JP6978234B2 - Positive electrode for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery - Google Patents

Description

The present invention relates to a positive electrode for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery.

The non-aqueous electrolyte secondary battery is required to have a higher energy density. In the non-aqueous electrolyte secondary battery, high energy density may be achieved by charging / discharging at a high voltage, for example, Li as the counter electrode and a voltage of 4.55 V or higher.

On the other hand, it has been pointed out that when charging / discharging is performed under high temperature and high voltage, oxidative decomposition of the electrolytic solution occurs in the vicinity of the positive electrode active material, and the battery characteristics after repeated charging / discharging are extremely deteriorated (for example). Patent Document 1). In order to deal with such a problem, Patent Document 1 discloses a positive electrode for a lithium ion secondary battery in which at least a part of the surface of the positive electrode active material particles is coated with an organic coat layer.

Japanese Unexamined Patent Publication No. 2014-96343

However, such a non-aqueous electrolyte secondary battery has not yet been sufficiently excellent in cycle characteristics under high temperature and high voltage. Further, there is still a demand for higher capacity of non-aqueous electrolyte secondary batteries.

An object of the present invention is to provide a positive electrode for a non-aqueous electrolyte secondary battery capable of improving the cycle life under high temperature and high voltage, and a non-aqueous electrolyte secondary battery provided with the positive electrode. Further, the positive electrode for a non-aqueous electrolyte secondary battery provided in the present invention can be used for a high-capacity non-aqueous electrolyte secondary battery at the same time.

In order to solve the above problems, according to a certain viewpoint of the present invention, a current collector and a positive electrode active material layer bonded to the current collector are provided.
The positive electrode active material layer has the following formula (1):
_{Li x Co y M z O 2} (1)
In the formula (1), M is aluminum (Al), nickel (Ni), manganese (Mn), chromium (Cr), iron (Fe), vanadium (V), magnesium (Mg), titanium (Ti), Zirconium (Zr), Niob (Nb), Molybdenum (Mo), Tungsten (W), Copper (Cu), Zinc (Zn), Gallium (Ga), Indium (In), Tin (Sn), Lantern (La), It is one or more metal elements selected from the group consisting of cerium (Ce), and x, y, z are 0.20 ≦ x ≦ 1.20, 0.95 ≦ y ≦ 1.00, 0.0. It is a value within the range of ≦ z ≦ 0.05 and y + z = 1.
Positive electrode active material particles having the composition shown in
An inorganic coating layer covering at least a part of the positive electrode active material particles,
It has a polymer containing acrylonitrile as a monomer unit, which covers at least a part of the positive electrode active material particles.
The inorganic coating layer has the following (i) to (iii).
(Ii) Lithium Phosphate, Metallic Lithium Phosphate and Aluminum Compounds (ii) Lithium Phosphate and Aluminum Compounds (iii) A positive electrode for a non-aqueous electrolyte secondary battery comprising any of lithium metal phosphate and an aluminum compound is provided. To.

According to this viewpoint, it is possible to achieve a high capacity of the non-aqueous electrolyte secondary battery and improve the cycle life when the non-aqueous electrolyte secondary battery is charged and discharged under high temperature and high voltage.

Here, the aluminum compound may contain one or more selected from the group consisting of aluminum oxide, aluminum fluoride and aluminum phosphate.

According to this viewpoint, it is possible to improve the cycle life when the non-aqueous electrolyte secondary battery is charged and discharged under high temperature and high voltage.

Further, the inorganic coating layer may contain the aluminum compound having a molar ratio of 0.025 mol% or more and 0.3 mol% or less with respect to the positive electrode active material particles.

According to this viewpoint, it is possible to improve the cycle life when the non-aqueous electrolyte secondary battery is charged and discharged under high temperature and high voltage.

Further, the metallic lithium phosphate may contain one or more metals selected from the group consisting of aluminum, titanium, cobalt and zirconium.

According to this viewpoint, it is possible to improve the cycle life when the non-aqueous electrolyte secondary battery is charged and discharged under high temperature and high voltage.

Further, the inorganic coating layer may contain the lithium phosphate and / or the metallic lithium phosphate in a molar ratio of 0.1 mol% or more and 1.0 mol% or less with respect to the positive electrode active material particles.

According to this viewpoint, it is possible to improve the cycle life when the non-aqueous electrolyte secondary battery is charged and discharged under high temperature and high voltage.

Further, the inorganic coating layer has a first layer that covers at least a part of the positive electrode active material particles, a first layer, and a second layer that covers the positive electrode active material particles.
The first layer has a higher content of lithium phosphate and / or metallic lithium phosphate than the second layer.
The second layer may have a higher content of the aluminum compound than the first layer.

According to this viewpoint, it is possible to improve the cycle life when the non-aqueous electrolyte secondary battery is charged and discharged under high temperature and high voltage.

Further, the average thickness of the first layer may be 1.0 nm or more and 150 nm or less.

According to this viewpoint, it is possible to improve the cycle life when the non-aqueous electrolyte secondary battery is charged and discharged under high temperature and high voltage.

Further, the average thickness of the second layer may be 1.0 nm or more and 10 nm or less.

According to this viewpoint, it is possible to improve the cycle life when the non-aqueous electrolyte secondary battery is charged and discharged under high temperature and high voltage.

Further, the polymer may contain 90 mol% or more of acrylonitrile as a monomer unit.

According to this viewpoint, it is possible to improve the cycle life when the non-aqueous electrolyte secondary battery is charged and discharged under high temperature and high voltage.

前記式（２）中、ｌ、ｍは、それぞれ１以上の整数であり、Ｒ_１、Ｒ_２は、それぞれ水素またはメチル基である、
で表される構造を有してもよい。 Further, the polymer has the following formula (2):

In the above formula (2), l and m are integers of 1 or more, respectively, and R ₁ and R ₂ are hydrogen or methyl groups, respectively.
It may have a structure represented by.

According to this viewpoint, it is possible to improve the cycle life when the non-aqueous electrolyte secondary battery is charged and discharged under high temperature and high voltage.

Further, the mass average molecular weight of the polymer may be 200,000 or more and 800,000 or less.

According to this viewpoint, it is possible to improve the cycle life when the non-aqueous electrolyte secondary battery is charged and discharged under high temperature and high voltage.

According to another aspect of the present invention, there is provided a non-aqueous electrolyte secondary battery comprising the positive electrode for the non-aqueous electrolyte secondary battery described above.

According to this viewpoint, it is possible to achieve a high capacity of the non-aqueous electrolyte secondary battery and improve the cycle life when the non-aqueous electrolyte secondary battery is charged and discharged under high temperature and high voltage.

As described above, according to the present invention, it is possible to achieve a high capacity of the non-aqueous electrolyte secondary battery and improve the cycle life when the non-aqueous electrolyte secondary battery is charged and discharged under high temperature and high voltage. Can be done.

It is explanatory drawing which shows the schematic structure of the non-aqueous electrolyte secondary battery which concerns on embodiment of this invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and the drawings, components having substantially the same functional configuration are designated by the same reference numerals, so that duplicate description will be omitted.

<1. Overview of non-aqueous electrolyte secondary batteries>
First, an overview of the non-aqueous electrolyte secondary battery according to the present embodiment will be described together with the studies up to the present invention by the present inventors.

When a lithium transition metal composite oxide containing cobalt (Co) as a main component is used as the positive electrode active material, the capacity of the non-aqueous electrolyte secondary battery is increased by using Li as the counter electrode and raising the charging start voltage to 4.55 V or higher. Can be set to 200 mAh / g or more. This is because 70% or more of Li can be removed and inserted from the theoretical capacity of 273 mAh / g of the non-aqueous electrolyte secondary battery.

Focusing on this point, the present inventors have investigated the use of a lithium transition metal composite oxide containing cobalt as a main component as a positive electrode active material. However, the present inventors use a lithium transition metal composite oxide containing cobalt as a main component as a positive electrode active material, and when the positive electrode active material is used at a charging start voltage of 4.55 V or higher as described above, the charged positive electrode active material is used. As a result of the increased oxidizing power, not only the decomposition of the electrolytic solution was accelerated, but also the stability of the delithiated positive electrode active material itself was lost, and the problem of cobalt elution into the electrolytic solution was faced. In such a case, the cycle characteristics of the non-aqueous secondary battery rapidly deteriorate under high temperature and high voltage.

As a result of diligent studies to solve the above problems, the present inventors used a lithium transition metal composite oxide containing a specific cobalt as a main component as a positive electrode active material, and further used particles of the positive electrode active material as phosphoric acid. By covering with an inorganic coating layer containing a lithium compound and / or a metallic lithium phosphate and an aluminum compound, and further covering the periphery with a polymer containing acrylonitrile as a monomer unit, oxidative decomposition of the electrolytic solution can be prevented and the electrolytic solution of cobalt can be prevented. It was found that the elution to can be prevented.

Therefore, the positive electrode for a non-aqueous electrolyte secondary battery according to the present invention has a current collector and a positive electrode active material layer bonded to the current collector.
The positive electrode active material layer has the following formula (1):
_{Li x Co y M z O 2} (1)
In the formula (1), M is aluminum (Al), nickel (Ni), manganese (Mn), chromium (Cr), iron (Fe), vanadium (V), magnesium (Mg), titanium (Ti), Zirconium (Zr), Niob (Nb), Molybdenum (Mo), Tungsten (W), Copper (Cu), Zinc (Zn), Gallium (Ga), Indium (In), Tin (Sn), Lantern (La), It is one or more metal elements selected from the group consisting of cerium (Ce), and x, y, z are 0.20 ≦ x ≦ 1.20, 0.95 ≦ y ≦ 1.00, 0.0. It is a value within the range of ≦ z ≦ 0.05 and y + z = 1.
A positive electrode active material particle having the composition shown by, an inorganic coating layer covering a small part of the positive electrode active material particle, and a polymer containing acrylonitrile as a monomer unit covering at least a part of the positive electrode active material particle. Have,
The inorganic coating layer has the following (i) to (iii).
(I) Lithium Phosphate, Metallic Lithium Phosphate and Aluminum Compounds (ii) Lithium Phosphate and Aluminum Compounds (iii) Includes any of lithium metal phosphates and aluminum compounds.

<2. Configuration of non-aqueous electrolyte secondary battery>
Hereinafter, a specific configuration of the non-aqueous electrolyte secondary battery 10 according to the above-described embodiment of the present invention will be described with reference to FIG. 1. FIG. 1 is an explanatory diagram illustrating a configuration of a non-aqueous electrolyte secondary battery according to an embodiment of the present invention.

As shown in FIG. 1, the non-aqueous electrolyte secondary battery 10 includes a positive electrode 20, a negative electrode 30, and a separator layer 40. The form of the non-aqueous electrolyte secondary battery 10 is not particularly limited. For example, the non-aqueous electrolyte secondary battery 10 may be any of a cylindrical shape, a square shape, a laminate type, a button type, and the like.

The positive electrode 20 includes a positive electrode current collector 21 and a positive electrode active material layer 22. The positive electrode current collector 21 is made of, for example, aluminum. Further, the positive electrode active material layer 22 contains at least positive electrode active material particles and a polymer having acrylonitrile as a monomer unit (hereinafter, also referred to as “acrylonitrile-based polymer”), and further contains a conductive auxiliary agent and / or a binder. You may be.

The positive electrode active material particles have a composition represented by the following formula (1).
_{Li x Co y M z O 2} (1)
In formula (1), M is aluminum (Al), nickel (Ni), manganese (Mn), chromium (Cr), iron (Fe), vanadium (V), magnesium (Mg), titanium (Ti), zirconium. (Zr), Niob (Nb), Molybdenum (Mo), Tungsten (W), Copper (Cu), Zinc (Zn), Gallium (Ga), Indium (In), Tin (Sn), Lantern (La), Cerium One or more metal elements selected from the group consisting of (Ce).
Further, x, y, and z are values within the range of 0.20 ≦ x ≦ 1.20, 0.95 ≦ y ≦ 1.00, 0.0 ≦ z ≦ 0.05 and y + z = 1.

The positive electrode active material particles represented by the formula (1) can have a sufficiently large capacity of the non-aqueous electrolyte secondary battery 10 by being used at a high driving voltage of 4.55 V, for example, with Li as the counter electrode. can.

Further, an inorganic coating layer containing lithium phosphate and / or metallic lithium phosphate and an aluminum compound is formed on at least a part of the surface of the positive electrode active material particles. Specifically, the inorganic coating layer is the following (i) to (iii).
(I) Lithium Phosphate, Metallic Lithium Phosphate and Aluminum Compounds (ii) Lithium Phosphate and Aluminum Compounds (iii) Includes any of lithium metal phosphates and aluminum compounds.

Lithium phosphate and metallic lithium phosphate in the inorganic coating layer function as solid electrolytes in the inorganic coating layer. As a result, lithium ions can be exchanged between the electrolytic solution and the positive electrode active material even when the electrolytic solution and the positive electrode active material do not come into direct contact with each other. In addition, lithium phosphate and metallic lithium phosphate, together with the aluminum compound and acrylonitrile-based polymer described later, can prevent direct contact of the electrolytic solution with the positive electrode active material particles and prevent oxidative decomposition of the electrolytic solution. ..

The metal element other than lithium contained in the metallic lithium phosphate is not particularly limited, and is, for example, magnesium (Mg), aluminum (Al), titanium (Ti), manganese (Mn), nickel (Ni), cobalt ( Co), zirconium (Zr) and the like can be mentioned. As the metallic lithium phosphate, two or more kinds of metallic lithium phosphate or metallic lithium phosphate composed of a plurality of metal elements may be used. Among the above, lithium metal phosphate preferably contains one or more metals selected from the group consisting of aluminum, titanium, cobalt, and zirconium.

Further, in the inorganic coating layer, lithium phosphate and / or metallic lithium phosphate may exist as _{, for example, LiMA 2} (PO ₄ ) ₃ , Li ₃ PO ₄ , MAO ₂ , LiMAO _{2, and the like.} In the above formula, "MA" indicates the above-mentioned metal element.

In addition, the inorganic coating layer has a total molar ratio of lithium phosphate of 0.1 mol% or more and 1.0 mol% or less, more preferably 0.1 mol% or more and 0.8 mol% or less with respect to the positive electrode active material particles. And contains metallic lithium phosphate. Thereby, the cycle characteristics of the non-aqueous electrolyte secondary battery 10 can be further improved. Further, by setting the content of the inorganic coating layer to the above upper limit value or less, it is possible to prevent a decrease in the discharge capacity. Further, it is possible to prevent an increase in resistance on the surface of the positive electrode active material, and it is possible to prevent deterioration of high load characteristics.

The aluminum compound in the inorganic coating layer can contribute to maintaining the bulk crystal structure of the positive electrode active material particles, and can suppress deterioration of cycle characteristics and storage stability due to crystal collapse of the positive electrode active material particles. Further, the inorganic coating layer can be coated almost uniformly on the surface of the positive electrode active material particles by adjusting the firing conditions, elution of cobalt ions at a high potential, and direct contact with the positive electrode active material particles of the electrolytic solution. Prevents contact with the particles more reliably.

Such an aluminum compound exists in the inorganic coating layer as a composite of, for example, aluminum fluoride, aluminum oxide, aluminum phosphate, and cobalt which is a constituent element of the positive electrode active material bulk. From the viewpoint of chemical and electrochemical stability, the aluminum compound preferably contains at least one selected from the group consisting of aluminum oxide, aluminum fluoride, and aluminum phosphate.

The inorganic coating layer contains, for example, an aluminum compound having a molar ratio of 0.025 mol% or more and 0.3 mol% or less, preferably 0.05 mol% or more and 0.2 mol% or less with respect to the positive electrode active material particles. Thereby, the effect of the above-mentioned aluminum compound can be obtained more remarkably.

The thickness of the inorganic coating layer is not particularly limited, but is, for example, 1 nm or more and 150 nm or less, preferably 10 nm or more and 100 nm or less. This makes it possible to more reliably improve the cycle characteristics of the non-aqueous electrolyte secondary battery 10. The thickness of the inorganic coating layer and the first layer and the second layer, which will be described later, can be measured by a transmission electron microscope (TEM).

The inorganic coating layer may exist as one layer, or may be formed by laminating a plurality of layers. For example, the inorganic coating layer may have a first layer that covers at least a part of the positive electrode active material particles, and a first layer and a second layer that covers the positive electrode active material particles.

In this case, the first layer can be an island-shaped layer that directly covers at least a part of the surface of the positive electrode active material particles. Further, in the case of the production method as described later, the first layer contains lithium phosphate and / or metallic lithium phosphate as a main component, and contains lithium phosphate and / or metallic lithium phosphate more than the second layer. The amount can be large.

On the other hand, the second layer can be a continuous layer covering the positive electrode active material particles and the first layer. Further, in the case of the production method as described later, the second layer contains an aluminum compound as a main component, and the content of the aluminum compound may be larger than that of the first layer.

Further, in the above case, the average thickness of the first layer is, for example, 1.0 nm or more and 150 nm or less, preferably 50 nm or more and 100 nm or less. The average thickness of the second layer is, for example, 1.0 nm or more and 10 nm or less, preferably 1.0 nm or more and 5 nm or less.

Further, for example, the inorganic coating layer is an island-shaped first layer containing lithium phosphate and / or metallic lithium phosphate as a main component, and a second layer existing in the gap thereof and containing an aluminum compound as a main component. It may be composed of.

Further, the surface of at least a part of the positive electrode active material particles is coated with an acrylonitrile-based polymer. Such an acrylonitrile-based polymer, together with the above-mentioned inorganic coating layer, prevents the elution of the components of the positive electrode active material particles such as cobalt into the electrolytic solution. The acrylonitrile-based polymer may cover the surface of the positive electrode active material particles alone, or may cover the positive electrode active material particles together with other components described later. Further, the acrylonitrile-based polymer has a higher coating property on the positive electrode active material particles than other components such as a binder described later, and preferentially performs positive electrode activity when mixing the materials of the positive electrode active material layer. It easily adheres to the surface of material particles. Therefore, an acrylonitrile-based polymer layer is likely to be formed on the inorganic coating layer of the positive electrode active material particles.

Such an acrylonitrile-based polymer may contain acrylonitrile as a monomer unit, but preferably contains acrylonitrile as a monomer unit in an amount of 90 mol% or more, more preferably 95 mol% or more. When 100 mol% of acrylonitrile is contained as a monomer unit, the acrylonitrile-based polymer is polyacrylonitrile.

Further, the acrylonitrile-based polymer is, for example, the following formula (2) :.

In the above formula (2), l and m are integers of 1 or more, respectively, and R ₁ and R ₂ are hydrogen or methyl groups, respectively.
It is preferable to have a structure represented by. In this case, when acrylonitrile is contained in an amount of 90 mol% or more as a monomer unit, the relationship of l> 9.0 × m can be satisfied. The acrylonitrile-based polymer preferably satisfies the relationship of 9.5 × m <l <9.9 × m.

The mass average molecular weight of the acrylonitrile-based polymer described above is, for example, 200,000 or more and 800,000 or less, preferably 500,000 or more and 800,000 or less. When the mass average molecular weight of the acrylonitrile-based polymer is not more than the above upper limit value, the fluidity at room temperature can be sufficiently sufficient. On the other hand, when the mass average molecular weight of the acrylonitrile-based polymer is at least the above lower limit value, the coating effect of the acrylonitrile-based polymer can be sufficiently obtained. As described above, by setting the mass average molecular weight of the acrylonitrile-based polymer within the above-mentioned range, the cycle characteristics can be further improved. The mass average molecular weight of the polymer can be determined by matrix-assisted laser desorption / ionization time-of-flight mass spectrometry (MALDI TOF-MS, for example, SHIMADZU AXIMA).

The content of the acrylonitrile polymer in the positive electrode active material layer 22 is, for example, 0.5% by mass or more and 2% by mass or less, preferably 1% by mass or more and 2% by mass or less, based on the mass of the positive electrode active material particles. Can be.

Examples of the conductive auxiliary agent include carbon black such as ketjen black, acetylene black, and furnace black. Of these, any one or more types of carbon black may be contained. Of these carbon blacks, a preferred example is acetylene black. Acetylene black has fewer defects than other carbon blacks. The defective portion of the carbon black may react with the electrolytic solution when the non-aqueous electrolyte secondary battery 10 is charged and discharged under a high voltage. When the reaction occurs, gas is generated, and the non-aqueous electrolyte secondary battery 10 may expand or the like. From this point of view, the carbon black is preferably acetylene black.

The binder is, for example, polyvinylidene difluoride, ethylene propylene diene ternary copolymer (ethylene-polylene-diene terpolymer), styrene butadiene rubber (styrene-butadiene rubber rubber) ), Fluororelastomer, polyvinyl acetate, polymethylmethacrylate, polyethylene, nitrocellulose and the like. The binder is not particularly limited as long as it can bind the positive electrode active material and the conductive auxiliary agent onto the positive electrode current collector 21. The content of the binder is not particularly limited, and may be any content as long as it is applicable to the positive electrode active material layer of the non-aqueous electrolyte secondary battery.

The positive electrode active material layer 22 is, for example, a slurry in which a positive electrode active material, a conductive auxiliary agent, and a binder are dispersed in a suitable organic solvent (for example, N-methyl-2-pyrrolidone). (Slurry) is applied onto the positive electrode current collector 21, dried, and rolled.

The negative electrode 30 includes a negative electrode current collector 31 and a negative electrode active material layer 32. The negative electrode current collector 31 is made of, for example, copper, nickel, or the like.

The negative electrode active material layer 32 may be any material as long as it is used as the negative electrode active material layer of the non-aqueous electrolyte secondary battery. For example, the negative electrode active material layer 32 may contain a negative electrode active material and may further contain a binder. The negative electrode active material is, for example, graphite active material (artificial graphite, natural graphite, a mixture of artificial graphite and natural graphite, natural graphite coated with artificial graphite, etc.), silicon (Si) or tin (Sn), or an oxide thereof. Mixtures of fine particles and graphite active material, fine particles of silicon or tin, alloys based on silicon or tin, titanium oxide (TIO _x ) -based compounds such as _{Li 4} Ti ₅ O _{12 can be used.} .. The oxide of silicon is represented by SiO _x (0 ≦ x ≦ 2). In addition to these, for example, metallic lithium or the like can be used as the negative electrode active material.

Further, as the binder, for example, styrene-butadiene rubber (SBR) or the like is used. The mass ratio of the negative electrode active material to the binder is not particularly limited, and the mass ratio adopted in the conventional non-aqueous electrolyte secondary battery can be applied in the present invention.

The separator layer 40 contains a separator and an electrolytic solution.
The separator contained in the separator layer 40 is not particularly limited. Any separator contained in the separator layer 40 can be used as long as it is used as a separator for a non-aqueous electrolyte secondary battery. For example, as the separator, it is preferable to use a porous membrane, a non-woven fabric, or the like exhibiting excellent high-rate discharge performance alone or in combination. Examples of the material constituting the separator include a polyolefin (polylefine) resin typified by polyethylene, polypropylene, etc., a polyethylene terephthalate, a polybutylene terephthalate, and the like. Polyester-based resin, polyvinylidene difluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-perfluorovinyl ether (perfluorovinyldiethylene) copolymer, fluoride. (Tetrafluoroothylene) polymer, vinylidene fluoride-trifluoroethylenee copolymer, vinylidene fluoride-fluoroethylene (fluoroethylene) copolymer, vinylidene fluoride-hexafluoroacetonee copolymer, fluoride. Vinylidene-ethylene copolymer, vinylidene fluoride-propylene copolymer, vinylidene fluoride-trifluoropropanol copolymer, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer , Vinylidene fluoride-ethylene-tetrafluoroethylene copolymer and the like can be used. The porosity of the separator is not particularly limited, and the porosity of the separator of the non-aqueous electrolyte secondary battery can be arbitrarily applied.

Further, the separator may have a coating layer containing an inorganic filler. Specifically, the coating layer may contain at least one of _{Mg (OH) 2 and} Al ₂ O _{3 as an inorganic filler.} According to this configuration, the coating layer containing the inorganic filler prevents the positive electrode and the separator from coming into direct contact with each other, so that the electrolytic solution generated on the surface of the positive electrode during high-temperature storage is prevented from being oxidized and decomposed, and the electrolytic solution is decomposed and generated. It is possible to suppress the generation of gas, which is a substance.

Here, the coating layer containing the inorganic filler may be formed on both sides of the separator, or may be formed only on one side of the separator on the positive electrode side. If the coating layer containing the inorganic filler is formed at least on the positive electrode side, direct contact between the positive electrode and the electrolytic solution can be prevented.

Further, the present invention is not limited to the above examples. For example, the coating layer containing the inorganic filler may be formed on the positive electrode instead of on the separator. In such a case, the coating layer containing the inorganic filler can be formed on both sides of the positive electrode to prevent direct contact between the positive electrode and the separator. Needless to say, the coating layer containing the inorganic filler may be formed on both the positive electrode and the separator.

As the electrolytic solution, the same non-aqueous electrolytic solution conventionally used for a lithium secondary battery can be used without particular limitation. Here, the electrolytic solution has a composition in which an electrolyte salt is contained in a non-aqueous solvent. Examples of the non-aqueous solvent include propylene carbonate (polyline carbonate), ethylene carbonate (ethylene carbonate), butylene carbonate (butyrene carbononate), chloroethylene carbonate (chloroethylene carbononate), vinylene carbonate (vinylene carbonate), and the like. ) Classes; cyclic esters such as γ-butyrolactone and γ-valerolactone; chains of dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate and the like. Carbonates; Chain esters such as methyl formate, methyl acetate, methyl butyrate; tetrahydrofuran or derivatives thereof; 1,3-dioxane (1,3-dioxane) ), 1,4-dioxane (1,4-dioxane), 1,2-dimethoxyethane (1,2-dimethoxyester), 1,4-dibutoxyethane (1,4-dibutoxyethane), methyldiglyclyme. Ethers such as ester; nitriles such as acetonitrile and benzonitrile; dioxolane or derivatives thereof; ethylene sulfide, sulfolane, sulfone and the like. Alternatively, a derivative thereof or the like can be used alone or in combination of two or more thereof, but the present invention is not limited thereto.

Examples of the electrolyte salt include LiClO ₄ , LiBF ₄ , _{LiAsF 6} , LiPF ₆ , LiSCN, LiBr, LiI, Li ₂ SO ₄ , Li ₂ B ₁₀ Cl ₁₀ , NaClO ₄ , NaI, NaSCN, NaBr, KClO _4. , KSCN and other inorganic ion salts containing one of lithium (Li), sodium (Na) or potassium (K), LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) ₃ , (CH ₃ ) ₄ NBF ₄ , (CH ₃ ) ₄ NBr, (C ₂ H ₅ ) ₄ NClO ₄ , (C ₂ H ₅ ) ₄ NI, (C ₃ H ₇ ) ₄ NBr, (n-C ₄ H ₉ ) ₄ NClO ₄ , (n-C ₄ H ₉₎ ) ₄ NI, (C ₂ H ₅ ) ₄ N-malate, (C ₂ H ₅ ) ₄ N-benzoate, (C ₂ H ₅ ) ₄ N-phaltate, lithium stearyl sulfate, octyl sulfonic acid Organic ion salts such as lithium (lithium octyl sulfate) and lithium dodecylbenzene sulphonate can be used. These ionic compounds can be used alone or in combination of two or more. Further, the concentration of the electrolyte salt may be the same as that of the non-aqueous electrolyte solution used in the conventional lithium secondary battery, and is not particularly limited. In the present invention, an electrolytic solution containing an appropriate lithium compound (electrolyte salt) at a concentration of about 0.5 to 2.0 mol / L can be used.

<3. Manufacturing method of non-aqueous electrolyte secondary battery ＞
(3-1. Manufacturing method of positive electrode active material)
First, a method for producing a positive electrode active material will be described. The positive electrode active material can be obtained by synthesizing positive electrode active material particles and further forming an inorganic coating layer on the positive electrode active material.

The method for synthesizing the positive electrode active material particles is not particularly limited, and for example, a coprecipitation method can be used. Specifically, first, the positive electrode active material precursor particles are synthesized by the coprecipitation method. A mixed powder is produced by mixing the obtained dry powder with a lithium source, for example, lithium carbonate (Li ₂ CO _3). The obtained mixed powder can be calcined at 950 to 1050 ° C. for 6 hours in an air atmosphere to synthesize positive electrode active material particles. Here, the molar ratio of Li and Co + M (= Me) is determined according to the composition of the lithium cobalt composite oxide. For example, _{in the case of producing Li 1.00} Co _0.99 Al _0.0025 Mg _0.005 Ti _0.0025 O ₂ , the molar ratio Li: Me of Li and Me is 1.00: 1.00. The Li: Me ratio of the obtained lithium cobalt composite oxide is confirmed by ICP-OES (for example, HORIBA ULTIMA2), and the Li: Me ratio after firing is set to 1.00: 1.00 in advance. The amount of lithium carbonate can be adjusted for production.

Next, an inorganic coating layer is formed on the positive electrode active material particles. The inorganic coating layer forms an island-shaped first layer containing, for example, lithium phosphate or metallic lithium phosphate on the positive electrode active material particles, and then contains an aluminum compound on the positive electrode active material particles and the first layer. It can be formed by covering a continuous second layer.

The first layer is a slurry obtained by mixing the constituent materials of the first layer and the positive electrode active material particles in a dispersion medium, and the dispersion medium is removed by spray drying or an evaporator, and the surface of the positive electrode active material particles is fired. Formed on top.

As an example, isopropanol is used as a dispersion medium, and the constituent material of the first layer is added thereto to obtain a mixed solution. As the constituent material of the first layer, for example, when the main component of the first layer is lithium phosphate (Li ₃ PO ₄ ), P ₂ O ₅ and CH ₃ O Li are used in a molar ratio of 1/2: 3. .. For example, when the main component of the first layer is LZP (LiZr ₂ (PO ₄ ) ₃ ), CH ₃ OLi, 70% zirconium propoxide, and P ₂ O ₅ are used in a molar ratio of 1: 2: 3/2. .. Also, if for example the main component of the first layer is a _{LTP (LiTi 2 (PO 4)} 3), CH 3 OLi, tetraisopropyl _{orthotitanate,} the _{P 2 O 5 1: 2:} 3/2 molar ratio of Used in.

Positive electrode active material particles are added to the mixed solution in which the constituent materials of the first layer are mixed, and stirring is performed. Then, the dispersion medium is removed by spray drying or an evaporator.

Finally, firing is performed to form a first layer on the surface of the positive electrode active material particles. The firing conditions can be, for example, 6 hours at 700 to 800 ° C. in an atmospheric atmosphere.

The positive electrode active material particles and the first layer are then coated with a continuous second layer containing the aluminum compound. In the second layer, for example, the positive electrode active material particles are dispersed in an aqueous solution in which an aluminum source is dissolved, the obtained dispersion liquid is heat-treated, and then the positive electrode active material particles in the dispersion liquid are fired. Can be formed.

Specifically, first, the positive electrode active material particles having the first layer formed are dispersed in an aqueous solution containing an aluminum source to obtain a dispersion liquid. Examples of the aluminum source include aluminum nitrate, aluminum sulfate, aluminum chloride and the like. Further, in order to dissolve the aluminum source in the aqueous solution, a known acid or the like may be used as appropriate.

Further, if necessary, a component of an aluminum compound other than the aluminum source may be added to the dispersion liquid. For example, when the aluminum compound is aluminum fluoride, a compound containing, for example, fluoride ions, for example, ammonium fluoride can be added to the dispersion liquid.

Then, the obtained dispersion is heated to 70 to 100 ° C. and stirred for 5 to 12 hours. As a result, the aluminum compound or its precursor adheres to the positive electrode active material particles. Then, the dispersion medium in the dispersion liquid is removed. The dispersion medium can be removed by evaporation to dryness with an evaporator or the like or by filtration.
Finally, firing is performed to form a second layer containing the aluminum compound on the surface of the positive electrode active material particles. As a result, an inorganic coating layer is formed. Depending on the firing conditions, the first layer and the second layer are integrated into one inorganic coating layer. Further, depending on the firing conditions, a component, for example, cobalt in the positive electrode active material particles is partially diffused into the second layer during firing. The firing conditions can be, for example, in a nitrogen atmosphere at 350 to 500 ° C. for 4 to 6 hours.

(3-2. Manufacturing method of non-aqueous electrolyte secondary battery)
Subsequently, an example of a method for manufacturing the non-aqueous electrolyte secondary battery 10 will be described. The manufacturing method described below is merely an example, and it goes without saying that the non-aqueous electrolyte secondary battery 10 can be manufactured by another method.

The positive electrode 20 is manufactured as follows. First, by dispersing the materials constituting the positive electrode active material layer 22 (for example, positive electrode active material, conductive auxiliary agent, acrylonitrile-based polymer and binder) in an organic solvent (for example, N-methyl-2-pyrrolidone). Form a slurry.

Specifically, the solution in which the acrylonitrile-based polymer is dissolved is mixed with the solution in which the binder is dissolved in the organic solvent. Further, if necessary, a conductive auxiliary agent is added.

Next, the obtained mixture is kneaded and mixed, and further, positive electrode active material particles are added and kneaded and mixed. Finally, an organic solvent is added to adjust the viscosity to obtain a slurry.

Next, the slurry is applied onto the positive electrode current collector 21 and dried to form the positive electrode active material layer 22. Further, the positive electrode active material layer 22 is compressed to a desired thickness by a compressor. As a result, the positive electrode 20 is manufactured. Here, the thickness of the positive electrode active material layer 22 is not particularly limited as long as it is the thickness of the positive electrode active material layer of the non-aqueous electrolyte secondary battery. The step of applying the positive electrode active material to the current collector may be performed in a dry environment.
Here, as described above, the acrylonitrile-based polymer tends to adhere to the positive electrode active material particles more easily than the general binder, and tends to form a layer on the surface of the positive electrode active material particles. Therefore, in the kneading mixing and drying of the slurry, the surface of the positive electrode active material particles is coated with the acrylonitrile-based polymer, and a layer of the acrylonitrile-based polymer is formed.

The negative electrode 30 is obtained by first mixing a negative electrode active material, carboxymethyl cellulose (CMC) and a conductive auxiliary agent in a desired ratio, adding a predetermined amount of ion-exchanged water, and kneading and mixing them. Then, ion-exchanged water is further added to adjust the viscosity, and a styrene-butadiene rubber (SBR) binder is added to form a negative electrode slurry. Next, the slurry is applied onto the negative electrode current collector 31 and dried to form the negative electrode active material layer 32. Further, the negative electrode active material layer 32 is compressed to a desired thickness by a compressor. As a result, the negative electrode 30 is manufactured. Here, the thickness of the negative electrode active material layer 32 is not particularly limited as long as it is the thickness of the negative electrode active material layer of the non-aqueous electrolyte secondary battery. When metallic lithium is used as the negative electrode active material layer 32, the metallic lithium foil may be laminated on the negative electrode current collector 31.

Subsequently, the electrode structure is manufactured by sandwiching the separator between the positive electrode 20 and the negative electrode 30. Next, the electrode structure is processed into a desired shape (for example, cylindrical shape, square shape, laminated shape, button shape, etc.) and inserted into the container of the desired shape. Further, by injecting an electrolytic solution having a desired composition into the container, each pore in the separator is impregnated with the electrolytic solution. As a result, the non-aqueous electrolyte secondary battery 10 is manufactured.

Hereinafter, examples according to the present embodiment will be described.
<1. Cell manufacturing>
(Example 1)
(Preparation of positive electrode active material)
By the following method, positive electrode active material particles having a composition formula of _{Li 1.00} Co _0.99 Al _0.0025 Mg _0.005 Ti _0.0025 O _{2 were synthesized.} First, positive electrode active material precursor particles having a composition represented by the composition formula Co _0.99 Al _0.0025 Mg _0.005 Ti _0.0025 (OH) _{2 were synthesized by the coprecipitation method.} The obtained dry powder and lithium carbonate (Li ₂ CO ₃ ) were mixed to produce a mixed powder. The obtained powder was calcined at 950 to 1050 ° C. for 6 hours in an air atmosphere to synthesize positive electrode active material particles. Here, since the molar ratio of Li and Co + M (= Me) is determined according to the composition of the lithium cobalt composite oxide, Li _1.00 Co _0.99 Al _0.0025 Mg _0.005 Ti _{0. When 0025} O ₂ is produced, the molar ratio Li: Me of Li and Me is 1.00: 1.00. The Li: Me ratio of the obtained lithium-cobalt composite oxide was confirmed by ICP-OES (for example, HORIBA ULTIMA2), and the Li: Me ratio after firing was 1.00: 1.00 in advance. Manufactured by adjusting the amount of lithium carbonate. For example, the molar ratio of Li and Me is adjusted between 1.03: 1.00 to 1.07: 1.00 so that the Li: Me ratio after firing is 1.00: 1.00. Manufactured.

The average particle size (arithmetic mean value of the sphere equivalent diameter) of the positive electrode active material particles was calculated by analyzing the SEM image. That is, the sphere-equivalent diameters of the plurality of positive electrode active materials were calculated based on the SEM image, and the arithmetic mean value of these was taken as the average particle size. As a result, the average particle size was 15 μm.

_{Then, CH 3} OLi and P ₂ O ₅ were added to isopropanol as a constituent material of the first layer in a molar ratio of 3: 1/2. Then, the synthesized positive electrode active material particles were added to the mixed solution and stirred. The amount of the positive electrode active material particles added was adjusted so that the obtained first layer was 0.6 mol% with respect to the positive electrode active material particles. Then, isopropanol was removed by a spray dryer to obtain a powder.

The obtained powder was calcined at 700 to 800 ° C. for 6 hours in an air atmosphere to form _{a Li 3} PO _{4 layer as a first layer on the surface of the positive electrode active material particles.}

Then, the obtained positive electrode active material particles were dispersed in an aqueous solution in which aluminum nitrate / nine hydrate was dissolved to obtain a dispersion liquid. The aluminum nitrate was dissolved in the aqueous solution so that the aluminum oxide formed on the positive electrode active material particles was 0.1 mol%. Then, the dispersion was stirred at 80 ° C. for 5 hours to evaporate and dry the water. The obtained solid material was calcined in nitrogen at 400 ° C. for 5 hours to form a second layer containing aluminum oxide on the surface of the positive electrode active material particles. As a result, the inorganic coating layer was formed on the positive electrode active material particles.

(Making a coin half cell)
A coin half cell was produced by the following processing. First, positive electrode active material particles, acetylene black, polyvinylidene fluoride and acrylonitrile-based polymer were mixed at a mass ratio of 96: 2: 1: 1. This mixture (positive electrode mixture) was dispersed in N-methyl-2-pyrrolidone to form a slurry. The acrylonitrile-based polymer has acrylonitrile and acrylic acid as monomers, and the molar ratio of these is acrylonitrile: acrylic acid = 97.5: 2.5. The mass average molecular weight of the acrylonitrile polymer was 500,000 as measured by matrix-assisted laser desorption / ionization time-of-flight mass spectrometry (MALDI TOF-MS).

The slurry was applied onto the positive electrode current collector 21 and dried to form the positive electrode active material layer 22. Then, the positive electrode 20 was manufactured by rolling so that the thickness of the positive electrode active material layer 22 was 50 μm. The volume density of the positive electrode active material layer 22 was 4.0 g / cc, and the area density was 20 mg / cm ² .

The negative electrode 30 was produced by applying a negative electrode slurry in which graphite was dispersed in ion-exchanged water onto a copper foil, which is a negative electrode current collector 31, and drying the negative electrode 30. Then, a porous polypropylene film having a thickness of 12 μm (with magnesium hydroxide coating on both sides; manufactured by Teijin Limited) is prepared as a separator, and the separator is placed between the positive electrode 20 and the negative electrode 30 to form an electrode. The structure was manufactured. Next, the electrode structure was processed to the size of a coin half cell and stored in a coin half cell container.

Then, an electrolytic solution was produced by dissolving lithium hexafluorophosphate at a concentration of 1.3 M in a non-aqueous solvent in which ethylene carbonate and dimethyl carbonate were mixed at a volume ratio of 3: 7. Next, the coin half cell according to Example 1 was produced by injecting the electrolytic solution into the coin half cell and impregnating the separator with the electrolytic solution.

(Making a coin full cell)
The electrode structure was manufactured in the same manner as the coin half cell. Then, the electrode structure was processed to the size of a coin full cell and stored in a coin full cell container.

Then, an electrolytic solution was produced by dissolving lithium hexafluorophosphate at a concentration of 1.3 M in a non-aqueous solvent in which ethylene carbonate and dimethyl carbonate were mixed at a volume ratio of 3: 7. Then, the electrolytic solution was injected into the coin full cell and the separator was impregnated with the electrolytic solution to produce the coin full cell according to Example 1.

(Examples 2 to 6)
A coin half cell and a coin full cell were prepared in the same manner as in Example 1 except that the coating amount of the inorganic coating layer was changed as shown in Table 1.

(Examples 7 to 12)
A coin half cell and a coin full cell were prepared in the same manner as in Example 1 except that the composition and the coating amount of the inorganic coating layer were changed as shown in Table 1.

(Example 13)
_{First, in the same manner as in Example 1, a Li 3} PO ₄ layer as a first layer was formed on the surface of the positive electrode active material particles.

Then, the obtained positive electrode active material particles were dispersed in an aqueous solution in which aluminum nitrate / nine hydrate was dissolved to obtain a dispersion liquid. The aluminum nitrate was dissolved in the aqueous solution so that the aluminum fluoride formed on the positive electrode active material particles was 0.2 mol%. An aqueous solution of ammonium fluoride was added dropwise to this dispersion. The addition amount was appropriately adjusted so that the molar ratio of fluoride ion to aluminum ion was 3: 1. Then, the mixed solution was stirred at 80 ° C. for 5 hours to evaporate and dry the water. The obtained solid material was calcined in nitrogen at 400 ° C. for 5 hours to form a second layer on the surface of the positive electrode active material particles. As a result, the inorganic coating layer was formed on the positive electrode active material particles.
For the subsequent procedure, a coin half cell and a coin full cell were created in the same manner as in Example 1.

(Examples 14 to 24)
A coin half cell and a coin full cell were prepared in the same manner as in Example 13 except that the composition and the coating amount of the inorganic coating layer were changed as shown in Table 1.

(Comparative Example 1)
A coin half cell and a coin full cell were prepared in the same manner as in Example 1 except that the second layer was not formed.
(Comparative Examples 2 to 11)
A coin half cell and a coin full cell were prepared in the same manner as in Example 1 except that the composition and the coating amount of the first layer were changed as shown in Table 1 without forming the second layer.

(Comparative Example 12)
A coin half cell and a coin full cell were prepared in the same manner as in Example 1 except that the first layer and the second layer were not formed.
(Comparative Example 13)
Acrylonitrile-based high height using positive electrode active material particles, acetylene black and polyvinylidene fluoride in a mass ratio of 96: 2: 2 as constituent materials of the positive electrode active material layer without forming the first layer and the second layer. A coin half cell and a coin full cell were prepared in the same manner as in Example 1 except that no molecule was used.
Table 1 summarizes the manufacturing conditions in each of the above Examples, Comparative Examples, and Reference Examples. The film thickness of each layer of the inorganic coating layer was measured with a transmission electron microscope.

<2. Evaluation>
Next, the discharge capacity, initial efficiency, and cycle characteristics were evaluated using the coin half cell and coin full cell obtained in each Example and Comparative Example.
(Discharge capacity and initial efficiency)
The coin half cells obtained in each Example and Comparative Example were charged / discharged at the charge / discharge rate (rate) and cut off voltage (unit: V) shown in Table 2 below. The temperature during charging and discharging was room temperature (25 ° C.). CC-CV means constant current and constant voltage, and CC means constant current. Then, the discharge capacity of the first cycle is measured, and this value is used as the initial discharge capacity, and the initial efficiency is the capacity retention rate of the discharge capacity of the first cycle (0.1C) with respect to the charge capacity of the first cycle (0.1C). Was evaluated.

(Charge / discharge cycle test)
Full cells were charged and discharged at the charge / discharge rate (rate) and cut off voltage (unit: V) shown in Table 3 below. The temperature during charging and discharging was set to a high temperature (45 ° C.). CC-CV means constant current and constant voltage, and CC means constant current. Then, the discharge capacity of the third cycle was measured, this value was set as the initial capacity, the discharge capacity of the 101st cycle was measured, and this value was set as the capacity of the 100th cycle. The cycle characteristics (1C cycle capacity retention rate) were evaluated by the capacity retention rate of the discharge capacity at the 101st cycle (1.0C) with respect to the discharge capacity at the 3rd cycle (1.0C). In addition, the 1C / 0.2C load characteristics were evaluated based on the capacity retention rates of the discharge capacities in the second and third cycles.

The above results are shown in Table 1.

<3. Contrast>
First, comparing Examples 1 to 24 and Comparative Examples 1 to 13, the coin full cell according to Examples 1 to 24 has a cycle at a higher temperature (45 ° C.) than the coin full cell according to Comparative Examples 1 to 13. The characteristics and 1C cycle capacity retention rate were significantly improved.

Specifically, first, when Examples 1 to 24 are compared with Comparative Example 13, an inorganic coating layer containing lithium phosphate and / or metallic lithium phosphate and an aluminum compound is formed, and an acrylonitrile-based polymer is used as a positive electrode. When coated with material particles, the cycle characteristics and 1C cycle capacity retention rate could be dramatically improved while preventing a decrease in discharge capacity and initial efficiency.
Further, comparing Examples 1 to 24 with Comparative Example 12, simply coating the acrylonitrile-based polymer without forming the inorganic coating layer dramatically improves the cycle characteristics and the 1C cycle capacity retention rate. It was shown that it cannot be done.

Further, comparing Examples 1 to 6 with Comparative Examples 1 and 2, and Examples 7 to 12 with Comparative Examples 3 and 4, respectively, in the formation of the inorganic coating layer, the second layer containing the aluminum compound was not formed. It was shown that the cycle characteristics and the 1C cycle capacity retention rate cannot be sufficiently improved even when the inorganic coating layer does not contain the aluminum compound.

Further, when Examples 1 and 3 are compared with Comparative Examples 5 and 6 and Examples 13 and 15 with Comparative Examples 7 and 8, respectively, the first layer is replaced with the first layer containing lithium phosphate or metallic lithium phosphate. When a layer containing an aluminum compound is formed as the layer of the above, that is, when the inorganic coating layer does not contain either lithium phosphate or metallic lithium phosphate, the cycle characteristics and the 1C cycle capacity retention rate are similarly sufficient. It was shown that it cannot be improved.

Further, referring to Comparative Examples 9 to 11, even when the inorganic coating layer is formed of a compound other than lithium phosphate, lithium metal phosphate and an aluminum compound, the cycle characteristics and the 1C cycle capacity retention rate are similarly sufficiently sufficient. It was shown that it cannot be improved.

Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person having ordinary knowledge in the field of technology to which the present invention belongs can come up with various modifications or modifications within the scope of the technical ideas described in the claims. , These are also naturally understood to belong to the technical scope of the present invention.

10 Non-aqueous electrolyte secondary battery 20 Positive electrode 21 Positive electrode current collector 22 Positive electrode active material layer 30 Negative electrode 31 Negative electrode current collector 32 Negative electrode active material layer 40 Separator layer

Claims (11)

It has a current collector and a positive electrode active material layer bonded to the current collector.
The positive electrode active material layer has the following formula (1):
_{Li x Co y MzO 2 (1} )
In the formula (1), M is aluminum (Al), nickel (Ni), manganese (Mn), chromium (Cr), iron (Fe), vanadium (V), magnesium (Mg), titanium (Ti), Zirconium (Zr), Niob (Nb), Molybdenum (Mo), Tungsten (W), Copper (Cu), Zinc (Zn), Gallium (Ga), Indium (In), Tin (Sn), Lantern (La), It is one or more metal elements selected from the group consisting of cerium (Ce), and x, y, z are 0.20 ≦ x ≦ 1.20, 0.95 ≦ y ≦ 1.00, 0.0. It is a value within the range of ≦ z ≦ 0.05 and y + z = 1.
Positive electrode active material particles having the composition shown in
An inorganic coating layer covering at least a part of the positive electrode active material particles,
It has a polymer containing acrylonitrile as a monomer unit, which covers at least a part of the positive electrode active material particles.
The inorganic coating layer has the following (i) to (iii).
(I) lithium phosphate, any of a phosphoric acid metal lithium and aluminum compounds (ii) lithium phosphate and aluminum compound (iii) phosphoric acid metal lithium and aluminum compounds seen including,
It has a first layer that covers at least a part of the positive electrode active material particles, a first layer, and a second layer that covers the positive electrode active material particles.
The first layer has a higher content of lithium phosphate and / or metallic lithium phosphate than the second layer.
The second layer is a positive electrode for a non-aqueous electrolyte secondary battery having a higher content of the aluminum compound than the first layer. The positive electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein the aluminum compound contains at least one selected from the group consisting of aluminum oxide, aluminum fluoride and aluminum phosphate. The positive electrode for a non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the inorganic coating layer contains the aluminum compound having a molar ratio of 0.025 mol% or more and 0.3 mol% or less with respect to the positive electrode active material particles. .. The positive electrode for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the metallic lithium phosphate contains one or more metals selected from the group consisting of aluminum, titanium, cobalt and zirconium. .. Any of claims 1 to 4, wherein the inorganic coating layer contains the lithium phosphate and / or the metallic lithium phosphate in a molar ratio of 0.1 mol% or more and 1.0 mol% or less with respect to the positive electrode active material particles. The positive electrode for a non-aqueous electrolyte secondary battery according to item 1. The positive electrode for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 5, wherein the average thickness of the first layer is 1.0 nm or more and 150 nm or less. The positive electrode for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 6, wherein the average thickness of the second layer is 1.0 nm or more and 10 nm or less. The positive electrode for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 7 , wherein the polymer contains 90 mol% or more of acrylonitrile as a monomer unit. The polymer has the following formula (2):

In the above formula (2), l and m are integers of 1 or more, respectively, and R ₁ and R ₂ are hydrogen or methyl groups, respectively.
The positive electrode for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 8 , which has a structure represented by. The positive electrode for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 9 , wherein the polymer has a mass average molecular weight of 200,000 or more and 800,000 or less. A non-aqueous electrolyte secondary battery comprising the positive electrode for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 10.

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