JP2012087039A - Method for producing transition metal hydroxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a transition metal hydroxide which is a precursor of a positive electrode active material of a secondary battery at high productivity.SOLUTION: This production method includes following steps (1), (2) and (3); step (1): a step of obtaining stock solution slurry containing a precipitate component that contains a transition metal hydroxide as a main component by bringing a solution containing a transition metal element into contact with alkali; step (2): a step of obtaining concentrated slurry by concentrating the precipitate component in the slurry by cross-flow filtration; and step (3): a step of direct drying of the concentrated slurry. According to the production method, since the concentrated slurry containing the transition metal hydroxide is obtained by the cross-flow filtration and direct drying, the transition metal hydroxide can be produced as a dry product with little impurity without passing through wet cake, and the transition metal hydroxide which is suitable as a raw material of a secondary battery positive electrode material can be produced at high productivity.

Description

  The present invention relates to a method for producing a transition metal hydroxide.

  Lithium composite metal oxide is used as a positive electrode active material contained in a positive electrode constituting a 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.

  As a method for producing a lithium composite metal oxide, as disclosed in Patent Document 1, a solution containing a transition metal element such as Ni or Mn is brought into contact with an alkali to have a transition metal hydroxide as a main component. A solid solution slurry containing solid content is obtained, and the obtained stock solution slurry is solid-liquid separated by filtration to obtain a transition metal hydroxide wet cake, and the wet cake is dried to obtain a dried product composed of a transition metal hydroxide. A method is known in which a dried product obtained is mixed with a lithium compound and fired.

International Publication No. 09/041722 Pamphlet

  In the above-mentioned production method, the solid content of the transition metal hydroxide in the stock slurry obtained by bringing the transition metal element-containing solution into contact with alkali is fine, so depending on the filtration method, the filter medium may be clogged by the solid content. There is a problem that it is easy to cause.

Further, the wet cake obtained by filtration contains impurities such as the raw material remaining in the step of obtaining the raw material slurry. If this impurity remains in the dried product obtained after drying the wet cake, a by-product is generated when the mixture of the dried product and the lithium compound is baked, causing the quality deterioration of the lithium composite metal oxide. Become. For this reason, impurities are usually removed by washing such as passing the washing liquid through the wet cake or dispersing the wet cake in the washing liquid and filtering again before drying the wet cake. In order to sufficiently reduce the concentration of impurities in the cake, multiple washings are required.
In general, wet cake has a relatively high viscosity, so it easily adheres to a filtration device and a drying device, and operation troubles such as blockage of piping are likely to occur.

  As described above, a conventional method for producing a transition metal hydroxide having a step of obtaining a wet cake and drying the obtained wet cake has not necessarily been suitable for mass production. Under such circumstances, an object of the present invention is to produce a transition metal hydroxide in a method for producing a transition metal hydroxide, which can efficiently recover the transition metal hydroxide contained in the raw slurry, and is a high quality dried transition metal hydroxide. It is to provide a method that can be obtained.

  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 method for producing a transition metal hydroxide comprising the following steps (1), (2) and (3).
Step (1) Step (2) for obtaining a stock solution slurry containing a solid content mainly composed of a transition metal hydroxide by bringing a solution containing a transition metal element into contact with an alkali. The slurry is obtained by performing cross-flow filtration. Step (3) of concentrating solid content to obtain concentrated slurry Step of directly drying said concentrated slurry <2> In step (2) of obtaining concentrated slurry, washing of solid content in stock solution slurry or concentrated slurry The method for producing a transition metal hydroxide according to <1>, wherein the step is performed.
<3> The process for producing a transition metal hydroxide according to <1> or <2>, wherein the concentrated slurry is dried with hot air in the step (3) of directly drying the concentrated slurry.
<4> The method for producing a transition metal hydroxide according to any one of <1> to <3>, wherein the solid content concentration of the concentrated slurry is 3% by weight or more.
<5> The method for producing a transition metal hydroxide according to any one of <1> to <4>, wherein the transition metal element is one or more elements selected from the group consisting of Ni and Mn.
<6> The above-described <1> to <4>, wherein the transition metal element is one or more elements selected from the group consisting of Ni and Mn and one or more elements selected from the group consisting of Co and Fe Of producing a transition metal hydroxide.
<7> A lithium composite metal oxide obtained by obtaining a transition metal hydroxide by the production method according to any one of <1> to <6>, mixing the obtained transition metal hydroxide with a lithium compound, and firing the mixture. Manufacturing method.

<8> The cross flow filtration in the step (2) is performed while forcibly generating a shearing force in the vicinity of the surface of the filter medium while peeling off the solid content layer formed on the filter medium surface. Of producing a lithium composite metal oxide.
<9> The method for producing a transition metal hydroxide according to <8>, wherein in step (2), the vicinity of the surface of the filter medium is agitated to forcibly generate a shearing force in the vicinity of the surface of the filter medium.
<10> The method for producing a transition metal hydroxide according to <8> or <9>, wherein the stock solution slurry or the concentrated slurry is washed in the step (2).
<11> The method for producing a transition metal hydroxide according to any one of <8> to <10>, wherein the concentrated slurry is dried with hot air in the step (3).
<12> The method for producing a transition metal hydroxide according to any one of <8> to <11>, wherein the solid content concentration in the concentrated slurry is 3% by weight or more.
<13> Production of transition metal hydroxide according to any one of <8> to <12>, wherein the transition metal element in step (1) is one or more elements selected from the group consisting of Ni and Mn. Method.
<14> From <8> to <12, wherein the transition metal element in step (1) is one or more elements selected from the group consisting of Ni and Mn and one or more elements selected from the group consisting of Co and Fe. The manufacturing method of the transition metal hydroxide in any one of>.
<15> A lithium composite metal oxide obtained by obtaining a transition metal hydroxide by the production method according to any one of <8> to <14>, mixing the obtained transition metal hydroxide with a lithium compound, and firing the mixture. Manufacturing method.

  According to the present invention, a concentrated slurry containing a transition metal hydroxide is obtained by cross-flow filtration, and this is directly dried, so that the transition metal hydroxide can be produced as a dry product with less impurities without going through a wet cake. it can. For this reason, it becomes possible to manufacture the transition metal hydroxide suitable as a raw material of the secondary battery positive electrode material with high productivity.

It is a conceptual diagram of crossflow filtration. It is the schematic of the crossflow filtration apparatus which concerns on the manufacturing method of this invention. It is the schematic of the crossflow filtration system which concerns on the manufacturing method of this invention. It is a schematic diagram of the crossflow filtration system which concerns on Example 1 of this invention.

The present invention is a method for producing a transition metal hydroxide comprising the following steps (1), (2) and (3).
Step (1): A stock solution slurry containing a solid content mainly composed of a transition metal hydroxide (hereinafter sometimes referred to as “precipitate slurry”) by bringing a solution containing a transition metal element into contact with an alkali. Step (2) of obtaining: Step of obtaining a concentrated slurry by concentrating solids in the slurry by cross-flow filtration (3): Step of directly drying the concentrated slurry

[Step (1)]
In the production method of the present invention, as the transition metal element constituting the solution containing the transition metal element, the hydroxide can be mixed with a lithium compound and baked to become a positive electrode active material of a secondary battery. For example, Ni, Mn, Co, Fe, Cr, Ti, etc. can be mentioned.
From the viewpoint of obtaining a high-capacity positive electrode for a secondary battery, the solution preferably contains one or more elements selected from the group consisting of Ni and Mn. Furthermore, from the viewpoint of obtaining a positive electrode for a secondary battery having a higher capacity, in addition to one or more elements selected from the group consisting of Ni and Mn, one or more elements selected from the group consisting of Co and Fe are further added. It is preferable to contain.

Examples of the above solutions include simple metals, oxides, hydroxides, oxyhydroxides, carbonates, sulfates, nitrates, acetates, halides, ammonium salts, oxalates, alkoxides, and the like of the respective transition metal elements. Can be prepared by dissolving it in a solvent such as water or an organic solvent such as an alcohol capable of dissolving these, and water is usually used as the solvent, preferably pure water, ion-exchanged water or the like. 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 them, an aqueous solution obtained by dissolving a chloride of a transition metal element, for example, a chloride of Ni, a chloride of Mn, a chloride of Co and a chloride of Fe, 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 ( 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. Moreover, 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 NaOH and KOH anhydrides and hydrates thereof 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 stock solution slurry containing a transition metal hydroxide is obtained by bringing a solution containing a transition metal element into contact with an alkali. In addition, the undiluted | stock solution slurry obtained here is a slurry which consists mostly of solid content which consists of transition metal hydroxide, and solvents, such as water, The unreacted raw material, by-product, which remained in the process of obtaining undiluted | stock solution slurry, Additives, organic solvents and the like may be included.
As a method of bringing a solution containing a transition metal element into contact with an alkali, a method of adding an alkaline aqueous solution to a solution containing a transition metal element and mixing, and adding and mixing a solution containing a transition metal element into an alkaline aqueous solution Examples thereof include a method in which a solution containing a transition metal element and an aqueous alkali solution are added to a solvent such as water and mixed. In mixing these, it is preferable to involve stirring. In addition, among the above contact methods, the method of using water as a solvent and adding an aqueous solution containing a transition metal element to an alkaline aqueous solution and mixing is preferably used because it is easy to maintain the pH within a certain range. it can. In this case, as the aqueous 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 good to add the aqueous solution containing a transition metal element, adjusting so that. Further, when one or both of the aqueous solution containing the transition metal element and the alkaline aqueous solution are kept in contact at a temperature of 40 to 80 ° C., a slurry containing a solid content with a more uniform composition is obtained. This is preferable.

[Step (2)]
Next, step (2) will be described.
In the step (2), the concentrated slurry is obtained by concentrating the precipitate component contained as a solid content in the stock slurry obtained in the step (1) by cross-flow filtration. The precipitate component is a solid content contained in the stock slurry, and is a solid content mainly composed of a transition metal hydroxide. The “concentrated slurry” is a slurry having a solid content higher than that of the stock solution slurry by removing a part of the solvent component constituting the stock solution slurry obtained in the step (1).

FIG. 1 shows a conceptual diagram of cross flow filtration. Cross-flow filtration uses a cylindrical membrane filter, supplies the stock slurry containing solids as the filtration target liquid to the inside of the membrane filter, collects the filtrate that has passed through the membrane filter from the outer surface of the membrane filter, It is the filtration method which concentrates solid content in a stock solution slurry. In the conceptual diagram shown in FIG. 1, the membrane filter is used in a fixed manner.
In the production method of the present invention, the stock solution slurry obtained in the step (1) is used as the liquid to be filtered, and the solid content of the stock solution slurry is concentrated by cross-flow filtration. Specifically, by supplying the stock solution slurry to the inside of the membrane filter and discharging the solvent contained in the stock solution slurry as a filtrate to the outside of the membrane filter, other than transition metal hydroxide which is a solid content in the stock solution slurry While removing the impurities together with the solvent component, the transition metal hydroxide is concentrated to obtain a concentrated slurry.
Examples of impurities contained in the stock slurry include unreacted materials, by-products, additives, and organic solvents in the step (1) for obtaining the stock slurry.

  In cross-flow filtration, filtration is performed while flowing the stock solution slurry parallel to the inner wall of the filter. The shearing force of the slurry flowing parallel to the inner wall of the filter suppresses the solid content from accumulating as a cake layer, which prevents clogging even when the stock slurry contains a relatively high concentration of solid content. There are advantages. In addition, stable filtration can be performed for a long time even if the solid content concentration of the stock solution slurry varies.

  The solid content concentration of the concentrated slurry is preferably 3% by weight or more, and more preferably 10% by weight or more from the viewpoint of improving the efficiency of the drying step, which is a subsequent step. When the solid content concentration of the concentrated slurry is less than 3% by weight, the heat load during drying increases and drying may be insufficient.

  As a membrane filter used for crossflow filtration, a known fixed cylindrical membrane filter having a pore size of the filter smaller than the solid particle size contained in the stock slurry is used. As such a filter, either a ceramic membrane filter or an organic membrane filter can be used, but a ceramic membrane filter excellent in corrosion resistance, heat resistance and durability is preferably used. As the ceramic membrane filter, a ceramic raw material powder made of alumina, silica, zirconia or the like and using a known molding and sintering technique can be used.

The conditions for cross-flow filtration are appropriately determined under conditions that allow the intended concentrated slurry to be obtained. Specifically, the slurry flow rate (linear velocity) is 1 to 5 m / s (preferably 2 to 4 m / s), and the slurry supply pressure (gauge pressure) is 0.1 to 0.5 MPaG (preferably 0). .2 to 0.4 MPaG). The filtration temperature is preferably high as long as it does not affect the filter material.

Moreover, in order to further reduce impurities contained in the solid content in the concentrated slurry, it is preferable to wash the solid content in the stock slurry or the concentrated slurry.
In order to wash the solid content in the stock solution slurry, the washing solution may be added to the stock solution slurry and then applied to the step (2). The stock solution slurry to which the cleaning liquid is added is subjected to solid content cleaning simultaneously with the concentration by the cross-flow filtration in the step (2).
In the step (2), the solid content in the concentrated slurry is washed by cross-flow filtration to remove a part of the solvent component from the stock solution slurry to obtain a concentrated slurry. This can be done by cross-flow filtration. In order to further reduce the concentration of impurities in the concentrated slurry, the washing is preferably performed repeatedly.
As the cleaning liquid, the same solvent as that used when forming the stock solution slurry is usually used, but the cleaning liquid is not limited to this, and any cleaning liquid can be used as long as it can be removed in a subsequent drying step. Specific examples include water and alcohols such as ethanol.

  The cross-flow filtration in the step (2) is preferably performed while forcibly generating a shear force in the vicinity of the surface of the filter medium and peeling the solid content layer formed on the filter medium surface.

  By forcibly generating a shearing force in the vicinity of the surface of the filter medium, it is possible to avoid peeling and excessive deposition of a solid content layer (cake layer) formed on the surface of the filter medium. Therefore, even when the concentration of the solid content in the slurry is high, such as when obtaining a concentrated slurry having a high concentration, it is possible to avoid the cake layer from being deposited to a certain thickness or more on the surface of the filter medium, and clogging is less likely to occur. High filtration efficiency can be maintained.

  As a method for forcibly generating a shearing force in the vicinity of the surface of the filter medium, (a) a method of forcibly stirring the slurry in the vicinity of the surface of the filter medium by a stirring means with respect to a fixed filter medium, or (b) rotating the filter medium itself Although there is a method of moving the filter medium itself, for example, the method shown in (a) above is usually employed.

Hereinafter, a preferred embodiment of the step (2) will be described with reference to the drawings.
FIG. 2 is a schematic view of a crossflow filtration apparatus according to the production method of the present invention, and FIG. 3 shows a filtration system using the filtration apparatus.

2 includes a filtration chamber 2, a plurality of filtration plates 3 arranged at predetermined intervals in the filtration chamber 2, and a plurality of stirring plates 4 arranged adjacent to the filtration plate. And an electric motor 5 which is a drive mechanism for rotating the plurality of stirring plates 4.
As shown in FIG. 2, the filtration chamber 2 has a substantially cylindrical pressure-resistant structure, and is provided with a slurry supply port 6 to which the stock solution slurry is supplied on one end side in the axial direction, and concentrated after filtration on the other end side. A slurry discharge port 7 for discharging the slurry is provided.

The filter plate 3 has a filter cloth pasted on both surfaces of a plate provided with a filtrate discharge groove, and functions as a filter medium.
The filter cloth has an air permeability that prevents particles from leaking through the filter cloth depending on the particle size of the solid content in the slurry, specifically 1 mL / cm ² / min or less, preferably 0.3 mL. A filter cloth having an air permeability of not more than / cm ² / min is used.

The filtration plate 3 is arranged at a predetermined interval along the axial direction of the filtration chamber 2, and the inside of the filtration chamber 2 is divided into a plurality of spaces by the arranged filtration plate 3. The outlet of the filtrate discharge groove in the filter plate 3 communicates with the wall surface of the filtration chamber 2, and the filtrate can be discharged to the outside of the filtration chamber 2 from the outlet.
The stirring plate 4 is attached to the rotating shaft 4a so as to be alternately arranged with the filtration plate 3. The rotating shaft 4a is connected to a motor 5 provided with a torque control device 5a. When the motor 5 rotates, the stirring plate 4 attached to the rotating shaft 4a rotates, and the slurry in the vicinity of the filter plate 3 is stirred. can do.

FIG. 3 is a schematic view of a filtration system 10 including the crossflow filtration device 1.
As shown in FIG. 3, the filtration system 10 includes a crossflow filtration device 1, a slurry tank 11, a liquid feed pump 12, and a washing water supply facility 13 as main parts.

The slurry tank 11 is a tank for storing slurry. The slurry tank 11 is provided with a stirring device 11a including a stirring blade and a motor, and the slurry in the tank can be stirred as necessary.
The slurry tank 11 is connected to the slurry supply port 6 and the slurry discharge port 7 of the crossflow filtration device 1 via pipes P ₁ and P ₂ , respectively.
In the pipe P ₁ , a liquid feed pump 12 for pressure-feeding the slurry from the slurry tank 11 to the cross flow filtration device 1 is installed. Further, a slurry discharge valve 8 for controlling the discharge amount of the concentrated slurry from the cross flow filtration device 1 is provided in the vicinity of the slurry discharge port 7 in the pipe P ₂ .
In addition, the crossflow filtration apparatus 1 and the slurry tank 11 may be of an open type or a sealed type. If the type is a sealed type, the inside thereof is replaced with an inert gas. May be.

An operation method of the filtration system 10 having the above configuration will be described.
First, the stock solution slurry is stored in the slurry tank 11, and the stock solution slurry is pressurized and supplied to the filtration chamber 2 of the crossflow filtration device 1 through the pipe P ₁ by the feed pump 12.
The pressurized stock solution slurry moves from one end side (slurry supply port 6 side) of the filtration chamber 2 toward the other end side (slurry discharge port 7 side), and passes through the space separated by the filter plate 3. pass. The stock slurry is filtered and dehydrated by the filter plate 3 when passing through the space partitioned by the filter plate 3, and the solid content concentration in the slurry gradually increases toward the other end side.
The agitation plate 4 between the filtration plates 3 is always rotating during filtration, agitates the supplied slurry, forcibly generates a shearing force near the surface of the filtration plate 3, and the surface of the filtration plate 3. The cake layer formed in the step is peeled off. In addition, by controlling the rotational speed of the stirring plate 4, by controlling the deposition rate of the solid content in the slurry and the removal rate, the thickness of the cake layer generated on the surface of the filter plate 3 is made constant, Filtration resistance can be made constant.

The slurry (concentrated slurry) having reached the other end side and having a high solid content concentration is discharged from the slurry discharge port 7 and collected in the slurry tank 11.
As shown in FIG. 2, the motor 5 that is the drive device of the stirring plate 4 is controlled by the torque control device 5a, and the torque control device 5a operates in conjunction with the slurry discharge valve 8 that is an automatic valve. be able to. The solid content concentration of the slurry in the filtration chamber 2 is detected as a stirring torque, and the concentrated slurry whose concentration is controlled can be continuously discharged by controlling the slurry discharge valve 8. The solid content concentration of the concentrated slurry can be arbitrarily adjusted as long as the fluidity of the concentrated slurry is maintained.

  In addition, in the manufacturing method of this invention, the dried product of a transition metal hydroxide can be obtained continuously by supplying the concentrated slurry obtained in the step (2) sequentially to the drying step of the step (3). However, the solid content concentration in the concentrated slurry is preferably 3% by weight or more, and more preferably 10% by weight or more from the viewpoint of improving the efficiency of the drying step, which is a subsequent step. When the solid content concentration in the concentrated slurry is less than 3% by weight, the heat load during drying becomes large, and drying may be insufficient.

The concentrated slurry recovered in the slurry tank 11 may contain unreacted substances, by-products, additives, organic solvents, and the like in the process of obtaining the stock solution slurry as impurities other than the transition metal hydroxide.
When there are many such impurities, it is preferable to wash the concentrated slurry.
As the cleaning liquid, the same solvent as that used when forming the stock solution slurry is usually used, but the cleaning liquid is not limited to this, and any cleaning liquid can be used as long as it can be removed in a subsequent drying step. Specific examples include water and alcohols such as ethanol.
Specifically, the cleaning liquid is supplied from the cleaning water supply equipment 13 to dilute the slurry, and all or a part of the diluted slurry is supplied again to the crossflow filtration device 1 and filtered. By filtering the diluted slurry again, impurities are discharged together with the filtrate to reduce the impurity concentration in the slurry. In this way, the slurry is circulated between the cross-flow filtration device 1 and the slurry tank 11, and washing and concentration are repeated until the required concentrated slurry has a predetermined solid content concentration and a predetermined impurity concentration.

In addition, the structure of the crossflow filtration apparatus used by this invention is not restricted to the structure of this example. For example, the filter plate 3 may be configured to be rotationally driven, whereby the slurry in the filtration chamber may be stirred. The slurry tank may be divided into a raw water slurry dedicated tank and a concentrated slurry dedicated tank.
In addition, the filtration conditions only need to be able to obtain the target concentrated slurry, and are appropriately determined in consideration of the solid content concentration in the concentrated slurry, the configuration of the crossflow filtration device, and the like. Specific conditions are illustrated below, but are not limited to these conditions.
The filtration pressure (slurry supply pressure) is usually about 0.2 to 0.4 MPaG (gauge pressure). The higher the filtration pressure, the faster the filtration rate. However, if the filtration pressure is too high, the cake layer may be consolidated depending on the properties of the cake, and the filterability may deteriorate.
Moreover, the rotational speed of the stirring plate 4 is about 5-12 m / s at the peripheral speed at the time of steady operation. If the rotation speed is too low, the peeling effect of the cake layer deposited on the filter medium becomes insufficient, and the filtration speed decreases. Further, if the rotational speed is too high, the load is overloaded, and the slurry may leak from the seal portion of the apparatus.
Moreover, filtration temperature is about 15-50 degreeC normally. If the temperature is too low, the viscosity of the slurry becomes too high and the filtration rate may be insufficient. Moreover, if the temperature is too high, the transition metal hydroxide contained in the slurry may be altered, which may cause quality deterioration when the lithium composite metal oxide is obtained.

  In the production method of the present invention, the concentrated slurry obtained by the cross-flow filtration in the step (2) is sequentially supplied to the subsequent step (3) to continuously obtain a dried transition metal hydroxide. be able to.

[Step (3)]
Next, step (3) will be described.
Step (3) is a step of directly drying the concentrated slurry.
Here, “direct drying” means that the concentrated slurry is dried without undergoing a dehydration operation such as total filtration or centrifugation.
Examples of methods for directly drying the slurry include band drying, rotary drying, infrared drying, and far infrared drying, but the hot air drying method using a heated airflow (hot air) as a heat source can dry the slurry in a short time. preferable.
Moreover, when drying by hot air drying, the higher the temperature of the hot air, the higher the drying ability. However, if the temperature is too high, the quality of the dried product may be lowered.

By directly drying the concentrated slurry, a dried transition metal hydroxide can be obtained. 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 at the time of direct drying. 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.

[Production of lithium composite metal oxides]
A lithium composite metal oxide can be obtained by a method in which the dried transition metal hydroxide obtained by the production method of the present invention described above is mixed with a lithium compound and baked.
Examples of the lithium compound include one or more anhydrides selected from the group consisting of lithium hydroxide, lithium chloride, lithium nitrate, and lithium carbonate, and one or more hydrates thereof. The mixing may be 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.

The BET specific surface area of the obtained lithium composite metal oxide can be adjusted by the holding temperature when the dried product is mixed with the lithium compound and then fired. Usually, the higher the holding temperature, the smaller the BET specific surface area tends to be. The BET specific surface area tends to increase as the holding temperature is lowered.
The holding temperature is preferably in the range of 650 ° C. or higher and 900 ° C. or lower. The holding time at the holding temperature 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. As the firing atmosphere, air, oxygen, nitrogen, argon, or a mixed gas thereof can be used, but an air atmosphere is preferable.

In the firing, the mixture obtained by mixing the dried product with the lithium compound 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 Can be mentioned. Among these, the chloride, carbonate and sulfate of at least one element selected from the group consisting of Na, K, Rb, Cs, Ca, Mg, Sr and Ba can be mentioned, and more preferably KCl. , K ₂ CO ₃ , K ₂ SO ₄ . Moreover, a reaction accelerator may be used independently, respectively, and 2 or more types can also be used together.
When the mixture contains a reaction accelerator, it may be possible to improve the reactivity during firing of the mixture and adjust the BET specific surface area of the obtained lithium composite metal oxide.
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.
Further, the reaction accelerator may remain in the fired lithium composite metal oxide or may be removed by washing, evaporation or the like.
When a reaction accelerator is used, the mixing ratio of the mixture and the reaction accelerator is usually preferably 0.1 part by weight or more and 100 parts by weight or less in 100 parts by weight of the mixture, and 1.0 part by weight or more and 25 parts by weight or less. The following is more preferable.

  The lithium composite metal oxide obtained by firing may be pulverized using a ball mill or a jet mill. 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 above method becomes a positive electrode active material useful for secondary batteries, particularly nonaqueous electrolyte secondary batteries.

  The lithium composite metal 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 agglomeration of primary particles and primary particles of 0.1 μm or more and 100 μm. It consists of a mixture with secondary particles of the following average particle size. The average particle diameters of the primary particles and the secondary particles can be measured by observing with an SEM (scanning electron microscope).

The structure of the lithium composite metal oxide obtained by the above method is usually 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 obtained by the above method, the amount (mol) of Li is usually 0 with respect to the total amount (mol) of transition metal elements 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 the lithium composite metal oxide is represented 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. It is 1.4 or less.
Li _y (Ni _1-x M _x ) O ₂ (A)
(Here, M represents one or more transition metal elements, and x represents a number satisfying 0 <x <1.)

  In addition, in the lithium composite metal oxide of the present invention obtained by the above method, a part of the transition metal element may be substituted with another element 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.

  A compound different from the lithium composite metal oxide may be attached to the surface of the particles constituting the lithium composite metal 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 composite metal oxide obtained by the above method is useful as a positive electrode active material, and is suitable for a secondary battery, particularly a nonaqueous electrolyte secondary battery, particularly a lithium secondary battery positive electrode. The positive electrode active material used for the secondary battery may be composed mainly of the lithium composite metal oxide obtained by the above method.

  The positive electrode for a secondary battery can be produced by a known method, for example, the method described in WO 09/041722 using the lithium composite metal oxide obtained by the above method as a positive electrode active material. it can.

  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.

Example 1
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 dropping 100 parts by weight of the nickel-manganese-iron mixed aqueous solution, a precipitate was generated to obtain a precipitate slurry (stock slurry). When the pH at the end of the reaction was measured, the pH was 13.
Subsequently, it filtered and dried with the crossflow filtration and drying system shown in FIG.
100 parts by weight of the precipitate slurry obtained above is charged into the slurry storage tank A1 of the cross flow filtration system shown in FIG. 4, and the charged slurry is filtered with a pump (not shown) to filter A2 (ceramic membrane filter manufactured by NGK Corporation). 61 parts by weight of the filtrate was extracted and concentrated while performing pump circulation at room temperature via the (Cefilt UF membrane pore diameter 100 mm)). The operating conditions at this time were such that the filter inlet pressure was 0.3 MPaG (gauge pressure), the filter outlet pressure was 0.2 to 0.25 MPaG (gauge pressure), and the linear velocity of the slurry in the filter was 4 m / s.
Next, 61 parts by weight of distilled water was added to the slurry storage tank A1 to dilute the slurry, followed by filtration under the same conditions as the previous concentration. Similarly, the operation of adding distilled water and filtering was repeated. At this time, the solid content concentration in the slurry obtained in the slurry storage tank A1 was 10% by weight.
The concentrated slurry was directly dried with hot air at 120 ° C. in a shelf-type hot air dryer A3 to obtain a dried product.
100 parts by weight of the dried product, 52.1 parts by weight of lithium carbonate, and 14.3 parts by weight of potassium carbonate (reaction accelerator) were dry-mixed using a ball mill to obtain a mixture. Next, the mixture is put in an alumina firing container, and is fired by holding it in the atmosphere at 870 ° C. for 6 hours using an electric furnace, cooling to room temperature, obtaining a fired product, and obtaining the fired product. The powder was pulverized, filtered and washed with distilled water, and dried at 300 ° C. for 6 hours to obtain a powder.
The crystal structure of this powder was a crystal structure belonging to the R-3m space group.

(Example 2)
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 (alkali 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, 215 parts by weight of distilled water and 24.7 parts by weight of the aqueous potassium hydroxide solution were charged in another stirring tank, and then the aqueous solution of potassium hydroxide was 165 parts by weight while stirring at a liquid temperature of 30 ° C. By dropping 100 parts by weight of the nickel-manganese-iron mixed aqueous solution, a coprecipitate (solid content) was generated, and a stock slurry was obtained. When the pH (hydrogen ion concentration) at the end of the reaction was measured, the pH was 13.
Next, the slurry was concentrated using the filtration system having the configuration shown in FIG. In addition, as the crossflow filtration apparatus 1, the rotary filter RF-02 type (manufactured by Kotobuki Industries Co., Ltd.) having the configuration of FIG. 2 was used.
First, 100 parts by weight of the stock solution slurry is charged into the slurry tank 11, while pump circulation is performed at room temperature by circulating the charged slurry to the slurry tank 11 via the cross flow filtration device 1 using the liquid feed pump 12. Then, 50 parts by weight of the filtrate was extracted and concentrated.
The operating conditions at this time were such that the inlet pressure was 0.4 MPaG (gauge pressure). P2560C (made by Shikishima canvas) was used for the filter cloth.
Next, 50 parts by weight of distilled water was supplied from the washing water supply facility 13 into the slurry tank 11 to dilute the slurry, followed by filtration under the same conditions as the previous concentration. Similarly, the slurry was washed by repeating the operation of adding distilled water and filtering. After the washing, the filtrate was extracted under the same conditions as the previous concentration, and the slurry was concentrated. At this time, the solid content in the slurry obtained in the tank was 20 wt%.
This slurry was directly dried with hot air at 120 ° C. in a shelf hot air dryer to obtain a dried product.
100 parts by weight of the dried product, 52.1 parts by weight of lithium carbonate, and 14.3 parts by weight of potassium carbonate (reaction accelerator) were dry-mixed using a ball mill to obtain a mixture. Next, the mixture is placed in an alumina firing container, and is fired by holding it in the atmosphere at 870 ° C. for 6 hours using an electric furnace, and cooled to room temperature to obtain a fired product, which is pulverized and distilled. The mixture was filtered and washed with water, and dried at 300 ° C. for 6 hours to obtain a powder.
The crystal structure of this powder was a crystal structure belonging to the R-3m space group.

According to the present invention, a transition metal hydroxide that is a precursor of a positive electrode active material of a secondary battery can be continuously produced, which is industrially promising.

DESCRIPTION OF SYMBOLS 1 Cross flow filtration apparatus 2 Filtration chamber 3 Filtration plate 4 Stirring plate 4a Rotating shaft 5 Motor 5a Torque control device 6 Slurry supply port 7 Slurry discharge port 8 Slurry discharge valve 10 Filtration system 11 Slurry tank 11a Stirrer 12 Feed pump 13 Washing Water supply equipment P ₁ and P ₂ piping

A1 Slurry tank A2 Filter A3 Dryer

Claims (15)

The manufacturing method of the transition metal hydroxide characterized by including the following processes (1), (2), and (3).
Step (1) Step (2) for obtaining a stock solution slurry containing a solid content mainly composed of a transition metal hydroxide by bringing a solution containing a transition metal element into contact with an alkali in Step (1) Step (3) for obtaining a concentrated slurry by concentrating solids in the obtained stock solution slurry Step for directly drying the concentrated slurry obtained in step (2)   The method for producing a transition metal hydroxide according to claim 1, wherein in the step (2) of obtaining the concentrated slurry, the solid content in the stock solution slurry or the concentrated slurry is washed.   The method for producing a transition metal hydroxide according to claim 1 or 2, wherein in the step (3) of directly drying the concentrated slurry, the concentrated slurry is dried with hot air.   The method for producing a transition metal hydroxide according to any one of claims 1 to 3, wherein the concentrated slurry has a solid content concentration of 3% by weight or more.   The method for producing a transition metal hydroxide according to any one of claims 1 to 4, wherein the transition metal element is one or more elements selected from the group consisting of Ni and Mn.   The transition metal hydroxide according to any one of claims 1 to 4, wherein the transition metal element is one or more elements selected from the group consisting of Ni and Mn and one or more elements selected from the group consisting of Co and Fe. Manufacturing method.   A transition metal hydroxide is obtained by the production method according to claim 1, and the obtained transition metal hydroxide is mixed with a lithium compound and fired. Production method. The manufacturing method of the transition metal hydroxide characterized by including the following processes (1), (2), and (3).
Step (1) Step of obtaining a stock solution slurry containing a solid content mainly composed of a transition metal hydroxide by bringing a solution containing a transition metal element into contact with an alkali Step (2) Forcing a shear force near the surface of the filter medium Step of obtaining a concentrated slurry by concentrating the solid content in the stock slurry obtained in step (1) by cross-flow filtration performed while peeling off the solid content layer formed on the filter medium surface by generating 3) A step of directly drying the concentrated slurry obtained in the step (2).   The method for producing a transition metal hydroxide according to claim 8, wherein in the step (2), the vicinity of the surface of the filter medium is agitated to forcibly generate a shearing force in the vicinity of the surface of the filter medium.   The method for producing a transition metal hydroxide according to claim 8 or 9, wherein in the step (2), the solid content in the stock solution slurry or the concentrated slurry is washed.   The method for producing a transition metal hydroxide according to any one of claims 8 to 10, wherein the concentrated slurry is dried with hot air in the step (3).   The method for producing a transition metal hydroxide according to any one of claims 8 to 11, wherein the solid content concentration in the concentrated slurry is 3% by weight or more.   The method for producing a transition metal hydroxide according to any one of claims 8 to 12, wherein the transition metal element in step (1) is one or more elements selected from the group consisting of Ni and Mn.   The transition metal element in step (1) is one or more elements selected from the group consisting of Ni and Mn and one or more elements selected from the group consisting of Co and Fe. Of producing a transition metal hydroxide.   A transition metal hydroxide is obtained by the production method according to any one of claims 8 to 14, and the obtained transition metal hydroxide is mixed with a lithium compound and calcined. Production method.

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