JP2006127823A - Battery and manufacturing method of positive electrode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery using a positive electrode providing sufficient conductivity while the adding amount of a conducting auxiliary is reduced as little as possible, and to provide a manufacturing method of the positive electrode. <P>SOLUTION: An electrode is manufactured in such a way that slurry prepared by dispersing flake graphite powder and/or vapor phase growth carbon fibers, and a binder in a solvent is applied to a current collector, the flake graphite powder and/or the vapor phase growth carbon fibers are oriented by a magnetic field, and the solvent is removed by drying, and the obtained electrode is used as the positive electrode of a lithium ion secondary battery. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a battery and a method for producing a positive electrode.

  In recent years, portable electronic devices such as a camera-integrated VTR (Video Tape Recorder), a mobile phone, and a notebook PC (Personal Computer) have been reduced in size and weight. As portable electronic devices become smaller and lighter, secondary batteries used as power sources are required to improve energy density. Among secondary batteries, a lithium ion secondary battery is particularly promising because a large energy density can be obtained as compared with a lead battery and a nickel cadmium battery which are conventional aqueous electrolyte secondary batteries.

In the lithium ion secondary battery, in particular, LixMO ₂ used for the positive electrode (wherein M represents one or more transition metals, and the value of x varies depending on the charge / discharge state of the battery. Lithium composite oxides mainly having a numerical value of 05 ≦ x ≦ 1.10) are widely used because a high voltage can be obtained.

  However, a battery using a lithium composite oxide for the positive electrode shows a low resistance value when the positive electrode releases Li, but a high resistance value when the discharge state absorbs Li.

  Therefore, when lithium composite oxide is used as an active material, battery characteristics are secured by adding a conductive additive to the positive electrode or by thinning the reaction layer to increase current collection efficiency. Carbonaceous conductive assistants having a high potential and excellent stability are widely used as the conductive assistants for the positive electrode reaction layer of batteries having a voltage of 4 V or higher.

  The carbon conductive aid is generally used in any one of scale-like graphite, acetylene black, carbon black, or vapor-grown carbon fiber, or a mixture thereof. For example, the following Patent Document 1 and Patent Document 2 shows a specific example of the carbonaceous conductive additive.

JP-A-6-333558, JP 2000-58066 A

  As described above, in the positive electrode reaction layer of a conventional lithium ion secondary battery, it is common to use a carbon conductive aid in order to increase the current collection efficiency and ensure the battery characteristics. However, in order to ensure sufficient battery characteristics, it is necessary to add a considerable amount of conductive aid as a volume, and conductive aids that do not directly contribute to the battery reaction inhibit the filling of the reaction active material. There is a side that is.

  In addition, the conductive auxiliary agent is used only to assist the reaction of the battery, and since the conductive auxiliary agent itself does not contribute to the battery capacity, there is a technique that can impart conductivity with the minimum necessary addition amount. It is desired.

  Accordingly, an object of the present invention is to provide a battery using a positive electrode and a method for producing the positive electrode, which can exhibit sufficient conductivity while suppressing the addition amount of the conductive auxiliary agent as much as possible.

In order to solve the above-described problem, the first aspect of the present invention is:
A non-aqueous electrolyte battery,
Scalar graphite powder and / or vapor-grown carbon fiber and a binder dispersed in a solvent are applied to a current collector, and then the flaky graphite powder and / or vapor-grown carbon in the slurry is applied by a magnetic field. A battery characterized by using a positive electrode produced by orienting fibers and drying and removing a solvent.

The second aspect of the present invention is:
A method for producing a positive electrode for a non-aqueous electrolyte battery, comprising:
Scalar graphite powder and / or vapor-grown carbon fiber and a slurry in which a binder is dispersed in a solvent are applied to a current collector, and then the flake graphite powder and / or vapor-grown carbon fiber in the slurry is applied by a magnetic field. In which the solvent is dried and removed.

  According to this invention, there is an effect that it is possible to provide a lithium ion secondary battery having excellent characteristics while suppressing the addition amount of the conductive additive to a small amount.

  Embodiments of the present invention will be described below with reference to the drawings.

  The present invention is based on the following knowledge. As described above, scaly graphite, acetylene black, vapor grown carbon fiber, and the like are widely used as the conductive additive for the positive electrode.

  In general, the positive electrode reaction layer is formed as described below. A lithium composite oxide powder that is a positive electrode active material, a conductive additive powder, and a binder powder are dispersed in a solvent, applied as an slurry to an aluminum foil that is a metal current collector, and dried. Here, since the filling of the reaction layer is low as it is, good conductivity cannot be obtained. Therefore, the electrode having a high filling property by compression is used as the electrode.

  Since scaly graphite has high conductivity and high flexibility, it is arranged so as to fill the gaps between the active material particles and exhibits excellent conductivity. However, in order to obtain this effect, it is necessary to add a large amount of scaly graphite, so that the capacity charge rate decreases. In addition, a large amount of scaly graphite fills the gaps in the electrode reaction layer, thereby significantly reducing the contact area between the active material and the electrolyte and reducing the diffusibility of ions. Therefore, effective current collection is required with a smaller amount of conductive additive added.

  Moreover, the scaly graphite powder has anisotropy in the resistance in the particles, and the electrical resistivity in the in-plane direction of the layer surface (002) is about 1000 times the electrical resistivity in the surface direction. Therefore, if the layer surface of scaly graphite can be oriented perpendicularly to the current collector, the current collection efficiency can be increased and the amount added can be reduced.

  Furthermore, the flat graphite flake graphite, when applied to the current collector as a slurry, has the property of being easily oriented in parallel to the surface of the current collector, but immediately after forming the coating film from the slurry, Scale-like graphite can be oriented by applying a magnetic field to the coating film.

  The magnetic flux density of this magnetic field is preferably 100 mT to 1500 mT, and the application time can be appropriately adjusted depending on the magnetic flux density, slurry viscosity, coating thickness, and the like. Thereafter, the solvent can be quickly removed by drying to fix it in an oriented state.

  As for vapor-grown carbon fibers, since the resistance in the fiber length direction is lower, as described above, the addition is less by orienting the fiber length direction in the direction perpendicular to the surface of the current collector. High current collection capacity can be achieved.

  As described above, when the conductive additive is oriented in a direction perpendicular to the current collector, the resistance between the current collector and the reaction layer hardly increases even if the cycle is repeated.

  Therefore, it is particularly effective when the negative electrode has repeated large fluctuations in the pressure on the positive electrode reaction surface due to the use of a reaction layer having a large expansion / contraction, such as a metal compound capable of occluding and releasing lithium. .

Hereinafter, the positive electrode active material will be described. The positive electrode active material according to the present invention is Li _x MO ₂ (wherein M represents one or more transition metals, x varies depending on the charge / discharge state of the battery, and is generally 0.05 ≦ x ≦ 1.10.) Lithium composite oxide mainly composed of can be used. As the transition metal M constituting this lithium composite oxide, Co, Ni, Mn and the like are preferable.

Specific examples of such a lithium composite oxide include LiCoO ₂ , LiNiO ₂ , Li _x Ni _y Co _1-y O ₂ (wherein x and y vary depending on the charge / discharge state of the battery, and generally 0 <x <1, 0.7 <y <1.02), and lithium manganese composite oxide having a spinel structure.

  The lithium composite oxide described above can generate a high voltage and becomes a positive electrode active material excellent in energy density. For the battery positive electrode, a mixture of a plurality of these positive electrode active materials may be used.

  Hereinafter, the positive electrode current collector will be described. The material and form of the positive electrode current collector are appropriately selected in view of mechanical properties, chemical stability, conductivity, and the like. In the present invention, aluminum can be preferably used.

  Hereinafter, the positive electrode binder will be described. A known binder can be used for the positive electrode. For example, polyvinylidene fluoride, a copolymer of monomers copolymerizable with vinylidene fluoride, and the like can be suitably used.

  Hereinafter, the conductive agent will be described. Any carbon black can be suitably used for the present invention. Specifically, carbon black produced by a thermal method, an acetylene decomposition method, a contact method, a lamp / pine smoke method, a gas furnace method, and an oil furnace method can be exemplified.

  Specific examples of carbon black produced by these production methods include acetylene black, ketjen black, thermal black, and furnace black.

  The scaly graphite includes artificial graphite obtained by firing graphitizable carbon at about 2400 to 3000 ° C. and naturally occurring natural graphite. Any graphite can be suitably used that has a well-developed graphite crystal structure and high purity.

  Vapor-grown carbon fiber can be obtained by flowing an organic vapor such as benzene directly on a substrate having a temperature of about 1000 ° C. and growing carbon crystals using iron fine particles as a catalyst.

  In the case where fibrous carbon is produced by a vapor phase growth method, any organic substance that can be gaseous as a starting material can be used. For example, it is possible to use ethylene, propane or the like that exists in a gaseous state at room temperature, or an organic substance that can be heated and vaporized at a temperature lower than the thermal decomposition temperature.

  The vaporized organic matter is released directly onto a high-temperature substrate, so that the crystal grows as fibrous carbon. The temperature at this time is preferably about 400 ° C to 1500 ° C. The temperature is appropriately selected depending on the type of organic material that is the starting material. During crystal growth, a catalyst may be used to promote crystal growth.

  As the catalyst, finely divided iron, nickel, a mixture thereof, or the like can be used. A metal called a graphitization catalyst and its oxide also function as a catalyst. In addition, a catalyst is suitably selected according to the kind of organic substance which is a starting material. The obtained carbon fiber graphitized at 2000 ° C. or higher, preferably 2500 ° C. or higher can be suitably used. These fiber diameters and fiber lengths are appropriately selected.

  Hereinafter, slurry application will be described. The slurry is prepared by stirring and dispersing a positive electrode active material, a binder, a conductive agent composed of at least scaly graphite or / and vapor grown carbon fiber in N-methyl-2pyrrolidone (NMP). Further, other additives may be added to the slurry.

  FIG. 1 is a diagram schematically showing a manufacturing process of a positive electrode according to the present invention. The slurry 2 is uniformly applied to the current collector 1 as a base material by a coating film forming device such as a doctor blade 3, and a magnetic field is applied by the magnetic field applying device 4. The magnetic field to be applied is preferably 100 mT to 1500 mT, and the application time is appropriately adjusted depending on conditions such as the viscosity of the slurry, the thickness of the coating film, and the magnetic flux density. After applying a magnetic field to orient the scaly graphite or / and the vapor-grown carbon fiber, the solvent is dried and removed in the drying furnace 5 and fixed, and this is molded by the press 6 to be an electrode. Although FIG. 1 shows all the steps of slurry application continuously for convenience, each step may be processed in batches.

  Hereinafter, the negative electrode will be described. The negative electrode has, for example, a structure in which a negative electrode mixture layer is provided on one surface or both surfaces of a negative electrode current collector having a pair of opposed surfaces. The negative electrode mixture layer may be arranged so as to be surely opposed to at least the positive electrode reaction layer. As the negative electrode current collector, for example, a metal foil such as a copper (Cu) foil, a nickel foil or a stainless steel foil, or a metal mesh can be suitably used.

  The negative electrode mixture layer is configured to include particles of a negative electrode active material and a binder such as polyvinylidene fluoride as necessary. Examples of the negative electrode active material include metals, metalloids, alloys and compounds capable of inserting and extracting lithium, and in order to obtain a high capacity, it is preferable to include at least one of these.

  Here, the semimetal refers to a single metalloid element. In the present invention, the alloy includes an alloy composed of one or more metal elements and one or more metalloid elements in addition to an alloy composed of two or more metal elements. Some of the structures include solid solutions, eutectics (eutectic mixtures), intermetallic compounds, or those in which two or more of these coexist.

  Examples of metals or metalloids capable of inserting and extracting lithium include tin (Sn), lead (Pb), aluminum, indium (In), silicon (Si), zinc (Zn), antimony (Sb), bismuth ( Bi), cadmium (Cd), magnesium (Mg), boron (B), gallium (Ga), germanium (Ge), arsenic (As), silver (Ag), zirconium (Zr), yttrium (Y) or hafnium ( Hf).

As the capable of intercalating and deintercalating lithium alloys and compounds, for example, those represented by the chemical formula Ma _p Mb _q Mc _r. In these chemical formulas, Ma represents at least one metal element and metalloid element capable of forming an alloy with lithium, Mb represents at least one metal element, and Mc represents a metal element and metalloid other than Ma. Represents at least one of the elements; The values of p, q, and r are p> 0, q ≧ 0, and r ≧ 0, respectively.

Among these, an intermetallic compound represented by the chemical formula MII _a N _b (MII represents at least one of tin and silicon, and N represents at least one of elements other than tin and silicon, respectively) is preferable. . These may be crystalline or amorphous.

Specific examples of the intermetallic compound represented by the chemical formula MII _a N _b are AsSn, AuSn, CaSn ₃ , CeSn ₃ , CoCu ₂ Sn, Co ₂ MnSn, CoNiSn, CoSn ₂ , Co ₃ Sn ₂ , CrCu ₂ Sn. , Cu ₂ FeSn, CuMgSn, Cu ₂ MnSn, Cu ₄ MnSn, Cu ₂ NiSn, CuSn, Cu ₃ Sn, Cu ₆ Sn ₅ , FeSn ₂ , IrSn, IrSn ₂ , LaSn ₃ , MgNi ₂ Sn, Mg ₂ Sn, MnNi ₂ Sn, MnSn ₂ , Mn ₂ Sn, Mo ₃ Sn, Nb ₃ Sn, NdSn ₃ , NiSn, Ni ₃ Sn ₂ , PdSn, Pd ₃ Sn, Pd ₃ Sn ₂ , PrSn ₃ , PtSn, PtSn ₂ , Pt ₃ Sn , PuSn ₃ , RhSn, Rh ₃ Sn ₂ , RuSn ₂ , SbSn, SnTi ₂ , Sn ₃ U, SnV ₃ , BeSiZ r, CoSi ₂ , β-Cr ₃ Si, Cu ₃ Mg ₂ Si, Fe ₃ Si, Mg ₂ Si, MoSi ₂ , Nb ₃ Si, NiSi ₂ , θ-Ni ₂ Si, β-Ni ₃ Si, ReSi ₂ , Examples include α-RuSi, SiTa ₂ , Si ₂ Th, Si ₂ U, β-Si ₂ U, Si ₃ U, SiV ₃ , Si ₂ W, and SiZr ₂ .

A composite oxide containing at least one of tin and silicon is also preferable. As this complex oxide, for example, chemical formula SnMIII _c O _d (MIII represents at least one selected from the group consisting of silicon, germanium, lead, bismuth, antimony, phosphorus, boron, aluminum and arsenic, and c is 0 to 4 number, d represents each number of _{1~10.), SnMIV e O f} (MIV represents germanium, lead, bismuth, antimony, phosphorus, boron, at least one selected from the group consisting of aluminum and arsenic E represents a number from 0 to 4, f represents a number from 1 to 10, and SnSiM _g V _h O _i (MV represents a group consisting of germanium, lead, bismuth, antimony, phosphorus, boron, aluminum and arsenic). At least one of them is represented, and g, h, and i are numbers satisfying 0.1 ≦ g + h ≦ 4, 0.05 ≦ g ≦ 2, and 1.1 ≦ i ≦ 10, respectively. )

Specific examples of such composite oxides include SnSi _0.01 O _1.02 , SnGe _0.01 O _1.02 , SnPb _0.05 O _1.1 , SnSi _0.1 Ge _0.1 Pb _0.1 O _2.6 , SnSi _0.2 Ge _0.1 O _2.6 , SnSi _0.7 O _2.4 , SnGe _0.7 O _2.4 , SnSi _0.8 O _2.6 , SnSiO ₃ , SnPbO ₃ , SnSi _0.9 Ge _0.1 O ₃ , SnSi _0.8 Ge _0.2 O ₃ , SnSi _0.8 Pb _0.2 O ₃ , SnSi _0.8 Ge _0.1 Pb _0.1 O ₃ , SnSi _1.2 O _3.4 SnSi ₂ O ₆ , SnB _0.01 O _1.015 , SnAl _0.01 O _1.015 , SnP _0.01 O _2.015 , SnP _0.05 O _1.125 , SnB _0.05 O _1.075 , SnP _0.1 O _1.25 SnB _0.1 O _1.15 , SnP _0.3 O _1.75 , SnB _0.7 O _2.05 , _{SnP 0.8 O 3, SnPO 3.5,} SnBO 2.5, SnSi 0.25 P 0.2 B 0.2 O 3, SnSi 0.5 P 0.2 B 0.2 O 3, SnSi 0.8 _{0.2 O 3.1, SnSi 0.8 B 0.2} O 2.9, SnSi 0.8 Al 0.2 O 2.9, SnSi 0.6 Al 0.2 B 0.2 O 2.8, SnSi 0.6 Al 0.2 P 0.2 O 3, SnSi 0.6 B 0.2 P 0.2 O 3, SnSi 0.4 Al 0.2 B _0.4 O _2.7 , SnSi _0.6 Al _0.1 B _0.1 P _0.3 O _3.25 , SnSi _0.6 Al _0.1 B _0.3 P _0.1 O _3.05 , SnSi _0.5 Al _0.3 B _0.4 P _0.2 O _3.55 , SnSi _0.5 Al _0.3 B _0.4 P _0.5 O _4.30 or SnSi _0.8 Al _0.3 B _0.2 P _0.2 O _{3.85 and the} like.

  In addition, such a negative electrode active material is produced by, for example, a mechanical alloying method or a method in which raw materials are mixed and heat-treated in an inert atmosphere or a reducing atmosphere.

  Further, the negative electrode mixture layer may contain another negative electrode active material in addition to a single metal element or metalloid element capable of forming an alloy with lithium, an alloy or a compound.

Examples of other negative electrode active materials include carbonaceous materials, metal oxides, and polymer materials capable of inserting and extracting lithium. Examples of carbonaceous materials include non-graphitizable carbon, artificial graphite, natural graphite, pyrolytic carbons, cokes, graphites, glassy carbons, organic polymer compound fired bodies, carbon fibers, activated carbon or Examples thereof include carbon blacks. Of these, coke includes pitch coke, needle coke, and petroleum coke. Organic polymer compound fired bodies are carbonized by firing polymer materials such as phenol resin and furan resin at an appropriate temperature. What you did. Examples of the metal oxide include tin oxide (SnO ₂ ), and examples of the polymer material include polyacetylene and polypyrrole.

  Lithium may be occluded electrochemically in the negative electrode active material in the battery after the battery is manufactured, and supplied from a positive electrode or a lithium source other than the positive electrode after the battery is manufactured or before the battery is manufactured. It may be occluded by the substance. Moreover, you may make it contain in the case of the synthesis | combination of a negative electrode active material. In forming the negative electrode from such a material, a known binder or the like can be added.

  As the electrolyte, any of a nonaqueous electrolytic solution in which an electrolyte salt is dissolved in a nonaqueous solvent, a solid electrolyte in which an electrolyte salt is contained, and a gel electrolyte in which an organic polymer is impregnated with a nonaqueous solvent and an electrolyte salt are used. Can do.

  The nonaqueous electrolytic solution is prepared by appropriately combining an organic solvent and an electrolyte, and any organic solvent can be used as long as it is used for this type of battery. For example, propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4 Examples thereof include methyl 1,3 dioxolane, diethyl ether, sulfolane, methyl sulfolane, acetonitrile, propionitrile, anisole, acetate ester, butyrate ester, propionate ester and the like.

  As the solid electrolyte, any inorganic solid electrolyte or polymer solid electrolyte can be used as long as the material has lithium ion conductivity. Examples of inorganic solid electrolytes include lithium nitride and lithium iodide. A polymer solid electrolyte is composed of an electrolyte salt and a polymer compound that dissolves the electrolyte salt. The polymer compound is composed of an ether polymer such as poly (ethylene oxide) or a crosslinked product, a poly (methacrylate) ester, an acrylate, or the like. It can be used alone, copolymerized or mixed in the molecule.

  As the matrix of the gel electrolyte, various polymers can be used as long as they can gel by absorbing the non-aqueous electrolyte. For example, fluorine-based polymers such as poly (vinylidene fluoride) and poly (vinylidene fluoride-co-hexafluoropropylene), ether-based polymers such as poly (ethylene oxide) and cross-linked products thereof, and poly (acrylonitrile) Can be used. In particular, it is desirable to use a fluorine-based polymer from the viewpoint of redox stability. By containing an electrolyte salt, ionic conductivity is imparted.

Any electrolyte salt used in the electrolyte can be used as long as it is used in this type of battery. For example, LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , LiCH ₃ SO ₃ , LiCF ₃ SO ₃ , LiCl, LiBr, etc.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these examples.

<Example 1>
First, a composite lithium oxide represented by the general formula Li _x Ni _y Co _z Al _(1-yz) O ₂ was synthesized. Nickel sulfate and cobalt sulfate were dissolved in a predetermined composition, and a sodium hydroxide solution was added to this solution to obtain a coprecipitated hydroxide of nickel and cobalt. The average particle size of the coprecipitated hydroxide was 10 μm.

Next, the coprecipitated hydroxide was dried, aluminum hydroxide (Al (OH) ₃ ) was added as an aluminum compound, and the mixture was stirred and mixed. The aluminum hydroxide is adjusted in advance so that the average particle size is 5 μm and the maximum particle size is 10 μm or less. At this time, the addition amount of nickel, cobalt and aluminum is such that the element ratio in Li _x Ni _y CoAl _(1-yz) O ₂ after synthesis is Ni: Co: Al = 80: 15: 5. Prepared.

Next, lithium hydroxide monohydrate was mixed with the above mixture of the coprecipitated hydroxide and aluminum hydroxide to obtain a precursor. At this _{time, Li x Ni y Co z Al} (1-yz) element ratio in O ₂ in the synthesized lithium :( nickel + cobalt + aluminum) = 1: was prepared to be 1.

Next, this precursor was calcined at 800 ° C. for 5 hours in an oxygen atmosphere to obtain a composite lithium oxide represented by a composition of LiNi _0.8 Co _0.15 Al _0.05 O ₂ . As a result of performing powder X-ray diffraction on this composite lithium oxide, no peaks of impurities such as unreacted hydroxide and lithium aluminate were observed, and a uniform layer compound based on LiNiO ₂ was synthesized. all right.

Furthermore, when observed with an electron microscope, as shown in FIG. 2, the active material was secondary particles in which fine crystal particles were aggregated. A positive electrode mixture was prepared using 95 parts by weight of this LiNi _0.8 Co _0.15 Al _0.05 O ₂ , 3 parts by weight of polyvinylidene fluoride as a binder, and 2 parts by weight of flake graphite as a conductive agent. Subsequently, this positive electrode mixture was dispersed in N-methyl-2-pyrrolidone as a solvent to obtain a positive electrode mixture slurry.

  Next, the positive electrode mixture slurry was uniformly applied to a positive electrode current collector made of aluminum foil, and a magnetic flux density of 1000 mT was applied for 10 seconds with a pair of electromagnets so that a magnetic field was applied in a direction perpendicular to the application surface. Subsequently, this coating film was dried. The reaction layer was pressed so that the true specific gravity filling ratio was 75% to obtain an electrode having a thickness of 100 μm including the current collector and the reaction layer. This was punched into a circular pellet having a diameter of 15.5 mm to obtain a positive electrode.

  Next, a negative electrode was produced as described below. Copper and tin were weighed so as to be 50 parts by mass of copper and 50 parts by mass of tin, and then put into a quartz tube and melted in a high-frequency melting furnace in an argon (Ar) atmosphere. Thereafter, this was cast on a copper rotating disk having a diameter of 200 mm, a width of 20 mm, and a rotation speed of 3000 rpm, and quenched to obtain a ribbon-like copper tin (CuSn) alloy piece. The obtained ribbon-like copper-tin alloy piece was pulverized in an argon atmosphere using a ball mill to obtain a particulate powder. The obtained powder was classified with a 63 μm sieve to obtain a negative electrode active material. The average particle size of the powder obtained by classification was 25 μm.

  Next, carbon black and artificial graphite particulate powder were further prepared as the negative electrode active material, 60 g of the obtained copper tin alloy, 2 g of carbon black, 28 g of artificial graphite, and 10 g of polyvinylidene fluoride as a binder, Were mixed to prepare a negative electrode mixture.

  Subsequently, the negative electrode mixture is dispersed in N-methyl-2-pyrrolidone as a solvent to form a negative electrode mixture slurry, which is applied to a negative electrode current collector made of a copper foil having a thickness of 15 μm, dried, pressed and collected. An electrode having a thickness of 60 μm was obtained by combining the electric body and the reaction layer. This was punched into a circular pellet having a diameter of 16.5 mm to obtain a negative electrode.

The obtained positive electrode, negative electrode, and separator made of a microporous polypropylene film 3 having a thickness of 25 μm were sequentially laminated, and LiPF ₆ 1.5 mol in a mixed solvent of 20% by weight of ethylene carbonate (EC) and 80% by weight of dimethyl carbonate. A non-aqueous electrolyte in which / L was dissolved was injected to produce a coin-type cell having a diameter of 20 mm and a height of 1.6 mm. The battery can 5 used was an aluminum clad inside. This was designated as battery 1. Similarly, batteries 2 to 5 were prepared with the compositions shown in Table 1 below.

<Comparative Example 1>
Batteries 6 to 10 were produced in the same manner except that no magnetic field was applied in the production of the positive electrode of Example 1.

<Evaluation>
After assembling the battery, constant current and constant voltage charging was carried out at a positive electrode current density of 1 mA / cm ² and an upper limit voltage of 4.2 V until the current reached 0.01 mA / cm ² . Thereafter, the positive electrode current density was discharged at a constant current of up to 2.0 V at a current density of 0.5 mA / cm ² to obtain the initial capacity, and the battery was charged again and discharged at a constant current of 10 mA / cm 2 to 2.0 V at a constant current. The capacity retention rate of 10 mA / cm ² load relative to the initial capacity was calculated.

  Table 1 below summarizes the evaluation of Example 1 and Comparative Example 1 described above.

<Example 2>
96.4 parts by weight of LiNi _0.8 Co _0.15 Al _0.05 O ₂ , 3 parts by weight of polyvinylidene fluoride as a binder, 0.1 part by weight of vapor grown carbon fiber as a conductive agent, Ketjen black (Ketjen The positive electrode mixture was prepared as 0.5 part by weight of Black International). Subsequently, this positive electrode mixture was dispersed in N-methyl-2-pyrrolidone as a solvent to obtain a positive electrode mixture slurry. A battery 11 to a battery 15 were produced in the same manner as in Example 1 except for the above.

<Comparative example 2>
In the production of the positive electrode of Example 2, batteries 16 to 20 were produced in the same manner except that no magnetic field was applied.

<Evaluation>
After assembling the battery, as in the evaluation of Example 1 and Comparative Example 1, the current density of the positive electrode was 1 mA / cm ² , the constant voltage and constant voltage charging was performed at an upper limit voltage of 4.2 V, and the current was 0.01 mA / cm ² . It was carried out until. Thereafter, the positive electrode current density was discharged at a constant current of up to 2.0 V at a current density of 0.5 mA / cm ² to obtain an initial capacity, and the battery was charged again and discharged at 10 mA / cm ² at a constant current of up to 2.0 V. The capacity retention rate of 10 mA / cm ² load relative to the initial capacity was calculated.

  Table 2 below summarizes the evaluation of Example 2 and Comparative Example 2 described above.

<Example 3>
94.4 parts by weight of LiNi _0.8 Co _0.15 Al _0.05 O ₂ , 3 parts by weight of polyvinylidene fluoride as a binder, 2 parts by weight of flake graphite as a conductive agent, and 0.1 weight of vapor grown carbon fiber Part, ketjen black (manufactured by ketjen black international) 0.5 parts by weight, the positive electrode mixture was prepared. Subsequently, this positive electrode mixture was dispersed in N-methyl-2-pyrrolidone as a solvent to obtain a positive electrode mixture slurry. Except for this, the batteries 21 to 25 were produced in the same manner as in Example 1.

<Comparative Example 3>
In the production of the positive electrode of Example 3, batteries 26 to 30 were produced in the same manner except that no magnetic field was applied.

<Evaluation>
For Example 3 and Comparative Example 3, the same evaluation as described above was performed.

  Table 3 below summarizes the evaluation of Example 3 and Comparative Example 3 described above.

  From the comparison of the examples and comparative examples shown in Tables 1 to 3, it can be seen that the application of the magnetic field is effective. The difference in the effect tends to decrease as the amount of the conductive agent increases as a whole. However, if a certain amount or more of the conductive agent is added, the characteristics are easily ensured without application of a magnetic field.

  However, even if the composition is the same, it can be easily assumed that this is not the case when the electrode reaction layer is thickened or the filling property is changed.

  Therefore, a high effect can be expected by applying a magnetic field after appropriately adjusting the conductive agent composition according to the thickness and filling rate of the electrode reaction layer.

  The present invention is not limited to the above-described embodiment of the present invention, and various modifications and applications are possible without departing from the spirit of the present invention.

It is a schematic diagram of the manufacturing process of an electrode. It is the photographic image which observed the active material with the electron microscope.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Current collector 2 ... Slurry 3 ... Doctor blade 4 ... Magnetic field application apparatus 5 ... Drying furnace 6 ... Press

Claims (10)

A non-aqueous electrolyte battery,
Scalar graphite powder and / or vapor-grown carbon fiber and a binder dispersed in a solvent are applied to a current collector, and then the flaky graphite powder and / or vapor-grown carbon in the slurry is applied by a magnetic field. A battery characterized by using a positive electrode produced by orienting fibers and drying and removing a solvent. In claim 1,
By subjecting the layer surface (002) of the scaly graphite powder in the slurry and / or the fiber length direction of the vapor growth carbon fiber in the slurry to a direction perpendicular to the surface of the current collector by a magnetic field, and removing the solvent by drying. A battery comprising a manufactured positive electrode. In claim 1,
The positive electrode active material is a spherical particle. In claim 1,
The positive electrode active material is a lithium composite oxide. In claim 1,
The positive electrode active material is a lithium composite oxide comprising secondary particles in which fine crystal particles are aggregated. A method for producing a positive electrode for a non-aqueous electrolyte battery, comprising:
Scalar graphite powder and / or vapor-grown carbon fiber and a slurry in which a binder is dispersed in a solvent are applied to a current collector, and then the flake graphite powder and / or vapor-grown carbon fiber in the slurry is applied by a magnetic field. A method for producing a positive electrode, wherein the solvent is dried and removed. In claim 6,
By applying a magnetic field, the layer surface (002) of the flake graphite powder in the slurry and / or the fiber length direction of the vapor growth carbon fiber powder is oriented perpendicular to the surface of the current collector, and the solvent is removed by drying. A method for producing a positive electrode characterized by the above. In claim 6,
The positive electrode active material is a spherical particle. In claim 6,
The positive electrode active material is a lithium composite oxide. In claim 6,
The positive electrode active material is a lithium composite oxide composed of secondary particles in which fine crystal particles are aggregated.