JP2015046283A - Lithium ion battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium ion battery having a high input and output and a high volume energy density while ensuring the safety.SOLUTION: A lithium ion battery comprises: a group of wound electrodes arranged by winding a positive electrode, a negative electrode and a separator; and an electrolytic solution. The lithium ion battery has a capacity of 30 Ah or larger. The positive electrode has a current collector, and a positive electrode mixture formed on the current collector. The positive electrode mixture contains a lamellar type lithium-nickel-manganese-cobalt complex oxide (NMC), a spinel type lithium-manganese oxide (sp-Mn), and a conductive material. The proportion (NMC/sp-Mn) of NMC to sp-Mn by weight is 10/90 to 40/60. The conductive material contains acetylene black. The positive electrode mixture used in the present invention has a density of 2.4-2.7 g/cm, and the quantity of the applied positive electrode mixture is 170-250 g/cm. The acetylene black has preferably an average particle diameter of 20-100 nm.

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 external dimensions of the 18650-type lithium ion battery are 18 mm in diameter and 65 mm in height. 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 surfaces 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. Further, 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 carbonate is used as a solvent for the electrolyte. , A mixed solvent containing 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, energy stored in the battery is increased, so that ensuring safety during non-stationary conditions becomes an issue. For example, simply securing the battery capacity by enlarging the 18650 type lithium ion battery does not always ensure safety. Moreover, 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 that satisfies high input / output characteristics with high input and high output is desired.
Among the lithium ion battery members, in particular, the positive electrode has a low electronic conductivity of the active material used. For this reason, lowering the electrolytic transfer resistance in the positive electrode leads to improvement of input / output characteristics. Also, in terms of safety, the influence of the type of the positive electrode and the like is considered to be large.

  Accordingly, an object of the present invention is to provide a lithium ion battery with high input / output and high volume energy density while ensuring safety.

  As a result of intensive studies by the present inventors, a lithium ion battery having a battery capacity of 30 Ah or more comprising an electrode winding group in which a positive electrode, a negative electrode, and a separator are wound, and an electrolyte solution, the current collector and the collector A positive electrode composite formed on an electric body, the positive electrode composite comprising a layered lithium-nickel-manganese-cobalt composite oxide (hereinafter also referred to as NMC) and a spinel-type lithium-manganese oxide ( Hereinafter, the weight ratio of the layered lithium-nickel-manganese-cobalt composite oxide (NMC) and the spinel-type lithium-manganese oxide (sp-Mn) may be included. It has been found that the above problem can be solved if the lithium ion battery includes (NMC / sp-Mn) within a predetermined range and includes a specific compound as the conductive material. The present invention has been completed based on such findings.

  That is, the present invention is a lithium ion battery having a battery capacity of 30 Ah or more, comprising an electrode winding group in which a positive electrode, a negative electrode, and a separator are wound, and an electrolytic solution, and is formed on the current collector and the current collector. The positive electrode composite material includes a conductive material of layered lithium-nickel-manganese-cobalt composite oxide (NMC) and spinel-type lithium-manganese oxide (sp-Mn), The weight ratio (NMC / sp-Mn) of layered type lithium / nickel / manganese / cobalt composite oxide (NMC) to spinel type lithium / manganese oxide (sp-Mn) is 10/90 or more and 40/60 or less. And the lithium ion battery in which the said electrically-conductive material contains acetylene black is provided.

The density of the positive electrode mixture in the lithium ion battery according to the embodiment of the present invention can be 2.4 g / cm ³ or more and 2.7 g / cm ³ or less. Moreover, the single-sided coating amount of the positive electrode mixture can be 170 g / m ² or more and 250 g / m ² or less. Thereby, the lithium ion battery having a battery capacity of 30 Ah or more has more excellent input / output characteristics and volume energy density.

  The acetylene black contained in the conductive material in the lithium ion battery according to the embodiment of the present invention has an active material content of 1.1 wt% or more and 10 wt% or less with respect to the total amount of the positive electrode mixture. And the input / output characteristics of a lithium ion secondary battery are further improved.

  Further, the acetylene black contained in the conductive material in the lithium ion battery according to the embodiment of the present invention has further improved input / output characteristics when the average particle size is 20 nm or more and 100 nm or less.

  ADVANTAGE OF THE INVENTION According to this invention, even if it is a lithium ion battery whose battery capacity is 30 Ah or more, the lithium ion secondary battery which is excellent in input-output characteristics, volume energy density, and safety | security 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 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 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. In the present embodiment, the layered lithium / nickel / manganese / cobalt composite oxide (NMC) and the spinel lithium / A mixed active material with manganese oxide (sp-Mn) is included. The positive electrode mixture contains at least acetylene black as a conductive material for the purpose of forming a conductive network between the positive electrode active materials. This positive electrode mixture may be formed (applied) on both surfaces of the current collector, for example.

  For lithium-ion batteries, <1> overcharge due to failure of charge control system, <2> battery crash due to unexpected impact, <3> foreign object piercing, or <4> external short circuit In an abnormal state such as, a large current charge state or a large current discharge state may continue. In such a case, gas may be generated by an abrupt and continuous chemical reaction between the electrolytic solution and the active material in the positive electrode to increase the internal pressure of the battery container.

  Generally, a cylindrical lithium ion battery has an internal pressure reduction mechanism such as a safety valve or a cleavage valve that discharges gas to the outside of the container when a predetermined internal pressure is reached in order to prevent an increase in the internal pressure in the battery container. Yes. However, when the above-described rapid and continuous chemical reaction occurs, the battery container may be damaged (including cracks, expansion, and ignition) even when the internal pressure reduction mechanism is provided.

  On the other hand, in the present embodiment, a positive electrode mixture containing a layered lithium / nickel / manganese / cobalt composite oxide (NMC), a spinel type lithium / manganese oxide (sp-Mn), and a conductive material. NMC / sp-Mn, which is a weight ratio (mixing ratio) of layered lithium / nickel / manganese / cobalt composite oxide (NMC) and spinel type lithium / manganese oxide (sp-Mn), is 10/90. When the ratio is 40/60 or less and the conductive material contains acetylene black, it is possible to increase the capacity and input / output of the battery while ensuring safety even in an abnormal state. The weight ratio may be simply referred to as “weight ratio of active material”.

  When the weight ratio of active material (NMC / sp-Mn) is less than 10/90, the energy density of the battery tends to decrease. On the other hand, when the weight ratio (NMC / sp-Mn) of the active material exceeds 40/60, there is a concern about a decrease in safety, and other safety measures are required.

  Thus, in the positive electrode mixture, the weight ratio of active material (NMC / sp-Mn) is within the above range, and the conductive material contains acetylene black, so that in a high capacity lithium ion battery having a battery capacity of 30 Ah or more. However, it is possible to realize a battery with high input / output and high energy density while ensuring safety.

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. Preferably there is.
When the density is less than 2.4 g / cm ³ , the resistance of the positive electrode is increased and the input / output characteristics may be deteriorated. On the other hand, when the density of the positive electrode mixture exceeds 2.7 g / cm ³ , there is a concern that the safety may be lowered, and other safety measures may need to be strengthened. From this point of view, positive electrode density, more preferably at most 2.45 g / cm ³ or more 2.6 g / cm ^3.

When the coating amount on one side of the positive electrode mixture is less than 175 g / m ² , the amount of the active material contributing to charging / discharging is lowered, and the energy density of the battery may be lowered. On the other hand, when the coating amount on one side of the positive electrode mixture exceeds 250 g / m ² , the resistance of the positive electrode mixture increases, and the input / output characteristics may be deteriorated. 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.

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.

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.

  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. In the present invention, it is preferable to suppress the temperature rise of the battery surface due to heat generation in the positive electrode to less than 4 ° C. This is because if the temperature rise on the battery surface is 4 ° C. or higher, the possibility of inducing thermal runaway increases.

  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 a theoretical capacity equivalent to that of LiCoO ₂ which is widely used as a positive electrode active material for lithium ion batteries.

  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 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 surface active substance is impregnated and added to the positive electrode active material by adding the positive electrode active material to a liquid in which the surface adhesive substance is dissolved or suspended in a solvent. Thereafter, the positive electrode active material impregnated with the surface adhering substance is dried. In addition, 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, so that the precursor of the surface adhesion material is impregnated and added to the positive electrode active material. Thereafter, the positive electrode active material impregnated with the precursor of the surface adhering material is heated. Further, a liquid obtained by dissolving or suspending the precursor of the surface adhesion substance 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.

  The amount of the surface adhering substance is preferably in the following range with respect to the weight of the positive electrode active material. The lower limit of the range is preferably 0.1 ppm or more, more preferably 1 ppm or more, and even more preferably 10 ppm or more. The upper limit is preferably 20% or less, more preferably 10% or less, and still more preferably 5% 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.

  As the positive electrode active material particles of layered type lithium / nickel / manganese / cobalt composite oxide (NMC) and spinel type lithium / manganese oxide (sp-Mn), bulk, polyhedral, spherical, elliptical, plate, Needles, columns, 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.

  Median diameter d50 of primary active material particles of layered lithium / nickel / manganese / cobalt composite oxide (NMC) or spinel type lithium / manganese oxide (sp-Mn) (primary particles aggregate to form secondary particles) In this case, the range of the median diameter d50) of the secondary particles 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 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. 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 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 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 graphite (graphite) such as natural graphite and artificial graphite; carbon black such as acetylene black; and carbonaceous material such as amorphous carbon such as needle coke. Among them, the present invention is particularly characterized by using acetylene black. In a lithium ion battery having a battery capacity of 30 Ah or more, in order to achieve the effects of the present invention that all the characteristics of input / output characteristics, volume energy density, and safety are improved, the weight ratio (NMC) of the above active material is used. In addition to optimizing / sp-Mn), it is essential to include acetylene black as a conductive material. The reason is not necessarily clear, but it is thought that the powder physical properties of acetylene black have a great influence on the improvement of these properties. The effect of acetylene black will be described using examples described later.

The acetylene black used in the present invention is preferably particles having an average particle size of 20 nm or more and 100 nm or less, and there is no particular limitation as long as it is in this particle size 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. In the range of .0 to 1.2, the particle diameter of the present application refers to the major axis (DL).
Examples of the columnar shape include a substantially circular column and a substantially polygonal column, and the particle size in the present application 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.

  In the present invention, it is essential that acetylene black is contained as a conductive material, and one kind of acetylene black can be used alone. In addition, acetylene black may be used in combination with one or more of other carbonaceous materials such as natural graphite, graphite such as artificial graphite, and amorphous carbon such as needle coke. When combined with one or more other carbonaceous materials, a conductive agent having an average particle size of 1 μm or more and 10 μm or less is preferable. When combining two or more kinds of conductive materials, it is possible to freely adjust the dispersibility and battery characteristics of the conductive materials, and to easily obtain the desired effect, by using materials having different shapes and properties in combination. It is because it can do. However, even when acetylene black and another carbonaceous material are combined, the average particle size of the entire conductive material is preferably in the range of 20 nm to 100 nm in order to achieve the effects of the present invention. For example, when A1 is graphite having a median diameter d50 of 1 μm or more and 10 μm or less, and A2 is acetylene black having a median diameter d50 of 20 nm or more and 100 nm or less, the weight ratio A1 / A2 may be 0/100 or more and 75/25 or less. preferable.

  In addition, the average particle diameter of the conductive agent referred to in the present specification is an arithmetic average particle diameter obtained by measuring all the diameters of the in-image particle images taken with a scanning electron microscope photographed at a magnification of 200,000 times.

  The content of the conductive material composed of one kind of acetylene black or a combination of acetylene black and another carbonaceous material is 0.01% by weight or more, preferably 0.1% by weight or more with respect to the total amount of the positive electrode mixture. The upper limit of the content of the conductive material, more preferably 1% by weight or more, is 50% by weight or less, preferably 30% by weight or less, more preferably 15% by weight or less. If it is less than the said minimum, there exists a tendency for electroconductivity to become inadequate. Moreover, when the said upper limit is exceeded, battery capacity may fall.

  Furthermore, the content of acetylene black contained in the conductive material is preferably 1.1% by weight or more and 10% by weight or less based on the total amount of the positive electrode mixture. When the content of acetylene black is less than 1.1% by weight, the conductivity is insufficient. Even if the content of acetylene black is less than 1.1% by weight and the content of the total amount of the conductive material is 1.1% by weight or more by using another conductive material in combination, the large-capacity lithium of the present invention It is difficult to obtain desired input / output characteristics in an ion battery. When the content of acetylene black exceeds 10% by weight, a decrease in battery capacity is inevitable even if the content of the total amount of the conductive material is 15% by weight or less, which is a more preferable range.

  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.

  Regarding the content (addition amount, ratio, amount) of the binder, the range of the content of the binder relative to the weight of the positive electrode mixture is as follows. The lower limit of the range is 0.1% by weight or more, preferably 1% by weight or more, more preferably 3% by weight or more, and the upper limit is 80% by weight or less, preferably 60% by weight or less, more preferably 40% by weight. Hereinafter, it is particularly preferably 10% by weight 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.

  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.

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) 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. . 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 weight of the negative electrode mixture is as follows. The lower limit of the range is 1% by weight or more, preferably 2% by weight or more, more preferably 3% by weight or more, and the upper limit is 45% by weight or less, preferably 40% by weight 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 weight or more, more preferably 0.5% by weight or more, and further preferably 0.6% by weight or more with respect to the total amount of the negative electrode composite material. The upper limit of the binder content is 20% by weight or less, preferably 15% by weight or less, more preferably 10% by weight or less, and still more preferably 8% by weight 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 binder content with respect to the weight 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 weight or more, preferably 0.5% by weight or more, more preferably 0.6% by weight or more, and the upper limit is 5% by weight or less, preferably 3% by weight or less, more preferably. Is 2% by weight or less.

  In addition, the range of the binder content relative to the weight 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 weight or more, preferably 2% by weight or more, more preferably 3% by weight or more, and the upper limit is 15% by weight or less, preferably 10% by weight or less, more preferably 8% by weight 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 weight of the negative electrode mixture when the thickener is used is as follows. The lower limit of the range is 0.1% by weight or more, preferably 0.5% by weight or more, more preferably 0.6% by weight or more, and the upper limit is 5% by weight or less, preferably 3% by weight or less, more preferably. Is 2% by weight 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, 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 weight or more and 20% by weight or less, more preferably 0.1% by weight or more and 5% by weight 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 weight or more and 99% by weight. % Or less, more preferably 80% by weight or more and 98% by weight 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 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.

  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% or more, preferably 10% or more, more preferably 15% or more, and the upper limit is 50% or less, preferably 35% or less, more preferably 30% or less. 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% or more, preferably 8% or more, more preferably 15% or more, and the upper limit is 50% or less, preferably 35% or less, more preferably 30 % Or less, more preferably 25% 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 Sulfites such as sulfite and 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 perfluoroalkyl sulfonic acid, ammonium salt, potassium salt or lithium salt of perfluoroalkyl carboxylic acid; surfactants such as perfluoroalkyl polyoxyethylene ether and 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 weight or more, more preferably 0.1% by weight or more, still more preferably 0.2% by weight or more, and the upper limit is preferably 5%. % By weight or less, more preferably 3% by weight or less, still more preferably 2% by weight or less.

  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 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.

(Battery capacity of lithium ion secondary battery)
The battery capacity (discharge capacity at 0.2 C) of the lithium ion secondary battery of the present invention composed of the above components is 30 Ah or more. From the viewpoint of high input / output and high energy density while ensuring safety. Is preferably from 30 Ah to less than 110 Ah, more preferably from 40 Ah to less than 99 Ah, and still more preferably from 55 Ah to less than 95 Ah.

  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. Layered type lithium / nickel / manganese / cobalt composite oxide (NMC) and spinel type lithium / manganese oxide (sp-Mn) which are positive electrode active materials, weight ratio of predetermined active material (NMC / sp-Mn) Mixed. To this mixture of positive electrode active materials, flaky graphite (average particle size: 7 μm) and acetylene black (AB, average particle size: 50 nm) as conductive materials and polyvinylidene fluoride as binder are sequentially added and mixed. As a result, a mixture of positive electrode materials was obtained. The weight 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 uniformly and uniformly to a predetermined amount on both surfaces of a 20 μm thick aluminum foil as a positive electrode current collector. The single-sided coating amount of the positive electrode mixture on the aluminum foil was 200 g / m ² . 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. The density of the positive electrode mixture was 2.5 g / cm ³ .

In the production of the positive electrode plate, the density of the positive electrode mixture and the coating amount on one side thereof are adjusted in the range of 2.4 g / cm ^{3 to} 2.7 g / cm ³ and 170 g / m ^{2 to} 250 g / m ² , respectively. be able to. As described above, within this range, in the lithium ion battery of the present invention having a battery capacity of 30 Ah or more, the input / output characteristics, volume energy density, and safety should be improved in a well-balanced manner. Can do.
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, and the interval between adjacent lead pieces was 20 mm.

[Production of negative electrode plate]
The negative electrode plate was produced as follows. Amorphous carbon was used as the negative electrode active material. Specifically, the brand name Carbotron P (powder) manufactured by Kureha Chemical Industry Co., Ltd. was used. Polyvinylidene fluoride was added as a binder to the amorphous carbon. The weight ratio of these was 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 coating amount of the negative electrode mixture was 60 g / m ² . 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 negative electrode mixture density was 1.0 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, and the interval between adjacent lead pieces was 20 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.

  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 portion of the flange portion 7 on the positive electrode external terminal 1 side and the side portion of the flange portion 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 stainless steel battery container 5, and the wound group 6 is placed in the battery container 5. Inserted into. The battery container 5 had an outer diameter of 67 mm and an inner diameter of 66 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 cover 4 and project outside the battery cover 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 ′. 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 through 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 (battery capacity, output characteristics, safety (nail penetration test, external short circuit test))]
The battery characteristics of the lithium ion battery produced in this way were evaluated by the methods shown below.

  For the prepared lithium ion battery, the weight ratio of layered lithium / nickel / manganese / cobalt composite oxide (NMC), spinel type lithium / manganese oxide (sp-Mn), acetylene black (AB) and graphite as a conductive material The discharge characteristics and safety of the changed batteries were evaluated.

  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. 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 capacity. The output characteristics were calculated by the following formula.
Output characteristics = discharge capacity at a current value of 3 C / discharge capacity at a current value of 0.5 C

Safety was confirmed by a nail penetration test.
In the nail penetration test, 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 under an environment of 25 ° C. Further, after charging the battery to 4.2 V, a nail having a diameter of 5 mm was inserted into the center of the battery (cell) at a speed of 1.6 mm / second, and the positive electrode and the negative electrode were short-circuited inside the battery container. At this time, changes in the appearance of the battery were confirmed.

(Examples 1-9)
As shown in Table 1, a battery was fabricated using a positive electrode mixture in which the weight ratio of the active material (NMC and sp-Mn) and the conductive material (acetylene black or scaly graphite) was changed. In Examples 1 to 9 shown in Table 1, the content of acetylene black (AB) is in the range of 1.25 to 5% by weight with respect to the total amount of the positive electrode mixture. For the battery of each example shown in Table 1, the discharge capacity at a current value of 0.2C, output characteristics (discharge capacity at a current value of 3C / discharge capacity at a current value of 0.5C), volume energy density at a current value of 0.5C, And safety (nail penetration test) was evaluated. Specifically, the presence or absence of damage to the battery container was confirmed. Damage to the battery container includes cracks, expansion and ignition.

  In Examples 1 to 9, the battery capacity (discharge capacity) at a current value of 0.2 C was all about 75 Ah.

  The results are shown in Table 1. In the results of the output characteristics, “◎” is 95% or more, ○ is 90% or more and less than 95%, “×” is less than 90%, and in the result of volume energy density, “◎” is 220 Wh / L or more, “◯” is 190 Wh / L or more and less than 220 Wh / L, “Δ” is 150 Wh / L or more and less than 190 Wh / L, and “x” is less than 150 Wh / L. “OK (good)” for batteries without damage (excluding nails) and “NG (no)” for batteries with damage. In the test, it was “OK”, and “x” was “NG” in the nail penetration test.

(Comparative Examples 1-4)
As shown in Table 2, a battery was fabricated using a positive electrode mixture in which the weight ratio of the active material (NMC, sp-Mn) and the conductive material (AB, graphite) was changed. Discharge capacity at a current value of 0.5 C, output characteristics (discharge capacity at a current value of 3 C / discharge capacity at a current value of 0.5 C), volume energy density at a current value of 0.5 C, and safety (nail penetration test) were evaluated. . The results are shown in Table 2.

  About Examples 1-9 shown in Table 1, it has confirmed that a battery characteristic improved in comparison with Comparative Examples 1-4. This will be described in detail below.

  Comparing Examples 1 to 3 in Table 1 and Comparative Example 1 in Table 2, even when the weight ratio of active material (NMC / sp-Mn) is the same 30/70, the weight ratio of conductive material (graphite / It can be seen that the output characteristic decreases as AB) is decreased from 0/100. Therefore, in order to improve the output characteristics without changing the volumetric energy density and safety of the battery, it is necessary to use acetylene black alone as a conductive material or increase the blending ratio of acetylene black.

  Moreover, when Example 4 of Table 1 and Comparative Example 2 of Table 2 are compared, even if the weight ratio of the conductive material (graphite / AB) is the same, the weight ratio of the active material (NMC / sp-Mn) is increased. It can be seen that the volume energy density increases.

  Moreover, when Example 7 of Table 1 and Comparative Example 3 of Table 2 are compared, even if the weight ratio of the conductive material (graphite / AB) is the same, the weight ratio of the active material (NMC / sp-Mn) is decreased. It can be seen that the safety can be ensured. Moreover, as shown in Comparative Example 4, it can be seen that the safety test is inferior when the active material is only NMC.

From the above results, as a lithium ion battery, the weight ratio of active material (NMC / sp-Mn) is 10/90 to 40/60, and the weight ratio of conductive material (graphite / AB) is 75/15 to 0 /. By setting it to 100, that is, by containing acetylene black in the conductive material, it is possible to obtain a battery that is excellent in output characteristics and volume energy density and can ensure safety. Thus, the effect of the present invention is obtained by the synergistic effect of the configuration of both.

  Further, in the present embodiment, a preferable ratio of the positive electrode active material to the positive electrode mixture is 85% by weight or more and 95% by weight or less. When the ratio of the positive electrode active material to the positive electrode mixture is low, the volume energy density of the battery that can ensure the safety of the battery decreases. Moreover, when the ratio of the positive electrode active material to the positive electrode mixture is high, although the safety of the battery can be ensured, the output characteristics are deteriorated. On the other hand, by ensuring the proportion of the positive electrode active material in the above range, it is possible to increase the capacity while ensuring safety, and to improve input / output characteristics.

  When the ratio of the positive electrode active material is 85 wt% or more and 95 wt% or less, the range of the conductive material and the binder that can be mixed with the positive electrode mixture is 5 wt% or more and 15 wt% or less with respect to the positive electrode mixture. It becomes. Even when the conductive material and the binder are adjusted so as to be in such a range, the respective functions can be sufficiently exhibited. For example, according to the study by the present inventors, in this embodiment, the effect of acetylene black contained in the conductive material is increased by 1.1% by weight or more with respect to the total amount of the total positive electrode mixture, Saturates at about%. Therefore, 1.1 wt% or more and 10 wt% or less is sufficient as the content of acetylene black contained in the conductive material in the present embodiment. Moreover, as content of the binder in this Embodiment, 3 to 10 weight% is enough. That is, it is possible to adjust the conductive material and the binder within an effective range while ensuring a predetermined amount of the positive electrode active material.

  Thus, even when the ratio of the positive electrode active material to the positive electrode mixture is 85 wt% or more and 95 wt% or less, the battery characteristics can be improved in the same manner as in the above example. This has been confirmed by other studies by the present inventors in which the ratio of the active material: conductive material: binder to the positive electrode mixture is changed.

  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.

  In the above examples and comparative examples, the evaluation was performed without using other safety devices such as a cell controller having a current interruption mechanism in the safety evaluation, but the actual product includes the cell controller. It goes without saying that further safety measures are taken and safety is enhanced in a double and triple manner.

  As described above, the lithium ion battery of the present invention can have high input / output and high volume energy density while ensuring safety. Therefore, it can be applied not only to large-scale power storage system applications such as natural energy, but also to other applications that require high safety, high input / output, long life and high capacity secondary batteries. Its usefulness is extremely high.

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 9 Lead piece 10 Cleavage valve 11 Metal washer 12 O ring 13 Injection port 20 Cylindrical lithium ion battery

Claims (4)

  A lithium ion battery having a battery capacity of 30 Ah or more, comprising an electrode winding group in which a positive electrode, a negative electrode, and a separator are wound, and an electrolytic solution, wherein the positive electrode is formed on the current collector and the current collector The positive electrode composite material includes a layered lithium / nickel / manganese / cobalt composite oxide, a spinel type lithium / manganese oxide and a conductive material, and the layered lithium / nickel / manganese / cobalt. A lithium ion battery in which a weight ratio of the composite oxide to the spinel type lithium / manganese oxide is 10/90 or more and 40/60 or less, and the conductive material contains acetylene black. The density of the positive electrode mixture is 2.4 g / cm ³ or more and 2.7 g / cm ³ or less, and the single-side coating amount of the positive electrode mixture to the current collector is 170 g / m ² or more and 250 g / m ² or less. Item 2. The lithium ion battery according to Item 1.   3. The lithium ion battery according to claim 1, wherein a content of the acetylene black is 1.1 wt% or more and 10 wt% or less with respect to the total amount of the positive electrode mixture.   The lithium ion battery according to any one of claims 1 to 3, wherein an average particle diameter of the acetylene black is 20 nm or more and 100 nm or less.

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