JP4869629B2 - Method for producing positive electrode active material for lithium battery, positive electrode active material for lithium battery, and lithium battery - Google Patents

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. More specifically, the positive electrode active material for a lithium battery is continuously produced by a continuous synthesis apparatus to which a hydrothermal synthesis method is applied. By adjusting the form of the hydrothermal synthesis reaction during production, it is possible to prevent the precipitation particles from adhering inside the continuous synthesis apparatus and the interruption of the synthesis process due to the adhesion of the precipitation particles. The present invention relates to a technique that enables high-precision control of the shape and particle size of an active material and that can reduce the manufacturing cost.

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.
Solid-phase methods, spray pyrolysis methods, and hydrothermal synthesis methods are used as methods for synthesizing phosphate-based materials such as lithium transition metal phosphates. Recently, various organic methods have been used in hydrothermal synthesis methods. A method of obtaining fine crystals of a transition metal phosphate compound by using an acid has also been proposed (see Patent Document 3). With this method, it is possible to obtain fine powder with good crystallinity.
JP-A-9-134724 Japanese Patent Laid-Open No. 9-171827 JP 2004-95385 A

By the way, in the conventional hydrothermal synthesis method, generally, batch-type synthesis is performed using a pressure-resistant vessel such as an autoclave, which is time-consuming and time-consuming and expensive compared to other methods. There was a problem that there were many cases.
Therefore, for the purpose of reducing the manufacturing cost, the continuation of the hydrothermal synthesis method has been studied. For example, when a uniform solution obtained by adding an organic acid such as citric acid is used as a raw material, In the synthesis process for generating particles, the generated particles are clogged in the continuous synthesis apparatus, particularly in the piping, and this synthesis process is interrupted.
This interruption of the synthesis process contributes to a decrease in the shape and particle size uniformity of the produced particles, and also contributes to an increase in manufacturing cost.

  The present invention has been made in order to solve the above-described problem, and when the positive electrode active material for a lithium battery is continuously produced by a hydrothermal synthesis method, the adhesion of the precipitated particles inside the continuous synthesis apparatus and By preventing interruption of the synthesis process due to the adhesion of the precipitated particles, lithium can be further controlled in the shape and particle size of the positive electrode active material for lithium batteries, and the production cost can be reduced. It aims at providing the manufacturing method of the positive electrode active material for batteries, the positive electrode active material for lithium batteries, and a lithium battery.

The present inventors have intensively studied was performed _results in continuously manufacturing a positive active material for a lithium battery represented by Li _x A _y D z PO _4, the _Li x _A y _D z PO ₄ Lithium (Li) component, A component (where A is one selected from Co, Ni, Mn, Fe, Cu, Cr) and 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, one or more selected from rare earth elements and different from A) Of these, one or two or more of them is a phosphorus compound insoluble in a solvent containing water as a main component at normal temperature and pressure, and a temperature (1) in which lithium (Li) component, A component and D component are added to this solvent The slurry is maintained at a temperature (2) higher than the temperature (1) and flows. By temperature than the peripheral portion of the slurry to precipitate crystals nuclei at a low center vicinity is possible to avoid the interruption of the synthesis process due to sticking of fixation and the precipitated particles of precipitated particles in the interior of the continuous synthesizer The present inventors have found that the present invention can be accomplished and have completed the present invention.

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 continuously 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 above. ,
Phosphorus compound insoluble in a solvent containing water as a main component under normal temperature and normal pressure, one or more of lithium (Li) component, A component and D component as raw materials of Li _x A _y D _z PO ₄ age,
The lithium (Li) component, the A component, and the D component are added to the solvent to form a slurry having a temperature (1), and then the slurry is maintained at a temperature (2) higher than the temperature (1) to flow. Crystal nuclei are precipitated in the vicinity of the central portion where the temperature is lower than that of the peripheral edge of the slurry, and then the crystal nuclei in the slurry are grown at a temperature (3).

The phosphorus compound is preferably a lithium phosphorus compound.
The phosphorus compound may be composed of a lithium phosphorus compound and a phosphorus compound containing A and / or D.
The phosphorus compound is preferably a phosphate.

In the solvent, further, the _Li x _A y _D z PO is _four ingredients phosphorus (P) component may be added.
The phosphorus (P) component is preferably phosphoric acid.
The atmosphere for growing crystal nuclei in the slurry is preferably an inert atmosphere.

  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, one or more of the lithium (Li) component, the A component, and the D component, which are raw materials of the Li _x A _y D _z PO ₄ , A phosphorus compound that is insoluble in a solvent containing water as a main component at room temperature and normal pressure, and the lithium (Li) component, the A component, and the D component are added to the solvent to form a slurry of temperature (1). Holding at a temperature (2) higher than the temperature (1), crystal nuclei are precipitated in the vicinity of the central part where the temperature is lower than the peripheral part of the flowing slurry , and then the crystal nuclei in the slurry are heated to the temperature (3 ), The slurry flowing in the pipe during continuous synthesis has a low temperature at the center where the flow rate is fast, and a high temperature at the periphery where the flow rate is slow, and this slurry is maintained at temperature (2). Cross section perpendicular to the flow direction when In the temperature distribution at, a quadratic curve is drawn from the central portion, which is a low temperature portion, toward the peripheral portion, which is a high temperature portion.

As a result, crystal nuclei are precipitated in the vicinity of the center of the slurry, but crystal nuclei are not precipitated in the periphery of the slurry. Therefore, the inside of the continuous synthesis apparatus, particularly the inner wall of a pipe used as a tubular flow reactor Can prevent the precipitation particles from sticking and the interruption of the synthesis process due to the adhesion of the precipitation particles, can be continuously synthesized in a synthesis apparatus using a tubular flow reactor, and the size of the apparatus can be reduced. Can be planned. As a result, the production efficiency of the positive electrode active material for lithium batteries whose main component is Li _x A _y D _z PO ₄ can be improved, and the manufacturing cost can be reduced.

Further, since the crystal nucleus is precipitated in the vicinity of the center portion of the flowing slurry, the crystal nucleus shape and particle size can be controlled with high accuracy by precipitating the crystal nucleus in the low temperature portion, li _x a _y D _z PO ₄ can improve the characteristics of a lithium battery positive active material for mainly composed of.

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 The shape and particle size of the battery can be accurately controlled, and the quality of the positive electrode active material for a lithium battery can be improved.

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, lithium containing Li _x A _y D _z PO ₄ whose shape and particle size are accurately controlled as a main component By using the battery positive electrode active material, 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. .

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 continuously 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,
First, one or more of the lithium (Li) component, the A component, and the D component that are raw materials of the Li _x A _y D _z PO ₄ are insoluble in a solvent containing water as a main component at room temperature and normal pressure. A phosphorus compound,
Next, the Li component, the A component, and the D component are added to the solvent to form a slurry having a temperature (1), and then the slurry is maintained at a temperature (2) higher than the temperature (1) to precipitate crystal nuclei. Next, the crystal nuclei in this slurry are grown at temperature (3).

  Here, under normal temperature and normal pressure is a condition in which water, a main component, is not subjected to heating, cooling, pressurization, decompression, etc., for example, an air temperature of −10 ° C. to 40 ° C., It is in a natural environment of about 1 atm (−101.25 hPa) or in an active area such as a living space or a work space.

A method for controlling these temperatures (1) to (3) will be described in detail.
The slurry is maintained at a temperature (1), for example, -80 ° C. or higher and 300 ° C. or lower, and then the slurry is heated to a temperature (2) higher than the temperature (1) and not lower than room temperature (25 ° C.) and not higher than 800 ° C. crystal nucleus is precipitated mainly composed of Li _x a _y D _z PO ₄ to within the slurry held in, after which the slurry containing the crystal nucleus maintained at a temperature (3), growing a crystal nucleus in the slurry Let me.

In this method, the slurry at the temperature (1) is rapidly heated to the temperature (2) and held to cause a chemical reaction in the slurry, and the crystal nuclei of Li _x A _y D _z PO ₄ are precipitated in the slurry. Let Thereafter, the slurry containing crystal nuclei is maintained at a temperature (3), and the crystal nuclei in the slurry are grown to form microcrystals of Li _x A _y D _z PO ₄ .
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 slurry S as a raw material of a positive electrode active material for a lithium battery whose main component is Li _x A _y D _z PO ₄ , 2 is a pipe for carrying the slurry S, 3 is a pipe 2 The pump is provided to supply the slurry S stored in the raw material tank 1, and the raw material supply unit 4 is configured by the raw material tank 1, the pipe 2 and the pump 3.
This slurry S is a phosphorous that is insoluble in a solvent containing water as a main component at room temperature and normal pressure, with one or more of Li component, A component and D component as raw materials of Li _x A _y D _z PO _{4 being used.} Then, the Li component, the A component, and the D component were added to the solvent, and the mixture was stirred and mixed.

In addition, 5 is a pipe connected to the outlet side of the pump 3, and 6 is a temperature (1) for keeping the slurry S sent from the pump 3 and flowing in the pipe 5 at a temperature of, for example, −80 ° C. to 300 ° C. The low-temperature part 7 includes a heating means such as a heater and the slurry S fed from the low-temperature part 6 has a temperature (2) different from the temperature (1), for example, higher than the temperature (1) and above 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 slurry S changes rapidly, the slurry S chemically reacts to generate crystal nuclei of a lithium metal phosphate compound mainly composed of Li _x A _y D _z PO ₄ .

Further, 8 holds the slurry S ′ containing crystal nuclei sent out from the crystal nucleus precipitation part 7 at a temperature (3), for example, −80 ° C. or higher and temperature (2) or lower, and the crystal nuclei have a predetermined particle size and shape. It is a sealed reaction tank composed of an autoclave vessel or the like for growing into crystals.
The reaction vessel 8 includes a stirrer 11 for stirring the slurry S ′ containing crystal nuclei, a heater 12 for heating and holding the slurry S ′ containing crystal nuclei at a temperature (3), and a predetermined pressure within the reaction vessel 8. An Ar cylinder 13 for making an active atmosphere, for example, an argon (Ar) atmosphere, and a pressure gauge 14 for measuring the pressure of Ar gas are provided. In some cases, the inert atmosphere may be a nitrogen (N ₂ ) atmosphere.

Reference numeral 21 denotes a pipe for transporting a slurry S ″ containing lithium metal phosphate compound microcrystals mainly composed of Li _x A _y D _z PO ₄ grown in a predetermined size and shape in the reaction tank 8; Is a check valve provided in the pipe 21, 23 is a back pressure valve, 24 is a slurry S ″ containing lithium metal phosphate compound crystallites flowing out via the pipe 21, check valve 22 and back pressure valve 23. A container 25 is provided at an end of a 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 a closed type that is isolated from the external atmosphere until the slurry is recovered from the raw material tank 1 and then recovered in the container 24 via the pipes 2 and 5, the reaction tank 8, and the pipe 21. It is a 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 slurry S at the temperature (1). For example, a heater for heating is wound around the outer periphery of the double tube. A rotated tubular reactor is preferred. By using a double tube with a heater, it becomes easy to control the temperature of the 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, 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. Further, when the diameter of the pipe 5 communicating the low temperature part 6 and the crystal nucleus precipitation part 7 is sufficiently thin, cooling or heating is easy, and a temperature gradient is easily formed with respect to the slurry S flowing through the pipe 5; In addition, since the temperature gradient can be easily changed, 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 continuously 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, the slurry S, which is a raw material for Li _x A _y D _z PO ₄ , is prepared and stored in the raw material tank 1.
The slurry S is a solvent containing water as a main component, Li component as a raw material of Li _x A _y D _z PO ₄ , and A component (where A is selected from Co, Ni, Mn, Fe, Cu, Cr) 1 type), 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 or 2 or more selected from rare earth elements and different from the above A), and stirring and mixing to adjust.

In this case, one or more of the Li component, the A component, and the D component must be a phosphorus compound that is insoluble in a solvent containing water as a main component at normal temperature and pressure.
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.

Moreover, as a solvent which has water as a main component, a pure water, a water-alcohol solution, a water-ketone solution, a water-ether solution etc. are mentioned, Among these, a 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.
As the Li component, a Li compound as a raw material of Li _x A _y D _z PO ₄ , for example, a Li compound insoluble in a solvent containing water as a main component is preferable, and a lithium phosphorus compound is particularly preferable. As this lithium phosphorus compound, lithium phosphate (Li ₃ PO ₄ , 2Li ₃ PO ₄ .H ₂ O, etc.) is preferable.

As the A component, one of the metal salts of Co, Ni, Mn, Fe, Cu, and Cr is used. As the metal salt, for example, A is insoluble in a solvent containing water as a main component and A is used. The phosphorus compound containing is preferable, and the phosphate containing A is particularly preferable. For example, the Fe salt may be an Fe compound that is insoluble in water. For example, (ortho) iron phosphate (II) (Fe ₃ (PO ₄ ) ₂ ), (ortho) iron phosphate (III) (FePO ₄ ) is preferable, and (ortho) iron phosphate (II) (Fe ₃ (PO ₄ ) ₂ ) that is insoluble in water at room temperature or higher is particularly 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.

In addition to the above metal salt, the D component may be, for example, a phosphorus compound that is insoluble in a solvent containing water as a main component and contains D. For example, aluminum phosphate (AlPO ₄ ), phosphoric acid Magnesium (Mg ₃ (PO ₄ ) ₂ ), (ortho) manganese phosphate (II) (Mn ₃ (PO ₄ ) ₂ ), (ortho) manganese phosphate (III) (MnPO ₄ ) and the like may be used.

The phosphorus (P) component, Li component, other P components contained in the component A or D components, _further, may be added Li _x A _y D z raw material becomes P component of PO _4.
Examples of the P component include orthophosphoric acid (H ₃ PO ₄ ), phosphorous acid (H ₃ PO ₃ ), metaphosphoric acid (HPO ₃ ) and the like, as well as diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ), And ammonium hydrogen phosphate such as ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ).

Next, the slurry S is quantitatively supplied to the low temperature part 6 through the pipe 2 and the pump 3, and is maintained at a temperature (1) of −80 ° C. or more and 300 ° C. or less.
Here, if the slurry S is cooled using a cryogen composed of ethanol to which dry ice is added, the slurry S can be cooled to −80 ° C. or the vicinity thereof. Moreover, if the 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 slurry S sent out from the low temperature part 6 is moved to the crystal nucleus precipitation part 7 and kept at a temperature (2) higher than the temperature (1) and not lower than room temperature (25 ° C.) and not higher than 800 ° C. A chemical reaction is caused to precipitate crystal nuclei containing Li _x A _y D _z PO ₄ as the main component in the slurry S.
Since there is a steep temperature gradient between the low temperature part 6 and the crystal nucleus precipitation part 7, the slurry S passing therethrough has a very small Li _x A _y D _z PO ₄ due to a rapid chemical reaction due to a rapid temperature change. This produces a large amount of crystal nuclei instantaneously.

In the crystal nuclei precipitated portion 7, as shown in FIG. 2, the flow velocity V of the slurry S flowing is faster at the center S _C, slower at the periphery S _R. Thus, the distribution in a cross section perpendicular to the flow direction of the flow velocity V of the slurry S in the center S _C is the fastest, quadratic curve toward the periphery S _R from the center S _C, so that the draw example parabola .

Further, the slurry S is because it is heated by a heating means such as a heater incorporated in the crystal nuclei precipitated section 7, the peripheral portion S _R temperature is the highest, the central portion S _C is compared to the peripheral portion S _R The temperature goes down.
Therefore, the temperature in a cross section perpendicular to the flow direction at the time of holding the slurry S to a temperature (2) (T) distribution, the double toward the center S _C is the low temperature portion to the peripheral portion S _R at a high temperature portion primary A curve, for example a parabola, will be drawn.

Thus, although the central portion S _C vicinity of the slurry S is the crystal nuclei are precipitated, the temperature in the peripheral portion S _R of the slurry S is high, dissolved material constituting the slurry S, is not the crystal nuclei are precipitated . Therefore, it is possible to prevent precipitation particles from adhering to the inside of the continuous synthesis apparatus, particularly the inner wall of the pipe, and interruption of the synthesis process due to the adhesion of the precipitation particles. As a result, it is possible to improve the production efficiency of the positive electrode active material for a lithium battery containing Li _x A _y D _z PO ₄ as a main component, and to reduce the manufacturing cost.

Also, since the be deposited crystal nuclei in the heart S _C vicinity of the slurry S flowing, by precipitating the crystal nucleus temperature than the peripheral portion S _R is at a low temperature portion, the shape of the crystal nuclei In addition, the particle size can be controlled with high accuracy, and the characteristics of the positive electrode active material for a lithium battery containing Li _x A _y D _z PO ₄ as a main component can be improved.

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

The slurry S ′ is stirred by the stirrer 11 and simultaneously heated and held at the temperature (3) by the heater 12 to −80 ° C. or more and temperature (2) or less.
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).

By aging the slurry S ′ containing crystal nuclei in the reaction vessel 8 for a predetermined time, the crystal nuclei of Li _x A _y D _z PO ₄ grow, and Li _x A _y D _z having a predetermined particle diameter and shape is formed. PO ₄ microcrystals are formed.
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 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 passed through the back pressure valve 23 to the container 24. By narrowing down the back pressure valve 23, the pressure of the entire reaction system from the pipe 2 to the pipe 22 can be arbitrarily controlled.

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

According to this embodiment, one or more of Li component, A component, and D component, which are raw materials of Li _x A _y D _z PO ₄ , are insoluble in a solvent containing water as a main component at normal temperature and pressure. Since the phosphorus compound is used, it is possible to prevent the precipitation particles from adhering to the inside of the continuous production apparatus, particularly the inner wall of the pipe, and the interruption of the synthesis process due to the adhesion of the precipitation particles. As a result, it is possible to avoid the clogging of the crystal nucleus precipitation part, which was easy to occur in the conventional powder synthesis by the hydrothermal synthesis reaction, especially the powder synthesis using the solution as a raw material, and Li _x A _y D _z PO ₄ is the main component. The production efficiency of the positive electrode active material for a lithium battery can be improved, and the production cost can be reduced.

Also, since the be deposited crystal nuclei in the heart S _C vicinity of the slurry S flowing, by precipitating the crystal nucleus temperature than the peripheral portion S _R is at a low temperature portion, the shape of the crystal nuclei In addition, the particle size can be controlled with high accuracy. _Therefore, it is possible to improve the characteristics of the Li _x A _y D z A positive active material for PO ₄ as main components.

Since the positive electrode active material for a lithium battery of the present invention was obtained by the method for producing a positive electrode active material for a lithium battery of the present invention, the shape of the positive electrode active material for a lithium battery mainly comprising Li _x A _y D _z PO ₄ In addition, the particle size can be accurately controlled. Therefore, the quality of the positive electrode active material for lithium batteries can be improved.

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 made of Li _x A _y D _z PO ₄ microcrystals with high purity, and the shape and particle size of which are accurately controlled, so that the charge / discharge capacity is stabilized. Therefore, stable charge / discharge cycle characteristics can be realized, and the quality and size of the lithium battery electrode can be improved.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited by this Example.
(Example)
0.1 mol of lithium phosphate (Li ₃ PO ₄ ), 0.1 mol of iron phosphate octahydrate (Fe ₃ (PO ₄ ) ₂ · 8H ₂ O) and pure water, the total amount being 3 liters (L) The resulting mixture was mixed to obtain a slurry.

Subsequently, this slurry was made to react using the manufacturing 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 300 ° 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.

(Reference 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 was 2 L, and a uniform transparent solution was obtained.
Next, this transparent solution was reacted using the production apparatus shown in FIG. Conditions such as temperature and pressure of each part in the manufacturing apparatus were the same as those in the example.
Thereafter, the obtained product was separated and collected by filtration, washed with water and dried to obtain Sample 2.
In this example, the synthesis was performed continuously for about 2 days, but during this time, clogging occurred in the piping, and the production was interrupted.

Here, the scanning electron microscope image (SEM image) of the sample 1 obtained in the example is shown in FIG. 3, and the scanning electron microscope image (SEM image) of the sample 2 obtained in the reference example is shown in FIG. Show.
According to these figures, it was found that the sample 1 obtained in the example was an extremely fine crystallite of 100 nm or less, and more microcrystal than the sample 2 obtained in the reference example.

The present invention relates to a phosphorus compound that is insoluble in a solvent containing water as a main component at room temperature and normal pressure, using at least one of Li component, A component, and D component as raw materials for Li _x A _y D _z PO ₄ . Therefore, the fixation of the precipitated particles inside the continuous synthesis apparatus and the interruption of the synthesis process due to the fixation of the precipitated particles can be avoided. Therefore, Li _x A _y D _z PO ₄ is mainly used. It can be applied not only to long-term continuous synthesis of positive electrode active materials for lithium batteries as components, but also to long-term continuous synthesis of other microcrystals, and its industrial utility value is extremely high.

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 explanatory drawing which shows the flow velocity distribution and temperature distribution of the slurry in the crystal nucleus precipitation part of a manufacturing apparatus. 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 reference 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 (9)

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 continuously producing a positive electrode active material for a lithium battery,
Phosphorus compound insoluble in a solvent containing water as a main component under normal temperature and normal pressure, one or more of lithium (Li) component, A component and D component as raw materials of Li _x A _y D _z PO ₄ age,
The lithium (Li) component, the A component, and the D component are added to the solvent to form a slurry having a temperature (1), and then the slurry is maintained at a temperature (2) higher than the temperature (1) to flow. Production of a positive electrode active material for a lithium battery, characterized in that crystal nuclei are precipitated in the vicinity of a central part having a temperature lower than that of the peripheral edge of the slurry, and then the crystal nuclei in the slurry are grown at a temperature (3). Method.   The said phosphorus compound is a lithium phosphorus compound, The manufacturing method of the positive electrode active material for lithium batteries of Claim 1 characterized by the above-mentioned.   The said phosphorus compound consists of a lithium phosphorus compound and the phosphorus compound containing said A and / or D, The manufacturing method of the positive electrode active material for lithium batteries of Claim 1 characterized by the above-mentioned.   The said phosphorus compound is a phosphate, The manufacturing method of the positive electrode active material for lithium batteries of Claim 1, 2, or 3 characterized by the above-mentioned. 5. The positive electrode active material for a lithium battery according to claim 1, wherein a phosphorus (P) component that is a raw material of the Li _x A _y D _z PO ₄ is further added to the solvent. Manufacturing method.   The method for producing a positive electrode active material for a lithium battery according to claim 5, wherein the phosphorus (P) component is phosphoric acid.   The method for producing a positive electrode active material for a lithium battery according to any one of claims 1 to 6, wherein the atmosphere for growing crystal nuclei in the slurry is an inert atmosphere.   A positive electrode active material for a lithium battery obtained by the method for producing a positive electrode active material for a lithium battery according to any one of claims 1 to 7.   A lithium battery comprising the positive electrode active material for a lithium battery according to claim 8 as a positive electrode.

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