JP2011082133A - Positive electrode active material, positive electrode, and nonaqueous electrolyte cell, and method of preparing positive electrode active material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive-electrode active material having high capacity, superior capacity for charging/discharging cycle, and at the same time, with less degradation, when under high-temperature atmosphere. <P>SOLUTION: The positive-electrode active material is used with a composition such that at least one of sulfur (S), phosphorus (P), and fluorine (F) exists in the aggregate on the surface of a complex-oxide particle containing transition metal and metallic element M; and that the metallic element M has concentration gradient getting concentrated toward the surface from the center of the complex-oxide particle. The positive-electrode active material having such a composition can be constituted, by preliminarily mixing and burning the compound containing lithium, the compound containing the transition metal, and the compound containing the metallic element M; by depositing the compound containing at least one of sulfur (S), phosphorus (P) and fluorine (F) on the surface of the complex-oxide particle; and by burning it again. It is preferable that the compound or its thermolysis product have a melting point of ≥70°C and ≤600°C. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a positive electrode active material, a positive electrode, a nonaqueous electrolyte battery, and a method for producing a positive electrode active material, and in particular, realizes a high performance nonaqueous electrolyte battery with little capacity deterioration when charged and discharged in a high temperature environment. The present invention relates to a positive electrode active material, a positive electrode, a nonaqueous electrolyte battery, and a method for producing a positive electrode active material.

  In recent years, with the widespread use of portable devices such as video cameras and notebook personal computers, the demand for small, high-capacity secondary batteries has increased. Currently used secondary batteries include nickel-cadmium batteries and nickel-hydrogen batteries using an alkaline electrolyte, but the battery voltage is as low as about 1.2 V, and it is difficult to improve the energy density. For this reason, at present, lithium ion secondary batteries having a high voltage and a high energy density are widely used compared to other battery systems.

  However, the lithium ion secondary battery has a high charging voltage with respect to other battery systems, so that the capacity is deteriorated in a usage mode in which the lithium ion secondary battery is left in a charged state for a long time, and the battery life is shortened. In addition, when used in a high temperature environment, there is a problem that the internal resistance increases and a sufficient capacity cannot be taken out, and it is desired to solve these problems.

For example, Patent Document 1 below shows a method of adding a metal salt or hydroxide to a positive electrode. Patent Document 2 discloses a technique of covering the surface of lithium cobaltate (LiCoO ₂ ) with phosphorus (P). In patent document 3, the method of coat | covering a metal oxide on the surface of a positive electrode active material or a positive electrode is shown.

  Patent Document 4 and the like show a method of uniformly coating a lithium transition metal composite oxide on the particle surface and a method of diffusing from the surface. Patent Document 5 discloses a positive electrode active material in which a lump of metal oxide is attached on a metal oxide layer. Patent Document 6 discloses a positive electrode active material in which one or more surface treatment layers containing two or more coating elements are formed on the surface of a core containing a lithium compound.

  Patent Document 7 discloses a positive electrode active material having a coating film made of a metal fluoride on the particle surface, and Patent Document 8 shows a coating with a crystalline metal fluoride. Japanese Patent Application Laid-Open No. 2003-221235 discloses that the XPS energy value of fluorine on the particle surface is specified. When the positive electrode active material was produced by the method of mixing and heat treating the metal fluoride as disclosed by the present inventor, the effect on the high temperature storage performance was actually observed, but the effect on the particle surface was limited, The actual usage performance was insufficient. Further, Patent Document 9 discloses a material having a high affinity for lithium and a reaction between a compound supplying a cation and a lithium transition metal composite oxide.

Japanese Patent No. 3197763 JP-A-5-47383 Japanese Patent No. 3172388 JP 7-235292 A Japanese Patent Laid-Open No. 2001-256969 JP 2002-164053 A Japanese Patent No. 3157413 Japanese Patent No. 3141858 U.S. Pat. No. 7,364,793

  However, in the form added to the lithium transition metal oxide having a normal uniform form as in the method of Patent Document 1, the resistance of the electrode is increased and a sufficient capacity cannot be obtained. Further, the method of Patent Document 2 has a large capacity drop due to coating and is insufficient for actual use. In the method of Patent Document 3, the disclosed covering element, coating method, and coating form alone are not sufficient as a performance improvement technique in a high temperature environment. In order to inhibit diffusion, the charge / discharge current value in the practical range is insufficient because a sufficient capacity cannot be obtained.

  Although the method disclosed in Patent Document 4 can maintain a high capacity, it is insufficient for improving cycle characteristics to a high degree and further suppressing an increase in resistance during high temperature use. In patent document 5, when it manufactured with the disclosed manufacturing method and structure, sufficient charging / discharging efficiency was not obtained and it resulted in a capacity | capacitance falling significantly. In the method of Patent Document 6, the effect is limited only by the surface treatment, and when the positive electrode active material is produced by the actually disclosed manufacturing method, a uniform multi-layer is formed, particularly with respect to an increase in resistance at high temperature use. Was not effective.

  In Patent Document 8, simply by covering with a metal fluoride having low electron conductivity and low lithium ion conductivity, the charge / discharge performance is significantly lowered, and the effect on the charge / discharge characteristics in a high temperature environment is insufficient. Further, in Patent Document 9, when a positive electrode active material was produced by the method disclosed by the present inventors, unevenness and dropping of a material added as a coating material occurred, and an inert compound such as an oxide or lithium fluoride was produced. As a result, the covering function could not be fully exhibited. Moreover, since the movement of lithium ions during charge / discharge is inhibited at the solid-liquid interface, charge / discharge performance at a practical level could not be obtained. Moreover, since lithium was deprived from the lithium transition metal composite oxide, the capacity tended to decrease, which was insufficient.

  Accordingly, the present invention is intended to solve the above-described problems, and is a positive electrode active material, a positive electrode, a nonaqueous electrolyte battery, and a positive electrode that have a high capacity, excellent charge / discharge cycles, and at the same time, little deterioration when used in a high temperature environment. It aims at providing the manufacturing method of an active material.

In order to solve the above-described problem, the first invention mixes and fires a compound containing lithium, a compound containing a transition metal to be dissolved, and a compound containing a metal element M different from the transition metal. To form composite oxide particles,
A compound containing at least one of sulfur (S), phosphorus (P) and fluorine (F) is deposited on the surface of the composite oxide particle oxide particle,
By firing the composite oxide particles on which the compound containing at least one of sulfur (S), phosphorus (P) and fluorine (F) is deposited,
A concentration gradient in which the concentration of the metal element M increases from the center of the composite oxide particle toward the surface;
It is a positive electrode active material in which at least one of sulfur (S), phosphorus (P), and fluorine (F) is present in an aggregated form on the surface of the composite oxide particle.

In the second invention, a compound containing lithium, a compound containing a transition metal to be dissolved, and a compound containing a metal element M different from the transition metal are mixed and fired to form composite oxide particles. And
A compound containing at least one of sulfur (S), phosphorus (P) and fluorine (F) is deposited on the surface of the composite oxide particle oxide particle,
By firing the composite oxide particles to which the compound containing at least one of sulfur (S), phosphorus (P) and fluorine (F) is deposited,
A concentration gradient in which the concentration of the metal element M increases from the center of the composite oxide particle toward the surface;
It is a positive electrode including a positive electrode active material in which at least one of sulfur (S), phosphorus (P), and fluorine (F) is present in an aggregated state on the surface of the composite oxide particle.

A third invention comprises a positive electrode, a negative electrode, and an electrolyte,
The positive electrode
A compound containing lithium, a compound containing a transition metal to be dissolved, and a compound containing a metal element M different from the transition metal are mixed and fired to form composite oxide particles,
A compound containing at least one of sulfur (S), phosphorus (P) and fluorine (F) is deposited on the surface of the composite oxide particle oxide particle,
By firing the composite oxide particles on which the compound containing at least one of sulfur (S), phosphorus (P) and fluorine (F) is deposited,
A concentration gradient in which the concentration of the metal element M increases from the center of the composite oxide particle toward the surface;
The nonaqueous electrolyte battery includes a positive electrode active material in which at least one of sulfur (S), phosphorus (P), and fluorine (F) is present in an aggregated state on the surface of the composite oxide particle.

  In the first to third inventions, the compound containing at least one of sulfur (S), phosphorus (P) and fluorine (F) has a melting point of 70 ° C. or more and 600 ° C. or less and an average particle size of 30 μm or less. It is preferable.

The fourth invention is a composite in which a compound containing lithium, a compound containing a transition metal to be dissolved, and a compound containing a metal element M different from the transition metal are mixed and fired to form composite oxide particles. An oxide particle forming step;
A deposition step of depositing a compound containing at least one of sulfur (S), phosphorus (P) and fluorine (F) on the surface of the composite oxide particle oxide particles;
A firing step of firing composite oxide particles on which a compound containing at least one of sulfur (S), phosphorus (P) and fluorine (F) is deposited,
A concentration gradient in which the concentration of the metal element M increases from the center of the composite oxide particle toward the surface;
This is a method for producing a positive electrode active material in which at least one of sulfur (S), phosphorus (P), and fluorine (F) is present in an aggregated form on the surface of the composite oxide particle.

  In the fourth invention, a compound containing at least one of sulfur (S), phosphorus (P) and fluorine (F) deposited on the surface of the composite oxide particles or a pyrolyzate of the compound is melted, It is preferable to uniformly coat the surface of the composite oxide particles. Further, on the surface of the composite oxide particle, the cation of the compound containing at least one of sulfur (S), phosphorus (P), and fluorine (F) disappears, and the anion of the compound and the composite oxide particle include It is preferable to react with the element.

  In the fourth invention, a compound containing at least one of sulfur (S), phosphorus (P) and fluorine (F) having a melting point of 70 ° C. or more and 600 ° C. or less and an average particle size of 30 μm or less is used. preferable.

  In this invention, the metal element M has a concentration gradient that increases from the center of the composite oxide particle toward the surface, and sulfur (S), phosphorus (P), and fluorine (F) on the surface of the composite oxide particle. Since at least one of them is present in an aggregated form on the surface of the composite oxide particle, stabilization at the positive electrode active material and its interface can be achieved.

  According to the present invention, it is possible to realize a battery having a high capacity and excellent charge / discharge cycle, and at the same time, having little deterioration when used in a high temperature environment.

It is a perspective view which shows one structural example of the nonaqueous electrolyte battery by embodiment of this invention. It is sectional drawing along the II-II line of the winding electrode body 10 shown in FIG. It is sectional drawing which shows one structural example of the nonaqueous electrolyte battery by embodiment of this invention. FIG. 4 is an enlarged cross-sectional view illustrating a part of a wound electrode body 30 illustrated in FIG. 3. It is sectional drawing which shows one structural example of the nonaqueous electrolyte battery by embodiment of this invention.

Embodiments of the present invention will be described below with reference to the drawings. The embodiments described below are specific examples of the present invention, and various technically preferable limitations are given. However, the scope of the present invention is particularly limited in the following description. Unless stated to the effect, the present invention is not limited to the embodiment. The description will be given in the following order.
1. First Embodiment (First Example of Nonaqueous Electrolyte Battery)
2. Second embodiment (second example of nonaqueous electrolyte battery)
3. Third embodiment (third example of nonaqueous electrolyte battery)
4). Fourth Embodiment (Fourth Example of Nonaqueous Electrolyte Battery)
5). Other embodiment (modification)

[Outline of the Invention]
Lithium-containing transition metal oxides such as lithium cobaltate (LiCoO ₂ ) and lithium nickelate (LiNiO ₂ ) are widely used as positive electrode active materials for lithium ion secondary batteries. However, there is a problem in the stability in the charged state, in particular, the reactivity at the interface between the positive electrode active material and the electrolyte increases, so that the transition metal component is eluted from the positive electrode, the active material is deteriorated, and the eluted metal is The problem of precipitation on the negative electrode side arises. This causes inhibition of lithium (Li) storage / release.

  Further, it is considered that the degradation of the battery characteristics is caused by accelerating the decomposition reaction of the electrolyte solution at the interface, generating a film on the surface, and causing gas generation. In addition, by charging the battery so that the maximum charging voltage is 4.20V or higher, preferably 4.35V or higher, more preferably 4.40V or higher in a properly designed positive / negative ratio, It is possible to improve the energy density. However, as charging voltage is increased, when charging / discharging is repeated at a high charging voltage state of 4.25 V or higher, the deterioration of the active material or the electrolyte solution is accelerated, and the charge / discharge cycle life is reduced or after high temperature storage. It has been found that it causes performance degradation.

  Therefore, the present inventors have intensively studied this point, and in the lithium transition metal composite oxide whose particle surface has been modified, the presence of a metal compound on the particle surface has a great synergistic effect on the improvement of battery characteristics. And found new effects. The present invention is based on this fact, and provides a positive electrode active material for a lithium ion secondary battery that is highly improved in battery characteristics and reliability.

1. First Embodiment (First Example of Nonaqueous Electrolyte Battery)
FIG. 1 is a perspective view showing a configuration example of a nonaqueous electrolyte battery according to the first embodiment of the present invention. This nonaqueous electrolyte battery is, for example, a nonaqueous electrolyte secondary battery. This nonaqueous electrolyte battery has a configuration in which a wound electrode body 10 to which a positive electrode lead 11 and a negative electrode lead 12 are attached is housed inside a film-like exterior member 1 and has a flat shape. .

  Each of the positive electrode lead 11 and the negative electrode lead 12 has a strip shape, for example, and is led out from the inside of the exterior member 1 to the outside, for example, in the same direction. The positive electrode lead 11 is made of a metal material such as aluminum (Al), and the negative electrode lead 12 is made of a metal material such as nickel (Ni).

  The exterior member 1 is a laminated film having a structure in which, for example, an insulating layer, a metal layer, and an outermost layer are laminated in this order and bonded together by a lamination process or the like. For example, the exterior member 1 has the insulating layer side as the inner side, and the outer edge portions are in close contact with each other by fusion bonding or an adhesive.

  The insulating layer is made of, for example, a polyolefin resin such as polyethylene, polypropylene, modified polyethylene, modified polypropylene, or a copolymer thereof. This is because moisture permeability can be lowered and airtightness is excellent. The metal layer is made of foil-like or plate-like aluminum, stainless steel, nickel, iron, or the like. The outermost layer may be made of, for example, the same resin as the insulating layer, or may be made of nylon or the like. This is because the strength against tearing and piercing can be increased. The exterior member 1 may include a layer other than the insulating layer, the metal layer, and the outermost layer.

  Between the exterior member 1 and the positive electrode lead 11 and the negative electrode lead 12, an adhesion film 2 for improving the adhesion between the positive electrode lead 11 and the negative electrode lead 12 and the inside of the exterior member 1 and preventing intrusion of outside air. Has been inserted. The adhesion film 2 is made of a material having adhesion to the positive electrode lead 11 and the negative electrode lead 12. When the positive electrode lead 11 and the negative electrode lead 12 are made of the above-described metal material, it is preferably made of a polyolefin resin such as polyethylene, polypropylene, modified polyethylene, or modified polypropylene.

  FIG. 2 is a sectional view taken along line II-II of the spirally wound electrode body 10 shown in FIG. The wound electrode body 10 is obtained by stacking and winding a positive electrode 13 and a negative electrode 14 with a separator 15 and an electrolyte 16, and the outermost peripheral portion is protected by a protective tape 17.

[Positive electrode]
The positive electrode 13 includes, for example, a positive electrode current collector 13A and a positive electrode active material layer 13B provided on both surfaces of the positive electrode current collector 13A. As the positive electrode current collector 13A, for example, a metal foil such as an aluminum foil can be used.

  The positive electrode active material layer 13B further includes a conductive additive such as a carbon material and a binder such as polyvinylidene fluoride or polytetrafluoroethylene.

[Positive electrode active material]
The positive electrode active material includes, for example, a metal element M different from the main transition metal inside the composite oxide particle, and the metal element M has a concentration gradient from the center of the particle toward the particle surface. The concentration gradient is such that the concentration of the metal element M increases as it approaches the particle surface. A lithium-containing transition metal composite oxide containing at least one element selected from sulfur (S), phosphorus (P), and fluorine (F) in an aggregated form is used on the surface of the composite oxide particles. The state of the surface of the lithium transition metal composite oxide can be confirmed by observing the obtained powder with SEM / EDX (Scanning Electron Microscopy / Energy Dispersive X-ray spectrometer).

  The metal element M is not particularly limited, but the metal element M is present in advance in the composite oxide particle, and at least one selected from sulfur (S), phosphorus (P), and fluorine (F). A lithium-containing transition metal composite oxide in which the surface concentration of the metal element M is increased by reacting with a compound containing an element is preferable.

  By increasing the surface concentration after the metal element M is uniformly distributed in the composite oxide particles in advance, the metal element M can be present evenly on the surface. Thereby, the modification effect of the particle | grain surface by the metal element M can be exhibited to the maximum.

  The metal element M is preferably at least one element that can be substituted with the main transition metal element A in the composite oxide particle. Among them, manganese (Mn), magnesium (Mg), aluminum (Al ), Nickel (Ni), boron (B), titanium (Ti), cobalt (Co) and iron (Fe). It is effective that the metal element M is in a state in which the main transition metal element A is substituted on the particle surface or diffuses in the vicinity of the particle surface and has a continuous concentration distribution in the center direction of the particle.

  The magnesium concentration can be confirmed by cutting the cross section of the lithium transition metal composite oxide and measuring the radial element distribution by Auger electron spectroscopy.

  Furthermore, when reacting with a compound containing at least one element selected from sulfur (S), phosphorus (P) and fluorine (F) to increase the surface concentration of the metal element M, a lithium (Li) compound is allowed to coexist. Is preferred. This is because the Li amount in the lithium-containing composite oxide can be adjusted by coexisting the Li compound, and the capacity reduction due to surface modification can be suppressed.

  As the lithium transition metal composite oxide inside the particle, a known substance can be used, but it has a layered rock salt structure, and the main transition metal element A constituting it is at least nickel (Ni), cobalt (Co), manganese ( Mn) and iron (Fe) are preferably selected. This is because a high capacity can be obtained. It is also possible to use a known substance in which a small amount of additive element is replaced by solid solution.

  The composite oxide particles serving as the base material of the positive electrode are, for example, lithium composite oxide particles having a layered rock salt type structure whose average composition is represented by (Chemical Formula 1). The lithium composite oxide particles may be primary particles or secondary particles.

(Chemical formula 1)
Li _a A _b M _1-b O _c
(Wherein M is at least selected from manganese (Mn), magnesium (Mg), aluminum (Al), nickel (Ni), boron (B), titanium (Ti), cobalt (Co) and iron (Fe). It is preferable that the element is at least one element, and a, b, and c are values in the range of 0.2 ≦ a ≦ 1.4, 0 ≦ b ≦ 1.0, and 1.8 ≦ c ≦ 2.2, respectively Note that the composition of lithium varies depending on the state of charge and discharge, and the value of a represents the value in a fully discharged state.)

  Here, in (Chemical Formula 1), the range of a is, for example, 0.2 ≦ a ≦ 1.4. When this value is decreased, the layered rock salt structure of the basic crystal structure of the lithium composite oxide is destroyed, so that recharging becomes difficult and the capacity is significantly reduced. When this value increases, lithium diffuses out of the composite oxide particles described above, which hinders control of the basicity of the next processing step, and ultimately promotes gelation during kneading of the positive electrode paste. Causes harmful effects.

  Note that the lithium composite oxide of (Chemical Formula 1) may contain excessive lithium as compared with the conventional lithium composite oxide. That is, a indicating the lithium composition of the lithium composite oxide of (Chemical Formula 1) may be greater than 1.2. Here, the value of 1.2 is disclosed as the lithium composition of the conventional lithium composite oxide of this type, and the same action and effect in the present application can be obtained by the same crystal structure as in the case of a = 1. (For example, refer to Japanese Patent Application Laid-Open No. 2008-251434, which is a prior application of the present applicant).

  Even if a indicating the lithium composition of the lithium composite oxide of (Chemical Formula 1) is larger than 1.2, the crystal structure of the lithium composite oxide is the same as that when a is 1.2 or less. In addition, even if a indicating the lithium composition in Chemical Formula 1 is greater than 1.2 and 1.4 or less, the chemical state of the transition metal constituting the lithium composite oxide in the oxidation-reduction reaction associated with charge / discharge is: Compared with the case where a is 1.2 or less, there is no significant change.

  The range of b is, for example, 0 ≦ b ≦ 1.0. When the value decreases outside this range, the discharge capacity of the positive electrode active material decreases. If the value is increased outside this range, the stability of the crystal structure of the composite oxide particles decreases, which causes a decrease in the capacity of repeated charge / discharge of the positive electrode active material and a decrease in safety.

  The range of c is, for example, 1.8 ≦ c ≦ 2.2. When the value decreases outside this range and when the value increases outside this range, the stability of the crystal structure of the composite oxide particles decreases, the capacity of the positive electrode active material is repeatedly reduced and the safety decreases. As a result, the discharge capacity of the positive electrode active material decreases.

[Particle size]
The average particle diameter of the positive electrode active material is preferably 2.0 μm or more and 50 μm or less. When the average particle size is less than 2.0 μm, the positive electrode active material layer is peeled off when the positive electrode active material layer is pressed during the production of the positive electrode. Further, since the surface area of the positive electrode active material is increased, it is necessary to increase the amount of the conductive agent and the binder added, and the energy density per unit weight tends to be reduced. On the other hand, when the average particle diameter exceeds 50 μm, the particles tend to penetrate the separator and cause a short circuit.

  Such a positive electrode 13 preferably has a thickness of 250 μm or less.

[Negative electrode]
The negative electrode 14 includes, for example, a negative electrode current collector 14A and a negative electrode active material layer 14B provided on both surfaces of the negative electrode current collector 14A. The negative electrode current collector 14A is made of, for example, a metal foil such as a copper foil.

  The negative electrode active material layer 14B includes, for example, one or more negative electrode materials capable of occluding and releasing lithium as a negative electrode active material, and a conductive additive as necessary. And may contain a binder.

  Examples of the negative electrode material capable of inserting and extracting lithium include carbon materials such as graphite, non-graphitizable carbon, and graphitizable carbon. Any one of these carbon materials may be used alone, or two or more of them may be mixed and used, or two or more of them having different average particle diameters may be mixed and used.

  Further, examples of the negative electrode material capable of inserting and extracting lithium include a material containing a metal element or a metalloid element capable of forming an alloy with lithium as a constituent element. Specifically, a simple substance, alloy, or compound of a metal element capable of forming an alloy with lithium, or a simple substance, alloy, or compound of a metalloid element capable of forming an alloy with lithium, or one or more of these. The material which has these phases in at least one part is mentioned.

  Examples of such metal elements or metalloid elements include tin (Sn), lead (Pb), aluminum, indium (In), silicon (Si), zinc (Zn), antimony (Sb), and bismuth (Bi). , Cadmium (Cd), magnesium (Mg), boron (B), gallium (Ga), germanium (Ge), arsenic (As), silver (Ag), zirconium (Zr), yttrium (Y) or hafnium (Hf) Is mentioned. Among them, the group 14 metal element or metalloid element in the long-period periodic table is preferable, and silicon (Si) or tin (Sn) is particularly preferable. This is because silicon (Si) and tin (Sn) have a large ability to occlude and release lithium, and a high energy density can be obtained.

  As an alloy of silicon (Si), for example, as a second constituent element other than silicon (Si), tin (Sn), nickel (Ni), copper (Cu), iron (Fe), cobalt (Co), manganese (Mn), zinc (Zn), indium (In), silver (Ag), titanium (Ti), germanium (Ge), bismuth (Bi), antimony (Sb), and chromium (Cr). The thing containing 1 type is mentioned. As an alloy of tin (Sn), for example, as a second constituent element other than tin (Sn), silicon (Si), nickel (Ni), copper (Cu), iron (Fe), cobalt (Co), manganese (Mn), zinc (Zn), indium (In), silver (Ag), titanium (Ti), germanium (Ge), bismuth (Bi), antimony (Sb), and chromium (Cr). The thing containing 1 type is mentioned.

  Examples of the compound of silicon (Si) or tin (Sn) include those containing oxygen (O) or carbon (C), and in addition to silicon (Si) or tin (Sn), Two constituent elements may be included.

[Separator]
Any separator may be used as long as it is electrically stable, chemically stable with respect to the positive electrode active material, the negative electrode active material, or the solvent, and has no electrical conductivity. . For example, a polymer nonwoven fabric, a porous film, glass or ceramic fibers in a paper shape can be used, and a plurality of these may be laminated. In particular, a porous polyolefin film is preferably used, and a composite of this with a heat-resistant material made of polyimide, glass, ceramic fibers, or the like may be used.

[Electrolytes]
The electrolyte 16 contains an electrolytic solution and a holding body containing a polymer compound that holds the electrolytic solution, and is in a so-called gel form. The electrolytic solution includes an electrolyte salt and a solvent that dissolves the electrolyte salt. Examples of the electrolyte salt include lithium salts such as LiPF ₆ , LiClO ₄ , LiBF ₄ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , or LiAsF ₆ . Any one of the electrolyte salts may be used, or two or more of them may be mixed and used.

  Examples of the solvent include lactone solvents such as γ-butyrolactone, γ-valerolactone, δ-valerolactone, and ε-caprolactone, ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate. Carbonate ester solvents such as 1,2-dimethoxyethane, 1-ethoxy-2-methoxyethane, 1,2-diethoxyethane, ether solvents such as tetrahydrofuran or 2-methyltetrahydrofuran, nitrile solvents such as acetonitrile, Nonaqueous solvents such as sulfolane-based solvents, phosphoric acids, phosphate ester solvents, or pyrrolidones are mentioned. Any one type of solvent may be used alone, or two or more types may be mixed and used.

  The solvent preferably contains a compound in which part or all of hydrogen of the cyclic ester or chain ester is fluorinated. As the fluorinated compound, difluoroethylene carbonate (4,5-difluoro-1,3-dioxolan-2-one) is preferably used. Even when the negative electrode 14 containing a compound such as silicon (Si), tin (Sn), or germanium (Ge) is used as the negative electrode active material, the charge / discharge cycle characteristics can be improved. In particular, difluoroethylene carbonate is used. This is because the cycle characteristic improvement effect is excellent.

  The polymer compound may be any one that gels upon absorption of a solvent. For example, a fluorine-based polymer compound such as polyvinylidene fluoride or a copolymer of vinylidene fluoride and hexafluoropropylene, polyethylene oxide or polyethylene oxide. And ether-based polymer compounds such as crosslinked products containing polyacrylonitrile, polypropylene oxide, or polymethyl methacrylate as repeating units. Any one of these polymer compounds may be used alone, or two or more thereof may be mixed and used.

In particular, from the viewpoint of redox stability, a fluorine-based polymer compound is desirable, and among them, a copolymer containing vinylidene fluoride and hexafluoropropylene as components is preferable. Furthermore, this copolymer contains monoesters of unsaturated dibasic acids such as monomethylmaleic acid ester, halogenated ethylenes such as ethylene trifluorochloride, cyclic carbonates of unsaturated compounds such as vinylene carbonate, or epoxy group-containing compounds. An acrylic vinyl monomer may be included as a component. This is because higher characteristics can be obtained.

  Furthermore, as the solid electrolyte, any inorganic solid electrolyte or polymer solid electrolyte can be used as long as the material has lithium ion conductivity. Examples of the inorganic solid electrolyte include lithium nitride and lithium iodide. A polymer solid electrolyte is composed of an electrolyte salt and a polymer compound that dissolves the electrolyte salt. The polymer compound is composed of an ether polymer such as poly (ethylene oxide) or a crosslinked product, a poly (methacrylate) ester, an acrylate, or the like. It can be used alone, copolymerized or mixed in the molecule.

[Production method of positive electrode]
First, composite oxide particles containing the metal element M in the present invention are synthesized. The means for synthesizing the composite oxide particles is not particularly limited. Furthermore, various known methods can be applied to the method of increasing the surface concentration of the metal element M by reacting with a compound containing at least one element selected from sulfur (S), phosphorus (P) and fluorine (F). It is.

  As an example of a method for coating the surface of the composite oxide particles, a lithium transition metal composite oxide containing a metal element M and a compound containing sulfur (S), phosphorus (P) and fluorine (F) are mixed with a ball mill, It is possible to use a method of crushing and adhering using a crusher or a fine crusher. In this case, it is also effective to add a small amount of liquid which can be exemplified by water. Alternatively, the metal compound can be deposited by mechanochemical treatment or by a vapor phase method such as sputtering or CVD (Chemical Vapor Deposition).

  Furthermore, elemental sulfur (S), phosphorus (P) and fluorine (F) are mixed on the lithium transition metal composite oxide particles by mixing raw materials in a solvent such as water or ethanol, or by crystallization by neutralization in the liquid phase. ) Can also be formed. Thus, after sulfur (S), phosphorus (P), and fluorine (F) are present in the lithium transition metal composite slope including the metal element M, the surface concentration of the metal element M is increased by performing heat treatment. It is preferable. The heat treatment is performed at about 350 to 900 ° C., for example. The obtained lithium transition metal composite oxide may be subjected to a known technique such as adjustment of powder physical properties.

  Subsequently, a positive electrode active material, a binder, and a conductive additive such as a carbon material are mixed to prepare a positive electrode mixture, and this positive electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone. To prepare a positive electrode mixture slurry. As the binder, polyvinylidene fluoride or polytetrafluoroethylene is used.

  Next, this positive electrode mixture slurry is applied to the positive electrode current collector 13A and dried, and then compression-molded by a roll press or the like to form the positive electrode active material layer 13B, whereby the positive electrode 13 is obtained. In addition, a conductive additive such as a carbon material is mixed as necessary when preparing the positive electrode mixture.

[Production method of negative electrode]
Next, the negative electrode 14 is produced as follows. First, a negative electrode active material and a binder are mixed to prepare a negative electrode mixture, and this negative electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone to obtain a negative electrode mixture slurry. Next, after applying this negative electrode mixture slurry to the negative electrode current collector 14A and drying the solvent, the negative electrode active material layer 14B is formed by compression molding using a roll press or the like, and the negative electrode 14 is obtained.

[Method for producing non-aqueous electrolyte battery]
This non-aqueous electrolyte battery can be manufactured, for example, as follows. First, a precursor solution containing an electrolytic solution, a polymer compound, and a mixed solvent is applied to each of the positive electrode 13 and the negative electrode 14, and the mixed solvent is volatilized to form the electrolyte 16. After that, the positive electrode lead 11 is attached to the end of the positive electrode current collector 13A by welding, and the negative electrode lead 12 is attached to the end of the negative electrode current collector 14A by welding.

  Next, the positive electrode 13 and the negative electrode 14 on which the electrolyte 16 is formed are laminated through a separator 15 to form a laminated body, and then the laminated body is wound in the longitudinal direction and the protective tape 17 is adhered to the outermost peripheral portion. Thus, the wound electrode body 10 is formed. Finally, for example, the wound electrode body 10 is sandwiched between the exterior members 1 and the outer edge portions of the exterior member 1 are brought into close contact with each other by thermal fusion or the like and sealed. At that time, the adhesion film 2 is inserted between the positive electrode lead 11 and the negative electrode lead 12 and the exterior member 1. Thereby, the nonaqueous electrolyte battery shown in FIGS. 1 and 2 is completed.

  Further, this nonaqueous electrolyte battery may be manufactured as follows. First, the positive electrode 13 and the negative electrode 14 are prepared as described above, and the positive electrode lead 11 and the negative electrode lead 12 are attached to the positive electrode 13 and the negative electrode 14. And the positive electrode 13 and the negative electrode 14 are laminated | stacked and wound via the separator 15, the protective tape 17 is adhere | attached on the outermost periphery part, and the winding body which is the precursor of the winding electrode body 10 is formed. Next, the wound body is sandwiched between the exterior members 1, and the outer peripheral edge except for one side is heat-sealed to form a bag shape, which is stored inside the exterior member 1. Subsequently, an electrolyte composition including 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 necessary is prepared, and the interior of the exterior member 1 is prepared. Inject the solution.

  After injecting the electrolyte composition, the opening of the exterior member 1 is heat-sealed in a vacuum atmosphere and sealed. Next, heat is applied to polymerize the monomer to obtain a polymer compound, thereby forming the gel electrolyte 16 and assembling the nonaqueous electrolyte battery shown in FIGS.

  Details of the improvement in cycle characteristics and the like are not clear, but are presumed to be due to the following mechanism. Inside the lithium ion secondary battery in a charged state, the positive electrode is in a state having strong oxidizability, and the electrolytic solution in contact with the positive electrode is in an environment in which oxidative decomposition easily proceeds particularly in a high temperature environment. As decomposition of the electrolytic solution proceeds, an inactive film is formed on the positive electrode active material particles, thereby inhibiting electron transfer and lithium ion transfer.

  In addition, the decomposed components generate very active molecules in the electrolyte in the electrode pores, accelerating the deterioration of the electrolyte or attacking the positive electrode active material to dissolve the constituent elements and reduce the capacity I will let you. In other words, in order to suppress such a phenomenon, it is not sufficient to stabilize the interface between the positive electrode active material particles and the electrolyte solution. Furthermore, both active molecules are stabilized in the vicinity of the particles outside the positive electrode active material particles. Must be concerted.

  In the lithium-containing transition metal oxide according to the present invention, the metal element M different from the main transition metal inside the particle is arranged on the particle surface, thereby stabilizing the positive electrode active material and the electrolyte solution interface, and sulfur in the vicinity of the particle. By arranging a lithium transition metal composite oxide containing at least one element selected from (S), phosphorus (P) and fluorine (F) in an aggregated form, the active molecule can be stabilized. Thereby, it is considered that a very high level of battery performance improvement is realized by inducing a synergistic effect of the two.

  Furthermore, by making the metal element M uniformly present inside the particles in advance and then increasing the concentration of the metal element M on the surface, the surface state of the metal element M is made uniform, and the stabilization effect by the metal element M is maximized. It can be considered that the performance has been improved.

〔effect〕
According to the nonaqueous electrolyte battery of the first embodiment of the present invention, it is possible to suppress the deterioration of cycle characteristics and the increase in internal resistance due to charging / discharging in a high temperature environment, thereby achieving both high capacity and battery characteristics. it can.

2. Second embodiment (second example of nonaqueous electrolyte battery)
A second embodiment of the present invention will be described. The nonaqueous electrolyte battery according to the second embodiment of the present invention is the nonaqueous electrolyte battery according to the first embodiment, and includes a positive electrode using a positive electrode active material material coated with a coating material more uniformly. is there.

  The nonaqueous electrolyte battery according to the second embodiment is the same material and configuration as the nonaqueous electrolyte battery according to the first embodiment except for the positive electrode active material, and thus the description thereof is omitted.

[Positive electrode active material]
As in the first embodiment, the positive electrode active material includes, for example, a metal element M different from the main transition metal inside the composite oxide particle, and the metal element M has a concentration gradient from the center of the particle toward the particle surface. Have. The concentration gradient is such that the concentration of the metal element M increases as it approaches the particle surface. A lithium-containing transition metal composite oxide containing at least one element selected from sulfur (S), phosphorus (P) and fluorine (F) in an aggregated form is used on the surface of the composite oxide particles.

  In the second embodiment, the melting point of a compound containing at least one element selected from sulfur (S), phosphorus (P) and fluorine (F) used as a coating material, or the melting point of a thermal decomposition product of this compound Is 70 ° C. or more and 600 ° C. or less. The compound or thermal decomposition product of the compound deposited on the surface of the composite oxide particle by a ball mill or the like is melted by heating to become a liquid and can uniformly cover the surface of the composite oxide particle. Thereafter, a reaction occurs between the compound melted by heating or a thermal decomposition product of the compound and the composite oxide particles. Thereby, the coating material can be more efficiently and uniformly coated than the positive electrode active material of the first embodiment.

  In addition, when heat treatment is performed at a temperature exceeding 600 ° C., a reaction such as structural change occurs in the composite oxide particles themselves. However, in the positive electrode active material of the second embodiment, the coating material melts and covers the surface before a reaction such as a structural change occurs in the composite oxide particle itself. A stable structure can be formed before.

  Here, when the melting point of the compound or the thermal decomposition product of the compound exceeds 600 ° C., the coating treatment is started before the melting point is reached. That is, the reaction between the compound or the thermal decomposition product of the compound and the composite oxide particle is started before the composite oxide particle and the compound or the thermal decomposition product of the compound are melted to uniformly cover the surface of the composite oxide particle. In this case, since the reaction occurs only in the portion where the coating material is in contact with the composite oxide particles, the coating treatment becomes non-uniform, which is not preferable. In addition, when heat treatment is performed at a temperature exceeding 600 ° C., a reaction such as structural change occurs in the composite oxide particles themselves. On the other hand, when the melting point of the compound or the pyrolyzate of the compound is less than 70 ° C., the coating material is dissolved or decomposed when the coating material is coated on the surface of the composite oxide particles by a ball mill or the like. It is not preferable because it is not covered properly.

  The average particle diameter of the covering material is preferably 30 μm or less. This is because the coating material can be uniformly coated. When the average particle diameter of the coating material is too large, the coating material and the composite oxide particles are not sufficiently mixed. For this reason, it becomes impossible to deposit uniformly when the covering material is deposited by a ball mill or the like. In addition, there is no lower limit about the average particle diameter of a coating | covering material, and a coating | covering material adheres uniformly, so that an average particle diameter is small. However, the particle size of the coating material is adjusted by pulverization, and the lower limit of the particle size of particles that can be formed by pulverization is about 1 μm.

Examples of such a covering material include diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ), ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ), ammonium sulfate ((NH ₄ ) ₂ HPO ₄ ), and phosphoric acid. (H ₃ PO ₄ ) and the like. In these materials, cations are removed by evaporation or the like during the heat treatment. As a result, no impurities remain in the positive electrode active material, thereby preventing a decrease in capacity and preventing harmful effects due to the impurities.

  In the second embodiment, the surface concentration of the metal element M increases, and the concentration of the metal element M increases from the center of the composite oxide particle toward the surface. And the positive electrode active material after heat processing lose | disappears the cation of a coating | covering material on the surface, and sulfur (S), phosphorus (P), fluorine (F), etc. which originate in the anion of a coating | covering material are scattered uniformly. Further, the anion of the coating material reacts with the surface of the composite oxide particle, and from sulfur (S), phosphorus (P) and fluorine (F) resulting from the anion of the coating material, for example, lithium of the composite oxide particle Is present on the surface of the composite oxide particle.

  In addition, the metal element M different from the main transition metal contained in the composite oxide particles and the composite oxide particles can be the same material as in the first embodiment.

[Method for producing positive electrode active material]
The positive electrode in 2nd Embodiment can be produced as follows, for example.

  First, the surface of the composite oxide particle is coated with a coating material. As an example of the method for coating the surface of the composite oxide particles, as in the first embodiment, a lithium transition metal composite oxide containing a metal element M and sulfur (S), phosphorus (P), and fluorine (F ) Can be used to pulverize, mix and deposit using a ball mill, a pulverizer, a fine pulverizer or the like. In this case, it is also effective to add a small amount of liquid which can be exemplified by water. Alternatively, the metal compound can be deposited by mechanochemical treatment or by a vapor phase method such as sputtering or CVD (Chemical Vapor Deposition).

  Thus, after sulfur (S), phosphorus (P), and fluorine (F) are present in the lithium transition metal composite slope including the metal element M, the surface concentration of the metal element M is increased by performing heat treatment. It is preferable. The heat treatment is preferably performed at about 700 to 900 ° C., for example. The obtained lithium transition metal composite oxide may be subjected to a known technique such as adjustment of powder physical properties.

  At the time of heat treatment, the compound containing sulfur (S), phosphorus (P) and fluorine (F) is melted and becomes liquid, and the surface of the composite oxide particles is uniformly covered. Further, by continuing the heat treatment, the cation disappears after the coating material is thermally decomposed, and the anion reacts with the metal element M contained in the composite oxide particle. Note that after the coating material is melted on the surface of the composite oxide particles, the temperature of the heat treatment may be increased to cause the coating material and the composite oxide particles to react.

〔effect〕
In the second embodiment of the present invention, the surface of the composite oxide particle can be more uniformly covered with the coating material before the structural change or the like of the composite oxide particle occurs. For this reason, the function as a positive electrode active material can be improved, and the battery characteristic of a nonaqueous electrolyte battery can be improved more.

3. Third embodiment (third example of nonaqueous electrolyte battery)
A third embodiment of the present invention will be described. The nonaqueous electrolyte battery according to the third embodiment of the present invention uses an electrolyte solution instead of the gel electrolyte 16 in the nonaqueous electrolyte battery according to the first embodiment. In this case, the electrolytic solution is impregnated in the separator 15. As the electrolytic solution, the same one as in the first embodiment described above can be used.

  The nonaqueous electrolyte battery having such a configuration can be manufactured, for example, as follows. First, the positive electrode 13 and the negative electrode 14 are produced. Since the production of the positive electrode 13 and the negative electrode 14 is the same as that described in the first embodiment, a detailed description thereof is omitted here.

  Next, after attaching the positive electrode lead 11 and the negative electrode lead 12 to the positive electrode 13 and the negative electrode 14, the positive electrode 13 and the negative electrode 14 are laminated and wound via the separator 15, and the protective tape 17 is adhered to the outermost peripheral portion. .

  Thereby, in the structure of the wound electrode body 10, the wound electrode body of the structure which abbreviate | omitted the electrolyte 16 is obtained. After sandwiching the wound electrode body between the exterior members 1, the exterior member 1 is sealed by injecting an electrolytic solution. As described above, the nonaqueous electrolyte battery according to the third embodiment of the present invention is obtained.

〔effect〕
In the third embodiment of the present invention, the same effect as in the first embodiment described above can be obtained. That is, deterioration of cycle characteristics and increase in internal resistance due to charging / discharging in a high temperature environment can be suppressed, and both high capacity and battery characteristics can be achieved.

4). Fourth Embodiment (Fourth Example of Nonaqueous Electrolyte Battery)
Next, the configuration of a nonaqueous electrolyte battery according to a fourth embodiment of the present invention will be described with reference to FIGS. FIG. 3 shows a configuration of a nonaqueous electrolyte battery according to the fourth embodiment of the present invention.

  This non-aqueous electrolyte battery is a so-called cylindrical type, in which a strip-shaped positive electrode 31 and a strip-shaped negative electrode 32 are wound through a separator 33 inside a substantially hollow cylindrical battery can 21. An electrode body 30 is provided.

  The separator 33 is impregnated with an electrolytic solution that is a liquid electrolyte. The battery can 21 is made of, for example, iron (Fe) plated with nickel (Ni), and has one end closed and the other end open. Inside the battery can 21, a pair of insulating plates 22 and 23 are arranged perpendicular to the winding peripheral surface so as to sandwich the winding electrode body 30.

  At the open end of the battery can 21, a battery lid 24, a safety valve mechanism 25 and a heat sensitive resistance (PTC) element 26 provided inside the battery lid 24 are caulked via a gasket 27. It is attached by being. Thereby, the inside of the battery can 21 is sealed.

  The battery lid 24 is made of the same material as the battery can 21, for example. The safety valve mechanism 25 is electrically connected to the battery lid 24 via the heat sensitive resistance element 26. The safety valve mechanism 25 causes the disk plate 25 </ b> A to reverse and disconnect the electrical connection between the battery lid 24 and the wound electrode body 30 when the internal pressure of the battery exceeds a certain level due to an internal short circuit or external heating. It has become.

  When the temperature rises, the heat-sensitive resistor element 26 limits the current by increasing the resistance value, and prevents abnormal heat generation due to a large current. The gasket 27 is made of, for example, an insulating material, and asphalt is applied to the surface.

  The wound electrode body 30 is wound around a center pin 34, for example. A positive electrode lead 35 made of aluminum (Al) or the like is connected to the positive electrode 31 of the spirally wound electrode body 30, and a negative electrode lead 36 made of nickel (Ni) or the like is connected to the negative electrode 32. The positive electrode lead 35 is welded to the safety valve mechanism 25 to be electrically connected to the battery lid 24, and the negative electrode lead 36 is welded to and electrically connected to the battery can 21.

  4 is an enlarged cross-sectional view illustrating a part of the spirally wound electrode body 30 illustrated in FIG. The wound electrode body 30 is obtained by stacking and winding a positive electrode 31 and a negative electrode 32 with a separator 33 interposed therebetween.

  The positive electrode 31 includes, for example, a positive electrode current collector 31A and a positive electrode active material layer 31B provided on both surfaces of the positive electrode current collector 31A. The negative electrode 32 includes, for example, a negative electrode current collector 32A and a negative electrode active material layer 32B provided on both surfaces of the negative electrode current collector 32A. The configurations of the positive electrode current collector 31A, the positive electrode active material layer 31B, the negative electrode current collector 32A, the negative electrode active material layer 32B, the separator 33, and the electrolyte solution are respectively the positive electrode current collector 13A and the positive electrode active material in the first embodiment described above. This is the same as the material layer 13B, the negative electrode current collector 14A, the negative electrode active material layer 14B, the separator 15, and the electrolytic solution.

[Method for producing non-aqueous electrolyte battery]
Next explained is a method for manufacturing a nonaqueous electrolyte battery according to the fourth embodiment of the invention. The positive electrode 31 is produced as follows. First, a positive electrode active material and a binder are mixed to prepare a positive electrode mixture, and this positive electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone to prepare a positive electrode mixture slurry. Next, this positive electrode mixture slurry is applied to the positive electrode current collector 31A and dried, and then compression molded by a roll press machine or the like to form the positive electrode active material layer 31B, whereby the positive electrode 31 is obtained.

  The negative electrode 32 is produced as follows. First, a negative electrode active material and a binder are mixed to prepare a negative electrode mixture, and this negative electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone to obtain a negative electrode mixture slurry. Next, after applying this negative electrode mixture slurry to the negative electrode current collector 32A and drying the solvent, the negative electrode active material layer 32B is formed by compression molding using a roll press or the like, and the negative electrode 32 is obtained.

  Next, the positive electrode lead 35 is attached to the positive electrode current collector 31A by welding or the like, and the negative electrode lead 36 is attached to the negative electrode current collector 32A by welding or the like. Thereafter, the positive electrode 31 and the negative electrode 32 are wound through the separator 33, and the front end portion of the positive electrode lead 35 is welded to the safety valve mechanism 25 and the front end portion of the negative electrode lead 36 is welded to the battery can 21.

  Then, the wound positive electrode 31 and negative electrode 32 are sandwiched between a pair of insulating plates 22 and 23 and housed inside the battery can 21. After the positive electrode 31 and the negative electrode 32 are accommodated in the battery can 21, the electrolyte is injected into the battery can 21 and impregnated in the separator 33.

  Thereafter, the battery lid 24, the safety valve mechanism 25, and the heat sensitive resistance element 26 are fixed to the opening end portion of the battery can 21 by caulking through the gasket 27. As described above, the nonaqueous electrolyte battery shown in FIG. 3 is manufactured.

〔effect〕
In the nonaqueous electrolyte battery according to the fourth embodiment of the present invention, gas generation can be suppressed and damage due to an increase in internal pressure can be prevented.

5). Other embodiment (modification)
The present invention is not limited to the above-described embodiments of the present invention, and various modifications and applications are possible without departing from the spirit of the present invention. For example, the shape of the nonaqueous electrolyte battery is not limited to that described above. For example, it may be a coin type.

  Further, for example, a polymer solid electrolyte composed of an ion conductive polymer material or an inorganic solid electrolyte composed of an ion conductive inorganic material may be used as the electrolyte. Examples of the ion conductive polymer material include polyether, polyester, polyphosphazene, and polysiloxane. Examples of the inorganic solid electrolyte include ion conductive ceramics, ion conductive crystals, and ion conductive glass.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these examples.

<Example 1>
In Example 1, the amount of the coating material added to the composite oxide particles was changed, and the battery characteristics when using a positive electrode active material for which the distribution state of the coating material on the surface of the composite oxide particles was different were confirmed.
<Example 1-1>
[Production of positive electrode]
Lithium carbonate (Li ₂ CO ₃ ), cobalt oxide (Co ₃ O ₄ ), aluminum hydroxide (Al (OH) ₃ ), and magnesium carbonate (MgCO ₃ ) are mixed with Li: Co: Al: Mg = 1.00: 0. After mixing at a molar ratio of .98: 0.01: 0.01, the mixture was fired in air at 900 ° C. for 5 hours. As a result, a lithium-cobalt composite oxide (LiCo _0.98 Al _0.01 Mg _0.01 O ₂ ) was obtained. When the average particle size of the lithium-cobalt composite oxide was measured by a laser scattering method, the average particle size was 13 μm.

Subsequently, lithium carbonate (Li ₂ CO ₃ ) and diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) in atomic ratio to this lithium-cobalt composite oxide (LiCo _0.98 Al _0.01 Mg _0.01 O ₂ ). It was weighed and mixed so that Co: Li: P = 98: 1: 1. Then, the mixed material containing lithium-cobalt composite oxide was treated for 1 hour by a mechanochemical mical apparatus. As a result, a calcined precursor in which lithium carbonate and diammonium hydrogen phosphate were deposited on the surface of the lithium / cobalt composite oxide particles as a central material was produced.

The calcined precursor was heated at a rate of 3 ° C. per minute, held at 900 ° C. for 3 hours, and then gradually cooled to obtain a lithium transition metal composite oxide of the present invention. In the lithium transition metal composite oxide, magnesium (Mg) was uniformly distributed on the surface of the lithium / cobalt composite oxide particles. Further, the surface concentration of magnesium (Mg) was higher than that inside the particle, and lithium phosphate (Li ₃ PO ₄ ) was scattered on the particle surface.

  In addition, the state of the lithium transition metal complex oxide surface was confirmed by observing the obtained powder by SEM / EDX. It was confirmed that magnesium (Mg) was uniformly distributed on the particle surface and phosphorus (P) was scattered on the particle surface on the surface of the above-mentioned lithium transition metal composite oxide. The magnesium concentration was confirmed by cutting the cross section of the lithium transition metal composite oxide and measuring the elemental distribution in the radial direction by Auger electron spectroscopy. When the above-described lithium transition metal composite oxide was confirmed, it was observed that the magnesium concentration continuously changed from the surface.

Further, this was measured powder X-ray diffraction pattern using CuKα the powder diffraction peaks of Li ₃ PO ₄ was confirmed in addition to a diffraction peak corresponding to LiCoO ₂ having a layered rock salt structure.

  Using the lithium transition metal composite oxide obtained as described above as a positive electrode active material, a non-aqueous electrolyte secondary battery was prepared as described below, and changes in cycle characteristics and internal resistance at high temperatures were evaluated.

  A positive electrode mixture was prepared by mixing 98% by weight of the positive electrode active material described above, 1.5% by weight of amorphous carbon powder (Ketjen Black) and 3% by weight of polyvinylidene fluoride (PVdF). After this positive electrode mixture was dispersed in N-methyl-2-pyrrolidone (NMP) to produce a positive electrode mixture slurry, this positive electrode mixture slurry was uniformly applied to both surfaces of a positive electrode current collector made of a strip-shaped aluminum foil. . Subsequently, the positive electrode mixture slurry on the surface of the positive electrode current collector was dried with hot air, and then compression molded with a roll press to form a positive electrode mixture layer.

[Production of negative electrode]
A negative electrode mixture was prepared by mixing 95% by weight of graphite powder and 5% by weight of PVdF. After this negative electrode mixture was dispersed in N-methyl-2-pyrrolidone to produce a negative electrode mixture slurry, the negative electrode mixture slurry was uniformly applied to both sides of a negative electrode current collector made of a strip-shaped copper foil. Was subjected to hot press molding to form a negative electrode mixture layer.

[Preparation of electrolyte]
Lithium hexafluorophosphate (LiPF ₆ ) in a mixed solvent in which ethylene carbonate (EC) and methyl ethyl carbonate (MEC) are mixed at a volume ratio of 1: 1 so that the concentration becomes 1 mol / dm ^3. Was dissolved to prepare a non-aqueous electrolyte.

[Battery assembly]
The strip-like positive electrode and negative electrode produced as described above were wound many times through a separator made of a porous polyolefin film, to produce a spiral wound electrode body. This wound electrode body was housed in a nickel-plated iron battery can, and insulating plates were disposed on both the upper and lower winding surfaces of the wound electrode body. Next, a nickel negative electrode terminal connected to the negative electrode current collector was welded to the bottom of the battery can. Moreover, the positive electrode terminal made from aluminum connected with the positive electrode electrical power collector was welded to the protrusion part of the safety valve with which electrical conduction with the battery cover was ensured.

  Finally, after injecting the non-aqueous electrolyte into the battery can in which the above-described wound electrode body is incorporated, the safety can, the PTC element, and the battery lid are fixed by caulking the battery can through an insulating sealing gasket. . Thereby, a cylindrical battery having an outer diameter of 18 mm and a height of 65 mm was produced.

[Battery evaluation]
(A) Initial capacity The cylindrical battery manufactured as described above was subjected to constant current charging at a charging current of 1.5 A and a charging voltage of 4.35 V under an environment temperature of 45 ° C. Switching to voltage charging ended charging when the total charging time reached 2.5 hours. Thereafter, discharge was immediately performed at a discharge current of 2.0 A, and the discharge was terminated when the battery voltage reached 3.0 V. When the discharge capacity at this time was measured and used as the initial capacity, the initial capacity was 9.1 Wh.

(B) Capacity maintenance rate Charging / discharging was repeated under the same conditions as the charge / discharge conditions at the time of initial capacity measurement, the discharge capacity at the 300th cycle was measured, and the capacity maintenance rate relative to the initial capacity was determined. %Met.

<Example 1-2>
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1-1 except that the battery voltage during charging was changed to 4.20V. When the battery was evaluated, the initial capacity was 8.0 Wh, and the capacity retention rate was 85%. In Example 1-2 and later, the concentration distribution and surface state of the positive electrode active material are shown in Table 1 below.

<Example 1-3>
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1-1 except that the battery voltage at the time of charging was set to 4.4V. When the battery was evaluated, the initial capacity was 9.4 Wh and the capacity retention rate was 80%.

<Example 1-4>
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1-1 except that the battery voltage at the time of charging was set to 4.5V. When the battery was evaluated, the initial capacity was 10.0 Wh, and the capacity retention rate was 61%.

<Example 1-5>
Except that only the diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) was used as the deposition material to be deposited on the lithium-cobalt composite oxide (LiCo _0.98 Al _0.01 Mg _0.01 O ₂ ), Example 1- In the same manner as in Example 1, a nonaqueous electrolyte secondary battery was produced. When the battery was evaluated, the initial capacity was 9.1 Wh and the capacity retention rate was 80%.

<Example 1-6>
Example except that lithium-fluorophosphate (LiPF ₆ ) was used as the material to be deposited on lithium-cobalt composite oxide (LiCo _0.98 Al _0.01 Mg _0.01 O ₂ ) and the firing temperature was 700 ° C. A non-aqueous electrolyte secondary battery was produced in the same manner as in 1-1. When the battery was evaluated, the initial capacity was 9.1 Wh and the capacity retention rate was 81%.

<Example 1-7>
Example except that the deposition material to be deposited on lithium-cobalt composite oxide (LiCo _0.98 Al _0.01 Mg _0.01 O ₂ ) was lithium tetrafluoroborate (LiBF ₄ ) and the firing temperature was 700 ° C. A non-aqueous electrolyte secondary battery was produced in the same manner as in 1-1. When the battery was evaluated, the initial capacity was 9.1 Wh and the capacity retention rate was 76%.

<Example 1-8>
Except that the deposition material to be deposited on the lithium-cobalt composite oxide (LiCo _0.98 Al _0.01 Mg _0.01 O ₂ ) is sulfur (S) and the firing temperature is 700 ° C., the same as in Example 1-1. Thus, a non-aqueous electrolyte secondary battery was produced. When the battery was evaluated, the initial capacity was 9.1 Wh and the capacity retention rate was 64%.

<Example 1-9>
The mixing ratio of lithium-cobalt composite oxide (LiCo _0.98 Al _0.01 Mg _0.01 O ₂ ), lithium carbonate (Li ₂ CO ₃ ), and diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) in terms of atomic ratio is Co: Li : P = 98: 0.5: A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1-1 except that 0.5: 0.5. When the battery was evaluated, the initial capacity was 9.1 Wh and the capacity retention rate was 80%.

<Example 1-10>
The mixing ratio of lithium-cobalt composite oxide (LiCo _0.98 Al _0.01 Mg _0.01 O ₂ ), lithium carbonate (Li ₂ CO ₃ ), and diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) in terms of atomic ratio is Co: Li : P = 98: 2.5: A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1-1 except that 2.5: 2.5. When the battery was evaluated, the initial capacity was 8.9 Wh, and the capacity retention rate was 75%.

<Example 1-11>
The mixing ratio of lithium-cobalt composite oxide (LiCo _0.98 Al _0.01 Mg _0.01 O ₂ ), lithium carbonate (Li ₂ CO ₃ ), and diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) in terms of atomic ratio is Co: Li : P = 98: 5: 5 A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1-1 except that the ratio was changed to 98: 5: 5. When the battery was evaluated, the initial capacity was 8.2 Wh, and the capacity retention rate was 69%.

<Example 1-12>
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1-1 except that the composition ratio of the lithium-cobalt composite oxide was changed to (LiCo _0.97 Al _0.01 Mg _0.02 O ₂ ). When the battery was evaluated, the initial capacity was 9.0 Wh, and the capacity retention rate was 84%.

<Example 1-13>
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1-1 except that the composition ratio of the lithium-cobalt composite oxide was changed to (LiCo _0.95 Al _0.01 Mg _0.04 O ₂ ). When the battery was evaluated, the initial capacity was 8.8 Wh, and the capacity retention rate was 82%.

<Comparative Example 1-1>
A nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 1-1 except that the coating treatment of lithium-cobalt composite oxide (LiCo _0.98 Al _0.01 Mg _0.01 O ₂ ) was not performed. When the battery was evaluated, the initial capacity was 9.2 Wh, and the capacity retention rate was 31%.

<Comparative Example 1-2>
Non-aqueous electrolyte secondary as in Example 1-1, except that the coating treatment of lithium-cobalt composite oxide (LiCo _0.98 Al _0.01 Mg _0.01 O ₂ ) was not performed and the battery voltage during charging was changed to 4.2 V. A battery was produced. When the battery was evaluated, the initial capacity was 8.1 Wh, and the capacity retention rate was 71%.

<Comparative Example 1-3>
Non-aqueous electrolyte secondary as in Example 1-1, except that the coating treatment of lithium-cobalt composite oxide (LiCo _0.98 Al _0.01 Mg _0.01 O ₂ ) was not performed and the battery voltage during charging was set to 4.4 V. A battery was produced. When the battery was evaluated, the initial capacity was 9.5 Wh and the capacity retention rate was 25%.

<Comparative Example 1-4>
The composition ratio of the lithium cobalt complex oxide and (LiCoO _2), lithium cobalt complex oxide (LiCoO ₂₎ the deposition material lithium carbonate depositing respect (Li ₂ CO _3), magnesium carbonate (MgCO ₃ ) And diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ). A mixture ratio of lithium-cobalt composite oxide (LiCoO ₂ ), lithium carbonate (Li ₂ CO ₃ ), magnesium carbonate (MgCO ₃ ), and diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) in atomic ratio is Co: Weigh and mix so that Li: Mg: P = 100: 1: 1: 1. A nonaqueous electrolyte secondary battery was produced in the same manner as Example 1-1 except for this. When the battery was evaluated, the initial capacity was 9.1 Wh and the capacity retention rate was 32%.

<Comparative Example 1-5>
The composition ratio of the lithium cobalt complex oxide and (LiCoO _2), lithium cobalt complex oxide deposition material depositing respect (LiCoO ₂₎ was aluminum fluoride (AlF _3). Lithium / cobalt composite oxide (LiCoO ₂ ) and aluminum fluoride (AlF ₃ ) were weighed and mixed so that the atomic ratio was Co: Al = 100: 1. A nonaqueous electrolyte secondary battery was produced in the same manner as Example 1-1 except for this. When the battery was evaluated, the initial capacity was 9.1 Wh, and the capacity retention rate was 30%.

<Comparative Example 1-6>
The composition ratio of the lithium cobalt complex oxide and (LiCoO _2), and the aluminum phosphate deposition material depositing (AlPO ₄₎ with respect to lithium cobalt complex oxide (LiCoO _2). Lithium / cobalt composite oxide (LiCoO ₂ ) and aluminum phosphate (AlPO ₄ ) were weighed and mixed so that the atomic ratio of Co: Al = 100: 1. A nonaqueous electrolyte secondary battery was produced in the same manner as Example 1-1 except for this. When the battery was evaluated, the initial capacity was 9.1 Wh and the capacity retention rate was 25%.

<Comparative Example 1-7>
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1-1 except that the composition ratio of the lithium-cobalt composite oxide was changed to (LiCoO ₂ ). When the battery was evaluated, the initial capacity was 9.1 Wh and the capacity retention rate was 20%.

<Comparative Example 1-8>
The composition ratio of the lithium cobalt complex oxide and (LiCoO _2), and lithium phosphate deposition material depositing (Li ₃ PO ₄₎ with respect to lithium cobalt complex oxide (LiCoO _2). Lithium-cobalt composite oxide (LiCoO ₂ ) and lithium phosphate (Li ₃ PO ₄ ) were weighed and mixed so that the atomic ratio was Co: P = 100: 1. A nonaqueous electrolyte secondary battery was produced in the same manner as Example 1-1 except for this. When the battery was evaluated, the initial capacity was 9.1 Wh and the capacity retention rate was 15%.

<Comparative Example 1-9>
A nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 1-1 except that the firing temperature after the coating treatment with diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) was 300 ° C. When the battery was evaluated, the initial capacity was 8.6 Wh, and the capacity retention rate was 35%.

  Table 1 below shows the results of the evaluation.

  As can be seen from the evaluation results, the positive electrode active material in which magnesium (Mg) is uniform and has a concentration distribution from the inside of the particle to the surface, and the surface is coated with sulfur (S), phosphorus (P), etc. In the example using the above, it was possible to realize a high capacity retention ratio together with the initial capacity.

  On the other hand, in Comparative Examples 1-1 to 1-3 without the covering material, the capacity retention rate was significantly reduced as the charging voltage of the battery was increased. In the case of Comparative Examples 1-4 to 1-6 in which the magnesium (Mg) inside the particles is non-uniform, a high capacity retention rate could not be maintained even if there was a concentration distribution. . Further, in the absence of the metal element M as described above, the capacity retention rate was very low even if sulfur (S), phosphorus (P), etc. were scattered on the surface.

<Example 2>
In Example 2, battery characteristics when using coating materials having different melting points are confirmed.

<Example 2-1>
A deposition material to be deposited on lithium-cobalt composite oxide (LiCo _0.98 Al _0.01 Mg _0.01 O ₂ ) has an average particle diameter measured by a laser scattering method of 10 μm and a melting point of 190 ° C. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1-1 except that only ammonium ((NH ₄ ) ₂ HPO ₄ ) was used. When the battery was evaluated at a full charge pressure of 4.35 V in the same manner as in Example 1-1, the initial capacity was 9.1 Wh and the capacity retention rate was 85%.

<Example 2-2>
A material to be deposited on lithium-cobalt composite oxide (LiCo _0.98 Al _0.01 Mg _0.01 O ₂ ) has an average particle diameter measured by a laser scattering method of 10 μm and a melting point of 513 ° C. ammonium sulfate ((NH ₄ ) A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 2-1, except that ₂ HSO ₄ ) was used. When the battery was evaluated, the initial capacity was 9.1 Wh and the capacity retention rate was 87%.

<Example 2-3>
An adherent material to be deposited on lithium-cobalt composite oxide (LiCo _0.98 Al _0.01 Mg _0.01 O ₂ ) has an average particle diameter measured by a laser scattering method of 30 μm and a melting point of 190 ° C. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 2-1, except that ammonium ((NH ₄ ) ₂ HPO ₄ ) was used. When the battery was evaluated, the initial capacity was 9.1 Wh and the capacity retention rate was 80%.

<Example 2-4>
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 2-1, except that the composition of the lithium-cobalt composite oxide for coating the coating material was LiNi _0.79 Co _0.19 Al _0.01 Mg _0.01 O ₂ . When the battery was evaluated, the initial capacity was 10.9 Wh and the capacity retention rate was 81%.

<Example 2-5>
A non-aqueous electrolyte secondary battery is fabricated in the same manner as in Example 2-1, except that the composition of the lithium-cobalt composite oxide for coating the coating material is LiNi _0.49 Co _0.19 Mn _0.29 Al _0.02 Mg _0.01 O ₂ did. When the battery was evaluated, the initial capacity was 9.5 Wh, and the capacity retention rate was 80%.

<Example 2-6>
Phosphoric acid (H) having an average particle diameter measured by a laser scattering method of 10 μm and a melting point of 43 ° C. on an adherend to be deposited on lithium-cobalt composite oxide (LiCo _0.98 Al _0.01 Mg _0.01 O ₂ ) _A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 2-1, except that ₃ PO ₄ ) was used. When the battery was evaluated, the initial capacity was 9.1 Wh and the capacity retention rate was 53%.

<Example 2-7>
Ferric sulfate having an average particle diameter of 10 μm and a melting point of 480 ° C. measured by a laser scattering method for a deposition material deposited on lithium-cobalt composite oxide (LiCo _0.98 Al _0.01 Mg _0.01 O ₂ ) A nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 2-1, except that (Fe ₂ (SO ₄ ) ₃ ) was used. When the battery was evaluated, the initial capacity was 8.9 Wh, and the capacity retention rate was 80%.

<Example 2-8>
A deposition material to be deposited on lithium-cobalt composite oxide (LiCo _0.98 Al _0.01 Mg _0.01 O ₂ ) has an average particle diameter measured by a laser scattering method of 100 μm and a melting point of 190 ° C. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 2-1, except that ammonium ((NH ₄ ) ₂ HPO ₄ ) was used. When the battery was evaluated, the initial capacity was 9.1 Wh and the capacity retention rate was 58%.

<Example 2-9>
Lithium-cobalt composite oxide (LiCo _0.98 Al _0.01 Mg _0.01 O ₂ ) was deposited on a lithium phosphate having an average particle diameter of 10 μm measured by a laser scattering method and a melting point of 837 ° C. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 2-1, except that Li ₃ PO ₄ ) was used. When the battery was evaluated, the initial capacity was 9.0 Wh, and the capacity retention rate was 60%.

  Table 2 below shows the results of the evaluation. In Table 2, the results of Comparative Example 1-1 are also shown for comparison.

  As can be seen from the evaluation results, in Examples 2-1 to 2-5, the melting point of the phosphorus or fluorine-containing compound or the thermal decomposition product of the compound is in the range of 80 ° C. to 600 ° C. For this reason, when calcined at 900 ° C., the compound containing phosphorus and fluorine or a thermal decomposition product of the compound becomes liquid, so that the surfaces of the composite oxide particles are uniformly covered with the compound of sulfur, phosphorus and fluorine. It is considered that a positive electrode active material having a high capacity retention rate was obtained. In addition, the decomposition product ammonium vaporized, so that it did not remain in the active material, and the initial capacity was kept high.

  Further, in Example 2-4 and Example 2-5, lithium / nickel / cobalt composite oxide or lithium / nickel / cobalt / manganese composite oxide was used as the composite oxide particles as the central material of the positive electrode active material. Even when it was used, an active material having a concentration gradient in which the concentration of the metal element M was increased was obtained, and a positive electrode active material having a high capacity retention rate was obtained.

  Moreover, in Example 2-6, since phosphoric acid dissolved during the mechanochemical treatment of the coating, the capacity retention rate was improved, but the coating as good as Example 2-1 to Example 2-5 could be achieved. However, the improvement of the capacity retention rate by using the coating material was reduced. This is because the melting point of phosphoric acid is lower than the processing temperature generated by mechanochemical processing. In Example 2-7, although the melting point was in the range of 70 ° C. to 600 ° C. and a good coating was obtained, the iron compound remained as a decomposition product on the surface of the positive electrode. For this reason, the initial discharge capacity slightly decreased due to the presence of impurities that do not contribute to charge / discharge.

  In Example 2-8, since the average particle diameter of the coating material was too large, it was not sufficiently mixed with the composite oxide particles. For this reason, although the capacity retention rate was improved, the coating as good as Example 2-1 to Example 2-5 could not be achieved, and the improvement in the capacity retention rate due to the use of the coating material was reduced. This is because the coating state is divided into a good part and a bad part because the mixed state is insufficient. In Example 2-9, although the capacity retention rate was improved, the improvement was not as great as in Example 2-1 to Example 2-5. This is because the melting point of the coating material is 837 ° C., which is higher than 600 ° C., close to the firing temperature, and the reaction with the coating material starts to proceed locally before the coating material dissolves to form a good coating. It was because I could not get.

  By using the positive electrode active material of the present invention, a non-aqueous electrolyte battery having a high capacity and excellent charge / discharge cycle can be obtained.

DESCRIPTION OF SYMBOLS 1 ... Exterior member 2 ... Adhesion film 10, 30, 53 ... Winding electrode body 11, 35 ... Positive electrode lead 12, 36 ... Negative electrode lead 13, 31 ... Positive electrode 13A, 31A ... Positive current collector 13B, 31B ... Positive electrode active material layer 14, 32 ... Negative electrode 14A, 32A ... Negative electrode current collector 14B, 32B ... Negative electrode active material layer 15, 33 ... Separator 16 ... Electrolyte 17 ... Protective tape 21 ... Battery can 22,23 ... Insulating plate 24 ... Battery cover 25 ... Safety valve mechanism 25A ... Disk plate 26 ... Heat feeling Resistance element 27 ... Gasket 34 ... Center pin

Claims (18)

A compound containing lithium, a compound containing a transition metal to be dissolved, and a compound containing a metal element M different from the transition metal are mixed and fired to form composite oxide particles,
A compound containing at least one of sulfur (S), phosphorus (P) and fluorine (F) is deposited on the surface of the composite oxide particles,
By firing the composite oxide particles to which the compound containing at least one of the sulfur (S), phosphorus (P) and fluorine (F) is deposited,
A concentration gradient in which the concentration of the metal element M increases from the center of the composite oxide particle toward the surface;
A positive electrode active material in which at least one of sulfur (S), phosphorus (P), and fluorine (F) is present in an aggregated state on the surface of the composite oxide particles. The positive electrode active material according to claim 1, wherein the transition metal is selected from at least nickel (Ni), cobalt (Co), manganese (Mn), and iron (Fe). The metal element M is at least one of manganese (Mn), magnesium (Mg), aluminum (Al), nickel (Ni), boron (B), titanium (Ti), cobalt (Co) and iron (Fe). The positive electrode active material according to claim 1, wherein The composite oxide particles in which the compound containing lithium and the compound containing at least one of sulfur (S), phosphorus (P), and fluorine (F) are deposited are calcined in the presence of a compound containing lithium. The positive electrode active material as described. The melting point of a compound containing at least one of sulfur (S), phosphorus (P) and fluorine (F) or a thermal decomposition product of the compound is 70 ° C or higher and 600 ° C or lower. The positive electrode active material in any one. 5. The positive electrode according to claim 1, wherein the compound containing at least one of sulfur (S), phosphorus (P), and fluorine (F) or an average particle diameter of the compound is 30 μm or less. Active material. A compound containing lithium, a compound containing a transition metal to be dissolved, and a compound containing a metal element M different from the transition metal are mixed and fired to form composite oxide particles,
A compound containing at least one of sulfur (S), phosphorus (P) and fluorine (F) is deposited on the surface of the composite oxide particles,
By firing the composite oxide particles to which the compound containing at least one of the sulfur (S), phosphorus (P) and fluorine (F) is deposited,
A concentration gradient in which the concentration of the metal element M increases from the center of the composite oxide particle toward the surface;
A positive electrode comprising a positive electrode active material in which at least one of sulfur (S), phosphorus (P) and fluorine (F) is present in an aggregated state on the surface of the composite oxide particles. The positive electrode according to claim 7, wherein a melting point of a compound containing at least one of sulfur (S), phosphorus (P) and fluorine (F) or a thermal decomposition product of the compound is 70 ° C or higher and 600 ° C or lower. The positive electrode active material according to claim 7, wherein the compound containing at least one of sulfur (S), phosphorus (P), and fluorine (F) or an average particle diameter of the compound is 30 μm or less. A positive electrode, a negative electrode, and an electrolyte;
The positive electrode is
A compound containing lithium, a compound containing a transition metal to be dissolved, and a compound containing a metal element M different from the transition metal are mixed and fired to form composite oxide particles,
A compound containing at least one of sulfur (S), phosphorus (P) and fluorine (F) is deposited on the surface of the composite oxide particles,
By firing the composite oxide particles to which the compound containing at least one of the sulfur (S), phosphorus (P) and fluorine (F) is deposited,
A concentration gradient in which the concentration of the metal element M increases from the center of the composite oxide particle toward the surface;
A nonaqueous electrolyte battery comprising a positive electrode active material in which at least one of sulfur (S), phosphorus (P), and fluorine (F) is present on the surface of the composite oxide particles. The non-aqueous solution according to claim 10, wherein a melting point of a compound containing at least one of sulfur (S), phosphorus (P) and fluorine (F) or a thermal decomposition product of the compound is 70 ° C or higher and 600 ° C or lower. Electrolyte battery. The positive electrode active material according to claim 10, wherein the compound containing at least one of sulfur (S), phosphorus (P), and fluorine (F) or an average particle diameter of the compound is 30 μm or less. A composite oxide particle forming step of forming a composite oxide particle by mixing and firing a compound containing lithium, a compound containing a transition metal to be dissolved, and a compound containing a metal element M different from the transition metal When,
A deposition step of depositing a compound containing at least one of sulfur (S), phosphorus (P) and fluorine (F) on the surface of the composite oxide particles;
A firing step of firing the composite oxide particles to which the compound containing at least one of sulfur (S), phosphorus (P) and fluorine (F) is deposited,
A concentration gradient in which the concentration of the metal element M increases from the center of the composite oxide particle toward the surface;
A method for producing a positive electrode active material in which at least one of sulfur (S), phosphorus (P), and fluorine (F) is present in an aggregated form on the surface of the composite oxide particles. In the firing step,
Melting a compound containing at least one of the sulfur (S), phosphorus (P) and fluorine (F) deposited on the surface of the composite oxide particle or a thermal decomposition product of the compound;
The method for producing a positive electrode active material according to claim 13, wherein the surface of the composite oxide particles is uniformly coated with the molten compound or a thermal decomposition product of the compound. In the firing step,
While eliminating the cation of the compound containing at least one of the sulfur (S), phosphorus (P) and fluorine (F) deposited on the surface of the composite oxide particles,
The positive electrode active material according to claim 14, wherein an anion of a compound containing at least one of sulfur (S), phosphorus (P), and fluorine (F) is reacted with an element contained in the composite oxide particle. Production method. The positive electrode active according to any one of claims 13 to 15, wherein a compound containing at least one of sulfur (S), phosphorus (P) and fluorine (F) having a melting point of 70 ° C or higher and 600 ° C or lower is used. A method for producing a substance. The positive electrode active material according to any one of claims 13 to 15, wherein a compound containing at least one of sulfur (S), phosphorus (P) and fluorine (F) having an average particle size of 30 µm or less is used. Production method. The method for producing a positive electrode active material according to any one of claims 13 to 15, wherein a firing temperature in the firing step is 700 ° C or higher and 900 ° C or lower.

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