JP5688126B2 - Method for producing lithium manganese phosphate positive electrode active material - Google Patents

Description

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

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 compounds have been developed as positive electrode materials in such batteries. Lithium manganese phosphate is one of them, but because the material itself has low conductivity, it is desirable to coat it with a carbon material for effective use as a positive electrode active material, and the particles should be sufficiently covered. Miniaturization is also important.
Under these circumstances, for example, Patent Document 1 discloses a method of obtaining composite particles by wet-grinding and mixing inorganic particles such as LiFePo ₄ and LiMnPo ₄ with a conductive material using a planetary ball mill. It has also been shown that the resulting particles are highly conductive.

JP 2009-302044 A

  However, since the refined lithium manganese phosphate particles tend to aggregate secondary particles and easily form secondary particles, the method as described in Patent Document 1, Although it is possible to coat the carbon material on the outermost surface of the secondary particles, it is difficult to coat the surface of the primary particles with the carbon material, and further improving the conductivity as a positive electrode active material of a lithium ion battery. There is still room for improvement.

  Accordingly, an object of the present invention is to provide a lithium manganese phosphate positive electrode active material capable of obtaining a lithium manganese phosphate positive electrode active material capable of exhibiting excellent battery properties while using finely divided primary particles of lithium manganese phosphate. It is in providing the manufacturing method of.

  Accordingly, the present inventors have made various studies and as a result, primary particles of lithium manganese phosphate, which are fine particles, and a water-soluble organic compound and solvent having a specific quantitative relationship are used in a ball having a specific spherical diameter. It was found that by mixing by the ball mill method, a lithium manganese phosphate positive electrode active material in which the surface of both the primary particles and the secondary particles is effectively coated with a carbon material can be produced, and the present invention has been completed. .

That is, in the present invention, lithium manganese phosphate primary particles (X) having an average particle diameter of 200 nm or less, a water-soluble organic compound (Y), and a solvent (Z) composed of water and a low-boiling organic solvent, Including the step of mixing by the ball mill method used,
The amount of the solvent (Z) is 5,000 to 50,000 parts by mass with respect to 100 parts by mass of the water-soluble organic compound (Y) in terms of carbon atoms,
The water content in the solvent (Z) is 1 to 50% by mass, and the ball diameter is 2,000 to 200,000 with respect to the average particle diameter of the lithium manganese phosphate primary particles (X). The manufacturing method of the lithium manganese phosphate positive electrode active material which is double 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, while using lithium manganese phosphate, which is extremely fine primary particles, a carbon material is effectively applied to the surfaces of both the primary particles and the secondary particles. A positive electrode active material that can be coated and sufficiently enhanced in conductivity can be manufactured. 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 charging / discharging capacity curve of the battery obtained in Example 1 and Comparative Examples 1-3 is shown. The charge / discharge capacity curve of the battery obtained in Example 1 and Comparative Example 4 is shown.

Hereinafter, the present invention will be described in detail.
The method for producing a lithium manganese phosphate positive electrode active material of the present invention comprises primary lithium manganese phosphate particles (X) having an average particle size of 200 nm or less, a water-soluble organic compound (Y), water and a low-boiling organic solvent. A step of mixing the solvent (Z) by a ball mill method using a ball,
The amount of the solvent (Z) is 5,000 to 50,000 parts by mass with respect to 100 parts by mass of the water-soluble organic compound (Y) in terms of carbon atoms,
The water content in the solvent (Z) is 1 to 50% by mass, and the ball diameter is 2,000 to 200,000 with respect to the average particle diameter of the lithium manganese phosphate primary particles (X). Is double.

  In the present invention, lithium manganese phosphate primary particles (X) having an average particle diameter of 200 nm or less are used as a starting material. Since such primary particles are extremely fine, they have a property of being more easily aggregated than ordinary primary lithium manganese phosphate particles. However, according to the production method of the present invention, it is possible to effectively suppress the aggregation of the primary particles, or to satisfactorily loosen the aggregated primary particles, so that the surface of the primary particles is effectively coated with the carbon material. In addition, the surface of the secondary particles in which the primary particles are aggregated can be effectively coated with the carbon material.

  The average particle diameter of the lithium manganese phosphate primary particles (X) is 200 nm or less, and is preferably 10 to 100 nm, more preferably 10 from the viewpoint of enhancing the conductivity of the obtained lithium manganese phosphate positive electrode active material. ~ 50 nm.

The lithium manganese phosphate primary particles (X) are compounds containing at least manganese (Mn) as a transition metal. Specifically, for example, it is represented by the following formula (A).
Li Fe _a Mn _1-a PO ₄ (A)
(In the formula, a represents a number satisfying 0 ≦ a <0.5.)
In the above formula (A), a is preferably 0.05 to 0.4, more preferably 0.075 to 0.35 from the viewpoint of obtaining a lithium manganese phosphate positive electrode active material having higher battery properties. Yes, more preferably 0.1 to 0.3.

  In the production method of the present invention, the lithium manganese phosphate primary particles (X) are mixed with a water-soluble organic compound (Y) and a solvent (Z) composed of water and a low-boiling organic solvent. The water-soluble organic compound (Y) means an organic compound dissolved in 100 g of water at 25 ° C. in an amount of 0.4 g or more, preferably 1.0 g or more in terms of carbon atom of the water-soluble organic compound (Y). It functions as a carbon material that covers the surfaces of the lithium manganese oxide primary particles (X) and the secondary particles. Examples of the water-soluble organic compound (Y) include saccharides, polyols, polyethers, and organic acids. More specifically, for example, glucose, fructose, polyethylene glycol, polyvinyl alcohol, carboxymethyl cellulose, saccharose, starch, dextrin, citric acid and the like can be mentioned. Among these, glucose, fructose, saccharose, and dextrin are preferable, and glucose is more preferable from the viewpoint of enhancing the solubility and dispersibility in a solvent and effectively functioning as a carbon material.

  In the present invention, from the viewpoint of satisfactorily covering the surfaces of the lithium manganese phosphate primary particles (X) and the secondary particles, the carbon material other than the water-soluble organic compound (Y) is composed of lithium manganese phosphate primary particles ( It is preferable not to use it as a carbon material for coating the surface of X) and its secondary particles. Examples of the carbon material other than the water-soluble organic compound (Y) include conductive carbon materials such as carbon black such as acetylene black and ketjen black, and organic solvent-soluble organic compounds.

  The amount of the water-soluble organic compound (Y) is based on 100 parts by mass of the lithium manganese phosphate primary particles (X) from the viewpoint of satisfactorily covering the surfaces of the lithium manganese phosphate primary particles (X) and the secondary particles. In terms of carbon atom, it is preferably 2 to 20 parts by mass, more preferably 5 to 15 parts by mass, and still more preferably 8 to 13 parts by mass.

  When mixing the lithium manganese phosphate primary particles (X) with the water-soluble organic compound (Y) and the solvent (Z) composed of water and a low-boiling organic solvent, the amount of the solvent (Z) The amount of water in the solvent (Z) is 1 to 50% by mass with respect to 100 parts by mass in terms of carbon atom of the organic organic compound (Y). By mixing such a solvent (Z) with lithium manganese phosphate primary particles (X) and a water-soluble organic compound (Y), the water-soluble organic compound (Y) dissolves well in water in the solvent (Z). However, it can disperse | distribute uniformly in the whole solvent, and can coat | cover the surface of lithium manganese phosphate primary particle (X) and its secondary particle effectively.

  From the viewpoint of efficiently removing the solvent (Z) by performing drying or the like later to efficiently obtain the lithium manganese phosphate positive electrode active material, the low boiling point organic solvent has a boiling point of less than 100 ° C. at 1 atmosphere, That is, the organic solvent is preferably lower than the boiling point of water, and the boiling point at 1 atm is more preferably 90 ° C. or lower. More specifically, it is a primary alcohol, secondary alcohol, tertiary alcohol or ether having polarity, and examples thereof include ethanol, diethyl ether, dichloromethane, acetone, methanol, propanol and isopropyl alcohol. . Especially, from a viewpoint of disperse | distributing the water which the water-soluble organic compound (Y) melt | dissolved favorably, ethanol and acetone are preferable and ethanol is more preferable.

  The content of water in the solvent (Z) comprising water and a low-boiling organic solvent is such that the water-soluble organic compound (Y) is dissolved well and the solvent (Z) is uniformly dispersed throughout the solvent (Z). ) The total amount is preferably 1 to 50% by mass, more preferably 1 to 20% by mass, still more preferably 3 to 17% by mass, and even more preferably 5 to 15% by mass. By using such an amount of water and a low-boiling organic solvent in combination as a solvent, even if extremely fine lithium manganese phosphate primary particles (X) having the property of being easily aggregated are used, the aggregation of primary particles is effective. Therefore, it is possible to satisfactorily unravel the primary particles that have been suppressed or agglomerated without collapsing, and the surface of the primary particles as well as the surface of the secondary particles can be effectively coated with the carbon material.

The amount of the solvent (Z) composed of water and a low-boiling organic solvent is selected from the viewpoint of effectively covering the surfaces of the lithium manganese phosphate primary particles (X) and the secondary particles, and the carbon of the water-soluble organic compound (Y). Preferably it is 5,000-50,000 mass parts with respect to 100 mass parts of atom conversion amounts, More preferably, it is 10,000-40,000 mass parts.
Moreover, the amount of water is preferably 10 to 500 parts by mass, more preferably 10 to 200 parts by mass, and further preferably 30 to 170 parts by mass with respect to 100 parts by mass of lithium manganese phosphate primary particles (X). Part.

  The mixing order of the lithium manganese phosphate primary particles (X), the water-soluble organic compound (Y), and the solvent (Z) composed of water and a low-boiling organic solvent is not particularly limited, but the lithium manganese phosphate primary particles It is preferable to mix (X) and the water-soluble organic compound (Y), and add and mix the solvent (Z) composed of water and a low-boiling organic solvent.

  In the production method of the present invention, the lithium manganese phosphate primary particles (X), the water-soluble organic compound (Y) and the solvent (Z) are added to the average particle diameter of the lithium manganese phosphate primary particles (X) with 2, A process of mixing by a ball mill method using balls having a spherical diameter of 000 to 200,000 times is performed. A solvent (Z) in which the water-soluble organic compound (Y) is well dissolved and dispersed while suppressing aggregation of primary particles or loosening the aggregated primary particles by mixing using balls having such a spherical diameter. In addition, since the lithium manganese phosphate primary particles (X) can be mixed, the surface of the lithium manganese phosphate primary particles (X) and the secondary particles can be effectively coated with the water-soluble organic compound.

  The ball diameter of the balls used for mixing is 2,000 to 200,000 times the average particle diameter of the lithium manganese phosphate primary particles (X), from the viewpoint of effectively suppressing aggregation of the primary particles, or aggregation From the viewpoint of unraveling the primary particles, it is preferably 2,000 to 150,000 times, more preferably 2,000 to 100,000 times. The ball diameter of the balls used for mixing is preferably 50 to 5,000 μm, more preferably 50 to 500 μm.

  The mixing method using the balls is a ball mill method, and examples thereof include a planetary ball mill method, a rotating ball mill method, and a vibrating ball mill method, and an apparatus including a container made of steel, stainless steel, nylon, or the like is used. Among these, it is preferable to use the planetary ball mill method from the viewpoint of effectively suppressing aggregation of the lithium manganese phosphate primary particles (X), or from the viewpoint of satisfactorily loosening the aggregated primary particles.

Specifically, alumina balls, natural silica stones, iron balls, zirconia balls and the like are used as the balls. Moreover, it is preferable that the usage-amount of a ball | bowl is 0.3-0.5 g / cm < ³ > with respect to a container capacity | capacitance.

  The rotation speed of the ball mill during mixing is preferably 100 to 450 rpm, more preferably 300 to 450 rpm. The mixing time is preferably 5 to 60 minutes, more preferably 15 to 30 minutes.

  The obtained mixture is dried after filtration if necessary. Before drying, it is desirable to distill off the solvent (Z) in advance using an evaporator or the like. As the drying means, freeze drying or vacuum drying is used. Next, the firing is performed under an inert gas atmosphere or a reducing condition at 400 ° C. or higher, preferably 400 to 800 ° C. for 10 minutes to 3 hours, preferably 0.5 to 1.5 hours. preferable. By this treatment, a positive electrode active material in which the surface of the lithium manganese phosphate primary particles (X) and the secondary particles thereof are satisfactorily coated with a carbon material can be obtained.

  The lithium manganese phosphate positive electrode active material obtained by the production method of the present invention has a fine and uniform particle size, and the carbon material is effectively coated not only on the surface of the secondary particles but also on the surface of the primary particles. Therefore, high conductivity can be expressed, and it is extremely useful as a positive electrode material for a lithium ion battery. The average particle size of the lithium manganese phosphate positive electrode active material is preferably 10 to 100 nm, and more preferably 10 to 50 nm.

  In the production method of the present invention, the production method for obtaining the lithium manganese phosphate primary particles (X) having the above average particle size used as a starting material is not particularly limited. For example, the amount exceeds the solubility in water. The slurry water is stirred while dropping phosphoric acid into the slurry water containing lithium hydroxide, and after passing through the step (I) of obtaining a mixed slurry liquid having a pH of 9 to 11, the mixed slurry liquid thus obtained is obtained. It is preferable to use a lithium manganese phosphate precursor slurry obtained by passing through step (II) in which the reaction with the mixed slurry is completed by purging nitrogen. By using such a method, fine particles of lithium manganese phosphate primary particles (X) having the above average particle diameter can be easily obtained.

  Specifically, for example, 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 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 manner, dispersed particles of lithium manganese phosphate precursor are aggregated by adding phosphoric acid dropwise to a slurry liquid in which there is an excess amount of lithium hydroxide in a saturated state, and adding the mixture little by little, and stirring. Can be effectively suppressed and miniaturized effectively.
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 to obtain a lithium manganese phosphate precursor slurry liquid. In such a precursor slurry liquid, a lithium manganese phosphate 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), from the viewpoint of more effectively suppressing the oxidation of the lithium manganese phosphate precursor on the surface of the dispersed particles and miniaturizing the dispersed particles, the dissolved oxygen concentration in the mixed slurry liquid is 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 slurry liquid in which a lithium manganese phosphate 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 precursor (Li ₃ PO ₄ ) in the obtained slurry is preferably 30 to 5000 nm, more preferably 30 to 4,000 nm, and still more preferably 30 to 3 , 500 nm.
The average dispersed particle size of the lithium manganese phosphate precursor means a value measured using a dynamic light scattering nanotrack particle size analyzer (manufactured by Nikkiso Co., Ltd.).

  By including a step of adding a transition metal (M) compound containing at least a manganese compound and then subjecting it to a hydrothermal reaction, using the precursor slurry obtained by going through the steps (I) and (II). The lithium manganese phosphate primary particles (X) used in the production method of the present invention can be obtained.

  As the transition metal compound (M), at least a manganese compound is used. The manganese compound may be a divalent manganese compound, and examples thereof include manganese halide, manganese sulfate, and manganese acetate. These may be used alone or in combination of two or more. Among these, manganese sulfate is preferably used from the viewpoint of improving battery physical properties.

  Examples of other transition metal (M) compounds include iron compounds. 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 salt such as iron oxalate or iron acetate As well as hydrates thereof. Among these, iron sulfate is preferably used from the viewpoint of improving battery physical properties.

When a manganese compound and an iron compound are used as the transition metal (M) compound, the molar ratio used (manganese compound: iron compound) is preferably 99: 1 to 51:49, more preferably 95: 5 to 70. : 30, and more preferably 90:10 to 80:20. Moreover, the total addition amount of these transition metal compounds is preferably 0.99 to 1.01 mol with respect to 1 mol of lithium manganese phosphate precursor (Li ₃ PO ₄ ) contained in the precursor slurry liquid. More preferably, it is 0.995 to 1.005 mol.

The amount of water used for the hydrothermal reaction is determined based on the lithium manganese phosphate precursor contained in the precursor slurry from the viewpoint of the solubility of the transition metal compound, the ease of stirring, the efficiency of synthesis, and the like. to phosphate ion 1 mole of the body (Li ₃ PO _4), preferably 10 to 30 moles, more preferably 12.5 to 25 mol.

The order of addition of the transition metal (M) compound is not particularly limited. Moreover, while adding a transition metal compound, 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 mol with respect to 1 mol of the transition metal compound from the viewpoint of preventing the formation of lithium manganese phosphate by being added in excess. More preferably, it is 0.03-0.5 mol.

A mixed liquid obtained by adding a transition metal compound to the precursor slurry and adding an antioxidant or the like as required contains a large amount of lithium manganese phosphate precursor (trilithium phosphate: Li ₃ PO ₄ ). It is contained in. The content of the lithium manganese phosphate 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 a steam heating autoclave from the viewpoint of effectively preventing oxidation of the transition metal compound. 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 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 to 1 hour.

  After completion of the hydrothermal reaction, the produced lithium manganese phosphate 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. By this production method, lithium manganese phosphate primary particles (X) can be obtained.

Next, a lithium ion battery containing the lithium manganese phosphate positive electrode active material obtained by the method 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 battery. For example, carbonates, halogenated hydrocarbons, ethers, ketones, nitriles, lactones, oxolane A 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 sort of.

  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.

[Production Example 1: Production of primary lithium manganese phosphate particles (X)]
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 measured with a dynamic light scattering nanotrack particle size analyzer (manufactured by Nikkiso Co., Ltd.). there were.

Then, with respect to the precursor slurry _{21.7kg, FeSO 4 · 7H 2 O1.63kg} , added MnSO ₄ · H ₂ O 5.60kg, stirring speed 400rpm further added Na ₂ SO ₃ 46.8 g The mixture was obtained by stirring and mixing. 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%.

Next, the mixed solution was put into a synthesis container installed in a steam heating autoclave. 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 under conditions of 60 ° C. × 1 Torr to obtain lithium manganese phosphate primary particles (X) as a powder.
The average particle diameter of the obtained lithium manganese phosphate primary particles _{(X) (Li Fe 0.15 Mn} 0.85 PO 4) was 50nm.

[Example 1]
10 g of lithium manganese phosphate primary particles (X) obtained in Production Example 1 and 2.7 g of glucose were mixed and put into a container provided in a planetary ball mill (P-5, manufactured by Fritsch). A solvent obtained by mixing 90 g and 10 g of water was added.
Next, 100 g of a ball having a spherical diameter (100 μm) of 2,000 times the average particle diameter of the primary particles (X) was used and mixed at a rotational speed of 400 rpm for 1 hour. The obtained mixture was filtered, the solvent was distilled off using an evaporator, and then calcined at 600 ° C. for 1 hr in a reducing atmosphere to obtain a lithium manganese phosphate positive electrode active material.
The average particle diameter of the obtained lithium manganese phosphate positive electrode active material was 50 nm.

  Next, the obtained lithium manganese phosphate positive electrode active material, ketjen black (conductive agent), and polyvinylidene fluoride (binding agent) were mixed at a mixing ratio of 75:15:10, 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 (33 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 1.5 V. All temperatures were 30 ° C.
The discharge characteristics are shown in FIG. 1 from the results of the charge / discharge test.

[Comparative Example 1]
Manganese phosphate in the same manner as in Example 1 except that a solvent obtained by mixing 10 g of ethanol and 90 g of water was added to the mixture of lithium manganese phosphate primary particles (X) obtained in Production Example 1 and glucose. A lithium positive electrode active material was obtained.
The average particle diameter of the obtained lithium manganese phosphate positive electrode active material was 50 nm.
Next, in the same manner as in Example 1, a coin-type lithium ion battery (CR-2032) was produced using the obtained lithium manganese phosphate positive electrode active material, and a charge / discharge test was performed.
The discharge characteristics are shown in FIG. 1 from the results of the charge / discharge test.

[Comparative Example 2]
A lithium manganese phosphate positive electrode active material was obtained in the same manner as in Example 1 except that 100 g of ethanol was added as a solvent to the mixture of lithium manganese phosphate primary particles (X) obtained in Production Example 1 and glucose.
The average particle diameter of the obtained lithium manganese phosphate positive electrode active material was 50 nm.
Next, in the same manner as in Example 1, a coin-type lithium ion battery (CR-2032) was produced using the obtained lithium manganese phosphate positive electrode active material, and a charge / discharge test was performed.
The discharge characteristics are shown in FIG. 1 from the results of the charge / discharge test.

[Comparative Example 3]
A lithium manganese phosphate positive electrode active material was obtained in the same manner as in Example 1 except that 100 g of water was added as a solvent to the mixture of lithium manganese phosphate primary particles (X) obtained in Production Example 1 and glucose.
The average particle diameter of the obtained lithium manganese phosphate positive electrode active material was 50 nm.
Next, in the same manner as in Example 1, a coin-type lithium ion battery (CR-2032) was produced using the obtained lithium manganese phosphate positive electrode active material, and a charge / discharge test was performed.
The discharge characteristics are shown in FIG. 1 from the results of the charge / discharge test.

[Comparative Example 4]
A lithium manganese phosphate positive electrode active material was obtained in the same manner as in Example 1 except that a ball having a spherical diameter (12,500 μm) 250,000 times the average particle diameter of the primary particles (X) was used.
The average particle diameter of the obtained lithium manganese phosphate positive electrode active material was 50 nm.
Next, in the same manner as in Example 1, a coin-type lithium ion battery (CR-2032) was produced using the obtained lithium manganese phosphate positive electrode active material, and a charge / discharge test was performed.
The discharge characteristics from the results of the charge / discharge test are shown in FIG.

  From the results of FIGS. 1 and 2, the lithium ion battery using Example 1 as the positive electrode material showed excellent charge / discharge capacity, but Comparative Examples 1 to 3 and a predetermined ball without using a predetermined solvent were used. The charge / discharge capacity of a lithium ion battery using Comparative Example 4 in which the used mixing was not performed as a positive electrode material was not sufficient.

Claims (5)

Solvent (Z) comprising lithium manganese phosphate primary particles (X) having an average particle size of 200 nm or less, a water-soluble organic compound (Y), and a low-boiling organic solvent having a boiling point of less than 100 ° C. at 1 atm. Including a step of mixing by a ball mill method using a ball,
The amount of the solvent (Z) is 5,000 to 50,000 parts by mass with respect to 100 parts by mass of the water-soluble organic compound (Y) in terms of carbon atoms,
The water content in the solvent (Z) is 1 to 50% by mass, and the ball diameter is 2,000 to 200,000 with respect to the average particle diameter of the lithium manganese phosphate primary particles (X). The manufacturing method of the lithium manganese phosphate positive electrode active material which is double.   2. The lithium manganese phosphate positive electrode active material according to claim 1, wherein the carbon atom equivalent amount of the water-soluble organic compound (Y) is 2 to 20 parts by mass with respect to 100 parts by mass of the lithium manganese phosphate primary particles (X). Production method. The method for producing a lithium manganese phosphate positive electrode active material according to claim 1 or 2 , wherein the mixing by the ball mill method is a planetary ball mill method, a rotating ball mill method, or a vibration ball mill method. The lithium manganese phosphate primary particles (X) are represented by the following formula (A):
Li Fe _a Mn _1-a PO ₄ (A)
(In the formula, a represents a number satisfying 0 ≦ a <0.5.)
The manufacturing method of any one of Claims 1-3 represented by these. The lithium manganese phosphate positive electrode active material obtained by the manufacturing method of any one of Claims 1-4 .