JP2006269350A - Manufacturing method of positive electrode active material for lithium battery, positive electrode active material for lithium battery and lithium battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a positive electrode active material for a lithium battery for optimizing the shape, crystallinity and a particle diameter of the positive electrode active material for a lithium battery; to provide a positive electrode active material for a lithium battery, and also to provide a lithium battery. <P>SOLUTION: This manufacturing method of a positive electrode active material for a lithium battery is characterized in that an Li component, a P component, an A component and a D component used for materials of Li<SB>x</SB>A<SB>y</SB>D<SB>z</SB>PO<SB>4</SB>(where A is one kind selected from Co, Ni, Mn, Fe, Cu and Cr; D is one or more kinds selected from Mg, Ca, Fe, Ni, Co, Mn, Zn, Ge, Cu, Cr, Ti, Sr, Ba, Sc, Y, Al, Ga, In, Si, B and rare-earth elements and is different from A; 0<x<2; 0<y<1.5; and 0≤z<1.5) are added to a solvent containing water as a main component to prepare a solution at a temperature (1), then the solution is kept at a temperature (2) different from the temperature (1), and then the crystalline nucleus is grown at a temperature (3). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a positive electrode active material for a lithium battery, a positive electrode active material for a lithium battery, and a lithium battery, and more specifically, when a positive electrode active material for a lithium battery is continuously produced by a hydrothermal synthesis method. The present invention relates to a technique capable of optimizing the shape and particle size of a positive electrode active material for a lithium battery by appropriately adjusting the deposition conditions of the positive electrode active material for a lithium battery according to the form of the thermal synthesis reaction.

In recent years, secondary batteries have been developed as batteries for use in portable electronic devices, hybrid automobiles, and the like.
As typical secondary batteries, lead storage batteries, alkaline storage batteries, lithium batteries, and the like are known. In particular, lithium batteries can be reduced in size, weight, and capacity, and have high output and high capacity. Due to its energy density, it is highly anticipated and is actively researched.
This lithium battery includes a positive electrode having an active material capable of reversibly inserting and removing lithium ions, a negative electrode, and a non-aqueous electrolyte.

The positive electrode itself is composed of an electrode material containing a positive electrode active material, a conductive additive, and a binder, and is formed into a positive electrode by applying this electrode material to the surface of a metal foil called a current collector.
As the positive electrode active material, a metal oxide, a metal sulfide, a polymer, or the like is used. For example, titanium sulfide (TiS ₂ ), molybdenum sulfide (MoS ₂ ), niobium selenide (NbSe ₂ ), vanadium oxide (V Lithium-free compounds such as ₂ O ₅ ) or lithium composite oxides such as LiMO ₂ (M = Co, Ni, Mn, Fe, etc.) and LiMn ₂ O ₄ are known.

Conventionally, lithium cobalt oxide (LiCoO ₂ ) has been generally used as a positive electrode active material for lithium batteries because it is possible to form a battery having a high energy density and a high voltage.
However, since Co is unevenly distributed on the earth and is a scarce resource, there are problems that it is costly and that stable supply is difficult, so there are abundant resources on the earth as an alternative to Co. Positive electrode materials using inexpensive positive electrode active materials based on Ni or Mn, for example, lithium nickelate (LiNiO ₂ ), lithium manganate (LiMn ₂ O ₄ ), etc., have been proposed and put into practical use. It was.

However, although the positive electrode material using LiNiO ₂ has the advantages of a large theoretical capacity and a high discharge potential, the crystal structure of LiNiO ₂ collapses as the charge / discharge cycle is repeated. As a result, problems such as a decrease in discharge capacity and deterioration in thermal stability have occurred.
On the other hand, since LiMn ₂ O ₄ has a positive spinel structure and has a space group Fd3m, it has a high potential equivalent to 4V class LiCoO ₂ with respect to the lithium electrode, and is easy to synthesize and high. Since it has excellent characteristics such as battery capacity, it has attracted attention as a very promising material and has been put into practical use.
Although this LiMn ₂ O ₄ is such an excellent material, the battery using this LiMn ₂ O ₄ has a large capacity deterioration during high-temperature storage, and Mn may be dissolved in the electrolyte. Therefore, there remains a problem that stability and charge / discharge cycle characteristics are not sufficient.

Accordingly, a lithium battery using a transition metal phosphate compound such as Fe, Mn, Co, or Ni having an olivine structure as a positive electrode active material has been proposed (see Patent Document 1), and a transition metal phosphate having this olivine structure. As a compound, a lithium battery using LiFePO ₄ using Fe, which is a resource-rich and inexpensive metal, as a positive electrode active material has been proposed (see Patent Document 2).
This LiFePO ₄ exhibits a potential of about 3.3 V with respect to metallic lithium (Li), and can be used as a chargeable / dischargeable positive electrode material.
Phosphate-based materials such as lithium transition metal phosphates have conventionally used the so-called solid-phase method, but recently, by using various organic acids in the hydrothermal synthesis method, phosphoric acid of transition metals has been used. A method for obtaining compound crystallites has also been proposed (see Patent Document 3).
JP-A-9-134724 Japanese Patent Laid-Open No. 9-171827 JP 2004-95385 A

However, since lithium metal phosphate compounds such as conventional lithium transition metal phosphates are synthesized by the solid phase method, it is necessary to repeat firing and pulverization in an inert gas atmosphere, which is a complicated operation. There was a problem that it was necessary.
In the solid phase method, in order to reduce the particle size, it is better to fire at a lower temperature and in a shorter time. In this case, since the firing temperature at the time of synthesis is low, the crystallinity and grain size at the time of synthesis are reduced. It is difficult to control the diameter, and the obtained lithium metal phosphate compound has a structure in which small crystallites are arranged randomly. Therefore, the crystal phase of the lithium metal phosphate compound is not sufficiently generated / developed, the crystallinity is low, the diffusibility of ions in the particles and the electron conductivity are poor, and the polarization during charge / discharge increases. There was a point.

  In addition, there is a method of pulverizing after firing as a method of reducing the particle size, but this method cannot pulverize to a sufficiently small particle size, and excessive force is applied to the particles themselves during pulverization. , Distortion and cracking occur, and crystallinity also decreases. Therefore, when the lithium metal phosphate compound obtained by this method is used in a lithium battery, the volume change of the active material occurs due to the insertion / extraction of lithium ions by charging / discharging, and the particles are cracked by repeating this. Then, cracks progress and the particles are destroyed and refined. As a result, the ion diffusibility in the particles and the impedance between the particles increase, and the polarization during discharge increases. It was.

Therefore, an attempt has been made to apply a hydrothermal method capable of synthesizing a material having high crystallinity at a relatively low temperature to a lithium metal phosphate compound such as a lithium transition metal phosphate.
In the hydrothermal method, if a water-soluble organic acid that decomposes at a high temperature, such as citric acid, is added to the solution containing the raw material, the solution can be homogenized. A compound (Li _x A _y D ₂ PO ₄ ) is obtained. However, even in this hydrothermal method, when batch-type synthesis is performed using a pressure vessel such as an autoclave, if the size of the pressure vessel is increased in order to increase the yield, the rate of temperature increase is reduced along with the increase in size of the pressure vessel. There is a problem that the decomposition reaction rate of citric acid that affects atomization is limited.

  The present invention has been made in order to solve the above-described problems, and in the case of continuously producing a positive electrode active material for a lithium battery by a hydrothermal synthesis method, the lithium battery according to the form of the hydrothermal synthesis reaction. Method for producing positive electrode active material for lithium battery capable of optimizing shape, crystallinity and particle size of positive electrode active material for lithium battery by appropriately adjusting deposition conditions for positive electrode active material for lithium battery, and positive electrode active material for lithium battery An object of the present invention is to provide a lithium battery.

As a result of intensive studies, the present inventors have found that a lithium (Li) component, a phosphorus (P) component, an A component, and a raw material for a positive electrode active material for a lithium battery represented by Li _x A _y D _z PO ₄ The component D is added to a solvent containing water as a main component to form a solution or slurry at a temperature (1), and this solution or slurry is maintained at a temperature (2) different from the temperature (1) to precipitate crystal nuclei. By growing crystal nuclei in the solution or slurry at the temperature (3), it is possible to optimize the shape and particle size of the positive electrode active material for the lithium battery, and it is necessary for the synthesis of the positive electrode active material for the lithium battery. It has been found that the time can be shortened, and the present invention has been completed.

That is, the manufacturing method of the positive electrode active material for a lithium battery of the present invention is Li _x A _y D _z PO ₄ (where A is one selected from Co, Ni, Mn, Fe, Cu, Cr, and D is Mg , Ca, Fe, Ni, Co, Mn, Zn, Ge, Cu, Cr, Ti, Sr, Ba, Sc, Y, Al, Ga, In, Si, B, one or two selected from rare earth elements A method for producing a positive electrode active material for a lithium battery represented by 0 <x <2, 0 <y <1.5, 0 ≦ z <1.5, which is different from the above-described A, wherein water is a main component And adding a lithium (Li) component, a phosphorus (P) component, an A component and a D component as raw materials of the Li _x A _y D _z PO ₄ to a solution or slurry at a temperature (1), The solution or slurry is held at a temperature (2) different from the temperature (1) to form a crystal. Nuclear precipitating, then characterized by growing the crystal nuclei of the solution or slurry at a temperature (3).

In the method for producing a positive electrode active material for a lithium battery according to the present invention, it is preferable to add an organic acid soluble in water to the solvent.
The organic acid is preferably a hydroxycarboxylic acid or carboxylic acid, and the hydroxycarboxylic acid is preferably one or more selected from the group consisting of citric acid, malic acid, lactic acid, and tartaric acid.

  The positive electrode active material for a lithium battery of the present invention is obtained by the method for producing a positive electrode active material for a lithium battery of the present invention.

  The lithium battery of the present invention is characterized by using the positive electrode active material for a lithium battery of the present invention as a positive electrode.

According to the method for producing a positive electrode active material for a lithium battery of the present invention, a lithium (Li) component, a phosphorus (P) component, and A that are raw materials for Li _x A _y D _z PO ₄ are added to a solvent containing water as a main component. Component and component D are added to form a solution or slurry at temperature (1), and then the solution or slurry is maintained at a temperature (2) different from the temperature (1) to precipitate crystal nuclei, and then the solution or slurry Since the crystal nuclei in the slurry are grown at the temperature (3), the deposition conditions of the lithium battery positive electrode active material can be appropriately adjusted by changing the temperature. The particle size can be easily optimized.
Therefore, it is possible to easily produce a positive electrode active material for a lithium battery having Li _x A _y D _z PO ₄ having excellent crystallinity and having a uniform shape and particle size as a main component.

According to the positive electrode active material for a lithium battery of the present invention, it was obtained by the method for producing a positive electrode active material for a lithium battery of the present invention. Therefore, the positive electrode active material for a lithium battery mainly composed of Li _x A _y D _z PO ₄ Crystallinity can be improved, and the shape and particle size can be controlled.

According to the lithium battery of the present invention, since the positive electrode active material for a lithium battery of the present invention is used as a positive electrode, Li _x A _y D _z PO ₄ having excellent crystallinity, uniform shape and particle size is the main component. By using a positive active material for a lithium battery, the charge / discharge capacity can be stabilized, stable charge / discharge cycle characteristics can be realized, and the quality and size of the lithium battery electrode can be improved. Can do.

The manufacturing method of the positive electrode active material for lithium batteries of this invention, the positive electrode active material for lithium batteries, and the best form of a lithium battery are demonstrated.
This embodiment is specifically described for better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

The method for producing a positive electrode active material for a lithium battery of the present invention is Li _x A _y D _z PO ₄ (where A is one selected from Co, Ni, Mn, Fe, Cu, Cr, and D is Mg, Ca Fe, Ni, Co, Mn, Zn, Ge, Cu, Cr, Ti, Sr, Ba, Sc, Y, Al, Ga, In, Si, B, one or more selected from rare earth elements and A method for producing a positive electrode active material for a lithium battery represented by 0 <x <2, 0 <y <1.5, 0 ≦ z <1.5, which is different from A, and is mainly composed of water. Lithium (Li) component, phosphorus (P) component, A component and D component as raw materials of the Li _x A _y D _z PO ₄ are added to the solvent to make a solution or slurry at temperature (1), and then this solution Or the slurry is kept at a temperature (2) different from the temperature (1) to precipitate crystal nuclei. So, then, the crystal nuclei of the solution or slurry is a method of growing at a temperature (3).

There are the following two methods for controlling the temperature (1) and the temperature (2).
A. The solution or slurry is maintained at a temperature (1), for example, -80 ° C. or higher and 300 ° C. or lower, and then the solution or slurry is higher than temperature (1) and at room temperature (25 ° C.) or higher and 800 ° C. or lower. Crystal temperature nuclei mainly composed of Li _x A _y D _z PO ₄ are precipitated in the solution or slurry while maintaining the temperature (2), and then the solution or slurry containing the crystal nuclei is maintained at the temperature (3). A method of growing crystal nuclei in this solution or slurry.

In this method, a solution or slurry at a temperature (1) is rapidly heated to a temperature (2) and held to cause a chemical reaction in the solution or slurry, and Li _x A _y D _z PO is generated in the solution or slurry. ₄ crystal nuclei are precipitated. Thereafter, the solution or slurry containing the crystal nuclei is maintained at the temperature (3), and the crystal nuclei in the solution or slurry are grown to form Li _x A _y D _z PO ₄ microcrystals.
This _makes it possible to continuously manufacture microcrystals of _{Li x A y D z PO 4} .

B. The solution or slurry is maintained at a temperature (1), for example, room temperature (25 ° C.) or higher and 800 ° C. or lower, and then the solution or slurry is lower than temperature (1) and −80 ° C. or higher and 300 ° C. or lower. Crystal temperature nuclei mainly composed of Li _x A _y D _z PO ₄ are precipitated in the solution or slurry while maintaining the temperature (2), and then the solution or slurry containing the crystal nuclei is maintained at the temperature (3). A method of growing crystal nuclei in this solution or slurry.

In this method, the solution or slurry is maintained at a temperature (1) to cause a chemical reaction in the solution or slurry, and crystal nuclei of Li _x A _y D _z PO ₄ are precipitated in the solution or slurry. Thereafter, the chemical reaction of the solution or slurry is stopped by cooling the solution or slurry containing crystal nuclei to a temperature (2) state. Thereafter, the solution or slurry containing the crystal nuclei is maintained at the temperature (3), and the crystal nuclei in the solution or slurry are grown to form Li _x A _y D _z PO ₄ microcrystals.
This _makes it possible to continuously manufacture microcrystals of _{Li x A y D z PO 4} .

The method for producing a positive electrode active material for a lithium battery of the present invention will be described in more detail.
First, a manufacturing apparatus to which the method for manufacturing a positive electrode active material for a lithium battery of the present invention is applied will be described.
FIG. 1 is a schematic configuration diagram showing an apparatus for producing a positive electrode active material for a lithium battery. The positive electrode active for a lithium battery mainly composed of Li _x A _y D _z PO ₄ having controlled crystallinity, shape and particle size. It is a device that continuously manufactures substances.

In the figure, 1 is a raw material tank for storing a solution (or slurry) S that is a raw material of a positive electrode active material for a lithium battery mainly composed of Li _x A _y D _z PO ₄ , and 2 is for conveying the solution (or slurry) S A pipe 3 is provided in the pipe 2 and supplies a solution (or slurry) S stored in the raw material tank 1. The raw material supply unit 4 is constituted by the raw material tank 1, the pipe 2 and the pump 3. Yes.
This solution (or slurry) S is soluble in water as required by adding Li, P, A, and D components, which are components of a positive electrode active material for lithium batteries, to a solvent mainly composed of water. A simple organic acid is added and stirred and mixed.

Also, 5 is a pipe connected to the outlet side of the pump 3, and 6 is a temperature (1) of a solution (or slurry) S sent from the pump 3 and flowing in the pipe 5, for example, −80 ° C. or more and 300 ° C. or less. A low temperature part 7 that holds the temperature of the solution (or slurry) S sent from the low temperature part 6 at a temperature (2) different from the temperature (1), for example, higher than the temperature (1) and above the room temperature (25 ° C.) It is a crystal nucleus precipitation part that precipitates crystal nuclei while maintaining a high temperature of 800 ° C. or less, and a temperature gradient is formed in the pipe 5 by the low temperature part 6 and the crystal nucleus precipitation part 7, thereby flowing in the pipe 5. When the temperature of the solution (or slurry) S changes suddenly, the solution (or slurry) S chemically reacts to generate crystal nuclei of the lithium metal phosphate compound mainly composed of Li _x A _y D _z PO _4. It is like.

Reference numeral 8 denotes a solution (or slurry) S ′ containing crystal nuclei sent out from the crystal nucleation precipitation unit 7 at a temperature (3), for example, −80 ° C. or higher and temperature (2) or lower. It is a sealed reaction tank composed of an autoclave vessel or the like that grows into crystals of diameter and shape.
The reaction vessel 8 includes a stirrer 11 for stirring a solution (or slurry) S ′ containing crystal nuclei, a heater 12 for heating and holding the solution (or slurry) S ′ containing crystal nuclei at a temperature (3), and a reaction vessel. An Ar cylinder 13 for making the inside of an argon (Ar) gas atmosphere at a predetermined pressure inside 8 and a pressure gauge 14 for measuring the pressure of Ar gas are provided.

Reference numeral 21 denotes a solution (or slurry) S ″ containing lithium metal phosphate compound fine crystals mainly composed of Li _x A _y D _z PO ₄ grown in a predetermined size and shape in the reaction vessel 8. , 22 is a check valve provided in the pipe 21, 23 is a back pressure valve, 24 is a solution containing lithium metal phosphate microcrystals flowing out via the pipe 21, the check valve 22 and the back pressure valve 23 ( Or, a container 25 for collecting the slurry S ″, 25 is a water tank provided at the end of the pipe 26 communicating with the pipe 21 and stores pure water, and 27 is a pump.
In this manufacturing apparatus, each operation from the raw material tank 1 to the pump 27 is controlled by a control device (not shown).
This manufacturing apparatus is isolated from the external atmosphere until the solution (or slurry) is sent out from the raw material tank 1 and then collected in the container 24 via the pipes 2 and 5, the reaction tank 8 and the pipe 21. It is a closed reaction system.

  In this apparatus for producing a positive electrode active material for a lithium battery, the low temperature part 6 may be any one that can hold the solution (or slurry) S at the temperature (1). A tubular reactor around which the heater is wound is preferable. By using a double tube with a heater, it becomes easy to control the temperature of the solution (or slurry) S in a wide temperature range. The temperature of the low temperature part 6 is not particularly limited, but the lower limit temperature is −80 ° C., which is a temperature that can be reached by a cryogen composed of ethanol with dry ice added, and the upper limit temperature is generally It is preferable that the heat resistance temperature of the organic solvent used as the heat transfer medium is 300 ° C.

  The low temperature part 6 and the crystal nucleus precipitation part 7 are preferably adjacent to each other. In addition, when the diameter of the pipe 5 that communicates the low temperature part 6 and the crystal nucleus precipitation part 7 is sufficiently thin, cooling or heating is easy, and the temperature gradient with respect to the solution (or slurry) S flowing through the pipe 5 is easily achieved. In addition, it is possible to easily change the temperature gradient, so that it is possible to generate microcrystals accompanying a rapid temperature change in the crystal nucleus generation stage.

Further, the temperature range of the crystal nucleus precipitation part 7 is not particularly limited as long as it is a temperature range in which crystal nuclei can be precipitated. A range from room temperature (25 ° C.) to 800 ° C. which is the upper limit of the heat resistant temperature of stainless steel is preferable.
Further, the temperature range of the reaction vessel 8 may be a temperature range in which crystal nuclei can be grown into crystals having a predetermined size and shape, and is specifically limited as in the low temperature portion 6 and the crystal nucleus precipitation portion 7. Although it is not a thing, it can set from -80 degreeC to 800 degreeC by employ | adopting either the method of heating and cooling.

Next, a method for producing a positive electrode active material for a lithium battery having Li _x A _y D _z PO ₄ as a main component using the apparatus for producing a positive electrode active material for a lithium battery will be described.
First, a solution (or slurry) S that is a raw material of Li _x A _y D _z PO ₄ is prepared and stored in the raw material tank 1.
A solvent containing water as a main component, a Li component, a P component, and an A component (A is selected from Co, Ni, Mn, Fe, Cu, and Cr as raw materials for Li _x A _y D _z PO ₄ ) Seed), D component (where D is Mg, Ca, Fe, Ni, Co, Mn, Zn, Ge, Cu, Cr, Ti, Sr, Ba, Sc, Y, Al, Ga, In, Si, B, 1 type or 2 types or more selected from rare earth elements and different from the above-mentioned A) are added and stirred and mixed to prepare a solution (or slurry) S. Here, the rare earth elements are 15 elements of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu which are lanthanum series.

Here, examples of the solvent containing water as a main component include pure water, a water-alcohol solution, a water-ketone solution, and a water-ether solution. Among these, pure water is preferable.
The reason is that water is inexpensive and exhibits a large change in dielectric constant near the critical point, so that it is possible to easily control solvent physical properties such as solubility in each substance by manipulating temperature and pressure.

Examples of the Li component include lithium inorganic acid salts such as lithium hydroxide (LiOH), lithium carbonate (Li ₂ CO ₃ ), lithium phosphate (Li ₃ PO ₄ ), lithium acetate (LiCH ₃ COO), lithium oxalate ( Examples include lithium organic acid salts such as (COOLi) ₂ ).

Examples of the P component include phosphoric acid such as orthophosphoric acid (H ₃ PO ₄ ) and metaphosphoric acid (HPO ₃ ), diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ), and ammonium dihydrogen phosphate (NH ₄ Examples thereof include ammonium hydrogen phosphate such as H ₂ PO ₄ ), and orthophosphoric acid, diammonium hydrogen phosphate, and ammonium dihydrogen phosphate are preferable because of relatively high purity and easy composition control.

As the A component, one of metal salts of Co, Ni, Mn, Fe, Cu, and Cr is used. For example, as the Fe salt, iron (II) sulfate (FeSO ₄ ), iron (II) acetate. (Fe (CH ₃ COO) ₂ ), iron chloride (II) (FeCl ₂ ) and the like are preferable.
As D component, Mg, Ca, Fe, Ni, Co, Mn, Zn, Ge, Cu, Cr, Ti, Sr, Ba, Sc, Y, Al, Ga, In, Si, B, each of rare earth elements One or more metal salts of elements different from the component A are used. For example, sulfates such as Al ₂ (SO ₄ ) ₃ , MgSO ₄ , Ti (SO ₄ ) ₂ , Al (CH ₃ COO) ₃ , metal salts such as acetates such as Mg (CH ₃ COO) ₂ , chlorides such as AlCl ₃ , CaCl ₂ and TiCl ₄ , etc. are preferred.

An organic acid soluble in water may be added to the solution (or slurry) S.
By adding an organic acid that is soluble in water, it is possible to prepare a solution (or slurry) that has been made into a uniform solution without producing a hardly soluble substance.

  As the organic acid, hydroxycarboxylic acid or carboxylic acid is preferable. Examples of the hydroxycarboxylic acid include citric acid, malic acid, lactic acid, and tartaric acid. Examples of the carboxylic acid include malonic acid, acrylic acid, and polyacrylic acid. Examples include acid, methacrylic acid, formic acid, maleic acid, and succinic acid.

Among these, citric acid is particularly suitable for the following two reasons A and B.
(A) Since the chelating effect on metal ions is high, the growth of Li _x A _y D _z PO ₄ crystal nuclei such as LiFePO ₄ is suppressed.
(B) Since it shows reducibility at the time of decomposition, oxidation of A component and D component is prevented. For example, when Fe is used as the A component, oxidation of Fe from divalent to trivalent is prevented.
This organic acid may be added simultaneously with these components when adding the Li component, P component, A component and D component to adjust the starting material, or may be added after mixing these components. .

Next, this solution (or slurry) S is quantitatively supplied to the low temperature part 6 through the pipe 2 and the pump 3 and is kept at a temperature (1) of -80 ° C. or more and 300 ° C. or less.
Here, if the solution (or slurry) S is cooled using a cryogen composed of ethanol to which dry ice is added, the solution (or slurry) can be cooled to −80 ° C. or the vicinity thereof. Moreover, if the solution (or slurry) S is heated with a heater, it can be heated to 300 ° C., which is the heat resistant temperature of the organic solvent.

Next, the solution (or slurry) S sent out from the low-temperature part 6 is moved to the crystal nucleus precipitation part 7 and maintained at a temperature (2) higher than the temperature (1) and not lower than room temperature (25 ° C.) and not higher than 800 ° C. Then, a chemical reaction is caused in the solution (or slurry) S, and crystal nuclei mainly composed of Li _x A _y D _z PO ₄ are precipitated in the solution (or slurry) S.
Since there is a steep temperature gradient between the low temperature portion 6 and the crystal nucleus precipitation portion 7, the solution (or slurry) S passing through the low temperature portion 6 and the crystal nucleus precipitation portion 7 are extremely minute Li _x A _y due to a rapid chemical reaction due to a rapid temperature change. D _z PO ₄ crystal nuclei are instantly and produced in large quantities.

The solution (or slurry) S ′ containing crystal nuclei of minute Li _x A _y D _z PO ₄ generated in this way is sent into the reaction vessel 8. Since the inside of the reaction vessel 8 is set to an Ar gas atmosphere having a predetermined pressure by the Ar cylinder 13 and the pressure gauge 14, the solution (or slurry) S ′ is not likely to be altered by oxidation or the like.

This solution (or slurry) S ′ is stirred by the stirrer 11 and simultaneously heated and held at a temperature (3) not lower than −80 ° C. and not higher than temperature (2) by the heater 12.
At the same time, the atmosphere inside the reaction vessel 8 is maintained in an Ar atmosphere of, for example, 0.1 to 30 MPa by the Ar cylinder 13 and the pressure gauge 14.
Here, it is necessary to gradually grow Li _x A _y D _z PO ₄ microcrystals with good crystallinity and uniform grain size and shape based on the fine Li _x A _y D _z PO ₄ crystal nucleus. Therefore, it is preferable that the temperature (3) is equal to or lower than the temperature (2).

The solution (or slurry) S ′ containing the crystal nuclei is aged for a predetermined time in the reaction vessel 8, whereby crystal nuclei of Li _x A _y D _z PO ₄ grow, and Li _x having a predetermined particle size and shape is formed. the a _y D _z PO ₄ crystallites.
Here, since the temperature, atmosphere, and pressure during ripening are kept constant, Li _x A _y D _z PO ₄ microcrystals can be easily and continuously produced in large quantities based on the minute crystal nuclei. be able to.

The solution (or slurry) S ″ containing Li _x A _y D _z PO ₄ microcrystals is mixed with pure water sent from the water tank 25 after passing through the pipe 21 and the check valve 22, and then passes through the back pressure valve 23. Then, the pressure is recovered in the container 24. By narrowing the back pressure valve 23, the pressure of the entire reaction system from the pipe 2 to the pipe 22 can be arbitrarily controlled.

This solution (or slurry) S ″ containing Li _x A _y D _z PO ₄ microcrystals may be used as it is, or when Li _x A _y D _z PO ₄ microcrystals are used alone. The Li _x A _y D _z PO ₄ microcrystals may be separated from the solution (or slurry) S ″ by ultrafiltration or the like, and then dried by vacuum drying or the like.
_Thus, it is possible to continuously manufacture the Li _x A _y D z PO ₄ crystallites, or _Li x _A y _D z PO ₄ solution containing microcrystals (or slurry) S ".
Moreover, since the apparatus configuration is simple and inexpensive, the manufacturing cost can be greatly reduced.

According to this embodiment, the temperature conditions in the crystal nucleus generation stage of Li _x A _y D _z PO ₄ , which could not be achieved in the powder synthesis by the conventional hydrothermal synthesis reaction, and the Li _x A _y D _z PO ₄ The temperature conditions in the crystal nucleus growth stage can be set independently of each other. Therefore, the crystallite diameter and crystallinity control of the obtained Li _x A _y D _z PO ₄ microcrystals are various compared with the conventional one, and the size and shape of the Li _x A _y D _z PO ₄ microcrystals are controlled. A large amount of a solution or slurry containing crystals or Li _x A _y D _z PO ₄ microcrystals can be easily produced.

As described above, it is possible to separate the nucleation stage and the ripening stage of the generated particles, which could not be achieved in the powder synthesis by the conventional hydrothermal synthesis reaction, and to set independent temperature conditions. Compared with the conventional system, Li _x A crystal diameter of _y D _z PO ₄ crystallites, the crystallinity control is varied, fine crystals were obtained as compared with the conventional method.
Powder synthesis using the solution (or slurry) S of this embodiment as a raw material is applicable to hydrothermal synthesis for synthesizing powders of various metal oxides, phosphoric acid compounds, oxalic acid compounds, hydroxides and the like.

The lithium battery of the present invention uses, as a positive electrode, a positive electrode active material for a lithium battery mainly composed of Li _x A _y D _z PO ₄ microcrystals obtained by the method for producing a positive electrode active material for a lithium battery of the present invention. The negative electrode, electrolyte, separator, battery shape, etc. are not particularly limited. In this lithium battery, the positive electrode is formed of Li _x A _y D _z PO ₄ microcrystals, which are fine crystals with high purity and uniform particle size, and thus stable charge / discharge cycle performance is achieved. It is equipped, and high output is achieved.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited by this Example.
(Example)
0.2 mol of lithium acetate (LiCH ₃ COO), 0.1 mol of iron (II) sulfate (FeSO ₄ ), 0.1 mol of orthophosphoric acid (H ₃ PO ₄ ), 0.1 mol of citric acid and pure water, The mixture was mixed so that the total amount became 0.2 liters (L) to obtain a uniform transparent solution.

Next, this transparent solution was reacted using the production apparatus shown in FIG. Here, the temperature of the low temperature part 6 was 0 ° C., the temperature of the crystal nucleus precipitation part 7 was 200 ° C., and the temperature gradient between the low temperature part 6 and the crystal nucleus precipitation part 7 was 100 ° C./second.
Moreover, the inside of the reaction tank 8 was made into 8 MPa Ar atmosphere, and the temperature was 170 degreeC. Thereafter, the obtained product was separated and collected by filtration, washed with water and dried to obtain Sample 1.

(Comparative example)
0.2 mol of lithium acetate (LiCH ₃ COO), 0.1 mol of iron (II) sulfate (FeSO ₄ ), 0.1 mol of orthophosphoric acid (H ₃ PO ₄ ), 0.1 mol of citric acid and pure water, Mixing was performed so that the total amount became 0.2 L, and a uniform transparent solution was obtained.
Next, this transparent solution was stored in an autoclave having a capacity of 0.3 L, and kept at 170 ° C. for 3 hours under a nitrogen atmosphere to be reacted.
Thereafter, the product in the autoclave was separated and collected by filtration, washed with water and dried to obtain Sample 2.

Here, the scanning electron microscope image (SEM image) of the sample 1 obtained in the example is shown in FIG. 2, and the scanning electron microscope image (SEM image) of the sample 2 obtained in the comparative example is shown in FIG. Show.
According to these figures, it was found that Sample 1 obtained in the example was an extremely fine crystallite of about 100 nm. On the other hand, it was found that Sample 2 obtained in the comparative example was a coarse crystal of about 500 nm and had a large variation in crystal diameter.

The present invention relates to a temperature condition in the crystal nucleus generation stage of Li _x A _y D _z PO ₄ , which is a positive electrode active material for a lithium battery, and a temperature condition in the crystal nucleus growth stage of Li _x A _y D _z PO _4. By setting them independently of each other, extremely fine Li _x A _y D _z PO ₄ crystallites could be obtained, and of course, further stabilization of the charge / discharge cycle of the lithium battery was further achieved. The present invention can be applied to the field of secondary batteries that are expected to be reduced in size, weight, and capacity.

It is a schematic block diagram which shows the manufacturing apparatus with which the manufacturing method of the positive electrode active material for lithium batteries of this invention is applied. It is a figure which shows the scanning electron microscope image (SEM image) of the sample 1 obtained in the Example of this invention. It is a figure which shows the scanning electron microscope image (SEM image) of the sample 2 obtained by the comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Raw material tank 2 Piping 3 Pump 4 Raw material supply part 5 Piping 6 Low temperature part 7 Crystal nucleus precipitation part 8 Reaction tank 11 Stirrer 12 Heater 13 Ar cylinder 14 Pressure gauge 21 Piping 22 Check valve 23 Back pressure valve 24 Container 25 Water tank 26 Piping 27 pump

Claims (6)

Li _x A _y D _z PO ₄ (where A is one selected from Co, Ni, Mn, Fe, Cu, Cr, D is Mg, Ca, Fe, Ni, Co, Mn, Zn, Ge, Cu) , Cr, Ti, Sr, Ba, Sc, Y, Al, Ga, In, Si, B, one or more selected from rare earth elements and different from A, 0 <x <2, 0 <y <1.5, 0 ≦ z <1.5), a method for producing a positive electrode active material for a lithium battery,
A solution or slurry at temperature (1) by adding a lithium (Li) component, a phosphorus (P) component, an A component and a D component as raw materials of the Li _x A _y D _z PO ₄ to a solvent containing water as a main component. Next, the solution or slurry is maintained at a temperature (2) different from the temperature (1) to precipitate crystal nuclei, and then the crystal nuclei in the solution or slurry are grown at temperature (3). A method for producing a positive electrode active material for a lithium battery.   The method for producing a positive electrode active material for a lithium battery according to claim 1, wherein an organic acid soluble in water is further added to the solvent.   3. The method for producing a positive electrode active material for a lithium battery according to claim 2, wherein the organic acid is hydroxycarboxylic acid or carboxylic acid.   The said hydroxycarboxylic acid is 1 type, or 2 or more types selected from the group of a citric acid, malic acid, lactic acid, and tartaric acid, The manufacturing method of the positive electrode active material for lithium batteries of Claim 3 characterized by the above-mentioned.   A positive electrode active material for a lithium battery, which is obtained by the method for producing a positive electrode active material for a lithium battery according to any one of claims 1 to 4.   A lithium battery comprising the positive electrode active material for a lithium battery according to claim 5 as a positive electrode.

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