JP2019164974A - Electrode, secondary cell, battery pack and vehicle - Google Patents

Abstract

To provide a high output electrode excellent in high temperature durability.SOLUTION: An electrode is provided. This electrode contains an active material represented by general formula LiMO(0≤x≤1.33, 0.5≤y≤1, M contains at least one element selected from Ni, Co and Mn), and a binder. The binder contains a polymer containing a monomer containing nitrogen atom. In a pore size distribution of the electrode obtained by a method of mercury penetration, when representing the pore median diameter by D (μm), and the pore specific surface area by S (m/g), following expression (1) is satisfied. S/D≥35 ... (1)SELECTED DRAWING: Figure 10

Description

  Embodiments described herein relate generally to an electrode, a secondary battery, a battery pack, and a vehicle.

  Non-aqueous electrolyte batteries using lithium ions are expected to have higher capacities, longer lifespans, and higher outputs as they are applied to in-vehicle and stationary applications such as micro hybrid vehicles and idling stop systems. . Lithium titanium composite oxide has excellent cycle characteristics because of a small volume change accompanying charge / discharge. Further, in the lithium occlusion / release reaction of the lithium-titanium composite oxide, in principle, it is difficult for the lithium metal to precipitate, so that the performance deterioration is small even when charging and discharging with a large current are repeated.

  When a non-aqueous electrolyte battery using lithium ions is mounted in an engine room of a vehicle such as an automobile, wiring connected to the non-aqueous electrolyte battery can be simplified and the space in the vehicle can be expanded. However, since the engine room is in a high temperature environment of about 80 ° C., side reactions between the electrode active material of the nonaqueous electrolyte battery and the electrolyte, swelling and deterioration of the binder, and the like can occur. Therefore, it has been a problem that the output of the non-aqueous electrolyte battery using lithium ions is reduced and the life is shortened.

JP-A-2005-123183 JP-A-9-199179

  An object of the present invention is to provide an electrode having high output and excellent high-temperature durability, a secondary battery including the electrode, a battery pack including the secondary battery, and a vehicle including the battery pack. .

According to a first embodiment, an electrode is provided. This electrode has the general formula _{Li x M y O 2 (0} ≦ x ≦ 1.33,0.5 ≦ y ≦ 1, M includes at least one element selected Ni, Co and Mn) are represented by Active material and a binder. The binder includes a polymer including a monomer containing a nitrogen atom. In the pore diameter distribution of the electrode obtained by the mercury intrusion method, the following formula (1) is satisfied when the pore median diameter is represented by D [μm] and the pore specific surface area is represented by S [m ² / g]. .
S / D ≧ 35 (1)
According to the second embodiment, a secondary battery is provided. This secondary battery includes the electrode according to the first embodiment.

  According to the third embodiment, a battery pack is provided. This battery pack includes the secondary battery according to the second embodiment.

  According to a fourth embodiment, a vehicle is provided. This vehicle includes the battery pack according to the third embodiment.

Sectional drawing which shows schematically an example of the secondary battery which concerns on 2nd Embodiment. Sectional drawing which expanded the A section of the secondary battery shown in FIG. The partial notch perspective view which shows the other example of the secondary battery which concerns on 2nd Embodiment typically. Sectional drawing which expanded the B section of the secondary battery shown in FIG. The perspective view which shows roughly an example of the assembled battery which concerns on 2nd Embodiment. The exploded perspective view showing roughly an example of the battery pack concerning a 3rd embodiment. The block diagram which shows an example of the electric circuit of the battery pack shown in FIG. Sectional drawing which shows roughly an example of the vehicle which concerns on 4th Embodiment. The figure which showed roughly the other example of the vehicle which concerns on 4th Embodiment. The figure which shows the pore diameter distribution which concerns on an Example and a comparative example.

  Hereinafter, embodiments will be described with reference to the drawings. In addition, the same code | symbol shall be attached | subjected to a common structure through embodiment, and the overlapping description is abbreviate | omitted. Each figure is a schematic diagram for promoting explanation and understanding of the embodiment, and its shape, dimensions, ratio, etc. are different from the actual device, but these are the following explanations and known techniques. The design can be changed as appropriate.

(First embodiment)
According to a first embodiment, an electrode is provided. This electrode has the general formula _{Li x M y O 2 (0} ≦ x ≦ 1.33,0.5 ≦ y ≦ 1, M includes at least one element selected Ni, Co and Mn) are represented by Active material and a binder. The binder includes a polymer including a monomer containing a nitrogen atom. In the pore diameter distribution of the electrode obtained by the mercury intrusion method, the following formula (1) is satisfied when the pore median diameter is represented by D [μm] and the pore specific surface area is represented by S [m ² / g]. .
S / D ≧ 35 (1)
Conventionally, for example, a carbonate-based organic solvent has been used as an electrolyte of a lithium ion nonaqueous electrolyte battery. Since the electrode is exposed to an electrolyte containing such an organic solvent, it is desirable that the binder contained in the electrode is difficult to swell with respect to the electrolyte. When the binder swells, not only the output characteristics deteriorate, but also the cycle life characteristics deteriorate. For example, polyvinylidene fluoride (PVdF) used as a binder tends to swell when exposed to a carbonate-based electrolyte. In particular, the binder is more likely to swell in a high temperature environment of 80 ° C. or higher.

  The desired property of the binder is not only high resistance to swelling with respect to the electrolyte. It is desirable that the binder is capable of appropriately covering the surface of the active material particles. By covering the surface of the active material particles with the binder, a side reaction between the active material and the electrolyte can be suppressed. However, if the surface of the active material particles is excessively covered with the binder, the internal resistance of the electrode increases, which is not preferable.

The present inventors have found that in general formula _{Li x M y O 2 (0} ≦ x ≦ 1.33,0.5 ≦ y ≦ 1, M includes at least one element selected Ni, Co and Mn) In an electrode including an active material represented by the binder and a binder, the binder includes a polymer including a monomer including a nitrogen atom, and a pore median diameter (d50) in a pore diameter distribution obtained by a mercury intrusion method for the electrode. It was found that an electrode satisfying S / D ≧ 35 has high output and excellent high-temperature durability when D is represented by D [μm] and the pore specific surface area is represented by S [m ² / g]. .

Binder containing a polymer containing a monomer containing a nitrogen atom, for the polarity of the molecule is large, the general formula _{Li x M y O 2 (0} ≦ x ≦ 1.33,0.5 ≦ y ≦ 1, M is Ni , Including at least one element selected from Co and Mn). That is, according to such a combination, a side reaction between the active material and the electrolyte can be suppressed.

  Moreover, the binder containing the polymer containing the monomer containing a nitrogen atom hardly swells to the electrolyte even in a high temperature environment. Therefore, the capacity is unlikely to decrease when repeated charging and discharging are performed in a high temperature environment. That is, the electrode according to the embodiment is excellent in cycle life characteristics.

Furthermore, in the electrode according to the embodiment, in the pore diameter distribution of the electrode obtained by the mercury intrusion method, the pore median diameter (d50) is represented by D [μm], and the pore specific surface area is represented by S [m ² / g]. When expressed, the following formula (1) is satisfied.
S / D ≧ 35 (1)
When the electrode satisfies the above formula (1), the pore specific surface area S is sufficiently large, so that the reaction area between the active material and the electrolyte is large. Moreover, since the pore median diameter D is sufficiently small, an electron conduction path between the active materials is sufficiently formed. In addition, since the binder contains a polymer containing a monomer containing a nitrogen atom, an electrode having high output and excellent high-temperature durability can be provided. If the S / D is less than 35, the pore specific surface area S is small, so that the reaction area between the active material and the electrolyte tends to decrease and the output characteristics tend to be inferior. Alternatively, since the pore median diameter D is large, the number of locations where the electron conductive path between the active materials is divided tends to increase and the output characteristics tend to be inferior. The dimension of S / D is [m / g]. S / D is preferably 35 or more, and more preferably 50 or more. According to one aspect, S / D may be 100 or less, and may be 200 or less.

  As described above, the binder according to the embodiment hardly contains an electrolyte even in a high-temperature environment, and hardly swells. Therefore, the value of S / D hardly changes even after repeating the charge / discharge cycle. On the other hand, for example, when a binder that easily swells with respect to an electrolyte such as PVdF is used, the S / D value tends to change by repeating the charge / discharge cycle.

The pore specific surface area S [m ² / g] is a value calculated when the mercury intrusion method is performed on the electrode and each pore is assumed to be cylindrical. Although the measurement method of the mercury intrusion method will be described later, the weight of the current collector included in the electrode is not taken into account when calculating the pore specific surface area. Pore specific surface area S is preferably in the range of 3.5m ² / g~15m ² / g, and more preferably in the range of 3.5m ² /g~8.0m ² / g. If the pore specific surface area S is excessively small, the reaction area between the active material and the electrolyte may decrease, resulting in poor output characteristics. If the pore specific surface area S is excessively large, side reactions with the electrolyte on the active material surface may increase, and the battery life characteristics may deteriorate.

  The pore median diameter D (d50) can be determined from the pore diameter distribution obtained by performing the mercury intrusion method on the electrode. The pore median diameter D is preferably in the range of 0.05 μm to 0.2 μm, and more preferably in the range of 0.06 μm to 0.15 μm. If the pore median diameter D is excessively small, the ionic conductivity in the active material-containing layer may be lowered. When the pore median diameter D is excessively large, the number of locations where the electron conductive path between the active materials is divided may increase and the output characteristics may deteriorate.

  The pore median diameter D and the pore specific surface area S are values measured for pore diameters existing in the range of 0.003 μm to 0.5 μm in the pore diameter distribution of the electrode obtained by the mercury intrusion method described later. It is preferable. That is, in the pore diameter distribution of the electrode obtained by the mercury intrusion method, the pore median diameter D and the pore specific surface area S measured from the pore diameter existing in the range of 0.003 μm to 0.5 μm are S / D. It is preferable to satisfy ≧ 35, and it is more preferable to satisfy S / D ≧ 50. By considering only pores having a size in the range of 0.003 μm to 0.5 μm, it is possible to eliminate the influence of very large pores formed due to unexpected factors. The lower limit of 0.003 μm is set to exclude pores smaller than the measurement limit of the mercury intrusion method.

  Hereinafter, the electrode according to the embodiment will be described in detail. The electrode which concerns on embodiment can be used as an electrode for secondary batteries, for example. The electrode which concerns on embodiment can be used as a positive electrode and / or a negative electrode for secondary batteries, for example.

The electrode according to the embodiment can include a current collector and an active material-containing layer. The active material-containing layer can be formed on one side or both sides of the current collector. In the active material-containing layer is represented by the general formula _{Li x M y O 2 (0} ≦ x ≦ 1.33,0.5 ≦ y ≦ 1, M includes at least one element selected Ni, Co and Mn) And a binder containing a polymer containing a monomer containing a nitrogen atom. The active material-containing layer includes a plurality of pores. The plurality of pores can be formed between the active material particles and the binder, for example. The plurality of pores can include pores present in the active material particles. The active material-containing layer may contain a conductive agent. Note that Table, the general formula _{Li x M y O 2 (0} ≦ x ≦ 1.33,0.5 ≦ y ≦ 1, M includes at least one element selected Ni, Co and Mn) less active material that is a, may be referred to as "the general formula Li _x M _y O ₂ in the active material is represented."

Active material-containing layer comprises at least one selected from the general formula Li _x M _y O ₂ oxide, expressed as active material. Examples of the oxide represented by the general formula Li _x M _y O _2, the manganese dioxide (MnO _2), nickel oxide, lithium-manganese composite oxide (e.g., Li _x Mn ₂ O ₄ or Li _x MnO _2; 0 _<x ≦ 1), lithium nickel composite oxide (for example, Li _x NiO ₂ ; 0 <x ≦ 1), lithium cobalt composite oxide (for example, Li _x CoO ₂ ; 0 <x ≦ 1), lithium nickel cobalt composite oxide (for example, _{Li x Ni 1-y Co y} O 2; 0 <x ≦ 1,0 <y <1), lithium-manganese-cobalt composite oxide (e.g., _{Li x Mn y Co 1-y} O 2; 0 <x ≦ 1,0 <Y <1), lithium manganese nickel composite oxide having a spinel structure (for example, Li _x Mn _{2 -y} Ni _y O ₄ ; 0 <x ≦ 1, 0 <y <2), lithium nickel cobalt manganese composite oxide ( Li _x Ni _1-yz Co _y Mn _z O ₂ 0 <x ≦ 1, 0 <y <1, 0 <z <1, y + z <1).

The active material-containing layer may further contain an active material other than these oxides. Other active materials, for example iron oxide, copper oxide, lithium phosphates having an olivine structure (e.g., _{Li x FePO 4; 0 <x} ≦ 1, Li x Fe 1-y Mn y PO 4; 0 <x ≦ 1, 0 <y <1, Li _x CoPO ₄ ; 0 <x ≦ 1), iron sulfate (Fe ₂ (SO ₄ ) ₃ ), vanadium oxide (for example, V ₂ O ₅ ), and the like.

Active material-containing layer is represented by the general formula Li _x M _y Among oxide represented by O _2, a lithium manganese composite oxide (e.g., Li _x Mn ₂ O ₄ or _{Li x MnO 2; 0 <x} ≦ 1), lithium Nickel composite oxide (for example, Li _x NiO ₂ ; 0 <x ≦ 1), lithium cobalt composite oxide (for example, Li _x CoO ₂ ; 0 <x ≦ 1), lithium nickel cobalt composite oxide (for example, Li _x Ni _{1− y Co y O 2; 0 <} x ≦ 1,0 <y <1), lithium-manganese-cobalt composite oxide (e.g., _{Li x Mn y Co 1-y} O 2; 0 <x ≦ 1,0 <y <1) , lithium-nickel-cobalt-manganese composite oxide _{(Li x Ni 1-yz Co} y Mn z O 2; 0 <x ≦ 1,0 <y <1,0 <z <1, y + z <1) lithium having a spinel structure manganese Nickel composite oxide (eg Li _x Mn _{2 -y} Ni _y O ₄ ; It is preferable to include at least one selected from the group consisting of 0 <x ≦ 1, 0 <y <2). By including such an oxide, a secondary battery having high output and excellent life characteristics can be manufactured.

Occupied in the weight of Zenkatsu substance active material-containing layer contains the percentage of the weight of the general formula Li _x M _y O ₂ with active material represented, for example in the range of 50% to 100% by weight, preferably It is in the range of 80% to 100% by weight.

Active material represented by the general formula Li _x M _y O ₂ has, for example, a particle shape and includes primary particles and / or secondary particles. As long as the electrode according to the embodiment meets the S / D ≧ 35, the active material represented by the general formula Li _x M _y O ₂ may be present as primary particles, present as secondary particles Also good.

The average particle diameter of the general formula Li _x M _y O ₂ represented by the active material particles, for example in the range of 0.1Myuemu～50myuemu, preferably in the range of 3Myuemu～15myuemu. When the average particle diameter of the general formula Li _x M _y O ₂ represented by the active material particles is within the above range, it is possible to produce an excellent secondary battery with high output and life characteristics.

  The binder (binder) included in the active material-containing layer is blended to fill a gap between the dispersed active materials and bind the active material and the current collector. The binder includes a polymer including a monomer containing a nitrogen atom. The binder may consist only of a polymer containing a monomer containing a nitrogen atom. In the present specification, “polymer” includes the concept of a polymer composed of one type of monomer and the concept of a copolymer containing a plurality of types of monomers. When the binder includes a copolymer, for example, at least one of monomer components constituting the copolymer includes a nitrogen atom. It is preferable that all of the monomer components constituting the copolymer contain a nitrogen atom. Since a polymer including a monomer containing a nitrogen atom has a large intramolecular polarity, the interaction with the active material particles is large. As a result, such a polymer tends to cover the surface of the active material particles, and thus the side reaction between the active material particles and the electrolyte tends to be reduced.

  The polymer contained in the binder may consist only of a monomer containing a nitrogen atom. However, the polymer contained in the binder is preferably a copolymer. When the polymer is a copolymer, the copolymer includes, for example, (meth) acrylate, (meth) acrylamide, vinyl cyanide monomer, carboxyl monomer and the like in addition to the monomer containing a nitrogen atom. May be included. In this case, the flexibility of the active material containing layer is improved. The copolymer contained in the binder preferably contains a monomer containing a nitrogen atom in a proportion of 50 mol% to 95 mol%. If the proportion of the monomer containing nitrogen atoms in the copolymerization component is excessively low, the binding property of the binder may be reduced when the secondary battery is operated or stored in a high temperature environment. It is not preferable.

  Examples of monomers containing nitrogen atoms include acrylonitrile and imide compounds. The polymer preferably contains acrylonitrile as a monomer component from the viewpoint of suppressing a decrease in binding property when the secondary battery is operated or stored in a high temperature environment.

  The polymer contained in the binder is preferably a polyacrylonitrile-based copolymer. Since the polyacrylonitrile-based copolymer does not easily swell with respect to the electrolyte described later, there is an advantage that the electrode structure is not easily changed even when charging and discharging are repeated in a high temperature environment. The polyacrylonitrile copolymer may contain (meth) acrylate, (meth) acrylamide, vinyl cyanide monomer, carboxyl monomer and the like in addition to acrylonitrile as a monomer.

  The ratio of the weight of the polymer containing the monomer containing a nitrogen atom to the weight of the binder is preferably 60% by weight or more. If this proportion is less than 60% by weight, the high temperature durability tends to be inferior. This is presumably because the content of the binder of a different type from the polymer containing the monomer containing a nitrogen atom is large with respect to the weight of the binder, and such a binder easily swells in a high temperature environment. The ratio of the weight of the polymer containing the monomer containing a nitrogen atom to the weight of the binder is preferably 70% by weight or more, more preferably 80% by weight or more, and 90% by weight or more. Further preferred. This proportion is most preferably 100% by weight.

  The ratio of the weight of the polyacrylonitrile copolymer to the weight of the binder is, for example, 50% by weight or more, and the higher the ratio, the more preferable. If this ratio is less than 50% by weight, the binder may easily swell in a high temperature environment. When the binder swells, there is a possibility that the output characteristics and the life characteristics may be deteriorated due to a decrease in binding properties.

  The binder includes a polymer containing a monomer containing a nitrogen atom, a copolymer containing a methacrylate having a phosphate group, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine. It may contain at least one of a base rubber, a polyacrylic acid compound, carboxyl methyl cellulose (CMC), and a salt of CMC.

  Among these, it is preferable that a binder further contains the copolymer containing the methacrylate which has a phosphoric acid group. When the binder contains a copolymer containing a methacrylate having a phosphate group, the binding property of the active material particles and the conductive agent in the active material-containing layer, and the binding between the active material-containing layer and the current collector The sex can be increased. Examples of the copolymer containing a methacrylate having a phosphoric acid group include a copolymer of a methacrylate having a phosphoric acid group and acrylonitrile.

  The conductive agent can be blended in order to enhance current collection performance and suppress contact resistance between the active material and the current collector. Examples of the conductive agent include vapor grown carbon fiber (VGCF), carbon black such as acetylene black, carbonaceous materials such as graphite, carbon nanofiber, and carbon nanotube. One of these may be used as a conductive agent, or a combination of two or more may be used as a conductive agent. Alternatively, instead of using a conductive agent, a carbon coat or an electronically conductive inorganic material coat may be applied to the surface of the active material particles.

  In the active material-containing layer, the active material and the binder are preferably blended in proportions of 80% by mass to 95% by mass and 2% by mass to 17% by mass, respectively.

  By setting the amount of the binder to 2% by mass or more, sufficient electrode strength can be obtained. The binder can also function as an insulator. Therefore, when the amount of the binder is 17% by mass or less, the amount of the insulator included in the electrode is reduced, so that the internal resistance can be reduced.

  When adding a conductive agent, it is preferable to mix the conductive agent in a proportion of 3% by mass or more and 18% by mass or less in the active material-containing layer. The effect mentioned above can be exhibited by making the quantity of a electrically conductive agent 3 mass% or more. Moreover, the ratio of the electrically conductive agent which contacts an electrolyte can be made low by making the quantity of an electrically conductive agent 18 mass% or less. When this ratio is low, decomposition of the electrolyte can be reduced under high temperature storage.

  The current collector is preferably an aluminum foil or an aluminum alloy foil containing one or more elements selected from Mg, Ti, Zn, Ni, Cr, Mn, Fe, Cu, and Si. In consideration of expansion and contraction of the active material accompanying charging / discharging of the secondary battery, it is more desirable to use a current collector of electrolytic foil whose surface is roughened.

  The thickness of the aluminum foil or aluminum alloy foil is preferably 5 μm or more and 20 μm or less, and more preferably 15 μm or less. The purity of the aluminum foil is preferably 99% by mass or more. The content of transition metals such as iron, copper, nickel, and chromium contained in the aluminum foil or aluminum alloy foil is preferably 1% by mass or less.

  In addition, the current collector can include a portion where the active material-containing layer is not formed on the surface thereof. This part can act as a current collecting tab.

  The density (excluding the current collector) of the electrode according to the embodiment is, for example, in the range of 2.5 g / cc to 3.8 g / cc, and preferably in the range of 2.8 g / cc to 3.6 g / cc. Is in. It is preferable that the density of the electrode be in this range because it is excellent in energy density and electrolyte retention.

<Mercury intrusion method>
The mercury intrusion method performed on the electrode will be described. Thereby, a pore size distribution diagram of the active material-containing layer included in the electrode can be obtained, and the pore specific surface area and the pore median diameter can be obtained. The current collector does not contain pores that can be detected by mercury porosimetry. Therefore, the measurement result of the pore size distribution for the electrode can be regarded as the measurement result of the pore size distribution for the active material-containing layer.

  In order to obtain an electrode to be measured, the battery is placed in a glove box filled with argon gas, and the battery is disassembled therein. From the disassembled battery, take out the electrode as the measurement target. The extracted electrode is washed with an ethyl methyl carbonate solvent and dried.

  Next, a plurality of samples (including a current collector) having a size of about 50 mm × 50 mm are cut out from the dried electrode. The total weight of the cut out plurality of samples is about 1 g including the current collector. These are put in a measurement cell and measured under conditions of an initial pressure of 5 kPa (about 0.7 psia, pore diameter of about 250 μm) and a final pressure of about 60,000 psia (pore diameter of about 0.003 μm). By this measurement, a pore diameter distribution diagram of the active material-containing layer is obtained, and the pore specific surface area and the pore median diameter can be obtained. When calculating the pore specific surface area, the weight of the current collector is subtracted from the weight of the electrode as a sample placed in the measurement cell. For example, when an aluminum foil is used as the current collector, the weight of the current collector is calculated in consideration of the specific gravity of 2.7 g / cc of aluminum, and the weight of the current collector is subtracted from the weight of the sample.

  For example, a Shimadzu Autopore 9520 type can be used as a mercury intrusion measuring apparatus. From the pore diameter distribution obtained by the mercury intrusion method, the pore volume, the pore median diameter (d50), and the mode diameter can be obtained.

  The analysis principle of the mercury intrusion method is based on Washburn's formula (A).

D = −4γcos θ / P (A) where P is the applied pressure, D is the pore diameter, γ is the surface tension of mercury (480 dyne · cm ⁻¹ ), and θ is the contact angle between mercury and the pore wall surface. °. Since γ and θ are constants, the relationship between the applied pressure P and the pore diameter D can be obtained from the Washburn equation. By measuring the mercury intrusion volume at that time, the pore diameter and its volume distribution can be derived. it can.

<Identification of the presence or absence of nitrogen atoms>
It can be confirmed by glow discharge optical emission spectrometry (GD-OES) that the binder contains a polymer containing a monomer containing a nitrogen atom.

  First, the battery to be measured is placed in a glove box filled with argon gas, and the battery is disassembled therein. The electrode to be measured is taken out from the disassembled battery. The extracted electrode is washed with an ethyl methyl carbonate solvent and dried. The presence or absence of the N element can be identified by performing glow discharge optical emission spectrometry on the electrode surface after drying.

  Further, the type of polymer contained in the binder can be identified by performing infrared absorption spectroscopy (IR) by the following procedure.

  First, the battery to be measured is placed in a glove box filled with argon gas, and the battery is disassembled therein. The electrode to be measured is taken out from the disassembled battery. The extracted electrode is washed with an ethyl methyl carbonate solvent and dried.

  Next, in order to extract the binder from the active material-containing layer, the binder contained in the active material-containing layer is dissolved with dimethylformamide. When the active material and / or the conductive agent contained in the active material-containing layer are mixed in the solution after extraction, these are removed, for example, by filtration. The binder can be obtained by evaporating dimethylformamide from the solution in which the binder is dissolved. Measurement by IR spectroscopy is performed on the extracted binder. By this IR spectroscopy measurement, the binder polymer contained in the active material-containing layer can be identified.

For example, in the infrared absorption spectrum, when a peak derived from a nitrile bond can be confirmed in the vicinity of 2200 cm ⁻¹ , it can be determined that the binder contains polyacrylonitrile or a polyacrylonitrile-based copolymer. In the infrared absorption spectrum, when a peak derived from a carbon-fluorine bond can be confirmed near 1200 cm ⁻¹ , it can be determined that the binder contains polyvinylidene fluoride (PVdF).

  Further, in the infrared absorption spectrum obtained by the IR spectroscopy, each component contained in the binder can be quantified from the detected peak intensity ratio.

<Measurement of average particle diameter of active material particles>
The average particle diameter of the active material particles can be measured by performing a laser diffraction method according to the following procedure.
As a measuring device, for example, a laser diffraction type distribution measuring device (Shimadzu SALD-300) is used. When the active material is incorporated in the battery, it can be taken out as follows. First, the battery is discharged. For example, the battery can be put into a discharged state by discharging the battery to a rated end voltage with a current of 0.1 C in a 25 ° C. environment. Next, the discharged battery is disassembled and an electrode (for example, a positive electrode) is taken out. The extracted electrode is washed with, for example, methyl ethyl carbonate.

  Next, an active material is extracted from the electrode to obtain a measurement sample. In the extraction treatment, for example, the binder component is removed by washing with N-methyl-2-pyrrolidone (NMP) or the like, and then the conductive agent is removed with a mesh having an appropriate opening. If these components remain slightly, they may be removed by heat treatment in the atmosphere (for example, at 250 ° C. for 30 minutes).

  Thereafter, about 0.1 g of the sample, a surfactant, and 1 to 2 mL of distilled water are added to a beaker, and the mixture is sufficiently stirred and poured into a stirred water tank to prepare a sample solution. Using this sample solution, the luminous intensity distribution is measured 64 times at intervals of 2 seconds, and the particle size distribution data is analyzed.

<Method for producing electrode>
When the active material-containing layer is formed on one side or both sides of the current collector, if the solvent containing the slurry containing the binder according to the embodiment is rapidly vaporized, binder migration tends to occur. Migration is a phenomenon in which the binder moves in the opposite direction to the current collector when the solvent is dried after applying the slurry to the current collector. When migration occurs, the binder is simultaneously aggregated and filled in the pores in the electrode. As a result, the pore median diameter D is slightly reduced and the pore specific surface area S is greatly reduced as compared with the case where no migration occurs. Since the decrease rate of the pore specific surface area S is larger than the decrease rate of the pore median diameter D, the ratio S / D decreases when migration occurs.

  By manufacturing the electrode under conditions where migration is unlikely to occur, the pore median diameter D can be reduced, and the pore specific surface area S can be increased, so that the ratio S / D can be increased. In order to prevent migration during electrode production, it is effective to include a step of drying the applied slurry stepwise. The stepwise drying process includes, for example, a two-stage process including a preliminary drying process performed at a relatively low temperature and a main drying process performed at a relatively high temperature. The preliminary drying step is a drying step that is performed at a lower temperature than the main drying step.

  Note that migration tends to occur when a binder having a low specific gravity is used. For example, when a binder containing a polyacrylonitrile-based copolymer is used, migration tends to occur.

Therefore, the electrode according to the embodiment is manufactured as follows, for example.
First, an active material, a conductive agent, and a binder are suspended in a solvent to prepare a slurry. This slurry is applied to one side or both sides of the current collector. Next, the applied slurry is pre-dried at a temperature of 80 ° C to 100 ° C. The preliminary drying is performed, for example, for 1 second to 60 seconds. Then, this is further dried at a temperature of 130 ° C. or higher. The main drying is performed for 5 seconds to 300 seconds, for example. In this way, a laminate of the active material containing layer and the current collector is obtained. Thereafter, the laminate is pressed. In this way, an electrode is produced.

  The ratio S / D can be adjusted by appropriately setting the average particle diameter of the active material to be used, the presence or absence of preliminary drying, the press pressure of the electrode, the amount of conductive agent, and the like.

For example, when the average particle diameter of the active material is increased, the pore specific surface area S is increased and the pore median diameter D is decreased, so that the ratio S / D tends to increase. Further, for example, when pre-drying is performed, the ratio S / D tends to increase as compared to the case where this is not performed.
For example, if the amount of the conductive agent is increased, the specific surface area S of the pores is increased, so that the ratio S / D tends to be increased.

According to a first embodiment, an electrode is provided. This electrode has the general formula _{Li x M y O 2 (0} ≦ x ≦ 1.33,0.5 ≦ y ≦ 1, M includes at least one element selected Ni, Co and Mn) are represented by Active material and a binder. The binder includes a polymer including a monomer containing a nitrogen atom. In the pore diameter distribution of the electrode obtained by the mercury intrusion method, the following formula (1) is satisfied when the pore median diameter is represented by D [μm] and the pore specific surface area is represented by S [m ² / g]. .
S / D ≧ 35 (1)
Therefore, according to the embodiment, an electrode having high output and excellent high-temperature durability can be provided.

(Second Embodiment)
The secondary battery according to the embodiment includes a positive electrode, a negative electrode, and an electrolyte. This secondary battery includes the electrode according to the first embodiment as a positive electrode. The secondary battery may further include a separator disposed between the positive electrode and the negative electrode. The positive electrode, the negative electrode, and the separator can constitute an electrode group. The electrolyte can be held on the electrode group.

  The secondary battery may further include an exterior member that accommodates the electrode group and the electrolyte.

  The secondary battery may further include a negative electrode terminal electrically connected to the negative electrode and a positive electrode terminal electrically connected to the positive electrode.

  The secondary battery can be, for example, a lithium ion secondary battery. The secondary battery includes a non-aqueous electrolyte secondary battery including a non-aqueous electrolyte.

  Hereinafter, the positive electrode, the negative electrode, the electrolyte, the separator, the exterior member, the negative electrode terminal, and the positive electrode terminal will be described in detail.

(1) Positive Electrode The positive electrode can include a positive electrode current collector and a positive electrode active material-containing layer. The positive electrode current collector and the positive electrode active material-containing layer can be a current collector and an active material-containing layer that can be included in the electrode according to the first embodiment, respectively.

  The electrode according to the first embodiment can function as the positive electrode according to the present embodiment.

(2) Negative electrode The negative electrode can include a negative electrode current collector and a negative electrode active material-containing layer. The negative electrode active material-containing layer can be formed on one side or both sides of the negative electrode current collector. The negative electrode active material-containing layer can contain a negative electrode active material, and optionally a conductive agent and a binder.

Examples of the negative electrode active material include lithium titanate having a ramsdellite structure (for example, Li _{2 + y} Ti ₃ O ₇ , 0 ≦ y ≦ 3), and lithium titanate having a spinel structure (for example, Li _{4 + x} Ti ₅ O ₁₂ , 0 ≦ x ≦ 3), monoclinic titanium dioxide (TiO ₂ ), anatase titanium dioxide, rutile titanium dioxide, hollandite titanium composite oxide, orthorhombic titanium-containing composite oxide, and single An example is an oblique niobium titanium composite oxide.

Examples of the orthorhombic titanium-containing composite oxide include compounds represented by Li _{2 + a} M (I) _{2 -b} Ti _{6 -c} M (II) _d O _{14 + σ} . Here, M (I) is at least one selected from the group consisting of Sr, Ba, Ca, Mg, Na, Cs, Rb and K. M (II) is at least one selected from the group consisting of Zr, Sn, V, Nb, Ta, Mo, W, Y, Fe, Co, Cr, Mn, Ni, and Al. The subscripts in the composition formula are 0 ≦ a ≦ 6, 0 ≦ b <2, 0 ≦ c <6, 0 ≦ d <6, and −0.5 ≦ σ ≦ 0.5. A specific example of the orthorhombic titanium-containing composite oxide is Li _{2 + a} Na ₂ Ti ₆ O ₁₄ (0 ≦ a ≦ 6).

Examples of the monoclinic niobium titanium composite oxide include compounds represented by Li _x Ti _1-y M1 _y Nb ₂ -z M2 _z O _{7 + δ} . Here, M1 is at least one selected from the group consisting of Zr, Si, and Sn. M2 is at least one selected from the group consisting of V, Ta, and Bi. The subscripts in the composition formula are 0 ≦ x ≦ 5, 0 ≦ y <1, 0 ≦ z <2, and −0.3 ≦ δ ≦ 0.3. A specific example of the monoclinic niobium titanium complex oxide is Li _x Nb ₂ TiO ₇ (0 ≦ x ≦ 5).

As another example of the monoclinic niobium titanium composite oxide, a compound represented by Ti _1-y M3 _{y + z} Nb _2-z O _7-δ can be given. Here, M3 is at least one selected from Mg, Fe, Ni, Co, W, Ta, and Mo. The subscripts in the composition formula are 0 ≦ y <1, 0 ≦ z ≦ 2, and −0.3 ≦ δ ≦ 0.3.

  The conductive agent is blended in order to improve current collection performance and suppress contact resistance between the active material and the current collector. Examples of the conductive agent include vapor grown carbon fiber (VGCF), carbon black such as acetylene black, and carbonaceous material such as graphite. One of these may be used as a conductive agent, or a combination of two or more may be used as a conductive agent. Alternatively, instead of using a conductive agent, a carbon coat or an electronically conductive inorganic material coat may be applied to the surface of the active material particles.

  The binder is blended to fill a gap between the dispersed active materials and to bind the active material and the negative electrode current collector. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine rubber, styrene butadiene rubber, polyacrylic acid compound, imide compound, carboxymethyl cellulose (carboxymethyl). cellulose; CMC), and salts of CMC. One of these may be used as a binder, or a combination of two or more may be used as a binder.

  The mixing ratio of the negative electrode active material, the conductive agent, and the binder in the negative electrode active material-containing layer can be appropriately changed according to the use of the negative electrode. For example, the negative electrode active material, the conductive agent, and the binder are preferably blended at a ratio of 70% by mass to 96% by mass, 2% by mass to 28% by mass, and 2% by mass to 28% by mass, respectively. . By setting the amount of the conductive agent to 2% by mass or more, the current collecting performance of the negative electrode active material-containing layer can be improved. Further, by setting the amount of the binder to 2% by mass or more, the binding property between the negative electrode active material-containing layer and the current collector becomes sufficient, and excellent cycle performance can be expected. On the other hand, the conductive agent and the binder are each preferably 28% by mass or less in order to increase the capacity.

The negative electrode current collector is a material that is electrochemically stable at a potential at which lithium (Li) is inserted into and desorbed from the active material, for example, a potential nobler than 1.0 V (vs. Li / Li ⁺ ). Is used. For example, the current collector is preferably made of copper, nickel, stainless steel or aluminum or an aluminum alloy containing one or more elements selected from Mg, Ti, Zn, Mn, Fe, Cu, and Si. The thickness of the current collector is preferably 5 μm or more and 20 μm or less. The current collector having such a thickness can balance the strength and weight reduction of the electrode.

  Further, the negative electrode current collector can include a portion where the negative electrode active material-containing layer is not formed on the surface thereof. This part can serve as a negative electrode current collecting tab.

The density of the negative electrode active material-containing layer (not including the current collector) is preferably 1.8 g / cm ³ or more and 2.8 g / cm ³ or less. A negative electrode in which the density of the negative electrode active material-containing layer is within this range is excellent in energy density and electrolyte retention. The density of the negative electrode active material-containing layer is more preferably 2.1 g / cm ³ or more and 2.6 g / cm ³ or less.

  The negative electrode can be produced, for example, by the following method. First, a negative electrode active material, a conductive agent, and a binder are suspended in a solvent to prepare a slurry. This slurry is applied to one side or both sides of the negative electrode current collector. Next, the applied slurry is dried to obtain a laminate of the negative electrode active material-containing layer and the negative electrode current collector. Thereafter, the laminate is pressed. In this way, a negative electrode is produced.

  Or you may produce a negative electrode with the following method. First, a negative electrode active material, a conductive agent, and a binder are mixed to obtain a mixture. The mixture is then formed into pellets. Subsequently, a negative electrode can be obtained by disposing these pellets on a negative electrode current collector.

(3) Electrolyte As the electrolyte, for example, a liquid nonaqueous electrolyte or a gelled nonaqueous electrolyte can be used. The liquid non-aqueous electrolyte is prepared by dissolving an electrolyte salt as a solute in an organic solvent. The concentration of the electrolyte salt is preferably 0.5 mol / L or more and 2.5 mol / L or less.

Examples of electrolyte salts include lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium arsenic hexafluoride (LiAsF ₆ ), trifluoromethane Lithium salts such as lithium sulfonate (LiCF ₃ SO ₃ ) and lithium bistrifluoromethylsulfonylimide (LiN (CF ₃ SO ₂ ) ₂ ) and mixtures thereof are included. The electrolyte salt is preferably one that is difficult to oxidize even at a high potential, and LiPF ₆ is most preferred.

  Examples of the organic solvent include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), and vinylene carbonate (VC); diethyl carbonate (DEC) and dimethyl carbonate. (Dimethyl carbonate; DMC), chain carbonates such as methyl ethyl carbonate (MEC); tetrahydrofuran (tetrahydrofuran; THF), 2-methyl tetrahydrofuran (2-Mexy tetrahydrofuran; 2MeTHF), dioxolane (DOX) Cyclic ethers such as: dimethoxyethane (DME), chain ethers such as diethoxyethane (DEE); γ-butyrolactone (GBL), acetonitrile (acetonitrile) AN), and sulfolane (Sulfolane; include SL). These organic solvents can be used alone or as a mixed solvent.

  As a preferable organic solvent, for example, a mixed solvent in which two or more of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC) are mixed, And a mixed solvent containing γ-butyrolactone (GBL). By using such a mixed solvent, a secondary battery having excellent low-temperature characteristics can be obtained.

  The gel nonaqueous electrolyte is prepared by combining a liquid nonaqueous electrolyte and a polymer material. Examples of the polymer material include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), or a mixture thereof.

  Alternatively, as the non-aqueous electrolyte, in addition to the liquid non-aqueous electrolyte and the gel-like non-aqueous electrolyte, a room temperature molten salt (ionic melt) containing lithium ions, a polymer solid electrolyte, an inorganic solid electrolyte, and the like are used. Also good.

  A room temperature molten salt (ionic melt) refers to a compound that can exist as a liquid at room temperature (15 ° C. or more and 25 ° C. or less) among organic salts formed by a combination of an organic cation and an anion. Room temperature molten salt includes room temperature molten salt that exists as a liquid alone, room temperature molten salt that becomes liquid when mixed with electrolyte salt, room temperature molten salt that becomes liquid when dissolved in organic solvent, or a mixture thereof It is. Generally, the melting point of the room temperature molten salt used for the secondary battery is 25 ° C. or less. The organic cation generally has a quaternary ammonium skeleton.

  The polymer solid electrolyte is prepared by dissolving an electrolyte salt in a polymer material and solidifying it.

  The inorganic solid electrolyte is a solid material having Li ion conductivity.

(4) Separator The separator is formed of, for example, a porous film containing polyethylene (PE), polypropylene (PP), cellulose, or polyvinylidene fluoride (PVdF), or a synthetic resin nonwoven fabric. . From the viewpoint of safety, it is preferable to use a porous film formed from polyethylene or polypropylene. This is because these porous films can be melted at a constant temperature to interrupt the current.

(5) Exterior Member As the exterior member, for example, a container made of a laminate film or a metal container can be used.

  The thickness of the laminate film is, for example, 0.5 mm or less, and preferably 0.2 mm or less.

  As the laminate film, a multilayer film including a plurality of resin layers and a metal layer interposed between these resin layers is used. The resin layer contains, for example, a polymer material such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET). It is preferable that a metal layer consists of aluminum foil or aluminum alloy foil for weight reduction. The laminate film can be formed into the shape of the exterior member by sealing by heat sealing.

  The thickness of the wall of the metal container is, for example, 1 mm or less, more preferably 0.5 mm or less, and still more preferably 0.2 mm or less.

  The metal container is made of, for example, aluminum or an aluminum alloy. The aluminum alloy preferably contains elements such as magnesium, zinc, and silicon. When an aluminum alloy contains transition metals, such as iron, copper, nickel, and chromium, it is preferable that the content is 100 mass ppm or less.

  The shape of the exterior member is not particularly limited. The shape of the exterior member may be, for example, a flat type (thin type), a square type, a cylindrical type, a coin type, or a button type. The exterior member can be appropriately selected according to the battery size and the application of the battery.

(6) Negative electrode terminal A negative electrode terminal can be formed from the material provided with the electrical stability and electroconductivity in which the electric potential with respect to lithium exists in the range of 1V-3V (vs Li / Li ^<+> ), for example. Specifically, the negative electrode terminal material includes copper, nickel, stainless steel, or aluminum, or at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. An aluminum alloy is mentioned. As a material for the negative electrode terminal, aluminum or an aluminum alloy is preferably used. In order to reduce the contact resistance with the negative electrode current collector, the negative electrode terminal is preferably made of the same material as the negative electrode current collector.

(7) Positive electrode terminal The positive electrode terminal is formed from a material that is electrically stable and has conductivity in a potential range (vs. Li ^/ Li ⁺ ) of 3 V to 4.5 V with respect to the oxidation-reduction potential of lithium. be able to. Examples of the material of the positive electrode terminal include aluminum or an aluminum alloy containing at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. The positive electrode terminal is preferably formed of the same material as the positive electrode current collector in order to reduce contact resistance with the positive electrode current collector.

  Next, the secondary battery according to the embodiment will be described more specifically with reference to the drawings.

  FIG. 1 is a cross-sectional view schematically illustrating an example of the secondary battery according to the embodiment. 2 is an enlarged cross-sectional view of a portion A of the secondary battery shown in FIG.

  A secondary battery 100 shown in FIGS. 1 and 2 includes the bag-shaped exterior member 2 shown in FIG. 1, the electrode group 1 shown in FIGS. 1 and 2, and an electrolyte (not shown). The electrode group 1 and the electrolyte are housed in a bag-shaped exterior member 2. An electrolyte (not shown) is held by the electrode group 1.

  The bag-shaped exterior member 2 is made of a laminate film including two resin layers and a metal layer interposed therebetween.

  As shown in FIG. 1, the electrode group 1 is a flat wound electrode group. As shown in FIG. 2, the flat and wound electrode group 1 includes a negative electrode 3, a separator 4, and a positive electrode 5. The separator 4 is interposed between the negative electrode 3 and the positive electrode 5.

  The negative electrode 3 includes a negative electrode current collector 3a and a negative electrode active material-containing layer 3b. In the negative electrode 3, the portion located in the outermost shell of the wound electrode group 1 has the negative electrode active material containing layer 3 b formed only on the inner surface side of the negative electrode current collector 3 a as shown in FIG. 2. In other portions of the negative electrode 3, negative electrode active material-containing layers 3b are formed on both surfaces of the negative electrode current collector 3a.

  The positive electrode 5 includes a positive electrode current collector 5a and positive electrode active material-containing layers 5b formed on both surfaces thereof.

  As shown in FIG. 1, the negative electrode terminal 6 and the positive electrode terminal 7 are located in the vicinity of the outer peripheral end of the wound electrode group 1. The negative electrode terminal 6 is connected to a portion located in the outermost shell of the negative electrode current collector 3a. Moreover, the positive electrode terminal 7 is connected to the part located in the outermost shell of the positive electrode collector 5a. The negative electrode terminal 6 and the positive electrode terminal 7 are extended to the outside from the opening of the bag-shaped exterior member 2. A thermoplastic resin layer is provided on the inner surface of the bag-shaped exterior member 2, and the opening is closed by heat-sealing it.

  The secondary battery according to the third embodiment is not limited to the secondary battery having the configuration illustrated in FIGS. 1 and 2, and may be, for example, a battery having the configuration illustrated in FIGS. 3 and 4.

  FIG. 3 is a partially cutaway perspective view schematically showing another example of the secondary battery according to the third embodiment. 4 is an enlarged cross-sectional view of part B of the secondary battery shown in FIG.

  The secondary battery 100 shown in FIGS. 3 and 4 includes the electrode group 1 shown in FIGS. 3 and 4, the exterior member 2 shown in FIG. 3, and an electrolyte (not shown). The electrode group 1 and the electrolyte are housed in the exterior member 2. The electrolyte is held in the electrode group 1.

  The exterior member 2 is made of a laminate film including two resin layers and a metal layer interposed therebetween.

  The electrode group 1 is a stacked electrode group as shown in FIG. The stacked electrode group 1 has a structure in which negative electrodes 3 and positive electrodes 5 are alternately stacked with a separator 4 interposed therebetween.

  The electrode group 1 includes a plurality of negative electrodes 3. Each of the plurality of negative electrodes 3 includes a negative electrode current collector 3a and a negative electrode active material-containing layer 3b supported on both surfaces of the negative electrode current collector 3a. The electrode group 1 includes a plurality of positive electrodes 5. Each of the plurality of positive electrodes 5 includes a positive electrode current collector 5a and a positive electrode active material-containing layer 5b supported on both surfaces of the positive electrode current collector 5a.

  The negative electrode current collector 3a of each negative electrode 3 includes, on one side thereof, a portion 3c where the negative electrode active material-containing layer 3b is not supported on any surface. This portion 3c serves as a negative electrode current collecting tab. As shown in FIG. 4, the portion 3 c serving as the negative electrode current collecting tab does not overlap the positive electrode 5. The plurality of negative electrode current collecting tabs (part 3 c) are electrically connected to the strip-shaped negative electrode terminal 6. The tip of the strip-like negative electrode terminal 6 is drawn out of the exterior member 2.

  Moreover, although not shown in figure, the positive electrode collector 5a of each positive electrode 5 contains the part by which the positive electrode active material content layer 5b is not carry | supported on either surface in the one side. This portion serves as a positive electrode current collecting tab. The positive electrode current collecting tab does not overlap the negative electrode 3, similarly to the negative electrode current collecting tab (part 3 c). Further, the positive electrode current collecting tab is located on the opposite side of the electrode group 1 with respect to the negative electrode current collecting tab (part 3c). The positive electrode current collecting tab is electrically connected to the belt-like positive electrode terminal 7. The front end of the strip-like positive electrode terminal 7 is located on the opposite side of the negative electrode terminal 6 and is drawn out of the exterior member 2.

  The secondary battery according to the embodiment may constitute an assembled battery. The assembled battery includes a plurality of secondary batteries according to the embodiment.

  In the assembled battery according to the embodiment, each unit cell may be arranged by being electrically connected in series or in parallel, or may be arranged by combining series connection and parallel connection.

  An example of the assembled battery according to the embodiment will be described with reference to the drawings.

  FIG. 5 is a perspective view schematically showing an example of the assembled battery according to the embodiment. The assembled battery 200 shown in FIG. 5 includes five unit cells 100 a to 100 e, four bus bars 21, a positive electrode side lead 22, and a negative electrode side lead 23. Each of the five single cells 100a to 100e is a secondary battery according to the embodiment.

  The bus bar 21 connects, for example, the negative electrode terminal 6 of one single cell 100a and the positive electrode terminal 7 of the single cell 100b located next to the single cell 100a. In this way, the five unit cells 100 are connected in series by the four bus bars 21. That is, the assembled battery 200 of FIG. 5 is a 5-series assembled battery.

  As shown in FIG. 5, the positive electrode terminal 7 of the single cell 100 a located at the left end among the five single cells 100 a to 100 e is connected to the positive electrode side lead 22 for external connection. Moreover, the negative electrode terminal 6 of the unit cell 100e located at the right end among the five unit cells 100a to 100e is connected to the negative electrode side lead 23 for external connection.

  The secondary battery according to the second embodiment includes the electrode according to the first embodiment. Therefore, the secondary battery according to the embodiment has high output and excellent high-temperature durability.

(Third embodiment)
According to the third embodiment, a battery pack is provided. This battery pack includes the secondary battery according to the second embodiment. This battery pack may include one secondary battery according to the second embodiment, or may include an assembled battery including a plurality of secondary batteries.

  The battery pack according to the embodiment may further include a protection circuit. The protection circuit has a function of controlling charging / discharging of the secondary battery. Or you may use the circuit contained in the apparatus (for example, electronic device, a motor vehicle, etc.) which uses a battery pack as a power supply as a protection circuit of a battery pack.

  The battery pack according to the embodiment can further include an external terminal for energization. The external terminal for energization is for outputting a current from the secondary battery to the outside and / or for inputting a current from the outside to the secondary battery. In other words, when the battery pack is used as a power source, current is supplied to the outside through the external terminal for energization. Further, when charging the battery pack, a charging current (including regenerative energy of motive power of an automobile or the like) is supplied to the battery pack through an external terminal for energization.

  Next, an example of the battery pack according to the embodiment will be described with reference to the drawings.

  FIG. 6 is an exploded perspective view schematically showing an example of the battery pack according to the embodiment. FIG. 7 is a block diagram showing an example of an electric circuit of the battery pack shown in FIG.

  The battery pack 300 shown in FIG.6 and FIG.7 is equipped with the storage container 31, the lid | cover 32, the protection sheet 33, the assembled battery 200, the printed wiring board 34, the wiring 35, and the insulating board which is not shown in figure. .

  The storage container 31 shown in FIG. 6 is a bottomed rectangular container having a rectangular bottom surface. The container 31 is configured to accommodate the protective sheet 33, the assembled battery 200, the printed wiring board 34, and the wiring 35. The lid 32 has a rectangular shape. The lid 32 houses the assembled battery 200 and the like by covering the housing container 31. Although not shown, the storage container 31 and the lid 32 are provided with an opening or a connection terminal for connection to an external device or the like.

  The assembled battery 200 includes a plurality of single cells 100, a positive electrode side lead 22, a negative electrode side lead 23, and an adhesive tape 24.

  The unit cell 100 has the structure shown in FIGS. At least one of the plurality of unit cells 100 is a secondary battery according to the second embodiment. The plurality of single cells 100 are laminated so that the negative electrode terminal 6 and the positive electrode terminal 7 extending to the outside are aligned in the same direction. Each of the plurality of unit cells 100 is electrically connected in series as shown in FIG. The plurality of single cells 100 may be electrically connected in parallel, or may be connected in combination of series connection and parallel connection. When the plurality of single cells 100 are connected in parallel, the battery capacity is increased as compared to the case where they are connected in series.

  The adhesive tape 24 fastens a plurality of unit cells 100. Instead of the adhesive tape 24, a plurality of single cells 100 may be fixed using a heat shrink tape. In this case, the protective sheets 33 are arranged on both side surfaces of the assembled battery 200, the heat shrink tape is circulated, and then the heat shrink tape is heat shrunk to bind the plurality of unit cells 100 together.

  One end of the positive electrode side lead 22 is connected to the positive electrode terminal 7 of the unit cell 100 located in the lowermost layer in the stacked body of the unit cells 100. One end of the negative electrode side lead 23 is connected to the negative electrode terminal 6 of the unit cell 100 located in the uppermost layer in the stacked body of the unit cells 100.

  The printed wiring board 34 is installed along one short side surface of the inner surface of the container 31. The printed wiring board 34 includes a positive connector 341, a negative connector 342, a thermistor 343, a protection circuit 344, wirings 345 and 346, an external terminal 347 for energization, a positive wiring 348a, and a negative wiring. 348b. One main surface of the printed wiring board 34 faces the surface of the assembled battery 200 from which the negative electrode terminal 6 and the positive electrode terminal 7 extend. An insulating plate (not shown) is interposed between the printed wiring board 34 and the assembled battery 200.

  The positive connector 341 is provided with a through hole. By inserting the other end of the positive electrode side lead 22 into this through hole, the positive electrode side connector 341 and the positive electrode side lead 22 are electrically connected. The negative electrode side connector 342 is provided with a through hole. By inserting the other end of the negative electrode side lead 23 into this through hole, the negative electrode side connector 342 and the negative electrode side lead 23 are electrically connected.

  The thermistor 343 is fixed to one main surface of the printed wiring board 34. The thermistor 343 detects the temperature of each unit cell 100 and transmits the detection signal to the protection circuit 344.

  The external terminal 347 for energization is fixed to the other main surface of the printed wiring board 34. The external terminal 347 for energization is electrically connected to a device existing outside the battery pack 300.

  The protection circuit 344 is fixed to the other main surface of the printed wiring board 34. The protection circuit 344 is connected to the external terminal 347 for energization through the plus side wiring 348a. The protection circuit 344 is connected to the external terminal 347 for energization via the minus side wiring 348b. Further, the protection circuit 344 is electrically connected to the positive connector 341 via the wiring 345. The protection circuit 344 is electrically connected to the negative connector 342 through the wiring 346. Further, the protection circuit 344 is electrically connected to each of the plurality of single cells 100 via the wiring 35.

  The protective sheet 33 is disposed on both inner side surfaces of the storage container 31 in the long side direction and on the inner side surface in the short side direction facing the printed wiring board 34 via the assembled battery 200. The protective sheet 33 is made of, for example, resin or rubber.

  The protection circuit 344 controls charging / discharging of the plurality of single cells 100. In addition, the protection circuit 344 performs electrical connection between the protection circuit 344 and the energization external terminal 347 based on the detection signal transmitted from the thermistor 343 or the detection signal transmitted from each individual battery 100 or the assembled battery 200. Block connections.

  As a detection signal transmitted from the thermistor 343, for example, a signal detected that the temperature of the unit cell 100 is equal to or higher than a predetermined temperature can be cited. As a detection signal transmitted from each unit cell 100 or the assembled battery 200, for example, a signal that detects overcharge, overdischarge, and overcurrent of the unit cell 100 can be cited. When detecting an overcharge or the like for each unit cell 100, the battery voltage may be detected, or the positive electrode potential or the negative electrode potential may be detected. In the latter case, a lithium electrode used as a reference electrode is inserted into each unit cell 100.

  Note that as the protection circuit 344, a circuit included in a device (for example, an electronic device, an automobile, or the like) that uses the battery pack 300 as a power source may be used.

  Further, the battery pack 300 includes the external terminals 347 for energization as described above. Therefore, this battery pack 300 can output the current from the assembled battery 200 to the external device via the external terminal 347 for energization, and can input the current from the external device to the assembled battery 200. In other words, when the battery pack 300 is used as a power source, the current from the assembled battery 200 is supplied to the external device through the external terminal 347 for energization. When charging the battery pack 300, charging current from an external device is supplied to the battery pack 300 through the external terminal 347 for energization. When this battery pack 300 is used as a vehicle-mounted battery, regenerative energy of vehicle power can be used as a charging current from an external device.

  The battery pack 300 may include a plurality of assembled batteries 200. In this case, the plurality of assembled batteries 200 may be connected in series, may be connected in parallel, or may be connected by combining series connection and parallel connection. Further, the printed wiring board 34 and the wiring 35 may be omitted. In this case, the positive electrode side lead 22 and the negative electrode side lead 23 may be used as external terminals for energization.

  Such a battery pack is used, for example, in applications that require excellent cycle performance when a large current is taken out. Specifically, this battery pack is used, for example, as a power source for electronic devices, a stationary battery, and an in-vehicle battery for various vehicles. An example of the electronic device is a digital camera. This battery pack is particularly preferably used as an in-vehicle battery.

  The battery pack according to the third embodiment includes the secondary battery according to the second embodiment. Therefore, this battery pack has high output and excellent high temperature durability.

(Fourth embodiment)
According to a fourth embodiment, a vehicle is provided. This vehicle is equipped with the battery pack according to the third embodiment.

  In the vehicle according to the embodiment, the battery pack collects, for example, regenerative energy of the power of the vehicle. The vehicle may include a mechanism that converts the kinetic energy of the vehicle into regenerative energy.

  Examples of the vehicle include a two-wheel to four-wheel hybrid electric vehicle, a two-wheel to four-wheel electric vehicle, an assist bicycle, and a railway vehicle.

  The mounting position of the battery pack in the vehicle is not particularly limited. For example, when the battery pack is mounted on an automobile, the battery pack can be mounted on the engine room of the vehicle, behind the vehicle body, or under the seat.

  The vehicle may be equipped with a plurality of battery packs. In this case, the battery packs may be electrically connected in series, electrically connected in parallel, or may be electrically connected by combining series connection and parallel connection.

An example of a vehicle according to an embodiment will be described with reference to the drawings.
FIG. 8 is a cross-sectional view schematically illustrating an example of a vehicle according to the embodiment.

  A vehicle 400 shown in FIG. 8 includes a vehicle main body 40 and the battery pack 300 according to the third embodiment. In the example shown in FIG. 8, the vehicle 400 is a four-wheeled automobile.

  This vehicle 400 may be equipped with a plurality of battery packs 300. In this case, the battery pack 300 may be connected in series, may be connected in parallel, or may be connected by a combination of series connection and parallel connection.

  FIG. 8 illustrates an example in which the battery pack 300 is mounted in an engine room located in front of the vehicle main body 40. As described above, the battery pack 300 may be mounted, for example, behind the vehicle body 40 or under the seat. The battery pack 300 can be used as a power source for the vehicle 400. In addition, the battery pack 300 can recover the regenerative energy of the power of the vehicle 400.

  Next, an embodiment of the vehicle according to the embodiment will be described with reference to FIG.

  FIG. 9 is a diagram schematically illustrating an example of a vehicle according to the embodiment. A vehicle 400 shown in FIG. 9 is an electric vehicle.

  A vehicle 400 shown in FIG. 9 includes a vehicle main body 40, a vehicle power supply 41, a vehicle ECU (ECU: Electric Control Unit) 42, which is a higher-level control means of the vehicle power supply 41, and an external terminal (external power supply). Terminal 43), an inverter 44, and a drive motor 45.

  The vehicle 400 has a vehicle power supply 41 mounted, for example, in an engine room, behind a vehicle body or under a seat. In addition, in the vehicle 400 shown in FIG. 9, the mounting location of the vehicle power supply 41 is schematically shown.

  The vehicle power supply 41 includes a plurality of (for example, three) battery packs 300a, 300b, and 300c, a battery management unit (BMU) 411, and a communication bus 412.

  The three battery packs 300a, 300b, and 300c are electrically connected in series. The battery pack 300a includes an assembled battery 200a and an assembled battery monitoring device 301a (for example, VTM: Voltage Temperature Monitoring). The battery pack 300b includes an assembled battery 200b and an assembled battery monitoring device 301b. The battery pack 300c includes an assembled battery 200c and an assembled battery monitoring device 301c. The battery packs 300 a, 300 b, and 300 c can be detached independently and can be replaced with another battery pack 300.

  Each of the assembled batteries 200a to 200c includes a plurality of single cells connected in series. At least one of the plurality of unit cells is the secondary battery according to the first embodiment. The assembled batteries 200a to 200c are charged and discharged through the positive terminal 413 and the negative terminal 414, respectively.

  The battery management device 411 communicates with the assembled battery monitoring devices 301a to 301c in order to collect information related to the maintenance of the vehicle power supply 41, and the battery management device 411 includes the single batteries included in the assembled batteries 200a to 200c included in the vehicle power supply 41. Information on the voltage and temperature of the battery 100 is collected.

  A communication bus 412 is connected between the battery management device 411 and the assembled battery monitoring devices 301a to 301c. The communication bus 412 is configured to share a set of communication lines with a plurality of nodes (battery management device and one or more assembled battery monitoring devices). The communication bus 412 is a communication bus configured based on, for example, a CAN (Control Area Network) standard.

  The assembled battery monitoring devices 301a to 301c measure the voltage and temperature of individual cells constituting the assembled batteries 200a to 200c based on a command from the battery management device 411 through communication. However, the temperature can be measured at only a few locations per assembled battery, and the temperature of all the cells need not be measured.

  The vehicle power supply 41 can also include an electromagnetic contactor (for example, a switch device 415 shown in FIG. 9) for turning on and off the connection between the positive terminal 413 and the negative terminal 414. The switch device 415 includes a precharge switch (not shown) that is turned on when the assembled batteries 200a to 200c are charged, and a main switch (not shown) that is turned on when the battery output is supplied to the load. Is included. The precharge switch and the main switch include a relay circuit (not shown) that is turned on or off by a signal supplied to a coil disposed in the vicinity of the switch element.

  The inverter 44 converts the input DC voltage into a three-phase alternating current (AC) high voltage for driving the motor. The three-phase output terminals of the inverter 44 are connected to the three-phase input terminals of the drive motor 45. The inverter 44 controls the output voltage based on a control signal from the battery management device 411 or the vehicle ECU 42 for controlling the operation of the entire vehicle.

  The drive motor 45 is rotated by electric power supplied from the inverter 44. This rotation is transmitted to the axle and the drive wheels W via, for example, a differential gear unit.

  Although not shown, the vehicle 400 includes a regenerative brake mechanism. The regenerative brake mechanism rotates the drive motor 45 when the vehicle 400 is braked, and converts the kinetic energy into regenerative energy as electric energy. The regenerative energy recovered by the regenerative brake mechanism is input to the inverter 44 and converted into a direct current. The direct current is input to, for example, a battery pack included in the vehicle power supply 41.

  One terminal of the connection line L1 is connected to the negative terminal 414 of the vehicle power supply 41 via a current detection unit (not shown) in the battery management device 411. The other terminal of the connection line L <b> 1 is connected to the negative input terminal of the inverter 44.

  One terminal of the connection line L <b> 2 is connected to the positive terminal 413 of the vehicle power supply 41 via the switch device 415. The other terminal of the connection line L2 is connected to the positive input terminal of the inverter 44.

  The external terminal 43 is connected to the battery management device 411. The external terminal 43 can be connected to an external power source, for example.

  The vehicle ECU 42 manages the entire vehicle by cooperatively controlling the battery management device 411 together with other devices in response to an operation input from the driver or the like. Between the battery management device 411 and the vehicle ECU 42, data transfer relating to maintenance of the vehicle power source 41 such as the remaining capacity of the vehicle power source 41 is performed via a communication line.

  The vehicle according to the fourth embodiment includes the battery pack according to the third embodiment. Therefore, according to this embodiment, it is possible to provide a vehicle equipped with a battery pack that can achieve excellent high-temperature durability, high output, and long life.

[Example]
Examples will be described below, but the present invention is not limited to the examples described below as long as the gist of the present invention is not exceeded.

(Example 1)
A nonaqueous electrolyte battery according to Example 1 was produced in the following procedure.

<Preparation of positive electrode>
As the positive electrode active material, lithium nickel cobalt manganese composite oxide (LiNi _0.34 Co _0.33 Mn _0.33 O ₂ ) having an average particle size of 5 μm was used. As the conductive agent, 3% by weight of acetylene black and 3% by weight of graphite were used. As the binder, 3% by weight of polyacrylonitrile copolymer (PAN copolymer) and 1% by weight of copolymer of acrylonitrile and phosphate group-containing methacrylate (P-PAN) were used. The polyacrylonitrile copolymer contained 50 mol% or more of acrylonitrile as a monomer component. N-methyl-2-pyrrolidone (NMP) was added to and mixed with the positive electrode active material, the conductive agent, and the binder to prepare a slurry. This slurry was applied to both surfaces of a positive electrode current collector made of an aluminum foil having a thickness of 15 μm to obtain a laminate. The laminate was pre-dried at 80 ° C. for 10 seconds, then fully dried at 130 ° C. for 120 seconds, and pressed to obtain a positive electrode. The positive electrode density was 3.2 g / cc.

<Production of negative electrode>
As the negative electrode active material, 90% by weight of lithium titanate (Li ₄ Ti ₅ O ₁₂ ) having a spinel structure with an average particle diameter of 1 μm was used. As a conductive agent, 7% by weight of graphite and 3% by weight of an acrylic binder as a binder were used. These and NMP were mixed to prepare a slurry. This slurry was applied to both surfaces of a negative electrode current collector made of an aluminum foil having a thickness of 15 μm to obtain a laminate. The laminate was dried at 130 ° C. and pressed to obtain a negative electrode. The negative electrode density was 2.25 g / cc.

<Production of electrode group>
As the separator, a cellulose nonwoven fabric having a thickness of 25 μm was used. A positive electrode, a separator, a negative electrode, and a separator were laminated in this order to obtain a laminate. Next, this laminate was wound in a spiral shape. This was heated and pressed at 80 ° C. to produce a flat electrode group. The electrode group was housed in a pack (exterior member) made of a laminate film having a three-layer structure of nylon layer / aluminum layer / polyethylene layer and a thickness of 0.1 mm. This was dried in vacuum at 80 ° C. for 16 hours.

<Preparation of liquid nonaqueous electrolyte>
A non-aqueous electrolyte was prepared by dissolving 1 mol / L of LiPF ₆ as an electrolyte salt in a mixed solvent in which propylene carbonate (PC) and diethyl carbonate (DEC) were mixed at a volume ratio of 1: 2. After injecting a non-aqueous electrolyte into the laminate film pack containing the electrode group, the pack was completely sealed by heat sealing. A non-aqueous electrolyte battery was thus obtained.

<Measurement of pore size distribution>
The pore size distribution of the positive electrode was measured according to the method for measuring the pore size distribution by the mercury intrusion method described in the first embodiment. Moreover, the pore specific surface area S and the pore median diameter D of the positive electrode (positive electrode active material-containing layer) were measured. As an apparatus, Shimadzu Autopore IV 9520 was used. The obtained pore distribution chart is shown in FIG. FIG. 10 also shows the results of Example 3, Example 6 and Comparative Example 1 described later. The pore specific surface area S of the positive electrode (positive electrode active material-containing layer) according to Example 1 was 4.9 m ² / g, and the pore median diameter D was 0.14 μm. The pore specific surface area S of the positive electrode (positive electrode active material-containing layer) according to Example 3 was 4.24 m ² / g, and the pore median diameter D was 0.078 μm. The pore specific surface area S of the positive electrode (positive electrode active material-containing layer) according to Example 6 was 7.75 m ² / g, and the pore median diameter D was 0.053 μm. The positive electrode (positive electrode active material-containing layer) according to Comparative Example 1 had a pore specific surface area S of 3.57 m ² / g and a pore median diameter D of 0.21 μm.

<80 ° C cycle life evaluation>
In a high temperature environment of 80 ° C., the manufactured nonaqueous electrolyte battery was charged to a voltage of 2.7 V with a constant current of 5 A (5 C), and then a cycle of discharging to 1.8 V at 5 A (5 C) was repeated until the initial capacity was reached. On the other hand, the cycle number when the capacity reached 80% was defined as the cycle life (times).

<25 ° C output density measurement>
In a 25 ° C environment, the manufactured nonaqueous electrolyte battery is charged at a constant current of 1A (1C) to a charge depth of 50%, then discharged at a constant power of 1.5V, and the maximum power capable of discharging for 10 seconds. The value was determined. The power density was calculated by dividing the maximum power value by the nonaqueous electrolyte battery weight.

  The above results are summarized in Table 1 below. Table 1 also shows the results of Examples 2 to 12 and Comparative Examples 1 to 7 described later. Table 2 below shows the results of Examples 13 to 17 and Comparative Examples 8 to 12 and 14 to 17 described later.

  Table 3 below shows the results of Examples 19 to 22 described later.

(Examples 2 to 4)
A nonaqueous electrolyte battery was produced and evaluated in the same manner as described in Example 1 except that the press load was changed so that the positive electrode density became the value shown in Table 1.

(Examples 5 to 9)
The positive electrode active material is the same as that described in Example 1 except that a material having an average particle diameter shown in Table 1 is used and the press load is changed so that the positive electrode density becomes the value shown in Table 1. A nonaqueous electrolyte battery was prepared and evaluated by the method described above.

(Comparative Example 1)
A nonaqueous electrolyte battery was prepared and evaluated in the same manner as described in Example 1 except that the press load was changed so that the positive electrode density was 3 g / cc.

(Comparative Example 2)
At the time of producing the positive electrode, preliminary drying at 80 ° C. was not performed, and only main drying at 130 ° C. was performed. Except for this, a nonaqueous electrolyte battery was prepared and evaluated in the same manner as described in Example 1.

(Comparative Examples 3 and 4)
The same as described in Comparative Example 2 except that 4% by weight of polyvinylidene fluoride (PVdF) was used as the binder for the positive electrode, and the press load was changed so that the positive electrode density was the value shown in Table 1. A nonaqueous electrolyte battery was prepared and evaluated by the method described above.

(Example 10)
Using lithium nickel cobalt manganese composite oxide (LiNi _0.5 Co _0.2 Mn _0.3 O ₂ ) with an average particle size of 5 μm as the positive electrode active material, and changing the press load so that the positive electrode density is 3.35 g / cc. Except for this, a non-aqueous electrolyte battery was prepared and evaluated in the same manner as described in Example 1.

(Example 11)
As described in Example 1, except that lithium cobalt composite oxide (LiCoO ₂ ) having an average particle size of 5 μm was used as the positive electrode active material, and the press load was changed so that the positive electrode density was 3.35 g / cc. A nonaqueous electrolyte battery was prepared and evaluated in the same manner as described above.

Example 12
As described in Example 1, except that lithium manganese composite oxide (LiMn ₂ O ₄ ) having an average particle size of 5 μm was used as the positive electrode active material, and the press load was changed so that the positive electrode density was 3 g / cc. A nonaqueous electrolyte battery was prepared and evaluated in the same manner as described above.

(Comparative Example 5)
At the time of producing the positive electrode, preliminary drying at 80 ° C. was not performed, and only main drying at 130 ° C. was performed. Except for this, a nonaqueous electrolyte battery was prepared and evaluated in the same manner as described in Example 10.

(Comparative Example 6)
At the time of producing the positive electrode, preliminary drying at 80 ° C. was not performed, and only main drying at 130 ° C. was performed. Except for this, a nonaqueous electrolyte battery was prepared and evaluated in the same manner as described in Example 11.

(Comparative Example 7)
At the time of producing the positive electrode, preliminary drying at 80 ° C. was not performed, and only main drying at 130 ° C. was performed. Except for this, a nonaqueous electrolyte battery was prepared and evaluated in the same manner as described in Example 12.

(Example 13)
As a positive electrode binder, 1.5% by weight of a polyacrylonitrile copolymer and 0.5% by weight of a copolymer of acrylonitrile and a phosphate group-containing methacrylate were used, and the positive electrode density was 3.2 g / cc. A nonaqueous electrolyte battery was prepared and evaluated in the same manner as described in Example 1 except that the press load was changed so that

(Example 14)
As the positive electrode binder, 7.5% by weight of polyacrylonitrile copolymer and 2.5% by weight of copolymer of acrylonitrile and phosphate group-containing methacrylate were used, and the positive electrode density was 3.5 g / cc. A nonaqueous electrolyte battery was prepared and evaluated in the same manner as described in Example 1 except that the press load was changed so that

(Comparative Example 8)
At the time of producing the positive electrode, preliminary drying at 80 ° C. was not performed, and only main drying at 130 ° C. was performed. Except for this, a nonaqueous electrolyte battery was prepared and evaluated in the same manner as described in Example 13.

(Comparative Example 9)
At the time of producing the positive electrode, preliminary drying at 80 ° C. was not performed, and only main drying at 130 ° C. was performed. Except for this, a non-aqueous electrolyte battery was prepared and evaluated in the same manner as described in Example 14.

(Example 15)
As described in Example 1, except that 4% by weight of polyacrylonitrile copolymer was used as the positive electrode binder and the press load was changed so that the positive electrode density was 3.35 g / cc. A nonaqueous electrolyte battery was prepared and evaluated by the method described above.

(Comparative Example 10)
At the time of producing the positive electrode, preliminary drying at 80 ° C. was not performed, and only main drying at 130 ° C. was performed. Except for this, a nonaqueous electrolyte battery was prepared and evaluated in the same manner as described in Example 15.

(Example 16)
The same as described in Example 1, except that 4% by weight of polyacrylonitrile polymer was used as the binder for the positive electrode and the press load was changed so that the positive electrode density was 3.35 g / cc. A non-aqueous electrolyte battery was prepared by the method and evaluated.

(Comparative Example 11)
At the time of producing the positive electrode, preliminary drying at 80 ° C. was not performed, and only main drying at 130 ° C. was performed. Except for this, a nonaqueous electrolyte battery was prepared and evaluated in the same manner as described in Example 16.

(Example 17)
As a positive electrode binder, 2.25% by weight of a polyacrylonitrile copolymer (PAN copolymer), 0.75% by weight of a copolymer of acrylonitrile and phosphate group-containing methacrylate (P-PAN), and In the same manner as described in Example 1, except that 1% by weight of polyvinylidene fluoride (PVdF) was used and the press load was changed so that the positive electrode density was 3.35 g / cc. An electrolyte battery was fabricated and evaluated. The weight ratio of PAN copolymer and P-PAN to PVdF was 75:25.

(Comparative Example 12)
As a positive electrode binder, 2.25% by weight of a polyacrylonitrile copolymer (PAN copolymer), 0.75% by weight of a copolymer of acrylonitrile and phosphate group-containing methacrylate (P-PAN), and Example 1 except that polyvinylidene fluoride (PVdF) was used in an amount of 1% by weight, the press load was changed so that the positive electrode density was 3.35 g / cc, and preliminary drying was not performed. A non-aqueous electrolyte battery was prepared and evaluated in the same manner as described above. The weight ratio of PAN copolymer and P-PAN to PVdF was 75:25.

(Comparative Example 14)
Preliminary drying at 80 ° C. was performed before the main drying at 130 ° C. during the production of the positive electrode. Except for this, a nonaqueous electrolyte battery was prepared and evaluated in the same manner as described in Comparative Example 3.

(Comparative Example 15)
As a positive electrode binder, 15% by weight of a polyacrylonitrile copolymer (PAN copolymer) and 5% by weight of a copolymer of acrylonitrile and phosphate group-containing methacrylate (P-PAN) were used. A nonaqueous electrolyte battery was prepared and evaluated in the same manner as described in Example 1 except that the press load was changed so that the density was 3.5 g / cc.

(Comparative Example 16)
In the same manner as described in Comparative Example 2, except that LiFePO ₄ having an average particle diameter of 3 μm was used as the positive electrode active material and the press load was changed so that the positive electrode density was 2.8 g / cc. A nonaqueous electrolyte battery was fabricated and evaluated.

(Comparative Example 17)
Preliminary drying at 80 ° C. was performed before the main drying at 130 ° C. during the production of the positive electrode. Except for this, a nonaqueous electrolyte battery was prepared and evaluated in the same manner as described in Comparative Example 16.

(Example 19)
As a positive electrode binder, 1.65% by weight of polyacrylonitrile copolymer (PAN copolymer), 0.55% by weight of copolymer of acrylonitrile and phosphate group-containing methacrylate (P-PAN), and A nonaqueous electrolyte battery was prepared and evaluated in the same manner as described in Example 1 except that 1.8% by weight of polyvinylidene fluoride (PVdF) was used. The weight ratio of PAN copolymer and P-PAN to PVdF was 55:45.

(Example 20)
As a positive electrode binder, polyacrylonitrile copolymer (PAN copolymer) is 2.4% by weight, copolymer of acrylonitrile and phosphate group-containing methacrylate (P-PAN) is 1.8% by weight, and A nonaqueous electrolyte battery was prepared and evaluated in the same manner as described in Example 1 except that 1.6% by weight of polyvinylidene fluoride (PVdF) was used. The weight ratio of the PAN copolymer and P-PAN to PVdF was 60:40.

(Example 21)
As a positive electrode binder, 2.6% by weight of polyacrylonitrile copolymer (PAN copolymer), 1.95% by weight of copolymer of acrylonitrile and phosphate group-containing methacrylate (P-PAN), and A non-aqueous electrolyte battery was prepared and evaluated in the same manner as described in Example 1 except that 0.65% by weight of polyvinylidene fluoride (PVdF) was used. The weight ratio of PAN copolymer and P-PAN to PVdF was 65:35.

(Example 22)
As a positive electrode binder, 2.8% by weight of a polyacrylonitrile copolymer (PAN copolymer), 2.1% by weight of a copolymer of acrylonitrile and phosphate group-containing methacrylate (P-PAN), and A nonaqueous electrolyte battery was prepared and evaluated in the same manner as described in Example 1 except that 0.7% by weight of polyvinylidene fluoride (PVdF) was used. The weight ratio of the PAN copolymer and P-PAN to PVdF was 70:30.

From comparison between Examples and Comparative Examples, at least one element general formula _{Li x M y O 2 (0} ≦ x ≦ 1.33,0.5 ≦ y ≦ 1, M is selected Ni, Co and Mn In the pore size distribution obtained by the mercury intrusion method, the pore median diameter is D [ μm], and when the pore specific surface area is represented by S [m ² / g], the secondary battery including the positive electrode satisfying S / D ≧ 35 is excellent in high temperature durability, output characteristics, and life characteristics. I understand that

  For example, Examples 3 and 5 in which S / D is 50 or more are superior in 80 ° C. cycle life and 25 ° C. output density compared to Examples 1 and 2 in which S / D is 35 or more and less than 50. Comparative Examples 1 and 2 having an S / D of less than 35 are inferior in 80 ° C. cycle life and 25 ° C. output density as compared with Examples 1-9.

  For example, Examples 3 and 5 in which the pore median diameter D is in the range of 0.05 μm to 0.2 μm are superior in 80 ° C. cycle life and 25 ° C. output density as compared to Example 4 outside this range. .

For example, Example 8 pore specific surface area S is within the range of 3.5m ² / g~15m ² / g is excellent in the 80 ° C. cycle life compared to Example 9 which are outside this range.

  As is clear from Examples 10 to 12 and Comparative Examples 5 to 7, even if the type of the positive electrode active material is changed, if S / D ≧ 35 is satisfied, the high temperature durability, output characteristics, and life characteristics are excellent. I understand that.

  As is clear from Examples 13 and 14 and Comparative Examples 8 and 9, even when the amount of the binder in the active material-containing layer was increased or decreased, as long as S / D ≧ 35 was satisfied, high-temperature durability, output characteristics, and life characteristics It turns out that it is excellent in.

  As shown in Examples 15 and 16, even when the binder does not contain a copolymer containing a methacrylate having a phosphate group, it has excellent high-temperature durability, output characteristics, and life characteristics. I understand.

  As shown in Examples 17 and 19 to 22, even when the binder contains not only a polymer containing a monomer containing a nitrogen atom but also a binder such as PVdF, S / D ≧ 35 must be satisfied. It can be seen that the high temperature durability, output characteristics and life characteristics are excellent.

  Among Examples 17 and 19-22, Examples 17 and 20-22 in which S / D ≧ 35 and the ratio of the weight of the polymer to the weight of the binder is 60% by weight or more are particularly high temperatures. It can be seen that the durability (80 ° C. cycle life) is excellent. These examples show that the content of a binder that swells easily with respect to the electrolyte, such as PVdF, tends to be excellent in high-temperature durability.

  As shown in Comparative Examples 16 and 17, when a lithium phosphorus oxide having an olivine structure is used as the positive electrode active material, the improvement in battery performance by satisfying S / D ≧ 35 is not significant.

The electrode according to at least one of the embodiments and examples described above, the general formula _{Li x M y O 2 (0} ≦ x ≦ 1.33,0.5 ≦ y ≦ 1, M is Ni, Co and Mn An active material represented by (including at least one selected element) and a binder. The binder includes a polymer including a monomer containing a nitrogen atom. In the pore diameter distribution of the electrode obtained by the mercury intrusion method, the following formula (1) is satisfied when the pore median diameter is represented by D [μm] and the pore specific surface area is represented by S [m ² / g]. .
S / D ≧ 35 (1)
Therefore, an electrode having high output and excellent high-temperature durability can be provided.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... Electrode group, 2 ... Exterior member, 3 ... Negative electrode, 3a ... Negative electrode collector, 3b ... Negative electrode active material content layer, 3c ... Negative electrode current collection tab, 4 ... Separator, 5 ... Positive electrode, 5a ... Positive electrode collector 5 ... Positive electrode active material containing layer, 6 ... Negative electrode terminal, 7 ... Positive electrode terminal, 21 ... Bus bar, 22 ... Positive electrode side lead, 23 ... Negative electrode side lead, 24 ... Adhesive tape, 31 ... Container, 32 ... Cover, 33 DESCRIPTION OF SYMBOLS ... Protective sheet, 34 ... Printed wiring board, 35 ... Wiring, 40 ... Vehicle main body, 41 ... Vehicle power supply, 42 ... Electric control device, 43 ... External terminal, 44 ... Inverter, 45 ... Drive motor, 100 ... Secondary battery 200 ... assembled battery, 200a ... assembled battery, 200b ... assembled battery, 200c ... assembled battery, 300 ... battery pack, 300a ... battery pack, 300b ... battery pack, 300c ... battery pack, 301a ... assembled battery monitoring device, 301b ... set Pond monitoring device, 301c ... assembled battery monitoring device, 341 ... positive electrode side connector, 342 ... negative electrode side connector, 343 ... thermistor, 344 ... protection circuit, 345 ... wiring, 346 ... wiring, 347 ... external terminal for energization, 348a ... Positive side wiring, 348b ... negative side wiring, 400 ... vehicle, 411 ... battery management device, 412 ... communication bus, 413 ... positive terminal, 414 ... negative terminal, 415 ... switch device, L1 ... connection line, L2 ... connection line, W: Drive wheel.

Claims (13)

Formula _{Li x M y O 2 (0} ≦ x ≦ 1.33,0.5 ≦ y ≦ 1, M includes at least one element selected Ni, Co and Mn) and the active material represented by An electrode including a binder,
The binder includes a polymer including a monomer containing a nitrogen atom,
In the pore diameter distribution of the electrode obtained by the mercury intrusion method, when the pore median diameter is represented by D [μm] and the pore specific surface area is represented by S [m ² / g], the following formula (1) is obtained. Filling electrode.
S / D ≧ 35 (1)   The electrode according to claim 1, wherein a ratio of a weight of the polymer to a weight of the binder is 60% by weight or more. The electrode according to claim 1 or 2, which satisfies the following formula (2).
S / D ≧ 50 (2) The pore median diameter D is in the range of 0.05Myuemu～0.2Myuemu, the pore specific surface area S is, of claims 1 to 3 in the range of 3.5m ² / g~15m ² / g The electrode according to any one of the above.   The electrode according to any one of claims 1 to 4, wherein the polymer is a polyacrylonitrile-based copolymer.   The electrode according to claim 1, wherein the binder further includes a copolymer containing a methacrylate having a phosphate group.   7. The pore median diameter D and the pore specific surface area S are values measured for pore diameters existing in the range of 0.003 μm to 0.5 μm in the pore diameter distribution. The electrode according to claim 1. A secondary battery comprising a positive electrode, a negative electrode, and an electrolyte,
The said positive electrode is a secondary battery which is an electrode of any one of Claims 1-7.   A battery pack comprising the secondary battery according to claim 8.   The battery pack according to claim 9, further comprising an external terminal for energization and a protection circuit.   The battery pack according to claim 9 or 10, comprising a plurality of the secondary batteries, wherein the plurality of secondary batteries are electrically connected in series, parallel, or a combination of series and parallel.   A vehicle comprising the battery pack according to any one of claims 9 to 11.   The vehicle according to claim 12, comprising a mechanism that converts kinetic energy of the vehicle into regenerative energy.