JP2007103119A - Positive electrode material, positive electrode and battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive electrode material capable of enhancing reversibility of lithium ions and to provide a positive electrode and a battery using the positive electrode material. <P>SOLUTION: The positive electrode 21 and a negative electrode 22 are faced through a separator 23. The positive electrode 21 contains a lithium transition metal composite oxide, carbon fluoride, and lithium fluoride. The reversibility of lithium is enhanced, and battery characteristics can be enhanced even under high temperature environment or even if charging voltage is increased. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a positive electrode material containing a lithium transition metal composite oxide containing lithium (Li) and a transition metal, and a positive electrode and a battery using the same.

  In recent years, many portable electronic devices such as camera-integrated VTRs, mobile phones, laptop computers and the like have appeared, and the demand is rapidly expanding. As these electronic devices become smaller and lighter, research and development for improving the energy density of batteries, particularly secondary batteries, as portable power sources are being actively promoted. Among them, a lithium ion secondary battery has a large demand for energy 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 addition, it is expected to expand the application range by improving the environmental resistance, particularly characteristics at high temperatures, or by improving the discharge performance at high output.

  As a positive electrode active material of this lithium ion secondary battery, for example, a lithium / cobalt composite oxide or lithium / nickel composite oxide having a layered rock salt structure, or a lithium / manganese composite oxide having a spinel structure is known. . Among these, lithium-cobalt composite oxides are most widely used because they can obtain a high capacity and are excellent in thermal stability.

For batteries using these positive electrode active materials, various means have been proposed for improving cycle characteristics or environmental resistance. For example, Patent Documents 1 and 2 describe means for adding a specific metal salt or defining the amount of the binder in the positive electrode mixture. Patent Document 3 discloses lithium-nickel-cobalt composite oxide with aluminum (Al), manganese (Mn), tin (Sn), indium (In), iron (Fe), copper (Cu), magnesium (Mg), A means for improving the discharge capacity by dissolving titanium (Ti), zinc (Zn), molybdenum (Mo) or the like is described. Patent Documents 4 to 7 propose means for replacing with halogen. Patent Documents 8 and 9 propose means for coating the particle surface of the positive electrode active material with a metal halide.
Japanese Patent Application Laid-Open No. 07-192721 Japanese Patent Laid-Open No. 10-302768 Japanese Patent No. 3244314 Japanese Patent No. 296705 JP 2002-184402 A JP 2002-29884 A JP 2004-296098 A Japanese Patent No. 3157413 Japanese Patent No. 3141858

  However, particularly under a high temperature environment, there is a problem that the reversibility of lithium ions at the time of charging / discharging is reduced and the characteristics are deteriorated. Recently, in order to further increase the energy density, it has been proposed to improve the utilization rate of the positive electrode by increasing the upper limit charging voltage, and it is required to improve the reversibility of lithium ions. ing.

  The present invention has been made in view of such problems, and an object thereof is to provide a positive electrode material capable of improving the reversibility of lithium ions, and a positive electrode and a battery using the positive electrode material.

  The positive electrode material according to the present invention contains lithium transition metal composite oxide particles containing lithium and a transition metal, graphite fluoride, and metal fluoride.

  The positive electrode according to the present invention contains a positive electrode material containing lithium transition metal composite oxide particles containing lithium and a transition metal, fluorinated graphite, and a metal fluoride.

  A battery according to the present invention is provided with an electrolyte together with a positive electrode and a negative electrode, and the positive electrode includes a lithium transition metal composite oxide particle containing lithium and a transition metal, fluorinated graphite, and a metal fluoride. Contains materials.

  According to the positive electrode material of the present invention, since lithium transition metal composite oxide particles containing lithium and a transition metal, graphite fluoride, and metal fluoride are included, the reversibility of lithium ions is improved. Can do. Therefore, according to the positive electrode and battery of the present invention using this positive electrode material, excellent battery characteristics can be obtained even in a high temperature environment or even when the charging voltage is increased.

  In addition, the ratio of graphite fluoride and metal fluoride to the lithium transition metal composite oxide particles (total of graphite fluoride and metal fluoride / lithium transition metal composite oxide particles) is 0.1 mol% or more and 20 mol% or less. If so, or if fluorinated graphite and metal fluoride are deposited on at least a part of the surface of the lithium transition metal composite oxide particles, or fluorine (F) is applied to the lithium transition metal composite oxide particles. If it is made to contain, a higher effect can be acquired.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  The positive electrode material according to one embodiment of the present invention is capable of occluding and releasing lithium, lithium transition metal composite oxide particles containing lithium and a transition metal, fluorinated graphite, and metal fluoride. And may contain other positive electrode active materials capable of inserting and extracting lithium as necessary. This is because the reversibility of lithium is lowered only with lithium transition metal composite oxide particles, but the reversibility of lithium ions can be improved by including graphite fluoride and metal fluoride.

Examples of the lithium transition metal composite oxide include those containing at least one of cobalt (Co), nickel (Ni), and manganese as the transition metal. Specifically, Li _x MO _2-y F _z (M includes at least one member selected from the group consisting of cobalt, nickel, and manganese, and optionally includes titanium, vanadium (V), chromium (Cr), iron, copper, zinc, molybdenum, Tin, antimony (Sb), bismuth (Bi), calcium (Ca), strontium (Sr), tungsten (W), niobium (Nb), yttrium (Y), zirconium (Zr), magnesium, aluminum, boron (B) , At least one selected from the group consisting of silicon (Si) and gallium (Ga), 0.8 ≦ x ≦ 1.2, And lithium transition metal composite oxide having an average composition represented by 0.1 ≦ y ≦ 0.2,0 ≦ z ≦ 0.1).

  In this lithium transition metal composite oxide, fluorine is not an essential constituent element, but preferably contains fluorine. This is because the reversibility of lithium ions can be further improved.

  In the lithium transition metal composite compound, the proportion of cobalt is preferably as high as possible. For example, the total amount of metal excluding lithium contained in the positive electrode material is preferably 20 mol% or more. This is because high electron conductivity and reversibility can be obtained.

Examples of the metal fluoride include LiF, NiF ₂ , CaF _{2, and} AlF ₃ .

  The fluorinated graphite and the metal fluoride may be present in the gap between the lithium transition metal composite oxide particles, but are preferably deposited on at least a part of the surface of the lithium transition metal composite oxide particles. This is because graphite fluoride and metal fluoride are considered to function in the vicinity of the surface of the lithium transition metal composite oxide particles, and the reversibility of lithium ions can be further improved.

  Examples of a method of depositing fluorinated graphite and metal fluoride on lithium transition metal composite oxide particles include, for example, a method of depositing by vapor deposition or sputtering, a method of depositing a predetermined metal, etc., and then treating with a fluorine-based gas. For example, a method for forming a coating film electrochemically, or a method for depositing by a mechanochemical method as described in Japanese Patent No. 3396414.

  Ratio of fluorinated graphite and metal fluoride to lithium transition metal composite oxide particles (total of fluorinated graphite and metal fluoride / lithium transition metal composite oxide particles) is in the range of 0.1 mol% or more and 20 mol% or less. It is preferable that This is because if the ratio is small, the effect of improving the reversibility of lithium ions is not sufficient, and if the ratio is high, the conductivity decreases.

  This positive electrode material is used for a secondary battery as follows, for example.

(First secondary battery)
FIG. 1 shows a cross-sectional structure of a first secondary battery using the positive electrode material according to the present embodiment. This secondary battery is a so-called lithium ion secondary battery in which lithium is used as an electrode reactant and the capacity of the negative electrode is represented by a capacity component due to insertion and extraction of lithium. This secondary battery is called a so-called cylindrical type, and is a winding in which a pair of strip-like positive electrode 21 and strip-like negative electrode 22 are wound through a separator 23 inside a substantially hollow cylindrical battery can 11. A rotating electrode body 20 is provided. Inside the battery can 11, an electrolytic solution that is a liquid electrolyte is injected and impregnated in the separator 23. The battery can 11 is made of, for example, iron plated with nickel, and has one end closed and the other end open. Inside the battery can 11, a pair of insulating plates 12 and 13 are arranged perpendicular to the winding peripheral surface so as to sandwich the winding electrode body 20.

  At the open end of the battery can 11, a battery lid 14, a safety valve mechanism 15 provided inside the battery lid 14 and a heat sensitive resistance element (Positive Temperature Coefficient; PTC element) 16 are interposed via a gasket 17. It is attached by caulking, and the inside of the battery can 11 is sealed. The battery lid 14 is made of, for example, the same material as the battery can 11. The safety valve mechanism 15 is electrically connected to the battery lid 14 via the heat sensitive resistance element 16, and the disk plate 15A is reversed when the internal pressure of the battery exceeds a certain level due to an internal short circuit or external heating. Thus, the electrical connection between the battery lid 14 and the wound electrode body 20 is cut off. When the temperature rises, the heat sensitive resistance element 16 limits the current by increasing the resistance value and prevents abnormal heat generation due to a large current. The gasket 17 is made of, for example, an insulating material, and asphalt is applied to the surface.

  For example, a center pin 24 is inserted in the center of the wound electrode body 20. A positive electrode lead 25 made of aluminum or the like is connected to the positive electrode 21 of the spirally wound electrode body 20, and a negative electrode lead 26 made of nickel or the like is connected to the negative electrode 22. The positive electrode lead 25 is electrically connected to the battery lid 14 by being welded to the safety valve mechanism 15, and the negative electrode lead 26 is welded to and electrically connected to the battery can 11.

  FIG. 2 shows an enlarged part of the spirally wound electrode body 20 shown in FIG. The positive electrode 21 has, for example, a structure in which a positive electrode active material layer 21B is provided on both surfaces of a positive electrode current collector 21A having a pair of opposed surfaces. Although not shown, the positive electrode active material layer 21B may be provided only on one surface of the positive electrode current collector 21A. The positive electrode current collector 21A is made of, for example, a metal foil such as an aluminum foil, a nickel foil, or a stainless steel foil.

  The positive electrode active material layer 21B includes, for example, a positive electrode material according to the present embodiment, and a conductive agent such as graphite and a binder such as polyvinylidene fluoride as necessary.

  Moreover, it is preferable that the positive electrode active material layer 21B has a space | gap within the range of 10 volume% or more and 30 volume% or less. This is because when the number of voids is small, the permeability of the electrolytic solution is lowered, and when the number of voids is large, the filling amount of the positive electrode material is decreased.

  The negative electrode 22 has, for example, a structure in which a negative electrode active material layer 22B is provided on both surfaces of a negative electrode current collector 22A having a pair of opposed surfaces. Although not shown, the negative electrode active material layer 22B may be provided only on one surface of the negative electrode current collector 22A. The negative electrode current collector 22A is made of, for example, a metal foil such as a copper foil, a nickel foil, or a stainless steel foil having good electrochemical stability, electrical conductivity, and mechanical strength.

  The negative electrode active material layer 22B includes one or more negative electrode materials capable of inserting and extracting lithium as the negative electrode active material, and the positive electrode active material layer 21B as necessary. It is comprised including the binder similar to.

  In this secondary battery, the charge capacity of the negative electrode material capable of inserting and extracting lithium is larger than the charge capacity of the positive electrode 21 so that lithium metal does not deposit on the negative electrode 22 during the charge. It has become.

  As a negative electrode material capable of occluding and releasing lithium, a material capable of occluding and releasing lithium at a potential of 2.0 V or less with respect to lithium metal is preferably exemplified. This is because high energy density of the battery can be easily realized. Specifically, carbon such as non-graphitizable carbon, artificial graphite, natural graphite, pyrolytic carbons, cokes, graphites, glassy carbons, organic polymer compound fired bodies, carbon fiber, activated carbon or carbon black Materials. Among these, examples of coke include pitch coke, needle coke, and petroleum coke. The organic polymer compound fired body is obtained by firing and polymerizing a polymer material such as phenol resin or furan resin at an appropriate temperature.

  Examples of the negative electrode material capable of inserting and extracting lithium also include a material including at least one of a metal element and a metalloid element as a constituent element. This is because a high energy density can be obtained by using such a material. In particular, the use with a carbon material is more preferable because a high energy density can be obtained and excellent cycle characteristics can be obtained. The negative electrode material may be a single element, alloy or compound of a metal element or metalloid element, or may have at least a part of one or more of these phases. In the present invention, alloys include those containing one or more metal elements and one or more metalloid elements in addition to those composed of two or more metal elements. Moreover, the nonmetallic element may be included. There are structures in which a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or two or more of them coexist.

  Examples of the metal element or metalloid element constituting the negative electrode material include magnesium, boron, aluminum, gallium, indium, silicon, germanium (Ge), tin, lead (Pb), bismuth, cadmium (Cd), silver ( Ag), zinc, hafnium (Hf), zirconium, yttrium, palladium (Pd) or platinum (Pt). These may be crystalline or amorphous.

  Among these, as the negative electrode material, a material containing a 4B group metal element or a semimetal element in the short-period type periodic table as a constituent element is preferable, and at least one of silicon and tin is particularly preferable as a constituent element. This is because silicon and tin have a large ability to occlude and release lithium, and a high energy density can be obtained.

  As a negative electrode material capable of inserting and extracting lithium, lithium can be inserted and extracted at a relatively low potential such as iron oxide, ruthenium oxide, molybdenum oxide, tungsten oxide, titanium oxide or tin oxide. Possible oxides or nitrides are mentioned.

  The separator 23 is made of, for example, a porous film made of synthetic resin such as polytetrafluoroethylene, polypropylene, or polyethylene, or a porous film made of ceramic, and has a structure in which two or more kinds of porous films are laminated. May be. Among these, a porous film made of polyolefin is preferable because it is excellent in short-circuit preventing effect and can improve the safety of the battery due to the shutdown effect.

  The electrolytic solution includes, for example, a nonaqueous solvent such as an organic solvent and an electrolyte salt dissolved in the nonaqueous solvent. Examples of the non-aqueous solvent include ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3- Examples include dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methyl sulfolane, acetonitrile, propionitrile, anisole, acetate ester, butyrate ester, or propionate ester. One non-aqueous solvent may be used alone, or two or more non-aqueous solvents may be mixed and used.

As electrolyte salt, lithium salt is mentioned, for example, 1 type may be used independently, and 2 or more types may be mixed and used for it. Examples of the lithium salt include LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiClO ₄ , LiB (C ₆ H ₅ ) ₄ , LiCH ₃ SO ₃ , LiCF ₃ SO ₃ , LiCl, or LiBr.

  Note that the open circuit voltage (that is, the battery voltage) when the secondary battery is fully charged may be 4.20V, but is designed to be higher than 4.20V and not lower than 4.25V and lower than 6.00V. It is preferable. The energy density can be increased by increasing the battery voltage, and according to the present embodiment, the reversibility of lithium ions in the positive electrode material has been improved. This is because characteristics can be obtained. In that case, since the amount of lithium released per unit mass increases even with the same positive electrode material than when the battery voltage is set to 4.20 V, the amounts of the positive electrode material and the negative electrode active material are adjusted accordingly.

  For example, the secondary battery can be manufactured as follows.

  First, for example, the positive electrode active material layer 21B is formed on the positive electrode current collector 21A to produce the positive electrode 21. The positive electrode active material layer 21B is prepared, for example, by mixing a positive electrode material, a conductive agent, and a binder to prepare a positive electrode mixture, and then dispersing the positive electrode mixture in a solvent such as N-methyl-2-pyrrolidone. Thus, a paste-like positive electrode mixture slurry is formed, and this positive electrode mixture slurry is applied to the positive electrode current collector 21A, the solvent is dried, and compression molding is performed by a roll press machine or the like.

  Further, for example, the negative electrode active material layer 22B is formed on the negative electrode current collector 22A to produce the negative electrode 22. The negative electrode active material layer 22B may be formed by, for example, any one of a vapor phase method, a liquid phase method, a baking method, and coating, or a combination of two or more thereof. As the vapor phase method, for example, a physical deposition method or a chemical deposition method can be used. Specifically, a vacuum deposition method, a sputtering method, an ion plating method, a laser ablation method, a thermal CVD (Chemical Vapor Deposition) A chemical vapor deposition method) or a plasma CVD method can be used. As the liquid phase method, a known method such as electrolytic plating or electroless plating can be used. As for the firing method, a known method can be used. For example, an atmosphere firing method, a reaction firing method, or a hot press firing method can be used. In the case of application, it can be formed in the same manner as the positive electrode 21.

  Subsequently, the positive electrode lead 25 is attached to the positive electrode current collector 21A by welding or the like, and the negative electrode lead 26 is attached to the negative electrode current collector 22A by welding or the like. After that, the positive electrode 21 and the negative electrode 22 are wound through the separator 23, and the tip of the positive electrode lead 25 is welded to the safety valve mechanism 15, and the tip of the negative electrode lead 26 is welded to the battery can 11. The positive electrode 21 and the negative electrode 22 are sandwiched between a pair of insulating plates 12 and 13 and stored in the battery can 11. After the positive electrode 21 and the negative electrode 22 are accommodated in the battery can 11, the electrolytic solution is injected into the battery can 11 and impregnated in the separator 23. After that, the battery lid 14, the safety valve mechanism 15, and the heat sensitive resistance element 16 are fixed to the opening end of the battery can 11 by caulking through a gasket 17. Thereby, the secondary battery shown in FIGS. 1 and 2 is formed.

  In the secondary battery, when charged, lithium ions are released from the positive electrode active material layer 21B and inserted in the negative electrode active material layer 22B through the electrolytic solution. Next, when discharging is performed, lithium ions are released from the negative electrode active material layer 22B and inserted into the positive electrode active material layer 21B through the electrolytic solution. In this embodiment, since the positive electrode material described above is used, the reversibility of lithium ions is improved, and excellent characteristics can be obtained even in a high temperature environment or a high voltage.

(Secondary secondary battery)
FIG. 3 shows a configuration of a second secondary battery using the positive electrode material according to the present embodiment. In this secondary battery, a wound electrode body 30 to which a positive electrode lead 31 and a negative electrode lead 32 are attached is accommodated in a film-like exterior member 40, and can be reduced in size, weight, and thickness. ing.

  The positive electrode lead 31 and the negative electrode lead 32 are led out from the inside of the exterior member 40 to the outside, for example, in the same direction. The positive electrode lead 31 and the negative electrode lead 32 are each made of a metal material such as aluminum, copper, nickel, or stainless steel, and each have a thin plate shape or a mesh shape.

  The exterior member 40 is made of, for example, a rectangular aluminum laminated film in which a nylon film, an aluminum foil, and a polyethylene film are bonded together in this order. For example, the exterior member 40 is disposed so that the polyethylene film side and the wound electrode body 30 face each other, and the outer edge portions are in close contact with each other by fusion bonding or an adhesive. An adhesive film 41 is inserted between the exterior member 40 and the positive electrode lead 31 and the negative electrode lead 32 to prevent intrusion of outside air. The adhesion film 41 is made of a material having adhesion to the positive electrode lead 31 and the negative electrode lead 32, for example, a polyolefin resin such as polyethylene, polypropylene, modified polyethylene, or modified polypropylene.

  The exterior member 40 may be made of a laminated film having another structure, a polymer film such as polypropylene, or a metal film instead of the above-described aluminum laminated film.

  FIG. 4 shows a cross-sectional structure taken along line II of the spirally wound electrode body 30 shown in FIG. The wound electrode body 30 is formed by laminating a pair of a positive electrode 33 and a negative electrode 34 via a separator 35 and an electrolyte layer 36, and the outermost peripheral portion is protected by a protective tape 37.

  The positive electrode 33 has a structure in which a positive electrode active material layer 33B is provided on both surfaces of a positive electrode current collector 33A, and the negative electrode 34 has a structure in which a negative electrode active material layer 34B is provided on both surfaces of the negative electrode current collector 34A. have. The configurations of the positive electrode current collector 33A, the positive electrode active material layer 33B, the negative electrode current collector 34A, the negative electrode active material layer 34B, and the separator 35 are respectively the positive electrode current collector 21A, the positive electrode active material layer 21B, and the negative electrode current collector 22A. The same as the negative electrode active material layer 22B and the separator 23.

  The electrolyte layer 36 includes an electrolytic solution and a polymer compound serving as a holding body that holds the electrolytic solution, and has a so-called gel shape. The gel electrolyte layer 36 is preferable because high ion conductivity can be obtained and liquid leakage can be prevented. The configuration of the electrolytic solution is the same as that of the first secondary battery. Examples of the polymer compound include fluorine-based polymer compounds such as polyvinylidene fluoride or a copolymer of vinylidene fluoride and hexafluoropropylene, ether-based polymer compounds such as polyethylene oxide or a crosslinked product containing polyethylene oxide, Examples include acrylonitrile. In particular, a fluorine-based polymer compound is desirable from the viewpoint of redox stability. Any one of these polymer compounds may be used alone, or two or more thereof may be mixed and used.

  For example, the secondary battery can be manufactured as follows.

  First, after the positive electrode 33 and the negative electrode 34 are manufactured in the same manner as the first secondary battery, a precursor solution containing an electrolytic solution, a polymer compound, and a mixed solvent is applied to each of the positive electrode 33 and the negative electrode 34. Then, the mixed solvent is volatilized to form the electrolyte layer 36. After that, the positive electrode lead 31 is attached to the positive electrode current collector 33A, and the negative electrode lead 32 is attached to the negative electrode current collector 34A. Next, the positive electrode 33 and the negative electrode 34 on which the electrolyte layer 36 is formed are laminated via a separator 35 to form a laminated body, and then the laminated body is wound in the longitudinal direction, and a protective tape 37 is adhered to the outermost peripheral portion. Thus, the wound electrode body 30 is formed. Finally, for example, the wound electrode body 30 is sandwiched between the exterior members 40, and the outer edges of the exterior members 40 are sealed and sealed by heat fusion or the like. At that time, the adhesion film 41 is inserted between the positive electrode lead 31 and the negative electrode lead 32 and the exterior member 40. Thereby, the secondary battery shown in FIGS. 3 and 4 is completed.

  Further, this secondary battery may be manufactured as follows. First, the positive electrode 33 and the negative electrode 34 are prepared as described above, and after the positive electrode lead 31 and the negative electrode lead 32 are attached to the positive electrode 33 and the negative electrode 34, the positive electrode 33 and the negative electrode 34 are stacked via the separator 35 and wound. Rotate and adhere the protective tape 37 to the outermost periphery to form a wound body that is a precursor of the wound electrode body 30. Next, the wound body is sandwiched between the exterior members 40, and the outer peripheral edge portion excluding one side is heat-sealed to form a bag shape, and is stored inside the exterior member 40. Subsequently, an electrolyte composition containing an electrolytic solution, a monomer that is a raw material of the polymer compound, and other materials such as a polymerization initiator or a polymerization inhibitor as necessary is injected into the exterior member 40, The opening of the exterior member 40 is sealed. After that, if necessary, heat is applied to polymerize the monomer to form a polymer compound, thereby forming the gel electrolyte layer 36 and assembling the secondary battery shown in FIGS.

  This secondary battery operates in the same manner as the first secondary battery.

  As described above, according to the present embodiment, the positive electrode 21 contains the positive electrode material containing lithium transition metal composite oxide particles containing lithium and transition metal, fluorinated graphite, and metal fluoride. Therefore, reversibility of lithium ions can be improved, and excellent battery characteristics can be obtained even in a high temperature environment or even when the charging voltage is increased.

  Further, if the ratio of the fluorinated graphite and the metal fluoride to the lithium transition metal composite oxide particles is 0.1 mol% or more and 20 mol% or less, or the fluorinated graphite and the metal fluoride are converted into the lithium transition metal composite oxide. A higher effect can be obtained if it is deposited on at least a part of the surface of the product particles or if the lithium transition metal composite oxide particles contain fluorine.

  Further, specific embodiments of the present invention will be described in detail.

(Example 1-1)
First, the positive electrode material was produced as follows. While thoroughly stirring an aqueous solution obtained by mixing commercially available nickel nitrate and cobalt nitrate so that the ratio of nickel to cobalt (nickel: cobalt) is 0.2: 0.8, the aqueous ammonia is added. The solution was added dropwise to obtain a composite hydroxide powder. Next, this composite hydroxide powder and lithium hydroxide powder were mixed to form a mixed hydroxide powder, and then heated at 900 ° C. for 7 hours using an electric furnace, pulverized, and lithium transition metal composite oxidation A product powder was obtained. When the obtained lithium transition metal composite oxide powder was subjected to fluorescent X-ray analysis, it was confirmed that it had a composition of Li _1.01 Ni _0.20 Co _0.80 O _1.98 . Further, when the particle size was measured by a laser diffraction method, the average particle size was about 12 μm. Furthermore, when X-ray diffraction measurement was performed, it was confirmed that it was similar to the diffraction pattern of LiCoO ₂ described in ICDD 50-0653 and formed the same layered rock salt structure as LiCoO ₂ . Furthermore, when observed by SEM (Scanning Electron Microscope), spherical particles in which primary particles of 0.1 μm to 5 μm aggregated were confirmed. Subsequently, this lithium transition metal composite oxide powder, commercially available graphite fluoride, and lithium fluoride (LiF) were mixed in an automatic mortar and dried at 150 ° C. to produce a positive electrode material. The mixing amount of lithium fluoride and graphite fluoride was 3 mol% with respect to the lithium transition metal composite oxide powder.

  The secondary battery shown in FIGS. 1 and 2 was produced using the produced positive electrode material. First, 86 mass% of the produced positive electrode material, 10 mass% of graphite as a conductive agent, and 4 mass% of polyvinylidene fluoride as a binder were mixed to prepare a positive electrode mixture, and then this positive electrode mixture was used as a solvent. A paste positive electrode mixture slurry dispersed in N-methyl-2-pyrrolidone, and this positive electrode mixture slurry was applied to both surfaces of a positive electrode current collector 21A made of an aluminum foil having a thickness of 20 μm and dried, and a roll press machine The positive electrode 21 was produced by compression molding to form the positive electrode active material layer 21B. After that, an aluminum positive electrode lead 25 was attached to one end of the positive electrode current collector 21A.

  Further, after preparing 90% by mass of artificial graphite powder as a negative electrode active material and 10% by mass of polyvinylidene fluoride as a binder, a negative electrode mixture was prepared, and then using this negative electrode mixture as a solvent, N-methyl-2- Dispersed in pyrrolidone to form a paste-like negative electrode mixture slurry, and this negative electrode mixture slurry was applied to both surfaces of a negative electrode current collector 22A made of a copper foil having a thickness of 10 μm, dried, and compression-molded with a roll press. The negative electrode 22 was produced by forming the active material layer 22B. At that time, the amounts of the positive electrode material and the negative electrode active material are adjusted, the open circuit voltage at the time of full charge is 4.40 V, and the capacity of the negative electrode 22 is represented by a capacity component due to insertion and extraction of lithium. Designed. Next, a negative electrode lead 26 made of nickel was attached to one end of the negative electrode current collector 22A.

After preparing the positive electrode 21 and the negative electrode 22, a separator 23 made of a porous polyolefin film is prepared, and the negative electrode 22, the separator 23, the positive electrode 21, and the separator 23 are laminated in this order, and this laminate is wound many times in a spiral shape. A wound electrode body 20 was produced. Next, the wound electrode body 20 is sandwiched between the pair of insulating plates 12 and 13, the negative electrode lead 26 is welded to the battery can 11, and the positive electrode lead 25 is welded to the safety valve mechanism 15, and is wound together with the heat sensitive resistance element 16. The electrode body 20 was housed in a nickel-plated iron battery can 11, and an electrolyte solution was injected into the battery can 11. As the electrolytic solution, a solution obtained by dissolving LiPF ₆ as an electrolyte salt to 1.0 mol / l in a solvent in which ethylene carbonate and ethylmethyl carbonate were mixed at an equal volume ratio was used. Thereafter, the battery lid 14 was caulked to the battery can 11 via the gasket 17 to obtain a cylindrical secondary battery having an outer diameter of 18 mm and a height of 65 mm.

  As Comparative Examples 1-1 to 1-3 for Example 1-1, except that graphite fluoride and lithium fluoride were not used, or that only lithium fluoride was not used, or graphite fluoride A secondary battery was fabricated in the same manner as in Example 1-1 except that only was not used.

  The secondary batteries of Example 1-1 and Comparative Examples 1-1 to 1-3 were charged and discharged at 45 ° C., and the initial capacity and cycle retention at a high temperature were examined. Charging was performed under the conditions of a current value of 1000 mA, a charging upper limit voltage of 4.40 V and a charging time of 2.5 hours, and discharging was performed under the conditions of a current value of 800 mA and a final voltage of 2.75 V. The initial capacity was the discharge capacity at the first cycle. The cycle retention rate was obtained from the discharge capacity retention rate at the 100th cycle relative to the first cycle, that is, (discharge capacity at the 100th cycle / discharge capacity at the first cycle) × 100%. The results are shown in Table 1.

  As can be seen from Table 1, according to Example 1-1 in which lithium transition metal composite oxide, fluorinated graphite, and lithium fluoride were mixed, comparative example in which fluorinated graphite and lithium fluoride were not mixed 1-1, or Comparative Example 1-2 in which lithium fluoride was not mixed, or Comparative Example 1-3 in which graphite fluoride was not mixed was improved in initial capacity and cycle retention.

  That is, if lithium transition metal composite oxide, fluorinated graphite, and metal fluoride are used as the positive electrode material, excellent battery characteristics can be obtained even in a high temperature environment or at a high charging voltage. It turns out that you can get.

(Example 2-1)
A secondary battery was fabricated in the same manner as in Example 1-1 except that a positive electrode material was produced by depositing graphite fluoride and lithium fluoride on lithium transition metal composite oxide powder by a mechanochemical method. Produced. When the positive electrode material was observed by SEM, it was confirmed that graphite fluoride and lithium fluoride were uniformly deposited on the surface of the lithium transition metal composite oxide particles.

  As Comparative Example 2-1 with respect to Example 2-1, a secondary battery was fabricated in the same manner as in Example 2-1, except that graphite fluoride was not used.

  For the secondary batteries of Example 2-1 and Comparative Example 2-1, the initial capacity and cycle retention at a high temperature were examined in the same manner as in Example 1-1. The results are shown in Table 2.

  As can be seen from Table 2, in the same manner as in Example 1-1, according to Example 2-1 using a positive electrode material in which fluorinated graphite and lithium fluoride were applied to a lithium transition metal composite oxide, More than Comparative Example 1-1 in which graphite fluoride and lithium fluoride were not used, or Comparative Example 1-2 in which lithium fluoride was not used, or Comparative Examples 1-3 and 2-1 in which graphite fluoride was not used The initial capacity and cycle retention rate were improved. Further, according to Example 2-1, in which a positive electrode material in which fluorinated graphite and lithium fluoride were applied to lithium transition metal composite oxide particles was used, a lithium transition metal composite oxide, fluorinated graphite, The cycle retention rate was improved as compared with Example 1-1 using a positive electrode material mixed with lithium fluoride.

  That is, it has been found that it is preferable to apply graphite fluoride and lithium fluoride to the lithium transition metal composite oxide particles.

(Examples 3-1 to 3-3)
A secondary battery was fabricated in the same manner as in Example 1-1 except that another lithium transition metal composite oxide was used instead of Li _1.01 Ni _0.20 Co _0.80 O _1.98 . At that time, the lithium transition metal composite oxide is LiCoO _{2 in} Example 3-1, Li _1.02 Ni _0.70 Co _0.30 O _1.98 in Example 3-2, and Li _1.01 Ni _0.20 Co _0.80 O in Example 3-3. _1.98 and Li _1.03 Ni _0.35 Co _0.30 Mn _0.35 O _1.97 were mixed at a mass ratio of Li _1.01 Ni _0.20 Co _0.80 O _1.98 : Li _1.03 Ni _0.35 Co _0.30 Mn _0.35 O _1.97 = 80: 20. LiCoO ₂ was prepared by mixing commercially available cobalt oxide and lithium carbonate and firing at 950 ° C. for 7 hours. Further, Li _1.02 Ni _0.70 Co _0.30 O _1.98 was prepared in the same manner as in Example 1-1 except that the ratio of nickel nitrate to cobalt nitrate was changed, and a lithium transition metal composite oxide was produced. Furthermore, Li _1.03 Ni _0.35 Co _0.30 Mn _0.35 O _1.97 is not only nickel nitrate and cobalt nitrate, but also manganese nitrate, except that an aqueous solution in which these are mixed to a predetermined ratio is used. A lithium transition metal composite oxide was produced in the same manner as in Example 1-1. Furthermore, in Example 3-3, Li _1.03 Ni _0.35 Co _0.30 Mn _0.35 O _1.97 is prepared by mixing Li _1.01 Ni _0.20 Co _0.80 O _1.98 , fluorinated graphite, and lithium fluoride with an automatic mortar. The positive electrode material was mixed when producing a positive electrode mixture. The positive electrode 21 produced in Example 3-3 was analyzed by X-ray diffraction measurement and TOF-SIMS (Time Of Fright-Secondary Ion Mass Spectroscopy). Lithium fluoride was confirmed.

  For the secondary batteries of Examples 3-1 to 3-3, the initial capacity and the cycle maintenance ratio at high temperatures were examined in the same manner as in Example 1-1. The results are shown in Table 3.

  As can be seen from Table 3, according to Examples 3-1 to 3-3 using other lithium transition metal composite oxides as in Example 1-1, the cycle retention ratio was improved.

  That is, even if other lithium transition metal composite oxides are used, excellent battery characteristics can be obtained even in high temperature environments or at high charging voltages by using graphite fluoride and metal fluoride. It turns out that you can get.

(Examples 4-1 to 4-5)
A positive electrode material and a secondary battery were produced in the same manner as in Example 1-1 except that the mixing amount of lithium fluoride and graphite fluoride with respect to the lithium transition metal composite oxide powder was changed. The mixing amount of lithium fluoride and graphite fluoride was 20 mol% in Example 4-1, and 10 mol% in Example 4-2, respectively, with respect to the lithium transition metal composite oxide powder. Example 4-3 In Example 4-4, it was 1 mol%, and in Example 4-4, it was 0.05 mol%, respectively.

  For the secondary batteries of Examples 4-1 to 4-5, the initial capacity and the cycle maintenance ratio at high temperatures were examined in the same manner as in Example 1-1. The results are shown in Table 4.

  As can be seen from Table 4, the initial capacity tended to decrease as the mixing amount of lithium fluoride and graphite fluoride with respect to the lithium transition metal composite oxide powder increased. In addition, the cycle retention ratio increased as the amount of lithium fluoride and graphite fluoride mixed with the lithium transition metal composite oxide powder increased, showed a maximum value, and then decreased and became almost constant.

  That is, it has been found that it is preferable that the mixing amount of lithium fluoride and graphite fluoride with respect to the lithium transition metal composite oxide powder is 0.01 mol% or more and 20 mol% or less.

(Example 5-1)
A secondary battery was fabricated in the same manner as in Example 1-1 except that lithium transition metal composite oxide containing fluorine was used instead of Li _1.01 Ni _0.20 Co _0.80 O _1.98 . At that time, the lithium transition metal composite oxide containing fluorine was the same as in Example 1-1 except that 5 mol% of the entire lithium hydroxide powder was changed to lithium fluoride. Was made. When the produced lithium transition metal composite oxide was subjected to fluorescent X-ray analysis, it was confirmed that it had a composition of Li _1.01 Ni _0.20 Co _0.80 O _1.94 F _0.05 .

  For the secondary battery of Example 5-1, the initial capacity and cycle retention ratio at high temperatures were examined in the same manner as in Example 1-1. The results are shown in Table 5.

  As can be seen from Table 5, according to Example 5-1 using a lithium transition metal composite oxide containing fluorine, the cycle was higher than Example 1-1 using a lithium transition metal composite oxide containing no fluorine. Maintenance rate improved.

  That is, it has been found that it is preferable to include fluorine in the lithium transition metal composite oxide.

(Examples 6-1 to 6-3)
Example 1-1 except that nickel fluoride (NiF ₂ ), calcium fluoride (CaF ₂ ), or aluminum fluoride (AlF ₃ ) was used in place of lithium fluoride as the metal fluoride. In the same manner as above, a positive electrode material and a secondary battery were produced.

  For the secondary batteries of Examples 6-1 to 6-3, the initial capacity and the cycle maintenance ratio at high temperatures were examined in the same manner as in Example 1-1. The results are shown in Table 6.

  As can be seen from Table 6, in Examples 6-1 to 6-3 using nickel fluoride, calcium fluoride, or aluminum fluoride as the metal fluoride as in Example 1-1, the initial capacity and High values were obtained for both cycle retention rates.

  In other words, even if other metal fluorides are used, if lithium transition metal composite oxide and fluorinated graphite are used, excellent battery characteristics can be obtained even in a high temperature environment or at a high charging voltage. It turns out that you can get.

(Examples 7-1 to 7-5)
By adjusting the amount of the positive electrode material and the amount of the negative electrode active material, the open circuit voltage at the time of full charge is 4.60 V in Example 7-1, 4.50 V in Example 7-2, and in Example 7-3. A secondary battery was fabricated in the same manner as in Example 1-1 except that it was designed to be 4.30 V, 4.25 V in Example 7-4, and 4.20 V in Example 7-5. .

  As Comparative Examples 7-1 to 7-6 with respect to Examples 7-1 to 7-5, except that graphite fluoride and lithium fluoride were not used or only lithium fluoride was not used, Otherwise, a secondary battery was fabricated in the same manner as in Example 7-1 or Example 7-5 except that only fluorinated graphite was not used. In addition, the open circuit voltage at the time of complete charge is 4.60V in Comparative Examples 7-1 to 7-3, and 4.20V in Comparative Examples 7-4 to 7-6.

  For the secondary batteries of Examples 7-1 to 7-5 and Comparative examples 7-1 to 7-6, the initial capacity and cycle retention ratio at high temperatures were examined in the same manner as in Example 1-1. At that time, the charging upper limit voltage was 4.60 V in Example 7-1 and Comparative Examples 7-1 to 7-3, 4.50 V in Example 7-2, 4.30 V in Example 7-3, Example 7-4 was set to 4.25 V, and Example 7-5 and Comparative Examples 7-4 to 7-6 were set to 4.20. The results are shown in Table 7.

  As can be seen from Table 7, even when the open circuit voltage at full charge was set to 4.60 V or 4.20 V, the cycle retention ratio was improved in the same manner as in Example 1-1. In addition, the effect of improving the cycle retention rate was particularly high in Examples 1-1 and 7-1 in which the open circuit voltage at the time of full charge was over 4.20V. Furthermore, in Examples 7-2 to 7-4 in which the open circuit voltage at the time of full charge was 4.50 V, 4.30 V, or 4.25 V, the cycle retention rate was similarly improved.

  That is, it has been found that a high effect can be obtained when the open circuit voltage at the time of full charge is set in the range of 4.25V to 6.00V.

  Although the present invention has been described with reference to the embodiments and examples, the present invention is not limited to the above embodiments and examples, and various modifications can be made. For example, in the above-described embodiment or example, the case of using an electrolytic solution that is a liquid electrolyte or a gel electrolyte in which the electrolytic solution is held in a polymer compound has been described, but other electrolytes may be used. Also good. Examples of the other electrolyte include a solid electrolyte having ionic conductivity, or a mixture of a solid electrolyte and a gel electrolyte or an electrolytic solution.

  As the solid electrolyte, for example, a polymer solid electrolyte in which an electrolyte salt is dispersed in a polymer compound having ion conductivity, or an inorganic solid electrolyte made of ion conductive glass or ionic crystals can be used. In this case, as the polymer compound, for example, an ether polymer compound such as polyethylene oxide or a crosslinked product containing polyethylene oxide, an ester polymer compound such as polymethacrylate or polyacrylate, or a mixture thereof, or in the molecule It can be used after being copolymerized. As the inorganic solid electrolyte, lithium nitride, lithium iodide, or the like can be used.

  In the above embodiments and examples, a so-called lithium ion secondary battery in which the capacity of the negative electrode is represented by a capacity component due to insertion and extraction of lithium has been described. However, the present invention relates to lithium metal as the negative electrode active material. The capacity of the negative electrode used is a so-called lithium metal secondary battery whose capacity is represented by the deposition and dissolution of lithium, or the negative electrode material capable of occluding and releasing lithium is more charged than the positive electrode. The same applies to a secondary battery in which the capacity of the negative electrode includes a capacity component due to insertion and extraction of lithium and a capacity component due to precipitation and dissolution of lithium, and is expressed by the sum thereof, by reducing the capacity. be able to.

  Further, in the above embodiments and examples, the secondary battery having a winding structure has been described, but the present invention is similarly applied to a secondary battery having another structure in which the positive electrode and the negative electrode are folded or stacked. can do. In addition, the present invention can also be applied to secondary batteries having other shapes such as a so-called coin type, button type, sheet type, or square type.

It is sectional drawing showing the structure of the 1st secondary battery using the positive electrode material which concerns on one embodiment of this invention. It is sectional drawing which expands and represents a part of winding electrode body in the secondary battery shown in FIG. It is a disassembled perspective view showing the structure of the 2nd secondary battery using the positive electrode material which concerns on one embodiment of this invention. It is sectional drawing along the II line | wire of the winding electrode body shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Battery can, 12, 13 ... Insulation board, 14 ... Battery cover, 15 ... Safety valve mechanism, 15A ... Disc board, 16 ... Heat sensitive resistance element, 17 ... Gasket, 20, 30 ... Winding electrode body, 21, 33 ... Positive electrode, 21A, 33A ... Positive electrode current collector, 21B, 33B ... Positive electrode active material layer, 22, 34 ... Negative electrode, 22A, 34A ... Negative electrode current collector, 22B, 34B ... Negative electrode active material layer, 23, 35 ... Separator , 24 ... Center pin, 25, 31 ... Positive electrode lead, 26, 32 ... Negative electrode lead, 36 ... Electrolyte layer, 37 ... Protective tape, 40 ... Exterior member, 41 ... Adhesion film.

Claims (13)

  A positive electrode material comprising lithium transition metal composite oxide particles containing lithium (Li) and a transition metal, fluorinated graphite, and a metal fluoride.   The ratio of the graphite fluoride and the metal fluoride to the lithium transition metal composite oxide particles (total of graphite fluoride and metal fluoride / lithium transition metal composite oxide particles) is 0.1 mol% or more and 20 mol% or less. The positive electrode material according to claim 1, wherein:   The positive electrode material according to claim 1, wherein the fluorinated graphite and the metal fluoride are attached to at least a part of the surface of the lithium transition metal composite oxide particles.   The positive electrode material according to claim 1, wherein the lithium transition metal composite oxide particles contain fluorine (F).   A positive electrode comprising a positive electrode material containing lithium transition metal composite oxide particles containing lithium (Li) and a transition metal, fluorinated graphite, and a metal fluoride.   The ratio of the fluorinated graphite and the metal fluoride to the lithium transition metal composite oxide particles (total of fluorinated graphite and metal fluoride / lithium transition metal composite oxide particles) is 0.1 mol% or more and 20 mol% or less. The positive electrode according to claim 5, wherein:   6. The positive electrode according to claim 5, wherein the fluorinated graphite and the metal fluoride are deposited on at least a part of the surface of the lithium transition metal composite oxide particles.   The positive electrode according to claim 5, wherein the lithium transition metal composite oxide particles contain fluorine (F). A battery comprising an electrolyte together with a positive electrode and a negative electrode,
The positive electrode contains a positive electrode material containing lithium transition metal composite oxide particles containing lithium (Li) and a transition metal, fluorinated graphite, and a metal fluoride.   The ratio of the graphite fluoride and the metal fluoride to the lithium transition metal composite oxide particles (total of graphite fluoride and metal fluoride / lithium transition metal composite oxide particles) is 0.1 mol% or more and 20 mol% or less. The battery according to claim 9.   The battery according to claim 9, wherein the fluorinated graphite and the metal fluoride are attached to at least a part of the surface of the lithium transition metal composite oxide particles.   The battery according to claim 10, wherein the lithium transition metal composite oxide particles contain fluorine (F).   The battery according to claim 10, wherein an open circuit voltage in a fully charged state per pair of positive electrode and negative electrode is in a range of 4.25 V or more and 6.00 V or less.

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