JP2007066839A - Cathode active material, manufacturing method of the same, and battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cathode activator which further improves chemical stability, a manufacturing method of the same, and a battery. <P>SOLUTION: The cathode activator is manufactured by applying a heat treatment to a mixed compound containing a first precursor having covering precursor containing Ni or Mn on Li<SB>1+x</SB>Co<SB>1-y</SB>M1<SB>y</SB>O<SB>2-z</SB>(M1 is another metallic element, or semi-metallic element, -0.10≤x≤0.10, 0≤y<0.50, -0.10≤z≤0.20), a second precursor containing an oxide or hydroxide of which average composition of metallic element and semi-metallic element is expressed by Co<SB>1-a-b-c</SB>Ni<SB>a</SB>Mn<SB>b</SB>M2<SB>c</SB>(M2 is another metallic element or semi-metallic element, 0≤a<0.85, 0≤b<0.50, 0≤c<0.10, 0<a+b+c≤1), and lithium compound. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a positive electrode active material capable of inserting and extracting lithium (Li), a method for producing the same, and a battery using the same.

  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. Therefore, a secondary battery that repeats charge and discharge by using a carbon material such as coke for 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, the high temperature characteristics are lowered, and it is difficult to increase the charge voltage.

Conventionally, as a means for improving the stability of the positive electrode active material, a small amount of lithium nickel manganese composite oxide or the like is used by mixing (for example, see Patent Document 2), or a coating layer is formed on the surface of the composite oxide particles. It is known to form (see, for example, Patent Document 3).
JP 62-90863 A JP 2002-1003007 A JP 2003-221234 A

  However, in order to increase the charging voltage, it is necessary to further improve the chemical stability, and further improvement has been demanded.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a positive electrode active material capable of further improving chemical stability, a method for producing the same, and a battery.

The positive electrode active material according to the present invention includes an oxide containing at least one covering element of nickel (Ni) and manganese (Mn) in at least part of the first composite oxide particles having an average composition represented by Chemical Formula 1 A first positive electrode active material having a first coating layer formed thereon and a second positive electrode active material containing a second composite oxide having an average composition represented by chemical formula 2; The two positive electrode active material is an average composition of a first precursor in which a first coating precursor made of a hydroxide of the coating element is provided on at least a part of the first composite oxide particles, and a metal element and a metalloid element Is obtained by heat-treating a mixture containing a second precursor containing at least one of an oxide and a hydroxide represented by Chemical Formula 3 and a lithium compound.
(Chemical formula 1)
Li _{(1 + x)} Co _(1-y) M1 _y O _(2-z)
(In Chemical Formula 1, M1 is magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), manganese, iron (Fe), nickel, copper (Cu). , Zinc (Zn), molybdenum (Mo), tin (Sn), tungsten (W), zirconium (Zr), yttrium (Y), niobium (Nb), calcium (Ca) and strontium (Sr) X, y, and z are values in the ranges of -0.10 ≦ x ≦ 0.10, 0 ≦ y <0.50, and −0.10 ≦ z ≦ 0.20, respectively. is there.)
(Chemical formula 2)
Li _{(1 + d)} Co _(1-abc) Ni _a Mn _b M2 _c O _(2-e)
(Chemical formula 3)
Co _(1-abc) Ni _a Mn _b M2 _c
(In Chemical Formula 2 and Chemical Formula 3, M2 represents at least one selected from the group consisting of magnesium, aluminum, boron, titanium, vanadium, chromium, iron, copper, zinc, molybdenum, tin, tungsten, zirconium, yttrium, niobium, calcium, and strontium. A, b, c, d and e are 0 ≦ a <0.85, 0 ≦ b <0.50, 0 ≦ c <0.10, 0 <a + b + c ≦ 1, −0. (The values are within the range of 10 ≦ d ≦ 0.10 and −0.10 ≦ e ≦ 0.20.)

The method for producing a positive electrode active material according to the present invention includes a first coating comprising a hydroxide containing at least one of nickel and manganese in at least a part of the first composite oxide particles having an average composition represented by Chemical Formula 1. A first precursor provided with a precursor, a second precursor containing at least one of an oxide and a hydroxide whose average composition of a metal element and a metalloid element is represented by Chemical Formula 3, and a lithium compound It includes a step of heat-treating the mixture to be contained.
(Chemical formula 1)
Li _{(1 + x)} Co _(1-y) M1 _y O _(2-z)
(In the chemical formula 1, M1 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. .)
(Chemical formula 3)
Co _(1-abc) Ni _a Mn _b M2 _c
(In Chemical Formula 3, M2 is at least one member selected from the group consisting of magnesium, aluminum, boron, titanium, vanadium, chromium, iron, copper, zinc, molybdenum, tin, tungsten, zirconium, yttrium, niobium, calcium, and strontium. A, b and c are values within the range of 0 ≦ a <0.85, 0 ≦ b <0.50, 0 ≦ c <0.10, and 0 <a + b + c ≦ 1, respectively.)

A battery according to the present invention is provided with an electrolyte together with a positive electrode and a negative electrode, and the positive electrode includes at least a part of the first composite oxide particles represented by chemical formula 1 among nickel and manganese. 1st positive electrode active material in which the 1st coating layer which consists of an oxide containing at least one coating element was formed, and the 2nd positive electrode active material containing the 2nd complex oxide particle whose average composition is represented by Chemical formula 2 The first positive electrode active material and the second positive electrode active material include a first precursor in which a first coating precursor made of a hydroxide of the coating element is provided on at least a part of the first composite oxide particles; Obtained by heat-treating a mixture containing a lithium compound and a second precursor containing at least one of an oxide and a hydroxide whose average composition of metal element and metalloid element is represented by Chemical Formula 3 It is what was done.
(Chemical formula 1)
Li _{(1 + x)} Co _(1-y) M1 _y O _(2-z)
(In the chemical formula 1, M1 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. .)
(Chemical formula 2)
Li _{(1 + d)} Co _(1-abc) Ni _a Mn _b M2 _c O _(2-e)
(Chemical formula 3)
Co _(1-abc) Ni _a Mn _b M2 _c
(In Chemical Formula 2 and Chemical Formula 3, M2 represents at least one selected from the group consisting of magnesium, aluminum, boron, titanium, vanadium, chromium, iron, copper, zinc, molybdenum, tin, tungsten, zirconium, yttrium, niobium, calcium, and strontium. A, b, c, d and e are 0 ≦ a <0.85, 0 ≦ b <0.50, 0 ≦ c <0.10, 0 <a + b + c ≦ 1, −0. (The values are within the range of 10 ≦ d ≦ 0.10 and −0.10 ≦ e ≦ 0.20.)

  According to the positive electrode active material and the method for producing the same of the present invention, a mixture containing a first precursor obtained by providing a first coating precursor on the first composite oxide particles, a second precursor, and a lithium compound, Since the heat treatment is performed, chemical stability can be improved. In addition, since the formation of the first coating layer and the synthesis of the second positive electrode active material are performed by the same heat treatment, the manufacturing process can be simplified and the manufacturing cost can be reduced. Therefore, according to the battery of the present invention using this positive electrode active material, a high capacity can be obtained and the charge / discharge efficiency can be improved more easily.

  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 includes an oxide containing at least one covering element of nickel and manganese in at least a part of the first composite oxide particles having an average composition represented by Chemical Formula 1 The 1st positive electrode active material in which the 1st coating layer which consists of was provided is contained.

(Chemical formula 1)
Li _{(1 + x)} Co _(1-y) M1 _y O _(2-z)
In Formula 1, M1 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, M1 in Chemical Formula 1 is not an essential constituent element. A higher cobalt content is preferable because a high capacity can be obtained and a discharge potential can be increased. However, if M1 is included, the stability can be improved.

  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 first coating layer functions as a reaction suppression layer. The composition ratio of nickel and manganese in the first coating layer is preferably in the range of 100: 0 to 30:70, and 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 oxide of the first coating layer further includes a group consisting of magnesium, aluminum, boron, titanium, vanadium, chromium, iron, cobalt, copper, zinc, molybdenum, tin, tungsten, zirconium, yttrium, niobium, calcium, and strontium. At least one of them may be included as a constituent element. This is because the stability of the first 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, more preferably 20 mol% with respect to the total of nickel, manganese and these elements in the first coating layer. % Or less 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 first positive electrode active material decreases. Note that these elements may or may not be dissolved in the oxide.

  The amount of the first coating layer is preferably in the range of 0.5% by mass or more and 50% by mass or less of the first composite oxide particles, and is in the range of 1.0% by mass or more and 40% by mass or less. More preferably, it is more preferably in the range of 2.0 to 35% by mass. This is because if the amount of the first coating layer is large, the capacity decreases, and if it is small, the stability cannot be sufficiently improved.

  In addition to the first positive electrode active material, the positive electrode active material contains a second positive electrode active material containing a second composite oxide having an average composition represented by Chemical Formula 2. This is because chemical stability can be further improved.

(Chemical formula 2)
Li _{(1 + d)} Co _(1-abc) Ni _a Mn _b M2 _c O _(2-e)
In Chemical Formula 2, M2 is at least one member selected from the group consisting of magnesium, aluminum, boron, titanium, vanadium, chromium, iron, copper, zinc, molybdenum, tin, tungsten, zirconium, yttrium, niobium, calcium, and strontium. .

  a is a value within a range of 0 ≦ a <0.85, and more preferably within a range of 0 ≦ a <0.80. The capacity can be improved by including nickel, but the potential decreases if the content is large. b is a value within the range of 0 ≦ b <0.50, and more preferably within the range of 0 ≦ b <0.45. It is because charging / discharging efficiency can be improved by containing manganese, but when there is much content, capacity | capacitance will fall. c is a value within a range of 0 ≦ c <0.10, and more preferably within a range of 0 ≦ c <0.08. It is because charging / discharging efficiency can be improved by including M2, but if the content is large, the capacity decreases. Note that a + b + c is in the range of 0 <a + b + c ≦ 1.

  d is a value in the range of −0.10 ≦ d ≦ 0.10, more preferably in the range of −0.08 ≦ d ≦ 0.08, and −0.06 ≦ d ≦ 0.06. It is more preferable if it is within the range. e is a value within the range of −0.10 ≦ e ≦ 0.20, more preferably within the range of −0.08 ≦ e ≦ 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 these ranges.

  The second positive electrode active material may be composed of particles of the second composite oxide, but a second coating layer made of an oxide containing manganese is formed on at least a part of the particles made of the second composite oxide. More preferably, it is provided. This is because chemical stability can be further improved.

  In addition, a 1st coating layer or a 2nd coating layer can be confirmed by investigating the concentration change which goes to the inside from the surface of the element which comprises a 1st positive electrode active material or a 2nd positive electrode active material. This concentration change is caused by, for example, auger electron spectroscopy (AES) or SIMS (secondary ion mass spectrometry) while scraping the first positive electrode active material or the second positive electrode active material by sputtering or the like. Analysis). It is also possible to dissolve the first positive electrode active material or the second positive electrode active material slowly in an acidic solution and measure the time change of the elution by inductively coupled plasma (ICP) spectroscopy. It is.

  The average particle diameter of the first positive electrode active material and the second 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.

  In addition, the positive electrode active material includes an average composition of a first precursor in which a first coating precursor made of a hydroxide of a coating element is provided on at least a part of the first composite oxide particles, and a metal element and a metalloid element. Is obtained by heat-treating a mixture containing a second precursor containing at least one of an oxide and a hydroxide represented by Chemical Formula 3 and a lithium compound. Specifically, it is manufactured as follows.

  FIG. 1 shows a process of one manufacturing method of this positive electrode active material. First, for example, a first coating precursor of a hydroxide containing a coating element is formed on at least a part of the first composite oxide particles having an average composition represented by Chemical Formula 1 to produce a first precursor (step) S101). The first composite oxide particles may be used after the secondary particles are crushed by a ball mill or a crusher as required. The first coating precursor is preferably formed, for example, in an aqueous solution having a hydrogen ion exponent pH of 12 or more. This is because by depositing a hydroxide in an aqueous solution having a hydrogen ion exponent pH of 12 or more, the deposition rate of the hydroxide can be slowed down, and a denser and more uniform film can be formed. In the present invention, a hydroxide means a broad concept including a metal hydrated oxide and an indefinite intermediate state between the oxide and the hydroxide.

  For example, the first coating precursor is obtained by dispersing the first composite oxide particles in an aqueous solution having a hydrogen ion exponent pH of 12 or more, and then adding the compound of the coating element to the aqueous solution to precipitate the hydroxide. Alternatively, the first composite oxide particles may be dispersed in an aqueous solution in which the compound of the covering element is dissolved, and then the hydrogen ion exponent pH of the aqueous solution is adjusted to 12 or more to adjust the water. It may be formed by depositing an oxide. However, it is preferable to add the compound of the covering element after dispersing the first composite oxide particles in an aqueous solution having a hydrogen ion index of pH 12 or higher. This is because a denser and more uniform film can be formed.

  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.

  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 when forming the first coating precursor is adjusted, for example, by adding an alkali to the aqueous solution. 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 by adjusting the amount of aqueous solution deposited when separating the first composite oxide particles forming the first coating precursor from the aqueous solution, lithium in the first coating layer can be obtained. This is because the lithium content in the second positive electrode active material can also 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 first coating precursor can be formed. Moreover, it is preferable that the temperature of aqueous solution shall be 40 degreeC or more, More preferably, it is 60 degreeC or more, More preferably, it is 80 degreeC or more, and is good also as 100 degreeC or more. This is because a more uniform first coating precursor can be formed by increasing the temperature.

  Further, for example, a second precursor containing at least one of an oxide and a hydroxide whose average composition of the metal element and the metalloid element is represented by Chemical Formula 3 is prepared (step S102).

(Chemical formula 3)
Co _(1-abc) Ni _a Mn _b M2 _c
In Chemical Formula 3, M2, a, b and c are the same as in Chemical Formula 2, respectively.

  At that time, if necessary, manganese is contained in at least a part of the central precursor particles composed of at least one of an oxide and a hydroxide whose average composition of the metal element and the metalloid element is represented by Chemical Formula 3. A second coating precursor made of hydroxide may be provided. For example, the second coating precursor is preferably formed in an aqueous solution having a hydrogen ion exponent pH of 12 or more. This is because, like the first coating precursor, a denser and uniform film can be formed.

  The second coating precursor can be formed in the same manner as the first coating precursor. The second coating precursor and the first coating precursor may use different aqueous solutions, but the same aqueous solution may be used. For example, the first composite oxide particles are dispersed in an aqueous solution having a hydrogen ion index pH of 12 or more, and a coating element compound is added to the aqueous solution to form a first coating precursor. The precursor particles may be dispersed to form a second coating precursor. The first composite oxide particles on which the first coating precursor is formed may be separated from the aqueous solution before the central precursor particles are dispersed, but after the second coating precursor is formed on the central precursor particles. In addition, it may be separated from the aqueous solution.

  The second coating precursor is preferably formed under oxidizing conditions. Since the compound of manganese (II) has high solubility, changing the valence of manganese ions from manganese (II) to manganese (IV) can lower the solubility of manganese hydroxide and form a good film. Because it can. As a method for making the oxidizing condition, a gas such as air, oxygen, ozone, or nitrogen oxide may be blown into the aqueous solution, or an oxidizing agent such as hydrogen peroxide may be added to the aqueous solution. .

  Next, after mixing the first precursor and the second precursor, heat treatment is performed by adding a lithium compound as necessary. Thereby, the hydroxide of the first coating precursor is dehydrated to form the first coating layer, the first positive electrode active material is obtained, and the second positive electrode active material is synthesized (step S103). In addition, when lithium hydroxide is used when forming the first precursor or the second precursor, and lithium hydroxide is attached or impregnated therein, it is not necessary to newly add a lithium compound, The addition amount is adjusted as necessary.

  When adding a lithium compound, for example, lithium hydroxide, lithium carbonate, lithium nitrate, lithium fluoride, lithium chloride, lithium bromide, lithium iodide, lithium chlorate, lithium perchlorate, lithium bromate, iodine Lithium oxide, 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, lithium hydrogen carbonate, etc. Inorganic compounds such as methyllithium, vinyllithium, isopropyllithium, butyllithium, phenyllithium, lithium oxalate, or lithium acetate may be used.

  Further, after preparing the first positive electrode active material and the second positive electrode active material, the particle size of the positive electrode active material may be adjusted by performing a light pulverization or classification operation as necessary.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

As electrolyte salt, lithium salt is mentioned, for example, 1 type may be used independently, and 2 or more types may be mixed and used for it. The lithium _{salt, LiPF 6, LiBF 4, LiAsF} 6, LiClO 4, LiB (C 6 H 5) 4, LiCH 3 SO 3, LiCF 3 SO 3, LiN (SO 2 CF 3) 2, LiC (SO 2 CF ₃ ) ₃ , LiAlCl ₄ , LiSiF ₆ , LiCl, difluoro [oxolato-O, O ′] lithium borate, lithium bisoxalate borate, or LiBr.

  Note that the open circuit voltage (that is, the battery voltage) at the time of full charge of the secondary battery may be 4.20V, but it is designed to be higher than 4.20V and not lower than 4.25V and lower than 4.80V. It is preferable. The energy density can be increased by increasing the battery voltage, and according to the present embodiment, the chemical stability of the positive electrode active material is improved, so that an excellent cycle even if the battery voltage is increased. This is because characteristics can be obtained. In that case, since the amount of lithium released per unit mass increases even with the same positive electrode active material than when the battery voltage is set to 4.20 V, the amounts of the positive electrode active material and the negative electrode active material are adjusted accordingly. .

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

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

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

  Subsequently, the positive electrode lead 25 is attached to the positive electrode current collector 21A by welding or the like, and the negative electrode lead 26 is attached to the negative electrode current collector 22A by welding or the like. After that, the positive electrode 21 and the negative electrode 22 are wound through the separator 23, and the tip of the positive electrode lead 25 is welded to the safety valve mechanism 15, and the tip of the negative electrode lead 26 is welded to the battery can 11. The positive electrode 21 and the negative electrode 22 are sandwiched between a pair of insulating plates 12 and 13 and stored in the battery can 11. After the positive electrode 21 and the negative electrode 22 are accommodated in the battery can 11, the electrolytic solution is injected into the battery can 11 and impregnated in the separator 23. After that, the battery lid 14, the safety valve mechanism 15, and the heat sensitive resistance element 16 are fixed to the opening end of the battery can 11 by caulking through a gasket 17. Thereby, the secondary battery shown in FIGS. 2 and 3 is formed.

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

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

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

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

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

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

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

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

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

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

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

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

  Thus, according to the present embodiment, by heat-treating the mixture including the first precursor in which the first coating precursor is provided on the first composite oxide particles, the second precursor, and the lithium compound, Since the first positive electrode active material and the second positive electrode active material are produced, the chemical stability of the positive electrode active material can be improved. Therefore, a high capacity can be obtained and charge / discharge efficiency can be improved. In addition, since the formation of the first coating layer and the synthesis of the second positive electrode active material are performed by the same heat treatment, the manufacturing process can be simplified and the manufacturing cost can be reduced.

  In particular, if the second positive electrode active material has a second coating layer made of an oxide containing manganese on at least a part of the particles made of the second composite oxide, chemical stability can be further improved. Can do.

  If the first coating precursor is formed in an aqueous solution having a hydrogen ion index of pH 12 or higher, a coating element compound is further added to the aqueous solution having a hydrogen ion index of pH 12 or higher in which the first composite oxide particles are dispersed. Thus, a denser and more uniform film can be formed, and a more dense and uniform first coating layer can be formed.

  In addition, if the second coating precursor is formed in an aqueous solution having a hydrogen ion index of pH 12 or higher, a denser and more uniform film can be formed. The first composite oxide particles are dispersed in an aqueous solution having a hydrogen ion exponent pH of 12 or more, and a coating element compound is added to the aqueous solution to form a first coating precursor. If the precursor particles are dispersed to form the second coating precursor, the manufacturing process can be simplified and the manufacturing cost can be reduced.

  Furthermore, when the second coating precursor is formed, it is possible to easily precipitate a hydroxide containing manganese and to form a good film if the oxidizing condition is used. .

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

  As Examples 1 to 7 and Comparative Example 1 corresponding thereto, positive electrode active materials were prepared as follows.

Example 1
First, 20 parts by mass of first 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 measured by a laser scattering method were added to 300 parts by mass of pure water at 80 ° C. Stir for 1 hour to disperse. Next, 1.60 parts by mass of a commercially available reagent nickel nitrate (Ni (NO ₃ ) ₂ .6H ₂ O) and a commercially available reagent manganese nitrate (Mn (NO ₃ ) ₂ .6H ₂ O) 65 parts by mass were added. Subsequently, a 2N aqueous lithium hydroxide solution was added to this until the hydrogen ion exponent pH was 13 over 30 minutes, and stirring and dispersion were continued at 80 ° C. for 3 hours to obtain the surface of the first composite oxide particles. After depositing a first coating precursor of hydroxide containing nickel and manganese, it was allowed to cool (step S101; see FIG. 1). Thereafter, the dispersion was washed and filtered, and dried at 120 ° C. to obtain a first precursor. When the molar ratio of the metal elements was analyzed for the obtained first precursor, Li: Co: Ni: Mn: Al: Mg = 1.00: 0.94: 0.02: 0.02: 0.01: 0.01.

Further, 29.1 parts by mass of cobalt nitrate (Co (NO ₃ ) ₂ .6H ₂ O) as a commercially available reagent, 29.1 parts by mass of nickel nitrate as a commercially available reagent, and 28.7 parts by mass of manganese nitrate as a commercially available reagent. Then, after dissolving in 1000 parts by mass of water and stirring at 50 ° C., a 2N aqueous lithium hydroxide solution was added over 2 hours until the hydrogen ion exponent pH reached 10, followed by further stirring for 2 hours, cobalt and nickel Hydroxide particles containing equimolar amounts of manganese and manganese were precipitated. Thereafter, the dispersion was washed and filtered, and dried at 120 ° C. to obtain a second precursor (step S102; see FIG. 1). The average particle diameter of the obtained second precursor was 8.5 μm.

  Next, 20 parts by mass of the first precursor, 10 parts by mass of the second precursor, and 60 parts by mass of a 2N aqueous lithium hydroxide solution were mixed and then 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. The 2nd positive electrode active material was produced and the positive electrode active material was obtained (step S103; refer FIG. 1).

(Example 2)
20 parts by mass of the first complex oxide particles in the same lot as in Example 1 were dispersed in 300 parts by mass of an aqueous lithium hydroxide solution at 80 ° C. and 2N (hydrogen ion index pH 14.3) for 2 hours. Next, nickel nitrate and manganese nitrate are mixed in the same amount as in Example 1, and pure water is added thereto to make 10 parts by mass. Then, 10 parts by mass of this aqueous solution is dispersed in the first composite oxide particles. To the aqueous lithium hydroxide solution over 30 minutes. 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, this was stirred and dispersed at 80 ° C. for 3 hours to deposit a first coating precursor of hydroxide containing nickel and manganese on the surface of the first composite oxide particles, and allowed to cool (step S101; (See FIG. 1). After that, the dispersion was allowed to stand to precipitate dispersed particles, and the supernatant was removed to obtain a first precursor to which lithium hydroxide was attached.

  Next, 10 parts by mass of the second precursor prepared in the same manner as in Example 1 was added to 20 parts by mass of the first precursor, mixed, dried at 120 ° C., and then the same as in Example 1. By performing heat treatment, a first positive electrode active material and a second positive electrode active material were produced, and a positive electrode active material was obtained (step S103; see FIG. 1).

(Example 3)
Nickel nitrate and manganese nitrate were mixed twice as much as in Example 1, and pure water was added thereto to make 20 parts by mass. Then, 20 parts by mass of this aqueous solution was dispersed in the first composite oxide particles. A positive electrode active material was produced in the same manner as in Example 2 except that it was added to the lithium hydroxide aqueous solution over 1 hour.

Example 4
Mix nickel nitrate and manganese nitrate twice as much as Example 1, add 0.86 parts by mass of commercially available reagent aluminum nitrate (Al (NO ₃ ) ₃ .9H ₂ O), and add pure water. In addition, after 20 parts by mass, the same as Example 2 except that 20 parts by mass of this aqueous solution was added to the lithium hydroxide aqueous solution in which the first composite oxide particles were dispersed over 1 hour. Thus, a positive electrode active material was produced.

(Example 5)
20 parts by mass of the first complex oxide particles of the same lot as in Example 1 were stirred for 2 hours while flowing nitrogen gas through 300 parts by mass of a lithium hydroxide aqueous solution of 2N (hydrogen ion index pH 14.3) at 80 ° C. And dispersed. Next, nickel nitrate and manganese nitrate are mixed in the same amount as in Example 1, and pure water is added thereto to make 10 parts by mass. Then, 10 parts by mass of this aqueous solution is dispersed in the first composite oxide particles. Then, nitrogen gas was added to the aqueous lithium hydroxide solution over 30 minutes to precipitate a first coating precursor of hydroxide containing nickel and manganese on the surface of the first composite oxide particles (step S101). See FIG. 1).

  Subsequently, 10 parts by mass of hydroxide particles produced in the same manner as in Example 1 were dispersed in this dispersion system as the central precursor particles, and stirred at 80 ° C. for 3 hours while circulating air instead of nitrogen gas. Then, a second coating precursor of hydroxide containing manganese was deposited on the surface of the central precursor particles (step S102; see FIG. 1). Thereafter, the dispersion was allowed to stand to precipitate dispersed particles, and the supernatant was removed to obtain a first precursor and a second precursor to which lithium hydroxide was attached. Subsequently, after drying this at 120 degreeC, it heat-processed like Example 1, and produced the 1st positive electrode active material and the 2nd positive electrode active material, and obtained the positive electrode active material (step S103; figure) 1).

(Example 6)
Nickel nitrate and manganese nitrate were mixed twice as much as in Example 1, and pure water was added thereto to make 20 parts by mass. Then, 20 parts by mass of this aqueous solution was dispersed in the first composite oxide particles. A positive electrode active material was produced in the same manner as in Example 5 except that it was added to the lithium hydroxide aqueous solution over 1 hour.

(Example 7)
Nickel nitrate and manganese nitrate were mixed twice as much as Example 1, 0.86 parts by mass of aluminum nitrate was added thereto, and pure water was added to make 20 parts by mass. A positive electrode active material was prepared in the same manner as in Example 5 except that was added to the lithium hydroxide aqueous solution in which the first composite oxide particles were dispersed over 1 hour.

(Comparative Example 1)
The first complex oxide particles of the same lot as in Examples 1 to 7 are used as they are as the first precursor, mixed with the second precursor and 60 parts by mass of lithium hydroxide aqueous solution, dried, and then heat-treated. Otherwise, a positive electrode active material was produced in the same manner as in Example 1.

  Using the produced positive electrode active materials of Examples 1 to 7 and Comparative Example 1, secondary batteries shown in FIGS. First, 86% by mass of the prepared positive electrode active material powder, 10% by mass of graphite as a conductive agent, and 4% by mass of polyvinylidene fluoride as a binder 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 7, the discharge capacity retention rate could be significantly improved as compared with Comparative Example 1 in which the first coating layer was not formed. That is, if a mixture containing the first precursor in which the first coating precursor is provided on the first composite oxide particles, the second precursor, and the lithium compound is heat-treated, the chemical stability of the positive electrode active material is improved. As a result, it was found that the cycle characteristics can be improved.

  As can be seen from a comparison between Example 1 and Example 2, Example 1 in which the first composite oxide particles were dispersed in an aqueous solution in which the compound of the covering element was dissolved and then the hydrogen ion exponent pH was adjusted. However, Example 2 in which the compound of the covering element was added after the first composite oxide particles were dispersed in the aqueous solution with the adjusted hydrogen ion index pH was able to improve the discharge capacity retention rate. That is, if the first complex oxide particles are dispersed in an aqueous solution having a hydrogen ion index pH of 12 or more and then the coating element compound is added, the chemical stability of the positive electrode active material can be further improved. I understood that I could do it.

  Furthermore, as can be seen from a comparison between Examples 2 to 4 and Examples 5 to 7, Examples 5 to 7 in which the second coating layer is provided on the second positive electrode active material have a discharge capacity retention rate. We were able to improve more. That is, it has been found that the chemical stability of the positive electrode active material can be further improved by providing the second coating layer.

  Although the present invention has been described with reference to the embodiments and examples, the present invention is not limited to the above embodiments and examples, and various modifications can be made. For example, in the above-described embodiment or example, the case of using an electrolyte solution that is a liquid electrolyte or a gel electrolyte in which an electrolyte solution is held in a polymer compound has been described. However, other electrolytes may be used. Good. Other electrolytes include, for example, a polymer electrolyte in which an electrolyte salt is dispersed in a polymer compound having ion conductivity, an inorganic solid electrolyte made of ion conductive ceramics, ion conductive glass, or ionic crystals, or a molten salt electrolyte. Or a mixture thereof.

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

  Further, in the above embodiments and examples, the secondary battery having a winding structure has been described, but the present invention is similarly applied to a secondary battery having another structure in which the positive electrode and the negative electrode are folded or stacked. can do. In addition, the present invention can also be applied to secondary batteries having other shapes such as a so-called coin type, button type, or square type. Moreover, not only a secondary battery but a primary battery is applicable.

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

Explanation of symbols

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

Claims (17)

A first coating layer made of an oxide containing at least one coating element of nickel (Ni) and manganese (Mn) is formed on at least a part of the first composite oxide particles represented by chemical formula 1 A first positive electrode active material,
A second positive electrode active material containing a second composite oxide having an average composition represented by Chemical Formula 2;
The first positive electrode active material and the second positive electrode active material include a first precursor in which a first coating precursor made of a hydroxide of the coating element is provided on at least a part of the first composite oxide particles, and a metal a second precursor containing at least one of oxides and hydroxides represented by the element and the average composition of the third semi-metal element, a mixture containing a lithium compound, obtained by heat treatment A positive electrode active material characterized by the above.
(Chemical formula 1)
Li _{(1 + x)} Co _(1-y) M1 _y O _(2-z)
(In Chemical Formula 1, M1 is magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), manganese, iron (Fe), nickel, copper (Cu). , Zinc (Zn), molybdenum (Mo), tin (Sn), tungsten (W), zirconium (Zr), yttrium (Y), niobium (Nb), calcium (Ca) and strontium (Sr) X, y, and z are values in the ranges of -0.10 ≦ x ≦ 0.10, 0 ≦ y <0.50, and −0.10 ≦ z ≦ 0.20, respectively. is there.)
(Chemical formula 2)
Li _{(1 + d)} Co _(1-abc) Ni _a Mn _b M2 _c O _(2-e)
(Chemical formula 3)
Co _(1-abc) Ni _a Mn _b M2 _c
(In Chemical Formula 2 and Chemical Formula 3, M2 represents at least one selected from the group consisting of magnesium, aluminum, boron, titanium, vanadium, chromium, iron, copper, zinc, molybdenum, tin, tungsten, zirconium, yttrium, niobium, calcium, and strontium. A, b, c, d and e are 0 ≦ a <0.85, 0 ≦ b <0.50, 0 ≦ c <0.10, 0 <a + b + c ≦ 1, −0. (The values are within the range of 10 ≦ d ≦ 0.10 and −0.10 ≦ e ≦ 0.20.) The second positive electrode active material has a second coating layer made of an oxide containing manganese on at least a part of the particles made of the second composite oxide,
A second coating made of a hydroxide containing manganese on at least a part of the central precursor particles made of at least one of an oxide and a hydroxide whose average composition of the metal element and the metalloid element is represented by chemical formula 3 The positive electrode active material according to claim 1, wherein the positive electrode active material is obtained by heat-treating a mixture containing a second precursor provided with a precursor together with the first precursor and a lithium compound.   2. The positive electrode active material according to claim 1, wherein the composition ratio of nickel and manganese in the first coating layer is in a range of 100: 0 to 30:70 as a molar ratio of nickel: manganese.   The oxide of the first coating layer is further composed of magnesium, aluminum, boron, titanium, vanadium, chromium, iron, cobalt, copper, zinc, molybdenum, tin, tungsten, zirconium, yttrium, niobium, calcium, and strontium. The positive electrode active material according to claim 1, comprising at least one selected from the group consisting of:   2. The positive electrode active material according to claim 1, wherein an amount of the first coating layer is in a range of 0.5 mass% to 50 mass% of the first composite oxide particles.   2. The positive electrode active material according to claim 1, wherein an average particle size of the first positive electrode active material and the second positive electrode active material is in a range of 2.0 μm to 50 μm. A first coating precursor made of a hydroxide containing at least one of nickel (Ni) and manganese (Mn) was provided on at least part of the first composite oxide particles represented by chemical formula 1 A mixture containing a first precursor, a second precursor containing at least one of an oxide and a hydroxide whose average composition of a metal element and a metalloid element is represented by Chemical Formula 3, and a lithium compound, The manufacturing method of the positive electrode active material characterized by including the process of heat-processing.
(Chemical formula 1)
Li _{(1 + x)} Co _(1-y) M1 _y O _(2-z)
(In Chemical Formula 1, M1 is magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), manganese, iron (Fe), nickel, copper (Cu). , Zinc (Zn), molybdenum (Mo), tin (Sn), tungsten (W), zirconium (Zr), yttrium (Y), niobium (Nb), calcium (Ca) and strontium (Sr) X, y, and z are values in the ranges of -0.10 ≦ x ≦ 0.10, 0 ≦ y <0.50, and −0.10 ≦ z ≦ 0.20, respectively. is there.)
(Chemical formula 3)
Co _(1-abc) Ni _a Mn _b M2 _c
(In Chemical Formula 3, M2 is at least one member selected from the group consisting of magnesium, aluminum, boron, titanium, vanadium, chromium, iron, copper, zinc, molybdenum, tin, tungsten, zirconium, yttrium, niobium, calcium, and strontium. A, b and c are values within the ranges of 0 ≦ a <0.85, 0 ≦ b <0.50, 0 ≦ c <0.10, and 0 <a + b + c ≦ 1, respectively.)   The method for producing a positive electrode active material according to claim 7, wherein the first coating precursor is formed in an aqueous solution having a hydrogen ion exponent pH of 12 or more.   The first coating precursor is formed by dispersing the first composite oxide particles in an aqueous solution having a hydrogen ion exponent pH of 12 or more, and then adding the coating element compound to the aqueous solution. The method for producing a positive electrode active material according to claim 8.   The method for producing a positive electrode active material according to claim 8, wherein lithium hydroxide is added to the aqueous solution.   The second precursor is provided with a second coating precursor made of a hydroxide containing manganese on at least a part of central precursor particles made of at least one of the oxide and the hydroxide. The method for producing a positive electrode active material according to claim 7, wherein:   12. The method for producing a positive electrode active material according to claim 11, wherein the second coating precursor is formed in an aqueous solution having a hydrogen ion exponent pH of 12 or more.   The first composite oxide particles are dispersed in an aqueous solution having a hydrogen ion exponent pH of 12 or more, and the coating element compound is added to the aqueous solution to form the first coating precursor. The method for producing a positive electrode active material according to claim 11, wherein the central precursor particles are dispersed to form the second coating precursor.   The method for producing a positive electrode active material according to claim 13, wherein the second coating precursor is formed under oxidizing conditions.   The method for producing a positive electrode active material according to claim 12, wherein lithium hydroxide is added to the aqueous solution. A battery including an electrolyte together with a positive electrode and a negative electrode,
The positive electrode comprises a first oxide comprising an oxide containing at least one of a covering element of nickel (Ni) and manganese (Mn) in at least part of the first composite oxide particles represented by chemical formula 1 A first positive electrode active material having a coating layer formed thereon, and a second positive electrode active material containing a second composite oxide having an average composition represented by Chemical Formula 2;
The first positive electrode active material and the second positive electrode active material include a first precursor in which a first coating precursor made of a hydroxide of the coating element is provided on at least a part of the first composite oxide particles, and a metal It was obtained by heat-treating a mixture containing a lithium compound and a second precursor containing at least one of an oxide and a hydroxide whose average composition of elements and metalloid elements is represented by chemical formula 3 A battery characterized by that.
(Chemical formula 1)
Li _{(1 + x)} Co _(1-y) M1 _y O _(2-z)
(In Chemical Formula 1, M1 is magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), manganese, iron (Fe), nickel, copper (Cu). , Zinc (Zn), molybdenum (Mo), tin (Sn), tungsten (W), zirconium (Zr), yttrium (Y), niobium (Nb), calcium (Ca) and strontium (Sr) X, y, and z are values in the ranges of -0.10 ≦ x ≦ 0.10, 0 ≦ y <0.50, and −0.10 ≦ z ≦ 0.20, respectively. is there.)
(Chemical formula 2)
Li _{(1 + d)} Co _(1-abc) Ni _a Mn _b M2 _c O _(2-e)
(Chemical formula 3)
Co _(1-abc) Ni _a Mn _b M2 _c
(In Chemical Formula 2 and Chemical Formula 3, M2 represents at least one selected from the group consisting of magnesium, aluminum, boron, titanium, vanadium, chromium, iron, copper, zinc, molybdenum, tin, tungsten, zirconium, yttrium, niobium, calcium, and strontium. A, b, c, d and e are 0 ≦ a <0.85, 0 ≦ b <0.50, 0 ≦ c <0.10, 0 <a + b + c ≦ 1, −0. (The values are within the range of 10 ≦ d ≦ 0.10 and −0.10 ≦ e ≦ 0.20.) The second positive electrode active material has a second coating layer made of an oxide containing manganese on at least a part of the particles made of the second composite oxide,
A second coating made of a hydroxide containing manganese on at least a part of the central precursor particles made of at least one of an oxide and a hydroxide whose average composition of the metal element and the metalloid element is represented by chemical formula 3 The battery according to claim 16, wherein the battery is obtained by heat-treating a mixture containing a second precursor provided with a precursor together with the first precursor and a lithium compound.

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