WO2015136684A1 - Matériau actif d'électrode négative pour batteries secondaires au lithium-ion, procédé de fabrication de matériau actif d'électrode négative pour batteries secondaires au lithium-ion et batterie secondaire au lithium-ion - Google Patents

Matériau actif d'électrode négative pour batteries secondaires au lithium-ion, procédé de fabrication de matériau actif d'électrode négative pour batteries secondaires au lithium-ion et batterie secondaire au lithium-ion Download PDF

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WO2015136684A1
WO2015136684A1 PCT/JP2014/056824 JP2014056824W WO2015136684A1 WO 2015136684 A1 WO2015136684 A1 WO 2015136684A1 JP 2014056824 W JP2014056824 W JP 2014056824W WO 2015136684 A1 WO2015136684 A1 WO 2015136684A1
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lithium ion
ion secondary
negative electrode
active material
electrode active
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PCT/JP2014/056824
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English (en)
Japanese (ja)
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岡井　誠
京谷　隆
康人 干川
孝文 石井
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株式会社日立製作所
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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
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • 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
    • H01M4/366—Composites as layered products
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a negative electrode active material for a lithium ion secondary battery, a method for producing a negative electrode active material for a lithium ion secondary battery, and a lithium ion secondary battery.
  • Graphite-based carbon materials are widely used as negative electrode active materials for lithium ion secondary batteries.
  • the stoichiometric composition when graphite is filled with lithium ions is LiC 6 , and its theoretical capacity can be calculated as 372 mAh / g.
  • the stoichiometric composition when silicon is filled with lithium ions is Li 22 Si 5 , and the theoretical capacity can be calculated as 4197 mAh / g.
  • silicon is an attractive material that can be filled with 11.3 times as much lithium as graphite.
  • Patent Document 1 describes an example of doping silicon nanowires.
  • Patent Document 1 only describes a conductive inner core wire (for example, to provide conductivity necessary for electron transfer) (which may or may not be doped). There is no description about the effect on the high-speed charge / discharge of the lithium ion secondary battery in the case where silicon nanowire is used as the negative electrode active material for the secondary battery and specific electrical conductivity or electrical conductivity is imparted.
  • An object of the present invention is to provide a negative electrode active material for a lithium ion secondary battery having a desired electric conductivity.
  • a negative electrode active material for a lithium ion secondary battery having a desired electrical conductivity can be provided.
  • 1 schematically illustrates the structure of a negative electrode active material for a lithium ion secondary battery according to an embodiment of the present invention.
  • 1 schematically illustrates the structure of a negative electrode active material for a lithium ion secondary battery according to an embodiment of the present invention.
  • It is a scanning electron micrograph of the impurity doped silicon nanowire which interrupted growth. It is a scanning electron micrograph of the impurity doped silicon nanowire grown on the graphite surface.
  • 2 is a transmission electron micrograph of impurity-doped silicon nanowires grown on a graphite surface.
  • 1 schematically illustrates the structure of a negative electrode active material for a lithium ion secondary battery according to an embodiment of the present invention.
  • 1 schematically illustrates the structure of a negative electrode active material for a lithium ion secondary battery according to an embodiment of the present invention.
  • 1 schematically illustrates the structure of a negative electrode active material for a lithium ion secondary battery according to an embodiment of the present invention. It is a scanning electron micrograph of impurity-doped silicon nanowires coated with carbon. It is a scanning electron micrograph of impurity-doped silicon nanowires coated with carbon. It is a transmission electron micrograph of impurity-doped silicon nanowires coated with carbon. It is a transmission electron micrograph of impurity-doped silicon nanowires coated with carbon.
  • FIG. 1 shows a calculation model according to an embodiment of the present invention.
  • the silicon nanowire 110 exists in contact with the surface of the carbon substrate 100, and the applied voltage at the base of the silicon nanowire 110 is V.
  • the current I flows from the root toward the tip of the silicon nanowire 110, and the voltage drop at the tip of the silicon nanowire 110 is ⁇ V. It is assumed that the voltage drop amount ⁇ V is entirely due to the electric resistance of the silicon nanowire 110.
  • the voltage drop amount ⁇ V is given by Equation (1).
  • L is the length of the silicon nanowire 110
  • ⁇ is the electrical resistivity of the silicon nanowire 110
  • R Si is the radius of the silicon nanowire 110
  • ⁇ is the circumference.
  • the current I is given by Equation (2).
  • Equation (3) D is the density of silicon
  • R is the number of lithium that can be filled per silicon
  • F is the Faraday constant
  • x is the charging rate, that is, 1 / x hours.
  • M is the atomic weight of silicon.
  • R v is expressed by Equation (4).
  • Equation (5) The results calculated using Equation (5) are shown in FIG.
  • the electrical conductivity of non-doped silicon is about 0.001 S / m, it is desirable to improve the electrical conductivity by doping the silicon nanowire 110 in order to achieve the above electrical conductivity.
  • the length of the silicon nanowire 110 depends on the growth conditions, but is considered not to exceed 5 ⁇ m. Moreover, if the charging speed is assumed to be 10 C, it is considered sufficient for most applications. From the above, it is considered practically sufficient if the electrical conductivity of the silicon nanowire 110 is 10 S / m or more, particularly 100 S / m.
  • FIG. 3 schematically represents the structure of a negative electrode active material for a lithium ion secondary battery according to an embodiment of the present invention.
  • the negative electrode active material 1000 is composed of impurity-doped silicon nanowires 200.
  • the diameter D si of the impurity-doped silicon nanowire 200 doped with impurities is 2 nm or more and 100 nm or less.
  • the diameter D si of the impurity-doped silicon nanowire 200 is less than 2 nm, it may be naturally oxidized in the atmosphere and become SiO 2 as a whole. In this case, it may not function as a negative electrode active material for a lithium ion secondary battery. There is.
  • the diameter D si of the impurity-doped silicon nanowire 200 is more than 100 nm, was destroyed by mechanical strain at the time of repeated charging and discharging of the lithium ion, there is a possibility that the electric capacity of the lithium ion secondary battery is depleted .
  • the diameter of the silicon nanowire sufficiently thin, such as 100 nm or less, it is possible to suppress the mechanical structural breakdown of silicon particles that occurs during repeated filling and releasing of lithium ions. And since the increase of the irreversible capacity resulting from structural destruction can be reduced significantly, the lifetime improvement of a lithium ion secondary battery is realizable.
  • the length of the impurity-doped silicon nanowire 200 is not limited, but a length of several microns to several tens of microns is considered optimal for the electrode manufacturing process.
  • High electrical conductivity can be imparted by doping silicon nanowires with impurities. Thereby, even when the silicon nanowire is broken in the middle or peeled off from the carbon substrate, electrical conduction with the current collector can be ensured and electrical isolation can be prevented. Due to this effect, the increase in irreversible capacity can be significantly reduced, and thus the life of the lithium ion secondary battery can be extended.
  • a dopant for the silicon nanowire a general dopant for a silicon substrate can be used. Among them, it is desirable to dope elements such as boron, phosphorus, arsenic, and nitrogen as dopants.
  • the doping amount is desirably 10 ⁇ 10 15 atoms / cm 3 or more, and the electric conductivity after doping is desirably 10 S / m or more, and particularly desirably 100 S / m or more. If the electrical conductivity is lower than that, it may not be possible to improve the fast charge / discharge characteristics.
  • a method of introducing ultrafine structures such as nanoparticles and nanowires is effective. This is because the specific surface area of the silicon material increases due to the introduction of the ultrafine structure, so lithium ions can be filled more quickly. This is because release is possible.
  • a method of imparting high electrical conductivity to the silicon material itself is effective. This is because the voltage drop inside the silicon material can be greatly reduced, and as a result, the diffusion rate of lithium ions in silicon can be increased.
  • FIG. 17 shows the internal structure of a lithium ion secondary battery according to an embodiment of the present invention.
  • 1401 is a positive electrode
  • 1402 is a separator
  • 1403 is a negative electrode
  • 1404 is a battery can
  • 1405 is a positive current collecting tab
  • 1406 is a negative current collecting tab
  • 1407 is an inner lid
  • 1408 is an internal pressure release valve
  • 1409 is a gasket
  • 1410 is a positive temperature coefficient (PTC) resistive element
  • 1411 is a battery lid.
  • the battery lid 1411 is an integrated part including an inner lid 1407, a pressure release valve 1408, a gasket 1409, and a positive temperature coefficient resistance element 1410.
  • the positive electrode 1401 is manufactured by the following procedure. LiMn 2 O 4 is used as the positive electrode active material. To 85.0 wt% of the positive electrode active material, 7.0 wt% and 2.0 wt% of graphite powder and acetylene black are added as conductive materials, respectively. Further, a solution dissolved in 6.0 wt% polyvinylidene fluoride (hereinafter abbreviated as PVDF) and 1-methyl-2-pyrrolidone (hereinafter abbreviated as NMP) is added as a binder, and the mixture is mixed with a planetary mixer. Further, air bubbles in the slurry are removed under vacuum to prepare a homogeneous positive electrode mixture slurry.
  • PVDF polyvinylidene fluoride
  • NMP 1-methyl-2-pyrrolidone
  • This slurry is uniformly and evenly applied to both surfaces of an aluminum foil having a thickness of 20 ⁇ m using an applicator. After the application, compression molding is performed by a roll press so that the electrode density is 2.55 g / cm 3 . This is cut with a cutting machine to produce a positive electrode 1401 having a thickness of 100 ⁇ m, a length of 900 mm, and a width of 54 mm.
  • the negative electrode 1403 can be manufactured by the following procedure.
  • the negative electrode active material the negative electrode active material for a lithium ion secondary battery in one embodiment of the present invention can be used.
  • a solution prepared by dissolving 5.0 wt% PVDF as a binder in NMP is added to 95.0 wt% of the material. It is mixed with a planetary mixer, and bubbles in the slurry are removed under vacuum to prepare a homogeneous negative electrode mixture slurry.
  • This slurry is uniformly and evenly applied to both surfaces of a rolled copper foil having a thickness of 10 ⁇ m with an applicator.
  • the electrode is compression-molded by a roll press to make the electrode density 1.3 g / cm 3 . This is cut with a cutting machine to produce a negative electrode 1403 having a thickness of 110 ⁇ m, a length of 950 mm, and a width of 56 mm.
  • the positive electrode current collecting tab 1405 and the negative electrode current collecting tab 1406 are ultrasonically welded to the positive electrode 1401 produced as described above and the uncoated part (current collector exposed surface) of the negative electrode 1403, respectively.
  • the positive electrode current collecting tab 1405 can be an aluminum lead piece
  • the negative electrode current collecting tab 1406 can be a nickel lead piece.
  • a separator 1402 made of a porous polyethylene film having a thickness of 30 ⁇ m is inserted into the positive electrode 1401 and the negative electrode 1403, and the positive electrode 1401, the separator 1402, and the negative electrode 1403 are wound.
  • the wound body is accommodated in the battery can 1404, and the negative electrode current collecting tab 1406 is connected to the bottom of the battery can 1404 by a resistance welder.
  • the positive electrode current collecting tab 1405 is connected to the bottom surface of the inner lid 1407 by ultrasonic welding.
  • a non-aqueous electrolyte is injected.
  • the solvent of the electrolytic solution is composed of, for example, ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC), and the volume ratio is 1: 1: 1.
  • the electrolyte is LiPF 6 at a concentration of 1 mol / L (about 0.8 mol / kg). Such an electrolytic solution is dropped from above the electrode group, and the battery lid 1411 is caulked and sealed in the battery can 1404 to obtain a lithium ion secondary battery.
  • FIG. 4 schematically represents the structure of a negative electrode active material for a lithium ion secondary battery according to an embodiment of the present invention.
  • the negative electrode active material 1000 is composed of impurity-doped silicon nanowires 200 and graphite 300.
  • impurity-doped silicon nanowires 200 were formed on the surface of graphite 300.
  • the impurity-doped silicon nanowire 200 is directly bonded to the surface of the graphite 300 and grows from the surface of the graphite 300.
  • FIG. 5 is a scanning electron micrograph of an impurity-doped silicon nanowire whose growth has been interrupted.
  • an infinite number of impurity-doped silicon nanoparticles having a diameter of several tens of nm were present on the surface of the graphite 300. From this fact, it can be inferred that silicon nanoparticles first grow on the surface of graphite 300 and the silicon nanoparticles grow into impurity-doped silicon nanowires 200.
  • FIG. 6 is a scanning electron micrograph of impurity-doped silicon nanowires grown on the graphite surface.
  • the impurity-doped silicon nanowires 200 can be manufactured very densely.
  • This sample was a composite material containing silicon and carbon, and the weight ratio of silicon measured by thermogravimetry was 23 wt%. The weight ratio of silicon can be adjusted by changing the growth conditions.
  • FIG. 7 is a transmission electron micrograph of the same sample. Since the diameter is 30 nm and the inside shows silicon lattice stripes, the silicon nanowire 200 is considered to have crystallinity, particularly a polycrystalline structure. When silicon nanowire 200 has crystallinity, the diffusion rate of lithium ions increases. As a result, the charging and discharging speed of lithium ions is fast, and the high-speed charge / discharge characteristics are improved. In addition, a natural oxide film layer of less than 3 nm exists on the surface of the impurity-doped silicon nanowire 200.
  • the impurity-doped silicon nanowire 200 is directly bonded to the surface of the graphite 300, and a chemical bond is formed between the silicon atom of the impurity-doped silicon nanowire 200 and the carbon atom on the surface of the graphite 300 at the bonding surface. It is conceivable that.
  • the graphite 300 used as the base material for the growth of the impurity-doped silicon nanowire 200 can use any kind and form of graphite such as artificial graphite, natural graphite, graphite oxide, and thermally expanded graphite. is there.
  • FIG. 8 schematically represents the structure of a negative electrode active material for a lithium ion secondary battery according to an embodiment of the present invention.
  • the negative electrode active material 1000 is composed of impurity-doped silicon nanowires 200 and carbon nanotubes 400.
  • the present embodiment is different from the second embodiment in that carbon nanotubes 400 are used as a carbon base material and impurity-doped silicon nanowires 200 are grown on the surface thereof.
  • the carbon nanotube 400 was used as the base material for the growth of the impurity-doped silicon nanowire 200, but it is possible to use any form of carbon-based nanostructure such as carbon nanohorn, acetylene black, ketjen black, etc. It is.
  • FIG. 9 schematically represents the structure of a negative electrode active material for a lithium ion secondary battery according to an embodiment of the present invention.
  • the impurity-doped silicon nanowire 200 is grown on the carbon substrate, and then the carbon substrate and the impurity-doped silicon nanowire 200 are separated, and only the impurity-doped silicon nanowire 200 is used as the negative electrode material.
  • the weight ratio of silicon to the total weight can be greatly increased, so that the electric capacity can be dramatically increased.
  • FIG. 10 schematically represents the structure of a negative electrode active material for a lithium ion secondary battery according to an embodiment of the present invention.
  • the negative electrode active material 1000 is composed of impurity-doped silicon nanowires 200 and an electrically conductive carbon thin film 500.
  • the negative electrode active material 1000 has a structure in which the surface of the impurity-doped silicon nanowire 200 is partially or entirely covered with the electrically conductive carbon thin film 500.
  • the electrically conductive carbon thin film 500 is formed on the surface of the impurity-doped silicon nanowire 200.
  • the electrically conductive carbon thin film 500 has a structure in which nanographene is laminated in multiple layers, and has an electrical conductivity of 1000 S / m or more.
  • electrical conductivity can be added to the impurity-doped silicon nanowire 200. Accordingly, even when the impurity-doped silicon nanowire 200 is broken in the middle or when the impurity-doped silicon nanowire 200 is peeled off from the electrically conductive carbon thin film 500, electrical conduction with the current collector is ensured and electrical isolation is achieved. Therefore, the irreversible capacity of the lithium ion secondary battery can be reduced.
  • the film thickness L c of the electrically conductive carbon thin film 500 is not less than 0.2 nm and not more than 100 nm. Thickness L c of electrically conductive carbon film 500, is less than 0.2 nm, the coating strength is inadequate, there is a possibility that peeling partially, in which case, to ensure a sufficient electrical conductivity It may not be possible.
  • the thickness L c of electrically conductive carbon film 500 if it exceeds 100 nm, it is difficult to the weight of silicon to the total weight 20 wt%, can not be able to consequently obtain a sufficient electric capacity There is sex.
  • FIG. 11 is a scanning electron micrograph of an impurity-doped silicon nanowire coated with carbon. In this way, the carbon-coated impurity-doped silicon nanowire 200 can be grown very densely.
  • FIG. 12 is an enlarged photograph of the same sample. It is considered that the surface of the carbon-doped impurity-doped silicon nanowire 200 is uniformly covered with the electrically conductive carbon thin film 500.
  • FIG. 13 is a transmission electron micrograph of carbon-coated impurity-doped silicon nanowires.
  • an impurity-doped silicon nanowire 200 having a lattice pattern can be observed.
  • an electrically conductive carbon thin film 500 having a nanographene multilayer structure oriented along the axial direction of the impurity-doped silicon nanowire 200 can be observed. Since the electrically conductive carbon thin film 500 is oriented along the axial direction of the impurity-doped silicon nana wire 200, the electrically conductive carbon thin film 500 becomes a strong film that is difficult to peel off.
  • the diameter of the impurity-doped silicon nanowire 200 was 18 nm, and the thickness of the electrically conductive carbon thin film 500 was 6.44-8.17 nm.
  • FIG. 14 shows a transmission electron micrograph of another sample.
  • FIG. 14 is a transmission electron micrograph of impurity-doped silicon nanowires coated with carbon.
  • the diameter of the impurity-doped silicon nanowire 200 was 18 nm, and the thickness of the electrically conductive carbon thin film 500 was 10 nm.
  • FIG. 15 is a schematic diagram of a thermal vapor deposition apparatus for forming impurity-doped silicon nanowires on the surface of a carbon substrate.
  • Liquid silicon tetrachloride was used as the silicon raw material, and was introduced into the reactor by bubbling with hydrogen gas (the bottom line on the left in FIG. 15).
  • the vapor pressure of silicon tetrachloride at 20 ° C. is 30 kPa, and when bubbling is introduced, the amount of silicon tetrachloride introduced is 34%. Therefore, when introducing a smaller amount of silicon tetrachloride, it is necessary to cool the silicon tetrachloride or to provide another hydrogen gas line (middle line on the left in FIG. 15). In this example, a hydrogen line that was not bubbled was provided separately, joined with the bubbling line, and introduced into the reactor.
  • a dopant line (the uppermost line on the left in FIG. 15) was provided, and an organic compound containing elements such as boron, phosphorus, arsenic, and nitrogen as dopants was introduced as a dopant raw material.
  • the organic compound was a gas, it was introduced by mixing with an inert gas such as argon. In the case of a liquid, it was introduced by bubbling with an inert gas such as argon.
  • boron-containing organic compounds include various boronic esters
  • phosphorus-containing organic compounds include various phosphonic esters
  • various phosphoric esters include various phosphites
  • nitrogen-containing organic compounds include various amines, various amides, various types It is possible to use imine and various nitriles.
  • the procedure for growing carbon-coated impurity-doped silicon nanowires is as follows. Put the carbon substrate in the sample boat and install it near the center of the reactor. As the carbon substrate, any form of carbon material such as graphite, thermally expanded graphite oxide, graphite oxide, carbon nanotube, carbon nanohorn, etc. can be used.
  • the reactor is made of quartz and has a diameter of 5 cm and a length of 40 cm. In the middle left hydrogen line of FIG. 15, hydrogen is allowed to flow at a flow rate of 200 mL / min, and the lower bubbling hydrogen line is closed, and the growth furnace is heated from room temperature to 1000 ° C. at a rate of 10 ° C./min. did.
  • the flow rate of the upper hydrogen line was changed to 100 mL / min, and the flow rate of the hydrogen line of the lower bubbling hydrogen line was set to 100 mL / min.
  • 17% silicon tetrachloride can be introduced.
  • a dopant raw material was introduced from the dopant line.
  • the dopant line and the lower bubbling hydrogen line were closed and the flow rate of the upper hydrogen line was changed to 200 mL / min and held at 1000 ° C. for 30 minutes. Thereby, it is possible to produce the impurity-doped silicon nanowire 200 having a diameter of 20 nm on the surface of the carbon substrate.
  • the diameter and growth weight of the impurity-doped silicon nanowire 200 can be changed by changing the temperature at the time of growth of the impurity-doped silicon nanowire 200, the amount of silicon tetrachloride introduced, and the growth time. Moreover, it is possible to change the doping amount to the impurity-doped silicon nanowire 200 by changing the introduction amount of the dopant raw material.
  • both hydrogen lines were closed, and argon gas (the argon line is not shown in FIG. 15) was flowed at a flow rate of 200 mL / min, the temperature was lowered at a rate of 10 ° C./min, and the temperature was lowered to 800 ° C.
  • propylene gas (the propylene line is not shown in FIG. 15) was introduced at a flow rate of 10 mL / min, and at the same time the argon gas flow rate was set to 190 mL / min, It grew for 1 hour.
  • the production of the impurity-doped silicon nanowire 200 and the subsequent production of the electrically conductive carbon thin film 500 were continuously performed. In this way, the production of the impurity-doped silicon nanowire 200 and the subsequent production of the electrically conductive carbon thin film 500 are continuously performed, thereby preventing the formation of a natural oxide film and eliminating the process of reducing and removing the natural oxide film. become.
  • the impurity-doped silicon nanowire 200 is grown, the impurity-doped silicon nanowire 200 is once taken out into the air and then heat-treated in a reducing atmosphere to remove the natural oxide film on the surface of the impurity-doped silicon nanowire 200, and then the electrically conductive carbon thin film 500 is produced. It is also possible. The productivity is improved by growing the impurity-doped silicon nanowires 200 and producing the electrically conductive carbon thin film 500 in separate reactors. Further, the diameter and growth weight of the impurity-doped silicon nanowire 200 can be changed by changing the temperature at the time of growth of the impurity-doped silicon nanowire 200, the amount of silicon tetrachloride introduced, and the growth time.
  • the film thickness of the electrically conductive carbon thin film 500 can be controlled.
  • various hydrocarbon gases such as acetylene gas, propane gas, and methane gas can be used for producing the electrically conductive carbon thin film 500.
  • FIG. 16 shows the calculation result of the dependence of the negative electrode capacitance on the weight ratio Si / (Si + C) of silicon with respect to the total weight of the composite material of silicon and carbon.
  • the stoichiometric composition when filled with lithium ions was assumed to be LiC 6 and its electric capacity was 372 mAh / g.
  • the stoichiometric composition when lithium ions are filled is assumed to be Li 15 Si 4, and the electric capacity is assumed to be 3577 mAh / g, and Li 22 Si 5 is assumed, It calculated about the case where the electric capacity was 4197 mAh / g.
  • the weight ratio is 20% or more, particularly 40% or more, more preferably 80%, with respect to the negative electrode active material for lithium ion secondary battery. It is desirable to contain more than% silicon.

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Abstract

L'invention porte sur un matériau actif d'électrode négative pour batteries secondaires au lithium-ion, qui est pourvu d'une conductivité électrique souhaitée, et qui peut être fourni en utilisant un matériau actif d'électrode négative pour batteries secondaires au lithium-ion contenant des nanofils de silicium qui sont dopés avec une impureté et ont une conductivité électrique de 10 S/m ou plus. Les caractéristiques d'une batterie secondaire au lithium-ion peuvent être améliorées en utilisant ce matériau actif d'électrode négative pour batteries secondaires au lithium-ion dans la batterie secondaire au lithium-ion.
PCT/JP2014/056824 2014-03-14 2014-03-14 Matériau actif d'électrode négative pour batteries secondaires au lithium-ion, procédé de fabrication de matériau actif d'électrode négative pour batteries secondaires au lithium-ion et batterie secondaire au lithium-ion WO2015136684A1 (fr)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2016021320A (ja) * 2014-07-14 2016-02-04 住友金属鉱山株式会社 非水電解質二次電池用負極活物質及びその製造方法
CN106532010A (zh) * 2016-12-21 2017-03-22 上海杉杉科技有限公司 一种硅‑氮化硅‑碳复合材料及制备方法及应用方法

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