JP2014007090A - Method for producing secondary battery positive electrode active material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a positive electrode material that has excellent conductivity and is also capable of sufficiently enhancing battery performance, while using an olivine type silicate compound.SOLUTION: In a method for producing a secondary battery positive electrode active material containing an olivine type silicate compound that includes a transition metal M (M represents Fe, Ni, Co, Al, Zn, Mn, V or Zr), a water-insoluble carbon-containing compound is added before a mixture including a lithium-containing compound, a transition metal compound and a silicic acid compound is subjected to a hydrothermal reaction.

Description

  The present invention relates to a production method for obtaining a secondary battery positive electrode active material capable of realizing a secondary battery having excellent battery properties.

  A secondary battery such as a lithium ion battery is a kind of non-aqueous electrolyte battery, and is used in a wide range of fields such as a mobile phone, a digital camera, a notebook PC, a hybrid vehicle, and an electric vehicle. 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.

Examples of the positive electrode material include lithium cobalt oxide (LiCoO ₂ ), lithium manganate (LiMnO ₂ ), lithium iron phosphate (LiFePO ₄ ), lithium iron silicate (Li ₂ FeSiO ₄ ), and lithium iron borate (LiFeBO ₃ ). Various things are known. Among these, LiFePO ₄ , Li ₂ FeSiO ₄ , LiFeBO _{3 and the} like are so-called olivine type lithium compounds having an olivine structure, and in particular, the olivine type silicate compound is extremely useful as a positive electrode material for a high capacity secondary battery. .

  In order to manufacture a secondary battery using these olivine type lithium compounds, the olivine type lithium compound is mixed with a binder solution to prepare a coating solution, and the obtained coating solution is used as a positive electrode current collector such as an aluminum foil. After coating on the body, a positive electrode is obtained through a drying process and the like. At this time, since the olivine type lithium compound itself has low electron conductivity, it is preliminarily subjected to a treatment for imparting electron conductivity to the positive electrode material of the secondary battery.

  As a treatment for imparting electron conductivity to an olivine-type lithium compound, for example, Patent Document 1 discloses a method of depositing an organic substance serving as a carbon source on the surface of a positive electrode material such as an olivine-type lithium compound and performing a carbonization treatment. Has been. Patent Document 2 discloses a method of obtaining composite particles that can be used as a positive electrode material by pulverizing and mixing a positive electrode material and a conductive substance such as carbon black using a planetary ball mill.

JP 2001-15111 A JP 2009-302044 A

  However, even with such a method, sufficient electronic conductivity cannot be imparted to the olivine-type lithium compound, and among them, the olivine-type silicate compound is still obtained because it has particularly low electron conductivity. It is in a situation where improvement of battery physical properties cannot be expected.

  Therefore, an object of the present invention is to provide a method for producing a positive electrode material that has excellent electronic conductivity and can sufficiently enhance battery performance while using an olivine type silicate compound.

  Therefore, the present inventors, in producing a secondary battery positive electrode active material containing an olivine-type silicate compound, by adding a water-insoluble carbon-containing compound when hydrothermal reaction of a mixture containing a predetermined compound, The inventors have found that a secondary battery positive electrode active material capable of dramatically improving battery performance can be obtained, and have completed the present invention.

That is, the present invention is a method for producing a secondary battery positive electrode active material containing an olivine-type silicate compound containing a transition metal M (M is Fe, Ni, Co, Al, Zn, Mn, V or Zr),
Provided is a method for producing a positive active material for a secondary battery, comprising adding a water-insoluble carbon-containing compound before hydrothermal reaction of a mixture containing a lithium-containing compound, a transition metal compound and a silicate compound. is there.
Moreover, this invention provides the secondary battery which has a positive electrode containing the secondary battery positive electrode active material obtained by the said manufacturing method.

  The secondary battery positive electrode active material 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 a secondary battery.

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 by the comparative example 1 is shown. The charging / discharging curve of the battery using the positive electrode material obtained by the comparative example 2 is shown.

Hereinafter, the present invention will be described in detail.
In the production method of the present invention, an olivine-type silicate compound containing transition metal M (M is Fe, Ni, Co, Al, Zn, Mn, V or Zr), that is, lithium ion and transition metal M (M is Fe, Ni, In obtaining a secondary battery positive electrode active material containing an olivine-type silicate compound containing Co, Al, Zn, Mn, V or Zr) ions and containing silicate ions (SiO ₄ ^4- ), first, a lithium-containing compound The mixture containing the transition metal compound and the silicate compound is subjected to a hydrothermal reaction.

Examples of the obtained ribin silicate compound include the following.
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 a1 Fe x Mn y Al z} SiO 4 ··· (2)
(Wherein a ¹ , x, y and z are 1 <a ¹ ≦ 2, 0 ≦ x <1, 0 ≦ y <1, 0 <z <1, a ¹ + 2x + 2y + 3z = 4 and x + y ≠ 0. Indicates the number to satisfy.)
Li ₂ M ¹ SiO _4-x1 F _2x1 (3)
(In the formula, M ¹ represents one or more selected from Fe, Mn, Co and Ni, and x ¹ represents a number satisfying 0 <x ¹ ≦ 8.)
_{Li a2 Fe x Mn y V z} SiO 4 ··· (4)
(Wherein a ² , x, y and z are 1 <a ² ≦ 2, 0 ≦ x <1, 0 ≦ y <1, 0 <z <1, a ² + 2x + 2y + (2-5) 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 _a3 Ni _b Co _c Mn _d Zr _x2 SiO ₄ (6)
(Wherein, a, b, c and d satisfy a + b + c + d = 1−2x, and x ² represents a number satisfying 0 <x ² <0.5)

  The olivine-type silicate compound may contain F, Zr, Co, Al, or the like by doping.

  In subjecting to a hydrothermal reaction, a mixture containing a lithium-containing compound, a transition metal compound and a silicate compound is prepared.

Examples of the lithium-containing 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-containing compound in the aqueous dispersion is preferably 0.30 to 3.00 mol / l, more preferably 1.00 to 1.50 mol / l.

  As the transition metal compound, an iron compound, a manganese compound, a cobalt compound, a nickel compound, an aluminum compound, or a zirconium compound may be used.

  The iron compound, manganese compound, cobalt compound, and nickel compound may be a divalent iron compound, a divalent manganese compound, a divalent cobalt compound, or a divalent nickel compound. Halides such as manganese, cobalt halide and nickel halide, sulfates such as iron sulfate, manganese sulfate, cobalt sulfate and nickel sulfate, and organic acid salts such as iron oxalate, iron acetate, manganese acetate, cobalt acetate and nickel acetate Is mentioned.

  The aluminum compound may be a trivalent compound, and examples thereof include halides such as aluminum halide, metal sulfates such as aluminum sulfate, and metal organic acid salts such as aluminum acetate and aluminum lactate.

  The zirconium compound may be a tetravalent compound, and examples thereof include organic acid salts such as zirconium halide, zirconium sulfate, zirconium diacetate oxide, zirconium octoate, and zirconium laurate oxide.

  The concentration of the transition metal compound in the reaction mixture is preferably 0.15 to 1.50 mol / l, more preferably 0.50 to 0.75 mol / l.

The silicic acid compound is not particularly limited as long as it is a reactive silica compound, and amorphous silica, Na ₄ SiO ₄ and Na ₄ SiO ₄ .nH ₂ O (for example, Na ₄ SiO ₄ .H ₂ O) can be used. preferable. Of these, the use of Na ₄ SiO ₄ is more preferable because the reaction mixture becomes basic.
The concentration of the silicate compound is preferably 0.15 to 1.50 mol / l, more preferably 0.50 to 0.75 mol / l.

A mixture is obtained using the lithium-containing compound, transition metal compound and silicic acid compound. Such a mixture is preferably a basic aqueous dispersion using water from the viewpoint of the solubility of the silicic acid compound in order to prevent side reactions. Specifically, the pH of the aqueous dispersion is preferably 12.0 to 14.5. 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.

  In producing an aqueous dispersion, as a transition metal compound, for example, when a metal sulfate is used, a lithium compound and a silicate compound, an antioxidant, It is preferable to prepare a basic aqueous dispersion containing In this case, the aqueous dispersion and the metal sulfate are mixed and subjected to a hydrothermal reaction. 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.

  Further, for example, when an organic acid salt is used as the transition metal compound, it is preferable to prepare a basic aqueous dispersion containing a lithium compound and a silicate compound and an antioxidant and further containing an organic acid 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.

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.

  In the present invention, the water-insoluble carbon-containing compound is added before the mixture is hydrothermally reacted. As a result, the water-insoluble carbon-containing compound serving as the carbon source is uniformly dispersed between the primary particles of the fine olivine-type silicate compound, and then sufficient electrons are formed when the primary particles aggregate to form secondary particles. Conductivity can be ensured.

  The water-insoluble carbon-containing compound means a carbon-containing compound that is insoluble in water (for example, the solubility in water at 25 ° C. is 0.1 g / 100 g or less). Specific examples include cellulose, lignin, chitosan, chitin, carbon nanotubes, graphene, carbon black, acetylene black, ketjen black, graphite, graphite, and synthetic fibers. These may be used alone or in combination of two or more. Especially, it is preferable that it is a compound which has a fibrous form, for example, a cellulose (crystalline cellulose), a carbon nanotube, and a synthetic fiber are mentioned as a preferable water-insoluble carbon containing compound. The amount of the water-insoluble carbon-containing compound added is 0.5 to 20% by mass in terms of carbon atoms contained in the water-insoluble carbon-containing compound in the theoretical amount of the olivine-type silicate compound obtained after the hydrothermal reaction. Is preferably added in an amount of 2 to 15% by mass.

  Further, the water-insoluble carbon-containing compound may be used after being subjected to pretreatment such as fine pulverization with a bead mill or an attritor, or fiberizing treatment.

In adding the water-insoluble carbon-containing compound, it is preferable to make a solution using a solvent from the viewpoint of improving dispersibility. The concentration of the water-insoluble carbon-containing compound in such a solution is preferably 40% by mass or less, more preferably 20% by mass or less.
Examples of the solvent include distilled water, ion-exchanged water, and the like, and it is preferable that the O ₂ concentration in the solution is 0.5 mg / L or less by deoxygenation treatment such as nitrogen aeration. A small amount of a dispersant may be added.
In order to add the water-insoluble carbon-containing compound, a mixture such as an aqueous dispersion containing a lithium-containing compound, a transition metal compound, and a silicate compound may be added to the solution of the water-insoluble carbon-containing compound. In addition, a solution of a water-insoluble carbon-containing compound may be added. All of these are mixed and then subjected to a hydrothermal reaction.

  130-250 degreeC is preferable and the temperature at the time of attaching | subjecting to a hydrothermal reaction has more preferable 150-200 degreeC. The hydrothermal reaction is preferably performed in a pressure vessel. When the reaction is performed at 130 to 250 ° C, the pressure at this time is 0.3 to 4.0 MPa, and the pressure when the reaction is performed at 150 to 200 ° C is 0. 5 to 1.6 MPa. The hydrothermal reaction time is preferably 0.5 to 24 hours, and more preferably 3 to 12 hours.

By the hydrothermal reaction, an olivine-type silicate compound is obtained in high yield, and its crystallinity is also high.
After the hydrothermal reaction, the produced olivine-type silicate compound is collected by filtration and washed to obtain primary particles. Washing is preferably carried out with water using a filtration device having a cake washing function.
Here, the average particle diameter of the obtained primary particles is preferably 10 to 500 nm, and more preferably 10 to 100 nm.

Then, drying is performed. As the drying means, a box-type dryer, freeze-drying, vacuum drying, fluidized bed dryer, or spray-type dryer (spray dryer) can be used.
About the obtained dried material, you may crush using a mortar, a pin mill, a roll mill, a crusher, etc.

  Thereafter, carbon is supported on primary particles or secondary particles of the obtained olivine-type silicate compound. By doing in this way, the electron conduction area (electron conduction path) of an olivine type silicate compound will increase, and more sufficient electronic conductivity can be ensured.

  Examples of the treatment for supporting carbon include a treatment in which a slurry containing the obtained olivine-type silicate compound and a conductive carbon material is prepared and fired after granulation. The slurry may appropriately contain an organic binder and an inorganic binder. By performing such treatment, a carbon thin film can be formed on the surface of secondary particles formed from primary particles, and electron conductivity can be further enhanced.

  Examples of the conductive carbon material include glucose, polyvinyl alcohol, carboxymethyl cellulose, and carbon black.

Examples of the binder include glucose, polyvinyl alcohol and carboxymethyl cellulose which can also be used as a conductive carbon material, as well as fructose, polyethylene glycol, saccharose, starch, dextrin, citric acid and the like.
Among these, glucose, polyvinyl alcohol, and carboxymethyl cellulose are preferable, and glucose is more preferable because it functions as a carbon source by adjusting the amount used and can also be used as a conductive carbon material.

  Examples of the inorganic binder include scaly silica (silicon dioxide), silica-titania, silicon glass, colloidal silica, silica sol, and alumina sol.

  The amount of the conductive carbon material used in the process of preparing the slurry and firing after granulation is based on 100 parts by mass of the olivine-type silicate compound in the slurry from the viewpoint of good charge / discharge capacity and economy. An amount of 0.5 to 20 parts by mass in terms of carbon atoms is preferable, and an amount of 2 to 10 parts by mass is more preferable.

  Moreover, you may use water or an organic solvent as a solvent, and water is preferable from an economical viewpoint. The content (slurry concentration) of the olivine-type silicate compound and the conductive carbon material in the slurry is preferably 30 to 60% by mass, and more preferably 45 to 55% by mass. The slurry viscosity at 25 ° C. is preferably 3 to 3000 m · Pa, more preferably 10 to 100 m · Pa. Furthermore, the pH of the slurry is preferably adjusted to 10.5 to 11.2.

The granulation treatment is not particularly limited as long as secondary particles having a desired particle diameter can be obtained, but it is preferably by spray drying, and most preferably by spray drying by a spray drying method. . The average particle size of the secondary particles obtained after the granulation treatment is preferably 1 μm to 500 μm, and more preferably 20 μm to 50 μm.
The obtained secondary particles can then be used as a positive electrode active material for a secondary battery by firing.

  In addition to the above granulation treatment, for example, a method of pulverizing / compositing / mixing a mixture containing the obtained olivine-type silicate compound and a conductive carbon material may be used as a carbon support treatment. By performing such treatment, secondary particles in which the primary particles of the olivine silicate compound and the conductive carbon material are combined can be formed, and the conductivity can be further increased.

  Examples of the conductive carbon material used in the pulverization treatment include the same conductive carbon materials that can be used in the granulation treatment. Of these, carbon black is preferable, and acetylene black and ketjen black are more preferable. The addition amount of the conductive carbon material in the pulverization treatment is preferably 0.5 to 20 parts by mass in terms of carbon atom with respect to 100 parts by mass of the primary particles of the olivine silicate compound from the viewpoint of good discharge capacity and economy. Furthermore, 2-10 mass parts is preferable.

  The mixture containing the olivine-type silicate compound and the conductive carbon material is pulverized / composited / mixed in a dry manner. At this time, a small amount of diethylene glycol, ethanol or the like may be added as an auxiliary agent.

  As an apparatus for pulverizing / combining / mixing, a normal ball mill may be used, but a planetary ball mill (manufactured by Fritsch) capable of rotating and revolving is preferred, and nobilta (manufactured by Hosokawa Micron), multipurpose mixer (manufactured by Nippon Coke Industries, Ltd.). ), Or a hybridizer (manufactured by Nara Machinery Co., Ltd.), etc., as long as it can perform a mechanochemical action / combination treatment on an object to be processed.

  Examples of the container of the device used in the planetary ball mill include steel, stainless steel, and nylon, and the inner wall includes alumina brick, magnetic material, natural silica, rubber, urethane, and the like. As the ball, alumina sphere, natural silica, iron ball, zirconia ball or the like is used. The size of the ball is preferably 0.1 mm to 20 mm, more preferably 0.5 mm to 5 mm. The filling amount of the balls is preferably set to a ratio that the filling volume of the balls occupies 5 to 50% with respect to the internal volume of the mill to be used.

  Mixing using a planetary ball mill is performed, for example, under conditions of revolution of 50 to 800 rpm and rotation of 100 to 1,600 rpm, preferably 5 minutes to 24 hours, more preferably 0.5 to 6 hours, and further preferably 1 to 3 hours.

  Firing of the secondary particles subjected to the treatment for supporting carbon as described above is preferably performed at 500 to 800 ° C. for 10 minutes to 24 hours, more preferably at 600 to 700 ° C. in an inert gas atmosphere or under reducing conditions. It is preferable to carry out for 0.5 to 3 hours. By this treatment, a positive electrode active material that is secondary particles in which carbon is further firmly supported on the surface of the olivine-type silicate compound can be obtained. The apparatus used for firing is not particularly limited as long as the firing atmosphere and temperature can be adjusted, and any of a batch system, a continuous system, and a heating system (indirect or direct) can be used. . Examples of such an apparatus include tubular electric furnaces such as an external heat kiln and a roller hearth.

  The average particle diameter of the obtained secondary particles is preferably 1 to 100 μm, more preferably 5 to 50 μm. The tap density is preferably 0.5 g / ml or more, more preferably 0.7 g / ml or more.

  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.

[Example 1]
In a glove box in a nitrogen atmosphere, 1.8 g of crystalline cellulose (carbon atom conversion amount: 0.40 g) was mixed with 80 cm ³ of ultrapure water, and then 8.56 g (0.2 mol) of LiOH.H ₂ O, 29.21 g (0.1 mol) of Na ₄ SiO ₄ .nH ₂ O was added and mixed (pH at this time was about 13.8). To this aqueous dispersion, 7.92 g (0.0282 mol) of FeSO ₄ .7H ₂ O, 16.18 g (0.0658 mol) of MnSO ₄ .5H ₂ O, 1.18 g (3 mmol) of Zr (SO ₄ ) ₂ .4H ₂ O were added. And mixed. The obtained mixed solution was put into an autoclave and subjected to a hydrothermal reaction at 170 ° C. for 1 hour. The reaction solution was filtered and then lyophilized to obtain primary particles (Li ₂ Fe _0.282 Mn _0.658 Zr _0.03 SiO ₄ ) having an average particle size of 50 nm.

  To 100 g of the obtained primary particles, 22.5 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 46% by mass, the viscosity at 20 ° C. as measured with a digital viscometer was 100 mPa · s, and the pH was 10.70.

Subsequently, the obtained slurry was granulated using a spray drying apparatus (micro mist dryer equipped with a four-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.
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: 60 g / min

[Comparative Example 1]
A slurry was prepared in the same manner as in Example 1 except that 1.08 g of glucose powder (carbon conversion amount: 0.40 g) was used instead of crystalline cellulose. The content of primary particles of the obtained slurry was 8.0% 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.

[Comparative Example 2]
At a glove box in a nitrogen _{atmosphere, LiOH · H 2 O 8.56g (} 0.2mol), and ultrapure water 80 cm ³ in addition to _{Na 4 SiO 4 · nH 2 O} 29.21g (0.1mol) mixed (The pH at this time was about 13.8). To this aqueous dispersion, 7.92 g (0.0282 mol) of FeSO ₄ .7H ₂ O, 16.18 g (0.0658 mol) of MnSO ₄ .5H ₂ O, 1.18 g (3 mmol) of Zr (SO ₄ ) ₂ .4H ₂ O were added. And mixed. The obtained mixed solution was put into an autoclave and subjected to a hydrothermal reaction at 170 ° C. for 1 hour. The reaction solution was filtered and then lyophilized to obtain primary particles (Li ₂ Fe _0.282 Mn _0.658 Zr _0.03 SiO ₄ ) having an average particle size of 50 nm.

To 100 g of the obtained primary particles, 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 46% by mass, the viscosity at 20 ° C. measured by using a digital viscometer was 88 mPa · s, and the pH was 10.50.
Next, granulation was performed in the same manner as in Example 1, followed by firing to produce secondary particles.

[Test Example 1]
Using the fired products obtained in Example 1 and Comparative Examples 1 and 2, positive electrodes of lithium ion secondary batteries were produced. The fired product obtained in Example 1 and Comparative Examples 1-2, 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. 1, the charge / discharge curve of the battery constructed with the positive electrode material obtained in Comparative Example 1 is obtained in FIG. FIG. 3 shows a charge / discharge curve of a battery constructed with the positive electrode material.

  1 to 3, the lithium ion 2 using the positive electrode material of Comparative Example 1 obtained using a water-soluble carbon-containing compound and the positive electrode material of Comparative Example 2 obtained by adding a carbon source after the hydrothermal reaction. Compared to the secondary battery, it can be seen that the lithium ion secondary battery using the positive electrode material obtained by the production method of the present invention has excellent battery properties.

Claims (10)

A method for producing a positive electrode active material for a secondary battery containing an olivine-type silicate compound containing a transition metal M (M is Fe, Ni, Co, Al, Zn, Mn, V or Zr),
A method for producing a positive electrode active material for a secondary battery, comprising adding a water-insoluble carbon-containing compound before hydrothermal reaction of a mixture containing a lithium-containing compound, a transition metal compound and a silicate compound.   The method for producing a secondary battery positive electrode active material according to claim 1, wherein the amount of the water-insoluble carbon-containing compound added is 0.5 to 20% by mass in terms of carbon atoms contained in the water-insoluble carbon-containing compound.   The method for producing a secondary battery positive electrode active material according to claim 1 or 2, wherein after the hydrothermal reaction is completed, carbon is supported on the obtained olivine-type silicate compound and then baked.   The method for producing a secondary battery positive electrode active material according to claim 3, wherein the carbon support is a process of preparing and granulating a slurry containing the obtained olivine-type silicate compound and a conductive carbon material.   The method for producing a secondary battery positive electrode active material according to claim 3, wherein the carbon support is a treatment for pulverizing the obtained mixture containing the olivine-type silicate compound and the conductive carbon material.   The secondary battery positive electrode according to claim 4, wherein the amount of the conductive carbon material added in the granulating process is 0.5 to 20 parts by mass in terms of carbon atoms with respect to 100 parts by mass of the olivine-type silicate compound in the slurry. A method for producing an active material.   The secondary battery positive electrode according to claim 5, wherein the conductive carbon material is added in an amount of 0.5 to 20 parts by mass in terms of carbon atoms with respect to 100 parts by mass of the primary particles of the olivine silicate compound in the pulverization treatment. A method for producing an active material.   The water-insoluble carbon-containing compound is at least one selected from the group consisting of cellulose, lignin, chitosan, chitin, carbon nanotubes, graphene, carbon black, acetylene black, ketjen black, graphite, graphite and synthetic fibers. The manufacturing method of the secondary battery positive electrode active material of any one of -7.   Conductive carbon material is glucose, polyvinyl alcohol, carboxymethylcellulose, fructose, polyethylene glycol, saccharose, starch, dextrin, citric acid, cellulose, lignin, chitosan, chitin, carbon nanotube, graphene, carbon black, acetylene black, ketjen black The method for producing a positive electrode active material for a secondary battery according to any one of claims 4 to 8, which is at least one selected from the group consisting of graphite, graphite and synthetic fibers.   The secondary battery which has a positive electrode containing the secondary battery positive electrode active material obtained by the manufacturing method of any one of Claims 1-9.