JP5040074B2 - Method for producing positive electrode active material for lithium ion secondary battery and lithium ion secondary battery - Google Patents

Description

The present invention, lithium (Li) and cobalt (Co) composite oxide particle method for manufacturing a lithium ion secondary battery positive electrode active material forming the coating layer, and thus obtained lithium ion secondary battery comprising The present invention relates to a lithium ion secondary battery using a positive electrode active material.

  In recent years, with the widespread use of portable devices such as video cameras or laptop computers, the demand for small, high-capacity secondary batteries has increased. Currently used secondary batteries include nickel-cadmium batteries using an alkaline electrolyte, but the battery voltage is as low as 1.2 V, and it is difficult to improve the energy density. Therefore, development of a so-called lithium metal secondary battery using lithium metal having a specific gravity of 0.534, which is the lightest among solid solids, has a very low potential, and has the largest current capacity per unit mass among metal anode materials. Has been studied. However, the lithium metal secondary battery has a problem that lithium is dendriticly grown on the negative electrode with charge / discharge and cycle characteristics are deteriorated or an internal short circuit is caused by breaking through the separator. Accordingly, a secondary battery that repeats charge and discharge by using a carbon material such as coke as the negative electrode and occludes and releases alkali metal ions has been developed, and deterioration of the negative electrode due to charge and discharge has been improved (for example, Patent Document 1). reference).

  On the other hand, transition metal chalcogenides containing alkali metals are known as positive electrode active materials that can obtain a battery voltage of around 4V. Among these, composite oxides such as lithium cobaltate or lithium nickelate are promising in terms of high potential, stability, and long life. In particular, lithium cobaltate exhibits high potential, so by increasing the charging voltage. It is expected to improve the energy density.

  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, 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 dispersed in an aqueous solution, and the metal hydroxide is deposited on the surface of the composite oxide particles by adjusting the hydrogen ion exponent pH, followed by heating. What is processed is known (for example, refer to Patent Documents 2 and 3).
JP 62-90863 A JP-A-9-265985 JP-A-11-71114

  However, when a coating layer is formed by applying a hydroxide containing at least one of nickel and manganese on the surface of the composite oxide particle and then heat-treating it, it is difficult to form the coating layer uniformly. There was a problem. Therefore, further improvement has been required to further improve the characteristics.

The present invention has been made in view of such problems, and an object of the present invention is to provide a method for producing a positive electrode active material for a lithium ion secondary battery capable of improving the uniformity of the coating layer, and a positive electrode active material obtained thereby. An object of the present invention is to provide a lithium ion secondary battery using a substance.

In the method for producing a positive electrode active material for a lithium ion secondary battery according to the present invention, at least part of the composite oxide particles having an average composition represented by Chemical Formula 1 is coated with lithium and at least one of nickel and manganese. A positive electrode active material for a lithium ion secondary battery in which an oxide covering layer is formed, and an intermediate precursor layer of a hydroxide containing cobalt is formed on at least a part of the composite oxide particles A step of forming an intermediate precursor layer, a step of forming a coating precursor layer of a hydroxide containing a coating element on at least a part of the composite oxide particles, and a heat treatment after forming the coating precursor layer. The process of forming a coating layer by this.
(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.)

A lithium ion secondary battery according to the present invention is provided with an electrolyte together with a positive electrode and a negative electrode. The positive electrode includes lithium and nickel in at least part of the composite oxide particles whose average composition is represented by Chemical Formula 1. And a positive electrode active material in which an oxide coating layer containing at least one of the coating elements of manganese is formed. The positive electrode active material contains cobalt (Co) in at least a part of the composite oxide particles. After the hydroxide intermediate precursor layer is formed, a hydroxide coating precursor layer containing a coating element is formed and heat-treated.
(Chemical formula 1)
_{Li (1 + x) Co (} 1-y) M y O (2-z)
(In the chemical formula 1, M is 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. X, y, and z are values in the range of −0.10 ≦ x ≦ 0.10, 0 ≦ y <0.50, and −0.10 ≦ z ≦ 0.20, respectively. .)

According to the method for producing a positive electrode active material for a lithium ion secondary battery of the present invention, after forming an intermediate precursor layer of a hydroxide containing cobalt on the composite oxide particles, a coating precursor of the hydroxide containing a coating element Since the layer is formed, the uniformity of the coating precursor layer can be increased, and the uniformity of the coating layer can be improved.

In addition, according to the lithium ion secondary battery of the present invention, since the positive electrode active material obtained by the method for producing a positive electrode active material for a lithium ion secondary battery of the present invention is used, the charge voltage can be increased. High chemical stability can be obtained. Therefore, a high capacity can be obtained and charge / discharge efficiency can be improved.

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

  FIG. 1 shows the steps of a method for producing a positive electrode active material according to an embodiment of the present invention. In this manufacturing method, after forming an intermediate precursor layer of a hydroxide containing cobalt on at least a part of the composite oxide particles having an average composition represented by Chemical Formula 1 (step S110), at least one of nickel and manganese A coating precursor layer of hydroxide containing one coating element is formed (step S120), and the hydroxide is dehydrated by heat treatment to form an oxide coating layer containing lithium and the coating element ( Step S130). Thus, by forming the coating precursor layer of the hydroxide containing the coating element through the intermediate precursor layer of the hydroxide containing cobalt, the uniformity of the coating precursor layer can be improved, and the more uniform It is because a coating layer can be formed.

(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.

The amount of cobalt in the intermediate precursor layer is preferably in the range of 1.0 × 10 ⁻⁵ mol or more and 1.0 × 10 ⁻² mol or less per 1 m ² of the surface area of the composite oxide particles, It is more preferable if it is in the range of 10 ⁻⁵ mol or more and 5.0 × 10 ⁻³ mol or less, and further in the range of 1.0 × 10 ⁻⁴ mol or more and 1.0 × 10 ⁻³ mol or less. This is because the uniformity of the coating precursor layer can be further improved within this range.

  The intermediate precursor layer and the coating precursor layer are preferably formed, for example, in an aqueous solution having a hydrogen ion exponent pH of 12 or more. By precipitating hydroxide in an aqueous solution having a hydrogen ion exponent pH of 12 or more, the precipitation rate of hydroxide can be slowed down, and a denser and more uniform intermediate precursor layer and coating precursor layer can be formed. Because it can.

  At this time, the composite oxide particles are dispersed in an aqueous solution having a hydrogen ion exponent pH of 12 or more, and then a cobalt compound or a coating element compound is added to the aqueous solution to precipitate the hydroxide. In addition, the composite oxide particles are dispersed in an aqueous solution in which a cobalt compound or a covering element compound is dissolved, and then the hydroxide is precipitated by adjusting the hydrogen ion exponent pH of the aqueous solution to 12 or more. May be. However, it is preferable to add the cobalt compound or the covering element compound after the composite oxide particles are dispersed in an aqueous solution having a hydrogen ion exponent of pH 12 or more. This is because a denser precursor layer can be formed. In that case, after forming the intermediate precursor layer, the compound of the coating element may be added to form the coating precursor layer while the composite oxide particles are dispersed without being separated from the aqueous solution.

  Examples of cobalt compounds include cobalt hydroxide, cobalt carbonate, cobalt nitrate, cobalt fluoride, cobalt chloride, cobalt bromide, cobalt iodide, cobalt perchlorate, cobalt bromate, cobalt iodate, cobalt oxide, and peroxide. Examples thereof include inorganic compounds such as cobalt, cobalt sulfide, cobalt sulfate, cobalt hydrogen sulfate, cobalt nitrite, cobalt phosphate, and cobalt thiocyanate, and organic compounds such as cobalt oxalate and cobalt acetate. A cobalt compound may be used individually by 1 type, but 2 or more types may be mixed and used for it.

  As the compound of the covering element, if it is a nickel compound, for example, nickel hydroxide, nickel carbonate, nickel nitrate, nickel fluoride, nickel chloride, nickel bromide, nickel iodide, nickel perchlorate, nickel bromate, iodine Inorganic compounds such as nickel oxide, nickel oxide, nickel peroxide, nickel sulfide, nickel sulfate, nickel hydrogen sulfate, nickel nitride, nickel nitrite, nickel phosphate, or nickel thiocyanate, or nickel oxalate or nickel acetate These organic compounds are mentioned.

  If it is a manganese compound, for example, manganese hydroxide, manganese carbonate, manganese nitrate, manganese fluoride, manganese chloride, manganese bromide, manganese iodide, manganese chlorate, manganese perchlorate, manganese bromate, manganese iodate, Inorganic compounds such as manganese oxide, manganese phosphinate, manganese sulfide, manganese hydrogen sulfide, manganese sulfate, manganese hydrogen sulfate, manganese thiocyanate, manganese nitrite, manganese phosphate, manganese dihydrogen phosphate, or manganese hydrogen carbonate, or And organic compounds such as manganese oxalate and manganese acetate. Among these, a manganese (II) compound is preferable. This is because sufficient solubility in an aqueous solution can be obtained.

  As the compound of the covering element, one kind may be used alone, or two or more kinds may be mixed and used.

  The hydrogen ion exponent pH of the aqueous solution is adjusted, for example, by adding an alkali. Examples of the alkali include lithium hydroxide, sodium hydroxide, and potassium hydroxide. One kind may be used alone, or two or more kinds may be mixed and used. However, it is preferable to use lithium hydroxide. The purity of the positive electrode active material can be improved, the adhesion of the precursor layer is excellent, and the amount of the aqueous solution attached is adjusted when separating the composite oxide particles forming the precursor layer from the aqueous solution. This is because it is possible to control the lithium content in the oxide that forms the.

  The hydrogen ion exponent pH of the aqueous solution is preferably higher, more preferably 13 or more, and even more preferably 14 or more. This is because the higher the hydrogen ion exponent pH, the more uniform intermediate precursor layer and coating precursor layer can be formed. The temperature of the aqueous solution when forming the intermediate precursor layer and the coating precursor layer is preferably 40 ° C. or higher, more preferably 60 ° C. or higher, still more preferably 80 ° C. or higher, and may be 100 ° C. or higher. . This is because a more uniform precursor layer can be formed by increasing the temperature.

  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. This heat treatment diffuses lithium from the composite oxide particles into the coating layer. If necessary, in order to adjust the lithium content in the coating layer, before the heat treatment is performed after forming the coating precursor layer, for example, The coating precursor layer may be impregnated with a lithium compound. Examples of the lithium compound include lithium hydroxide, lithium carbonate, lithium nitrate, lithium fluoride, lithium chloride, lithium bromide, lithium iodide, lithium chlorate, lithium perchlorate, lithium bromate, lithium iodate, Inorganic systems such as lithium oxide, lithium peroxide, lithium sulfide, lithium hydrogen sulfide, lithium sulfate, lithium hydrogen sulfate, lithium nitride, lithium azide, lithium nitrite, lithium phosphate, lithium dihydrogen phosphate, or lithium hydrogen carbonate The compound may be an organic compound such as methyl lithium, vinyl lithium, isopropyl lithium, butyl lithium, phenyl lithium, lithium oxalate, or lithium acetate.

  The composition ratio of nickel and manganese in the coating layer is preferably in the range of 100: 0 to 30:70, preferably in the range of 100: 0 to 40:60, as the molar ratio of nickel: manganese. More preferable. This is because when the amount of manganese increases, the amount of occlusion of lithium in the coating layer decreases and the capacity of the positive electrode active material decreases. The composition ratio of nickel and manganese in the coating layer can be controlled, for example, by adjusting the molar ratio of nickel ions and manganese ions in the aqueous solution when forming the coating precursor layer.

  The coating layer is made of magnesium, aluminum, boron, titanium, vanadium, chromium, iron, cobalt, copper, zinc, molybdenum, tin, tungsten, zirconium, yttrium, niobium, calcium and strontium in addition to nickel or manganese. You may make it form with the oxide containing at least 1 sort (s) of a group. This is because the chemical stability of the positive electrode active material can be further improved and the diffusibility of lithium ions can be improved. The composition of the coating layer may be adjusted by dissolving a compound containing these elements in an aqueous solution when forming the coating precursor layer, and heating may be performed without adding these elements to the coating precursor layer. You may make it adjust by making it diffuse from a complex oxide particle in a process. In this case, the content of these elements in the coating layer is preferably 40 mol% or less, more preferably 30 mol% or less, still more preferably 20 mol% with respect to the total of nickel, manganese and these elements in the coating layer. % Or less. This is because when the content of these elements increases, the occlusion amount of lithium in the coating layer 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 0.5% by mass or more and 50% by mass or less of the composite oxide particles, more preferably 1.0% by mass or more and 40% by mass or less, and further preferably 2.0%. It is within the range of not less than 35% 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. The amount of the coating layer can be adjusted by adjusting the amount of the coating precursor layer.

  The average particle size of the positive electrode active material is preferably in the range of 2.0 μm to 50 μm. When 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. This is because the amount of addition 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 average particle size of the positive electrode active material can be controlled by adjusting the average particle size of the composite oxide particles and the thickness of the coating layer. Moreover, after forming a coating layer, you may make it adjust by light grinding | pulverization or classification as needed. The composite oxide particles may be used after the secondary particles have been crushed by a ball mill or a crusher as required.

  As described above, according to the method for producing a positive electrode active material according to the present embodiment, after forming an intermediate precursor layer of a hydroxide containing cobalt on the composite oxide particles, a coating precursor of the hydroxide containing a covering element is formed. Since the layer is formed, the uniformity of the coating precursor layer can be improved. Therefore, the uniformity of the coating layer can be improved, and the chemical stability of the positive electrode active material can be further improved.

  In particular, if the intermediate precursor layer and the coating precursor layer are formed in an aqueous solution having a hydrogen ion exponent pH of 12 or more, the precipitation rate of hydroxide can be reduced, and the denser and more uniform intermediate precursor layer. Further, a coating precursor layer can be formed, and a denser and uniform coating layer can be formed.

  Further, when the intermediate precursor layer and the coating precursor layer are formed, a finer density can be obtained by adding a cobalt compound or a compound of a coating element to an aqueous solution having a hydrogen ion exponent of pH 12 or higher in which composite oxide particles are dispersed. And uniformity can be improved.

Further, if the amount of cobalt in the intermediate precursor layer is set to 1.0 × 10 ⁻⁵ mol or more and 1.0 × 10 ⁻² mol or less per 1 m ² of the surface area of the composite oxide particles, a higher effect can be obtained. Obtainable.

  The positive electrode active material thus manufactured 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 a positive electrode active material obtained by the manufacturing method 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 positive electrode active material layer 21B includes, for example, a particulate positive electrode active material manufactured by the method for manufacturing a positive electrode active material according to the present embodiment, and a conductive agent such as graphite and a binder such as polyvinylidene fluoride as necessary. It is comprised including. 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-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. 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. 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 the present embodiment, since the positive electrode active material obtained by the above-described manufacturing method 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 deterioration reaction of the electrolytic solution are suppressed.

(Secondary secondary battery)
FIG. 4 shows a configuration of a second secondary battery using the positive electrode active material obtained by the manufacturing method 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 positive electrode active material obtained by the above-described manufacturing method is used, high chemical stability can be obtained even when the charging voltage is increased. Therefore, a high capacity can be obtained and charge / discharge efficiency can be improved.

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

  As Examples 1 to 4 and Comparative Examples 1 to 5 corresponding thereto, positive electrode active materials were prepared as follows.

Example 1
First, 20 parts by mass of composite oxide particles having an average composition of Li _1.03 Co _0.98 Al _0.01 Mg _0.01 O _2.02 , an average particle diameter measured by a laser scattering method of 13 μm, and a specific surface area of 0.8 m ² / g were measured at 80 ° C. The mixture was stirred and dispersed in 300 parts by mass of pure water for 1 hour. Next, after adding 0.36 parts by mass of a commercially available reagent, cobalt nitrate (Co (NO ₃ ) ₂ .6H ₂ O), to this dispersion solution, a 2N aqueous lithium hydroxide solution was added over 30 minutes to a hydrogen ion exponent pH. Was added until an intermediate precursor layer of hydroxide containing cobalt was deposited on the surface of the composite oxide particles (step S110; see FIG. 1). Subsequently, the dispersion solution was washed by filtration.

Thereafter, the composite oxide particles on which the intermediate precursor layer was formed were dispersed again by stirring in 300 parts by mass of pure water at 80 ° C. for 1 hour. Next, 1.60 parts by mass of commercially available nickel nitrate (Ni (NO ₃ ) ₂ .6H ₂ O) and manganese nitrate (Mn (NO ₃ ) ₂ .6H ₂ O) 1. After adding 65 parts by mass, a 2N aqueous lithium hydroxide solution was added over 30 minutes until the hydrogen ion exponent pH became 13, and stirring and dispersion were continued at 80 ° C. for 3 hours to add nickel and manganese. The coating precursor layer of the hydroxide containing was deposited (step S120; refer FIG. 1). Subsequently, the dispersion solution was allowed to cool, washed by filtration, and dried at 120 ° C. When the molar ratio of the metal element was analyzed about the composite oxide particle which formed the intermediate | middle precursor layer and coating precursor layer which were obtained by this, Li: Co: Ni: Mn: Al: Mg = 1.00: 0.94: It was 0.02: 0.02: 0.01: 0.01.

  Thereafter, 2 parts by mass of a 2N aqueous lithium hydroxide solution was impregnated with 10 parts by mass of the composite oxide particles on which the coating precursor layer was formed in order to adjust the amount of lithium, and uniformly mixed and dried. Subsequently, this was heated at a rate of 5 ° C./min using an electric furnace, held at 950 ° C. for 5 hours, and then cooled to 150 ° C. at a rate of 7 ° C./min to form a coating layer. A positive electrode active material was obtained (step S130; see FIG. 1).

(Example 2)
20 parts by mass of complex oxide particles of the same lot as in Example 1 were stirred and dispersed in 300 parts by mass of an aqueous lithium hydroxide solution at 2O 0 C, 2N (hydrogen ion index pH 14.3) for 1 hour. Next, a lithium hydroxide aqueous solution in which composite oxide particles are dispersed in an aqueous solution in which pure water is added to 0.36 parts by mass of cobalt nitrate (Co (NO ₃ ) ₂ .6H ₂ O) as a commercially available reagent. After adding for 10 minutes, the mixture was stirred at 80 ° C. for 1 hour to precipitate an intermediate precursor layer of hydroxide containing cobalt (step S110; see FIG. 1). The hydrogen ion exponent pH of the aqueous lithium hydroxide solution after addition of the aqueous cobalt nitrate solution is 14.2.

  Subsequently, an aqueous solution in which pure water was added to 10 parts by mass of 1.60 parts by mass of commercially available nickel nitrate and 1.65 parts by mass of manganese nitrate as a commercial reagent was added to this dispersion solution over 30 minutes. Then, it stirred at 80 degreeC for 3 hours, and the coating precursor layer of the hydroxide containing nickel and manganese was deposited (step S120; refer FIG. 1). The hydrogen ion exponent pH of the aqueous lithium hydroxide solution after adding the aqueous solution of nickel nitrate and manganese nitrate is 14.2. Thereafter, the dispersion was allowed to cool, washed by filtration and dried at 120 ° C. When the molar ratio of the metal element was analyzed about the composite oxide particle which formed the intermediate | middle precursor layer and coating precursor layer which were obtained by this, Li: Co: Ni: Mn: Al: Mg = 1.04: 0.94: It was 0.02: 0.02: 0.01: 0.01. Next, the composite oxide particles on which the coating precursor layer was formed were heat-treated under the same conditions as in Example 1 to form a coating layer, thereby obtaining a positive electrode active material (Step S130; see FIG. 1).

(Example 3)
When adding cobalt nitrate to 0.24 parts by mass, adding nickel nitrate to 3.20 parts by mass, adding manganese nitrate to 3.30 parts by mass, and adding nickel nitrate and manganese nitrate A positive electrode active material was prepared under the same conditions as in Example 2 except that an aqueous solution containing 20 parts by mass of pure water was added thereto over 1 hour. In addition, the hydrogen ion exponent pH of the lithium hydroxide aqueous solution after adding the aqueous solution of nickel nitrate and manganese nitrate is 14.2. Moreover, when the molar ratio of the metal element was analyzed about the composite oxide particle which formed the intermediate | middle precursor layer and the coating precursor layer, Li: Co: Ni: Mn: Al: Mg = 1.03: 0.88: 0.05 : 0.05: 0.01: 0.01.

Example 4
Add 0.86 parts by mass of commercially available reagent aluminum nitrate (Al (NO ₃ ) ₃ .9H ₂ O) to nickel nitrate and manganese nitrate, and then add an aqueous solution to which 20 parts by mass of pure water is added. A positive electrode active material was produced under the same conditions as in Example 3 except that the precursor layer was formed. When the molar ratio of the metal elements was analyzed for the composite oxide particles on which the intermediate precursor layer and the coating precursor layer were formed, Li: Co: Ni: Mn: Al: Mg = 1.03: 0.88: 0.05: 0 .05: 0.02: 0.01.

(Comparative Example 1)
The composite oxide particles in the same lot as in Examples 1 to 4 were used as the positive electrode active material as they were.

(Comparative Examples 2 to 5)
Comparative Example 2 was the same as Example 1, Comparative Example 3 was the same as Example 2, Comparative Example 4 was the same as Example 3, and Comparative Example 5 was the same except that no intermediate precursor layer was formed. In the same manner as in Example 4, each positive electrode active material was produced.

  The secondary batteries shown in FIGS. 2 and 3 were produced using the produced positive electrode active materials of Examples 1 to 4 and Comparative Examples 1 to 5. 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 are mixed and dispersed in N-methyl-2-pyrrolidone as a solvent. After that, it was applied to both surfaces of a positive electrode current collector 21A made of a strip-shaped aluminum foil having a thickness of 20 μm, dried, and compression-molded to form a positive electrode active material layer 21B, whereby the positive electrode 21 was produced. Next, the positive electrode lead 25 made of aluminum was attached to the positive electrode current collector 21A.

  Further, 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 which is a solvent. The negative electrode current collector 22A made of a foil was applied on both sides, dried, and compression molded to form a negative electrode active material layer 22B to produce a negative electrode 22. Next, a negative electrode lead 26 made of nickel was attached to the negative electrode current collector 22A. At that time, the amount of the positive electrode active material and the negative electrode active material is adjusted, the open circuit voltage at the time of full charge is 4.40 V, and the capacity of the negative electrode 22 is expressed by the capacity component due to insertion and extraction of lithium. did.

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, and is stored inside the battery can 11. did. 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 diethyl carbonate were mixed at a volume ratio of 1: 1 was used.

  The produced secondary battery was charged and discharged at 45 ° C., and the discharge capacity at the first cycle was determined as the initial capacity, and the discharge capacity retention rate at the 200th cycle relative to the first cycle was examined. Charging is performed at a constant current of 1000 mA until the battery voltage reaches 4.40 V, and then charged at a constant voltage of 4.40 V until the total charging time is 2.5 hours. The discharge was performed at a constant current of 800 mA until the battery voltage reached 2.75V. The obtained results are shown in Table 1.

  As shown in Table 1, according to Examples 1 to 4, the initial capacity and the discharge capacity retention ratio could be greatly improved as compared with Comparative Example 1 in which no coating layer was formed. Moreover, the discharge capacity maintenance rate could be improved more than Comparative Examples 2 to 5 in which no intermediate precursor layer was formed. That is, it was found that if the intermediate precursor layer of hydroxide containing cobalt is formed, the uniformity of the coating layer can be improved and the cycle characteristics can be improved.

  Further, as can be seen from a comparison between Example 1 and Example 2, when forming the intermediate precursor layer and the coating precursor layer, the composite oxide particles are dispersed in an aqueous solution in which a cobalt compound or a compound of a coating element is dissolved. Example 2 in which composite oxide particles are dispersed in an aqueous solution in which the hydrogen ion exponent pH is adjusted and a cobalt compound or a compound of a coating element is added is more preferable than in Example 1 in which the hydrogen ion exponent pH is adjusted. High values were obtained for both the initial capacity and the discharge capacity retention rate. That is, if the composite oxide particles are dispersed in an aqueous solution having a hydrogen ion index pH of 12 or more and then a cobalt compound or a coating element compound is added, the uniformity of the coating layer can be further improved. I understood.

  Further, as can be seen from a comparison between Example 2 and Example 3, Example 3 with an increased amount of the coating layer was able to improve the discharge capacity retention rate although the initial capacity was reduced. In addition, as can be seen from a comparison between Example 3 and Example 4, the initial capacity was lower in Example 4 in which the coating layer was formed of an oxide containing aluminum in addition to lithium, nickel and magnesium. The discharge capacity maintenance rate of the product could be improved. In other words, the chemical stability of the positive electrode active material is further improved when the amount of the coating layer is increased or when the coating layer is further formed of an oxide containing other elements such as aluminum. I found out that

  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, 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 (10)

Lithium ion secondary particles in which an oxide coating layer containing lithium (Li) and at least one of the coating elements of nickel and manganese is formed on at least a part of the composite oxide particles represented by chemical formula 1 A method for producing a positive electrode active material for a secondary battery , comprising:
Forming a hydroxide intermediate precursor layer containing cobalt (Co) on at least a part of the composite oxide particles;
After forming the intermediate precursor layer, forming a hydroxide coating precursor layer containing a coating element on at least a part of the composite oxide particles;
Forming a coating precursor layer and then forming the coating layer by heat treatment. A method for producing a positive electrode active material for a lithium ion secondary battery .
(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 for a lithium ion secondary battery according to claim 1 , wherein the intermediate precursor layer and the coating precursor layer are formed in an aqueous solution having a hydrogen ion exponent pH of 12 or more. The intermediate precursor layer is formed by adding a cobalt compound to an aqueous solution having a hydrogen ion exponent pH of 12 or more in which the composite oxide particles are dispersed,
The positive electrode active for a lithium ion secondary battery according to claim 2 , wherein the coating precursor layer is formed by adding a compound of a coating element to an aqueous solution in which the composite oxide particles are dispersed and having a hydrogen ion exponent pH of 12 or more. A method for producing a substance. Adding lithium hydroxide to the aqueous solution, the production method of the positive electrode active material for a lithium ion secondary battery of claim 2 wherein. The amount of cobalt in the intermediate precursor layer, the composite oxide is less particle surface area 1 m ² per 1.0 × 10 ^-5 mol or more 1.0 × 10 ^-2 mol of lithium ion secondary of claim 1, wherein the primary A method for producing a positive electrode active material for a battery . 2. The production of a 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 a molar ratio of nickel: manganese within a range of 100: 0 to 30:70. Method. The coating layer further includes at least one 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 manufacturing method of the positive electrode active material for lithium ion secondary batteries of Claim 1 formed with the oxide containing a seed | species. Wherein the amount of the coating layer, the composite oxide is 50 wt% or less than 0.5 wt% of the particles, the production method of the positive electrode active material for a lithium ion secondary battery of claim 1, wherein. And the average range of particle diameter less 50μm or 2.0μm of the positive active material for a lithium ion secondary battery, a manufacturing method of claim 1 for a lithium ion secondary battery positive electrode active material according. A cathode and an anode, e Bei electrolyte,
In the positive electrode, an oxide coating layer containing lithium (Li) and at least one coating element of nickel and manganese is formed on at least a part of the composite oxide particles represented by chemical formula 1 Containing a positive electrode active material,
In this positive electrode active material, after forming an intermediate precursor layer of a hydroxide containing cobalt (Co) on at least a part of the composite oxide particles, a coating precursor layer of a hydroxide containing a covering element is formed, A lithium ion secondary battery obtained by heat treatment.
(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.)

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