JP2014120365A - Process of manufacturing positive electrode active material for lithium ion battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new process of manufacturing a positive electrode active material containing carbon coated lithium iron silicate.SOLUTION: The process of manufacturing a positive electrode active material for a lithium ion battery includes: mixing by using a ball mill, olivine silicate compound fine particles containing a transition metal (M) (M represents Fe, Ni, Co, Al, Zn, V, Zr, or Mn. However, not containing lithium iron silicate.), a conductive carbon material, and a dispersion liquid containing a solvent soluble organic compound and a solvent; drying; and then calcinating.

Description

  The present invention relates to a method for producing a positive electrode active material for a lithium ion battery.

  Lithium ion batteries are a type of non-aqueous electrolyte battery and are used in a wide range of fields such as mobile phones, digital cameras, notebook PCs, hybrid cars, and electric cars. Lithium ion batteries mainly use lithium metal oxide as a positive electrode material and a carbon material such as graphite as a negative electrode material.

As this positive electrode material, lithium cobaltate (LiCoO ₂ ), lithium manganate (LiMnO ₂ ), lithium iron phosphate (LiFePO ₄ ), lithium iron silicate (Li ₂ FeSiO ₄ ) and the like are known. Among these, Li ₂ FeSiO _{4 and the} like are olivine silicate compounds having an olivine structure and useful as a positive electrode material for a high capacity lithium ion battery.

As a method for producing an olivine silicate compound positive electrode material such as Li ₂ FeSiO _4, a solid phase method is generally used in which a mixture of a Li source, a transition metal (M) source and a silicate source is pulverized and fired at 500 to 900 ° C. (Patent Documents 1 and 2). However, in the solid phase method, it is necessary to perform firing and pulverization in an inert gas atmosphere, which requires complicated operations and it is difficult to control the particle size and crystallinity.
In contrast, Non-Patent Documents 1 and 2 have a description that Li ₂ Mn _1-y Fe _y SiO ₄ (y = 0 to 1) can be obtained by hydrothermal synthesis.

JP 2001-266882 A JP 2002-198050 A

GS Yuasa Technical Report June 2009, Vol. 6, No. 1, p21-26 R. Dominiko et al, Journal of Power Sources 184 (2008), p462-468.

An olivine silicate compound such as lithium iron silicate obtained by hydrothermal synthesis is extremely useful as a positive electrode material because of its small particle size and uniformity. However, in order to make a positive electrode active material, these compounds need to be coated with a conductive material such as carbon black. However, when a carbon source is added to a hydrothermal synthesis reaction system, lithium iron silicate is a by-product. It turns out that the problem of generating.
Therefore, an object of the present invention is to provide a new method for producing a positive electrode active material containing a carbon-coated olivine silicate compound.

  Therefore, as a result of various studies on carbon coating means of olivine silicate compounds other than lithium iron silicate, the present inventor has obtained a sufficient discharge capacity in the method of mixing and grinding the olivine silicate compound and a carbon source such as a conductive carbon material. Despite the fact that the positive electrode active material can not be obtained, it is quite surprising that a liquid in which an olivine silicate compound, a conductive carbon material and a solvent-soluble organic compound are dispersed in a solvent is mixed using a ball mill, and then dried. Then, the inventors have found that a positive electrode active material having a high discharge capacity can be obtained by firing, and the present invention has been completed.

That is, the present invention provides olivine silicate compound fine particles containing transition metal (M) (M represents Fe, Ni, Co, Al, Zn, V, Zr or Mn, but does not contain lithium iron silicate). A method for producing a positive electrode active material for a lithium ion battery, comprising mixing a dispersion containing a conductive carbon material, a solvent-soluble organic compound and a solvent using a ball mill, drying and firing. is there.
Moreover, this invention provides the lithium ion battery which has a positive electrode containing the positive electrode active material obtained by said manufacturing method.

  The positive electrode active material obtained by the method of the present invention has a high discharge capacity and is useful as a positive electrode active material for lithium ion batteries. In addition, since a positive electrode active material having a high discharge capacity can be obtained with a small amount of carbon source, the cost of the lithium ion battery can be reduced.

The X-ray diffraction pattern of the powder obtained in Example 1 is shown. The X-ray diffraction pattern of the powder obtained in Example 2 is shown. The X-ray diffraction pattern of the powder obtained in Example 3 is shown.

  The manufacturing method of the positive electrode active material for lithium ion batteries of this invention shows the olivine silicate compound microparticles | fine-particles (M is Fe, Ni, Co, Al, Zn, V, Zr, or Mn containing a transition metal (M). However, It is characterized in that it does not contain lithium iron silicate), a conductive carbon material, a solvent-soluble organic compound and a dispersion containing a solvent are mixed using a ball mill, dried, and then fired.

Specifically, the olivine silicate compound fine particles containing the transition metal (M) are fine particles comprising an olivine silicate compound represented by any one of the following formulas (1) to (5). Such a compound does not include Li ₂ FeSiO ₄ .
Li ₂ M'SiO ₄ (1)
(In the formula, M ′ represents one or more selected from Ni, Co and Mn.)
_{Li a 'Fe x Mn y Al} z SiO 4 ··· (2)
(Where, a ′, x, y and z are 1 <a ′ ≦ 2, 0 ≦ x <1, 0 ≦ y <1, 0 <z <2/3, a ′ + 2x + 2y + 3z = 4, and x + y ≠ Indicates a number satisfying 0.)
_{Li a "Fe x Mn y V} z 'SiO 4 ··· (3)
(Where a ^" , x, y and z 'are 1 <a ^" ≤2, 0≤x <1, 0≤y <1, 0 <z'<1, a ^" + 2x + 2y + (2-5) z '= 4 and a number satisfying x + y ≠ 0.)
_{Li a "Fe x Mn y Zr} z" SiO 4 ··· (4)
(Where a ^" , x, y and z ^" are 1 <a ^" ≤2, 0≤x <1, 0≤y <1, 0 <z ^" <0.5, a ^" + 2x + 2y + 4z ^" = 4, And a number satisfying x + y ≠ 0.)
_{Li 2 Fe x Mn y Zn q} SiO 4 ··· (5)
(In the formula, x, y, and q represent numbers satisfying 0 ≦ x <1, 0 ≦ y <1, 0 <q <1, x + y + q = 1, and x + y ≠ 0.)

  The olivine silicate compound may be obtained by a solid phase method in which a mixture of a Li source, a transition metal (M) source and a silicate source is pulverized and fired at 500 to 900 ° C., but the silicate source, the transition metal ( It is preferable to use a product obtained by hydrothermal reaction of a mixture of M) source and lithium source in that a uniform particle size can be obtained.

  As a method for producing olivine silicate compound fine particles, (A) a basic aqueous dispersion containing a lithium compound, a silicate compound and an antioxidant, and a transition metal (M) sulfate are mixed, and the resulting mixture is obtained. A method of hydrothermal reaction; or (B) a method of hydrothermal reaction of a basic aqueous dispersion containing a lithium compound, a silicate compound and a transition metal (M) organic acid salt is preferred.

  First, the method (A) will be described.

In the method (A), a basic aqueous dispersion containing a lithium compound, a silicate compound and an antioxidant is prepared separately from the transition metal (M) sulfate from the viewpoint of suppressing side reactions. Is preferred. Examples of the lithium compound include lithium hydroxide (for example, LiOH.H ₂ O), lithium carbonate (Li ₂ CO ₃ ), lithium sulfate, and lithium acetate, and lithium hydroxide and lithium carbonate are particularly preferable.

The silicic acid compound is not particularly limited as long as it is a reactive silica compound, and amorphous silica and Na ₄ SiO ₄ (for example, Na ₄ SiO ₄ .H ₂ O) are preferable. Of these, the use of Na ₄ SiO ₄ is more preferable because the aqueous dispersion becomes basic.

As the antioxidant, sodium hydrosulfite (Na ₂ S ₂ O ₄ ), aqueous ammonia, sodium sulfite and the like can be used. The content of the antioxidant in the aqueous dispersion is preferably equal to or less than the transition metal (M) because the formation of the olivine silicate compound is suppressed when added in a large amount. The molar ratio is more preferably 0.5 or less.

It is preferable that the lithium compound, the silicate compound and the antioxidant be a basic aqueous dispersion, separately from the transition metal (M) sulfate, in order to prevent side reactions and dissolve the silicate compound. The pH of the aqueous dispersion may be basic, but it is 12.0 to 13.5 to prevent side reactions (generation of transition metal oxides), solubility of silicic acid compounds and progress of the reaction. Particularly preferred in terms. The pH of the aqueous dispersion may be adjusted by adding a base such as sodium hydroxide, but it is particularly preferable to use Na ₄ SiO ₄ as the silicate compound.

  The concentration of the lithium compound in the aqueous dispersion is preferably 0.30 to 3.00 mol / l, more preferably 1.00 to 1.50 mol / l. The concentration of the silicate compound is preferably 0.15 to 1.50 mol / l, more preferably 0.50 to 0.75 mol / l. In preparing the aqueous dispersion, the order of addition of the lithium compound, the silicate compound and the antioxidant is not particularly limited, and these three components may be added to water.

  The amount of transition metal (M) sulfate added is preferably 0.15 to 1.50 mol / l in the reaction mixture, and more preferably 0.50 to 0.75 mol / l.

  Moreover, as for content of Si and Li in a reaction liquid mixture, 2 mol or more is preferable with respect to a transition metal (M).

In the method (A), the aqueous dispersion and the transition metal (M) sulfate are mixed and subjected to a hydrothermal reaction. Hydrothermal reaction should just be 100 degreeC or more, 130-180 degreeC is preferable, Furthermore 140-1
60 ° C. is preferred. The hydrothermal reaction is preferably performed in a pressure vessel. When the reaction is performed at 130 to 180 ° C, the pressure at this time is 0.3 to 0.9 MPa, and the pressure when the reaction is performed at 140 to 160 ° C is 0. 3 to 0.4 MPa. The hydrothermal reaction time is preferably 1 to 24 hours, more preferably 3 to 12 hours.

  By the hydrothermal reaction, an olivine silicate compound is obtained in high yield. Moreover, the average particle diameter of the obtained olivine silicate compound becomes 10-100 nm, and the crystallinity is also high.

  The obtained olivine silicate compound can be isolated by drying after filtration. As the drying means, freeze drying or vacuum drying is used.

  Next, the method (B) will be described. As the lithium compound and silicic acid compound, those similar to the method (A) are used.

  The method (B) is characterized in that a hydrothermal reaction is performed using a transition metal (M) organic acid salt as a transition metal (M) source. Usually, transition metal (M) organic acid salts are raw materials used in the solid phase method, and it was completely unexpected that side reactions can be suppressed by using them in hydrothermal reactions. As an organic acid used, a C1-C20 organic acid is preferable and a C2-C12 organic acid is more preferable. More specific organic acids include dicarboxylic acids such as oxalic acid and fumaric acid, hydroxycarboxylic acids such as lactic acid, and fatty acids such as acetic acid.

  In the method (B), Si and Li are preferably used in a molar ratio of 2 times or more with respect to the transition metal (M), and Si: Li: transition metal (M) is 1: 1: 2.5 to 1: 1. : About 3 is more preferable.

  The concentration of the lithium compound in the aqueous dispersion is preferably 0.30 to 3.00 mol / l, more preferably 1.00 to 1.50 mol / l. The concentration of the silicate compound is preferably 0.15 to 1.50 mol / l, more preferably 0.50 to 0.75 mol / l. The concentration of the transition metal (M) organic acid salt is preferably 0.15 to 1.50 mol / l, more preferably 0.50 to 0.75 mol / l.

In addition, an antioxidant may be added to the aqueous dispersion as necessary. As the antioxidant, sodium hydrosulfite (Na ₂ S ₂ O ₄ ), aqueous ammonia, sodium sulfite and the like can be used. The content of the antioxidant in the aqueous dispersion is preferably equal to or less than the transition metal (M) because the formation of the olivine silicate compound is suppressed when added in a large amount. The molar ratio is more preferably 0.5 or less.

The aqueous dispersion of these components is preferably basic in order to prevent side reactions and dissolve the silicate compound. The pH of the aqueous dispersion may be basic, but it is 12.0 to 13.5 to prevent side reactions (generation of transition metal oxides), solubility of silicic acid compounds and progress of the reaction. Particularly preferred in terms. The pH of the aqueous dispersion may be adjusted by adding a base such as sodium hydroxide, but it is particularly preferable to use Na ₄ SiO ₄ as the silicate compound.

  The addition order of the lithium compound, silicate compound, and transition metal (M) organic acid salt is not particularly limited. Moreover, atmospheric conditions may be sufficient.

  In the method (B), the aqueous dispersion is then subjected to a hydrothermal reaction. The hydrothermal reaction is preferably the same as in the method (A).

  By the hydrothermal reaction, an olivine silicate compound is obtained in high yield. Moreover, the average particle diameter of the obtained olivine silicate compound becomes 10-100 nm, and the crystallinity is also high.

  The obtained olivine silicate compound can be isolated by drying after filtration. As the drying means, freeze drying or vacuum drying is used.

  The average particle size of the olivine silicate compound fine particles used in the present invention is preferably 10 to 1000 nm from the viewpoint of the discharge capacity when a lithium ion battery is used.

  The conductive carbon material used in the present invention is preferably carbon black, more preferably acetylene black or ketjen black. The amount of the conductive carbon material used is preferably 0.01 to 20 parts by mass, more preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the olivine silicate compound fine particles from the viewpoint of good discharge capacity and economy. .

  The solvent-soluble organic compound may be either a water-soluble organic compound or an organic solvent-soluble organic compound, more preferably a water-soluble organic compound, and particularly preferably a water-soluble alcoholic organic compound or a water-soluble fatty acid. Specific examples include glucose, fructose, polyethylene glycol, polyvinyl alcohol, carboxymethylcellulose, saccharose, starch, dextrin, citric acid and the like, and sugars such as glucose, fructose, saccharose, dextrin are more preferred. The amount of the solvent-soluble organic compound used is preferably 0.01 to 20 parts by mass, more preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the olivine silicate compound fine particles from the viewpoint of good discharge capacity and economy.

  In the present invention, the mass ratio of the conductive carbon material and the solvent-soluble organic compound is preferably 1:10 to 10: 1, and preferably 1: 5 to 5: from the viewpoint of obtaining a synergistic effect by the combined use of these components. 1 is more preferable, and 1: 3 to 3: 1 is more preferable. The total amount of the conductive carbon material and the solvent-soluble organic compound is preferably 0.02 to 30 parts by mass, more preferably 0.2 to 30 parts by mass with respect to 100 parts by mass of the olivine silicate compound fine particles, from the viewpoint of discharge capacity and economy. 20 parts by mass is preferable, and 0.2 to 15 parts by mass is particularly preferable.

  The solvent may be either water or an organic solvent, but water is preferred.

  The olivine silicate compound fine particles, the conductive carbon material and the solvent-soluble organic compound are dispersed in a solvent. The amount of the solvent used is preferably 200 to 500 parts by mass, more preferably 200 to 300 parts by mass with respect to 100 parts by mass of the olivine silicate compound fine particles. Is preferred.

The ball mill apparatus used for mixing the obtained dispersion liquid may be an apparatus used for ordinary ball milling. Examples of the container used include steel, stainless steel, and nylon, and examples of the inner wall include alumina brick, magnetic material, natural silica, rubber, and urethane. As the ball, alumina sphere, natural silica, iron ball, zirconia ball or the like is used. The size of the ball is preferably ³ mm to 20 mm, and the amount of the ball used is preferably 0.5 to 1.0 g / cm ³ with respect to the container capacity.

  Ball mill mixing is preferably performed for 10 minutes or more, more preferably for 3 hours or more, and even more preferably for 6 hours or more under the condition of 10 to 100 revolutions / minute. Further, from the viewpoint of economy, it is preferably 24 hours or less.

  The obtained mixture is dried after filtration if necessary. 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 carbon is supported on the surface of the olivine silicate compound can be obtained.

  The obtained positive electrode active material is excellent in terms of discharge capacity, and is useful as a positive electrode material for lithium ion batteries. The lithium ion battery to which the positive electrode active material of the present invention can be applied is not particularly limited as long as it is a lithium ion secondary battery and 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 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 Next, an Example is given and this invention is demonstrated in detail.

[Reference Example 1]
Ion-exchanged water (75 cm ³ ) was added to LiOH · H ₂ O 4.20 g (0.1 mol) and Na ₄ SiO ₄ · nH ₂ O 1.40 g (0.05 mol), and the mixture was stirred for 12 hours. Obtained. Also, 75 cm ³ of ion exchange water was added to 3.00 g (0.05 mol) of 28% ammonia water, and after bubbling nitrogen gas, 6.26 g (0.0225 mol) of FeSO ₄ .7H ₂ O, MnSO ₄ .5H ₂ O 5.42 g (0.0225 mol) and Zr (SO ₄ ) ₂ .4H ₂ O 0.71 g (0.0025 mol) were added and stirred for 0.5 hour to obtain a dispersion (B). Next, the dispersion (A) and the dispersion (B) were mixed and stirred for 10 minutes while bubbling nitrogen gas. The obtained liquid mixture was thrown into the autoclave and hydrothermal reaction was performed at 150 degreeC for 12 hours. The pressure in the autoclave was 0.48 MPa. The produced crystals were filtered and then washed with water, and then the crystals were lyophilized for about 12 hours to obtain 4.2 g of Li ₂ Fe _0.45 Mn _0.45 Zr _0.05 SiO ₄ powder.

[Reference Example 2]
Ion-exchanged water (75 cm ³ ) was added to LiOH · H ₂ O 4.20 g (0.1 mol) and Na ₄ SiO ₄ · nH ₂ O 1.40 g (0.05 mol), and the mixture was stirred for 12 hours. Obtained. Also, 75 cm ³ of ion exchange water was added to 3.00 g (0.05 mol) of 28% ammonia water, and after bubbling nitrogen gas, 6.26 g (0.0225 mol) of FeSO ₄ .7H ₂ O, MnSO ₄ .5H ₂ O 5.42 g (0.0225 mol) and ZnSO ₄ .7H ₂ O 1.31 g (0.005 mol) were added and stirred for 0.5 hour to obtain a dispersion (B). Next, the dispersion (A) and the dispersion (B) were mixed and stirred for 10 minutes while bubbling nitrogen gas. The obtained liquid mixture was thrown into the autoclave and hydrothermal reaction was performed at 150 degreeC for 12 hours. The pressure in the autoclave was 0.48 MPa. The produced crystals were filtered and then washed with water, and then the crystals were freeze-dried for about 12 hours to obtain 4.1 g of Li ₂ Fe _0.45 Mn _0.45 Zn _0.05 SiO ₄ powder.

[Reference Example 3]
LiOH.H ₂ O 4.20 g (0.1 mol), Na ₄ SiO ₄ .nH ₂ O 1.40 g (0.05 mol) and Al (OH) ₃ 0.257 g (0.0033 mol) were added to ion-exchanged water 75 cm ^3. And stirred for 12 hours to obtain a dispersion (A). Also, 75 cm ³ of ion exchange water was added to 3.00 g (0.05 mol) of 28% ammonia water, and after bubbling nitrogen gas, 6.26 g (0.0225 mol) of FeSO ₄ .7H ₂ O, MnSO ₄ .5H ₂ O 5.42 g (0.0225 mol) was added and stirred for 0.5 hour to obtain a dispersion (B). Next, the dispersion (A) and the dispersion (B) were mixed and stirred for 10 minutes while bubbling nitrogen gas. The obtained liquid mixture was thrown into the autoclave and hydrothermal reaction was performed at 170 degreeC for 9 hours. The pressure in the autoclave was 0.48 MPa. The produced crystals were filtered and then washed with water, and then the crystals were lyophilized for about 12 hours to obtain 4.3 g of Li ₂ Fe _0.3 Mn _0.7 Al _0.066 SiO ₄ powder.

[Example 1]
10 g of water was added to 3.34 g of the Li ₂ Fe _0.45 Mn _0.45 Zr _0.05 SiO ₄ powder obtained in Reference Example 1, 0.19 g of ketjen black, and 0.45 g of glucose. The obtained dispersion was put into a ball mill pulverizer having a capacity of 400 cm ³ , and 320 g of zirconia balls (φ5 mm) was added thereto and mixed for 12 hours under the condition of 60 rpm. The obtained mixture was vacuum-dried at 80 ° C. and baked at 600 ° C. for 1 hour under a reducing atmosphere condition.

[Comparative Example 1]
The Li ₂ Fe _0.45 Mn _0.45 Zr _0.05 SiO ₄ powder 3.34 g obtained in Reference Example 1 and 0.9 g of glucose were put into a ball mill pulverizer having a capacity of 400 cm ³ , and 320 g of zirconia balls (φ5 mm) were put therein. The mixture was mixed for 12 hours at 60 rpm. The obtained mixture was baked at 600 ° C. for 1 hour under a reducing atmosphere condition.

[Comparative Example 2]
10 g of water was added to 3.34 g of the Li ₂ Fe _0.45 Mn _0.45 Zr _0.05 SiO ₄ powder obtained in Reference Example 1 and 0.38 g of Ketjen Black. The obtained dispersion was put into a ball mill pulverizer having a capacity of 400 cm ³ , and 320 g of zirconia balls (φ5 mm) was added thereto and mixed for 12 hours under the condition of 60 rpm. The obtained mixture was vacuum-dried at 80 ° C. and baked at 600 ° C. for 1 hour under a reducing atmosphere condition.

[Example 2]
10 g of water was added to 3.34 g of the Li ₂ Fe _0.45 Mn _0.45 Zn _0.05 SiO ₄ powder obtained in Reference Example 2, 0.19 g of ketjen black, and 0.45 g of glucose. The obtained dispersion was put into a ball mill pulverizer having a capacity of 400 cm ³ , and 320 g of zirconia balls (φ5 mm) was added thereto and mixed for 12 hours under the condition of 60 rpm. The obtained mixture was vacuum-dried at 80 ° C. and baked at 600 ° C. for 1 hour under a reducing atmosphere condition.

[Comparative Example 3]
3.34 g of Li ₂ Fe _0.45 Mn _0.45 Zn _0.05 SiO ₄ powder obtained in Reference Example 2 and 0.9 g of glucose were put into a ball mill pulverizer having a capacity of 400 cm ³ , and 320 g of zirconia balls (φ5 mm) were put into this. And mixed for 12 hours under the condition of 60 rpm. The obtained mixture was baked at 600 ° C. for 1 hour under a reducing atmosphere condition.

[Comparative Example 4]
10 g of water was added to 3.34 g of Li ₂ Fe _0.45 Mn _0.45 Zn _0.05 SiO ₄ powder obtained in Reference Example 2 and 0.38 g of Ketjen Black. The obtained dispersion was put into a ball mill pulverizer having a capacity of 400 cm ³ , and 320 g of zirconia balls (φ5 mm) was added thereto and mixed for 12 hours under the condition of 60 rpm. The obtained mixture was vacuum-dried at 80 ° C. and baked at 600 ° C. for 1 hour under a reducing atmosphere condition.

[Example 3]
10 g of water was added to 3.34 g of Li ₂ Fe _0.3 Mn _0.7 Al _0.066 SiO ₄ powder obtained in Reference Example 3, 0.19 g of _ketjen black, and 0.45 g of glucose. The obtained dispersion was put into a ball mill pulverizer having a capacity of 400 cm ³ , and 320 g of zirconia balls (φ5 mm) was added thereto and mixed for 12 hours under the condition of 60 rpm. The obtained mixture was vacuum-dried at 80 ° C. and baked at 600 ° C. for 1 hour under a reducing atmosphere condition.

[Comparative Example 5]
3.34 g of Li ₂ Fe _0.3 Mn _0.7 Al _0.066 SiO ₄ powder obtained in Reference Example 3 and 0.9 g of glucose were put into a ball mill pulverizer with a capacity of 400 cm ³ , and 320 g of zirconia balls (φ5 mm) were put therein. And mixed for 12 hours under the condition of 60 rpm. The obtained mixture was baked at 600 ° C. for 1 hour under a reducing atmosphere condition.

[Comparative Example 6]
10 g of water was added to 3.34 g of the Li ₂ Fe _0.3 Mn _0.7 Al _0.066 SiO ₄ powder obtained in Reference Example 3 and 0.38 g of Ketjen Black. The obtained dispersion was put into a ball mill pulverizer having a capacity of 400 cm ³ , and 320 g of zirconia balls (φ5 mm) was added thereto and mixed for 12 hours under the condition of 60 rpm. The obtained mixture was vacuum-dried at 80 ° C. and baked at 600 ° C. for 1 hour under a reducing atmosphere condition.

[Test Example 1]
X-ray diffraction of the fired products obtained in Examples 1 to 3 was performed. The obtained X-ray diffraction patterns are shown in FIGS.
[Test Example 2]
Using the fired products obtained in Examples 1 to 3 and Comparative Examples 1 to 6, positive electrodes of lithium ion secondary batteries were produced. The fired product (active material), ketjen black (conductive agent), and polyvinylidene fluoride (binding agent) obtained in Examples 1 to 3 and Comparative Examples 1 to 6 were mixed at a weight ratio of 75:15:10. And N-methyl-2-pyrrolidone was added thereto and kneaded sufficiently 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 secondary 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 with a dew point of −50 ° C. or lower to produce a coin-type lithium secondary battery (CR-2032).
A charge / discharge test at a constant current density was performed using the manufactured lithium ion secondary battery. The charging conditions at this time were constant current charging with a current of 0.1 CA (33 mA / g) 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 obtained discharge capacity is shown in Table 1.

  From Table 1, it can be seen that the lithium ion batteries using Examples 1 to 3 which are the positive electrode materials of the present invention have excellent battery characteristics even though the amount of carbon is small.

Claims (9)

  Olivine silicate compound fine particles containing transition metal (M) (M represents Fe, Ni, Co, Al, Zn, V, Zr or Mn, but does not contain lithium iron silicate), conductive carbon material, A method for producing a positive electrode active material for a lithium ion battery, wherein a dispersion containing a solvent-soluble organic compound and a solvent is mixed using a ball mill, dried and then fired.   The method according to claim 1, wherein the conductive carbon material is carbon black.   The process according to claim 1 or 2, wherein the solvent-soluble organic compound is a compound selected from a water-soluble alcoholic organic compound and a water-soluble fatty acid.   The method according to any one of claims 1 to 3, wherein the conductive carbon material is carbon black, the solvent-soluble organic compound is a water-soluble alcoholic organic compound, and the solvent is water.   The manufacturing method according to any one of claims 1 to 4, wherein the mass ratio of the conductive carbon material and the solvent-soluble organic compound is 1:10 to 10: 1.   The manufacturing method according to any one of claims 1 to 5, wherein the total amount of the conductive carbon material and the solvent-soluble organic compound is 0.1 to 20 parts by mass with respect to 100 parts by mass of the lithium iron silicate fine particles.   The olivine silicate compound fine particles containing a transition metal (M) are obtained by hydrothermal reaction of a mixture of a silicate source, a transition metal (M) source, and a lithium source. Manufacturing method.   The production method according to any one of claims 1 to 7, wherein the firing conditions are 400 ° C or higher and 10 minutes to 3 hours under an inert gas atmosphere or reducing conditions.   The lithium ion battery which has a positive electrode containing the positive electrode active material obtained by the manufacturing method of any one of Claims 1-8.

Images