Negative electrode material in container, method for transferring negative electrode material, negative electrode material storage container, method for storing negative electrode material, and method for manufacturing negative electrode

Abstract

To provide a negative electrode material in a container which is less degraded even when being stored in high-temperature high-moisture environments, a method for transferring the negative electrode material using the container, a negative electrode material storage container which can suppress degradation of the negative electrode material when being stored in high-temperature high-moisture environments, a method for storing the negative electrode material, and a method for manufacturing a negative electrode.SOLUTION: The negative electrode material in a container includes a container and a negative electrode material in the container. The container has a water vapor transmission amount of 150 g / (m2 d) (40°C / 90%RH) at a maximum, and the negative electrode material is a carbon material with a micro hole capacity of 0.40×10-3 m3 / kg at a maximum.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a negative electrode material in a container, a method for transporting the negative electrode material, a storage container for the negative electrode material, a method for storing the negative electrode material, and a method for manufacturing a negative electrode.

Background Art

[0002] Lithium-ion secondary batteries are widely used as power sources for portable devices such as notebook computers and mobile phones by taking advantage of their characteristics of being lightweight and having a high energy density. Furthermore, they are also used as power sources for large-scale energy storage systems for in-vehicle applications, solar power generation, wind power generation, and other natural energy applications.

[0003] As a negative electrode active material (hereinafter also referred to as a negative electrode material) used for the negative electrode of a lithium-ion secondary battery, carbon materials are widely used (for example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, the demand for lithium-ion secondary batteries has been increasing worldwide, and the transportation routes for negative electrode materials have also become diversified. For this reason, for example, when transporting negative electrode materials across the equator from the Northern Hemisphere to the Southern Hemisphere, there is a concern about quality deterioration due to exposure to a more severe high-temperature and high-humidity environment than before.

[0006] In view of the above circumstances, an object of one embodiment of the present disclosure is to provide a negative electrode material in a container in which deterioration of the negative electrode material is suppressed when stored in a high-temperature and high-humidity environment, and a method for transporting the negative electrode material using the same. Another object of the present disclosure is to provide a negative electrode material storage container, a method for storing a negative electrode material, and a method for manufacturing a negative electrode in which deterioration of the negative electrode material is suppressed when stored in a high-temperature and high-humidity environment.

Means for Solving the Problems

[0007] Specific means for solving the above problems are as follows. <1> including a container and a negative electrode material housed in the container, the water vapor transmission rate of the container is 150 g / (m 2 ·d) (40 °C / 90% RH) or less, and the negative electrode material is a carbon material having a micropore volume of 0.40 × 10 -3 m 3 / kg or less, a negative electrode material in a container. <2> The volume of the container is 6000 cm 3 or more and 40000 cm 3 or less, the negative electrode material in a container according to <1>. <3> The filling rate of the negative electrode material in the container is 20% or more and 90% or less, the negative electrode material in a container according to <1> or <2>. <4> The negative electrode material is a negative electrode material of a lithium ion secondary battery, the negative electrode material in a container according to any one of <1> to <3>. <5> The container contains polyethylene, the negative electrode material in a container according to any one of <1> to <4>. <6> The container is deformable, the negative electrode material in a container according to any one of <1> to <5>. <7> A method for transporting a negative electrode material, including a step of transporting the negative electrode material in a container according to any one of <1> to <6>. <8> The method of transportation is sea transportation, the method for transporting a negative electrode material according to <7>. <9> A container for storing a negative electrode material that is a carbon material having a micropore volume of 0.40 × 10 -3 m 3 / kg or less, and the water vapor transmission rate is 150 g / (m 2·d)(40°C / 90%RH) or less, a negative electrode material storage container. <10>The micropore volume is 0.40×10 -3 m 3 / kg or less, and a process of storing the negative electrode material in a container having a water vapor transmission rate of 150 g / (m 2 ·d)(40°C / 90%RH) or less, a method for storing a negative electrode material. <11>A step of taking out the negative electrode material from the container of the negative electrode material in the container according to any one of <1> to <6>, and A step of manufacturing a negative electrode using the negative electrode material taken out from the container, a method for manufacturing a negative electrode. <12>The step of taking out the negative electrode material from the container and the step of manufacturing a negative electrode using the negative electrode material taken out from the container are continuously performed, the method for manufacturing a negative electrode according to <11>.

Advantages of the Invention

[0008] According to one embodiment of the present disclosure, there is provided a negative electrode material in a container in which deterioration of the negative electrode material when stored in a high-temperature and high-humidity environment is suppressed, and a method for transporting the negative electrode material using the same. According to another embodiment of the present disclosure, there are provided a negative electrode material storage container, a method for storing a negative electrode material, and a method for manufacturing a negative electrode in which deterioration of the negative electrode material when stored in a high-temperature and high-humidity environment is suppressed.

Brief Description of the Drawings

[0009]

Figure 1

Modes for Carrying Out the Invention

[0010] Hereinafter, modes for carrying out the present disclosure will be described in detail. However, the present disclosure is not limited to the following embodiments. In the following embodiments, the constituent elements (including element steps, etc.) are not essential unless otherwise specified. The same applies to numerical values and their ranges, which do not limit the present invention. Also, various changes and modifications can be made by those skilled in the art within the scope of the technical idea of the present disclosure. In the present disclosure, in the numerical range indicated by "~", the numerical values described before and after "~" are included as the minimum value and the maximum value, respectively. In the numerical ranges described step by step in the present disclosure, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in other step-by-step descriptions. Further, in the numerical ranges described in the present disclosure, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples. In the present disclosure, the content rate and ratio of each component mean the total content rate and ratio of the plurality of substances corresponding to each component, unless otherwise specified when there are a plurality of substances corresponding to each component. In the present disclosure, the particle diameter of each component means the value for the mixture of the plurality of types of particles, unless otherwise specified when there are a plurality of types of particles corresponding to each component. In the present disclosure, the term "layer" includes the case where it is formed only in a part of the region, in addition to the case where it is formed over the entire region when observing the region where the layer exists. In the present disclosure, the average thickness of the layer is defined as the average value of the thickness of the layer at any 10 locations. In the present disclosure, the "solid content" of the positive electrode active material or the negative electrode active material means the remaining components obtained by removing volatile components such as organic solvents from the slurry of the positive electrode active material or the slurry of the negative electrode active material.

[0011] <Negative electrode material in a container> The negative electrode material in a container of the present disclosure includes a container and a negative electrode material housed in the container. The container has a water vapor transmission rate of 150 g / (m 2 ·d) (40 °C / 90% RH) or less, and the negative electrode material is a carbon material having a micropore volume of 0.40 × 10 -3 m 3 / kg or less, and is a negative electrode material in a container.

[0012] As a result of the studies by the present inventors, a negative electrode material that is a carbon material having a micropore volume of 0.40 × 10 -3 m 3 / kg or less and having a water vapor transmission rate of 150 g / (m 2·d)(40°C / 90%RH) or less, it was found that the deterioration of the quality of the negative electrode material after storage in a high-temperature and high-humidity environment was effectively suppressed.

[0013] The reason for this is not necessarily clear. For example, carbon materials with a micropore volume of 0.40×10 -3 m 3 / kg or less have a small impact on the properties of the negative electrode material due to contact with water vapor in a high-temperature and high-humidity environment, and it is considered that further deterioration of the negative electrode material can be suppressed by storing this negative electrode material in a container with a water vapor transmission rate of 150 g / (m 2 ·d)(40°C / 90%RH) or less to suppress contact with water vapor.

[0014] (Negative electrode material) The negative electrode material in the present disclosure is not particularly limited as long as it is a carbon material with a micropore volume of 0.40×10 -3 m 3 / kg or less. The type of carbon material is not particularly limited and may be either graphite-based or non-graphite-based. In the present disclosure, a graphite-based material means one with an interplanar spacing (d002) of less than 0.340 nm in wide-angle X-ray diffraction, and a non-graphite-based material means one with an interplanar spacing (d002) of 0.340 nm or more in wide-angle X-ray diffraction. Among non-graphite-based carbon materials, those with an interplanar spacing (d002) of 0.340 nm or more and less than 0.350 nm are sometimes referred to as soft carbon (easily graphitizable carbon), and those with an interplanar spacing (d002) of 0.350 nm or more are sometimes referred to as hard carbon (difficultly graphitizable carbon).

[0015] The interplanar spacing (d002) of the carbon material is an index indicating the degree of disorder of the crystal structure of the carbon material. The interplanar spacing (d002) can be calculated using Bragg's equation from the diffraction peak corresponding to the carbon 002 plane that appears around a diffraction angle 2θ of 24° - 27° from the diffraction profile obtained by irradiating the sample with X-rays (CuKα rays) and measuring the diffraction lines with a goniometer. Specifically, it can be measured under the following conditions. Radiation source: CuKα rays (wavelength = 0.15418 nm) Output: 40 kV, 20 mA Sampling width: 0.010° Scanning range: 10° to 35° Scan speed: 0.5° / min

[0016] Bragg's equation: 2dsinθ = nλ In the equation, d represents the length of one period, θ represents the diffraction angle, n represents the order of reflection, and λ represents the X-ray wavelength.

[0017] The negative electrode material is preferably a particulate graphite-based carbon material (hereinafter also referred to as graphite particles). As the graphite particles, those obtained by pulverizing massive natural graphite may be used. Since the graphite particles obtained by pulverizing massive natural graphite may contain impurities, it is preferable to purify natural graphite to a high purity by a purification treatment. The method of the purification treatment of natural graphite is not particularly limited, and it can be appropriately selected from commonly used purification treatment methods. For example, flotation, electrochemical treatment, chemical treatment, etc. can be mentioned.

[0018] The purity of natural graphite is preferably 99.8% or more (ash content 0.2% or less), more preferably 99.9% or more (ash content 0.1% or less) on a mass basis. When the purity is 99.8% or more, the safety of the battery is further improved, and the battery performance tends to be further improved. The purity of natural graphite can be calculated, for example, by measuring the remaining amount derived from the ash content after leaving 100 g of graphite in a furnace at 800°C for 48 hours or more in an air atmosphere.

[0019] As the graphite particles, those obtained by pulverizing artificial graphite obtained by firing resin-based materials such as epoxy resin and phenolic resin, pitch-based materials obtained from petroleum, coal, etc. may be used.

[0020] The method for obtaining artificial graphite is not particularly limited. For example, there is a method of calcining raw materials such as thermoplastic resin, naphthalene, anthracene, phenanthroline, coal tar, and tar pitch in an inert atmosphere at 800 °C or higher to obtain artificial graphite as the calcined product. Next, the obtained calcined product is pulverized by a known method such as a jet mill, a vibration mill, a pin mill, or a hammer mill, and graphite particles derived from artificial graphite can be produced by adjusting the average particle diameter to about 2 μm to 40 μm. Further, the raw material may be heat-treated in advance before calcination. When the raw material is heat-treated, for example, it is heat-treated in advance by a device such as an autoclave, coarsely pulverized by a known method, and then the raw material heat-treated in an inert atmosphere at 800 °C or higher is calcined in the same manner as above, and the obtained artificial graphite as the calcined product is pulverized to adjust the average particle diameter to about 2 μm to 40 μm, whereby graphite particles derived from artificial graphite can be obtained.

[0021] In the present disclosure, the micropore volume of the negative electrode material is calculated from the adsorption amount of CO2 gas at 0 °C using an automatic gas adsorption / desorption measurement device.

[0022] The micropore volume of the negative electrode material may be 0.40×10 -3 m 3 / kg or less, may be 0.35×10 -3 m 3 / kg or less, and may be 0.30×10 -3 m 3 / kg or less. The smaller the micropore volume of the negative electrode material, the more the storage characteristics tend to be improved. The micropore volume of the negative electrode material may be 0.05×10 -3 m 3 / kg or more, may be 0.07×10 -3 m 3 / kg or more, and may be 0.09×10 -3 m 3 / kg or more. The larger the micropore volume of the negative electrode material, the more the input characteristics tend to be improved. The micropore volume of the negative electrode material can be adjusted by the precursor species of low-crystalline carbon, the heat treatment temperature, the amount of low-crystalline carbon, and the like.

[0023] The volume average particle diameter of the negative electrode material is preferably 2 μm to 30 μm, more preferably 2.5 μm to 25 μm, still more preferably 3 μm to 20 μm, and particularly preferably 5 μm to 20 μm. When the volume average particle diameter of the negative electrode material is 30 μm or less, the discharge capacity and discharge characteristics tend to improve. When the volume average particle diameter of the negative electrode material is 2 μm or more, the initial charge-discharge efficiency tends to improve. In the present disclosure, the volume average particle diameter of the negative electrode is a value obtained as the median diameter (d50) in the volume-based particle size distribution obtained by the laser diffraction / scattering method.

[0024] The range of the BET specific surface area of the negative electrode is preferably 0.8 m 2 / g to 8 m 2 / g, more preferably 1 m 2 / g to 7 m 2 / g, still more preferably 1.5 m 2 / g to 6 m 2 / g, particularly preferably 2 m 2 / g to 6 m 2 / g. When the BET specific surface area of the negative electrode is 0.8 m 2 / g or more, the contact surface with the electrolytic solution is sufficiently ensured, and excellent battery performance tends to be obtained. When the BET specific surface area of the negative electrode is 8 m 2 / g or less, the tap density tends to increase, and the miscibility with other materials such as a binder and a conductive agent tends to be good.

[0025] The BET specific surface area of the negative electrode material can be measured from the nitrogen adsorption ability according to JIS Z 8830:2013. As the evaluation apparatus, AUTOSORB-1 (trade name) manufactured by QUANTACHROME can be used. When measuring the BET specific surface area, since it is considered that the moisture adsorbed on the sample surface and in the structure affects the gas adsorption ability, first, a pretreatment for removing moisture by heating is performed. After the pretreatment, the evaluation temperature is set to 77 K, and the BET specific surface area is measured with the evaluation pressure range being less than 1 in terms of relative pressure (equilibrium pressure with respect to the saturated vapor pressure). In the pretreatment, a measurement cell into which 0.05 g of a measurement sample is introduced is depressurized to 10 Pa or less with a vacuum pump. Then, it is heated at 110°C and held for 3 hours or more. Then, it is naturally cooled to room temperature (25°C) while maintaining the depressurized state.

[0026] The negative electrode material may be in a state of having a layer of a carbon material (low-crystalline carbon layer) with lower crystallinity than graphite on the surface of the graphite particles serving as the core. When the graphite particles have a low-crystalline carbon layer on the surface of the graphite, the ratio (mass ratio) of the low-crystalline carbon layer to 1 part by mass of graphite is preferably 0.005 to 10, more preferably 0.005 to 5, and even more preferably 0.005 to 0.08. When the ratio (mass ratio) of the low-crystalline carbon layer to graphite is 0.005 or more, it tends to be excellent in initial charge-discharge efficiency and life characteristics. Also, when it is 10 or less, it tends to be excellent in output characteristics.

[0027] When the graphite particles contain graphite and components other than graphite, the content rates of graphite and components other than graphite contained in the graphite particles can be calculated, for example, by TG-DTA (Thermogravimetry-Differential Thermal Analysis, simultaneous measurement of differential thermal and thermogravimetry), measuring the weight change in an air stream, and calculating from the weight reduction ratio from 500°C to 600°C. Note that the weight change in the temperature range from 500°C to 600°C can be attributed to the weight change derived from components other than graphite. On the other hand, the remainder after the heat treatment can be attributed to the amount of graphite.

[0028] The method for producing graphite particles having a low-crystalline carbon layer on the surface of the core graphite particles is not particularly limited. For example, it preferably includes a step of heat-treating a mixture containing the core graphite particles and a precursor of the low-crystalline carbon layer. According to this method, the above-described graphite particles can be efficiently produced.

[0029] The precursor of the low-crystalline carbon layer is not particularly limited, and examples include pitch, organic polymer compounds, etc. Examples of pitch include ethylene heavy-end pitch, crude oil pitch, coal tar pitch, pitch produced by pyrolyzing polyvinyl chloride, etc., and pitch produced by polymerizing naphthalene, etc. in the presence of a super-strong acid. Examples of organic polymer compounds include thermoplastic resins such as polyvinyl chloride, polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, and natural substances such as starch and cellulose.

[0030] The temperature during the heat treatment of the mixture is not particularly limited, but from the viewpoint of improving the input / output characteristics in a lithium-ion secondary battery, it is preferably 900 °C to 1500 °C. In the above method, the content ratios of the graphite particles serving as nuclei and the precursor of the low-crystalline carbon layer in the mixture before heat treatment are not particularly limited. From the viewpoint of improving the input / output characteristics in a lithium-ion secondary battery, the content ratio of the graphite particles serving as nuclei is preferably 85% by mass to 99.9% by mass based on the total mass of the mixture.

[0031] The Raman R value (ID / IG) of the negative electrode material is preferably 0.10 to 0.60, more preferably 0.15 to 0.55, still more preferably 0.20 to 0.50, and particularly preferably 0.25 to 0.40. The Raman R value (ID / IG) of the negative electrode material is the ratio of the peak intensity (ID) in the range of 1300 cm -1 ~1620 cm -1 to the peak intensity (IG) in the range of 1580 cm -1 ~1400 cm -1 in the Raman spectrum when the negative electrode material is irradiated with a laser beam of 532 nm. The Raman spectroscopic spectrum can be measured using a Raman spectrometer (for example, DXR manufactured by Thermo Fisher Scientific).

[0032] (Container) The container for housing the negative electrode material has a water vapor transmission rate of 150 g / (m 2·d) If it is below (40°C / 90%RH), there is no particular limitation. The water vapor transmission rate in the present disclosure is measured by the infrared sensor method defined in JIS K7129-2:2019. In the present disclosure, "accommodating" the negative electrode material means disposing the negative electrode material in a closed space, and "container" means an object in which the negative electrode material can be disposed in a closed space.

[0033] Examples of the material of the container include resin, rubber, metal, carbon, etc. The material of the container may be only one type or a combination of two or more types. Examples of the resin include polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polycarbonate, polystyrene, polyamide, polyimide, polyetherimide, polyurethane, polyvinyl chloride, acrylic resin, epoxy resin, silicone resin, and various thermoplastic elastomers. Among these resins, polyethylene is preferred.

[0034] If necessary, the surface of the container may have a gas barrier coating. Examples of the gas barrier coating include those containing inorganic materials such as metal, silica, alumina, and carbon.

[0035] The volume of the container may be 6000 cm 3 or more, and may be 8000 cm 3 or more, and may be 10000 cm 3 or more. The larger the volume of the container, the more excellent the loading efficiency tends to be. The volume of the container may be 40000 cm 3 or less, and may be 35000 cm 3 or less, and may be 30000 cm 3 or less. The smaller the volume of the container, the easier it is to transport.

[0036] The filling rate of the negative electrode material in the container is not particularly limited, and may be 20% or more, may be 25% or more, and may be 50% or more. The larger the filling rate of the negative electrode material, the more excellent the loading efficiency tends to be. The filling ratio of the negative electrode material in the container is not particularly limited and may be 90% or less, may be 85% or less, or may be 80% or less. The smaller the filling ratio of the negative electrode material, the easier it is to transport. The filling ratio of the negative electrode material is the ratio (%) of the volume (cm 3 ) of the negative electrode material in the container to the volume (cm 3 ) of the container.

[0037] The shape of the container is not particularly limited. For example, it may be cylindrical, rectangular parallelepiped, bag-shaped (such as a flexible container), etc. If necessary, the container may have a multiple structure such as a double structure. Examples of containers having a multiple structure include flexible containers having a metal inner bag such as aluminum and an outer bag. When the container has a multiple structure, at least one layer satisfies the above-described conditions for the water vapor transmission rate.

[0038] The container may be deformable or non-deformable. When the purpose of putting the negative electrode material into the container is the transportation of the negative electrode material (especially long-distance transportation such as import and export), the container is preferably deformable. Examples of deformable containers include bag-shaped containers such as flexible containers.

[0039] The negative electrode material contained in the container containing the negative electrode material is used, for example, in the manufacture of the negative electrode of a lithium-ion secondary battery. The configuration of the lithium-ion secondary battery is not particularly limited and can be selected from known configurations. In one embodiment, the lithium-ion secondary battery has a negative electrode containing the above-described negative electrode material, a positive electrode containing a positive electrode active material, a separator disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte. Hereinafter, the positive electrode, negative electrode, non-aqueous electrolyte, separator, and other components that may be provided as necessary, which are components of the lithium-ion secondary battery, will be sequentially described.

[0040] (Positive electrode) The positive electrode (positive electrode plate) included in a lithium-ion secondary battery has a current collector (positive electrode current collector) and a positive electrode mixture layer disposed on its surface. The positive electrode mixture layer is a layer containing at least a positive electrode active material disposed on the surface of the current collector.

[0041] As the positive electrode active material, it is preferable to include a layered lithium nickel manganese cobalt composite oxide (hereinafter, sometimes referred to as NMC). NMC has a high capacity and tends to be excellent in safety. From the viewpoint of further improving safety, it is preferable to use a mixture of NMC and a spinel-type lithium manganese composite oxide (hereinafter, sometimes referred to as sp-Mn) as the positive electrode active material. From the viewpoint of increasing the capacity of the battery, the content of NMC is preferably 65% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more based on the total amount of the positive electrode mixture layer.

[0042] As NMC, it is preferable to use those represented by the following compositional formula (Chemical Formula 1). Li (1+δ) Mn x Ni y Co (1-x-y-z) M z O2…(Chemical Formula 1) In the compositional formula (Chemical Formula 1), (1 + δ) represents the composition ratio of Li (lithium), x represents the composition ratio of Mn (manganese), y represents the composition ratio of Ni (nickel), (1 - x - y - z) represents the composition ratio of Co (cobalt), respectively. z represents the composition ratio of element M. The composition ratio of O (oxygen) is 2. Element M is at least one element selected from the group consisting of Ti (titanium), Zr (zirconium), Nb (niobium), Mo (molybdenum), W (tungsten), Al (aluminum), Si (silicon), Ga (gallium), Ge (germanium), and Sn (tin). Also, -0.15 < δ < 0.15, 0.1 < x ≦ 0.5, 0.6 < x + y + z < 1.0, 0 ≦ z ≦ 0.1.

[0043] As sp-Mn, it is preferable to use those represented by the following compositional formula (Formula 2). Li (1+η) Mn (2-λ) M’ λ O4…(Formula 2) In the compositional formula (Formula 2), (1 + η) represents the composition ratio of Li, (2 - λ) represents the composition ratio of Mn, λ represents the composition ratio of the element M’, respectively. The composition ratio of O (oxygen) is 4. The element M’ is preferably at least one element selected from the group consisting of Mg (magnesium), Ca (calcium), Sr (strontium), Al, Ga, Zn (zinc) and Cu (copper). 0 ≦ η ≦ 0.2, 0 ≦ λ ≦ 0.1. As the element M’ in the compositional formula (Formula 2), it is preferable to use Mg or Al. By using Mg or Al, the battery life tends to be extended. Also, the battery safety tends to be improved. Furthermore, by adding the element M’, the elution of Mn can be reduced, so the storage characteristics and charge-discharge cycle characteristics tend to be improved.

[0044] As the positive electrode active material, those other than NMC and sp-Mn may be used. As the positive electrode active material other than NMC and sp-Mn, those commonly used in this field can be used, and examples include lithium-containing composite metal oxides other than NMC and sp-Mn, olivine-type lithium salts, chalcogen compounds, manganese dioxide, etc. The lithium-containing composite metal oxide is a metal oxide containing lithium and a transition metal or a metal oxide in which a part of the transition metal in the metal oxide is substituted by a different element. Here, examples of the different element include Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, V and B, and Mn, Al, Co, Ni and Mg are preferable. The different element may be used alone or in combination of two or more. As the lithium-containing composite metal oxide other than NMC and sp-Mn, Li x CoO2, Li x NiO2, Li xMnO2, Li x Co y Ni 1-y O2, Li x Co y M 1 1-y O z (Li x Co y M 1 1-y O z In, M 1 represents at least one element selected from the group consisting of Na, Mg, Sc, Y, Mn, Fe, Ni, Cu, Zn, Al, Cr, Pb, Sb, V, and B. ), Li x Ni 1-y M 2 y O z (Li x Ni 1-y M 2 y O z In, M 2 represents at least one element selected from the group consisting of Na, Mg, Sc, Y, Mn, Fe, Co, Cu, Zn, Al, Cr, Pb, Sb, V, and B. ).) and the like. Here, x is in the range of 0 < x ≤ 1.2, y is in the range of 0 to 0.9, and z is in the range of 2.0 to 2.3. Also, the x value indicating the molar ratio of lithium increases or decreases during charge and discharge. Examples of the olivine-type lithium salt include LiFePO4 and the like. Examples of the chalcogen compound include titanium disulfide, molybdenum disulfide, and the like. The positive electrode active material may be used alone or in combination of two or more.

[0045] Next, the positive electrode mixture layer and the current collector will be described in detail. The positive electrode mixture layer contains a positive electrode active material, a binder, and the like, and is disposed on the current collector. There is no limitation on the method of forming the positive electrode mixture layer, and it is formed, for example, as follows. The positive electrode active material, the binder, and other materials such as a conductive agent and a thickener used as necessary are mixed in a dry manner to form a sheet, which is then pressed onto the current collector (dry method) to form the positive electrode mixture layer. In addition, the positive electrode active material, the binder, and other materials such as a conductive agent and a thickener used as necessary are dissolved or dispersed in a dispersion solvent to form a slurry of the positive electrode mixture, which is then applied to the current collector and dried (wet method) to form the positive electrode mixture layer. As described above, it is preferable to use layered lithium-nickel-manganese-cobalt composite oxide (NMC) as the positive electrode active material. The positive electrode active material is used in powder (granular) form and mixed. The particles of the positive electrode active material such as NMC or sp-Mn may have a shape such as a block, polyhedron, sphere, oval sphere, plate, needle, or column. The average particle diameter (d50) of the particles of the positive electrode active material such as NMC or sp-Mn (the average particle diameter (d50) of the secondary particles when the primary particles are aggregated to form secondary particles) is preferably 1 μm to 30 μm, more preferably 3 μm to 25 μm, and even more preferably 5 μm to 15 μm, from the viewpoints of tap density (packing property) and mixability with other materials when forming an electrode. The average particle diameter (d50) of the particles of the positive electrode active material can be measured in the same manner as in the case of graphite particles.

[0046] The BET specific surface area of the particles of the positive electrode active material such as NMC and sp-Mn is in the range of 0.2 m 2 / g~4.0m 2 / g, and preferably 0.3m 2 / g~2.5m 2 More preferably, it is 0.4m 2 / g~1.5m 2 It is more preferable that the molecular weight is / g. The BET specific surface area of the positive electrode active material particles is 0.2 m 2If it is / g or more, excellent battery performance tends to be obtained. Further, when the BET specific surface area of the particles of the positive electrode active material is 4.0 m 2 / g or less, the tap density tends to increase, and the miscibility with other materials such as a binder and a conductive agent tends to be good. The BET specific surface area can be measured in the same manner as in the case of graphite particles.

[0047] Examples of the conductive agent for the positive electrode include metal materials such as copper and nickel; graphite (graphite) such as natural graphite and artificial graphite; carbon black such as acetylene black; and carbonaceous materials such as amorphous carbon such as needle coke. The conductive agent for the positive electrode may be used alone or in combination of two or more. The content rate of the conductive agent with respect to the mass of the positive electrode mixture layer is preferably 0.01 mass% to 50 mass%, more preferably 0.1 mass% to 30 mass%, and even more preferably 1 mass% to 15 mass%. When the content rate of the conductive agent is 0.01 mass% or more, sufficient conductivity tends to be obtained. If the content rate of the conductive agent is 50 mass% or less, a decrease in battery capacity can be suppressed.

[0048] The binder for the positive electrode is not particularly limited. When forming the positive electrode mixture layer by a wet method, a material having good solubility or dispersibility in a dispersion solvent is selected. Specifically, resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polyimide, and cellulose; rubber-like polymers such as SBR (styrene-butadiene rubber) and NBR (acrylonitrile-butadiene rubber); fluorine-based polymers such as polyvinylidene fluoride (PVdF), polytetrafluoroethylene, polytetrafluoroethylene-vinylidene fluoride copolymer, and fluorinated polyvinylidene fluoride; and polymer compositions having ionic conductivity of alkali metal ions (particularly lithium ions) and the like can be mentioned. The binder for the positive electrode may be used alone or in combination of two or more. From the viewpoint of the stability of the positive electrode, it is preferable to use a fluorine-based polymer such as polyvinylidene fluoride (PVdF) or a polytetrafluoroethylene-vinylidene fluoride copolymer as the binder. The content rate of the binder with respect to the mass of the positive electrode active material layer is preferably 0.1% by mass to 60% by mass, more preferably 1% by mass to 40% by mass, and still more preferably 3% by mass to 10% by mass. When the content rate of the binder is 0.1% by mass or more, the positive electrode active material can be sufficiently bound, sufficient mechanical strength of the positive electrode active material layer can be obtained, and the battery performance such as cycle characteristics tends to be improved. When the content rate of the binder is 60% by mass or less, sufficient battery capacity and conductivity tend to be obtained.

[0049] The thickener is effective for adjusting the viscosity of the slurry. There is no particular limitation on the thickener. Specifically, for example, carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof can be mentioned. The thickener may be used alone or in combination of two or more. The content rate of the thickener with respect to the mass of the positive electrode active material layer when using the thickener is preferably 0.1% by mass to 20% by mass, more preferably 0.5% by mass to 15% by mass, and still more preferably 1% by mass to 10% by mass from the viewpoints of input-output characteristics and battery capacity.

[0050] As the dispersion solvent for forming the slurry, there is no limitation on the type as long as it is a solvent capable of dissolving or dispersing the positive electrode active material, the binder, and the conductive agent or thickener used as necessary. Either an aqueous solvent or an organic solvent may be used. Examples of the aqueous solvent include water, alcohol, and a mixed solvent of water and alcohol. Examples of the organic solvent include N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, tetrahydrofuran (THF), toluene, acetone, diethyl ether, dimethyl sulfoxide, benzene, xylene, hexane, and the like. In particular, when using an aqueous solvent, it is preferable to use a thickener.

[0051] The positive electrode mixture layer formed on the current collector using a wet method or a dry method is preferably densified by hand pressing, roller pressing, or the like in order to improve the packing density of the positive electrode active material. From the viewpoint of further improving the input / output characteristics and safety, the density of the densified positive electrode mixture layer is 2.5 g / cm 3 ~3.5 g / cm 3 Preferably in the range of, more preferably 2.55 g / cm 3 ~3.15 g / cm 3 In the range of, and even more preferably 2.6 g / cm 3 ~3.0 g / cm 3 In the range of. From the viewpoint of energy density and input / output characteristics, the single-sided coating amount of the positive electrode mixture slurry on the current collector when forming the positive electrode mixture layer is, as the solid content of the positive electrode mixture, 30 g / m 2 ~170 g / m 2 Preferably, more preferably 40 g / m 2 ~160 g / m 2 And even more preferably 40 g / m 2 ~150 g / m 2 In the range of. Considering the single-sided coating amount of the positive electrode mixture slurry on the current collector and the density of the positive electrode mixture layer, the average thickness of the positive electrode mixture layer is preferably 19 μm to 68 μm, more preferably 23 μm to 64 μm, and even more preferably 36 μm to 60 μm.

[0052] The material of the current collector for the positive electrode is not particularly limited. The material of the current collector is preferably a metal material, and more preferably aluminum. Specifically, examples of the current collector include metal foil, metal plate, metal thin film, expanded metal, etc. Among them, it is preferable to use a metal thin film. The metal thin film may be in a mesh shape. The average thickness of the current collector is not particularly limited. From the viewpoint of obtaining the required strength and good flexibility as the current collector, it is preferably 1 μm to 1 mm, more preferably 3 μm to 100 μm, and even more preferably 5 μm to 100 μm.

[0053] (Negative electrode) The negative electrode (negative electrode plate) included in the lithium-ion secondary battery has a current collector (negative electrode current collector) and a negative electrode mixture layer disposed on its surface. The negative electrode mixture layer is a layer containing at least a negative electrode material disposed on the surface of the current collector.

[0054] The method for forming the negative electrode mixture layer is not particularly limited. For example, a negative electrode material and other materials such as a binder, a conductive agent, and a thickening agent that are used as necessary are dissolved or dispersed in a dispersion solvent to form a slurry of the negative electrode mixture, which is then applied to the current collector and dried (wet method) to form the negative electrode mixture layer.

[0055] As the conductive agent for the negative electrode, graphite (graphite) such as natural graphite and artificial graphite, carbon black such as acetylene black, and amorphous carbon such as needle coke can be used. The conductive agent for the negative electrode may be used alone or in combination of two or more. Adding a conductive agent tends to have effects such as reducing the resistance of the electrode.

[0056] The content rate of the conductive agent with respect to the mass of the negative electrode mixture layer is preferably 1% by mass to 45% by mass, more preferably 2% by mass to 42% by mass, and even more preferably 3% by mass to 40% by mass from the viewpoints of improving conductivity and reducing the initial irreversible capacity. When the content rate of the conductive agent is 1% by mass or more, sufficient conductivity tends to be obtained. When the content rate of the conductive agent is 45% by mass or less, a decrease in battery capacity tends to be suppressed.

[0057] Specific examples of the binder for the negative electrode include resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, cellulose, and nitrocellulose; rubber-like polymers such as SBR (styrene-butadiene rubber) and NBR (acrylonitrile-butadiene rubber); fluorine-based polymers such as polyvinylidene fluoride (PVdF), polytetrafluoroethylene, and fluorinated polyvinylidene fluoride; and polymer compositions having ionic conductivity of alkali metal ions (particularly lithium ions). Among these, it is preferable to use SBR, fluorine-based polymers typified by polyvinylidene fluoride, etc. The binder for the negative electrode may be used alone or in combination of two or more kinds.

[0058] The content of the binder with respect to the mass of the negative electrode mixture layer is preferably 0.1% by mass to 20% by mass, more preferably 0.5% by mass to 15% by mass, and still more preferably 0.6% by mass to 10% by mass. When the content of the binder is 0.1% by mass or more, the negative electrode material can be sufficiently bound, and a sufficient mechanical strength of the negative electrode mixture layer tends to be obtained. When the content of the binder is 20% by mass or less, sufficient battery capacity and conductivity tend to be obtained.

[0059] When using a fluorine-based polymer represented by polyvinylidene fluoride as the main component as the binder, the content of the binder with respect to the mass of the negative electrode mixture layer is preferably 1% by mass to 15% by mass, more preferably 2% by mass to 10% by mass, and still more preferably 3% by mass to 8% by mass.

[0060] The thickener is used to adjust the viscosity of the slurry. Specifically, examples of the thickener include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. The thickener may be used alone or in combination of two or more kinds.

[0061] When using a thickener, the content of the thickener with respect to the mass of the negative electrode mixture layer is preferably 0.1% by mass to 5% by mass, more preferably 0.5% by mass to 3% by mass, and still more preferably 0.6% by mass to 2% by mass from the viewpoints of input-output characteristics and battery capacity.

[0062] As the dispersion solvent for forming the slurry, there is no limitation on the type as long as it can dissolve or disperse the negative electrode material, the binder, and the conductive agent or thickener used as necessary, and either an aqueous solvent or an organic solvent may be used. Examples of the aqueous solvent include water, alcohol, and a mixed solvent of water and alcohol. Examples of the organic solvent include N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, tetrahydrofuran (THF), toluene, acetone, diethyl ether, dimethyl sulfoxide, benzene, xylene, hexane, etc. Particularly when using an aqueous solvent, it is preferable to use a thickener.

[0063] The density of the negative electrode mixture layer is preferably 0.7 g / cm 3 ~2 g / cm 3 and more preferably 0.8 g / cm 3 ~1.9 g / cm 3 and even more preferably 0.9 g / cm 3 ~1.8 g / cm 3 When the density of the negative electrode mixture layer is 0.7 g / cm or more, the conductivity between the negative electrode materials is improved, the increase in battery resistance can be suppressed, and the capacity per unit volume tends to be improved. When the density of the negative electrode mixture layer is 2 g / cm 3 or less, the possibility of causing an increase in the initial irreversible capacity and deterioration of the discharge characteristics due to a decrease in the permeability of the non-aqueous electrolyte near the interface between the current collector and the negative electrode material tends to decrease. 3 From the viewpoints of energy density and input / output characteristics, the one-sided coating amount of the slurry of the negative electrode mixture on the current collector when forming the negative electrode mixture layer is preferably 30 g / m ~150 g / m 2 as the solid content of the negative electrode mixture, and more preferably 40 g / m 2 ~140 g / m 2 and even more preferably 45 g / m 2 ~130 g / m 2 ~130 g / m 2 When the density of the negative electrode mixture layer is 2 g / cm Considering the single-sided coating amount of the slurry of the negative electrode active material on the current collector and the density of the negative electrode active material layer, the average thickness of the negative electrode active material layer is preferably 10 μm to 150 μm, more preferably 15 μm to 140 μm, and even more preferably 15 μm to 120 μm.

[0064] The material of the current collector for the negative electrode is not particularly limited. Examples of the material of the current collector include metal materials such as copper, nickel, stainless steel, and nickel-plated steel. From the viewpoints of ease of processing and cost, copper is preferred. Specific examples of the current collector include metal foils, metal plates, metal thin films, expanded metals, etc. Among them, metal thin films are preferred, and copper foils are more preferred. The copper foil may be either a rolled copper foil formed by a rolling method or an electrolytic copper foil formed by an electrolysis method. The average thickness of the current collector is not particularly limited. For example, the average thickness of the current collector is preferably 5 μm to 50 μm, more preferably 8 μm to 40 μm, and even more preferably 9 μm to 30 μm. In addition, when the average thickness of the current collector is less than 25 μm, the strength can be improved by using a copper alloy stronger than pure copper (such as phosphor bronze, titanium copper, Corson alloy, Cu-Cr-Zr alloy, etc.).

[0065] (Non-aqueous electrolyte) The non-aqueous electrolyte generally contains a non-aqueous solvent and a lithium salt (electrolyte). Examples of the non-aqueous solvent include cyclic carbonates, chain carbonates, and cyclic sulfonic acid esters. As for the cyclic carbonate, those having 2 to 6 carbon atoms in the alkylene group constituting the cyclic carbonate are preferred, and those having 2 to 4 carbon atoms are more preferred. Examples include ethylene carbonate, propylene carbonate, butylene carbonate, etc. Among them, ethylene carbonate and propylene carbonate are preferred. As the chain carbonate, dialkyl carbonate is preferred. The carbon number of the two alkyl groups is preferably 1 to 5, more preferably 1 to 4 respectively. Symmetric chain carbonates such as dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate; asymmetric chain carbonates such as ethyl methyl carbonate, methyl-n-propyl carbonate, ethyl-n-propyl carbonate and the like can be mentioned. Among them, dimethyl carbonate and ethyl methyl carbonate are preferred. Dimethyl carbonate is superior to diethyl carbonate in oxidation resistance and reduction resistance, so it tends to improve cycle characteristics. Ethyl methyl carbonate has an asymmetric molecular structure and a low melting point, so it tends to improve low-temperature characteristics. A mixed solvent combining ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate is particularly preferred because it can ensure battery characteristics in a wide temperature range. From the viewpoint of battery characteristics, the content of cyclic carbonate and chain carbonate is preferably 85% by mass or more, more preferably 90% by mass or more, and further preferably 95% by mass or more based on the total amount of non-aqueous solvents. In addition, from the viewpoint of battery characteristics, when cyclic carbonate and chain carbonate are used in combination, the mixing ratio of cyclic carbonate and chain carbonate is preferably such that the cyclic carbonate / chain carbonate (volume ratio) is 1 / 9 to 6 / 4, more preferably 2 / 8 to 5 / 5. Examples of the cyclic sulfonic acid ester include 1,3-propanesultone, 1-methyl-1,3-propanesultone, 3-methyl-1,3-propanesultone, 1,4-butanesultone, 1,3-propene sultone, 1,4-butene sultone and the like. Among them, 1,3-propanesultone and 1,4-butanesultone are particularly preferred from the viewpoint of reducing direct current resistance. The non-aqueous electrolyte may further contain a chain ester, a cyclic ether, a chain ether, a cyclic sulfone and the like. Examples of the chain ester include methyl acetate, ethyl acetate, propyl acetate, methyl propionate, etc. Among these, it is preferable to use methyl acetate from the viewpoint of improving the low-temperature characteristics. Examples of the cyclic ether include tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, etc. Examples of the chain ether include dimethoxyethane, dimethoxymethane, etc. Examples of the cyclic sulfone include sulfolane, 3-methylsulfolane, etc.

[0066] The non-aqueous electrolyte may contain a silyl phosphate compound. Specific examples of the silyl phosphate compound include tris(trimethylsilyl) phosphate, dimethyltrimethylsilyl phosphate, methylbis(trimethylsilyl) phosphate, diethyltrimethylsilyl phosphate, ethylbis(trimethylsilyl) phosphate, dipropyltrimethylsilyl phosphate, propylbis(trimethylsilyl) phosphate, dibutyltrimethylsilyl phosphate, butylbis(trimethylsilyl) phosphate, dioctyltrimethylsilyl phosphate, octylbis(trimethylsilyl) phosphate, diphenyltrimethylsilyl phosphate, phenylbis(trimethylsilyl) phosphate, di(trifluoroethyl)(trimethylsilyl) phosphate, trifluoroethylbis(trimethylsilyl) phosphate, compounds in which the trimethylsilyl group of the aforementioned silyl phosphate is substituted with a triethylsilyl group, a triphenylsilyl group, a t-butyldimethylsilyl group, etc., and compounds having a structure of so-called condensed phosphate ester in which phosphate esters are condensed and phosphorus atoms are bonded through oxygen. Among these, it is preferable to use tris(trimethylsilyl) phosphate (TMSP). Tris(trimethylsilyl) phosphate can suppress the increase in resistance with a smaller addition amount compared to other silyl phosphate compounds. These silyl phosphates may be used alone or in combination of two or more. When the non-aqueous electrolyte contains a silyl phosphate compound, the content of the silyl phosphate compound is preferably 0.1% by mass to 5% by mass, more preferably 0.3% by mass to 3% by mass, and even more preferably 0.4% by mass to 2% by mass with respect to the total amount of the non-aqueous electrolyte. In particular, when the non-aqueous electrolyte contains tris(trimethylsilyl) phosphate (TMSP), the content of tris(trimethylsilyl) phosphate (TMSP) is preferably 0.1% by mass to 0.5% by mass, more preferably 0.1% by mass to 0.4% by mass, and even more preferably 0.2% by mass to 0.4% by mass with respect to the total amount of the non-aqueous electrolyte. When the content of TMSP is within the above range, the life characteristics tend to be improved by the action of a thin Solid Electrolyte Interphase (SEI) or the like.

[0067] Also, the non-aqueous electrolyte may contain vinylene carbonate (VC). By using VC, a stable film is formed on the surface of the negative electrode during charging of the lithium-ion secondary battery. This film has the effect of suppressing the decomposition of the non-aqueous electrolyte on the negative electrode surface. The content of vinylene carbonate is preferably 0.3% by mass to 1.6% by mass, more preferably 0.3% by mass to 1.5% by mass, and even more preferably 0.3% by mass to 1.3% by mass with respect to the total amount of the non-aqueous electrolyte. When the content of vinylene carbonate is within the above range, the life characteristics can be improved, and the action of excessive VC being decomposed during charge and discharge of the lithium-ion secondary battery to reduce the charge and discharge efficiency can be prevented.

[0068] Next, the lithium salt (electrolyte) will be described. The lithium salt is not particularly limited as long as it is a lithium salt that can be used as an electrolyte for a non-aqueous electrolyte of a lithium-ion secondary battery, and examples include the following inorganic lithium salts, fluorine-containing organic lithium salts, oxalatoborate salts, and the like. Examples of inorganic lithium salts include inorganic fluoride salts such as LiPF6, LiBF4, LiAsF6, and LiSbF6; perhalogenate salts such as LiClO4, LiBrO4, and LiIO4; and inorganic chloride salts such as LiAlCl4. Examples of fluorine-containing organic lithium salts include perfluoroalkane sulfonate salts such as LiCF3SO3; perfluoroalkane sulfonyl imide salts such as LiN(CF3SO2)2, LiN(CF3CF2SO2)2, and LiN(CF3SO2)(C4F9SO2); perfluoroalkane sulfonyl methide salts such as LiC(CF3SO2)3; and fluoroalkyl phosphoric acid fluoride salts such as Li[PF5(CF2CF2CF3)], Li[PF4(CF2CF2CF3)2], Li[PF3(CF2CF2CF3)3], Li[PF5(CF2CF2CF2CF3)], Li[PF4(CF2CF2CF2CF3)2], and Li[PF3(CF2CF2CF2CF3)3]. Examples of oxalatoborate salts include lithium bis(oxalato)borate and lithium difluorooxalatoborate. These lithium salts may be used alone or in combination of two or more. Among them, lithium hexafluorophosphate (LiPF6) is preferred when comprehensively considering solubility in the solvent, charge-discharge characteristics, output characteristics, cycle characteristics, etc. of the lithium-ion secondary battery.

[0069] There is no particular limitation on the concentration of the electrolyte in the non-aqueous electrolyte. The concentration range of the electrolyte is as follows. The lower limit of the concentration is 0.5 mol / L or more, preferably 0.6 mol / L or more, more preferably 0.7 mol / L or more. The upper limit of the concentration is 2 mol / L or less, preferably 1.8 mol / L or less, more preferably 1.7 mol / L or less. When the concentration of the electrolyte is 0.5 mol / L or more, the electric conductivity of the non-aqueous electrolyte tends to be sufficient. When the concentration of the electrolyte is 2 mol / L or less, the increase in the viscosity of the non-aqueous electrolyte is suppressed, and thus the electric conductivity tends to increase. As the electric conductivity of the non-aqueous electrolyte increases, the performance of the lithium-ion secondary battery tends to improve.

[0070] (Separator) The separator is not particularly limited as long as it has ion permeability while electronically insulating between the positive electrode and the negative electrode, and has resistance to oxidation on the positive electrode side and reduction on the negative electrode side. As a material (material quality) of the separator that satisfies such characteristics, resins, inorganic substances, etc. are used. As the resin, olefin polymers, fluorine polymers, cellulose polymers, polyimides, nylons, etc. are used. It is preferably selected from materials that are stable to non-aqueous electrolytes and have excellent liquid retention properties, and it is preferable to use a porous sheet or non-woven fabric made of polyolefins such as polyethylene and polypropylene as raw materials. As the inorganic substance, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, glass, etc. are used. For example, a material obtained by attaching the above inorganic substance in fiber shape or particle shape to a base material in the shape of a non-woven fabric, a woven fabric, or a thin film such as a microporous film can be used as a separator. As the thin film-shaped base material, those with a pore diameter of 0.01 μm to 1 μm and an average thickness of 5 μm to 50 μm are preferably used. Also, a material obtained by forming a composite porous layer of the above inorganic substance in fiber shape or particle shape using a binder such as a resin can be used as a separator. Further, this composite porous layer can be formed on the surface of another separator to form a multilayer separator. Furthermore, this composite porous layer can be formed on the surface of the positive electrode or the negative electrode to be used as a separator.

[0071] (Other components) As other components of the lithium ion secondary battery, a rupture valve may be provided. By the opening of the rupture valve, the pressure rise inside the battery can be suppressed, and the safety can be improved. Also, a component that releases an inert gas (for example, carbon dioxide) as the temperature rises may be provided. By providing such a component, when the temperature inside the battery rises, the rupture valve can be quickly opened by the generation of the inert gas, and the safety can be improved. As the material used for the above component, lithium carbonate, polyethylene carbonate, polypropylene carbonate, etc. are preferable. Next, with reference to the drawings, embodiments in which the present disclosure is applied to a cylindrical lithium-ion secondary battery of the 18650 type will be described. FIG. 1 is a cross-sectional view of a lithium-ion secondary battery to which the present disclosure is applied.

[0072] (Configuration example of a lithium-ion secondary battery) A configuration example of a lithium-ion secondary battery is shown in FIG. 1. In the lithium-ion secondary battery 1 shown in FIG. 1, an electrode winding group 5 in which a strip-shaped positive electrode plate 2 and a negative electrode plate 3 are wound in a cross-sectional spiral shape via a separator 4 is housed in a battery container 6. A positive electrode tab terminal having one end fixed to the positive electrode plate 2 is led out from the upper end surface of the electrode winding group 5. The other end of the positive electrode tab terminal is joined to the lower surface of a disk-shaped battery lid that is disposed above the electrode winding group 5 and serves as a positive electrode external terminal. On the other hand, a negative electrode tab terminal having one end fixed to the negative electrode plate 3 is led out from the lower end surface of the electrode winding group 5. The other end of the negative electrode tab terminal is joined to the inner bottom of the battery container 6. Therefore, the positive electrode tab terminal and the negative electrode tab terminal are led out to opposite sides of both end surfaces of the electrode winding group 5, respectively. Note that an insulating coating (not shown) is provided on the entire outer peripheral surface of the electrode winding group 5. The battery lid is caulked and fixed to the upper part of the battery container 6 via an insulating resin gasket. For this reason, the inside of the lithium-ion secondary battery 1 is sealed. Further, a non-aqueous electrolyte (not shown) is poured into the battery container 6.

[0073] <Transport method of the negative electrode material> The transport method of the negative electrode material of the present disclosure is a transport method of the negative electrode material including a step of transporting the negative electrode material in the container as described above. In the above method, the transport method is not particularly limited and can be selected from land transport, sea transport, water transport, air transport, etc. The means of transport is not particularly limited and can be selected from railways, trucks, ships, airplanes, etc. In the above method, since the negative electrode material is transported in the state of the negative electrode material in the container as described above, deterioration of the negative electrode material is effectively suppressed even when transporting in a high-temperature and high-humidity environment. For this reason, for example, it can be suitably used when transporting the negative electrode material by sea across the equator. In the above method, the period from the destination to the arrival at the arrival point is not particularly limited. For example, it may be selected from between 1 day and 1 year.

[0074] The details and preferred embodiments of the container and the negative electrode material used in the above method are the same as the details and preferred embodiments of the container and the negative electrode material in the negative electrode material in a container described above.

[0075] <Negative electrode material storage container> The negative electrode material storage container of the present disclosure is a container for storing a negative electrode material that is a carbon material having a micropore volume of 0.40×10 -3 m 3 / kg or less, and is a negative electrode material storage container having a water vapor transmission rate of 150 g / (m 2 ·d) (40°C / 90%RH) or less.

[0076] The above negative electrode material storage container is used for storing a negative electrode material that is a carbon material having a micropore volume of 0.40×10 -3 m 3 / kg or less. By using the above negative electrode material storage container, deterioration of the negative electrode material during storage in a high-temperature and high-humidity environment is effectively suppressed.

[0077] The details and preferred embodiments of the negative electrode material storage container and the negative electrode material stored using the same are the same as the details and preferred embodiments of the container and the negative electrode material in the negative electrode material in a container described above.

[0078] The negative electrode material storage container may be deformable or non-deformable. When the purpose of putting the negative electrode material into the negative electrode material storage container is transportation of the negative electrode material (particularly long-distance transportation such as import and export), the negative electrode material storage container is preferably deformable. Examples of the deformable negative electrode material storage container include bag-shaped containers such as flexible containers.

[0079] <Method for storing negative electrode material> The method for storing a negative electrode material of the present disclosure is to store a negative electrode material that is a carbon material having a micropore volume of 0.40×10 -3 m 3 / kg or less in a container having a water vapor transmission rate of 150 g / (m 2·d) A method for storing a negative electrode material, including a step of storing it in a container at a temperature of (40°C / 90%RH) or lower.

[0080] According to the above method, when storing a negative electrode material that is a carbon material with a micropore volume of 0.40×10 -3 m 3 / kg or less in a high-temperature and high-humidity environment, the deterioration of the negative electrode material is effectively suppressed.

[0081] Details and preferred embodiments of the container and the negative electrode material used in the above method are the same as those of the container and the negative electrode material in the negative electrode material in a container described above.

[0082] The container may be deformable or non-deformable. When the purpose of putting the negative electrode material into the container is the transportation of the negative electrode material (especially long-distance transportation such as import and export), the container is preferably deformable. Examples of deformable containers include bag-shaped containers such as flexible containers.

[0083] <Method for manufacturing a negative electrode> The method for manufacturing a negative electrode of the present disclosure includes a step of taking out the negative electrode material from the container of the negative electrode material in a container described above, and a step of manufacturing a negative electrode using the negative electrode material taken out from the container, and is a method for manufacturing a negative electrode.

[0084] In the above method, the step of taking out the negative electrode material from the container and the step of manufacturing a negative electrode using the negative electrode material taken out from the container may be performed continuously.

[0085] In a general method for manufacturing a negative electrode, the manufacturing line is designed to manufacture a negative electrode by sucking it up from the upper part of a non-deformable container such as a drum or using the negative electrode material taken out by inverting the container. Therefore, when the negative electrode material carried into the manufacturing site is in a deformable container, a step of transferring the negative electrode material to a non-deformable container occurs. By continuously performing the step of taking out the negative electrode material from the container and the step of manufacturing the negative electrode using the negative electrode material (that is, without going through the operation of transferring the negative electrode material taken out from the container to another container), the productivity can be improved. The method of taking out the negative electrode material from the deformable container is not particularly limited, and examples include a method of opening and taking out the lower part of the lifted container, a method of sucking it up from the upper part of the container, and the like.

[0086] The details and preferred embodiments of the container and the negative electrode material used in the above method are the same as the details and preferred embodiments of the container and the negative electrode material in the negative electrode material in the container described above. The method of manufacturing the negative electrode material in the above method is not particularly limited and can be carried out by a known method.

Example

[0087] Hereinafter, the above-described embodiments will be described in more detail based on examples. Note that the present disclosure is not limited by the following examples.

[0088] (1) Fabrication of negative electrode material 100 parts by mass of spherical natural graphite and 10 parts by mass of coal tar pitch (softening point 90 ° C, residual carbon rate (carbonization rate) 50%) were mixed to obtain a mixture. Next, the mixture was heat-treated to produce graphite particles having a low-crystalline carbon layer on the surface. The heat treatment was performed by raising the temperature from 25 ° C to 1000 ° C at a heating rate of 200 ° C / hour under nitrogen flow and holding at 1000 ° C for 1 hour. The obtained graphite particles were crushed with a cutter mill and sieved with a 300-mesh sieve, and the fraction passing through the sieve was used as negative electrode material 1.

[0089] Graphite particles obtained in the same manner as negative electrode material 1 except that the heat treatment temperature was changed to 900 ° C were used as negative electrode material 2. Graphite particles obtained in the same manner as negative electrode material 1 except that the heat treatment temperature was changed to 850 ° C were used as negative electrode material 3. The obtained negative electrode materials 1 to 3 had the following micropore volume, volume average particle diameter, Raman R value, and BET specific surface area.

[0090] <Negative electrode material 1> Micropore volume: 0.18×10 -3 m 3 / kg Volume average particle diameter: 10 μm R value: 0.34 BET specific surface area: 4.5 m 2 / g

[0091] <Negative electrode material 2> Micropore volume: 0.34×10 -3 m 3 / kg Volume average particle diameter: 15 μm R value: 0.40 BET specific surface area: 3.5 m 2 / g

[0092] <Negative electrode material 3> Micropore volume: 0.55×10 -3 m 3 / kg Volume average particle diameter: 10 μm R value: 0.42 BET specific surface area: 4.0 m 2 / g

[0093] (2) Storage test Negative electrode materials 1 to 3 were each filled into a container made of ultra-high molecular weight polyethylene with a volume of 20,000 cm 3 (height 80 cm, bottom area 250 cm 2 ) and a water vapor transmission rate of 7.5 g / (m 2 ·d) (40 °C / 90% RH), and sealed. The filling rate of the negative electrode material was 70%. Subsequently, a storage test was carried out by leaving the containers filled with the negative electrode material in an environment of 80 °C and 90% RH for 2160 hours. For comparison, the same storage test was also carried out on the containers filled with negative electrode material 1 or negative electrode material 3 without sealing (no container).

[0094] (3) Measurement of initial efficiency The negative electrode plate was fabricated as follows. To each of the negative electrode materials 1 to 3 after the storage test, carboxymethyl cellulose (CMC) as a thickening agent and styrene butadiene rubber (SBR) as a binder were added. The mass ratio of these was negative electrode material: CMC: SBR = 98: 1: 1. Purified water, which is a dispersion solvent, was added thereto and kneaded to form slurries for each example and comparative example. This slurry was applied to both sides of a rolled copper foil with an average thickness of 10 μm, which is a current collector for the negative electrode, substantially evenly and homogeneously in a predetermined amount. The density of the negative electrode mixture layer was 1.3 g / cm 3 was set.

[0095] A negative electrode plate punched out to a size of 14 mm in diameter and a lithium metal plate punched out to a size of 15 mm in diameter were prepared as the negative electrode and the positive electrode, respectively. A coin-type battery was fabricated with a single-layer separator of polyethylene with an average thickness of 30 μm (trade name: Hypore, manufactured by Asahi Kasei Corporation, "Hypore" is a registered trademark) sandwiched therebetween. As the non-aqueous electrolyte for the coin-type battery, ethylene carbonate (EC), which is a cyclic carbonate, dimethyl carbonate (DMC), which is a chain carbonate, and ethyl methyl carbonate (EMC) were mixed in a mixed solvent such that their volume ratios were 2: 3: 2, and lithium hexafluorophosphate (LiPF6) as a lithium salt (electrolyte) was dissolved therein at a concentration of 1.2 mol / L, and furthermore vinylene carbonate (VC) was added at 1.0 mass%.

[0096] The fabricated coin-type battery was charged at a constant current of 0.2 CA to 0 V (Li / Li+) in an environment at 25°C, and then charged at a constant voltage with the voltage at the time when 0 V (Li / Li+) was reached until the current value became 0.01 CA (first charge). Thereafter, it was discharged at a constant current of 0.2 CA until 1.5 V (first discharge). A 30-minute rest was inserted between each charge and discharge. The value obtained by dividing the first charge (mAh) by the mass (g) of the negative electrode material contained in the negative electrode used was defined as the first charge capacity. Similarly, the value obtained by dividing the first discharge (mAh) by the mass (g) of the negative electrode material contained in the negative electrode used was defined as the first discharge capacity. The first efficiency was calculated from the following formula. Initial efficiency (%) = (Initial discharge capacity (mAh / g) / Initial charge capacity (mAh / g)) × 100

[0097] (4) Evaluation of storage characteristics The negative electrode prepared in the same manner as the measurement of the initial efficiency and the positive electrode prepared by the following method were each cut into a predetermined size, and a laminate in a state where a single-layer separator of polyethylene with an average thickness of 30 μm (product name: Hypore, manufactured by Asahi Kasei Corporation, "Hypore" is a registered trademark) was sandwiched between them was wound to form a roll-shaped electrode body. At this time, the lengths of the positive electrode, negative electrode, and separator were adjusted so that the diameter of the electrode body became 17.15 mm. A current collector lead was attached to this electrode body, inserted into a 18650-type battery case, and then a non-aqueous electrolyte was injected into the battery case. As the non-aqueous electrolyte, ethylene carbonate (EC) which is a cyclic carbonate, dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) which are chain carbonates were mixed in a volume ratio of 2:3:2, and lithium hexafluorophosphate (LiPF6) as a lithium salt (electrolyte) was dissolved at a concentration of 1.2 mol / L. Vinylene carbonate (VC) was added at 1.0 mass%. Finally, the battery case was sealed to complete a lithium-ion secondary battery.

[0098] (Method for preparing positive electrode) As the positive electrode active material, layered lithium-nickel-manganese-cobalt composite oxide (NMC, BET specific surface area is 0.4 m 2 / g, an average particle diameter (d50) of 6.5 μm) was used. To this positive electrode active material, acetylene black (trade name: HS-100, average particle diameter 48 nm (catalog value of Denka Co., Ltd.), manufactured by Denka Co., Ltd.) as a conductive agent and polyvinylidene fluoride as a binder were sequentially added and mixed to obtain a mixture of the positive electrode material. The mass ratio was set to positive electrode active material:conductive agent:binder = 90:5:5. Further, N-methyl-2-pyrrolidone (NMP), which is a dispersion solvent, was added to the above mixture and kneaded to obtain a slurry-like positive electrode mixture. The positive electrode mixture was applied substantially evenly and homogeneously to both sides of an aluminum foil with an average thickness of 20 μm, which is a current collector for the positive electrode. Then, a drying treatment was performed, and it was densified by pressing until the density reached 2.7 g / cm 3 was achieved. The coating amount per side of the positive electrode mixture was such that the mass of the solid content of the positive electrode mixture was 40 g / m 2 was achieved.

[0099] The fabricated lithium-ion secondary battery was charged at a constant current of 0.5 C to 4.2 V in an environment at 25°C, and then charged at a constant voltage at 4.2 V until the current value reached 0.01 C when 4.2 V was reached. Then, it was discharged at a constant current of 0.5 C to 2.7 V. This was carried out for 3 cycles. A 30-minute rest was inserted between each charge and discharge. The lithium-ion secondary battery after 3 cycles is referred to as the "battery in the initial state".

[0100] Using the battery in the initial state, the storage characteristics were evaluated according to the following procedure. (1) The battery in the initial state was charged at a constant current of 0.5 C to 4.2 V, and then charged at a constant voltage of 4.2 V until the current value reached 0.01 C. (2) After a 30-minute rest period, it was discharged at a constant current of 0.5 C to 2.7 V. The discharge capacity A (mAh) at this time was measured. (3) After a 30-minute rest period, it was charged at a constant current of 0.5 C to 4.2 V, and then charged at a constant voltage of 4.2 V until the current value reached 0.01 C. (4) The battery in (3) was left at 60°C for 30 days. (5) It was discharged at a constant current of 0.5 CA until 2.7 V. The discharge capacity B (mAh) at this time was measured. (6) From the discharge capacity A and the discharge capacity B, the storage characteristics were calculated using the following formula. Storage characteristics (%) = (discharge capacity B / discharge capacity A) × 100

[0101]

Table 1

[0102] As shown in Table 1, for Example 1 and Example 2 in a state where the negative electrode materials 1 and 2 with a micropore volume of 0.40×10 -3 m 3 / kg or less were stored in a container with a water vapor transmission rate of 150 g / (m 2 ·d) (40°C / 90%RH) or less, the values of the initial efficiency and storage characteristics after the storage test were large, and it is considered that the deterioration of the negative electrode material was effectively suppressed when stored in a high-temperature and high-humidity environment.

[0103] For Comparative Example 1 in a state where the negative electrode material 3 with a micropore volume exceeding 0.40×10 -3 m 3 / kg was stored in a container with a water vapor transmission rate of 150 g / (m 2 ·d) (40°C / 90%RH) or less, and for Comparative Example 2 in a state where the negative electrode material 1 with a micropore volume of 0.40×10 -3 m 3 / kg or less was not stored in a container, the values of the initial efficiency and storage characteristics after the storage test were small, and it is considered that the deterioration of the negative electrode material advanced when stored in a high-temperature and high-humidity environment.

[0104] For the difference in the initial efficiency and storage characteristics after the storage test between the state where the negative electrode material 3 with a micropore volume exceeding 0.40×10 -3 m 3 / kg was stored in a container (Comparative Example 1) and the state where the negative electrode material 3 was not stored in a container (Comparative Example 3), the micropore volume was 0.40×10 -3 m 3It is smaller than the difference in the initial efficiency and storage characteristics after the storage test between the state where the negative electrode material 1 below / kg is accommodated in the container (Example 1) and the state where the negative electrode material 1 is not accommodated in the container (Comparative Example 2). From this, it can be seen that the negative electrode material in the container of the present disclosure has a remarkable effect of suppressing the deterioration when the micropore volume of the negative electrode material is 0.40×10 -3 m 3 / kg or less.

[0105] The disclosure of International Patent Application No. 2020 / 045907 is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described in this specification are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually stated to be incorporated by reference.

Claims

1. comprising a container and a negative electrode material accommodated in the container, The container has a water vapor transmission rate of 150 g / (m ２ ·d) (40 °C / 90% RH) or less, and the negative electrode material is a carbon material with a micropore volume of 0.40 × 10 －３ m ３ / kg or less. The negative electrode material is in a container.

2. The volume of the container is 6000 cm ３ or more and 40000 cm ３ or less. The negative electrode material in a container according to claim 1.

3. The filling rate of the negative electrode material in the container is 20% or more and 90% or less. The negative electrode material in a container according to Claim 1 or Claim 2.

4. The negative electrode material is a negative electrode material of a lithium-ion secondary battery. The negative electrode material in a container according to any one of Claims 1 to 3.

5. The container contains polyethylene. The negative electrode material in a container according to any one of Claims 1 to 4.

6. The container is deformable. The negative electrode material in a container according to any one of Claims 1 to 5.

7. A method for transporting a negative electrode material, comprising a step of transporting the negative electrode material in a container according to any one of Claims 1 to 6.

8. The method of transportation is sea transportation. The method for transporting a negative electrode material according to Claim 7.

9. A container for storing a negative electrode material which is a carbon material having a micropore volume of 0.40×10 －３ m ３ / kg or less, and having a water vapor transmission rate of 150 g / (m ２ ·d) (40°C / 90% RH) or less, the negative electrode material storage container.

10. A method for storing a negative electrode material, comprising the step of storing a negative electrode material, which is a carbon material having a micropore volume of 0.40×10 －３ m ３ / kg or less, in a container having a water vapor transmission rate of 150 g / (m ２ ·d) (40°C / 90% RH) or less.

11. a step of taking out the negative electrode material from the container of the negative electrode material in a container according to any one of Claims 1 to 6; and a step of manufacturing a negative electrode using the negative electrode material taken out from the container. A method for manufacturing a negative electrode.

12. The step of taking out the negative electrode material from the container and the step of manufacturing a negative electrode using the negative electrode material taken out from the container are continuously performed. The method for manufacturing a negative electrode according to Claim 11.

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