JP5017806B2 - Positive electrode active material for secondary battery, method for producing the same, and secondary battery - Google Patents

Description

The present invention relates to a positive electrode active material for a secondary battery containing a lithium composite oxide, a method for producing the same, and a secondary 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. 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 4 V. Among them, lithium cobaltate or lithium nickelate is high potential and stable. Promising in terms of sex and long life. In particular, lithium nickelate is cheaper than lithium cobaltate, has a stable supply, and is a 4V class active material, but its charge potential is somewhat lower, so the electrolyte is decomposed. There are advantages such as being suppressed, and research is ongoing.

  In recent years, it has been studied to further improve the capacity by using these positive electrode active materials and increasing the charging voltage. However, when the charging voltage is increased, there is a problem that the positive electrode active material and the electrolyte are easily deteriorated and the capacity is reduced.

Conventionally, as means for improving the stability of the positive electrode active material, aluminum (Al), manganese (Mn), tin (Sn), indium (In), iron (Fe), copper (Cu), magnesium (Mg) ), Titanium (Ti), zinc (Zn), molybdenum (Mo), and other foreign elements have been reported to be dissolved (see, for example, Patent Documents 2 to 5).
JP 62-90863 A Japanese Patent No. 3244314 Japanese Patent No. 3281829 Japanese Patent No. 3064655 Japanese Patent Laid-Open No. 08-37007

  However, in the technology for dissolving different elements, 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. Could not improve.

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 for a secondary battery capable of increasing capacity and improving charge / discharge efficiency, a method for producing the same, and the method thereof. It is providing the secondary battery using this.

Positive electrode active material for a secondary battery according to the present invention, the average composition of _{Li (1 + a) A b} Co (1-xyz) Ni x Mn y M z O (2-c) F d ( wherein, A is calcium (Ca), strontium (Sr) and barium (Ba) are at least one first element, and M is magnesium (Mg), aluminum (Al), boron (B), titanium (Ti). , Vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), tungsten (W), zirconium (Zr), yttrium (Y) And at least one second element selected from the group consisting of niobium (Nb), where x, y, and z are 0 <x <0.85, 0 <y <0.55, and 0 ≦ z <0, respectively. .10, x + y + z ≦ 1, the values a, b, c and d are (Respectively within a range of −0.10 ≦ a ≦ 0.10, 0 <b ≦ 0.10, −0.10 ≦ c ≦ 0.20, and 0 <d ≦ 0.10). It includes a composite oxide particles represented, composite oxide particles, oxide composition of cobalt and nickel, and manganese and second element M is represented by _{Co (1-xyz) Ni x} Mn y M z, water the oxide or precursor particles consisting of these water-containing material, by the material of the first element a is heat-treated by deposition, Rutotomoni is added first element a, the first element a precursor particles added After or when it is added, fluorine is added, and the first element A and fluorine in the composite oxide particles are present at a higher concentration on the particle surface than inside the particles.

The manufacturing method of the positive electrode active material for secondary batteries by this invention is a manufacturing method of the positive electrode active material containing the composite oxide particle whose average composition is represented by Formula (1), Comprising: Cobalt, nickel, manganese, and 2nd oxide composition and element M is represented by _{Co (1-xyz) Ni x} Mn y M z, the precursor particles consisting of hydroxides or their hydrate, to deposit a material of the first element a by heat treatment Te, saw including a step of adding a first element a, after addition of the first element a precursor particles, or the time of addition is to add fluorine.
_{Li (1 + a) A b} Co (1-xyz) Ni x Mn y M z O (2-c) F d ····· (1)
(Wherein, A is at least one first element selected from the group consisting of calcium, strontium and barium, and M is magnesium, aluminum, boron, titanium, vanadium, chromium, iron, copper, zinc, molybdenum, tin. , Tungsten, zirconium, yttrium, and niobium, x, y, and z are 0 <x <0.85, 0 <y <0.55, and 0 ≦, respectively. The values in the range of z <0.10, x + y + z ≦ 1, a, b, c, and d are −0.10 ≦ a ≦ 0.10, 0 <b ≦ 0.10, −0.10 ≦ c, respectively. ≦ 0.20, 0 <d ≦ 0.10.

Secondary battery according to the present invention, together with positive and negative electrodes, there is provided with an electrolyte, the positive electrode, the average composition of _{Li (1 + a) A b} Co (1-xyz) Ni x Mn y M z O ( _2-c) F _d (wherein A is at least one first element selected from the group consisting of calcium, strontium and barium, and M is magnesium, aluminum, boron, titanium, vanadium, chromium, iron, copper) , Zinc, molybdenum, tin, tungsten, zirconium, yttrium and niobium are at least one second element, where x, y and z are 0 <x <0.85 and 0 <y <, respectively. 0.55, 0 ≦ z <0.10, x + y + z ≦ 1, values a, b, c and d are −0.10 ≦ a ≦ 0.10, 0 <b ≦ 0.10, −0.10 ≦ c ≦ 0.20, 0 <d ≦ 0. 0 is a value within the range of. Includes composite oxide particles represented by), the composite oxide particles, cobalt and nickel and manganese and the composition of the second element _{M Co (1-xyz) Ni} x Mn oxide represented by _y M _z, the hydroxide or precursor particles consisting of these water-containing material, by the material of the first element a heat treatment are adhered, the first element a is added is Rutotomoni Fluorine is added after or when the first element A is added to the precursor particles, and the first element A and fluorine in the composite oxide particles are higher on the particle surface than inside the particles. Is present in the concentration.

According to the positive electrode active material for a secondary battery of the present invention is represented by Li average composition described above _{(1 + a) A b Co} (1-xyz) Ni x Mn y M z O (2-c) F d in the composite oxide particles that consist of cobalt, nickel, and manganese oxides the composition of the second element M is represented by _{Co (1-xyz) Ni x} Mn y M z, hydroxides or their hydrates of the precursor particles, by the material of the first element a heat treatment are adhered, the first element a is added Rutotomoni, after first element a is added to the precursor particles, or when they are added In addition, since fluorine is added so that the first element A and fluorine are present at a high concentration on the particle surface, the chemical stability of the positive electrode active material for the secondary battery can be improved. Therefore, according to the secondary battery of the present invention using the positive electrode active material for the secondary battery, even if the battery voltage is increased, high charge / discharge efficiency can be obtained, and capacity deterioration can be suppressed. .

According to the method for producing a positive electrode active material for a secondary battery of the present invention, the first element A is added to the precursor particles by applying the raw material of the first element A to the precursor particles and performing a heat treatment. Since fluorine is added after or when the first element A is added, the positive electrode active material for a secondary battery of the present invention can be easily manufactured.

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

  The positive electrode active material according to an embodiment of the present invention includes composite oxide particles having an average composition represented by Chemical Formula 1.

(Chemical formula 1)
_{Li (1 + a) A b} Co (1-xyz) Ni x Mn y M z O (2-c) F d
In Formula 1, A is at least one first element selected from the group consisting of calcium, strontium and barium, and M is magnesium, aluminum, boron, titanium, vanadium, chromium, iron, copper, zinc, molybdenum, tin. , Tungsten, zirconium, yttrium, and niobium.

a is a value in the range of −0.10 ≦ a ≦ 0.10, more preferably in the range of −0.08 ≦ a ≦ 0.08, and −0.06 ≦ a ≦ 0.06. It is more preferable if it is within the range. This small discharge capacity is lowered than, tends to gel in making larger Ri recognize this as positive, because manufacturing becomes difficult.

b is a value in the range of 0 <b ≦ 0.10, more preferably in the range of 0.005 ≦ b ≦ 0.08, and in the range of 0.01 ≦ b ≦ 0.06. Further preferred. Charge-discharge efficiency and also Ri recognize this small it tends to decrease, than larger the discharge capacity which tend to decrease.

  c is a value within the range of −0.10 ≦ c ≦ 0.20, more preferably within the range of −0.08 ≦ c ≦ 0.18, and −0.06 ≦ c ≦ 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.

d is a value in the range of 0 <d ≦ 0.10, more preferably in the range of 0.005 ≦ d ≦ 0.08, and in the range of 0.01 ≦ d ≦ 0.06. Further preferred. Charge-discharge efficiency and also Ri recognize this small it tends to decrease, than larger the discharge capacity which tend to decrease.

  x is a value within a range of 0 ≦ x <0.85, and more preferably within a range of 0 ≦ x <0.80. Nickel is not an essential constituent element, and if nickel is included, the capacity can be improved, but this is because increasing the nickel content makes it difficult to increase the charging voltage.

  y is a value within a range of 0 ≦ y <0.55, and more preferably within a range of 0 ≦ y <0.45. Manganese is not an essential constituent element, and it is preferable to contain manganese, since charge / discharge efficiency can be improved. However, when the manganese content increases, it is possible to maintain a crystal structure that functions as a positive electrode active material. This is because it becomes difficult and the capacity tends to decrease.

  z is a value in the range of 0 ≦ z <0.10, and more preferably in the range of 0 ≦ z <0.08. The second element M is not an essential constituent element, and it is preferable to include the second element M because the chemical stability of the positive electrode active material can be improved. However, when the content of the second element M increases. This is because the capacity decreases.

  X, y, and z are values in the range of x + y + z ≦ 1. That is, cobalt is not an essential constituent element, and the total composition of cobalt, nickel, manganese, and second element M is adjusted to be 1.

  Further, in this composite oxide particle, the first element A and fluorine are present at a higher concentration on the particle surface than inside the particle, so that the chemical stability of the positive electrode active material can be improved. It has become. The average composition of the composite oxide particles can be measured by inductively coupled plasma (ICP) spectroscopy or atomic absorption analysis after dissolving the composite oxide particles in an acidic solution or the like. The distribution state of elements on the particle surface can be measured by X-ray photoelectron spectroscopy (XPS) or the like. By comparing with the average composition, the first element A and fluorine are present on the particle surface. It can be confirmed that it is present at a high concentration. Further, the change in the concentration of elements from the particle surface toward the inside may be measured by Auger Electron Spectroscopy (AES) or SIMS (Secondary Ion Mass Spectrometry) while scraping by sputtering or the like. Alternatively, the composite oxide particles may be slowly dissolved in an acidic solution and the time change of the elution may be measured by ICP spectroscopic analysis or the like.

  In the composite oxide particles, primary particles having an average particle diameter of 0.01 μm or more and 5.0 μm or less are preferably aggregated to form secondary particles, and the average particle diameter of the secondary particles is 2.0 μm. It is preferable that it is in the range of 50 μm or less. When the average particle size of the primary particles is smaller than 0.01 μm, synthesis is difficult, and the separator may be clogged when used in a battery. This is because the adhesion between the particles decreases due to the expansion and contraction associated with charge and discharge, and the ion conductivity decreases. In addition, when the average particle size of the secondary particles is less than 2.0 μm, the positive electrode active material is easily separated from the positive electrode current collector in the pressing process when the positive electrode is produced, and the surface area of the positive electrode active material is increased. This is because the amount of addition of a conductive agent or a binder must be increased, and the energy density per unit mass becomes small. Conversely, when the average particle size of the secondary particles exceeds 50 μm, the positive electrode active material penetrates the separator, and the possibility of causing a short circuit increases.

FIG. 1 shows a process of one manufacturing method of this positive electrode active material. First, cobalt oxide compositions of the nickel and the manganese and the second element M is represented by _{Co (1-xyz) Ni x} Mn y M z, the precursor particles consisting of hydroxides or their hydrate, The first element A is added by depositing the raw material of the first element A and performing heat treatment (step S110). At that time, a lithium compound may be deposited together with the raw material of the first element (step S111), and an oxide, hydroxide, or hydrate thereof containing lithium is used as the precursor particle. (Step S112). Thus, while lithium easily diffuses inside the particle, the first element A hardly diffuses inside the particle, so that it exists at a high concentration on the particle surface.

In addition, when depositing the raw material of the first element A, the raw material of the first element A is adhered to the surface of the precursor particle by mixing the precursor particles and the raw material of the first element A. Alternatively, the raw material of the first element A may be deposited or adhered to the surface of the precursor particles by a liquid phase method or a gas phase method. The heat treatment is preferably performed in an oxidizing atmosphere such as air or pure oxygen, and the heating temperature is preferably 500 ° C. or higher and 950 ° C. or lower. Further, if necessary, after preliminary firing at a temperature of 300 ° C. or higher and 850 ° C. or lower in an oxidizing atmosphere and pulverizing secondary particles using a ball mill or a grinder, the temperature is 500 ° C. or higher in an oxidizing atmosphere. 950 ° C. may be baked formed at a temperature.

  The raw material of the first element A may be a single element or a compound of the first element A. In the case of a compound, it may be an inorganic compound or an organic compound. For example, as a calcium compound, if it is an inorganic compound, calcium hydroxide, calcium carbonate, calcium nitrate, calcium fluoride, calcium chloride, calcium bromide, calcium iodide, calcium hypochlorite, calcium chlorite, chlorine Calcium oxide, calcium perchlorate, calcium bromate, calcium iodate, calcium oxide, calcium peroxide, calcium sulfide, calcium hydrogen sulfide, calcium thiosulfate, calcium sulfate, calcium hydrogen sulfate, calcium nitride, calcium azide, nitrous acid Examples include calcium, calcium phosphate, calcium monohydrogen phosphate, calcium dihydrogen phosphate, calcium metaphosphate, calcium bicarbonate, or calcium borate. For organic compounds, dimethyl calcium, divinyl carbonate Siumu, diisopropyl calcium, dibutyl calcium, diphenyl, calcium oxalate or calcium acetate and the like.

  As the strontium compound, if it is an inorganic compound, strontium hydroxide, strontium carbonate, strontium nitrate, strontium fluoride, strontium chloride, strontium bromide, strontium iodide, strontium hypochlorite, strontium chlorite, strontium chlorate Strontium perchlorate, strontium bromate, strontium iodate, strontium oxide, strontium peroxide, strontium sulfide, strontium hydrogen sulfide, strontium thiosulfate, strontium sulfate, strontium hydrogen sulfate, strontium nitride, strontium azide, strontium nitrite, Strontium phosphate, strontium monohydrogen phosphate, strontium dihydrogen phosphate, strontium metaphosphate, carbonated water Strontium or the like, such as boric acid strontium, as long as it is an organic compound, dimethyl strontium, divinyl strontium, diisopropyl strontium, dibutyl strontium, diphenyl strontium, strontium oxalate, or the like strontium acetate and the like.

  As the barium compound, if it is an inorganic compound, barium hydroxide, barium carbonate, barium nitrate, barium fluoride, barium chloride, barium bromide, barium iodide, barium hypochlorite, barium chlorite, barium chlorate , Barium perchlorate, barium bromate, barium iodate, barium oxide, barium peroxide, barium sulfide, barium hydrogen sulfide, barium thiosulfate, barium sulfate, barium hydrogen sulfate, barium nitride, barium azide, barium nitrite, Examples include barium phosphate, barium monohydrogen phosphate, barium dihydrogen phosphate, barium metaphosphate, barium hydrogen carbonate, or barium borate. For organic compounds, dimethyl barium, divinyl barium, diisopropyl barium, dibutyl barium , Diphenyl barium, Oxalic acid barium, or a barium acetate and the like.

  As the lithium compound, if it is an inorganic compound, lithium hydroxide, lithium carbonate, lithium nitrate, lithium fluoride, lithium chloride, lithium bromide, lithium iodide, lithium chlorate, lithium perchlorate, lithium bromate , Lithium iodate, lithium oxide, lithium peroxide, lithium sulfide, lithium hydrogen sulfide, lithium sulfate, lithium hydrogen sulfate, lithium nitride, lithium azide, lithium nitrite, lithium phosphate, lithium dihydrogen phosphate, or hydrogen carbonate Examples of the organic compound include methyl lithium, vinyl lithium, isopropyl lithium, butyl lithium, phenyl lithium, lithium oxalate, and lithium acetate.

  Next, fluorine is added to the precursor particles to which the first element A has been added (step S120). Fluorine may be added by exposing the precursor particles to a fluorine gas atmosphere, or may be added by mixing the precursor particles with a fluorine compound and heating. At that time, fluorine can be unevenly distributed on the particle surface by controlling the partial pressure of fluorine gas, the amount of fluorine compound added, and the heating temperature.

  As the fluorine compound, a fluorine metal salt may be used, but an ammonium salt which volatilizes by heat treatment is preferable because there is a possibility that the characteristics may deteriorate due to residual metal. Organic fluorine compounds are also preferred. This is because residual carbon can be used as a conductive material. Examples of the organic fluorine compound include a polar compound having a group adsorbed on a precursor particle such as a perfluoroalkyl group, or a fluorine-based polymer compound having a skeleton of polytetrafluoroethylene or polyvinylidene fluoride. .

  Further, instead of adding fluorine after adding the first element A, fluoride may be used as a raw material of the first element A, and fluorine may be added together with the first element A. Thereby, a positive electrode active material is obtained. In addition, after adding fluorine, 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-dioxolane, diethyl ether, sulfolane, methylsulfolane, propionitrile, anisole, acetate, butyrate, or A propionic acid ester is mentioned. One non-aqueous solvent may be used alone, or two or more non-aqueous solvents may be mixed and used.

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

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

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

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

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

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

  In this secondary battery, when charged, lithium ions are released from the positive electrode active material layer 21B, and the negative electrode material that can occlude and release lithium contained in the negative electrode active material layer 22B via the electrolytic solution. Occluded. Next, when discharging is performed, lithium ions stored in the negative electrode material capable of inserting and extracting lithium in the negative electrode active material layer 22B are released, and are inserted into the positive electrode active material layer 21B through the electrolytic solution. . In 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.

According to this embodiment, the composite oxide particles having an average composition represented by _{Li (1 + a) A b} Co (1-xyz) Ni x Mn y M z O (2-c) F d In the above, since the first element A and fluorine are present in high concentration on the particle surface, the chemical stability of the positive electrode active material can be improved. Therefore, even if the battery voltage is increased, high charge / discharge efficiency can be obtained, and capacity deterioration can be suppressed.

  In addition, since the first element A is added by depositing the raw material of the first element A on the precursor particles and performing heat treatment, the positive electrode active material of the present invention can be easily manufactured.

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

( Experimental example 1)
Aqueous ammonia is added dropwise to an aqueous solution in which commercially available cobalt nitrate, nickel nitrate, and manganese nitrate are mixed so that the ratio of cobalt, nickel, and manganese is equimolar with sufficient stirring. A powder was obtained. Next, the composite hydroxide powder was used as precursor particles, which were mixed with calcium nitrate and lithium nitrate powder, and then first heated using an electric furnace. At that time, heating was performed by raising the temperature at a rate of 5 ° C. per minute, holding at 950 ° C. for 5 hours, and then cooling to 150 ° C. at a rate of 7 ° C. per minute. The obtained fired product was mixed with an ethanol solution of perfluorohexanoic acid, and further heated to diffuse fluorine to obtain a positive electrode active material powder composed of composite oxide particles. At that time, heating was performed by heating at a rate of 5 ° C. per minute, holding at 850 ° C. for 5 hours, and then cooling to 150 ° C. at a rate of 7 ° C. per minute.

When the composition of the produced positive electrode active material powder was analyzed by ICP spectroscopy, it was confirmed that it had an average composition of Li _1.03 Ca _0.05 Co _0.34 Ni _0.33 Mn _0.33 O _1.96 F _0.07 . Moreover, when the particle size was measured by the laser scattering method, the average particle size was 13 μm. Furthermore, when observed by SEM, spherical particles in which primary particles of 0.1 μm to 5 μm aggregated were confirmed. In addition, when the state of element distribution on the particle surface was examined by X-ray electron spectroscopy, it was confirmed that fluorine and calcium were present at a higher concentration than in the interior of the particle.

( Experimental example 2)
A positive electrode active material powder was prepared in the same manner as in Experimental Example 1 except that strontium nitrate was used instead of calcium nitrate.

When the composition of the produced positive electrode active material powder was analyzed in the same manner as in Experimental Example 1, it was confirmed that it had an average composition of Li _1.03 Sr _0.04 Co _0.33 Ni _0.34 Mn _0.33 O _1.85 F _0.08 . Moreover, when the particle size was measured by the laser scattering method, the average particle size was 18 μm. Furthermore, when observed by SEM, spherical particles in which primary particles of 0.1 μm to 5 μm aggregated were confirmed. In addition, when the distribution of fluorine and strontium on the particle surface was analyzed by X-ray electron spectroscopy, it was confirmed that it was present at a higher concentration on the particle surface than inside the particle.

( Experimental example 3)
A positive electrode active material powder was prepared in the same manner as in Experimental Example 1 except that barium nitrate was used instead of calcium nitrate.

When the composition of the produced positive electrode active material powder was analyzed in the same manner as in Experimental Example 1, it was confirmed that it had an average composition of Li _1.03 Ba _0.03 Co _0.33 Ni _0.34 Mn _0.33 O _1.91 F _0.07 . Moreover, when the particle size was measured by the laser scattering method, the average particle size was 15 μm. Furthermore, when observed by SEM, spherical particles in which primary particles of 0.1 μm to 5 μm aggregated were confirmed. In addition, when the distribution of fluorine and barium on the particle surface was analyzed by X-ray electron spectroscopy, it was confirmed that it was present at a higher concentration on the particle surface than inside the particle.

( Experimental example 4)
A positive electrode active material powder was prepared in the same manner as in Experimental Example 1 except that nickel nitrate and manganese nitrate were not used.

When the composition of the produced positive electrode active material powder was analyzed in the same manner as in Experimental Example 1, it was confirmed that it had an average composition of Li _1.03 Ca _0.04 Co _1.00 O _1.99 F _0.08 . Moreover, when the particle size was measured by the laser scattering method, the average particle size was 18 μm. Furthermore, when observed by SEM, spherical particles in which primary particles of 0.1 μm to 5 μm aggregated were confirmed. In addition, when the distribution of fluorine and calcium on the particle surface was analyzed by X-ray electron spectroscopy, it was confirmed that they were present at a higher concentration on the particle surface than inside the particle.

( Experimental example 5)
A positive electrode active material powder was prepared in the same manner as in Experimental Example 1 except that nickel nitrate and manganese nitrate were not used and the mixed amount of calcium nitrate was doubled.

When the composition of the produced positive electrode active material powder was analyzed in the same manner as in Experimental Example 1, it was confirmed that it had an average composition of Li _1.03 Ca _0.08 Co _1.00 O _2.02 F _0.08 . Moreover, when the particle size was measured by the laser scattering method, the average particle size was 16 μm. Furthermore, when observed by SEM, spherical particles in which primary particles of 0.1 μm to 5 μm aggregated were confirmed. In addition, when the distribution of fluorine and calcium on the particle surface was analyzed by X-ray electron spectroscopy, it was confirmed that they were present at a higher concentration on the particle surface than inside the particle.

( Experimental example 6)
A positive electrode active material powder was prepared in the same manner as in Experimental Example 1 except that aluminum nitrate was used instead of nickel nitrate and manganese nitrate. At that time, cobalt nitrate and aluminum nitrate were mixed so that the ratio of cobalt to aluminum was a molar ratio of cobalt: aluminum = 0.98: 0.02.

When the composition of the produced positive electrode active material powder was analyzed in the same manner as in Experimental Example 1, it was confirmed that it had an average composition of Li _1.03 Ca _0.04 Co _0.98 Al _0.02 O _2.02 F _0.08 . Moreover, when the particle size was measured by the laser scattering method, the average particle size was 15 μm. Furthermore, when observed by SEM, spherical particles in which primary particles of 0.1 μm to 5 μm aggregated were confirmed. In addition, when the distribution of fluorine and calcium on the particle surface was analyzed by X-ray electron spectroscopy, it was confirmed that they were present at a higher concentration on the particle surface than inside the particle.

(Comparative Example 1)
The positive electrode active material powder was the same as in Experimental Example 1 except that nickel nitrate, manganese nitrate and calcium nitrate were not used, and the mixture was not mixed with an ethanol solution of perfluorohexanoic acid and secondly heated. Was made. When the composition of the produced positive electrode active material powder was analyzed in the same manner as in Experimental Example 1, it was confirmed that it had an average composition of Li _1.03 Co _1.00 O _2.00 . Moreover, when the particle diameter was measured by the laser scattering method, the average particle diameter of the secondary particles was 15 μm.

(Comparative Example 2)
A positive electrode active material powder was prepared in the same manner as in Experimental Example 1, except that nickel nitrate and manganese nitrate were not used, and further, mixing with ethanol solution of perfluorohexanoic acid and second heating were not performed. . When the composition of the produced positive electrode active material powder was analyzed in the same manner as in Experimental Example 1, it was confirmed that it had an average composition of Li _1.03 Ca _0.03 Co _1.00 O _2.00 . Moreover, when the particle size was measured by the laser scattering method, the average particle size of the secondary particles was 12 μm.

(Comparative Example 3)
A positive electrode active material powder was prepared in the same manner as in Experimental Example 1 except that the amount of calcium nitrate mixed was changed and nickel nitrate and manganese nitrate were not used. When the composition of the produced positive electrode active material powder was analyzed in the same manner as in Experimental Example 1, it was confirmed that it had an average composition of Li _1.03 Ca _0.11 Co _1.00 O _2.06 F _0.08 . Moreover, when the particle size was measured by the laser scattering method, the average particle size of the secondary particles was 13 μm.

(Comparative Example 4)
A positive electrode active material powder was prepared in the same manner as in Experimental Example 1 except that the concentration of perfluorohexanoic acid was changed. When the composition of the produced positive electrode active material powder was analyzed in the same manner as in Experimental Example 1, it was confirmed that it had an average composition of Li _1.03 Ca _0.05 Co _0.34 Ni _0.33 Mn _0.33 O _1.96 F _0.12 . Moreover, when the particle size was measured by the laser scattering method, the average particle size of the secondary particles was 12 μm.

Next, secondary batteries shown in FIGS. 2 and 3 were produced using the produced positive electrode active material powders of Experimental Examples 1 to 6 and Comparative Examples 1 to 4. First, 86% by mass of positive electrode active material powder, 10% by mass of graphite as a conductive agent, and 4% by mass of polyvinylidene fluoride as a binder were mixed and dispersed in N-methyl-2-pyrrolidone as a solvent. The positive electrode current collector 21A made of a strip-shaped aluminum foil having a thickness of 20 μm was coated on both surfaces, dried, and compression molded to form the positive electrode active material layer 21B, whereby the positive electrode 21 was produced. At that time, the porosity of the positive electrode active material layer 21B was set to 26% by volume. 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 amounts of the positive electrode active material and the negative electrode active material are adjusted, the open circuit voltage at the time of full charge is 4.40 V or 4.20 V, and the capacity of the negative electrode 22 is represented by a capacity component due to insertion and extraction of lithium. Designed to be.

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. For a secondary battery with an open circuit voltage of 4.40 V when fully charged, charge 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. Constant voltage charging was performed until the total time reached 2.5 hours, and discharging was performed at a constant current of 800 mA until the battery voltage reached 2.75V. Further, in a secondary battery having an open circuit voltage of 4.20 V at the time of full charge, charging is performed at a constant current of 1000 mA until the battery voltage reaches 4.20 V, and then a constant voltage of 4.20 V is charged. Then, constant voltage charging was performed until the total charging time reached 2.5 hours, and discharging was performed at a constant current of 800 mA until the battery voltage reached 2.75V. The obtained results are shown in Table 1. Table 1 shows initial capacities of secondary batteries having an open circuit voltage of 4.40 V during full charge.

As shown in Table 1, the average composition is represented by _{Li (1 + a) A b} Co (1-xyz) Ni x Mn y M z O (2-c) F d, and the first element A According to Experimental Examples 1 to 6 using a positive electrode active material in which certain calcium, strontium or barium and fluorine are present at a higher concentration on the particle surface than in the inside of the particle, the comparison does not include the first element A and fluorine Both the initial capacity and the discharge capacity maintenance ratio were improved as compared with Examples 1 and 2. Particularly, a high value was obtained in a secondary battery having an open circuit voltage of 4.40 V during full charge. Further, the initial capacity was improved as compared with Comparative Examples 3 and 4 in which the composition of the first element A or fluorine was out of the range.

That is, the average composition is represented by _{Li (1 + a) A b} Co (1-xyz) Ni x Mn y M z O (2-c) F d, the first element A and fluorine as compared with the inside of the grain particles It was found that the capacity and cycle characteristics can be improved by using a positive electrode active material present at a high concentration on the surface.

  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 (9)

During average composition _{Li (1 + a) A b} Co (1-xyz) Ni x Mn y M z O (2-c) F d ( wherein, A is calcium (Ca), strontium (Sr) and barium (Ba ) M is magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron At least of the group consisting of (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), tungsten (W), zirconium (Zr), yttrium (Y) and niobium (Nb) X, y, and z are values within the ranges of 0 <x <0.85, 0 <y <0.55, 0 ≦ z <0.10, and x + y + z ≦ 1, respectively. a, b, c and d are −0.10 ≦ a ≦ 0.10 and 0, respectively. b ≦ 0.10, wherein the composite oxide particles represented by a.) a value in the range of -0.10 ≦ c ≦ 0.20,0 <d ≦ 0.10,
The composite oxide particles is composed of cobalt and composition of the nickel and the manganese and the second element M _{Co (1-xyz) Ni x} Mn y M oxide represented by _z, hydroxides or their hydrates of the precursor particles, by the material of the first element a is heat-treated by depositing, Rutotomoni first element a is added, after the first element a is added to the precursor particles, or is added When fluorine is added ,
The first element A and fluorine in the composite oxide particles are present in a higher concentration on the particle surface than in the particles, and a positive electrode active material for a secondary battery.   2. The positive electrode active material for a secondary battery according to claim 1, wherein the composite oxide particles are formed by depositing a lithium compound together with a raw material of the first element on the precursor particles.   2. The positive electrode active material for a secondary battery according to claim 1, wherein the composite oxide particles are formed using an oxide, a hydroxide, or a hydrate thereof containing lithium as the precursor particles. A method for producing a positive electrode active material comprising composite oxide particles having an average composition represented by formula (1),
Cobalt oxide compositions of the nickel and the manganese and the second element M is represented by _{Co (1-xyz) Ni x} Mn y M z, the precursor particles consisting of hydroxides or their hydrate, first the raw material of the element a by heat treatment are adhered to, look including the step of adding a first element a,
A method for producing a positive electrode active material for a secondary battery , wherein fluorine is added after or when the first element A is added to the precursor particles .
_{Li (1 + a) A b} Co (1-xyz) Ni x Mn y M z O (2-c) F d ····· (1)
(In the formula, A is at least one first element selected from the group consisting of calcium (Ca), strontium (Sr), and barium (Ba), and M is magnesium (Mg), aluminum (Al), boron ( B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), tungsten (W), zirconium ( Zr), yttrium (Y), and niobium (Nb), at least one second element, where x, y, and z are 0 <x <0.85 and 0 <y <0. 55, 0 ≦ z <0.10, values in the range of x + y + z ≦ 1, a, b, c and d are −0.10 ≦ a ≦ 0.10, 0 <b ≦ 0.10, −0, respectively. .10 ≦ c ≦ 0.20, 0 <d ≦ 0.10 Is the value of the 囲内.) The manufacturing method of the positive electrode active material for secondary batteries of Claim 4 which makes a lithium compound adhere to the said precursor particle | grain with the raw material of a 1st element. The manufacturing method of the positive electrode active material for secondary batteries of Claim 4 using the oxide, hydroxide, or these hydrates containing lithium as said precursor particle | grains. Along with a positive electrode and a negative electrode, an electrolyte is provided,
The positive electrode, the average composition of _{Li (1 + a) A b} Co (1-xyz) Ni x Mn y M z O (2-c) F d ( wherein, A is calcium (Ca), strontium (Sr) And at least one first element selected from the group consisting of barium (Ba), and M is magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium ( The group consisting of Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), tungsten (W), zirconium (Zr), yttrium (Y) and niobium (Nb) X, y, and z are ranges of 0 <x <0.85, 0 <y <0.55, 0 ≦ z <0.10, and x + y + z ≦ 1, respectively. The values a, b, c and d are -0.10 ≦ a ≦ .10,0 <b ≦ 0.10, wherein the composite oxide particles represented by a value within a range of -0.10 ≦ c ≦ 0.20,0 <d ≦ 0.10.),
The composite oxide particles is composed of cobalt and composition of the nickel and the manganese and the second element M _{Co (1-xyz) Ni x} Mn y M oxide represented by _z, hydroxides or their hydrates of the precursor particles, by the material of the first element a is heat-treated by depositing, Rutotomoni first element a is added, after the first element a is added to the precursor particles, or is added When fluorine is added ,
The secondary battery in which the first element A and fluorine in the composite oxide particles are present at a higher concentration on the particle surface than in the inside of the particle. The secondary battery according to claim 7 , wherein the composite oxide particles are formed by depositing a lithium compound together with a raw material of the first element on the precursor particles. The secondary battery according to claim 7 , wherein the composite oxide particles are formed using an oxide, a hydroxide, or a hydrate thereof containing lithium as the precursor particles.

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