JP5557220B2 - Method for producing positive electrode material for secondary battery - Google Patents

Description

  The present invention relates to a method for producing a positive electrode material for a secondary battery useful for a lithium ion secondary 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, LiFePO ₄ and Li ₂ FeSiO ₄ have an olivine structure and are useful as a positive electrode material for a high capacity lithium ion battery. Among these, lithium metal phosphate-based positive electrode materials such as LiFePO ₄ are known in which the particle size, particle size distribution, shape, and the like of the formed particles are controlled in order to further improve the physical properties of the obtained battery ( Patent Documents 1 and 2).

On the other hand, as a method for producing a lithium silicate metal positive electrode material such as Li ₂ FeSiO ₄ , a solid phase method in which a mixture of a Li source, an iron (metal) source and a silicate source is pulverized and fired at 500 to 900 ° C. Is common (Patent Documents 3 and 4). 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.
On the other hand, Non-Patent Document 1 describes that Li ₂ Mn _1-y Fe _y SiO ₄ (y = 0 to 1) can be obtained by hydrothermal synthesis. A lithium metal silicate-based positive electrode material obtained by hydrothermal synthesis is extremely useful as a positive electrode material because of its small particle size and uniformity.

Japanese Patent No. 4190912 JP 2006-32241 A JP 2001-266882 A JP 2002-198050 A

GS Yuasa Technical Report June 2009, Vol. 6, No. 1, p21-26

  Under these circumstances, by not only reducing the primary particle size constituting the lithium metal silicate positive electrode material by the inventors, but also controlling the particle size, density and shape of the secondary particles obtained therefrom, the battery physical properties can be improved. Although it was proved to improve further, as in the past, the lithium source, the iron source and the silicate source were mixed with water and subjected to a hydrothermal reaction, and even after undergoing granulation, drying and firing processes, The actual situation is that the particle size and the like of the obtained secondary particles cannot be sufficiently controlled.

  Therefore, the subject of this invention is providing the manufacturing method of the positive electrode material for secondary batteries which can form the secondary particle of the olivine type | mold silicate compound by which the particle size, density, and shape were controlled. .

  Therefore, the present inventors have a specific particle size and shape using a slurry adjusted in viscosity and pH while having a specific content of primary particles of an olivine-type silicate compound formed by hydrothermal reaction. By forming spherical secondary particles, it was found that a positive electrode material for a secondary battery exhibiting excellent battery physical properties was obtained, and the present invention was completed.

That is, according to the present invention, an olivine-type silicate compound containing a transition metal M (M represents Fe, Ni, Co, Al, Zn, V, or Mn) is subjected to a hydrothermal reaction to have an average particle size of 10 to 100 nm. Formed into primary particles,
A slurry containing 30 to 60% by mass of the obtained primary particles, a viscosity at 20 ° C. of 5 to 1000 mPa · s, and a pH of 10.00 to 13.0 is produced.
The slurry thus obtained is granulated to form spherical secondary particles having an average particle diameter of 1 to 100 μm, and is fired as necessary. A method for producing a positive electrode material for a secondary battery is provided.
Moreover, this invention provides the secondary battery which has a positive electrode containing the positive electrode material for secondary batteries obtained by said manufacturing method.

  The positive electrode material for secondary batteries obtained by the production method of the present invention has a high charge / discharge capacity and is very useful as a positive electrode material for secondary batteries.

The SEM image of the secondary particle which comprises the olivine type | mold silicate compound obtained in Example 1 is shown. The SEM image of the secondary particle which comprises the olivine type | mold silicate compound obtained in Example 2 is shown. The SEM image of the secondary particle which comprises the olivine type | mold silicate compound obtained by the comparative example 1 is shown. The charging / discharging curve of the battery using the positive electrode material obtained in Example 1 is shown. The charging / discharging curve of the battery using the positive electrode material obtained in Example 2 is shown. The charging / discharging curve of the battery using the positive electrode material obtained by the comparative example 1 is shown.

Hereinafter, the present invention will be described in detail.
In the production method of the present invention, first, an olivine-type silicate compound containing a transition metal M (M represents Fe, Ni, Co, Al, Zn, V, Mn, or Zr) is subjected to a hydrothermal reaction to obtain an average particle size. Primary particles having a diameter of 10 to 100 nm are formed. The olivine-type silicate compound containing the transition metal M is specifically represented by any of the following formulas (1) to (5).
Li ₂ Fe _x Mn _y Co _z SiO ₄ (1)
(In the formula, x, y, and z represent numbers satisfying 0 ≦ x <1, 0 ≦ y <1, 0 <z <1, x + y + z = 1, and x + y ≠ 0.)
_{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 <1, a ′ + 2x + 2y + 3z = 4, and x + y ≠ 0. Indicates the number to satisfy.)
Li ₂ M'SiO _{4-x '} F _2x' (3)
(In the formula, M ′ represents one or more selected from Fe, Mn, Co and Ni, and x ′ represents a number satisfying 0 <x ′ ≦ 8.)
_{Li a "Fe x Mn y V} z SiO 4 ··· (4)
(Where a ″, x, y and z are 1 <a ″ ≦ 2, 0 ≦ x <1, 0 ≦ y <1, 0 <z <1, a ″ + 2x + 2y + (2 to 5) z = 4. , And a number satisfying x + y ≠ 0.)
Li ₂ Fe _x Mn _y Zn _z SiO ₄ (5)
(In the formula, x, y, and z represent numbers satisfying 0 ≦ x <1, 0 ≦ y <1, 0 <z <1, x + y + z = 1, and x + y ≠ 0.)
_{Li 2 Fe w Mn x "Co} y" Zr z "SiO 4 ··· (6)
(Where w, x ", y" and z "are 0≤w≤1, 0≤x" ≤1, 0≤y "≤1, 0≤z" ≤0.5, and w + x "+ y". = Indicates a number satisfying 1-2z ".)

  In subjecting the olivine-type silicate compound to a hydrothermal reaction, a basic aqueous dispersion containing a lithium compound, a silicate compound and an antioxidant is used by using a transition metal (M) source and, if necessary, a fluorine source. It is good to make.

Examples of the transition metal (M) source include transition metal sulfate represented by MSO ₄ (wherein M represents Fe, Ni, Co, Al, Zn, V, Mn, or Zr) or (R) _2. An organic acid transition metal salt represented by M (wherein R represents an organic acid residue, M represents Fe, Ni, Co, Al, Zn, V, Mn or Zr), or (R) ₂ M (Wherein, R represents an organic acid residue, and M represents Fe, Ni, Co, Al, Zn, V, Mn, or Zr).

Specific examples of the transition metal sulfate MSO ₄ include FeSO ₄ , NiSO ₄ , CoSO ₄ , Al ₂ (SO ₄ ) ₃ , ZnSO ₄ , VOSO ₄ , MnSO ₄ or Zr (SO ₄ ) _2, which are You may use 1 type or in mixture of 2 or more types. When using a transition metal sulfate, a basic aqueous dispersion containing a lithium compound, a silicate compound and an antioxidant is prepared in advance separately from the transition metal sulfate from the viewpoint of suppressing side reactions. preferable. In this case, the aqueous dispersion and the transition metal sulfate are mixed and subjected to a hydrothermal reaction. The amount of transition metal 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. In this case, the content of Si and Li in the reaction mixture is preferably 2 mol or more with respect to M.

The organic acid represented by an organic acid transition metal salt (R) of ₂ M R, preferably an organic acid having 1 to 20 carbon atoms, more preferably an organic acid having 2 to 12 carbon atoms. 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. When using an organic acid transition metal salt, it is preferable to prepare a basic aqueous dispersion containing a lithium compound, a silicic acid compound and an antioxidant, and further containing an organic acid transition metal salt. Usually, an organic acid salt is a raw material used in a solid phase method, but side reactions can be suppressed by using it in a hydrothermal reaction. In this case, Si and Li in the reaction mixture are preferably used in a molar ratio of 2 or more with respect to the transition metal, and Si: Li: M is from 1: 1: 2.5 to 1: 1: 3. The degree is more preferable.

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 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 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. The concentration of the silicate compound in the aqueous dispersion is preferably 0.15 to 1.50 mol / l, more preferably 0.50 to 0.75 mol / l.

As the fluorine source, a fluorine compound can be used, and examples thereof include NH ₄ F.

Examples of the antioxidant include sodium hydrosulfite (Na ₂ S ₂ O ₄ ), aqueous ammonia, sodium sulfite and the like. 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-type silicate compound is suppressed when added in a large amount. The molar ratio is more preferably 0.5 or less.

When transition metal sulfate MSO ₄ (wherein M represents Fe, Ni, Co, Al, Zn, V, Mn, or Zr) is used as the transition metal source, transition metal sulfate from the viewpoint of suppressing side reactions. Apart from this, it is preferable to prepare in advance a basic aqueous dispersion containing a lithium compound, a silicate compound and an antioxidant. In this case, the aqueous dispersion and the transition metal sulfate are mixed and subjected to a hydrothermal reaction. 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 aqueous dispersion is preferably basic in terms of preventing side reactions and dissolving the silicate compound. Specifically, the pH of the aqueous dispersion is preferably 12.0 to 13.5. The pH of the aqueous dispersion may be adjusted by adding a base such as sodium hydroxide, but it is preferable to use Na ₄ SiO ₄ as the silicate compound.

  The hydrothermal reaction should just be 100 degreeC or more, 130-180 degreeC is preferable and 140-160 degreeC is more preferable. 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, Li ₂ MSiO ₄ (M is the same as described above) is obtained in a high yield, and its crystallinity is also high. After the hydrothermal reaction, it is preferable to obtain primary particles by collecting and washing the produced LiMSiO ₄ by filtration. The washing is preferably carried out with water using a filtration device having a cake washing function, and then primary particles are obtained by drying. As the drying means, freeze drying or vacuum drying can be used. The average particle diameter of the primary particles is 10 to 100 nm, preferably 10 to 60 nm or less.
In addition, the average particle diameter of a primary particle means the value calculated | required by SEM observation. Specifically, in the 1100 × 800 nm ² field of view, it means the average of the values of the particle sizes obtained by randomly extracting 20 primary particles.

  Next, in the manufacturing method of this invention, the specific slurry containing the obtained primary particle is produced. In the present invention, it is important to use such a specific slurry in order to obtain spherical secondary particles whose particle size, density and shape are controlled. Content of a primary particle is 30-60 mass% in a slurry whole quantity, Preferably it is 45-55 mass%, More preferably, it is 47-52 mass%. By setting the content of the primary particles within the above range, spherical secondary particles having a desired average particle diameter can be obtained, and the density of the spherical secondary particles can be increased. If the content of the primary particles is less than 30% by mass, the surface of the obtained secondary particles is liable to be depressed and the physical properties of the battery may be deteriorated. If the content exceeds 60% by mass, the viscosity of the slurry is necessary. There is a risk that it will rise above and cause troubles such as nozzle clogging in the granulation process.

  The viscosity of the slurry at 20 ° C. is 5 to 1000 mPa · s, preferably 8 to 300 mPa · s, and more preferably 10 to 100 mPa · s. By making the viscosity of the slurry within the above range, secondary particles having a desired particle size, density, and shape are secured together with primary particles having a predetermined content while ensuring good operability in the granulation step. Can be easily obtained. The viscosity of the slurry can be measured under a condition of 20 ° C. using a digital viscometer (manufactured by Brukefield).

Further, the pH of the slurry is from 10.00 to 13.00, preferably from 10.00 to 12.00, more preferably from 10.30 to 11.50. If the pH exceeds 13.00, the viscosity of the slurry may increase more than necessary and the operability in the granulation process may be reduced. If the pH is less than 10.00, the transition metal oxidation reaction is promoted. May generate impurities. The pH of the slurry is adjusted with a base and an organic acid. As the base, for example, sodium hydroxide, lithium hydroxide, ammonia or the like may be added. ₄ SiO ₄ is preferably used. As the organic acid, for example, acetic acid, citric acid, or the like can be used.

  The slurry preferably further contains a binder and / or a conductive material. As the binder, either an organic binder or an inorganic binder may be used, or these may be used in combination. The amount of the binder used is preferably 0.01 to 20 parts by mass, and preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the primary particles from the viewpoint of good charge / discharge capacity and economy.

  Examples of the organic binder include glucose, fructose, polyethylene glycol, polyvinyl alcohol, carboxymethyl cellulose, saccharose, starch, dextrin, and citric acid. Of these, glucose, polyvinyl alcohol, and carboxymethylcellulose are preferred because they can function as a carbon source by adjusting the amount used. Examples of the inorganic binder include scaly silica (silicon dioxide), silica-titania, silicon glass, colloidal silica, silica sol, and alumina sol.

When an inorganic binder is used as the binder, it is preferable to use a conductive material in combination.
Examples of the conductive material include conductive metal oxides such as zinc oxide, conductive polymers such as ponianiline, polypyrrole, polyethyleneoxythiophene, and polythiophene, carbon nanotubes, graphene, and carbon black. Among them, acetylene black and ketjen black are used. preferable.

  About these electroconductive materials, you may use together with an organic binder, and the usage-amount of electroconductive material is 0.01-20 with respect to the said primary particle 100 mass part from the point of favorable charging / discharging capacity | capacitance and economical efficiency. Part by mass is preferable, and 0.1 to 10 parts by mass is preferable.

  Further, the composite material / mixing / pulverization treatment of the conductive material and the olivine type silicate compound may be used as a slurry raw material, for example, dry and / or wet treatment using a planetary ball mill or a ball mill. Also good.

  The solvent for the wet treatment is not particularly limited, but water, methanol, ethanol, isopropyl alcohol, acetone, toluene, methyl ethyl ketone, or the like may be used.

Next, in the production method of the present invention, the obtained slurry is granulated to obtain spherical secondary particles. At this time, water or an organic solvent may be used for the slurry as a solvent.
The granulation method is not particularly limited, but is preferably by spray drying, and spray drying by spray drying is the most suitable. As a spray drying apparatus by the spray drying method, for example, a micro mist dryer (manufactured by Fujisaki Electric Co., Ltd.) having a four-fluid nozzle can be used.

As processing conditions of the apparatus used for spray drying, the air pressure is preferably 0.3 to 0.8 MPa, more preferably 0.5 to 0.7 MPa, and the air flow rate is 20 to 60 LN / min. It is preferable that it is 50-60 LN / min. Also, the hot air amount is preferably from 0.6~1.2m ³ / min, and more preferably 0.8~1.1m ³ / min.

  Furthermore, the inlet temperature is preferably 100 to 250 ° C., more preferably 150 to 200 ° C. when water is used as a solvent. If the inlet temperature exceeds 250 ° C., the transition metal oxidation reaction may be promoted and impurities may be generated. If the inlet temperature is less than 100 ° C., the drying becomes insufficient. The progress of the graining process may be hindered.

  Moreover, it is preferable that exhaust temperature is 70-150 degreeC, and it is more preferable that it is 80-120 degreeC. If the exhaust temperature exceeds 150 ° C., the filter cloth in the apparatus may be burned out, and if it is less than 70 ° C., the slurry may adhere to the apparatus and the progress of the granulation process may be hindered.

  The slurry flow rate is preferably from 20 to 70 g / min, more preferably from 50 to 70 g / min, and more preferably from the viewpoint of obtaining spherical secondary particles having a desired average particle diameter.

The average particle diameter of the spherical secondary particles formed by the granulation is 1 to 100 μm, preferably 5 to 30 μm. When the average particle diameter is within this range, the resulting positive electrode material has good fluidity when formed into a slurry, and when applying the slurry to the positive electrode current collector in producing the positive electrode, Can be increased.
In addition, the average particle diameter of the spherical secondary particles means a value obtained by a laser diffraction particle size measuring device (manufactured by Nikkiso Co., Ltd.).

  Further, as described above, the spherical secondary particle means a secondary particle having a shape that grows almost equally in the three-dimensional direction, and is not limited to a true spherical particle, and includes a particle that approximates a spherical shape. Therefore, at least plate-like or flat-shaped particles are not included. Among these, particles that are close to true spheres are preferable because spherical secondary particles are more uniformly filled as a positive electrode material to improve battery physical properties.

  Furthermore, the tap density of the spherical secondary particles is preferably 0.5 g / mL or more, and more preferably 0.7 g / mL or more. When the tap density is within the above range, the charge capacity of the obtained battery can be increased.

  The obtained spherical secondary particles can then be used as a positive electrode material for a secondary battery by firing. 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 this treatment, a positive electrode material in which carbon is supported on the olivine type silicate compound surface can be obtained.

  However, when the secondary particles are formed at the stage where secondary particles are formed, such as when an electrically conductive material is used in combination with an inorganic binder, it is not always necessary to fire, and if necessary, further moisture Drying to reduce the amount is good.

  Although the drying equipment for moisture reduction is not particularly limited, a freezing or vacuum dryer may be used, and drying may be performed at 80 ° C. to 120 ° C. for 3 hours or more using a box dryer.

  The carbon content of the spherical secondary particles after firing / drying is preferably 1 to 10% by mass, and more preferably 2 to 8% by mass from the viewpoint of securing good battery physical properties. Further, the water content is preferably 1% by mass or less, and more preferably 0.01% by mass or less.

  The obtained positive electrode material for a secondary battery is excellent in terms of charge / discharge capacity, and a very useful secondary battery can be obtained. The secondary battery to which the positive electrode material for the secondary battery obtained by the production method of the present invention can be applied may be a lithium ion secondary battery, as long as it has a positive electrode, a negative electrode, an electrolyte, and a separator as essential components. There is no particular limitation.

  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.
[Production Example 1]
LiOH.H ₂ O 4.20 g (0.1 mol), Na ₄ SiO ₄ .nH ₂ O 13.98 g (0.05 mol), Al ₂ (SO ₄ ) ₃ 0.67 g (0.0033 mol) and ultrapure water 75 cm ³ was added and mixed (the pH at this time was about 13). To this aqueous dispersion, 13.75 g (0.0135 mol) of FeSO ₄ .7H ₂ O and 7.59 g (0.0315 mol) of MnSO ₄ .5H ₂ O were added and mixed. The obtained mixed solution was put into an autoclave and subjected to a hydrothermal reaction at 150 ° C. for 12 hours. The reaction solution was filtered and then lyophilized to obtain primary particles (Li ₂ Fe _0.27 Mn _0.63 Al _0.066 SiO ₄ ) having an average particle size of 50 nm.

[Production Example 2]
LiOH.H ₂ O 42.0 g (1.0 mol), Na ₄ SiO ₄ .nH ₂ O 140.0 g (0.5 mol), Na ₂ S ₂ O ₄ 8.7 g (0.05 mol) and ultrapure water 400 cm ³ was added and mixed (the pH at this time was about 13). In this aqueous dispersion, 62.6 g (0.225 mol) of FeSO ₄ .7H ₂ O, 54.2 g (0.225 mol) of MnSO ₄ .5H ₂ O and 7.1 g (0. 25 mol) of Zr (SO ₄ ) ₂ .4H ₂ O were added. 025 mol) was added and mixed. The obtained mixed liquid was put into an autoclave and subjected to a hydrothermal reaction at 150 ° C. for 16 hours. The reaction solution was filtered and then lyophilized to obtain primary particles (Li ₂ Fe _0.45 Mn _0.45 Zr _0.05 SiO ₄ ) having an average particle size of 56 nm.

[Example 1]
To 100 g of the primary particles obtained in Production Example 1, 45 g of glucose (60% aqueous solution) and 100 g of ultrapure water were added and dispersed for 3 minutes with a homogenizer to prepare a slurry. The content of primary particles of the obtained slurry was 41% by mass , the viscosity at 20 ° C. was 100 mPa · s, and the pH was 10.70 as measured using a digital viscometer.

Next, the obtained slurry was granulated using a spray drying apparatus (micro mist dryer equipped with a 4-fluid nozzle: manufactured by Fujisaki Electric Co., Ltd.) under the following conditions, and then fired at 600 ° C. for 1 hr in a reducing atmosphere. Secondary particles were prepared. The physical properties of the obtained secondary particles are shown in Table 1, and the SEM image is shown in FIG.
Air pressure: 0.6 MPa
Air flow rate: 50LN / min
Hot air volume: 1.0 m ³ / min
Inlet temperature: 180 ° C
Exhaust temperature: 100 ° C
Slurry flow rate: 55 g / min

[Example 2]
To 100 g of the primary particles obtained in Production Example 2, 45 g of glucose (60% aqueous solution) and 100 g of ultrapure water were added and dispersed for 3 minutes with a homogenizer to prepare a slurry. The content of primary particles of the obtained slurry was 41% by mass , the viscosity at 20 ° C. measured by using a digital viscometer was 130 mPa · s, and the pH was 10.90.

Next, the obtained slurry was granulated using a spray drying apparatus (micro mist dryer equipped with a 4-fluid nozzle: manufactured by Fujisaki Electric Co., Ltd.) under the following conditions, and then fired at 600 ° C. for 1 hr in a reducing atmosphere. Secondary particles were prepared. The physical properties of the obtained secondary particles are shown in Table 1, and the SEM image is shown in FIG.
Air pressure: 0.6 MPa
Air flow rate: 50LN / min
Hot air volume: 1.0 m ³ / min
Inlet temperature: 180 ° C
Exhaust temperature: 100 ° C
Slurry flow rate: 50 g / min

[Comparative Example 1]
A slurry was prepared in the same manner as in Example 1 except that 100 g of the primary particles obtained in Production Example 1 was used and 900 g of ultrapure water was used. The content of primary particles of the obtained slurry was 9.6% by mass , the viscosity at 20 ° C. measured by using a digital viscometer was 4.5 mPa · s, and the pH was 9.8.
Next, the slurry obtained in the same manner as in Example 1 was granulated and then fired to produce secondary particles. The physical properties of the obtained secondary particles are shown in Table 1, and the SEM image is shown in FIG.

[Test Example 1]
Using the fired products obtained in Examples 1 and 2 and Comparative Example 1, positive electrodes of lithium ion secondary batteries were produced. The fired products obtained in Examples 1 and 2 and Comparative Example 1, Ketjen Black (conductive agent), and polyvinylidene fluoride (binding agent) were mixed at a weight ratio of 75:15:10, and N was added thereto. -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 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).

  Charging / discharging at a constant current density was performed for 4 cycles using the manufactured lithium ion secondary battery. The charging conditions at this time were constant current and constant voltage 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 charge / discharge curve of the battery constructed with the positive electrode material obtained in Example 1 is obtained in FIG. 4, the charge / discharge curve of the battery constructed with the positive electrode material obtained in Example 2 is obtained in FIG. FIG. 6 shows a charge / discharge curve of a battery constructed with the positive electrode material.

  1 to 3, it can be seen that according to the manufacturing method of the present invention, spherical secondary particles having no depression on the surface can be easily obtained. Moreover, it turns out that the lithium ion secondary battery using the positive electrode material obtained by the manufacturing method of this invention has the outstanding battery physical property from FIGS.

Claims (5)

By subjecting to hydrothermal reaction, the transition metal M (M is Fe, Ni, Co, Al, Zn, V, indicating the Mn or Zr) an average particle size 10~100nm primary particles consisting of olivine-type silicate compounds including Forming a slurry containing 30-60% by mass of the primary particles obtained, having a viscosity at 20 ° C. of 5 to 1000 mPa · s, and a pH of 10.00 to 13.00,
A method for producing a positive electrode material for a secondary battery, wherein the obtained slurry is granulated to form spherical secondary particles having an average particle diameter of 1 to 100 μm.   The method for producing a positive electrode material for a secondary battery according to claim 1, wherein the formed spherical secondary particles are further fired.   The method for producing a positive electrode material for a secondary battery according to claim 1, wherein the tap density of the spherical secondary particles is 0.5 to 1.2 g / mL.   The manufacturing method of the positive electrode material for secondary batteries of Claim 1 or 2 in which a slurry contains a binder and / or an electroconductive material.   The method for producing a positive electrode material for a secondary battery according to any one of claims 1 to 3, wherein the granulation is performed by spray drying.