JP2008084826A - Cathode powder and cathode mixture - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cathode powder which is useful for a nonaqueous electrolyte secondary battery which can demonstrate a high discharging capacity and a high output in a high current rate and provide a cathode mixture composed of the cathode powder and a binder. <P>SOLUTION: The cathode powder contains a cathode active material powder which is composed of primary particles and cohered particles of the primary particles and in which a particle diameter of particles of a number of 90% or more out of the primary particles and the cohered particles of the primary particles in the powder is 0.01 μm or more and 5 μm or less and a graphite powder which is composed of graphite particles and in which a maximum particle diameter of particles of a number of 90% or more out of the graphite particles in the powder is 0.1 μm or more and 10 μm or less. The cathode mixture is provided with the cathode powder and a binder. The cathode for the nonaqueous electrolyte secondary battery is provided with the cathode powder and the binder. The nonaqueous electrolyte secondary battery is provided with the cathode for the nonaqueous electrolyte secondary battery. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a positive electrode powder and a positive electrode mixture. More specifically, the present invention relates to a positive electrode powder and a positive electrode mixture containing a positive electrode active material powder and a graphite powder.

  A positive electrode powder containing a positive electrode active material powder and a graphite powder is used in a non-aqueous electrolyte secondary battery such as a lithium secondary battery. Non-aqueous electrolyte secondary batteries have already been put to practical use as power sources for mobile phones and notebook computers, and are also being applied to medium and large applications such as automobiles and power storage.

  As a conventional positive electrode powder, Patent Document 1 discloses a positive electrode powder containing a positive electrode active material having an average particle diameter of 9.1 μm to 20.5 μm and graphite having an average particle diameter of 3.3 μm to 51.5 μm. It is specifically described.

Japanese Patent Laid-Open No. 11-40140

  However, non-aqueous electrolyte secondary batteries obtained using conventional positive electrode powders are used for applications that require high output at high current rates because of the high internal resistance of the positive electrode, such as automobile applications and electric tools. It is not enough for the power tool application. An object of the present invention is to provide a positive electrode powder useful for a nonaqueous electrolyte secondary battery that exhibits a high discharge capacity and a high output at a high current rate, and a positive electrode mixture comprising the positive electrode powder and a binder. Is to provide.

  As a result of various studies in view of the above circumstances, the present inventors have found that a nonaqueous electrolyte secondary battery obtained by using a specific positive electrode powder or a positive electrode mixture having the positive electrode powder and a binder has a high discharge capacity. And the present inventors found that it is possible to show a high output at a high current rate.

That is, this invention is comprised from the following invention.
<1> A positive electrode active material powder comprising primary particles and agglomerated particles of primary particles, and the particle size of 90% or more of the primary particles and the agglomerated particles of the primary particles in the powder is 0.01 μm or more and 5 μm or less. A positive electrode active material powder and a graphite powder composed of graphite particles, and the particle size of the number of particles of 90% or more of the graphite particles in the powder is 0.1 μm or more and 10 μm or less. A positive electrode powder containing graphite powder.
<2> The positive electrode powder as described in <1>, wherein the average particle diameter of primary particles and aggregated particles of the primary particles in the positive electrode active material powder is 0.1 μm or more and 3 μm or less.
<3> The positive electrode powder as described in <1> or <2>, wherein an average value of the particle diameters of the graphite particles in the graphite powder is 1 μm or more and 6 μm or less.
<4> The positive electrode powder according to any one of <1> to <3>, wherein the graphite particles are scaly graphite particles.
<5> The positive electrode powder according to any one of <1> to <4>, wherein the composition of the positive electrode active material is represented by Formula (1).
Li _x1 Ni _1-y1 M ¹ _y1 O ₂ (1)
(In formula (1), x1 and y1 are 0.9 ≦ x1 ≦ 1.2 and 0 ≦ y1 ≦ 0.5, respectively, and M ¹ is Co.)
<6> The positive electrode powder according to any one of <1> to <4>, wherein the composition of the positive electrode active material is represented by Formula (2).
Li _x2 Ni _1-y2 M ² _y2 O ₂ (2)
(In the formula (2), x2 and y2 are 0.9 ≦ x2 ≦ 1.2 and 0.3 ≦ y2 ≦ 0.9, respectively, and M ² is Co and Mn.)
<7> The positive electrode powder according to any one of <1> to <6>, further containing a non-graphitic carbonaceous material.
<8> The positive electrode powder according to any one of <1> to <7>, further containing a fibrous carbon material.
<9> A positive electrode active material powder comprising primary particles and agglomerated particles of primary particles, and the particle size of 90% or more of the primary particles and the agglomerated particles of the primary particles in the powder is 0.01 μm or more and 5 μm or less. A positive electrode active material powder and a graphite powder composed of graphite particles, and the particle size of the number of particles of 90% or more of the graphite particles in the powder is 0.1 μm or more and 10 μm or less. The manufacturing method of the powder for positive electrodes which mixes the graphite powder which is.
<10> The method for producing a positive electrode powder as described in <9>, wherein the positive electrode active material powder has a BET specific surface area of 1 m ² / g or more and 7 m ² / g or less.
<11> The method for producing a positive electrode powder as described in <9> or <10>, wherein the graphite powder has a BET specific surface area of 12 m ² / g or more and 20 m ² / g or less.
<12> The method for producing a positive electrode powder according to any one of <9> to <11>, wherein the graphite powder is 5 parts by weight to 20 parts by weight with respect to 100 parts by weight of the positive electrode active material powder.
<13> The method for producing a positive electrode powder according to any one of <9> to <12>, further comprising mixing a non-graphitic carbonaceous material.
<14> The method for producing a positive electrode powder according to any one of <9> to <13>, wherein a fibrous carbon material is further mixed.
<15> A positive electrode having a positive electrode powder according to any one of <1> to <8> or a positive electrode powder obtained by the production method according to any one of <9> to <14> and a binder. Mixture.
<16> The positive electrode powder according to any one of <1> to <8> or the positive electrode powder obtained by the production method according to any one of <9> to <14> and a binder. Positive electrode for water electrolyte secondary battery.
<17> A nonaqueous electrolyte secondary battery comprising the positive electrode for a nonaqueous electrolyte secondary battery according to <16>.

  When the positive electrode powder of the present invention or the positive electrode mixture having the positive electrode powder and a binder is used in a non-aqueous electrolyte secondary battery, it exhibits a high discharge capacity and a high output at a high current rate. The positive electrode powder and the positive electrode mixture having the positive electrode powder and a binder can be used for non-aqueous electrolyte secondary batteries, and in particular, applications that require high output at a high current rate, that is, automotive applications. The present invention can be suitably used for non-aqueous electrolyte secondary batteries for power tools such as power tools and the like, and the present invention is extremely useful industrially.

  The positive electrode powder of the present invention is a positive electrode active material powder composed of primary particles and aggregated particles of primary particles, and the particle size of 90% or more of the primary particles and aggregated particles of the primary particles in the powder is 0. A positive electrode active material powder having a particle size of not less than 0.01 μm and not more than 5 μm and a graphite powder, and a particle size of 90% or more of the graphite particles in the powder has a maximum particle size of 0 And a graphite powder having a size of 1 μm or more and 10 μm or less.

  In the present invention, the values measured from a scanning electron micrograph are used as the particle size of the primary particles and the aggregated particles of the primary particles in the positive electrode active material powder. Arbitrary 50 particles are extracted from the primary particles and aggregated particles of the primary particles photographed in the photograph, and each particle size is measured. The particle size of 90% or more, that is, 45 or more particles is 0.01 μm or more. If it is 5 micrometers or less, it is a positive electrode active material powder in this invention. Here, the particles in the positive electrode active material powder refer to primary particles and aggregated particles of primary particles. Moreover, the value measured from a scanning electron micrograph is also used for the particle size of the graphite particles in the graphite powder, which shows the maximum value. That is, an arbitrary 50 particles are extracted from the graphite particles photographed in the photograph, and a particle size showing the maximum value in the particle size of each graphite particle (hereinafter, sometimes referred to as the maximum particle size). When measured, if the maximum diameter of 90% or more, that is, 45 or more graphite particles is 0.1 μm or more and 10 μm or less, it is a graphite powder in the present invention. In the present invention, by setting the particle size of the positive electrode active material powder and the graphite powder within the above range, the non-aqueous electrolyte can exhibit high discharge capacity and high output at a high current rate. It can be used as a positive electrode powder for a secondary battery. If the number of particles smaller than 0.01 μm in the positive electrode active material powder is 10% or more, the compatibility with the binder is not good, and the binding property with the positive electrode current collector described later is lowered. In addition, the discharge capacity and cycle performance of the nonaqueous electrolyte secondary battery are undesirably reduced. Further, if the number of particles in the positive electrode active material powder exceeding 5 μm is 10% or more, it is not preferable because the obtained nonaqueous electrolyte secondary battery does not sufficiently exhibit high output at a high current rate. . Further, when the number of particles having a maximum diameter of graphite particles smaller than 0.1 μm in the graphite powder is 10% or more, the energy density in the positive electrode described later, binding property with the positive electrode current collector at the time of producing the positive electrode, etc. It is not preferable in terms of operability. Further, if the number of particles having a maximum diameter of graphite particles larger than 10 μm in the graphite powder is 10% or more, the discharge capacity of the nonaqueous electrolyte secondary battery is consequently reduced due to an increase in internal resistance value in the positive electrode described later. In addition, it is not preferable because the battery does not exhibit high output at a high current rate.

  In order to further increase the discharge capacity of the nonaqueous electrolyte secondary battery, the average particle size of the primary particles and the aggregated particles of the primary particles in the positive electrode active material powder is preferably 0.1 μm or more and 3 μm or less. Here, the value measured from said scanning electron micrograph is used for an average particle diameter. That is, 50 particles are arbitrarily extracted from the primary particles and the aggregated particles of the primary particles photographed in the photograph, each particle size is measured, and the average value is defined as the average particle size. The average particle size is preferably 0.1 μm or more and 2 μm or less, more preferably 0.1 μm or more and 1.5 μm or less. By setting the average particle size within the above range, it is possible to obtain a positive electrode powder for a non-aqueous electrolyte secondary battery that can exhibit a higher discharge capacity and a higher output at a high current rate. .

  In order to further increase the discharge capacity of the nonaqueous electrolyte secondary battery, it is preferable that the average value of the particle diameters of the graphite particles in the graphite powder, which shows the maximum value, is 1 μm or more and 6 μm or less. Here, the value measured from said scanning electron micrograph is used for an average value. That is, 50 arbitrary particles are extracted from the graphite particles photographed in the photograph, the particle size showing the maximum value (the maximum particle size) is measured by the particle size of each particle, and the average value is used. In addition, the average value of the maximum diameter of the graphite particles is 1 μm or more and 4 μm or less, so that a positive electrode powder for a non-aqueous electrolyte secondary battery that can exhibit higher output at a high current rate is obtained. it can.

  The graphite powder in the present invention is preferably flake graphite particles. When the shape of the graphite powder is flake shaped, the conductivity of the positive electrode described later can be increased.

  Moreover, as a composition of the positive electrode active material powder in this invention, the following representative compositions, ie, the composition represented by Formula (1), the composition represented by Formula (2), can be mentioned.

Li _x1 Ni _1-y1 M ¹ _y1 O ₂ (1)
(In formula (1), x1 and y1 are 0.9 ≦ x1 ≦ 1.2 and 0 ≦ y1 ≦ 0.5, respectively, and M ¹ is Co.)
Here, in order to increase the discharge capacity, x1 is preferably 1.0 or more and 1.1 or less, and more preferably 1.0 or more and 1.05 or less. In the same meaning, y1 is preferably 0.05 or more and 0.3 or less, more preferably 0.1 or more and 0.2 or less.

Li _x2 Ni _1-y2 M ² _y2 O ₂ (2)
(In the formula (2), x2 and y2 are 0.9 ≦ x2 ≦ 1.2 and 0.3 ≦ y2 ≦ 0.9, respectively, and M ² is Co and Mn.)
Here, in order to increase the discharge capacity, x2 is preferably 1.0 or more and 1.1 or less, and more preferably 1.0 or more and 1.05 or less. In the same meaning, y2 is preferably 0.4 or more and 0.8 or less, and more preferably 0.5 or more and 0.7 or less. M ² is preferably in the range of 50:50 to 20:80, more preferably in the range of 40:60 to 30:70, in terms of molar ratio of Co: Mn.

Further, a part of the elements of M ¹ and M ² may be B, Al, Ga, In, Si, Ge, Sn, Mg, Sc, Y, Ti, Zr, and Hf within a range not impairing the effects of the present invention. V, Nb, Ta, Cr, Mo, W, Tc, Fe, Ru, Rh, Ir, Pd, Cu, Ag, Zn, and the like may be substituted.

In the positive electrode active material powder of the present invention, the crystal structure specified by powder X-ray diffraction measurement is usually a NaFeO ₂ type crystal structure.

  The positive electrode powder of the present invention may further contain a non-graphitic carbonaceous material. Examples of the non-graphite carbonaceous material include carbon black and acetylene black. Moreover, the powder for positive electrodes of this invention may contain a fibrous carbon material further.

When the positive electrode powder of the present invention contains a fibrous carbon material, when the length of the fibrous carbon material is a and the diameter of the cross section perpendicular to the length direction of the material is b, a / b is usually 20-1000. Moreover, in the fibrous carbon material, it is better that the electric conductivity is high. The electrical conductivity of the fibrous carbon material is measured on a sample obtained by molding the fibrous carbon material so as to have a density of 1.0 to 1.5 g / cm ^{3. In} this case, the electrical conductivity is usually 1 S / cm. It is above, Preferably it is 2 S / cm or more.

  Further, the positive electrode active material powder of the present invention is used as a core material, and the surface of the particles further contains one or more elements selected from B, Al, Ga, In, Si, Ge, Sn, Mg and transition metal elements. You may make it adhere with the compound to do. Among the above elements, one or more selected from B, Al, Mg, Co, Cr, Mn and Fe are preferable, and Al is more preferable from the viewpoint of operability. Examples of the compound include oxides, hydroxides, oxyhydroxides, carbonates, nitrates, organic acid salts, and mixtures of the above elements. Of these, oxides, hydroxides, oxyhydroxides, carbonates or mixtures thereof are preferred.

Next, a method for producing the positive electrode active material powder in the present invention will be described.
The positive electrode active material powder in this invention can be manufactured by baking the metal compound mixture which can become a positive electrode active material powder by baking. That is, a compound containing a corresponding metal element is weighed so as to have a predetermined composition and can be produced by firing a metal compound mixture obtained after mixing. For example, a composite oxide represented by Li _1.08 [Ni _0.35 Mn _0.44 Co _0.21 ] O ₂ , which is one of the preferred compositions, includes lithium hydroxide, dinickel trioxide, manganese carbonate, and cobalt oxide in Li: Ni: Mn. : Co can be obtained by firing the metal compound mixture obtained by weighing and mixing so that the molar ratio of Co is 1.08: 0.35: 0.44: 0.21.

  As the compound containing the metal element, for example, a compound containing a metal element of Li, Al, Ni, Mn, Co, Fe, an oxide is used, or hydroxide, oxyhydroxide, carbonic acid is used. A salt, nitrate, acetate, halide, oxalate, alkoxide, or the like that can be decomposed and / or oxidized to form an oxide at a high temperature can be used. Among these, a hydroxide and / or carbonate is preferable as the compound containing Li, a hydroxide and / or oxide is preferable as the compound containing Al, and a hydroxide is used as the compound containing Ni. And / or oxides are preferred, carbonates and / or oxides are preferred as compounds containing Mn, oxides and / or hydroxides are preferred as compounds containing Co, and compounds containing Fe are preferred as compounds containing Fe Hydroxides and / or oxides are preferred. Moreover, you may use the composite compound containing 2 or more types of said metal element as a compound containing a metal element.

  In order to increase the crystallinity of the positive electrode active material powder, the metal compound mixture before firing may further contain a compound containing boron. The content of the boron-containing compound may be usually 0.00001 mol% or more and 5 mol% or less in terms of boron with respect to the total mol of the metal element excluding lithium in the metal compound mixture. . Preferably, it is 0.0001 mol% or more and 3 mol% or less in terms of boron. Examples of the compound containing boron include boron oxide and boric acid, and boric acid is preferable. The boron further contained in the metal compound mixture here may remain in the fired positive electrode active material powder of the present invention, or may be removed by washing, evaporation or the like.

  The compound containing the metal element may be mixed by either dry mixing or wet mixing, but simpler dry mixing is preferable, and examples of the dry mixing apparatus include a V-type mixer, a W-type mixer, and a ribbon mixer. , Drum mixer, dry ball mill and the like.

  In addition, from the viewpoint of promoting the solid phase reaction during firing, the volume-based average particle diameter of the metal compound mixture is preferably a value in the range of 1 μm to 20 μm. Here, the volume-based average particle size of the metal compound mixture means the particle size (D50) seen from the microparticle side when 50% accumulated in the volume-based cumulative particle size distribution, and is laser diffraction scattering. It is measured by a legal particle size distribution measuring device.

  After the metal compound mixture is compression-molded as necessary, a fired product is obtained by, for example, holding and firing in a temperature range of 700 ° C. or more and 1200 ° C. or less for 2 to 30 hours. In firing, it is preferable to rapidly reach the holding temperature as long as the firing vessel containing the metal compound mixture is not damaged. As the firing atmosphere, although depending on the composition, air, oxygen, nitrogen, argon, or a mixed gas thereof can be used, but an atmosphere containing oxygen is preferable.

  Next, the fired product can be pulverized using a pulverizer to obtain a positive electrode active material powder. From the viewpoint of setting the particle size of 90% or more of the primary particles and the aggregated particles of the primary particles in the positive electrode active material powder to 0.01 μm or more and 5 μm or less, it is preferable to use a jet mill as the pulverizer. In the case of a jet mill, since the particles constituting the fired product are accelerated by a jet stream and pulverized by collision between particles, there is little distortion of the crystal structure due to collision, and pulverization is easy in a short time. Generation of particles other than the intended purpose can be suppressed. In place of the jet mill, pulverization may be performed using a vibration mill or a dry ball mill. However, in that case, the process may be complicated, for example, requiring an air classification operation. Moreover, it is more preferable to use a fluidized bed jet mill with a built-in classifier as the jet mill. Examples of the jet mill include a counter jet mill (manufactured by Hosokawa Micron Corporation, product name).

  A positive electrode active material powder comprising the above primary particles and agglomerated particles of the primary particles, wherein the particle size of 90% or more of the primary particles and the agglomerated particles of the primary particles in the powder is 0.01 μm or more and 5 μm or less. A graphite powder composed of a certain positive electrode active material powder and graphite particles, and the particle size of 90% or more of the graphite particles in the powder, and the maximum particle size is 0.1 μm or more and 10 μm or less By mixing with a certain graphite powder, the positive electrode powder of the present invention can be produced. Mixing can be performed using devices such as a V-type mixer, a W-type mixer, a ribbon mixer, a drum mixer, and a dry ball mill. From the viewpoint of preventing the pulverization from proceeding, the V-type mixer and the W-type mixer are used. It is preferable to use a ribbon mixer or a drum mixer.

From the viewpoint of storage characteristics and operability of the positive electrode active material powder, the BET specific surface area of the positive electrode active material powder is preferably 1 m ² / g or more and 7 m ² / g or less, more preferably 2.5 m ² / g or more and 7 m or less. ^{It is 2} / g or less, and more preferably 3 m ² / g or more and 4 m ² / g or less.

The BET specific surface area of the graphite powder is 12 m ² / g or more and 20 m ² / g or less in the sense that it is a positive electrode powder for a non-aqueous electrolyte secondary battery that can exhibit higher output at a high current rate. It is preferably 16 m ² / g or more and 19 m ² / g or less.

  In the production of the positive electrode powder of the present invention, the weight ratio of the positive electrode active material powder to the graphite powder is usually 5 parts by weight or more and 20 parts by weight or less of the graphite powder with respect to 100 parts by weight of the positive electrode active material powder. . Further, a non-graphitic carbonaceous material may be mixed. Examples of the non-graphite carbonaceous material include carbon black and acetylene black. Since carbon black and acetylene black are fine particles and have a large surface area, they can be added to the positive electrode mixture, which will be described later, to improve the conductivity inside the positive electrode and improve the charge / discharge efficiency and rate characteristics. As a result, the binding property between the positive electrode mixture by the binder and the positive electrode current collector, which will be described later, is lowered, and the internal resistance is increased. Therefore, when mixing the non-graphitic carbonaceous material, the graphite powder and the non-graphitic carbonaceous material are preferably 5 parts by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the positive electrode active material powder. Further, a fibrous carbon material may be further mixed. Specific examples of the fibrous carbon material include graphitized carbon fiber and carbon nanotube. The carbon nanotube may be either a single wall or a multiwall. As the fibrous carbon material, a commercially available material may be appropriately pulverized and used. The pulverization may be either dry or wet. Examples of the dry pulverization include pulverization using a ball mill, a rocking mill, and a planetary ball mill. Examples of the wet pulverization include pulverization using a ball mill and a day spa mat. The ratio at the time of mixing the fibrous carbon material is usually 0.1 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the positive electrode active material powder.

  Next, the positive electrode mixture of the present invention will be described. The positive electrode mixture of the present invention is characterized by having a positive electrode powder obtained by the positive electrode powder or the positive electrode powder manufacturing method and a binder. That is, a positive electrode active material powder composed of primary particles and aggregated particles of primary particles, and the particle size of 90% or more of primary particles and aggregated particles of primary particles in the powder is 0.01 μm or more and 5 μm or less. A graphite powder composed of a certain positive electrode active material powder and graphite particles, and the particle size of 90% or more of the graphite particles in the powder, and the maximum particle size is 0.1 μm or more and 10 μm or less It has a certain graphite powder and a binder. The positive electrode active material powder and the graphite powder in the positive electrode mixture of the present invention may be the positive electrode active material powder in the present invention and the graphite powder in the present invention, respectively.

  As the binder in the positive electrode material mixture of the present invention, a thermoplastic resin can be used. Specifically, polyvinylidene fluoride (hereinafter sometimes referred to as PVDF), polytetrafluoroethylene (hereinafter referred to as PTFE). Fluorine) such as tetrafluoroethylene / hexafluoropropylene / vinylidene fluoride copolymer, hexafluoropropylene / vinylidene fluoride copolymer, tetrafluoroethylene / perfluorovinyl ether copolymer, etc. Examples thereof include polyolefin resins such as resin, polyethylene, and polypropylene. Moreover, you may mix and use these 2 or more types. Further, by using a fluororesin and a polyolefin resin as a binder, the ratio of the fluororesin to the positive electrode mixture is 1 to 10% by weight, and the ratio of the polyolefin resin is 0.1 to 2% by weight, It is preferable because a positive electrode mixture having excellent binding properties with the positive electrode current collector can be obtained.

  The binder may be dissolved in an organic solvent. Examples of the organic solvent include amine solvents such as N, N-dimethylaminopropylamine and diethylenetriamine, ether solvents such as tetrahydrofuran, ketone solvents such as methyl ethyl ketone, ester solvents such as methyl acetate, dimethylacetamide, 1- Examples include amide solvents such as methyl-2-pyrrolidone.

  Examples of the method for producing the positive electrode mixture of the present invention include the following production methods. That is, a method of mixing a positive electrode powder and a binder, a method of mixing a positive electrode active material powder, a graphite powder, and a binder, a method of mixing a positive electrode active material powder, a graphite powder, a non-graphitic carbonaceous material, and a binder, a positive electrode Examples thereof include a method of mixing an active material powder, a graphite powder, a fibrous carbon material, and a binder, and a method of mixing a positive electrode active material powder, a graphite powder, a non-graphitic carbonaceous material, a fibrous carbon material, and a binder. The binder may be dissolved in an organic solvent.

Next, a method for producing the positive electrode for a nonaqueous electrolyte secondary battery of the present invention will be described. The positive electrode can be produced by supporting the positive electrode mixture on a positive electrode current collector.
As the positive electrode current collector, Al, Ni, stainless steel or the like can be used, but Al is preferable in that it is easily processed into a thin film and is inexpensive. As a method of supporting the positive electrode mixture on the positive electrode current collector, a method of pressure molding, or a positive electrode mixture pasted using an organic solvent is applied to the positive electrode current collector, dried and pressed, etc. And a method of fixing. Examples of the method of applying the positive electrode mixture to the positive electrode current collector include a slit die coating method, a screen coating method, a curtain coating method, a knife coating method, a gravure coating method, and an electrostatic spray method. By the method mentioned above, the positive electrode for nonaqueous electrolyte secondary batteries of this invention can be manufactured.

Next, a non-aqueous electrolyte secondary battery having the positive electrode for a non-aqueous electrolyte secondary battery of the present invention will be described using a lithium secondary battery as an example of the battery.
A lithium secondary battery is a separator, a negative electrode in which a negative electrode mixture is supported on a negative electrode current collector, and an electrode group obtained by laminating and winding the above positive electrode in a battery can, It can be produced by impregnating an electrolytic solution composed of an organic solvent containing an electrolyte.

  As the shape of the electrode group, for example, a shape in which the cross section when the electrode group is cut in a direction perpendicular to the winding axis is a circle, an ellipse, a rectangle, a rectangle with rounded corners, etc. Can be mentioned. In addition, examples of the shape of the battery include a paper shape, a coin shape, a cylindrical shape, and a square shape.

As the negative electrode, a negative electrode mixture containing a material capable of doping and dedoping lithium ions supported on a negative electrode current collector, lithium metal or lithium alloy, etc. can be used, and lithium ions can be doped and dedoped. Specific examples of such materials include carbonaceous materials such as natural graphite, artificial graphite, cokes, carbon black, pyrolytic carbons, carbon fibers, and fired organic polymer compounds, and have a lower potential than the positive electrode. It is also possible to use chalcogen compounds such as oxides and sulfides that can be doped and dedoped with lithium ions. As the carbonaceous material, a carbonaceous material mainly composed of graphite such as natural graphite or artificial graphite is preferable because of high potential flatness and low average discharge potential. The shape of the carbonaceous material may be, for example, a flake shape such as natural graphite, a spherical shape such as mesocarbon microbeads, a fibrous shape such as graphitized carbon fiber, or an aggregate of fine powder.
In the case where the electrolytic solution does not contain ethylene carbonate, which will be described later, when a negative electrode mixture containing polyethylene carbonate is used, the cycle characteristics and large current discharge characteristics of the resulting battery are preferably improved.

  The negative electrode mixture may contain a binder as necessary. Examples of the binder include a thermoplastic resin, and specific examples include PVDF, thermoplastic polyimide, carboxymethyl cellulose, polyethylene, and polypropylene.

  The chalcogen compounds such as oxides and sulfides used as a material capable of doping and dedoping lithium ions contained in the negative electrode mixture are mainly composed of elements of Groups 13, 14, and 15 of the periodic table. Examples thereof include chalcogen compounds such as crystalline or amorphous oxides and sulfides, and specific examples include amorphous compounds mainly composed of tin oxide. These can contain a carbonaceous material as a conductive material as required.

Examples of the negative electrode current collector include Cu, Ni, and stainless steel. Cu is preferable because it is difficult to form an alloy with lithium and it can be easily processed into a thin film.
The method of supporting the negative electrode mixture on the negative electrode current collector is the same as in the case of the positive electrode. The method is a method of pressure molding, pasted using a solvent, etc., coated on the negative electrode current collector, dried, pressed and pressed. And the like.

  As the separator, for example, a material having a form such as a porous membrane, a nonwoven fabric, a woven fabric made of a polyolefin resin such as polyethylene and polypropylene, a fluororesin, a nitrogen-containing aromatic polymer, and the like can be used. Moreover, it is good also as a separator which used 2 or more types of these materials. Examples of the separator include separators described in JP 2000-30686 A, JP 10-324758 A, and the like. The thickness of the separator is preferably as thin as possible as long as the mechanical strength is maintained in that the volume energy density of the battery is increased and the internal resistance is reduced, and is preferably about 10 to 200 μm, more preferably about 10 to 30 μm. .

In the electrolyte, the _{electrolyte, LiClO 4, LiPF 6, LiAsF} 6, LiSbF 6, LIBF 4, LiCF 3 SO 3, LiN (SO 2 CF 3) 2, LiC (SO 2 CF 3) 3, Li 2 B Examples thereof include lithium salts such as ₁₀ Cl ₁₀ , a lower aliphatic carboxylic acid lithium salt, and LiAlCl _4, and a mixture of two or more of these may be used. The lithium salt is selected from the group consisting of fluorine-containing LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ and LiC (SO ₂ CF ₃ ) ₃ among these. It is preferable to use those containing at least one kind.

In the electrolytic solution, examples of the organic solvent include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 4-trifluoromethyl-1,3-dioxolan-2-one, 1,2-di ( Carbonates such as methoxycarbonyloxy) ethane; 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropyl methyl ether, 2,2,3,3-tetrafluoropropyl difluoromethyl ether, tetrahydrofuran, 2-methyl Ethers such as tetrahydrofuran; esters such as methyl formate, methyl acetate and γ-butyrolactone; nitriles such as acetonitrile and butyronitrile; N, N-dimethylformamide, N, N-dimethylacetate Amides such as amides; Carbamates such as 3-methyl-2-oxazolidone; Sulfur-containing compounds such as sulfolane, dimethyl sulfoxide and 1,3-propane sultone, or those obtained by further introducing a fluorine substituent into the above organic solvent Usually, two or more of these are mixed and used. Among these, a mixed solvent containing carbonates is preferable, and a mixed solvent of cyclic carbonate and acyclic carbonate or cyclic carbonate and ether is more preferable.
The mixed solvent of cyclic carbonate and non-cyclic carbonate has a wide operating temperature range, excellent load characteristics, and is hardly decomposable even when a graphite material such as natural graphite or artificial graphite is used as the negative electrode active material. In addition, a mixed solvent containing ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate is preferable.
Further, in view of particularly excellent safety improving effect is obtained, it is preferable to use an electrolytic solution containing an organic solvent having a lithium salt and a fluorine substituent containing fluorine such as LiPF _6. A mixed solvent containing ethers having fluorine substituents such as pentafluoropropyl methyl ether and 2,2,3,3-tetrafluoropropyl difluoromethyl ether and dimethyl carbonate has excellent high-current discharge characteristics, preferable.

A solid electrolyte may be used instead of the above electrolytic solution.
As the solid electrolyte, for example, a polymer electrolyte such as a polyethylene oxide polymer compound, a polymer compound including at least one of a polyorganosiloxane chain or a polyoxyalkylene chain can be used. Moreover, what is called a gel type which hold | maintained the nonaqueous electrolyte solution in the polymer | macromolecule can also be used. The _{Li 2 S-SiS 2, Li} 2 S-GeS 2, Li 2 S-P 2 S 5, Li 2 sulfide electrolyte such as S-B ₂ S _3, or _{Li 2 S-SiS 2 -Li 3} PO 4 When an inorganic compound electrolyte containing a sulfide such as Li ₂ S—SiS ₂ —Li ₂ SO ₄ is used, safety may be further improved.

  Hereinafter, the present invention will be described in more detail with reference to examples. Unless otherwise specified, the electrodes for the charge / discharge test and the flat battery were prepared by the following method. The particle size distribution measurement of the positive electrode active material powder and the BET specific surface area of the positive electrode active material powder were measured by the following methods.

(1) Particle Size Measurement of Positive Electrode Active Material Powder Particles A scanning electron micrograph (SEM photograph) was taken and determined by the above method.
(2) Measurement of maximum particle size of graphite powder particles A scanning electron micrograph (SEM photograph) was taken and obtained by the above method.

(3) Measurement of BET specific surface area of positive electrode active material powder and graphite powder 1 g of powder was dried in a nitrogen stream at 150 ° C. for 15 minutes, and then measured using Flowsorb II2300 manufactured by Micromeritics.

(4) Production of flat battery for charge / discharge test Positive electrode active material powder, graphite powder, acetylene black, and PVDF 1-methyl-2-pyrrolidone (hereinafter sometimes referred to as NMP) solution as binder, Thickness of a positive electrode active material powder: graphite powder: acetylene black: PVDF mixed and kneaded so that the weight ratio is 87: 9: 1: 3 to obtain a paste-like positive electrode mixture, which becomes a positive electrode current collector The positive electrode mixture is applied to a 20 μm Al foil, dried in a hot air dryer at 60 ° C. for 1 hour, then vacuum dried at 50 ° C. for 8 hours, and subjected to a consolidation treatment with a roll press. A positive electrode was obtained by cutting into a size of × 2 cm. The weight of the obtained positive electrode was measured, the weight of the Al foil was subtracted from the weight of the positive electrode, the weight of the positive electrode mixture was calculated, and the weight of the positive electrode active material powder was calculated from the weight ratio of the paste-like positive electrode mixture. .
The obtained positive electrode, and ethylene carbonate (hereinafter sometimes referred to as EC), dimethyl carbonate (hereinafter sometimes referred to as DMC), and ethyl methyl carbonate (hereinafter sometimes referred to as EMC) as an electrolytic solution. A 30:35:35 (volume ratio) mixture of LiPF ₆ dissolved to 1 mol / liter (hereinafter sometimes referred to as LiPF ₆ / EC + DMC + EMC), a polyethylene porous membrane as a separator, Further, metallic lithium was used as a counter electrode and a reference electrode, and these were combined to produce a flat battery.

Example 1
(1) Synthesis of positive electrode active material powder Nickel hydroxide (manufactured by Kansai Catalysts Chemical Co., Ltd.), manganese oxide (manufactured by high purity chemical), lithium carbonate (manufactured by Honjo Chemical Co., Ltd.), cobalt oxide (manufactured by Shodo Chemical Co., Ltd.), After weighing boric acid (Yoneyama Chemical) so that the molar ratio of each element is Li: Ni: Mn: Co: B = 1.07: 0.35: 0.44: 0.21: 0.03 The powder was obtained by pulverizing and mixing for 4 hours (circumferential speed 0.7 m / s) by a dry ball mill using 15 mmφ alumina balls as media. This powder was put into a tunnel-type continuous furnace and fired in air at 1040 ° C. for 4 hours to obtain a fired product. The fired product is coarsely pulverized with a roll crusher, and then subjected to main pulverization using a jet mill (spiral jet mill NPK100 type manufactured by Nippon Pneumatic Co., Ltd.) under the conditions of a powder supply amount of 2 kg / h and a pressure of 4 kg / cm ^2. As a result, a pulverized powder was obtained. Coarse particles were removed from the pulverized powder with a sieve having an opening of 45 μm to obtain a positive electrode active material powder 1. In the SEM photograph of the positive electrode active material powder 1, it was found that 90% or more of the particles were 0.01 μm or more and 5 μm or less. The average particle size was 1.4 μm. Further, the BET specific surface area of the powder was 3.3 m ² / g.

(2) Charge / Discharge Performance Evaluation of Lithium Secondary Battery The positive electrode active material powder 1 is used as the positive electrode active material powder, and the maximum diameter of 90% or more of the constituting particles is 0.1 μm or more and 10 μm as the graphite powder. A flat battery was prepared using powder composed of flake graphite particles having an average maximum particle diameter of 3 μm and a BET specific surface area of 18 m ² / g. A charge / discharge test was conducted by constant voltage charge and constant current discharge. The obtained results are shown in Table 1.
Charging / discharging conditions:
The current value per unit weight of the positive electrode active material is set to 1C = 150 mA / g, and the current value of 1C is calculated by multiplying the weight of the positive electrode active material powder obtained as described above.
Charging is performed under conditions of maximum charging voltage 4.3V, charging time 8 hours, charging current 0.2C, and discharging is performed under conditions of minimum discharging voltage 3.0V, discharging currents 0.2C, 1C, 5C and 10C. It was. In addition, before each discharge test, it charged on the same conditions.

Example 2
(1) Synthesis of positive electrode active material powder Nickel hydroxide (manufactured by Kansai Catalysts Chemical Co., Ltd.), manganese oxide (manufactured by high purity chemical), lithium carbonate (manufactured by Honjo Chemical Co., Ltd.), cobalt oxide (manufactured by Shodo Chemical Co., Ltd.), After weighing boric acid (Yoneyama Chemical) so that the molar ratio of each element is Li: Ni: Mn: Co: B = 1.08: 0.35: 0.44: 0.21: 0.03 The powder was obtained by pulverizing and mixing for 4 hours (circumferential speed 0.7 m / s) by a dry ball mill using 15 mmφ alumina balls as media. This powder was put into a tunnel-type continuous furnace and fired in air at 1040 ° C. for 4 hours to obtain a fired product. The fired product was pulverized for 13 hours (peripheral speed 0.7 m / s) by a dry ball mill using 15 mmφ alumina balls as a medium, and using an air classifier (Specic Classifier SPC-250 manufactured by Seishin Enterprise Co., Ltd.) Air classification was performed under the conditions of a powder supply rate of 1 kg / h, an air flow rate of 20 m ³ / min, and a rotor rotation speed of 2000 rpm, and coarse particles were removed to obtain a positive electrode active material powder 2. In the SEM photograph of the positive electrode active material powder 2, it was found that 90% or more of the particles were 0.01 μm or more and 5 μm or less. The average particle size was 1.6 μm. Further, the BET specific surface area of the powder was 2.3 m ² / g.

(2) Evaluation of charge / discharge performance of lithium secondary battery Using the positive electrode active material powder 2 as the positive electrode active material powder, the maximum diameter of 90% or more of the constituting particles as the graphite powder is 0.1 μm or more and 10 μm or less. A flat battery was prepared using powder composed of flake graphite particles having an average maximum particle diameter of 6 μm and a BET specific surface area of 14 m ² / g. The same conditions as in Example 1 The charging / discharging test by constant current constant voltage charge and constant current discharge was implemented. The obtained results are shown in Table 1.

Example 3
Except that the molar ratio of each element was Li: Ni: Mn: Co: B = 1.10: 0.36: 0.42: 0.21: 0.03, the same as in Example 1. A positive electrode active material powder 3 was obtained. As a result of the SEM photograph of the positive electrode active material powder 3, the result of the BET specific surface area was the same as in Example 1. Using the positive electrode active material powder 3, a flat battery was produced in the same manner as in Example 1, and a charge / discharge test by constant current and constant voltage charge and constant current discharge was conducted in the same manner as in Example 1. The same result as in Example 1 was obtained.

Example 4
Except that the molar ratio of each element was Li: Ni: Mn: Co: B = 1.11: 0.36: 0.42: 0.21: 0.03, the same as in Example 2. A positive electrode active material powder 4 was obtained. As a result of the SEM photograph of the positive electrode active material powder 4, the result of the BET specific surface area was the same as that of Example 2. Using the positive electrode active material powder 4, a flat battery was produced in the same manner as in Example 2, and a charge / discharge test by constant current and constant voltage charge and constant current discharge was performed in the same manner as in Example 2. Results similar to those of Example 2 were obtained.

Comparative Example 1
Evaluation of charge / discharge performance of lithium secondary battery Using positive electrode active material powder 2 as the positive electrode active material powder, the maximum diameter of 54% of the constituting particles as the graphite powder is 0.1 μm or more and 10 μm or less. A flat battery was produced using powder composed of flaky graphite particles having an average maximum diameter of 13 μm and a BET specific surface area of 11 m ² / g, and a constant current was obtained under the same conditions as in Example 1. A charge / discharge test was conducted by constant voltage charge and constant current discharge. The obtained results are shown in Table 1.

  From the discharge capacity data and the 0.2C versus rate characteristic data in Example 1, Example 2 and Comparative Example 1 shown in Table 1, the battery using the positive electrode active material powder of Example 1 has a high discharge current. Even so (for example, 10 C), it can be seen that the discharge capacity is large and the output is particularly high.

Claims (17)

  A positive electrode active material powder comprising primary particles and agglomerated particles of primary particles, wherein a particle size of 90% or more of primary particles and agglomerated particles of primary particles in the powder is 0.01 μm or more and 5 μm or less Graphite powder comprising active material powder and graphite particles, and the maximum particle size of the graphite particles in the powder is 90% or more of the graphite particles, and the particle size is 0.1 μm or more and 10 μm or less. A positive electrode powder containing powder.   2. The positive electrode powder according to claim 1, wherein an average particle size of primary particles and aggregated particles of the primary particles in the positive electrode active material powder is 0.1 μm or more and 3 μm or less.   3. The positive electrode powder according to claim 1, wherein an average value of particle diameters showing the maximum value among the particle diameters of the graphite particles in the graphite powder is 1 μm or more and 6 μm or less.   The powder for positive electrodes according to claim 1, wherein the graphite particles are scaly graphite particles. The positive electrode powder according to claim 1, wherein the composition of the positive electrode active material is represented by Formula (1).
Li _x1 Ni _1-y1 M ¹ _y1 O ₂ (1)
(In formula (1), x1 and y1 are 0.9 ≦ x1 ≦ 1.2 and 0 ≦ y1 ≦ 0.5, respectively, and M ¹ is Co.) The positive electrode powder according to claim 1, wherein the composition of the positive electrode active material is represented by Formula (2).
Li _x2 Ni _1-y2 M ² _y2 O ₂ (2)
(In the formula (2), x2 and y2 are 0.9 ≦ x2 ≦ 1.2 and 0.3 ≦ y2 ≦ 0.9, respectively, and M ² is Co and Mn.)   Furthermore, the powder for positive electrodes in any one of Claims 1-6 containing a non-graphite carbonaceous material.   Furthermore, the powder for positive electrodes in any one of Claims 1-7 containing a fibrous carbon material.   A positive electrode active material powder comprising primary particles and agglomerated particles of primary particles, wherein a particle size of 90% or more of primary particles and agglomerated particles of primary particles in the powder is 0.01 μm or more and 5 μm or less Graphite powder comprising active material powder and graphite particles, and the maximum particle size of the graphite particles in the powder is 90% or more of the graphite particles, and the particle size is 0.1 μm or more and 10 μm or less. The manufacturing method of the powder for positive electrodes which mixes powder. The method for producing a positive electrode powder according to claim 9, wherein the positive electrode active material powder has a BET specific surface area of 1 m ² / g or more and 7 m ² / g or less. The method for producing a positive electrode powder according to claim 9 or 10, wherein the graphite powder has a BET specific surface area of 12 m ² / g or more and 20 m ² / g or less.   The method for producing a positive electrode powder according to claim 9, wherein the graphite powder is 5 parts by weight or more and 20 parts by weight or less based on 100 parts by weight of the positive electrode active material powder.   Furthermore, the manufacturing method of the powder for positive electrodes in any one of Claims 9-12 which mixes a non-graphite carbonaceous material.   Furthermore, the manufacturing method of the powder for positive electrodes in any one of Claims 9-13 which mixes a fibrous carbon material.   The positive electrode mixture which has the powder for positive electrodes in any one of Claims 1-8, or the powder for positive electrodes obtained by the manufacturing method in any one of Claims 9-14, and a binder.   A positive electrode for a nonaqueous electrolyte secondary battery comprising the positive electrode powder according to any one of claims 1 to 8 or the positive electrode powder obtained by the production method according to any one of claims 9 to 14 and a binder.   The nonaqueous electrolyte secondary battery which has a positive electrode for nonaqueous electrolyte secondary batteries of Claim 16.