WO2014129346A1 - Si-based alloy negative electrode material for storage device, and electrode obtained using same - Google Patents

Si-based alloy negative electrode material for storage device, and electrode obtained using same Download PDF

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Publication number
WO2014129346A1
WO2014129346A1 PCT/JP2014/053039 JP2014053039W WO2014129346A1 WO 2014129346 A1 WO2014129346 A1 WO 2014129346A1 JP 2014053039 W JP2014053039 W JP 2014053039W WO 2014129346 A1 WO2014129346 A1 WO 2014129346A1
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phase
negative electrode
electrode material
crystallite size
based alloy
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PCT/JP2014/053039
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French (fr)
Japanese (ja)
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友紀 廣野
哲嗣 久世
哲朗 仮屋
澤田　俊之
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山陽特殊製鋼株式会社
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Priority to CN201480008723.4A priority Critical patent/CN104995771B/en
Priority to KR1020157021216A priority patent/KR102120238B1/en
Publication of WO2014129346A1 publication Critical patent/WO2014129346A1/en

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    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C28/00—Alloys based on a metal not provided for in groups C22C5/00 - C22C27/00
    • 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
    • H01G11/50—Electrodes characterised by their material specially adapted for lithium-ion capacitors, e.g. for lithium-doping or for intercalation
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • 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
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • 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
    • H01M4/386—Silicon or alloys based on silicon
    • 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 uses a Si-based alloy negative electrode material having excellent conductivity for an electricity storage device that involves movement of lithium ions during charging and discharging, such as a lithium ion secondary battery, a hybrid capacitor, and an all solid lithium ion secondary battery, and the same. It relates to an electrode.
  • Si has attracted attention as a material that can replace carbonaceous materials.
  • the reason is that Si can form a compound represented by Li 22 Si 5 and occlude a large amount of lithium, so that the capacity of the negative electrode can be greatly increased compared to the case of using a carbonaceous material.
  • the storage capacity of the lithium ion secondary battery, the hybrid capacitor, or the all solid state battery can be increased.
  • the Si phase is pulverized by repetition of expansion when alloying with lithium during charging and contraction when dealloying with lithium during discharging.
  • problems such as the Si phase dropping off from the electrode substrate or the electrical conductivity between the Si phases being lost may occur. For this reason, there has been a problem that the life as an electricity storage device is extremely short.
  • Si has poor electrical conductivity compared to carbonaceous materials and metal-based materials, and the efficient movement of electrons associated with charge / discharge is limited. Therefore, as a negative electrode material, a material that supplements conductivity, such as a carbonaceous material. Often used in combination. However, even in such a case, particularly initial charge / discharge and charge / discharge characteristics with high efficiency are problems.
  • Patent Document 1 Japanese Patent Application Laid-Open No. 2001-297757
  • Patent Document 2 Japanese Patent Application Laid-Open No. 10-318044
  • the problem to be solved by the present invention is to control lithium ion secondary batteries and hybrids by highly controlling the chemical composition, structure, structure size, etc. of the Si phase and intermetallic compound phase in the Si-based alloy. It is to propose a Si-based alloy negative electrode material that is excellent in charge / discharge characteristics with respect to an electricity storage device that moves lithium ions during charge / discharge, such as a capacitor and an all solid state battery.
  • the inventors have intensively developed, and as a result, refinement of the structure, excellent ion conductivity and electron conductivity, control of the component system that enhances the stress relaxation effect, Si phase and
  • the present inventors have found a Si-based alloy negative electrode material capable of obtaining excellent battery characteristics by controlling the crystallite size of the intermetallic compound phase.
  • a negative electrode material made of a Si-based alloy for an electricity storage device accompanied by movement of lithium ions during charge and discharge has a Si main phase made of Si, and a compound phase made of one or more elements other than Si and Si, The compound phase comprises a phase composed of Si and Cr or Si, Cr and Ti;
  • a negative electrode material made of a Si-based alloy for an electricity storage device accompanied by movement of lithium ions during charge / discharge wherein the negative electrode material made of the Si-based alloy is composed of a Si main phase made of Si and one or more elements other than Si and Si. And the compound phase has a phase comprising Si and Cr, or a phase composed of Si, Cr and Ti, and the Si main phase has a Si crystallite size of 30 nm or less, and There is provided a negative electrode material comprising a Si-based alloy for an electricity storage device, wherein the crystallite size of a compound phase comprising Si and Cr or Si, Cr and Ti is 40 nm or less.
  • the total content of Cr and Ti of the negative electrode material made of the Si-based alloy is 12 to 21 at.
  • a negative electrode material made of a Si-based alloy for an electricity storage device is provided, in which Cr% / (Cr% + Ti%), which is a ratio of Cr and Ti, is 0.15 to 1.00. .
  • At least one selected from the group consisting of Cu, V, Mn, Fe, Ni, Nb, Zn, and Al is used as the compound phase of the negative electrode material made of the Si-based alloy for power storage devices.
  • the total content is 0.05 at. % To 5 at. %, A negative electrode material made of a Si-based alloy for power storage devices is provided.
  • the compound phase of the negative electrode material made of the Si-based alloy for an electricity storage device includes at least one element selected from the group consisting of Mg, B, P, and Ga, and contains the total amount The amount is 0.05 at. % To 5 at. %, A negative electrode material made of a Si-based alloy for power storage devices is provided.
  • a negative electrode made of an Si-based alloy for an electricity storage device characterized in that, in the electrode using the negative electrode material made of the Si-based alloy for an electricity storage device, a polyimide-based binder is included. .
  • Cr is an essential element for generating Si 2 Cr effective for forming a fine eutectic structure with the Si phase
  • Ti is substituted for Cr to increase the lattice constant of Si 2 Cr, thereby increasing the lithium ion. Presumed to increase conductivity.
  • crystallite size of the Si phase to 30 nm or less, and the crystallite size of the compound phase of Si and Cr or the compound phase of Si, Cr and Ti to 40 nm or less, when lithium is occluded / released in Si It is presumed that excellent charge / discharge cycle characteristics can be obtained because it relieves the stress caused by the volume expansion of the metal and prevents electrical isolation due to the atomization of Si.
  • charge / discharge cycle characteristics can be obtained by controlling the chemical components of the Si-based alloy negative electrode material for power storage devices.
  • the total content of Cr and Ti in the phase composed of Si and Cr or Si, Cr and Ti is 12 to 21 at. %, And Cr% / (Cr% + Ti%) is controlled within the range of 0.15 to 1.00, the effect is large.
  • a first sample comprising Cu, V, Mn, Fe, Ni, Nb, Pd, Zn, and Al in a sample containing Si and Cr or a sample containing Si, Cr and Ti as a Si-based alloy negative electrode material for an electricity storage device.
  • One or more additive elements in the group with a total amount of 0.05 at. % To 5 at.
  • the compound phase surrounds the fine Si phase and relieves stress caused by Si pulverization and volume expansion during the insertion and extraction of lithium into and from Si.
  • it plays the role of preventing the collapse of the electrode and the electrical isolation of Si.
  • excellent battery characteristics are provided.
  • a sample containing Si and Cr, or a sample containing Si, Cr and Ti, of the Si-based alloy negative electrode material for an electricity storage device a total of one or more additive elements of the second group consisting of Mg, B, P and Ga
  • the amount is 0.05 at. % To 5 at.
  • the compound phase surrounds the periphery of the fine Si phase and relieves the stress caused by Si pulverization and volume expansion when lithium is absorbed into and released from Si. And it plays the role which prevents the collapse of an electrode and the electrical isolation of Si. Also, by taking a P-type semiconductor structure by adding B, it plays a role of improving the electrical conductivity of Si.
  • the present invention has an excellent effect of providing a Si-based alloy negative electrode material for an electricity storage device having a high capacity and excellent cycle characteristics during repeated charge and discharge.
  • Cross-sectional SEM image of the Si-Si 2 Cr eutectic alloy is a diagram showing a. 3 is an XRD spectrum of a Si—Si 2 Cr eutectic alloy with a changed Cr / Ti ratio. SEM images of Cr and the total amount of change in the Si-Si 2 Cr eutectic alloy was of Ti is a diagram showing a. (A) is an image when the total amount of Cr and Ti is 17%, and (b) is an image when the total amount of Cr and Ti is 19%.
  • the charge / discharge capacity of a lithium ion secondary battery is determined by the amount of lithium transferred. Therefore, there is a demand for a substance that can occlude and release a large amount of lithium. It is most efficient to use lithium metal for the negative electrode material, but there is a possibility of battery ignition caused by the formation of dendrites accompanying charging and discharging. Therefore, studies on alloys that can occlude and release more lithium are currently underway, and among these alloys, Si is promising as a substance that can occlude and release lithium in large quantities. Therefore, Si is adopted as the main phase of the alloy phase.
  • Si causes volume expansion of about 400% when lithium is occluded / released, Si is peeled off or dropped from the electrode, or Si cannot maintain contact with the current collector. A sudden drop in capacity occurs.
  • Si phase size is too large, Si does not react with lithium up to the internal Si phase, expands from the surface layer where Si and lithium easily react, cracks occur, and then the internal unreacted Si phase expands.
  • repeated generation of cracks causes fine powdering of Si. As a result, Si peels off from the electrode, or Si cannot maintain contact with the current collector, resulting in a rapid decrease in charge / discharge capacity associated with the cycle.
  • FIG. 1 is a cross-sectional structure diagram of a Si—Si 2 Cr eutectic alloy according to the present invention, taken by a scanning electron micrograph, wherein the black phase is the Si phase and the white phase is the Si 2 Cr phase. As shown in FIG. 1, both the Si phase and the CrSi 2 phase are extremely fine. In addition, compared with other elements, such as Fe and V, the following is estimated about the cause by which Cr addition produces an extremely fine eutectic structure
  • the amount of additive element necessary to obtain the eutectic of the Si phase and silicide is determined by the type of element, for example, 26.5% for Fe and 3% for V. These can be read from the phase diagrams of Si and additive elements.
  • an element that requires a relatively large amount of addition, such as Fe is used in order to obtain a eutectic, the amount of silicide is inevitably increased, and it tends to be coarse. Therefore, the ratio of the Si phase that occludes / releases Li decreases, and a high discharge capacity cannot be obtained.
  • the Si—Si 2 Cr eutectic alloy can have both a high discharge capacity and an excellent cycle life.
  • charge / discharge characteristics can be further improved by substituting a part of Cr with Ti.
  • the inventor conducted detailed studies on replacing Cr with Ti in the Si—Si 2 Cr eutectic alloy. As a result, Ti was replaced with Cr in Si 2 Cr, and the lattice constant was changed without changing the crystal structure. I thought it would increase.
  • FIG. 2 is a diagram showing X-ray diffraction of a Si—Si 2 Cr eutectic alloy with a changed Cr / Ti ratio. As shown in this figure, by replacing a part of Cr with Ti, the diffraction peak position of Si 2 Cr is shifted to the lower angle side without changing the crystal structure, and the lattice constant is increased. It is considered a thing.
  • the increase in the lattice constant of Si 2 Cr due to the substitution of Ti with Cr in the present invention may play a role of smoothing the passage of Li in the silicide and reducing the accompanying volume change.
  • the characteristics of the lithium ion secondary battery can be further improved by controlling the crystallite size. If the Si phase size is too large, Si does not react with lithium up to the internal Si phase, but expands from the surface layer that easily reacts with lithium in the Si phase, causing cracks, and then the internal unreacted Si phase expands. In addition, repeated generation of cracks causes fine powdering of Si. As a result, Si peels off from the electrode, or Si cannot maintain contact with the current collector, resulting in a rapid decrease in charge / discharge capacity associated with the cycle.
  • the crystallite size of the Si phase of the negative electrode material for lithium ion secondary batteries is controlled to 25 nm or less. In particular, it is desirable to control to 10 nm or less.
  • the crystallite size of the Si phase can be controlled by controlling the cooling rate during solidification after dissolving the raw material powder in addition to the control of the components defined above.
  • Examples of the production method include water atomization, single-roll quenching method, twin-roll quenching method, gas atomization method, disk atomization method, and centrifugal atomization, but are not limited thereto.
  • mechanical milling or the like can be performed.
  • Examples of the milling method include a ball mill, a bead mill, a planetary ball mill, an attritor, and a vibration ball mill, but are not limited thereto.
  • TEM transmission electron microscope
  • XRD powder X-ray diffraction
  • the crystallite size not only the Si main phase but also the crystallite size of the intermetallic compound phase is important.
  • an intermetallic compound such as Si and Cr or Si, Cr and Ti
  • the crystallite size of the intermetallic compound it is possible to contact the Si phase with a larger specific surface area than large particles, and to efficiently absorb and relax the stress due to the volume expansion and contraction of the Si phase. .
  • the crystallite size is controlled to 40 nm or less.
  • the crystallite size is controlled to 20 nm or less. In particular, it is desirable to control to 10 nm or less.
  • the crystallite size of the intermetallic compound can also be directly observed with a transmission electron microscope (TEM). Or it can also confirm by using powder X-ray diffraction.
  • TEM transmission electron microscope
  • a relatively broad diffraction peak is observed as the crystallite size decreases.
  • the crystallite size of the intermetallic compound can be controlled by controlling the cooling rate during solidification after dissolving the raw material powder.
  • Examples of the production method include water atomization, single-roll quenching method, twin-roll quenching method, gas atomization method, disk atomization method, and centrifugal atomization, but are not limited thereto. Further, when the cooling effect is insufficient in the above process, mechanical milling or the like can be performed. Examples of the milling method include a ball mill, a bead mill, a planetary ball mill, an attritor, and a vibration ball mill, but are not limited thereto.
  • the normal eutectic structure is a unique structure with a single additive element amount. If the added amount fluctuates back and forth, it becomes a hypoeutectic or hypereutectic alloy, and an extremely coarse primary crystal is crystallized. Therefore, a high production technique is required to obtain a eutectic structure strictly.
  • a fine structure is obtained in a wide range where the total of Cr and Ti is about 12 to 21%, and the added amount fluctuates back and forth depending on the production lot. But there is no extreme organizational change. FIG.
  • FIG. 3 is a cross-sectional structure diagram of a scanning electron micrograph of a Si—Si 2 Cr eutectic alloy in which the total amount of Cr and Ti is changed.
  • FIG. 3A shows a case where the total amount of Cr and Ti is 17%
  • FIG. 3B shows a case where the total amount of Cr and Ti is 19%.
  • Cr is an essential element that forms Si 2 Cr that forms a fine eutectic structure with the Si phase
  • Ti is an effective element that replaces Cr and increases the lattice constant of Si 2 Cr.
  • Cr% / (Cr% + Ti%) to that in the range 0.15 to 1.00 It is suppressed that Si 2 Ti phase is produced in addition to the Si 2 Cr phase, the coarsening of the Si phase This is preferable in that the effect on the cycle life can be suppressed as described above. Therefore, a more preferable range of the total of Cr and Ti is set to 13 to 20%, and more preferably set to 14 to 19%. Further, a more preferable range of Cr% / (Cr% + Ti%) is 0.15 to 0.90, and more preferably 0.20 to 0.80.
  • the Si x (Cr, Ti) y phase Is preferably x> y.
  • the negative electrode material for a lithium ion secondary battery besides Cr and Ti, an eutectic alloy is formed with Si to obtain a fine Si phase, and a flexible intermetallic compound having better conductivity than Si is obtained.
  • One or more selected from an additive element of the first group consisting of Cu, V, Mn, Fe, Ni, Nb, Zn and Al to be formed can be further contained.
  • the compound phase surrounds the periphery of the fine Si phase, relieving the stress caused by volumetric expansion when Si is pulverized and lithium is absorbed into and released from Si. And it plays the role which prevents the collapse of an electrode and the electrical isolation of Si.
  • the negative electrode material for a lithium ion secondary battery besides Cr and Ti, an eutectic alloy is formed with Si to obtain a fine Si phase, and a flexible intermetallic compound having better conductivity than Si is obtained.
  • One or more elements selected from the second group of additive elements consisting of Mg, B, P and Ga are formed at 0.05 at. % To 5 at. % Can be contained.
  • the compound phase surrounds the periphery of the fine Si phase, mitigating stress caused by volumetric expansion at the time of Si pulverization and insertion / extraction of lithium to / from Si, It plays a role in preventing collapse and electrical isolation of Si.
  • a P-type semiconductor structure by adding B it plays a role of improving the electrical conductivity of Si.
  • By taking an N-type semiconductor structure by adding P it plays a role of improving the electrical conductivity of Si.
  • the total content of Cu, V, Mn, Fe, Ni, Nb, Pd, Zn and Al is 0.05 at. % Or more is necessary, but 5 at. If it exceeds 50%, the amount of lithium inert elements increases, which causes a decrease in charge / discharge capacity. For this reason, the total content of at least one additive element selected from the first group consisting of Cu, V, Mn, Fe, Ni, Nb, Pd, Zn, and Al is 0.05 at. % To 5 at. % Is desirable. More preferably, 0.1 at. % To 3 at. %. In addition, Co, Zr, Pd, Bi, In, Sb, Sn, and Mo aiming at the same effect are also set to 0.05 at. % To 5 at. % Is desirable.
  • the total content of Mg, B, P and Ga is 0.05 at. % Or more is necessary, but 5 at. If it exceeds 50%, the amount of lithium inactive elements increases, which causes a decrease in charge / discharge capacity. For this reason, the total content of at least one additive element selected from the second group consisting of Mg, B, P and Ga is 0.05 at. % To 5 at. % Is desirable. More preferably, 0.1 at. % To 3 at. %. In addition, for Co, Zr, Pd, Bi, In, Sb, Sn, and Mo aiming at similar effects, the total content of at least one additive element is 0.05 at. % To 5 at. % Is desirable.
  • the lithium ion secondary battery negative electrode material according to the present invention By using the lithium ion secondary battery negative electrode material according to the present invention described above, battery characteristics with high capacity, excellent cycle characteristics during repeated charge / discharge, and excellent charge / discharge efficiency at the initial cycle are exhibited.
  • the electrode using the lithium ion secondary battery negative electrode material by including a polyimide-based binder having excellent binding properties, the adhesion with a current collector such as Cu is improved, and charging and discharging are performed while maintaining a high capacity. The effect of improving cycle characteristics is expected.
  • Negative electrode material powders for lithium ion secondary batteries having the compositions shown in Tables 1 and 2 were prepared by a single roll quenching method, a gas atomizing method, or the like described below.
  • a liquid quenching method which is a single roll quenching method
  • a raw material having a predetermined composition is placed in a quartz tube having pores at the bottom, melted at a high frequency in an Ar atmosphere to form a molten metal, and a copper roll that rotates this molten metal.
  • a quenching ribbon was prepared in which the crystallite size of the Si phase was refined by the quenching effect of the copper roll.
  • the milled ribbon is then sealed in an Ar atmosphere together with zirconia balls, SUS304 balls, or SUJ2 balls in a zirconia, SUS304, or SUJ2 pot container and milled for the purpose of processing into particles. It was.
  • a ball mill, a bead mill, a planetary ball mill, an attritor, a vibrating ball mill, and the like can be given.
  • a raw material having a predetermined composition is placed in a quartz crucible having pores at the bottom, heated and melted in a high-frequency induction melting furnace in an Ar gas atmosphere, and then subjected to gas injection in an Ar gas atmosphere and a tapping hot water. Then, gas atomized fine powder was obtained by rapid solidification.
  • a raw material having a predetermined composition is placed in a quartz crucible having pores at the bottom, heated and melted in a high-frequency induction melting furnace in an Ar gas atmosphere, and then in an Ar gas atmosphere, 40000 to 60000 r. p. m.
  • Hot water was poured onto a (revolutions per minute) rotating disk and rapidly solidified to obtain a disk atomized fine powder.
  • the atomized fine powder produced is sealed in a zirconia or SUS304 / SUJ2 pot container with zirconia balls, SUS304 balls, or SUJ2 balls in an Ar atmosphere, and powdered by mechanical milling to control the crystallite size. went.
  • mechanical milling include a ball mill, a bead mill, a planetary ball mill, an attritor, and a vibrating ball mill.
  • the crystallite size of the atomized powder and the intermetallic compound using rapid solidification can be controlled by setting the milling time and the number of rotations.
  • a so-called bipolar coin-type cell using lithium metal as a counter electrode was used.
  • a negative electrode active material Si—Cr—Ti, etc.
  • a conductive material acetylene black
  • a binder material polyimide, polyvinylidene fluoride, etc.
  • a dispersion N-methylpyrrolidone
  • the solvent was evaporated under reduced pressure in a vacuum dryer, and then roll-pressed as necessary, and then punched into a shape that fits the coin cell. Similarly, lithium for the counter electrode was punched into a shape that fits the coin cell.
  • the vacuum drying of the slurry-coated electrode when the polyimide binder material was used, it was dried at a temperature of 200 ° C. or higher in order to fully exhibit the performance. When using polyvinylidene fluoride or the like, it was dried at a temperature of about 160 ° C.
  • the electrolyte used for the lithium ion battery was a 3: 7 mixed solvent of ethylene carbonate and dimethyl carbonate, LiPF 6 (lithium hexafluorophosphate) was used as the supporting electrolyte, and 1 mol was dissolved in the electrolyte. Since the electrolyte solution must be handled in an inert atmosphere with dew point control, the cells were all assembled in a glove box with an inert atmosphere. The separator was cut out in a shape suitable for a coin cell and then held in the electrolyte for several hours under reduced pressure in order to sufficiently permeate the electrolyte into the separator. Thereafter, the negative electrode punched out in the previous step, the separator, and the counter electrode lithium were combined in this order, and the inside of the battery was sufficiently filled with the electrolytic solution.
  • LiPF 6 lithium hexafluorophosphate
  • the measurement of the charge capacity and the discharge capacity is carried out using the above-mentioned bipolar cell, at a temperature of 25 ° C., charging at a current density of 0.50 mA / cm 2 until the potential is equal to the metal lithium electrode (0 V), Furthermore, discharging was performed up to 1.5 V at the same current value (0.50 mA / cm 2 ), and this charging-discharging was made one cycle. In addition, as the cycle life, the above measurement was repeated.
  • No. Nos. 1 to 55 are examples of the present invention.
  • Reference numerals 56 to 126 show comparative examples. These characteristics are judged based on the initial discharge capacity and the discharge capacity maintenance ratio after 50 cycles.
  • the standard is that the initial discharge capacity is 1000 mAh / g or more and the cycle life is 60% or more [discharge capacity maintenance ratio (%) after 50 cycles].
  • example 1 to 12 include the Si main phase and the phase composed of Si, Cr and Ti, the crystallite size of Si is 30 nm or less, and the crystallite size of the compound phase composed of Si, Cr and Ti satisfies the condition of 40 nm or less is doing.
  • Invention Example No. 4 includes Si main phase, Si, Cr, and Ti, the crystallite size of Si is 4 nm, and the crystallite size of Si is 30 nm or less.
  • the crystallite size of the compound phase composed of Si, Cr and Ti is 30 nm, and the crystallite size of the compound phase composed of Si, Cr and Ti satisfies the condition of 40 nm or less.
  • the conditions of the present invention were satisfied, the initial discharge capacity was 1289 mAh / g, the discharge capacity retention rate after 50 cycles was 72%, and both the charge / discharge capacity and the cycle life showed good characteristics.
  • No. of the invention example 13 to 18 include a Si main phase and a phase composed of Si and Cr, the crystallite size of Si is 30 nm or less, and the crystallite size of the compound phase composed of Si and Cr satisfies the condition of 40 nm or less.
  • No. No. 14 contains a Si main phase, Si, and Cr, the crystallite size of Si is 7 nm, and the crystallite size of Si is 30 nm or less. Moreover, the crystallite size of the compound phase consisting of Si and Cr is 15 nm, and the crystallite size of the compound phase consisting of Si and Cr satisfies the condition of 40 nm or less. Further, as described above, the conditions of the present invention were satisfied, the discharge capacity was 1389 mAh / g, the discharge capacity retention rate after 50 cycles was 68%, and both the charge / discharge capacity and the cycle life showed good characteristics.
  • No. of the invention example. 19 to 24 include a Si main phase and a phase composed of Si, Cr, and Ti.
  • the crystallite size of Si is 30 nm or less, and the crystallite size of the compound phase composed of Si, Cr, and Ti is 40 nm or less. is doing.
  • No. No. 23 includes a Si main phase and a phase composed of Si, Cr, and Ti, the Si crystallite size is 8 nm, and satisfies the condition that the Si crystallite size is 30 nm or less. And the crystallite size of the compound phase consisting of Si, Cr and Ti is 16 nm, and the crystallite size of the compound phase consisting of Si, Cr and Ti is 40 nm or less. Further, as described above, the present invention conditions were satisfied, the discharge capacity was 1174 mAh / g, the discharge capacity retention rate after 50 cycles was 87%, and both the charge / discharge capacity and the cycle life showed good characteristics.
  • No. of the invention example 25 to 55 include a Si main phase and a phase composed of Si and Cr, or Si, Cr and Ti.
  • the Si main phase has a Si crystallite size of 30 nm or less, and is composed of Si and Cr, or Si, Cr and Ti.
  • the crystallite size of the compound phase satisfies the condition of 40 nm or less.
  • the total content of at least one additive element selected from the first group consisting of Cu, V, Mn, Fe, Ni, Nb, Zn, and Al is 0.05 at. % To 5 at. %.
  • the total content of at least one additive element selected from the second group consisting of Mg, B, P, and Ga is 0.05 at. % To 5 at. %.
  • No. No. 39 includes a Si main phase and a phase composed of Si, Cr, and Ti, the crystallite size of Si is 17 nm, and the crystallite size of Si is 30 nm or less.
  • the crystallite size of the compound phase composed of Si, Cr and Ti is 38 nm, and the crystallite size of the compound phase composed of Si, Cr and Ti satisfies the condition of 40 nm or less.
  • 0.01 at. % Cu, 0.03 at. % V, 0.01 at. % Mn, 0.01 at. % Fe, 0.01 at. % Ni, 0.02 at. % Zn and 0.02 at. % Al is contained.
  • % B, 1.03 at. % P and 1.12 at. % Ga is contained. As described above, the conditions of the present invention were satisfied, the discharge capacity was 1179 mAh / g, the discharge capacity retention rate after 50 cycles was 80%, and both the charge / discharge capacity and the cycle life showed good characteristics.
  • Comparative Example No. 73 to 90 include a phase composed of Si and Cr or Si, Cr and Ti, and the crystallite size of the compound phase composed of Si and Cr or Si, Cr and Ti satisfies the condition of 40 nm or less. Since the Si crystallite size of the Si main phase does not satisfy the condition of 30 nm or less, the conditions of the present invention are not satisfied. Comparative Example No. 91 to 108 include a phase composed of Si and Cr, or Si, Cr and Ti, and the Si crystallite size of the Si main phase satisfies the condition of 30 nm or less. However, Si and Cr, or Si and Cr Since the crystallite size of the compound phase composed of Ti does not satisfy the condition of 40 nm or less, the present invention condition is not satisfied.
  • Comparative Example No. 109 to 126 include a phase composed of Si and Cr or Si and Cr and Ti, but the Si main phase does not satisfy the condition that the Si crystallite size is 30 nm or less, and Si and Cr, or Si and Cr and Ti. Since the crystallite size of the compound phase consisting of does not satisfy the condition of 40 nm or less, the condition of the present invention is not satisfied.

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Abstract

An Si-based alloy negative electrode material and an electrode are provided, the negative electrode material being capable of giving excellent battery characteristics because the negative electrode material has a microfined structure, has a controlled composition system whereby ionic conductivity, electronic conductivity, and an enhancing stress relaxation effect are heightened, and comprises an Si phase and an intermetallic-compound phase which have regulated crystallite sizes. This negative electrode material, which is for storage devices that involve the movement of lithium ions when charged/discharged, comprises an Si-based alloy. The negative electrode material comprising an Si-based alloy includes a main Si phase constituted of Si and a compound phase comprising Si and one or more other elements. The compound phase comprises a phase constituted of Si and Cr or of Si, Cr, and Ti. The main Si phase has an Si crystallite size of 30 nm or less, and the compound phase constituted of Si and Cr or of Si, Cr, and Ti has a crystallite size of 40 nm or less.

Description

蓄電デバイス用Ｓｉ系合金負極材料およびそれを用いた電極Si-based alloy negative electrode material for power storage device and electrode using the same 関連出願の相互参照Cross-reference of related applications
　この出願は、２０１３年２月１９日に出願された日本国特許出願２０１３－２９８４６号及び２０１３年８月２０日に出願された日本国特許出願２０１３－１７０１４５号に基づく優先権を主張するものであり、これらの全体の開示内容が参照により本明細書に組み込まれる。 This application claims priority based on Japanese Patent Application No. 2013-29846 filed on February 19, 2013 and Japanese Patent Application No. 2013-170145 filed on August 20, 2013. The entire disclosures of which are incorporated herein by reference.
　本発明は、リチウムイオン二次電池やハイブリットキャパシタ、全固体リチウムイオン二次電池など、充放電時にリチウムイオンの移動を伴う蓄電デバイス用の、導電性に優れるＳｉ系合金負極材料およびそれを用いた電極に関するものである。 The present invention uses a Si-based alloy negative electrode material having excellent conductivity for an electricity storage device that involves movement of lithium ions during charging and discharging, such as a lithium ion secondary battery, a hybrid capacitor, and an all solid lithium ion secondary battery, and the same. It relates to an electrode.
　近年、携帯機器の普及に伴い、リチウムイオン電池を中心とした高性能二次電池の開発が盛んに行われている。さらに、自動車用や家庭用定置用蓄電デバイスとしてリチウムイオン二次電池やその反応機構を負極に適用したハイブリットキャパシタの開発も盛んになっている。それらの蓄電デバイスの負極材料として、リチウムイオンを吸蔵及び放出することができる、天然黒鉛や人造黒鉛、コークスなどの炭素質材料が用いられている。しかし、これらの炭素質材料は、リチウムイオンを炭素面間に挿入するため、負極に用いた際の理論容量は３７２ｍＡｈ／ｇが限界である。このことから、高容量化を目的とした、炭素質材料に代わる新規材料の探索が盛んに行われている。 In recent years, with the widespread use of portable devices, development of high-performance secondary batteries centering on lithium-ion batteries has been actively conducted. Furthermore, lithium-ion secondary batteries and hybrid capacitors using the reaction mechanism of the lithium ion secondary battery as a negative electrode as active storage devices for automobiles and households have been actively developed. Carbonaceous materials such as natural graphite, artificial graphite, and coke that can occlude and release lithium ions are used as negative electrode materials for these electricity storage devices. However, since these carbonaceous materials insert lithium ions between the carbon surfaces, the theoretical capacity when used for the negative electrode is limited to 372 mAh / g. For this reason, a search for new materials to replace carbonaceous materials for the purpose of increasing the capacity has been actively conducted.
　一方、炭素質材料に代わる材料として、Ｓｉが注目されている。その理由は、ＳｉはＬｉ22Ｓｉ5 で表される化合物を形成して、大量のリチウムを吸蔵することができるため、炭素質材料を使用した場合に比較して負極の容量を大幅に増大でき、結果としてリチウムイオン二次電池やハイブリットキャパシタ、全固体電池の蓄電容量を増大することができる可能性を持っているためである。 On the other hand, Si has attracted attention as a material that can replace carbonaceous materials. The reason is that Si can form a compound represented by Li 22 Si 5 and occlude a large amount of lithium, so that the capacity of the negative electrode can be greatly increased compared to the case of using a carbonaceous material. As a result, there is a possibility that the storage capacity of the lithium ion secondary battery, the hybrid capacitor, or the all solid state battery can be increased.
　しかし、Ｓｉを単独で負極材として使用した場合には、充電時にリチウムと合金化する際の膨張と、放電時にリチウムと脱合金化する際の収縮との繰返しによって、Ｓｉ相が微粉化されて、使用中に電極基板からＳｉ相が脱落したり、Ｓｉ相間の電気伝導性が取れなくなるなどの不具合が生じることがある。このことから、蓄電デバイスとしての寿命が極めて短いといった課題があった。 However, when Si is used alone as a negative electrode material, the Si phase is pulverized by repetition of expansion when alloying with lithium during charging and contraction when dealloying with lithium during discharging. During use, problems such as the Si phase dropping off from the electrode substrate or the electrical conductivity between the Si phases being lost may occur. For this reason, there has been a problem that the life as an electricity storage device is extremely short.
　また、Ｓｉは炭素質材料や金属系材料に比べて電気伝導性が悪く、充放電に伴う電子の効率的な移動が制限されているため、負極材としては炭素質材料など導電性を補う材料と組合せて使用されることが多い。しかし、そのような場合でも、特に初期の充放電や高効率での充放電特性が課題となっている。 In addition, Si has poor electrical conductivity compared to carbonaceous materials and metal-based materials, and the efficient movement of electrons associated with charge / discharge is limited. Therefore, as a negative electrode material, a material that supplements conductivity, such as a carbonaceous material. Often used in combination. However, even in such a case, particularly initial charge / discharge and charge / discharge characteristics with high efficiency are problems.
　このようなＳｉ相を負極として利用する際の欠点を解決する方法として、Ｓｉなどの親リチウム相の少なくとも一部を、Ｓｉと遷移金属に代表される金属との金属間化合物で包囲した材料を用いる方法が提案されている。そのような材料やその製造方法は、例えば、特開２００１－２９７７５７号公報（特許文献１）や特開平１０－３１２８０４号公報（特許文献２）に提案されている。 As a method for solving the drawbacks of using such a Si phase as a negative electrode, a material in which at least a part of a parent lithium phase such as Si is surrounded by an intermetallic compound of Si and a metal typified by a transition metal is used. A method of using it has been proposed. Such a material and a manufacturing method thereof are proposed in, for example, Japanese Patent Application Laid-Open No. 2001-297757 (Patent Document 1) and Japanese Patent Application Laid-Open No. 10-318044 (Patent Document 2).
　また、別の解決方法として、Ｓｉ相を含む活物質の相を、リチウムと合金化しないＣｕなどの導電性材料で被覆した電極を用いる方法がある。そのような電極やその製造方法は、例えば、特開２００４－２２８０５９号公報（特許文献３）や特開２００５－４４６７２号公報（特許文献４）に提案されている。 As another solution, there is a method using an electrode in which an active material phase containing a Si phase is coated with a conductive material such as Cu that is not alloyed with lithium. Such an electrode and a manufacturing method thereof are proposed in, for example, Japanese Patent Application Laid-Open No. 2004-228059 (Patent Document 3) and Japanese Patent Application Laid-Open No. 2005-44672 (Patent Document 4).
特開２００１－２９７７５７号公報JP 2001-297757 A 特開平１０－３１２８０４号公報JP 10-31804 A 特開２００４－２２８０５９号公報JP 2004-228059 A 特開２００５－４４６７２号公報JP 2005-44672 A
　しかしながら、上述した活物質の相をＣｕなどの導電性材料で被覆する方法では、Ｓｉ相を含む活物質を電極に形成する工程の前または後に、Ｃｕめっきなどの方法で被覆する必要があり、また、被覆膜厚の制御なども必要となるため、工業的に手間がかかるという問題がある。また、Ｓｉなどの親リチウム相の少なくとも一部を金属間化合物で包囲した材料は、溶融後の凝固プロセス中に親リチウム相と金属間化合物が形成されるため、工業的に好ましいプロセスといえるが、それだけでは十分な充放電サイクル特性が得られない可能性があり、改良の余地があった。 However, in the above-described method of coating the active material phase with a conductive material such as Cu, it is necessary to coat the active material containing the Si phase with a method such as Cu plating before or after the step of forming the active material on the electrode. Moreover, since control of a coating film thickness etc. is needed, there exists a problem that it takes an industrial effort. A material in which at least a part of a parent lithium phase such as Si is surrounded by an intermetallic compound is an industrially preferable process because a parent lithium phase and an intermetallic compound are formed during the solidification process after melting. In that case, sufficient charge / discharge cycle characteristics may not be obtained, and there is room for improvement.
　そこで、本発明が解決しようとする課題は、Ｓｉ系合金中のＳｉ相や金属間化合物相の化学組成、構造、組織の大きさ等を高度に制御することで、リチウムイオン二次電池やハイブリットキャパシタ、全固体電池など、充放電時にリチウムイオンの移動を伴う蓄電デバイスに関し、充放電特性に優れるＳｉ系合金負極材料を提案することである。 Therefore, the problem to be solved by the present invention is to control lithium ion secondary batteries and hybrids by highly controlling the chemical composition, structure, structure size, etc. of the Si phase and intermetallic compound phase in the Si-based alloy. It is to propose a Si-based alloy negative electrode material that is excellent in charge / discharge characteristics with respect to an electricity storage device that moves lithium ions during charge / discharge, such as a capacitor and an all solid state battery.
　上述のような問題を解消するために、発明者らは鋭意開発を進めた結果、組織の微細化、優れたイオン伝導性と電子伝導性、応力緩和効果を高める成分系の制御とＳｉ相や金属間化合物相の結晶子サイズを制御することで、優れた電池特性が得られるＳｉ系合金負極材料を見出した。 In order to solve the problems as described above, the inventors have intensively developed, and as a result, refinement of the structure, excellent ion conductivity and electron conductivity, control of the component system that enhances the stress relaxation effect, Si phase and The present inventors have found a Si-based alloy negative electrode material capable of obtaining excellent battery characteristics by controlling the crystallite size of the intermetallic compound phase.
　本発明の一態様によれば、
　充放電時にリチウムイオンの移動が伴う蓄電デバイス用のＳｉ系合金からなる負極材料であって、
　前記Ｓｉ系合金からなる負極材料が、ＳｉからなるＳｉ主要相と、ＳｉとＳｉ以外の一種以上の元素からなる化合物相とを有し、
　前記化合物相が、ＳｉとＣｒ、あるいはＳｉとＣｒとＴｉからなる相を含んでなり、
　前記Ｓｉ主要相のＳｉ結晶子サイズが３０ｎｍ以下であり、かつ、ＳｉとＣｒ、あるいはＳｉとＣｒとＴｉからなる化合物相の結晶子サイズが４０ｎｍ以下である
　Ｓｉ系合金からなる負極材料が提供される。 According to one aspect of the invention,
A negative electrode material made of a Si-based alloy for an electricity storage device accompanied by movement of lithium ions during charge and discharge,
The negative electrode material made of the Si-based alloy has a Si main phase made of Si, and a compound phase made of one or more elements other than Si and Si,
The compound phase comprises a phase composed of Si and Cr or Si, Cr and Ti;
Provided is a negative electrode material made of a Si-based alloy in which the Si crystallite size of the Si main phase is 30 nm or less and the crystallite size of a compound phase composed of Si and Cr or Si, Cr and Ti is 40 nm or less. The
　本発明の他の一態様によれば、
　充放電時にリチウムイオンの移動が伴う蓄電デバイス用Ｓｉ系合金からなる負極材料であって、前記Ｓｉ系合金からなる負極材料が、ＳｉからなるＳｉ主要相とＳｉとＳｉ以外の一種以上の元素からなる化合物相を有し、前記化合物相が、ＳｉとＣｒ、あるいはＳｉとＣｒとＴｉからなる相を含んでなる相を有し、前記Ｓｉ主要相のＳｉ結晶子サイズが３０ｎｍ以下であり、かつ、ＳｉとＣｒ、あるいはＳｉとＣｒとＴｉからなる化合物相の結晶子サイズが４０ｎｍ以下であることを特徴とする蓄電デバイス用Ｓｉ系合金からなる負極材料が提供される。 According to another aspect of the invention,
A negative electrode material made of a Si-based alloy for an electricity storage device accompanied by movement of lithium ions during charge / discharge, wherein the negative electrode material made of the Si-based alloy is composed of a Si main phase made of Si and one or more elements other than Si and Si. And the compound phase has a phase comprising Si and Cr, or a phase composed of Si, Cr and Ti, and the Si main phase has a Si crystallite size of 30 nm or less, and There is provided a negative electrode material comprising a Si-based alloy for an electricity storage device, wherein the crystallite size of a compound phase comprising Si and Cr or Si, Cr and Ti is 40 nm or less.
　本発明の好ましい態様によれば、上記蓄電デバイス用Ｓｉ系合金からなる負極材料において、前記Ｓｉ系合金からなる負極材料のＣｒとＴｉの合計含有量が１２～２１ａｔ．％含み、ＣｒとＴｉの比率であるＣｒ％／（Ｃｒ％＋Ｔｉ％）が０．１５～１．００の範囲であることを特徴とする蓄電デバイス用Ｓｉ系合金からなる負極材料が提供される。 According to a preferred aspect of the present invention, in the negative electrode material made of the Si-based alloy for an electricity storage device, the total content of Cr and Ti of the negative electrode material made of the Si-based alloy is 12 to 21 at. A negative electrode material made of a Si-based alloy for an electricity storage device is provided, in which Cr% / (Cr% + Ti%), which is a ratio of Cr and Ti, is 0.15 to 1.00. .
　本発明の好ましい態様によれば、上記蓄電デバイス用Ｓｉ系合金からなる負極材料の前記化合物相に、Ｃｕ、Ｖ、Ｍｎ、Ｆｅ、Ｎｉ、Ｎｂ、Ｚｎ、Ａｌからなる群から選択される少なくとも一種以上の元素を含み、合計含有量が０．０５ａｔ．％～５ａｔ．％であることを特徴とする蓄電デバイス用Ｓｉ系合金からなる負極材料が提供される。 According to a preferred aspect of the present invention, at least one selected from the group consisting of Cu, V, Mn, Fe, Ni, Nb, Zn, and Al is used as the compound phase of the negative electrode material made of the Si-based alloy for power storage devices. The total content is 0.05 at. % To 5 at. %, A negative electrode material made of a Si-based alloy for power storage devices is provided.
　本発明の好ましい態様によれば、上記蓄電デバイス用Ｓｉ系合金からなる負極材料の前記化合物相に、Ｍｇ、Ｂ、Ｐ、Ｇａからなる群から選択される少なくとも一種以上の元素を含み、合計含有量が０．０５ａｔ．％～５ａｔ．％であることを特徴とする蓄電デバイス用Ｓｉ系合金からなる負極材料が提供される。 According to a preferred aspect of the present invention, the compound phase of the negative electrode material made of the Si-based alloy for an electricity storage device includes at least one element selected from the group consisting of Mg, B, P, and Ga, and contains the total amount The amount is 0.05 at. % To 5 at. %, A negative electrode material made of a Si-based alloy for power storage devices is provided.
　本発明の好ましい態様によれば、上記蓄電デバイス用Ｓｉ系合金からなる負極材料を用いた電極において、特にポリイミド系バインダーを含むことを特徴とする蓄電デバイス用Ｓｉ系合金からなる負極が提供される。 According to a preferred aspect of the present invention, there is provided a negative electrode made of an Si-based alloy for an electricity storage device, characterized in that, in the electrode using the negative electrode material made of the Si-based alloy for an electricity storage device, a polyimide-based binder is included. .
　本発明合金においてＣｒはＳｉ相と微細共晶組織を形成するのに有効なＳｉ2 Ｃｒを生成する必須元素であり、ＴｉはＣｒと置換されてＳｉ2 Ｃｒの格子定数を増加させ、リチウムイオン伝導性を高めると推測される。さらに、Ｓｉ相の結晶子サイズを３０ｎｍ以下に、またＳｉとＣｒの化合物相あるいはＳｉとＣｒとＴｉの化合物相の結晶子サイズを４０ｎｍ以下とすることで、Ｓｉへのリチウムの吸蔵・放出時の体積膨張により生じる応力を緩和し、Ｓｉの微粉化による電気的孤立を防ぐ役割を果たすため、優れた充放電サイクル特性が得られると推測される。 In the alloy of the present invention, Cr is an essential element for generating Si 2 Cr effective for forming a fine eutectic structure with the Si phase, and Ti is substituted for Cr to increase the lattice constant of Si 2 Cr, thereby increasing the lithium ion. Presumed to increase conductivity. Furthermore, by reducing the crystallite size of the Si phase to 30 nm or less, and the crystallite size of the compound phase of Si and Cr or the compound phase of Si, Cr and Ti to 40 nm or less, when lithium is occluded / released in Si It is presumed that excellent charge / discharge cycle characteristics can be obtained because it relieves the stress caused by the volume expansion of the metal and prevents electrical isolation due to the atomization of Si.
　また、前記蓄電デバイス用Ｓｉ系合金負極材料の化学成分を制御することで、優れた充放電サイクル特性が得られる。ＳｉとＣｒ、あるいはＳｉとＣｒとＴｉからなる相のＣｒとＴｉの合計含有量を１２～２１ａｔ．％とし、Ｃｒ％／（Ｃｒ％＋Ｔｉ％）を０．１５～１．００の範囲に制御した場合に、その効果が大きい。 Also, excellent charge / discharge cycle characteristics can be obtained by controlling the chemical components of the Si-based alloy negative electrode material for power storage devices. The total content of Cr and Ti in the phase composed of Si and Cr or Si, Cr and Ti is 12 to 21 at. %, And Cr% / (Cr% + Ti%) is controlled within the range of 0.15 to 1.00, the effect is large.
　また、蓄電デバイス用Ｓｉ系合金負極材料のＳｉとＣｒを含む試料、またはＳｉとＣｒとＴｉを含む試料にＣｕ、Ｖ、Ｍｎ、Ｆｅ、Ｎｉ、Ｎｂ、Ｐｄ、ＺｎおよびＡｌからなる第１の群の添加元素を一種以上、合計量が０．０５ａｔ．％～５ａｔ．％となるように含ませ、結晶子サイズを制御することで、化合物相が微細Ｓｉ相の周囲を取り囲み、Ｓｉの微粉化およびＳｉへのリチウムの吸蔵・放出時の体積膨張により生じる応力を緩和し、電極の崩壊およびＳｉの電気的孤立を防ぐ役割を果たす。これらの蓄電デバイス用Ｓｉ系合金負極材料を用いた電極において、特に、結合力の高いポリイミドバインダーを含んだ場合、優れた電池特性が提供される。 Further, a first sample comprising Cu, V, Mn, Fe, Ni, Nb, Pd, Zn, and Al in a sample containing Si and Cr or a sample containing Si, Cr and Ti as a Si-based alloy negative electrode material for an electricity storage device. One or more additive elements in the group, with a total amount of 0.05 at. % To 5 at. By controlling the crystallite size, the compound phase surrounds the fine Si phase and relieves stress caused by Si pulverization and volume expansion during the insertion and extraction of lithium into and from Si. In addition, it plays the role of preventing the collapse of the electrode and the electrical isolation of Si. In an electrode using these Si-based alloy negative electrode materials for power storage devices, particularly when a polyimide binder having a high binding force is included, excellent battery characteristics are provided.
　また、蓄電デバイス用Ｓｉ系合金負極材料のＳｉとＣｒを含む試料、またはＳｉとＣｒとＴｉを含む試料に、Ｍｇ、Ｂ、ＰおよびＧａからなる第２の群の添加元素を一種以上、合計量が０．０５ａｔ．％～５ａｔ．％となるように含ませ、結晶子サイズを制御することで、化合物相が微細Ｓｉ相の周囲を取り囲み、Ｓｉの微粉化、Ｓｉへのリチウムの吸蔵・放出時の体積膨張により生じる応力を緩和し、電極の崩壊、Ｓｉの電気的孤立を防ぐ役割を果たす。また、Ｂ添加によるＰ型半導体構造をとることで、Ｓｉの電気伝導性の向上の役割を果たす。Ｐ添加によるＮ型半導体構造をとることで、Ｓｉの電気伝導性の向上の役割を果たす。これらの蓄電デバイス用Ｓｉ系合金負極材料を用いた電極において、特に、結合力の高いポリイミドバインダーを含んだ場合、優れた電池特性が提供される。 Further, a sample containing Si and Cr, or a sample containing Si, Cr and Ti, of the Si-based alloy negative electrode material for an electricity storage device, a total of one or more additive elements of the second group consisting of Mg, B, P and Ga The amount is 0.05 at. % To 5 at. By controlling the crystallite size, the compound phase surrounds the periphery of the fine Si phase and relieves the stress caused by Si pulverization and volume expansion when lithium is absorbed into and released from Si. And it plays the role which prevents the collapse of an electrode and the electrical isolation of Si. Also, by taking a P-type semiconductor structure by adding B, it plays a role of improving the electrical conductivity of Si. By taking an N-type semiconductor structure by adding P, it plays a role of improving the electrical conductivity of Si. In an electrode using these Si-based alloy negative electrode materials for power storage devices, particularly when a polyimide binder having a high binding force is included, excellent battery characteristics are provided.
　以上述べたように、本発明は高容量かつ繰り返し充放電時のサイクル特性に優れた蓄電デバイス用Ｓｉ系合金負極材料を提供できる極めて優れた効果を奏するものである。 As described above, the present invention has an excellent effect of providing a Si-based alloy negative electrode material for an electricity storage device having a high capacity and excellent cycle characteristics during repeated charge and discharge.
Ｓｉ－Ｓｉ2 Ｃｒ共晶合金の断面のＳＥＭ画像を示す図である。Cross-sectional SEM image of the Si-Si 2 Cr eutectic alloy is a diagram showing a. Ｃｒ／Ｔｉ比を変化させたＳｉ－Ｓｉ2 Ｃｒ共晶合金のＸＲＤスペクトルである。3 is an XRD spectrum of a Si—Si 2 Cr eutectic alloy with a changed Cr / Ti ratio. ＣｒとＴｉの合計量を変化させたＳｉ－Ｓｉ2 Ｃｒ共晶合金のＳＥＭ画像を示す図である。（ａ）はＣｒとＴｉの合計量が１７％の場合の画像であり、（ｂ）はＣｒとＴｉの合計量が１９％の場合の画像である。SEM images of Cr and the total amount of change in the Si-Si 2 Cr eutectic alloy was of Ti is a diagram showing a. (A) is an image when the total amount of Cr and Ti is 17%, and (b) is an image when the total amount of Cr and Ti is 19%.
　以下、本発明について詳細に説明する。特段の明示が無いかぎり、本明細書において「％」はａｔ％を意味するものとする。 Hereinafter, the present invention will be described in detail. In the present specification, “%” means at% unless otherwise specified.
　リチウムイオン二次電池の充放電容量はリチウムの移動量で決まってくる。したがって、リチウムを多量に吸蔵・放出できる物質が求められている。負極材料にリチウム金属を使用することが一番効率が良いが、充放電に伴うデンドライドの形成により引き起こされる電池の発火などの可能性がある。そこで、現在はリチウムをより多く吸蔵・放出できる合金の研究が進んでおり、それら合金の中でもＳｉは多量にリチウムを吸蔵・放出できる物質として有望視されている。そのため、合金相の主要相としてＳｉを採用する。 The charge / discharge capacity of a lithium ion secondary battery is determined by the amount of lithium transferred. Therefore, there is a demand for a substance that can occlude and release a large amount of lithium. It is most efficient to use lithium metal for the negative electrode material, but there is a possibility of battery ignition caused by the formation of dendrites accompanying charging and discharging. Therefore, studies on alloys that can occlude and release more lithium are currently underway, and among these alloys, Si is promising as a substance that can occlude and release lithium in large quantities. Therefore, Si is adopted as the main phase of the alloy phase.
　しかし、Ｓｉはリチウムの吸蔵・放出時に約４００％もの体積膨張を引き起こすため、電極からＳｉが剥離・脱落したり、Ｓｉが集電体との接触を保てなくなることで、サイクルに伴う充放電容量の急激な低下が起こる。また、ＳｉはＳｉ相サイズが大きすぎると、内部のＳｉ相までリチウムと反応せず、Ｓｉとリチウムが反応しやすい表層から膨張し、亀裂が生じ、次に内部の未反応Ｓｉ相が膨張し、また亀裂が生じるといったことを繰り返して、Ｓｉの微粉化が引き起こされる。これにより、電極からＳｉが剥離・脱落したり、Ｓｉが集電体との接触を保てなくなることで、サイクルに伴う充放電容量の急激な低下が起こる。 However, since Si causes volume expansion of about 400% when lithium is occluded / released, Si is peeled off or dropped from the electrode, or Si cannot maintain contact with the current collector. A sudden drop in capacity occurs. In addition, if the Si phase size is too large, Si does not react with lithium up to the internal Si phase, expands from the surface layer where Si and lithium easily react, cracks occur, and then the internal unreacted Si phase expands. In addition, repeated generation of cracks causes fine powdering of Si. As a result, Si peels off from the electrode, or Si cannot maintain contact with the current collector, resulting in a rapid decrease in charge / discharge capacity associated with the cycle.
　本発明における特徴は、共晶合金を得るための添加元素としてＣｒを用いたことである。図１は、本発明に係るＳｉ－Ｓｉ2 Ｃｒの共晶合金の走査型電子顕微鏡写真による断面組織図で、黒い相がＳｉ相、白い相がＳｉ2 Ｃｒ相である。この図１に示す通り、Ｓｉ相およびＣｒＳｉ2 相ともに極めて微細である。なお、ＦｅやＶなど他の元素と比較し、Ｃｒ添加が極端に微細な共晶組織をもたらし、充放電特性にも優れる原因については、以下のことが推測される。 A feature of the present invention is that Cr is used as an additive element for obtaining a eutectic alloy. FIG. 1 is a cross-sectional structure diagram of a Si—Si 2 Cr eutectic alloy according to the present invention, taken by a scanning electron micrograph, wherein the black phase is the Si phase and the white phase is the Si 2 Cr phase. As shown in FIG. 1, both the Si phase and the CrSi 2 phase are extremely fine. In addition, compared with other elements, such as Fe and V, the following is estimated about the cause by which Cr addition produces an extremely fine eutectic structure | tissue and is excellent also in a charge / discharge characteristic.
　Ｓｉ相と珪化物の共晶を得るために必要な添加元素量は元素の種類によって決まっており、例えばＦｅの場合は２６．５％、Ｖの場合は３％の添加が必要である。なお、これらはいずれもＳｉと添加元素の状態図から読み取ることができる。ここで、共晶を得るためにＦｅのように比較的多くの添加量が必要な元素を用いる場合は、必然的に珪化物の量が多くなり粗大化しやすい。そのため、Ｌｉを吸蔵・放出するＳｉ相の割合が低下し、高い放電容量が得られない。 The amount of additive element necessary to obtain the eutectic of the Si phase and silicide is determined by the type of element, for example, 26.5% for Fe and 3% for V. These can be read from the phase diagrams of Si and additive elements. Here, when an element that requires a relatively large amount of addition, such as Fe, is used in order to obtain a eutectic, the amount of silicide is inevitably increased, and it tends to be coarse. Therefore, the ratio of the Si phase that occludes / releases Li decreases, and a high discharge capacity cannot be obtained.
　一方、Ｖのように極端に少ない添加量で共晶となる場合、共晶組織中の珪化物の割合が少なく、必然的にＳｉ相が粗大化しやすくなり、充放電時のＳｉ相の体積変化を制御する珪化物の効果が得られない。一方、Ｃｒは共晶となる添加量がこれらの中間であり、Ｓｉ相および珪化物の両者が微細になると考えられる。したがって、Ｓｉ－Ｓｉ2 Ｃｒ共晶合金は高い放電容量と優れたサイクル寿命を兼備することができる。 On the other hand, when it becomes eutectic with an extremely small addition amount like V, the proportion of silicide in the eutectic structure is small, and the Si phase tends to be coarsened, and the volume change of the Si phase during charge / discharge The effect of the silicide to control is not obtained. On the other hand, Cr is added in the middle amount of eutectic, and it is considered that both the Si phase and the silicide become fine. Therefore, the Si—Si 2 Cr eutectic alloy can have both a high discharge capacity and an excellent cycle life.
　また、Ｃｒの一部をＴｉで置換することにより、さらに充放電特性を改善できる。発明者は、Ｓｉ－Ｓｉ2 Ｃｒ共晶合金において、ＣｒをＴｉに置換する検討を詳細に行った結果、ＴｉはＳｉ2 ＣｒのＣｒと置換され、その結晶構造を変化させることなく格子定数を増加させると考えた。 Further, the charge / discharge characteristics can be further improved by substituting a part of Cr with Ti. The inventor conducted detailed studies on replacing Cr with Ti in the Si—Si 2 Cr eutectic alloy. As a result, Ti was replaced with Cr in Si 2 Cr, and the lattice constant was changed without changing the crystal structure. I thought it would increase.
　図２は、Ｃｒ／Ｔｉ比を変化させたＳｉ－Ｓｉ2 Ｃｒ共晶合金のＸ線回折を示す図である。この図に示すように、Ｃｒの一部をＴｉに置換することにより、Ｓｉ2 Ｃｒは結晶構造を変化させることなく回折ピーク位置が低角度側にシフトしており、格子定数が増加しているものと考えられる。 FIG. 2 is a diagram showing X-ray diffraction of a Si—Si 2 Cr eutectic alloy with a changed Cr / Ti ratio. As shown in this figure, by replacing a part of Cr with Ti, the diffraction peak position of Si 2 Cr is shifted to the lower angle side without changing the crystal structure, and the lattice constant is increased. It is considered a thing.
　本発明におけるＣｒへのＴｉ置換によるＳｉ2 Ｃｒの格子定数増加は、珪化物中のＬｉの通過をスムーズにし、これに伴う体積変化を軽減する役割を果たしている可能性がある。このように、Ｓｉと珪化物の共晶系合金をリチウムイオン電池負極活物質に利用する検討で、珪化物の構造にまで踏み込んだ研究はこれまでにほとんど見られない。 The increase in the lattice constant of Si 2 Cr due to the substitution of Ti with Cr in the present invention may play a role of smoothing the passage of Li in the silicide and reducing the accompanying volume change. Thus, in the study of utilizing a eutectic alloy of Si and silicide as a negative electrode active material for a lithium ion battery, there has been almost no research so far that has gone into the structure of silicide.
　上記ＳｉとＣｒ、あるいはＳｉとＣｒとＴｉの共晶組織の形成に加えて、結晶子サイズを制御することで、さらにリチウムイオン二次電池特性の改善が見込まれる。ＳｉはＳｉ相サイズが大きすぎると、内部のＳｉ相までリチウムと反応せずに、Ｓｉ相のリチウムと反応しやすい表層から膨張し、亀裂が生じ、次に内部の未反応Ｓｉ相が膨張し、また亀裂が生じるといったことを繰り返して、Ｓｉの微粉化が引き起こされる。これにより、電極からＳｉが剥離・脱落したり、Ｓｉが集電体との接触を保てなくなることで、サイクルに伴う充放電容量の急激な低下が起こる。このことから、微粉化が起こらないサイズまで微細組織にする必要があり、前記リチウムイオン二次電池用負極材料のＳｉ相の結晶子サイズを３０ｎｍ以下に制御する必要がある。好ましくは、結晶子サイズを２５ｎｍ以下に制御することが望ましい。特に、好ましくは１０ｎｍ以下に制御することが望ましい。 In addition to the formation of the eutectic structure of Si and Cr or Si, Cr and Ti, the characteristics of the lithium ion secondary battery can be further improved by controlling the crystallite size. If the Si phase size is too large, Si does not react with lithium up to the internal Si phase, but expands from the surface layer that easily reacts with lithium in the Si phase, causing cracks, and then the internal unreacted Si phase expands. In addition, repeated generation of cracks causes fine powdering of Si. As a result, Si peels off from the electrode, or Si cannot maintain contact with the current collector, resulting in a rapid decrease in charge / discharge capacity associated with the cycle. For this reason, it is necessary to make the microstructure fine enough to prevent pulverization, and it is necessary to control the crystallite size of the Si phase of the negative electrode material for lithium ion secondary batteries to 30 nm or less. Preferably, the crystallite size is controlled to 25 nm or less. In particular, it is desirable to control to 10 nm or less.
　Ｓｉ相の結晶子サイズの制御については、上記に定めた成分の制御に加えて、原料粉末を溶解した後の凝固時の冷却速度の制御によって可能である。製造方法としては、水アトマイズ、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、遠心アトマイズ等があるが、この限りではない。また、上記プロセスで冷却効果が不十分な場合、メカニカルミリング等を行うことも可能である。ミリング方法としては、ボールミル、ビーズミル、遊星ボールミル、アトライタ、振動ボールミル等があるが、この限りではない。 The crystallite size of the Si phase can be controlled by controlling the cooling rate during solidification after dissolving the raw material powder in addition to the control of the components defined above. Examples of the production method include water atomization, single-roll quenching method, twin-roll quenching method, gas atomization method, disk atomization method, and centrifugal atomization, but are not limited thereto. Further, when the cooling effect is insufficient in the above process, mechanical milling or the like can be performed. Examples of the milling method include a ball mill, a bead mill, a planetary ball mill, an attritor, and a vibration ball mill, but are not limited thereto.
　また、Ｓｉ主要相のＳｉ結晶子サイズは、透過型電子顕微鏡（ＴＥＭ）により直接観察できる。または、粉末Ｘ線回折（ＸＲＤ）を用いることによって確認することができる。Ｘ線源として波長１．５４０５９ÅのＣｕＫα線を用い、２θ＝２０度～８０度の範囲で測定を行う。得られる回折スペクトルにおいては、結晶子サイズが小さくなるにつれて、比較的ブロードな回折ピークが観測される。結晶子の大きさは、粉末Ｘ線回折分析で得られるピークの半値幅から、Ｓｃｈｅｒｒｅｒの式を用いて求めることができる（Ｄ（Å）＝（Ｋ×λ）／（β×ｃｏｓθ）、Ｄ：結晶子の大きさ、Ｋ：Ｓｃｈｅｒｒｅｒの定数、λ：使用した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）。 Also, the Si crystallite size of the Si main phase can be directly observed with a transmission electron microscope (TEM). Alternatively, it can be confirmed by using powder X-ray diffraction (XRD). A CuKα ray having a wavelength of 1.54059 mm is used as an X-ray source, and measurement is performed in the range of 2θ = 20 degrees to 80 degrees. In the obtained diffraction spectrum, a relatively broad diffraction peak is observed as the crystallite size decreases. The size of the crystallite can be obtained from the half width of the peak obtained by powder X-ray diffraction analysis using the Scherrer equation (D (Å) = (K × λ) / (β × cos θ), D : Crystallite size, K: Scherrer constant, λ: wavelength of the X-ray tube used, β: broadening of diffraction lines depending on crystallite size, θ: diffraction angle).
　結晶子サイズにおいて、Ｓｉ主要相のみならず、金属間化合物相の結晶子サイズも重要になる。ＳｉとＣｒ、あるいはＳｉとＣｒとＴｉ等の金属間化合物の結晶子サイズを小さくすることで、金属間化合物の降伏応力を高めることや延性、靭性の向上が期待ができる。このことから、膨張等の影響を受けた際に、亀裂の発生等を抑制し、良好なイオン伝導性、電子伝導性を確保できる。また、金属間化合物の結晶子サイズが小さくなることで、大きな粒子よりもＳｉ相とより大きな比表面積で接触し、Ｓｉ相の体積膨張収縮による応力を効率良く吸収・緩和することが可能になる。さらに、Ｓｉ相とより大きな比表面積で接触することで、リチウムイオン伝導性や電子伝導性パスが増え、よりスムーズな充放電反応を行うことが期待される。そのため、結晶子サイズを４０ｎｍ以下に制御する必要がある。好ましくは、結晶子サイズを２０ｎｍ以下に制御することが望ましい。特に、好ましくは１０ｎｍ以下に制御することが望ましい。 In the crystallite size, not only the Si main phase but also the crystallite size of the intermetallic compound phase is important. By reducing the crystallite size of an intermetallic compound such as Si and Cr or Si, Cr and Ti, it is possible to increase the yield stress of the intermetallic compound and to improve ductility and toughness. From this, when affected by expansion or the like, the occurrence of cracks and the like can be suppressed, and good ion conductivity and electron conductivity can be ensured. In addition, by reducing the crystallite size of the intermetallic compound, it is possible to contact the Si phase with a larger specific surface area than large particles, and to efficiently absorb and relax the stress due to the volume expansion and contraction of the Si phase. . Furthermore, contact with the Si phase with a larger specific surface area is expected to increase the lithium ion conductivity and the electron conductivity path, and to perform a smoother charge / discharge reaction. Therefore, it is necessary to control the crystallite size to 40 nm or less. Preferably, the crystallite size is controlled to 20 nm or less. In particular, it is desirable to control to 10 nm or less.
　金属間化合物の結晶子サイズも、透過型電子顕微鏡（ＴＥＭ）により直接観察することができる。または、粉末Ｘ線回折を用いることによって確認することもできる。Ｘ線源として波長１．５４０５９ÅのＣｕＫα線を用い、２θ＝２０度～８０度の範囲で測定を行う。得られる回折スペクトルにおいて、結晶子サイズが小さくなるにつれて、比較的ブロードな回折ピークが観測される。結晶子の大きさは、粉末Ｘ線回折分析で得られるピークの半値幅から、Ｓｃｈｅｒｒｅｒの式を用いて求めることができる（Ｄ（Å）＝（Ｋ×λ）／（β×ｃｏｓθ）、Ｄ：結晶子の大きさ、Ｋ：Ｓｃｈｅｒｒｅｒの定数、λ：使用した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）。金属間化合物の結晶子サイズの制御は、原料粉末を溶解した後の凝固時の冷却速度の制御によって可能である。製造方法としては、水アトマイズ、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、遠心アトマイズ等があるが、この限りではない。また、上記プロセスで冷却効果が不十分な場合、メカニカルミリング等を行うことも可能である。ミリング方法としては、ボールミル、ビーズミル、遊星ボールミル、アトライタ、振動ボールミル等があるが、この限りではない。 The crystallite size of the intermetallic compound can also be directly observed with a transmission electron microscope (TEM). Or it can also confirm by using powder X-ray diffraction. A CuKα ray having a wavelength of 1.54059 mm is used as an X-ray source, and measurement is performed in the range of 2θ = 20 degrees to 80 degrees. In the obtained diffraction spectrum, a relatively broad diffraction peak is observed as the crystallite size decreases. The size of the crystallite can be obtained from the half width of the peak obtained by powder X-ray diffraction analysis using the Scherrer equation (D (Å) = (K × λ) / (β × cos θ), D : Crystallite size, K: Scherrer constant, λ: wavelength of the X-ray tube used, β: broadening of diffraction lines depending on crystallite size, θ: diffraction angle). The crystallite size of the intermetallic compound can be controlled by controlling the cooling rate during solidification after dissolving the raw material powder. Examples of the production method include water atomization, single-roll quenching method, twin-roll quenching method, gas atomization method, disk atomization method, and centrifugal atomization, but are not limited thereto. Further, when the cooling effect is insufficient in the above process, mechanical milling or the like can be performed. Examples of the milling method include a ball mill, a bead mill, a planetary ball mill, an attritor, and a vibration ball mill, but are not limited thereto.
　さらに、Ｃｒの一部をＴｉへ置換する効果については、詳細な原因は不明であるが、次のような意外な利点も見出された。通常の共晶組織は、添加元素量が一点の特異的な組織であり、少しでも添加量が前後に振れると、亜共晶もしくは過共晶合金となり、著しく粗大な初晶が晶出してしまうため、厳密に共晶組織を得るためには、高い製造技術を要する。しかしながら、Ｃｒの一部をＴｉに置換した本発明合金では、ＣｒとＴｉの合計が約１２～２１％程度の広い範囲で微細な組織が得られ、製造ロットにより多少は添加量が前後に振れても極端な組織変化がない。なお、図３はＣｒとＴｉの合計量を変化させたＳｉ－Ｓｉ2 Ｃｒ系共晶合金の走査型電子顕微鏡写真による断面組織図である。なお、図３（ａ）はＣｒとＴｉの合計量が１７％の場合であり、図３（ｂ）はＣｒとＴｉの合計量が１９％の場合である。 Furthermore, although the detailed cause is unknown about the effect which substitutes a part of Cr to Ti, the following unexpected advantages were also discovered. The normal eutectic structure is a unique structure with a single additive element amount. If the added amount fluctuates back and forth, it becomes a hypoeutectic or hypereutectic alloy, and an extremely coarse primary crystal is crystallized. Therefore, a high production technique is required to obtain a eutectic structure strictly. However, in the alloy of the present invention in which a part of Cr is replaced with Ti, a fine structure is obtained in a wide range where the total of Cr and Ti is about 12 to 21%, and the added amount fluctuates back and forth depending on the production lot. But there is no extreme organizational change. FIG. 3 is a cross-sectional structure diagram of a scanning electron micrograph of a Si—Si 2 Cr eutectic alloy in which the total amount of Cr and Ti is changed. FIG. 3A shows a case where the total amount of Cr and Ti is 17%, and FIG. 3B shows a case where the total amount of Cr and Ti is 19%.
　ＣｒとＴｉを合計で１２～２１％含み（ただしＴｉが０ａｔ．％の場合を含む）、Ｃｒ％／（Ｃｒ％＋Ｔｉ％）が０．１５～１．００の範囲とした理由は、本発明合金においてＣｒはＳｉ相と微細共晶組織を形成するＳｉ2 Ｃｒを生成する必須元素であり、ＴｉはＣｒと置換しＳｉ2 Ｃｒの格子定数を増加させる有効な元素である。その合計量を１２％以上とすることで亜共晶組織の形成による粗大な初晶Ｓｉ相の晶出を抑制できる点で好ましく、２１％以下とすることで、過共晶組織となって粗大なＳｉ2 Ｃｒを晶出することを抑制できる点で好ましく、サイクル寿命への影響が抑えられる。また、Ｃｒ％／（Ｃｒ％＋Ｔｉ％）を０．１５～１．００の範囲とすることで、Ｓｉ2 Ｃｒ相の他にＳｉ2 Ｔｉ相が生成することが抑えられ、Ｓｉ相の粗大化を抑制し、上記同様にサイクル寿命への影響が抑えられる点で好ましい。したがって、ＣｒとＴｉの合計のより好ましい範囲を１３～２０％とし、さらに好ましくは１４～１９％とした。また、Ｃｒ％／（Ｃｒ％＋Ｔｉ％）のより好ましい範囲を、０．１５～０．９０とし、さらに好ましくは０．２０～０．８０とした。 The reason why the total content of Cr and Ti is 12 to 21% (including the case where Ti is 0 at.%) And Cr% / (Cr% + Ti%) is in the range of 0.15 to 1.00. In the alloy, Cr is an essential element that forms Si 2 Cr that forms a fine eutectic structure with the Si phase, and Ti is an effective element that replaces Cr and increases the lattice constant of Si 2 Cr. By making the total amount 12% or more, it is preferable in that crystallization of a coarse primary crystal Si phase due to the formation of a hypoeutectic structure can be suppressed, and by making the total amount 21% or less, a hypereutectic structure becomes coarse. It is preferable in that it is possible to suppress crystallization of simple Si 2 Cr, and the influence on the cycle life can be suppressed. Further, Cr% / (Cr% + Ti%) to that in the range 0.15 to 1.00 It is suppressed that Si 2 Ti phase is produced in addition to the Si 2 Cr phase, the coarsening of the Si phase This is preferable in that the effect on the cycle life can be suppressed as described above. Therefore, a more preferable range of the total of Cr and Ti is set to 13 to 20%, and more preferably set to 14 to 19%. Further, a more preferable range of Cr% / (Cr% + Ti%) is 0.15 to 0.90, and more preferably 0.20 to 0.80.
　さらに、Ｓｉと金属間化合物を形成するＣｒとの合金であるＳｉｘＣｒｙ合金、Ｃｒ、Ｔｉとの合金であるＳｉｘ（Ｃｒ、Ｔｉ）ｙ合金において、Ｓｉｘ（Ｃｒ、Ｔｉ）ｙ相の組成がｘ＞ｙであることが好ましい。高容量に欠かせないＳｉ主要相が晶出するのがｘ＞ｙのときであり、好ましくはｘ＝２、ｙ＝１とする。 Further, in the Si x C r y alloy that is an alloy of Si and Cr that forms an intermetallic compound, and the Si x (Cr, Ti) y alloy that is an alloy of Cr and Ti, the Si x (Cr, Ti) y phase Is preferably x> y. The Si main phase indispensable for high capacity is crystallized when x> y, and preferably x = 2 and y = 1.
　また、本発明によるリチウムイオン二次電池用負極材料に関して、ＣｒおよびＴｉ以外にも、Ｓｉと共晶合金を形成し微細Ｓｉ相が得られ、Ｓｉよりも導電性がよく柔軟な金属間化合物を形成する、Ｃｕ、Ｖ、Ｍｎ、Ｆｅ、Ｎｉ、Ｎｂ、ＺｎおよびＡｌからなる第１の群の添加元素から選択される一種以上を更に含有させることができる。これらの添加により金属間化合物の結晶子サイズを制御することで、化合物相が微細Ｓｉ相の周囲を取り囲み、Ｓｉの微粉化、Ｓｉへのリチウムの吸蔵・放出時の体積膨張により生じる応力を緩和し、電極の崩壊、Ｓｉの電気的孤立を防ぐ役割を果たす。 Further, regarding the negative electrode material for a lithium ion secondary battery according to the present invention, besides Cr and Ti, an eutectic alloy is formed with Si to obtain a fine Si phase, and a flexible intermetallic compound having better conductivity than Si is obtained. One or more selected from an additive element of the first group consisting of Cu, V, Mn, Fe, Ni, Nb, Zn and Al to be formed can be further contained. By controlling the crystallite size of the intermetallic compound by adding these, the compound phase surrounds the periphery of the fine Si phase, relieving the stress caused by volumetric expansion when Si is pulverized and lithium is absorbed into and released from Si. And it plays the role which prevents the collapse of an electrode and the electrical isolation of Si.
　また、本発明によるリチウムイオン二次電池用負極材料に関して、ＣｒおよびＴｉ以外にも、Ｓｉと共晶合金を形成し微細Ｓｉ相が得られ、Ｓｉよりも導電性がよく柔軟な金属間化合物を形成する、Ｍｇ、Ｂ、ＰおよびＧａからなる第２の群の添加元素から選択される一種以上を、０．０５ａｔ．％～５ａｔ．％含有することができる。これらの添加により結晶子サイズを制御することで、化合物相が微細Ｓｉ相の周囲を取り囲み、Ｓｉの微粉化、Ｓｉへのリチウムの吸蔵・放出時の体積膨張により生じる応力を緩和し、電極の崩壊、Ｓｉの電気的孤立を防ぐ役割を果たす。また、Ｂ添加によるＰ型半導体構造をとることで、Ｓｉの電気伝導性の向上の役割を果たす。Ｐ添加によるＮ型半導体構造をとることで、Ｓｉの電気伝導性の向上の役割を果たす。 Further, regarding the negative electrode material for a lithium ion secondary battery according to the present invention, besides Cr and Ti, an eutectic alloy is formed with Si to obtain a fine Si phase, and a flexible intermetallic compound having better conductivity than Si is obtained. One or more elements selected from the second group of additive elements consisting of Mg, B, P and Ga are formed at 0.05 at. % To 5 at. % Can be contained. By controlling the crystallite size by these additions, the compound phase surrounds the periphery of the fine Si phase, mitigating stress caused by volumetric expansion at the time of Si pulverization and insertion / extraction of lithium to / from Si, It plays a role in preventing collapse and electrical isolation of Si. Also, by taking a P-type semiconductor structure by adding B, it plays a role of improving the electrical conductivity of Si. By taking an N-type semiconductor structure by adding P, it plays a role of improving the electrical conductivity of Si.
　Ｓｉの体積膨張収縮により生じる応力を緩和する効果等の効果を付与するには、Ｃｕ、Ｖ、Ｍｎ、Ｆｅ、Ｎｉ、Ｎｂ、Ｐｄ、ＺｎおよびＡｌの合計含有量が０．０５ａｔ．％以上必要であるが、一方、５ａｔ．％を超えるとリチウム不活性元素量が増えるため、充放電容量の低下を引き起こす。このため、Ｃｕ、Ｖ、Ｍｎ、Ｆｅ、Ｎｉ、Ｎｂ、Ｐｄ、ＺｎおよびＡｌからなる第１の群から選択される少なくとも一種含まれる添加元素の合計含有量は０．０５ａｔ．％～５ａｔ．％であるのが望ましい。より好ましくは０．１ａｔ．％～３ａｔ．％である。他にも同様の効果を狙った、Ｃｏ、Ｚｒ、Ｐｄ、Ｂｉ、Ｉｎ、Ｓｂ、ＳｎおよびＭｏについても、少なくとも一種含まれる添加元素の合計含有量を０．０５ａｔ．％～５ａｔ．％とすることが望ましい。 In order to impart effects such as the effect of relaxing the stress caused by the volume expansion and contraction of Si, the total content of Cu, V, Mn, Fe, Ni, Nb, Pd, Zn and Al is 0.05 at. % Or more is necessary, but 5 at. If it exceeds 50%, the amount of lithium inert elements increases, which causes a decrease in charge / discharge capacity. For this reason, the total content of at least one additive element selected from the first group consisting of Cu, V, Mn, Fe, Ni, Nb, Pd, Zn, and Al is 0.05 at. % To 5 at. % Is desirable. More preferably, 0.1 at. % To 3 at. %. In addition, Co, Zr, Pd, Bi, In, Sb, Sn, and Mo aiming at the same effect are also set to 0.05 at. % To 5 at. % Is desirable.
　Ｓｉの体積膨張収縮により生じる応力を緩和する効果等の効果を付与するには、Ｍｇ、Ｂ、ＰおよびＧａの合計含有量が０．０５ａｔ．％以上必要であるが、一方、５ａｔ．％超えであるとリチウム不活性元素量が増えるため、充放電容量の低下を引き起こす。このため、Ｍｇ、Ｂ、ＰおよびＧａからなる第２の群から選択される少なくとも一種含まれる添加元素の合計含有量は、０．０５ａｔ．％～５ａｔ．％であるのが望ましい。より好ましくは０．１ａｔ．％～３ａｔ．％である。他にも同様の効果を狙ったＣｏ、Ｚｒ、Ｐｄ、Ｂｉ、Ｉｎ、Ｓｂ、ＳｎおよびＭｏについても、少なくとも一種含まれる添加元素の合計含有量を０．０５ａｔ．％～５ａｔ．％とすることが望ましい。 In order to impart effects such as the effect of relieving stress caused by volume expansion and contraction of Si, the total content of Mg, B, P and Ga is 0.05 at. % Or more is necessary, but 5 at. If it exceeds 50%, the amount of lithium inactive elements increases, which causes a decrease in charge / discharge capacity. For this reason, the total content of at least one additive element selected from the second group consisting of Mg, B, P and Ga is 0.05 at. % To 5 at. % Is desirable. More preferably, 0.1 at. % To 3 at. %. In addition, for Co, Zr, Pd, Bi, In, Sb, Sn, and Mo aiming at similar effects, the total content of at least one additive element is 0.05 at. % To 5 at. % Is desirable.
　上記の本発明によるリチウムイオン二次電池負極材料を用いることにより、高容量かつ繰り返し充放電時のサイクル特性に優れ、またサイクル初期の充放電効率に優れた電池特性が示される。また、上記リチウムイオン二次電池負極材料を用いた電極において、結合性に優れるポリイミド系バインダーを含むことで、Ｃｕ等の集電体との密着性を高め、高容量を保持したまま、充放電サイクル特性を改善する効果が期待される。 By using the lithium ion secondary battery negative electrode material according to the present invention described above, battery characteristics with high capacity, excellent cycle characteristics during repeated charge / discharge, and excellent charge / discharge efficiency at the initial cycle are exhibited. In addition, in the electrode using the lithium ion secondary battery negative electrode material, by including a polyimide-based binder having excellent binding properties, the adhesion with a current collector such as Cu is improved, and charging and discharging are performed while maintaining a high capacity. The effect of improving cycle characteristics is expected.
　以下、本発明について、実施例により具体的に説明する。
　表１～２に示す組成のリチウムイオン二次電池用負極材料粉末を、以下に述べる単ロール急冷法、ガスアトマイズ法等により作製した。単ロール急冷法である液体急冷法については、所定組成の原料を底部に細孔を設けた石英管内に入れ、Ａｒ雰囲気中で高周波溶解して溶湯を形成し、この溶湯を回転する銅ロールの表面に出湯した後、銅ロールによる急冷効果によりＳｉ相の結晶子サイズの微細化を図った急冷リボンを作製した。その後、作製した急冷リボンをジルコニア製あるいはＳＵＳ３０４製、ＳＵＪ２製のポット容器内にジルコニアボールあるいはＳＵＳ３０４ボール、ＳＵＪ２ボールとともにＡｒ雰囲気中にて密閉し、粒子状に加工することを目的としたミリングを行った。ミリングに関しては、ボールミル、ビーズミル、遊星ボールミル、アトライタ、振動ボールミル等が挙げられる。 Hereinafter, the present invention will be specifically described with reference to examples.
Negative electrode material powders for lithium ion secondary batteries having the compositions shown in Tables 1 and 2 were prepared by a single roll quenching method, a gas atomizing method, or the like described below. For the liquid quenching method, which is a single roll quenching method, a raw material having a predetermined composition is placed in a quartz tube having pores at the bottom, melted at a high frequency in an Ar atmosphere to form a molten metal, and a copper roll that rotates this molten metal. After the hot water was discharged on the surface, a quenching ribbon was prepared in which the crystallite size of the Si phase was refined by the quenching effect of the copper roll. The milled ribbon is then sealed in an Ar atmosphere together with zirconia balls, SUS304 balls, or SUJ2 balls in a zirconia, SUS304, or SUJ2 pot container and milled for the purpose of processing into particles. It was. As for milling, a ball mill, a bead mill, a planetary ball mill, an attritor, a vibrating ball mill, and the like can be given.
　ガスアトマイズ法については、所定組成の原料を、底部に細孔を設けた石英坩堝内に入れ、Ａｒガス雰囲気中で高周波誘導溶解炉により加熱溶融した後、Ａｒガス雰囲気中で、ガス噴射させるとともに出湯させて、急冷凝固することでガスアトマイズ微粉末を得た。ディスクアトマイズ法については、所定組成の原料を、底部に細孔を設けた石英坩堝内に入れ、Ａｒガス雰囲気中で高周波誘導溶解炉により加熱溶融した後、Ａｒガス雰囲気中で、４００００～６００００ｒ．ｐ．ｍ．(revolutions per minute)の回転ディスク上に出湯させて、急冷凝固することでディスクアトマイズ微粉末を得た。その後、作製したアトマイズ微粉末をジルコニア製あるいはＳＵＳ３０４製、ＳＵＪ２製のポット容器内にジルコニアボールあるいはＳＵＳ３０４ボール、ＳＵＪ２ボールとともにＡｒ雰囲気中にて密閉し、メカニカルミリングにより粉末化し、結晶子サイズの制御を行った。メカニカルミリングに関しては、ボールミル、ビーズミル、遊星ボールミル、アトライタ、振動ボールミル等が挙げられる。メカニカルミリングによる処理では、ミリング時間や回転数等を設定することで、急冷凝固を利用したアトマイズ粉末のＳｉ結晶子サイズや金属間化合物の結晶子サイズを制御することができる。 Regarding the gas atomization method, a raw material having a predetermined composition is placed in a quartz crucible having pores at the bottom, heated and melted in a high-frequency induction melting furnace in an Ar gas atmosphere, and then subjected to gas injection in an Ar gas atmosphere and a tapping hot water. Then, gas atomized fine powder was obtained by rapid solidification. In the disk atomization method, a raw material having a predetermined composition is placed in a quartz crucible having pores at the bottom, heated and melted in a high-frequency induction melting furnace in an Ar gas atmosphere, and then in an Ar gas atmosphere, 40000 to 60000 r. p. m. Hot water was poured onto a (revolutions per minute) rotating disk and rapidly solidified to obtain a disk atomized fine powder. After that, the atomized fine powder produced is sealed in a zirconia or SUS304 / SUJ2 pot container with zirconia balls, SUS304 balls, or SUJ2 balls in an Ar atmosphere, and powdered by mechanical milling to control the crystallite size. went. Examples of mechanical milling include a ball mill, a bead mill, a planetary ball mill, an attritor, and a vibrating ball mill. In the processing by mechanical milling, the crystallite size of the atomized powder and the intermetallic compound using rapid solidification can be controlled by setting the milling time and the number of rotations.
　以下、具体的な負極作製方法について述べる。
　上記負極の単極での電極性能を評価するために、対極にリチウム金属を用いた、いわゆる二極式コイン型セルを用いた。まず、負極活物質（Ｓｉ－Ｃｒ－Ｔｉなど）、導電材料（アセチレンブラック）、結着材料（ポリイミド、ポリフッ化ビニリデン等）を電子天秤で秤量し、分散液（Ｎ－メチルピロリドン）と共に混合スラリー状態とした後、集電体（Ｃｕ等）上に均一に塗布した。塗布後、真空乾燥機で減圧乾燥し溶媒を蒸発させた後、必要に応じてロールプレスした後、コインセルに合う形状に打ち抜いた。対極のリチウムも同様に金属リチウム箔をコインセルに合う形状に打ち抜いた。前記スラリー塗布電極の真空乾燥において、ポリイミド結着材料使用時は性能を十分に発揮するため２００℃以上の温度で乾燥した。ポリフッ化ビニリデン等使用時は約１６０℃の温度で乾燥した。 Hereinafter, a specific method for preparing a negative electrode will be described.
In order to evaluate the electrode performance of the negative electrode as a single electrode, a so-called bipolar coin-type cell using lithium metal as a counter electrode was used. First, a negative electrode active material (Si—Cr—Ti, etc.), a conductive material (acetylene black), a binder material (polyimide, polyvinylidene fluoride, etc.) are weighed with an electronic balance, and mixed with a dispersion (N-methylpyrrolidone). After making it into a state, it was uniformly applied on a current collector (Cu or the like). After coating, the solvent was evaporated under reduced pressure in a vacuum dryer, and then roll-pressed as necessary, and then punched into a shape that fits the coin cell. Similarly, lithium for the counter electrode was punched into a shape that fits the coin cell. In the vacuum drying of the slurry-coated electrode, when the polyimide binder material was used, it was dried at a temperature of 200 ° C. or higher in order to fully exhibit the performance. When using polyvinylidene fluoride or the like, it was dried at a temperature of about 160 ° C.
　リチウムイオン電池に使用する電解液はエチレンカーボネートとジメチルカーボネートの３：７混合溶媒を用い、支持電解質にはＬｉＰＦ6 （六フッ化リン酸リチウム）を用い、電解液に対して１モル溶解した。その電解液は露点管理された不活性雰囲気中で取り扱う必要があるため、セルの組立ては、全て不活性雰囲気のグローブボックス内で行った。セパレータはコインセルにあった形状に切り抜いた後セパレータ内に電解液を十分浸透させるために、減圧下で数時間電解液中に保持した。その後、前工程で打ち抜いた負極、セパレータ、対極リチウムの順に組合せ、電池内部を電解液で十分満たした形で構築した。 The electrolyte used for the lithium ion battery was a 3: 7 mixed solvent of ethylene carbonate and dimethyl carbonate, LiPF 6 (lithium hexafluorophosphate) was used as the supporting electrolyte, and 1 mol was dissolved in the electrolyte. Since the electrolyte solution must be handled in an inert atmosphere with dew point control, the cells were all assembled in a glove box with an inert atmosphere. The separator was cut out in a shape suitable for a coin cell and then held in the electrolyte for several hours under reduced pressure in order to sufficiently permeate the electrolyte into the separator. Thereafter, the negative electrode punched out in the previous step, the separator, and the counter electrode lithium were combined in this order, and the inside of the battery was sufficiently filled with the electrolytic solution.
　充電容量、放電容量の測定は、上記二極式セルを用いて、温度２５℃、充電は０．５０ｍＡ／ｃｍ2 の電流密度で、金属リチウム極と同等の電位（０Ｖ）になるまで行い、さらに同じ電流値（０．５０ｍＡ／ｃｍ2 ）で、放電を１．５Ｖまで行い、この充電－放電を１サイクルとした。また、サイクル寿命としては、上記測定を繰返し行うことを実施した。 The measurement of the charge capacity and the discharge capacity is carried out using the above-mentioned bipolar cell, at a temperature of 25 ° C., charging at a current density of 0.50 mA / cm 2 until the potential is equal to the metal lithium electrode (0 V), Furthermore, discharging was performed up to 1.5 V at the same current value (0.50 mA / cm 2 ), and this charging-discharging was made one cycle. In addition, as the cycle life, the above measurement was repeated.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000005
Figure JPOXMLDOC01-appb-T000005
　表１～３に示すように、Ｎｏ．１～５５は本発明例であり、表３～５に示すようにＮｏ．５６～１２６は比較例を示す。これらの特性は、初期放電容量と５０サイクル後の放電容量維持率にて判断する。初期放電容量が１０００ｍＡｈ／ｇ以上であり、かつサイクル寿命が６０％以上〔５０サイクル後の放電容量維持率（％）〕であることを基準とする。 As shown in Tables 1 to 3, No. Nos. 1 to 55 are examples of the present invention. Reference numerals 56 to 126 show comparative examples. These characteristics are judged based on the initial discharge capacity and the discharge capacity maintenance ratio after 50 cycles. The standard is that the initial discharge capacity is 1000 mAh / g or more and the cycle life is 60% or more [discharge capacity maintenance ratio (%) after 50 cycles].
　本発明例のＮｏ．１～１２はＳｉ主要相とＳｉとＣｒとＴｉからなる相を含み、Ｓｉの結晶子サイズが３０ｎｍ以下であり、ＳｉとＣｒとＴｉからなる化合物相の結晶子サイズが４０ｎｍ以下の条件を満足している。 No. of the invention example 1 to 12 include the Si main phase and the phase composed of Si, Cr and Ti, the crystallite size of Si is 30 nm or less, and the crystallite size of the compound phase composed of Si, Cr and Ti satisfies the condition of 40 nm or less is doing.
　例えば、本発明例Ｎｏ．４では、Ｓｉ主要相とＳｉとＣｒとＴｉを含み、Ｓｉの結晶子サイズは４ｎｍであり、Ｓｉの結晶子サイズが３０ｎｍ以下の条件を満たしている。かつ、ＳｉとＣｒとＴｉからなる化合物相の結晶子サイズが３０ｎｍであり、ＳｉとＣｒとＴｉからなる化合物相の結晶子サイズが４０ｎｍ以下の条件を満足している。また、上記のように本発明条件を満たし、初期放電容量が１２８９ｍＡｈ／ｇ、５０サイクル後の放電容量維持率が７２％であり、充放電容量とサイクル寿命のいずれも良好な特性を示した。 For example, Invention Example No. 4 includes Si main phase, Si, Cr, and Ti, the crystallite size of Si is 4 nm, and the crystallite size of Si is 30 nm or less. In addition, the crystallite size of the compound phase composed of Si, Cr and Ti is 30 nm, and the crystallite size of the compound phase composed of Si, Cr and Ti satisfies the condition of 40 nm or less. Further, as described above, the conditions of the present invention were satisfied, the initial discharge capacity was 1289 mAh / g, the discharge capacity retention rate after 50 cycles was 72%, and both the charge / discharge capacity and the cycle life showed good characteristics.
　本発明例のＮｏ．１３～１８はＳｉ主要相とＳｉとＣｒからなる相を含み、Ｓｉの結晶子サイズが３０ｎｍ以下であり、ＳｉとＣｒからなる化合物相の結晶子サイズが４０ｎｍ以下の条件を満足している。 No. of the invention example 13 to 18 include a Si main phase and a phase composed of Si and Cr, the crystallite size of Si is 30 nm or less, and the crystallite size of the compound phase composed of Si and Cr satisfies the condition of 40 nm or less.
　例えば、Ｎｏ．１４では、Ｓｉ主要相とＳｉとＣｒを含み、Ｓｉの結晶子サイズは７ｎｍであり、Ｓｉの結晶子サイズが３０ｎｍ以下の条件を満たしている。かつ、ＳｉとＣｒからなる化合物相の結晶子サイズが１５ｎｍであり、ＳｉとＣｒからなる化合物相の結晶子サイズが４０ｎｍ以下の条件を満足している。また、上記のように本発明条件を満たし、放電容量が１３８９ｍＡｈ／ｇ、５０サイクル後の放電容量維持率が６８％であり、充放電容量とサイクル寿命のいずれも良好な特性を示した。 For example, No. No. 14 contains a Si main phase, Si, and Cr, the crystallite size of Si is 7 nm, and the crystallite size of Si is 30 nm or less. Moreover, the crystallite size of the compound phase consisting of Si and Cr is 15 nm, and the crystallite size of the compound phase consisting of Si and Cr satisfies the condition of 40 nm or less. Further, as described above, the conditions of the present invention were satisfied, the discharge capacity was 1389 mAh / g, the discharge capacity retention rate after 50 cycles was 68%, and both the charge / discharge capacity and the cycle life showed good characteristics.
　本発明例のＮｏ．１９～２４はＳｉ主要相とＳｉとＣｒとＴｉからなる相を含み、Ｓｉの結晶子サイズが３０ｎｍ以下であり、ＳｉとＣｒとＴｉからなる化合物相の結晶子サイズが４０ｎｍ以下の条件を満足している。 No. of the invention example. 19 to 24 include a Si main phase and a phase composed of Si, Cr, and Ti. The crystallite size of Si is 30 nm or less, and the crystallite size of the compound phase composed of Si, Cr, and Ti is 40 nm or less. is doing.
　例えば、Ｎｏ．２３では、Ｓｉ主要相とＳｉとＣｒとＴｉからなる相を含み、Ｓｉの結晶子サイズは８ｎｍであり、Ｓｉの結晶子サイズ３０ｎｍ以下の条件を満たしている。かつ、ＳｉとＣｒとＴｉからなる化合物相の結晶子サイズが１６ｎｍであり、ＳｉとＣｒとＴｉからなる化合物相の結晶子サイズ４０ｎｍ以下の条件を満足している。また、上記のように本発明条件を満たし、放電容量が１１７４ｍＡｈ／ｇ、５０サイクル後の放電容量維持率が８７％と充放電容量とサイクル寿命のいずれも良好な特性を示した。 For example, No. No. 23 includes a Si main phase and a phase composed of Si, Cr, and Ti, the Si crystallite size is 8 nm, and satisfies the condition that the Si crystallite size is 30 nm or less. And the crystallite size of the compound phase consisting of Si, Cr and Ti is 16 nm, and the crystallite size of the compound phase consisting of Si, Cr and Ti is 40 nm or less. Further, as described above, the present invention conditions were satisfied, the discharge capacity was 1174 mAh / g, the discharge capacity retention rate after 50 cycles was 87%, and both the charge / discharge capacity and the cycle life showed good characteristics.
　本発明例のＮｏ．２５～５５はＳｉ主要相とＳｉとＣｒ、あるいはＳｉとＣｒとＴｉからなる相を含み、Ｓｉ主要相のＳｉ結晶子サイズが３０ｎｍ以下であり、ＳｉとＣｒ、あるいはＳｉとＣｒとＴｉからなる化合物相の結晶子サイズが４０ｎｍ以下の条件を満足している。また、Ｃｕ、Ｖ、Ｍｎ、Ｆｅ、Ｎｉ、Ｎｂ、ＺｎおよびＡｌからなる第１の群から選択される少なくとも一種含まれる添加元素の合計含有量は、０．０５ａｔ．％～５ａｔ．％である。また、Ｍｇ、Ｂ、ＰおよびＧａからなる第２の群から選択される少なくとも一種類含まれる添加元素の合計含有量は０．０５ａｔ．％～５ａｔ．％である。同様の効果を狙った、Ｃｏ、Ｚｒ、Ｐｄ、Ｂｉ、Ｉｎ、ＳｂおよびＳｎ等の微量添加も含む。 No. of the invention example 25 to 55 include a Si main phase and a phase composed of Si and Cr, or Si, Cr and Ti. The Si main phase has a Si crystallite size of 30 nm or less, and is composed of Si and Cr, or Si, Cr and Ti. The crystallite size of the compound phase satisfies the condition of 40 nm or less. Further, the total content of at least one additive element selected from the first group consisting of Cu, V, Mn, Fe, Ni, Nb, Zn, and Al is 0.05 at. % To 5 at. %. In addition, the total content of at least one additive element selected from the second group consisting of Mg, B, P, and Ga is 0.05 at. % To 5 at. %. Including a small amount of addition of Co, Zr, Pd, Bi, In, Sb, Sn, etc. aiming at the same effect.
　例えば、Ｎｏ．３９では、Ｓｉ主要相とＳｉとＣｒとＴｉからなる相を含み、Ｓｉの結晶子サイズは１７ｎｍであり、Ｓｉの結晶子サイズが３０ｎｍ以下の条件を満たしている。かつ、ＳｉとＣｒとＴｉからなる化合物相の結晶子サイズが３８ｎｍであり、ＳｉとＣｒとＴｉからなる化合物相の結晶子サイズが４０ｎｍ以下の条件を満足している。加えて、０．０１ａｔ．％のＣｕ、０．０３ａｔ．％のＶ、０．０１ａｔ．％のＭｎ、０．０１ａｔ．％のＦｅ、０．０１ａｔ．％のＮｉ、０．０２ａｔ．％のＺｎおよび０．０２ａｔ．％のＡｌを含んでいる。また、１．０１ａｔ．％のＭｇ、１．７９ａｔ．％のＢ、１．０３ａｔ．％のＰおよび１．１２ａｔ．％のＧａを含んでいる。上記のように本発明条件を満たし、放電容量が１１７９ｍＡｈ／ｇ、５０サイクル後の放電容量維持率が８０％であり、充放電容量とサイクル寿命のいずれも良好な特性を示した。 For example, No. No. 39 includes a Si main phase and a phase composed of Si, Cr, and Ti, the crystallite size of Si is 17 nm, and the crystallite size of Si is 30 nm or less. The crystallite size of the compound phase composed of Si, Cr and Ti is 38 nm, and the crystallite size of the compound phase composed of Si, Cr and Ti satisfies the condition of 40 nm or less. In addition, 0.01 at. % Cu, 0.03 at. % V, 0.01 at. % Mn, 0.01 at. % Fe, 0.01 at. % Ni, 0.02 at. % Zn and 0.02 at. % Al is contained. In addition, 1.01 at. % Mg, 1.79 at. % B, 1.03 at. % P and 1.12 at. % Ga is contained. As described above, the conditions of the present invention were satisfied, the discharge capacity was 1179 mAh / g, the discharge capacity retention rate after 50 cycles was 80%, and both the charge / discharge capacity and the cycle life showed good characteristics.
　比較例Ｎｏ．５６～５８、６８～６９はＣｒを含まないため、本発明条件を満たさない。比較例Ｎｏ．５９～６１、７０はＣｒを含まず、Ｓｉの結晶子サイズが３０ｎｍ以下の条件を満たさないため、本発明条件を満たさない。比較例Ｎｏ．６２～６４、７１はＳｉの結晶子サイズが３０ｎｍ以下の条件を満たすが、Ｃｒを含まず、化合物相の結晶子サイズが４０ｎｍ以下の条件を満たさないため、本発明条件を満たさない。比較例Ｎｏ．６５～６７、７２はＣｒを含まず、Ｓｉの結晶子サイズが３０ｎｍ以下の条件を満たさず、化合物相の結晶子サイズが４０ｎｍ以下の条件も満たさないため、本発明条件を満たさない。 Comparative Example No. Since 56 to 58 and 68 to 69 do not contain Cr, the conditions of the present invention are not satisfied. Comparative Example No. 59 to 61 and 70 do not contain Cr and do not satisfy the condition of the present invention because the crystallite size of Si does not satisfy the condition of 30 nm or less. Comparative Example No. 62-64 and 71 satisfy the condition that the crystallite size of Si is 30 nm or less, but do not contain Cr and do not satisfy the condition of the present invention because the crystallite size of the compound phase does not satisfy the condition of 40 nm or less. Comparative Example No. 65 to 67 and 72 do not contain Cr, do not satisfy the condition of the present invention because the crystallite size of Si does not satisfy the condition of 30 nm or less, and the crystallite size of the compound phase does not satisfy the condition of 40 nm or less.
　比較例Ｎｏ．７３～９０はＳｉとＣｒ、あるいはＳｉとＣｒとＴｉからなる相を含んでおり、ＳｉとＣｒ、あるいはＳｉとＣｒとＴｉからなる化合物相の結晶子サイズが４０ｎｍ以下の条件を満たしているが、Ｓｉ主要相のＳｉ結晶子サイズが３０ｎｍ以下の条件を満たさないため、本発明条件を満たさない。比較例Ｎｏ．９１～１０８はＳｉとＣｒ、あるいはＳｉとＣｒとＴｉからなる相を含んでおり、Ｓｉ主要相のＳｉ結晶子サイズが３０ｎｍ以下の条件を満たしているが、ＳｉとＣｒ、あるいはＳｉとＣｒとＴｉからなる化合物相の結晶子サイズが４０ｎｍ以下の条件を満たさないため、本発明条件を満たさない。比較例Ｎｏ．１０９～１２６はＳｉとＣｒ、あるいはＳｉとＣｒとＴｉからなる相を含んでいるが、Ｓｉ主要相のＳｉ結晶子サイズが３０ｎｍ以下の条件を満たさず、ＳｉとＣｒ、あるいはＳｉとＣｒとＴｉからなる化合物相の結晶子サイズも４０ｎｍ以下の条件を満たしていないため、本発明条件を満たさない。 Comparative Example No. 73 to 90 include a phase composed of Si and Cr or Si, Cr and Ti, and the crystallite size of the compound phase composed of Si and Cr or Si, Cr and Ti satisfies the condition of 40 nm or less. Since the Si crystallite size of the Si main phase does not satisfy the condition of 30 nm or less, the conditions of the present invention are not satisfied. Comparative Example No. 91 to 108 include a phase composed of Si and Cr, or Si, Cr and Ti, and the Si crystallite size of the Si main phase satisfies the condition of 30 nm or less. However, Si and Cr, or Si and Cr Since the crystallite size of the compound phase composed of Ti does not satisfy the condition of 40 nm or less, the present invention condition is not satisfied. Comparative Example No. 109 to 126 include a phase composed of Si and Cr or Si and Cr and Ti, but the Si main phase does not satisfy the condition that the Si crystallite size is 30 nm or less, and Si and Cr, or Si and Cr and Ti. Since the crystallite size of the compound phase consisting of does not satisfy the condition of 40 nm or less, the condition of the present invention is not satisfied.
　以上のように、組織の微細化、優れたイオン伝導性と電子伝導性、応力緩和効果を高める成分の制御と、Ｓｉ相結晶子サイズの制御、あるいはさらに金属間化合物相の結晶子サイズも制御することによって、よりスムーズな充放電反応を行うことができ、充放電サイクル特性の向上を可能とする。さらに、ポリイミド系バインダーを含むことで、Ｃｕ等の集電体との密着性を高め、かつＳｉの体積膨張収縮による応力にも耐えうる強度を有するため、高い充放電容量と優れたサイクル寿命を兼備する極めて優れた効果を有する。 As described above, refinement of the structure, control of components that enhance the excellent ion conductivity and electron conductivity, stress relaxation effect, control of the Si phase crystallite size, and further control of the crystallite size of the intermetallic compound phase By doing so, a smoother charge / discharge reaction can be performed, and charge / discharge cycle characteristics can be improved. Furthermore, by including a polyimide-based binder, it has high strength to withstand current stress due to volume expansion and contraction of Si, and has high charge / discharge capacity and excellent cycle life. It has an extremely excellent effect.

Claims (5)

  1. 　充放電時にリチウムイオンの移動が伴う蓄電デバイス用のＳｉ系合金からなる負極材料であって、
    　前記Ｓｉ系合金からなる負極材料が、ＳｉからなるＳｉ主要相と、ＳｉとＳｉ以外の一種以上の元素からなる化合物相とを有し、
    　前記化合物相が、ＳｉとＣｒ、あるいはＳｉとＣｒとＴｉからなる相を含んでなり、
    　前記Ｓｉ主要相のＳｉ結晶子サイズが３０ｎｍ以下であり、かつ、ＳｉとＣｒ、あるいはＳｉとＣｒとＴｉからなる化合物相の結晶子サイズが４０ｎｍ以下である
    　Ｓｉ系合金からなる負極材料。     A negative electrode material made of a Si-based alloy for an electricity storage device accompanied by movement of lithium ions during charge and discharge,
    The negative electrode material made of the Si-based alloy has a Si main phase made of Si, and a compound phase made of one or more elements other than Si and Si,
    The compound phase comprises a phase composed of Si and Cr or Si, Cr and Ti;
    A negative electrode material comprising a Si-based alloy, wherein the Si crystallite size of the Si main phase is 30 nm or less, and the crystallite size of a compound phase comprising Si and Cr or Si, Cr and Ti is 40 nm or less.
  2. 　前記Ｓｉ系合金からなる負極材料におけるＣｒとＴｉの合計含有量が１２～２１ａｔ．％であり、Ｃｒ％／（Ｃｒ％＋Ｔｉ％）が０．１５～１．００の範囲内である、請求項１に記載のＳｉ系合金からなる負極材料。 The total content of Cr and Ti in the negative electrode material made of the Si-based alloy is 12 to 21 at. The negative electrode material comprising a Si-based alloy according to claim 1, wherein Cr is% and Cr% / (Cr% + Ti%) is in the range of 0.15 to 1.00.
  3. 　前記化合物相が、Ｃｕ、Ｖ、Ｍｎ、Ｆｅ、Ｎｉ、Ｎｂ、ＺｎおよびＡｌからなる第１の群から選択される少なくとも一種以上の元素を含み、前記第１の群から選択される元素の合計含有量が０．０５ａｔ．％～５ａｔ．％である、請求項１または２に記載のＳｉ系合金からなる負極材料。 The compound phase includes at least one element selected from the first group consisting of Cu, V, Mn, Fe, Ni, Nb, Zn, and Al, and the total of the elements selected from the first group The content is 0.05 at. % To 5 at. The negative electrode material which consists of Si type alloy of Claim 1 or 2 which is%.
  4. 　前記化合物相が、Ｍｇ、Ｂ、ＰおよびＧａからなる第２の群から選択される少なくとも一種以上の元素を含み、前記第２の群から選択される元素の合計含有量が０．０５ａｔ．％～５ａｔ．％である、請求項１～３のいずれか一項に記載のＳｉ系合金からなる負極材料。 The compound phase contains at least one element selected from the second group consisting of Mg, B, P and Ga, and the total content of elements selected from the second group is 0.05 at. % To 5 at. The negative electrode material comprising a Si-based alloy according to any one of claims 1 to 3, wherein
  5. 　請求項１～４のいずれか１項に記載のＳｉ系合金からなる負極材料と、ポリイミド系バインダーとを含む電極。 An electrode comprising a negative electrode material comprising the Si-based alloy according to any one of claims 1 to 4 and a polyimide-based binder.
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