WO2022270539A1 - Particules de carbone composites et leur utilisation - Google Patents

Particules de carbone composites et leur utilisation Download PDF

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WO2022270539A1
WO2022270539A1 PCT/JP2022/024885 JP2022024885W WO2022270539A1 WO 2022270539 A1 WO2022270539 A1 WO 2022270539A1 JP 2022024885 W JP2022024885 W JP 2022024885W WO 2022270539 A1 WO2022270539 A1 WO 2022270539A1
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composite carbon
carbon particles
mass
silicon
composite
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PCT/JP2022/024885
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Japanese (ja)
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貴行 栗田
祐司 伊藤
浩文 井上
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昭和電工株式会社
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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
    • C01B32/00—Carbon; Compounds 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
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements 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
    • H01M4/58—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
    • 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 novel composite carbon particles, negative electrode materials for lithium ion secondary batteries containing the composite carbon particles, and lithium ion secondary batteries.
  • the secondary batteries used in IT devices such as smart phones and tablet PCs, vacuum cleaners, power tools, electric bicycles, drones, and automobiles require negative electrode active materials that have both high capacity and high output.
  • Silicon theoretical specific capacity: 4200 mAh/g
  • graphite theoretical specific capacity: 372 mAh/g
  • silicon expands and contracts up to about 3-4 times in volume as it is electrochemically intercalated and deintercalated with lithium.
  • the silicon particles self-destruct or separate from the electrodes, so that lithium-ion secondary batteries using silicon are known to have extremely low cycle characteristics.
  • the use of a structure in which the degree of expansion and contraction of the negative electrode material as a whole is reduced is being extensively researched.
  • Patent Document 1 Japanese Patent Publication No. 2018-534720, Patent Document 1
  • Japanese Patent Publication No. 2018-534720, Patent Document 1 Japanese Patent Publication No. 2018-534720, Patent Document 1
  • a negative electrode material for a lithium secondary battery with low overvoltage, high discharge capacity, and little cycle deterioration (a) at least one metal capable of forming an alloy with lithium is contained in the pores of the activated carbon particles. (b) at least one alloy of two or more elements containing a metal capable of forming an alloy with lithium; and (c) oxides, nitrides and other compounds of metals capable of forming an alloy with lithium.
  • a negative electrode material containing at least one of them has also been disclosed (Japanese Unexamined Patent Application Publication No. 2001-143692, Patent Document 2).
  • Patent Document 1 and Patent Document 2 attempts are made to improve the cycle characteristics mainly by arranging the active material in the pores of the porous carbon. have come to be expected, and these did not necessarily meet such expectations.
  • an object of the present invention is to provide composite carbon particles that can further improve cycle characteristics.
  • the present inventors have made intensive studies, and as a result, have found that the above problems can be sufficiently solved by adopting composite carbon particles containing a predetermined amount of phosphorus element, and have completed the present invention. rice field.
  • the configuration of the present invention is as follows. [1] Composite carbon particles having a porous carbon material and a silicon component, wherein at least a portion of the pores of the porous carbon material contain the silicon component, and the composite carbon particles contain 40 ppm by mass of elemental phosphorus. Composite carbon particles in an amount of not less than 8000 mass ppm. [2] The composite carbon particles according to [1], wherein the porous carbon material contains 100 mass ppm or more and less than 25600 mass ppm of phosphorus element.
  • the ratio (I Si /I G ) of the peak intensity (I Si ) near 470 cm ⁇ 1 and the peak intensity (I G ) near 1580 cm ⁇ 1 measured by Raman spectroscopy is 1.00 or less.
  • the R value (I D /I G ) which is the ratio of the peak intensity (I D ) near 1350 cm ⁇ 1 to the peak intensity ( IG ) near 1580 cm ⁇ 1 , is 0.80 or more and 1.50 or less
  • FWHM(a)/FWHM(b) is 1.20 or more, where FWHM(b) is the half-value width of a nearby peak, according to any one of [1] to [9].
  • Composite carbon particles [11] Let A Si , A O , and A be the atomic number ratios according to the Narrow spectrum of Si, O, and C in the X-ray photoelectron spectroscopy of the composite carbon atoms, respectively, and of the Si species ratios according to the Si2p spectrum state analysis , where B SiO2 and B SiO are the ratios of SiO 2 and SiO, respectively, A Si is 0.05 or more, and at least one of the following formulas (1) and (2) is satisfied: [1] to [10] The composite carbon particles according to any one of .
  • the composite carbon particles of the present invention it is possible to provide a lithium ion secondary battery with improved cycle characteristics.
  • Composite carbon particles are composite carbon particles having a porous carbon material and a silicon component, and having the silicon component in at least part of the pores of the porous carbon material.
  • the composite carbon particles contain a phosphorus element in an amount of 40 ppm by mass or more and less than 8000 ppm by mass.
  • the phosphorus element is contained in the composite carbon particles at 40 ppm by mass or more. The present inventors believe that this reduces the electronic resistance associated with reaction with silicon and improves cycle characteristics. From this point of view, the phosphorus element is preferably contained in the composite carbon particles in an amount of 50 mass ppm or more, more preferably 70 mass ppm or more.
  • the phosphorus element is contained in the composite carbon particles at less than 8000 ppm by mass. It is believed that this stabilizes the pore structure of the porous carbon material, and makes it possible to achieve both energy density and cycle characteristics. From this point of view, the phosphorus element is more preferably contained in the composite carbon particles in an amount of less than 7900 ppm by mass.
  • the content of the phosphorus element in the composite carbon particles can be determined by fluorescent X-ray analysis using the fundamental parameter method (FP method).
  • FP method fundamental parameter method
  • the content of phosphorus element in the composite carbon particles can be determined by burning the composite carbon particles to remove the carbon content and completely dissolving the unburned ash in acid or alkali. , inductively coupled plasma emission spectroscopy (ICP-AES), or the like.
  • the porous carbon material that constitutes the composite carbon particles preferably contains 100 ppm by mass or more and less than 25600 ppm by mass of elemental phosphorus.
  • the porous carbon material does not contain elemental phosphorus, there is no bias in charge between the porous carbon material and silicon in the composite carbon particles.
  • the phosphorus element is contained in the porous carbon material, since the phosphorus element is electron-rich, an electric charge bias occurs between the porous carbon material and silicon, and silicon is relatively displaced from the porous carbon material. It has a positive charge. As a result, electrons tend to flow to the silicon side, and the effect of reducing the electronic resistance related to the reaction of silicon is exhibited. The inventors consider that this leads to an improvement in cycle characteristics.
  • the porous carbon material preferably contains 100 mass ppm or more of phosphorus element, more preferably 200 mass ppm or more of phosphorus element.
  • the activation progress rate increases, and it becomes "difficult to control the pore structure" of the activated porous carbon material.
  • An example of "difficult to control the pore structure” here means that the pore volume and pore distribution are not equal even if a nitrogen adsorption test is performed on porous carbon obtained by activating under the same conditions. Say. Activation under the same conditions includes errors in switching timing of activation gas, temperature switching timing, activation end timing, and the like.
  • a state in which the pore volume and pore distribution are greatly changed due to an allowable error in the activation operation is said to be "difficult to control the pore structure.”
  • the rate of progress of activation slows down, making it easier to control the pore structure.
  • the elemental phosphorus content of 25,600 ppm by mass or more makes it difficult to control by low-temperature activation.
  • the low temperature of low temperature activation refers to a temperature about 50° C. to 100° C. lower than the activation temperature when producing a porous carbon material containing no elemental phosphorus, but is not limited to this definition.
  • the pore structure of the porous carbon material is directly linked to the cycle characteristics, and if it becomes "difficult to control the pore structure", the cycle characteristics will deteriorate due to excessive pore volume and reduction of micropores. Conversely, due to "difficulty in controlling the pore structure", if the pore volume is small, the silicon content in the composite carbon particles will decrease and the specific capacity of the composite carbon particles will decrease. This leads to a decrease in battery energy density. In other words, when it is less than 25,600 ppm by mass, the pore structure of the porous carbon material is stabilized, and the porous carbon material can achieve both energy density and cycle characteristics. From this point of view, the porous carbon material preferably contains less than 25000 ppm by mass of phosphorus element, more preferably less than 24000 ppm by mass of the porous carbon material.
  • the phosphorus element exists within the carbon phase.
  • "existing in the carbon phase” means being integrated with the carbon material and existing.
  • Phosphorus element may be contained alone in the porous carbon material, or may exist as an oxide or carbide. It should be noted that the improvement of the cycle characteristics means not only that the decrease in capacity is less likely to occur when charging and discharging are repeated, but also that the Li insertion average potential is maintained high, and the rest potential after Li insertion. It also includes the fact that it becomes difficult to change.
  • the content of phosphorus element in the porous carbon material can be measured by elemental analysis such as fluorescent X-ray analysis.
  • the phosphorus element content in the porous carbon material can be measured by elemental analysis such as fluorescent X-ray analysis after the silicon component is eluted by treating the composite carbon particles with an alkaline solution.
  • the composite carbon particles are stirred in a 0.5 mol/L KOH aqueous solution at a temperature of 50° C. for 1 to 5 days, and vacuum is drawn every other day. After that, filtration, washing, and drying can be mentioned.
  • concentration of the KOH aqueous solution and the number of treatment days may be adjusted each time according to the type of porous carbon material. It is sufficient to appropriately select conditions under which silicon is dissolved but the porous carbon material is not dissolved.
  • the composite carbon particles according to this embodiment contain a silicon component together with the porous carbon material described above.
  • the silicon component may be contained anywhere in the composite carbon particles, but the silicon component is deposited in at least part of the pores of the porous carbon material. Moreover, the silicon component may be deposited on the surface other than the pores of the porous carbon material. Note that the silicon component is substantially absent in the carbon phase of the carbon material. Since the silicon component is deposited in the pores, a sufficient electron conduction path around the silicon component can be ensured within the electrode when the lithium ion secondary battery is formed. Moreover, since such a silicon component has a size similar to that of the pores of the porous carbon material, it is less likely to crack due to expansion/contraction associated with insertion/extraction of lithium. Furthermore, since the number of contact points between the silicon component and the electrolyte is reduced, a battery with excellent initial coulombic efficiency can be obtained.
  • an EDX peak derived from the silicon component inside the porous carbon material is detected. Further, by mapping, it can be confirmed that the silicon component is distributed throughout the porous carbon material from the periphery to the center.
  • the silicon component is not particularly limited as long as it contains silicon, but is preferably one or more selected from simple silicon and silicon oxide, and more preferably simple silicon. More preferably, the silicon component is amorphous silicon alone. Amorphous silicon expands and contracts isotropically during insertion and extraction of lithium, so that the cycle characteristics can be improved. Amorphous silicon is known to have a peak at 460-495 cm ⁇ 1 in Raman spectra measured by Raman spectroscopy. An example of silicon oxide is SiO x (0 ⁇ x ⁇ 2). Other silicon components include silicon carbide (SiC, etc.).
  • the content of silicon element in the composite carbon particles according to the present embodiment is preferably 15.0% by mass or more.
  • the composite carbon particles can have a high specific capacity. From this point of view, the silicon element content is more preferably 25.0% by mass or more, and even more preferably 35.0% by mass or more.
  • the content of silicon element in the composite carbon particles is preferably 85.0% by mass or less.
  • the silicon element content is 85.0% by mass or less, the particles of the porous carbon material serving as the carrier can absorb the volume change due to expansion and contraction. From this point of view, the silicon element content is more preferably 70.0% by mass or less, and even more preferably 60.0% by mass or less.
  • the silicon element content in the composite carbon particles can be determined by fluorescent X-ray analysis using a fundamental parameter method (FP method).
  • FP method fundamental parameter method
  • the content of phosphorus element and silicon element in the composite carbon particles can be determined by burning the composite carbon particles to remove the carbon content and completely converting the unburned ash into acid or alkali. After dissolving, it can be quantified by inductively coupled plasma emission spectroscopy (ICP-AES) or the like.
  • ICP-AES inductively coupled plasma emission spectroscopy
  • the composite carbon particles according to an embodiment of the present invention preferably have a peak at 460 to 495 cm -1 , for example around 470 cm -1 in Raman spectrum measured by Raman spectroscopy. This peak is considered to originate from amorphous silicon. The intensity of this peak is denoted as I Si . Furthermore, it is more preferable that the Raman spectrum has a peak at 460 to 495 cm -1 and does not have a peak at 510 to 530 cm -1 . The peak at 510-530 cm -1 is believed to originate from crystalline silicon.
  • the peak intensity near 1350 cm -1 be ID and the peak intensity near 1580 cm -1 be IG .
  • the peak intensity is the height from the baseline to the peak apex after correcting the baseline.
  • a peak near 1350 cm ⁇ 1 and a peak near 1580 cm ⁇ 1 are derived from carbon.
  • the ratio of the peak intensity (I Si ) around 470 cm ⁇ 1 to the peak intensity (IG ) around 1580 cm ⁇ 1 is preferably 1.00 or less.
  • the appearance of silicon peaks in the Raman spectrum indicates that a large amount of silicon is deposited near and/or on the surface inside the composite carbon particles.
  • the fact that I Si /I G is 1.00 or less indicates that silicon is mainly deposited inside the pores of the porous carbon material and is hardly deposited on the surface of the porous carbon material.
  • I Si /I G is preferably 0.70 or less, more preferably 0.45 or less. Also, I Si /I G is preferably 0.10 or more. When it is 0.10 or more, silicon is present at a sufficient concentration near the surface inside the composite carbon particles, and the rate characteristics of the battery are excellent.
  • the composite carbon particles according to one embodiment of the present invention have an R value (I D /I G ), which is the ratio of the peak intensity (I D ) near 1350 cm ⁇ 1 to the peak intensity ( IG ) near 1580 cm ⁇ 1 . It is preferably 0.80 or more. When the R value is 0.80 or more, the reaction resistance is sufficiently low, leading to an improvement in the rate characteristics of the battery.
  • the R value is more preferably 0.90 or more, and even more preferably 1.00 or more.
  • the R value is preferably 1.50 or less.
  • An R value of 1.50 or less means that there are few defects on the surface of the composite carbon particles, and side reactions are reduced in the battery, resulting in an increase in coulombic efficiency in the early stages of charge-discharge cycles. From this point of view, the R value is more preferably 1.40 or less, even more preferably 1.20 or less.
  • the composite carbon particles according to one embodiment of the present invention preferably have a 50% particle diameter D V50 of 0.5 ⁇ m or more in the volume-based cumulative particle size distribution according to the laser diffraction method. If it is 0.5 ⁇ m or more, the powder is excellent in handleability, it is easy to prepare a slurry having a viscosity and density suitable for coating, and it is easy to increase the density when it is used as an electrode. From this point of view, D V50 is more preferably 2.0 ⁇ m or more, further preferably 3.0 ⁇ m or more.
  • the composite carbon particles according to one embodiment of the present invention preferably have D V50 of 20.0 ⁇ m or less. If it is 20.0 ⁇ m or less, the diffusion length of lithium in each particle is short, so the rate characteristics of the lithium ion battery are excellent, and when the slurry is applied to the current collector, streaking and abnormal unevenness are prevented. does not occur. From this point of view, D V50 is more preferably 17.0 ⁇ m or less, and even more preferably 15.0 ⁇ m or less.
  • Composite carbon particles having the average particle diameter as described above have a large effect of reducing the resistance related to the reaction of silicon.
  • the effect is manifested more.
  • D V50 can be measured by laser diffraction.
  • the composite carbon particles according to this embodiment preferably have an average circularity of 0.95 or more and 1.00 or less.
  • the circularity of a particle is the ratio of (the area of the projected image of the particle multiplied by 4 ⁇ ) to (the square of the perimeter of the projected image of the particle).
  • the average circularity of 100 or more composite carbon particles is taken as the average circularity of the composite carbon particles.
  • Composite carbon particles having an average circularity within the above range are spherical and expand isotropically when lithium is inserted, so damage to the electrode can be reduced.
  • the composite carbon particles of one embodiment of the present invention preferably have a coating layer containing carbon on the surface. More preferably, the coat layer further contains oxygen.
  • the structure of this composite carbon particle has the following features.
  • the atomic number ratios of Si, O, and C in the X-ray Photoelectron Spectroscopy (XPS) of the composite carbon particles are A Si , A O , and A C , respectively, and Si by Si2p spectrum state analysis.
  • B SiO2 and B SiO be the ratios of SiO 2 and SiO in the seed ratio, A Si is 0.05 or more, and at least one of the following formulas (1) and (2) is satisfied.
  • XPS is a technique for obtaining knowledge about the types, abundances, and chemical bonding states of elements present on the surface of a substance, and is known to be able to obtain information up to a depth of several nanometers from the surface of the substance.
  • a Si A Si of less than 0.05 means that the coating layer is too thick. If the coating layer is too thick, the resistance of the composite carbon particles will increase.
  • a Si is preferably 0.15 or more, more preferably 0.25 or more. Since the analysis depth of XPS is as shallow as several nanometers, the fact that Si can be observed to some extent means that the coat layer is an extremely thin layer.
  • a C /(A C +A Si ⁇ (B SiO2 +B SiO )) The value of AC / ( AC + A Si ⁇ (B SiO2 + B SiO )) is an index of the concentration of carbon at a position from the surface of the composite carbon particle to a depth of several nm (depth of spatial resolution in XPS). is.
  • Si exists as oxides such as SiO 2 and SiO on the surfaces of the composite carbon particles, and that most of the surfaces of the composite carbon particles are formed of carbon and silicon oxides such as SiO 2 and SiO. It's for. However, since A C also includes information on carbon other than the coat layer, this index does not reflect the carbon concentration of only the coat layer.
  • a small value of Ac/( Ac+ASi*(BSiO2 + BSiO ) ) indicates that the carbon concentration on the surface of the composite carbon particles is low. If this carbon concentration becomes low, the oxidation suppressing ability will decrease. That is, the composite carbon particles are easily oxidized.
  • the oxidation suppressing ability is sufficiently exhibited even if the carbon concentration on the surface of the composite carbon particle decreases.
  • the silicon concentration near the surface of the composite carbon particles increases, that is, as I Si /I G increases, the silicon that can be oxidized is oxidized due to the presence of a composite of hydrocarbon-derived carbon and silicon oxide. It is thought that this is because it becomes difficult to be That is, the index of carbon concentration represented by A C /(A C +A Si ⁇ (B SiO2 +B SiO )) is affected by the silicon concentration in the vicinity of the composite carbon particle surface.
  • the composite carbon particles according to the present invention satisfy the following formula (1).
  • Y that is, A C /(A C +A Si ⁇ (B SiO2 +B SiO )) is preferably 0.85 or more.
  • Y that is, A C /(A C +A Si ⁇ (B SiO2 +B SiO )) is preferably 0.98 or less.
  • the structure of the coat layer cannot be specified, it is preferably a thin film layer in which surface carbon and silicon oxide are combined.
  • the value of Ac /( Ac+ASi*(BSiO2 + BSiO ) ) is determined, for example, by the reaction temperature, reaction time, reaction pressure, or amount of hydrocarbon in step (B) in the method for producing composite carbon particles described later. It can be changed by adjusting the type or concentration.
  • the coat layer preferably contains a hydrocarbon-derived compound.
  • the fact that the coating layer contains a hydrocarbon-derived compound is confirmed by thermal decomposition GC-MC measurement of the composite carbon particles, and the gas generated from the composite carbon particles between 200 ° C. and 600 ° C. contains a hydrocarbon-derived compound. It can be determined from the fact that
  • the coating layer can be produced by contacting the Si/C particles with a carbon source having unsaturated bonds at a low temperature and then oxidizing the resulting material. Details will be described later.
  • Si/C particles is another name for composite carbon particles before forming a coat layer.
  • Porous Carbon Material The porous carbon material constituting the composite carbon particles of the present invention is a carbon material having pores.
  • the shape of the porous carbon material is not particularly limited as long as it satisfies the shape of the composite carbon particles described above.
  • the porous carbon material has the following properties in the nitrogen adsorption test:
  • the maximum value of the relative pressure P/ P0 is the ratio between the maximum achievable nitrogen gas pressure and the saturated vapor pressure P0 of nitrogen gas under the conditions under the measuring equipment and conditions used in the nitrogen adsorption test. be.
  • the maximum value of the relative pressure P/P 0 is theoretically 1, but in some cases it may not be possible to reach 1 due to restrictions on the measurement device. Any of the following is acceptable.
  • the adsorption isotherm by the gas adsorption method is analyzed by a known method.
  • the adsorbed gas in the measurement is nitrogen gas in this embodiment. That is, in order to examine the pore structure of the porous carbon material in this embodiment, a nitrogen adsorption test is performed.
  • the adsorption isotherm is a curve in which the horizontal axis indicates the relative pressure and the vertical axis indicates the adsorption amount of the adsorbed gas. At lower relative pressures, the adsorbed gas adsorbs in pores with smaller diameters.
  • micropores 0.1 Pores corresponding to the nitrogen adsorption volume in the range of ⁇ P/P 0 ⁇ 0.96 are defined as mesopores, and pores corresponding to the nitrogen adsorption volume in the range of 0.96 ⁇ P/P 0 are defined as macropores. do.
  • pores are pores having a diameter of about 2 nm to about 50 nm, while “micropores” are pores having a diameter of less than about 2 nm.
  • a “macropore” is a pore having a diameter greater than about 50 nm.
  • the pore volume V x (cc/g) at each level x when the relative pressure P/P 0 is a predetermined value is the cumulative adsorbate adsorption at each level x when the relative pressure P/P 0 is a predetermined value.
  • v x (cc(STP)/g; STP refers to standard conditions 0° C., 1 atm) the adsorbate molecular weight M a and the adsorbate liquid density ⁇ a (g/cm 3 ), from equation (1) Desired.
  • V x (v x ⁇ M a )/(22414 ⁇ a ) Equation (1)
  • nitrogen is used as the adsorbate
  • the adsorbate molecular weight M a is 28.013
  • the adsorbate liquid density ⁇ a (g/cm 3 ) is 0.8080.
  • the total pore volume V 0 is the pore volume obtained by applying the formula (1) to the cumulative nitrogen gas adsorption amount v 0 (cc (STP) / g) when the relative pressure P / P 0 is the maximum value.
  • the V 3 is the pore volume obtained by applying the formula (1) to the accumulated nitrogen gas adsorption amount v 3 (cc(STP)/g) when the relative pressure P/P 0 is 10 ⁇ 2 .
  • V 3 /V 0 is within the above range means that a certain amount of pores containing a silicon component and pores not containing a silicon component are present in the composite carbon particles.
  • the silicon component for intercalation of lithium is sufficiently present in the composite carbon particles, and at the same time, when lithium is intercalated and deintercalated, the pores not containing the silicon component are filled with the silicon component. Since the volume change due to the expansion/contraction is sufficiently absorbed, the expansion/contraction of the composite carbon particles can be kept small, which leads to the suppression of the expansion/contraction of the electrode. Therefore, the capacity and cycle characteristics of the lithium ion secondary battery can be improved.
  • the porous carbon material preferably has a total pore volume V 0 of 0.4 cc/g or more and 1.2 cc/g or less in a nitrogen adsorption test, and more preferably 0.5 cc/g or more and 1.1 cc/g or less. It is more preferable to have A porous carbon material having a V 0 within such a range can contain a certain amount of silicon component. Therefore, the amount of lithium inserted into the composite carbon particles can be increased.
  • the porous carbon material further has, in a nitrogen adsorption test,
  • the BET specific surface area is preferably 800 m 2 /g or more.
  • V 1 represents the pore volume obtained by applying the formula (1) to the accumulated nitrogen gas adsorption amount v 1 (cc(STP)/g) when the relative pressure P/P 0 is 0.1.
  • V 1 /V 0 ⁇ >0.75.
  • V 1 /V 0 0.75 or more, it means that the ratio of micropores to all pores is large and at the same time the ratio of mesopores and macropores is small.
  • the size of the silicon component deposited in the pores of the porous carbon material depends on the size of the pores. The proportion of sized silicon components formed in the composite carbon particles will be reduced.
  • a silicon component having a size of mesopores or macropores is a coarse silicon component, and may crack due to expansion and contraction of the silicon component due to charging and discharging.
  • the silicon component having a size of about micropores is a fine silicon component, and is less likely to crack during the charging and discharging. Therefore, by using a porous carbon material having V 1 /V 0 greater than 0.75, the cycle characteristics of the lithium ion secondary battery can be improved. From this point of view, V 1 /V 0 is more preferably 0.77 or more. V 1 /V 0 is not particularly limited as long as V 3 /V 0 >0.5 is satisfied.
  • V 2 is the pore volume obtained by applying the formula (1) to the accumulated nitrogen gas adsorption amount v 2 (cc(STP)/g) when the relative pressure P/P 0 is 10 ⁇ 7 .
  • V 2 /V 0 indicates the existence ratio of micropores that are so small that the silicon-containing gas for the deposition of the silicon component cannot enter.
  • V 2 /V 0 of 0.10 or less indicates that the proportion of very small micropores in which no silicon component exists is small. Therefore, it is possible to prevent a situation in which the capacity of the battery is low due to a large number of pores in which no silicon component exists.
  • very small micropores means pores corresponding to the nitrogen adsorption volume at a relative pressure P/P 0 of 10 -7 or less, according to the Horvath-Kawazoe method (HK method).
  • the pore diameter is about 0.4 nm or less.
  • V 2 /V 0 is more preferably V 2 /V 0 ⁇ 0.09.
  • the porous carbon material preferably has a BET specific surface area of 800 m 2 /g or more. With such a specific surface area, a predetermined amount of silicon component is present on the inner and outer surfaces of the pores of the porous carbon material, so that a sufficiently high specific capacity can be obtained as a negative electrode material. From this point of view, the specific surface area of the porous carbon material is more preferably 1000 m 2 /g or more, more preferably 1400 m 2 /g or more.
  • electrode material refers to a negative electrode material or a positive electrode material. Usually, it can be obtained by dividing the discharge capacity or charge capacity obtained in a half cell by the mass of the electrode material used.
  • the carbon that constitutes the porous carbon material has a structure in which crystallites of hexagonal network layers mainly composed of carbon atoms are aggregated or bonded in random directions, and lithium ions are mainly present in the gaps between the crystallites. It is thought that charging and discharging are performed by moving in and out.
  • FWHM(a), 2 ⁇ / ⁇ 44 deg.
  • the value of FWHM(a)/FWHM(b) is preferably 1.20 or more, where FWHM(b) is the half-value width of a nearby peak.
  • 2 ⁇ / ⁇ is a notation that reflects the measurement method, and has the same meaning as the 2 ⁇ notation numerically.
  • FWHM (a) contains a lot of information about the direction of the (002) plane of carbon constituting the porous carbon material, that is, the regularity of the hexagonal network layer direction of carbon, and FWHM (b) is the porous carbon material.
  • FWHM(a)/FWHM(b) is 1.20 or more
  • the hexagonal network area of carbon constituting the porous carbon material Since the regularity in the layer direction is reduced and the turbostratic structure in the porous carbon material is increased, the diffusibility of Li ions is improved.
  • the value of FWHM(a)/FWHM(b) is more preferably 1.25 or more, more preferably 1.30 or more.
  • Phosphorus element is used in the present embodiment, but even if titanium element or zirconium element is used, the regularity of the hexagonal mesh area layer direction of carbon constituting the porous carbon material becomes low, as with the phosphorus element. Turbulent structure increases. This improves the diffusibility of Li ions. However, unlike the use of elemental phosphorus, the interior of the porous carbon material does not become electron-rich, so the electron conductivity is not improved, and the improvement in cycle characteristics is insufficient.
  • the silicon component can be eluted from the pores and surfaces of the composite carbon particles to recover the porous carbon material in the composite carbon particles. Thereby, the physical property values of the porous carbon material that constitutes the composite carbon particles can be examined.
  • the physical properties of the porous carbon material used in the production may be measured in advance by the production method described below and used as the physical properties of the porous carbon material. In the present invention, it is possible to employ either physical property value without any particular limitation.
  • ⁇ 2> Method for Producing Composite Carbon Particles Composite carbon particles according to an embodiment of the present invention can be produced, for example, by the following steps (1) and (2).
  • Step (1) A step of preparing a porous carbon material.
  • Step (2) A silicon-containing gas such as silane gas is allowed to act on the heated porous carbon material to deposit a silicon component on the surface and in the pores of the porous carbon material, thereby containing the porous carbon material and the silicon component.
  • Step (1) By adding elemental phosphorus during or after step (1), the content of elemental phosphorus in the finally obtained composite carbon particles is adjusted to 40 ppm by mass or more and less than 8000 ppm by mass.
  • Step (1) Both commercially available and manufactured porous carbon materials can be used.
  • a method for producing a porous carbon material is to thermally decompose a carbon precursor such as a specific resin or organic substance under specific conditions. For example, synthesizing resins and organic substances, and examining changes in the V 0 , V 1 , V 2 , V 3 , and BET specific surface areas, adjusting the conditions for thermally decomposing them, and carbonaceous materials such as carbon black. For example, it may be prepared to have the above-described characteristics by subjecting it to oxidation treatment, activation treatment, or the like. By adding a compound containing elemental phosphorus at any point in this process, the porous carbon material and the composite carbon particles can contain a predetermined amount of elemental phosphorus. Although the content of elemental phosphorus in the porous carbon material is not particularly limited, it is preferable that the amount of elemental phosphorus in the porous carbon material is 100 ppm by mass or more and less than 25600 ppm by mass.
  • the carbon precursor is not particularly limited, and those listed in known documents such as Japanese Patent No. 6328107, for example, can be used, but phenol resins and copolymers of resorcinol and formaldehyde are preferred.
  • the resin Prior to carbonization, the resin may be cured by heat treating at 50° C.-300° C. for 1-18 hours. After curing, the resin may be pulverized to have a particle size of about 0.5 to 5.0 mm.
  • each element is added to the phenolic resin.
  • a compound containing a phosphorus element, a titanium element, and a compound containing a zirconium element in the raw material, each element is added to the phenolic resin.
  • Methods for adding the compound containing the phosphorus element include a method of mixing it with the raw material, a method of adding it during the reaction, and a method of impregnating the synthesized resin.
  • two or more types can also be used as a compound. When two or more are used, they may be added simultaneously or individually.
  • phosphorus-containing compounds include phosphoric acid such as phosphoric acid, metaphosphoric acid, polyphosphoric acid, condensates thereof, salts thereof, dimethyl phosphate, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, tricresyl phosphate, dilauryl hydrochloride,
  • phosphoric acid such as phosphoric acid, metaphosphoric acid, polyphosphoric acid, condensates thereof, salts thereof, dimethyl phosphate, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, tricresyl phosphate, dilauryl hydrochloride
  • Examples include zenphosphite, trioleylphosphite, tetrahydroxymethylphosphonium sulfate, phosphorylated starch, deoxyribonucleic acid, ribonucleic acid, and phosphate esters and salts such as lecithin.
  • a porous carbon material similarly containing titanium element and zirconium element can be obtained.
  • the above resin can be carbonized by holding it in an inert gas atmosphere at a temperature of 400° C. to 1100° C. for 1 to 20 hours. During this carbonization, depending on the type of carbon precursor used, entraining 10-1000 ppm by volume of water vapor with the inert gas is desirable for adjusting the requirements of the present invention.
  • Activation treatment is performed to develop pores, if necessary.
  • the activation treatment includes a method of contacting the carbide with an activation gas such as steam or CO 2 gas at a high temperature. Another method is to contact KOH or the like with the carbide at a high temperature. Activation with water vapor or CO 2 gas proceeds by vaporizing carbon, whereas activation with KOH causes less carbon loss because potassium expands the distance between carbon layers and develops pores.
  • the carbide is heated in an inert gas atmosphere to 800° C. to 1100° C., then switched to CO 2 gas, and held at that temperature for 0.1 to 20 hours.
  • This treatment causes the carbide to develop more pores.
  • the activation gas may contain an inert gas such as nitrogen or argon or a reducing gas such as hydrogen as long as the activation is not inhibited.
  • the pore size distribution and BET specific surface area of the obtained porous carbon material may be examined, and heat treatment may be performed in an inert gas such as Ar in order to adjust them.
  • the temperature is maintained at 1000° C. to 2000° C. for 1 to 20 hours.
  • the pores are made smaller, and a porous carbon material having desired V 0 , V 1 , V 2 , V 3 and BET specific surface area can be obtained.
  • the effect of increasing the rate of activation can be obtained.
  • Step (2) After manufacturing the composite carbon particles through step (2), the particles may aggregate together. In that case, it is preferable to crush the carbon material to restore the shape and particle size distribution of the raw material porous carbon material. However, if excessive energy is applied at that time to pulverize the composite carbon particles to change the particle shape, the surface area of the composite carbon particles without the coating layer increases, and the oxidation suppressing ability may decrease.
  • Step (2) includes the following step (2-A) and optionally step (2-B).
  • Silane gas A step of bringing a gas containing hydrocarbon having an unsaturated bond into contact with the Si/C particles at 400° C. or lower Silane gas can be preferably used as the silicon-containing gas.
  • Silane gas may be used mixed with an inert gas such as helium or argon, or a reducing gas such as hydrogen.
  • a porous carbon material is placed in a reactor, and a silicon-containing gas is brought into contact with the porous carbon material to deposit silicon in the pores and on the surface of the porous carbon material, Si/C This is the step of obtaining particles.
  • the shape of the reactor is not limited.
  • a stationary furnace a furnace having a powder stirring function such as a fluidized bed furnace or a rotary kiln, or a continuous furnace such as a roller hearth kiln or a pusher furnace can be used.
  • the reaction temperature is not limited as long as it decomposes the silicon-containing gas such as silane gas and deposits silicon in the pores of the porous carbon material, but is preferably 250°C or higher and 550°C or lower. 300° C. or higher and 450° C. or lower is more preferable. If the temperature is less than 250° C., the silane gas is not sufficiently decomposed, so that the deposition of silicon becomes insufficient. When the temperature exceeds 550°C, decomposition of the silane gas occurs within the pores of the porous carbon material, and silicon deposits on the surface of the porous carbon material (including the openings of the pores) rather than depositing silicon within the pores. Since the openings of the pores are clogged with the deposited silicon, deposition in the pores becomes insufficient.
  • the silicon-containing gas such as silane gas and deposits silicon in the pores of the porous carbon material
  • step (2-B) the Si/C particles obtained in step (2-A) are charged into a reactor, and a gas containing hydrocarbons having unsaturated bonds is added to the Si/C particles at 400° C. or less. This is the step of contacting with C particles.
  • a layer containing hydrocarbon is formed on the surface of the Si/C particles in step (2-B), and this layer is referred to as a coat layer in this specification.
  • a method of depositing carbon on the surface, such as carbon CVD, which may form a thick carbon coating, is to react Si—H groups on the surface of Si/C particles with hydrocarbons having unsaturated bonds.
  • This coat layer may contain a substance obtained by reacting hydrocarbons with each other.
  • a hydrocarbon gas having an unsaturated bond a hydrocarbon gas having a double bond or a triple bond can be used. If the hydrocarbon is a compound that has a low vapor pressure and does not gasify at normal pressure, the hydrocarbon may be used at a pressure lower than normal pressure. Acetylene, ethylene, propylene, and 1,3-butadiene, which are gases at normal pressure, are preferred, and acetylene and ethylene are more preferred. At this time, multiple kinds of hydrocarbons may be used. Also, an inert gas such as helium or argon, or a reducing gas such as hydrogen may be mixed and used.
  • step (2-B) treatment at a low temperature of 400°C or less is necessary in order to react the Si—H groups and the unsaturated bonds.
  • this temperature is exceeded, the amount of decomposed Si—H groups increases, making it difficult for the desired reaction, ie, the reaction between the Si—H groups on the surface of the Si/C particles and the unsaturated bonds of hydrocarbons, to occur.
  • the desired reaction ie, the reaction between the Si—H groups on the surface of the Si/C particles and the unsaturated bonds of hydrocarbons.
  • the reaction between the porous carbon material and silicon occurs at a high temperature exceeding 400° C., and silicon carbide is produced, thereby reducing the silicon content. put away.
  • the lower limit of the reaction temperature is not limited as long as it is a temperature at which the hydrocarbon having an unsaturated bond reacts on the surface of the Si/C particles. However, if the reaction temperature is low, the reaction rate is low. The above is more preferable.
  • the thickness of the coating layer may be a thickness corresponding to a monomolecular layer of hydrocarbon, or may be a thickness corresponding to several molecular layers. Also, part of the hydrocarbons may be decomposed. Even if part of the hydrocarbon is decomposed into carbon, the coating layer is preferably a thin film because it is a material with high resistance unlike the carbon coating. Therefore, it is preferable that the weight change before and after step (2-B) is small.
  • the increase in the mass of the Si/C particles having the coat layer obtained in step (2-B) relative to the mass of the Si/C particles before step (2-B) is 1.0% by mass or less. is more preferable, and 0.5% by mass or less is even more preferable.
  • step (2-B) is not necessarily required, when step (2-B) is performed, it is preferable to perform step (2-A) and step (2-B) continuously. Since the silicon on the surface of the Si/C particles obtained in the step (2-A) is highly active, it is oxidized when exposed to the atmosphere, and Si—H groups on the surface are reduced. Therefore, it is preferable to continuously perform steps (2-A) and (2-B) without exposure to the atmosphere (air).
  • the time between steps (2-A) and (2-B) is not limited as long as the Si/C particles are not exposed to the atmosphere.
  • step (2-B) may be performed after storage in an inert gas atmosphere. If the Si/C particles obtained in step (2-A) do not come into contact with the atmosphere, steps (2-A) and (2-B) may be carried out using separate devices.
  • step (2-B) may be oxidized.
  • This oxidation treatment is a step of introducing oxygen into the coating layer (the layer containing hydrocarbon formed on the surface of the Si/C particles in step (2-B)).
  • the presence of oxygen in the coat layer improves the ability to suppress oxidation and lowers the resistance.
  • Oxidation can be performed by contacting the coat layer with an oxygen-containing gas (more specifically, an oxidizing gas).
  • the oxygen-containing gas preferably has an oxygen concentration of 1 to 25% by volume, more preferably 1 to 20% by volume, even more preferably 5 to 20% by volume. In that case the oxygen is diluted with argon or nitrogen.
  • Air may be used as the oxygen-containing gas, but it is preferable to adjust the humidity of the air and keep it constant for stable oxidation.
  • the reaction temperature that is, the temperature at which the coat layer is brought into contact with the oxygen-containing gas, is preferably room temperature or higher and 200°C or lower. If the temperature exceeds 200° C., decomposition of the coat layer or excessive oxidation of silicon may occur.
  • the reaction time that is, the time during which the coating layer is brought into contact with the oxygen-containing gas is, for example, 0.1 to 120 hours.
  • the oxidation treatment may vary the oxygen concentration.
  • the temperature during heat treatment is preferably 400° C. or less.
  • Heat treatment at 400° C. or lower decomposes unreacted Si—H groups and converts them to silicon, so that the coating layer can be stably combined with oxygen.
  • the heat treatment time is, for example, 0.1 to 100 hours.
  • an apparatus different from the step (2-B) may be used.
  • the step (2-B) and the oxidation treatment may be performed multiple times. For example, there is a method of performing the step (2-B) after performing the oxidation treatment, or performing the step (2-B) after performing the oxidation treatment and then performing the oxidation treatment.
  • the composite carbon particles according to the present invention have a layer outside the above-described composite carbon particles having the Si/C particles and the coat layer on the surface of the Si/C particles (hereinafter also referred to as “composite carbon particle body"). You may have In order to distinguish from the above-mentioned “coat layer”, the layer arranged further outside the composite carbon particle body is here referred to as “surface coat layer”.
  • Examples of the method of forming the surface coat layer include a method of forming a layer on at least part of the surface of the composite carbon particles, specifically by carbon coating, inorganic oxide coating or polymer coating.
  • Carbon coating techniques include chemical vapor deposition (CVD) and physical vapor deposition (PVD).
  • Inorganic oxide coating techniques include chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), and wet processes.
  • the wet method includes a method in which the composite carbon particle body is coated with a liquid obtained by dissolving and/or dispersing an inorganic oxide precursor in a solvent, and the solvent is removed by heat treatment or the like.
  • the type of polymer coating may be a method of coating using a polymer solution, a method of coating using a polymer precursor containing a monomer and polymerizing by the action of temperature or light, or a combination thereof.
  • the surface coating layer of the composite carbon particles can be analyzed by performing surface analysis of the composite carbon particles.
  • Examples of surface analysis include SEM-EDS, Auger electron spectroscopy, XPS, microscopic infrared spectroscopy, microscopic Raman spectroscopy, and the like.
  • the temperature during coating should be less than 500 ° C., or PVD
  • the polymer-coated composite carbon particles contain inorganic particles made of one or more selected from graphite and carbon black and a polymer component on at least part of the surface of the composite carbon particle body, and the content of the polymer component is It has an inorganic particle-containing polymer component coating layer of 0.1 to 10.0% by mass as a surface coating layer.
  • the production of polymer-coated composite carbon particles is preferably carried out by a wet method. Specifically, in a solvent, inorganic particles made of one or more selected from graphite and carbon black, a polymer component, and a composite carbon particle main body are mixed, and the mixture is dried to remove the solvent.
  • a liquid in which each component is dissolved or dispersed may be prepared in advance and then mixed. Since it is preferable that the inorganic particles are smaller than the main body of the composite carbon particles, it is preferable to use a liquid in which the inorganic particles are dispersed in advance. When preparing a liquid in which inorganic particles are dispersed, it is more preferable to apply a shearing force using a ball mill, bead mill, or the like, because the fine particles can be uniformly dispersed. When dispersing the inorganic particles, a dispersing aid may be added as appropriate. A dispersing aid can be freely selected from known substances and used.
  • the type of polymer component is not particularly limited.
  • polysaccharides, cellulose derivatives, animal water-soluble polymers, lignin derivatives and water-soluble synthetic polymers monosaccharides, disaccharides, oligosaccharides, amino acids, gallic acid, tannin, saccharin, salts of saccharin, butynediol, sorbitol, etc.
  • At least one selected from the group consisting of polyhydric alcohols such as sugar alcohols, glycerin, 1,3-butanediol, and dipropylene glycol can be used.
  • the solvent is not particularly limited as long as it can dissolve and disperse the above materials, but water is preferred.
  • a plurality of types of solvents may be mixed.
  • the temperature during mixing is preferably 50°C to 200°C. Since the composite carbon particles according to the present invention are hardly oxidized in water, it is possible to form a surface coat layer by a wet method using water, which is less burdensome to the working environment, and furthermore, the surface of the composite carbon particle main body can be In addition, a uniform surface coat can be easily formed.
  • the temperature during drying is not particularly limited as long as the polymer component is not decomposed and distilled off, and can be selected, for example, from 50°C to 200°C. Drying in an inert gas atmosphere or drying under vacuum may be performed.
  • the obtained polymer-coated composite carbon particles may optionally be subjected to a crushing step or a sieving step to remove coarse aggregated particles.
  • the content of the polymer component can be determined, for example, by heating sufficiently dried polymer-coated composite carbon particles to a temperature higher than the temperature at which the polymer component decomposes and lower than the temperature at which silicon or carbon is oxidized (for example, 300° C.). It can be confirmed by measuring the mass of the composite material after the polymer component is decomposed. Specifically, when the mass of the polymer-coated composite carbon particles before heating is Ag, and the mass of the composite carbon particles after heating is Bg, (AB) is the content of the polymer component. The content can be calculated by ⁇ (AB)/A ⁇ 100.
  • thermogravimetry TG
  • TG thermogravimetry
  • Suppression of oxidation of silicon inside the composite carbon particles over time means suppression of oxidation of the silicon component over time when the composite carbon particles are exposed to air or an oxygen-containing atmosphere. .
  • the presence of the surface coat layer on the composite carbon particles can suppress the entry of air or oxygen-containing gas into the interior of the composite carbon particles.
  • Improving the initial coulombic efficiency means reducing the amount of lithium ions trapped in the composite carbon particles when the lithium ions are first inserted into the composite carbon particles inside the lithium ion battery.
  • an electrolytic solution decomposition product coating (SEI ⁇ Solid Electrolyte Interface> coating) is formed on the surface of the composite carbon particles or on the lithium ion entrance to the composite carbon particles.
  • SEI Solid Electrolyte Interface> coating
  • the presence of the surface coating layer on the surface of the composite carbon particles prevents lithium ion insertion into the pores that are likely to be blocked by the SEI coating. can improve the first coulombic efficiency.
  • Improving cycle characteristics here means suppressing a decrease in capacity when the composite carbon particles are applied to a lithium ion battery and charging and discharging are repeated. It is thought that when charging and discharging are repeated in a lithium ion battery, the silicon component in the composite carbon particles reacts with fluorine, which is a component element of the electrolytic solution, and is eluted as a silicon fluoride compound. The elution of the silicon component reduces the specific capacity of the composite carbon particles. When the coating layer is present on the surface of the composite carbon particles, elution of the silicon component is suppressed, and a decrease in the specific capacity of the composite carbon particles can be suppressed.
  • Negative electrode material The composite carbon particles of one embodiment of the present invention can be widely used as an electrode material for metal ion secondary batteries. It can be used preferably.
  • the term "negative electrode material” refers to a negative electrode active material or a composite of a negative electrode active material and other materials.
  • the composite carbon particles may be used alone, but may also be used together with other negative electrode materials for the purpose of, for example, adjusting the battery capacity or absorbing volume changes due to expansion/contraction of the composite carbon particles. good.
  • negative electrode materials those commonly used in lithium ion secondary batteries can be used. When other negative electrode materials are used, composite carbon particles are usually mixed with other negative electrode materials.
  • Examples of other negative electrode materials include graphite, hard carbon, lithium titanate (Li 4 Ti 5 O 12 ), alloy-based active materials such as silicon and tin, and composite materials thereof. These negative electrode materials are usually used in the form of particles. As the negative electrode material other than the composite carbon particles, one kind or two or more kinds may be used. Among them, graphite and hard carbon are particularly preferably used.
  • the form of the negative electrode material of the present invention containing composite carbon particles and graphite particles is one of the preferred forms from the viewpoint of adjusting the capacity and reducing the volume change of the entire negative electrode mixture layer.
  • the negative electrode mixture layer according to the present invention contains the negative electrode material.
  • the negative electrode mixture layer of one embodiment of the present invention can be used as a negative electrode mixture layer for a lithium ion secondary battery.
  • the negative electrode mixture layer is generally composed of a negative electrode material, a binder, and a conductive aid as an optional component.
  • a slurry for forming a negative electrode mixture layer is prepared using a negative electrode material, a binder, a conductive additive as an optional component, and a solvent.
  • the slurry is applied to a current collector such as copper foil and dried. After vacuum-drying this, it is roll-pressed, and then cut into a required shape and size, or punched out.
  • the pressure during roll pressing is usually 100-500 MPa.
  • the obtained product is sometimes called a negative electrode sheet.
  • a negative electrode sheet is obtained by pressing and consists of a negative electrode mixture layer and a current collector.
  • any binder commonly used in the negative electrode mixture layer of lithium ion secondary batteries can be freely selected and used.
  • examples include polyethylene, polypropylene, ethylene propylene terpolymer, butadiene rubber, styrene butadiene rubber, butyl rubber, acrylic rubber, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene oxide, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, carboxymethylcellulose and its salts, polyacrylic acid, polyacrylamide, and the like.
  • a binder may be used individually by 1 type, or may use 2 or more types.
  • the amount of the binder is preferably 0.5 to 30 parts by mass with respect to 100 parts by mass of the negative electrode material.
  • the conductive aid is not particularly limited as long as it serves to impart conductivity and dimensional stability (the effect of absorbing volume changes of the composite carbon particles during lithium insertion/extraction) to the electrode.
  • carbon nanotubes, carbon nanofibers, vapor-grown carbon fibers e.g., "VGCF (registered trademark)-H” manufactured by Showa Denko KK
  • conductive carbon blacks e.g., "Denka Black (registered trademark)” Denka Co., Ltd.
  • SUPER C65 by Imerys Graphite & Carbon
  • SUPER C45 by Imerys Graphite & Carbon
  • conductive graphite for example, "KS6L” by Imerys Graphite & Carbon
  • SFG6L by Imerys Graphite & Carbon Co.
  • the amount of the conductive aid is preferably 1 to 30 parts by mass with respect to 100 parts by mass of the negative electrode material.
  • carbon nanotubes, carbon nanofibers, and vapor-grown carbon fibers are preferably contained, and the fiber length of these conductive aids is preferably 1/2 or more of D v50 of the composite carbon particles. With this length, these conductive aids bridge between the electrode active materials containing the composite carbon particles, and the cycle characteristics can be improved.
  • Single-wall type and multi-wall type carbon nanotubes and carbon nanofibers with a fiber diameter of 15 nm or less are preferable because the number of cross-links increases with the same amount of addition compared to those with a larger fiber diameter. . Moreover, since it is more flexible, it is more preferable from the viewpoint of increasing the electrode density.
  • Solvents used in preparing slurry for electrode coating are not particularly limited, and include N-methyl-2-pyrrolidone, dimethylformamide, isopropanol, water and the like. In the case of a binder using water as a solvent, it is also preferable to use a thickener together. The amount of the solvent is adjusted so that the slurry has a viscosity that facilitates coating on the current collector.
  • Lithium Ion Secondary Battery includes the negative electrode mixture layer.
  • the lithium ion secondary battery is generally composed of a negative electrode composed of the negative electrode mixture layer and the current collector, a positive electrode composed of the positive electrode mixture layer and the current collector, and a non-aqueous electrolyte and a non-aqueous polymer electrolyte present therebetween. It includes at least one, a separator, and a battery case that houses them.
  • the lithium ion secondary battery only needs to include the negative electrode material mixture layer, and other configurations including conventionally known configurations can be employed without particular limitations.
  • the positive electrode mixture layer usually consists of a positive electrode material, a conductive aid, and a binder.
  • a positive electrode in the lithium ion secondary battery may have a general configuration in a normal lithium ion secondary battery.
  • the positive electrode material is not particularly limited as long as it can be electrochemically intercalated and deintercalated with lithium and the redox potential of these reactions is sufficiently higher than the redox potential of the negative electrode reaction.
  • LiCoO 2 , LiNiO 2 , LiMn 2 O 4 , LiCo 1/3 Mn 1/3 Ni 1/3 O 2 , carbon-coated LiFePO 4 and mixtures thereof can be suitably used.
  • the term “positive electrode material” refers to a positive electrode active material, or a composite of a positive electrode active material and another material.
  • the conductive aid As the conductive aid, the binder, and the solvent for slurry preparation, those mentioned in the section of the negative electrode can be used.
  • Aluminum foil is preferably used as the current collector.
  • the non-aqueous electrolyte and non-aqueous polymer electrolyte used in the lithium ion secondary battery are not particularly limited.
  • nonaqueous electrolytic solution examples include lithium salts such as LiClO4, LiPF6 , LiAsF6 , LiBF4 , LiSO3CF3 , CH3SO3Li , ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate,
  • organic electrolytic solutions dissolved in non-aqueous solvents such as propylene carbonate, butylene carbonate, acetonitrile, propionitrile, dimethoxyethane, tetrahydrofuran, and ⁇ -butyrolactone.
  • non-aqueous polymer electrolytes examples include gel-like polymers containing polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, and the like, and the non-aqueous solvent, or polymers having ethylene oxide bonds.
  • a solid polymer containing the above lithium salt can be used.
  • a small amount of additives used in electrolyte solutions for general lithium-ion batteries may be added to the non-aqueous electrolyte solution.
  • examples of such substances include vinylene carbonate (VC), biphenyl, propane sultone (PS), fluoroethylene carbonate (FEC), ethylene sultone (ES) and the like.
  • VC and FEC are preferred.
  • the amount to be added is preferably 0.01 to 20% by mass with respect to 100% by mass of the non-aqueous electrolytic solution.
  • the separator can be freely selected from materials that can be used in general lithium-ion secondary batteries, including combinations thereof, and examples thereof include microporous films made of polyethylene or polypropylene. Moreover, it is also possible to use such a separator mixed with particles such as SiO 2 or Al 2 O 3 as a filler, or a separator adhered to the surface.
  • the battery case is not particularly limited as long as it can accommodate the positive electrode, the negative electrode, the separator, and the electrolytic solution.
  • those standardized in the industry such as commercially available battery packs, 18650-type cylindrical cells, coin-type cells, etc., they can be freely designed and used, such as those packed in aluminum packaging. can.
  • the lithium ion secondary battery according to the present invention is a power source for electronic devices such as smart phones, tablet PCs, and personal digital assistants; a power source for electric motors such as electric tools, vacuum cleaners, electric bicycles, drones, and electric vehicles; It can be used for storage of electric power obtained by photovoltaic power generation, wind power generation, or the like.
  • the ratio of the peak intensity (I Si ) of the peak within the range of 460 to 495 cm ⁇ 1 to the peak intensity (I G ) of the peak around 1580 cm ⁇ 1 was defined as (I Si /I G ) i .
  • the ratio of the peak intensity (I D ) of the peak around 1350 cm ⁇ 1 to the peak intensity (I G ) of the peak around 1580 cm ⁇ 1 in the Raman spectrum was defined as the R i value (I D /I G ) i .
  • Adsorbed gas Nitrogen gas Pretreatment: Under vacuum, 400°C, 3 hours Lower limit of relative pressure (P/P 0 ): 10 ⁇ 8 order Upper limit of relative pressure (P/P 0 ): 0.990 or more Relative pressure P/ The total pore volume at the maximum value of P 0 was defined as V 0 (P 0 is saturated vapor pressure).
  • the maximum value of P/P 0 was 0.993 to 0.999.
  • Fluorescent X-ray analyzer Rigaku NEX CG Tube voltage: 50kV Tube current: 1.00mA Sample cup: ⁇ 32 12mL CH1530 Sample weight: 3g Sample height: 11mm Powder was introduced into a sample cup, and silicon, phosphorus and titanium contents were measured by the FP method. [Confirmation of silicon in composite carbon particles] After powder cross-section polishing, it was carried out with an electron microscope. Specifically, a carbon double-sided tape is attached to a Si wafer, and after the powder of composite carbon particles is supported on the carbon tape, the powder of composite carbon particles supported on the end face of the carbon tape is removed by a cross session polisher (registered trademark; Japan).
  • a cross session polisher registered trademark; Japan
  • ⁇ X-ray diffractometer Rigaku SmartLab (registered trademark)
  • ⁇ X-ray type Cu-K ⁇ ray
  • K ⁇ ray elimination method Ni filter ⁇ X-ray output: 45 kV, 200 mA ⁇ Measurement range (2 ⁇ / ⁇ ): 10.0 to 80.0 deg.
  • ⁇ Scan speed 2.0 deg. /min.
  • the obtained waveform was subjected to profile fitting after removal of background (Sonneveld-Visser method) and removal of K ⁇ 2 components using X-ray analysis software PDXL.
  • FWHM(b) was defined as the half-value width of a nearby peak. FWHM(a)/FWHM(b) were calculated. [C, O, Si atomic number ratios A C , A O , A Si and Si species state ratios B SiO2 , B SiO , B Si on the surface of composite carbon particles] Analysis was performed by X-ray Photoelectron Spectroscopy (XPS).
  • Si divalent means SiO.
  • Si tetravalent means SiO2 . Since monovalent and trivalent Si have low intensity, they are excluded because the accuracy of peak fitting is lowered.
  • Silicon carbide is also generally included in the Si 2 valence, but looking at the peak shape of the C 1s Narrow spectrum, the peak shape disturbance ( Since no shoulder peak or tailing was observed, the abundance of silicon carbide was considered to be below the detection limit. Therefore, the Si divalent peak was thought to represent only SiO.
  • SBR Styrene-butadiene rubber
  • CMC carboxymethylcellulose
  • Carbon black (SUPER C45, manufactured by Imerys Graphite & Carbon Co., Ltd.) and vapor-grown carbon fiber (VGCF (registered trademark)-H, manufactured by Showa Denko Co., Ltd.) are mixed at a mass ratio of 3:2 as a mixed conductive agent. prepared.
  • the slurry for forming the electrode mixture layer was uniformly coated on a copper foil having a thickness of 20 ⁇ m using a doctor blade so as to have a thickness of 150 ⁇ m and a width of 6 cm. got a sheet.
  • the dried electrode was pressed by a roll press for one pass under a load of 20 tons, a roll speed of 2.0 m/min, and an upper and lower roll gap of 30 ⁇ m to obtain an electrode sheet for battery evaluation.
  • the electrode density should be in the range of 1.3 to 1.6 g/cm 3 . If the electrode density is not obtained under the above roll-press conditions, the roll-press conditions are appropriately changed.
  • the pressed electrode sheet (collector + electrode mixture layer) was punched into a circular shape with a diameter of 16 mm, and its mass and thickness were measured. From these values, the mass and thickness of the electrode mixture layer were obtained by subtracting the mass and thickness of the separately measured current collector (circular shape with a diameter of 16 mm).
  • the electrolyte in the three-electrode laminate type half cell described later is a solvent obtained by mixing ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a volume ratio of 3:5:2, 1% by mass of vinylene carbonate (VC), fluoro It is a liquid obtained by mixing 2% by mass of ethylene carbonate (FEC) and further dissolving the electrolyte LiPF 6 in this to a concentration of 1 mol/L.
  • VC vinylene carbonate
  • FEC ethylene carbonate
  • a material having a higher oxidation-reduction potential than the working electrode for example, lithium cobalt oxide, nickel manganese lithium cobalt oxide, etc. is opposed to the working electrode, so the working electrode becomes the negative electrode.
  • a Ni tab with a width of 5 mm was prepared for a counter electrode and a reference electrode, and a Ni mesh of 5 mm ⁇ 20 mm was attached so as to overlap a 5 mm portion of the tip.
  • Ni tabs and the 5 mm width of the Ni mesh were aligned and attached.
  • a Ni tab for the working electrode was also attached to the Cu foil tab portion of the electrode piece.
  • the Ni mesh at the end of the Ni tab for the counter electrode was attached to the corner of the Li piece so as to be perpendicular to the 3.0 cm side of the Li piece for the counter electrode.
  • the Ni mesh at the tip of the reference electrode Ni tab was attached to the center of the 1.5 cm side of the Li piece so as to be perpendicular to the 1.5 cm side of the reference electrode Li piece.
  • a polypropylene microporous film was sandwiched between the working electrode and the counter electrode, and the reference electrode was close to the working electrode and connected via the polypropylene microporous film so as not to cause a short circuit.
  • This state was sandwiched between two rectangular aluminum-laminated wrapping materials with all the ends of the Ni tabs protruding outside, and the three sides were heat-sealed. Then, an electrolytic solution was injected through the opening. After that, the opening was sealed by heat sealing to prepare a three-electrode laminate type half cell for evaluation.
  • the current value corresponding to 0.1 C is the capacity of the working electrode estimated from the mass and theoretical specific capacity of silicon and graphite in the negative electrode material contained in the working electrode (4200 mAh / g and 372 mAh / g, respectively). , is the magnitude of the current that can be discharged in 10 hours.
  • a 0.2 C constant current test was performed for 5 cycles under the following conditions.
  • the first constant current discharge was performed at 0.2C, and the potential was 0.005V vs.
  • the discharge was switched to constant potential discharge, and the cutoff current at that time was set to 0.05C.
  • the cutoff potential is set to 1.5 V vs.
  • a constant current charge of 0.2 C with Li/Li + was performed.
  • a discharge-charge cycle test was conducted by the following method. First, a constant current discharge at 1C and a potential of 0.005V vs. When Li/Li + was reached, the discharge was switched to constant potential discharge, and the cutoff current at that time was set to 0.05C. Next, the cutoff potential is set to 1.5 V vs. A constant current charge of 1C was performed as Li/Li + .
  • This discharging and charging operation was regarded as one cycle, and 20 cycles were performed, and in the 21st cycle, a low rate test was performed in which the above discharging and charging rate was changed to 0.1C. This 21-cycle test was repeated three times to obtain a total of 63 cycles.
  • the charging (Li desorption) capacity retention rate at the 50th cycle was defined and calculated by the following equation.
  • 50th cycle charging (Li desorption) capacity retention rate (%) ⁇ (50th cycle charge capacity)/(1st cycle charge capacity) ⁇ 100
  • the charge capacity in the first cycle in the above formula means the charge capacity in the first cycle in the charge/discharge cycle test at 1C after the constant current test at 0.2C.
  • This charge (Li desorption) specific capacity in the first cycle is called initial charge (Li desorption) specific capacity and is defined by the following equation.
  • a mixed solvent of pure water: ethanol 2:1 (w/w) was added to the obtained resin-containing solution, followed by washing with stirring and suction filtration, and unreacted substances and the like were removed as a filtrate.
  • the obtained solid was dried at 80° C. under reduced pressure of 50 mmHg to synthesize a phenolic resin containing phosphorus.
  • a phenolic resin containing phosphorus was cured by holding it in a nitrogen atmosphere at 250° C. for 3 hours in a firing furnace, and then carbonized by heating at 900° C. for 1 hour.
  • 5 g of the obtained carbide was placed in a ceramic boat and set in a tubular electric furnace. After the atmosphere was sufficiently replaced by flowing nitrogen gas at 500 sccm, the electric furnace was heated to 950° C. and activated by switching to a carbon dioxide gas flow of 250 sccm.
  • a calibration curve of the change in the total pore volume depending on the activation time under the conditions and the activation rate were calculated. Using the calibration curve, the activation time was adjusted to obtain porous carbon materials shown in Table 1-1.
  • the porous carbon material was treated in a tube furnace having a silane gas flow of 100% by volume at a set temperature of 400° C. and a flow rate of 65 sccm for 120 minutes to obtain composite carbon particles containing silicon shown in Table 1-1. rice field.
  • Example 2 A phosphorus-containing phenolic resin was synthesized in the same manner as in Example 1, except that 0.5763 g of the 74.1% by mass tetrahydroxymethylphosphonium sulfate aqueous solution (THPS) was used.
  • THPS tetrahydroxymethylphosphonium sulfate aqueous solution
  • Porous carbon materials shown in Table 1-1 were obtained in the same manner as in Example 1 using a phenolic resin containing phosphorus. Using the above porous carbon material and treating in the same manner as in Example 1, composite carbon particles containing silicon shown in Table 1-1 were obtained.
  • Example 3 A phenolic resin containing phosphorus was synthesized in the same manner as in Example 1, except that 2.056 g of the 74.1% by mass tetrahydroxymethylphosphonium sulfate aqueous solution (THPS) was used.
  • THPS tetrahydroxymethylphosphonium sulfate aqueous solution
  • Porous carbon materials shown in Table 1-1 were obtained in the same manner as in Example 1 using a phenolic resin containing phosphorus. Using the above porous carbon material and treating in the same manner as in Example 1, composite carbon particles containing silicon shown in Table 1-1 were obtained.
  • Example 4 A phosphorus-containing phenolic resin was synthesized in the same manner as in Example 1, except that 3.280 g of the 74.1% by mass tetrahydroxymethylphosphonium sulfate aqueous solution (THPS) was used.
  • THPS tetrahydroxymethylphosphonium sulfate aqueous solution
  • Porous carbon materials shown in Table 1-1 were obtained in the same manner as in Example 1 using a phenolic resin containing phosphorus. Using the above porous carbon material and treating in the same manner as in Example 1, composite carbon particles containing silicon shown in Table 1-1 were obtained.
  • Example 5 In a flask equipped with a condenser and a stirrer, 180.0 g of phenol (manufactured by Kanto Kagaku Co., Ltd.), 216.0 g of polyvinyl alcohol (GM-14R (solid content 18% by mass aqueous solution), manufactured by Mitsubishi Chemical Corporation), and 117 g of water.
  • SCMG registered trademark, manufactured by Showa Denko KK
  • a mixed solvent of pure water: ethanol 2:1 (w/w) was added to the obtained resin-containing solution, followed by washing with stirring and suction filtration, and unreacted substances and the like were removed as a filtrate.
  • the obtained solid was dried at 80° C. under reduced pressure of 50 mmHg to synthesize a phenolic resin containing phosphorus.
  • a phenolic resin containing phosphorus was cured by holding it in a nitrogen atmosphere at 250° C. for 3 hours in a firing furnace, and then carbonized by heating at 900° C. for 1 hour.
  • 5 g of carbonized phenolic resin was placed in a ceramic boat and set in a tubular electric furnace. After the atmosphere was sufficiently replaced by flowing nitrogen gas at 500 sccm, the electric furnace was heated to 950° C. and activated by switching to a carbon dioxide gas flow of 250 sccm.
  • a calibration curve of the change in the total pore volume depending on the activation time under the conditions and the activation rate were calculated. Using the calibration curve, the activation time was adjusted to obtain porous carbon materials shown in Table 1-1.
  • the porous carbon material was treated in a tube furnace having a silane gas flow of 100% by volume at a set temperature of 400° C. and a flow rate of 65 sccm for 125 minutes to obtain composite carbon particles containing silicon shown in Table 1-1. rice field.
  • Example 6 In a flask equipped with a condenser and a stirrer, 180.0 g of phenol (manufactured by Kanto Kagaku Co., Ltd.), 261.0 g of polyvinyl alcohol (GM-14R (solid content 18% by mass aqueous solution), manufactured by Mitsubishi Chemical Corporation), 81 g of water was charged and mixed with stirring at 50 ° C. and 150 rpm, 0.0795 g of 74.1% by mass tetrahydroxymethylphosphonium sulfate aqueous solution (THPS, manufactured by Tokyo Chemical Industry Co., Ltd.) was added and stirred at 50 ° C. and 250 rpm.
  • phenol manufactured by Kanto Kagaku Co., Ltd.
  • G-14R solid content 18% by mass aqueous solution
  • THPS tetrahydroxymethylphosphonium sulfate aqueous solution
  • the resulting resin-containing solution was washed with stirring while adding water, and suction filtered to remove unreacted substances and the like as a filtrate.
  • the obtained solid matter was dried in a hot air dryer at 120° C. for 18 hours to synthesize a phenolic resin containing phosphorus.
  • a phenol resin containing phosphorus was carbonized by heating in a nitrogen atmosphere at 900° C. for 1 hour. 10 g of the obtained carbide was placed in a sagger and set in a quartz tubular furnace. After sufficiently replacing the atmosphere by flowing nitrogen gas at 2000 sccm, the quartz tubular furnace was heated to 950° C. and activated by switching to a carbon dioxide gas flow of 1500 sccm. A calibration curve of the change in the total pore volume depending on the activation time under the conditions and the activation rate were calculated. The calibration curve was used to adjust the activation time to obtain porous carbon materials shown in Table 1-2.
  • porous carbon material was placed in a tubular furnace and the interior of the tubular furnace was replaced with argon, a mixed gas of 100% by volume silane gas (flow rate 60 sccm) and argon gas (flow rate 70 sccm) was flowed at a set temperature of 400° C. to obtain Si. was precipitated. Subsequently, after the inside of the tube furnace was replaced with argon at 350° C., the pressure was reduced and treated with an ethylene+argon mixed gas (ethylene gas concentration: 20% by volume, flow rate: 300 sccm).
  • silane gas flow rate 60 sccm
  • argon gas flow rate 70 sccm
  • Example 7 A phenolic resin containing phosphorus was synthesized in the same manner as in Example 6, except that 0.636 g of the 74.1% by mass tetrahydroxymethylphosphonium sulfate aqueous solution (THPS) was used.
  • THPS tetrahydroxymethylphosphonium sulfate aqueous solution
  • Porous carbon materials shown in Table 1-2 were obtained in the same manner as in Example 6 using a phenolic resin containing phosphorus. Using the porous carbon material, the same treatment as in Example 6 was performed to obtain composite carbon particles containing silicon shown in Table 1-2.
  • Example 8 A phenolic resin containing phosphorus was synthesized in the same manner as in Example 6, except that 1.590 g of the 74.1% by mass tetrahydroxymethylphosphonium sulfate aqueous solution (THPS) was used.
  • THPS tetrahydroxymethylphosphonium sulfate aqueous solution
  • Porous carbon materials shown in Table 1-2 were obtained in the same manner as in Example 6 using a phenolic resin containing phosphorus. Using the porous carbon material, the same treatment as in Example 6 was performed to obtain composite carbon particles containing silicon shown in Table 1-2.
  • Example 9 A phosphorus-containing phenolic resin was synthesized in the same manner as in Example 6, except that 9.143 g of the 74.1% by mass tetrahydroxymethylphosphonium sulfate aqueous solution (THPS) was used.
  • THPS tetrahydroxymethylphosphonium sulfate aqueous solution
  • a porous carbon material shown in Table 1-2 was obtained in the same manner as in Example 6 except that a phenolic resin containing phosphorus was used and the activation temperature was changed to 850°C. Using the porous carbon material, the same treatment as in Example 6 was performed to obtain composite carbon particles containing silicon shown in Table 1-2.
  • Example 6 Using the porous carbon material, the same treatment as in Example 6 was performed to obtain composite carbon particles containing silicon shown in Table 1-2. 9.7 parts by mass of the obtained composite carbon particles and 90.3 parts by mass of SCMG (registered trademark, manufactured by Showa Denko KK) as graphite particles were mixed in an agate mortar to obtain a negative electrode material.
  • SCMG registered trademark, manufactured by Showa Denko KK
  • Example 6 Using the porous carbon material, the same treatment as in Example 6 was performed to obtain composite carbon particles containing silicon shown in Table 1-2. 9.7 parts by mass of the obtained composite carbon particles and 90.3 parts by mass of SCMG (registered trademark, manufactured by Showa Denko KK) as graphite particles were mixed in an agate mortar to obtain a negative electrode material.
  • SCMG registered trademark, manufactured by Showa Denko KK
  • Example 1 A phenolic resin was synthesized in the same manner as in Example 1, except that the 74.1% by mass tetrahydroxymethylphosphonium sulfate aqueous solution (THPS) was not used and the treatment time with silane gas was changed to 88 minutes. .
  • THPS tetrahydroxymethylphosphonium sulfate aqueous solution
  • a porous carbon material shown in Table 1-1 was obtained in the same manner as in Example 1 using the phenol resin. Phosphorus is not contained in the porous carbon material. Using the above porous carbon material and treating in the same manner as in Example 1, composite carbon particles containing silicon shown in Table 1-1 were obtained.
  • the surface of the composite carbon particles of Comparative Example 1 was analyzed by X-ray photoelectron spectroscopy (XPS) for C, O, and Si atomic ratios A C , A O , A Si , and Si species state ratios B SiO2 , B SiO , B Si was evaluated.
  • XPS X-ray photoelectron spectroscopy
  • XPS Narrow spectrum atomic number ratio (atom ratio) A C is 0.22
  • XPS Narrow spectrum atomic number ratio (atom ratio) A O is 0.33
  • XPS Narrow spectrum atomic number ratio (atom ratio) A Si is 0.45
  • a Si /(A C +A O +A Si ) is 0.45
  • XPS Si2p spectrum state analysis Si species ratio B SiO2 tetravalent 103 eV
  • XPS Si2p spectrum state analysis Si species ratio B SiO (divalent 101 eV) is 0.07
  • XPS Si2p spectrum state analysis Si species ratio B Si (zero valence 99 eV) was 0.67
  • Y value AC /( AC +A Si ⁇ (B SiO2 +B SiO )) was 0.60.
  • Example 2 A phosphorus-containing phenolic resin was synthesized in the same manner as in Example 1, except that 9.71 g of the 74.1% by mass tetrahydroxymethylphosphonium sulfate aqueous solution (THPS) was used.
  • THPS tetrahydroxymethylphosphonium sulfate aqueous solution
  • Porous carbon materials shown in Table 1-1 were obtained in the same manner as in Example 1 using a phenolic resin containing phosphorus. Using the above porous carbon material and treating in the same manner as in Example 1, composite carbon particles containing silicon shown in Table 1-1 were obtained.
  • a mixed solvent of pure water: ethanol 2:1 (w/w) was added to the obtained resin, followed by washing with stirring and suction filtration, and unreacted substances and the like were removed as a filtrate.
  • the obtained solid was dried at 80° C. under reduced pressure of 50 mmHg to synthesize a phenolic resin containing titanium.
  • a phenolic resin containing titanium was cured by holding it in a nitrogen atmosphere at 250° C. for 3 hours in a firing furnace, and then carbonized by heating at 900° C. for 1 hour.
  • 5 g of the obtained carbide was placed in a ceramic boat and set in a tubular electric furnace. After the atmosphere was sufficiently replaced by flowing nitrogen gas at 500 sccm, the electric furnace was heated to 950° C. and activated by switching to a carbon dioxide gas flow of 250 sccm.
  • a calibration curve of the change in the total pore volume depending on the activation time under the conditions and the activation rate were calculated. The calibration curve was used to adjust the activation time to obtain porous carbon materials shown in Table 1-1.
  • the porous carbon material was treated in a tube furnace having a silane gas flow of 100% by volume at a set temperature of 400° C. and a flow rate of 65 sccm for 135 minutes to obtain composite carbon particles containing silicon shown in Table 1-1. rice field.
  • a hydrate (TAS-FINE, manufactured by Furuuchi Chemical Co., Ltd.) was added so that the titanium content was as shown in Table 1-1, and the reaction was carried out for 2.0 hours while continuously stirring at 95° C. and 500 rpm. rice field.
  • a mixed solvent of pure water: ethanol 2:1 (w/w) was added to the obtained resin, followed by washing with stirring and suction filtration, and unreacted substances and the like were removed as a filtrate.
  • the obtained solid was dried at 80° C. under reduced pressure of 50 mmHg to synthesize a phenolic resin containing titanium.
  • Porous carbon materials shown in Table 1-1 were obtained in the same manner as in Example 1 using a phenolic resin containing titanium.
  • Composite carbon particles containing silicon shown in Table 1-1 were obtained in the same manner as in Example 1 except that the porous carbon material was used and the silane gas treatment time was changed to 102 minutes.
  • a hydrate (TAS-FINE, manufactured by Furuuchi Chemical Co., Ltd.) was added so that the titanium content was as shown in Table 1-1, and the reaction was carried out for 2.0 hours while continuously stirring at 95 ° C. and 500 rpm. .
  • a mixed solvent of pure water: ethanol 2:1 (w/w) was added to the obtained resin, followed by washing with stirring and suction filtration, and unreacted substances and the like were removed as a filtrate.
  • the obtained solid was dried at 80° C. under reduced pressure of 50 mmHg to synthesize a phenolic resin containing titanium.
  • Porous carbon materials shown in Table 1-1 were obtained in the same manner as in Example 1 using a phenolic resin containing titanium.
  • Composite carbon particles containing silicon shown in Table 1-1 were obtained in the same manner as in Example 1 except that the porous carbon material was used and the treatment time with silane gas was changed to 103 minutes.
  • Example 6 Using the porous carbon material, the same treatment as in Example 6 was performed to obtain composite carbon particles containing silicon shown in Table 1-2. 9.8 parts by mass of the obtained composite carbon particles and 90.2 parts by mass of SCMG (registered trademark, manufactured by Showa Denko KK) as graphite particles were mixed in an agate mortar to obtain a negative electrode material.
  • SCMG registered trademark, manufactured by Showa Denko KK
  • Si deposition treatment was performed in the same manner as in Example 6, except that the treatment with an ethylene + argon mixed gas was not performed, to obtain composite carbon particles containing silicon shown in Table 1-2. Obtained.
  • Examples 6 to 11 which also have a high silicon element content, have a high discharge (Li insertion) average potential. It was found that the effect can also be expressed in As described above, according to the present invention, it is possible to provide composite carbon particles for negative electrode materials, which enable lithium-ion secondary batteries with improved cycle characteristics to be obtained.

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Abstract

La présente invention concerne des particules de carbone composites avec lesquelles il est possible d'obtenir une batterie secondaire au lithium-ion présentant des caractéristiques de cycle améliorées　Les particules de carbone composite contiennent chacune un matériau carboné poreux et un composant silicium. Le composant silicium est inclus dans au moins une partie des pores du matériau carboné poreux. Les particules de carbone composite contiennent des éléments phosphore en une quantité qui est supérieure à 40 ppm en masse mais inférieure à 8000 ppm en masse.
PCT/JP2022/024885 2021-06-22 2022-06-22 Particules de carbone composites et leur utilisation WO2022270539A1 (fr)

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Citations (5)

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JP2008273816A (ja) * 2007-04-04 2008-11-13 Sony Corp 多孔質炭素材料及びその製造方法、並びに、吸着剤、マスク、吸着シート及び担持体
JP2011527982A (ja) * 2008-07-15 2011-11-10 ユニバーシテート デュースブルク−エッセン 多孔質炭素基板へのシリコン及び／若しくは錫の差込
JP2013030464A (ja) * 2011-06-24 2013-02-07 Semiconductor Energy Lab Co Ltd 蓄電装置とその電極及び蓄電装置の作製方法
JP2018534720A (ja) * 2015-08-28 2018-11-22 エナジーツー・テクノロジーズ・インコーポレイテッドＥｎｅｒｇ２ Ｔｅｃｈｎｏｌｏｇｉｅｓ， Ｉｎｃ． リチウムの非常に耐久性のある挿入を有する新規な材料およびその製造方法
JP2020501301A (ja) * 2016-11-23 2020-01-16 ジーアールエスティー・インターナショナル・リミテッド ２次バッテリーのためのアノードスラリーの作製方法

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008273816A (ja) * 2007-04-04 2008-11-13 Sony Corp 多孔質炭素材料及びその製造方法、並びに、吸着剤、マスク、吸着シート及び担持体
JP2011527982A (ja) * 2008-07-15 2011-11-10 ユニバーシテート デュースブルク−エッセン 多孔質炭素基板へのシリコン及び／若しくは錫の差込
JP2013030464A (ja) * 2011-06-24 2013-02-07 Semiconductor Energy Lab Co Ltd 蓄電装置とその電極及び蓄電装置の作製方法
JP2018534720A (ja) * 2015-08-28 2018-11-22 エナジーツー・テクノロジーズ・インコーポレイテッドＥｎｅｒｇ２ Ｔｅｃｈｎｏｌｏｇｉｅｓ， Ｉｎｃ． リチウムの非常に耐久性のある挿入を有する新規な材料およびその製造方法
JP2020501301A (ja) * 2016-11-23 2020-01-16 ジーアールエスティー・インターナショナル・リミテッド ２次バッテリーのためのアノードスラリーの作製方法

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