JP4992200B2 - Cathode active material for lithium ion secondary battery and lithium ion secondary battery - Google Patents

Description

The present invention relates to a lithium ion secondary battery using a lithium ion secondary battery positive electrode active material containing a composite oxide and it containing lithium (Li) and cobalt (Co).

  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, a different element such as aluminum (Al), magnesium (Mg), zirconium (Zr) or titanium (Ti) is dissolved (see Patent Document 2). ), A mixture of a small amount of lithium nickel manganese composite oxide or the like (see Patent Document 3), or lithium cobalt manganate having a spinel structure on the surface of lithium cobaltate, lithium titanate having a spinel structure, or nickel cobalt composite Coating with an oxide (see Patent Documents 4 and 5) has been reported.
International Publication No. WO03 / 0197131 Pamphlet JP 2004-303459 A JP 2002-1003007 A JP-A-10-333573 JP-A-10-372470 Japanese Patent Laid-Open No. 2987358 JP 2004-227869 A Japanese Patent Laid-Open No. 10-236826

  However, the technique of dissolving different elements in a solid solution has a problem that the high temperature characteristics or the cycle characteristics cannot be sufficiently improved if the amount of the solid solution is small, and the capacity decreases if the amount of the solid solution is large. Further, the technique using a mixture of lithium nickel manganese composite oxide and the like has a problem that the characteristics cannot be sufficiently improved. Furthermore, the technology of coating with lithium manganate or lithium titanate has a problem that the capacity is reduced, and in the case of lithium manganate, there is also a problem that the characteristics are deteriorated due to elution of manganese (patent). References 6 and 7). In addition, the technique of coating with nickel-cobalt composite oxide reduces thermal stability (see Patent Document 8), and has a lower discharge potential than lithium cobaltate, which is disadvantageous for increasing the energy density. There was also a problem of being.

The present invention has been made in view of such a problem, and an object of the present invention is to provide a positive electrode active material for a lithium ion secondary battery capable of increasing capacity and improving high-temperature characteristics or cycle characteristics, and the same. It is in providing the used lithium ion secondary battery.

Cathode active material for a lithium ion secondary battery according to the present invention, the average composition of _{Li (1 + x) Co (} 1-y) M y O (2-z) ( where, M is magnesium, aluminum, boron (B) , Titanium, vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), tungsten ( W), zirconium, yttrium (Y), niobium (Nb), calcium (Ca), and strontium (Sr), and x, y, and z are each −0.10 ≦ x ≦ 0.10, 0 ≦ y <0.50, and −0.10 ≦ z ≦ 0.20.) And at least one of the composite oxide particles And lithium, nickel, man And a coating layer made of oxide containing emissions, oxide containing lithium, nickel and manganese, which consists of lithium, nickel, and manganese, and oxygen, or lithium, and nickel, At least one selected from the group consisting of manganese and magnesium, aluminum, boron, titanium, vanadium, chromium, iron, cobalt (Co), copper, zinc, molybdenum, tin, tungsten, zirconium, yttrium, niobium, calcium, and strontium And the content of at least one element of the group in the coating layer is 40 mol% or less with respect to the total of nickel and manganese in the coating layer and at least one element of the group ones, and the in the diffraction peaks obtained by CuKα X-ray powder diffraction, the composite oxide particle Than the diffraction angle 2θ of the diffraction peak assigned to [101] plane of the lower angle side in the range of 0.2 ° or more 1.0 ° or less, and has a diffraction peak of the coating layer.

A lithium ion secondary battery according to the present invention is provided with an electrolyte together with a positive electrode and a negative electrode, and the positive electrode contains a positive electrode active material in which a coating layer is provided on at least a part of the composite oxide particles. oxide particles, average composition _{Li (1 + x) Co (} 1-y) M y O (2-z) ( where, M is magnesium, aluminum, boron, titanium, vanadium, chromium, manganese, iron, nickel , Copper, zinc, molybdenum, tin, tungsten, zirconium, yttrium, niobium, calcium, and strontium, and x, y, and z are −0.10 ≦ x ≦ 0.10, respectively. , 0 ≦ y <0.50, −0.10 ≦ z ≦ 0.20), and the coating layer is made of an oxide containing lithium, nickel, and manganese. , lithium The oxide containing nickel, nickel, and manganese is composed of lithium, nickel, manganese, and oxygen, or lithium, nickel, manganese, magnesium, aluminum, boron, titanium, vanadium, chromium, At least one element of the group consisting of iron, cobalt (Co), copper, zinc, molybdenum, tin, tungsten, zirconium, yttrium, niobium, calcium and strontium, and at least of the group in the coating layer The content of one element is 40 mol% or less with respect to the total of at least one element of nickel and manganese in the coating layer, and the positive electrode active material is obtained by CuKα powder X-ray diffraction. In the obtained diffraction peak, the diffraction peak attributed to the [101] plane of the composite oxide particle. It has a diffraction peak of the coating layer on the lower angle side within the range of 0.2 ° to 1.0 ° with respect to the diffraction angle 2θ of the copper.

According to the lithium ion secondary battery positive electrode active material of the present invention, the lithium composite oxide particles having an average composition represented by _{Li (1 + x) Co (} 1-y) M y O (2-z) A coating layer made of an oxide containing nickel and manganese is provided, and the diffraction angle 2θ of the diffraction peak attributed to the [101] plane of the composite oxide particles is within the range of 0.2 ° or more and 1.0 ° or less. Since the diffraction peak of the coating layer is provided on the low angle side, the chemical stability of the positive electrode active material can be improved while taking advantage of the high capacity and high potential of the composite oxide particles. Therefore, according to the lithium ion secondary battery of the present invention using the positive electrode active material for the lithium ion secondary battery, it is possible to obtain a high capacity, it can improve the high temperature characteristics or cycle characteristics.

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

  The positive electrode active material according to one embodiment of the present invention has a coating layer provided on at least a part of the composite oxide particles having an average composition represented by Chemical Formula 1. In this positive electrode active material, a high capacity and a high discharge potential can be obtained by configuring the average composition of the composite oxide particles as shown in Chemical Formula 1.

(Chemical formula 1)
_{Li (1 + x) Co (} 1-y) M y O (2-z)
In Formula 1, M is at least one selected from the group consisting of magnesium, aluminum, boron, titanium, vanadium, chromium, manganese, iron, nickel, copper, zinc, molybdenum, tin, tungsten, zirconium, yttrium, niobium, calcium, and strontium. One type.

  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.

  A coating layer functions as a reaction suppression layer, and is comprised with the oxide containing lithium, nickel, and manganese. This is because by having such a composition, chemical stability can be improved while suppressing a decrease in capacity.

  This coating layer has a diffraction peak obtained by CuKα powder X-ray diffraction in a range of 0.2 ° or more and 1.0 ° or less than the diffraction angle 2θ of the diffraction peak attributed to the [101] plane of the composite oxide particle. The diffraction peak is present on the lower angle side. The diffraction peak of the coating layer present on the lower angle side than the diffraction peak attributed to the [101] plane of the composite oxide particle is not within the above range, and the difference is within a range smaller than 0.2 °. In this case, when the coating layer is formed, the solid oxide particles and the coating layer are solid-dissolved, and the effect as the reaction suppressing layer is reduced, and the difference is within a range larger than 1.0 °. This is because the coating layer has poor adhesion and a good coating state cannot be obtained. In particular, it is more preferable if the diffraction peak of the coating layer is in the range of 0.3 ° or more and 0.55 ° or less on the lower angle side than the diffraction peak attributed to the [101] plane of the composite oxide particle. This is because a higher effect can be obtained.

  In the X-ray diffraction measurement, Cu-Kα1 (wavelength 0.15405 nm) is used as the X-ray source, and the diffraction angle 2θ of the diffraction peak of the coating layer and the composite oxide particles is derived from Cu-Kα1. Read at the peak top position.

  Composition ratio of nickel and manganese in the coating layer The nickel: manganese molar ratio is preferably in the range of 90:10 to 30:70, and in the range of 70:30 to 40:60. More preferred. This is because if the amount of manganese is larger than this, the occlusion amount of lithium in the coating layer decreases, the capacity of the positive electrode active material decreases, and the electrical resistance increases. Moreover, when there is more nickel than this, the thermal stability of a coating layer will fall and a high temperature characteristic will fall. That is, by setting the composition ratio of nickel and manganese within this range, the stability at high temperature can be further increased and the capacity can be further increased.

  The oxide of the covering 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.

  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.

  The positive electrode active material is obtained, for example, by forming a precursor layer of a coating layer on the above-described composite oxide particles and firing at a temperature of 300 ° C. to 1000 ° C. in an oxidizing atmosphere such as air or pure oxygen. be able to. As a material for the precursor layer, a material that can be converted into an oxide by firing such as hydroxide, carbonate or nitrate containing an element constituting the coating layer can be used, and the oxide or coating layer constituting the coating layer can be used. A plurality of oxides containing the element to be used may be used. Further, the precursor layer can be applied by, for example, using a ball mill, a jet mill, a pulverizer or a fine powder pulverizer, and pulverizing and mixing the composite oxide particles and the material of the precursor layer. A dispersion medium such as water or a solvent may be used. Alternatively, it may be deposited by a mechanochemical treatment such as mechanofusion, or a vapor phase method such as sputtering or chemical vapor deposition (CVD), or a precursor layer of hydroxide by a neutralization titration method. You may make it adhere. In addition, after forming a coating layer, you may adjust a particle size by performing a light grinding | pulverization or classification operation as needed.

  This positive electrode active 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 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. 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 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), and 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-dikilolane, 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. Lithium salts include 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) 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 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. 1 and 2 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. 3 shows 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. 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 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. 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, 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 obtain 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 diffraction angle 2θ of the diffraction peak attributed to the [101] plane of the composite oxide particle is on the lower angle side within the range of 0.2 ° to 1.0 °. Since the positive electrode active material having the diffraction peak of the coating layer is used, the chemical stability of the positive electrode active material can be improved while taking advantage of the high capacity and high potential of the composite oxide particles. Therefore, a high capacity can be obtained, and high temperature characteristics or cycle characteristics can be improved.

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

(Examples 1-1 to 1-9)
A positive electrode active material was 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 a raw material for the coating layer Lithium carbonate (Li ₂ CO ₃ ) powder, nickel hydroxide (Ni (OH) ₂ ) powder, and manganese carbonate (MnCO ₃ ) powder, Li ₂ CO ₃ : Ni (OH) ₂ : MnCO ₃ = A precursor powder mixed at a molar ratio of 1.08: 1: 1 was prepared. Next, the precursor powder is added to 100 parts by mass of this lithium cobaltate powder so as to be 10 parts by mass in terms of Li _1.08 Ni _0.5 Mn _0.5 O ₂ , and 100 parts by mass of pure water at 25 ° C. is used. After stirring and dispersing for 1 hour, it was dried under reduced pressure at 70 ° C. to form a precursor layer on the surface of the composite oxide particles. 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, except that the same precursor powder as in Example 1-1 was pulverized with a ball mill device until the average particle size became 1 μm or less and mixed with the composite oxide particles, Example 1 was otherwise used. A positive electrode active material was produced in the same manner as in -1.

In Example 1-3, the same precursor powder as in Example 1-1 was pulverized until the average particle size became 1 μm or less with respect to 100 parts by mass of composite oxide particles similar to Example 1-1. By adding 10 parts by mass in terms of Li _1.08 Ni _0.5 Mn _0.5 O ₂ and processing with a mechanofusion apparatus to form a precursor layer, the same heat treatment as in Example 1-1 was performed. A coating layer was formed to produce a positive electrode active material.

  In Example 1-4, a positive electrode active material was produced in the same manner as in Example 1-1 except that the heat treatment temperature was 750 ° C.

  In Example 1-5, a positive electrode active material was produced in the same manner as in Example 1-1 except that the rate of temperature increase during heat treatment was 10 ° C./min and the holding time at 800 ° C. was 2 hours. did.

In Example 1-6, a composite oxide powder having an average composition of Li _1.03 Co _0.98 Al _0.01 Mg _0.01 O ₂ was used as the composite oxide particles, and a precursor powder similar to that in Example 1-1 was averaged using a ball mill device. A positive electrode active material was produced in the same manner as in Example 1-1 except that the mixture was pulverized until the diameter became 1 μm or less and mixed with the composite oxide particles.

In Example 1-7, 100 parts by mass of composite oxide particles similar to Example 1-1, and 10 mass of lithium nickel manganate powder having an average composition of Li _1.03 Ni _0.5 Mn _0.5 O ₂ and an average particle diameter of 3 μm A coating layer is formed by performing a heat treatment at a heating rate of 3 ° C./min, a heat treatment temperature of 650 ° C., and a holding time of 3 hours. Was made.

In Example 1-8, 100 parts by mass of the same composite oxide particles as in Example 1-1, and lithium nickel cobalt manganate having an average composition of Li _1.03 Ni _0.33 Co _0.33 Mn _0.33 O ₂ and an average particle diameter of 3 μm After forming 10 parts by mass of the powder with a mechanofusion device to form a precursor layer, a coating layer is formed by performing a heat treatment at a heating rate of 3 ° C / min, a heat treatment temperature of 650 ° C, and a holding time of 3 hours A positive electrode active material was prepared.

In Example 1-9, first, as a raw material for the coating layer, lithium carbonate powder, nickel hydroxide powder, and manganese carbonate powder were used. Li ₂ CO ₃ : Ni (OH) ₂ : MnCO ₃ = 1.08: The mixture was mixed at a molar ratio of 1.6: 0.4 and pulverized until the average particle size became 1 μm or less to obtain a precursor powder. Next, with respect to 100 parts by mass of the same composite oxide particles as in Example 1-1, this precursor powder is added so as to be 10 parts by mass in terms of Li _1.08 Ni _0.8 Mn _0.2 O ₂ , and a mechanofusion apparatus. After forming a precursor layer by processing, a coating layer was formed by performing the same heat treatment as in Example 1-1, and a positive electrode active material was produced.

Moreover, as Comparative Example 1-1 with respect to the present example, the lithium cobalt oxide powder used as the composite oxide particle in Example 1-1 was used as a positive electrode active material as it was. As Comparative Example 1-2, lithium carbonate (Li ₂ CO ₃ ) powder, cobalt hydroxide (Co (OH) ₂ ) powder, nickel hydroxide (Ni (OH) ₂ ) powder, and manganese carbonate (MnCO ₃ ) The powder was mixed at a molar ratio of Li ₂ CO ₃ : Co (OH) ₂ : Ni (OH) ₂ : MnCO ₃ = 0.52: 0.91: 0.045: 0.045 and averaged by a ball mill device. After pulverizing until the particle size became 1 μm or less, a positive electrode active material was produced by performing a heat treatment at a heating rate of 3 ° C./min, a heating temperature of 900 ° C., and a holding time of 3 hours.

As Comparative Example 1-3, a positive electrode active material was produced in the same manner as in Example 1-1 except that the heat treatment temperature was 1000 ° C. As Comparative Example 1-4, lithium carbonate (Li ₂ CO ₃ ) powder and nickel hydroxide (Ni (OH) ₂ ) powder were used as the raw material for the coating layer, and Li ₂ CO ₃ : Ni (OH) ₂ = 0. A positive electrode active material was prepared in the same manner as in Example 1-1, except that the precursor powder mixed in a molar ratio of .54: 1 was used, and the heat treatment temperature was 700 ° C. As Comparative Example 1-5, lithium carbonate (Li ₂ CO ₃ ) powder and manganese carbonate (MnCO ₃ ) powder were mixed with the raw material of the coating layer at a molar ratio of Li ₂ CO ₃ : MnCO ₃ = 1: 4. Using the prepared precursor powder, a positive electrode active material was produced in the same manner as in Example 1-1 except that the heat treatment temperature was 900 ° C.

  The produced positive electrode active materials of Examples 1-1 to 1-9 and Comparative Examples 1-1 to 1-5 were subjected to powder X-ray diffraction measurement using Cu—Kα1 as an X-ray source. RINT2000 manufactured by Rigaku Denki Co., Ltd. is used as the X-ray diffraction apparatus, the tube voltage is 40 kV, the current is 200 mA, the divergence slit is 0.5 °, the scattering slit is 0.5 °, and the light receiving slit width is 0.15 mm. A meter was used. The measurement was performed under the conditions of a scanning speed of 2 ° / min, a scanning step of 0.02 °, and a scanning axis of 2θ / θ. Of these, the measurement profiles obtained for Example 1-1, Example 1-3, and Comparative Example 1-2 are shown in FIGS.

  As a result, as shown in FIGS. 5 and 6, in each of Examples 1-1 to 1-9, the diffraction peak of the composite oxide particles having a layered rock salt structure, and the lithium oxide containing nickel and manganese And a diffraction peak of the coating layer that is considered to correspond to. The difference in the diffraction angle 2θ between the diffraction peak attributed to the [101] plane of the complex oxide particles seen in the vicinity of 37 ° and the diffraction peak of the coating layer located on the lower angle side than that is the example 1-1. Is 0.44 °, Example 1-2 is 0.40 °, Example 1-3 is 0.24 °, Example 1-4 is 0.52 °, and Example 1-5 is 0.44 °. Example 1-6 was 0.35 °, Example 1-7 was 0.80 °, Example 1-8 was 0.58 °, and Example 1-9 was 0.37 °. The results are shown in Table 1. The diffraction angle of each diffraction peak was read at the peak top position of the obtained measurement profile as described in the embodiment.

  On the other hand, in Comparative Example 1-1 and Comparative Example 1-2, as shown in FIG. 7, the diffraction peak of the complex oxide having a layered rock salt structure is observed, which is observed around 37 ° [101]. There was one diffraction peak attributed to the surface. In Comparative Examples 1-3 to 1-5, similarly to Examples 1-1 to 1-9, the diffraction peak of the composite oxide particles and the diffraction peak of the coating layer were observed, and [ 101] The difference in the diffraction angle 2θ between the diffraction peak attributed to the plane and the diffraction peak of the coating layer located on the lower angle side is 0.1 ° or less in Comparative Example 1-3 and Comparative Example 1-4. Comparative Example 1-5 was 1.10 °. The results are also shown in Table 1.

  Further, the produced positive electrode active materials of Examples 1-1 to 1-9 were scanned 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, and nickel and manganese are composite oxides. It was observed that the particles were present almost uniformly on the surface of the particles. Moreover, all of the average particle diameters of the positive electrode active material were between 2 μm and 50 μm.

  Next, a secondary battery as shown in FIGS. 1 and 2 was produced using these produced positive electrode active materials. 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 1-9 and Comparative examples 1-1 to 1-5 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, the embodiment has a diffraction peak of the coating layer on the low angle side within the range of 0.2 ° to 1.0 ° from the diffraction peak attributed to the [101] plane of the composite oxide particle. According to Examples 1-1 to 1-9, the initial capacities were almost the same as those of Comparative Examples 1-1 and 1-2 in which no coating layer was provided, and the capacity retention rate could be greatly improved. On the other hand, Comparative Examples 1-3 and 1 where the diffraction peak of the coating layer is located on the low angle side within a range of less than 0.2 ° from the diffraction peak attributed to the [101] plane of the composite oxide particle. In Comparative Example 1-5, which is located on the low angle side within the range exceeding 4 and 1.0 °, the capacity retention rate was improved as compared with Comparative Examples 1-1 and 1-2, but The degree was slight. In Comparative Examples 1-4 and 1-5, the initial capacity was also reduced.

  That is, if the diffraction peak of the coating layer is on the low angle side within the range of 0.2 ° or more and 1.0 ° or less than the diffraction peak attributed to the [101] plane of the composite oxide particle, the capacity is increased. It has been found that high temperature characteristics and cycle characteristics can be improved as well as higher.

(Examples 2-1 to 2-4)
A positive electrode active material and a secondary battery were produced in the same manner as in Example 1-2, except that the coating amount of the coating layer on the composite oxide particles was changed as shown in Table 2. For the prepared positive electrode active materials of Examples 2-1 to 2-4, powder X-ray diffraction measurement using Cu-Kα1 as the X-ray source was performed in the same manner as in Example 1-2. As a result, as in Example 1-2, the diffraction peak of the composite oxide particle and the diffraction peak of the coating layer were observed, and the diffraction peak attributed to the [101] plane of the composite oxide particle was higher than that. The difference in diffraction angle 2θ from the diffraction peak of the coating layer located on the low angle side is 0.28 ° in Example 2-1, 0.36 ° in Example 2-2, and 0. 2 in Example 2-3. 42 ° and Example 2-4 were 0.45 °, both being in the range of 0.2 ° to 1.0 °. In addition, for the fabricated secondary batteries of Examples 2-1 to 2-4, the initial capacity and cycle characteristics were examined in the same manner as in Example 1-2. The results are shown in Table 2.

  As shown in Table 2, according to Examples 2-1 to 2-4, it was possible to significantly improve the capacity retention rate as in Example 1-2. Further, as the amount of the coating layer was increased, the capacity retention rate was improved, but the initial 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 3-1 to 3-3)
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 3-1 to 3-3 for this example, the same positive electrode active material as that of 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.

  For the fabricated secondary batteries of Examples 3-1 to 3-3 and Comparative Examples 3-1 to 3-3, charging and discharging were performed 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 3.

  As shown in Table 3, according to Comparative Examples 1-1 and 3-1 to 3-3 in which no coating layer is provided, the initial capacity is improved as the charging voltage is increased, but the capacity retention rate is greatly increased. Declined. On the other hand, according to Examples 1-1, 3-1 to 3-3 provided with the above-described coating layers, the decrease in the capacity retention rate is small, and Comparative Examples 1-1, 3-1 to 3-3. 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 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. 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, so-called coin type, Ru can be applied for a secondary battery having other shape such as a button type or square type.

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 | wire of the winding electrode body shown in FIG. It is a powder X-ray-diffraction measurement profile of the positive electrode active material which concerns on Example 1-1. It is a powder X-ray-diffraction measurement profile of the positive electrode active material which concerns on Example 1-3. It is a powder X-ray-diffraction measurement profile of the positive electrode active material which concerns on Comparative Example 1-2.

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 (9)

Average composition _{Li (1 + x) Co (} 1-y) M y O (2-z) ( where, 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 each −0.10 ≦ x ≦ 0. .10, 0 ≦ y <0.50, −0.10 ≦ z ≦ 0.20)).
Provided in at least a part of the composite oxide particles, and having a coating layer made of an oxide containing lithium (Li), nickel, and manganese,
The oxide containing lithium, nickel and manganese is
Lithium, nickel, manganese and oxygen
Or from lithium, nickel, manganese, magnesium, aluminum, boron, titanium, vanadium, chromium, iron, cobalt (Co), copper, zinc, molybdenum, tin, tungsten, zirconium, yttrium, niobium, calcium and strontium At least one element of the group, and the content of at least one element of the group in the coating layer is at least one of nickel and manganese in the coating layer and the group 40 mol% or less of the total of the elements,
The diffraction peak obtained by CuKα powder X-ray diffraction has a low angle within the range of 0.2 ° or more and 1.0 ° or less than the diffraction angle 2θ of the diffraction peak attributed to the [101] plane of the composite oxide particle. On the side, it has a diffraction peak of the coating layer
Positive electrode active material for lithium ion secondary batteries . 2. The positive electrode active material for a lithium ion secondary battery according to claim 1 , wherein the composition ratio of nickel and manganese in the coating layer is in a molar ratio of 90:10 to 30:70. The amount of the said coating layer is a positive electrode active material for lithium ion secondary batteries of Claim 1 which exists in the range of 2 mass% or more and 30 mass% or less of the said complex oxide particle. The positive electrode active material for a lithium ion secondary battery according to claim 1 , wherein the average particle diameter is in the range of 2.0 μm or more and 50 μm or less. A cathode and an anode, e Bei electrolyte,
The positive electrode contains a positive electrode active material in which a coating layer is provided on at least a part of the composite oxide particles,
The composite oxide particles have an average composition of _{Li (1 + x) Co (} 1-y) M y O (2-z) ( where, 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), It is at least one member selected from the group consisting of tungsten (W), zirconium (Zr), yttrium (Y), niobium (Nb), calcium (Ca), and strontium (Sr), and x, y, and z are each − 0.10 ≦ x ≦ 0.10, 0 ≦ y <0.50, and −0.10 ≦ z ≦ 0.20.)
The coating layer is made of an oxide containing lithium (Li), nickel, and manganese,
The oxide containing lithium, nickel and manganese is
Lithium, nickel, manganese and oxygen
Or from lithium, nickel, manganese, magnesium, aluminum, boron, titanium, vanadium, chromium, iron, cobalt (Co), copper, zinc, molybdenum, tin, tungsten, zirconium, yttrium, niobium, calcium and strontium At least one element of the group, and the content of at least one element of the group in the coating layer is at least one of nickel and manganese in the coating layer and the group 40 mol% or less of the total of the elements,
The positive electrode active material has a diffraction peak obtained by CuKα powder X-ray diffraction of 0.2 ° or more and 1.0 ° or less than the diffraction angle 2θ of the diffraction peak attributed to the [101] plane of the composite oxide particle. The diffraction peak of the coating layer is present on the low angle side within the range of
Lithium ion secondary battery. The lithium ion secondary battery according to claim 5 , 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 4.80 V or less. 6. The lithium ion secondary battery according to claim 5 , wherein a composition ratio of nickel and manganese in the coating layer is in a range of 90:10 to 30:70 in terms of a molar ratio of nickel: manganese. Wherein the amount of the coating layer, the composite is an oxide in the range of 30 wt% or more 2% by weight of the particles, the lithium ion secondary battery according to claim 5, wherein. The lithium ion secondary battery according to claim 5 , wherein an average particle diameter of the positive electrode active material is in a range of 2.0 μm to 50 μm.

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