Composite particle, producing method for composite particle, and nonaqueous electrolyte secondary battery

Abstract

The present invention addresses the problem of providing: composite particles serving as a battery material (positive electrode active material) which is particularly suitable for nonaqueous electrolyte secondary batteries, retains the capacity even at a high rate, and exhibits excellent cycle characteristics, and a producing method by which said composite particles can be easily obtained; and a high-performance nonaqueous electrolyte battery.　In order to solve the abovementioned problem, provided are: composite particles in which Li-containing nanoparticles are adhered to the surfaces of positive electrode active material particles, and in which the respective BET specific surface areas of the positive electrode active material particles, the Li-containing nanoparticles, and the composite particles are in a numerical range satisfying a specific relationship; and a producing method for said composite particles. Further provided is a nonaqueous electrolyte secondary battery in which said composite particles are used as a positive electrode active material.

Description

Composite particles, method for producing composite particles, and non-aqueous electrolyte secondary battery

[0001] The present invention relates to composite particles, a method for producing composite particles, and a non-aqueous electrolyte secondary battery.

[0002] BACKGROUND ART In recent years, various efforts have been made to improve the electrical properties of secondary batteries such as lithium ion batteries by developing positive electrode active materials and coating their surfaces.

[0003] For example, Patent Document 1 discloses that a lithium nickel composite oxide, which is a positive electrode active material for a non-aqueous electrolyte secondary battery, is controlled in its crystal structure so that the crystal axis length falls within a specific range, and that a compound coating containing W and Li is formed on the surface of the primary particle, thereby achieving both high capacity and high output. Patent Document 2 also discloses a positive electrode active material particle for a non-aqueous electrolyte secondary battery and a LiAlF ４ , LiF and Li ３ AlF ６ Furthermore, Patent Document 3 discloses a method for improving battery capacity and cycle retention rate by forming a coated positive electrode active material having a coating layer containing a ferroelectric first element and other elements. Furthermore, Patent Document 3 discloses a method for manufacturing a positive electrode material for a lithium ion battery, which has improved high-speed charge / discharge rate characteristics, by a manufacturing method in which a dispersion liquid made of a powdered raw material containing a first element of a ferroelectric and other elements is supported on a powdered active material raw material for a lithium ion battery positive electrode by a sol-gel method, and an electrode material manufactured by this method. Alternatively, Patent Document 4 discloses that the rate characteristics of a non-aqueous electrolyte secondary battery can be improved by using a mixed positive electrode active material made of lithium manganese phosphate doped with a metal such as Co and carbon, and also discloses an easy method for manufacturing the positive electrode active material. In addition, Non-Patent Document 1 discloses a method for manufacturing a positive electrode active material for a lithium ion battery, which has improved high-speed charge / discharge rate characteristics, by using a mixed positive electrode active material made of lithium manganese phosphate doped with a metal such as Co and carbon, and a method for easily manufacturing the positive electrode active material. ０．５ Mn １．５ O ４ It is disclosed that the surface of the positive electrode material is thinly coated with a fluoride solid electrolyte to improve the charge / discharge characteristics of the lithium ion secondary battery, thereby achieving high cycle characteristics.

[0004] JP 2017-084513 A JP 2023-009668 A JP 2016-149270 A JP 2008-130525 A

[0005] ACS Applied Energy Materials, 2021, Vol. 4, No. 9, p9866-9870

[0006] However, with conventional battery materials, particularly battery materials that function as positive electrode active materials, it is difficult to maintain high rate characteristics while exhibiting the effect of improving cycle characteristics.

[0007] An object of the present invention is to provide a composite particle that serves as a battery material (positive electrode active material) suitable for nonaqueous electrolyte batteries, particularly nonaqueous electrolyte secondary batteries, that retains capacity even at high rates and has excellent cycle characteristics, a method for easily obtaining the composite particle, and a high-performance nonaqueous electrolyte battery. Note that the description of the above object does not preclude the existence of other objects.

[0008] In order to solve the above problems, the present invention provides the following [1] to

[11] . [1] Composite particles having Li-containing nanoparticles attached to the surfaces of positive electrode active material particles in a scattered manner, characterized in that the ratio (x / S) of the difference (x) obtained by subtracting the BET specific surface area of ​​the positive electrode active material particles from the BET specific surface area of ​​the composite particles to the BET specific surface area (S) of the Li-containing nanoparticles satisfies the following formula (2): 0.0005≦x / S≦0.063 ... formula (2) [2] The BET specific surface area of ​​the Li-containing nanoparticles is 1 to 200 m ２ / g, and the BET specific surface area of ​​the composite particles is 0.1 to 30 m ２ / g. [3] The composite particle according to [1], characterized in that the average particle size of the Li-containing nanoparticles is 1 to 300 nm, the content of the positive electrode active material particles is 90.00 to 99.99 mass %, and the content of the Li-containing nanoparticles is 0.01 to 10.00 mass %. [4] The composite particle according to [1], characterized in that the Li-containing nanoparticles are dispersed and attached to the surfaces of the positive electrode active material particles, and then the composite particle is heat-treated at a heat treatment temperature of 200 to 700°C. [5] The composite particle according to any one of [1] to [4], characterized in that the Li-containing nanoparticles contain Li and F. [6] The composite particle according to any one of [1] to [3], characterized in that the composite particle is heat-treated in a state in which the Li-containing nanoparticles are attached to the surfaces of the positive electrode active material particles. [7] The composite particle according to [6], characterized in that the heat treatment is performed at a heat treatment temperature of 200 to 700°C. [8] A method for producing composite particles, comprising the steps of: preparing positive electrode active material particles; preparing Li-containing nanoparticles; and adhering the Li-containing nanoparticles to surfaces of the positive electrode active material particles to form composite particles, wherein a ratio (x / S) of a difference (x) obtained by subtracting the BET specific surface area of ​​the positive electrode active material particles from the BET specific surface area of ​​the composite particles to a BET specific surface area (S) of the Li-containing nanoparticles satisfies the following formula (2): 0.0005≦x / S≦0.063...formula (2) [9] The method for producing composite particles according to [8], further comprising a heat treatment step of performing heat treatment after the step of forming the composite particles.

[10] The method for producing composite particles according to [9], characterized in that the heat treatment step is performed at a heat treatment temperature of 200 to 700°C.

[11] A nonaqueous electrolyte secondary battery, characterized in that it contains the composite particles according to any one of [1] to [4].

[0009] According to the present invention, it is possible to provide composite particles that serve as a battery material (positive electrode active material) suitable for nonaqueous electrolyte batteries, particularly nonaqueous electrolyte secondary batteries, that retain capacity even at high rates and have excellent cycle characteristics, and a manufacturing method for easily obtaining the composite particles. Furthermore, according to the present invention, it is possible to provide a high-performance nonaqueous electrolyte battery by using the composite particles as a positive electrode active material.

[0010] 1 is a schematic explanatory diagram showing an example of the structure of a non-aqueous electrolyte secondary battery according to the present invention; ３ AlF ６ 1 is an XRD profile of Li, which is one embodiment of the Li-containing nanoparticles of the present invention. ３ AlF ６ FT-IR (ATR) measurement results of the Li-containing nanoparticles according to one embodiment of the present invention. ３ AlF ６ 1 is a result of FE-SEM observation of composite particles (LAF-LCO particles) in which LAF is attached to the surface of an LCO, which is an embodiment of the composite particles of the present invention. 2 is a diagram showing the cycle characteristics (3-4.3 V) and rate characteristics of a nonaqueous electrolyte secondary battery using, as a positive electrode active material, LAF-LCO particles, which is an embodiment of the nonaqueous electrolyte secondary battery of the present invention.

[0011] Hereinafter, embodiments of the composite particles, the method for producing the composite particles, and the nonaqueous electrolyte secondary battery using the composite particles according to the present invention will be described in detail. First, the composite particles of the present invention will be described, followed by the method for producing the composite particles. Furthermore, the nonaqueous electrolyte secondary battery of the present invention will be described. The composite particles, the method for producing the composite particles, and the nonaqueous electrolyte secondary battery using the composite particles described in the embodiments are merely examples used to explain the composite particles, the method for producing the composite particles, and the nonaqueous electrolyte secondary battery using the composite particles according to the present invention, and are not limited thereto. Furthermore, the descriptions of the features of the composite particle invention, the features of the method for producing the composite particles, and the features of the nonaqueous electrolyte secondary battery invention can be mutually substituted for the descriptions in each invention.

[0012] [Composite Particles] The composite particles of the present invention are composite particles in which Li-containing nanoparticles are attached to and scattered on the surfaces of positive electrode active material particles, and more specifically, have the following characteristics.

[0013] One embodiment of the composite particles of the present invention is characterized in that the difference (x) obtained by subtracting the BET specific surface area of ​​the positive electrode active material particles from the BET specific surface area of ​​the composite particles, relative to the BET specific surface area (S) of the Li-containing nanoparticles, satisfies the following formula (1): 0.0005S≦x≦0.063S ... formula (1) In other words, the BET specific surface area of ​​the composite particles is increased from the BET specific surface area of ​​the positive electrode active material particles before the Li-containing nanoparticles are attached, and this increase satisfies formula (1).

[0014] Furthermore, when formula (1) is converted into the ratio (x / S) of the difference (x) obtained by subtracting the BET specific surface area of ​​the positive electrode active material particles from the BET specific surface area of ​​the composite particles to the BET specific surface area (S) of the Li-containing nanoparticles, the ratio satisfies the following formula (2): 0.0005≦x / S≦0.063 (2)

[0015] In another embodiment of the composite particles of the present invention, the BET specific surface area of ​​the Li-containing nanoparticles is 1 to 200 m ２ / g, and the BET specific surface area of ​​the composite particles is 0.1 to 30 m ２ / g.

[0016] Furthermore, another embodiment of the composite particles of the present invention is characterized in that the average particle size of the Li-containing nanoparticles is 1 to 300 nm, the content of the positive electrode active material particles is 90.00 to 99.99 mass%, and the content of the Li-containing nanoparticles is 0.01 to 10.00 mass%.

[0017] In addition, another embodiment of the composite particles of the present invention is characterized by being heat-treated at a heat treatment temperature of 200 to 700°C.

[0018] According to the composite particles of the present invention, the Li-containing nanoparticles can be dispersed evenly on the surface of the positive electrode active material particles without uneven distribution, and can be easily attached at an appropriate coverage ratio. This makes it possible to obtain a material that can achieve high ionic conductivity between the ion-conducting material in the electrolyte and the positive electrode active material. Furthermore, when the composite particles are used as a battery material, the deposition of reaction products and the generation of impurities generated on the surface of the positive electrode active material during charge and discharge can be suppressed, thereby improving charge and discharge characteristics.

[0019] The positive electrode active material particles and Li-containing nanoparticles constituting the composite particles of the present invention will be described below. Although the following description will be primarily focused on Li-ion secondary batteries, the present invention can also be applied to other secondary batteries (such as Na-ion, Mg-ion, K-ion, Ca-ion, Al-ion, and other metal-ion batteries, anion-ion batteries such as F-ion batteries, dual-ion batteries, alkaline batteries, acid batteries, and solid-state batteries), as well as various electrolytes and electrochemical capacitors.

[0020] [Positive electrode active material particles] The positive electrode active material particles can be suitably used as a constituent material of non-aqueous electrolyte batteries, particularly non-aqueous electrolyte secondary batteries. The positive electrode active material particles of this embodiment can function as an electrode active material of secondary batteries by inserting and extracting various cations. In this embodiment, lithium ions are particularly preferred as the cations to be inserted and extracted.

[0021] The positive electrode active material particles are not particularly limited as long as they are, for example, a lithium-containing transition metal oxide or a substance capable of electrochemically absorbing and releasing lithium ions. Examples of lithium-containing transition metal oxides include LiCoO ２ Li-Co based composite oxides such as LiNiO ２ Li-Ni composite oxides such as LiCo １／３ Ni １／３ Mn １／３ O ２ , LiCo ０．８ Ni ０．１ Mn ０．１ O ２ , LiCo ０．６ Ni ０．２ Mn０．２ O ２ , LiCo ０．５ Ni ０．２ Mn ０．３ O ２ Lithium composite oxides with a layered rock salt structure, such as Li-Ni-Co-Mn composite oxides, LiMn ２ O ４ Li-Mn based composite oxides such as LiNi ０．５ Mn １．５ O ４ , and LiTi ２ O ４ Lithium composite oxides having a spinel structure such as LiFePO ４ , LiMnPO ４ and LiCoPO ４ These compounds may be used alone or in combination. The shape of the positive electrode active material particles is not particularly limited, but spherical particles are preferred.

[0022] The median diameter (D50) of the positive electrode active material particles is not particularly limited, but is, for example, 0.1 to 20 μm. The lower limit of this median diameter is preferably 0.5 μm or more, more preferably 1 μm or more. The upper limit of this median diameter is preferably 15 μm or less, more preferably 12 μm or less, and particularly preferably 10 μm or less. In the present invention, the median diameter is a value calculated as the median diameter measured using a laser diffraction particle size distribution analyzer or the like. For example, the median diameter can be measured using a laser diffraction particle size distribution analyzer manufactured by Shimadzu Corporation (product name: SALD-2300), a laser diffraction / scattering particle size distribution analyzer manufactured by Nikkiso Co., Ltd. (product name: Microtrac MT3000II), or an apparatus of the same type.

[0023] The BET specific surface area of ​​the positive electrode active material particles is not particularly limited, but is, for example, 0.1 to 30 m ２ The lower limit of the BET specific surface area is preferably 0.2 m ２ / g or more, more preferably 0.3m ２The BET specific surface area can be measured using a fully automatic specific surface area measuring device ("Macsorb" manufactured by Mountech Co., Ltd.) based on the BET flow method.

[0024] [Li-containing nanoparticles] By attaching the Li-containing nanoparticles to the surface of the above-mentioned positive electrode active material particles, they have the effect of suppressing the migration of ions at the interface of the positive electrode active material, the deposition of reaction products generated on the surface of the positive electrode active material by charge and discharge, and the generation of impurities. The Li-containing nanoparticles may be nanoparticles containing Li, and particularly preferably contain Li and F. As the Li salt, Li ３ AlF ６ , LiAlF ４ , and LiF, etc.

[0025] The average particle size of the Li-containing nanoparticles, as observed in SEM images, can be in the range of 1 to 300 nm. The lower limit of this average particle size is preferably 5 nm or more, more preferably 10 nm or more. The upper limit of this average particle size is preferably 200 nm or less, more preferably 100 nm or less, and particularly preferably 60 nm or less. In the present invention, the average particle size of the Li-containing nanoparticles is, unless otherwise specified, calculated as the average particle size of 30 randomly selected particles in an image in which 30 to 50 particles can be observed using an observation method such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The particle size of the particles is the maximum diameter of the particles. The average particle size of the Li-containing nanoparticles used is at least smaller than the average particle size of the positive electrode active material particles.

[0026] The BET specific surface area of ​​the Li-containing nanoparticles is not particularly limited, but is, for example, 1 to 200 m ２ The lower limit of the BET specific surface area is preferably 3 m ２ The upper limit of the BET specific surface area is preferably 150 m ２ / g or less, more preferably 100m ２ / g or less, and more preferably 60m ２ / g or less.

[0027] (Content of Positive Electrode Active Material Particles and Li-Containing Nanoparticles) The content of the positive electrode active material particles in the composite particles is not particularly limited, but may be, for example, 90.00 to 99.99% by mass. The lower limit of this content is preferably 95.00% by mass or more, more preferably 97.00% by mass or more, and particularly preferably 98.00% by mass or more. The upper limit of this content is preferably 99.95% by mass or less, more preferably 99.90% by mass or less, and particularly preferably 99.70% by mass or less. On the other hand, the content of the Li-containing nanoparticles in the composite particles is 0.01 to 10.00% by mass. The lower limit of this content is preferably 0.05% by mass or more, more preferably 0.10% by mass or more, and particularly preferably 0.30% by mass or more. The upper limit of this content is preferably 5.00% by mass or less, more preferably 3.00% by mass or less, and particularly preferably 2.00% by mass or less.

[0028] (Specific Surface Area (BET Specific Surface Area) of Composite Particles) The specific surface area of ​​the composite particles of the present invention is evaluated using the BET specific surface area measured by the BET method. The BET specific surface area of ​​the composite particles is not particularly limited, but is, for example, 0.1 to 30 m ２ The lower limit of the BET specific surface area is preferably 0.2 m ２ The upper limit of the BET specific surface area is preferably 20 m ２ / g or less, more preferably 10m ２ / g or less, and more preferably 5m ２ / g or less, and particularly preferably 2m ２ / g or less.

[0029] The composite particles of the present invention are composite particles in which Li-containing nanoparticles are attached in an island-like manner to the surface of positive electrode active material particles. Here, "island-like" refers to a state in which the Li-containing nanoparticles are scattered as primary particles on the surface of the positive electrode active material particles at an appropriate coverage ratio without being unevenly distributed, or a state in which the primary particles remain scattered on the surface of the positive electrode active material particles even after sintering and growth by heat treatment. Generally, when all or part of the surface of the positive electrode active material particles is covered by coating in the prior art, the BET specific surface area of ​​the composite particles is expected to be smaller than the BET specific surface area of ​​the positive electrode active material. In contrast, the present invention forms composite particles by attaching pre-synthesized Li-containing nanoparticles to the surface of the positive electrode active material, and the BET specific surface area of ​​the composite particles of the present invention is larger than the BET specific surface area of ​​the positive electrode active material particles before composite formation, i.e., the BET specific surface area of ​​the positive electrode active material particles before the Li-containing nanoparticles are attached.

[0030] More specifically, in the composite particles of the present invention, the difference (x) obtained by subtracting the BET specific surface area of ​​the positive electrode active material particles from the BET specific surface area of ​​the composite particles, relative to the BET specific surface area (S) of the Li-containing nanoparticles, satisfies the following formula (1): 0.0005S≦x≦0.063S ... formula (1) When the BET specific surface area of ​​the composite particles satisfies the above range, the Li-containing nanoparticles can be attached in an island-like manner to the surfaces of the positive electrode active material particles.

[0031] Furthermore, when formula (1) is converted into the ratio (x / S) of the difference (x) obtained by subtracting the BET specific surface area of ​​the positive electrode active material particles from the BET specific surface area of ​​the composite particles to the BET specific surface area (S) of the Li-containing nanoparticles, the ratio satisfies the following formula (2): 0.0005≦x / S≦0.063 ...formula (2) Here, the upper limit of x / S is preferably 0.060 or less, more preferably 0.050 or less, even more preferably 0.030 or less, and particularly preferably 0.010 or less.

[0032] The BET specific surface area (value of S) of the Li-containing nanoparticles is not particularly limited, but may be, for example, 1 to 200 m ２The coverage of the Li-containing nanoparticles present on the surface of the positive electrode active material particles is within a range of 5 to 90%, preferably 10 to 70%, as calculated from an SEM observation image.

[0033] [Method for Producing Composite Particles] One embodiment of the method for producing composite particles of the present invention includes the steps of preparing positive electrode active material particles, preparing Li-containing nanoparticles, and attaching the Li-containing nanoparticles to surfaces of the positive electrode active material particles to form composite particles, wherein the difference (x) obtained by subtracting the BET specific surface area of ​​the positive electrode active material particles from the BET specific surface area of ​​the composite particles satisfies the following formula (1) with respect to the BET specific surface area (S) of the Li-containing nanoparticles: 0.0005S≦x≦0.063S ... formula (1)

[0034] Furthermore, when formula (1) is converted into the ratio (x / S) of the difference (x) obtained by subtracting the BET specific surface area of ​​the positive electrode active material particles from the BET specific surface area of ​​the composite particles to the BET specific surface area (S) of the Li-containing nanoparticles, the ratio satisfies the following formula (2): 0.0005≦x / S≦0.063 (2)

[0035] Furthermore, one embodiment of the method for producing composite particles of the present invention includes the steps of preparing positive electrode active material particles and preparing a positive electrode active material having a BET specific surface area of ​​1 to 200 m ２ / g of Li-containing nanoparticles; and attaching the Li-containing nanoparticles to the surfaces of the positive electrode active material particles to form composite particles, wherein the BET specific surface area of ​​the composite particles is 0.1 to 30 m. ２ / g.

[0036] Furthermore, one embodiment of the method for producing composite particles of the present invention comprises the steps of preparing positive electrode active material particles, preparing Li-containing nanoparticles having an average particle size of 1 to 300 nm, and attaching the Li-containing nanoparticles to surfaces of the positive electrode active material particles to form composite particles, wherein the content of the positive electrode active material particles is 90.00 to 99.99 mass %, and the content of the Li-containing nanoparticles is 0.01 to 10.00 mass %.

[0037] In each of the above embodiments, the step of preparing the Li-containing nanoparticles includes pulverizing the Li-containing nanoparticles or preparing a dispersion containing the Li-containing nanoparticles, as will be described in detail later.

[0038] Each step of the method for producing composite particles of the present invention will be described below.

[0039] (Preparation of Positive Electrode Active Material Particles) In the step of preparing the positive electrode active material particles, commercially available positive electrode active materials can be used. For example, LiCoO ２ In the case of particles, lithium cobalt oxide (product name "Cellseed" C-5H) manufactured by Nippon Chemical Industry Co., Ltd., LiNi １／３ Co １／３ Mn １／３ O ２ In this case, a prepared product (NCM111) manufactured by Nichia Corporation can be used.

[0040] (Preparation of Li-containing nanoparticles) In the preparation step of Li-containing nanoparticles, Li-containing nanoparticles prepared from a lithium-containing compound (lithium-containing salt) as a lithium source can be used. More specifically, Li-containing nanoparticles can be prepared by using lithium sulfate (lithium sulfate) as a lithium source. ３ AlF ６ Examples of the synthesis include:

[0041] Below, Li ３ AlF ６ An example of the synthesis of LAF (hereinafter also referred to as "LAF") will be described. Predetermined amounts of lithium sulfate monohydrate as a lithium source and aluminum sulfate hydrate as an aluminum source are weighed and dissolved in a predetermined amount of pure water at room temperature. A predetermined amount of hydrogen fluoride (HF) of a predetermined concentration is dropped into the aqueous solution, and the resulting slurry is filtered using filter paper to form a cake on the filter paper. After washing with pure water from above and drying, the resulting white solid is pulverized and extracted with Li. ３ AlF ６ A white powder of Li can be obtained. ３ AlF ６The timing of nanoparticle formation is not particularly limited as long as it is before the Li is attached to the surface of the positive electrode active material particles. ３ AlF ６ The nanoparticles may be formed by drying and pulverizing the white powder, or the white powder may be further pulverized to form nanoparticles. ３ AlF ６ Here, the above-mentioned Li may be made into nanoparticles. ３ AlF ６ The method for pulverizing the white solid in the synthesis process is not particularly limited, and for example, the white solid can be pulverized using a mortar, a ball mill, a bead mill, a vibration mill, an impact pulverizer, a mixer, an airflow pulverizer, a rotary mill, a coffee mill, a mechanical mill, a mechanical crusher, or the like.

[0042] In addition, Li ３ AlF ６ The lithium source in the synthesis of (1) is not limited to the sulfate (lithium sulfate) described above, but other lithium-containing compounds (lithium-containing salts) can also be used. More specifically, lithium nitrate, lithium carbonate, lithium acetate, lithium hydroxide, lithium chloride, lithium oxalate, etc. can also be used.

[0043] As described above, the average particle size of the Li-containing nanoparticles is preferably in the range of 1 to 300 nm. This is the size necessary to obtain an appropriate particle size for the Li-containing nanoparticles, which are relatively small particles, when the positive electrode active material particles, which are relatively large particles in the composite particles, have a particle size of 10 μm or less.

[0044] [Formation of Composite Particles (Surface Treatment of Cathode Active Material Particles)] In preparing the composite particles of the present invention, a step of adhering Li-containing nanoparticles to the surface of cathode active material particles to form composite particles is performed. The step of forming composite particles is, in other words, a step of performing surface treatment on the cathode active material particles. Among the steps of forming composite particles, the step of adhering Li-containing nanoparticles to the surface of the cathode active material particles (performing a coating treatment) is hereinafter referred to as the adhering step. Here, in order to properly distribute the Li-containing nanoparticles on the surface of the cathode active material particles without uneven distribution and to adhere them in an island-like pattern with an appropriate coating ratio, it is necessary to adjust the particle sizes of the particles having a relatively large particle size (hereinafter referred to as "large particle size particles") and the particles having a relatively small particle size (hereinafter referred to as "small particle size particles") to values ​​within a predetermined range, and to efficiently apply the required physical energy to the particles.

[0045] Hereinafter, as an example, LiCoO ２ The following describes a method in which the LAF obtained by the above-described method is used as the Li-containing nanoparticles, and an attachment step (coating treatment) is performed to attach the LAF to the surface of the positive electrode active material particles. ２ A method of mixing powders by adding LAF particles as powder particles, or a method of mixing a dispersion of LAF powder with ethanol and LiCoO ２ and then drying the resulting mixed slurry.

[0046] (Adhesion by Mixing Powders (Coating Treatment)) First, as an example of the adhering step, a process in which pulverized Li-containing nanoparticles are mixed with and adhered to positive electrode active material particles will be described. In this case, an example of a specific means for the adhering step is mixing powders. More specifically, for example, a mixing device can be used to mix Li-containing nanoparticles, which are small particle diameter particles, with positive electrode active material particles, which are large particle diameter particles. This makes it possible to obtain composite particles in which Li-containing nanoparticles are attached in an island-like manner to the surfaces of the positive electrode active material particles.

[0047] (Adhesion (Coating Treatment) Using Dispersion Liquid) Next, as another example of the adhering step, a step in which Li-containing nanoparticles dispersed in a dispersion liquid are adhered to the positive electrode active material particles will be described. The dispersion liquid is the above-mentioned Li-containing nanoparticles (Li ３ AlF ６ ) as a starting material, and mix it with an appropriate amount of ethanol to obtain a slurry, which is then crushed. At this time, the specific composition of the dispersion liquid can be, for example, Li as the Li-containing nanoparticles. ３ AlF ６ An ethanol slurry containing 10 wt % of the above, 2 wt % of a wetting dispersant, and the remainder being ethanol can be used. In order to obtain a homogeneous and fine dispersion, the mixing and crushing is preferably performed using a crushing device such as a mechanical mill, an ultrasonic disperser, a microbead mill, or a shaker. For example, when a microbead mill is used as the mixing and crushing device for preparing the dispersion, zirconia beads with a bead diameter of 0.05 mm are used to crush the Li-containing nanoparticles in the ethanol slurry into nano-sized primary particles, thereby obtaining a homogeneous dispersion.

[0048] Furthermore, an example of a specific means for the adhesion step when using a dispersion liquid is contact mixing of the dispersion liquid with powder. More specifically, for example, an agitation-type mixing and drying device can be used to mix and dry Li-containing nanoparticles dispersed as small particle diameter particles and positive electrode active material particles corresponding to large particle diameter particles. For mixing and drying, a type that rotates blades at high speed in a container (e.g., a Henschel mixer), a type that rotates ribbon blades in a conical container (e.g., a Ribocone), or a type that sprays a slurry in a fluidized bed (e.g., a Spiraflow) can be used. Also, a vibration dryer or a spray dryer can be used.

[0049] A specific example of the adhesion step using a dispersion will be described below. The dispersion (ethanol slurry) is added in an amount equivalent to 0.3 g of LAF to the positive electrode active material particles (LiCoO ２15 g of the Li-containing nanoparticles are mixed and processed. The mixed slurry is dried to obtain composite particles. Drying may be performed while mixing, or the mixture may be dried. For example, the mixed slurry is dried while mixing at 50°C using an open-type mixer dryer to obtain a powder, and then the powder is left to dry using a dryer heated to 120°C to obtain composite particles. This allows composite particles to be obtained in which Li-containing nanoparticles are attached in an island-like manner to the surfaces of the positive electrode active material particles.

[0050] [Heat Treatment of Composite Particles] In addition, in the preparation of the composite particles of the present invention, after the adhesion step as a step for forming the composite particles, a heat treatment step may be further performed in which the composite particles having Li-containing nanoparticles adhered to the surfaces of the positive electrode active material particles are heat-treated. The heat treatment temperature in the heat treatment step may be 200 to 700°C. The upper limit of this heat treatment temperature is preferably 700°C or less, more preferably 600°C or less, and particularly preferably 500°C or less.

[0051] The heat treatment temperature in the heat treatment step can be raised to a predetermined temperature through a stepwise process of performing treatment under predetermined temperature conditions for a predetermined time. The heating time in the heat treatment step is not particularly limited and can be set appropriately as needed.

[0052] An example of the heat treatment step is to heat treat the composite particles in an air atmosphere using a box furnace at 300°C for 3 hours. The heat treatment step can also be performed in an inert gas atmosphere. Examples of inert gases include, but are not limited to, nitrogen, helium, neon, and argon. After the heat treatment, the composite particles are cooled naturally to room temperature in a predetermined atmosphere, or cooled under specified cooling conditions. This allows the heat-treated composite particles to be obtained.

[0053] [Non-aqueous electrolyte battery] The composite particles described above can be used as an electrode active material (cathode active material) for an electrode. In particular, the composite particles described above are suitable for use in non-aqueous electrolyte batteries. The non-aqueous electrolyte can be in various forms, including not only liquid electrolytes but also solid electrolytes and gel electrolytes containing a solvent. A solution in which an electrolyte is dissolved in an aprotic non-aqueous solvent is used as the liquid electrolyte. Furthermore, the solid electrolyte can be inorganic solid electrolytes, such as the above-mentioned lithium compounds, such as oxides, sulfides, nitrides, and halides. Examples of polymer solid electrolytes include polymers of polyethylene oxide, polypropylene oxide, phosphate esters, polymethacrylate, polyacrylate, and polycarbonate, as well as polymers of their derivatives. Furthermore, materials for forming the gel electrolyte can be used without particular limitation as long as they can absorb the liquid electrolyte and gel, and examples thereof include fluorine-containing polymers such as poly(vinylidene fluoride) and vinylidene fluoride / hexafluoropropylene copolymers.

[0054] The electrode containing the composite particles described above can be suitably used as an electrode for batteries of various shapes, such as coin-shaped, cylindrical, and prismatic. For example, the composite particles can be compression-molded to form an electrode in the form of a pellet. Furthermore, a plate- or sheet-shaped electrode can be formed by attaching the composite particles to a current collector made of a conductive material such as a metal.

[0055] (Battery Structure) An example of a nonaqueous electrolyte battery using composite particles according to one embodiment as a positive electrode active material will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a schematic configuration of the battery. In this figure, the nonaqueous electrolyte battery 1 generally comprises a negative electrode member 2 functioning as the battery's external negative electrode, a positive electrode member 3 functioning as the battery's external positive electrode, and a negative electrode current collector 4, a negative electrode active material 5, a separator 8, a positive electrode active material 7, and a positive electrode current collector 6, arranged in this order between the two members. The negative electrode member 2 is approximately cylindrical and is configured to accommodate the negative electrode current collector 4 and the negative electrode active material 5 therein. Meanwhile, the positive electrode member 3 is also approximately cylindrical and is configured to accommodate the positive electrode current collector 6 and the positive electrode active material 7 therein. The radial dimensions of the positive electrode member 3 and the separator 8 are set slightly larger than those of the negative electrode member 2, so that the peripheral edges of the negative electrode member 2 overlap with the peripheral edges of the separator 8 and the positive electrode member 3. The space inside the battery is filled with a non-aqueous electrolyte 9, and a sealant 10 is applied to the overlapping peripheral edges of the negative electrode member 2, separator 8 and positive electrode member 3, keeping the inside of the battery airtight.

[0056] The nonaqueous electrolyte secondary battery of the present invention is produced using a positive electrode prepared using as a positive electrode active material the lithium-containing transition metal composite oxide described above, in particular the lithium-containing transition metal composite oxide obtained by the above-described production method, and is high-capacity, high-power, and highly safe.

[0057] The structure of the nonaqueous electrolyte secondary battery of the present invention will be described below. The nonaqueous electrolyte secondary battery of the present invention (hereinafter simply referred to as secondary battery) has substantially the same structure as a general nonaqueous electrolyte secondary battery, except that the composite particles of the present invention are used as a positive electrode active material for nonaqueous electrolyte secondary batteries (hereinafter simply referred to as positive electrode active material).

[0058] Specifically, the secondary battery of the present invention has a structure including a case, and a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator housed within the case. More specifically, the positive electrode and the negative electrode are stacked with the separator interposed therebetween to form an electrode assembly, the resulting electrode assembly is impregnated with a non-aqueous electrolyte, and the positive electrode current collector of the positive electrode and the negative electrode current collector of the negative electrode are connected to the external terminal using current collector leads or the like, and the battery is then sealed in a case to form the secondary battery of the present invention. It goes without saying that the structure of the secondary battery of the present invention is not limited to the above example, and various shapes, such as a cylindrical shape or a laminated shape, can also be adopted for the external shape.

[0059] (Positive Electrode) First, the positive electrode, which is a feature of the secondary battery of the present invention, will be described. The positive electrode is a sheet-like member, and can be formed by applying a positive electrode mixture containing the composite particles of the present invention as a positive electrode active material to the surface of an aluminum foil current collector and drying it, for example, but the method for producing the positive electrode is not particularly limited. For example, a positive electrode can also be produced by supporting a positive electrode mixture containing a positive electrode active material (composite particles) and a binder on a strip-shaped positive electrode core material (positive electrode current collector). The positive electrode is processed appropriately depending on the battery to be used. For example, cutting to form the electrode into an appropriate size depending on the target battery, or pressure compression using a roll press or the like to increase the electrode density, is performed.

[0060] (Positive electrode mixture) The positive electrode mixture can be formed by adding a solvent to a positive electrode agent formed by mixing the powdered composite particles of the present invention with a conductive material and a binder, and kneading the mixture. Hereinafter, materials constituting the positive electrode mixture other than the composite particles (positive electrode active material) will be described.

[0061] (Binder) As the binder for the positive electrode mixture, either a thermoplastic resin or a thermosetting resin may be used, but a thermoplastic resin is preferred. Examples of thermoplastic resins include ethylene-methyl acrylate copolymers or ethylene-acrylic acid copolymers, ethylene-chlorotrifluoroethylene copolymers, ethylene-tetrafluoroethylene copolymers, ethylene-methyl methacrylate copolymers, ethylene-methacrylic acid copolymers, styrene-butadiene rubber, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers, tetrafluoroethylene-hexafluoroethylene copolymers, tetrafluoroethylene-hexafluoropropylene copolymers, vinylidene fluoride-chlorotrifluoroethylene copolymers, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymers, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymers, vinylidene fluoride-hexafluoropropylene copolymers, vinylidene fluoride-pentafluoropropylene copolymers, propylene-tetrafluoroethylene copolymers, polyethylene, polychlorotrifluoroethylene, polytetrafluoroethylene, polyvinylidene fluoride, polypropylene, and the like. The above resins may be used alone or in combination of two or more. In addition, these may contain Na ＋ It may be a crosslinked body using ions or the like.

[0062] (Conductive material) The conductive material of the positive electrode mixture is not particularly limited, as long as it is a chemically stable electron conductive material in the battery.For example, graphites such as natural graphite (such as flake graphite) and artificial graphite, carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black, conductive fibers such as carbon fiber and metal fiber, metal powders such as aluminum, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, organic conductive materials such as polyphenylene derivatives, and carbon fluorides can be used.These materials can be used alone or in combination of two or more.

[0063] The amount of the conductive material added to the positive electrode mixture is not particularly limited, but is preferably 0.5 to 50 mass %, more preferably 0.5 to 30 mass %, and even more preferably 0.5 to 15 mass %, relative to the positive electrode active material particles contained in the positive electrode mixture.

[0064] (Solvent) The solvent dissolves the binder and disperses the positive electrode active material, the conductive material, etc. in the binder. This solvent is not particularly limited, but examples thereof include cyclic ethers such as 1,2-dimethoxyethane and 1,3-dioxolane, cyclic ethers such as 1,3-dimethyl-2-imidazolidinone, 1,3-propane sultone and 2-methyltetrahydrofuran, 2-methoxytetrahydrofuran, 3-methyl-2-oxazolidinone, N,N-diethylacetamide, N,N-diethylformamide, N,N-dimethylacetamide, N,N-dimethylpropionamide, N,N-dimethylformamide, N-ethylacetamide, N-ethylformamide, N-methyl-2-pyrrolidone, N-methylacetamide, N-methylformamide, lactones such as γ-valerolactone, esters such as γ-butyrolactone, acetamide, acetonitrile, anisole, ethers such as ethyl ether, ethyl methyl carbonate, ethyl monoglyme, ethylene carbonate, and ethylene glycol phenyl ether, chain ethers such as ethoxymethoxyethane (EME), methyl formate, diethyl Examples of suitable sulfur-containing compounds include ethers such as ether, diethyl carbonate, diethylene glycol dimethyl ether, diethylene glycol monobutyl ether, and diethoxyethane, chain carbonates such as dioxolane, dioxolane derivatives, and dipropyl carbonate, sulfur-containing compounds such as dimethyl carbonate, dimethyl sulfoxide, dimethylformamide, sulfolane, and sulfolane, cyclic carbonates such as methyl ethyl ketone, tetrahydrofuran, tetrahydrofuran derivatives, trimethoxymethane, nitromethane, and vinylene carbonate (VC), aliphatic carboxylic acid esters such as butylene carbonate and ethyl propionate, amides such as methyl propionate, propylnitrile, propylene oxide, propylene carbonate, propylene carbonate derivatives, and hexamethylphosphorylamide, dialkyl ketones such as dimethyl sulfoxide, formamide, and methyl isobutyl ketone, ethylene oxide, methyl sulfolane, phosphoric acid triesters, and methyl acetate. These may be used alone or in combination of two or more.

[0065] (Positive electrode core material) The positive electrode includes at least a positive electrode layer, and optionally includes a positive electrode current collector. Examples of the positive electrode current collector include a chemically stable electronically conductive material in the battery, such as a metal material containing one or more elements selected from the group consisting of Cu, Ni, Al, V, Au, Pt, Mg, Fe, Ti, Co, Cr, Zn, Ge, and In, as well as carbon or a conductive resin. The shape of the positive electrode current collector is not particularly limited, and can be various shapes such as foil, sheet, and mesh. Among these, aluminum foil, aluminum alloy foil, etc. are more preferred.

[0066] Here, a carbon or titanium layer or an oxide layer can be applied to the surface of the foil or sheet. Furthermore, the surface of the foil or sheet can be made uneven, and a net, punched sheet, lath, porous body, foam, fiber group molded body, etc. can also be used. The thickness of the positive electrode core material is not particularly limited, but is preferably, for example, 1 to 500 μm.

[0067] [Constituent Elements Other Than Positive Electrode] Next, among the constituent elements of the nonaqueous electrolyte secondary battery of the present invention, the constituent elements other than the positive electrode will be described. The nonaqueous electrolyte secondary battery of the present invention is characterized in that the above composite particles are used as a positive electrode active material, and the other constituent elements can be appropriately selected depending on the application and required performance, and are not limited to those described below.

[0068] (Negative electrode) The negative electrode is not particularly limited as long as it can charge and discharge lithium. For example, a negative electrode mixture containing a negative electrode active material and a binder, and optionally containing a conductive material and a thickener, supported on a negative electrode core material can be used. Such a negative electrode can be produced by the same method as the positive electrode.

[0069] The negative electrode active material may be any material capable of electrochemically charging and discharging lithium. For example, graphite, non-graphitizable carbon materials, lithium alloys, etc. may be used. A mixture of these materials may also be used. While the lithium alloy is not particularly limited, an alloy containing at least one element selected from the group consisting of silicon, tin, aluminum, zinc, and magnesium is preferred. The average particle size of the negative electrode active material is not particularly limited, and is preferably 1 to 30 μm, for example.

[0070] The negative electrode is composed of a negative electrode member 2 as an external negative electrode, a negative electrode current collector 4 in contact with the negative electrode member 2, and a layer of a negative electrode active material 5 formed on the negative electrode current collector. The negative electrode current collector may be, for example, a nickel foil or a copper foil. The negative electrode active material may be one that can be doped / dedoped with lithium, and specifically may be metallic lithium, a lithium alloy, a lithium-doped conductive polymer, a layered compound (carbon material, metal oxide, etc.), or the like.

[0071] (Binder) As the binder for the negative electrode mixture, either a thermoplastic resin or a thermosetting resin may be used, but a thermoplastic resin is preferred. The thermoplastic resin is not particularly limited, but for example, polyethylene, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, styrene butadiene rubber, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer, polychlorotrifluoroethylene, vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer, etc.

[0072] These may be used alone or in combination of two or more. ＋ It may be a crosslinked body using ions or the like.

[0073] (Conductive Material) The conductive material of the negative electrode mixture is not particularly limited as long as it is an electron-conductive material that is chemically stable in the battery. For example, graphites such as natural graphite (e.g., flake graphite) and artificial graphite, carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black, conductive fibers such as carbon fiber and metal fiber, metal powders such as copper and nickel, and organic conductive materials such as polyphenylene derivatives can be used. These may be used alone or in combination of two or more.

[0074] The amount of the conductive material added is not particularly limited, but is preferably 1 to 30% by mass, and more preferably 1 to 10% by mass, based on the negative electrode active material particles contained in the negative electrode mixture.

[0075] (Negative electrode core material) The negative electrode core material (negative electrode current collector) is not particularly limited as long as it is an electron conductor that is chemically stable in the battery. For example, foils or sheets made of stainless steel, nickel, copper, titanium, carbon, conductive resin, etc. can be used, with copper and copper alloys being preferred. Furthermore, since metallic lithium foil can be used not only as the negative electrode active material but also as the negative electrode current collector, the use of metallic lithium foil in the negative electrode can simplify the battery structure.

[0076] The surface of this foil or sheet can be provided with a layer of carbon, titanium, nickel, etc., or an oxide layer can be formed. In addition, the surface of the foil or sheet can be provided with irregularities, and a net, punched sheet, lath body, porous body, foam body, fiber group molded body, etc. can also be used.

[0077] The thickness of the negative electrode core material is not particularly limited, but is preferably 1 to 500 μm, for example.

[0078] (Non-aqueous electrolyte) The non-aqueous electrolyte is preferably a non-aqueous solvent in which a lithium salt is dissolved. The non-aqueous solvent to be used is not particularly limited, but may be selected from the group consisting of cyclic carbonates such as ethylene carbonate, propylene carbonate, propylene carbonate derivatives, butylene carbonate, and vinylene carbonate, chain carbonates such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and dipropyl carbonate, chloroethylene carbonate, fluoroethylene carbonate, diethyl fluorocarbonate, and dimethyl fluorocarbonate, aliphatic carboxylic acid esters such as methyl formate, methyl acetate, methyl butyrate, methyl propionate, and ethyl propionate, lactones such as γ-butyrolactone and γ-valerolactone, chain ethers such as 1,2-dimethoxyethane, 1,2-diethoxyethane, 1,4-dibutoxyethane, and ethoxymethoxyethane, and tetrahydrofuran. Examples of suitable solvents include cyclic ethers such as tetrahydrofuran and 2-methyltetrahydrofuran, ethylene glycol monopropyl ether, propylene glycol monopropyl ether, 1,3-dioxolane, dioxolane derivatives, 1,3-dioxane, 1,4-dioxane, formamide, acetamide, dimethylformamide, dioxolane, acetonitrile, propylnitrile, benzonitrile, methyl diglyme, nitromethane, ethyl monoglyme, phosphate triester, trimethoxymethane, sulfolane, methyl sulfolane, ethylene sulfide, sultone, 1,3-dimethyl-2-imidazolidinone, 3-methyl-2-oxazolidinone, tetrahydrofuran derivatives, ethyl ether, 1,3-propane sultone, anisole, dimethyl sulfoxide, and N-methyl-2-pyrrolidone. These may be used alone or in combination of two or more.

[0079] In particular, it is preferable to use a mixed solvent of a cyclic carbonate and a chain carbonate, or a mixed solvent of a cyclic carbonate, a chain carbonate and an aliphatic carboxylic acid ester.

[0080] (Lithium Salt) The lithium salt that dissolves in the non-aqueous electrolyte solution is not particularly limited, but for example, Li(CF ３ SO２ ) ２ , LiAlCl ４ , LiAsF ６ , LiB １０ Cl １０ , LiBF ４ , LiBr, LiCF ３ CO ２ , LiCF ３ SO ３ , LiCl, LiClO ４ , LiI, LiN(CF ３ SO ２ ) ２ , LiN(FSO ２ ) ２ , LiPF ６ , LiSbF ６ , LiSCN, lithium chloroborane, lithium bis(oxalato)borate, lithium tetraphenylborate, lithium lower aliphatic carboxylate, lithium imide salt, etc. These may be used alone or in combination of two or more. ６ , and / or LiN(FSO ２ ) ２ It is preferable to use

[0081] The concentration of the lithium salt in the non-aqueous solvent is not particularly limited, but is preferably 0.2 to 2 mol / L, more preferably 0.5 to 1.5 mol / L.

[0082] (Other Additives) In addition to the lithium salt, various additives may be added to the non-aqueous electrolyte solution for the purpose of improving the charge / discharge characteristics of the battery. The additives are not particularly limited, but examples thereof include triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, pyridine, hexaphosphoric acid triamide, nitrobenzene derivatives, crown ethers, quaternary ammonium salts, and ethylene glycol dialkyl ethers.

[0083] (Separator) A fine separator is interposed between the positive electrode and the negative electrode. This separator is not particularly limited, but a microporous thin film that has high ion permeability, a predetermined mechanical strength, and is insulating is preferred. In particular, the microporous thin film is preferably one that has the function of closing its pores at a certain temperature or higher, thereby increasing the resistance.

[0084] The material of the microporous thin film is not particularly limited, but examples thereof include polyolefins such as polypropylene and polyethylene, which have excellent resistance to organic solvents and hydrophobic properties. Also usable are sheets, nonwoven fabrics, woven fabrics, etc., made from glass fibers, etc.

[0085] When the separator is a microporous thin film, the pore size of the pores formed in the separator is not particularly limited, but is preferably, for example, 0.01 to 1 μm. The porosity of the separator is also not particularly limited, but is generally preferably 30 to 80%. The thickness of the separator is also not particularly limited, but is generally preferably 10 to 300 μm.

[0086] Furthermore, the separator may be separate from the positive and negative electrodes, or a polymer electrolyte consisting of a non-aqueous electrolyte solution and a polymer material that retains the solution may be integrated with the positive or negative electrode to be used as the separator. The polymer material may be any material that can retain the non-aqueous electrolyte solution, but is preferably a copolymer of vinylidene fluoride and hexafluoropropylene.

[0087] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

[0088] <Examples 1 to 3, Comparative Example 1> [Example 1] Preparation of Sample 1 Composite particles (Sample 1) of Example 1 were prepared according to the following procedures 1-1 to 1-3. 1-1. Li ３ AlF ６ Synthesis of (LAF) Using sulfate raw material, Li ３ AlF ６The synthesis of the above was carried out. 453 g of lithium sulfate monohydrate as a lithium source and 745 g of aluminum sulfate hydrate as an aluminum source were dissolved in 2.5 L of pure water at room temperature. 500 mL of a 48% aqueous solution of hydrofluoric acid was added dropwise to the aqueous solution. The addition was carried out over 45 minutes, and the resulting slurry was filtered using filter paper. A cake was formed on the filter paper, which was then washed with pure water from above and left to dry for 10 hours using a vacuum dryer heated to 120°C. After drying, the resulting white solid was pulverized into powder using a pulverizer, yielding a white powder of LAF with an average particle size of 41 nm. 1-2. Surface Treatment of Positive Electrode Active Material Particles The positive electrode active material particles were prepared using LiCoO ２ (hereinafter also referred to as "LCO") was used. ２ ("LCO Cell Seed C-5H" manufactured by Nippon Chemical Industry Co., Ltd., median diameter (D50) 9 μm) was taken in an amount of 15 g, and the above Li ３ AlF ６ The mixture was mixed with a mortar stirrer for 3 hours and dried in a dryer at 100°C. The median diameter of LCO was measured with a laser diffraction particle size distribution analyzer (Shimadzu Corporation's "Laser Diffraction Particle Size Distribution Analyzer SALD-2300"). 1-3. Heat Treatment Step Sample 1 was not subjected to a heat treatment step. The prepared composite particles had LAF nanoparticles attached to the surface of LCO particles. Hereinafter, these composite particles will also be referred to as LAF-LCO particles.

[0089] [Example 2] Preparation of Sample 2 Composite particles (Sample 2) of Example 2 were prepared according to the following procedures 2-1 to 2-3. 2-1. Li ３ AlF ６ Synthesis of Li obtained in 1-1. ３ AlF ６ 2-2. Surface treatment of positive electrode active material particles (LiCoO ２ (Use) Treatment was carried out in the same manner as in 1-2. 2-3. Heat Treatment Step The LAF-LCO particles obtained in 2-2 were placed in a box furnace and heat treated at 300°C for 3 hours in an air atmosphere. After the heat treatment, the particles were cooled to room temperature to obtain Sample 2.

[0090] [Comparative Example 1] Preparation of Sample 3 Composite particles (Sample 3) of Comparative Example 1 were prepared according to the following procedures 3-1 to 3-3. 3-1. Li３ AlF ６ Synthesis of Li obtained in 1-1. ３ AlF ６ 3-2. Surface treatment of positive electrode active material particles (LiCoO ２ In Sample 3, the Li-containing nanoparticles were added to ethanol, and then the resulting dispersion was crushed and used for the surface treatment. (Preparation of Dispersion) First, the dispersion was prepared by the following method. ３ AlF ６ An ethanol slurry containing 10 wt % of the above and 2 wt % of a wetting dispersant (DISPERBYK-111) was prepared, and the slurry was crushed using a microbead mill (Ultra Apex Mill UAM-015 (Hiroshima Metal & Machinery Co., Ltd.)). Zirconia beads with a bead diameter of 0.05 mm were used. After the crushing process, positive electrode active material particles (LiCoO ２ 15 g of the powder (particles) was mixed to obtain a mixed slurry. The obtained mixed slurry was powdered using an open mixer dryer, and then left to dry in a dryer heated to 120°C to obtain Sample 3. 3-3. Heat Treatment Step Sample 3 was not subjected to a heat treatment step.

[0091] [Example 3] Preparation of Sample 4 Composite particles (Sample 4) of Example 3 were prepared according to the following procedures 4-1 to 4-3. 4-1. Li ３ AlF ６ Synthesis of Li obtained in 1-1 above ３ AlF ６ 4-2. Surface treatment of positive electrode active material particles (LiCoO ２ (Use) The same treatment as in 3-2 above was carried out. 4-3. Heat Treatment Step The LAF-LCO particles obtained in 4-2 above were placed in a box furnace and heat treated at 400°C for 3 hours in an air atmosphere. After the heat treatment, the particles were cooled to room temperature to obtain Sample 4.

[0092] [Evaluation of Composite Particles] The obtained composite particles were evaluated by the following measurement and observation means.

[0093] First, in order to evaluate the surface condition of the composite particles, measurements and observations were carried out for each sample by the following methods. (XRD Measurement) ３ AlF ６ The powder X-ray diffraction pattern (XRD pattern) was measured using a powder X-ray diffractometer ("SMARTLAB" manufactured by Rigaku Corporation) and the results are shown in Figure 2. From the results shown in Figure 2, it can be seen that the product is Li ３ AlF ６ Furthermore, the X-ray diffraction pattern shown in Figure 2 did not reveal any residual lithium sulfate or aluminum sulfate, which were the raw materials.

[0094] (FT-IR measurement) Li used in samples 1 to 4 ３ AlF ６ FT-IR measurement was carried out on this product using an FT-IR (ALPHA manufactured by Bruker). The results are shown in Figure 3. As can be seen from Figure 3, no particularly conspicuous functional groups of impurities were observed in the spectrum obtained by FT-IR measurement.

[0095] (Observation by FE-SEM) 1. Li ３ AlF ６ FE-SEM observation results of Li used in preparing samples 1 to 4 ３ AlF ６ The results are shown in Figure 4. From Figure 4, it can be seen that the FE-SEM observation ３ AlF ６ It was confirmed that the particle diameter size of the composite particles was in the range of 20 to 100 nm. 2. FE-SEM Observation Results of Composite Particles FE-SEM images of the particle shapes of the composite particles (LAF-LCO particles) of Samples 1 to 4 were obtained using an FE-SEM ("SU8220" manufactured by Hitachi High-Technologies). The results are shown in Figure 5. From Figure 5, it can be seen that the particle diameter size of the LiCoO, which is the positive electrode active material particle in the examples, was 0.01 mm in both the case where the adhesion step was powder mixing (Samples 1 and 2) and the case where the dispersion liquid was added (Samples 3 and 4). ２ Li-containing nanoparticles were observed dispersed on the surface.

[0096] (Measurement of Specific Surface Area) The specific surface area was measured using a fully automatic specific surface area measuring device ("Macsorb" manufactured by Mountech Co., Ltd.) based on the BET flow method. ３ AlF ６ The specific surface area of ​​the Li-containing nanoparticles used in samples 1 to 4 was 19.3 m ２ / g. 2. Measurement Results of Composite Particles The specific surface area of ​​the composite particles of Samples 1 to 4 increased with the addition of Li-containing nanoparticles. More specifically, the specific surface area of ​​the positive electrode active material particles not coated with Li-containing nanoparticles (hereinafter referred to as "uncoated LCO") in Control Test 1 was 0.42 m ２ / g, and the specific surface areas of the composite particles of Samples 1 to 4 were 1.07, 0.77, 1.66 and 1.27 m, respectively. ２ / g. The specific surface area of ​​the composite particles at this time was the increase x (m ２ / g) are 0.65, 0.35, 1.24 and 0.85 m, respectively. ２ / g.

[0097] A nonaqueous electrolyte secondary battery was fabricated using the uncoated LCO of Control Test 1 and the composite particles obtained in Examples 1 to 3 and Comparative Example 1. [Fabrication of Nonaqueous Electrolyte Secondary Battery] A lithium secondary battery was fabricated using the uncoated LCO of Control Test 1 and the composite particles (Samples 1 to 4) of Examples 1 to 3 and Comparative Example 1 as the positive electrode active material. N-methyl-2-pyrrolidone was used as the solvent, and the positive electrode active material, conductive material, and binder (polyvinylidene fluoride) were mixed in a weight ratio of 80:10:10. The resulting paste-like slurry was applied to an aluminum foil current collector, dried, and then punched into a circle with a diameter of 15 mm to form a positive electrode. A porous polyethylene sheet with a diameter of 22 mm and a thickness of 0.02 mm was used as the separator. The electrolyte was a 1 mol / L LiPF in a 1:1 volumetric ratio mixed solvent of ethylene carbonate and dimethyl carbonate. ６ A simple lithium secondary battery was fabricated using a solution containing the above and a disk of metallic lithium punched out to a diameter of 15 mm and a thickness of 0.2 mm as the negative electrode. The entire battery assembly process was carried out in a dry box under an argon atmosphere.

[0098] [Charge-Discharge Measurement of Nonaqueous Electrolyte Secondary Battery] A charge-discharge test was conducted on the fabricated simple lithium secondary battery. The charge-discharge test was conducted at 25°C, with a potential range of 3000 to 4300 mV, and the rate increased from 0.1 C x 2 cycles to 0.5 C x 2 cycles to 1 C x 2 cycles to 2 C x 2 cycles, 5 C x 2 cycles to 10 C x 2 cycles. Then, 0.1 C x 2 cycles were performed, and subsequent cycling was performed at 1 C. All tests were conducted at C.C-C.V. The discharge capacity of the prototype cell for each cycle is shown in Figure 6. Figure 6 shows that the nonaqueous electrolyte secondary batteries using Samples 1 to 4 (LAF-LCO particles) in Examples 1 to 3 and Comparative Example 1 exhibited improved cycle characteristics compared to the nonaqueous electrolyte secondary battery using uncoated LCO (Control Test 1). In particular, it was found that the use of composite particles (Samples 2 and 4) that were heat-treated during preparation further significantly improved cycle characteristics. 6 also shows that the nonaqueous electrolyte secondary batteries using Samples 1 to 4 (LAF-LCO particles) in Examples 1 to 3 and Comparative Example 1 have improved rate characteristics compared to the nonaqueous electrolyte secondary battery using uncoated LCO in Control Test 1. In particular, it was found that the rate characteristics were further greatly improved by using composite particles (Samples 2 and 4) that had been heat-treated during preparation.

[0099] <Examples 4 to 8, Comparative Examples 2 and 3> [Example 4] Preparation of Sample 5 Composite particles (Sample 5) of Example 4 were prepared according to the following procedures 5-1 to 5-3. 5-1. Li ３ AlF ６ Synthesis of Li using nitrate raw material ３ AlF ６ The synthesis of was carried out. 1508 g of lithium nitrate as a lithium source and 2696 g of aluminum nitrate nonahydrate as an aluminum source were dissolved in 3.75 L of pure water at room temperature. 1500 mL of a 48% aqueous solution of hydrofluoric acid was added dropwise to the aqueous solution. The addition was carried out over 65 minutes, and the resulting slurry was filtered using filter paper. A cake was formed on the filter paper, washed with pure water from above, and then left to dry for 24 hours in a vacuum dryer heated to 120°C. After drying, the resulting white solid was pulverized into powder using a pulverizer to obtain Li nitrate with an average particle size of 54 nm. ３ AlF ６ A white powder with a specific surface area of ​​21.0 m was obtained.２ In addition, as a result of the XRD measurement, the Li ３ AlF ６ 5-2. Surface treatment of positive electrode active material particles (LiCoO ２ (Use) The LAF obtained in 5-1 above was used, and the processing was carried out in the same manner as in 1-2 above, except that the amount added was 5 mass % and the mixing time with the mortar stirrer was 1 hour. 5-3. Heat treatment step Sample 5 was not subjected to a heat treatment step.

[0100] [Example 5] Preparation of Sample 6 Composite particles (Sample 6) of Example 5 were prepared according to the following procedures 6-1 to 6-3. 6-1. Li ３ AlF ６ Synthesis of Li obtained in the same manner as in 5-1 above ３ AlF ６ The average particle size is 26 nm and the specific surface area is 56.8 m ２ / g nanoparticles were used. 6-2. Surface treatment of positive electrode active material particles (LiCoO ２ Use) The treatment was carried out in the same manner as in 5-2 above, except that the amount added was 0.05 mass %. 6-3. Heat Treatment Step Sample 6 was not subjected to a heat treatment step.

[0101] [Example 6] Preparation of Sample 7 Composite particles (Sample 7) of Example 6 were prepared according to the following procedures 7-1 to 7-3. 7-1. Li ３ AlF ６ Synthesis of Li obtained in the same manner as in 5-1 above ３ AlF ６ The average particle size is 212 nm and the specific surface area is 4.0 m ２ / g nanoparticles were used. 7-2. Surface treatment of positive electrode active material particles (LiCoO ２ 7-3. Heat Treatment Step Sample 7 was not subjected to a heat treatment step.

[0102] [Example 7] Preparation of Sample 8 Composite particles (Sample 8) of Example 7 were prepared according to the following procedures 8-1 to 8-3. 8-1. Li ３ AlF ６Synthesis of Li obtained in the same manner as in 5-1 above ３ AlF ６ The average particle size is 23 nm and the specific surface area is 86.0 m ２ / g nanoparticles were used. 8-2. Surface treatment of positive electrode active material particles (LiCoO ２ Use) Treatment was carried out in the same manner as in 5-2 above, except that the amount added was 0.5 mass %. 8-3. Heat treatment step Treatment was carried out in the same manner as in 2-3 above.

[0103] [Example 8] Preparation of Sample 9 Composite particles (Sample 9) of Example 8 were prepared according to the following procedures 9-1 to 9-3. 9-1. Li ３ AlF ６ Synthesis of Li obtained in 5-1 above ３ AlF ６ 9-2. Surface treatment of positive electrode active material particles (LiCoO ２ 9-3. Heat Treatment Step Sample 9 was not subjected to a heat treatment step.

[0104] [Comparative Example 2] Preparation of Sample 10 Composite particles (sample 10) of Comparative Example 2 were prepared according to the following procedures 10-1 to 10-3. 10-1. Li ３ AlF ６ Synthesis of Li obtained in 5-1 above ３ AlF ６ 10-2. Surface treatment of positive electrode active material particles (LiCoO ２ Use) The same treatment as in 3-2 above was carried out. 10-3. Heat Treatment Step The same treatment as in 4-3 above was carried out, except that the heating temperature was set to 500°C.

[0105] [Comparative Example 3] Preparation of Sample 11 Composite particles (Sample 11) of Comparative Example 3 were prepared according to the following procedures 11-1 to 11-3. 11-1. Li ３ AlF ６ Synthesis of the same Li as in 6-1 above ３ AlF ６ 11-2. Surface treatment of positive electrode active material particles (LiCoO ２Use) The same treatment as in 5-2 above was carried out. 11-3. Heat Treatment Step The same treatment as in 2-3 above was carried out, except that the heating temperature was set to 500°C.

[0106] [Evaluation of Charge-Discharge Characteristics of Non-Electrolyte Secondary Batteries] The specific surface areas of the prepared composite particle (LAF-LCO particle) samples 5 to 11 were measured, and then non-aqueous electrolyte secondary batteries were fabricated using them, and charge-discharge tests were performed. The specific surface area measurement method, non-aqueous electrolyte secondary battery fabrication method, and charge-discharge test method were the same as those applied to samples 1 to 4. Battery characteristics were evaluated from the charge-discharge test results of samples 1 to 11. (Evaluation Method) Rate characteristics were evaluated by the capacity retention rate of the non-aqueous electrolyte secondary battery capacity at the 10th cycle (5C) based on the non-aqueous electrolyte secondary battery capacity at the 2nd cycle (0.1C). Cycle characteristics were evaluated by the capacity retention rate of the non-aqueous electrolyte secondary battery capacity at the 50th cycle (1C) based on the non-aqueous electrolyte secondary battery capacity at the 16th cycle (1C). Regarding the rate characteristics and cycle characteristics, a capacity retention rate of 90% or more was evaluated as ⊚, a capacity retention rate of 85% or more was evaluated as ○, a capacity retention rate of 80% or more was evaluated as △, and a capacity retention rate of less than 80% was evaluated as ×, and a capacity retention rate of 80% or more was evaluated as pass. The evaluation results of the rate characteristics and cycle characteristics of the nonaqueous electrolyte secondary batteries using Control Test 1 (uncoated LCO) and Samples 1 to 11 (LAF-LCO particles) in Examples 1 to 8 and Comparative Examples 1 to 3 are shown in Table 1 below.

[0107] Referring to Table 1, when the ratio (x / S) of the difference (x) obtained by subtracting the BET specific surface area of ​​the positive electrode active material particles from the BET specific surface area of ​​the composite particles to the BET specific surface area (S) of the Li-containing nanoparticles was less than 0.0005 (Comparative Examples 2 and 3) or more than 0.063 (Comparative Example 1), the rate characteristics and cycle characteristics were unacceptable. Furthermore, when Example 1 and Example 2, and Comparative Example 1 and Example 3 were compared, the effect of improving the rate characteristics and cycle characteristics by performing heat treatment was confirmed.

[0108] <Examples 9 to 12> [Example 9] Preparation of Sample 12 Composite particles (Sample 12) of Example 9 were prepared according to the following procedures 12-1 to 12-3. 12-1. Li ３ AlF ６Synthesis of the same Li as in 5-1 above ３ AlF ６ 12-2. Surface treatment of positive electrode active material particles (NCM111 used) NCM111 (LiNi) was used as the positive electrode active material particles. １／３ Co １／３ Mn １／３ O ２ The same treatment as in 5-2 above was carried out, except that the heating temperature was set to 200°C.

[0109] [Example 10] Preparation of Sample 13 Composite particles (Sample 13) of Example 10 were prepared according to the following procedures 13-1 to 13-3. 13-1. Li ３ AlF ６ Synthesis of the same Li as in 5-1 above ３ AlF ６ 13-2. Surface treatment of positive electrode active material particles (NCM111 used) NCM111 (LiNi) was used as the positive electrode active material particles. １／３ Co １／３ Mn １／３ O ２ The same treatment as in 3-2 above was carried out, except that the heating temperature was 200°C.

[0110] [Example 11] Preparation of Sample 14 Composite particles (Sample 14) of Example 11 were prepared according to the following procedures 14-1 to 14-3. 14-1. Li ３ AlF ６ Synthesis of the same Li as in 6-1 above ３ AlF ６ 14-2. Surface treatment of positive electrode active material particles (NCM111 used) NCM111 (LiNi) was used as the positive electrode active material particles. １／３ Co １／３ Mn １／３ O ２ The same treatment as in 5-2 above was carried out, except that the amount of nanoparticles added was 0.1 mass %. 14-3. Heat Treatment Step Sample 14 was not subjected to a heat treatment step.

[0111] [Example 12] Preparation of Sample 15 Composite particles (Sample 15) of Example 12 were prepared according to the following procedures 15-1 to 15-3. 15-1. Li ３ AlF ６ Synthesis of the same Li as in 6-1 above ３ AlF ６ 15-2. Surface treatment of positive electrode active material particles (NCM111 used) NCM111 (LiNi) was used as the positive electrode active material particles. １／３ Co １／３ Mn １／３ O ２ The same treatment as in 5-2 above was carried out, except that the amount of nanoparticles added was 0.5 mass %. 15-3. Heat Treatment Step Sample 15 was not subjected to a heat treatment step.

[0112] [Evaluation of Charge-Discharge Characteristics of Non-Electrolyte Secondary Batteries] The specific surface areas of the composite particles (LAF-NCM particles) Samples 12 to 15 prepared using the Li-Ni-Co-Mn-based composite oxide were measured, and non-aqueous electrolyte secondary batteries were fabricated using them, followed by charge-discharge tests. The battery characteristics were evaluated based on the results of the charge-discharge tests for Samples 12 to 15. The methods for measuring the specific surface area, fabricating the non-aqueous electrolyte secondary batteries, and conducting charge-discharge tests were the same as those applied to Samples 1 to 4, except that the potential was 4500 mV. The battery characteristics were evaluated using the same method as that applied to the LAF-LCO particles. The results of the rate and cycle performance evaluations of the non-aqueous electrolyte secondary batteries using Control Test 2 (uncoated NCM111) and Samples 12 to 15 (LAF-NCM particles) in Examples 9 to 12 are shown in Table 2 below.

[0113] Referring to Table 2, the effect of the present invention was observed even when NCM111 was used as the positive electrode active material.

[0114] <Examples 13 to 16, Comparative Example 4> [Example 13] Preparation of Sample 16 Composite particles (Sample 16) of Example 13 were prepared according to the following procedures 16-1 to 16-3. 16-1. Li ３ AlF ６ Synthesis of the same Li as in 5-1 above ３ AlF ６16-2. Surface treatment of positive electrode active material particles (NCM811 used) NCM811 (LiNi) was used as the positive electrode active material particles. ０．８ Co ０．１ Mn ０．１ O ２ The same treatment as in 3-2 above was carried out, except that the heating temperature was set to 300°C and heating was carried out in a nitrogen atmosphere.

[0115] [Comparative Example 4] Preparation of Sample 17 Composite particles (Sample 17) of Comparative Example 4 were prepared according to the following procedures 17-1 to 17-3. 17-1. Li ３ AlF ６ Synthesis of the same Li as in 5-1 above ３ AlF ６ 17-2. Surface treatment of positive electrode active material particles (NCM811 used) NCM811 (LiNi) was used as the positive electrode active material particles. ０．８ Co ０．１ Mn ０．１ O ２ The same treatment as in 3-2 above was carried out, except that the heating temperature was set to 300°C and heating was carried out in a nitrogen atmosphere.

[0116] [Example 14] Preparation of Sample 18 Composite particles (Sample 18) of Example 14 were prepared according to the following procedures 18-1 to 18-3. 18-1. Li ３ AlF ６ Synthesis of the same Li as in 5-1 above ３ AlF ６ 18-2. Surface treatment of positive electrode active material particles (NCM622 used) NCM622 (LiNi) was used as the positive electrode active material particles. ０．６ Co ０．２ Mn ０．２ O ２ The same treatment as in 5-2 above was carried out, except that the nanoparticles were added in an amount of 2 mass%. 18-3. Heat Treatment Step The same treatment as in 2-3 above was carried out, except that heating was carried out under a nitrogen atmosphere.

[0117] [Example 15] Preparation of Sample 19 Composite particles (Sample 19) of Example 15 were prepared according to the following procedures 19-1 to 19-3. 19-1. Li ３ AlF ６ Synthesis of the same Li as in 5-1 above ３ AlF ６ 19-2. Surface treatment of positive electrode active material particles (NCM622 used) NCM622 (LiNi) was used as the positive electrode active material particles. ０．６ Co ０．２ Mn ０．２ O ２ The same treatment as in 3-2 above was carried out, except that the heating temperature was set to 300°C and heating was carried out in a nitrogen atmosphere.

[0118] [Example 16] Preparation of Sample 20 Composite particles (Sample 20) of Example 16 were prepared according to the following procedures 20-1 to 20-3. 20-1. Li ３ AlF ６ Synthesis of the same Li as in 5-1 above ３ AlF ６ 20-2. Surface treatment of positive electrode active material particles (NCM523 used) NCM523 (LiNi) was used as the positive electrode active material particles. ０．５ Co ０．２ Mn ０．３ O ２ The same treatment as in 5-2 above was carried out, except that the nanoparticles were added in an amount of 2 mass%. 20-3. Heat Treatment Step The same treatment as in 2-3 above was carried out, except that heating was carried out under a nitrogen atmosphere.

[0119] [Evaluation of Charge-Discharge Characteristics of Non-Electrolyte Secondary Batteries] The specific surface areas of the composite particles (LAF-NCM particles) Samples 16 to 20 prepared using the Li-Ni-Co-Mn-based composite oxide were measured, and non-aqueous electrolyte secondary batteries were fabricated using them, followed by charge-discharge tests. The battery characteristics were evaluated based on the results of the charge-discharge tests for Samples 16 to 20. The specific surface area measurement method, non-aqueous electrolyte secondary battery fabrication method, and charge-discharge test method were the same as those applied to Samples 1 to 4, except that the potential was 4500 mV. The battery characteristics were evaluated using the same method as that applied to the LAF-LCO particles. The rate characteristics and cycle characteristics of the non-aqueous electrolyte secondary batteries using Control Test 3 (uncoated NCM811), Control Test 4 (uncoated NCM622), and Samples 16 to 20 (LAF-NCM particles) in Examples 13 to 16 and Comparative Example 4 are shown in Table 3 below.

[0120] Referring to Table 3, the effects of the present invention were observed even when NCM811, NCM622, or NCM523 was used as the positive electrode active material. Furthermore, even when NCM811 was used, the rate characteristics and cycle characteristics were unacceptable when the ratio (x / S) of the difference (x) obtained by subtracting the BET specific surface area of ​​the positive electrode active material particles from the BET specific surface area of ​​the composite particles to the BET specific surface area (S) of the Li-containing nanoparticles exceeded 0.063 (Comparative Example 4).

[0121] The composite particles and the method for producing the composite particles of the present invention can be used as battery materials using other active materials, such as lithium batteries, which can maintain high-rate characteristics while exhibiting the effect of improving cycle characteristics. Furthermore, the nonaqueous electrolyte secondary battery of the present invention can be used in various electrical products, hybrid or electric vehicles, etc.

[0122] REFERENCE SIGNS LIST 1 non-aqueous electrolyte battery, 2 negative electrode member, 3 positive electrode member, 4 negative electrode current collector, 5 negative electrode active material, 6 positive electrode current collector, 7 positive electrode active material, 8 separator, 9 non-aqueous electrolyte, 10 sealing material

Claims

1. Composite particles having Li-containing nanoparticles scattered and attached to the surfaces of positive electrode active material particles, characterized in that the ratio (x / S) of the difference (x) obtained by subtracting the BET specific surface area of ​​the positive electrode active material particles from the BET specific surface area of ​​the composite particles to the BET specific surface area (S) of the Li-containing nanoparticles satisfies the following formula (2): 0.0005≦x / S≦0.063 ... formula (2) 2. The BET specific surface area of ​​the Li-containing nanoparticles is 1 to 200 m ２ / g, and the BET specific surface area of ​​the composite particles is 0.1 to 30 m ２ The composite particle according to claim 1, wherein the particle size is 1 / g.

3. The composite particles according to claim 1, wherein the average particle size of the Li-containing nanoparticles is 1 to 300 nm, the content of the positive electrode active material particles is 90.00 to 99.99 mass%, and the content of the Li-containing nanoparticles is 0.01 to 10.00 mass%.

4. The composite particles according to claim 1, characterized in that Li-containing nanoparticles are dispersed and attached to the surface of positive electrode active material particles, and then heat-treated at a heat treatment temperature of 200 to 700°C.

5. Composite particles according to any one of claims 1 to 4, characterized in that the Li-containing nanoparticles contain Li and F.

6. The composite particles according to any one of claims 1 to 3, characterized in that the positive electrode active material particles are heat-treated in a state in which the Li-containing nanoparticles are attached to the surfaces of the positive electrode active material particles.

7. The composite particles according to claim 6, wherein the heat treatment is carried out at a heat treatment temperature of 200 to 700°C.

8. A method for producing composite particles, comprising the steps of: preparing positive electrode active material particles; preparing Li-containing nanoparticles; and adhering the Li-containing nanoparticles to the surfaces of the positive electrode active material particles to form composite particles, wherein the ratio (x / S) of the difference (x) obtained by subtracting the BET specific surface area of ​​the positive electrode active material particles from the BET specific surface area of ​​the composite particles to the BET specific surface area (S) of the Li-containing nanoparticles satisfies the following formula (2): 0.0005≦x / S≦0.063...formula (2) 9. The method for producing composite particles according to claim 8, further comprising a heat treatment step of performing heat treatment after the step of forming the composite particles.

10. The method for producing composite particles according to claim 9, wherein the heat treatment step is carried out at a heat treatment temperature of 200 to 700°C.

11. A non-aqueous electrolyte secondary battery comprising the composite particles according to any one of claims 1 to 4.

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