, a conductive material, a binder, and an organic solvent is prepared. Examples of the organic solvent include amine solvents such as N, N-dimethylaminopropylamine and diethylenetriamine, ether solvents such as tetrahydrofuran, ketone solvents such as methyl ethyl ketone, ester solvents such as methyl acetate, dimethylacetamide, N-methyl- Examples include amide solvents such as 2-pyrrolidone.

  Examples of the method for applying the positive electrode mixture to the positive electrode current collector include a slit die coating method, a screen coating method, a curtain coating method, a knife coating method, a gravure coating method, and an electrostatic spray method. By the method mentioned above, the positive electrode for nonaqueous electrolyte secondary batteries can be manufactured.

  Using the positive electrode for a non-aqueous electrolyte secondary battery, a non-aqueous electrolyte secondary battery can be manufactured as follows. That is, an electrode group obtained by laminating and winding the separator, the negative electrode, and the positive electrode is housed in a battery can and then impregnated with an electrolytic solution composed of an organic solvent containing an electrolyte. Can do.

  As the shape of the electrode group, for example, a shape in which the cross section when the electrode group is cut in a direction perpendicular to the winding axis is a circle, an ellipse, a rectangle, a rectangle with rounded corners, etc. Can be mentioned. In addition, examples of the shape of the battery include a paper shape, a coin shape, a cylindrical shape, and a square shape.

  The negative electrode only needs to be capable of doping and dedoping lithium ions at a lower potential than the positive electrode, and an electrode in which a negative electrode mixture containing a negative electrode material is supported on a negative electrode current collector, or an electrode made of a negative electrode material alone Can be mentioned. Examples of the negative electrode material include carbonaceous materials, chalcogen compounds (oxides, sulfides, and the like), nitrides, metals, and alloys that can be doped / undoped with lithium ions at a lower potential than the positive electrode. Moreover, you may use these negative electrode materials in mixture.

The negative electrode material is exemplified below. Specific examples of the carbonaceous material include graphite such as natural graphite and artificial graphite, coke, carbon black, pyrolytic carbon, carbon fiber, and fired organic polymer compound. As the oxide, specifically, an oxide of silicon represented by the formula SiO _x (where x is a positive real number) such as SiO ₂ and SiO, a formula TiO _x such as TiO ₂ and TiO (where x is x) Is a positive oxide of titanium, V ₂ O ₅ , VO _2, etc., and VO _x (where x is a positive real number), vanadium oxide, Fe ₃ O ₄ , Fe ₂ O ₃ , FeO and the like FeO _x (where x is a positive real number) Iron oxide, SnO ₂ , SnO and the like SnO _x (where x is a positive real number) Tin oxide, WO ₃ , WO _{2 and} other tungsten oxides represented by the general formula WO _x (where x is a positive real number), Li ₄ Ti ₅ O ₁₂ , LiVO ₂ (for example Li _1.1 V _0.9 O and the like containing mixed metal oxide for the ₂₎ and lithium such as titanium and / or vanadium Door can be. Specific examples of the sulfide include titanium sulfides represented by the formula TiS _x (where x is a positive real number) such as Ti ₂ S ₃ , TiS ₂ , and TiS, V ₃ S ₄ , VS _2, VS and other formulas VS _x (where x is a positive real number), vanadium sulfide, Fe ₃ S ₄ , FeS ₂ , FeS and other formulas FeS _x (where x is a positive real number) Iron sulfide, Mo ₂ S ₃ , MoS _{2 and the} like MoS _x (where x is a positive real number) molybdenum sulfide, SnS _2, SnS and other formula SnS _x (where x is Tin sulfide represented by positive real number), WS _{2 and} other formulas WS _x (where x is a positive real number), tungsten sulfide represented by SbS _x such as Sb ₂ S ₃ (where, x is antimony represented by a positive real _{number), Se 5 S 3, SeS} 2, SeS formula SeS _x (wherein such, Mention may be made of such sulfide selenium represented by a positive real number). Specific examples of the nitride include lithium-containing nitrides such as Li ₃ N, Li _3-x A _x N (where A is Ni and / or Co, and 0 <x <3). Can be mentioned. These carbonaceous materials, oxides, sulfides, and nitrides may be used in combination, and may be crystalline or amorphous. Further, these carbonaceous materials, oxides, sulfides and nitrides are mainly carried on the negative electrode current collector and used as electrodes.

Specific examples of the metal include lithium metal, silicon metal, and tin metal. Examples of the alloy include lithium alloys such as Li—Al, Li—Ni, and Li—Si, silicon alloys such as Si—Zn, Sn—Mn, Sn—Co, Sn—Ni, Sn—Cu, and Sn—La. In addition to tin alloys such as Cu ₂ Sb, La ₃ Ni ₂ Sn _{7 and the} like can also be mentioned. These metals and alloys are mainly used alone as electrodes (for example, used in a foil shape).

  Among the negative electrode materials, a carbonaceous material mainly composed of graphite such as natural graphite or artificial graphite is preferably used from the viewpoint of high potential flatness, low average discharge potential, and good cycleability. The shape of the carbonaceous material may be, for example, a flake shape such as natural graphite, a spherical shape such as mesocarbon microbeads, a fibrous shape such as graphitized carbon fiber, or an aggregate of fine powder.

  The negative electrode mixture may contain a binder as necessary. Examples of the binder include thermoplastic resins, and specific examples include PVdF, thermoplastic polyimide, carboxymethyl cellulose, polyethylene, and polypropylene.

  Examples of the negative electrode current collector include Cu, Ni, and stainless steel. Cu may be used because it is difficult to form an alloy with lithium and it is easy to process into a thin film. The method of supporting the negative electrode mixture on the negative electrode current collector is the same as in the case of the positive electrode. The method is a method of pressure molding, pasted using a solvent, etc., coated on the negative electrode current collector, dried, pressed and pressed. And the like.

  As the separator, for example, a material having a form such as a porous membrane, a nonwoven fabric, a woven fabric made of a polyolefin resin such as polyethylene and polypropylene, a fluororesin, a nitrogen-containing aromatic polymer, and the like can be used. Moreover, it is good also as a separator using 2 or more types of the said material, and the said material may be laminated | stacked. Examples of the separator include separators described in JP 2000-30686 A, JP 10-324758 A, and the like. The thickness of the separator is preferably about 5 to 200 μm, and preferably about 5 to 40 μm, as long as the mechanical strength is maintained because the volume energy density of the battery is increased and the internal resistance is reduced.

  The separator preferably has a porous film containing a thermoplastic resin. In a non-aqueous electrolyte secondary battery, normally, when an abnormal current flows in the battery due to a short circuit between the positive electrode and the negative electrode, the function of shutting down the current and preventing the excessive current from flowing (shut down) It is preferable to have. Here, the shutdown is performed by closing the micropores of the porous film in the separator when the normal use temperature is exceeded. After the shutdown, even if the temperature in the battery rises to a certain high temperature, it is preferable to maintain the shutdown state without breaking the film due to the temperature. Examples of such a separator include a laminated film in which a heat-resistant porous layer and a porous film are laminated. By using the film as a separator, the heat resistance of the secondary battery in the present invention can be further increased. . Here, the heat-resistant porous layer may be laminated on both surfaces of the porous film.

  Hereinafter, a laminated film in which the heat-resistant porous layer and the porous film are laminated will be described.

  In the laminated film, the heat resistant porous layer is a layer having higher heat resistance than the porous film, and the heat resistant porous layer may be formed of an inorganic powder or may contain a heat resistant resin. When the heat resistant porous layer contains a heat resistant resin, the heat resistant porous layer can be formed by an easy technique such as coating. Examples of the heat resistant resin include polyamide, polyimide, polyamideimide, polycarbonate, polyacetal, polysulfone, polyphenylene sulfide, polyetherketone, aromatic polyester, polyethersulfone, and polyetherimide, from the viewpoint of further improving heat resistance. , Polyamide, polyimide, polyamideimide, polyethersulfone, and polyetherimide are preferable, and polyamide, polyimide, and polyamideimide are more preferable. Even more preferred are nitrogen-containing aromatic polymers such as aromatic polyamides (para-oriented aromatic polyamides, meta-oriented aromatic polyamides), aromatic polyimides, aromatic polyamideimides, and particularly preferred are aromatic polyamides and production surfaces. Particularly preferred is para-oriented aromatic polyamide (hereinafter sometimes referred to as “para-aramid”). Further, examples of the heat resistant resin include poly-4-methylpentene-1 and cyclic olefin polymers. By using these heat resistant resins, the heat resistance of the laminated film, that is, the thermal film breaking temperature of the laminated film can be further increased. Among these heat-resistant resins, when using a nitrogen-containing aromatic polymer, because of the polarity in the molecule, compatibility with the electrolyte, that is, the liquid retention in the heat-resistant porous layer may be improved, The rate of impregnation of the electrolytic solution during the production of the nonaqueous electrolyte secondary battery is also high, and the charge / discharge capacity of the nonaqueous electrolyte secondary battery is further increased.

  The thermal film breaking temperature of such a laminated film depends on the type of heat-resistant resin, and is selected and used according to the use scene and purpose of use. More specifically, as the heat resistant resin, the cyclic olefin polymer is used at about 400 ° C. when the nitrogen-containing aromatic polymer is used, and at about 250 ° C. when poly-4-methylpentene-1 is used. When using, the thermal film breaking temperature can be controlled to about 300 ° C., respectively. In addition, when the heat resistant porous layer is made of an inorganic powder, the thermal film breaking temperature can be controlled to, for example, 500 ° C. or higher.

  The para-aramid is obtained by condensation polymerization of a para-oriented aromatic diamine and a para-oriented aromatic dicarboxylic acid halide, and the amide bond is in the para position of the aromatic ring or an oriented position equivalent thereto (for example, 4,4′- It consists essentially of repeating units bonded at opposite orientations, such as biphenylene, 1,5-naphthalene, 2,6-naphthalene, etc., oriented in the opposite direction coaxially or in parallel. Specifically, poly (paraphenylene terephthalamide), poly (parabenzamide), poly (4,4′-benzanilide terephthalamide), poly (paraphenylene-4,4′-biphenylenedicarboxylic acid amide), poly ( Para-aligned or para-oriented such as paraphenylene-2,6-naphthalenedicarboxylic acid amide), poly (2-chloro-paraphenylene terephthalamide), paraphenylene terephthalamide / 2,6-dichloroparaphenylene terephthalamide copolymer Examples include para-aramid having a structure according to the type.

  The aromatic polyimide is preferably a wholly aromatic polyimide produced by condensation polymerization of an aromatic dianhydride and a diamine. Specific examples of the dianhydride include pyromellitic dianhydride, 3,3 ′, 4,4′-diphenylsulfone tetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic Examples thereof include acid dianhydride, 2,2′-bis (3,4-dicarboxyphenyl) hexafluoropropane, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, and the like. Specific examples of the diamine include oxydianiline, paraphenylenediamine, benzophenonediamine, 3,3′-methylenedianiline, 3,3′-diaminobenzophenone, 3,3′-diaminodiphenylsulfone, 1,5 -Naphthalene diamine etc. are mentioned. Moreover, a polyimide soluble in a solvent can be preferably used. An example of such a polyimide is a polycondensate polyimide of 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride and an aromatic diamine.

  As the above-mentioned aromatic polyamideimide, those obtained from condensation polymerization using aromatic dicarboxylic acid and aromatic diisocyanate, those obtained from condensation polymerization using aromatic diacid anhydride and aromatic diisocyanate Is mentioned. Specific examples of the aromatic dicarboxylic acid include isophthalic acid and terephthalic acid. Specific examples of the aromatic dianhydride include trimellitic anhydride. Specific examples of the aromatic diisocyanate include 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, orthotolylane diisocyanate, m-xylene diisocyanate, and the like.

  In order to further enhance the ion permeability, the heat-resistant porous layer is preferably a thin heat-resistant porous layer having a thickness of 1 μm to 10 μm, more preferably 1 μm to 5 μm, particularly 1 μm to 4 μm. The heat-resistant porous layer has fine pores, and the size (diameter) of the pores is usually 3 μm or less, preferably 1 μm or less. Moreover, when a heat resistant porous layer contains a heat resistant resin, a heat resistant porous layer can also contain the below-mentioned filler.

  In the laminated film, the porous film preferably has fine pores and has a shutdown function. In this case, the porous film contains a thermoplastic resin. The size of the micropores in the porous film is usually 3 μm or less, preferably 1 μm or less. The porosity of the porous film is usually 30 to 80% by volume, preferably 40 to 70% by volume. In the nonaqueous electrolyte secondary battery, when the normal use temperature is exceeded, the porous film containing the thermoplastic resin can close the micropores by softening the thermoplastic resin constituting the porous film.

  What is necessary is just to select the thermoplastic resin which does not melt | dissolve in the electrolyte solution in a nonaqueous electrolyte secondary battery. Specific examples include polyolefin resins such as polyethylene and polypropylene, and thermoplastic polyurethane resins, and a mixture of two or more of these may be used. It is preferable to contain polyethylene in the sense of softening and shutting down at a lower temperature. Specific examples of the polyethylene include polyethylene such as low density polyethylene, high density polyethylene, and linear polyethylene, and ultra high molecular weight polyethylene having a molecular weight of 1,000,000 or more. In the sense of further increasing the puncture strength of the porous film, the thermoplastic resin constituting the film preferably contains at least ultrahigh molecular weight polyethylene. In addition, in terms of production of the porous film, the thermoplastic resin may preferably contain a wax made of polyolefin having a low molecular weight (weight average molecular weight of 10,000 or less).

  Moreover, the thickness of the porous film in a laminated | multilayer film is 3-30 micrometers normally, More preferably, it is 3-25 micrometers. In the present invention, the thickness of the laminated film is usually 40 μm or less, preferably 20 μm or less. Moreover, when the thickness of the heat resistant porous layer is A (μm) and the thickness of the porous film is B (μm), the value of A / B is preferably 0.1 or more and 1 or less.

  Moreover, when the heat resistant porous layer contains a heat resistant resin, the heat resistant porous layer may contain one or more fillers. The filler may be selected from organic powder, inorganic powder, or a mixture thereof as the material thereof. The particles constituting the filler preferably have an average particle size of 0.01 μm or more and 1 μm or less.

  Examples of the organic powder include styrene, vinyl ketone, acrylonitrile, methyl methacrylate, ethyl methacrylate, glycidyl methacrylate, glycidyl acrylate, and methyl acrylate, or a copolymer of two or more kinds, polytetrafluoroethylene, 4 fluorine. Examples include fluorine-containing resins such as fluorinated ethylene-6-propylene-propylene copolymer, tetrafluoroethylene-ethylene copolymer, and polyvinylidene fluoride; melamine resin; urea resin; polyolefin; and powders made of organic substances such as polymethacrylate. . The organic powder may be used alone or in combination of two or more. Among these organic powders, polytetrafluoroethylene powder is preferable from the viewpoint of chemical stability.

  Examples of the inorganic powder include powders made of inorganic substances such as metal oxides, metal nitrides, metal carbides, metal hydroxides, carbonates, sulfates, etc. Among these, they are made of inorganic substances having low conductivity. Powder is preferably used. Specific examples include powders made of alumina, silica, titanium dioxide, calcium carbonate, or the like. The inorganic powder may be used alone or in combination of two or more. Among these inorganic powders, alumina powder is preferable from the viewpoint of chemical stability. Here, it is more preferable that all of the particles constituting the filler are alumina particles, and it is even more preferable that all of the particles constituting the filler are alumina particles, and part or all of them are substantially spherical alumina particles. It is embodiment which is. Incidentally, when the heat-resistant porous layer is formed from an inorganic powder, the inorganic powder exemplified above may be used, and may be mixed with a binder as necessary.

  The filler content when the heat-resistant porous layer contains a heat-resistant resin depends on the specific gravity of the filler material. For example, when all of the particles constituting the filler are alumina particles, When the total weight is 100, the weight of the filler is usually 5 or more and 95 or less, preferably 20 or more and 95 or less, more preferably 30 or more and 90 or less. These ranges can be appropriately set depending on the specific gravity of the filler material.

  Examples of the shape of the filler include a substantially spherical shape, a plate shape, a columnar shape, a needle shape, a whisker shape, and a fibrous shape, and any particle can be used. It is preferable that Examples of the substantially spherical particles include particles having a particle aspect ratio (particle major axis / particle minor axis) in the range of 1 to 1.5. The aspect ratio of the particles can be measured by an electron micrograph.

  In the present invention, from the viewpoint of ion permeability, the separator preferably has an air permeability of 50 to 300 seconds / 100 cc, more preferably 50 to 200 seconds / 100 cc in terms of air permeability by the Gurley method. preferable. Moreover, the porosity of a separator is 30-80 volume% normally, Preferably it is 40-70 volume%. The separator may be a laminate of separators having different porosity.

In the secondary battery, the electrolytic solution is usually composed of an organic solvent containing an electrolyte. Examples of the electrolyte include LiClO ₄ , LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LIBF ₄ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiN (SO ₂ CF ₃ ) (COCF ₃ ), Li (C ₄ F ₉ SO ₃ ), LiC (SO ₂ CF ₃ ) ₃ , Li ₂ B ₁₀ Cl ₁₀ , LiBOB (where BOB is bis (oxalato) borate). ), Lithium salts such as lower aliphatic carboxylic acid lithium salts and LiAlCl _4, and a mixture of two or more of these may be used. The lithium salt is usually selected from the group consisting of LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ and LiC (SO ₂ CF ₃ ) ₃ containing fluorine among these. Those containing at least one selected are used.

In the electrolytic solution, examples of the organic solvent include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 4-trifluoromethyl-1,3-dioxolan-2-one, 1,2-di ( Carbonates such as methoxycarbonyloxy) ethane; 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropyl methyl ether, 2,2,3,3-tetrafluoropropyl difluoromethyl ether, tetrahydrofuran, 2-methyl Ethers such as tetrahydrofuran; esters such as methyl formate, methyl acetate and γ-butyrolactone; nitriles such as acetonitrile and butyronitrile; N, N-dimethylformamide, N, N-dimethylacetate Amides such as amides; Carbamates such as 3-methyl-2-oxazolidone; Sulfur-containing compounds such as sulfolane, dimethyl sulfoxide and 1,3-propane sultone, or those obtained by further introducing a fluorine substituent into the above organic solvent Usually, two or more of these are mixed and used. Among these, a mixed solvent containing carbonates is preferable, and a mixed solvent of cyclic carbonate and acyclic carbonate or cyclic carbonate and ether is more preferable. The mixed solvent of cyclic carbonate and non-cyclic carbonate has a wide operating temperature range, excellent load characteristics, and is hardly decomposable even when a graphite material such as natural graphite or artificial graphite is used as the negative electrode active material. In addition, a mixed solvent containing ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate is preferable. Further, in view of particularly excellent safety improving effect is obtained, it is preferable to use an electrolytic solution containing an organic solvent having a lithium salt and a fluorine substituent containing fluorine such as LiPF _6. A mixed solvent containing ethers having fluorine substituents such as pentafluoropropyl methyl ether and 2,2,3,3-tetrafluoropropyl difluoromethyl ether and dimethyl carbonate has excellent high-current discharge characteristics, preferable.

A solid electrolyte may be used instead of the above electrolytic solution. As the solid electrolyte, for example, an organic polymer electrolyte such as a polyethylene oxide polymer compound, a polymer compound containing at least one of a polyorganosiloxane chain or a polyoxyalkylene chain can be used. Moreover, what is called a gel type which hold | maintained the nonaqueous electrolyte solution in the high molecular compound can also be used. The _{Li 2 S-SiS 2, Li} 2 S-GeS 2, Li 2 S-P 2 S 5, Li 2 S-B 2 S 3, Li 2 S-SiS 2 -Li 3 PO 4, Li 2 S-SiS _An inorganic solid electrolyte containing a sulfide such as _2- Li ₂ SO ₄ may be used. Using these solid electrolytes, safety may be further improved. In the nonaqueous electrolyte secondary battery of the present invention, when a solid electrolyte is used, the solid electrolyte may serve as a separator, and in that case, the separator may not be required.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, unless it exceeds the summary of this invention, it is not limited to a following example.

<Powder X-ray diffraction measurement>
The powder X-ray diffraction measurement (XRD) was performed using Ultima IVASC-10 manufactured by Rigaku Corporation. The measurement is performed by filling a powder sample on a dedicated substrate and using a CuKα ray source under the conditions of a voltage of 40 kV and a current of 40 mA in a diffraction angle range of 2θ = 10 ° to 90 ° to obtain a powder X-ray diffraction pattern. It was.
<BET specific surface area measurement>
1 g of the powder was dried at 150 ° C. for 15 minutes in a nitrogen atmosphere, and then measured using a Micrometrics Flowsorb II2300.

Example 1
In a polypropylene beaker, 71.00 g of potassium hydroxide was added to 930 ml of distilled water and dissolved by stirring to completely dissolve potassium hydroxide to prepare an aqueous potassium hydroxide solution (alkali aqueous solution). Further, in a glass beaker, 150 ml of distilled water, 55.86 g of nickel (II) chloride hexahydrate, 47.50 g of manganese (II) chloride tetrahydrate and iron (II) chloride tetrahydrate 4. 97 g was added and dissolved by stirring to obtain a nickel-manganese-iron mixed aqueous solution. While stirring the potassium hydroxide aqueous solution, the nickel-manganese-iron mixed aqueous solution was added dropwise thereto to produce a coprecipitate, thereby obtaining a coprecipitate slurry. Further, the pH at the end of the reaction was measured and found to be 13.
Next, the coprecipitate slurry was filtered and washed with distilled water to remove alkali components (KOH) and by-product salt components (KCl), and then dried at 120 ° C. to obtain a dried product P ₁ . As a result of the composition analysis of the dried product P ₁ , the molar ratio of Ni: Mn: Fe was 0.47: 0.48: 0.05.
40.00 g of the dried product (P ₁ ), 21.66 g of lithium hydroxide monohydrate, and 12.62 g of potassium chloride were dry-mixed using a ball mill to obtain a raw material mixture M ₁ . Next, 40 g of the raw material mixture (M ₁ ) was placed in an alumina firing vessel, and air adjusted to a carbon dioxide concentration of 6% by volume using an electric tubular furnace was supplied at 1 L / min, and at 800 ° C. for 3.5 hours. This was held and then fired at 950 ° C. for 1 hour and cooled to room temperature to obtain a fired product. Then, the fired product was pulverized, washed with distilled water by decantation, after filtration, and dried 6 hours at 300 ° C., to obtain a powder B _1.
The BET specific surface area of the powder B ₁ was 8.7 m ² / g. As a result of the powder X-ray diffraction measurement, it was found that the crystal structure of the powder B _{1 was} a crystal structure belonging to the R-3m space group.

(Example 2)
40 g of the raw material mixture (M ₁ ) produced in Example 1 was put in an alumina firing vessel, and air adjusted to a carbon dioxide concentration of 6% by volume using an electric tubular furnace was supplied at 1 L / min, at 950 ° C. It baked for 1 hour and then held at 800 ° C. for 3.5 hours and cooled to room temperature to obtain a baked product. Then, the fired product was pulverized, washed with distilled water by decantation, after filtration, and dried 6 hours at 300 ° C., to obtain a powder B _2.
The BET specific surface area of the powder B ₂ was 8.2 m ² / g. As a result of the powder X-ray diffraction measurement, it was found that the crystal structure of the powder B _{2 was} a crystal structure belonging to the R-3m space group.

(Example 3)
40 g of the raw material mixture (M ₁ ) prepared in Example 1 was put in an alumina firing vessel, and air adjusted to a carbon dioxide concentration of 6% by volume using an electric tubular furnace was supplied at 1 L / min, at 800 ° C. Firing was performed for 6 hours, and the mixture was cooled to room temperature to obtain a fired product. Then, the fired product was pulverized, washed with distilled water by decantation, after filtration, and dried 6 hours at 300 ° C., to obtain a powder B _3.
The BET specific surface area of the powder B ₃ was 19.8 m ² / g. As a result of the powder X-ray diffraction measurement, the crystal structure of the powder B ₃ was found to be a crystal structure belonging to the R-3m space group.

Example 4
40 g of the raw material mixture (M ₁ ) prepared in Example 1 was put in an alumina firing container, and air adjusted to a carbon dioxide concentration of 6% by volume using an electric tubular furnace was supplied at 1 L / min, at 700 ° C. Firing was performed for 6 hours, and the mixture was cooled to room temperature to obtain a fired product. Then, the fired product was pulverized, washed with distilled water by decantation, after filtration, and dried 6 hours at 300 ° C., to obtain a powder B _4.
The BET specific surface area of the powder B ₄ was 22.4 m ² / g. As a result of the powder X-ray diffraction measurement, the crystal structure of the powder B ₄ was found to be a crystal structure belonging to the R-3m space group.

(Comparative Example 1)
40 g of the raw material mixture (M ₁ ) prepared in Example 1 was put in an alumina firing vessel, and air adjusted to a carbon dioxide concentration of 6% by volume using an electric tubular furnace was supplied at 1 L / min, at 600 ° C. Firing was performed for 6 hours, and the mixture was cooled to room temperature to obtain a fired product. Then, the fired product was pulverized, washed with distilled water by decantation, after filtration, and dried 6 hours at 300 ° C., to obtain a powder B _5.
The BET specific surface area of the powder B ₅ was 30.7 m ² / g. As a result of the powder X-ray diffraction measurement, the crystal structure of the powder B ₅ was found to be a crystal structure belonging to the R-3m space group.

(Reference Example 1)
40 g of the raw material mixture (M ₁ ) produced in Example 1 was put in an alumina firing vessel, and air that had not been adjusted in carbon dioxide concentration was supplied at 1 L / min using an electric tubular furnace, and 6 at 800 ° C. Time firing was performed and the mixture was cooled to room temperature to obtain a fired product. Then, the fired product was pulverized, washed with distilled water by decantation, after filtration, and dried 6 hours at 300 ° C., to obtain a powder B _6.
The BET specific surface area of the powder B ₆ was 6.4 m ² / g. As a result of powder X-ray diffraction measurement, it was found that the crystal structure of the powder B _{6 was} a crystal structure belonging to the R-3m space group.

(Example 5)
In a stirring tank, 100 parts by weight of potassium hydroxide was added to 538 parts by weight of distilled water and dissolved by stirring to completely dissolve potassium hydroxide, thereby preparing an aqueous potassium hydroxide solution (alkaline aqueous solution).
In another stirring tank, 138 parts by weight of distilled water, 51.5 parts by weight of nickel (II) chloride hexahydrate, 43.9 parts by weight of manganese (II) chloride tetrahydrate and iron chloride (II) ) 4.6 parts by weight of tetrahydrate was added and dissolved by stirring to obtain a nickel-manganese-iron mixed aqueous solution.
Next, after adding 215 parts by weight of distilled water and 24.7 parts by weight of the aqueous potassium hydroxide solution to another stirring tank, 165 parts by weight of the aqueous potassium hydroxide solution with stirring at a liquid temperature of 30 ° C. By adding 100 parts by weight of the nickel-manganese-iron mixed aqueous solution dropwise, a coprecipitate was generated to obtain a coprecipitate slurry. When the pH at the end of the reaction was measured, the pH was 13.
Next, 100 parts by weight of the coprecipitate slurry was filtered with a filter press (“Roll Fit Filter Press Dryer”, distributor: Eurotech Co., Ltd.) under a pressure of 0.4 MPaG and room temperature for 50 minutes. Distilled water was supplied at a washing pressure of 0.4 to 0.6 MPaG at room temperature to perform washing with water. After washing with water, pressing was performed at a pressing pressure of 0.7 MPaG for 15 minutes. Next, the inside of the filter press was evacuated to a pressure of 10 kPa, 90 ° C. warm water was passed through the jacket of each filter chamber, and preliminary drying was performed for 170 minutes to recover 3.73 parts by weight of the wet cake. The moisture content of the wet cake at this time was 13.3% on a wet basis.
The moisture content of “wet standard” is calculated by dividing the weight of water contained in the wet cake by the weight of the wet cake (the total weight of water and solids) (= water weight / (water Weight + solids weight) × 100).

The wet cake was dried at 120 ° C. with a shelf dryer and then crushed with a crusher to obtain a dried product P ₂ . As a result of the composition analysis of P ₂ , the molar ratio of Ni: Mn: Fe was 0.47: 0.48: 0.05.
100 parts by weight of the dried product (P ₂ ), 52.1 parts by weight of lithium carbonate, and 14.3 parts by weight of potassium carbonate were dry-mixed using a ball mill to obtain a raw material mixture M ₂ . Next, 1.8 kg of the mixture M ₂ was put into a porous ceramic firing vessel, LPG was used as a fuel, and the flame was introduced into the furnace, and a gas firing furnace (Takasago Industrial 2m ³ shuttle kiln) was used. Firing was performed at 860 ° C. for 6 hours. The atmosphere during firing was an oxygen concentration of 11 to 13% by volume and carbon dioxide of 6 to 8% by volume.
After the completion of firing, the product was cooled to room temperature to obtain a fired product. It was ground, subjected to filtration and washed with distilled water and dried for 6 hours at 300 ° C., to obtain a powder B _7.
BET specific surface area of the powder B ₇ was 10.4 m ² / g. The crystal structure of the powder B ₇ was found to be a crystal structure belonging to the R-3m space group.

<Preparation of nonaqueous electrolyte secondary battery>
A coin-type non-aqueous electrolyte secondary battery using the produced powders B _{1 to} B ₇ as a positive electrode active material was produced, and a charge / discharge test was performed.
To a mixture of a positive electrode active material (powder B _{1 to} B ₇ ) and a conductive material (a mixture of acetylene black and graphite at 9: 1 (weight ratio)), N-methyl-2-pyrrolidone of PVdF (hereinafter referred to as “binder”) is used. NMP.) The solution is added to the composition of active material: conductive material: binder = 87: 10: 3 (weight ratio) and kneaded to obtain a paste, and the thickness is 40 μm to be a current collector. The paste was applied to an Al foil and vacuum dried at 150 ° C. for 8 hours to obtain a positive electrode.
To the obtained positive electrode, 30 of ethylene carbonate (hereinafter sometimes referred to as EC), dimethyl carbonate (hereinafter sometimes referred to as DMC) and ethyl methyl carbonate (hereinafter sometimes referred to as EMC) as electrolytes. : 35:35 (volume ratio) LiPF ₆ dissolved in a mixed solution to 1 mol / liter (hereinafter sometimes referred to as LiPF ₆ / EC + DMC + EMC), a laminated film as a separator, and a negative electrode A coin-type battery (R2032) was manufactured by combining metallic lithium.
Using the above coin-type battery, a charge / discharge test was performed under the conditions shown below while maintaining at 25 ° C. The results are shown in Table 1.

<Charge / discharge test>
Maximum charging voltage 4.3V, charging time 8 hours, charging current 0.176 mA / cm ²
During discharge, the minimum discharge voltage was kept constant at 3.0 V, and discharge was performed by changing the discharge current in each cycle as follows. Higher discharge capacity due to discharge in each cycle means higher output.
First cycle discharge (0.2 C): discharge current 0.176 mA / cm ²
Second cycle discharge (1C): discharge current 0.879 mA / cm ²
3rd cycle discharge (5C): discharge current 4.40 mA / cm ²

  According to the production method of the present invention, a lithium composite metal oxide that can be suitably used as a positive electrode active material of a nonaqueous electrolyte secondary battery is produced even in a firing atmosphere containing carbon dioxide at a concentration higher than the concentration of carbon dioxide in the air. can do. A non-aqueous electrolyte secondary battery using the produced lithium composite metal oxide as a positive electrode active material has excellent charge / discharge characteristics and is extremely useful.

Claims (8)

  A lithium compound, Ni metal or a compound thereof, and a metal composed of one or more transition metal elements selected from the group consisting of Mn and Fe or a compound thereof are mixed, and the obtained raw material mixture is mixed with a carbon dioxide concentration of 1% by volume. A method for producing a lithium composite metal oxide, comprising firing at 630 ° C. or higher in an atmosphere of 15 volume% or less. Dioxide and a lithium compound, a Ni metal or its compound, Mn, T i, by mixing a metal or a compound consisting of one or more transition metal elements selected from the group consisting of Cr and Fe, the obtained raw material mixture A method for producing a lithium composite metal oxide, comprising firing in a gas furnace using a combustion gas flame as a heat source at 630 ° C. or higher in an atmosphere having a carbon concentration of 1% by volume to 15% by volume. Dioxide and a lithium compound, a Ni metal or its compound, Mn, T i, by mixing a metal or a compound consisting of one or more transition metal elements selected from the group consisting of Cr and Fe, the obtained raw material mixture A method for producing a lithium composite metal oxide that is fired at 630 ° C. or higher in an atmosphere having a carbon concentration of 1% by volume to 15% by volume,
The raw material mixture is one or more selected from the group consisting of carbonates, sulfates and chlorides of one or more elements selected from the group consisting of Na, K, Rb, Cs, Ca, Mg, Sr and Ba. A method for producing a lithium composite metal oxide, comprising a reaction accelerator comprising a compound.   The method for producing a lithium composite metal oxide according to claim 3, wherein the transition metal elements are Mn and Fe, and the reaction accelerator is a carbonate.   The method for producing a lithium composite metal oxide according to claim 3 or 4, wherein the raw material mixture is fired in a gas furnace using a flame of combustion gas as a heat source.   The method for producing a lithium composite metal oxide according to any one of claims 1 to 5, wherein an oxygen concentration in the firing is an oxygen concentration of 1 vol% or more and 50 vol% or less.   The method for producing a lithium composite metal oxide according to any one of claims 1 to 6, wherein a firing time at 630 ° C or more is 0.5 hours or more and 24 hours or less.   The method for producing a lithium composite metal oxide according to any one of claims 1 to 7, further comprising a step of holding at a temperature lower than the firing temperature by 30 ° C or higher and at a temperature of 600 ° C or higher.