JP2014107033A - Lithium ion secondary battery electrode material, method for manufacturing lithium ion secondary battery electrode material, and lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery electrode material having a good rate property.SOLUTION: A lithium ion secondary battery electrode material of the invention comprises: conductive carbon powder; and particles of a spinel type oxide expressed by the general formula, LiMMnO(where M represents one or more kinds of metals selected from a group consisting of metals other than Mn, and x satisfies the condition, 0<x≤0.15), which stick to the conductive carbon powder. The spinel type oxide particles are substantially crystalline primary particles having particle diameters of 10-50 nm. The electrode material can be obtained by causing the conductive carbon powder to hold a spinel type oxide fine precursor thereon by means of an ultracentrifugal treatment, followed by a heat treatment in an oxygen-containing atmosphere.

Description

  The present invention relates to an electrode material that provides a lithium ion secondary battery having excellent rate characteristics, and a lithium ion secondary battery that includes a positive electrode using the electrode material. The present invention also relates to a method for producing an electrode material for a lithium ion secondary battery suitable for producing the electrode material.

  Lithium ion secondary batteries that use non-aqueous electrolytes with high energy density are widely used as the power source for information devices such as mobile phones and laptop computers. The performance of these information devices and the amount of information handled In order to cope with an increase in power consumption associated with an increase in battery life, it is desired to improve the discharge capacity of lithium ion secondary batteries. In addition, from the viewpoints of reducing oil consumption, mitigating air pollution, and reducing carbon dioxide emissions that cause global warming, we are working on low-pollution vehicles such as electric vehicles and hybrid vehicles that replace gasoline and diesel vehicles. Expectations are increasing, and it is desired to develop a large-sized lithium ion secondary battery having a high discharge capacity as a motor drive power source for these low-pollution vehicles.

A lithium ion secondary battery using a current non-aqueous electrolyte includes lithium cobalt oxide (LiCoO ₂ ) as a positive electrode active material, graphite as a negative electrode active material, and a lithium salt such as lithium hexafluorophosphate (LiPF ₆ ). The mainstream is an electrolyte obtained by dissolving a solution in a non-aqueous solvent such as ethylene carbonate or propylene carbonate. However, lithium cobaltate, which is a positive electrode active material, has a problem that it is difficult to use in large quantities because cobalt is expensive. Therefore, LiMn ₂ O _{4 which} is mainly composed of resource-rich and inexpensive Mn and can obtain a high battery voltage of about 4 V has been attracting attention as a next-generation positive electrode active material. Since LiMn ₂ O ₄ having a spinel structure has a passage through which lithium ions can move in the crystal structure, lithium ions can be diffused quickly, and excellent output characteristics are exhibited. However, LiMn ₂ O ₄ has a problem that cycle stability is poor because the crystal structure is likely to change due to yarn-Taylor strain as charge and discharge are repeated, and Mn ³⁺ ions are easily eluted into the electrolyte. Yes.

In order to solve this problem, studies have been made on a positive electrode active material in which Mn ³⁺ at the (16d) site in LiMn ₂ O ₄ is substituted with a metal ion such as Li, Mg, Al (for example, Patent Document 1 ( JP-A-11-71115), Patent Document 2 (JP-A 2002-104827), Patent Document 3 (JP-A 2002-226214), Patent Document 4 (JP-A 2006-114408), Patent Document 5 (Japanese Patent Laid-Open No. 2011-108406) and Patent Document 6 (Japanese Patent Laid-Open No. 2011-219354). Metal substitution stabilizes the crystal structure and improves cycle characteristics. This substituted oxide has the general formula LiM _x Mn _(2-x) O ₄ (wherein M represents one or more metals selected from the group consisting of metals other than Mn, and X represents the amount of substitution) Hereinafter, it can be expressed simply as “spinel oxide”).

These spinel type oxides are generally produced by a solid phase reaction method or a spray pyrolysis method. Patent Document 1 discloses that an average aggregate particle diameter is 1 to 50 μm by mixing and firing a manganese compound having an average aggregate particle diameter of 0.5 to 50 μm, a lithium compound, and a compound containing another metal. A method for obtaining a spinel oxide having a BET specific surface area of 0.1 to ⁵ m ² / g is proposed. Patent Document 2 discloses a heat treatment of fine particles mainly composed of manganese oxide having an average primary particle size of 0.01 μm or more and 0.2 μm or less, a lithium-containing compound, and a metal compound except manganese and lithium. To obtain a spinel oxide having an average primary particle size of 0.01 μm or more and 0.2 μm or less and an average secondary particle size of 0.2 μm or more and 100 μm or less. ing. In Patent Document 3, a mixture of a manganese compound having an average oxidation number of manganese of 8/3 or more, a lithium compound, and a compound containing another metal is first baked at a temperature of 500 ° C. or lower. The second baking is performed at a temperature exceeding 500 ° C. and not more than 950 ° C., and then cooling to 500 ° C. is performed at a rate of 20 ° C. or less per hour. A method for producing a spinel oxide having a surface area of 1.0 m ² / g or less and an average crystallite size of 1000 angstroms or more is proposed.

  Patent Document 4 discloses primary particles having a crystallite size of 30 to 150 nm by firing solid spinel oxide particles obtained by a spray pyrolysis method in an air atmosphere at 650 to 850 ° C. for 1 to 24 hours. Has proposed a method for producing a spinel oxide composed of nanostructures in which nuclei are aggregated. Patent Document 5 generates a solution in which a lithium compound, a manganese compound, and another metal compound are dispersed with a thickener, sprays the obtained solution, and heats the sprayed mist to form a precursor. It has been proposed to produce a spinel oxide comprising aggregated secondary particles by firing and firing this precursor. In Patent Document 6, a manganese composite aqueous solution containing other metals and manganese, an aqueous ammonia solution, and an aqueous oxalic acid solution are mixed to produce a manganese composite oxalate, and the manganese composite oxalate is dried and then heat treated to produce manganese. A composite oxide is manufactured, and then the obtained manganese composite oxide and a lithium compound are mixed and fired at a high temperature, whereby primary particles of 100 to 2000 nm aggregate to form secondary particles of 5 to 20 μm. A method for producing a spinel oxide is provided.

  The positive electrode active material composed of the spinel oxide obtained by the methods of Patent Documents 1 to 6 is mixed with conductive carbon powder and used as an electrode material for a positive electrode of a lithium ion secondary battery. The conductive carbon powder mixed with the spinel oxide plays a role of imparting conductivity to the electrode material in combination with an active material having low conductivity. It also acts as a matrix that absorbs the accompanying volume change, and also plays a role of securing an electron conduction path even if the active material is mechanically damaged.

  As described above, a method in which an active material is manufactured and then mixed with conductive carbon powder is common, but there is also a method of manufacturing an active material in the presence of conductive carbon powder. As a method for supporting the generated metal oxide on the conductive carbon powder as the conductive agent together with the generation of the active material composed of the metal oxide, the applicant disclosed in Patent Document 7 (Japanese Patent Application Laid-Open No. 2007-160151). We propose a reaction method in which a chemical reaction is advanced by applying shear stress and centrifugal force to the reactants in the reactor.

JP-A-11-71115 JP 2002-104827 A JP 2002-226214 A JP 2006-114408 A JP 2011-108406 A JP2011-219354A JP 2007-160151 A

As described above, by using a positive electrode active material made of a spinel oxide in which Mn ³⁺ at the (16d) site in LiMn ₂ O ₄ is replaced with a metal ion such as Li, Mg, Al, etc., the lithium ion secondary battery Although the cycle characteristics are improved, the lithium ion secondary battery is required not only to have excellent cycle characteristics but also to exhibit a high discharge capacity even in charge / discharge at a high rate. In particular, for lithium-ion secondary batteries for hybrid vehicles, power assist performance when the vehicle starts and accelerates, and kinetic energy regeneration performance when the vehicle decelerates are important. Therefore, the ability to take in and out a large current is required, and a high capacity in charge / discharge at a rate of 10 C or higher is required.

  Patent Documents 4 to 6 also describe rate characteristics of lithium ion secondary batteries using the obtained spinel oxide. In the lithium ion secondary battery using the spinel oxide obtained by the manufacturing method of Patent Document 4 for the positive electrode, the capacity in charge / discharge at the rate of 10C is about 60 to 98 of the capacity in charge / discharge at the rate of 5C. The capacity is remarkably reduced when charging / discharging at a rate of 15 C or higher (see Table 3 of this document). Moreover, the lithium ion secondary battery using the spinel oxide obtained by the manufacturing method of Patent Document 5 for the positive electrode showed a capacity of 120 mAh / g in charge / discharge at a rate of 1C, but at a rate of 10C. In the charging / discharging, the capacity is reduced to 90 mAh / g (see FIG. 7 of this document). The lithium ion secondary battery using the spinel type oxide obtained by the manufacturing method of Patent Document 6 for the positive electrode showed a capacity of about 107 mAh / g in charge / discharge at a rate of 1C, but at a rate of 4C. In charge / discharge, the capacity is reduced to about 90 to 100 mAh / g (see FIG. 11 of this document).

  Therefore, a positive electrode active material made of a spinel oxide that can meet the above-described demand for high capacity in charge / discharge at a rate of 10 C or higher has not been known so far.

  Accordingly, an object of the present invention is to provide an electrode material that leads to a lithium ion secondary battery having excellent rate characteristics based on a spinel oxide having improved cycle characteristics.

  The inventors examined the applicability of the reaction method disclosed in Patent Document 7. In this reaction method, one or more kinds of metal oxide nanoparticles can be supported on the conductive carbon powder, and the metal oxide is supported on the conductive carbon powder. A mixing step is unnecessary, or the amount of the conductive agent can be reduced. However, Patent Document 7 specifically shows only the formation reaction of titanium oxide, ruthenium oxide, etc. by the sol-gel reaction accelerated by applying shear stress and centrifugal force. Has not been suggested, and the application of this reaction method has not yet been fully studied.

  As a result of investigations by the inventors, it has been found that by using the reaction method of Patent Document 7, an electrode material in which fine spinel-type oxide crystals are deposited on conductive carbon powder can be obtained. Moreover, the fine spinel-type oxide particles are polyhedral crystal grains and exist in the form of primary particles having a particle size of 10 to 50 nm, like the spinel-type oxides in Patent Documents 1 to 6. No agglomerated secondary particles were formed. And the lithium ion secondary battery using this electrode material for the positive electrode showed excellent rate characteristics, and was able to answer the above-mentioned demand for high capacity in charge / discharge at a rate of 10 C or higher. .

Therefore, the present invention first comprises a conductive carbon powder and a general formula LiM _x Mn _(2-x) O ₄ (wherein M is a metal other than Mn, attached to the conductive carbon powder _). One or more metals selected from the group consisting of spinel oxide particles represented by 0 <x ≦ 0.15), and the spinel oxide particles substantially comprising: Provided is an electrode material for a lithium ion secondary battery, characterized by being crystalline primary particles having a particle size of 10 to 50 nm. When x exceeds 0.15, trivalent Mn contributing to the oxidation-reduction reaction during charging / discharging is decreased, and as a result, the discharge capacity of the lithium ion secondary battery is decreased, which is not preferable. Here, “substantially crystalline primary particles having a particle size of 10 to 50 nm” means that 90% or more of the spinel-type oxide particles are crystalline primary particles having a particle size of 10 to 50 nm. The particle diameter is obtained from the observation result by TEM.

  In the electrode material of the present invention, the crystal particles of the spinel oxide having a polyhedral shape are present in the form of primary particles having a particle size of 10 to 50 nm. Therefore, the effective reaction area of the charge exchange / charge transfer reaction can be increased, and the movement distance of lithium ions during charge / discharge can be shortened. Moreover, since it is manufactured using the reaction method of Patent Document 7, fine crystal particles of spinel oxide and conductive carbon powder are uniformly mixed, and the crystal particles are conductive carbon. It adheres well to the powder. These are considered to be the factors for obtaining a lithium ion secondary battery having a high capacity even in charge and discharge at a high rate.

  FIG. 1 is a conceptual diagram illustrating the operation of an electrode material, and the reason why a lithium ion secondary battery having a high capacity can be obtained even when charging / discharging at a high rate by using the electrode material of the present invention. Will be described in more detail. In the conventional electrode material, as shown in FIG. 1B, the secondary particles of the spinel oxide having a large particle size are joined by the conductive carbon powder. Bonding with carbon powder and bonding between carbon powders are not dense. Therefore, it takes time for the secondary particles of lithium to diffuse into the solid, and the electron conduction path to the current collector that occurs simultaneously through the carbon powder is not good. On the other hand, in the electrode material of the present invention, as shown in FIG. 1 (a), the crystalline primary particles of the spinel oxide having a particle size of 10 to 50 nm are closely bonded to the conductive carbon powder. In addition, the bonding between the carbon powders is also good. Therefore, the diffusion of lithium in the solid is fast and the electron conduction path is also good. Thus, it is considered that a lithium ion secondary battery excellent in rate characteristics can be obtained by using the electrode material of the present invention.

M in the general formula LiM _x Mn _(2-x) O ₄ is preferably a metal selected from Mg, Al, Co, Cr, Fe and Ni. This is because substitution of Mn ^{3+ at} the (16d) site with ions of these metals provides an electrode material that leads to a lithium ion secondary battery having excellent cycle stability.

  The reaction method shown in Patent Document 7 is that a reaction liquid is introduced into a swirlable reactor, and then the reactor is swirled to apply shear stress and centrifugal force to the reaction liquid. Suitable for forming spinel oxide particles.

Therefore, the present invention also includes a conductive carbon powder and a general formula LiM _x Mn _(2-x) O ₄ (wherein M is a metal other than Mn ₎ attached to the conductive carbon powder. A spinel-type oxide particle represented by one or more selected metals represented by 0 <x ≦ 0.15), and a method for producing an electrode material for a lithium ion secondary battery,
a1) A preparation step of introducing a reaction solution obtained by adding conductive carbon powder to a solution in which an active material raw material containing a compound containing Li and a compound containing Mn is dissolved, into a swirlable reactor,
b1) A supporting step of supporting the active material raw material and / or the reaction product thereof on the conductive carbon powder by swirling the reactor and applying shear stress and centrifugal force to the reaction liquid; and
c1) The conductive carbon powder supporting the active material raw material and / or the reaction product thereof is mixed with the compound containing the metal represented by M and then heat-treated, whereby the conductive carbon powder is heated. A first manufacturing method is provided, which includes a heat treatment step of forming the spinel oxide. By the first production method, the electrode material of the present invention can be suitably obtained.

The centrifugal force applied to the reaction solution by swirling the reactor in the loading step of b1) is a centrifugal force in a range generally referred to as “ultracentrifugal force”, preferably 1500 kgms ⁻² or more, particularly preferably 70000 kgms ^{− 2} or more centrifugal force. By the centrifugal force in this range, the Li compound and Mn compound constituting the spinel oxide and / or the reaction product thereof are supported on the conductive carbon powder as fine particles of uniform size. In the present specification, the process of applying shear stress and centrifugal force to the reaction solution in a swirling reactor may be referred to as “ultracentrifugation process”. As the reactor, any reactor can be used as long as it can apply an ultracentrifugal force to the reaction solution. However, a concentric cylinder of an outer cylinder and an inner cylinder described in FIG. It is preferable to use a reactor in which a through hole is provided in a side surface of a rotatable inner cylinder, and a slat is arranged in an opening of the outer cylinder. The description relating to the reactor in US Pat. In the reactor, the distance between the inner cylinder outer wall surface and the outer cylinder inner wall surface is preferably 5 mm or less, and more preferably 2.5 mm or less.

And after mixing the product of the b1) process with the compound containing the metal represented by M, the said spinel type oxide is formed on the said conductive carbon powder by heat-processing. The heat treatment is generally performed in an oxygen-containing atmosphere. The heating temperature is generally 200 to 300 ° C. Prolonged heating at a temperature exceeding 300 ° C. promotes burning and disappearance of the conductive carbon powder. However, the heat treatment may be performed by flash heating at a high temperature of 600 to 700 ° C. for a short time, for example, 3 to 5 minutes. Here, the “flash heat treatment” means a treatment in which the temperature is rapidly raised to a heating temperature of 600 to 700 ° C. and is rapidly cooled after heating. When performing flash heating, the surface of the conductive carbon powder is a metal oxide nanoparticle selected from the group consisting of tin oxide, iron oxide, aluminum oxide, titanium oxide, silicon oxide and zirconium oxide and / or It is preferable to partially cover with a thin film. This is because these oxides suppress the burning and disappearance of the conductive carbon powder due to heating during the preparation of the electrode material, and these oxides do not adversely affect the formation of the spinel oxide. However, if the amount of the metal oxide is too large, the electrical conductivity of the electrode material is lowered and the discharge capacity of the lithium ion secondary battery is lowered, which is not preferable. The conductivity of the electrode material is preferably 10 ⁻³ S / cm or more. The term “nanoparticle” means a particle having a diameter of 200 nm or less in the case of a spherical particle, and a diameter (short axis) of a particle cross section in the case of a needle-like, tubular or fibrous particle of 200 nm or less. Means particles. The nanoparticles may be primary particles or secondary particles.

The present invention also includes a conductive carbon powder and a general formula LiM _x Mn _(2-x) O ₄ (wherein M is selected from the group consisting of metals other than Mn ₎ attached to the conductive carbon powder. And a spinel-type oxide particle represented by 0 <x ≦ 0.15), and a method for producing an electrode material for a lithium ion secondary battery,
a2) Reactor capable of turning a reaction liquid obtained by adding conductive carbon powder to a solution in which an active material raw material containing a compound containing Li, a compound containing Mn, and a compound containing a metal represented by M is dissolved The preparation process to be introduced in,
b2) a supporting step of supporting the active material raw material and / or the reaction product thereof on the conductive carbon powder by rotating the reactor and applying shear stress and centrifugal force to the reaction solution; and
c2) including a heat treatment step of forming the spinel oxide on the conductive carbon powder by heat-treating the conductive carbon powder supporting the active material raw material and / or the reaction product thereof. A second manufacturing method is provided. This method is a method in which the compound containing the metal represented by M used in step c1) in the first production method is previously contained in the reaction solution prepared in step a2). It can also be said to be a modified method. Also in this case, the ultracentrifugation process can be suitably performed using the reactor described in FIG. 1 of Patent Document 7, and the magnitude of the centrifugal force applied to the reaction solution and the outer wall surface of the inner cylinder and the outside The above description regarding the distance from the cylinder inner wall surface also applies in this case. The description relating to the heat treatment in the first manufacturing method also applies to this case. The electrode material of the present invention can be suitably obtained by the second production method.

The present invention also includes a conductive carbon powder and a general formula LiM _x Mn _(2-x) O ₄ (wherein M is selected from the group consisting of metals other than Mn ₎ attached to the conductive carbon powder. And a spinel-type oxide particle represented by 0 <x ≦ 0.15), and a method for producing an electrode material for a lithium ion secondary battery,
a3) Preparation step for introducing a reaction solution containing water, a Li hydroxide, a compound containing Mn, and a conductive carbon powder and having a pH in the range of 9 to 11 into a swirlable reactor ,
b3) The reactor is swirled to apply shear stress and centrifugal force to the reaction solution to generate Mn hydroxide nuclei, and the generated Mn hydroxide nuclei and the conductive carbon. A supporting step of dispersing the powder and simultaneously supporting a hydroxide of Mn on the conductive carbon powder; and
c3) The conductive carbon powder supporting the Mn hydroxide, the compound containing Li, and the compound containing the metal represented by M are mixed and heat-treated, whereby the conductive carbon powder is mixed. A third manufacturing method is provided, comprising a heat treatment step of forming the spinel oxide on a powder. This method includes water, a Li hydroxide, a compound containing Mn, and a conductive carbon powder as a reaction solution in the step a1) of the first production method, and has a pH in the range of 9 to 11. It is a method for preparing a reaction solution having the same, and can be said to be a modification method of the first manufacturing method. Here, Mn (OH) ₃ (Mn ₂ O ₃ .nH ₂ O), which is not actually present but is conventionally expressed as a hydroxide, is also included in the above-mentioned “hydroxide” range. In the step b3), almost all of Mn contained in the reaction solution is supported as fine particles on the conductive carbon powder, so that an electrode material can be obtained efficiently. The ultracentrifugation treatment can be suitably performed using the reactor described in FIG. 1 of Patent Document 7, and the magnitude of the centrifugal force applied to the reaction liquid and the inner cylinder outer wall surface and the outer cylinder inner wall surface The above description regarding the spacing also applies here. The description relating to the heat treatment in the first manufacturing method also applies to this case. By the third manufacturing method, the electrode material of the present invention can be suitably obtained.

The present invention also includes a conductive carbon powder and a general formula LiM _x Mn _(2-x) O ₄ (wherein M is selected from the group consisting of metals other than Mn ₎ attached to the conductive carbon powder. A spinel-type oxide particle represented by: 0 <x ≦ 0.15), and a method for producing an electrode material for a lithium ion secondary battery,
a4) A reaction liquid containing water, a hydroxide of Li, a compound containing Mn, a compound containing a metal represented by M and a conductive carbon powder, and having a pH in the range of 9 to 11. A preparation process to be introduced into the swirlable reactor,
b4) The reactor was swirled to apply shear stress and centrifugal force to the reaction solution, thereby generating a Mn hydroxide and a metal hydroxide nucleus represented by M. Mn hydroxide and the metal hydroxide nucleus represented by M and the conductive carbon powder are dispersed, and at the same time, the Mn hydroxide and the metal represented by M are dispersed in the conductive carbon powder. A supporting step for supporting a hydroxide of, and
c4) Conductive carbon powder carrying the hydroxide of Mn and the metal hydroxide represented by M and a compound containing Li are mixed and heat-treated, whereby the conductive carbon is obtained. A fourth production method is provided, comprising a heat treatment step of forming the spinel oxide on the powder. This method is a method in which the compound containing the metal represented by M used in step c3) in the third production method is previously contained in the reaction solution prepared in step a4). It can be said that it is a modified method of the method, and therefore also a modified method of the first manufacturing method. The electrode material of the present invention can be suitably obtained by the fourth production method. This method is particularly suitable when M contains Fe, Ni, and Co. Here, Fe (OH) ₃ (Fe ₂ O ₃ .nH ₂ O), Co (OH) ₃ (Co ₂ O ₃ .nH ₂ O), Ni (), which are not actually present but are conventionally expressed as hydroxides. Oxide hydroxides or hydrated oxides such as (OH) ₃ (Ni ₂ O ₃ .nH ₂ O) are also included in the above-mentioned “hydroxide” range. In step b4), almost all of Mn contained in the reaction solution and Fe, Co and Ni, if present, are supported as fine particles on the conductive carbon powder, so that an electrode material can be obtained efficiently. The ultracentrifugation treatment can be suitably performed using the reactor described in FIG. 1 of Patent Document 7, and the magnitude of the centrifugal force applied to the reaction liquid and the inner cylinder outer wall surface and the outer cylinder inner wall surface The above description regarding the spacing also applies here. The description relating to the heat treatment in the first manufacturing method also applies to this case.

  With the electrode material of the present invention, a lithium ion secondary battery having excellent rate characteristics exhibiting a high capacity even in charge and discharge at a high rate can be obtained. Therefore, this invention relates also to the lithium ion secondary battery provided with the positive electrode which has an active material layer containing the electrode material of this invention.

  In the electrode material of the present invention, the spinel oxide present in the form of crystalline primary particles having a particle size of substantially 10 to 50 nm adheres to the conductive carbon powder with good adhesion and uniformity, and charge exchange -The effective reaction area of the charge transfer reaction can be increased, and the movement distance of lithium ions during charge / discharge can be shortened. Therefore, by using the electrode material of the present invention for the positive electrode, a lithium ion secondary battery having excellent rate characteristics exhibiting a high capacity even in charge and discharge at a rate of 10 C or higher can be obtained.

It is a conceptual diagram for demonstrating operation | movement of an electrode material, (a) is a figure regarding the electrode material of this invention, (b) is a figure regarding the conventional electrode material. It is a TEM photograph of the electrode material of the present invention. It is the figure which showed the rate characteristic in the lithium ion secondary battery using the electrode material of this invention. It is the figure which showed the cycling characteristics in the lithium ion secondary battery using the electrode material of this invention.

(A) Electrode material An electrode material for a lithium ion secondary battery of the present invention comprises a conductive carbon powder and a general formula LiM _x Mn _(2-x) O ₄ (wherein M represents one or more metals selected from the group consisting of metals other than Mn, and 0 <x ≦ 0.15.) Fine spinel oxide particles represented by: The fine spinel-type oxide particles are polyhedral crystal grains, and exist substantially in the form of primary particles having a particle size of 10 to 50 nm. Not formed.

In the general formula LiM _x Mn _(2-x) O ₄ , M represents one or more metals selected from the group consisting of metals other than Mn, and preferably one or more metals having an average valence of +3 or less. Represents. Specifically, in addition to Li, B, Mg, Ca, Ba, Al, Si, Sc, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Nb, Mo, Ru , Sn, In, Sb, La, Ce, Pr, Nd, Hf, Ta, Pb, Te, and W. It is particularly preferred that M is a metal selected from Mg, Al, Co, Cr, Fe and Ni. This is because substitution of Mn ^{3+ at} the (16d) site with these metals yields an electrode material that leads to a lithium ion secondary battery having excellent cycle stability.

  An electrode material for a lithium ion secondary battery including conductive carbon powder and spinel oxide particles adhering to the conductive carbon powder is obtained by the following first to fourth manufacturing methods. Can do. By these methods, the electrode material of the present invention can be suitably obtained.

(I) First manufacturing method The first manufacturing method is:
a1) A preparation step of introducing a reaction solution obtained by adding conductive carbon powder to a solution in which an active material raw material containing a compound containing Li and a compound containing Mn is dissolved, into a swirlable reactor,
b1) A supporting step of supporting the active material raw material and / or the reaction product thereof on the conductive carbon powder by swirling the reactor and applying shear stress and centrifugal force to the reaction liquid; and
c1) The conductive carbon powder supporting the active material raw material and / or the reaction product thereof is mixed with the compound containing the metal represented by M and then heat-treated, whereby the conductive carbon powder is heated. And a heat treatment step of forming the spinel oxide.

  In the preparation step of a1), a reaction liquid is obtained by adding a compound containing Li as an active material raw material, a compound containing Mn, and conductive carbon powder to a solvent, and dissolving the compound in the solvent.

  As the solvent, any solvent that does not adversely influence the reaction can be used without particular limitation, and water, methanol, ethanol, isopropyl alcohol, and the like can be suitably used. Two or more solvents may be mixed and used. Water can be preferably used.

  As the compound containing Li as an active material material and the compound containing Mn, a compound that can be dissolved in the solvent can be used without any particular limitation. Examples include inorganic metal salts such as halides, nitrates, sulfates and carbonates of the above metals, organometallic salts such as formate, acetate, oxalate, methoxide, ethoxide, isopropoxide, or mixtures thereof. Can be used. With respect to one kind of metal, a single compound may be used, or two or more kinds of compounds may be mixed and used.

  As the conductive carbon powder, any conductive carbon powder can be used without particular limitation. Examples include carbon black such as ketjen black, acetylene black, channel black, fullerene, carbon nanotube, carbon nanofiber, amorphous carbon, carbon fiber, natural graphite, artificial graphite, graphitized ketjen black, activated carbon, mesoporous carbon And so on. Also, vapor grown carbon fiber can be used. These carbon powders may be used alone or in combination of two or more. It is preferable that at least a part of the carbon powder is a carbon nanofiber. This is because a highly conductive electrode material can be obtained. When the conductive carbon is a spherical particle, the particle diameter is preferably in the range of 10 nm to 300 nm, more preferably in the range of 10 to 100 nm, particularly in the range of 10 to 50 nm. preferable. When the conductive carbon is acicular, tubular or fibrous particles, the diameter (short axis) of the particle cross section is preferably in the range of 10 nm to 300 nm, and more preferably in the range of 10 to 100 nm. The range of 10 to 50 nm is particularly preferable.

  As the reactor capable of turning, any reactor can be used as long as it can apply a supercentrifugal force to the reaction solution. However, it is described in FIG. 1 of Patent Document 7 (Japanese Patent Laid-Open No. 2007-160151). A reactor having a concentric cylinder of an outer cylinder and an inner cylinder, in which a through-hole is provided in a side surface of the rotatable inner cylinder, and a slat plate is disposed at an opening of the outer cylinder is preferably used. . Hereinafter, the form which uses this suitable reactor is demonstrated.

A reaction solution for reaction in an ultracentrifugal force field is introduced into the inner cylinder of the reactor. A reaction liquid prepared in advance may be introduced into the inner cylinder, or may be introduced by preparing the reaction liquid in the inner cylinder. It is only necessary to obtain a reaction solution in which the active material raw material is dissolved in the solvent and the conductive carbon powder is dispersed in the liquid. The order of addition of the compound containing Li, the compound containing Mn, and the conductive carbon powder to the solvent There is no limitation. It is preferable to add a compound containing lithium after adding a compound containing Mn and conductive carbon powder to the solvent, stirring the resulting liquid to disperse the conductive carbon powder in the liquid. This is because by increasing the dispersibility of the conductive carbon powder, the active material raw material and / or the reaction product thereof are more uniformly and finely supported on the carbon powder in the following supporting step. Stirring may be performed using a stirring means such as a homogenizer, or when preparing a reaction liquid in the reactor, the stirring may be performed by rotating the reactor. Further, a reaction accelerator can be added to the reaction solution in order to support the target reaction product on the conductive carbon in the following supporting step. Examples of the reaction accelerator include NaOH, KOH, NH ₄ OH, Na ₂ O ₃ , NaHCO _{3 and the} like that promote the hydrolysis reaction.

  In the supporting step of b1), the active carbon material and / or the reaction product thereof are supported on the conductive carbon powder by rotating the reactor and applying shear stress and centrifugal force to the reaction liquid. Depending on the type of reaction solution, a large amount of active material raw material may be supported, and a large amount of reaction product such as hydroxide may be supported.

Conversion from the active material raw material to the reaction product, and loading of the active material raw material and / or the reaction product onto the conductive carbon powder are realized by the mechanical energy of shear stress and centrifugal force applied to the reaction liquid. However, the shear stress and the centrifugal force are generated by the centrifugal force applied to the reaction liquid by the rotation of the inner cylinder. The centrifugal force applied to the reaction solution in the inner cylinder is a centrifugal force in a range generally referred to as “ultracentrifugal force”, and is generally 1500 kgms ⁻² or more, preferably 70000 kgms ⁻² or more, particularly preferably 270000 kgms ⁻² or more. .

  The embodiment using the preferred reactor having the outer cylinder and the inner cylinder described above will be described. When the inner cylinder of the reactor into which the reaction liquid has been introduced is swung, the centrifugal force generated by the swirling of the inner cylinder causes The reaction liquid moves to the outer cylinder through the through hole, and the reaction liquid between the outer wall of the inner cylinder and the inner wall of the outer cylinder rises to the upper part of the inner wall of the outer cylinder. As a result, shear stress and centrifugal force are applied to the reaction liquid, and this mechanical energy causes reaction products from the active material raw material between the outer wall surface of the inner cylinder and the inner wall surface of the outer cylinder depending on the type of the reaction liquid. And conversion of the active material raw material and / or its reaction product onto the conductive carbon powder occurs. The active material raw material and / or the reaction product thereof are supported on the conductive carbon powder as very fine particles by a reaction in the ultracentrifugal field with good dispersibility.

  In the above reaction, the smaller the distance between the outer wall surface of the inner cylinder and the inner wall surface of the outer cylinder, the larger the mechanical energy that can be applied to the reaction solution. The distance between the inner cylinder outer wall surface and the outer cylinder inner wall surface is preferably 5 mm or less, more preferably 2.5 mm or less, and particularly preferably 1.0 mm or less. The distance between the inner cylinder outer wall surface and the outer cylinder inner wall surface can be set by the width of the reactor plate and the amount of the reaction liquid introduced into the reactor.

  The turning time of the inner cylinder is not strictly limited and varies depending on the amount of the reaction solution and the turning speed (centrifugal force) of the inner cylinder, but is generally in the range of 0.5 to 10 minutes. . After completion of the reaction, the inner cylinder stops turning, and the conductive carbon powder carrying the active material material and / or the reaction product thereof is collected and dried.

  In the heat treatment step c1), the recovered material is mixed with a compound containing a metal represented by M, and then heat-treated to form a spinel oxide on the conductive carbon powder. Here, a compound containing a metal represented by M can be used without any particular limitation. For example, inorganic metal salts such as hydroxide, carbonate, halide, nitrate, sulfate, formate, acetic acid Organic metal salts such as salts, oxalates and lactates, or mixtures thereof can be used. These compounds may be used alone or in combination of two or more.

  By combining the recovered material obtained in the step b1) and the compound containing a metal represented by M with an appropriate amount of a dispersion medium as necessary, and kneading while evaporating the dispersion medium as necessary. Get kneaded. As a dispersion medium for kneading, any medium that does not adversely affect the composite can be used without particular limitation, and water, methanol, ethanol, isopropyl alcohol, and the like can be preferably used. It can be particularly preferably used.

  Next, by applying heat treatment, the active material raw material supported on the conductive carbon powder and / or the reaction product thereof is reacted with a compound containing a metal represented by M to be converted into spinel oxide particles. . The heat treatment is generally performed in an oxygen-containing atmosphere. When heated in an oxygen-free atmosphere, the reaction product may be reduced and the desired spinel oxide may not be obtained. The reaction temperature is generally 200-300 ° C. The heating time is generally in the range of 0.5 to 5 hours. Prolonged heating at a temperature exceeding 300 ° C. is not preferable because it promotes combustion and disappearance of the conductive carbon powder.

  In the supporting step, since the active material raw material and / or the reaction product thereof are supported as fine particles on the conductive carbon powder with good dispersibility, the spinel-type oxide generated in the heat treatment step is fine and has a uniform size. It becomes.

  The heat treatment may also be performed by flash heating at a high temperature of 600 to 700 ° C. for a short time, for example, 3 to 5 minutes. Prior to the flash heat treatment, preheating can also be performed at a low temperature. Preheating is not essential. The preheating atmosphere is not strictly limited and may be preheating in vacuum, preheating in an inert atmosphere such as nitrogen or argon, or preheating in an oxygen-containing atmosphere such as oxygen or air. But it ’s okay. In general, heat treatment in an oxygen-containing atmosphere or inert atmosphere is performed at a temperature of 200 to 300 ° C. for 3 minutes to 2 hours, and preheating in a vacuum is performed at a temperature of room temperature to 200 ° C. for 3 minutes to 2 hours. Done in a range.

  The flash heating can be performed using a known flash heating device, for example, a flash heating device including a flash lamp. The conditions for flash heating are 600 to 700 ° C. for 3 to 5 minutes in an oxygen-containing atmosphere. In flash heating in an atmosphere not containing oxygen, the spinel oxide is reduced, and the target active material cannot be obtained. If the flash heating temperature is higher than 700 ° C., and if the flash heating time is longer than 5 minutes, the conductive carbon powder burns and disappears too much, and the conductivity of the electrode material decreases.

When performing flash heating, prior to the preparation step of a1),
p) partially coating the surface of the conductive carbon powder with nanoparticles of metal oxide selected from the group consisting of tin oxide, iron oxide, aluminum oxide, titanium oxide, silicon oxide and zirconium oxide. It is preferable to carry out. These oxides suppress the burning and disappearance of the conductive carbon powder due to the flash heating at the time of preparing the electrode material.

  The step p) includes a solvent, a compound containing a metal selected from the group consisting of Sn, Fe, Al, Ti, Si, and Zr, a hydrolysis accelerator, and a conductive carbon powder as necessary. It can carry out using the liquid containing.

  As the solvent, any solvent that does not adversely influence the reaction can be used without particular limitation, and water, methanol, ethanol, isopropyl alcohol, and the like can be suitably used. Two or more solvents may be mixed and used. Water can be preferably used.

  As the compound containing Sn, Fe, Al, Ti, Si, and Zr, a compound that can be dissolved in the solvent can be used without any particular limitation. Examples include inorganic metal salts such as halides, nitrates, sulfates and carbonates of the above metals, organometallic salts such as formate, acetate, oxalate, methoxide, ethoxide, isopropoxide, or mixtures thereof. Can be used. A single compound may be used, or two or more compounds may be mixed and used.

As the hydrolysis accelerator, NaOH, KOH, NH ₄ OH, Na ₂ O ₃ , NaHCO ₃ or the like can be used.

  After adding a compound containing a metal selected from the group consisting of Sn, Fe, Al, Ti, Si, and Zr, a hydrolysis accelerator and conductive carbon powder as necessary, a solvent, a homogenizer, After stirring and homogenizing by sonication, etc., the conductive carbon powder is filtered and dried, and then subjected to heat treatment, whereby the conductive carbon powder whose surface is partially coated with the metal oxide nanoparticles is obtained. Can be obtained.

  The conductive carbon powder whose surface is partially coated with the metal oxide nanoparticles can be obtained by a process similar to the above-described a1) to c1). In this case, in the preparation of the reaction solution, the compound containing Sn, Fe, Al, Ti, Si, Zr described above is used instead of the active material. In this case, heat treatment in a vacuum, heat treatment in an inert atmosphere such as nitrogen or argon, or heat treatment in an oxygen-containing atmosphere such as oxygen or air may be used. Also in this case, the ultracentrifugation process can be suitably performed using the reactor described in FIG. 1 of Patent Document 7, and the magnitude of the centrifugal force applied to the reaction solution and the outer wall surface of the inner cylinder and the outside The above description regarding the distance from the cylinder inner wall surface also applies in this case.

Prior to the preparation step a1),
p) ′ bonding a coupling agent selected from the group consisting of a silane coupling agent, an aluminate coupling agent, a titanate coupling agent, and a zirconate coupling agent to the surface of the conductive carbon powder. It can also be implemented. In the step c1), the coupling agent bonded to the surface of the conductive carbon powder is changed into a thin film of silicon oxide, aluminum oxide, titanium oxide, and zirconium oxide to cover the surface of the conductive carbon powder.

  In the step p) ′, a known coupling agent can be used without particular limitation as a silane coupling agent, an aluminate coupling agent, a titanate coupling agent, or a zirconate coupling agent. Examples include methyltrimethoxysilane, γ-aminopropyltriethoxysilane, N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, N-phenylaminomethyltrimethoxysilane, vinylmethyldiethoxysilane, aceto Alkoxy aluminum diisopropylate, aluminum isopropylate, aluminum ethylate, aluminum tris (ethyl acetoacetate), aluminum diisopropoxy monoethyl acetoacetate, isopropyl triisostearoyl titanate, isopropyl tris (dioctyl pyrophosphate) titanate, tetraoctyl bis ( Ditridecyl phosphite) titanate, bis (dioctylpyrophosphate) oxyacetate titanate, zirconium tetrakis Cetyl acetonate, zirconium dibutoxy bis acetylacetonate, may be mentioned zirconium tetrakis ethyl acetoacetate.

  Add the coupling agent and conductive carbon powder to an organic solvent such as isopropyl alcohol that can dissolve the coupling agent, stir and homogenize by homogenizer, ultrasonic irradiation, etc., and then filter the conductive carbon powder. By drying, a conductive carbon powder in which the coupling agent is bonded to the surface can be obtained.

(Ii) Second manufacturing method The second manufacturing method is:
a2) Reactor capable of turning a reaction liquid obtained by adding conductive carbon powder to a solution in which an active material raw material containing a compound containing Li, a compound containing Mn, and a compound containing a metal represented by M is dissolved The preparation process to be introduced in,
b2) a supporting step of supporting the active material raw material and / or the reaction product thereof on the conductive carbon powder by rotating the reactor and applying shear stress and centrifugal force to the reaction solution; and
c2) It includes a heat treatment step of forming the spinel oxide on the conductive carbon powder by heat-treating the conductive carbon powder carrying the active material raw material and / or the reaction product thereof.

  The second production method is a method in which the compound containing the metal represented by M used in step c1) in the first production method is previously contained in the reaction solution prepared in step a2). This can be said to be a modification of the manufacturing method 1.

  In the preparation step of a2), a compound containing Li as an active material raw material, a compound containing Mn, a compound containing a metal represented by M, and a conductive carbon powder are added to a solvent, and the compound is used as a solvent. A reaction liquid is obtained by dissolving.

  As the solvent, any liquid that does not adversely affect the reaction can be used without particular limitation. As the active material, a compound containing Li, a compound containing Mn, and a compound containing a metal represented by M are solvents. A compound that can be dissolved in can be used without particular limitation. Examples include inorganic metal salts such as halides, nitrates, sulfates and carbonates of the above metals, organometallic salts such as formate, acetate, oxalate, methoxide, ethoxide, isopropoxide, or mixtures thereof. Can be used. With respect to one kind of metal, a single compound may be used, or two or more kinds of compounds may be mixed and used. As the conductive carbon powder, any conductive carbon powder can be used without particular limitation. Also in this case, it is only necessary to obtain a reaction liquid in which the active material raw material is dissolved in the solvent and the conductive carbon powder is dispersed in the liquid. The compound containing Li, the compound containing Mn, There is no limitation in the addition order of the compound containing the represented metal and the conductive carbon powder. A compound containing Mn, a compound containing a metal represented by M and a conductive carbon powder are added to a solvent, and the obtained liquid is stirred to disperse the conductive carbon powder in the liquid, and then a compound containing lithium is added. It is preferable to add. This is because by increasing the dispersibility of the conductive carbon powder, the active material raw material and / or the reaction product thereof are more uniformly and finely supported on the carbon powder in the following supporting step. Stirring may be performed using a stirring means such as a homogenizer, or when preparing a reaction liquid in the reactor, the stirring may be performed by rotating the reactor.

  In the supporting step of b2), the active carbon material and / or the reaction product thereof are supported on the conductive carbon powder by rotating the reactor and applying shear stress and centrifugal force to the reaction solution. Also in this case, the ultracentrifugation process can be suitably performed using the reactor described in FIG. 1 of Patent Document 7, and the magnitude of the centrifugal force applied to the reaction solution and the outer wall surface of the inner cylinder and the outside The above description regarding the distance from the cylinder inner wall surface and the turning time also applies to this case.

  In the heat treatment step c2), the recovered material is heat-treated to be converted into spinel oxide particles. Since the description regarding the heat treatment in the first manufacturing method is applicable also in this case, further description is omitted.

(Iii) Third Manufacturing Method The third manufacturing method is
a3) Preparation step for introducing a reaction solution containing water, a Li hydroxide, a compound containing Mn, and a conductive carbon powder and having a pH in the range of 9 to 11 into a swirlable reactor ,
b3) The reactor is swirled to apply shear stress and centrifugal force to the reaction solution to generate Mn hydroxide nuclei, and the generated Mn hydroxide nuclei and the conductive carbon. A supporting step of dispersing the powder and simultaneously supporting a hydroxide of Mn on the conductive carbon powder; and
c3) The conductive carbon powder supporting the Mn hydroxide, the compound containing Li, and the compound containing the metal represented by M are mixed and heat-treated, whereby the conductive carbon powder is mixed. A heat treatment step of forming the spinel oxide on the powder.

  The 3rd manufacturing method contains water, the hydroxide of Li, the compound containing Mn, and the conductive carbon powder as a reaction liquid in the a1) process of the 1st manufacturing method, The range of 9-11 This corresponds to a method for preparing a reaction solution having a pH of 5 and can be said to be a modified method of the first production method.

  As the compound containing Mn, a water-soluble compound can be used without any particular limitation. For example, Mn halides, inorganic metal salts such as nitrates and sulfates, organometallic salts such as formates and acetates, or mixtures thereof can be used. A single compound may be used, or two or more kinds may be mixed and used.

When the pH of a solution in which a compound containing Mn is dissolved in water is increased, OH ⁻ is coordinated to Mn, and when the pH is further increased, the hydroxide of Mn is eventually insolubilized. In the preparation step of a3), a reaction liquid whose pH is adjusted to a range of 9 to 11 is placed in a swirlable reactor, or the reaction liquid is prepared in a swirlable reactor. Although Mn hydroxide insolubilized in the reaction solution may be observed, in the preparation step a3), most of Mn in the reaction solution is not supported on the conductive carbon powder.

  The pH of the reaction solution is adjusted with Li hydroxide. The reaction solution is easy by mixing a solution in which a compound containing Mn is dissolved in water and a conductive carbon powder is dispersed in a solution and a solution in which Li hydroxide is dissolved in water. Can be prepared. A compound containing Mn and conductive carbon powder are added to water, and the obtained liquid is stirred to disperse the conductive carbon powder in the liquid, and then mixed with a liquid in which Li hydroxide is dissolved in water. It is preferable to do this. This is because by increasing the dispersibility of the conductive carbon powder, the hydroxide of Mn is more uniformly and finely supported on the carbon powder in the following supporting process. Stirring may be performed using a stirring means such as a homogenizer, or when preparing a reaction liquid in the reactor, the stirring may be performed by rotating the reactor.

  Next, in the loading step b3), the reactor is swirled. Also in this case, the ultracentrifugation process can be suitably performed using the reactor described in FIG. 1 of Patent Document 7, and the magnitude of the centrifugal force applied to the reaction solution and the outer wall surface of the inner cylinder and the outside The above description regarding the distance from the cylinder inner wall surface and the turning time also applies to this case. Mn hydroxide nuclei are generated by shear stress and centrifugal force due to the rotation of the reactor, that is, by mechanical energy. The nuclei grow uniformly while being dispersed in the rotating reactor, and are supported on the conductive carbon powder as fine particles of uniform size. Moreover, since almost all of Mn in the reaction solution is supported on the conductive carbon powder as a hydroxide, the efficiency is good. If the pH of the reaction solution is less than 9, the efficiency of generation of hydroxide nuclei in the supporting step and the supporting efficiency of the generated hydroxide on the conductive carbon powder are low, and if the pH exceeds 11, the hydroxylation in the supporting step The insolubilization speed of the product is too fast, and it is difficult to obtain a fine hydroxide. Therefore, after adjusting the pH of the reaction solution in the range of 9 to 11, mechanical energy is applied in the reactor swirling to the reaction solution, thereby efficiently generating hydroxide nuclei in the reaction solution. As a result, the hydroxide can be supported on the conductive carbon powder as fine particles of uniform size.

  In the heat treatment step c3), the conductive carbon powder in which Mn hydroxide is supported as fine particles having a uniform size is mixed with a compound containing Li and a compound containing a metal represented by M, and then heated. Process.

  The compound containing Li can be used without particular limitation as long as it contains Li. For example, inorganic metal salts such as Li hydroxide, carbonate, halide, nitrate, sulfate, formate, acetic acid, etc. Organic metal salts such as salts, oxalates and lactates, or mixtures thereof can be used. The compound containing a metal represented by M can be used without particular limitation as long as it contains a metal represented by M. For example, inorganic compounds such as hydroxide, carbonate, halide, nitrate, sulfate, etc. Metal salts, formate salts, acetate salts, oxalate salts, organometallic salts such as lactate salts, or mixtures thereof can be used. These compounds may be used alone or in combination of two or more.

  A conductive carbon powder carrying fine particles of Mn hydroxide obtained in the carrying step of b3), a compound containing Li, and a compound containing a metal represented by M are appropriately added as necessary. A kneaded product is obtained by combining with a dispersion medium and kneading while evaporating the dispersion medium as necessary. As a dispersion medium for kneading, any medium that does not adversely affect the composite can be used without particular limitation.

  Next, by performing a heat treatment, the hydroxide of Mn supported on the conductive carbon powder is reacted with a compound containing Li and a compound containing a metal represented by M to be converted into spinel oxide particles. . Since the description regarding the heat treatment in the first manufacturing method is applicable also in this case, further description is omitted.

(Iv) Fourth Manufacturing Method The fourth manufacturing method is
a4) A reaction liquid containing water, a hydroxide of Li, a compound containing Mn, a compound containing a metal represented by M and a conductive carbon powder, and having a pH in the range of 9 to 11. A preparation process to be introduced into the swirlable reactor,
b4) The reactor was swirled to apply shear stress and centrifugal force to the reaction solution, thereby generating a Mn hydroxide and a metal hydroxide nucleus represented by M. Mn hydroxide and the metal hydroxide nucleus represented by M and the conductive carbon powder are dispersed, and at the same time, the Mn hydroxide and the metal represented by M are dispersed in the conductive carbon powder. A supporting step for supporting a hydroxide of, and
c4) Conductive carbon powder carrying the hydroxide of Mn and the metal hydroxide represented by M and a compound containing Li are mixed and heat-treated, whereby the conductive carbon is obtained. A heat treatment step of forming the spinel oxide on the powder.

  The fourth production method is a method in which the compound containing the metal represented by M used in step c3) in the third production method is previously contained in the reaction solution prepared in step a4). 3 can be said to be a modified method of the first manufacturing method. This method is particularly suitable when M contains Fe, Ni, and Co.

  The step a4) includes water, a hydroxide of Li, a compound containing Mn, a compound containing a metal represented by M, and a conductive carbon powder, and has a pH in the range of 9 to 11. Prepare a reaction solution.

  As the compound containing Mn and the compound containing a metal represented by M, a water-soluble compound can be used without any particular limitation. For example, a metal halide represented by Mn or M, an inorganic metal salt such as nitrate or sulfate, an organic metal salt such as formate or acetate, or a mixture thereof can be used. With respect to one kind of metal, a single compound may be used, or two or more kinds may be mixed and used.

  The pH of the reaction solution is adjusted with Li hydroxide. In the reaction solution, a compound containing Mn and a compound containing a metal represented by M are dissolved in water, and a conductive carbon powder is dispersed in the solution, and Li hydroxide is dissolved in water. It can be easily prepared by mixing the liquid. A compound containing Mn, a compound containing a metal represented by M and conductive carbon powder are added to water, and the obtained liquid is stirred to disperse the conductive carbon powder in the liquid. It is preferable to mix with a solution in which an oxide is dissolved. This is because by increasing the dispersibility of the conductive carbon powder, the hydroxide of Mn and the metal hydroxide represented by M are more uniformly and finely supported on the carbon powder in the following supporting process. Stirring may be performed using a stirring means such as a homogenizer, or when preparing a reaction liquid in the reactor, the stirring may be performed by rotating the reactor.

  Next, in the loading step b4), the reactor is swirled. Also in this case, the ultracentrifugation process can be suitably performed using the reactor described in FIG. 1 of Patent Document 7, and the magnitude of the centrifugal force applied to the reaction solution and the outer wall surface of the inner cylinder and the outside The above description regarding the distance from the cylinder inner wall surface and the turning time also applies to this case. Mn hydroxide and metal hydroxide nuclei represented by M are generated by shear stress and centrifugal force due to the swirling of the reactor, that is, mechanical energy. The nuclei grow uniformly while being dispersed in the rotating reactor, and are supported on the conductive carbon powder as fine particles of uniform size.

  Then, in the heat treatment step of c4), after mixing the conductive carbon powder in which the hydroxide of Mn and the hydroxide of the metal represented by M are supported as fine particles of uniform size with the compound containing Li, Heat treatment is performed. Any compound containing Li can be used without particular limitation as long as it contains Li.

  A conductive carbon powder carrying fine particles of Mn hydroxide and metal hydroxide represented by M obtained in the carrying step of b4) above, and a Li compound, if necessary, an appropriate amount of dispersion A kneaded product is obtained by combining with a medium and kneading while evaporating the dispersion medium as necessary. As a dispersion medium for kneading, any medium that does not adversely affect the composite can be used without particular limitation.

  Next, by performing a heat treatment, the hydroxide of Mn supported on the conductive carbon powder and the metal hydroxide represented by M are reacted with a compound containing Li to be converted into particles of spinel oxide. Let Since the description regarding the heat treatment in the first manufacturing method is applicable also in this case, further description is omitted.

  When the positive electrode of the lithium ion secondary battery is formed using the electrode material of the present invention that can be suitably obtained by the first to fourth manufacturing methods, a high discharge capacity is exhibited even in charge and discharge at a high rate, and a hybrid A lithium ion secondary battery having excellent rate characteristics that can sufficiently meet the demand for high capacity in charge / discharge at a rate of 10 C or higher required for lithium ion secondary batteries for automobiles is obtained. It is done. The electrode material of the present invention is also mixed with spinel-type oxide particles having a primary particle size or secondary particle size larger than 50 nm, for example, spinel-type oxide particles obtained by the production methods of Patent Documents 1 to 6. Can also be used. By mixing with a spinel oxide having a large particle size, a lithium ion secondary battery having a high energy density can be obtained.

(B) Lithium ion secondary battery The electrode material of this invention is suitable for the positive electrode of a lithium ion secondary battery. Therefore, the present invention also provides a lithium ion battery comprising a positive electrode having an active material layer containing the electrode material of the present invention, a negative electrode, and a separator holding a non-aqueous electrolyte disposed between the negative electrode and the positive electrode. Provide the next battery.

  The active material layer for the positive electrode is dispersed in a solvent in which a binder is dissolved, if necessary, by dispersing the electrode material of the present invention on the current collector by a doctor blade method or the like, and then dried. Can be created. Further, the obtained dispersion may be formed into a predetermined shape and may be pressure-bonded on the current collector.

  As the current collector, a conductive material such as platinum, gold, nickel, aluminum, titanium, steel, or carbon can be used. As the shape of the current collector, any shape such as a film shape, a foil shape, a plate shape, a net shape, an expanded metal shape, and a cylindrical shape can be adopted.

  As the binder, known binders such as polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, polyvinyl fluoride, and carboxymethyl cellulose are used. The content of the binder is preferably 1 to 30% by mass with respect to the total amount of the mixed material. If it is 1% by mass or less, the strength of the active material layer is not sufficient, and if it is 30% by mass or more, disadvantages such as a decrease in the discharge capacity of the negative electrode and an excessive internal resistance occur.

As the negative electrode, in addition to the graphite electrode used in a general lithium ion secondary battery, a negative electrode including an active material layer containing a known negative electrode active material can be used without any particular limitation. Examples of the negative electrode active material include Fe ₂ O ₃ , MnO, MnO ₂ , Mn ₂ O ₃ , Mn ₃ O ₄ , CoO, Co ₃ O ₄ , NiO, Ni ₂ O ₃ , TiO, TiO ₂ , SnO, SnO ₂ , oxides such as SiO ₂ , RuO ₂ , WO, WO ₂ , ZnO, metals such as Sn, Si, Al, Zn, composite oxides such as LiVO ₂ , Li ₃ VO ₄ , Li ₄ Ti ₅ O ₁₂ , Examples thereof include nitrides such as Li _2.6 Co _0.4 N, Ge ₃ N ₄ , Zn ₃ N ₂ , and Cu ₃ N.

  The active material layer for the negative electrode is dispersed on the current collector by the doctor blade method or the like by dispersing the negative electrode active material and the conductive agent in a solvent in which a binder is dissolved as necessary. And can be made by drying. Further, the obtained dispersion may be formed into a predetermined shape and may be pressure-bonded on the current collector.

  Regarding the current collector and binder, the description of the current collector and binder for the positive electrode also applies to the negative electrode. As the conductive agent, carbon powder such as carbon black, natural graphite, and artificial graphite can be used.

  As the separator, for example, a polyolefin fiber nonwoven fabric or a glass fiber nonwoven fabric is preferably used. As the electrolytic solution retained in the separator, an electrolytic solution in which an electrolyte is dissolved in a non-aqueous solvent is used, and a known non-aqueous electrolytic solution can be used without any particular limitation.

  As the solvent for the non-aqueous electrolyte, electrochemically stable ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, sulfolane, 3-methyl sulfolane, γ-butyrolactone, acetonitrile, and dimethoxyethane, N-methyl-2-pyrrolidone, dimethylformamide or a mixture thereof can be preferably used.

As a solute of the nonaqueous electrolytic solution, a salt that generates lithium ions when dissolved in an organic electrolytic solution can be used without any particular limitation. For _{example, LiPF 6, LiBF 4, LiClO} 4, LiN (CF 3 SO 2) 2, LiCF 3 SO 3, LiC (SO 2 CF 3) 3, LiN (SO 2 C 2 F 5) 2, LiAsF 6, LiSbF 6 Or a mixture thereof can be preferably used. As a solute of the nonaqueous electrolytic solution, a quaternary ammonium salt or a quaternary phosphonium salt having a quaternary ammonium cation or a quaternary phosphonium cation can be used in addition to a salt that generates lithium ions. For example, a cation represented by R ¹ R ² R ³ R ⁴ N ⁺ or R ¹ R ² R ³ R ⁴ P ⁺ (where R ¹ , R ² , R ³ and R ⁴ are alkyl having 1 to 6 carbon atoms) Group), PF ₆ ⁻ , BF ₄ ⁻ , ClO ₄ ⁻ , N (CF ₃ SO ₃ ) ₂ ⁻ , CF ₃ SO ₃ ⁻ , C (SO ₂ CF ₃ ) ₃ ⁻ , N (SO ₂ C ₂ A salt composed of an anion composed of F ₅ ) ₂ ⁻ , AsF ₆ ^— or SbF ₆ ^— , or a mixture thereof can be suitably used.

  The present invention will be described with reference to the following examples, but the present invention is not limited to the following examples.

  (I) Production of electrode material

Example 1: Electrode material containing LiAl _0.05 Mn _1.95 O ₄ Consisting of a concentric cylinder of an outer cylinder and an inner cylinder shown in FIG. 1 of JP 2007-160151 A, on the side surface of the inner cylinder An inner cylinder of a reactor in which a through-hole is provided and a dam plate is arranged at the opening of the outer cylinder is filled with 1.54 g of Mn (CH ₃ COO) ₂ .4H ₂ O and a mass ratio of 0.21 g. Chain black (particle size: about 40 nm): carbon nanofiber (diameter: about 20 nm, length: several hundreds of nm) = a mixture obtained by adding a carbon mixture mixed in 1: 1 to 75 mL of water, and a centrifugal force of 70000 kgms ^-2 The inner cylinder was swung for 300 seconds so as to be applied to the reaction solution, and Mn (CH ₃ COO) ₂ .4H ₂ O was dissolved and the carbon mixture was dispersed. The turning of the inner cylinder was once stopped, and a solution obtained by dissolving 0.6 g of LiOH.H ₂ O in water was added to the inner cylinder. The pH of the liquid was 10. Next, the inner cylinder was rotated for 300 seconds so that a centrifugal force of 70000 kgms- ² was applied to the reaction solution again. During this time, a nucleus of Mn hydroxide was formed between the inner wall of the outer cylinder and the outer wall of the inner cylinder, and this nucleus grew and was supported on the surface of the carbon mixture. After the inner cylinder stopped rotating, the carbon mixture was collected by filtration and dried in air at 100 ° C. for 12 hours. When the filtrate was confirmed by ICP spectroscopic analysis, it was found that 95% or more of Mn contained in the Mn (CH ₃ COO) ₂ .4H ₂ O raw material was supported. Next, the powder after drying, and LiOH.H ₂ O in an amount such that Mn: Li becomes 1.95: 1 and Al (NO ₃ ) in an amount such that Mn: Al becomes 1.95: 0.05 by mass ratio. _An aqueous solution containing 3.9H ₂ O was mixed and kneaded, dried, and then heat-treated in air at 300 ° C. for 1 hour to obtain an electrode material. FIG. 2 shows a TEM photograph of the obtained electrode material. It can be seen that primary particles of LiAl _0.05 Mn _1.95 O _{4 having} a particle size of about 20 to about 30 nm are formed with good dispersibility. It can also be seen that the primary particles are crystal particles having a polyhedral shape and do not aggregate to form secondary particles.

Example 2 Electrode Material Containing LiAl _0.10 Mn _1.90 O _{4 An} amount of LiOH.H ₂ O and Mn: Al in a ratio of Mn: Li of 1.95: 1 is 1.95: 0. Instead of an aqueous solution containing Al (NO ₃ ) ₃ · 9H ₂ O in an amount of 05, LiOH · H ₂ O and Mn: Al in an amount of Mn: Li of 1.90: 1 are 1 by mass. The procedure of Example 1 was repeated except that an aqueous solution containing Al (NO ₃ ) ₃ .9H ₂ O in an amount of .90: 0.10 was used. Similar to Example 1, crystalline primary particles having a particle size of about 20 to about 30 nm were formed with good dispersibility.

(Ii) Evaluation as a half-cell The electrode material of Examples 1 and 2 was molded by adding 10% by mass of polyvinylidene fluoride as a positive electrode, and a 1M LiPF ₆ ethylene carbonate / diethyl carbonate 1: 1 solution was electrolyzed. A half-cell was prepared in which the liquid was used and the counter electrode was lithium. Although this evaluation is an evaluation as a half battery, the same effect can be expected in all batteries using a negative electrode.

About the obtained half battery, charge / discharge characteristics were evaluated in the range of 3.0-4.3V with respect to Li / Li ^{+ on} the conditions of the electric current density of wide range at normal temperature. FIG. 3 is a diagram showing the relationship between the rate and the discharge capacity for the half-cells using the electrode materials of Example 1 and Example 2.

As can be seen from FIG. 3, the lithium ion secondary battery using the electrode material of Example 1 shows a high capacity of 122 mAhg ⁻¹ at rate 1C, and 117 mAhg ⁻¹ (capacity of rate 1C at rate 10C). 96%) and 111 mAhg ⁻¹ (91% of the capacity at rate 1C) even at a rate of 30C. The lithium ion secondary battery using the electrode material of Example 2 shows a high capacity of 116 mAhg ^{−1 at} a rate of 1C, 112 mAhg ⁻¹ (97% of the capacity at a rate of 1C) even at a rate of 10C, and at a rate of 30C. Also showed 103 mAhg ⁻¹ (89% of capacity at rate 1C). When these results are compared with the rate characteristics in the lithium ion secondary batteries of Patent Documents 4 to 6 shown at the beginning of the present specification, the rates significantly improved by using the electrode materials of Example 1 and Example 2. It turns out that the lithium ion secondary battery which has a characteristic was obtained. As a result, in the electrode materials of Example 1 and Example 2, the spinel oxide existing in the form of crystalline primary particles having a particle size of about 20 to about 30 nm substantially adheres to the conductive carbon powder. It is well and uniformly attached, reflecting the fact that the effective reaction area of the charge exchange / charge transfer reaction can be increased, and the movement distance of lithium ions during charge / discharge can be shortened. The electrode material of the present invention and a lithium ion secondary battery using the same are required for a high capacity in charge / discharge at a rate of 10 C or higher, which is particularly required for lithium ion secondary batteries for hybrid vehicles. It could be answered enough.

Next, a cycle test in which charging / discharging in the range of 3.0 to 4.3 V with respect to Li / Li ⁺ was repeated 100 cycles under the condition of a rate of 1C was shown in FIG. As can be seen from FIG. 4, it can be seen that a lithium ion secondary battery having excellent cycle stability is obtained by using the electrode material of the present invention. In general, it is said that an increase in the specific surface area of a spinel type oxide has a disadvantageous effect on cycle stability. In the electrode materials of Example 1 and Example 2, the spinel-type oxide is present in the form of crystalline primary particles having a particle size of about 20 to about 30 nm, so that it is used for a conventional lithium ion secondary battery. Compared with a spinel type oxide, for example, the spinel type oxides of Patent Documents 1 to 6, the specific surface area is remarkably large. The reason why excellent cycle stability was obtained even at such a remarkably large specific surface area is not clear at present, but in the electrode materials of Example 1 and Example 2, a fine and highly crystalline spinel oxide is used. This is probably because the crystal is stabilized as a result of being adhered to the conductive carbon powder with good adhesion and uniformity.

  According to the present invention, a lithium ion secondary battery having excellent rate characteristics can be obtained.

Claims (8)

Conductive carbon powder;
The general formula LiM _x Mn _(2-x) O ₄ (wherein M represents one or more metals selected from the group consisting of metals other than Mn, attached to the conductive carbon powder, and 0 < x ≦ 0.15.) Spinel oxide particles represented by:
Including
The electrode material for a lithium ion secondary battery, wherein the spinel-type oxide particles are substantially crystalline primary particles having a particle size of 10 to 50 nm. The electrode material for a lithium ion secondary battery according to claim 1, wherein M in the general formula LiM _x Mn _(2-x) O ₄ represents a metal selected from Mg, Al, Co, Cr, Fe and Ni. . Conductive carbon powder;
The general formula LiM _x Mn _(2-x) O ₄ (wherein M represents one or more metals selected from the group consisting of metals other than Mn, attached to the conductive carbon powder, and 0 < x ≦ 0.15.) Spinel oxide particles represented by:
A method for producing an electrode material for a lithium ion secondary battery comprising:
a1) A preparation step of introducing a reaction solution obtained by adding conductive carbon powder to a solution in which an active material raw material containing a compound containing Li and a compound containing Mn is dissolved, into a swirlable reactor,
b1) a supporting step of supporting the active material raw material and / or the reaction product thereof on the conductive carbon powder by swirling the reactor and applying shear stress and centrifugal force to the reaction liquid; and
c1) The conductive carbon powder supporting the active material raw material and / or the reaction product thereof is mixed with the compound containing the metal represented by M, and then heat-treated, whereby the conductive carbon powder is heated. A method for producing an electrode material for a lithium ion secondary battery, comprising: a heat treatment step for forming the spinel oxide. Conductive carbon powder;
The general formula LiM _x Mn _(2-x) O ₄ (wherein M represents one or more metals selected from the group consisting of metals other than Mn, attached to the conductive carbon powder, and 0 < x ≦ 0.15.) Spinel oxide particles represented by:
A method for producing an electrode material for a lithium ion secondary battery comprising:
a2) Reactor capable of turning a reaction solution obtained by adding conductive carbon powder to a solution in which an active material raw material containing a compound containing Li, a compound containing Mn, and a compound containing a metal represented by M is dissolved The preparation process to be introduced in,
b2) A supporting step of supporting the active material raw material and / or the reaction product thereof on the conductive carbon powder by rotating the reactor and applying shear stress and centrifugal force to the reaction solution; and
c2) including a heat treatment step of forming the spinel oxide on the conductive carbon powder by heat-treating the conductive carbon powder supporting the active material raw material and / or a reaction product thereof. A method for producing an electrode material for a lithium ion secondary battery. Conductive carbon powder;
The general formula LiM _x Mn _(2-x) O ₄ (wherein M represents one or more metals selected from the group consisting of metals other than Mn, attached to the conductive carbon powder, and 0 < x ≦ 0.15.) Spinel oxide particles represented by:
A method for producing an electrode material for a lithium ion secondary battery comprising:
a3) Preparation step for introducing a reaction solution containing water, a Li hydroxide, a compound containing Mn, and a conductive carbon powder and having a pH in the range of 9 to 11 into a swirlable reactor ,
b3) Rotating the reactor to apply shear stress and centrifugal force to the reaction solution to generate Mn hydroxide nuclei, and the generated Mn hydroxide nuclei and the conductive carbon. A supporting step of dispersing a powder and simultaneously supporting a hydroxide of Mn on the conductive carbon powder; and
c3) The conductive carbon powder carrying the hydroxide of Mn, the compound containing Li, and the compound containing the metal represented by M are mixed and heat-treated, whereby the conductive carbon powder is mixed. A method for producing an electrode material for a lithium ion secondary battery, comprising a heat treatment step of forming the spinel oxide on a powder. Conductive carbon powder;
The general formula LiM _x Mn _(2-x) O ₄ (wherein M represents one or more metals selected from the group consisting of metals other than Mn, attached to the conductive carbon powder, and 0 < x ≦ 0.15.) Spinel oxide particles represented by:
A method for producing an electrode material for a lithium ion secondary battery comprising:
a4) a reaction solution containing water, a hydroxide of Li, a compound containing Mn, a compound containing a metal represented by M, and a conductive carbon powder, and having a pH in the range of 9 to 11. A preparation process to be introduced into the swirlable reactor,
b4) The reactor is swirled to apply shear stress and centrifugal force to the reaction solution, thereby generating a Mn hydroxide and a metal hydroxide nucleus represented by M. Mn hydroxide and a metal hydroxide nucleus represented by M and the conductive carbon powder are dispersed, and at the same time, Mn hydroxide and the metal represented by M are dispersed in the conductive carbon powder. A supporting step for supporting a hydroxide of, and
c4) The conductive carbon powder obtained by mixing and heat-treating a conductive carbon powder carrying the hydroxide of Mn and the metal hydroxide represented by M and a compound containing Li. A method for producing an electrode material for a lithium ion secondary battery, comprising a heat treatment step of forming the spinel oxide on a powder.   The manufacturing method of the electrode material for lithium ion secondary batteries of any one of Claims 3-6 which performs the heat processing in the said heat processing process at the temperature of 200-300 degreeC in oxygen containing atmosphere.   The lithium ion secondary battery provided with the positive electrode which has an active material layer containing the electrode material of Claim 1 or 2.