JP2007026959A - Positive electrode active substance, its manufacturing method and battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive electrode active substance improving covering property of a covering layer and easily controlling composition of the covering layer, its method of manufacture and a battery using it. <P>SOLUTION: The positive electrode active substance is manufactured by: being covered by having at least one part of composite oxide particles including Li and Co mixed with precursor particles including Li, Ni and Mn (step 101) and having the oxide covered layer formed by heat processing (step 102). The precursor particle used is hydroxide, oxy-hydroxide, carbonate or hydrogen carbonate. It is preferable that the precursor is mixed by applying shearing force while being compressed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a positive electrode active material in which a coating layer is formed on composite oxide particles containing lithium (Li) and cobalt (Co), a manufacturing method thereof, and a battery using the same.

  In recent years, with the increase in functionality and performance of portable devices, the power consumption of the devices is increasing, and a further increase in capacity is required for the battery serving as the power source. Among these, from the viewpoint of economy and reduction in size and weight of equipment, there is a great demand for secondary batteries. As a battery that can meet such a demand, for example, there is a lithium secondary battery.

  Currently used lithium secondary batteries use lithium cobaltate for the positive electrode and a carbon material for the negative electrode, and the operating voltage is in the range of 4.2V to 2.5V. Thus, in the case of a lithium secondary battery that operates at a maximum of 4.2 V, the positive electrode active material such as lithium cobaltate used for the positive electrode only uses about 60% of its theoretical capacity. . For this reason, it is theoretically possible to utilize the remaining capacity by further increasing the charging voltage, and in fact, by increasing the voltage during charging to 4.25 V or higher, a higher energy density can be realized. It is known (see Patent Document 1). In particular, examples of the positive electrode active material include lithium nickelate and lithium manganate having a spinel structure in addition to lithium cobaltate, and lithium cobaltate is preferable because it can maximize the potential.

  However, when the charging voltage is increased, the oxidizing atmosphere in the vicinity of the positive electrode becomes strong, and there is a problem that the electrolyte is likely to be deteriorated by oxidative decomposition or cobalt is easily eluted from the positive electrode. As a result, the charge / discharge efficiency is lowered, the cycle characteristics are lowered, the high temperature characteristics are lowered, and it is difficult to increase the charge voltage.

Conventionally, as a means for improving the stability of the positive electrode active material, it is known to form a coating layer on the surface of the composite oxide particles. As a method for forming the coating layer, the composite oxide particles are mixed with an oxide constituting the coating layer and refired (for example, refer to Patent Document 2), or the surface of the composite oxide particles is mixed. It is known that a metal hydroxide is deposited by a Japanese titration method and then heat-treated (for example, see Patent Documents 3 and 4).
International Publication No. WO03 / 0197131 Pamphlet JP-A-11-162466 JP-A-9-265985 JP-A-11-71114

  However, the method of mixing the oxide with the composite oxide particles and re-firing has a problem that it is difficult to form the coating layer uniformly and the adhesion between the composite oxide particles and the coating layer is low. In addition, the method of heat-treatment after depositing hydroxide by neutralization titration method is excellent in that the hydroxide can be deposited uniformly, but the composition of the coating layer can be controlled. There was also a problem that it was difficult.

  The present invention has been made in view of such problems, and the object thereof is to improve the coverage of the coating layer and easily control the composition, a method for producing the same, and a method for producing the same. It is to provide a used battery.

  The positive electrode active material according to the present invention is a coating of an oxide containing a covering element of at least one of lithium, nickel (Ni) and manganese (Mn) on at least a part of a composite oxide particle containing lithium and cobalt. The coating layer is a precursor including at least one member selected from the group consisting of hydroxides, oxyhydroxides, carbonates and bicarbonates of the coating elements in the composite oxide particles. The particles are formed by adhering by mixing and heat treatment.

  In the method for producing a positive electrode active material according to the present invention, an oxide covering layer containing a covering element of at least one of lithium, nickel, and manganese is formed on at least part of a composite oxide particle containing lithium and cobalt. And at least a part of the composite oxide particles is coated with at least one member selected from the group consisting of hydroxide, oxyhydroxide, carbonate and bicarbonate of the covering element. It includes a step of adhering by mixing the precursor particles, and a step of forming a coating layer by applying heat treatment after depositing the precursor particles.

  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 at least one of lithium, nickel, and manganese on at least a part of the composite oxide particles containing thium and cobalt. A cathode active material in which a coating layer of an oxide containing a coating element is formed, the coating layer comprising composite oxide particles, hydroxide, oxyhydroxide, carbonate and hydrogencarbonate of the coating element Precursor particles containing at least one kind in the group are deposited by mixing and formed by heat treatment.

  According to the positive electrode active material and the manufacturing method thereof of the present invention, since the precursor particles are mixed and deposited on the composite oxide particles, the binding property of the precursor particles to the composite oxide particles is improved. And the coverage of the coating layer can be improved. Further, the composition of the coating layer can be easily controlled. Therefore, according to the battery of the present invention using this positive electrode active material, a high capacity can be obtained and the charge / discharge efficiency can be improved.

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

  The positive electrode active material according to an embodiment of the present invention is obtained by providing a coating layer on at least a part of composite oxide particles containing lithium and cobalt. The average composition of the composite oxide particles is preferably represented by Chemical Formula 1. This is because the capacity and discharge potential can be increased.

(Chemical formula 1)
_{Li (1 + x) Co (} 1-y) M y O (2-z)
In the chemical formula 1, M is magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), manganese, iron (Fe), nickel, copper (Cu), Of the group consisting of zinc (Zn), molybdenum (Mo), tin (Sn), tungsten (W), zirconium (Zr), yttrium (Y), niobium (Nb), calcium (Ca) and strontium (Sr) At least one.

  x is a value in the range of −0.10 ≦ x ≦ 0.10, more preferably in the range of −0.08 ≦ x ≦ 0.08, and −0.06 ≦ x ≦ 0.06. It is more preferable if it is within the range. If it is smaller than this, the discharge capacity will be reduced, and if it is larger than this, lithium will diffuse when the coating layer is formed, and it may be difficult to control the process.

  y is a value within the range of 0 ≦ y <0.50, more preferably within the range of 0 ≦ y <0.40, and even more preferably within the range of 0 ≦ y <0.30. That is, M in Chemical Formula 1 is not an essential constituent element. Lithium cobalt oxide is preferable because it can obtain a high capacity and has a high discharge potential, and is preferable because it can improve stability if it contains M. However, if the amount of M increases, lithium cobalt oxide is preferable. This is because the above characteristics are impaired and the capacity and the discharge potential are lowered.

  z is a value in the range of −0.10 ≦ z ≦ 0.20, more preferably in the range of −0.08 ≦ z ≦ 0.18, and −0.06 ≦ z ≦ 0.16. It is more preferable if it is within the range. This is because the discharge capacity can be further increased within this range.

  The coating layer functions as a reaction suppression layer, and is composed of an oxide containing a coating element of lithium and at least one of nickel and manganese. The composition ratio of nickel and manganese in the coating layer is preferably a molar ratio of nickel: manganese within a range of 90:10 to 30:70, and more preferably within a range of 70:30 to 40:60. preferable. This is because when the amount of manganese is large, the amount of occlusion of lithium in the coating layer decreases, the capacity of the positive electrode active material decreases, and the electrical resistance increases. In addition, if the amount of nickel is large, the thermal stability of the coating layer is lowered and the high temperature characteristics are lowered.

  The oxide of the coating layer further includes magnesium, aluminum, boron, titanium, vanadium, chromium, iron, cobalt, copper, zinc, molybdenum, tin, tungsten, zirconium, yttrium, niobium, calcium and strontium. May be contained as a constituent element. This is because the stability of the positive electrode active material can be further improved and the diffusibility of lithium ions can be further improved. In this case, the total content of these elements is preferably 40 mol% or less, more preferably 35 mol% or less, based on the total of nickel, manganese, and these elements in the coating layer. This is because when the content of these elements increases, the amount of occlusion of lithium decreases and the capacity of the positive electrode active material decreases. Note that these elements may or may not be dissolved in the oxide.

  The amount of the coating layer is preferably in the range of 2% by mass to 30% by mass of the composite oxide particles, and more preferably in the range of 5% by mass to 20% by mass. This is because when the amount of the coating layer is large, the capacity decreases, and when the amount is small, the stability cannot be sufficiently improved. Further, the total content of nickel and manganese in this positive electrode active material, that is, the total content of nickel and manganese combined with the composite oxide particles and the coating layer is the total of metal elements and metalloid elements excluding lithium. It is preferable that it is 30 mol% or less. This is because as the contents of nickel and manganese increase, the capacity decreases.

  In addition, a coating layer can be confirmed by investigating the concentration change which goes to the inside from the surface of the element which comprises a positive electrode active material. This concentration change can be measured by, for example, Auger Electron Spectroscopy (AES) or SIMS (Secondary Ion Mass Spectrometry) while scraping the positive electrode active material by sputtering or the like. It is. It is also possible to slowly dissolve the positive electrode active material in an acidic solution or the like, and to measure the time change of the eluted portion by inductively coupled plasma (ICP) spectroscopic analysis or the like.

  The average particle diameter of the positive electrode active material is preferably in the range of 2.0 μm to 50 μm. If the thickness is less than 2.0 μm, the positive electrode active material is easily peeled off from the positive electrode current collector in the pressing step when the positive electrode is produced, and the surface area of the positive electrode active material is increased, so that a conductive agent or a binder is added. This is because the amount must be increased, and the energy density per unit mass becomes small. On the other hand, when the thickness exceeds 50 μm, there is a high possibility that the positive electrode active material penetrates the separator and causes a short circuit.

  Further, the positive electrode active material is obtained by mixing precursor particles containing at least one member selected from the group consisting of hydroxides, oxyhydroxides, carbonates and hydrogencarbonates of the covering elements on the composite oxide particles. The coating layer is formed by wearing and heat treatment. Thereby, in this positive electrode active material, the covering property of the coating layer is improved, the composition of the coating layer can be easily controlled, and the chemical stability can be improved. Specifically, it is manufactured as follows.

  FIG. 1 shows a process of one manufacturing method of this positive electrode active material. First, it adheres by mixing the precursor particle | grains containing a covering element to at least one part of complex oxide particle (step S101). This is because the binding property of the precursor particles to the composite oxide particles can be enhanced, and the composition ratio of the covering elements can be easily controlled. As described above, it is preferable to use a composite oxide particle having an average composition represented by Chemical Formula 1.

  The deposition of the precursor particles may be performed by a dry method or a wet method in which a liquid component such as water is added, and may be performed using, for example, a ball mill, a jet mill, a grinder, or a fine grinder. it can. In particular, it is preferable to mix by applying a shearing force while compressing. This is because the binding property of the precursor particles to the composite oxide particles can be enhanced. Specifically, a mechanical method such as mechanofusion can be used.

  As the precursor particles, at least one selected from the group consisting of hydroxides, oxyhydroxides, carbonates and bicarbonates of the covering elements is used. Those that produce strongly acidic chemical species due to decomposition of nitrates, etc. cause degradation of the active material, such as elution of metal components from the surface of the composite oxide particles by the strong acid, and also due to decomposition of organic acid salts, etc. The reason why a large amount of carbon is generated is that it is not preferable because the oxidation number of transition metals such as nickel is affected by the reducing ability, and the charging / discharging ability is adversely affected. Specifically, if it is a lithium compound, lithium hydroxide anhydride, lithium hydroxide monohydrate, lithium carbonate, lithium hydrogen carbonate, etc. may be mentioned, and if it is a nickel compound, nickel hydroxide, nickel carbonate, Or nickel oxyhydroxide etc. are mentioned, If it is a manganese compound, manganese hydroxide, manganese oxyhydroxide, manganese carbonate etc. will be mentioned.

  The precursor particles may also include other elements described above, magnesium, aluminum, boron, titanium, vanadium, chromium, iron, cobalt, copper, zinc, molybdenum, tin, tungsten, zirconium, yttrium, niobium, calcium, or strontium. One or more of these hydroxides, oxyhydroxides, carbonates or bicarbonates may be mixed.

  Next, the composite oxide particles coated with the precursor particles are heat-treated to form an oxide coating layer containing a coating element (step S102). The heat treatment is preferably performed at a temperature of about 300 ° C. to 1000 ° C. in an oxidizing atmosphere such as air or pure oxygen. In that case, the decomposition | disassembly with the decomposition | disassembly of precursor particle | grains and the sintering on the surface of complex oxide particle | grains occurs, and the coverage of a coating layer and the uniformity of a composition are improved.

  In addition, before forming a precursor layer, you may make it complex oxide particle | grains crush secondary particles with a ball mill or a crusher etc. as needed. Moreover, after forming a coating layer, you may make it adjust the particle size of a positive electrode active material by performing a light grinding | pulverization or classification operation etc. as needed.

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

(First secondary battery)
FIG. 2 shows a cross-sectional structure of a first secondary battery using the positive electrode active 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.

  The wound electrode body 20 is wound around a center pin 24, for example. 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. 3 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 cathode active material layer 21B includes, for example, a particulate cathode active material according to the present embodiment, and a conductive agent such as graphite and a binder such as polyvinylidene fluoride as necessary. Furthermore, you may contain the other 1 type, or 2 or more types of positive electrode active material.

  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.

  Examples of the negative electrode material capable of inserting and extracting lithium include non-graphitizable carbon, graphitizable carbon, graphite, pyrolytic carbons, cokes, glassy carbons, and fired organic polymer compounds , Carbon materials such as carbon fiber or activated carbon. Among these, examples of coke include pitch coke, needle coke, and petroleum coke. An organic polymer compound fired body is a carbonized material obtained by firing a polymer material such as a phenol resin or a furan resin at an appropriate temperature, and part of it is non-graphitizable carbon or graphitizable carbon. Some are classified as: These carbon materials are preferable because the change in crystal structure that occurs during charge and discharge is very small, a high charge and discharge capacity can be obtained, and good cycle characteristics can be obtained. In particular, graphite is preferable because it has a high electrochemical equivalent and can provide a high energy density. Further, non-graphitizable carbon is preferable because excellent cycle characteristics can be obtained. Furthermore, those having a low charge / discharge potential, specifically, those having a charge / discharge potential close to that of lithium metal are preferable because a high energy density of the battery can be easily realized.

  Examples of the negative electrode material capable of inserting and extracting lithium include materials capable of inserting and extracting lithium and containing 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 metal elements or metalloid elements constituting the negative electrode material include magnesium, boron, aluminum, gallium (Ga), indium (In), silicon (Si), germanium (Ge), tin, lead (Pb), bismuth ( Bi), 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.

  Examples of the negative electrode material capable of inserting and extracting lithium further include other metal compounds or polymer materials. Other metal compounds include oxides such as iron oxide, ruthenium oxide, molybdenum oxide, tungsten oxide, titanium oxide or tin oxide, sulfides such as nickel sulfide or molybdenum sulfide, or nitrides such as lithium nitride, Examples of the polymer material include polyacetylene and polypyrrole.

  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, N-methylpyrrolidone, acetonitrile, N, N— Dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methylsulfolane, propionitrile, anisole, acetate, butyrate, or A propionic acid ester is mentioned. 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. The lithium _{salt, LiPF 6, LiBF 4, LiAsF} 6, LiClO 4, LiB (C 6 H 5) 4, LiCH 3 SO 3, LiCF 3 SO 3, LiN (SO 2 CF 3) 2, LiC (SO 2 CF ₃ ) ₃ , LiAlCl ₄ , LiSiF ₆ , LiCl, difluoro [oxolato-O, O ′] lithium borate, lithium bisoxalate borate, or LiBr.

  Note that the open circuit voltage (that is, the battery voltage) at the time of full charge of the secondary battery may be 4.20V, but it is designed to be higher than 4.20V and not lower than 4.25V and lower than 4.80V. It is preferable. The energy density can be increased by increasing the battery voltage, and according to the present embodiment, the chemical stability of the positive electrode active material is improved, so that an excellent cycle even if the battery voltage is increased. 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 active material than when the battery voltage is set to 4.20 V, the amounts of the positive electrode active 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 active material, a conductive agent, and a binder to prepare a positive electrode mixture, and then using the positive electrode mixture in a solvent such as N-methyl-2-pyrrolidone. It is formed by dispersing to form a paste-like positive electrode mixture slurry, applying this positive electrode mixture slurry to the positive electrode current collector 21A, drying the solvent, and compression molding with a roll press 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. 2 and 3 is formed.

  In this secondary battery, when charged, lithium ions are released from the positive electrode active material layer 21B, and the negative electrode material that can occlude and release lithium contained in the negative electrode active material layer 22B via the electrolytic solution. Occluded. Next, when discharging is performed, lithium ions stored in the negative electrode material capable of inserting and extracting lithium in the negative electrode active material layer 22B are released, and are inserted into the positive electrode active material layer 21B through the electrolytic solution. . In this embodiment, since the positive electrode active material described above is used, the chemical stability of the positive electrode 21 is high, and even if the open circuit voltage during full charge is increased, the positive electrode 21 and the electrolyte are deteriorated. The reaction is suppressed.

(Secondary secondary battery)
FIG. 4 illustrates a configuration of a second secondary battery using the positive electrode active 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. 5 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 obtained by stacking and winding a positive electrode 33 and a negative electrode 34 with a separator 35 and an electrolyte layer 36 interposed therebetween, 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 polyacrylonitrile, polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polytetrafluoroethylene, polyhexafluoropropylene, polyethylene oxide, polypropylene oxide, polyphosphazene, and polysiloxane. , Polyvinyl acetate, polyvinyl alcohol, polymethyl methacrylate, polyacrylic acid, polymethacrylic acid, styrene-butadiene rubber, nitrile-butadiene rubber, polystyrene or polycarbonate. In particular, from the viewpoint of electrochemical stability, polyacrylonitrile, polyvinylidene fluoride, polyhexafluoropropylene, or polyethylene oxide is preferable.

  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. 4 and 5 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, a polymerization initiator, and other materials such as a polymerization inhibitor as required is injected into the exterior member 40. The opening of the exterior member 40 is sealed. Thereafter, heat is applied to polymerize the monomer to form a polymer compound, thereby forming a 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.

  Thus, according to the present embodiment, since the precursor particles are mixed and deposited on the composite oxide particles, the binding property of the precursor particles to the composite oxide particles can be improved, The coverage of the coating layer can be improved. Further, the composition of the coating layer can be easily controlled. Therefore, the chemical stability of the positive electrode active material can be improved, high capacity can be obtained, and charge / discharge efficiency can be improved.

  In particular, a higher effect can be obtained if the precursor particles are deposited on the composite oxide particles by applying a shearing force while compressing.

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

(Examples 1-1 to 1-3)
As Examples 1-1 to 1-3 and Comparative Examples 1-1 and 1-2 corresponding thereto, positive electrode active materials were prepared as follows.

In Example 1-1, first, as the composite oxide particles, lithium cobaltate powder having an average composition of Li _1.03 CoO ₂ and an average particle diameter measured by a laser scattering method of 13 μm was prepared, and as precursor particles A mixture prepared by mixing lithium carbonate powder, nickel hydroxide powder, and manganese carbonate powder at a molar ratio of Li ₂ CO ₃ : Ni (OH) ₂ : MnCO ₃ = 1.08: 1: 1 was prepared. Then, the precursor particles, then the average particle size by a wet process is ground to a 1μm or less by ball mill, and dried under reduced pressure at 70 ° C., the composite oxide particles 100 parts by weight, Li _1.08 Ni _0.5 Mn It was added in an amount of 10 parts by weight in terms of _0.5 O _2, and the precursor particles is deposited in one hour to the surface of the composite oxide particles by mechanofusion device. Subsequently, this was heated at a rate of 3 ° C./min, held at 800 ° C. for 3 hours, and then gradually cooled to form a coating layer to obtain a positive electrode active material.

In Example 1-2, lithium hydroxide powder, nickel hydroxide powder, and manganese hydroxide powder were used as precursor particles, LiOH ₃ : Ni (OH) ₂ : Mn (OH) ₂ = 1.08: A positive electrode active material was produced in the same manner as in Example 1-1 except that a mixture with a molar ratio of 0.5: 0.5 was used.

In Example 1-3, as precursor particles, lithium carbonate powder, nickel oxyhydroxide powder, and manganese oxyhydroxide powder were mixed at a molar ratio of Li ₂ CO ₃ : NiOOH: MnOOH = 1.08: 1: 1. A positive electrode active material was produced in the same manner as in Example 1-1 except that a mixture in a ratio was used.

  Using the produced positive electrode active materials of Examples 1-1 to 1-3 together with a scanning electron microscope (SEM) and an energy dispersive X-ray fluorescence spectrometer (EDX) As a result, oxide particles containing nickel and manganese having a particle size of about 0.1 μm to 5 μm are deposited on the surface of the composite oxide particles. It was observed that it was present almost uniformly on the surface. The average particle diameter of the positive electrode active material was about 13.5 μm.

On the other hand, in Comparative Example 1-1, the lithium cobaltate powder used as the composite oxide particles in Examples 1-1 to 1-3 was used as a positive electrode active material as it was. In Comparative Example 1-2, first, lithium nitrate powder, nickel nitrate powder, and manganese nitrate powder were used as precursor particles, and LiNO ₃ : Ni (NO ₃ ) ₂ .6H ₂ O: Mn (NO ₃ ) _2. A mixture of 6H ₂ O = 1.08: 0.5: 0.5 is prepared, and 10 parts by mass in terms of Li _1.08 Ni _0.5 Mn _0.5 O ₂ is converted into 300 parts by mass of pure water. After being added and dissolved, 100 parts by mass of the same composite oxide particles as in Examples 1-1 to 1-3 were added and mixed, and evaporated to dryness to the surface of the composite oxide particles. Precursor particles were deposited. Subsequently, this was heat-processed on the same conditions as Example 1-1 to 1-3, the coating layer was formed, and the positive electrode active material was obtained.

  Using the produced positive electrode active materials of Examples 1-1 to 1-3 and Comparative Examples 1-1 and 1-2, secondary batteries as shown in FIGS. First, 86% by mass of the prepared positive electrode active material powder, 10% by mass of graphite as a conductive agent, and 4% by mass of polyvinylidene fluoride as a binder were mixed, and N-methyl-2-pyrrolidone as a solvent was mixed. After being dispersed to form a positive electrode mixture slurry, it is uniformly coated on both surfaces of a positive electrode current collector 21A made of a 20 μm-thick striped aluminum foil, dried, and compression-molded with a roll press to form a positive electrode active material layer 21B Thus, the positive electrode 21 was produced. After that, an aluminum positive electrode lead 25 was attached to one end of the positive electrode current collector 21A.

  In addition, 90% by mass of artificial graphite powder as a negative electrode active material and 10% by mass of polyvinylidene fluoride as a binder are mixed and dispersed in N-methyl-2-pyrrolidone as a solvent to form a negative electrode mixture slurry. After that, the negative electrode 22 was produced by uniformly applying and drying both sides of the negative electrode current collector 22A made of a strip-shaped copper foil having a thickness of 10 μm, and compression forming with a roll press to form the negative electrode active material layer 22B. . At that time, the amounts of the positive electrode active material and the negative electrode active material are adjusted so that the open circuit voltage at the time of full charge is 4.4 V, and the capacity of the negative electrode 22 is represented by a capacity component due to insertion and extraction of lithium. Designed. After that, a nickel negative electrode lead 26 was attached to one end of the negative electrode current collector 22A.

Next, the produced positive electrode 21 and negative electrode 22 were wound many times through a separator 23 made of a porous polyolefin film, to produce a wound electrode body 20. Subsequently, 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. It was stored inside a plated iron battery can 11. After that, by injecting an electrolyte into the battery can 11 and caulking the battery can 11 through the gasket 17, the safety valve mechanism 15, the heat sensitive resistance element 16 and the battery lid 14 are fixed, and the outer diameter is 18 mm. A cylindrical secondary battery having a height of 65 mm was obtained. 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 dimethyl carbonate were mixed at an equal volume ratio was used.

  The fabricated secondary batteries of Examples 1-1 to 1-3 and Comparative Examples 1-1 and 1-2 were charged and discharged at 45 ° C., and the initial capacity and cycle characteristics were examined. Charging is performed at a constant current of 1000 mA until the battery voltage reaches 4.4 V, and then charged at a constant voltage until the total charging time reaches 2.5 hours. did. The discharge was performed at a constant current of 800 mA until the battery voltage reached 3.0 V, and the battery was completely discharged. The initial capacity was the discharge capacity at the first cycle, and the cycle characteristics were obtained by calculating the capacity retention ratio of the discharge capacity at the 200th cycle relative to the initial capacity by (discharge capacity at the 200th cycle / initial capacity) × 100. The obtained results are shown in Table 1.

  As shown in Table 1, according to Examples 1-1 to 1-3 in which precursor particles were deposited by mechanofusion, Comparative Example 1-1 in which a coating layer was not formed, and precursor particles Compared with Comparative Example 1-2 deposited by evaporation to dryness, the discharge capacity retention rate could be greatly improved. That is, it was found that if the precursor particles are deposited by mixing, the chemical stability of the positive electrode active material is improved and the cycle characteristics can be improved. It has also been found that good results can be obtained if at least one of hydroxide, oxyhydroxide and carbonate is used for the precursor particles.

(Examples 2-1 and 2-2)
Except that the average composition of the composite oxide particles was changed, the precursor particles were deposited by mechanofusion in the same manner as in Example 1-1 to produce a positive electrode active material and a secondary battery. At that time, in Example 2-1, composite oxide particles having an average composition of Li _1.03 Co _0.98 Al _0.01 Mg _0.01 O ₂ were used, and in Example 2-2, an average composition of Li _1.03 Co _0.333 Ni _0.333 Mn _0.333 O ₂ was used. Composite oxide particles were used. Further, as Comparative Example 2-1 for this example, evaporation to dryness was performed in the same manner as Comparative Example 1-2, except that composite oxide particles having an average composition of Li _1.03 Co _0.98 Al _0.01 Mg _0.01 O ₂ were used. Thus, the precursor particles were deposited to prepare a positive electrode active material and a secondary battery.

  For the fabricated secondary batteries of Examples 2-1 and 2-2 and Comparative Example 2-1, the initial capacity and cycle characteristics were examined in the same manner as in Example 1-1. The results are shown in Table 2 together with the results of Example 1-1 and Comparative example 1-2.

  As shown in Table 2, also in Examples 2-1 and 2-2, as in Example 1-1, from Comparative Examples 1-2 and 2-1 where precursor particles were deposited by evaporation to dryness Even the capacity maintenance rate could be greatly improved. Further, Examples 2-1 and 2-2 using composite oxide particles in which a part of cobalt was substituted with another element M had a capacity retention rate higher than that of Example 1-1 using lithium cobaltate. We were able to improve more. However, in Example 2-2 in which the substitution amount of the other element M was increased, a decrease in capacity was observed. That is, composite oxide particles in which a part of cobalt is substituted with another element M may be used, but it has been found that the composition ratio of the element M is preferably smaller than 0.5.

(Examples 3-1 to 3-5)
Except that the composition of the precursor particles was changed to change the composition of the coating layer, except that the precursor particles were deposited by mechanofusion in the same manner as in Example 1-1 to obtain the positive electrode active material and the secondary battery. Produced. At that time, in Example 3-1, the lithium carbonate powder, the nickel hydroxide powder, and the manganese carbonate powder were mixed with Li ₂ CO ₃ : Ni (OH) ₂ : MnCO ₃ = 1.08: 1.6: 0. Precursor particles mixed at a molar ratio of .4 were used. In Example 3-2, precursor particles in which lithium carbonate powder and nickel hydroxide powder were mixed at a molar ratio of Li ₂ CO ₃ : Ni (OH) ₂ = 0.54: 1 were used. In Example 3-3, precursor particles in which lithium carbonate powder and manganese hydroxide powder were mixed at a molar ratio of Li ₂ CO ₃ : Mn (OH) ₂ = 0.27: 1 were used. In Example 3-4, lithium carbonate powder, nickel hydroxide powder, manganese carbonate powder, and cobalt hydroxide powder were mixed with Li ₂ CO ₃ : Ni (OH) ₂ : MnCO ₃ : Co (OH) ₂ = Precursor particles mixed at a molar ratio of 1.06: 0.333: 0.333: 0.333 were used. In Example 3-5, lithium carbonate powder, nickel hydroxide powder, manganese carbonate powder, and cobalt hydroxide powder were mixed with Li ₂ CO ₃ : Ni (OH) ₂ : MnCO ₃ : Co (OH) ₂ = Precursor particles mixed at a molar ratio of 1.06: 0.5: 0.3: 0.2 were used.

  For the fabricated secondary batteries of Examples 3-1 to 3-5, the initial capacity and the cycle characteristics were examined in the same manner as in Example 1-1. The results are shown in Table 3 together with the results of Example 1-1 and Comparative Examples 1-1 and 1-2.

  As shown in Table 3, Examples 1-1 and 3-1 in which a coating layer containing nickel and manganese was formed had Examples 3-2 and 3 in which a coating layer containing only one of them was formed. Compared to -3, a higher capacity retention rate could be obtained. That is, it has been found that it is preferable to include nickel and manganese in the coating layer because the chemical stability can be further improved.

  In addition, in Examples 3-4 and 3-5 in which the coating layer is formed by adding other elements in addition to nickel and manganese, the capacity retention rate can be improved as in Example 1-1. It was. That is, it has been found that the coating layer may be formed by adding elements other than nickel and manganese.

(Examples 4-1 to 4-5, 5-1 and 5-2)
Example 1-1 or Example except that the amount of the precursor particles added to 100 parts by mass of the composite oxide particles was changed to Li _1.08 Ni _0.5 Mn _0.5 O ₂ and changed as shown in Table 4. In the same manner as in 2-1, a positive electrode active material and a secondary battery were produced. At that time, in Examples 4-1 to 4-5, Li _1.03 CoO ₂ was used for the composite oxide particles as in Example 1-1, and in Examples 5-1 and 5-2, Example 2- As in 1, Li _1.03 Co _0.98 Al _0.01 Mg _0.01 O ₂ was used for the composite oxide particles.

  For the fabricated secondary batteries of Examples 4-1 to 4-5, 5-1 and 5-2, the initial capacity and cycle characteristics were examined in the same manner as in Examples 1-1 and 2-1. The results are shown in Table 4 together with the results of Example 1-1 and Example 2-1.

  As shown in Table 4, when the amount of the coating layer was increased, the capacity retention ratio was improved, but the capacity tended to decrease. That is, the amount of the coating layer is preferably in the range of 2% by mass to 30% by mass of the composite oxide particles, and more preferably in the range of 5% by mass to 20% by mass. .

(Examples 6-1 to 6-3)
Using the same positive electrode active material as in Example 1-1, the amounts of the positive electrode active material and the negative electrode active material were adjusted so that the open circuit voltage at the time of full charge was 4.2 V, 4.3 V, or 4.5 V. Except for this, a secondary battery was fabricated in the same manner as in Example 1-1. Further, as Comparative Examples 6-1 to 6-3 for this example, the same positive electrode active material as Comparative Example 1-1, that is, lithium cobaltate used for the composite oxide particles in Example 1-1 was used as the positive electrode active material. Example 1-1 except that the amounts of the positive electrode active material and the negative electrode active material were adjusted so that the open circuit voltage during full charge was 4.2 V, 4.3 V, or 4.5 V. A secondary battery was fabricated in the same manner as described above.

  The fabricated secondary batteries of Examples 6-1 to 6-3 and Comparative Examples 6-1 to 6-3 were charged and discharged in the same manner as in Example 1-1, and the initial capacity and cycle characteristics were examined. . At that time, the charging voltage was changed to 4.2V, 4.3V, or 4.5V, respectively. The results are shown in Table 5.

  As shown in Table 5, according to Comparative Examples 1-1, 6-1 to 6-3 in which no coating layer is provided, the initial capacity is improved as the charging voltage is increased, but the capacity maintenance rate is greatly increased. Declined. On the other hand, according to Examples 1-1, 6-1 to 6-3 provided with the above-described coating layers, the decrease in the capacity retention rate is small, and Comparative Examples 1-1, 6-1 to 6-3. It was possible to improve significantly compared to. In addition, the effect was greater as the charging voltage was increased. That is, it was found that a higher effect can be obtained when the battery voltage is higher than 4.2V.

  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 electrolyte solution that is a liquid electrolyte or a gel electrolyte in which an electrolyte solution is held in a polymer compound has been described. However, other electrolytes may be used. Good. Other electrolytes include, for example, a polymer electrolyte in which an electrolyte salt is dispersed in a polymer compound having ion conductivity, an inorganic solid electrolyte made of ion conductive ceramics, ion conductive glass, or ionic crystals, or a molten salt electrolyte. Or a mixture thereof.

  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, or square type. Moreover, not only a secondary battery but a primary battery is applicable.

It is a flowchart showing the manufacturing method of the positive electrode active material which concerns on one embodiment of this invention. It is sectional drawing showing the structure of the 1st secondary battery using the positive electrode active 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 active material which concerns on one embodiment of this invention. It is sectional drawing along the II line 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 (15)

An oxide coating layer containing a coating element of at least one of lithium, nickel (Ni), and manganese (Mn) is formed on at least a part of the composite oxide particles containing lithium (Li) and cobalt (Co). A positive electrode active material formed,
The coating layer adheres the composite oxide particles by mixing precursor particles containing at least one of the group consisting of hydroxide, oxyhydroxide, carbonate and bicarbonate of the coating element. And a positive electrode active material formed by heat treatment. 2. The positive electrode active material according to claim 1, wherein an average composition of the composite oxide particles is represented by Chemical Formula 1. 3.
(Chemical formula 1)
_{Li (1 + x) Co (} 1-y) M y O (2-z)
(In chemical formula 1, M is magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni ), Copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), tungsten (W), zirconium (Zr), yttrium (Y), niobium (Nb), calcium (Ca) and strontium (Sr) ), And x, y, and z are −0.10 ≦ x ≦ 0.10, 0 ≦ y <0.50, and −0.10 ≦ z ≦ 0.20, respectively. It is a value within the range.)   2. The positive electrode active material according to claim 1, wherein a composition ratio of nickel and manganese in the coating layer is in a range of 90:10 to 30:70 as a molar ratio of nickel: manganese.   The oxide of the coating layer is further selected from the group consisting of magnesium, aluminum, boron, titanium, vanadium, chromium, iron, cobalt, copper, zinc, molybdenum, tin, tungsten, zirconium, yttrium, niobium, calcium and strontium. The positive electrode active material according to claim 1, comprising at least one of the following.   2. The positive electrode active material according to claim 1, wherein an amount of the coating layer is in a range of 2% by mass to 30% by mass of the composite oxide particles.   2. The positive electrode active material according to claim 1, wherein an average particle diameter is in a range of 2.0 μm to 50 μm. An oxide coating layer containing a coating element of at least one of lithium, nickel (Ni), and manganese (Mn) is formed on at least a part of the composite oxide particles containing lithium (Li) and cobalt (Co). A method for producing a formed positive electrode active material, comprising:
A mixture of precursor particles containing at least one member selected from the group consisting of hydroxide, oxyhydroxide, carbonate and bicarbonate of the covering element is mixed with at least a part of the composite oxide particles. Wearing process;
Forming a coating layer by applying a heat treatment after depositing the precursor particles. 8. The method for producing a positive electrode active material according to claim 7, wherein the composite oxide particles are those having an average composition represented by chemical formula (1).
(Chemical formula 1)
_{Li (1 + x) Co (} 1-y) M y O (2-z)
(In chemical formula 1, M is magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni ), Copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), tungsten (W), zirconium (Zr), yttrium (Y), niobium (Nb), calcium (Ca) and strontium (Sr) ), And x, y, and z are −0.10 ≦ x ≦ 0.10, 0 ≦ y <0.50, and −0.10 ≦ z ≦ 0.20, respectively. It is a value within the range.)   The method for producing a positive electrode active material according to claim 7, wherein the precursor particles are applied to the composite oxide particles by applying a shearing force while being compressed. A battery including an electrolyte together with a positive electrode and a negative electrode,
The positive electrode includes an oxide containing a covering element of at least one of lithium, nickel (Ni), and manganese (Mn) in at least part of a composite oxide particle containing lithium (Li) and cobalt (Co). Containing a positive electrode active material with a coating layer of
The coating layer adheres the composite oxide particles by mixing precursor particles containing at least one of the group consisting of hydroxide, oxyhydroxide, carbonate and bicarbonate of the coating element. And a battery formed by heat treatment. The battery according to claim 10, wherein an average composition of the composite oxide particles is represented by Chemical Formula 1.
(Chemical formula 1)
_{Li (1 + x) Co (} 1-y) M y O (2-z)
(In chemical formula 1, M is magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni ), Copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), tungsten (W), zirconium (Zr), yttrium (Y), niobium (Nb), calcium (Ca) and strontium (Sr) ), And x, y, and z are −0.10 ≦ x ≦ 0.10, 0 ≦ y <0.50, and −0.10 ≦ z ≦ 0.20, respectively. It is a value within the range.)   11. The battery according to claim 10, wherein a composition ratio of nickel and manganese in the coating layer is in a range of 90:10 to 30:70 as a molar ratio of nickel: manganese.   The oxide of the coating layer is further selected from the group consisting of magnesium, aluminum, boron, titanium, vanadium, chromium, iron, cobalt, copper, zinc, molybdenum, tin, tungsten, zirconium, yttrium, niobium, calcium and strontium. The battery according to claim 10, comprising at least one of the following.   11. The battery according to claim 10, wherein the amount of the coating layer is in the range of 2% by mass to 30% by mass of the composite oxide particles.   The battery according to claim 10, wherein the average particle diameter is in a range of 2.0 μm to 50 μm.

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