JP2012201587A - Method for producing lithium transition metal complex oxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a lithium transition metal complex oxide having stabilized quality even in the case of using a gas firing furnace using flame of a hydrocarbon fuel or an oxygen-containing hydrocarbon fuel as a heat source.SOLUTION: The method for producing the lithium transition metal complex oxide comprises firing of a raw material mixture obtained by mixing a lithium compound and a compound containing a transition metal with a gas firing furnace furnished with a plurality of burners blowing flames formed by burning a hydrocarbon and/or oxygen-containing hydrocarbon fuel with a combustion-supporting gas, wherein the multiple burners comprise wall surface burners to blow horizontal flames from the side wall of the gas firing furnace to the inside of the gas firing furnace, and ceiling burners to blow vertical flames from the ceiling of the gas firing furnace to the inside of the gas firing furnace.

Description

  The present invention relates to a method for producing a lithium transition metal composite oxide used for a positive electrode active material of a lithium secondary battery.

  Lithium transition metal composite oxide is used as a positive electrode active material in a positive electrode in a non-aqueous electrolyte secondary battery such as a lithium secondary battery. 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.

  The lithium transition metal composite oxide can be obtained by mixing and firing raw materials such as a lithium compound and a transition metal compound. 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. in an air atmosphere.

  In the method for producing a lithium transition metal composite oxide, there has been a problem that the activity of the positive electrode is reduced due to the presence of carbon dioxide in the atmosphere during firing. In the conventional method for producing a lithium transition metal composite oxide, firing is performed under conditions that contain as little carbon dioxide as possible by using a heating furnace body that can circulate air or control the atmosphere as required, such as an electric furnace. (For example, see Patent Document 2).

  On the other hand, in producing a large amount of lithium transition metal composite oxides, which are rapidly increasing in demand as a positive electrode active material for non-aqueous electrolyte secondary batteries, from the viewpoint of improving the mass productivity of lithium transition metal composite oxides and reducing costs, As a firing furnace for obtaining transition metal composite oxides, it is desired to use a versatile gas firing furnace that uses a flame of a hydrocarbon such as propane or an oxygen-containing hydrocarbon fuel as a heat source. Yes.

However, in a gas firing furnace using a flame as a heat source, it is generally difficult to control the temperature in the furnace as compared to an electric furnace, and the temperature in the furnace tends to be uneven. As a result, when firing in a gas firing furnace, there was a problem that uneven firing of the lithium transition metal composite oxide was likely to occur.
As a result, the quality of the synthesized lithium transition metal composite oxide varies, and when the non-aqueous electrolyte secondary battery is manufactured using the lithium transition metal composite oxide as a positive electrode active material, stable battery performance is obtained. I couldn't.

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

  Under such circumstances, the object of the present invention is to produce a lithium transition metal composite oxide having a stable quality even when a gas firing furnace using a flame of a hydrocarbon or an oxygen-containing hydrocarbon fuel as a heat source is used. Is to provide a method.

  As a result of intensive studies to solve the above problems, the present inventor has 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> A plurality of jets of a flame in which a raw material mixture obtained by mixing a lithium compound and a compound containing a transition metal element is burned with a hydrocarbon and / or an oxygen-containing hydrocarbon fuel and a combustion-supporting gas A method for producing a lithium transition metal composite oxide fired in a gas firing furnace equipped with a burner of
As a plurality of burners, a wall surface burner that ejects a horizontal flame from the side wall of the gas firing furnace into the gas firing furnace, and a vertical flame that ejects from the ceiling of the gas firing furnace into the gas firing furnace A method for producing a lithium transition metal composite oxide comprising a ceiling burner.
<2> The lithium transition according to <1>, wherein the ratio Q ₁ / Q ₂ between the amount of heat Q ₁ supplied by the flame of the wall burner and the amount of heat Q ₂ supplied by the flame of the ceiling burner is 0.01 to 100 A method for producing a metal composite oxide.
<3> The above <1> or <1>, wherein the supply rate of the combustion-supporting gas when forming a flame ejected from the ceiling burner is 1 meter or more per second when the same amount of combustion-supporting gas is supplied at 25 ° C. 2> A method for producing a lithium transition metal composite oxide according to item 2.
<4> The method for producing a transition metal hydroxide according to any one of <1> to <3>, wherein the transition metal element includes one or more elements selected from Ni and Mn.
<5> The transition metal according to any one of <1> to <4>, wherein the transition metal element includes one or more elements selected from Co and Fe in addition to one or more elements selected from Ni and Mn. Method for producing hydroxide.

  According to the present invention, even when a gas firing furnace using a flame of a hydrocarbon or an oxygen-containing hydrocarbon fuel as a heat source is used, a lithium transition metal composite oxide with small variations in quality can be produced with good reproducibility. .

It is a perspective view which shows the gas baking furnace which concerns on embodiment of the manufacturing method of the lithium transition metal complex oxide of this invention. It is a front view which shows the gas baking furnace shown in FIG. 1 in a door open state. It is sectional drawing in the XX line of FIG. It is a perspective view which shows the baking container which accommodates a raw material mixture in a baking process. It is a figure which shows the temperature rising process of the center baking container (saya) and the other baking container (saya) in the gas baking furnace of embodiment of this invention (a broken line is a center sheath and a continuous line shows another sheath). ). It is a figure which shows the temperature rising process of the center baking container (saya) and another baking container (saya) in a normal gas baking furnace (a broken line is a center sheath, and a continuous line shows another sheath).

The present invention ejects a flame in which a raw material mixture obtained by mixing a lithium compound and a compound containing a transition metal element is burned with a hydrocarbon and / or an oxygen-containing hydrocarbon fuel and a combustion-supporting gas. A method for producing a lithium transition metal composite oxide that is fired in a gas firing furnace equipped with a plurality of burners,
As a plurality of burners, a wall surface burner that ejects a horizontal flame from the side wall of the gas firing furnace into the gas firing furnace, and a vertical flame that ejects from the ceiling of the gas firing furnace into the gas firing furnace The present invention relates to a method for producing a lithium transition metal composite oxide including a ceiling burner.

First, the manufacturing method of a raw material mixture is demonstrated.
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. Can do.
Among these, lithium hydroxide or lithium carbonate, which is low in cost and does not generate corrosive gas during heating, is preferably used.

The transition metal element is not particularly limited as long as the compound is mixed with a lithium compound and baked to be a transition metal element that can become a positive electrode active material of a secondary battery. Specific examples of such transition metal elements include Ni, Mn, Co, Fe, Cr, Ti and the like, and these elements may contain one or more of these elements.
Among these, from the viewpoint of obtaining a high-capacity positive electrode for a secondary battery, the transition metal element preferably contains one or more elements selected from Ni and Mn. Furthermore, from the viewpoint of obtaining a higher capacity positive electrode for a secondary battery, in addition to one or more elements selected from Ni and Mn, the transition metal element further includes one or more elements selected from Co and Fe. It is preferable to contain.

  Transition metal elements used as raw materials are in the form of individual metals, oxides, hydroxides, oxyhydroxides, carbonates, sulfates, nitrates, acetates, halides, ammonium salts, and oxalates. And alkoxides.

A raw material mixture obtained by mixing a lithium compound and a compound containing a transition metal element (hereinafter sometimes simply referred to as “raw material mixture”) is a dry-mixing, wet-mixing, liquid-phase mixing, or combination thereof. It may be obtained by any mixing method, and the mixing order is not particularly limited.
In addition, the raw material lithium compound and transition metal compound are not only physically mixed, but also a reaction product obtained by reacting a part of these raw materials after mixing, and the remaining raw materials May be mixed.
In particular, when two or more kinds of transition metal elements are included as raw materials, lithium is synthesized after synthesizing the composite transition metal compound from the viewpoint of enhancing the reactivity during firing and synthesizing a more uniform lithium transition metal complex oxide. It is preferable to mix with a compound.
The method for synthesizing this composite transition metal compound is not particularly limited, but after the coprecipitate slurry obtained by bringing an aqueous solution containing each element into contact with an alkali (liquid phase mixing) is subjected to solid-liquid separation, drying is performed. It is preferable that it is the composite metal hydroxide manufactured by doing.

  Hereinafter, as a typical method for producing the composite transition metal compound, a case where a composite transition metal hydroxide is produced by bringing a solution containing a transition metal element into contact with an alkali will be specifically described.

The solution containing the transition metal element is a simple substance of each transition metal element as a raw material, oxide, hydroxide, oxyhydroxide, carbonate, sulfate, nitrate, acetate, halide, ammonium salt, oxalic acid It can be prepared by dissolving a salt, alkoxide, etc. in a solvent such as water or an organic solvent such as an alcohol that can dissolve these, and water is usually used as the solvent, preferably pure water, ion Exchange water or the like is used.
If the transition metal element alone or compound is difficult to dissolve in the solvent, it may be prepared by dissolving them in a solution containing hydrochloric acid, sulfuric acid, nitric acid, acetic acid or the like.
Among these, an aqueous solution obtained by dissolving a sulfate of a transition metal element, for example, a sulfate of Ni, a sulfate of Mn, a sulfate of Co and a sulfate of Fe, in water is preferable. The Fe sulfate is preferably a divalent Fe sulfate.

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 ( Mention may be made of one or more anhydrides selected from the group consisting of (potassium carbonate) and (NH ₄ ) ₂ CO ₃ (ammonium carbonate) and one or more hydrates.
Ammonia can also be mentioned as an alkali.
Alkali is usually used as an aqueous solution. The concentration of alkali in this alkaline aqueous solution is usually about 0.5 to 10 mol / L, preferably about 1 to 8 mol / L. Further, from the viewpoint of production cost, it is preferable to use an anhydride or hydrate of 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 for the alkaline aqueous solution used as these solvents 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 transition metal hydroxide is obtained by bringing a solution containing a transition metal element into contact with an alkali (liquid phase mixing). The “coprecipitate slurry” is mostly a slurry composed of a coprecipitate made of a transition metal hydroxide and water, and the raw material, by-product salt (for example, remaining in the process of coprecipitate preparation) , KCl, K ₂ SO _4, etc.) additives, organic solvents, etc. may be included, but they may be removed by washing with pure water or organic solvents.
As a method of contact (liquid phase mixing), a method of adding an alkaline aqueous solution to a solution containing a transition metal element and mixing, a method of adding a solution containing a transition metal element to an alkaline aqueous solution and mixing, and a transition metal element The method of mixing the solution containing and aqueous alkali solution can be mentioned. In mixing these, it is preferable to involve stirring. Among the above contact (liquid phase mixing) methods, a method of adding a solution containing a transition metal element to an alkaline aqueous solution and mixing can be preferably used because it is easy to maintain the pH within a certain range. In this case, as the solution containing the transition metal element 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 a solution containing a transition metal element while adjusting the flow rate. Further, when one or both of a solution containing a transition metal element and an aqueous alkali solution are kept in contact with each other while maintaining a temperature of 40 to 80 ° C. (liquid phase mixing), a coprecipitate having a more uniform composition is formed. It is preferable because it tends to be obtained.

Next, the coprecipitate slurry is solid-liquid separated and dried to obtain a dried transition metal hydroxide (hereinafter sometimes simply referred to as “dried product”).
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 150 m ² / g or less. The BET specific surface area of the dried product is preferably 20 m ² / g or more in order to promote the reactivity during firing described later. From the viewpoint of operability, the BET specific surface area of the dried product is preferably 130 m ² / g or less.

Next, in order to produce a raw material mixture, the dried product 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.

Next, the firing step in the production method of the present invention will be described.
In the production method of the present invention, the firing step (hereinafter sometimes simply referred to as “calcination step”) is a plurality of jets of flames in which hydrocarbons and / or oxygen-containing hydrocarbon fuels and combustion-supporting gases are burned. From a side wall of the gas firing furnace and a wall burner that ejects a horizontal flame toward the inside of the gas firing furnace, and a ceiling of the gas firing furnace. And a ceiling burner for ejecting a flame in the vertical direction toward the gas firing furnace.
Examples of the hydrocarbon fuel include methane, ethane, propane, butane, acetylene, and a mixture 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.
Examples of the oxygen-containing hydrocarbon fuel include alcohols such as ethanol and ethers such as diethyl ether.
A mixture of two or more hydrocarbons and oxygen-containing hydrocarbons can be used at any ratio. Various fuel oils including hydrocarbons such as kerosene and oxygen-containing hydrocarbons can also be used.
Among these fuels, liquefied petroleum gas (LPG) is preferable because it has a large amount of heat during combustion and is relatively inexpensive.
Note that the “flammable gas” is a gas having a property of helping a substance burn, and specifically includes air, oxygen, or a mixed gas of these and an inert gas. A gas containing 18% by volume or more of oxygen is suitable as a combustion-supporting gas in the firing step, and air is usually used.

A wall burner is suitable for convection of the furnace gas in the entire furnace, heated by a flame that is jetted horizontally in the furnace. Since the convection effect cannot be greatly exerted up to the center side sheath, particularly when the volume of the heating furnace is increased, temperature distribution tends to occur in the furnace.
Here, in the firing process of the lithium transition metal composite oxide, the firing temperature is usually about 600 to 1000 ° C., but the temperature distribution caused by the flames ejected in the horizontal direction described above is the set temperature of the heating furnace. The higher the value, the more prominent.
On the other hand, the ceiling burner has an advantage that the convection effect is greatly exerted in a narrow range such as between the rows of the sheaths, and the sheath on the center side can be heated.
In the production method of the present invention, by using a gas firing furnace that uses both a wall burner and a ceiling burner, non-uniformity of heat distribution due to insufficient convection between the Saya rows of the wall burner, As an auxiliary burner, it can be supplemented by a ceiling burner, so that the heat uniformity in the furnace is increased. As a result, regardless of the installation position of the raw material mixture in the furnace, a fired product with no variation in quality (lithium transition metal composite oxide) Obtainable.

Here, the ratio of the amount of heat Q ₁ supplied by the flame of the wall burner in the heating furnace to the amount of heat Q ₂ supplied by the flame of the ceiling burner, Q ₁ / Q ₂ is preferably 0.01 to 100, It is more preferable that it is 1-50.
By setting the caloric ratio Q ₁ / Q ₂ in such a range, even if the furnace temperature is 600 ° C. or higher, it is possible to obtain a fired product (lithium transition metal composite oxide) with less variation in quality. .

Further, the supply speed of the combustion-supporting gas when forming a flame ejected from the ceiling burner is preferably 1 meter or more per second when the same amount of combustion-supporting gas is supplied at 25 ° C., and 5 meters per second. More preferably.
By setting the supply speed of the combustion-supporting gas in such a range, a large convection effect of the furnace gas can be obtained, and the temperature distribution in the furnace can be further reduced. The flow rate of the fuel gas is very small compared to the flow rate of the combustion-supporting gas, and is linked to the flow rate of the combustion-supporting gas to set the furnace temperature to the target value. It can be said that the flow rate of the flammable gas is governed by the supply speed.

  Hereinafter, an embodiment of a gas firing furnace suitable for the firing step in the method for producing a lithium transition metal composite oxide according to the present invention will be specifically described with reference to the drawings. In addition, this invention is not limited to what was shown to embodiment which concerns on the gas baking furnace demonstrated below, In the range which does not change the summary of invention, it can change suitably and can implement.

FIG. 1 is a perspective view showing a gas firing furnace according to an embodiment of the method for producing a lithium transition metal composite oxide of the present invention, and FIG. 2 is a front view showing the gas firing furnace shown in FIG. 3 is a cross-sectional view taken along line XX in FIG.
As shown in FIGS. 1 to 3, the gas firing furnace 10 has a total of six wall surfaces that eject horizontal flames HF from the left and right side walls 11 </ b> L and 11 </ b> R of the firing furnace body 11 into the firing furnace body 11. Burners 12a, 12b, 12c, 13a, 13b, 13c, and a total of two ceiling burners 14a, 14b for ejecting a vertical flame VF from the ceiling 11C of the firing furnace body 11 into the firing furnace body 11 I have.

Three side burners 12a, 12b, and 12c are disposed in the depth direction of the firing furnace body 11 (horizontal direction connecting the door 11A and the back wall 11B) in the region near the floor surface 11F of the left side wall 11L of the firing furnace body 11. Are arranged at a predetermined distance along.
The three side burners 13a, 13b, and 13c are arranged at a predetermined distance along the depth direction of the firing furnace body 11 in a region near the ceiling 11c of the right side wall 11R of the firing furnace body 11.
The two ceiling burners 14a and 14b are arranged at a predetermined distance in the left-right width direction (the direction connecting the left and right side walls 11L and 11R) in a region near the center in the depth direction of the ceiling 11C.
Further, a hydrocarbon gas supply facility (not shown) for supplying hydrocarbon fuel and a combustion-supporting gas to the wall surface burners 12a, 12b, 12c, 13a, 13b, and 13c and the ceiling burners 14a and 14b, and a combustion-supporting gas. A supply facility (not shown) is provided.

As the fuel, the above-described hydrocarbons or oxygen-containing hydrocarbons can be used. A suitable fuel is LPG. The LPG may be any gas that is normally used as LPG, and examples thereof include LPG having a volume ratio of butane: propane = 7: 3 as a main component.
Further, as the combustion-supporting gas, a gas containing oxygen is preferable, a gas containing 18% by volume or more of oxygen is preferable, and air is usually used. In addition, in order to increase the oxidizability of the atmosphere, air with an increased oxygen concentration may be used.

  The heating furnace body 1 is formed of a heat-resistant metal such as stainless steel, a heat-resistant ceramic, or the like, and can be heated to about 1500 ° C. The dimensions in the furnace are not particularly limited as long as the temperature distribution is not uniform.

  In addition, although the gas baking furnace 10 which concerns on this embodiment is what is called a batch type, it is not limited to this. For example, a continuous furnace such as a belt furnace, a rotary kiln, or a roller hearth kiln may be used. Moreover, the trolley | bogie furnace which moves the trolley | bogie which laminated | stacked the baking container in the multistage in a furnace, and fires may be sufficient.

  As shown in FIGS. 2 and 3, the raw material mixture (not shown) is heated and fired in the firing furnace body 11 of the gas firing furnace 10 while being contained in a firing container 20 called “saya”. On the floor surface 11F in the firing furnace main body 11, three sets of pedestals 15 capable of holding the firing container 20 at a position higher than the ejection area of the flame HF of the side burners 12a, 12b, and 12c, in the depth direction, in the width direction. Three sets are arranged. These nine sets of mounts 15 are equally arranged on the entire floor surface 11F at equal intervals. In addition, seven firing containers 20 are stacked on each base 15. Further, the firing container 20 at the uppermost position on each pedestal 20 is disposed so as to be positioned lower than the ejection area of the flame HF of the side burners 13a, 13b, 13c and the flame VF of the ceiling burners 14a, 14b. . Furthermore, the firing container 20 on the gantry 15 located at the center in the width direction of the firing furnace body 11 is disposed so as to be located between the ceiling burners 14a and 14b.

  Here, with reference to FIG. 4, the baking container 20 is demonstrated. As shown in FIG. 4, the firing container 20 is a box-like member having a substantially quadrangular shape in plan view and an upper surface opened, and is made of a material: alumina. A cutout portion 20d that is concave toward the bottom portion 20b is provided at the center of the straight portion of the upper edge of the four peripheral walls 20a that are erected so as to surround the bottom portion 20b, and is formed in a portion other than the cutout portion 20d on the upper edge. Is provided with a ridge 20e along its longitudinal direction. The ridges 20e are for preventing corners from hitting and breaking the sheaths when stacking the sheaths.

  Since the peripheral wall 20a is provided with the notches 20d, the air permeability in each baking container 20 can be ensured even when a plurality of baking containers 20 are stacked as shown in FIG.

  As shown in FIGS. 2 and 3, a plurality of firing containers 20 containing a raw material mixture (not shown) are arranged in the firing furnace main body 11 of the gas firing furnace 10, and the side burner is closed with the door 11A closed. When 12a, 12b, 12c, 13a, 13b, 13c and the ceiling burners 14a, 14a are operated, the horizontal burners ejected from the side burners 12a, 12b, 12c, 13a, 13b, 13c into the firing furnace body 11 respectively. The interior of the firing furnace body 11 is evenly heated by the vertical flames VF ejected from the flame HF and the ceiling burners 14a and 14b into the firing furnace body 11 respectively. Thereby, since the raw material mixture (not shown) in the plurality of firing containers 20 arranged in the firing furnace body 11 is heated evenly without being influenced by the placement position in the firing furnace body 11, the quality A fired product (lithium transition metal composite oxide) can be obtained.

  Hereinafter, other conditions in the firing step of the production method of the present invention will be described.

  As described above, in the production method of the present invention, the firing temperature is preferably 650 ° C. or higher, more preferably 750 ° C. or higher, more preferably 830 ° C. or higher, from the viewpoint of promoting the reaction of the raw materials.

  The carbon dioxide concentration in the heating furnace is preferably 4% by volume or less, particularly preferably 3% by volume or less. By setting the carbon dioxide concentration to 3% by volume or less (for example, 2 to 3% by volume), a lithium transition metal composite oxide having higher activity can be obtained.

  The holding time of the raw material mixture in the firing step is usually 0.1 to 20 hours, preferably 0.5 to 8 hours. The rate of temperature rise to the holding temperature is usually 50 ° C. to 400 ° C./hour, and the rate of temperature drop from the holding temperature to room temperature is usually 10 ° C. to 400 ° C./hour.

During the firing, the 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, the 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 KCl. , K ₂ CO ₃ , K ₂ SO ₄ . Two or more reaction accelerators can be used in combination.

When the mixture contains a reaction accelerator, the reactivity during firing of the mixture may be improved, and the BET specific surface area of the obtained lithium transition metal composite oxide may be adjusted.
In order to contain the reaction accelerator in the mixture, for example, the reaction accelerator may be added when the transition metal hydroxide is mixed with the lithium compound.
The mixing ratio of the mixture and the reaction accelerator is preferably from 0.1 to 100 parts by weight, more preferably from 1.0 to 25 parts by weight, in 100 parts by weight of the mixture.

  Further, the lithium transition metal composite oxide is obtained by the firing, and the lithium transition metal composite 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 transition metal composite oxide by grinding. Moreover, you may repeat a grinding | pulverization and baking twice or more. Further, the lithium transition metal composite oxide can be washed or classified as required.

  The lithium transition metal composite oxide obtained by the above method is usually composed of primary particles having an average particle diameter of 0.05 μm or more and 1 μm or less, and is formed by aggregation of primary particles and primary particles of 0.1 μm or more. It consists of a mixture with secondary particles having an average particle size of 100 μm or less. The average particle diameters of the primary particles and the secondary particles can be measured by observing with an SEM (scanning electron microscope).

The lithium transition metal composite oxide obtained by the above-described method 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 from a powder X-ray diffraction pattern obtained by powder X-ray diffraction measurement using CuKα as a radiation source for the lithium transition metal composite oxide.

As the composition of Li in the lithium transition metal composite oxide obtained by the above method, the amount (mol) of Li is usually relative to the total amount (mol) of transition metal elements M such as Ni, Mn, Fe, and Co. 0.5 or more and 1.5 or less, and preferably 0.95 or more and 1.5 or less, more preferably 1.0 or more and 1.4 or less, in order to further increase 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, and x is 0 <x <1.)

  In addition, in the lithium transition metal composite oxide of the present invention obtained by the above method, a part of the transition metal element may be substituted with another element as long as the effects of the present invention are not impaired. 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.

  A compound different from the lithium transition metal composite oxide may be attached to the surface of the particles constituting the lithium transition metal composite oxide obtained by the above method. As such a compound, for example, a compound containing one or more elements selected from the group consisting of B, Al, Ga, In, Si, Ge, Sn, Mg and a transition metal element, preferably B, Al, A compound containing one or more elements selected from the group consisting of Mg, Ga, In, and Sn, more preferably, a compound of Al can be mentioned. Compounds, oxyhydroxides, carbonates, nitrates, and organic acid salts. Preferred are oxides, hydroxides, and oxyhydroxides. Moreover, you may use these compounds in mixture. Among these compounds, a particularly preferred compound is alumina. Moreover, you may heat after adhesion.

  The lithium transition metal composite oxide obtained by the above method is useful as a positive electrode active material, and is suitable for a secondary battery, particularly a positive electrode of a nonaqueous electrolyte secondary battery. The positive electrode active material used for the secondary battery may be composed mainly of the lithium transition metal composite oxide obtained by the above method.

  The positive electrode for the secondary battery is prepared by a known method, for example, the method described in International Publication No. 09/041722, using the lithium transition metal composite oxide obtained by the above method as the positive electrode active material. Can do.

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

<Powder X-ray diffraction measurement>
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 stirring tank, 100 parts by weight of potassium hydroxide was added to 535 parts by weight of distilled water, and potassium hydroxide was completely dissolved by stirring to prepare an aqueous potassium hydroxide solution (alkali aqueous solution).
Further, in another stirring tank, 255 parts by weight of distilled water, 98.4 parts by weight of nickel (II) sulfate hexahydrate, 64.6 parts by weight of manganese (II) sulfate monohydrate, and iron sulfate (II ) 11.1 parts by weight of heptahydrate was added and dissolved by stirring to obtain a nickel-manganese-iron mixed aqueous solution.
Next, after adding 936 parts by weight of distilled water and 15.8 parts by weight of the potassium hydroxide aqueous solution to another stirring tank, the solution was stirred at a liquid temperature of 30 ° C. By dropping 95.1 parts by weight of a nickel-manganese-iron mixed aqueous solution, a precipitate composed of a transition metal hydroxide was generated, and a stock solution slurry was obtained. When the pH at the end of the reaction was measured, the pH was 13.
Subsequently, solid-liquid separation of the slurry obtained by the filter press was performed. For the filter press, a “roll fit filter press dryer” (distributor: Eurotech Co., Ltd.) was used. 100 parts by weight of the slurry was supplied to a filter press and filtered under conditions of room temperature at a filtration pressure of 0.4 MPaG and a filtration time of 50 minutes.
Next, 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 and dewatering was performed at a pressing pressure of 0.7 MPaG for 15 minutes. Next, the pressure inside the filtration chamber of the vacuum filter press was set to 10 kPa, and 90 ° C. hot water was passed through the fluid supply path of each filtration chamber of the filter press, and preliminary drying was performed for 170 minutes. After preliminary drying, 4.62 parts by weight of the wet cake discharged from the filter press was recovered. The water content of the wet cake at this time was 29.5% by weight on a wet basis.
The obtained wet cake is charged into a drying vat, dried using a shelf dryer (general-purpose dryer AT-20 (manufacturer: Asahi Kagaku Co., Ltd.)) at 120 ° C. for 8 hours, and then milled with a feather mill. It was carried out to obtain a powdery dried product X _1. The water content of the obtained dried product X ₁ was 3% by weight.
With respect to the dry matter P ₁ 100 parts by weight, and lithium carbonate 52.2 parts by weight, and 18.0 parts by weight of potassium sulfate were mixed 4 hr at rocking mill containing the alumina balls, to obtain a raw material mixture M _1.

Next, 1.8 kg of the raw material mixture (M ₁ ) is put into a firing container 20 shown in FIG. 4 and fired in a gas firing furnace 10 having a wall burner and a ceiling burner shown in FIGS. went. As shown in FIGS. 2 and 3, the firing container 20 was arranged by stacking seven containers in three rows and three columns. In addition, the dimension in the furnace of the heating furnace main body 11 is length 1.8m x width 1.8m x height 1.6m.
In the arrangement of the baking containers 20 in FIGS. 2 and 3, the fourth baking container 20 in the center row is called a central baking container, and the other baking containers are called outer baking containers.
From the burner wall, the fuel gas LPG (main component butane about 70 vol%, propane about 30 vol%) of total 5~8.5m ³ / h feed, total air combustion supporting gas 420 m ³ / h supplied, the ceiling of the burner, the fuel gas LPG (main component butane about 70 vol%, propane about 30 vol%) and a total 0.84 m ³ / h supplied, total air combustion supporting gas 70m ³ / h was supplied for firing. The firing conditions are a furnace set temperature of 880 ° C. and a holding time of 6 hours.

Further, Q ₁ / Q _2, which is a ratio between the amount of heat Q ₁ supplied by the flame HF of the side burners 12a, 12b, 12c, 13a, 13b, and 13c and the amount of heat Q ₂ supplied by the flame VF of the ceiling burners 14a and 14b. Was 10.3, and the supply rate of the combustion-supporting gas forming the flame VF ejected from the ceiling burners 14a and 14b was 8 meters per second at a rate measured at 25 ° C.

FIG. 5 shows the temperature raising process of the central firing container (saya) and the outer firing container (saya) when the temperature of the gas firing furnace 10 is raised under the above conditions.
As shown in FIG. 5, the powder charged in the central baking container was heated without any particular delay as compared with the powder charged in the outer baking container.

After firing the raw material mixture under the above conditions, it was naturally cooled to room temperature to obtain a fired product. Then, beating baked product, it was washed by nutsche filtration with pure water, after filtration, and dried 6 hours at 300 ° C., to obtain a powder B _1.
BET specific surface area of the powder B ₁ represents, 9.3m ² / g, was outside the sheath 9.3 m ² / g in sheath of the center. 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.

(Comparative Example 1)
The raw material mixture (M ₁ ) produced in Example 1 was placed in an alumina firing vessel in the same manner as in Example 1 by 1.8 kg, and placed in an ordinary gas firing furnace (manufactured by Takasago Industry Co., Ltd.) equipped with only a horizontal burner. Was fired. The structure of the furnace is a state in which the ceiling burners 14a and 14b in FIGS. 1 to 3 are removed. The firing conditions are a furnace set temperature of 880 ° C. and a holding time of 6 hours.

FIG. 6 shows the temperature rising process of the central firing container (saya) and the outer firing container (saya) when the temperature is raised in a normal gas firing furnace under the above conditions.
As shown in FIG. 6, the temperature at the central sheath was raised with a special delay compared to the outer sheath.

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.
BET specific surface area of the powder B ₂ is the center 9.0 m ² / g at a firing container was 9.2m at ² / g on the outside of the firing vessel. 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.

<Preparation of nonaqueous electrolyte secondary battery>
A coin-type nonaqueous electrolyte secondary battery using the produced powders B ₁ and B ₂ as a positive electrode active material was produced, and a charge / discharge test was performed.
N-methyl-2-pyrrolidone (hereinafter referred to as NMP) of PVdF as a binder to a mixture of a positive electrode active material (powder B ₁ , B ₂ ) and a conductive material (a mixture of acetylene black and graphite at 9: 1). The solution is added to the composition of active material: conductive material: binder = 87: 10: 3 (weight ratio) and kneaded to form a paste, which is used as a current collector for an Al foil having a thickness of 40 μm. The paste was applied and vacuum dried at 150 ° C. for 8 hours to obtain a positive electrode.
To the obtained positive electrode, a 30:35:35 (volume ratio) mixed solution of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) as an electrolytic solution was LiPF ₆ at 1 mol / liter. (LiPF ₆ / EC + DMC + EMC), a laminated film as a separator, and metal lithium as a negative electrode were combined to produce a coin-type battery (R2032).
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 2.5 V, and the discharge current in each cycle was changed as follows to perform discharge. 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 (2C): discharge current 1.76 mA / cm ²
Discharge at the fourth cycle (5C): discharge current 4.40 mA / cm ²

  As can be seen from Table 1, in Example 1 using the gas firing furnace 10 according to the embodiment of the present invention, the battery according to the position of the firing container (sheath) than in Comparative Example 1 using a normal gas firing furnace. As a result, the performance distribution was small, and a uniform product was obtained.

  INDUSTRIAL APPLICABILITY The present invention can be widely used as a technique for producing a lithium transition metal composite oxide used for a positive electrode active material of a lithium secondary battery.

DESCRIPTION OF SYMBOLS 10 Gas firing furnace 11 Firing furnace main body 11A Door 11B Back wall 11C Ceiling 11F Floor surface 11L, 11R Side wall 12a, 12b, 12c, 13a, 13b, 13c Side burner 14a, 14b Ceiling burner 15 Base 20 Firing container 20a Perimeter wall 20b Bottom 20d Notch 20e ridge

Claims (5)

A plurality of burners for injecting a flame in which a raw material mixture obtained by mixing a lithium compound and a compound containing a transition metal element is burned with a hydrocarbon and / or an oxygen-containing hydrocarbon fuel and a combustion-supporting gas. A method for producing a lithium transition metal composite oxide fired in a gas firing furnace provided,
As the plurality of burners, a wall surface burner for ejecting a horizontal flame from the side wall of the gas firing furnace into the gas firing furnace, and a vertical direction from the ceiling of the gas firing furnace into the gas firing furnace A method for producing a lithium transition metal composite oxide comprising a ceiling burner for ejecting a flame. _2. The lithium transition metal composite according to claim 1, wherein Q ₁ / Q ₂ , which is a ratio of the amount of heat Q ₁ supplied by the flame of the wall burner and the amount of heat Q ₂ supplied by the flame of the ceiling burner, is 0.01-100. Production method of oxide.   3. The lithium transition according to claim 1, wherein a supply speed of the combustion-supporting gas when forming a flame ejected from the ceiling burner is 1 meter or more per second when the same amount of combustion-supporting gas is supplied at 25 ° C. 3. A method for producing a metal composite oxide.   The method for producing a transition metal hydroxide according to any one of claims 1 to 3, wherein the transition metal element contains one or more elements selected from Ni and Mn.   The method for producing a transition metal hydroxide according to any one of claims 1 to 4, wherein the transition metal element contains one or more elements selected from Co and Fe in addition to one or more elements selected from Ni and Mn. .