JP2015046237A - Lithium ion battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-capacity, long-life lithium ion battery having high input and output and a feature of high heat dissipation.SOLUTION: A lithium ion battery comprises: a group of wound electrodes arranged by winding a positive electrode, a negative electrode and a separator; an electrolytic solution; and a battery container in which the group of wound electrodes and the electrolytic solution are enclosed. The lithium ion battery has a discharge capacity X of 30 to less than 110 Ah. The positive electrode has: a current collector; a positive electrode mixture applied to both sides of the current collector; and current collector lead pieces. The ratio of the number n of the current collector lead pieces to the discharge capacity X satisfies the following relational expression: 11.5<n/X<3.5 (Relational Expression 1).

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 employ 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 77.04 Ah or more, and uses a positive electrode in which a predetermined amount of an active material mixture containing a lithium / manganese composite oxide is applied to both sides of a current collector.

  Patent Document 2 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 battery capacity of 3 Ah or more and an output of 400 W or more. In addition, a positive electrode active material mixture containing lithium-manganese composite oxide is used for the positive electrode, a negative electrode active material mixture containing amorphous carbon is used for the negative electrode, and ethylene is used as a solvent for the electrolyte. A mixed solvent containing carbonate, dimethyl carbonate and diethyl carbonate is used.

Japanese Patent No. 3541723 Japanese Patent No. 3433695

However, when the 18650 type lithium ion battery is used for the large-scale power storage system as described above, about 1 million batteries are required.
Usually, a lithium ion battery has a cell controller attached to each battery and detects the state of the battery. Therefore, in a system using a large number of batteries, the number of necessary cell controllers also increases, resulting in a significant increase in cost.

  Therefore, it is desired to increase the capacity per battery to reduce the number of batteries and the number of cell controllers required for the system.

  As described above, when the capacity of the battery is increased, there is a problem in that the heat dissipating property inside the battery is lowered and the life is reduced. Further, in a large-scale power storage system, it is necessary to be able to cope with high-speed load fluctuations, and a lithium ion battery satisfying a long life and high input / output characteristics is desired.

  Therefore, an object of the present invention is to provide a long-life, high-input / output, high-capacity lithium ion battery having a high heat dissipation characteristic.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

An electrode winding group in which a positive electrode, a negative electrode, and a separator are wound, and an electrolytic solution are provided in a battery container, and discharge capacity X (Ah) (the unit of “discharge capacity X” described below is Ah) .) In a lithium ion battery of 30 Ah or more and less than 110 Ah, the positive electrode has a current collector and a positive electrode mixture applied to both surfaces of the current collector and a current collector lead piece, and the current collector lead piece The ratio of the number n to the discharge capacity X is the following relational expression 1
1.5 <n / X <3.5 (Relational formula 1)
Meet.

  An electrode winding group in which a positive electrode, a negative electrode, and a separator are wound, and an electrolyte solution are provided in a battery container, and a discharge capacity is applied to a current collector and both surfaces thereof in a lithium ion battery having a discharge capacity of 30 Ah or more and less than 110 Ah. The positive electrode composite material of the positive electrode having the positive electrode composite material has the following configuration. The positive electrode mixture contains a mixed active material of layered lithium / nickel / manganese / cobalt composite oxide (NMC) and spinel type lithium / manganese oxide (sp-Mn), and layered lithium / nickel / manganese / cobalt. The mass ratio (NMC / sp-Mn) between the composite oxide (NMC) and the spinel type lithium manganese oxide (sp-Mn) is 10/90 or more and 60/40 or less.

The mixed active material is composed of a layered lithium / nickel / manganese / cobalt composite oxide represented by the following composition formula (Formula 1) and a spinel type lithium / manganese oxide represented by the following composition formula (Formula 2). And a mixture of
Li _{(1 + δ)} Mn _x Ni _y Co _(1-xyz) M _z O ₂ (Formula 1)
(M is at least one element selected from the group consisting of Ti, Zr, Nb, Mo, W, Al, Si, Ga, Ge, and Sn, and −0.15 <δ <0.15, 0 0.1 <x ≦ 0.5, 0.6 <x + y + z ≦ 1.0, and 0 ≦ z ≦ 0.1.)
Li _{(1 + η)} Mn _(2-λ) M ′ _λ O ₄ (Chemical formula 2)
(M ′ is at least one element selected from the group consisting of Mg, Ca, Sr, Al, Ga, Zn and Cu, and 0 ≦ η ≦ 0.2 and 0 ≦ λ ≦ 0.1. .)
In the composition formula (Formula 2), M ′ is at least one element selected from the group consisting of Mg and Al.

Among the inventions disclosed in the present application, effects obtained by typical ones will be briefly described as follows.
According to the present invention, it is possible to provide a lithium ion battery having a high capacity and a long life, high input / output, and high capacity.

It is sectional drawing of the lithium ion battery of this Embodiment. It is a positive electrode (current collector, positive electrode mixture, and current collector lead piece for positive electrode) of the present 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, a positive electrode, a negative electrode, an electrolytic solution, a separator, and other components that are components of the lithium ion battery according to the present embodiment will be sequentially described.

1. Positive electrode In this embodiment mode, 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 includes a current collector and a positive electrode mixture (positive electrode mixture) formed on the surface portion thereof. The current collector has a portion referred to as a lead piece having a protruding portion where the positive electrode mixture is not formed on the surface portion. Current flows in and out of the positive electrode through the lead piece, and charging / discharging is performed. At the same time, part of the heat generated by the charge / discharge reaction is also released to the outside of the battery through the lead piece. A configuration example of an actual positive electrode will be described later (for example, see FIG. 2). The positive electrode mixture is a layer including at least a positive electrode active material provided on the surface portion of the current collector. In one embodiment of the present invention, for example, a layered lithium-nickel-manganese-cobalt composite oxide ( NMC) and a mixed active material of spinel type lithium / manganese oxide (spinel type lithium / manganese composite oxide, sp-Mn). The positive electrode mixture is formed (applied) on both surfaces of the current collector, for example.

  In the 18650 type lithium ion battery that has been widely used in the past, since the number of lead pieces in the battery is small, there are few places where current flows in and out, and it is difficult to cope with a large current. Further, in a large-capacity lithium ion battery, in particular, a cylindrical type including a wound group therein has a poor heat dissipation property and may have a short life due to thermal deterioration.

In contrast, in the present embodiment, a lithium ion battery having an electrode winding group in which a positive electrode, a negative electrode, and a separator are wound, and an electrolytic solution, and a discharge capacity X of 30 Ah or more and less than 110 Ah. The positive electrode has a current collector, a positive electrode mixture applied to both surfaces of the current collector, and current collector lead pieces, and the ratio of the number n of the current collector lead pieces to the discharge capacity X is as follows: Relational expression 1
1.5 <n / X <3.5 (Relational formula 1)
Meet. Further, the mass ratio (mixing ratio) of layered lithium / nickel / manganese / cobalt composite oxide (NMC) and spinel type lithium / manganese oxide (sp-Mn) is 10/90 or more. By setting it to 60/40 or less, it has characteristics of high heat dissipation, and can achieve a long battery life and high input / output. The mass ratio may be simply referred to as “mass ratio of active material”.

  When the ratio of the number n of positive electrode current collector lead pieces to the discharge capacity X (n / X) is 1.5 or less, the release of heat generated during charge and discharge is insufficient, and the life may be shortened due to thermal deterioration. There is. In addition, there are few places where current flows in and out, and input / output characteristics may be inferior. On the other hand, when n / X is 3.5 or more, there is a risk that the battery capacity / volume energy density may be reduced, for example, by reducing the width of the positive electrode mixture, in order to secure the volume for storing the lead pieces in the battery can.

  If the mass ratio (NMC / sp-Mn) of the active material is less than 10/90, the energy density of the battery may be reduced. On the other hand, when the mass ratio (NMC / sp-Mn) of the active material exceeds 60/40, there is a concern that the safety may be lowered, and it is necessary to strengthen other safety measures.

  Thus, in the positive electrode, by setting the ratio (n / X) of the number n of the current collector lead pieces for the positive electrode to the discharge capacity X and the mass ratio of the active material (NMC / sp-Mn) within the above ranges, the discharge capacity Even in a high capacity lithium ion battery of 30 Ah or more, it is possible to realize a high capacity battery with a long life and high input / output characteristics with high heat dissipation characteristics.

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 (Chemical 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 elements M are 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.

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.

  Thus, a mixture of layered lithium / nickel / manganese / cobalt composite oxide (NMC) and spinel type lithium / manganese oxide (sp-Mn) 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.

  Mg or Al is preferably used as the element M ′ in the composition formula (Formula 2). 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, since the elution of Mn can be reduced by adding the element M ′, storage characteristics and charge / discharge cycle characteristics can be improved.

Thus, spinel type lithium manganese oxide (sp-Mn) has useful characteristics, but spinel type lithium manganese oxide (sp-Mn) itself has a small theoretical capacity and a low density. Therefore, when only a spinel type lithium manganese oxide (sp-Mn) is used as a positive electrode active material to constitute a battery, it is difficult to increase the battery capacity (discharge capacity). On the other hand, the layered lithium / nickel / manganese / cobalt composite oxide (NMC) has a large theoretical capacity, and has the same theoretical capacity as LiCoO ₂ which is widely used as a positive electrode active material for lithium ion batteries.

  Therefore, in this embodiment, layered lithium / nickel / manganese / cobalt composite oxide (NMC) and spinel type lithium / manganese oxide (sp-Mn) are used in combination to further increase the density of the positive electrode mixture. As a result, it has become possible to provide a battery with high capacity and excellent safety. In addition, it is possible to provide a battery having excellent storage characteristics and charge / discharge cycle characteristics.

  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, For example, it forms as follows. A positive electrode active material, a binder, and other materials such as a conductive material and a thickener used as needed are mixed in a dry form to form a sheet, which is then pressure-bonded to a current collector (dry method). Alternatively, a positive electrode active material, a binder, and other materials such as a conductive material 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 described above, layered lithium / nickel / manganese / cobalt composite oxide (NMC) and spinel lithium / manganese oxide (sp-Mn) are used as the positive electrode active material. These are used in powder form (granular) and mixed.
A substance having a composition different from that of the substance constituting the main cathode active material may be adhered to the surface of the cathode active material. Surface adhesion substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, sulfuric acid Examples thereof include sulfates such as calcium and aluminum sulfate, carbonates such as lithium carbonate, calcium carbonate and magnesium carbonate, and carbon.

  There are the following methods for attaching the surface adhering substance. For example, the positive electrode active material is added to the positive electrode active material by impregnating and adding the positive electrode active material to a liquid obtained by dissolving or suspending the surface adhesive material in a solvent. Thereafter, the positive electrode active material impregnated with the surface adhering substance is dried. Alternatively, the positive electrode active material is added to a liquid obtained by dissolving or suspending the precursor of the surface adhesion material in a solvent, thereby impregnating and adding the precursor of the surface adhesion material to the positive electrode active material. Thereafter, the positive electrode active material impregnated with the precursor of the surface adhering material is heated. Alternatively, a liquid obtained by dissolving or suspending the precursor of the surface adhesion material and the precursor of the positive electrode active material in a solvent is baked. By these methods, the surface adhering substance can be attached to the surface of the positive electrode active material.

  About the quantity of a surface adhesion substance, it is preferable to set it as the following range with respect to the mass of a positive electrode active material. The lower limit of the range is preferably 0.1 ppm by mass or more, more preferably 1 ppm by mass or more, and further preferably 10 ppm by mass or more. An upper limit becomes like this. Preferably it is 20 mass% or less, More preferably, it is 10 mass% or less, More preferably, it is 5 mass% or less.

  The surface adhering substance can suppress the oxidation reaction of the non-aqueous electrolyte solution on the surface of the positive electrode active material, and can improve the battery life. However, when the adhesion amount is too small, the above effect is not sufficiently exhibited. When the adhesion amount is too large, the resistance may increase in order to inhibit the entry and exit of lithium ions. Therefore, the above range is preferable.

  The positive electrode active material particles of layered lithium / nickel / manganese / cobalt composite oxide (NMC) and spinel type lithium / manganese oxide (sp-Mn) are in the form of lumps, polyhedrons, spheres, ellipses. A spherical shape, a plate shape, a needle shape, a columnar shape, or the like can be 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 this case, it is preferable that the average particle diameter of the secondary particles satisfies the following relational expression 2.
1 <D _sp-Mn / D _NMC <3 (Relational formula 2)
Here, _DNMC represents the average particle size of layered lithium-nickel-manganese-cobalt composite oxide (NMC), and _Dsp-Mn represents the average particle size of spinel-type lithium-manganese oxide (sp-Mn). Represent.

  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.

Median diameter d50 of primary active material particles of layered lithium / nickel / manganese / cobalt composite oxide (NMC) and spinel type lithium / manganese oxide (sp-Mn) (primary particles aggregate to form secondary particles) In this case, the median diameter d50) of the secondary particles can be adjusted within the following range. 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 30 μm or less, preferably 25 μm or less, more preferably 15 μm or less.
If it is less than the above lower limit, the tap density (fillability) may be lowered, and a desired tap density may not be obtained. If the upper limit is exceeded, it takes time to diffuse lithium ions in the particles, so that the battery performance is lowered. 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. 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, further 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 more 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 of layered lithium / nickel / manganese / cobalt composite oxide (NMC) or 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 at most 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 metal materials such as copper and nickel; graphite such as natural graphite and artificial graphite (graphite); carbon black such as acetylene black; and carbonaceous materials such as amorphous carbon such as needle coke. Can be mentioned. Of these, one type may be used alone, or two or more types may be used in combination.

  About the content (addition amount, ratio, amount) of the conductive material, the range of the content of the conductive material with respect to the mass of the positive electrode mixture is as follows. The lower limit of the range is 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 1% by mass or more, and the upper limit is 50% by mass or less, preferably 30% by mass or less, more preferably 15%. It is below mass%. If it is less than the above lower limit, the conductivity may be insufficient. Moreover, when the said upper limit is exceeded, there exists a possibility that battery capacity may fall.

  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, polyvinyl acetate , Ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer and other soft resinous polymers; polyvinylidene fluoride (PVdF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymer Examples thereof include fluorine polymers such as polymers and polytetrafluoroethylene / vinylidene fluoride copolymers; polymer compositions having ion conductivity of alkali metal ions (particularly lithium ions). 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.

  Regarding the content (addition amount, ratio, amount) of the binder, the range of the content of the binder with respect to the mass of the positive electrode mixture is as follows. The lower limit of the range is 0.1% by mass or more, preferably 1% by mass or more, more preferably 3% by mass or more, and the upper limit is 80% by mass or less, preferably 60% by mass or less, more preferably 40% by mass. Hereinafter, it is more preferably 10% by mass or less. If the content of the binder is too low, the positive electrode active material cannot be sufficiently bound, the positive electrode has insufficient mechanical strength, and battery performance such as cycle characteristics may be deteriorated. On the other hand, if it is too high, battery capacity and conductivity may be reduced.

  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.

  Examples of the material of the current collector for the positive electrode 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.

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 (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, and metals that can form alloys with lithium such as Sn and Si. 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, and 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 the 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) having a carbon network surface layer (d002) of 0.34 nm or more is excellent in rapid charge / discharge and low-temperature characteristics, and is preferable. However, since a material having a wide carbon network surface layer (d002) may have a low capacity and charge / discharge efficiency at the initial stage of charging, it is preferable to select a material having a carbon network surface layer (d002) of 0.39 nm or less. .

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. As the amorphous material, a material having the following characteristics (1) to (2) may be used.
(1) the intensity ratio of the peak intensity in the range of 1300～1400Cm ^-1 as measured by Raman spectroscopy (ID) and the peak intensity in the range of 1580～1620Cm ^-1 as measured by Raman spectroscopy spectra (IG) The R value (ID / IG) is 0.5 or more and 1.5 or less.
(2) The crystallite size Lc (002) in the c-axis direction is not less than 1 and not more than 10 nm.
Battery performance can be improved by using an amorphous material under such conditions as the negative electrode active material.

  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).

  The range of the median diameter d50 of the carbonaceous material particles 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, further preferably 7 μm or more, and the upper limit is 100 μm or less, preferably 50 μm or less, more preferably 40 μm or less, more preferably 30 μm or less, Particularly preferably, it is 25 μm or less. If it is less than the lower limit, the irreversible capacity increases, which may cause a loss of initial battery capacity. On the other hand, when the above upper limit is exceeded, the application surface of the negative electrode mixture becomes non-uniform during the formation of the electrode, which may hinder the electrode formation.

The range of the BET specific surface area of the carbonaceous material particles is as follows. The lower limit of the range is 0.1 m ² / g or more, preferably 0.7 m ² / g or more, more preferably 1.0 m ² / g or more, and further preferably 1.5 m ² / g or more. The upper limit is 100 m ² / g or less, preferably 25 m ² / g or less, more preferably 15 m ² / g or less, and still more preferably 10 m ² / g or less. If it is less than the said minimum, the occlusion of the lithium ion in a negative electrode will fall easily at the time of charge, and there exists a possibility that lithium may precipitate on the negative electrode surface. Moreover, when the said upper limit is exceeded, the reactivity with a non-aqueous electrolyte solution will increase and there exists a possibility that the generated gas in the negative electrode vicinity may increase.

The ranges of the tap density of the carbonaceous material particles are as follows. The lower limit of the tap density is 0.1 g / cm ³ or more, preferably 0.2 g / cm ³ or more, more preferably 0.3 g / cm ³ or more, and further preferably 0.5 g / cm ³ or more. The upper limit is preferably 2 g / cm ³ or less, more preferably 1.5 g / cm ³ or less, and still more preferably 1.0 g / cm ³ or less. If it is less than the said minimum, the filling density of the negative electrode active material in a negative electrode compound material may fall, and there exists a possibility that a predetermined battery capacity cannot be ensured. Moreover, when the said upper limit is exceeded, the space | gap between the negative electrode active materials in a negative electrode compound material will decrease, and it may become difficult to ensure the electroconductivity between particle | grains.

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 a preferred form, there is a form using a carbonaceous material that is not symmetrical when the volume-based particle size distribution is centered on the median diameter as the second carbonaceous material (conductive material). Further, as the second carbonaceous material (conductive material), a form using a carbonaceous material having a Raman R value different from that of the first carbonaceous material used as the negative electrode active material, or as the second carbonaceous material (conductive material), There is a form using a carbonaceous material having a different X-ray parameter from the first carbonaceous material used as a substance.

  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, it is possible to use a copper alloy (phosphor bronze, titanium copper, Corson alloy, Cu—Cr—Zr alloy, etc.) that is stronger than pure copper. Strength can be improved.

Although there is no restriction | limiting in particular in the structure of the negative electrode compound material formed using the negative electrode active material, The range of the negative electrode compound material density is as follows. The lower limit of the negative electrode composite density is preferably 0.7 g / cm ³ or more, more preferably 0.8 g / cm ³ , still more preferably 0.9 g / cm ³ or more, and the upper limit is 2 g / cm ³ or less. Preferably it is 1.9 g / cm ³ or less, more preferably 1.8 g / cm ³ or less, and even more preferably 1.7 g / cm ³ or less.
When the above upper limit is exceeded, particles of the negative electrode active material are likely to be destroyed, and a high current is generated due to an increase in the initial irreversible capacity and a decrease in the permeability of the non-aqueous electrolyte solution near the interface between the current collector and the negative electrode active material. The density charge / discharge characteristics may be deteriorated. In addition, if it is less than the above lower limit, the conductivity between the negative electrode active materials is lowered, so that the battery resistance is increased and the capacity per unit volume may be lowered.

  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 ( Rubber-like polymers such as acrylonitrile-butadiene rubber) and ethylene-propylene rubber; styrene / butadiene / styrene block copolymers or hydrogenated products 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 and propylene / α-olefin copolymer; Fluorine-based polymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene / ethylene copolymer Polymers: Polymer compositions having ionic conductivity of alkali metal ions (particularly lithium ions), and the like. These may be used alone or in combination of two or more.

  As the dispersion solvent for forming the slurry, any kind of solvent can be used as long as it can dissolve or disperse the negative electrode active material, the binder, and the conductive material or 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, 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.

Regarding the content (addition amount, ratio, amount) of the binder, the range of the content of the binder with respect to the mass of the negative electrode mixture is as follows. The lower limit of the range 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. The upper limit 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, there exists a possibility of causing the fall of the intensity | strength of negative electrode compound material.
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 solution for a lithium ion battery. For example, the following inorganic lithium salts, fluorine-containing organic lithium salts, and oxalate borate salts are used. Can be mentioned.
Examples of the inorganic lithium _salt, LiPF _6, and LiBF _4, inorganic fluoride salts LiAsF 6, LiSbF _{6, etc.,} LiClO _4, Libro 4, and perhalogenate of LiIO ₄ or the like, and inorganic chloride salts such as LiAlCl ₄ 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 ] and other fluoroalkyl fluorophosphates.
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, output characteristics, cycle characteristics, and the like.

A preferable example in the case of using two or more lithium salts is a combination of LiPF ₆ and LiBF ₄ . In this case, the proportion of LiBF _{4 in} the total of both is preferably 0.01% by mass or more and 20% by mass or less, and more preferably 0.1% by mass or more and 5% by mass or less. . Another preferred example is the combined use of an inorganic fluoride salt and a perfluoroalkanesulfonylimide salt. In this case, the proportion of the inorganic fluoride salt in the total of both is 70% by mass or more and 99% by mass. % Or less, more preferably 80% by mass or more and 98% by mass or less. According to the above two preferred examples, characteristic deterioration due to high temperature storage can be suppressed.

  Although there is no restriction | limiting in particular in the density | concentration of the electrolyte in a non-aqueous electrolyte solution, The density | 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 lithium ion batteries. For example, the following cyclic carbonates, chain carbonates, chain esters, cyclic ethers and chain ethers 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.
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 ethyl methyl carbonate, methyl-n-propyl carbonate, and ethyl-n-propyl carbonate Is mentioned. Of these, dimethyl carbonate, diethyl carbonate, and ethyl methyl 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, battery cycle characteristics and high-temperature storage characteristics (particularly, remaining capacity and high-load discharge capacity after high-temperature storage) 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 ethyl methyl carbonate, ethylene carbonate and dimethyl carbonate and diethyl carbonate, ethylene carbonate and dimethyl carbonate And ethyl methyl carbonate, ethylene carbonate, diethyl carbonate, and ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

  A combination in which propylene carbonate is further added to the combination of these ethylene carbonates and chain carbonates is also a preferable combination. When propylene carbonate is contained, the volume ratio of ethylene carbonate to propylene carbonate is preferably 99: 1 to 40:60, and more preferably 95: 5 to 50:50. Further, the range of the amount of propylene carbonate in the non-aqueous solvent is as follows. The lower limit of the amount of propylene carbonate is 0.1% by volume or more, preferably 1% by volume or more, more preferably 2% by volume or more, and the upper limit is 10% by volume or less, preferably 8% by volume or less, more preferably 5% by volume or less. According to such a combination, the low temperature characteristics can be further improved while maintaining the characteristics of the combination of ethylene carbonate and chain carbonates.

  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 ethyl methyl carbonate, ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate. Such a combination of ethylene carbonate, symmetric chain carbonates and asymmetric chain carbonates can improve cycle characteristics and large current discharge characteristics. Among these, those in which the asymmetric chain carbonates are ethyl methyl carbonate are preferable, and those in which the alkyl group constituting the dialkyl carbonate has 1 to 2 carbon atoms are preferable.

  Another example of a preferable mixed solvent is one containing a chain ester. In particular, those containing a chain ester in the mixed solvent of the cyclic carbonates and the chain carbonates are preferable from the viewpoint of improving the low-temperature characteristics of the battery. As the chain ester, methyl acetate and ethyl acetate are particularly preferable. The lower limit of the capacity of the chain ester in the non-aqueous solvent is 5% by volume or more, preferably 8% 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, it is 30 volume% or less, More preferably, it is 25 volume% or less.

  Examples of other preferable non-aqueous solvents are one organic solvent selected from the group consisting of ethylene carbonate, propylene carbonate and butylene carbonate, or a mixed solvent consisting of two or more organic solvents selected from this group. The volume of the mixed solvent in the non-aqueous solvent is 60% by volume or more. These mixed solvents are preferably adjusted by selecting various solvents so that the flash point is 50 ° C. or higher, and more preferably adjusted so that the flash point is 70 ° C. or higher. A non-aqueous electrolyte using such a mixed solvent is less likely to evaporate or leak when used at high temperatures. Among them, the total of ethylene carbonate and propylene carbonate in the non-aqueous solvent is 80% by volume or more, preferably 90% by volume or more, and the volume ratio of ethylene carbonate to propylene carbonate is 30:70 to 60:40. If some are used, cycle characteristics, large current discharge characteristics, and the like can be improved.

  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.

  The heterocyclic compound containing nitrogen, sulfur or nitrogen and sulfur is not particularly limited, but 1-methyl-2-pyrrolidinone, 1,3-dimethyl-2-pyrrolidinone, 1,5-dimethyl-2-pyrrolidinone, Pyrrolidinones such as 1-ethyl-2-pyrrolidinone and 1-cyclohexyl-2-pyrrolidinone; Oxazolidinones such as 3-methyl-2-oxazolidinone, 3-ethyl-2-oxazolidinone and 3-cyclohexyl-2-oxazolidinone; Piperidones such as methyl-2-piperidone and 1-ethyl-2-piperidone; imidazolidinones such as 1,3-dimethyl-2-imidazolidinone and 1,3-diethyl-2-imidazolidinone; sulfolane; Sulfolanes such as 2-methylsulfolane and 3-methylsulfolane; sulfolene; ethylene monkey Sulfites such as propylene sulfite, 1,3-propane sultone, 1-methyl-1,3-propane sultone, 3-methyl-1,3-propane sultone, 1,4-butane sultone, 1,3- And sultone such as propene sultone and 1,4-butene sultone. Among them, 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 1,3-propane sultone, 1,4-butane sultone, 1,3-propene sultone, 1,4-butene sultone, etc., prolong the battery life. From the viewpoint of

  The cyclic carboxylic acid ester is not particularly limited, but γ-butyrolactone, γ-valerolactone, γ-hexalactone, γ-heptalactone, γ-octalactone, γ-nonalactone, γ-decalactone, and γ-undecalactone. , Γ-dodecalactone, α-methyl-γ-butyrolactone, α-ethyl-γ-butyrolactone, α-propyl-γ-butyrolactone, α-methyl-γ-valerolactone, α-ethyl-γ-valerolactone, α, α-dimethyl-γ-butyrolactone, α, α-dimethyl-γ-valerolactone, δ-valerolactone, δ-hexalactone, δ-octalactone, δ-nonalactone, δ-decalactone, δ-undecalactone, δ- Examples include dodecalactone. Among these, γ-butyrolactone, γ-valerolactone, and the like are particularly preferable from the viewpoint of extending the battery life.

  The fluorine-containing cyclic carbonate is not particularly limited, and examples thereof include fluoroethylene carbonate, difluoroethylene carbonate, trifluoroethylene carbonate, tetrafluoroethylene carbonate, and trifluoropropylene carbonate. Among these, fluoroethylene carbonate and the like are particularly preferable from the viewpoint of extending the life of the battery.

  Other compounds having an unsaturated bond in the molecule include vinylene carbonate, vinyl ethylene carbonate, divinyl ethylene carbonate, methyl vinyl carbonate, ethyl vinyl carbonate, propyl vinyl carbonate, divinyl carbonate, allyl methyl carbonate, allyl ethyl carbonate, allyl propyl. Carbonates such as carbonate, diallyl carbonate, dimethallyl carbonate; vinyl acetate, vinyl propionate, vinyl acrylate, vinyl crotonate, vinyl methacrylate, allyl acetate, allyl propionate, methyl acrylate, ethyl acrylate, propyl acrylate , Esters such as methyl methacrylate, ethyl methacrylate, propyl methacrylate; divinyl sulfone, methyl vinyl sulfone Sulfones such as ethyl vinyl sulfone, propyl vinyl sulfone, diallyl sulfone, allyl methyl sulfone, allyl ethyl sulfone, allyl propyl sulfone; sulfites such as divinyl sulfite, methyl vinyl sulfite, ethyl vinyl sulfite, diallyl sulfite; Examples of the sulfonates include vinyl methane sulfonate, vinyl ethane sulfonate, allyl methane sulfonate, allyl ethane sulfonate, methyl vinyl sulfonate, and ethyl vinyl sulfonate; and sulfates such as divinyl sulfate, methyl vinyl sulfate, ethyl vinyl sulfate, and diallyl sulfate. Among these, vinylene carbonate, dimethallyl carbonate, vinyl ethylene carbonate, divinyl ethylene carbonate, vinyl acetate, vinyl propionate, vinyl acrylate, divinyl sulfone, vinyl methanesulfonate, and the like are particularly preferable from the viewpoint of extending the life of the battery.

  In addition to the above additives, other additives such as an overcharge preventing 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.

  As an overcharge preventing material, aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran; 2-fluorobiphenyl, Partially fluorinated products of the above aromatic compounds such as o-cyclohexylfluorobenzene and p-cyclohexylfluorobenzene; 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, 3,5-difluoroanisole and the like And a fluorine-containing anisole compound. Of these, aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, terphenyl partially hydrogenated, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran are preferable. These overcharge prevention materials may be used in combination of two or more. When using 2 or more types together, it is particularly preferable to use cyclohexylbenzene or terphenyl (or a partially hydrogenated product thereof) together with t-butylbenzene or t-amylbenzene.

  Examples of the negative electrode film-forming material include succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, cyclohexanedicarboxylic anhydride, and the like. Of these, succinic anhydride and maleic anhydride are preferable. Two or more of these negative electrode film forming materials may be used in combination.

  As a positive electrode protective material, dimethyl sulfoxide, diethyl sulfoxide, dimethyl sulfite, diethyl sulfite, methyl methanesulfonate, busulfan, methyl toluenesulfonate, dimethyl sulfate, diethyl sulfate, dimethyl sulfone, diethyl sulfone, diphenyl sulfide, thioanisole, And diphenyl disulfide. Of these, methyl methanesulfonate, busulfan, and dimethylsulfone are preferable. Two or more of these positive electrode protective materials may be used in combination.

  Examples of the high input / output material include surfactants such as perfluoroalkylsulfonic acid, ammonium salt, potassium salt or lithium salt of perfluoroalkylcarboxylic acid; perfluoroalkyl polyoxyethylene ether, fluorinated alkyl ester. Among these, perfluoroalkyl polyoxyethylene ether and fluorinated alkyl ester are preferable.

  Although there is no limitation in particular in the ratio of the additive in a non-aqueous electrolyte solution, the range is as follows. In addition, when using a some additive, the ratio of each additive is meant. The lower limit of the ratio of the additive to the non-aqueous electrolyte is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, still more preferably 0.2% by mass or more, and the upper limit is preferably 5%. It is at most 3% by mass, more preferably at most 3% by mass, even more preferably at most 2% by mass.

  By using the other additives, it is possible to suppress a rapid electrode reaction at the time of abnormality due to overcharge, improve capacity maintenance characteristics and cycle characteristics after high temperature storage, and improve input / output characteristics.

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 (d90) 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. Examples of the polyalkylene carbonate resin include polyethylene carbonate, polypropylene carbonate, poly (1,2-dimethylethylene carbonate), polybutene carbonate, polyisobutene carbonate, polypentene carbonate, polyhexene carbonate, polycyclopentene carbonate, polycyclohexene carbonate, and polycyclohexane. Examples include heptene carbonate, polycyclooctene carbonate, and polylimonene carbonate. As a material used for the said structural part, lithium carbonate, polyethylene carbonate, and polypropylene carbonate are preferable.

  Hereinafter, the present embodiment will be described in more detail based on examples. The present invention is not limited to the following examples.

[Production of positive electrode plate]
The positive electrode plate was produced as follows. The positive electrode active material layered type lithium / nickel / manganese / cobalt composite oxide (NMC) and spinel type lithium / manganese oxide (sp-Mn) are mass ratio of predetermined active material (NMC / sp-Mn). Mixed. To this mixture of positive electrode active materials, scaly graphite (average particle size: 20 μm) and acetylene black as conductive materials and polyvinylidene fluoride as binder are sequentially added and mixed to obtain a mixture of positive electrode materials. It was. The mass ratio was active material: conductive material: binder = 90: 5: 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 2.5 g / cm ³ . The aluminum foil had a rectangular shape with a short side (width) of 350 mm, and an uncoated portion with a width of 50 mm was left along the long side on one side. Then, the drying process was performed and it consolidated by the press to the predetermined density. Next, a positive electrode plate having a width of 350 mm was obtained by cutting. At this time, a notch was made in the uncoated part, and the remaining part of the notch was used as a lead piece. The width of the lead piece was 10 mm.

[Production of negative electrode plate]
The negative electrode plate was produced as follows. Amorphous carbon was used as the negative electrode active material. Polyvinylidene fluoride was added as a binder to the amorphous carbon. These mass ratios were 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 rolled copper foil had a rectangular shape with a short side (width) of 355 mm, and left an uncoated part with a width of 50 mm along the long side on one side. Then, the drying process was performed and it consolidated by the press to the predetermined density. The density of the negative electrode mixture was 1.2 g / cm ³ . Next, a negative electrode plate having a width of 355 mm was obtained by cutting. At this time, a notch was made in the uncoated part, and the remaining part of the notch was used as a lead piece. The width of the lead piece was 10 mm.

[Production of battery]
FIG. 1 shows a cross-sectional view of a lithium ion battery. The positive electrode plate and the negative electrode plate are wound with a polyethylene separator having a thickness of 30 μm interposed therebetween so that they are not in direct contact with each other. At this time, the lead piece of the positive electrode plate and the lead piece of the negative electrode plate are respectively positioned on the opposite end surfaces of the winding group. Further, the lengths of the positive electrode plate, the negative electrode plate, and the separator were adjusted, and the wound group diameter was set to 65 ± 0.1 mm or 40 ± 0.1 mm.

  Next, as shown in FIG. 1, the lead pieces 9 led out from the positive electrode plate are deformed, and all of them are gathered near the bottom of the flange 7 on the positive electrode side and brought into contact with each other. The positive electrode side flange portion 7 is integrally formed so as to protrude from the periphery of the pole column (positive electrode external terminal 1) substantially on the extension line of the axis of the wound group 6, and has a bottom portion and a side portion. Thereafter, the lead piece 9 is connected and fixed to the bottom of the flange 7 by ultrasonic welding. The lead piece 9 led out from the negative electrode plate and the bottom of the flange 7 on the negative electrode side are similarly connected and fixed. The negative electrode side flange portion 7 is integrally formed so as to protrude from the periphery of the pole column (negative electrode external terminal 1 ′) substantially on the extension line of the axis of the wound group 6, and has a bottom portion and a side portion.

  Thereafter, an insulating coating 8 was formed using an adhesive tape to cover the side of the flange 7 on the positive electrode external terminal 1 side and the side of the flange 7 of the negative electrode external terminal 1 ′. Similarly, an insulating coating 8 was formed on the outer periphery of the wound group 6. For example, this adhesive tape is stretched from the side of the flange 7 on the positive electrode external terminal 1 side to the outer peripheral surface of the winding group 6 and further from the outer periphery of the winding group 6 to the negative electrode external terminal 1 ′ side. Insulating coating 8 is formed by winding several times over the side of 7. As the insulating coating (adhesive tape) 8, an adhesive tape in which the base material was polyimide and an adhesive material made of hexamethacrylate was applied on one surface thereof was used. The thickness of the insulating coating 8 (the number of windings of the adhesive tape) is adjusted so that the maximum diameter portion of the wound group 6 is slightly smaller than the inner diameter of the battery case 5 made of stainless steel. Inserted inside. The battery container 5 had an outer diameter of 67 mm or 42 mm and an inner diameter of 66 mm or 41 mm.

  Next, as shown in FIG. 1, the ceramic washer 3 ′ is fitted into a pole column whose tip constitutes the positive electrode external terminal 1 and a pole column whose tip constitutes the negative electrode external terminal 1 ′. The ceramic washer 3 ′ is made of alumina, and the thickness of the portion in contact with the back surface of the battery lid 4 is 2 mm, the inner diameter is 16 mm, and the outer diameter is 25 mm. Next, with the ceramic washer 3 placed on the battery lid 4, the positive external terminal 1 is passed through the ceramic washer 3, and with the other ceramic washer 3 placed on the other battery lid 4, the negative external terminal Pass 1 'through another ceramic washer 3. The ceramic washer 3 is made of alumina and has a flat plate shape with a thickness of 2 mm, an inner diameter of 16 mm, and an outer diameter of 28 mm.

Thereafter, the peripheral end surface of the battery lid 4 is fitted into the opening of the battery container 5 and the entire area of both contact portions is laser welded. At this time, the positive electrode external terminal 1 and the negative electrode external terminal 1 ′ pass through a hole (hole) in the center of the battery lid 4 and project outside the battery lid 4. The battery lid 4 is provided with a cleavage valve 10 that cleaves in response to an increase in the internal pressure of the battery. Note that the cleavage pressure of the cleavage valve 10 was set to 13 to 18 kgf / cm ² .

  Next, as shown in FIG. 1, the metal washer 11 is fitted into the positive external terminal 1 and the negative external terminal 1 ′, respectively. Thereby, the metal washer 11 is disposed on the ceramic washer 3. The metal washer 11 is made of a material smoother than the bottom surface of the nut 2.

  Next, the metal nut 2 is screwed to the positive electrode external terminal 1 and the negative electrode external terminal 1 ′, and the battery lid 4 is connected to the flange portion 7 and the nut 2 via the ceramic washer 3, the metal washer 11, and the ceramic washer 3 ′. Secure by tightening between. The tightening torque value at this time was 70 kgf · cm. The metal washer 11 did not rotate until the tightening operation was completed. In this state, the power generation element inside the battery container 5 is shielded from the outside air by the compression of the rubber (EPDM) O-ring 12 interposed between the back surface of the battery lid 4 and the flange 7.

Thereafter, a predetermined amount of electrolytic solution was injected into the battery container 5 from the injection port 13 provided in the battery lid 4, and then the injection port 13 was sealed to complete the cylindrical lithium ion battery 20.
As an electrolytic solution, 1.2 mol / L of lithium hexafluorophosphate (LiPF ₆ ) was dissolved in a mixed solution in which ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate were mixed at a volume ratio of 2: 3: 2. What was done was used. Note that the cylindrical lithium ion battery 20 manufactured in this example is not provided with a current interrupting mechanism that operates to interrupt the current in accordance with the increase in the internal pressure of the battery container 5.

[Evaluation of battery characteristics (discharge capacity, output characteristics, life test)]
The battery characteristics of the lithium ion battery produced in this way were evaluated by the methods shown below.
Regarding the produced lithium ion battery, the ratio (n / X) between the number n of positive electrode current collector leads and the discharge capacity X, and the layered lithium / nickel / manganese / cobalt composite oxide (NMC) and spinel type lithium / The discharge characteristics and lifetime characteristics of the batteries in which the mass ratio (NMC / sp-Mn) to manganese oxide (sp-Mn) was changed were evaluated.

As for the discharge 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. Furthermore, after charging the battery to 4.2 V at 0.5 C, discharging was performed by constant current discharge with 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 discharge capacity. Here, “C” means “current value (A) / discharge capacity (Ah)”.
The output characteristics are as follows. After measuring the above discharge capacity, the battery is charged to 4.2 V at 0.5 C, discharged at a constant current of 2.7 V with a current value of 3 C, and the capacity at the time of discharge is expressed as current. The discharge characteristics at the value 3C were used, and the output characteristics were calculated by the following formula.
Output characteristics = discharge capacity / discharge capacity at a current value of 3C

In the life test, in a voltage range of 4.2 to 2.7 V in an environment of 25 ° C., the discharge capacity after 100 charge / discharge cycles with a current value of 0.5 C (discharge capacity after 100 cycles) is measured. The lifetime was evaluated by the following formula.
Life = discharge capacity after 100 cycles / discharge capacity

(Examples 1-6)
As shown in Table 1, a positive electrode mixture was produced in which the ratio (n / X) between the number n of positive electrode current collector leads and the discharge capacity X and the mass ratio of active materials (NMC / sp-Mn) were changed. A battery having a wound group diameter of 40 mm, an outer diameter of 42 mm, and an inner diameter of 41 mm was produced. The discharge capacity at a current value of 0.5 C, the output characteristics (discharge capacity at a current value of 3 C / discharge capacity at a current value of 0.5 C), and lifetime were evaluated. The results are shown in Table 1.

(Examples 7 to 12)
As shown in Table 2, a positive electrode mixture in which the ratio (n / X) of the number n of positive electrode current collector leads to the discharge capacity X and the mass ratio of active material (NMC / sp-Mn) was changed was prepared. A battery having a wound group diameter of 65 mm, an outer diameter of 67 mm, and an inner diameter of 66 mm was produced. The discharge capacity at a current value of 0.5 C, the output characteristics (discharge capacity at a current value of 3 C / discharge capacity at a current value of 0.5 C), and lifetime were evaluated. The results are shown in Table 2.

(Comparative Examples 1-2)
As shown in Table 3, a positive electrode mixture in which the ratio (n / X) of the number n of positive electrode current collector leads to the discharge capacity X and the mass ratio of active material (NMC / sp-Mn) was changed was prepared. A battery having a wound group diameter of 40 mm, an outer diameter of 42 mm, and an inner diameter of 41 mm was produced. The discharge capacity at a current value of 0.5 C, the output characteristics (discharge capacity at a current value of 3 C / discharge capacity at a current value of 0.5 C), and lifetime were evaluated. The results are shown in Table 3.

(Comparative Examples 3-4)
As shown in Table 4, a positive electrode mixture in which the ratio (n / X) of the number n of positive electrode current collector leads to the discharge capacity X and the mass ratio of active material (NMC / sp-Mn) was changed was prepared. A battery having a wound group diameter of 65 mm, an outer diameter of 67 mm, and an inner diameter of 66 mm was produced. The discharge capacity at a current value of 0.5 C, the output characteristics (discharge capacity at a current value of 3 C / discharge capacity at a current value of 0.5 C), and lifetime were evaluated. The results are shown in Table 4.

About Examples 1-12 shown in Table 1-Table 2, it has confirmed that a battery characteristic improved in comparison with the comparative example shown in Table 3 and Table 4. This will be described in detail below.
When Example 1 in Table 1 and Comparative Example 1 in Table 3 are compared, even if the mass ratio of active materials (NMC / sp-Mn) is the same 100/0, the number of positive electrode current collector leads is n and It can be seen that increasing the ratio (n / X) to the discharge capacity X from 1 to 2 improves the output characteristics and life. In addition, when Example 1 in Table 1 and Comparative Example 2 in Table 3 are compared, (n / X) can be increased from 4 to 2, thereby increasing the discharge capacity and improving the volume energy density. I was able to. Further, from Examples 3 and 5-6, even when the mass ratio of active materials (NMC / sp-Mn) is 30/70, respectively, the output characteristics / lifetime improve as n / X increases. I understand.

  Similarly, when Example 7 in Table 2 and Comparative Example 3 in Table 4 are compared, even if the mass ratio of active materials (NMC / sp-Mn) is 100/0, the number of positive electrode current collector lead pieces It can be seen that increasing the ratio of n to discharge capacity X (n / X) from 1 to 2 improves the output characteristics and life. In addition, when Example 1 in Table 1 and Comparative Example 2 in Table 3 are compared, (n / X) can be increased from 4 to 2, thereby increasing the discharge capacity and improving the volume energy density. I was able to. Further, from Examples 9 and 11 to 12, even when the mass ratio of active materials (NMC / sp-Mn) is the same 30/70, the output characteristics / lifetime are improved as n / X increases. I understand.

From the above results, as a lithium ion battery having a discharge capacity of 30 Ah or more, the ratio (n / X) between the number n of positive electrode current collector lead pieces and the discharge capacity X is the following relational expression 1
1.5 <n / X <3.5 (Relational formula 1)
By satisfying the above, it has been found that a lithium ion battery with high input / output, long life and high capacity can be obtained.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiments and examples. However, the present invention is not limited to the above-described embodiments and examples, and does not depart from the gist of the invention. Various changes can be made.

  The present invention is effective when applied to a lithium ion battery.

DESCRIPTION OF SYMBOLS 1 Positive electrode external terminal 1 'Negative electrode external terminal 2 Nut 3 Ceramic washer 3' Ceramic washer 4 Battery cover 5 Battery container 6 Winding group 7 鍔 part 8 Insulation coating (adhesive tape)
9 Lead piece 10 Cleavage valve 11 Metal washer 12 O-ring 13 Injection port 20 Cylindrical lithium ion battery 30 Current collector lead piece 31 Current collector (uncoated part)
32 Positive electrode composite

Claims (3)

In a lithium ion battery having an electrode winding group in which a positive electrode, a negative electrode, and a separator are wound, and an electrolyte, and a discharge capacity X of 30 Ah or more and less than 110 Ah, the positive electrode includes the current collector and the current collector. It has a positive electrode mixture and current collector lead pieces applied on both sides of the electric current, and the ratio of the number of current collector lead pieces n to the discharge capacity X is the following relational expression 1
1.5 <n / X <3.5 (Relational formula 1)
The lithium ion battery characterized by satisfy | filling. An electrode winding group in which a positive electrode, a negative electrode, and a separator are wound, and an electrolyte solution are provided in a battery container, and a discharge capacity is a lithium ion battery having a discharge capacity of 30 Ah or more and less than 110 Ah,
The positive electrode has a current collector and a positive electrode mixture applied to both sides of the current collector,
The positive electrode mixture contains a mixed active material of layered lithium / nickel / manganese / cobalt composite oxide (NMC) and spinel type lithium / manganese oxide (sp-Mn), and the layered lithium / nickel / manganese The mass ratio (NMC / sp-Mn) of the cobalt composite oxide (NMC) to the spinel type lithium manganese oxide (sp-Mn) is 10/90 or more and 60/40 or less. Item 2. The lithium ion battery according to Item 1. The mixed active material is
A layered lithium-nickel-manganese-cobalt composite oxide represented by the following composition formula (Formula 1);
Li _{(1 + δ)} Mn _x Ni _y Co _(1-xyz) M _z O ₂ (Formula 1)
(M is at least one element selected from the group consisting of Ti, Zr, Nb, Mo, W, Al, Si, Ga, Ge, and Sn, and −0.15 <δ <0.15, 0 0.1 <x ≦ 0.5, 0.6 <x + y + z ≦ 1.0, and 0 ≦ z ≦ 0.1.)
A spinel type lithium manganese oxide represented by the following composition formula (Formula 2):
Li _{(1 + η)} Mn _(2-λ) M ′ _λ O ₄ (Chemical formula 2)
(M ′ is at least one element selected from the group consisting of Mg, Ca, Sr, Al, Ga, Zn, and Cu, and 0 ≦ η ≦ 0.2 and 0 ≦ λ ≦ 0.1. is there.)
The lithium ion battery according to claim 2, comprising a mixture of

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