JP2015038849A - Method for manufacturing lithium manganese phosphate positive electrode active material precursor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium manganese phosphate positive electrode active material precursor capable of exhibiting an excellent battery physical property as a positive electrode material of a lithium ion battery, and a method for manufacturing the same.SOLUTION: A method for manufacturing a lithium manganese phosphate positive electrode active material comprises: a step (I) of obtaining a mixed slurry liquid having a pH of 9 to 11 by stirring a slurry liquid containing lithium hydroxide in an amount exceeding solubility to water, while dropping phosphoric acid to the slurry liquid; a step (II) of obtaining the lithium manganese phosphate positive electrode active material precursor as a precursor slurry liquid by purging nitrogen to the resulting mixed slurry liquid and completing the reaction in the mixed slurry liquid; and a step (III) of adding a manganese compound, an iron compound and a compound containing metal M (M is Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd or Gd) to the resulting precursor slurry liquid and subjecting the resulting precursor slurry liquid to hydrothermal reaction.

Description

  The present invention relates to a lithium manganese phosphate positive electrode active material capable of expressing high battery properties and a method for producing the same.

  Conventionally, highly conductive substances have been used as positive electrode materials and negative electrode materials in order to improve battery performance. In recent years, next-generation batteries such as lithium ion batteries have been increasingly used, and various positive electrode materials for such batteries have been developed. Lithium manganese phosphate is one of them. Phosphoric acid, manganese compound and water are mixed to make an acidic solution, and lithium hydroxide is added dropwise to make it alkaline and subjected to hydrothermal reaction. An obtained method is known (see Non-Patent Document 1).

Under these circumstances, lithium manganese phosphate itself has low conductivity, and therefore, in order to effectively use it as a positive electrode active material, it is necessary to sufficiently refine the particles to ensure good battery properties. Various production methods are known for obtaining the substance. For example, in Patent Document 1, a lithium-containing composite oxide is manufactured by mixing a solution containing lithium and a solution containing phosphorus, forming a weakly alkaline mixed solution, and dropping the solution into a solution that can contain manganese or the like. A method is disclosed. In Patent Document 2, a precursor mixture containing a Li ⁺ source, a PO ₄ ³⁻ source, a manganese source, and the like is generated, and the obtained precursor mixture is dispersed or pulverized to obtain a LiMPO ₄ compound. A method is disclosed.

JP 2012-211072 A JP 2007-511458 A

Hongmei Ji et al, Elestrochimica Acta 56 (2011), p3093-3100

  However, in any of the methods described in any of the above documents, there is still room for improvement, including what solution should be prepared or what procedure should be mixed, and the like. I haven't come to get.

  Accordingly, an object of the present invention is to provide a lithium manganese phosphate positive electrode active material capable of exhibiting excellent battery properties as a positive electrode material of a lithium ion battery, and a method for producing the same.

  Accordingly, the present inventors have made various studies, and by using a slurry process containing a specific amount of lithium hydroxide and including a specific process, a lithium manganese phosphate positive electrode formed with extremely fine dispersed particles. While finding that a slurry liquid of an active material precursor can be obtained, it has also been found that a lithium manganese phosphate positive electrode active material with very fine particles can be obtained by adding a specific compound while using this. The invention has been completed.

That is, the present invention is a step (I) of obtaining a mixed slurry liquid having a pH of 9 to 11 by stirring the slurry water while dropping phosphoric acid into slurry water containing an amount of lithium hydroxide exceeding the solubility in water. ,
Step (II) of obtaining a lithium manganese phosphate positive electrode active material precursor as a precursor slurry liquid by purging nitrogen with respect to the obtained mixed slurry liquid to complete a reaction in the mixed slurry liquid, and obtaining a precursor slurry liquid A compound containing a manganese compound, an iron compound, and a metal M (M represents Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd) is added to the obtained precursor slurry liquid And then subjecting to a hydrothermal reaction (III)
The manufacturing method of the lithium manganese phosphate positive electrode active material containing this is provided.
Moreover, this invention provides the lithium manganese phosphate positive electrode active material obtained by the said manufacturing method.

  According to the method for producing a lithium manganese phosphate positive electrode active material of the present invention, since the slurry liquid in which the lithium manganese phosphate positive electrode active material precursor exists as extremely fine dispersed particles is used, the resulting lithium manganese phosphate positive electrode active material In this case, the particles can be sufficiently miniaturized. If the lithium manganese phosphate positive electrode active material thus obtained is used, a lithium ion battery having good battery properties can be easily realized.

The schematic of the steam heating type autoclave used by this invention is shown.

Hereinafter, the present invention will be described in detail.
In the method for producing a lithium manganese phosphate positive electrode active material of the present invention, the slurry water is stirred while dripping phosphoric acid into slurry water containing lithium hydroxide in an amount exceeding the solubility in water. Step (I) for obtaining a mixed slurry liquid,
Step (II) of obtaining a lithium manganese phosphate positive electrode active material precursor as a precursor slurry liquid by purging nitrogen with respect to the obtained mixed slurry liquid to complete a reaction in the mixed slurry liquid, and obtaining a precursor slurry liquid A compound containing a manganese compound, an iron compound, and a metal M (M represents Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd) is added to the obtained precursor slurry liquid And then subjecting to a hydrothermal reaction (III)
including.

  In the step (I), slurry water containing lithium hydroxide in an amount exceeding the solubility in water (g number of lithium hydroxide dissolved in 100 g of the saturated aqueous solution) is used. In this way, by using slurry water containing lithium hydroxide in an excessive amount exceeding the solubility in water, a lithium manganese phosphate positive electrode capable of expressing high battery properties in combination with the steps described below. It becomes possible to obtain a lithium manganese phosphate positive electrode active material precursor for obtaining an active material as fine dispersed particles.

  In order to prepare such slurry water, water and lithium hydroxide in an amount exceeding the solubility in water may be mixed. Such slurry water preferably contains 1.5 to 3.5 times the amount of lithium hydroxide, based on the solubility of lithium hydroxide in water, and 2.2 to 3.3 times the amount of hydroxide. It is more preferable to contain lithium, and it is more preferable to contain lithium hydroxide in an amount of 2.5 to 3.2 times. Moreover, it is preferable to contain 20-50 mass parts lithium hydroxide with respect to 100 mass parts of water, It is more preferable to contain 25-48 mass parts lithium hydroxide, 30-45 mass parts hydroxylation More preferably, it contains lithium.

More specifically, for example, in the case of slurry water containing 100 g of water at 20 ° C., it is preferable to contain 21 to 49 g of lithium hydroxide and 30 to 46 g of lithium hydroxide in the slurry water. More preferably, it contains 35 to 44 g of lithium hydroxide. In the case of slurry water containing 100 g of 40 ° C. water, it is preferable to contain 22 to 51 g of lithium hydroxide, more preferably 31 to 47 g of lithium hydroxide, and 36 to 45 g of lithium hydroxide. It is preferable to do this.
As the lithium hydroxide, for example, it may be used a hydrate of such LiOH · H ₂ O, in this case, the content is a value obtained by converting the lithium hydroxide (LiOH) content.

In step (I), the slurry water is stirred while dropping phosphoric acid into the slurry water to obtain a mixed slurry liquid having a pH of 9 to 11. In this way, dispersed particles of lithium manganese phosphate positive electrode active material precursor by stirring while adding phosphoric acid dropwise to a slurry liquid in which an excessive amount of lithium hydroxide is present while being in a saturated state. Can be effectively miniaturized by effectively suppressing the aggregation.
Phosphoric acid is so-called orthophosphoric acid (H ₃ PO ₄ ) and is preferably used as an aqueous solution having a concentration of 70 to 90% by mass. The dropping rate of phosphoric acid into the slurry water is preferably 15 to 50 mL / min, more preferably 20 to 45 mL / min, and further preferably 28 to 40 ml / min.
In the step (I), when stirring the slurry water while dropping phosphoric acid, the stirring speed of the slurry water is preferably 250 to 600 rpm, more preferably 300 to 550 rpm, further preferably 350 to 500 rpm. It is.

The temperature of the slurry water when stirring slurry water while dropping phosphoric acid depends on the dropping rate of phosphoric acid, but is preferably 20 to 90 ° C, more preferably 20 to 70 ° C. .
In addition, when stirring slurry water, although it depends also on the dripping speed | rate of phosphoric acid, it is preferable to cool to below the boiling point temperature of slurry water. Specifically, cooling to 80 ° C. or lower is preferable, and cooling to 20 to 60 ° C. is more preferable.

  The mixed slurry obtained in the step (I) preferably contains 0.28 to 0.38 mol of phosphoric acid, more preferably 0.30 to 0.36 mol, per 1 mol of lithium hydroxide. The content is preferably 0.32 to 0.34 mol. Moreover, it is preferable to contain 115-155 mass parts of phosphoric acid with respect to 100 mass parts of lithium hydroxide, It is more preferable to contain 123-147 mass parts, It is preferable to contain 131-139 mass parts.

  The mixed slurry is finally adjusted to pH 9-11, preferably pH 9.5 to 11.0. Thereby, the growth of by-products and particles can be effectively suppressed. Under the present circumstances, you may use pH adjusters, such as sodium hydroxide and a sulfuric acid, as needed.

In the step (II), the mixed slurry liquid obtained in the above step (I) is purged with nitrogen to complete the reaction in the mixed slurry liquid, whereby the lithium manganese phosphate positive electrode active material precursor is precursor. Obtained as body slurry liquid. When nitrogen is purged, the reaction can proceed in a state where the dissolved oxygen concentration in the mixed slurry liquid is reduced, and the dissolved oxygen concentration in the resulting precursor slurry liquid is also effectively reduced. Oxidation of the compound containing manganese compound, iron compound and metal M added in the next step (III) can be suppressed. In such a precursor slurry liquid, a lithium manganese phosphate positive electrode active material precursor (trilithium phosphate: Li ₃ PO ₄ ) exists as fine dispersed particles.

The pressure in the step (II) is preferably 0.1 to 0.2 MPa, more preferably 0.1 to 0.15 MPa. Moreover, the temperature of a mixed slurry liquid becomes like this. Preferably it is 20-80 degreeC, More preferably, it is 20-60 degreeC. The reaction time is preferably 5 to 60 minutes, more preferably 15 to 45 minutes.
Moreover, when purging nitrogen, it is preferable to stir a mixed slurry liquid from a viewpoint of making reaction progress favorable. The stirring speed at this time is preferably 250 to 600 rpm, more preferably 350 to 500 rpm.

  Further, in the step (II), the dissolved oxygen concentration in the mixed slurry liquid is reduced from the viewpoint of more effectively suppressing the oxidation of the lithium manganese phosphate positive electrode active material precursor on the surface of the dispersed particles and miniaturizing the dispersed particles. 0.5 mg / L or less is preferable, and 0.2 mg / L or less is more preferable.

  By passing through the said process (I) and process (II), the precursor slurry liquid in which a lithium manganese phosphate positive electrode active material precursor exists as a fine dispersed particle can be obtained. The dissolved oxygen concentration in the precursor slurry is preferably adjusted to 0.5 mg / L or less, and more preferably adjusted to 0.2 mg / L or less.

The average dispersed particle diameter of the lithium manganese phosphate positive electrode active material precursor (Li ₃ PO ₄ ) in the obtained precursor slurry is preferably 30 to 5000 nm, more preferably 30 to 4000 nm, and still more preferably. 30-3500 nm.
The average dispersed particle diameter of the lithium manganese phosphate positive electrode active material precursor means a value measured using a dynamic light scattering nanotrack particle size analyzer (manufactured by Nikkiso Co., Ltd.).

In step (III), manganese compound, iron compound and metal M (M is Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd or Gd are added to the obtained precursor slurry. The compound containing) is added and then subjected to a hydrothermal reaction. Thus, the above steps (I) and step (II) is obtained by passing through the precursor slurry while the slurry liquid, by using a lithium manganese cathode active material precursor phosphate (Li ₃ PO ₄₎ Thus, it is possible to obtain a lithium manganese phosphate compound that is very fine particles and is very useful as a positive electrode active material.
Hereinafter, the compound containing the manganese compound, the iron compound and the metal M added in the step (III) is also collectively referred to as “metal compound (III)”.

  The manganese compound may be a divalent manganese compound or a hydrate thereof, and examples thereof include manganese halide, manganese sulfate, manganese acetate, and a hydrate thereof. These may be used alone or in combination of two or more. Among these, from the viewpoint of improving battery physical properties, it is preferable to use manganese sulfate or a hydrate thereof.

  The iron compound may be a divalent iron compound or a hydrate thereof, for example, a halide such as iron halide; a sulfate such as iron sulfate; an organic acid such as iron oxalate or iron acetate Salts; and hydrates thereof. Especially, it is preferable to use iron sulfate or its hydrate from a viewpoint of improving battery physical property.

  The use molar ratio of the manganese compound and the iron compound (manganese compound: iron compound) is preferably more than 100: 0 and not more than 51:49, more preferably 99: 1 to 51:49, and still more preferably 95: 5-70: 30, and more preferably 90: 10-80: 20.

As a compound containing metal M (M represents Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd or Gd), a compound having a valence corresponding to the valence of metal M And hydrates thereof, and examples thereof include halides, sulfates, nitrates, organic acid salts such as oxalates and acetates, and hydrates thereof. Especially, it is preferable to use a sulfate or its hydrate from a viewpoint of improving battery physical property. The total addition amount of these manganese compound, iron compound and compound containing metal M (metal compound (III)) is the lithium manganese phosphate positive electrode active material precursor (Li ₃ PO ₄ ) 1 contained in the precursor slurry liquid. Preferably it is 0.95-1.01 mol with respect to mol, More preferably, it is 0.97-1.005 mol.

The amount of water used for the hydrothermal reaction is manganese phosphate contained in the precursor slurry from the viewpoints of solubility of the metal compound (III), ease of stirring, and efficiency of synthesis. to phosphate ion 1 mole of lithium positive electrode active material precursor (Li ₃ PO _4), preferably 10 to 30 moles, more preferably 12.5 to 25 mol.

The order of addition of the metal compound (III) is not particularly limited. Moreover, while adding metal compound (III), you may add antioxidant as needed. As such an antioxidant, sodium sulfite (Na ₂ SO ₃ ), hydrosulfite sodium (Na ₂ S ₂ O ₄ ), aqueous ammonia and the like can be used. The addition amount of the antioxidant is preferably 0.01 to 1 with respect to 1 mole of the metal compound (III) from the viewpoint of preventing the excessive formation of the lithium manganese phosphate compound from being suppressed. Mol, more preferably 0.03 to 0.5 mol.

A mixed liquid obtained by adding the metal compound (III) to the precursor slurry and adding an antioxidant or the like as required is a lithium manganese phosphate positive electrode active material precursor (trilithium phosphate: Li ₃ It contains a large amount of PO ₄ ). Thus, by subjecting a mixed liquid containing a large amount of lithium manganese phosphate positive electrode active material precursor formed by forming fine dispersed particles to a hydrothermal reaction, phosphorous of extremely fine particles useful as a positive electrode active material is obtained. A lithium manganese oxide compound can be obtained. The content of the lithium manganese phosphate positive electrode active material precursor in the mixed solution is preferably 10 to 50% by mass, more preferably 15 to 45% by mass, and further preferably 20 to 40% by mass. .

  In subjecting the obtained mixed solution to a hydrothermal reaction, it is preferable to use, for example, a steam heating autoclave as shown in FIG. 1 from the viewpoint of effectively preventing oxidation of the metal compound (III). The steam-heated autoclave accepts saturated steam and pressurizes and heats it, so that the autoclave is filled with saturated steam and effectively oxidizes the metal in the metal compound (III) in the autoclave during hydrothermal synthesis. Can be prevented. Moreover, since saturated steam does not generate anything other than water (drain water) even when cooled, it is possible to suppress oxidation of the metal in the metal compound (III) even in the process. When the saturated steam is introduced into the autoclave and heating is started, it is preferable to further reduce the oxygen remaining in the autoclave by performing an operation to push out (replace) the air in the autoclave with the saturated steam.

  The saturated steam is produced by heating water, but it is preferable to deoxidize the water used in the boiler for heating the water. The water for producing the steam preferably has a dissolved oxygen concentration of 0.5 mg / L or less, more preferably a dissolved oxygen concentration of 0.2 mg / L or less. Such deoxidized water can be easily produced by, for example, bubbling nitrogen gas in water or using a membrane separation device.

  The reaction temperature in hydrothermal reaction should just be 100 degreeC or more, Preferably it is 130-250 degreeC, More preferably, it is 140-230 degreeC. When using a steam-heated autoclave, it is only necessary to seal in the autoclave and heat with steam. When the reaction is performed at 130 to 250 ° C, the pressure is 0.3 to 1.5 MPa, and the reaction is performed at 140 to 230 ° C. When performing, it will be 0.4-1.0 MPa. The reaction time is preferably 10 minutes to 3 hours, more preferably 10 minutes to 1 hour.

  After completion of the hydrothermal reaction, the produced lithium manganese phosphate compound is preferably collected by filtration and washed. Washing is preferably performed with water using a filtration device having a cake washing function. The obtained crystals are dried if necessary. Examples of the drying means include spray drying, vacuum drying, freeze drying and the like.

The obtained lithium manganese phosphate compound can be used as a positive electrode active material for a lithium ion battery. Specifically, for example, it is represented by the following formula (A).
LiFe _a Mn _b M _c PO ₄ (A)
(In the formula, M represents Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd or Gd. A, b and c are 0 <a <0.5, 0.5 <B <1, and 0 <c ≦ 0.2, and 2a + 2b + (M valence) × c = 2).
M in the formula (A) is preferably Zr or La, more preferably La, from the viewpoint of obtaining a lithium manganese phosphate compound having higher battery properties.

  The obtained lithium manganese phosphate compound is preferably supported on carbon and then fired to form a positive electrode active material. For carbon loading, a carbon source such as glucose, fructose, polyethylene glycol, polyvinyl alcohol, carboxymethylcellulose, saccharose, starch, dextrin, citric acid and water may be added to a lithium manganese phosphate compound by a conventional method and then fired. . The firing conditions are 400 ° C. or higher, preferably 400 to 800 ° C. for 10 minutes to 3 hours, preferably 0.5 to 1.5 hours under an inert gas atmosphere or reducing conditions. By such treatment, a positive electrode active material in which carbon is supported on the particle surface of the lithium manganese phosphate compound can be obtained. 3-15 mass parts is preferable as carbon contained in a carbon source with respect to 100 mass parts of lithium manganese phosphate compounds, and, as for the usage-amount of a carbon source, 5-10 mass parts is more preferable as carbon contained in a carbon source.

  The lithium manganese phosphate positive electrode active material obtained by the method of the present invention is useful as a positive electrode material for lithium ion batteries because of its fine and uniform particle size. Specifically, the average particle diameter of the lithium manganese phosphate positive electrode active material is preferably 10 to 100 nm, and more preferably 10 to 50 nm.

Next, a lithium ion battery containing the lithium manganese phosphate positive electrode active material of the present invention as a positive electrode material will be described.
The lithium ion battery to which the positive electrode material of the present invention can be applied is not particularly limited as long as it has a positive electrode, a negative electrode, an electrolytic solution, and a separator as essential components.

  Here, as long as lithium ions can be occluded at the time of charging and released at the time of discharging, the material structure is not particularly limited, and a known material structure can be used. For example, a carbon material such as lithium metal, graphite, or amorphous carbon. It is preferable to use an electrode formed of an intercalating material capable of electrochemically inserting and extracting lithium, particularly a carbon material.

  The electrolytic solution is obtained by dissolving a supporting salt in an organic solvent. The organic solvent is not particularly limited as long as it is an organic solvent that is usually used for an electrolyte solution of a lithium ion secondary battery. For example, carbonates, halogenated hydrocarbons, ethers, ketones, nitriles, lactones An oxolane compound or the like can be used.

The type of the supporting salt is not particularly limited, but an inorganic salt selected from LiPF ₆ , LiBF ₄ , LiClO ₄ and LiAsF ₆ , a derivative of the inorganic salt, LiSO ₃ CF ₃ , LiC (SO ₃ CF ₃ ) ₂ and LiN (SO ₃ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ and LiN (SO ₂ CF ₃ ) (SO ₂ C ₄ F ₉ ), and organic salt derivatives It is preferable that it is at least 1 type of these.

  The separator plays a role of electrically insulating the positive electrode and the negative electrode and holding the electrolytic solution. For example, a porous synthetic resin film, particularly a polyolefin polymer (polyethylene, polypropylene) porous film may be used.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.

[Example 1]
<< Preparation of precursor slurry liquid >>
4.9 kg of LiOH · H ₂ O and 11.7 kg of water were mixed to obtain slurry water. Subsequently, the obtained slurry water was stirred at a stirring speed of 400 rpm while maintaining the temperature at 25 ° C., and then 5.09 kg of a 70% phosphoric acid aqueous solution was dropped at 35 mL / min to obtain a mixed slurry liquid. . The pH of the mixed slurry was 10.0 and contained 0.33 mol of phosphoric acid with respect to 1 mol of lithium hydroxide.

Next, the obtained slurry mixture was purged with nitrogen while stirring at a speed of 400 rpm for 30 minutes to complete the reaction with the slurry mixture, and the precursor adjusted to a dissolved oxygen concentration of 0.5 mg / L. A body slurry liquid was obtained.
The average dispersed particle size of trilithium phosphate (Li ₃ PO ₄ ) in the obtained precursor slurry was 3000 nm as measured with a dynamic light scattering nanotrack particle size analyzer (manufactured by Nikkiso Co., Ltd.). .
An SEM image of dispersed particles of trilithium phosphate (Li ₃ PO ₄ ) in the precursor slurry is shown in FIG.

<< Manufacture of lithium manganese phosphate cathode active material >>
Then, with respect to the precursor slurry _{21.7kg, FeSO 4 · 7H 2 O1.52kg} , added MnSO ₄ · H ₂ O 5.60kg, and ZrSO ₄ · 4H ₂ O 71g, further Na ₂ SO ₃ 46 8 g was added and stirred and mixed at a stirring speed of 400 rpm to obtain a mixed solution. At this time, the molar ratio of FeSO ₄ and MnSO ₄ added (manganese compound: iron compound) was 85.9: 14.1, and the lithium manganese phosphate positive electrode active material precursor (Li ₃ PO ₄ ) in the mixed solution. ) Content was 24 mass%.
Next, the mixed solution was put into a synthesis container installed in the steam heating autoclave of FIG. The inside of the autoclave was heated at 170 ° C. for 1 hour using saturated steam obtained by heating water with a dissolved oxygen concentration of less than 0.5 mg / L using a membrane separator. During the heating, stirring of the mixed slurry in the container was continued. The pressure in the autoclave was 0.8 MPa. The formed crystals were filtered and then washed with water. The washed crystal was vacuum dried at 60 ° C. and 1 Torr. 8.4 g of the obtained powder was taken, glucose (10% as carbon concentration) and 10 cm ³ of ultrapure water were added thereto, and calcined at 600 ° C. for 1 hr in a reducing atmosphere to obtain a lithium manganese phosphate positive electrode active material. Obtained.
The average particle diameter of the obtained lithium manganese phosphate positive electrode active material (Li ₂ Fe _0.14 Mn _0.85 Zr _0.005 PO ₄ ) was 40 nm.

<Manufacture of lithium ion batteries>
The obtained lithium manganese phosphate positive electrode active material, ketjen black (conducting agent), and polyvinylidene fluoride (binding agent) were mixed at a weight ratio of 75: 20: 5, and this was mixed with N-methyl-2- Pyrrolidone was added and sufficiently kneaded to prepare a positive electrode slurry. The positive electrode slurry was applied to a current collector made of an aluminum foil having a thickness of 20 μm using a coating machine, and vacuum dried at 80 ° C. for 12 hours. Thereafter, it was punched into a disk shape of φ14 mm and pressed at 16 MPa for 2 minutes using a hand press to obtain a positive electrode.

Next, a coin-type lithium ion battery was constructed using the positive electrode. A lithium foil punched to φ15 mm was used for the negative electrode. As the electrolytic solution, a solution obtained by dissolving LiPF ₆ at a concentration of 1 mol / l in a mixed solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 1: 1 was used. As the separator, a known one such as a polymer porous film such as polypropylene was used. These battery components were assembled and housed in a conventional manner in an atmosphere having a dew point of −50 ° C. or lower to produce a coin-type lithium ion battery (CR-2032).

A charge / discharge test at a constant current density was performed using the manufactured lithium ion battery. The charging conditions at this time were constant current charging with a current of 0.1 CA (17 mAg) and a voltage of 4.5 V, and the discharging conditions were constant current discharging with a current of 0.1 CA and a final voltage of 2.0 V. All temperatures were 30 ° C.
Based on the values of the discharge capacity (mAh / g) and the average discharge voltage (V), the weight energy density (Wh / kg) was calculated to be 585 Wh / kg.

[Example 2]
A precursor slurry liquid was prepared in the same manner as in Example 1 except that 95 g of La ₂ (SO ₄ ) ₃ .9H ₂ O was used instead of 71 g of ZrSO ₄ .4H ₂ O, and this was used to Similarly, a lithium manganese phosphate positive electrode active material was produced.
The obtained lithium manganese phosphate positive electrode active material (Li ₂ Fe _0.14 Mn _0.85 La _0.007 PO ₄ ) had an average particle size of 40 nm.
Next, a coin-type lithium ion battery (CR-2032) was produced in the same manner as in Example 1, a charge / discharge test at a constant current density was performed, and the weight energy density (Wh / kg) was calculated in the same manner. It was 590 Wh / kg.

[Comparative Example 1]
A precursor slurry solution was prepared in the same manner as in Example 1 except that 4.31 kg of Li ₂ CO ₃ was used instead of 4.9 kg of LiOH.H ₂ O, and 21.7 kg of the precursor slurry solution was mixed with FeSO. 1.63 kg of ₄ · 7H ₂ O and 5.60 kg of MnSO ₄ · H ₂ O were added, and 46.8 g of Na ₂ SO _{3 was} further added, followed by stirring and mixing at a stirring speed of 400 rpm to obtain a mixed solution. At this time, the added FeSO ₄ and MnSO ₄ molar ratio (manganese compound: iron compound) was 85:15, and the content of lithium manganese phosphate positive electrode active material precursor (Li ₃ PO ₄ ) in the mixed solution Was 24 mass%.
Subsequently, a lithium manganese phosphate positive electrode active material was obtained in the same manner as in Example 1.
The average particle diameter of the obtained lithium manganese phosphate positive electrode active material (Li ₂ Fe _0.15 Mn _0.85 PO ₄ ) was 150 nm.
Next, a coin-type lithium ion battery (CR-2032) was produced in the same manner as in Example 1, a charge / discharge test at a constant current density was performed, and the weight energy density (Wh / g) was calculated in the same manner. It was 575 Wh / g.

<< Manufacture of lithium manganese phosphate cathode active material >>
Then, with respect to the precursor slurry _{21.7kg, FeSO 4 · 7H 2 O1.52kg} , added MnSO ₄ · H ₂ O 5.60kg, and ZrSO ₄ · 4H ₂ O 71g, further Na ₂ SO ₃ 46 8 g was added and stirred and mixed at a stirring speed of 400 rpm to obtain a mixed solution. At this time, the molar ratio of FeSO ₄ and MnSO ₄ added (manganese compound: iron compound) was 85.9: 14.1, and the lithium manganese phosphate positive electrode active material precursor (Li ₃ PO ₄ ) in the mixed solution. ) Content was 24 mass%.
Next, the mixed solution was put into a synthesis container installed in the steam heating autoclave of FIG. The inside of the autoclave was heated at 170 ° C. for 1 hour using saturated steam obtained by heating water with a dissolved oxygen concentration of less than 0.5 mg / L using a membrane separator. During the heating, stirring of the mixed slurry in the container was continued. The pressure in the autoclave was 0.8 MPa. The formed crystals were filtered and then washed with water. The washed crystal was vacuum dried at 60 ° C. and 1 Torr. 8.4 g of the obtained powder was taken, glucose (10% as carbon concentration) and 10 cm ³ of ultrapure water were added thereto, and calcined at 600 ° C. for 1 hr in a reducing atmosphere to obtain a lithium manganese phosphate positive electrode active material. Obtained.
The average particle diameter of the obtained lithium manganese phosphate positive electrode active material _{(Li Fe 0.14 Mn 0.85 Zr 0.005} PO 4) was 40 nm.

[Example 2]
A precursor slurry liquid was prepared in the same manner as in Example 1 except that 95 g of La ₂ (SO ₄ ) ₃ .9H ₂ O was used instead of 71 g of ZrSO ₄ .4H ₂ O, and this was used to Similarly, a lithium manganese phosphate positive electrode active material was produced.
The average particle diameter of the obtained lithium manganese phosphate positive electrode active material _{(Li Fe 0.14 Mn 0.85 La 0.007} PO 4) was 40 nm.
Next, a coin-type lithium ion battery (CR-2032) was produced in the same manner as in Example 1, a charge / discharge test at a constant current density was performed, and the weight energy density (Wh / kg) was calculated in the same manner. It was 590 Wh / kg.

[Comparative Example 1]
A precursor slurry solution was prepared in the same manner as in Example 1 except that 4.31 kg of Li ₂ CO ₃ was used instead of 4.9 kg of LiOH.H ₂ O, and 21.7 kg of the precursor slurry solution was mixed with FeSO. 1.63 kg of ₄ · 7H ₂ O and 5.60 kg of MnSO ₄ · H ₂ O were added, and 46.8 g of Na ₂ SO _{3 was} further added, followed by stirring and mixing at a stirring speed of 400 rpm to obtain a mixed solution. At this time, the added FeSO ₄ and MnSO ₄ molar ratio (manganese compound: iron compound) was 85:15, and the content of lithium manganese phosphate positive electrode active material precursor (Li ₃ PO ₄ ) in the mixed solution Was 24 mass%.
Subsequently, a lithium manganese phosphate positive electrode active material was obtained in the same manner as in Example 1.
The average particle diameter of the obtained lithium manganese phosphate positive electrode active material _{(Li Fe 0.15 Mn 0.85 PO 4} ) was 150 nm.
Next, a coin-type lithium ion battery (CR-2032) was produced in the same manner as in Example 1, a charge / discharge test at a constant current density was performed, and the weight energy density (Wh / g) was calculated in the same manner. It was 575 Wh / g.

Claims (9)

Step (I) of stirring slurry water while dripping phosphoric acid into slurry water containing an amount of lithium hydroxide exceeding the solubility in water to obtain a mixed slurry liquid having a pH of 9 to 11, and the obtained mixed slurry A step (II) of completing the reaction in the mixed slurry liquid by purging nitrogen with respect to the liquid to obtain a lithium manganese phosphate positive electrode active material precursor as a precursor slurry liquid, and the obtained precursor slurry A compound containing a manganese compound, an iron compound and a metal M (M represents Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd or Gd) is added to the liquid, and then hydrothermal Step for reaction (III)
The manufacturing method of a lithium manganese phosphate positive electrode active material containing this.   2. The lithium manganese phosphate positive electrode active material according to claim 1, wherein the slurry water in step (I) contains 1.5 to 3.5 times as much lithium hydroxide based on the solubility of lithium hydroxide in water. Manufacturing method.   3. The method for producing a lithium manganese phosphate positive electrode active material according to claim 1, wherein, in the step (I), when the slurry water is stirred while dropping phosphoric acid, the slurry water is cooled to a boiling point temperature or lower.   4. The lithium manganese phosphate according to claim 1, wherein the mixed slurry obtained in step (I) contains 0.28 to 0.38 mol of phosphoric acid with respect to 1 mol of lithium hydroxide. A method for producing a positive electrode active material.   The manufacturing method of the lithium manganese phosphate positive electrode active material of any one of Claims 1-4 which adjusts the dissolved oxygen concentration in a precursor slurry liquid to 0.5 mg / L or less in process (II).   The method for producing a lithium manganese phosphate positive electrode active material according to any one of claims 1 to 5, which is subjected to a hydrothermal reaction using a steam heating autoclave in step (III).   A lithium manganese phosphate positive electrode active material obtained by the production method according to claim 1. The lithium manganese phosphate positive electrode active material according to claim 7, comprising a lithium manganese phosphate compound represented by the following formula (A).
LiFe _a Mn _b M _c PO ₄ (A)
(In the formula, M represents Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd or Gd. A, b and c are 0 <a <0.5, 0.5 <B <1, and 0 <c ≦ 0.2, and 2a + 2b + (M valence) × c = 2).   A lithium ion battery containing the lithium manganese phosphate positive electrode active material according to claim 7 or 8 as a positive electrode material.