WO2019131860A1 - リチウムイオン二次電池用負極材 - Google Patents

リチウムイオン二次電池用負極材 Download PDF

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WO2019131860A1
WO2019131860A1 PCT/JP2018/048098 JP2018048098W WO2019131860A1 WO 2019131860 A1 WO2019131860 A1 WO 2019131860A1 JP 2018048098 W JP2018048098 W JP 2018048098W WO 2019131860 A1 WO2019131860 A1 WO 2019131860A1
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particles
negative electrode
secondary battery
lithium ion
mass
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PCT/JP2018/048098
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English (en)
French (fr)
Japanese (ja)
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貴行 栗田
祐司 伊藤
石井　伸晃
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昭和電工株式会社
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—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 a negative electrode material for a lithium ion secondary battery.
  • the speed-up of the power saving of the electronic components has advanced the multifunctionalization of portable electronic devices, and the power consumption of the portable electronic devices is increasing. Therefore, there is a strong demand for higher capacity and smaller size of the lithium ion secondary battery, which is the main power source of portable electronic devices. In addition, demand for electric vehicles is increasing, and there is a strong demand for higher capacity in lithium ion secondary batteries used therein.
  • an additive such as fluoroethylene carbonate (FEC) is added to the electrolytic solution, and active Li is obtained even with a large side reaction amount.
  • FEC fluoroethylene carbonate
  • Patent Document 1 is a negative electrode material for a lithium ion secondary battery formed by coating core particles made of silicon and a surface of core particles made of silicon with a coating made of carbon, and it is an average of core particles made of silicon.
  • XPS X-ray photoelectron analysis
  • Patent Document 2 is made of a composite material containing silicon-containing particles, graphitic carbon material particles, and carbonaceous carbon materials, and the composite material is silicon of about 103 eV, which is observed in X-ray photoelectron spectroscopy (XPS).
  • XPS X-ray photoelectron spectroscopy
  • Patent No. 6136963 (US Patent No. 9991510) Patent No. 5956690 (US Patent Application No. 2017-40610)
  • An object of the present invention is to provide a negative electrode material for obtaining a lithium ion secondary battery having high Coulombic efficiency, low consumption of electrolyte additive accompanying use, and high capacity retention.
  • Ion material for a lithium ion secondary battery including a composite (A) containing a matrix material (A3), wherein the composite (A) is observed at around 104 eV in measurement by X-ray photoelectron spectroscopy (XPS)
  • XPS X-ray photoelectron spectroscopy
  • the ratio of the peak area of Si single body observed in the vicinity of 100 eV to the peak area of SiO 2 is X
  • the peak area of Si single body observed in the vicinity of 100 eV and SiO x (0 ⁇ x ⁇
  • the ratio of the peak area of SiO 2 observed around 104 eV to the sum of the peak areas of 2) is Y, 0.35 ⁇ X ⁇ 1.50 and 0.25 ⁇ Y ⁇ 1.50
  • the particles (A2) have a 50% particle diameter DV50 in the volume-based cumulative particle size distribution of 2.0 ⁇ m to 20.0 ⁇ m, and a BET specific surface area (S BET ) of 1.0 m 2 / g to 10
  • the negative electrode material for a lithium ion secondary battery according to the above 1 or 2 which has a surface area of not more than 0 m 2 / g.
  • the particle (A2) has a ratio I 110 / I 004 of the peak intensity I 110 of the ( 110 ) plane to the peak intensity I 004 of the (004) plane by powder X-ray diffraction method of 0.10 or more 0.35 or less, the average interplanar spacing d 002 of the (002) plane by powder X-ray diffraction is 0.3360 nm or less, and the total fineness of pores with a diameter of 0.4 ⁇ m or less measured by nitrogen gas adsorption
  • FIG. 2 shows a Si2p spectrum obtained by XPS analysis of the complex (A) of Example 1.
  • FIG. 13 shows a Si2p spectrum obtained by XPS analysis of the complex (A) of Example 2.
  • the Si2p spectrum acquired by the XPS analysis of the complex (A) of the comparative example 1 is shown.
  • the negative electrode material for a lithium ion secondary battery includes a composite (A) containing particles (A1), particles (A2) and a carbonaceous material (A3).
  • the particles (A1) used in one embodiment of the present invention contain Si as a main component capable of inserting and extracting lithium ions.
  • the content of Si is preferably 90% by mass or more, more preferably 95% by mass or more.
  • the particles (A1) may be composed of a simple substance of Si or a compound containing a Si element, a mixture, a eutectic or a solid solution.
  • the particles (A1) before being complexed with the particles (A2) and the carbonaceous material (A3) may be aggregations of a plurality of fine particles, that is, secondary particles.
  • grains (A1) a lump shape, scale shape, spherical shape, fibrous shape etc. can be mentioned. Among these, spherical or massive is preferable.
  • the substance is a compound, a mixture, a eutectic or a solid solution containing the element M in a ratio of m moles to 1 mole of Si.
  • the element M which is an element other than Li include B, C, N, O, S, P, Na, Mg, Al, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Ru, Rh, Pd, Pt, Be, Nb, Nd, Ce, W, Ta, Ag, Au, Cd, Ga, In, Sb, Ba and the like can be mentioned.
  • m is preferably 0.01 or more, more preferably 0.10 or more, and still more preferably 0.30 or more.
  • the substance containing Si element include elemental Si, an alloy of Si and an alkaline earth metal; an alloy of Si and a transition metal; an alloy of Si and a semimetal; Si, Be, Ag, Al, Au , Cd, Ga, in, solid-solution alloys or KyoTorusei alloy of Sb or Zn; CaSi, CaSi 2, Mg 2 Si, BaSi 2, Cu 5 Si, FeSi, FeSi 2, CoSi 2, Ni 2 Si, NiSi 2, MnSi, MnSi 2, MoSi 2, CrSi 2, Cr 3 Si, TiSi 2, Ti 5 Si 3, NbSi 2, NdSi 2, CeSi 2, WSi 2, W 5 Si 3, TaSi 2, Ta 5 Si 3, It may be mentioned SiO 2, SiC, Si 3 N 4 and the like; PtSi, V 3 Si, VSi 2, PdSi, RuSi, silicides such RhSi.
  • the lower limit of the average particle diameter d AV of the primary particles of the particles (A1) is 5 nm, preferably 10 nm, and more preferably 35 nm. Further, the upper limit value of d AV of the primary particles is 95 nm, preferably 70 nm.
  • the d AV of the primary particles of the particles (A1) is larger than 95 nm, the volume of the particles (A1) expands and contracts due to charge and discharge, and the influence on the structure of the composite (A) containing the particles (A1) increases. Capacity retention rate decreases.
  • the d AV of the primary particles is smaller than 5 nm, the specific surface area of the particles (A1) is increased, and the amount of side reaction is increased.
  • Average particle diameter d AV [nm] 6 x 10 3 / ( ⁇ x S BET ) Defined by Here, [[g / cm 3 ] is the true density of Si particles, and the theoretical value of 2.3 [g / cm 3 ] is adopted. S BET [m 2 / g] is a specific surface area measured by the BET method using N 2 gas as an adsorption gas.
  • the particles (A1) are preferably coated at their surface with a thin amorphous carbon coating layer (A1C).
  • the upper limit of the thickness of the amorphous carbon coating layer (A1C) is 20 nm, preferably 10 nm, more preferably 5 nm. is there. This is to suppress the amount of side reaction between the electrolytic solution and the amorphous carbon coating layer (A1C).
  • the lower limit of the thickness of the amorphous carbon coating layer (A1C) is 1 nm, preferably 2 nm, and more preferably It is 3 nm.
  • the thickness of the amorphous carbon coating layer (A1C) can be determined by measuring the film thickness in an image taken by observation with a transmission electron microscope (TEM).
  • TEM transmission electron microscope
  • Device H9500 manufactured by Hitachi, Ltd. Acceleration voltage: 300kV
  • Preparation of sample A small amount of sample is taken in ethanol and dispersed by ultrasonic irradiation, and then placed on a microgrid observation mesh (without a supporting film) to make an observation sample.
  • Observation magnification 50,000 times (at the time of particle shape observation) and 400,000 times (at the time of thickness observation of an amorphous carbon layer).
  • a core-shell structure comprising the particles (A1) and an amorphous carbon coating layer (A1C) covering the particles (A1)
  • the body (hereinafter referred to as a structure ( ⁇ )) preferably has a BET specific surface area (S BET ) of 25 m 2 / g to 70 m 2 / g, more preferably 52 m 2 / g to 67 m 2 / g is there.
  • the density of primary particles is 2.2 g / cm 3 or more.
  • the BET specific surface area of the structure ( ⁇ ) is 25 m 2 / g or more, the particle diameter of the structure ( ⁇ ) does not become too large, and the electron transfer path and Li ion diffusion path in the structure ( ⁇ ) solid are It will not be long. That is, the resistance at the time of charge and discharge is kept low. Furthermore, the absolute value of the amount of expansion per particle of the structure ( ⁇ ) does not increase, and the possibility of destruction of the structure of the complex (A) around the structure ( ⁇ ) is low. In addition, when the density of the structure ( ⁇ ) is 2.2 g / cm 3 or more, it is also advantageous in terms of volumetric energy density.
  • the content of particles (A1) in the composite (A) is preferably 2% by mass to 95% by mass, more preferably 5% by mass to 80% by mass, and still more preferably 10% by mass to 70% by mass It is.
  • the content of the particles (A1) is 95% by mass or less, the amount of the particles (A2) for obtaining the required electron conductivity is secured, so the problem of the battery performance due to the increase of the electron resistance is It does not occur.
  • the content of the particles (A1) is 2% by mass or more, the superiority in terms of volume or weight energy density is maintained.
  • the structure ( ⁇ ) composed of the particles (A1) and the amorphous carbon coating layer (A1C) can be produced by any of the solid phase method, liquid phase method and gas phase method, but the gas phase method is preferable.
  • the graphite particles contained in the particles (A2) in the preferred embodiment of the present invention are preferably artificial graphite particles.
  • the size and shape of the optical structure are in a specific range, and an artificial graphite particle having an appropriate degree of graphitization can provide an electrode material having both excellent crushing characteristics and battery characteristics.
  • D V 50 represents a 50% particle size in a volume-based particle size distribution measured by a laser diffraction particle size distribution analyzer, and represents an apparent diameter of particles.
  • the 50% particle diameter D V50 in the volume-based cumulative particle size distribution of the graphite particles contained in the particles (A2) in the preferred embodiment of the present invention is preferably 2.0 ⁇ m or more and 20.0 ⁇ m or less, more preferably 5.0 ⁇ m or more 18 .0 ⁇ m or less. If the D V 50 is 2.0 ⁇ m or more, it is not necessary to grind with a special device at the time of grinding, and energy can be saved. Moreover, since it is hard to cause aggregation, the handling property at the time of coating is also good. Furthermore, since the specific surface area does not become excessively large, the decrease in the initial charge and discharge efficiency does not occur.
  • D V 50 is 20.0 ⁇ m or less, it does not take time to diffuse lithium in the negative electrode material, and hence the input / output characteristics are good. Further, since silicon-containing particles are uniformly compounded on the surface of the graphite particles, good cycle characteristics can be obtained.
  • Graphite particles contained in the particle (A2) in a preferred embodiment of the present invention BET specific surface area of preferably 1.0 m 2 / g or more 10.0 m 2 / g or less by N 2 gas adsorption method, 3.0 m 2 / g or more and 7.5 m 2 / g or less is more preferable.
  • BET specific surface area of the graphite particles is in the above range, a large area in contact with the electrolytic solution can be secured while suppressing an irreversible side reaction as a negative electrode material, so that the input / output characteristics are improved.
  • the artificial graphite particles contained in the particles (A2) in the preferred embodiment of the present invention have peak intensities I 110 of the (110) plane of the graphite crystal and peaks of the (004) plane in the diffraction peak profile obtained by powder X-ray diffraction. It preferably has a specific I 110 / I 004 intensity I 004 is 0.10 or more 0.35 or less.
  • the ratio is more preferably 0.18 or more and 0.30 or less, and still more preferably 0.21 or more and 0.30 or less. If the ratio is 0.10 or more, the orientation is not too high, and the current collector surface of the electrode is due to expansion and contraction associated with insertion and desorption (occluding and releasing) of lithium ions to Si and graphite in the negative electrode material.
  • the average interplanar spacing d 002 of the (002) plane according to powder X-ray diffraction method is preferably 0.3360 nm or less.
  • the thickness Lc in the C-axis direction of the crystallite of the artificial graphite particle is preferably 50 nm or more and 1000 nm or less from the viewpoint of weight energy density and crushability.
  • d 002 and Lc can be measured by powder X-ray diffraction (XRD) according to a known method (Michio Inagaki, “carbon”, 1963, No. 36, pages 25-34; Iwashita et al., Carbon vol. 42 (2004), p. 701-714).
  • XRD powder X-ray diffraction
  • the artificial graphite particles contained in the particles (A2) in the preferred embodiment of the present invention have a total pore volume of 5.0 ⁇ L / g or more of pores with a diameter of 0.4 ⁇ m or less according to nitrogen gas adsorption BET method under liquid nitrogen cooling. It is preferably 40.0 ⁇ L / g or less. More preferably, it is 25.0 ⁇ L / g or more and 40.0 ⁇ L / g or less.
  • An artificial graphite particle having a total pore volume of 5.0 ⁇ L / g or more tends to be complexed with the particle (A1) and the carbonaceous material (A3), and is preferable in terms of improvement of the cycle capacity retention rate.
  • the artificial graphite particles contained in the particles (A2) in a preferred embodiment of the present invention have a peak intensity I D of 1580 to 1620 cm of the peak derived from the amorphous component in the range of 1300 to 1400 cm.sup.- 1 measured by Raman spectroscopy.
  • the ratio I D / I G (R value) to the intensity I G of the peak derived from the graphite component in the range of -1 is preferably 0.04 or more and 0.18 or less, preferably 0.08 or more and 0.16 or less It is further preferred that If the R value is 0.04 or more, the crystallinity of graphite is not too high, and good rapid charge / discharge characteristics can be obtained.
  • the Raman spectrum can be measured, for example, by observing with a microscope attached using a laser Raman spectrophotometer (NRS-5100 manufactured by JASCO Corporation).
  • the graphite particles contained in the particles (A2) may be produced by heating particles obtained by crushing coke having a heat history of 1000 ° C. or less. it can.
  • a raw material of coke for example, petroleum pitch, coal pitch, coal pitch coke, petroleum coke and mixtures thereof can be used. That is, as the graphite particles contained in the particles (A2), it is preferable to use a material derived from petroleum-based coke and / or coal-based coke. Among these, those subjected to delayed coking under specific conditions are desirable.
  • the raw material to be passed through a delayed coker is a decanted oil from which the catalyst has been removed after fluid bed catalytic cracking has been performed on heavy fractions at the time of crude oil refining, coal tar extracted from bituminous coal, etc. And those obtained by sufficiently distilling the tar obtained by raising the temperature to 100 ° C. or higher.
  • the temperature of these liquids be raised to 450 ° C. or higher, 500 ° C. or higher, or even 510 ° C. or higher at least at the entrance of the drum.
  • the carbon content increases and the yield improves.
  • the pressure in the drum is preferably maintained at normal pressure or higher, more preferably 300 kPa or higher, and still more preferably 400 kPa or higher. This further increases the capacity as the negative electrode. As described above, by performing coking under more severe conditions than usual, the liquid can be reacted more and coke having a higher degree of polymerization can be obtained.
  • the obtained coke is cut out from the inside of the drum by a jet water flow, and the obtained mass is roughly crushed to about 5 cm with a gold crucible or the like.
  • a twin-roll crusher or a jaw crusher can also be used for the coarse grinding, it is preferable that the 1 mm sieve is ground to have 90% by mass or more.
  • the coke is then crushed.
  • the pulverization property is significantly reduced, so it is preferable to previously dry it at about 100 to 1000.degree. More preferably, it is 100 to 500 ° C.
  • the crushing strength becomes strong and the crushability deteriorates, and the crystal anisotropy develops, so that the cleavage property becomes strong and it becomes easy to be a scaly powder.
  • a known jet mill, hammer mill, roller mill, pin mill, vibration mill or the like can be used. Milling is preferably carried out as D V50 becomes 2.0 ⁇ m or 20.0 ⁇ m or less, and more preferably more than 5.0 .mu.m 18.0.
  • Graphitization is preferably performed at a temperature of 2400 ° C. or higher, more preferably 2800 ° C. or higher, still more preferably 3050 ° C. or higher, still more preferably 3150 ° C. or higher under an inert atmosphere (eg, nitrogen gas or argon gas atmosphere) Do.
  • an inert atmosphere eg, nitrogen gas or argon gas atmosphere
  • the graphitization temperature is preferably 3600 ° C. or less.
  • the carbon raw material be calcined to remove organic volatile components, that is, the fixed carbon content is 95% or more, more preferably 98% or more, and still more preferably 99% or more.
  • This firing can be performed, for example, by heating at 700 to 1500.degree. Since the reduction in mass at the time of graphitization is reduced by firing, the throughput of the graphitization processing apparatus can be increased once.
  • the carbonaceous material (A3) in a preferred embodiment of the present invention is a carbon material which is different from the particles (A2) and in which the development of crystals formed by carbon atoms is low, and a Raman spectrum by Raman scattering spectroscopy. Has a peak near 1360 cm -1 .
  • the carbonaceous material (A3) may be the same as the amorphous carbon coating layer (A1C).
  • the carbonaceous material (A3) can be produced, for example, by carbonizing a carbon precursor.
  • the carbon precursor is not particularly limited, but includes, but not limited to, thermal heavy oil, pyrolysis oil, straight asphalt, blown asphalt, petroleum-derived substances such as tar or petroleum pitch by-produced during ethylene production, coal tar produced during coal distillation,
  • the heavy component obtained by distilling off the low-boiling component of coal tar, and coal-derived materials such as coal tar pitch (coal pitch) are preferred, and petroleum pitch or coal pitch is particularly preferred.
  • Pitch is a mixture of multiple polycyclic aromatic compounds. When pitch is used, a carbonaceous material (A3) with few impurities can be produced at a high carbonization rate. Since the pitch has a low oxygen content, when the particles (A1) are coated with the carbonaceous material, the particles (A1) are less likely to be oxidized.
  • the pitch as a precursor of the carbonaceous material (A3) preferably has a softening point of 80 ° C. or more and 300 ° C. or less. If the softening point of pitch is 80 ° C. or higher, the average molecular weight of the polycyclic aromatic compound constituting it is not too small, and the volatile content is also relatively small, so the carbonization rate decreases, the manufacturing cost increases, and further There is no problem that a carbonaceous material (A3) having a large specific surface area containing many pores can be easily obtained. If the softening point of the pitch is 300 ° C. or less, the viscosity is not too high, so that it can be uniformly mixed with the particles (A1). The softening point of pitch can be measured by the Mettler method described in ASTM-D 3104-77.
  • the pitch of the carbonaceous material (A3) as a precursor is preferably 20% by mass to 70% by mass, and more preferably 25% by mass to 60% by mass, as a residual carbon ratio.
  • the residual carbon ratio of the pitch is 20% by mass or more, problems such as an increase in manufacturing cost and a carbonaceous material having a large specific surface area do not occur.
  • the residual carbon ratio of the pitch is 70% by mass or less, the viscosity is not too high, and therefore, it can be uniformly mixed with the particles (A1).
  • the residual coal rate is determined by the following method.
  • the solid pitch is ground in a mortar or the like, and the ground product is subjected to mass thermal analysis under a nitrogen gas flow.
  • the ratio of mass to charged mass at 1100 ° C. is defined as the residual carbon ratio.
  • the pitch used in the present invention preferably has a QI (quinoline insoluble content) content of 10% by mass or less, more preferably 5% by mass or less, and still more preferably 2% by mass or less.
  • the QI content of pitch is a value corresponding to the amount of free carbon.
  • the pitch containing a large amount of free carbon is heat-treated, the free carbon adheres to the surface of the sphere to form a three-dimensional network in the process of appearance of mesophase spheres, thereby hindering the growth of the sphere, and thus it tends to be a mosaic structure.
  • heat treatment is performed on a pitch having a small amount of free carbon, mesophase spheres grow large and tend to generate needle coke.
  • the QI content is in the above range, the electrode characteristics are further improved.
  • the pitch used in the present invention preferably has a TI (toluene insoluble content) content of 10% by mass to 70% by mass.
  • the pitch with low TI content has a low average carbon weight and high volatile content because the polycyclic aromatic compound constituting it has a low carbonization rate, an increase in production cost, and a large specific surface area including many pores. Carbonaceous materials are easily obtained.
  • the pitch with a high TI content has a high carbonization rate because the average molecular weight of the polycyclic aromatic compound constituting it is high, but the pitch with a high TI content is uniformly mixed with the particles (A1) since the viscosity is high. It tends to be difficult. When the TI content is in the above-mentioned range, it is possible to uniformly mix the pitch and the other components, and to obtain a negative electrode material having characteristics suitable as a battery active material.
  • the QI content and the TI content of the pitch used in the present invention can be measured by the method described in JIS K2425 or a method according thereto.
  • the mass ratio of the carbonaceous material (A3) to the total mass of the particles (A1), the particles (A2) and the carbonaceous material (A3) is preferably 2% by mass to 40% by mass, and more preferably 4% % Or more and 30% by mass or less.
  • the proportion of the carbonaceous material (A3) is 2% by mass or more, sufficient bonding between the particles (A1) and the particles (A2) can be obtained, and the surface of the particles (A1) can be a carbonaceous material (A3)
  • conductivity is easily imparted to the particles (A1), and an effect of suppressing surface reactivity of the particles (A1) and an effect of alleviating expansion and contraction are obtained, and good cycle characteristics are obtained.
  • the proportion of the carbonaceous material (A3) is 40% by mass or less, the initial efficiency does not decrease even if the proportion of the carbonaceous material (A3) is high.
  • the composite (A) according to one embodiment of the present invention comprises the particles (A1) or the structure ( ⁇ ) (when the particles (A1) are coated with the amorphous carbon coating layer (A1C)), and the particles (A2) and a carbonaceous material (A3), wherein at least a part of the particles (A1) or the structural body ( ⁇ ), the particles (A2) and the carbonaceous material (A3) are complexed with each other Is preferred.
  • the complexing is, for example, a state in which the particle (A1) or the structure ( ⁇ ) and the particle (A2) are fixed and bound by the carbonaceous material (A3), or the particle (A1) or the structure ( ⁇ ) And / or particles (A2) are coated with the carbonaceous material (A3).
  • the particle (A1) or the structure ( ⁇ ) is completely covered with the carbonaceous material (A3), and the surface of the particle (A1) or the structure ( ⁇ ) is not exposed.
  • the surface of the particles (A1) or the structure ( ⁇ ) is not exposed, so that the electrolytic solution decomposition reaction is suppressed and the coulombic efficiency can be maintained high, and the carbonaceous material (A3)
  • the conductivity between the particles (A2) and the particles (A1) or the structure ( ⁇ ) can be enhanced by linking the particles (A2), and the particles (A1) or the structure ( ⁇ ) are carbonaceous.
  • the particle (A2), the carbonaceous material (A3), the particle (A1) or the structure ( ⁇ ) alone is included, which is not complexed. May be It is preferable that the amount of the particles (A2), the carbonaceous material (A3), the particles (A1) or the structures ( ⁇ ) contained alone without being complexed is small, and specifically, the complex (A) Preferably it is 10 mass% or less with respect to the mass of.
  • DV50 of the complex (A) which concerns on one Embodiment of this invention
  • 2.0 micrometers or more and 20.0 micrometers or less are preferable. More preferably, it is 2.0 micrometers or more and 18.0 micrometers or less. If DV50 is 2.0 micrometers or more, economical manufacture is possible. Also, there is no difficulty in increasing the electrode density. Furthermore, since the specific surface area is not excessively increased, the decrease in the initial charge and discharge efficiency due to the side reaction with the electrolytic solution does not occur. Further, if the DV50 is 20.0 ⁇ m or less, good input / output characteristics and cycle characteristics can be obtained.
  • the BET specific surface area (S BET ) of the composite (A) is preferably 1.0 m 2 / g or more and 10.0 m 2 / g or less. More preferably, it is 1.0 m 2 / g or more and 5.0 m 2 / g or less. If the BET specific surface area (S BET ) is 1.0 m 2 / g or more, uniform distribution in the electrode is maintained without deterioration of input / output characteristics, and good cycle characteristics can be obtained. When the BET specific surface area (S BET ) is 10.0 m 2 / g or less, the handleability is good without the decrease in the coatability. In addition, it is easy to increase the electrode density without requiring a large amount of binder for electrode production, and it is possible to suppress the efficiency of the initial charge and discharge due to the side reaction with the electrolytic solution.
  • the composite (A) is a profile obtained when the surface of the composite (A) is measured by X-ray photoelectron spectroscopy (XPS).
  • XPS X-ray photoelectron spectroscopy
  • the ratio of the peak area of Si single body observed near 100 eV to the peak area of SiO 2 observed near 104 eV is defined as X
  • the peak area of Si single body observed near 100 eV And the ratio of the peak area of SiO 2 observed near 104 eV to the sum of the peak areas of SiO x (0 ⁇ x ⁇ 2) observed near 102 eV and 102 eV, 0.35 ⁇ X ⁇ 1.50 And 0.25 ⁇ Y ⁇ 1.50, preferably 0.45 ⁇ X ⁇ 1.50 and 0.25 ⁇ Y ⁇ 1.00, and more preferably 0.55 ⁇ X ⁇ 1. 50 and 0.25 It is ⁇ Y ⁇ 0.70.
  • the Si simple substance ratio on the outermost surface of the Si particles is high, the reaction resistance between Si particles and Li ions at the time of charge and discharge becomes low, and a good cycle capacity retention rate can be obtained.
  • the ratio X is 1.50 or less, the formation of SiO x (0 ⁇ x ⁇ 2) on the surface of the particle (A1) is suppressed, and the decrease in Li desorption capacity during charge and discharge is sufficient. Suppressed.
  • the complex (A) has a peak intensity I D of a peak in the range of 1300 to 1400 cm ⁇ 1 in a Raman spectrum obtained by measuring the particle end face with a microscopic Raman spectrometer.
  • the ratio I D / I G (R value) of the peak intensity to the peak intensity I G in the range of 1580 to 1620 cm -1 is preferably 0.15 or more and 1.0 or less. More preferably, it is 0.2 or more and 1.0 or less, still more preferably 0.4 or more and 1.0 or less.
  • the fact that the R value is too small means that the surface of the particles (A2) is exposed to a certain amount.
  • the particles (A2) and the particles (A1) are covered with the carbonaceous material (A3), and the effect of suppressing the surface reactivity of the particles (A1) or expansion and contraction Good cycle characteristics can be obtained because the effect of relieving is increased.
  • the R value is too large, it indicates that the carbonaceous material (A3) containing a large amount of amorphous carbon having a large initial irreversible capacity covers the surface of the particles (A2). Therefore, if R value is 1.0 or less, the fall of initial stage discharge efficiency is suppressed.
  • the complex (A) according to an embodiment of the present invention can be produced according to a known method.
  • the particles (A1) or the structure ( ⁇ ), the particles (A2), and the precursor of the carbonaceous material (A3) are mixed, and the resulting mixture is heat-treated to obtain the precursor as a carbonaceous material
  • the complex (A) can be obtained by the method including the step of (A3).
  • a mixture of the particles (A1) or the structure ( ⁇ ), the particles (A2) and the precursor of the carbonaceous material (A3) is, for example, a pitch which is one of the precursors of the carbonaceous material (A3) Melt, mix the molten pitch and the particles (A1) or the structure ( ⁇ ) in an inert atmosphere, solidify the mixture and then grind it, and mix the crushed material with the particles (A2)
  • a pitch which is one of the precursors of the carbonaceous material (A3) Melt, mix the molten pitch and the particles (A1) or the structure ( ⁇ ) in an inert atmosphere, solidify the mixture and then grind it, and mix the crushed material with the particles (A2)
  • dissolving the precursor in a precursor by means of mechanochemical treatment; or dissolving the precursor in a carbonaceous material (A3) in a solvent, the particles (A1) or the structure ( ⁇ ) and the particles (A) in the precursor solution A2) adding and mixing, removing the solvent and grinding the solid obtained Can be obtained by;
  • the means of grinding mainly by impact and shear such as a pin mill and a rotary cutter mill, tends to transmit shear force preferentially to large particle size particles and less to small particle size particles.
  • Such an apparatus can be used to grind or mix the particles (A1) or the structure ( ⁇ ) without promoting oxidation.
  • the non-oxidizing atmosphere an atmosphere filled with an inert gas such as argon gas or nitrogen gas can be mentioned.
  • the heat treatment for converting the carbonaceous material (A3) precursor to the carbonaceous material (A3) is preferably 200 ° C. or more and 2000 ° C. or less, more preferably 500 ° C. or more and 1500 ° C. or less, particularly preferably 600 ° C. or more and 1200 ° C. or less At a temperature of By this heat treatment, the carbonaceous material (A3) covers the structural body ( ⁇ ) and / or the particles (A2), and the carbonaceous material (A3) is between the particles (A1) or the structural body ( ⁇ ) Between the particles (A2) and between the particles (A1) and the particles (A2) or between the structure ( ⁇ ) and the particles (A2) to form a connected form it can.
  • the heat treatment is preferably performed in a non-oxidative atmosphere.
  • a non-oxidative atmosphere an atmosphere filled with an inert gas such as argon gas or nitrogen gas can be mentioned.
  • an inert gas such as argon gas or nitrogen gas
  • a crushing method a pulperizer using an impact force such as a hammer, a jet mill using a collision of objects to be crushed and the like are preferable.
  • a material containing the composite (A) and carbon for the purpose of improving battery performance as the negative electrode material for lithium ion secondary batteries and for the purpose of adjusting the capacity of the negative electrode material for lithium ion secondary batteries May be mixed.
  • a plurality of types of materials containing carbon to be mixed may be used.
  • As a material containing carbon graphite having a high capacity is preferable.
  • the graphite can be selected from natural graphite and artificial graphite.
  • the material containing carbon for adjusting the volume may be mixed with the composite (A) in advance, and additives such as a binder, a solvent, and a conductive additive may be added thereto to prepare a negative electrode paste.
  • the negative electrode paste may be prepared by simultaneously mixing the composite (A), a material containing carbon, a binder, a solvent, an additive such as a solvent, a conductive additive, and the like. The order and method of mixing may be appropriately determined in consideration of powder handling and the like.
  • the paste for an anode according to one embodiment of the present invention contains the above-mentioned anode material, a binder, a solvent, and, if necessary, an additive such as a conductive aid.
  • This negative electrode paste can be obtained, for example, by kneading the negative electrode material, the binder, the solvent, and the conductive auxiliary agent as needed.
  • the negative electrode paste can be formed into a sheet, a pellet, or the like.
  • Examples of the material used as the binder include polyethylene, polypropylene, ethylene propylene terpolymer, butadiene rubber, styrene butadiene rubber, butyl rubber, acrylic rubber, and a polymer compound having a large ion conductivity.
  • Examples of the polymer compound having large ion conductivity include polyvinylidene fluoride, polyethylene oxide, polyepichlorohydrin, polyphasphazen, polyacrylonitrile and the like.
  • the amount of the binder is preferably 0.5 parts by mass to 100 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 plays the role of imparting conductivity and electrode stability (buffering action against volume change in insertion and detachment of lithium ions) to the electrode.
  • carbon nanotubes, carbon nanofibers, vapor-grown carbon fibers for example, “VGCF (registered trademark)” manufactured by Showa Denko KK
  • conductive carbon for example, “Denka Black (registered trademark)” Electric Chemical Industry Co., Ltd.
  • the amount of the conductive additive is preferably 10 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the negative electrode material.
  • the solvent is not particularly limited, and N-methyl-2-pyrrolidone, dimethylformamide, isopropanol, water and the like can be used.
  • the binder which uses water as a solvent it is preferable to use a thickener together.
  • the amount of the solvent may be adjusted to have a viscosity such that the paste can be easily applied to the current collector.
  • Negative electrode sheet The negative electrode sheet which concerns on one Embodiment of this invention has an electrode layer which coat
  • a collector sheet-like things, such as nickel foil, copper foil, nickel mesh, or a copper mesh, are mentioned, for example.
  • the electrode layer contains a binder and the above-mentioned negative electrode material.
  • the electrode layer can be obtained, for example, by applying the above-mentioned paste on a current collector and drying it.
  • the application method of the paste is not particularly limited.
  • the thickness of the electrode layer is preferably 50 to 200 ⁇ m. If the electrode layer is too thick, it may not be possible to accommodate the negative electrode sheet in a standardized battery container. The thickness of the electrode layer can be adjusted by the amount of paste applied.
  • the electrode density of the negative electrode sheet can be calculated as follows. That is, the negative electrode sheet after pressing is punched into a circular shape having a diameter of 16 mm, and its mass and thickness are measured. The mass and thickness of the current collector foil (punched into a circular shape of 16 mm in diameter) separately measured therefrom are subtracted to obtain the mass and thickness of the electrode layer, and the electrode density is calculated based on the values.
  • a lithium ion secondary battery according to an embodiment of the present invention comprises at least one selected from the group consisting of a non-aqueous electrolytic solution and a non-aqueous polymer electrolyte, a positive electrode sheet and the negative electrode sheet.
  • a positive electrode sheet a sheet conventionally used in lithium ion secondary batteries, specifically, a sheet containing a positive electrode active material can be used.
  • the positive electrode active material include LiNiO 2 , LiCoO 2 , LiMn 2 O 4 , LiNi 0.34 Mn 0.33 Co 0.33 O 2 , LiFePO 4 and the like.
  • the non-aqueous electrolytic solution and the non-aqueous polymer electrolyte used for the lithium ion secondary battery are not particularly limited.
  • lithium carbonates such as LiClO 4 , LiPF 6 , LiAsF 6 , LiBF 4 , LiSO 3 CF 3 , CH 3 SO 3 Li, CF 3 SO 3 Li, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene Organic electrolytes dissolved in non-aqueous solvents such as carbonate, butylene carbonate, acetonitrile, propionitrile, dimethoxyethane, tetrahydrofuran, ⁇ -butyrolactone, etc. containing polyethylene oxide, polyacrylonitrile, polyfluorinated bilinidene, polymethyl methacrylate and the like Examples thereof include solid polymer electrolytes containing gel-like polymer electrolytes, polymers having ethylene oxide bonds, and the like.
  • a small amount of a substance that causes a decomposition reaction when charging a lithium ion secondary battery may be added to the electrolytic solution.
  • the substance include vinylene carbonate (VC), biphenyl, propane sultone (PS), fluoroethylene carbonate (FEC), ethylene sultone (ES) and the like.
  • VC vinylene carbonate
  • PS propane sultone
  • FEC fluoroethylene carbonate
  • ES ethylene sultone
  • the lithium ion secondary battery can be provided with a separator between the positive electrode sheet and the negative electrode sheet.
  • a separator for example, non-woven fabric mainly made of polyolefin such as polyethylene and polypropylene, cloth, microporous film, or a combination thereof can be mentioned.
  • Lithium-ion secondary batteries are used to power electronic devices such as mobile phones, personal computers and personal digital assistants; power sources for electric drills, electric vacuum cleaners and electric motors such as electric cars; fuel cells, solar power, wind power, etc. It can be used for storage of stored power.
  • the present invention will be described in more detail by way of Examples and Comparative Examples. Note that these are merely illustrative for the purpose of illustration, and the present invention is in no way limited thereto.
  • the average particle diameter d AV of the primary particles of the particles (A1), the thickness of the amorphous carbon coating layer (A1C), and the (002) plane of the artificial graphite particles by X-ray diffraction method The average interplanar spacing d 002, the thickness L c in the C-axis direction of the crystallite, and the R value in the Raman spectrum are measured by the methods described in the “Embodiments of the Invention” herein. Moreover, the measurement of other physical properties and battery evaluation were performed as follows.
  • the resulting (004) intensity ratio becomes orientation index from the peak intensity I 110 between the peak intensity I 004 (110) plane of the surface was calculated I 110 / I 004.
  • the peak of each surface selected the thing of the largest intensity among the following ranges as each peak. (004) plane: 54.0 to 55.0 deg, (110) plane: 76.5 to 78.0 deg.
  • Specific surface area Specific surface area / pore distribution measurement device (Quantam Chrome Instruments, NOVA 4200e), using nitrogen gas as a probe, BET specific surface area according to BET multipoint method with relative pressure of 0.1, 0.2, and 0.3 S BET (m 2 / g) was measured.
  • XPS X-ray Photoelectron Spectroscopic Analysis
  • the X-ray photoelectron spectroscopy (XPS) of the complex (A) was carried out to measure the Si2p spectrum under the following measurement device and measurement conditions.
  • CMC carboxymethylcellulose
  • CMC1300 carboxymethylcellulose
  • VGCF vapor grown carbon fiber
  • the negative electrode paste was uniformly coated on a copper foil with a thickness of 20 ⁇ m using a doctor blade with a gap of 300 ⁇ m, dried on a hot plate, and then vacuum dried to obtain a negative electrode sheet.
  • the dried electrode was pressed by a uniaxial press at a pressure of 300 MPa to obtain a negative electrode sheet for battery evaluation.
  • the negative electrode sheet evaluates the amount of discharge per mass of active material in the half cell of the counter electrode Li in advance, and the negative electrode with respect to the capacity (Q C ) of the positive electrode sheet
  • the capacity of the negative electrode sheet was finely adjusted so that the ratio of the sheet capacity (Q A ) was a constant value of 1.2.
  • the electrolytic solution was prepared by mixing 1% by mass of vinylene carbonate (VC) and 10 parts of fluoroethylene carbonate (FEC) in a solvent in which ethylene carbonate, ethyl methyl carbonate and diethyl carbonate were mixed in a volume ratio of 3: 5: 2. mixed mass%, a further liquid electrolyte LiPF 6 was dissolved to a concentration of 1 mol / L to this.
  • VC vinylene carbonate
  • FEC fluoroethylene carbonate
  • a negative electrode piece with an area of 4 cm 2 (with a Cu foil tab) punched out of the above negative electrode sheet, and an Li piece for counter electrode with an area of 7.5 cm 2 (3.0 cm ⁇ 2.5 cm) cut out with a Li roll, and an area of 3.75 cm 2 (1.5 cm x 2.5 cm) Li pieces for reference electrodes were obtained.
  • a 5 mm wide Ni tab for a counter electrode and a reference electrode was prepared, and a 5 mm ⁇ 20 mm Ni mesh was attached so as to overlap with the tip 5 mm portion. Under the present circumstances, 5 mm width of Ni tab and 5 mm width of Ni mesh were made to correspond.
  • the Cu foil tab of the above negative electrode piece was attached to the Ni tab of the working electrode.
  • the Ni mesh at the tip 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 Ni tab for the reference electrode 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 Li piece for the reference electrode.
  • a polypropylene film microporous membrane is sandwiched between the working electrode and the counter electrode, and the reference electrode is liquid-wound near the working electrode and through the polypropylene film microporous membrane so as to prevent a short circuit. It packed and the electrolyte solution was poured. Thereafter, the opening was sealed by heat fusion to prepare a battery for evaluation.
  • the electrolyte solution is 1% by mass of vinylene carbonate (VC) in a solvent in which ethylene carbonate, ethyl methyl carbonate and diethyl carbonate are mixed in a volume ratio of 3: 5: 2, as in the bipolar laminate type full cell, It is a liquid obtained by mixing 10% by mass of fluoroethylene carbonate (FEC) and further dissolving the electrolyte LiPF 6 so as to have a concentration of 1 mol / L.
  • VC vinylene carbonate
  • FEC fluoroethylene carbonate
  • the counter electrode is not Li metal, and a material having a redox potential higher than that of the above negative electrode sheet is applied. Therefore, the negative electrode sheet is treated as a negative electrode. Therefore, in the bipolar laminate full cell, charging means an operation of inserting Li into the negative electrode sheet, and discharging means an operation of releasing Li from the negative electrode operation.
  • the capacity at the time of Li release from the working electrode for the first time was taken as the initial de-Li capacity.
  • the ratio of the electric charge at the time of the first charge / discharge, ie, the result of expressing the amount of electric charge of Li released / the electric charge of Li as a percentage was taken as the initial coulombic efficiency.
  • This charge / discharge operation was performed as one cycle for 20 cycles, and at the 21st cycle, a low rate test was performed in which 1 C of the charge / discharge was replaced with 0.1 C. This 21 cycle test was repeated 5 times to give a total of 105 cycles of tests.
  • the charge (de-Li) capacity retention rate at the 100th cycle was defined and calculated by the following equation.
  • the average coulombic efficiency from the first cycle to the 100th cycle was defined by the following equation.
  • the first cycle charge capacity in the above equation means the first cycle after the end of aging.
  • the coulombic efficiency in the Nth cycle was calculated by setting (Nth cycle Li discharge electric charge) / (N cycle Li insertion electric charge) as a percentage.
  • the charge / discharge curve can be represented by the potential on the vertical axis and the electrical capacity on the horizontal axis.
  • the charge average potential was determined by averaging the potentials from the start to the end of Li release (charging). The lower the charging average potential, the smaller the reaction resistance between Si particles and Li ions during charging.
  • the discharge was carried out in CC mode up to 2.7 V with a current value of 0.1C.
  • the third cycle and the fourth cycle of the aging were under the same condition, and the current value in the second and the fifth cycle of the aging was replaced with 0.1 C to 0.2 C.
  • a charge / discharge cycle test was performed by the following method. The charging was performed to a voltage of 4.3 V in the CC mode with a current value of 1 C, and then switched to the discharge in the CV mode, and was performed with a cutoff current value of 0.05 C. Discharge was performed up to 3.0 V in CC mode with a current value of 1C.
  • This charge / discharge operation was performed as one cycle for 20 cycles, and at the 21st cycle, a low rate test was performed in which 1 C of the charge / discharge was replaced with 0.1 C. This 21 cycle test was repeated 24 times for a total of 504 cycles of test.
  • the first discharge capacity in this equation means the first cycle after the end of aging.
  • GC-MS The conditions of GC-MS are as follows.
  • GC Alignment 7890A
  • Column: DB-5MS (J & W Scientific), [30 mm ⁇ 0.32 mm, 0.25 ⁇ m], Oven: 40 ° C (5 min) ⁇ [20 ° C / min] ⁇ 320 ° C (10 min), Inlet Temperature: 250 ° C, Split: 1:20, Flow: He, 1.5 ml / min (Constant Flow), Injection: 0.2 ⁇ L, MS (JEOL JMS-Q1000) Mass Range: m / z 10-500, ( ⁇ Quantification; m / z 106) Mode: Scan, Detector Voltage: -1000V, Ionization Current: 300 ⁇ A, Ionization Energy: 70 eV, Ion Source Temperature: 200 ° C, GC-ITF Temperature: 250 ° C, Ionization: EI.
  • Si fine particles Silicon-containing particles
  • Table 1 Physical properties of Si particles and Si (1) to Si (3) used for the particles (A1) in Examples and Comparative Examples are shown in Table 1.
  • ⁇ is the true density (2.3 [g / cm 3 as theoretical value) of Si particles
  • S BET is the specific surface area [m 2 / g] measured by the BET method.
  • Pitch Petroleum pitch (softening point 220 ° C.) was used. It was 52 mass% when the residual carbon rate in 1100 degreeC was measured by thermal analysis under nitrogen gas distribution about this petroleum pitch. Further, the QI content of the petroleum pitch measured by the method described in JIS K2425 or a method according to the same was 0.62% by mass, and the TI content was 48.9% by mass.
  • Example 1 After petroleum-based coke is crushed by a bantam mill (manufactured by Hosokawa Micron Corporation), it is further crushed by a jet mill (manufactured by Seishin Enterprise Co., Ltd.) and heat-treated at 3000 ° C. in an Achison furnace to give a D V 50 of 7.5 ⁇ m. Artificial graphite particles (A2) -a having a BET specific surface area of 4.9 m 2 / g were obtained. Next, 16.4 parts by mass of the structure ( ⁇ ) -1 and 15.4 parts by mass of the petroleum pitch (as a mass after carbonizing the petroleum pitch), which is a precursor of the carbonaceous material (A3), are separated. It was charged into a bull flask.
  • Nitrogen gas was circulated to maintain an inert atmosphere, and the temperature was raised to 250 ° C.
  • the mixer was rotated at 500 rpm for agitation to uniformly mix the pitch and the silicon-containing particles. It was cooled and solidified to obtain a mixture.
  • 68.2 parts by mass of the above-mentioned artificial graphite particles which are particles (A2) -a are added to this mixture, charged into a rotary cutter mill, and mixed at a high speed of 25000 rpm and mixed while maintaining an inert atmosphere by flowing nitrogen gas. I did. This was put into a baking furnace, heated to 1100 ° C. at 150 ° C./h under nitrogen gas flow, and held at 1100 ° C.
  • D V50 is 12.1Myuemu, BET specific surface area of 2.5 m 2 / g Graphite (1) was obtained. Further, after pulverizing the petroleum coke with a bantam mill (manufactured by Hosokawa Micron Corporation), and further pulverized with a jet mill (Seishin Ltd. company), which was heat-treated at 3000 ° C. the at Acheson furnace, D V50 is 6. Graphite (2) having a BET specific surface area of 6.1 m 2 / g at 7 ⁇ m was obtained.
  • Negative electrode sheet using a mixture of composite (A) -a alone and 67.0 parts by mass of composite (A) -a, 16.5 parts by mass of graphite (1) and 16.5 parts by mass of graphite (2) Were prepared and the battery characteristics were measured. The results are shown in Table 3.
  • Example 2 A complex (A) -b was obtained in the same manner as in Example 1 except that the structure ( ⁇ ) -1 was changed to Si (2) in Table 1. The results of measurement of various physical properties of this complex (A) -b are shown in Table 3. Moreover, the Si2p spectrum obtained by XPS analysis is shown in FIG.
  • a negative electrode sheet was prepared using a mixture of composite (A) -b alone and 67.0 parts by mass of composite (A) -b, 16.5 parts by mass of graphite (1) and 16.5 parts by mass of graphite (2) It produced and measured battery characteristics. The results are shown in Table 3.
  • Comparative Example 1 A complex (A) -c was obtained in the same manner as in Example 1 except that the structure ( ⁇ ) -1 was changed to Si (3) in Table 1. The results of measurement of various physical properties of this complex (A) -c are shown in Table 3. Moreover, the Si2p spectrum obtained by XPS analysis is shown in FIG.
  • Negative electrode sheet using a mixture of composite (A) -c alone and 67.0 parts by mass of composite (A) -c, 16.5 parts by mass of graphite (1) and 16.5 parts by mass of graphite (2) Were prepared and the battery characteristics were measured. The results are shown in Table 3.
  • Example 1 in which the Si fine particles have a 2 nm thick amorphous carbon coating layer (A1C), no carbon coating layer is present.
  • A1C amorphous carbon coating layer
  • Example 1 and Example 2 are higher than Comparative Example 1. Even if the difference is only 0.01%, when 500 cycles of charge and discharge are repeated, the capacity retention rate and the amount of FEC consumption are reflected as a large difference. ).
  • Example 1 and Example 2 are compared with Comparative Example 1, Comparative Example 1 in which the ratio of Si single body is small is large in Example 1 and Example 2 in which the ratio of Si single body in XPS measurement is large. A relatively high capacity retention rate (cycle characteristics) is obtained. In addition, the consumption amount of FEC is lower in the first embodiment and the second embodiment. Although the Si fine particles of Example 2 do not have a carbon coating layer as in Comparative Example 1, the decrease in the capacity retention rate and the increase in the amount of FEC consumption are not so remarkable in Example 2. Accordingly, the fact that these characteristics are significantly inferior to those of Example 1 and Example 2 in Comparative Example 1 is considered to be due to the fact that the ratio of Si alone in XPS measurement is small.
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