JP4984436B2 - Positive electrode active material for lithium ion secondary battery, method for producing the same, positive electrode for lithium ion secondary battery, and lithium ion secondary battery - Google Patents

Description

The present invention relates to a positive electrode active material for a lithium ion secondary battery containing a composite oxide containing lithium (Li) and cobalt (Co), a method for producing the same, a positive electrode for a lithium ion secondary battery using the same, and lithium The present invention relates to an ion secondary battery.

  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 them, lithium cobaltate or lithium nickelate is promising in terms of high potential, stability and long life, and in particular, lithium cobaltate can increase the potential, and 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, a different element such as aluminum (Al), magnesium (Mg), zirconium (Zr) or titanium (Ti) is dissolved (see Patent Document 2). ), Using a mixture of a small amount of lithium nickel manganese composite oxide (see Patent Document 3), or coating the surface of lithium cobaltate with lithium manganate or nickel cobalt composite oxide having a spinel structure (Patent Document) 4 and 5) are reported.
JP 62-90863 A JP 2004-303459 A JP 2002-1003007 A JP-A-10-333573 JP-A-10-372470

  However, the technique of dissolving different elements in a solid solution has a problem that 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. In addition, the technology using a mixture of lithium nickel manganese composite oxide, etc., and the technology of coating with lithium manganate or nickel cobalt composite oxide cannot sufficiently improve the characteristics, and further improvement is required. It was.

The present invention has been made in view of such problems, and the object thereof is to increase the capacity and improve the charge / discharge efficiency, and a positive electrode active material for a lithium ion secondary battery and a method for producing the same, Another object is to provide a positive electrode for a lithium ion secondary battery and a lithium ion secondary battery using the same.

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, the concentration of manganese in the covering layer, towards the outer layer portion than the inner layer portion is rather high, oxide containing lithium, nickel and manganese, and lithium , Nickel, manganese, and oxygen, or lithium, nickel, manganese, 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 less than nickel in the coating layer 40 mol% or less based on the total of manganese and at least one element in the group .

According to the present invention, there is provided a method for producing a positive electrode active material for a lithium ion secondary battery , wherein at least part of the composite oxide particles having an average composition represented by chemical formula 1 A step of forming an internal precursor layer of a hydroxide containing manganese, and after forming the internal precursor layer, changing the valence of manganese ions contained in the aqueous solution, Forming a hydroxide outer precursor layer having a higher manganese concentration than the layer, and heat-treating the inner precursor layer and the outer precursor layer, so that at least a portion of the composite oxide particles includes lithium and nickel When made of a oxide containing manganese, saw including a step towards the outer layer is to form a high covering layer the concentration of manganese than the inner portion, lithium and nickel and manganese Oxides consisting of lithium, nickel, manganese, and oxygen, or lithium, nickel, manganese, magnesium, aluminum, boron, titanium, vanadium, chromium, iron, cobalt, 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 a coating. 40 mol% or less of the total of nickel and manganese in the layer and at least one element of the group .
(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. .)

The positive electrode for a lithium ion secondary battery according to the present invention contains a positive electrode active material in which a coating layer is provided on at least a part of the composite oxide particles, and the composite oxide particles have an average composition of Li _{(1 + x)} Co _{(1-y) MyO (2-z)} (where M is magnesium, aluminum, boron, titanium, vanadium, chromium, manganese, iron, nickel, copper, zinc, molybdenum, tin, tungsten, zirconium, yttrium, At least one member selected from the group consisting of niobium, calcium, and strontium, and x, y, and z are −0.10 ≦ x ≦ 0.10, 0 ≦ y <0.50, and −0.10 ≦ z, respectively. The coating layer is made of an oxide containing lithium, nickel, and manganese, and the concentration of manganese in the coating layer is higher than that of the inner layer portion. Part Is rather high, oxide containing lithium, nickel and manganese, lithium, nickel, and manganese, which consists of oxygen or a lithium, nickel, and manganese, magnesium, aluminum, boron, titanium, At least one element of the group consisting of vanadium, chromium, iron, cobalt, copper, zinc, molybdenum, tin, tungsten, zirconium, yttrium, niobium, calcium and strontium, and among the groups in the coating layer The content of at least one element is 40 mol% or less with respect to the total of at least one element of the group of nickel and manganese in 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. ,this The concentration of manganese in Kutsugaeso is towards the outer layer portion than the inner layer portion is rather high, oxide containing lithium, nickel and manganese, lithium, nickel, and manganese, which consists of oxygen or lithium And nickel, manganese and at least of the group consisting of magnesium, aluminum, boron, titanium, vanadium, chromium, iron, cobalt, 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% with respect to the total of nickel and manganese in the coating layer and at least one element in the group. It is as follows .

According to the positive electrode active material for lithium ion secondary battery of the present invention, the composite oxide particles having an average composition represented by _{Li (1 + x) Co (} 1-y) M y O (2-z), nickel And manganese, and the outer layer part is provided with a coating layer made of an oxide having a higher manganese concentration than the inner layer part, so that the positive electrode while taking advantage of the high capacity and high potential of the composite oxide particles. The chemical stability of the active material can be improved. Therefore, according to the positive electrode for a lithium ion secondary battery and the lithium ion secondary battery of the present invention using this positive electrode active material, a high capacity can be obtained and charge / discharge efficiency can be improved.

According to the method for producing a positive electrode active material for a lithium ion secondary battery of the present invention, after forming an internal precursor layer of a hydroxide containing nickel and manganese in an aqueous solution having a hydrogen ion index pH of 12 or more, manganese Since the external valence layer of hydroxide having a higher manganese concentration than the internal precursor layer is formed by changing the valence of ions, the positive electrode active material for lithium ion secondary batteries of the present invention is easily manufactured. be able to.

  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. The nickel and manganese concentrations in the coating layer change in the depth direction, and the manganese concentration is higher in the outer layer portion on the opposite side than in the inner layer portion on the composite oxide particle side. This is because the charge / discharge efficiency can be further improved by making the manganese concentration in the outer layer portion higher than the average composition of the coating layer.

  Note that the coating layer means a region until the change in concentration of nickel and manganese is substantially not seen when the change in concentration of nickel and manganese is examined from the surface to the inside of the positive electrode active material. Concentration change from the surface of nickel and manganese in the positive electrode active material toward the inside, for example, while the positive electrode active material is scraped by sputtering or the like, its composition is changed to Auger Electron Spectroscopy (AES) or SIMS (Secondary Ion Mass Spectrometry; Secondary ion mass spectrometry). It is also possible to slowly dissolve the positive electrode active material in an acidic solution or the like, and to measure the time change of the eluted portion by inductively coupled plasma (ICP) spectroscopic analysis or the like.

  The composition ratio of nickel and manganese in the coating layer is preferably in the range of 95: 5 to 20:80 in terms of nickel: manganese molar ratio, and more preferably in the range of 90:10 to 30:70. preferable. If the amount of manganese is large, the amount of occlusion of lithium in the coating layer decreases, the capacity of the positive electrode active material decreases, and the electrical resistance increases. If the amount of manganese is small, the charge / discharge efficiency is sufficiently improved. It is because it cannot be made to do.

  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 30 mol% or less, and more preferably 20 mol% or less with respect to the total of nickel, manganese and these elements in the coating layer. If it is more preferable. 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 0.5% by mass or more and 50% by mass or less of the composite oxide particles, more preferably in the range of 1.0% by mass or more and 40% by mass or less. More preferably, it is in the range of 0.0 mass% or more and 35 mass% or less. 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 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.

FIG. 1 shows a process of one manufacturing method of this positive electrode active material. First, at least a portion of the composite oxide particles represented by the average composition of 1, for example, in the hydrogen ion exponent pH is of 12 more aqueous solutions, the internal precursor layer including the hydroxide of nickel and manganese formed (Step S101). Thus, by depositing hydroxide in an aqueous solution having a hydrogen ion index pH of 12 or more, the deposition rate of hydroxide can be slowed down, and a denser and more uniform internal precursor layer can be formed. Because.

  When forming the internal precursor layer, as shown in FIG. 1, the composite oxide particles are dispersed in an aqueous solution having a hydrogen ion exponent pH of 12 or more (step S111), and then the nickel compound and the aqueous solution are added to the aqueous solution. The manganese compound may be added to precipitate the hydroxide (step S112), and the composite oxide particles are dispersed in an aqueous solution in which the nickel compound and the manganese compound are dissolved (step S121). The hydrogen ion exponent pH of this aqueous solution may be adjusted to 12 or more to precipitate the hydroxide (step S122).

  As a nickel compound that is a raw material of nickel, if it is an inorganic compound, nickel hydroxide, nickel carbonate, nickel nitrate, nickel fluoride, nickel chloride, nickel bromide, nickel iodide, nickel perchlorate, nickel bromate Nickel iodate, nickel oxide, nickel peroxide, nickel sulfide, nickel sulfate, nickel hydrogen sulfate, nickel nitride, nickel nitrite, nickel phosphate, or nickel thiocyanate. Examples thereof include nickel oxide and nickel acetate. A nickel compound may be used individually by 1 type, but 2 or more types may be mixed and used for it.

  As the manganese compound as a raw material of manganese, as long as it is an inorganic compound, manganese hydroxide, manganese carbonate, manganese nitrate, manganese fluoride, manganese chloride, manganese bromide, manganese iodide, manganese chlorate, manganese perchlorate , Manganese bromate, manganese iodate, manganese oxide, manganese phosphinate, manganese sulfide, manganese hydrogen sulfide, manganese sulfate, manganese hydrogen sulfate, manganese thiocyanate, manganese nitrite, manganese phosphate, manganese dihydrogen phosphate, or carbonic acid Examples of the organic compound include 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. A manganese compound may be used individually by 1 type, but 2 or more types may be mixed and used for it.

  Next, for example, an oxidizing gas such as air or oxygen is blown into the aqueous solution to change the valence of manganese ions in an aqueous solution having a hydrogen ion exponent pH of 12 or more. As a result, for example, manganese (II) ions are oxidized to manganese (IV) ions, and the solubility of manganese hydroxide in the aqueous solution decreases, so that an external precursor layer of hydroxide having a higher manganese concentration than the internal precursor layer is formed. It forms in at least one part of complex oxide particle (step S102).

  In addition, the hydrogen ion exponent pH at the time of forming an internal precursor layer and an external precursor layer is adjusted by adding an alkali to aqueous solution, for example. 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, and the content of lithium in the coating layer can be adjusted by adjusting the amount of aqueous solution deposited when separating the composite oxide particles forming the inner precursor layer and the outer precursor layer from the aqueous solution. This is because the amount can be controlled.

  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 the inner precursor layer and the outer precursor layer can be formed. In addition, the temperature of the aqueous solution when forming the inner precursor layer and the outer 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.

  Subsequently, the composite oxide particles forming the inner precursor layer and the outer precursor layer are separated from the aqueous solution, and the hydroxides of the inner precursor layer and the outer precursor layer are dehydrated by heat treatment, and lithium, nickel, and manganese are removed. An oxide covering layer is formed (step S103). 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. In order to adjust the lithium content in the coating layer, the internal precursor layer and the external precursor layer are impregnated with a lithium compound before heat treatment. You may do it. 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, and oxidation. Inorganic compounds such as lithium, 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 However, organic compounds such as methyl lithium, vinyl lithium, isopropyl lithium, butyl lithium, phenyl lithium, lithium oxalate, or lithium acetate may be used.

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

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

(First secondary battery)
FIG. 2 shows a cross-sectional structure of a first secondary battery using the positive electrode active material according to the present embodiment. This secondary battery is a so-called lithium ion secondary battery in which lithium is used as an electrode reactant and the capacity of the negative electrode is represented by a capacity component due to insertion and extraction of lithium. This secondary battery is called a so-called cylindrical type, and is a winding in which a pair of strip-like positive electrode 21 and strip-like negative electrode 22 are wound through a separator 23 inside a substantially hollow cylindrical battery can 11. A rotating electrode body 20 is provided. Inside the battery can 11, an electrolytic solution that is a liquid electrolyte is injected and impregnated in the separator 23. The battery can 11 is made of, for example, iron plated with nickel, and has one end closed and the other end open. Inside the battery can 11, a pair of insulating plates 12 and 13 are arranged perpendicular to the winding peripheral surface so as to sandwich the winding electrode body 20.

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

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

  FIG. 3 shows an enlarged part of the spirally wound electrode body 20 shown in FIG. The positive electrode 21 has, for example, a structure in which a positive electrode active material layer 21B is provided on both surfaces of a positive electrode current collector 21A having a pair of opposed surfaces. Although not shown, the positive electrode active material layer 21B may be provided only on one surface of the positive electrode current collector 21A. The positive electrode current collector 21A is made of, for example, a metal foil such as an aluminum foil, a nickel foil, or a stainless steel foil. The cathode active material layer 21B includes, for example, a particulate cathode active material according to the present embodiment, and a conductive agent such as graphite and a binder such as polyvinylidene fluoride as necessary. Furthermore, you may contain the other 1 type, or 2 or more types of positive electrode active material.

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

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

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

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

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

  Examples of metal elements or metalloid elements constituting the negative electrode material include magnesium, boron, aluminum, gallium (Ga), indium (In), silicon (Si), germanium (Ge), tin, lead (Pb), 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. 2 and 3 is formed.

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

(Secondary secondary battery)
FIG. 4 illustrates a configuration of a second secondary battery using the positive electrode active material according to the present embodiment. In this secondary battery, a wound electrode body 30 to which a positive electrode lead 31 and a negative electrode lead 32 are attached is accommodated in a film-like exterior member 40, and can be reduced in size, weight, and thickness. ing.

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

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

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

  FIG. 5 shows a cross-sectional structure taken along line II of the spirally wound electrode body 30 shown in FIG. The wound electrode body 30 is obtained by stacking and winding a positive electrode 33 and a negative electrode 34 with a separator 35 and an electrolyte layer 36 interposed therebetween, and the outermost peripheral portion is protected by a protective tape 37.

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

  The electrolyte layer 36 includes an electrolytic solution and a polymer compound serving as a holding body that holds the electrolytic solution, and has a so-called gel shape. The gel electrolyte layer 36 is preferable because high ion conductivity can be obtained and liquid leakage can be prevented. The configuration of the electrolytic solution is the same as that of the first secondary battery. Examples of the polymer compound include polyacrylonitrile, polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polytetrafluoroethylene, polyhexafluoropropylene, polyethylene oxide, polypropylene oxide, polyphosphazene, and polysiloxane. , Polyvinyl acetate, polyvinyl alcohol, polymethyl methacrylate, polyacrylic acid, polymethacrylic acid, styrene-butadiene rubber, nitrile-butadiene rubber, polystyrene or polycarbonate. In particular, from the viewpoint of electrochemical stability, polyacrylonitrile, polyvinylidene fluoride, polyhexafluoropropylene, or polyethylene oxide is preferable.

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

  First, after the positive electrode 33 and the negative electrode 34 are manufactured in the same manner as the first secondary battery, a precursor solution containing an electrolytic solution, a polymer compound, and a mixed solvent is applied to each of the positive electrode 33 and the negative electrode 34. Then, the mixed solvent is volatilized to form the electrolyte layer 36. After that, the positive electrode lead 31 is attached to the positive electrode current collector 33A, and the negative electrode lead 32 is attached to the negative electrode current collector 34A. Next, the positive electrode 33 and the negative electrode 34 on which the electrolyte layer 36 is formed are laminated via a separator 35 to form a laminated body, and then the laminated body is wound in the longitudinal direction, and a protective tape 37 is adhered to the outermost peripheral portion. Thus, the wound electrode body 30 is formed. Finally, for example, the wound electrode body 30 is sandwiched between the exterior members 40, and the outer edges of the exterior members 40 are sealed and sealed by heat fusion or the like. At that time, the adhesion film 41 is inserted between the positive electrode lead 31 and the negative electrode lead 32 and the exterior member 40. Thereby, the secondary battery shown in FIGS. 4 and 5 is completed.

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

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

  As described above, according to the present embodiment, the positive electrode active material in which the composite oxide particles include nickel and manganese, and the outer layer portion is provided with a coating layer having a higher manganese concentration than the inner layer portion. Therefore, chemical stability can be improved while taking advantage of the high capacity and high potential of the composite oxide particles. Therefore, high capacity can be obtained and cycle characteristics can be improved.

  In addition, in an aqueous solution having a hydrogen ion index pH of 12 or more, after forming an internal precursor layer of a hydroxide containing nickel and manganese, the valence of manganese ions is changed so that the manganese concentration is higher than that of the internal precursor layer. Since the high hydroxide external precursor layer is formed, the positive electrode active material according to the present embodiment can be easily manufactured.

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

  As Examples 1 to 3 and Comparative Examples 1 to 4 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 and an average particle diameter of 13 μm as measured by a laser scattering method were set at 80 ° C. and 2N (hydrogen ion index pH 14. The mixture was stirred and dispersed in 300 parts by mass of the lithium hydroxide aqueous solution 3) for 2 hours while circulating nitrogen gas (step S111; see FIG. 1). Next, 1.60 parts by mass of nickel nitrate (Ni (NO ₃ ) ₂ .6H ₂ O) as a commercially available reagent and 1.65 parts by mass of manganese nitrate (Mn (NO ₃ ) ₂ .6H ₂ O) as a commercially available reagent. After mixing and adding pure water to 10 parts by mass, all 10 parts by mass of this aqueous solution was added over 30 minutes while flowing nitrogen gas through the lithium hydroxide aqueous solution in which the composite oxide particles were dispersed. Then, a hydroxide internal precursor layer containing nickel and manganese was formed on the surface of the composite oxide particles (step S112; see 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.

  Subsequently, while flowing air into the aqueous solution instead of nitrogen gas, stirring and dispersion were continued at 80 ° C. for 3 hours to form a hydroxide external precursor layer containing nickel and manganese on the surface of the composite oxide particles. And allowed to cool (step S102; see FIG. 1). After that, it was filtered and dried at 120 ° C. without washing. When the molar ratio of the metal element was analyzed about the composite oxide particle which formed the internal precursor layer and external 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 inner precursor layer and the outer precursor layer are formed are heated at a rate of 5 ° C./min using an electric furnace, held at 950 ° C. for 5 hours, and then at a rate of 7 ° C./min. The coating layer was formed by cooling to 150 ° C. to obtain a positive electrode active material (step S103; see FIG. 1).

(Example 2)
After mixing 3.20 parts by mass of nickel nitrate and 3.30 parts by mass of manganese nitrate and adding pure water to 20 parts by mass, the composite oxide particles were dispersed in 20 parts by mass of the aqueous solution. A positive electrode active material was produced under the same conditions as in Example 1 except that the nitrogen gas was added to the aqueous lithium hydroxide solution over 1 hour while flowing. That is, the amount of nickel nitrate and manganese nitrate added was double that of Example 1. 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. Further, when the molar ratio of the metal elements was analyzed for the composite oxide particles in which the inner precursor layer and the outer precursor layer were formed, Li: Co: Ni: Mn: Al: Mg = 1.03: 0.88: 0.05 : 0.05: 0.01: 0.01.

Example 3
Add 0.86 parts by mass of commercially available aluminum nitrate (Al (NO ₃ ) ₃ .9H ₂ O) to 3.20 parts by mass of nickel nitrate and 3.30 parts by mass of manganese nitrate, and then add pure water. After 20 parts by mass, all the 20 parts by mass of this aqueous solution were added to the lithium hydroxide aqueous solution in which the composite oxide particles were dispersed over 1 hour while circulating nitrogen gas, and the others were the same as in Example 1. A positive electrode active material was produced under the same conditions. That is, in addition to nickel nitrate and manganese nitrate, aluminum nitrate was added to form an inner precursor layer and an outer precursor layer. When the molar ratio of the metal elements was analyzed for the composite oxide particles in which the inner precursor layer and the outer 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 of the same lot as in Examples 1 to 3 were used as the positive electrode active material as they were.

(Comparative Examples 2 to 4)
A positive electrode active material was produced under the same conditions as in Examples 1 to 3, except that the hydroxide was precipitated on the composite oxide particles without passing nitrogen gas and air through the aqueous solution. When the metal oxide molar ratio (Li: Co: Ni: Mn: Al: Mg) was analyzed for the composite oxide particles on which the hydroxide was precipitated, Comparative Example 2 was 1.04: 0.94: 0.02. : 0.02: 0.01: 0.01, Comparative Example 3 is 1.03: 0.88: 0.05: 0.05: 0.01: 0.01, Comparative Example 4 is 1.03: 0 .88: 0.05: 0.05: 0.02: 0.01.

  About the produced positive electrode active material of Examples 1-3 and Comparative Examples 2-4, the distribution state of the metal element in the surface was investigated by XPS (X-ray Photoelectron Spectroscopy; X-ray photoelectron spectroscopy). As a result, in Examples 1 to 3, it was confirmed that the concentration of manganese on the surface was higher than in Comparative Examples 2 to 4.

  Next, secondary batteries shown in FIGS. 2 and 3 were produced using the produced positive electrode active materials of Examples 1 to 3 and Comparative Examples 1 to 4. 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 3, 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 retention ratio could be further improved as compared with Comparative Examples 2 to 4 in which the external precursor layer was not formed. That is, if the manganese concentration in the coating layer is higher in the outer layer portion than in the inner layer portion, the chemical stability of the positive electrode active material can be further improved, and the capacity and cycle characteristics can be improved. I understood that I could do it.

  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 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 (17)

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 concentration of manganese in the coating layer is rather high, towards the outer layer portion than the inner layer portion,
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 The positive electrode active material for lithium ion secondary batteries which is 40 mol% or less with respect to the sum total of these elements . 2. The positive electrode active material for a lithium ion secondary battery according to claim 1 , wherein a composition ratio of nickel and manganese in the coating layer is a molar ratio of nickel: manganese and is in a range of 95: 5 to 20:80. 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 0.5 mass% or more and 50 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. An internal precursor layer of a hydroxide containing nickel (Ni) and manganese (Mn) in an aqueous solution having a hydrogen ion exponent pH of 12 or more in at least a part of the composite oxide particles represented by chemical formula 1 Forming a step;
After forming the internal precursor layer, the valence of manganese ions contained in the aqueous solution is changed, and at least part of the composite oxide particles, an external precursor layer of hydroxide having a higher manganese concentration than the internal precursor layer Forming a step;
By heat-treating these inner precursor layer and outer precursor layer, at least a part of the composite oxide particles is made of an oxide containing lithium, nickel, and manganese, and the outer layer portion is more than the inner layer portion. look including a step of concentration of the manganese to form a high covering layer,
An oxide containing lithium, nickel and manganese;
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 with respect to the total of the elements of
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.) Wherein in the step of forming the external precursor layer, changing the valence of manganese ions by blowing an oxidizing gas into the aqueous solution, the production method of the positive electrode active material for a lithium ion secondary battery according to claim 5, wherein. Adding lithium hydroxide to the aqueous solution, the production method of the positive electrode active material for a lithium ion secondary battery according to claim 5, wherein. Containing a positive electrode active material provided with a coating layer 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 concentration of manganese in the coating layer is rather high, towards the outer layer portion than the inner layer portion,
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 The positive electrode for lithium ion secondary batteries which is 40 mol% or less with respect to the sum total of these elements . 9. The positive electrode for a lithium ion secondary battery according to claim 8 , wherein the composition ratio of nickel and manganese in the coating layer is a molar ratio of nickel: manganese and is in the range of 95: 5 to 20:80. Wherein the amount of the coating layer, the composite is an oxide in the range of 0.5 wt% to 50 wt% of the particles, the lithium ion secondary battery positive electrode according to claim 8. The positive electrode for a lithium ion secondary battery according to claim 8 , wherein an average particle diameter of the positive electrode active material is in a range of 2.0 μm or more and 50 μm or less. The positive electrode active material forms an internal precursor layer of a hydroxide containing nickel and manganese in an aqueous solution having a hydrogen ion exponent pH of 12 or more on at least a part of the composite oxide particles, by changing the valence of manganese ions to form external precursor layer of high hydroxide concentration of manganese than the internal precursor layer contained, is obtained by heating this, according to claim 8 Positive electrode for lithium ion secondary battery . 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 concentration of manganese in the coating layer is rather high, towards the outer layer portion than the inner layer portion,
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 A lithium ion secondary battery that is 40 mol% or less with respect to the total of the elements . The lithium ion secondary battery according to claim 13 , wherein a composition ratio of nickel and manganese in the coating layer is a molar ratio of nickel: manganese and is in a range of 95: 5 to 20:80. Wherein the amount of the coating layer, said a composite oxide in the range of 0.5 wt% to 50 wt% of the particles, according to claim 13 lithium ion secondary battery according. The lithium ion secondary battery according to claim 13 , wherein an average particle diameter of the positive electrode active material is in a range of 2.0 μm to 50 μm. The positive electrode active material forms an internal precursor layer of a hydroxide containing nickel and manganese in an aqueous solution having a hydrogen ion exponent pH of 12 or more on at least a part of the composite oxide particles, changing the valence of manganese ions contained to form an outer precursor layer of high hydroxide concentration of manganese than the internal precursor layer, is obtained by heating this, claim 13, wherein Lithium ion secondary battery.

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