WO2018180212A1 - Negative electrode material for storage device - Google Patents

Negative electrode material for storage device Download PDF

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Publication number
WO2018180212A1
WO2018180212A1 PCT/JP2018/008122 JP2018008122W WO2018180212A1 WO 2018180212 A1 WO2018180212 A1 WO 2018180212A1 JP 2018008122 W JP2018008122 W JP 2018008122W WO 2018180212 A1 WO2018180212 A1 WO 2018180212A1
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Prior art keywords
negative electrode
electrode material
main phase
mass
metallic glass
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PCT/JP2018/008122
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French (fr)
Japanese (ja)
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友紀 廣野
一郎 高須
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山陽特殊製鋼株式会社
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Publication of WO2018180212A1 publication Critical patent/WO2018180212A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/08—Metallic powder characterised by particles having an amorphous microstructure
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C30/00—Alloys containing less than 50% by weight of each constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C45/00—Amorphous alloys
    • C22C45/02—Amorphous alloys with iron as the major constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C45/00—Amorphous alloys
    • C22C45/04—Amorphous alloys with nickel or cobalt as the major constituent
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a material suitable for a negative electrode of an electricity storage device that moves lithium ions during charge and discharge, such as a lithium ion secondary battery, an all solid lithium ion secondary battery, and a hybrid capacitor.
  • lithium ion secondary battery In recent years, cellular phones, portable music players, portable terminals, and the like are rapidly spreading. These portable devices have a lithium ion secondary battery. Electric vehicles and hybrid vehicles also have lithium ion secondary batteries. Further, lithium ion secondary batteries and hybrid capacitors are used as stationary electric storage devices for home use. In a lithium ion secondary battery, the negative electrode occludes lithium ions during discharge. When the lithium ion secondary battery is charged, lithium ions are released from the negative electrode.
  • the negative electrode has a current collector and an active material fixed to the surface of the current collector.
  • carbon-based materials such as natural graphite, artificial graphite, and coke are used as the active material in the negative electrode.
  • dendrites are less likely to occur due to repeated charge and discharge. Therefore, a short circuit caused by dendrite hardly occurs.
  • the theoretical capacity of the carbon-based material for lithium ions is only 372 mAh / g. A large capacity active material is desired.
  • Sn and Si have attracted attention as active materials in the negative electrode.
  • the theoretical capacity of Sn and Si is more than twice that of carbon-based materials. In particular, the theoretical capacity of Si is more than 10 times that of carbon-based materials.
  • Si reacts with lithium ions. This reaction forms a compound. A typical compound is Li 22 Si 5 . By this reaction, a large amount of lithium ions is occluded in the negative electrode. Si can increase the storage capacity of the negative electrode.
  • Japanese Patent Application Laid-Open No. 2007-095363 discloses the use of metallic glass as part of the negative electrode active material.
  • This metallic glass contains Sn.
  • This metallic glass is easy to deform. This metallic glass can prevent Sn from falling off and isolated.
  • the active material layer containing Si occludes lithium ions
  • the active material layer expands due to the generation of the aforementioned compound.
  • the expansion coefficient of the active material is about 400%.
  • the active material layer contracts.
  • the active material may fall off from the current collector due to repeated expansion and contraction, and may become isolated. This dropout and isolation reduces the storage capacity.
  • the conductivity between the active materials may be hindered by repeated expansion and contraction.
  • the lifetime of the conventional lithium ion secondary battery in which the negative electrode contains Si is not long.
  • the electrical conductivity of Si alone is lower than that of carbonaceous materials and metal-based materials. Therefore, the negative electrode material containing Si has insufficient efficiency during charging and discharging.
  • the metal glass disclosed in Japanese Patent Application Laid-Open No. 2007-095363 reacts with lithium itself. This reaction causes the volume of the metallic glass to expand by approximately 400%. The expansion hinders the structural stability of the metallic glass. There is also a risk that the metallic glass will collapse due to repeated charge and discharge. Further, the lithium active material contained in the metal glass disclosed in Japanese Patent Application Laid-Open No. 2007-095363 is a small amount. Therefore, in the negative electrode having this metallic glass, the charge / discharge amount is not sufficient. The negative electrode having this metallic glass cannot respond to the demand for higher capacity and the demand for higher output. Similar problems occur in various power storage devices other than lithium ion secondary batteries.
  • an object of the present invention is to provide a material that can provide a negative electrode having a large storage capacity and in which a decrease in the storage capacity due to repeated charge and discharge is suppressed.
  • a matrix made of metallic glass containing Fe and / or Ni and a Si main phase dispersed in the matrix are provided.
  • a negative electrode material for an electricity storage device in which the Si crystallite size in the Si main phase is 20 nm or less.
  • the Si main phase includes one or more selected from the group consisting of Ge, Al and B,
  • the total content of Ge, Al, and B in the negative electrode material is 0.01 mass. % Or more and 5.0 mass. % Of the negative electrode material for an electricity storage device is provided.
  • the ratio of the Si main phase in the negative electrode material is 20 mass. % Or more and 80 mass. % Of the negative electrode material for an electricity storage device is provided.
  • the negative electrode material according to the present invention includes a Si main phase, its storage capacity is large. In addition, in this negative electrode material, the reduction in the storage capacity due to repeated charge and discharge is suppressed by the metallic glass.
  • FIG. 2 is an enlarged cross-sectional view illustrating a part of a negative electrode of the battery of FIG. 1.
  • 2 is a TEM image showing a negative electrode material of the lithium ion secondary battery of FIG. 1.
  • the lithium ion secondary battery 2 conceptually shown in FIG. 1 has a tank 4, an electrolytic solution 6, a separator 8, a positive electrode 10, and a negative electrode 12.
  • the electrolytic solution 6 is stored in the tank 4.
  • This electrolytic solution 6 contains lithium ions.
  • the separator 8 partitions the tank 4 into a positive electrode chamber 14 and a negative electrode chamber 16.
  • the separator 8 prevents contact between the positive electrode 10 and the negative electrode 12.
  • the separator 8 has a large number of holes (not shown). Lithium ions can pass through this hole.
  • the positive electrode 10 is immersed in the electrolytic solution 6 in the positive electrode chamber 14.
  • the negative electrode 12 is immersed in the electrolytic solution 6 in the negative electrode chamber 16.
  • FIG. 2 shows a part of the negative electrode 12.
  • the negative electrode 12 includes a current collector 18 and an active material layer 20.
  • the active material layer 20 includes a large number of particles 22.
  • the particles 22 are fixed to other particles 22 that are in contact with the particles 22.
  • the particles 22 that come into contact with the current collector 18 are fixed to the current collector 18.
  • the active material layer 20 is porous.
  • the particles 22 of the active material layer 20 are referred to as “negative electrode material” in the present invention.
  • This negative electrode material has a matrix and a Si main phase dispersed in the matrix.
  • the main component of the Si main phase is Si. Si reacts with lithium ions.
  • the Si main phase can occlude a large amount of lithium ions.
  • This Si main phase can increase the storage capacity of the negative electrode 12.
  • the Si content in the Si main phase is 80 mass. % Or more, preferably 90 mass. % Or more is more preferable, 95 mass. % Or more is particularly preferable.
  • This content is 100 mass. %. In the case where the Si main phase contains other elements described later, this content is 99.99 mass. From the viewpoint that the Si main phase can sufficiently contain other elements. % Or less, 99.5 mass. % Or less is more preferable, and 99.0 mass. % Or less is particularly preferable.
  • the Si main phase may contain an element other than Si.
  • the Si main phase may contain two or more elements other than Si. Typical elements are Ge, Al and B.
  • Ge, Al and B can be dissolved in Si.
  • the Si main phase in which Ge, Al or B is solid-dissolved in Si cracks and cracks of Si during expansion and contraction due to lithium insertion and desorption from Si can be suppressed.
  • Ge, Al and B strengthen the Si main phase.
  • Ge, Al and B increase the electrical conductivity of the Si main phase. By suppressing cracks and cracks, the formation of a resistive film at the interface between the Si main phase and the electrolyte 6 during charging and discharging can be suppressed.
  • the negative electrode 12 having a small resistance film is excellent in cycle life.
  • the structure of the Si main phase in which Ge, Al or B is dissolved in Si is different from that of the Si single phase.
  • the electron density state of the Si main phase in which Ge, Al or B is dissolved in Si is also different from that of the Si single phase. Due to differences in structure, electron density state, and the like, the formation of a resistive film at the interface between the Si main phase and the electrolyte 6 can be suppressed.
  • the negative electrode 12 having a small resistance film is excellent in cycle life.
  • the total content of Ge, Al and B in the negative electrode material is 0.01 mass. % Or more and 5.0 mass. % Or less is preferable.
  • the total content is 0.01 mass. If the negative electrode material is at least%, Si cracking and cracking can be suppressed. From this point of view, the total content is 0.1 mass. % Or more is more preferable, and 0.5 mass. % Or more is particularly preferable.
  • the total content is 5.0 mass.
  • a negative electrode material that is less than or equal to% cracks, electrical isolation, and drop-off from the current collector 18 due to stress during charging and discharging are suppressed.
  • the total content is 5.0 mass. % Or less of the negative electrode material is excellent in cycle characteristics. From this viewpoint, the total content is 4.0 mass. % Or less is more preferable, and 3.5 mass. % Or less is particularly preferable.
  • the Si main phase does not contain Ge, Al and B, preferably, the Si main phase contains Si and the balance is inevitable impurities.
  • the Si main phase contains Ge, Al or B, preferably, the Si main phase contains Si, contains Ge, Al or B, and the balance is inevitable impurities.
  • the Si crystallite size in the Si main phase is preferably 20 nm or less.
  • the crystallite size is preferably 15 nm or less, and more preferably 10 nm or less.
  • the lower limit of the Si crystallite size is not particularly limited, but is typically 0.5 nm or more.
  • the Si main phase may be amorphous.
  • the crystallite size is measured by X-ray diffraction.
  • X-ray source a CuK ⁇ ray having a wavelength of 1.54059 mm is used. Measurement is performed in the range of 2 ⁇ from 20 degrees to 80 degrees. In the obtained diffraction spectrum, a relatively broad diffraction peak is observed as the crystallite size is smaller.
  • the crystallite size is calculated from the half width of the peak obtained by X-ray diffraction using the following Scherrer equation.
  • D ( ⁇ ) (K ⁇ ⁇ ) / ( ⁇ ⁇ cos ⁇ )
  • K Scherrer's constant
  • ⁇ Wavelength of X-ray tube used
  • ⁇ Spread of diffraction line depending on crystallite size
  • ⁇ Diffraction angle
  • the Si crystallite size can be controlled by adjusting the cooling rate during solidification after the raw material powder is dissolved.
  • the matrix is made of metallic glass containing Fe or Ni.
  • the metallic glass may contain both Fe and Ni.
  • Metallic glass is an amorphous metal excellent in corrosion resistance, strength and magnetism. This metallic glass is stronger than the crystalline alloy. This metallic glass suppresses stress due to expansion / contraction due to insertion / extraction of lithium ions to / from Si during charge / discharge. This metallic glass suppresses cracking of the electrode and the negative electrode material during charging and discharging. Therefore, electrical isolation of the negative electrode material is suppressed. This metallic glass contributes to the cycle characteristics of the negative electrode 12.
  • the negative electrode 12 having this metallic glass is excellent in cycle characteristics.
  • This metal glass hardly reacts with lithium ions. Therefore, the expansion and contraction of the metallic glass during charging / discharging hardly occur.
  • This matrix made of metallic glass is excellent in stability.
  • Ni-based metallic glass such as 60Ni15Nb20Ti5Zr, 53Ni20Nb10Ti8Zr6Co3Cu and 43.2Ni28.8Fe19.2B4.8Si4Nb; Base metal glass; Ti base metal glass such as 53Ti15Cu18.5Ni3Zr17Al3Si0.5B and 50Ti25Cu15Ni5Zr5Sn; Zr base metal glass such as 55Zr30Cu10Al5Ni and 65Zr15Cu10Al10Ni; Cu base metal glass; and 40Pd30Cu10Ni20P d group metallic glass are exemplified.
  • the metallic glass particularly suitable for the matrix is Ni-based metallic glass and / or Fe-based metallic glass. These metallic glasses suppress cracking and cracking of the Si main phase when the Si main phase occludes and releases lithium ions.
  • the component of the negative electrode material shown in FIG. 3 is Si—NiNbTiZr.
  • the negative electrode material includes a Si main phase and a Ni-based metallic glass.
  • Si—NiNbTiZr is detected by EDS analysis. Therefore, it can be seen that Si and NiNbTiZr (metallic glass) are finely dispersed, and the metallic glass is adjacent to the Si main phase.
  • the ratio of Si main phase in the negative electrode material is 20 mass. % Or more and 80 mass. % Or less is preferable. This ratio is 20 mass. % Of the negative electrode material has a large storage capacity. From this point of view, this ratio is 40 mass. % Or more is preferable, and 50 mass. % Or more is particularly preferable. This ratio is 80 mass. Since a sufficient amount of metallic glass is present in a negative electrode material that is less than or equal to%, cracking, electrical isolation, dropout, and the like of the negative electrode material during charging and discharging are suppressed. From this point of view, this ratio is 70 mass. % Or less is more preferable, and 65 mass. % Or less is particularly preferable.
  • Examples of the method for producing the particles 22 (or powder) as the negative electrode material include a water atomizing method, a single roll quenching method, a twin roll quenching method, a gas atomizing method, a disk atomizing method, and a centrifugal atomizing method.
  • Mechanical milling etc. may be given to the powder obtained by these methods. Examples of the mechanical milling include a ball mill method, a bead mill method, a planetary ball mill method, an attritor method, and a vibration ball mill method.
  • Preferred manufacturing methods are a single roll cooling method, a gas atomizing method, and a disk atomizing method. Hereinafter, an example of these manufacturing methods will be described in detail. Manufacturing conditions are not limited to those described below.
  • raw materials are put into a quartz tube having pores at the bottom.
  • This raw material is heated and melted by a high frequency induction furnace in an argon gas atmosphere.
  • the raw material flowing out from the pores is dropped on the surface of the copper roll and cooled to obtain a ribbon.
  • This ribbon is put into the pot together with the ball.
  • the ball material include zirconia, SUS304, and SUJ2.
  • the pot material include zirconia, SUS304, and SUJ2.
  • the pot is filled with argon gas and the pot is sealed.
  • the ribbon is pulverized by milling to obtain a powder. Examples of milling include a ball mill, a bead mill, a planetary ball mill, an attritor, and a vibrating ball mill.
  • raw materials are put into a quartz crucible having pores at the bottom. This raw material is heated and melted by a high frequency induction furnace in an argon gas atmosphere. In an argon gas atmosphere, argon gas or nitrogen gas is injected onto the raw material flowing out from the pores. The raw material is rapidly cooled and solidified to obtain a powder.
  • raw materials are put into a quartz crucible having pores at the bottom. This raw material is heated and melted by a high frequency induction furnace in an argon gas atmosphere. In an argon gas atmosphere, the raw material flowing out from the pores is dropped onto a disk that rotates at high speed. The rotation speed is 40000 rpm to 60000 rpm. The raw material is rapidly cooled by the disk and solidified to obtain a powder.
  • a structure may be formed.
  • the mechanical milling include a ball mill method, a bead mill method, a planetary ball mill method, an attritor method, and a vibration ball mill method.
  • the negative electrode described above can be applied not only to lithium ion secondary batteries but also to various power storage devices such as all solid lithium ion secondary batteries and hybrid capacitors.
  • the effect of the negative electrode material according to the present invention was confirmed using a bipolar coin cell.
  • raw materials having the compositions shown in Tables 1 to 3 were prepared. Particles were produced from each raw material by gas atomization and mechanical milling. Each particle, conductive material (acetylene black), binder (polyimide, polyvinylidene fluoride, etc.) and dispersion (N-methylpyrrolidone) were mixed to obtain a slurry. This slurry was apply
  • the solvent was evaporated by this drying to obtain an active material layer.
  • the active material layer and the copper foil were pressed with a roll. This active material layer and copper foil were punched into a shape suitable for a coin-type cell to obtain a negative electrode.
  • a mixed solvent of ethylene carbonate and dimethyl carbonate was prepared as an electrolytic solution.
  • the mass ratio of both was 3: 7.
  • lithium hexafluorophosphate (LiPF 6 ) was prepared as a supporting electrolyte.
  • the amount of the supporting electrolyte is 1 mol with respect to 1 L of the electrolytic solution. This supporting electrolyte was dissolved in the electrolytic solution.
  • a separator and a positive electrode having a shape suitable for a coin-type cell were prepared. This positive electrode was punched from a lithium foil. The separator was immersed in the electrolytic solution under reduced pressure and allowed to stand for 5 hours to fully infiltrate the separator with the electrolytic solution.
  • a negative electrode, a separator and a positive electrode were incorporated into a coin-type cell.
  • a coin-type cell was filled with an electrolytic solution to obtain a coin-type cell for evaluation.
  • electrolyte solution in the inert atmosphere it is necessary to handle electrolyte solution in the inert atmosphere by which dew point control was carried out. Therefore, the cell was assembled in a glove box with an inert atmosphere.
  • the battery was charged at a temperature of 25 ° C. and at a constant current / constant voltage until the potential difference between the positive electrode and the negative electrode became 0V. Thereafter, discharging was performed at a constant current until the potential difference became 1.5V. This charge and discharge was repeated 50 cycles.
  • the initial storage capacity X and the storage capacity Y after 50 cycles of charging and discharging were measured. Furthermore, the ratio (maintenance rate) of the storage capacity Y to the storage capacity X was calculated. The results are shown in Tables 1 to 3 below.
  • the negative electrode materials 1 to 35 include a matrix made of metallic glass containing Fe or Ni and a Si main phase dispersed in the matrix.
  • the Si crystallite size in the Si main phase is 20 nm or less.
  • the negative electrode material 13 consists of Si main phase and metallic glass (60Ni15Nb20Ti5Zr). This metallic glass contains Ni. In this negative electrode material, as shown in FIG. 3, the Si main phase and the metallic glass are finely dispersed. In this negative electrode material, metallic glass has a matrix structure. The Si crystallite size of the Si main phase is 3 nm. The initial storage capacity of this negative electrode material is as large as 1235 mAh / g, and the storage capacity retention rate after 50 cycles is also as large as 82%.
  • the metallic glass is 42Cu-42Zr-8Al-18Ag and does not contain Fe and Ni. Further, the crystallite size of the Si main phase is 38 nm, which is large. Accordingly, the initial storage capacity is as high as 2449 mAh / g, but the storage capacity maintenance rate after 50 cycles is 5%, which is inferior in cycle life.

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Abstract

Provided is a negative electrode material for a storage device, the material comprising: a matrix formed of a metal glass containing Fe and/or Ni; and an Si primary phase dispersed in the matrix. The Si crystallite size in the Si primary phase is 20 nm or smaller. According to the present invention, obtained is a negative electrode for a storage device, which has a large storage capacity, and for which a reduction in storage capacity due to repeated charging and discharging is suppressed.

Description

蓄電デバイス用負極材料Negative electrode material for electricity storage devices
　本発明は、リチウムイオン二次電池、全固体リチウムイオン二次電池、ハイブリットキャパシタ等の、充放電時にリチウムイオンの移動を伴う蓄電デバイスの負極に適した材料に関する。 The present invention relates to a material suitable for a negative electrode of an electricity storage device that moves lithium ions during charge and discharge, such as a lithium ion secondary battery, an all solid lithium ion secondary battery, and a hybrid capacitor.
　近年、携帯電話機、携帯音楽プレーヤー、携帯端末等が急速に普及している。これらの携帯機器は、リチウムイオン二次電池を有している。電気自動車及びハイブリッド自動車も、リチウムイオン二次電池を有している。さらに、家庭用の定置蓄電デバイスとして、リチウムイオン二次電池及びハイブリットキャパシタが用いられている。リチウムイオン二次電池では、放電時に負極がリチウムイオンを吸蔵する。リチウムイオン二次電池の充電時には、負極からリチウムイオンが放出される。負極は、集電体と、この集電体の表面に固着された活物質とを有している。 In recent years, cellular phones, portable music players, portable terminals, and the like are rapidly spreading. These portable devices have a lithium ion secondary battery. Electric vehicles and hybrid vehicles also have lithium ion secondary batteries. Further, lithium ion secondary batteries and hybrid capacitors are used as stationary electric storage devices for home use. In a lithium ion secondary battery, the negative electrode occludes lithium ions during discharge. When the lithium ion secondary battery is charged, lithium ions are released from the negative electrode. The negative electrode has a current collector and an active material fixed to the surface of the current collector.
　ところで、負極における活物質として、天然黒鉛、人造黒鉛、コークス等の炭素系材料が用いられている。炭素系材料では、充放電の繰り返しによってもデンドライトが生じにくい。従って、デンドライトに起因する短絡が生じにくい。しかし、炭素系材料の、リチウムイオンに対する理論上の容量は、３７２ｍＡｈ／ｇにすぎない。容量の大きな活物質が望まれている。 Incidentally, carbon-based materials such as natural graphite, artificial graphite, and coke are used as the active material in the negative electrode. In the case of carbon-based materials, dendrites are less likely to occur due to repeated charge and discharge. Therefore, a short circuit caused by dendrite hardly occurs. However, the theoretical capacity of the carbon-based material for lithium ions is only 372 mAh / g. A large capacity active material is desired.
　そこで、負極における活物質として、Ｓｎ及びＳｉが注目されている。Ｓｎ及びＳｉの理論上の容量は、炭素系材料のそれの２倍以上である。特に、Ｓｉの理論上の容量は、炭素系材料のそれの１０倍以上である。Ｓｉは、リチウムイオンと反応する。この反応により、化合物が形成される。典型的な化合物は、Ｌｉ２２Ｓｉ５である。この反応により、大量のリチウムイオンが負極に吸蔵される。Ｓｉは、負極の蓄電容量を高めうる。 Therefore, Sn and Si have attracted attention as active materials in the negative electrode. The theoretical capacity of Sn and Si is more than twice that of carbon-based materials. In particular, the theoretical capacity of Si is more than 10 times that of carbon-based materials. Si reacts with lithium ions. This reaction forms a compound. A typical compound is Li 22 Si 5 . By this reaction, a large amount of lithium ions is occluded in the negative electrode. Si can increase the storage capacity of the negative electrode.
　一方、特開２００７－０９５３６３号公報には、負極の活物質の一部としての、金属ガラスの使用が開示されている。この金属ガラスは、Ｓｎを含む。この金属ガラスは、変形が容易である。この金属ガラスは、Ｓｎの脱落及び孤立を阻止しうる。 On the other hand, Japanese Patent Application Laid-Open No. 2007-095363 discloses the use of metallic glass as part of the negative electrode active material. This metallic glass contains Sn. This metallic glass is easy to deform. This metallic glass can prevent Sn from falling off and isolated.
特開２００７－０９５３６３号公報JP 2007-095363 A
　しかしながら、Ｓｉを含む活物質層がリチウムイオンを吸蔵すると、前述の化合物の生成により、この活物質層が膨張する。活物質の膨張率は、約４００％である。活物質層からリチウムイオンが放出されると、この活物質層が収縮する。膨張と収縮との繰り返しにより、活物質が集電体から脱落することがあり、孤立することもある。この脱落及び孤立は、蓄電容量を低下させる。膨張と収縮との繰り返しにより、活物質間の導電性が阻害されることもある。負極がＳｉを含む従来のリチウムイオン二次電池の寿命は、長くない。しかも、Ｓｉの単体での電気伝導性は、炭素質材料及び金属系材料のそれに比べて低い。従って、Ｓｉを含む負極材料では、充放電時の効率が不十分である。 However, when the active material layer containing Si occludes lithium ions, the active material layer expands due to the generation of the aforementioned compound. The expansion coefficient of the active material is about 400%. When lithium ions are released from the active material layer, the active material layer contracts. The active material may fall off from the current collector due to repeated expansion and contraction, and may become isolated. This dropout and isolation reduces the storage capacity. The conductivity between the active materials may be hindered by repeated expansion and contraction. The lifetime of the conventional lithium ion secondary battery in which the negative electrode contains Si is not long. Moreover, the electrical conductivity of Si alone is lower than that of carbonaceous materials and metal-based materials. Therefore, the negative electrode material containing Si has insufficient efficiency during charging and discharging.
　また、特開２００７－０９５３６３号公報に開示された金属ガラスは、それ自体がリチウムと反応する。この反応により、金属ガラスの体積がほぼ４００％膨張する。膨張は、金属ガラスの構造状の安定性を阻害する。充放電の繰り返しにより、この金属ガラスが崩壊する恐れもある。さらに、特開２００７－０９５３６３号公報に開示された金属ガラスに含まれるリチウム活性物質は、少量である。従って、この金属ガラスを有する負極では、充放電量は十分ではない。この金属ガラスを有する負極では、高容量化への要請及び高出力化への要請に対応できない。同様の問題は、リチウムイオン二次電池以外の、様々な蓄電デバイスにおいても、生じている。 Further, the metal glass disclosed in Japanese Patent Application Laid-Open No. 2007-095363 reacts with lithium itself. This reaction causes the volume of the metallic glass to expand by approximately 400%. The expansion hinders the structural stability of the metallic glass. There is also a risk that the metallic glass will collapse due to repeated charge and discharge. Further, the lithium active material contained in the metal glass disclosed in Japanese Patent Application Laid-Open No. 2007-095363 is a small amount. Therefore, in the negative electrode having this metallic glass, the charge / discharge amount is not sufficient. The negative electrode having this metallic glass cannot respond to the demand for higher capacity and the demand for higher output. Similar problems occur in various power storage devices other than lithium ion secondary batteries.
　したがって、本発明の目的は、蓄電容量が大きく、かつ充放電の繰り返しによる蓄電容量低下が抑制された負極が得られる材料を提供することである。 Therefore, an object of the present invention is to provide a material that can provide a negative electrode having a large storage capacity and in which a decrease in the storage capacity due to repeated charge and discharge is suppressed.
　本発明の一態様によれば、Ｆｅ及び／又はＮｉを含む金属ガラスからなるマトリクスと、このマトリクスに分散したＳｉ主要相とを備えており、
　上記Ｓｉ主要相におけるＳｉ結晶子サイズが２０ｎｍ以下である蓄電デバイス用負極材料が提供される。 According to one aspect of the present invention, a matrix made of metallic glass containing Fe and / or Ni and a Si main phase dispersed in the matrix are provided.
Provided is a negative electrode material for an electricity storage device in which the Si crystallite size in the Si main phase is 20 nm or less.
　本発明の別の一態様によれば、上記Ｓｉ主要相が、Ｇｅ、Ａｌ及びＢからなる群から選択された１種又は２種以上を含んでおり、
　上記負極材料におけるＧｅ、Ａｌ及びＢの合計含有率が０．０１ｍａｓｓ．％以上５．０ｍａｓｓ．％以下である、上記蓄電デバイス用負極材料が提供される。 According to another aspect of the present invention, the Si main phase includes one or more selected from the group consisting of Ge, Al and B,
The total content of Ge, Al, and B in the negative electrode material is 0.01 mass. % Or more and 5.0 mass. % Of the negative electrode material for an electricity storage device is provided.
　本発明の更なる別の一態様によれば、上記負極材料における上記Ｓｉ主要相の比率が２０ｍａｓｓ．％以上８０ｍａｓｓ．％以下である、上記蓄電デバイス用負極材料が提供される。 According to still another aspect of the present invention, the ratio of the Si main phase in the negative electrode material is 20 mass. % Or more and 80 mass. % Of the negative electrode material for an electricity storage device is provided.
　本発明に係る負極材料は、Ｓｉ主要相を含むので、その蓄電容量が大きい。しかもこの負極材料では、充放電の繰り返しによる蓄電容量低下が、金属ガラスによって抑制される。 Since the negative electrode material according to the present invention includes a Si main phase, its storage capacity is large. In addition, in this negative electrode material, the reduction in the storage capacity due to repeated charge and discharge is suppressed by the metallic glass.
本発明の一実施形態に係る負極材料が用いられたリチウムイオン二次電池が示された概念図である。It is the conceptual diagram by which the lithium ion secondary battery using the negative electrode material which concerns on one Embodiment of this invention was shown. 図１の電池の負極の一部が示された拡大断面図である。FIG. 2 is an enlarged cross-sectional view illustrating a part of a negative electrode of the battery of FIG. 1. 図１のリチウムイオン二次電池の負極材料が示されたＴＥＭ像である。2 is a TEM image showing a negative electrode material of the lithium ion secondary battery of FIG. 1.
　以下、適宜図面が参照されつつ、好ましい実施形態に基づいて本発明が詳細に説明される。 Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.
　図１に概念的に示されたリチウムイオン二次電池２は、槽４、電解液６、セパレータ８、正極１０及び負極１２を有している。電解液６は、槽４に蓄えられている。この電解液６は、リチウムイオンを含んでいる。セパレータ８は、槽４を、正極室１４及び負極室１６に区画している。セパレータ８により、正極１０と負極１２との当接が防止される。このセパレータ８は、多数の孔（図示されず）を備えている。リチウムイオンは、この孔を通過しうる。正極１０は、正極室１４において、電解液６に浸漬されている。負極１２は、負極室１６において、電解液６に浸漬されている。 The lithium ion secondary battery 2 conceptually shown in FIG. 1 has a tank 4, an electrolytic solution 6, a separator 8, a positive electrode 10, and a negative electrode 12. The electrolytic solution 6 is stored in the tank 4. This electrolytic solution 6 contains lithium ions. The separator 8 partitions the tank 4 into a positive electrode chamber 14 and a negative electrode chamber 16. The separator 8 prevents contact between the positive electrode 10 and the negative electrode 12. The separator 8 has a large number of holes (not shown). Lithium ions can pass through this hole. The positive electrode 10 is immersed in the electrolytic solution 6 in the positive electrode chamber 14. The negative electrode 12 is immersed in the electrolytic solution 6 in the negative electrode chamber 16.
　図２には、負極１２の一部が示されている。この負極１２は、集電体１８と、活物質層２０とを備えている。活物質層２０は、多数の粒子２２を含んでいる。粒子２２は、この粒子２２に当接する他の粒子２２と固着されている。集電体１８に当接する粒子２２は、この集電体１８に固着されている。活物質層２０は、多孔質である。 FIG. 2 shows a part of the negative electrode 12. The negative electrode 12 includes a current collector 18 and an active material layer 20. The active material layer 20 includes a large number of particles 22. The particles 22 are fixed to other particles 22 that are in contact with the particles 22. The particles 22 that come into contact with the current collector 18 are fixed to the current collector 18. The active material layer 20 is porous.
　活物質層２０の粒子２２は、本発明では、「負極材料」と称される。 The particles 22 of the active material layer 20 are referred to as “negative electrode material” in the present invention.
　この負極材料のＴＥＭ像が、図３に示されている。この負極材料は、マトリクスと、このマトリクスに分散するＳｉ主要相とを有している。 TEM image of this negative electrode material is shown in FIG. This negative electrode material has a matrix and a Si main phase dispersed in the matrix.
　Ｓｉ主要相の主成分は、Ｓｉである。Ｓｉは、リチウムイオンと反応する。Ｓｉ主要相は、多量のリチウムイオンを吸蔵できる。このＳｉ主要相は、負極１２の蓄電容量を高めうる。蓄電容量の観点から、Ｓｉ主要相におけるＳｉの含有率は８０ｍａｓｓ．％以上が好ましく、９０ｍａｓｓ．％以上がより好ましく、９５ｍａｓｓ．％以上が特に好ましい。この含有率が１００ｍａｓｓ．％であってもよい。Ｓｉ主要相が後述される他の元素を含む場合は、このＳｉ主要相が他の元素を十分に含みうるとの観点から、この含有率は９９．９９ｍａｓｓ．％以下が好ましく、９９．５ｍａｓｓ．％以下がより好ましく、９９．０ｍａｓｓ．％以下が特に好ましい。 The main component of the Si main phase is Si. Si reacts with lithium ions. The Si main phase can occlude a large amount of lithium ions. This Si main phase can increase the storage capacity of the negative electrode 12. From the viewpoint of storage capacity, the Si content in the Si main phase is 80 mass. % Or more, preferably 90 mass. % Or more is more preferable, 95 mass. % Or more is particularly preferable. This content is 100 mass. %. In the case where the Si main phase contains other elements described later, this content is 99.99 mass. From the viewpoint that the Si main phase can sufficiently contain other elements. % Or less, 99.5 mass. % Or less is more preferable, and 99.0 mass. % Or less is particularly preferable.
　Ｓｉ主要相が、Ｓｉ以外の元素を含んでもよい。Ｓｉ主要相が、Ｓｉ以外の２種以上の元素を含んでもよい。典型的な元素は、Ｇｅ、Ａｌ及びＢである。Ｇｅ、Ａｌ及びＢは、Ｓｉに固溶しうる。Ｇｅ、Ａｌ又はＢがＳｉに固溶したＳｉ主要相では、Ｓｉへのリチウム挿入及び脱離による膨張収縮時の、Ｓｉのクラック及び割れが抑制されうる。換言すれば、Ｇｅ、Ａｌ及びＢは、Ｓｉ主要相を強化する。しかも、Ｇｅ、Ａｌ及びＢは、Ｓｉ主要相の電気伝導性を高める。クラック及び割れが抑制されることにより、充放電時の、Ｓｉ主要相と電解液６との界面での、抵抗被膜の形成が抑制されうる。抵抗被膜が少ない負極１２は、サイクル寿命に優れる。 The Si main phase may contain an element other than Si. The Si main phase may contain two or more elements other than Si. Typical elements are Ge, Al and B. Ge, Al and B can be dissolved in Si. In the Si main phase in which Ge, Al or B is solid-dissolved in Si, cracks and cracks of Si during expansion and contraction due to lithium insertion and desorption from Si can be suppressed. In other words, Ge, Al and B strengthen the Si main phase. Moreover, Ge, Al and B increase the electrical conductivity of the Si main phase. By suppressing cracks and cracks, the formation of a resistive film at the interface between the Si main phase and the electrolyte 6 during charging and discharging can be suppressed. The negative electrode 12 having a small resistance film is excellent in cycle life.
　Ｇｅ、Ａｌ又はＢがＳｉに固溶したＳｉ主要相の構造は、Ｓｉ単相のそれに比して異なる。Ｇｅ、Ａｌ又はＢがＳｉに固溶したＳｉ主要相の電子密度状態も、Ｓｉ単相のそれに比して異なる。構造、電子密度状態等の相違により、Ｓｉ主要相と電解液６との界面での、抵抗被膜の形成が抑制されうる。抵抗被膜が少ない負極１２は、サイクル寿命に優れる。 The structure of the Si main phase in which Ge, Al or B is dissolved in Si is different from that of the Si single phase. The electron density state of the Si main phase in which Ge, Al or B is dissolved in Si is also different from that of the Si single phase. Due to differences in structure, electron density state, and the like, the formation of a resistive film at the interface between the Si main phase and the electrolyte 6 can be suppressed. The negative electrode 12 having a small resistance film is excellent in cycle life.
　負極材料におけるＧｅ、Ａｌ及びＢの合計含有率は、０．０１ｍａｓｓ．％以上５．０ｍａｓｓ．％以下が好ましい。合計含有率が０．０１ｍａｓｓ．％以上である負極材料では、Ｓｉのクラック及び割れが抑制されうる。この観点から、この合計含有率は０．１ｍａｓｓ．％以上がより好ましく、０．５ｍａｓｓ．％以上が特に好ましい。合計含有率が５．０ｍａｓｓ．％以下である負極材料では、充放電時の応力に起因する、ひび割れ、電気的孤立及び集電体１８からの脱落が抑制される。合計含有率が５．０ｍａｓｓ．％以下である負極材料が、サイクル特性に優れる。この観点から、この合計含有率は４．０ｍａｓｓ．％以下がより好ましく、３．５ｍａｓｓ．％以下が特に好ましい。 The total content of Ge, Al and B in the negative electrode material is 0.01 mass. % Or more and 5.0 mass. % Or less is preferable. The total content is 0.01 mass. If the negative electrode material is at least%, Si cracking and cracking can be suppressed. From this point of view, the total content is 0.1 mass. % Or more is more preferable, and 0.5 mass. % Or more is particularly preferable. The total content is 5.0 mass. In a negative electrode material that is less than or equal to%, cracks, electrical isolation, and drop-off from the current collector 18 due to stress during charging and discharging are suppressed. The total content is 5.0 mass. % Or less of the negative electrode material is excellent in cycle characteristics. From this viewpoint, the total content is 4.0 mass. % Or less is more preferable, and 3.5 mass. % Or less is particularly preferable.
　Ｓｉ主要相がＧｅ、Ａｌ及びＢを含まない場合、好ましくは、Ｓｉ主要相は、Ｓｉを含みかつ残部は不可避的不純物である。Ｓｉ主要相がＧｅ、Ａｌ又はＢを含む場合、好ましくは、Ｓｉ主要相は、Ｓｉを含み、Ｇｅ、Ａｌ又はＢを含み、かつ残部は不可避的不純物である。 When the Si main phase does not contain Ge, Al and B, preferably, the Si main phase contains Si and the balance is inevitable impurities. When the Si main phase contains Ge, Al or B, preferably, the Si main phase contains Si, contains Ge, Al or B, and the balance is inevitable impurities.
　Ｓｉ主要相におけるＳｉ結晶子サイズは、２０ｎｍ以下が好ましい。結晶子サイズが２０ｎｍ以下である負極材料では、充放電時の応力に起因する、ひび割れ、電気的孤立及び集電体１８からの脱落が抑制される。この観点から、この結晶子サイズは１５ｎｍ以下が好ましく、１０ｎｍ以下がより好ましい。Ｓｉ結晶子サイズの下限は特に限定されるものではないが、典型的には０．５ｎｍ以上である。Ｓｉ主要相が非結晶質であってもよい。 The Si crystallite size in the Si main phase is preferably 20 nm or less. In the negative electrode material having a crystallite size of 20 nm or less, cracks, electrical isolation, and drop-off from the current collector 18 due to stress during charging and discharging are suppressed. From this viewpoint, the crystallite size is preferably 15 nm or less, and more preferably 10 nm or less. The lower limit of the Si crystallite size is not particularly limited, but is typically 0.5 nm or more. The Si main phase may be amorphous.
　結晶子サイズは、Ｘ線回折によって測定される。Ｘ線源として、波長が１．５４０５９ÅのＣｕＫα線が用いられる。２θが２０度から８０度までの範囲で、測定が行われる。得られる回折スペクトルでは、結晶子サイズが小さいほど、比較的ブロードな回折ピークが観測される。Ｘ線回折で得られるピークの半値幅から、下記のＳｃｈｅｒｒｅｒの式が用いられて、結晶子サイズが算出される。
　　Ｄ（Å）＝（Ｋ×λ）／（β×ｃｏｓθ）
　　　Ｄ：結晶子の大きさ
　　　Ｋ：Ｓｃｈｅｒｒｅｒの定数
　　　λ：使用X線管球の波長
　　　β：結晶子の大きさによる回折線の拡がり
　　　θ：回折角 The crystallite size is measured by X-ray diffraction. As an X-ray source, a CuKα ray having a wavelength of 1.54059 mm is used. Measurement is performed in the range of 2θ from 20 degrees to 80 degrees. In the obtained diffraction spectrum, a relatively broad diffraction peak is observed as the crystallite size is smaller. The crystallite size is calculated from the half width of the peak obtained by X-ray diffraction using the following Scherrer equation.
D (Å) = (K × λ) / (β × cos θ)
D: Crystallite size K: Scherrer's constant λ: Wavelength of X-ray tube used β: Spread of diffraction line depending on crystallite size θ: Diffraction angle
　Ｓｉのピーク及び化合物のピークはブロード化し、Ｓｉ結晶子サイズが２０ｎｍ以下であることが確認されている。また、Ｓｉ結晶子サイズは、原料粉末を溶解した後の凝固時の冷却速度の調整によって制御されうる。 It was confirmed that the Si peak and the compound peak were broadened and the Si crystallite size was 20 nm or less. The Si crystallite size can be controlled by adjusting the cooling rate during solidification after the raw material powder is dissolved.
　マトリクスは、Ｆｅ又はＮｉを含む金属ガラスからなる。金属ガラスが、Ｆｅ及びＮｉの両方を含んでもよい。金属ガラスは、耐食性、強度及び磁性に優れた、アモルファス金属である。この金属ガラスは、結晶性合金よりも強度が強い。この金属ガラスは、充放電時のＳｉへのリチウムイオン挿入・脱離による膨張収縮による応力を抑え込む。この金属ガラスは、充放電時の電極及び負極材料の割れを抑制する。従って、負極材料の電気的孤立が抑制される。この金属ガラスは、負極１２のサイクル特性に寄与する。 The matrix is made of metallic glass containing Fe or Ni. The metallic glass may contain both Fe and Ni. Metallic glass is an amorphous metal excellent in corrosion resistance, strength and magnetism. This metallic glass is stronger than the crystalline alloy. This metallic glass suppresses stress due to expansion / contraction due to insertion / extraction of lithium ions to / from Si during charge / discharge. This metallic glass suppresses cracking of the electrode and the negative electrode material during charging and discharging. Therefore, electrical isolation of the negative electrode material is suppressed. This metallic glass contributes to the cycle characteristics of the negative electrode 12.
　この金属ガラスは耐食性に優れるので、この金属ガラスによってＳｉと電解液６との界面で生じる電解液６の分解反応が抑制される。この金属ガラスを有する負極１２は、サイクル特性に優れる。 Since this metallic glass is excellent in corrosion resistance, decomposition reaction of the electrolytic solution 6 generated at the interface between Si and the electrolytic solution 6 is suppressed by this metallic glass. The negative electrode 12 having this metallic glass is excellent in cycle characteristics.
　この金属ガラスは、リチウムイオンとほとんど反応しない。従って、充放電時の金属ガラスの膨張及び収縮は、ほとんど生じない。この金属ガラスからなるマトリクスは、安定性に優れる。 This metal glass hardly reacts with lithium ions. Therefore, the expansion and contraction of the metallic glass during charging / discharging hardly occur. This matrix made of metallic glass is excellent in stability.
　金属ガラスとして、６０Ｎｉ１５Ｎｂ２０Ｔｉ５Ｚｒ、５３Ｎｉ２０Ｎｂ１０Ｔｉ８Ｚｒ６Ｃｏ３Ｃｕ及び４３．２Ｎｉ２８．８Ｆｅ１９．２Ｂ４．８Ｓｉ４ＮｂのようなＮｉ基金属ガラス；７７Ｆｅ３Ｇａ９．５Ｐ４Ｃ４Ｂ２．５Ｓｉ、５７．６Ｆｅ１４．４Ｃｏ４Ｓｉ２０Ｂ４Ｎｂ、３６Ｆｅ３６Ｃｏ４．８Ｓｉ１９．２Ｂ４Ｎｂ、７５Ｆｅ５Ｇａ１２Ｐ４Ｃ４Ｂ及び２２Ｆｅ４０Ｃｏ８Ｎｂ３０ＢのようなＦｅ基金属ガラス；５３Ｔｉ１５Ｃｕ１８．５Ｎｉ３Ｚｒ１７Ａｌ３Ｓｉ０．５Ｂ及び５０Ｔｉ２５Ｃｕ１５Ｎｉ５Ｚｒ５ＳｎのようなＴｉ基金属ガラス；５５Ｚｒ３０Ｃｕ１０Ａｌ５Ｎｉ及び６５Ｚｒ１５Ｃｕ１０Ａｌ１０ＮｉのようなＺｒ基金属ガラス；Ｃｕ基金属ガラス；並びに４０Ｐｄ３０Ｃｕ１０Ｎｉ２０ＰのようなＰｄ基金属ガラスが例示される。 As the metallic glass, Ni-based metallic glass such as 60Ni15Nb20Ti5Zr, 53Ni20Nb10Ti8Zr6Co3Cu and 43.2Ni28.8Fe19.2B4.8Si4Nb; Base metal glass; Ti base metal glass such as 53Ti15Cu18.5Ni3Zr17Al3Si0.5B and 50Ti25Cu15Ni5Zr5Sn; Zr base metal glass such as 55Zr30Cu10Al5Ni and 65Zr15Cu10Al10Ni; Cu base metal glass; and 40Pd30Cu10Ni20P d group metallic glass are exemplified.
　マトリクスに特に適した金属ガラスは、Ｎｉ基金属ガラス及び／又はＦｅ基金属ガラスである。これらの金属ガラスは、Ｓｉ主要相がリチウムイオンを吸蔵するとき、及び放出するときの、このＳｉ主要相のクラック及び割れを抑制する。 The metallic glass particularly suitable for the matrix is Ni-based metallic glass and / or Fe-based metallic glass. These metallic glasses suppress cracking and cracking of the Si main phase when the Si main phase occludes and releases lithium ions.
　図３に示された負極材料の成分は、Ｓｉ－ＮｉＮｂＴｉＺｒである。換言すれば、この負極材料は、Ｓｉ主要相と、Ｎｉ基金属ガラスとを含んでいる。この像のどの部分においても、ＥＤＳ分析によってＳｉ－ＮｉＮｂＴｉＺｒが検出される。従って、微細にＳｉとＮｉＮｂＴｉＺｒ（金属ガラス）とが分散しており、かつＳｉ主要相の周囲に金属ガラスが隣接している構造であることが分かる。 The component of the negative electrode material shown in FIG. 3 is Si—NiNbTiZr. In other words, the negative electrode material includes a Si main phase and a Ni-based metallic glass. In any part of the image, Si—NiNbTiZr is detected by EDS analysis. Therefore, it can be seen that Si and NiNbTiZr (metallic glass) are finely dispersed, and the metallic glass is adjacent to the Si main phase.
　負極材料におけるＳｉ主要相の比率は、２０ｍａｓｓ．％以上８０ｍａｓｓ．％以下が好ましい。この比率が２０ｍａｓｓ．％以上である負極材料は、蓄電容量が大きい。この観点から、この比率は４０ｍａｓｓ．％以上がより好ましく、５０ｍａｓｓ．％以上が特に好ましい。この比率が８０ｍａｓｓ．％以下である負極材料では、十分な量の金属ガラスが存在するので、充放電時の負極材料の割れ、電気的孤立、脱落等が抑制される。この観点から、この比率は７０ｍａｓｓ．％以下がより好ましく、６５ｍａｓｓ．％以下が特に好ましい。 The ratio of Si main phase in the negative electrode material is 20 mass. % Or more and 80 mass. % Or less is preferable. This ratio is 20 mass. % Of the negative electrode material has a large storage capacity. From this point of view, this ratio is 40 mass. % Or more is preferable, and 50 mass. % Or more is particularly preferable. This ratio is 80 mass. Since a sufficient amount of metallic glass is present in a negative electrode material that is less than or equal to%, cracking, electrical isolation, dropout, and the like of the negative electrode material during charging and discharging are suppressed. From this point of view, this ratio is 70 mass. % Or less is more preferable, and 65 mass. % Or less is particularly preferable.
　負極材料である粒子２２（又は粉末）の製造方法として、水アトマイズ法、単ロール急冷法、双ロール急冷法、ガスアトマイズ法、ディスクアトマイズ法及び遠心アトマイズ法が例示される。これらの方法によって得られた粉末に、メカニカルミリング等が施されてもよい。メカニカルミリングとして、ボールミル法、ビーズミル法、遊星ボールミル法、アトライタ法及び振動ボールミル法が例示される。好ましい製造方法は、単ロール冷却法、ガスアトマイズ法及びディスクアトマイズ法である。以下、これらの製造方法の一例が、詳説される。製造の条件は、下記に記載されたものに限定されない。 Examples of the method for producing the particles 22 (or powder) as the negative electrode material include a water atomizing method, a single roll quenching method, a twin roll quenching method, a gas atomizing method, a disk atomizing method, and a centrifugal atomizing method. Mechanical milling etc. may be given to the powder obtained by these methods. Examples of the mechanical milling include a ball mill method, a bead mill method, a planetary ball mill method, an attritor method, and a vibration ball mill method. Preferred manufacturing methods are a single roll cooling method, a gas atomizing method, and a disk atomizing method. Hereinafter, an example of these manufacturing methods will be described in detail. Manufacturing conditions are not limited to those described below.
　単ロール冷却法では、底部に細孔を有する石英管の中に、原料が投入される。この原料が、アルゴンガス雰囲気中で、高周波誘導炉によって加熱され、溶融する。細孔から流出する原料が、銅ロールの表面に落とされて冷却され、リボンが得られる。このリボンが、ボールと共にポットに投入される。ボールの材質として、ジルコニア、ＳＵＳ３０４及びＳＵＪ２が例示される。ポットの材質として、ジルコニア、ＳＵＳ３０４及びＳＵＪ２が例示される。ポットの中にアルゴンガスが充満され、このポットが密閉される。このリボンがミリングにより粉砕され、粉末が得られる。ミリングとして、ボールミル、ビーズミル、遊星ボールミル、アトライタ及び振動ボールミルが例示される。 In the single roll cooling method, raw materials are put into a quartz tube having pores at the bottom. This raw material is heated and melted by a high frequency induction furnace in an argon gas atmosphere. The raw material flowing out from the pores is dropped on the surface of the copper roll and cooled to obtain a ribbon. This ribbon is put into the pot together with the ball. Examples of the ball material include zirconia, SUS304, and SUJ2. Examples of the pot material include zirconia, SUS304, and SUJ2. The pot is filled with argon gas and the pot is sealed. The ribbon is pulverized by milling to obtain a powder. Examples of milling include a ball mill, a bead mill, a planetary ball mill, an attritor, and a vibrating ball mill.
　ガスアトマイズ法では、底部に細孔を有する石英坩堝の中に、原料が投入される。この原料が、アルゴンガス雰囲気中で、高周波誘導炉によって加熱され、溶融する。アルゴンガス雰囲気において、細孔から流出する原料に、アルゴンガスや窒素ガスが噴射される。原料は急冷されて凝固し、粉末が得られる。 In the gas atomization method, raw materials are put into a quartz crucible having pores at the bottom. This raw material is heated and melted by a high frequency induction furnace in an argon gas atmosphere. In an argon gas atmosphere, argon gas or nitrogen gas is injected onto the raw material flowing out from the pores. The raw material is rapidly cooled and solidified to obtain a powder.
　ディスクアトマイズ法では、底部に細孔を有する石英坩堝の中に、原料が投入される。この原料が、アルゴンガス雰囲気中で、高周波誘導炉によって加熱され、溶融する。アルゴンガス雰囲気において、細孔から流出する原料が、高速で回転するディスクの上に落とされる。回転速度は、４００００ｒｐｍから６００００ｒｐｍである。ディスクによって原料は急冷され、凝固して、粉末が得られる。 In the disc atomization method, raw materials are put into a quartz crucible having pores at the bottom. This raw material is heated and melted by a high frequency induction furnace in an argon gas atmosphere. In an argon gas atmosphere, the raw material flowing out from the pores is dropped onto a disk that rotates at high speed. The rotation speed is 40000 rpm to 60000 rpm. The raw material is rapidly cooled by the disk and solidified to obtain a powder.
　また、水アトマイズ法、単ロール急冷法、双ロール急冷法、ガスアトマイズ法、ディスクアトマイズ法及び遠心アトマイズ法等の方法によって得られた粉末を原料にして、数種類の粉末を組み合わせ、メカニカルミリング時に目的組成・構造を形成してもよい。メカニカルミリングとして、ボールミル法、ビーズミル法、遊星ボールミル法、アトライタ法及び振動ボールミル法が例示される。 In addition, using powder obtained by water atomizing method, single roll quenching method, twin roll quenching method, gas atomizing method, disk atomizing method and centrifugal atomizing method, etc. A structure may be formed. Examples of the mechanical milling include a ball mill method, a bead mill method, a planetary ball mill method, an attritor method, and a vibration ball mill method.
　以上説明された負極は、リチウムイオン二次電池のみならず、全固体リチウムイオン二次電池、ハイブリットキャパシタ等の、種々の蓄電デバイスにも適用されうる。 The negative electrode described above can be applied not only to lithium ion secondary batteries but also to various power storage devices such as all solid lithium ion secondary batteries and hybrid capacitors.
　以下、実施例によって本発明の効果が明らかにされるが、この実施例の記載に基づいて本発明が限定的に解釈されるべきではない。 Hereinafter, the effects of the present invention will be clarified by examples. However, the present invention should not be interpreted in a limited manner based on the description of the examples.
　本発明に係る負極材料の効果を、二極式コイン型セルを用いて確認した。まず、表１～３に示された組成の原料を準備した。各原料から、ガスアトマイズ法及びメカニカルミリングにより、粒子を製作した。それぞれの粒子、導電材（アセチレンブラック）、結着材（ポリイミド、ポリフッ化ビニリデン等）及び分散液（Ｎ－メチルピロリドン）を混合し、スラリーを得た。このスラリーを、集電体である銅箔の上に塗布した。このスラリーを、真空乾燥機で減圧乾燥した。乾燥温度は、ポリイミドが結着材である場合は２００℃以上であり、ポリフッ化ビニリデンが結着材である場合は１６０℃以上であった。この乾燥によって溶媒を蒸発させ、活物質層を得た。この活物質層及び銅箔を、ロールにて押圧した。この活物質層及び銅箔をコイン型セルに適した形状に打ち抜き、負極を得た。 The effect of the negative electrode material according to the present invention was confirmed using a bipolar coin cell. First, raw materials having the compositions shown in Tables 1 to 3 were prepared. Particles were produced from each raw material by gas atomization and mechanical milling. Each particle, conductive material (acetylene black), binder (polyimide, polyvinylidene fluoride, etc.) and dispersion (N-methylpyrrolidone) were mixed to obtain a slurry. This slurry was apply | coated on the copper foil which is a collector. This slurry was dried under reduced pressure using a vacuum dryer. The drying temperature was 200 ° C. or higher when polyimide was the binder, and 160 ° C. or higher when polyvinylidene fluoride was the binder. The solvent was evaporated by this drying to obtain an active material layer. The active material layer and the copper foil were pressed with a roll. This active material layer and copper foil were punched into a shape suitable for a coin-type cell to obtain a negative electrode.
　電解液として、エチレンカーボネートとジメチルカーボネートの混合溶媒を準備した。両者の質量比は、３：７であった。さらに、支持電解質として、六フッ化リン酸リチウム（ＬｉＰＦ６）を準備した。この支持電解質の量は、電解液１Ｌに対して１モルである。この支持電解質を、電解液に溶解させた。 A mixed solvent of ethylene carbonate and dimethyl carbonate was prepared as an electrolytic solution. The mass ratio of both was 3: 7. Furthermore, lithium hexafluorophosphate (LiPF 6 ) was prepared as a supporting electrolyte. The amount of the supporting electrolyte is 1 mol with respect to 1 L of the electrolytic solution. This supporting electrolyte was dissolved in the electrolytic solution.
　コイン型セルに適した形状のセパレータ及び正極を、準備した。この正極は、リチウム箔から打ち抜いた。減圧下で電解液にセパレータを浸漬し、５時間放置して、セパレータに電解液を充分に浸透させた。 A separator and a positive electrode having a shape suitable for a coin-type cell were prepared. This positive electrode was punched from a lithium foil. The separator was immersed in the electrolytic solution under reduced pressure and allowed to stand for 5 hours to fully infiltrate the separator with the electrolytic solution.
　コイン型セルに、負極、セパレータ及び正極を組み込んだ。コイン型セルに電解液を充填し、評価用コイン型セルを得た。なお、電解液は、露点管理された不活性雰囲気中で取り扱われる必要がある。従って、セルの組み立ては、不活性雰囲気のグローブボックスの中で行った。 負極 A negative electrode, a separator and a positive electrode were incorporated into a coin-type cell. A coin-type cell was filled with an electrolytic solution to obtain a coin-type cell for evaluation. In addition, it is necessary to handle electrolyte solution in the inert atmosphere by which dew point control was carried out. Therefore, the cell was assembled in a glove box with an inert atmosphere.
　上記コイン型セルにて、温度が２５℃であり、定電流・定電圧にて、正極と負極との電位差が０Ｖとなるまで充電を行った。その後、定電流にて電位差が１．５Ｖとなるまで放電を行った。この充電及び放電を、５０サイクル繰り返した。初期の蓄電容量Ｘ及び５０サイクルの充電及び放電を繰り返した後の蓄電容量Ｙを測定した。さらに、蓄電容量Ｘに対する蓄電容量Ｙの比率（維持率）を算出した。この結果が、下記の表１～３に示されている。 In the coin-type cell, the battery was charged at a temperature of 25 ° C. and at a constant current / constant voltage until the potential difference between the positive electrode and the negative electrode became 0V. Thereafter, discharging was performed at a constant current until the potential difference became 1.5V. This charge and discharge was repeated 50 cycles. The initial storage capacity X and the storage capacity Y after 50 cycles of charging and discharging were measured. Furthermore, the ratio (maintenance rate) of the storage capacity Y to the storage capacity X was calculated. The results are shown in Tables 1 to 3 below.
　下記の表１～３において、記載された成分の残部は、Ｓｉ及び不可避的不純物である。

  In Tables 1 to 3 below, the balance of the components listed is Si and inevitable impurities.

Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
　表１及び２に示されたＮｏ．１～３５の負極材料は、Ｆｅ又はＮｉを含む金属ガラスからなるマトリクスと、このマトリクスに分散したＳｉ主要相とを備えている。Ｓｉ主要相におけるＳｉ結晶子サイズは、２０ｎｍ以下である。これらの負極材料では、初期蓄電容量は大きく、かつ維持率も大きい。 No. shown in Tables 1 and 2. The negative electrode materials 1 to 35 include a matrix made of metallic glass containing Fe or Ni and a Si main phase dispersed in the matrix. The Si crystallite size in the Si main phase is 20 nm or less. These negative electrode materials have a large initial storage capacity and a high maintenance rate.
　例えば、Ｎｏ．１３の負極材料は、Ｓｉ主要相と金属ガラス（６０Ｎｉ１５Ｎｂ２０Ｔｉ５Ｚｒ）とからなる。この金属ガラスは、Ｎｉを含む。この負極材料では、図３に示されるように、Ｓｉ主要相と金属ガラスとが微細に分散している。この負極材料では、金属ガラスがマトリクス構造となっている。Ｓｉ主要相のＳｉ結晶子サイズは、３ｎｍである。この負極材料の初期蓄電容量は１２３５ｍＡｈ／ｇと大きく、かつ、５０サイクル後の蓄電容量維持率も８２％と大きい。 For example, No. The negative electrode material 13 consists of Si main phase and metallic glass (60Ni15Nb20Ti5Zr). This metallic glass contains Ni. In this negative electrode material, as shown in FIG. 3, the Si main phase and the metallic glass are finely dispersed. In this negative electrode material, metallic glass has a matrix structure. The Si crystallite size of the Si main phase is 3 nm. The initial storage capacity of this negative electrode material is as large as 1235 mAh / g, and the storage capacity retention rate after 50 cycles is also as large as 82%.
　一方、Ｎｏ．４１の負極材料では、金属ガラスが４２Ｃｕ－４２Ｚｒ－８Ａｌ－１８Ａｇであって、Ｆｅ及びＮｉを含まない。さらに、Ｓｉ主要相の結晶子サイズは３８ｎｍであり、大きい。従って、初期蓄電容量は２４４９ｍＡｈ／ｇと高いが、５０サイクル後の蓄電容量維持率は５％であり、サイクル寿命に劣る。 On the other hand, No. In the negative electrode material 41, the metallic glass is 42Cu-42Zr-8Al-18Ag and does not contain Fe and Ni. Further, the crystallite size of the Si main phase is 38 nm, which is large. Accordingly, the initial storage capacity is as high as 2449 mAh / g, but the storage capacity maintenance rate after 50 cycles is 5%, which is inferior in cycle life.
　以上の評価結果から、本発明の優位性は明らかである。
 
  From the above evaluation results, the superiority of the present invention is clear.

Claims (7)

  1. 　Ｆｅ及び／又はＮｉを含む金属ガラスからなるマトリクスと、このマトリクスに分散したＳｉ主要相とを備えており、
    　上記Ｓｉ主要相におけるＳｉ結晶子サイズが２０ｎｍ以下である、蓄電デバイス用負極材料。     Comprising a matrix made of metallic glass containing Fe and / or Ni, and a Si main phase dispersed in the matrix,
    The negative electrode material for electrical storage devices whose Si crystallite size in the said Si main phase is 20 nm or less.
  2. 　上記Ｓｉ主要相が、Ｇｅ、Ａｌ及びＢからなる群から選択された１種又は２種以上を含んでおり、
    　上記負極材料におけるＧｅ、Ａｌ及びＢの合計含有率が０．０１ｍａｓｓ．％以上５．０ｍａｓｓ．％以下である、請求項１に記載の蓄電デバイス用負極材料。     The Si main phase contains one or more selected from the group consisting of Ge, Al and B;
    The total content of Ge, Al, and B in the negative electrode material is 0.01 mass. % Or more and 5.0 mass. The negative electrode material for an electricity storage device according to claim 1, wherein the negative electrode material is 1% or less.
  3. 　上記負極材料における上記Ｓｉ主要相の比率が２０ｍａｓｓ．％以上８０ｍａｓｓ．％以下である、請求項１又は２に記載の蓄電デバイス用負極材料。 The ratio of the Si main phase in the negative electrode material is 20 mass. % Or more and 80 mass. The negative electrode material for an electricity storage device according to claim 1 or 2, wherein the negative electrode material is% or less.
  4. 　上記負極材料における上記Ｓｉ主要相の比率が４０ｍａｓｓ．％以上である、請求項１又は２に記載の蓄電デバイス用負極材料。 The ratio of the Si main phase in the negative electrode material is 40 mass. The negative electrode material for an electricity storage device according to claim 1 or 2, which is at least%.
  5. 　上記負極材料における上記Ｓｉ主要相の比率が７０ｍａｓｓ．％以下である、請求項１又は２に記載の蓄電デバイス用負極材料。 The ratio of the Si main phase in the negative electrode material is 70 mass. The negative electrode material for an electricity storage device according to claim 1 or 2, wherein the negative electrode material is% or less.
  6. 　上記Ｓｉ主要相におけるＳｉの含有率が８０ｍａｓｓ．％以上である、請求項１～５のいずれか一項に記載の蓄電デバイス用負極材料。 The Si content in the Si main phase is 80 mass. The negative electrode material for an electricity storage device according to any one of claims 1 to 5, which is at least%.
  7. 　上記金属ガラスがＮｉ基金属ガラス又はＦｅ基金属ガラスである、請求項１～６のいずれか一項に記載の蓄電デバイス用負極材料。 The negative electrode material for an electricity storage device according to any one of claims 1 to 6, wherein the metallic glass is a Ni-based metallic glass or a Fe-based metallic glass.
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