JP2016004683A - Lithium ion battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium ion battery excellent in storage stability, high in input/output, and high in volume energy density.SOLUTION: A lithium ion battery includes: a wound electrode group comprising a positive electrode, a negative electrode and a separator wound therein; and an electrolyte. The positive electrode includes a collector and a positive electrode mixture formed to the collector. The positive electrode mixture contains a spinel type lithium-manganese oxide, graphite, acetylene black and aluminum silicate.

Description

  The present invention relates to a lithium ion battery.

  Lithium ion batteries are secondary batteries with high energy density, and are used as power sources for portable devices such as notebook computers and mobile phones, taking advantage of their characteristics. There are various types of lithium ion batteries. Cylindrical lithium ion batteries adopt a wound structure of a positive electrode, a negative electrode, and a separator. For example, a positive electrode material and a negative electrode material are respectively applied to two strip-shaped metal foils, a separator is sandwiched therebetween, and these laminated bodies are wound in a spiral shape to form a wound group. The wound group is accommodated in a cylindrical battery can serving as a battery container, and after injecting an electrolytic solution, the cylindrical lithium ion battery is formed.

  As the cylindrical lithium ion battery, a 18650 type lithium ion battery is widely used as a consumer lithium ion battery. The outer diameter of the 18650 type lithium ion battery is 18 mm in diameter and is small with a height of about 65 mm. As the positive electrode active material of the 18650 type lithium ion battery, lithium cobaltate, which is characterized by high capacity and long life, is mainly used, and the battery capacity is generally 1.0 Ah to 2.0 Ah (3.7 Wh to 7. 4 Wh).

  In recent years, lithium-ion batteries are expected to be used not only for consumer applications such as portable devices but also for large-scale power storage systems for natural energy such as solar power and wind power generation. In a large-scale power storage system, the amount of power per system is required on the order of several MWh. For example, Patent Document 1 below discloses a cylindrical lithium ion battery having an electrode winding group in which a positive electrode, a negative electrode, and a separator are wound around a cylindrical battery container. This battery has a discharge capacity of 30 Ah or more, a positive electrode active material mixture containing lithium manganese composite oxide is used for the positive electrode, and a negative electrode active material mixture containing amorphous carbon is used for the negative electrode. Yes.

International Publication No. 2013/128677

In recent years, lithium ion secondary batteries have attracted attention as high input / output power sources used in electric vehicles, hybrid electric vehicles, and the like. In such an application to the automobile field, in addition to high output, high capacity, and long life, excellent input characteristics are also required for improving energy utilization efficiency by regeneration.
However, the lithium ion secondary battery described in Patent Document 1 revealed that the storage characteristics at high temperature (hereinafter sometimes referred to as storage characteristics) are not sufficient from the examination results of the present inventors. .
The object of the present invention has been made in view of the above problems, and is to provide a lithium ion battery having excellent storage characteristics.

A lithium ion battery according to the present invention is a lithium ion battery comprising an electrode winding group in which a positive electrode, a negative electrode, and a separator are wound, and an electrolytic solution, and the positive electrode is connected to the current collector and the current collector. The positive electrode composite material includes spinel-type lithium / manganese oxide, graphite, acetylene black, and aluminum silicate.
According to the lithium ion battery according to the present invention, excellent storage characteristics can be obtained.

It is preferable that content of the said aluminum silicate is 1 mass% or more and 5 mass% or less with respect to the whole quantity of positive electrode compound material. In this case, excellent input / output characteristics can be obtained in addition to the storage characteristics.
The content of the acetylene black is preferably 0.1% by mass or more and 15% by mass or less with respect to the total amount of the positive electrode mixture. In this case, more excellent input / output characteristics can be obtained in addition to the storage characteristics.

  ADVANTAGE OF THE INVENTION According to this invention, the lithium ion battery excellent in a storage characteristic can be provided.

It is sectional drawing of the lithium ion battery of this Embodiment.

  In the following embodiments, when ranges are shown as A to B, A or more and B or less are shown unless otherwise specified.

(Embodiment)
First, an outline of the lithium ion battery will be briefly described. The lithium ion battery has a positive electrode, a negative electrode, a separator, and an electrolytic solution in a battery container. A separator is disposed between the positive electrode and the negative electrode.

  When charging the lithium ion battery, a charger is connected between the positive electrode and the negative electrode. At the time of charging, lithium ions inserted into the positive electrode active material are desorbed and released into the electrolytic solution. The lithium ions released into the electrolytic solution move in the electrolytic solution, pass through a separator made of a microporous film, and reach the negative electrode. The lithium ions that have reached the negative electrode are inserted into the negative electrode active material constituting the negative electrode.

  When discharging, an external load is connected between the positive electrode and the negative electrode. At the time of discharging, the lithium ions inserted into the negative electrode active material are desorbed and released into the electrolytic solution. At this time, electrons are emitted from the negative electrode. Then, the lithium ions released into the electrolytic solution move in the electrolytic solution, pass through a separator made of a microporous film, and reach the positive electrode. The lithium ions reaching the positive electrode are inserted into the positive electrode active material constituting the positive electrode. At this time, when lithium ions are inserted into the positive electrode active material, electrons flow into the positive electrode. In this way, discharge is performed by the movement of electrons from the negative electrode to the positive electrode.

  In this manner, charging / discharging can be performed by inserting and desorbing lithium ions between the positive electrode active material and the negative electrode active material. A configuration example of an actual lithium ion battery will be described later (see, for example, FIG. 1).

  Next, the positive electrode, the negative electrode, the electrolytic solution, the separator, and other components of the lithium ion battery will be sequentially described.

1. Positive electrode In this embodiment, the positive electrode shown below is applicable to a high-capacity, high-input / output lithium ion battery. The positive electrode (positive electrode plate) of the present embodiment is made of a current collector and a positive electrode mixture formed thereon. The positive electrode mixture is a layer including at least a positive electrode active material provided on the current collector, and includes spinel-type lithium manganese oxide (sp-Mn) in the present embodiment. Moreover, this positive electrode mixture contains at least aluminum silicate, graphite, and acetylene black in addition to the positive electrode active material. Moreover, this positive electrode compound material may be formed (coated) on both surfaces of the current collector, for example.

Moreover, as a positive electrode active material, in addition to spinel type lithium manganese oxide (sp-Mn), lithium-containing composite metal oxide other than spinel type lithium manganese oxide, olivine type lithium salt, chalcogen compound, manganese dioxide, etc. May be included. 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 with a different element. Here, examples of the different element include Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, and B. Mn, Al, Co, Ni, Mg and the like are preferable. One kind or two or more kinds of different elements may be used. Among these, lithium-containing composite metal oxides are preferable. Examples of the lithium-containing composite metal oxide include LixCoO ₂ , LixNiO ₂ , LixCoyNi ₁ -yO ₂ , LixCoyM ₁ -yOz, LixNi ₁ -yMyOz, LiMPO ₄ , Li ₂ MPO ₄ F (wherein M is Na , Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, V, and B. x = 0 to 1. 2, y = 0 to 0.9, z = 2.0 to 2.3). Here, x value which shows the molar ratio of lithium increases / decreases by charging / discharging. Further, as the olivine type lithium salts, for example, LiFePO _4, and the like. Examples of the chalcogen compound include titanium disulfide and molybdenum disulfide. A positive electrode active material can be used individually by 1 type, or can use 2 or more types together.

  As the positive electrode active material, in addition to spinel type lithium / manganese oxide (sp-Mn), a layered type lithium / nickel / manganese / cobalt composite oxide (NMC) is used in combination from the viewpoint of increasing capacity. preferable. When spinel type lithium / manganese oxide (sp-Mn) and layered type lithium / nickel / manganese / cobalt composite oxide (NMC) are used as the positive electrode active material, the mass ratio (mixing ratio) of NMC / sp-Mn Is preferably 10/90 or more and 70/30 or less.

  When the mass ratio (NMC / sp-Mn) of the active material is 10/90 or more, the energy density of the battery tends to be improved. On the other hand, when the mass ratio (NMC / sp-Mn) of the active material is less than 70/30, the safety tends to be improved.

Moreover, it is preferable to use what is represented by the following compositional formula (Formula 2) as spinel type lithium manganese oxide (sp-Mn).
Li _{(1 + η)} Mn _(2-λ) M ′ _λ O ₄ (Chemical formula 2)
In the above composition formula (Formula 2), (1 + η) represents the composition ratio of Li, (2-λ) represents the composition ratio of Mn, and λ represents the composition ratio of the element M ′. The composition ratio of O (oxygen) is 4.
The element M ′ is 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 and 0 ≦ λ ≦ 0.1.

Further, as the layered lithium / nickel / manganese / cobalt composite oxide (NMC), it is preferable to use one represented by the following composition formula (Formula 1).
Li _{(1 + δ)} Mn _x Ni _y Co _(1-xyz) M _z O ₂ (Formula 1)
In the above composition formula (Formula 1), (1 + δ) is a composition ratio of Li (lithium), x is a composition ratio of Mn (manganese), y is a composition ratio of Ni (nickel), (1-xyz) Indicates the composition ratio of Co (cobalt). z represents the composition ratio of the element M. The composition ratio of O (oxygen) is 2.
The element M includes Ti (titanium), Zr (zirconium), Nb (niobium), Mo (molybdenum), W (tungsten), Al (aluminum), Si (silicon), Ga (gallium), Ge (germanium), and Sn. It is at least one element selected from the group consisting of (tin).
-0.15 <δ <0.15, 0.1 <x ≦ 0.5, 0.6 <x + y + z ≦ 1.0, 0 ≦ z ≦ 0.1.

  As described above, a mixture of spinel type lithium / manganese oxide (sp-Mn) and layered type lithium / nickel / manganese / cobalt composite oxide (NMC) is used as the positive electrode active material (positive electrode active material). Thus, even when the capacity is increased, the stability of the positive electrode during charging can be improved and heat generation can be suppressed. As a result, a battery with excellent safety can be provided. In addition, charge / discharge cycle characteristics and storage characteristics can be improved.

  As the element M ′ in the above composition formula (Formula 1), Mg or Al is preferably used. By using Mg or Al, the battery life can be extended. In addition, the safety of the battery can be improved.

  When spinel type lithium manganese oxide (sp-Mn) is used as the positive electrode active material, since Mn in the compound is stable in the charged state, heat generation due to the charging reaction can be suppressed. Thereby, the safety | security of a battery can be improved. That is, heat generation at the positive electrode can be suppressed, and the safety of the battery can be improved.

  Furthermore, by adding the element M ′, elution of Mn can be reduced, so that storage characteristics and charge / discharge cycle characteristics can be improved.

  Hereinafter, the positive electrode mixture and the current collector will be described in detail. The positive electrode mixture contains a positive electrode active material, a binder, and the like, and is formed on the current collector. Although there is no restriction | limiting in the formation method, it forms as follows, for example. Other materials such as a positive electrode active material, a conductive material, a binder, and a thickener used as necessary are mixed in a dry form to form a sheet, which is then pressure-bonded to a current collector (dry method). In addition, other materials such as a positive electrode active material, a conductive material, a binder, and a thickener used as necessary are dissolved or dispersed in a dispersion solvent to form a slurry, which is applied to a current collector and dried. (Wet method).

  As the particles of the positive electrode active material, those in the form of a lump, polyhedron, sphere, ellipsoid, plate, needle, column, etc. are used. Among them, it is preferable that the primary particles are aggregated to form secondary particles, and the shape of the secondary particles is spherical or elliptical.

  In an electrochemical element such as a battery, the active material in the electrode expands and contracts as it is charged / discharged, so that the active material is easily damaged by the stress or the conductive path is broken. For this reason, it is preferable to use particles in which primary particles are aggregated to form secondary particles, rather than using single particles of only primary particles, because the stress of expansion and contraction can be relieved and the above deterioration can be prevented. In addition, it is preferable to use spherical or oval spherical particles rather than plate-like particles having axial orientation, since the orientation in the electrode is reduced, so that the expansion and contraction of the electrode during charge / discharge is reduced. Further, it is preferable because other materials such as a conductive material are easily mixed uniformly when forming the electrode.

  Regarding the median diameter d50 of the positive electrode active material particles of spinel type lithium manganese oxide (sp-Mn) (when the primary particles are aggregated to form secondary particles, the median diameter d50 of the secondary particles), The range is as follows. The lower limit of the range is 0.1 μm or more, preferably 0.5 μm or more, more preferably 1 μm or more, further preferably 3 μm or more, and the upper limit is 20 μm or less, preferably 18 μm or less, more preferably 16 μm or less, and even more preferably. Is 15 μm or less. If it is less than the above lower limit, the tap density (fillability) may be reduced, and a desired tap density may not be obtained. There is a risk of inviting. Moreover, when the said upper limit is exceeded, there exists a possibility that a mixing property with other materials, such as a binder and a electrically conductive material, may fall at the time of formation of an electrode. Therefore, when this mixture is slurried and applied, it may not be applied uniformly, which may cause problems such as streaking. Here, the tap density (fillability) may be improved by mixing two or more kinds of positive electrode active materials having different median diameters d50. The median diameter d50 can be obtained from the particle size distribution obtained by the laser diffraction / scattering method.

  The range of the average particle size of the primary particles in the case where the primary particles are aggregated to form secondary particles is as follows. The lower limit of the range is 0.01 μm or more, preferably 0.05 μm or more, more preferably 0.08 μm or more, particularly preferably 0.1 μm or more, and the upper limit is 3 μm or less, preferably 2 μm or less, more preferably 1 μm. Hereinafter, it is particularly preferably 0.6 μm or less. When the above upper limit is exceeded, it becomes difficult to form spherical secondary particles, and battery performance such as output characteristics may be reduced due to a decrease in tap density (fillability) and a decrease in specific surface area. Moreover, if it is less than the said minimum, there exists a possibility of producing problems, such as the reversibility of charging / discharging degrading by crystallinity fall.

The range of the BET specific surface area of the positive electrode active material particles such as spinel type lithium manganese oxide (sp-Mn) is as follows. The lower limit of the range is 0.2 m ² / g or more, preferably 0.3 m ² / g or more, more preferably 0.4 m ² / g or more, and the upper limit is 4.0 m ² / g or less, preferably 2 .5m ² / g, more preferably not more than 1.5 m ² / g. If it is less than the said minimum, there exists a possibility that battery performance may fall. When the above upper limit is exceeded, the tap density is difficult to increase, and the miscibility with other materials such as a binder and a conductive material may be reduced. Therefore, there is a possibility that applicability at the time of slurrying and applying this mixture is deteriorated. The BET specific surface area is a specific surface area (area per unit g) determined by the BET method.

  Examples of the conductive material for the positive electrode include natural graphite, graphite such as artificial graphite, and acetylene black.

The acetylene black used in the present invention is preferably particles having an average particle diameter of 20 nm or more and 100 nm or less, and is not particularly limited as long as it is in this particle diameter range. Here, examples of the particles include granular, flake-like, spherical, columnar, and irregular shapes. The “granular” is not an irregular shape but a shape having almost equal dimensions (JIS Z2500: 2000). The flake shape (strip shape) is a plate-like shape (JIS Z2500: 2000), and is also referred to as a scaly shape because it is thin like a scale. In the present invention, the result of SEM observation The aspect ratio (particle diameter a / average thickness t) is in the range of 2-100. The particle diameter a here is defined as the square root of the area S when the flaky particles are viewed in plan, and this is the particle diameter of the present application. The “spherical shape” is a shape substantially close to a sphere (see JIS Z2500: 2000). Further, the shape does not necessarily need to be spherical, and the ratio of the major axis (DL) to the minor axis (DS) of the particle (DL) / (DS) (sometimes referred to as spherical coefficient or sphericity) is 1. It shall be in the range of .0 to 1.2, and the particle size shall mean the major axis (DL).
Examples of the columnar shape include a substantially cylindrical column and a substantially polygonal column, and the particle size refers to the height of the column.

  When the average particle diameter of acetylene black contained in the conductive material exceeds 100 nm, the number of contact points with the positive electrode active material is reduced, the conductive network between the active materials is hindered, and the input / output characteristics of the battery tend to deteriorate. On the other hand, when the average particle size is less than 20 nm, the dispersibility in the positive electrode mixture is deteriorated, and the battery performance is significantly deteriorated due to an adverse effect such as segregation of acetylene black. Thus, the average particle diameter of acetylene black is preferably 20 nm or more and 100 nm or less, more preferably 30 nm or more and 80 nm or less, and particularly preferably 40 nm or more and 60 nm or less.

  The conductive material includes graphite (graphite) such as natural graphite and artificial graphite. The average particle size of the graphite is preferably 1 μm or more and 10 μm or less. The graphite preferably has a carbon network plane interlayer (d002) in the X-ray wide angle diffraction method of 0.3354 nm or more and 0.337 nm or less. From the viewpoint of charge / discharge characteristics of the battery, the content ratio of acetylene black and graphite is, for example, acetylene black A1 and graphite is A2, and the mass ratio (A1 / (A1 + A2)) is 0.1 or more and 0.9 or less. Preferably, it is 0.4 or more and 0.85 or less.

  The average particle diameter of the conductive material is an arithmetic average particle diameter obtained by measuring all the diameters of the particle images in the image taken with a scanning electron microscope taken at 200,000 times.

  The content of the conductive material is preferably 0.2% by mass or more, more preferably 0.5% by mass or more, still more preferably 1% by mass or more based on the total amount of the positive electrode mixture, and the upper limit of the content of the conductive material Is preferably 30% by mass or less, more preferably 20% by mass or less, and still more preferably 10% by mass or less. Within the above range, the battery capacity and input / output characteristics are excellent.

  Furthermore, the content of acetylene black contained in the conductive material is preferably 0.1% by mass or more and 15% by mass or less, and preferably 1% by mass or more with respect to the total amount of the positive electrode mixture, from the viewpoint of conductivity and high capacity. 10 mass% or less is more preferable, and 2 mass% or more and 5 mass% or less are further more preferable. Within the above range, the battery capacity and input / output characteristics are excellent.

Aluminum silicate is an oxide salt of Si and Al. Since Si and Al have different valences, there are many OH groups in the oxide salt of Si and Al, which has ion exchange ability.
Hereinafter, the aluminum silicate will be described in detail.

(Aluminum silicate)
Examples of the aluminum silicate in the present invention include allophane, kaolin, zeolite, saponite, and imogolite. Of these, imogolite is preferred.
The imogolite in the present invention is an aluminum silicate having an element molar ratio Si / Al of 0.3 to 1.0. Such imogolite, for _{example, nSiO 2 · Al 2 O 3} · mH 2 O [n = 0.6~2.0, m = 0 or] include those having a composition represented by.
Moreover, as imogolite, it is preferable that element molar ratio Si / Al is 0.3-1.0. The element molar ratio Si / Al of imogolite is more preferably 0.4 or more and 0.6 or less, and further preferably 0.45 or more and 0.55 or less. By setting the element molar ratio Si / Al within this range, the above tendency is further increased.

Imogolite preferably has a peak in the vicinity of 3 ppm in the ²⁷ Al-NMR spectrum. ^{As the 27} Al-NMR measuring apparatus, for example, AV400WB manufactured by Bruker BioSpin can be used. Specific measurement conditions are as follows.
Resonance frequency: 104MHz
Measuring method: MAS (single pulse)
MAS rotation speed: 10 kHz
Measurement area: 52 kHz
Number of data points: 4096
resolution (measurement area / number of data points): 12.7 Hz
Pulse width: 3.0 μsec
Delay time: 2 seconds Chemical shift value standard: 3.94 ppm of α-alumina
window function: exponential function Line Broadening coefficient: 10 Hz

In addition, imogolite preferably has peaks in the vicinity of 2θ = 26.9 ° and 40.3 ° in a powder X-ray diffraction spectrum using CuKα ray as an X-ray source. Further, for example, Rigaku Corporation: Geigerflex RAD-2X (trade name) can be used as the X-ray diffractometer.
In addition, from the viewpoint of storage properties, it is preferable that imogolite does not have a tubular product having a length of 50 nm or more when observed at a magnification of 100,000 with a transmission electron microscope (TEM). Observation of aluminum silicate with a transmission electron microscope (TEM) is performed at an acceleration voltage of 100 kV.

The aluminum silicate in the present invention may be synthesized, or a commercially available product may be purchased and used.
In addition, the content of aluminum silicate contained in the conductive material is preferably 1% by mass or more and 5% by mass or less, and preferably 1% by mass or more and 4% by mass or more based on the total amount of the positive electrode mixture from the viewpoint of conductivity and high capacity. More preferably, it is more preferably 1% by mass or less and 3% by mass or less. Within the above range, the battery capacity and input / output characteristics are excellent.

When synthesizing an aluminum silicate, a step of mixing a solution containing silicate ions and a solution containing aluminum ions to obtain a reaction product, and heating the reaction product in an aqueous medium in the presence of an acid And can have other steps as necessary. From the viewpoint of the yield of the obtained aluminum silicate and structure formation, etc., at least after the heat treatment step, preferably before and after the heat treatment step, a washing step for performing desalting and solid separation Is preferred.
After desalting the coexisting ions from the solution containing the reaction product, aluminum silicate, heat treatment in the presence of an acid enables efficient production of aluminum silicate with excellent metal ion adsorption capacity. it can. Here, examples of the coexisting ions include sodium ions, chloride ions, perchlorate ions, nitrate ions, sulfate ions, and the like.
This can be considered as follows, for example. An aluminum silicate having a regular structure is formed by heat-treating the aluminum silicate from which coexisting ions that inhibit the formation of the regular structure are removed in the presence of an acid. It can be considered that when imogolite has a regular structure, affinity for metal ions is improved and metal ions can be adsorbed efficiently.

In the aluminum silicate according to the present invention, carbon may be arranged on the surface of the aluminum silicate. The arranged carbon is arranged on at least a part or all of the surface of the aluminum silicate.
The method for disposing carbon on the surface of the aluminum silicate is not particularly limited, and examples thereof include a wet mixing method, a dry mixing method, and a chemical vapor deposition method. Wet mixing method (referred to as “wet method”) because the thickness of carbon applied to the surface of aluminum silicate can be easily adjusted, the reaction system can be easily controlled, and processing under atmospheric pressure is possible. Or a dry mixing method (sometimes referred to as “gas phase method”) is preferred.
In the case of the wet mixing method, for example, aluminum silicate and a solution in which a carbon source is dissolved in a solvent are mixed, the carbon source solution is adhered to the surface of the aluminum silicate, and the solvent is added as necessary. The carbon source can be carbonized and removed by heat treatment under an inert atmosphere after removal. In addition, when a carbon source does not melt | dissolve in a solvent, it can also be set as the dispersion liquid which disperse | distributed the carbon source in the dispersion medium.
In the case of the dry mixing method, for example, an aluminum silicate and a carbon source are mixed with each other to form a mixture, and the carbon source is carbonized by heat-treating the mixture in an inert atmosphere. Carbon can be imparted to the salt surface. In addition, when mixing aluminum silicate and a carbon source, you may perform the process (for example, mechanochemical process) which adds mechanical energy.

In the case of chemical vapor deposition, a known method can be applied. For example, by applying heat treatment to aluminum silicate in an atmosphere containing a gas obtained by vaporizing a carbon source, carbon is imparted to the surface of the aluminum silicate. Can do.
When carbon is imparted to the surface of the aluminum silicate by the above method, the carbon source is not particularly limited, and may be any compound that can leave carbon by heat treatment. Specifically, a phenol resin, Polymeric compounds such as styrene resin, polyvinyl alcohol, polyvinyl chloride, polyvinyl acetate, polybutyral; heat ethylene heavy end pitch, coal pitch, petroleum pitch, coal tar pitch, asphalt cracking pitch, polyvinyl chloride (PVC), etc. Examples include pitches such as naphthalene pitch produced by polymerizing PVC pitch, naphthalene and the like produced by decomposition in the presence of a super strong acid; polysaccharides such as starch and cellulose; and the like. These carbon sources may be used alone or in combination of two or more.

  The binder for the positive electrode active material is not particularly limited, and when the positive electrode mixture is formed by a coating method, a material having good solubility and dispersibility in the dispersion solvent is selected. Specific examples include resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose; SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), fluorine Rubbery polymers such as rubber, isoprene rubber, butadiene rubber, ethylene-propylene rubber; styrene / butadiene / styrene block copolymer or hydrogenated product thereof, EPDM (ethylene / propylene / diene terpolymer), styrene / Thermoplastic elastomeric polymers such as ethylene / butadiene / ethylene copolymers, styrene / isoprene / styrene block copolymers or hydrogenated products thereof; syndiotactic-1,2-polybutadiene, polyacetic acid Soft resinous polymers such as Nyl, ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer; polyvinylidene fluoride (PVdF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene Fluoropolymers such as copolymers and polytetrafluoroethylene / vinylidene fluoride copolymers; polymer compositions having ion conductivity of alkali metal ions (particularly lithium ions), and the like. Of these, one type may be used alone, or two or more types may be used in combination. 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.

  The content of the binder with respect to the total amount of the positive electrode mixture is preferably 0.1% by mass or more, more preferably 1% by mass or more, and still more preferably 3% by mass or more. The upper limit is preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably 30% by mass or less, and particularly preferably 10% by mass or less. By setting it as the said range, battery performance, such as cycling characteristics, can be made more favorable.

  In order to improve the packing density of the positive electrode active material, the layer formed on the current collector using the wet method or the dry method is preferably consolidated by a hand press, a roller press, or the like.

  The material of the current collector for the positive electrode is not particularly limited, and specific examples include metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum; and carbonaceous materials such as carbon cloth and carbon paper. Of these, metal materials, particularly aluminum, are preferred.

There is no restriction | limiting in particular as a shape of an electrical power collector, The material processed into various shapes can be used. Specific examples of the metal material include a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, an expanded metal, a punch metal, and a foam metal, and the carbonaceous material includes a carbon plate, a carbon thin film, A carbon cylinder etc. are mentioned. Among these, it is preferable to use a metal thin film. In addition, you may form a thin film suitably in mesh shape. The thickness of the thin film is arbitrary, but the range is as follows. The lower limit of the range is 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and the upper limit is 1 mm or less, preferably 100 μm or less, more preferably 50 μm or less. If it is less than the said minimum, intensity | strength required as a collector may be insufficient. Moreover, when the said upper limit is exceeded, flexibility will fall and workability may deteriorate.
The positive electrode mixture used in the present invention has a density of 2.4 g / cm ³ or more and 2.7 g / cm ³ or less, and a single-side coating amount on the current collector of 170 g / m ² or more and 250 g / m ² or less. Is preferred.
When the density is within the above range, the input / output characteristics can be further improved. From such a viewpoint, the single-side coating amount of the positive electrode mixture on the positive electrode current collector is more preferably 180 g / m ² or more and 230 g / m ² or less, and 185 g / m ² or more and 220 g / m ² or less. More preferably.

2. Negative electrode In this embodiment, the negative electrode shown below is applicable to a high-capacity, high-input / output lithium-ion battery. The negative electrode (negative electrode plate) of the present embodiment is composed of a current collector and a negative electrode mixture formed on both surfaces thereof. The negative electrode mixture contains a negative electrode active material that can electrochemically occlude and release lithium ions.

  Examples of the negative electrode active material include carbonaceous materials, metal oxides such as tin oxide and silicon oxide, metal composite oxides, lithium alloys such as lithium alone and lithium aluminum alloys, metals that can form alloys with lithium such as Sn and Si, and the like Is mentioned. These may be used alone or in combination of two or more. Among these, a carbonaceous material or a lithium composite oxide is preferable from the viewpoint of safety.

  The metal composite oxide is not particularly limited as long as it can occlude and release lithium, but Ti (titanium), Li (lithium) or a material containing both Ti and Li has a high current density charge / discharge. It is preferable from the viewpoint of characteristics.

  Carbonaceous materials include amorphous carbon, natural graphite, composite carbonaceous materials in which a film formed by dry CVD (Chemical Vapor Deposition) method or wet spray method is formed on natural graphite, resins such as epoxy and phenol Carbonaceous materials such as artificial graphite and amorphous carbon material obtained by firing using raw materials or pitch materials obtained from petroleum or coal as raw materials can be used.

  In addition, lithium metal that can occlude and release lithium by forming a compound with lithium, or a group 4 element such as silicon, germanium, and tin that can occlude and release lithium by forming a compound with lithium and inserting it in a crystal gap. Oxides or nitrides may be used.

In particular, the carbonaceous material is a material having high conductivity, and excellent in terms of low temperature characteristics and cycle stability. Among the carbonaceous materials, a material having a wide carbon network surface layer (d002) (amorphous carbon) is preferable from the viewpoint of high input / output characteristics. For the carbon network surface layer (d002), it is preferable to select a material of 0.39 nm or less from the viewpoint of battery characteristics. Examples of the material (amorphous carbon) having a wide carbon network surface layer (d002) include hard carbon and soft carbon. Soft carbon is preferred from the viewpoint of cycle characteristics. The soft carbon preferably has a carbon network plane interlayer (d002) in the X-ray wide angle diffraction method of 0.34 nm or more and 0.36 nm or less, more preferably 0.341 nm or more and 0.355 nm or less. More preferably, it is 342 nm or more and 0.35 nm or less.
Such a carbonaceous material is sometimes referred to as pseudo-anisotropic carbon. Further, as the negative electrode active material, a carbonaceous material having high conductivity such as graphite, amorphous, activated carbon or the like may be mixed and used.

  The negative electrode mixture is formed on the current collector. Although there is no restriction | limiting in the formation method, it forms using a dry method and a wet method similarly to a positive electrode compound material. The negative electrode active material is used in the form of powder (granular).

  Moreover, you may add the 2nd carbonaceous material of a property different from this to the 1st carbonaceous material used as a negative electrode active material as a electrically conductive material. The above properties indicate one or more characteristics of X-ray diffraction parameters, median diameter, aspect ratio, BET specific surface area, orientation ratio, Raman R value, tap density, true density, pore distribution, circularity, and ash content. .

  As the second carbonaceous material (conductive material), a highly conductive carbonaceous material such as graphite, amorphous, activated carbon or the like can be used. Specifically, 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. These may be used alone or in combination of two or more. Thus, by adding the second carbonaceous material (conductive material), there are effects such as reducing the resistance of the electrode.

  Regarding the content (addition amount, ratio, amount) of the second carbonaceous material (conductive material), the range of the content of the conductive material relative to the mass of the negative electrode mixture is as follows. The lower limit of the range is 1% by mass or more, preferably 2% by mass or more, more preferably 3% by mass or more, and the upper limit is 45% by mass or less, preferably 40% by mass or less. If it is less than the above lower limit, it is difficult to obtain the effect of improving conductivity, and if it exceeds the above upper limit, the initial irreversible capacity may be increased.

  There is no restriction | limiting in particular as a material of the electrical power collector for negative electrodes, As a specific example, metal materials, such as copper, nickel, stainless steel, nickel plating steel, are mentioned. Among these, copper is preferable from the viewpoint of ease of processing and cost.

  There is no restriction | limiting in particular as a shape of an electrical power collector, The material processed into various shapes can be used. Specific examples include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punch metal, and foam metal. Among these, a metal thin film is preferable, and a copper foil is more preferable. The copper foil includes a rolled copper foil formed by a rolling method and an electrolytic copper foil formed by an electrolytic method, both of which are suitable for use as a current collector.

  The thickness of the current collector is not limited, but when the thickness is less than 25 μm, its strength can be increased by using a strong copper alloy (phosphor bronze, titanium copper, Corson alloy, Cu—Cr—Zr alloy, etc.) rather than pure copper. Can be improved.

  The binder for the negative electrode active material is not particularly limited as long as it is a material that is stable to the non-aqueous electrolyte and the dispersion solvent used when forming the electrode. Specifically, resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, nitrocellulose; SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluorine rubber, NBR ( Acrylonitrile-butadiene rubber), rubber-like polymers such as ethylene-propylene rubber; styrene / butadiene / styrene block copolymer or hydrogenated product thereof; EPDM (ethylene / propylene / diene terpolymer), styrene / ethylene / Thermoplastic elastomeric polymer such as butadiene / styrene copolymer, styrene / isoprene / styrene block copolymer or hydrogenated product thereof; syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene -Soft resinous polymers such as vinyl acetate copolymer, propylene / α-olefin copolymer; Fluorine such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymer Polymer polymers; polymer compositions having alkali metal ion (especially lithium ion) ion conductivity, and the like. These may be used alone or in combination of two or more.

  As the dispersion solvent for forming the slurry, any type of solvent can be used as long as it can dissolve or disperse the negative electrode active material, the binder, and the conductive material and the thickener used as necessary. There is no restriction, and either an aqueous solvent or an organic solvent may be used. Examples of the aqueous solvent include water, a mixed solvent of alcohol and water, etc., and examples of the organic solvent include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, Methyl acrylate, diethyltriamine, N, N-dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, diethyl ether, dimethylacetamide, hexamethylphosphalamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, Examples include methylnaphthalene and hexane. In particular, when an aqueous solvent is used, it is preferable to use a thickener. A dispersing agent or the like is added to the thickener, and a slurry such as SBR is made into a slurry. In addition, the said dispersion solvent may be used individually by 1 type, or may be used in combination of 2 or more type.

  The content of the binder is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and further preferably 0.6% by mass or more with respect to the total amount of the negative electrode composite material. The upper limit of the binder content is 20% by mass or less, preferably 15% by mass or less, more preferably 10% by mass or less, and still more preferably 8% by mass or less.

  When the upper limit is exceeded, the proportion of the binder that does not contribute to the battery capacity increases, which may lead to a decrease in battery capacity. Moreover, if it is less than the said minimum, the fall of the intensity | strength of a negative electrode compound material may be caused.

  In particular, the range of the content of the binder with respect to the mass of the negative electrode mixture when a rubbery polymer typified by SBR is used as the main component as the binder is as follows. The lower limit of the range is 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, and the upper limit is 5% by mass or less, preferably 3% by mass or less, more preferably. Is 2% by mass or less.

  The range of the binder content with respect to the mass of the negative electrode mixture when a fluorine-based polymer typified by polyvinylidene fluoride is used as the main component as the binder is as follows. The lower limit of the range is 1% by mass or more, preferably 2% by mass or more, more preferably 3% by mass or more, and the upper limit is 15% by mass or less, preferably 10% by mass or less, more preferably 8% by mass or less. is there.

  The thickener is used to adjust the viscosity of the slurry. The thickener is not particularly limited, and specific examples include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. These may be used alone or in combination of two or more.

  The range of the content of the thickener relative to the mass of the negative electrode mixture when the thickener is used is as follows. The lower limit of the range is 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, and the upper limit is 5% by mass or less, preferably 3% by mass or less, more preferably. Is 2% by mass or less.

  If it is less than the said minimum, there exists a possibility that the applicability | paintability of a slurry may fall. On the other hand, when the above upper limit is exceeded, the ratio of the negative electrode active material to the negative electrode mixture decreases, and there is a risk of a decrease in battery capacity and an increase in resistance between the negative electrode active materials.

3. Electrolytic Solution The electrolytic solution of the present embodiment is composed of a lithium salt (electrolyte) and a non-aqueous solvent that dissolves the lithium salt. You may add an additive as needed.

  The lithium salt is not particularly limited as long as it is a lithium salt that can be used as an electrolyte of a non-aqueous electrolyte for a lithium ion battery. For example, the following inorganic lithium salts, fluorine-containing organic lithium salts, oxalate borate salts, etc. Is mentioned.

Examples of the inorganic lithium _{salt, LiPF 6, LiBF 4, LiAsF} 6, LiSbF inorganic fluoride salts and the like _6, LiClO _4, Libro 4, LiIO and perhalogenate such as _4, an inorganic chloride salts such as LiAlCl _4, etc. Is mentioned.

Examples of the fluorine-containing organic lithium salt include perfluoroalkane sulfonates such as LiCF ₃ SO ₃ ; LiN (CF ₃ SO ₂ ) ₂ , LiN (CF ₃ CF ₂ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C Perfluoroalkanesulfonylimide salt such as ₄ F ₉ SO ₉ ); perfluoroalkanesulfonylmethide salt such as LiC (CF ₃ SO ₂ ) ₃ ; Li [PF ₅ (CF ₂ CF ₂ CF ₃ )], Li [PF ₄ (CF ₂ CF ₂ CF ₃ ) ₂ ], Li [PF ₃ (CF ₂ CF ₂ CF ₃ ) ₃ ], Li [PF ₅ (CF ₂ CF ₂ CF ₂ CF ₃ )], Li [PF ₄ (CF _{2 CF 2 CF 2 CF 3) 2} ], Li [PF 3 (CF 2 CF 2 CF 2 CF 3) 3] fluoroalkyl hexafluorophosphate salts such like.

  Examples of the oxalatoborate salt 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 (LiPF ₆ ) is preferable when comprehensively judging the solubility in a solvent, charge / discharge characteristics in the case of a secondary battery, input / output characteristics, cycle characteristics, and the like.

  Although there is no restriction | limiting in particular in the density | concentration of the electrolyte in a non-aqueous electrolyte solution, The concentration range of an 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. Further, 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. If the concentration is too low, the electric conductivity of the electrolytic solution may be insufficient. On the other hand, if the concentration is too high, the viscosity increases and the electrical conductivity may decrease. Such a decrease in electrical conductivity may reduce the performance of the lithium ion battery.

  The non-aqueous solvent is not particularly limited as long as it is a non-aqueous solvent that can be used as an electrolyte solvent for a lithium ion battery. For example, the following cyclic carbonate, chain carbonate, chain ester, cyclic ether, and chain ether are used. Etc.

As the cyclic carbonate, those having 2 to 6 carbon atoms of the alkylene group constituting the cyclic carbonate are preferable, and those having 2 to 4 are more preferable. Specific examples include ethylene carbonate, propylene carbonate, butylene carbonate, and the like. Of these, ethylene carbonate and propylene carbonate are preferable.
Moreover, the cyclic carbonate which has a double bond in a molecule | numerator, or a cyclic carbonate containing a halogen atom like vinylene carbonate or fluoroethylene carbonate can also be used. When using a carbon material as a negative electrode active material, it is preferable to contain vinylene carbonate from the viewpoint of cycle characteristics.

  As the chain carbonate, dialkyl carbonate is preferable, and the number of carbon atoms of the two alkyl groups is preferably 1 to 5, and more preferably 1 to 4. Specifically, symmetrical chain carbonates such as dimethyl carbonate, diethyl carbonate, and di-n-propyl carbonate; asymmetric chain carbonates such as methyl ethyl carbonate, methyl-n-propyl carbonate, and ethyl-n-propyl carbonate Is mentioned. Of these, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate are preferable.

  Examples of chain esters include methyl acetate, ethyl acetate, propyl acetate, and methyl propionate. Among them, 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 and the like. Of these, tetrahydrofuran is preferably used from the viewpoint of improving input / output characteristics.

  Examples of chain ethers include dimethoxyethane and dimethoxymethane.

  These may be used alone or in combination of two or more, but it is preferable to use a mixed solvent in which two or more compounds are used in combination. For example, it is preferable to use a high dielectric constant solvent of cyclic carbonates in combination with a low viscosity solvent such as chain carbonates or chain esters. One of the preferable combinations is a combination mainly composed of cyclic carbonates and chain carbonates. Among them, the total of the cyclic carbonates and the chain carbonates in the non-aqueous solvent is 80% by volume or more, preferably 85% by volume or more, more preferably 90% by volume or more, and the cyclic carbonates and the chain carbonates. It is preferable that the cyclic carbonates have a capacity in the following range with respect to the total of the above. The lower limit of the capacity of the cyclic carbonates is 5% by volume or more, preferably 10% by volume or more, more preferably 15% by volume or more, and the upper limit is 50% by volume or less, preferably 35% by volume or less, more preferably 30%. The capacity is less than%. By using such a combination of non-aqueous solvents, the cycle characteristics and storage characteristics of the battery are improved.

  Specific examples of preferred combinations of cyclic carbonates and chain carbonates include ethylene carbonate and dimethyl carbonate, ethylene carbonate and diethyl carbonate, ethylene carbonate and methyl ethyl carbonate, ethylene carbonate and dimethyl carbonate and diethyl carbonate, ethylene carbonate and dimethyl carbonate And methyl ethyl carbonate, ethylene carbonate, diethyl carbonate and methyl ethyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate.

  Among these combinations, those containing asymmetric chain carbonates as chain carbonates are more preferable. Specific examples include a combination of ethylene carbonate, dimethyl carbonate and methyl ethyl carbonate, ethylene carbonate, diethyl carbonate and methyl ethyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate. Such a combination of ethylene carbonate, symmetric chain carbonates, and asymmetric chain carbonates can improve cycle characteristics and input / output characteristics. Among these, those in which the asymmetric chain carbonate is methyl ethyl carbonate are preferable, and those in which the alkyl group constituting the dialkyl carbonate has 1 to 2 carbon atoms are preferable.

The additive is not particularly limited as long as it is an additive for a non-aqueous electrolyte solution of a lithium ion battery. For example, nitrogen, sulfur or a heterocyclic compound containing nitrogen and sulfur, a cyclic carboxylic acid ester, a fluorine-containing cyclic Examples thereof include carbonates and other compounds having an unsaturated bond in the molecule.
In addition to the above additives, other additives such as an overcharge prevention material, a negative electrode film forming material, a positive electrode protective material, and a high input / output material may be used depending on the required function.

4). Separator The separator is not particularly limited as long as it has ion permeability while electronically insulating the positive electrode and the negative electrode, and has resistance to oxidation on the positive electrode side and reducibility on the negative electrode side. As a material (material) of the separator satisfying such characteristics, a resin, an inorganic material, glass fiber, or the like is used.

  As the resin, an olefin polymer, a fluorine polymer, a cellulose polymer, polyimide, nylon, or the like is used. Specifically, it is preferable to select from materials that are stable with respect to non-aqueous electrolytes and have excellent liquid retention properties. For example, porous sheets or nonwoven fabrics made from polyolefins such as polyethylene and polypropylene may be used. preferable.

  As the inorganic material, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate are used. For example, what made the said inorganic substance of fiber shape or particle shape adhere to thin film-shaped base materials, such as a nonwoven fabric, a woven fabric, and a microporous film, can be used as a separator. As a thin film-shaped substrate, a substrate having a pore diameter of 0.01 to 1 μm and a thickness of 5 to 50 μm is preferably used. In addition, for example, a separator in which a composite porous layer is formed using the above-described inorganic material in a fiber shape or a particle shape by using a binder such as a resin can be used as a separator. Furthermore, this composite porous layer may be formed on the surface of the positive electrode or the negative electrode to form a separator. For example, a composite porous layer in which alumina particles having a 90% particle size of less than 1 μm are bound using a fluororesin as a binder may be formed on the surface of the positive electrode.

5. Other constituent members As other constituent members of the lithium ion battery, a cleavage valve may be provided. By opening the cleavage valve, it is possible to suppress an increase in pressure inside the battery and to improve safety.

  Moreover, you may provide the structure part which discharge | releases inert gas (for example, carbon dioxide etc.) with a temperature rise. By providing such a component, when the temperature inside the battery rises, the cleavage valve can be opened quickly due to the generation of inert gas, and safety can be improved. Examples of the material used for the above components include lithium carbonate and polyalkylene carbonate resin.

(Lithium ion secondary battery)
First, an embodiment in which the present invention is applied to a laminated battery will be described.
A laminate-type lithium ion secondary battery can be manufactured, for example, as follows. First, the positive electrode and the negative electrode are cut into squares, and tabs are welded to the respective electrodes to produce positive and negative electrode terminals. A laminated body in which the positive electrode, the insulating layer, and the negative electrode are laminated in this order is prepared, and in that state, accommodated in an aluminum laminate pack, and the positive and negative electrode terminals are taken out of the aluminum laminate pack and sealed. Next, the nonaqueous electrolyte is poured into the aluminum laminate pack, and the opening of the aluminum laminate pack is sealed. Thereby, a lithium ion secondary battery is obtained.
Next, an embodiment in which the present invention is applied to a 18650 type cylindrical lithium ion secondary battery will be described with reference to the drawings.
As shown in FIG. 1, the lithium ion secondary battery 1 of this embodiment has a bottomed cylindrical battery case 6 made of steel plated with nickel. The battery container 6 accommodates an electrode group 5 in which a strip-like positive electrode plate 2 and a negative electrode plate 3 are wound in a spiral shape with a separator 4 interposed therebetween. In the electrode group 5, the positive electrode plate 2 and the negative electrode plate 3 are wound in a spiral shape in cross section via a separator 4 made of a polyethylene porous sheet. For example, the separator 4 has a width of 58 mm and a thickness of 30 μm. A ribbon-like positive electrode tab terminal made of aluminum and having one end fixed to the positive electrode plate 2 is led out on the upper end surface of the electrode group 5. The other end of the positive electrode tab terminal is joined by ultrasonic welding to the lower surface of a disk-shaped battery lid that is disposed on the upper side of the electrode group 5 and serves as a positive electrode external terminal. On the other hand, a ribbon-like negative electrode tab terminal made of copper with one end fixed to the negative electrode plate 3 is led out on the lower end surface of the electrode group 5. The other end of the negative electrode tab terminal is joined to the inner bottom of the battery container 6 by resistance welding. Therefore, the positive electrode tab terminal and the negative electrode tab terminal are respectively led out to the opposite sides of the both end surfaces of the electrode group 5. In addition, the insulation coating which abbreviate | omitted illustration is given to the outer peripheral surface whole periphery of the electrode group 5. FIG. 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. In addition, a non-aqueous electrolyte (not shown) is injected into the battery container 6.

In the present invention, the capacity ratio of the negative electrode to the positive electrode (negative electrode capacity / positive electrode capacity) is preferably 1.03 to 1.8, more preferably 1.05 to 1.4 from the viewpoint of safety and energy density.
Here, the negative electrode capacity indicates [negative electrode discharge capacity], and the positive electrode capacity indicates [positive electrode initial charge capacity-negative electrode or positive electrode, whichever is greater, irreversible capacity]. Here, the “negative electrode discharge capacity” is defined to be calculated by the charge / discharge device when the lithium ions inserted into the negative electrode active material are desorbed. Further, the “initial charge capacity of the positive electrode” is defined as that calculated by the charge / discharge device when lithium ions are desorbed from the positive electrode active material.
The capacity ratio between the negative electrode and the positive electrode can be calculated from, for example, “discharge capacity of the lithium ion secondary battery / discharge capacity of the negative electrode”. The discharge capacity of the lithium ion battery is, for example, 4.2 V, 0.1 C to 0.5 C, 0.1 C to 0 after performing constant current and constant voltage (CCCV) charging with an end time of 2 to 5 hours. It can be measured under the conditions when a constant current (CC) is discharged to 2.7 V at 0.5 C. The discharge capacity of the negative electrode was prepared by cutting a negative electrode having a measured discharge capacity of the lithium ion secondary battery into a predetermined area, using lithium metal as a counter electrode, and preparing a single electrode cell through a separator impregnated with an electrolyte. Then, after performing constant current and constant voltage (CCCV) charging at 0 V, 0.1 C to 0.5 C, and a final current of 0.01 C, constant current (CC) discharging to 1.5 V at 0.1 C to 0.5 C It can be calculated by measuring the discharge capacity per predetermined area under the conditions obtained and converting this to the total area used as the negative electrode of the lithium ion battery. In this single electrode cell, the direction in which lithium ions are inserted into the negative electrode active material is defined as charging, and the direction in which lithium ions inserted into the negative electrode active material are desorbed is defined as discharging.
C means “current value (A) / battery discharge capacity (Ah)”.

Hereinafter, the present embodiment will be described in more detail based on examples. The present invention is not limited to the following examples.
[Manufacture of aluminum silicate]
[Production Example 1]
A concentration: 350 mmol / L sodium orthosilicate aqueous solution (500 mL) was added to a 700 mmol / L aluminum chloride aqueous solution (500 mL), and the mixture was stirred for 30 minutes. To this solution, 330 mL of an aqueous sodium hydroxide solution having a concentration of 1 mol / L was added to adjust the pH to 6.1.
After stirring pH adjusted solution for 30 minutes, TOMY Co. as a centrifugal separator: Suprema23 and using standard rotor NA-16, rotating speed: at 3,000min ^-1, was centrifuged for 5 minutes. After centrifugation, the supernatant solution was discharged, the gel precipitate was redispersed in pure water, and returned to the volume before centrifugation. Such desalting treatment by centrifugation was performed three times.
135 mL of hydrochloric acid having a concentration of 1 mol / L was added to the gel-like precipitate obtained after the supernatant was discharged for the third time in the desalting treatment, and the pH was adjusted to 3.5, followed by stirring for 30 minutes. The solution was then placed in a dryer and heated at 98 ° C. for 48 hours (2 days). 188 mL of a 1 mol / L sodium hydroxide aqueous solution was added to the solution after heating (aluminum silicate concentration 47 g / L) to adjust the pH to 9.1. By adjusting the pH, the aluminum silicate in the solution was aggregated, and the aggregate was precipitated by the same centrifugation as described above, and then the supernatant was discharged. The desalting process of adding pure water to the precipitate after discharging the supernatant and returning to the volume before centrifugation was performed three times. The gel-like precipitate obtained after the third desalting of the desalting treatment was dried at 60 ° C. for 16 hours to obtain 30 g of powder. This powder and polyvinyl alcohol powder (Wako Pure Chemical Industries, Ltd.) were mixed at a mass ratio of 100: 70 and baked at 850 ° C. for 1 hour in a nitrogen atmosphere to obtain the aluminum silicate of Production Example 1.

[Production of positive electrode plate]
The positive electrode plate was produced as follows. The layered lithium-nickel-manganese-cobalt composite oxide (NMC) and spinel-type lithium-manganese oxide (sp-Mn), which are positive electrode active materials, were mixed at a mass ratio shown in Table 1. In this mixture of positive electrode active materials, flaky graphite (average particle size: 7 μm) and acetylene black (average particle size 50 nm) as the conductive material, the aluminum silicate produced in Production Example 1, and polyfluoride as the binder. A mixture of positive electrode materials was obtained by sequentially adding and mixing vinylidene chloride (PVDF).
The contents of the positive electrode active material, graphite, acetylene black (AB) and aluminum silicate were changed as shown in Table 1. In addition, (positive electrode active material + graphite + acetylene black + aluminum silicate): binder = 95: 5.
Further, N-methyl-2-pyrrolidone (NMP) as a dispersion solvent was added to the above mixture and kneaded to form a slurry. This slurry was applied substantially evenly and uniformly to both surfaces of a 20 μm thick aluminum foil as a positive electrode current collector. Then, the drying process was performed and it consolidated by the press to the predetermined density. The density of the positive electrode mixture was 2.55 g / cm ^3, and the coating amount on one side of the positive electrode mixture was 190 g / m ² .

[Production of negative electrode plate]
The negative electrode plate was produced as follows. Amorphous carbon (soft carbon) was used as the negative electrode active material. Polyvinylidene fluoride was added as a binder to this negative electrode active material. These mass ratios were negative electrode active material: binder = 92: 8. A dispersion solvent N-methyl-2-pyrrolidone (NMP) was added thereto and kneaded to form a slurry. A predetermined amount of this slurry was applied to both surfaces of a rolled copper foil having a thickness of 10 μm, which is a negative electrode current collector, substantially uniformly and uniformly. The density of the negative electrode mixture was 1.15 g / cm ^3, and the coating amount on one side of the negative electrode mixture was 80 g / m ² .

[Production of battery]
Production of a laminate type battery A positive electrode cut into a 13.5 cm ² square was sandwiched between polyethylene porous sheet separators (trade name: Hypore, Asahi Kasei Co., Ltd., thickness 30 μm, “Hypore” is a registered trademark) Furthermore, the negative electrode cut | disconnected to the 14.3 cm < ² > square was piled up, and the laminated body was produced. This laminate is put into an aluminum laminate container (trade name: aluminum laminate film, manufactured by Dai Nippon Printing Co., Ltd.), and a non-aqueous electrolyte (ethylene carbonate / methyl ethyl carbonate / dimethyl carbonate = 2/2 / containing 1M LiPF ₆ ). 3 mixed solution (volume ratio) with 0.8% by mass of vinylene carbonate added to the total amount of the mixed solution, trade name: Sollite, manufactured by Mitsubishi Chemical Corporation, “Solite” is a registered trademark), An aluminum laminate container was thermally welded to produce a battery for electrode evaluation.

[Evaluation of battery characteristics (battery capacity, output characteristics, input characteristics)]
The battery characteristics of the lithium ion battery produced in this way were evaluated by the methods shown below.
As for the battery capacity, first, a charge / discharge cycle with a current value of 0.5 C was repeated twice in a voltage range of 4.2 to 2.7 V in an environment of 25 ° C. Further, after charging the battery to 4.2 V at a current value of 0.5 C, discharging was performed by constant current discharge at a final voltage of 2.7 V at a current value of 0.2 C, and the capacity at the time of discharge was defined as the battery capacity.

The output characteristics were calculated as follows.
First, the discharge capacity at a current value of 0.5 C and the discharge capacity at a current value of 3 C were measured. Note that “C” used as a unit of current value means “current value (A) / battery capacity (Ah)”.
After measuring the above battery capacity, the battery is charged to 4.2 V with a current value of 0.5 C, and a constant current discharge with a final voltage of 2.7 V is performed with a current value of 0.5 C. The discharge capacity was 0.5 C. Next, the battery is charged to 4.2 V with a current value of 0.5 C, and a constant current discharge with a final voltage of 2.7 V is performed with a current value of 3 C, and the capacity at the time of discharge is discharged at a current value of 3 C. The output characteristic was calculated by the following formula using the capacitance.
Output characteristics = discharge capacity at a current value of 3 C / discharge capacity at a current value of 0.5 C

The input characteristics were calculated as follows.
First, the charge capacity at a current value of 0.5 C and the charge capacity at a current value of 3 C were measured.
After measuring the battery capacity, the battery was discharged at a current value of 0.5 C to a final voltage of 2.7 V, and charged at a constant current of up to 4.2 V at a current value of 0.5 C. The charge capacity at 5C was used. Next, the battery is discharged to a lower limit voltage of 2.7 V with a current value of 0.5 C, and charged with an upper 4.2 V with a current value of 3 C. The capacity at the time of charging is the charge capacity at a current value of 3 C. It was. The input characteristics were calculated by the following formula.
Input characteristics = Charge capacity at a current value of 3C / Charge capacity at a current value of 0.5C

[Evaluation of storage characteristics]
The storage characteristics were calculated as follows.
The discharge capacity at a current value of 0.5 C was measured. After measuring the battery capacity, after charging the battery up to 4.2 V at a current value of 0.5 C in an environment of 25 ° C., discharging by a constant current discharge with a final voltage of 2.7 V at a current value of 0.5 C, The capacity at the time of discharge was defined as the discharge capacity before storage at a current value of 0.5C. After that, the battery is charged to 4.2 V at a current value of 0.5 C and then left for 2 months in an environment of 50 ° C. The battery after being left to stand is 4.2 V at a current value of 0.5 C in an environment of 25 ° C. After charging the battery, discharging was performed by constant current discharge at a final voltage of 2.7 V at a current value of 0.5 C, and the capacity at the time of discharge was defined as the discharge capacity after storage at a current value of 0.5 C.
The storage characteristics were calculated by the following formula.
Storage characteristics = Charge capacity after storage at a current value of 0.5 C / Charge capacity before storage at a current value of 0.5 C

  As shown in Table 1, Examples 1 to 3 of the present invention are superior in battery capacity, output characteristics, input characteristics and storage characteristics, whereas the positive electrode mixture does not contain aluminum silicate. It can be seen that Example 1 is slightly inferior in input characteristics and storage characteristics, and Comparative Example 2 that does not include acetylene black and Comparative Example 3 that does not include graphite are inferior in battery capacity, output characteristics, input characteristics, and storage characteristics.

  DESCRIPTION OF SYMBOLS 1 ... Lithium ion secondary battery, 2 ... Positive electrode plate, 3 ... Negative electrode plate, 4 ... Separator, 5 ... Electrode group, 6 ... Battery container.

Claims (3)

  A lithium ion battery comprising an electrode winding group in which a positive electrode, a negative electrode, and a separator are wound, and an electrolyte solution, wherein the positive electrode includes a current collector and a positive electrode mixture formed on the current collector. And the said positive electrode compound material is a lithium ion battery containing spinel type lithium manganese oxide, graphite, acetylene black, and aluminum silicate.   The lithium ion battery according to claim 1, wherein the content of the aluminum silicate is 1% by mass or more and 5% by mass or less based on the total amount of the positive electrode mixture.   The lithium ion battery according to claim 1 or 2, wherein the content of acetylene black is 0.1% by mass or more and 15% by mass or less based on the total amount of the positive electrode mixture.

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