WO2021005689A1 - Matériau actif d'électrode négative pour batterie secondaire au lithium-ion, électrode négative pour batterie secondaire au lithium-ion, batterie secondaire au lithium-ion et procédé de fabrication de matériau actif d'électrode négative pour batterie secondaire au lithium-ion - Google Patents

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

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WO2021005689A1
WO2021005689A1 PCT/JP2019/027011 JP2019027011W WO2021005689A1 WO 2021005689 A1 WO2021005689 A1 WO 2021005689A1 JP 2019027011 W JP2019027011 W JP 2019027011W WO 2021005689 A1 WO2021005689 A1 WO 2021005689A1
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Prior art keywords
negative electrode
active material
electrode active
ion secondary
secondary battery
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PCT/JP2019/027011
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English (en)
Japanese (ja)
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陽 安田
英介 羽場
望 陳
達也 西田
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昭和電工マテリアルズ株式会社
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Priority to JP2021530380A priority Critical patent/JPWO2021005689A1/ja
Priority to PCT/JP2019/027011 priority patent/WO2021005689A1/fr
Publication of WO2021005689A1 publication Critical patent/WO2021005689A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/113—Silicon oxides; Hydrates thereof
    • 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
    • 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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • 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
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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
    • 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 method for producing a negative electrode active material for a lithium ion secondary battery, a negative electrode for a lithium ion secondary battery, a lithium ion secondary battery, and a negative electrode active material for a lithium ion secondary battery.
  • graphite is mainly used as the negative electrode active material of lithium ion secondary batteries, but it is known that graphite has a theoretical capacity limit of 372 mAh / g in discharge capacity.
  • negative electrode active materials that can achieve even higher capacities for lithium-ion secondary batteries. Development is desired.
  • Patent Document 1 a peak derived from Si (111) is observed in X-ray diffraction, and the size of a silicon crystal obtained by the Scheller method based on the half-value width of the diffraction line is 1 to 500 nm.
  • a negative electrode active material in which the surface of particles having a structure in which fine crystals of silicon are dispersed in a silicon-based compound is coated with carbon.
  • silicon microcrystals or fine particles are dispersed in an inert and strong substance such as silicon dioxide, and carbon for imparting conductivity to at least a part of the surface is fused. It is said that by allowing the surface to be conductive, the structure becomes stable against changes in the volume of silicon due to occlusion and release of lithium, and as a result, long-term stability is obtained and the initial efficiency is improved. ing.
  • the surface of the silicon oxide particles is coated with a graphite film, the graphite coating amount is 3 to 40% by weight, the BET specific surface area is 2 to 30 m 2 / g, and the graphite film is Raman.
  • Negative electrode active materials having a spectrum peculiar to the graphite structure are disclosed in which Raman shifts in the spectral spectrum are around 1330 cm -1 and 1580 cm -1 .
  • the lithium ion secondary that can reach the characteristic level required by the market by controlling the physical properties of the graphite film that coats the surface of the material that can occlude and release lithium ions within a specific range. It is said that the negative electrode of the battery can be obtained.
  • Patent Document 3 discloses a negative electrode active material in which the surface of silicon oxide particles represented by the general formula SiO x is coated with a carbon film treated with thermal plasma. According to the technique of Patent Document 3, it is said that a negative electrode active material having excellent cycle characteristics can be obtained by solving the expansion of an electrode and the expansion of a battery due to gas generation, which are drawbacks of silicon oxide.
  • the present invention has been made in view of the above requirements, and is a negative electrode active material for a lithium ion secondary battery capable of improving the initial charge / discharge efficiency of the lithium ion secondary battery and suppressing deterioration, and lithium using the negative electrode active material.
  • An object of the present invention is to provide a negative electrode for an ion secondary battery, a lithium ion secondary battery, and a method for producing a negative electrode active material for a lithium ion secondary battery.
  • ⁇ 2> The negative electrode active material for a lithium ion secondary battery according to ⁇ 1>, wherein the proportion of particles having a particle diameter of 3.0 ⁇ m or more is 50% or more on a volume basis.
  • ⁇ 3> The lithium ion secondary battery according to ⁇ 1> or ⁇ 2>, wherein the carbon content is 0.5% by mass to 10.0% by mass of the total of the silicon oxide particles and the carbon.
  • Negative electrode active material for. ⁇ 4> The negative electrode active material for a lithium ion secondary battery according to any one of ⁇ 1> to ⁇ 3>, which has a BET specific surface area of 0.1 m 2 / g to 15 m 2 / g.
  • the ratio ( PSi / PSiO2 ) to the X-ray diffraction peak intensity ( PSi ) of ° to 29 ° is in the range of 1.0 to 2.6.
  • Negative electrode for lithium-ion secondary batteries. A lithium ion secondary battery comprising a positive electrode ⁇ 7>, a negative electrode for a lithium ion secondary battery according to ⁇ 6>, and an electrolyte.
  • a method for producing a negative electrode active material for a lithium ion secondary battery which comprises a step of adhering carbon to a part or all of the surface of silicon oxide particles.
  • the negative electrode active material for a lithium ion secondary battery is laser diffraction.
  • the particle size (vD50) when the accumulation from the small diameter side is 50% on a volume basis and the particle size when the accumulation from the small diameter side is 50% on a number basis (vD50).
  • a negative electrode active material for a lithium ion secondary battery capable of improving the initial charge / discharge efficiency and suppressing deterioration of the lithium ion secondary battery, a negative electrode for a lithium ion secondary battery using the active material, and lithium.
  • a method for producing an ion secondary battery and a negative electrode active material for a lithium ion secondary battery is provided.
  • the term "process” includes not only a process independent of other processes but also the process if the purpose of the process is achieved even if the process cannot be clearly distinguished from the other process. ..
  • the numerical range indicated by using "-" includes the numerical values before and after "-" as the minimum value and the maximum value, respectively.
  • the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of another numerical range described stepwise. ..
  • the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples.
  • each component may contain a plurality of applicable substances.
  • the content rate or content of each component is the total content rate or content of the plurality of substances present in the composition unless otherwise specified.
  • a plurality of types of particles corresponding to each component may be contained.
  • the particle size of each component means a value for a mixture of the plurality of particles present in the composition unless otherwise specified.
  • the term "layer” or “membrane” is used only in a part of the region in addition to the case where the layer or the membrane is formed in the entire region when the region in which the layer or the membrane exists is observed. The case where it is formed is also included.
  • laminated refers to stacking layers, and two or more layers may be bonded or the two or more layers may be removable.
  • the negative electrode active material for the lithium ion secondary battery of the present embodiment (hereinafter, may be simply referred to as “negative electrode active material”) is present on the silicon oxide particles and a part or all of the surface of the silicon oxide particles.
  • Particle size (vD50) when the accumulation from the small diameter side is 50% on a volume basis in the particle size distribution curve obtained by the laser diffraction / scattering method, and the accumulation from the small diameter side is 50 on a number basis.
  • the ratio (vD50 / nD50) to the particle size (nD50) when it becomes% is 1.3 or more.
  • vD50 / nD50 in the particle size distribution of the negative electrode active material tends to increase as the proportion of small-diameter particles increases.
  • the value of vD50 / nD50 is preferably 1.4 or more, more preferably 1.5 or more, and particularly preferably 2.0 or more.
  • the upper limit of the value of vD50 / nD50 is not particularly limited, but is preferably 5.0 or less, more preferably 4.0 or less, and further preferably 3.0 or less. When vD50 / nD50 is 5.0 or less, gas generation due to the reaction between the negative electrode active material and the electrolytic solution tends to be suppressed.
  • the negative electrode active material has a particle size (vD10) when the cumulative amount from the small diameter side is 10% on a volume basis in the particle size distribution curve obtained by the laser diffraction / scattering method, and 10% on a number basis.
  • the ratio (vD10 / nD10) to the particle size (nD10) at that time is preferably 1.2 or more, more preferably 1.3 or more, and further preferably 1.4 or more.
  • the upper limit of the value of vD10 / nD10 is not particularly limited, but is preferably 5.0 or less, more preferably 4.0 or less, and further preferably 3.0 or less.
  • the negative electrode active material has a particle size (vD90) when the accumulation from the small diameter side is 90% on a volume basis in the particle size distribution curve obtained by the laser diffraction / scattering method, and the accumulation from the small diameter side is 90% on a number basis.
  • the ratio (vD90 / nD90) to the particle size (nD90) at that time is preferably 1.2 or more, more preferably 1.3 or more, and further preferably 1.4 or more.
  • the upper limit of the value of vD90 / nD90 is not particularly limited, but is preferably 5.0 or less, more preferably 4.0 or less, and further preferably 3.0 or less.
  • the proportion of particles having a particle diameter of 3.0 ⁇ m or more is preferably 50% or more on a volume basis. That is, in the particle size distribution curve obtained by the laser diffraction / scattering method, the particle size (vD50, hereinafter also referred to as volume average particle size) when the accumulation from the small diameter side is 50% on a volume basis is 3.0 ⁇ m or more. Is preferable.
  • the upper limit of the volume average particle size of the negative electrode active material is not particularly limited, but is preferably 20.0 ⁇ m or less, more preferably 15.0 ⁇ m or less, and further preferably 10.0 ⁇ m or less.
  • At least a part of the negative electrode active material may form secondary particles. It is considered that the secondary particles of the negative electrode active material are formed, for example, by combining some particles when carbon is attached to the surface of the silicon oxide particles. The degree of formation of secondary particles can be controlled by, for example, the particle size distribution of silicon oxide particles before carbon is attached (ratio of small-diameter particles, etc.), the method of attaching carbon (type of device, etc.), and the like. ..
  • the "secondary particles” mean particles formed by fixing a plurality of particles to the extent that they do not separate under normal use conditions of the negative electrode active material.
  • Whether or not at least a part of the negative electrode active material forms secondary particles can be determined by, for example, observation with an electron microscope.
  • the state of each secondary particle is not particularly limited.
  • secondary particles in a state in which particles having a particle diameter of 1.0 ⁇ m or less are attached to particles having a particle diameter of 5.0 ⁇ m or more may be included.
  • the ratio is not particularly limited. For example, it may be 20% by mass or less of the whole silicon oxide particles, 10% by mass or less, or 5% by mass or less.
  • the particle size distribution and particle size of the negative electrode active material including the secondary particles mean the values measured in that state (not the state of the primary particles) of the particles forming the secondary particles.
  • the method of adjusting the particle size so that the negative electrode active material satisfies the above-mentioned particle size distribution condition is not particularly limited. For example, after pulverizing the massive silicon oxide as described in Examples described later, it can be adjusted by sieving or the like as necessary.
  • the negative electrode active material of the present embodiment occupies a relatively large proportion of small-diameter particles, it can be expected to realize, for example, a reduction in the amount of fine powder generated during production and omission of a step of removing fine powder. Therefore, it is also advantageous from the viewpoint of manufacturing efficiency.
  • the silicon oxide constituting the silicon oxide particles may be an oxide containing a silicon element, and examples thereof include silicon oxide, silicon dioxide, and silicon sulfite.
  • the silicon oxide contained in the silicon oxide particles may be only one type or a combination of two or more types.
  • silicon oxide and silicon dioxide are generally represented as silicon monoxide (SiO) and silicon dioxide (SiO 2 ), respectively, but in a surface state (eg, the presence of an oxide film) or
  • the actual measurement value (or conversion value) of the contained element may be represented by the composition formula SiO x (x is 0 ⁇ x ⁇ 2), and in this case as well, the silicon oxide according to the present disclosure is used.
  • the value of x in the composition formula can be calculated, for example, by quantifying the oxygen contained in the silicon oxide by the inert gas melting-non-dispersion infrared absorption method.
  • SiO-C particles silicon oxide particles in which carbon is present on a part or all of the surface may be referred to as "SiO-C particles".
  • examples of carbon present on a part or all of the surface of the silicon oxide particles include graphite, amorphous carbon and the like.
  • the organic substances and conductive particles described later do not correspond to "carbon" in the present disclosure.
  • the mode in which carbon is present on a part or all of the surface of the silicon oxide particles is not particularly limited. For example, continuous or discontinuous coating and the like can be mentioned.
  • the presence or absence of carbon in the negative electrode active material can be confirmed by, for example, laser Raman spectroscopy with an excitation wavelength of 532 nm.
  • the carbon content is preferably 0.5% by mass to 10.0% by mass of the total of the silicon oxide particles and carbon. With such a configuration, the initial discharge capacity and the initial charge / discharge efficiency tend to be further improved.
  • the carbon content is more preferably 1.0% by mass to 9.0% by mass, further preferably 2.0% by mass to 8.0% by mass, and particularly preferably 3.0% by mass to 7.0% by mass. ..
  • the carbon content can be determined, for example, by high-frequency firing-infrared analysis.
  • a carbon-sulfur simultaneous analyzer LECO Japan GK, CSLS600
  • the carbon content is reduced by heating the negative electrode active material to a temperature higher than the decomposition temperature (for example, 300 ° C.) to remove the mass loss derived from the organic substance in advance. Can be measured.
  • Carbon preferably has low crystallinity.
  • "low crystallinity" of carbon means that the R value of the negative electrode active material obtained by the method shown below is 0.5 or more.
  • the peak appearing in the vicinity of 1360 cm -1 is usually a peak identified to correspond to an amorphous structure, and means, for example, a peak observed in 1300 cm -1 to 1400 cm -1 .
  • the peak appearing near 1580 cm -1 generally a peak identified as corresponding to the graphite crystal structure, for example, refers to peaks observed at 1530cm -1 ⁇ 1630cm -1.
  • R value Raman spectrum measuring apparatus e.g., NSR-1000 type, manufactured by JASCO Corporation
  • the R value of the negative electrode active material is preferably 0.5 to 2.5, more preferably 0.7 to 2.3, and even more preferably 0.8 to 2.0.
  • the surface of the silicon oxide particles is sufficiently covered with low crystalline carbon in which carbon crystallites are diffusely oriented, so that the reactivity with the electrolytic solution can be reduced. Cycle characteristics tend to improve.
  • the method of imparting carbon to the surface of the silicon oxide particles is not particularly limited. Specific examples thereof include a wet mixing method, a dry mixing method, and a chemical vapor deposition method.
  • carbon When carbon is added by a wet mixing method, for example, a silicon oxide particle and a carbon raw material (carbon source) dissolved or dispersed in a solvent are mixed, and the carbon source is the surface of the silicon oxide particle.
  • carbon raw material carbon source
  • silicon oxide particles and a carbon source are mixed in a solid state to form a mixture, and the mixture is heat-treated in an inert atmosphere to obtain carbon as the carbon source.
  • a treatment for applying mechanical energy for example, a mechanochemical treatment
  • carbon When carbon is added by the chemical vapor deposition method, a known method can be applied. For example, carbon can be imparted to the surface of the silicon oxide particles by heat-treating the silicon oxide particles in an atmosphere containing a gas in which the carbon source is vaporized.
  • the carbon source used is not particularly limited as long as it is a substance that can be converted to carbon by heat treatment.
  • polymer compounds such as phenol resin, styrene resin, polyvinyl alcohol, polyvinyl chloride, polyvinyl acetate, and polybutyral; ethylene heavy end pitch, coal pitch, petroleum pitch, coal tar pitch, asphalt decomposition pitch, etc.
  • PVC pitch produced by thermal decomposition of polyvinyl chloride (PVC) and the like
  • pitches such as naphthalene pitch produced by polymerizing naphthalene and the like in the presence of a super strong acid
  • polysaccharides such as starch and cellulose can be mentioned.
  • These carbon sources may be used alone or in combination of two or more.
  • the carbon source used is an aliphatic hydrocarbon, an aromatic hydrocarbon, an alicyclic hydrocarbon, or the like, which is gaseous or easily gasified. It is preferable to use a possible substance. Specific examples thereof include methane, ethane, propane, toluene, benzene, xylene, styrene, naphthalene, cresol, anthracene, and derivatives thereof. These carbon sources may be used alone or in combination of two or more.
  • the heat treatment temperature at the time of carbonizing the carbon source is not particularly limited as long as the temperature at which the carbon source is carbonized, and is preferably 700 ° C. or higher, more preferably 800 ° C. or higher, and more preferably 900 ° C. or higher. It is more preferable to have.
  • the heat treatment temperature is preferably 1300 ° C. or lower, preferably 1200 ° C. or lower, from the viewpoint of obtaining low crystallinity carbon and producing silicon crystals in a desired size by a disproportionation reaction described later. It is more preferable that the temperature is 1100 ° C. or lower.
  • the heat treatment time for carbonizing the carbon source can be selected depending on the type and amount of the carbon source used. For example, 1 hour to 10 hours is preferable, and 2 hours to 7 hours is more preferable.
  • the heat treatment for carbonizing the carbon source is preferably carried out in an inert atmosphere such as nitrogen or argon.
  • the heat treatment apparatus is not particularly limited, and examples thereof include a heating apparatus capable of processing by a continuous method, a batch method, or the like. Specifically, it can be selected from a fluidized bed reactor, a rotary furnace, a vertical mobile bed reactor, a tunnel furnace, a batch furnace, and the like.
  • heat-treated product obtained by the heat treatment is in a state where a plurality of particles are agglomerated, further crushing treatment may be performed. Further, if adjustment to a desired average particle size is required, further pulverization treatment may be performed.
  • the ratio of the X-ray diffraction peak intensity ( PSi / PSiO2 ) of the negative electrode active material is a value measured with carbon, organic matter, conductive particles, etc. attached to the silicon oxide particles, but these adhere to the silicon oxide particles. It may be a value measured in a non-existing state.
  • Negative electrode active material containing particles As a negative electrode active material having an X-ray diffraction peak intensity ratio ( PSi / PSiO2 ) in the range of 1.0 to 2.6, a silicon oxide having a structure in which silicon crystallites are present in the silicon oxide. Negative electrode active material containing particles can be mentioned.
  • Silicon oxide particles having a structure in which silicon crystallites are dispersed in silicon oxide cause, for example, a disproportionation reaction (2SiO ⁇ Si + SiO 2 ) of silicon oxide to cause silicon in the silicon oxide particles. It can be produced by generating crystallites. By controlling the degree to which silicon crystallites are formed in the silicon oxide particles, the ratio of the X-ray diffraction peak intensities can be controlled to a desired value.
  • the advantage of having silicon crystallites present in the silicon oxide particles by the disproportionation reaction of the silicon oxide can be considered as follows.
  • the above-mentioned SiO x (x is 0 ⁇ x ⁇ 2) tends to be inferior in the initial charge / discharge characteristics because lithium ions are trapped during the initial charge. This is because the lithium ions are trapped by the dangling bonds (unpaired electron pairs) of oxygen existing in the amorphous SiO 2 phase. Therefore, it is considered preferable from the viewpoint of improving charge / discharge characteristics to suppress the generation of dangling bonds of active oxygen atoms by reconstructing the amorphous SiO 2 phase by heat treatment.
  • the ratio of the X-ray diffraction peak intensity ( PSi / P SiO2 ) of the negative electrode active material is 1.0 or more, the silicon crystallites in the silicon oxide particles are sufficiently grown and the ratio of SiO 2 is large. It does not become too much, a sufficient initial discharge capacity can be obtained, and a decrease in charge / discharge efficiency due to an irreversible reaction tends to be suppressed.
  • the ratio of the X-ray diffraction peak intensity ( PSi / PSiO2 ) is 2.6 or less, the crystallites of the produced silicon do not become too large and the expansion and contraction are easily relaxed, and the initial discharge capacity is lowered. Tends to be suppressed.
  • the ratio of X-ray diffraction peak intensities ( PSi / PSiO2 ) is preferably in the range of 1.5 to 2.0.
  • the ratio of the X-ray diffraction peak intensities of the negative electrode active material can be controlled, for example, by the conditions of the heat treatment that causes the disproportionation reaction of the silicon oxide. For example, by raising the heat treatment temperature or lengthening the heat treatment time, the formation and enlargement of silicon crystallites can be promoted, and the ratio of the X-ray diffraction peak intensity can be increased. On the other hand, by lowering the heat treatment temperature or shortening the heat treatment time, the formation of silicon crystallites can be suppressed, and the ratio of the X-ray diffraction peak intensities can be reduced.
  • the silicon oxide used as a raw material is, for example, a mixture of silicon dioxide and metallic silicon is heated to cool the gas of silicon monoxide produced. It can be obtained by a known sublimation method for precipitating. It can also be obtained from the market as silicon oxide, silicon monoxide and the like.
  • silicon crystallites are present in the silicon oxide particles.
  • XRD powder X-ray diffraction
  • the size of the silicon crystallites is preferably 8.0 nm or less, more preferably 6.0 nm or less.
  • the silicon crystallites are difficult to localize in the silicon oxide particles and tend to be dispersed throughout the particles. Therefore, in the silicon oxide particles. Lithium ions are easily diffused, and a good charging capacity is easily obtained.
  • the size of silicon crystallites is preferably 2.0 nm or more, more preferably 3.0 nm or more. When the size of the silicon crystallite is 2.0 nm or more, the reaction between the lithium ion and the silicon oxide is well controlled, and good charge / discharge efficiency can be easily obtained.
  • the method for forming silicon crystallites in the silicon oxide particles is not particularly limited.
  • it can be produced by heat-treating silicon oxide particles in a temperature range of 700 ° C. to 1300 ° C. in an inert atmosphere to cause a disproportionation reaction (2SiO ⁇ Si + SiO 2 ).
  • the heat treatment for causing the disproportionation reaction may be performed in the same step as the heat treatment for imparting carbon to the surface of the silicon oxide particles.
  • the heat treatment conditions for causing the disproportionation reaction of the silicon oxide are, for example, to carry out the silicon oxide in a temperature range of 700 ° C. to 1300 ° C., preferably 800 ° C. to 1200 ° C. in an inert atmosphere. Can be done. From the viewpoint of producing silicon crystals having a desired size, the heat treatment temperature is preferably more than 900 ° C, more preferably 950 ° C or higher. The heat treatment temperature is preferably less than 1150 ° C, more preferably 1100 ° C or lower.
  • the particle size distribution may be adjusted by performing a classification treatment after pulverization.
  • the classification method is not particularly limited, and can be selected from dry classification, wet classification, sieving and the like. From the viewpoint of productivity, it is preferable to perform crushing and classification at once.
  • a jet mill and cyclone coupling system can classify particles before they reaggregate, making it easy to obtain the desired particle size distribution shape.
  • the negative electrode active material after pulverization is further subjected to surface modification treatment to adjust the aspect ratio.
  • the apparatus for performing the surface modification treatment is not particularly limited. For example, a mechanofusion system, a nobilta, a hybridization system and the like can be mentioned.
  • the BET specific surface area of the negative electrode active material is preferably 0.1 m 2 / g to 15 m 2 / g, more preferably 0.5 m 2 / g to 10 m 2 / g, and 1.0 m 2 / g. more preferably from ⁇ 7.0m 2 / g, particularly preferably 1.0m 2 /g ⁇ 4.0m 2 / g.
  • the BET specific surface area of the negative electrode active material is 15 m 2 / g or less, the increase in the initial irreversible capacity of the obtained lithium ion secondary battery tends to be suppressed.
  • the amount of binder used when producing the negative electrode can be reduced.
  • the specific surface area of the negative electrode active material is 0.1 m 2 / g or more, a sufficient contact area between the negative electrode active material and the electrolytic solution is sufficiently secured, and good charge / discharge efficiency tends to be obtained.
  • the BET specific surface area of the negative electrode active material is measured by the BET method (nitrogen gas adsorption method).
  • the powder electrical resistance of the negative electrode active material is preferably 100 ⁇ ⁇ cm or less, more preferably 80 ⁇ ⁇ cm or less, and further preferably 50 ⁇ ⁇ cm or less at a pressure of 10 MPa.
  • the powder electrical resistance of the negative electrode active material can be measured using, for example, a powder electrical resistance device (MSP-PD51 type 4 probe probe, Mitsubishi Chemical Analytech Co., Ltd.).
  • the powder electrical resistance of the negative electrode active material may be 0.1 ⁇ ⁇ cm or more, preferably 1 ⁇ ⁇ cm or more, and more preferably 10 ⁇ ⁇ cm or more at a pressure of 10 MPa.
  • the negative electrode active material preferably contains conductive particles described later. By adhering the conductive particles to the surface of the SiO—C particles to form a protrusion structure, the resistance value of the entire negative electrode active material can be reduced.
  • the negative electrode active material may contain an organic substance.
  • the initial discharge capacity, the initial charge / discharge efficiency, and the recovery rate after charge / discharge tend to be further improved. It is considered that this is because the specific surface area of the negative electrode active material is lowered by containing an organic substance, and the reaction with the electrolytic solution is suppressed.
  • the organic substance contained in the negative electrode active material may be only one type or two or more types.
  • the content of organic matter is preferably 0.1% by mass to 5.0% by mass of the entire negative electrode active material.
  • the content of the organic substance in the entire negative electrode active material is more preferably 0.2% by mass to 3.0% by mass, and further preferably 0.3% by mass to 1.0% by mass.
  • the negative electrode active material contains an organic substance is determined by, for example, heating a sufficiently dried negative electrode active material to a temperature higher than the temperature at which the organic substance decomposes and lower than the temperature at which the carbon decomposes (for example, 300 ° C.). It can be confirmed by measuring the mass of the negative electrode active material after the organic matter is decomposed. Specifically, when the mass of the negative electrode active material before heating is A (g) and the mass of the negative electrode active material after heating is B (g), it is represented by ⁇ (AB) / A ⁇ ⁇ 100. When the rate of change of the mass is 0.1% or more, it can be determined that the negative electrode active material contains an organic substance.
  • the rate of change in the mass is preferably 0.1% to 5.0%, more preferably 0.3% to 1.0%.
  • the rate of change is 0.1% or more, a sufficient amount of organic matter is present on the surface of the SiO—C particles, so that the effect of containing the organic matter tends to be sufficiently obtained.
  • the type of organic matter is not particularly limited.
  • water-soluble cellulose derivative to a derivative of starch of C 6 H 10 O 5 as a basic structure C 6 H 10 O 5 a basic structure to viscous polysaccharide, a C 6 H 10 O 5 as a basic structure, polyuronide and At least one selected from the group consisting of water-soluble synthetic resins can be mentioned.
  • starch derivative having C 6 H 10 O 5 as a basic structure examples include hydroxyalkyl starches such as acetate starch, phosphoric acid starch, carboxymethyl starch and hydroxyethyl starch.
  • specific examples of the viscous polysaccharide having C 6 H 10 O 5 as a basic structure include pullulan and dextrin.
  • examples of the water-soluble cellulose derivative having C 6 H 10 O 5 as a basic structure include carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose and the like.
  • polyuronide examples include pectic acid, alginic acid and the like.
  • water-soluble synthetic resin examples include water-soluble acrylic resin, water-soluble epoxy resin, water-soluble polyester resin, water-soluble polyamide resin, and more specifically, polyvinyl alcohol, polyacrylic acid, polyacrylic acid salt, and polyvinyl.
  • examples thereof include sulfonic acid, polyvinyl sulfonate, poly4-vinylphenol, poly4-vinylphenol salt, polystyrene sulfonic acid, polystyrene sulfonate, polyaniline sulfonic acid and the like.
  • the organic substance may be used in the state of a metal salt, an alkylene glycol ester or the like.
  • the organic substance is a part or all of the SiO-C particles (when the conductive particles described later are present on the surface of the SiO-C particles, the surface thereof). It is preferable that the state is covered with.
  • the method for allowing the organic substance to be present on a part or all of the surface of the SiO—C particles is not particularly limited.
  • the organic substance can be attached to the SiO-C particles by putting the SiO-C particles in a liquid in which the organic substance is dissolved or dispersed and stirring the mixture as necessary. After that, the SiO-C particles to which the organic substance is attached are taken out from the liquid and dried if necessary, so that the SiO-C particles to which the organic substance is attached to the surface can be obtained.
  • the temperature of the liquid during stirring is not particularly limited and can be selected from, for example, 5 ° C to 95 ° C.
  • the temperature at the time of drying is not particularly limited and can be selected from, for example, 50 ° C to 200 ° C.
  • the content of the organic substance in the solution is not particularly limited and can be selected from, for example, 0.1% by mass to 20% by mass.
  • the negative electrode active material may contain conductive particles. Since the negative electrode active material contains conductive particles, even if the silicon oxide particles expand and contract, the conductive particles come into contact with each other, so that conduction can be easily ensured. In addition, the resistance value of the entire negative electrode active material tends to decrease. As a result, the decrease in capacity due to repeated charging and discharging is suppressed, and the cycle characteristics tend to be maintained well.
  • the conductive particles are present on the surface of the SiO—C particles.
  • the particles in which the conductive particles are present on the surface of the SiO-C particles may be referred to as "CP / SiO-C particles”.
  • the type of conductive particles is not particularly limited.
  • at least one selected from the group consisting of granular graphite and carbon black is preferable, and granular graphite is preferable from the viewpoint of improving cycle characteristics.
  • granular graphite include particles such as artificial graphite, natural graphite, and MC (mesophase carbon).
  • Examples of carbon black include acetylene black, ketjene black, thermal black, furnace black and the like, and acetylene black is preferable from the viewpoint of conductivity.
  • Granular graphite is preferably more crystalline than carbon present on the surface of silicon oxide particles from the viewpoint of improving both battery capacity and charge / discharge efficiency.
  • the average interplanar spacing (d 002 ) obtained by measuring based on the Gakushin method is preferably 0.335 nm to 0.347 nm, and 0.335 nm to 0.345 nm. It is more preferably 0.335 nm to 0.340 nm, and particularly preferably 0.335 nm to 0.337 nm.
  • the shape of the granular graphite is not particularly limited, and may be flat graphite or spheroidal graphite. From the viewpoint of improving cycle characteristics, flat graphite is preferable. Examples of flat graphite include graphite having a scale-like, scaly-like, and lump-like shape.
  • the aspect ratio of the conductive particles is not particularly limited, but from the viewpoint of ensuring continuity between the conductive particles and improving the cycle characteristics, the average value of the aspect ratio is preferably 0.3 or less. It is more preferably 2 or less.
  • the average value of the aspect ratios of the conductive particles is preferably 0.001 or more, and more preferably 0.01 or more.
  • the aspect ratio of the conductive particles is a value measured by observation by SEM. Specifically, for each of the 100 conductive particles arbitrarily selected in the SEM image, the length in the major axis direction is A, and the length in the minor axis direction (in the case of flat graphite, the length in the thickness direction) is set. It is a value calculated as B / A when B is set.
  • the average value of the aspect ratio is the arithmetic mean value of the aspect ratio of 100 conductive particles.
  • the conductive particles may be either primary particles (singular particles) or secondary particles (granulated particles) formed from a plurality of primary particles.
  • the flat graphite may be porous graphite particles.
  • the content of the conductive particles is preferably 1.0% by mass to 10.0% by mass, preferably 2.0% by mass to 9.0% by mass, based on the entire negative electrode active material from the viewpoint of improving the cycle characteristics. More preferably, it is more preferably 3.0% by mass to 8.0% by mass.
  • the content of conductive particles can be determined, for example, by high-frequency firing-infrared analysis.
  • a carbon-sulfur simultaneous analyzer CSLS600, LECO Japan GK
  • this measurement also includes the carbon content of the SiO—C particles, it may be subtracted from the separately measured carbon content obtained.
  • the method for producing the negative electrode active material containing the conductive particles is not particularly limited, and examples thereof include a wet method and a dry method.
  • a method for producing a negative electrode active material containing conductive particles by a wet method for example, SiO-C particles are added to a particle dispersion liquid in which conductive particles are dispersed in a dispersion medium, and after stirring, a dryer or the like is used. Then, a method of producing by removing the dispersion medium can be mentioned.
  • the dispersion medium used is not particularly limited, and water, an organic solvent, or the like can be used.
  • the organic solvent may be a water-soluble organic solvent such as alcohol or a water-insoluble organic solvent.
  • the dispersion medium may contain a dispersant from the viewpoint of increasing the dispersibility of the conductive particles and making the adhesion of the SiO—C particles to the surface more uniform.
  • the dispersant can be selected according to the type of dispersion medium used. For example, when the dispersion medium is an aqueous system, carboxymethyl cellulose is preferable from the viewpoint of dispersion stability.
  • Examples of the method for producing the negative electrode active material containing the conductive particles by the dry method include a method in which the conductive particles are added together with the carbon source when the carbon source of carbon is applied to the surface of the silicon oxide particles. .. Specifically, for example, a method of mixing a carbon source and conductive particles with silicon oxide particles and applying mechanical energy (for example, mechanochemical treatment) can be mentioned.
  • the obtained negative electrode active material may be further classified.
  • the classification process can be performed using a sieving machine or the like.
  • the negative electrode active material (SiO-based negative electrode active material) of the present embodiment may be used in combination with another negative electrode active material, if necessary.
  • it may be used in combination with a carbon-based negative electrode active material conventionally known as an active material for the negative electrode of a lithium ion secondary battery.
  • a carbon-based negative electrode active material conventionally known as an active material for the negative electrode of a lithium ion secondary battery.
  • improvement of charge / discharge efficiency, improvement of cycle characteristics, effect of suppressing expansion of electrodes, etc. can be obtained.
  • the carbon-based negative electrode active material used in combination with the negative electrode active material of the present embodiment may be only one type or two or more types.
  • Examples of the carbon-based negative electrode active material include natural graphite such as scaly natural graphite and spherical natural graphite obtained by spheroidizing scaly natural graphite, and a negative electrode active material made of a carbon material such as artificial graphite and amorphous carbon. Further, these carbon-based negative electrode active materials may have carbon (carbon or the like described above) on a part or all of the surface thereof.
  • the ratio (A: B) of the negative electrode active material (A) and the carbon-based negative electrode active material (B) of the present embodiment is determined. It can be adjusted as appropriate according to the purpose. For example, from the viewpoint of the effect of suppressing the expansion of the electrode, it is preferably 0.1: 99.9 to 20:80, and 0.5: 99.5 to 15:85 on a mass basis. More preferably, it is more preferably 1:99 to 10:90.
  • the method for producing a negative electrode active material for a lithium ion secondary battery of the present embodiment is a method for producing a negative electrode active material for a lithium ion secondary battery, which comprises a step of adhering carbon to a part or all of the surface of silicon oxide particles.
  • the negative electrode active material for lithium ion secondary batteries has the particle size (vD50) when the accumulation from the small diameter side is 50% on a volume basis in the particle size distribution curve obtained by the laser diffraction / scattering method, and the particle size from the small diameter side.
  • the ratio (vD50 / nD50) to the particle size (nD50) when the cumulative number is 50% on a number basis is 1.3 or more.
  • the above method may be for producing the negative electrode active material of the above-described embodiment. That is, the negative electrode active material produced by the above method may be the negative electrode active material of the above-described embodiment.
  • the method of carrying out the step of adhering carbon to a part or all of the surface of the silicon oxide particles is not particularly limited.
  • carbon can be added to the surface of the silicon oxide particles by the method described above.
  • the above method may include a step other than the step of adhering carbon to a part or all of the surface of the silicon oxide particles, if necessary.
  • pulverization of silicon oxide particles, particle size adjustment, heat treatment for disproportionation reaction, adhesion of organic substances or conductive particles, and the like may be carried out.
  • the negative electrode for a lithium ion secondary battery of the present embodiment (hereinafter, may be abbreviated as "negative electrode”) includes a current collector and a negative electrode material layer containing the above-mentioned negative electrode active material provided on the current collector. , Have.
  • the negative electrode can be produced, for example, by forming a negative electrode material layer on the current collector using the above-mentioned composition containing the negative electrode active material.
  • the composition containing the negative electrode active material include a mixture of the negative electrode active material with an organic binder, a solvent, a thickener, a conductive auxiliary agent, a carbon-based negative electrode active material, and the like.
  • organic binder examples include styrene-butadiene copolymers; ethylenic properties such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, (meth) acrylonitrile, and hydroxyethyl (meth) acrylate.
  • “(meth) acrylate” means “acrylate” and the corresponding "methacrylate”. The same applies to other similar expressions such as "(meth) acrylic copolymer”.
  • the organic binder may be one dispersed or dissolved in water, or one dissolved in an organic solvent such as N-methyl-2-pyrrolidone (NMP).
  • NMP N-methyl-2-pyrrolidone
  • One type of organic binder may be used alone, or two or more types may be used in combination.
  • the organic binder having a main skeleton of polyacrylonitrile, polyimide or polyamide-imide is preferable among the organic binders, the heat treatment temperature at the time of producing the negative electrode is low, and the flexibility of the electrode is excellent.
  • An organic binder having a main skeleton of polyacrylonitrile is more preferable.
  • Examples of the organic binder having polyacrylonitrile as a main skeleton include those obtained by adding acrylic acid that imparts adhesiveness and a linear ether group that imparts flexibility to a polyacrylonitrile skeleton.
  • the content of the organic binder in the negative electrode material layer is preferably 0.1% by mass to 20% by mass, more preferably 0.2% by mass to 20% by mass, and 0.3% by mass. It is more preferably to 15% by mass.
  • the content of the organic binder in the negative electrode material layer is 0.1% by mass or more, good adhesion is obtained, and the negative electrode is suppressed from being destroyed by expansion and contraction during charging and discharging. ..
  • the content of the organic binder in the negative electrode material layer is 20% by mass or less, an increase in electrode resistance can be suppressed.
  • thickener examples include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, polyacrylic acid (salt), oxidized starch, phosphorylated starch, casein and the like.
  • One type of thickener may be used alone, or two or more types may be used in combination.
  • the solvent examples include N-methylpyrrolidone, dimethylacetamide, dimethylformamide, ⁇ -butyrolactone and the like.
  • One type of solvent may be used alone, or two or more types may be used in combination.
  • the conductive auxiliary agent examples include carbon black, acetylene black, oxides showing conductivity, and nitrides showing conductivity.
  • One type of conductive auxiliary agent may be used alone, or two or more types may be used in combination.
  • the content of the conductive auxiliary agent in the negative electrode material layer is preferably 0.1% by mass to 20% by mass.
  • Examples of the material of the current collector include aluminum, copper, nickel, titanium, stainless steel, porous metal (foam metal), carbon paper, and the like.
  • Examples of the shape of the current collector include a foil shape, a perforated foil shape, and a mesh shape.
  • a coating liquid containing a negative electrode active material is applied onto the current collector to remove volatile substances such as a solvent.
  • Examples of the method of applying the coating liquid to the current collector include a metal mask printing method, an electrostatic coating method, a dip coating method, a spray coating method, a roll coating method, a doctor blade method, a gravure coating method, and a screen printing method. ..
  • the pressurization treatment after coating can be performed by a flat plate press, a calendar roll, or the like.
  • the integration of the negative electrode material layer and the current collector can be, for example, integration by a roll, integration by a press, or a combination thereof.
  • the negative electrode material layer formed on the current collector or the negative electrode material layer integrated with the current collector may be heat-treated according to the type of the organic binder used. For example, when using an organic binder having polyacrylonitrile as the main skeleton, it is preferable to heat-treat at 100 ° C. to 180 ° C., and when using an organic binder having polyimide or polyamide-imide as the main skeleton, 150 ° C. It is preferable to heat-treat at ° C to 450 ° C. By this heat treatment, the solvent is removed and the strength is increased by curing the organic binder, and the adhesion between the negative electrode active materials and the adhesion between the negative electrode active material and the current collector can be improved. In addition, these heat treatments are preferably carried out in an inert atmosphere such as helium, argon or nitrogen or in a vacuum atmosphere in order to prevent oxidation of the current collector during the treatment.
  • an inert atmosphere such as helium, argon or nitrogen or in a vacuum
  • the negative electrode material layer is pressed (pressurized) before the heat treatment.
  • the electrode density can be adjusted by pressurizing. Electrode density may, for example, more preferably is preferably 1.4g / cm 3 ⁇ 1.9g / cm 3, a 1.5g / cm 3 ⁇ 1.85g / cm 3, 1.6g / cm It is more preferably 3 to 1.8 g / cm 3 . Regarding the electrode density, the higher the value, the more the volume capacity of the negative electrode tends to improve, and the adhesion between the negative electrode active materials and the adhesion between the negative electrode active material and the current collector tend to improve. ..
  • the lithium ion secondary battery of the present embodiment includes a positive electrode, the above-mentioned negative electrode, and an electrolyte.
  • a lithium ion secondary battery is manufactured, for example, by arranging a negative electrode and a positive electrode in a battery container so as to face each other via a separator, and injecting an electrolytic solution obtained by dissolving an electrolyte in an organic solvent into the battery container. can do.
  • the positive electrode can be obtained by forming a positive electrode material layer on the surface of the current collector in the same manner as the negative electrode.
  • the same current collector as at the negative electrode can be used as the current collector at the positive electrode.
  • the material used for the positive electrode may be a compound capable of doping or intercalating lithium ions, and may be lithium cobalt oxide (LiCoO 2 ), lithium nickel oxide (LiNiO 2 ), or lithium manganate (LiMnO). 2 ) and the like.
  • a positive electrode material for example, a positive electrode material, an organic binder such as polyvinylidene fluoride, and a solvent such as N-methyl-2-pyrrolidone and ⁇ -butyrolactone are mixed to prepare a positive electrode coating solution, and this positive electrode coating solution is prepared.
  • a current collector such as an aluminum foil
  • a conductive auxiliary agent may be added to the positive electrode coating liquid.
  • the conductive auxiliary agent include carbon black, acetylene black, oxides exhibiting conductivity, nitrides exhibiting conductivity, and the like. These conductive auxiliaries may be used alone or in combination of two or more.
  • LiPF 6, LiClO 4, LiBF 4, LiClF 4, LiAsF 6, LiSbF 6, LiAlO 4, LiAlCl 4, LiN (CF 3 SO 2) 2, LiN (C 2 F 5 SO 2) 2, LiC ( CF 3 SO 2 ) 3 , LiCl, LiI and the like can be mentioned.
  • organic solvent that dissolves the electrolyte examples include propylene carbonate, ethylene carbonate, diethyl carbonate, ethylmethyl carbonate, vinylene carbonate, ⁇ -butyrolactone, 1,2-dimethoxyethane and 2-methyltetrahydrofuran.
  • separator examples include a paper separator, a polypropylene separator, a polyethylene separator, a glass fiber separator, and the like.
  • the manufacturing method of the lithium ion secondary battery is not particularly limited.
  • a cylindrical lithium ion secondary battery can be manufactured by the following steps. First, the two electrodes, the positive electrode and the negative electrode, are wound around the separator. The obtained spiral winding group is inserted into the battery can, and the tab terminal previously welded to the current collector of the negative electrode is welded to the bottom of the battery can. The electrolytic solution is injected into the obtained battery can. Further, the tab terminal welded to the current collector of the positive electrode in advance is welded to the lid of the battery, and the lid is arranged on the upper part of the battery can via the insulating gasket.
  • a lithium ion secondary battery can be obtained by crimping and sealing the portion where the lid and the battery can are in contact with each other.
  • the form of the lithium ion secondary battery is not particularly limited, and examples thereof include lithium ion secondary batteries such as paper type batteries, button type batteries, coin type batteries, laminated batteries, cylindrical batteries, and square batteries.
  • the negative electrode active material of the present embodiment is not limited to the lithium ion secondary battery, and can be applied to all electrochemical devices having a charging / discharging mechanism of inserting and removing lithium ions.
  • the obtained chemically vapor-deposited product was crushed with a mortar and sieved with a 300M (300 mesh) test sieve to obtain a negative electrode active material in which carbon was attached to the surface of silicon oxide particles.
  • the particle size distribution of the obtained negative electrode active material was measured. Specifically, the measurement sample (5 mg) was placed in a 0.01 mass% aqueous solution of a surfactant (Esomin T / 15, Lion Corporation) and dispersed with a vibration stirrer. The obtained dispersion was placed in a sample water tank of a laser diffraction type particle size distribution measuring device (SALD3000J, Shimadzu Corporation), circulated by a pump while applying ultrasonic waves, and measured by a laser diffraction type. The measurement conditions were as follows. Hereinafter, in the examples, the particle distribution was measured in the same manner. -Light source: Red semiconductor laser (690 nm) ⁇ Absorbance: 0.10 to 0.15 -Refractive index: 2.00 to 0.20
  • the results are shown in Table 1.
  • Example 1 Carbon was attached to the silicon oxide particles (before the execution of CVD) used in Comparative Example 1 in the same manner as in Comparative Example 1 except that the fine powder removed after pulverization was blended in an amount of 5% by mass of the whole. Silicon oxide particles (negative electrode active material) were prepared and their particle size distribution was measured. The results are shown in Table 1.
  • Example 2 Carbon adhered to the silicon oxide particles used in Comparative Example 1 (before the execution of CVD) in the same manner as in Comparative Example 1 except that the fine powder removed after pulverization was blended in an amount of 10% by mass of the whole. Silicon oxide particles (negative electrode active material) were prepared and their particle size distribution was measured. The results are shown in Table 1.
  • the negative electrode active material was analyzed using a powder X-ray diffraction measuring device (MultiFlex (2 kW), Rigaku Co., Ltd.) in the same manner as described above.
  • the carbon content (mass%) of the negative electrode active material was measured by a high-frequency firing-infrared analysis method.
  • the high-frequency firing-infrared analysis method is an analysis method in which a sample is heated and burned in an oxygen stream in a high-frequency furnace, carbon and sulfur in the sample are converted into CO 2 and SO 2 , respectively, and quantified by an infrared absorption method.
  • the measuring device, measuring conditions, etc. are as follows.
  • Battery capacity (initial discharge capacity and initial charge / discharge efficiency)
  • the prepared battery is placed in a constant temperature bath held at 25 ° C., charged at a constant current of 0.45 mA / cm 2 until it reaches 0 V, and then a value corresponding to a current of 0.09 mA / cm 2 at a constant voltage of 0 V.
  • the battery was further charged until it decayed to, and the initial charge capacity was measured.
  • the battery was discharged after a 30-minute rest period.
  • the discharge was performed at 0.45 mA / cm 2 until it reached 1.5 V, and the initial discharge capacity was measured. At this time, the capacity was converted to the mass of the negative electrode active material used.
  • the value obtained by multiplying the value obtained by dividing the initial discharge capacity by the initial charge capacity by 100 was calculated as the initial charge / discharge efficiency (%).
  • one charge and one discharge are combined into one cycle.
  • the battery of the example using silicon oxide particles having a ratio (vD50 / nD50) of 1.3 or more to the particle size (nD50) at 50% as the negative electrode active material does not satisfy this condition.
  • the expansion of the electrode was suppressed and the 10-cycle capacity retention rate was improved.

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  • Chemical Kinetics & Catalysis (AREA)
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  • Inorganic Chemistry (AREA)
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Abstract

L'invention concerne un matériau actif d'électrode négative pour une batterie secondaire au lithium-ion, ledit matériau comprenant : des particules d'oxyde de silicium ; et du carbone présent sur la totalité ou une partie des surfaces des particules d'oxyde de silicium. Dans une courbe de distribution de taille de particule obtenue au moyen du procédé de diffraction/diffusion laser, le rapport (vD50/nD50) du diamètre de particule (vD50) lorsque l'accumulation depuis le côté petit diamètre est de 50 % sur une base en volume et le diamètre de particule (nD50) lorsque l'accumulation depuis le côté petit diamètre est de 50 % sur la base du nombre de particules est d'au moins 1,3.
PCT/JP2019/027011 2019-07-08 2019-07-08 Matériau actif d'électrode négative pour batterie secondaire au lithium-ion, électrode négative pour batterie secondaire au lithium-ion, batterie secondaire au lithium-ion et procédé de fabrication de matériau actif d'électrode négative pour batterie secondaire au lithium-ion WO2021005689A1 (fr)

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