JP3241321B2 - Electrodes for secondary batteries - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrode for a secondary battery having a high capacity and excellent charge / discharge characteristics. Further, the present invention relates to a negative electrode of a secondary battery in which the active material is an alkali metal, preferably a lithium metal.

[0002]

2. Description of the Related Art It has been proposed to use a conductive polymer such as polyacetylene as an electrode for a lithium secondary battery. However, the conductive polymer has a doping amount of Li ions,
That is, it lacks electrode capacity and stable charge / discharge characteristics.

Attempts have also been made to use lithium metal for the negative electrode of a lithium secondary battery, but in this case, the charge / discharge cycle characteristics are extremely poor.

[0004] That is, when discharging the battery, lithium is converted from the negative electrode body into Li ions and moves into the electrolytic solution, and when charged, the Li ions are converted into lithium metal and electrodeposited on the negative electrode body again. Is repeated, the metal lithium deposited therewith becomes dendritic. Since the dendritic metallic lithium is an extremely active substance, it decomposes the electrolytic solution, and as a result, there is a disadvantage that the charge / discharge cycle characteristics of the battery deteriorate. When this further grows, finally, a problem arises that the dendritic lithium metal deposit penetrates through the separator to reach the positive electrode body, causing a short circuit phenomenon. In other words, there is a problem that the charge / discharge cycle life is short.

In order to avoid such a problem, a carbonaceous material obtained by firing an organic compound is used as a negative electrode as a carrier,
Attempts have been made to support lithium or an alkali metal mainly composed of lithium as an active material. By using such a negative electrode body, the charge / discharge cycle characteristics of the negative electrode were remarkably improved, but on the other hand, the electrode capacity of the negative electrode was not yet large enough to be satisfactory.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a negative electrode for a secondary battery having a large electrode capacity and excellent charge / discharge cycle characteristics under such technical background.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on the negative electrode in order to solve the above-mentioned problems. As a result, the support made of a carbonaceous material described later supported an alkali metal as an active material. The inventors have found that the electrode thus formed is extremely effective for the above purpose, and have accomplished the present invention.

That is, the electrode for a secondary battery of the present invention has a multi-phase structure, and comprises a carrier mainly composed of a carbonaceous material satisfying the following (1) and (2), and an alkali metal as an active material. Is an electrode for a secondary battery carrying the same. (1) The true density is 1.80 g / cm ³ or more. (2) In the differential thermal analysis, at least two exothermic peaks are shown, and the exothermic peak corresponding to the surface carbonaceous material is 81
0 ° C. and the exothermic peak for the core carbonaceous material is 8
10 ° C. or higher.

[0009] The carbonaceous material used in the present invention is characterized by its true density and Raman spectrum irrespective of the shape, fibrous shape or the like.

This carbonaceous material has a multiphase structure composed of at least two phases of a carbonaceous material forming a surface layer and a carbonaceous material included therein to form a nucleus. The fine structure of the carbonaceous material forming the surface layer contributes to the Raman spectrum. On the other hand, the true density is given as an average value of the density of the entire carbonaceous material included in the multiphase structure including the surface layer and the nucleus. Normally, as the density of the carbonaceous material increases, the peak intensity ratio R of the Raman spectrum decreases. The feature of the carbonaceous material of the present invention is that the true density is high, and in the differential thermal analysis, the exothermic peak for the surface carbonaceous material is less than 810 ° C, and the exothermic peak corresponding to the core carbonaceous material is 810 ° C.
This is characterized by the above, which is made possible only by the above-mentioned multiphase structure.

[0011] the carbonaceous material to be used in the present invention, the true density firstly is 1.80 g / cm ³ or higher, preferably 2.00 g / cm ³ or more, more preferably 2.05 g / cm ³ or more, more preferably 2. 10 g / cm ³ or more, particularly preferably 2.15 g / cm
³ or more, very preferably 2.18 g / cm ³ or more, and most preferably 2.20 g / cm ³ or more.

The carbonaceous material used in the present invention has the following spectral characteristics in Raman spectrum analysis using an argon ion laser beam having a wavelength of 5145 °. Hereinafter, unless otherwise specified, spectra and peaks are Raman spectra under the above conditions.

[0013] That is, a peak P _B in the range of 1,580～1,620Cm ^-1 peak P _A, in the range of 1,350~1,370cm ^-1. P _A is a peak observed corresponding to a crystal structure that grows and forms with the spread of the aromatic ring network plane, and P _B is a peak corresponding to a disordered amorphous structure. The ratio of both peak intensities _{I B · I A R (=} I B /
I _A) is a carbonaceous material, i.e. a carbonaceous particle, the larger the proportion of the amorphous structure portion in the surface, such as carbonaceous fibers, a larger value. R is 0.4 or more, preferably 0.6 or more, more preferably 0.9 or more, and particularly preferably 0.9 or more.
0 to 1.5, most preferably 0.90 to 1.3.

By using a carbonaceous material satisfying the above conditions of true density and differential thermal analysis as a carrier for the negative electrode, an electrode having an excellent balance between the size of the electrode capacity and the characteristics of the charge / discharge cycle can be obtained. be able to.

Further, the carbonaceous material used in the present invention is:
It has the following Raman spectrum.

[0016] That is, the position of P _A varies depending on the degree of completeness of a crystalline portion. Position of P _A carbon material for use in the present invention, as described above 1,580～1,620
cm- ¹ , but preferably 1,585 to 1,620c
m ^-1 , more preferably 1,590 to 1,620 cm ^-1 , still more preferably 1,595 to 1,615 cm ^-1 , particularly preferably 1600 to 1,610 cm ^-1 .

The half width at half maximum of the peak is narrower as the higher order structure of the carbonaceous material is more uniform. Half width at half maximum of the P _A of the carbonaceous material to be used in the present invention is preferably 25 cm ^-1 or more, more preferably 27cm ^-1 or more, more preferably 30~60c
m ^-1 , particularly preferably 35 to 55 cm ^-1 .

[0018] P _B usually has a peak at 1,360cm ^-1. Half width at half maximum of the P _B is preferably 20 cm ^-1 or more, more preferably 20～150Cm ^-1, more preferably 25
１２５125 cm ⁻¹ , particularly preferably 30-115 cm ⁻¹ , most preferably 40-110 cm ⁻¹ .

Further, the carbonaceous material used in the present invention is:
It is preferable that the diffractogram of the X-ray wide-angle diffraction has at least two diffraction line peaks corresponding to the above-mentioned multiphase structure.

That is, as a peak of a diffraction line corresponding to the crystal structure of the above-mentioned surface layer portion, the plane distance d of the (002) plane
₀₀₂ is preferably at least 3.45 °, more preferably 3.45 °.
47 ° or more, more preferably 3.49 to 3.75 °,
Particularly preferably, it is 3.50 to 3.70 °, most preferably 3.56 to 3.60 °. The crystallite size (L _C ) in the c-axis direction is preferably less than 150 °, more preferably 100 ° or less, further preferably 7 to 70 °, particularly preferably 10 to 40 °, and most preferably 12 to 30 °.
It is.

On the other hand, as a peak of a diffraction line corresponding to the structure of the carbonaceous material in the core portion included in the surface layer, d ₀₀₂ is preferably less than 3.45 °, more preferably 3.36 to less.
3.42 °, more preferably 3.37 to 3.41 °,
Particularly preferably, it is 3.37 to 3.40 °. Also L _C
But preferably at least 150 °, more preferably 180 °
As described above, it is more preferably 190 to 500 °, particularly preferably 200 to 300 °.

The carbonaceous material used in the present invention also has at least two carbonaceous materials in differential thermal analysis, depending on the multiphase structure.
It is preferable to show multiple exothermic peaks. That is, the peak corresponding to the carbonaceous material in the surface layer is preferably less than 810 ° C, more preferably 600 ° C or more and less than 800 ° C, further preferably 650 ° C or more and less than 800 ° C, particularly preferably 700 ° C or more and less than 800 ° C. It is. The peak corresponding to the core carbonaceous material is preferably at least 810 ° C, more preferably at least 820 ° C, even more preferably 850 to 1,
000 ° C.

The carbonaceous material used in the present invention may have any shape such as a granular shape or a fibrous shape, but is preferably granular or fibrous, and particularly preferably granular. When granular, the volume average particle size is preferably 200 μm or less, more preferably 100 μm or less, and still more preferably 0.5 to
80 μm, particularly preferably 1 to 30 μm, most preferably 2 to 20 μm.

In the case of a fibrous form, the diameter is preferably 1 to 25.
μm, more preferably 2 to 20 μm, and the length is preferably 10 mm or less, more preferably 5 mm or less.

The carbonaceous material used in the present invention is B
The specific surface area measured using the ET method is preferably 1 to 1
00m ² / g, more preferably 2~50m ² / g, more preferably from 3~30m ² / g.

Further, the carbonaceous material preferably has pores inside. The total pore volume and the average pore radius described below were measured using a constant volume method while measuring the amount of gas adsorbed (or desorbed gas) on the sample under several equilibrium pressures.
It is determined by measuring the amount of gas adsorbed on the sample.

The total pore volume, assuming that the pores are filled with liquid nitrogen, relative pressure P / P _O = 0.995
Calculated from the total amount of gas adsorbed in. P: Vapor pressure of adsorption gas (mmHg) P _O : Saturation vapor pressure of adsorption gas at cooling temperature (mmHg)

The total pore volume is determined by converting the amount of nitrogen gas adsorbed (V _ads ) into the amount of liquid nitrogen filled in the pores (V _liq ) using the following equation (1). V _liq = (P _atm · V _ads · V _m ) / RT (1)

Here, _Patm and T are the atmospheric pressures (k
gf / cm ² ) and absolute temperature (K), and R is a gas constant. V _m is the molecular volume of the adsorbed gas (34.7 for nitrogen)
cm ³ / mol).

The carbonaceous material used in the present invention preferably has a total pore volume of 1.5 × 10 ⁻³ ml / g or more as described above. More preferably the total pore volume is 2.0 ×
10 ⁻³ ml / g or more, more preferably 3.0 × 10 ⁻³ to 8
× 10 ⁻² ml / g, particularly preferably 4.0 × 10 ^{−3 to} 3 × 1
0 ^-2 ml / g.

The average pore radius (γ _P ) is calculated from the V _liq obtained from the above equation (1) and the specific surface area S obtained by the BET method using the following equation (2). . Here, it is assumed that the pores are cylindrical. γ _P = 2V _liq / S (2)

As described above, the average pore radius (γ _P ) of the carbonaceous material obtained from the adsorption of nitrogen gas is preferably from 8 to 100 °. More preferably 10 to 80 °, further preferably 12 to 60 °, particularly preferably 14 to 40 °.
Å.

Further, the carbonaceous material used in the present invention is:
The pore volume as determined by the mercury porosimeter is preferably 0.
05 ml / g or more, more preferably 0.10 ml / g or more, still more preferably 0.15 to 2 ml / g, particularly preferably 0.2
0 to 1.5 ml / g.

The carbonaceous material used in the present invention can be synthesized, for example, by the following method. That is, first, an organic compound is placed in an inert gas stream or in a vacuum,
It is decomposed by heating at a temperature of 3,000 ° C., carbonized and graphitized, and has a d ₀₀₂ of less than 3.45 ° and a true density of more than 2.00 g / cm ³ in an X-ray wide-angle diffractogram, preferably 2.05 to 2.23 g / cm ³ , more preferably 2.
A carbonaceous material of 10 to 2.23 g / cm ³ is obtained. The carbonaceous material can take any shape such as a granular shape and a fibrous shape.

Then, using the carbonaceous material obtained as described above as a nucleus, the organic compound is decomposed by heating under an inert gas flow, carbonized, and a surface layer of a new carbonaceous material is formed on the surface of the nucleus. Let it form.

Alternatively, the surface layer may be formed in the same manner using natural graphite or artificial graphite particles as nuclei.

As a method for forming a surface layer on the surface of a carbonaceous material serving as a nucleus, there are the following methods, which can be arbitrarily selected. (1) Relatively low-molecular organic compounds, for example, having 20 carbon atoms
Thermal decomposition of paraffins, olefins, aromatic compounds, etc., of a degree or less, deposits carbonaceous material in the surface layer. (2) The surface of a carbonaceous material serving as a nucleus is coated with an organic polymer compound, and thermally decomposed in a solid phase to form a carbonaceous material. (3) The condensed polycyclic hydrocarbon is heated and thermally decomposed in contact with the carbonaceous material serving as a nucleus in a liquid phase to form a surface carbonaceous material.

In particular, in the method of heating the condensed polycyclic hydrocarbon on the surface of the carbonaceous material serving as a nucleus, it is preferable to promote carbonization via a liquid crystal state called a mesophase to form a surface carbonaceous material.

The thermal decomposition temperature for forming the surface layer is usually lower than the temperature for synthesizing the core carbonaceous material,
~ 2000 ° C is preferred.

As described above, it has a multiphase structure, and in the differential thermal analysis, the exothermic peak corresponding to the surface carbonaceous material is lower than 810 ° C., and the exothermic peak corresponding to the core carbonaceous material is higher than 810 ° C. The carbonaceous material used in the present invention having a true density of 1.80 g / cm ³ or more can be obtained.

In the thus obtained carbonaceous material having a multiphase structure, the ratio of the core portion to the surface layer portion is preferably 20 to 99% by weight, more preferably 30 to 95% by weight, and still more preferably 40 to 95% by weight. -90% by weight, particularly preferably 50-85% by weight, most preferably 60-85% by weight
The surface layer is preferably 1 to 80% by weight, more preferably 5 to 70% by weight, still more preferably 10 to 60% by weight, particularly preferably 15 to 50% by weight, and most preferably 15 to 40% by weight. .

Such a carbonaceous material has a structure in which a nucleus made of one or more granular or fibrous carbonaceous materials is included in a surface layer made of a granular or fibrous carbonaceous material having another crystal structure. Take. An example of a schematic diagram of the shape is shown in FIG.

The core has a volume average particle size of preferably 30 μm.
It is more preferably 20 μm or less, further preferably 1 to 15 μm. In the composite multiphase carbonaceous material including the surface layer formed by enclosing the same, the ratio r of the core particle diameter to the total diameter thereof is preferably 0.5 or more, more preferably 0.6 or more, and further preferably 0 or more. 0.7 or more.

The thickness of the surface layer surrounding the nucleus is preferably 100 to 5 μm, more preferably 150 to 4 μm,
More preferably, it is 200 ° to 2 μm.

Starting materials for obtaining the carbonaceous material used in the present invention include simple compounds having three or more membered rings such as naphthalene, phenanthrene, anthracene, triphenylene, pyrene, chrysene, naphthacene, picene, perylene, pentaphen, and pentacene. A condensed polycyclic hydrocarbon compound obtained by condensing two or more cyclic hydrocarbon compounds with each other; or a derivative of the above compound such as carboxylic acid, carboxylic anhydride, or carboxylic imide; At least two or more heterocyclic monocyclic compounds having three or more members such as indole, isoindole, quinoline, isoquinoline, quinoxaline, phthalazine, carbazole, acridine, phenazine, and phenanthridine are bonded to each other; Or one or more three- or more-membered monocyclic hydrocarbon compounds Condensed heterocyclic compounds comprising bonded to;
Derivatives such as carboxylic acids, carboxylic anhydrides and carboxylic imides of the above compounds; aromatic monocyclic hydrocarbons such as benzene, toluene and xylene, and their carboxylic acids, carboxylic anhydrides and carboxylic imides And derivatives such as 1,2,4,5-tetracarboxylic acid, dianhydride or diimide thereof.

The above pitch will be described in more detail.
Examples include ethylene heavy-end pitch generated during the decomposition of naphtha, crude pitch generated during the decomposition of crude oil, coal pitch generated during the pyrolysis of coal, and asphalt cracked pitch generated by asphalt decomposition. Can be. In addition, these various pitches are further heated under an inert gas flow or the like, so that the quinoline insoluble content is preferably 80% or more, more preferably 90% or more, and further preferably a mesophase pitch of 95% or more. .

Further, aliphatic saturated or unsaturated hydrocarbons such as propane and propylene may be used.

Further, cellulose; phenolic resin; acrylic resins such as polyacrylonitrile and poly (α-halogenated acrylonitrile); halogenated vinyl resins such as polyvinyl chloride, polyvinylidene chloride and chlorinated polyvinyl chloride; polyamideimide resin A polyamide resin; and any organic polymer compound such as a conjugated resin such as polyacetylene and poly (p-phenylene).

Alternatively, a carbonaceous material such as carbon black or coke as a starting material may be further heated to appropriately advance carbonization to obtain a carbonaceous material used in the present invention. As described above, natural graphite or artificial graphite can be used as the carbonaceous material forming the nucleus.

The carbonaceous material used in the present invention is usually mixed with a polymer binder to form an electrode material, and then formed into an electrode shape. Examples of the polymer binder include the following.

Resin-like polymers such as polyethylene, polypropylene, polyethylene terephthalate, aromatic polyamide, and cellulose. Rubbery polymers such as styrene / butadiene rubber, isoprene rubber, butadiene rubber, and ethylene / propylene rubber. Thermoplastic elastomeric polymers such as styrene / butadiene / styrene block copolymers, their hydrogenated products, styrene / isoprene / styrene block copolymers, and their hydrogenated products. Soft resinous polymers such as syndiotactic 1,2-polybutadiene, ethylene / vinyl acetate copolymer, and propylene / α-olefin (2 or 4 to 12 carbon atoms) copolymer. A polymer composition having ionic conductivity of alkali metal ions, particularly Li ions.

The above-mentioned ion-conductive polymer composition includes a polymer compound such as polyethylene oxide, polypropylene oxide, polyepichlorohydrin, polyphosphazene, polyvinylidene fluoride, polyacrylonitrile, and a lithium salt or lithium as a main component. Or a system in which an organic compound having a high dielectric constant such as propylene carbonate, ethylene carbonate, or γ-butyrolactone is further added thereto. The polyphosphazene preferably has a polyether chain, particularly a polyoxyethylene chain in a side chain.

The ionic conductivity of such an ionic conductive polymer composition at room temperature is preferably 10 ⁻⁸ S · cm ^−1.
Or more, more preferably 10 ^-6 S.cm ^-1 or more, further preferably 10 ^-4 S.cm ^-1 or more, and particularly preferably 10 ^-3 S.cm ^-1.
cm ^-1 or more.

As the mixed form of the carbonaceous material used in the present invention and the above-mentioned polymer binder, various forms can be adopted. That is, a form in which both particles are simply mixed, a form in which the fibrous binder is mixed in a form entangled with the particles of the carbonaceous material, or the above rubber-like polymer, thermoplastic elastomer,
Examples include a form in which a layer of a binder such as a soft resin or an ion-conductive polymer composition is attached to the surface of particles of a carbonaceous material.

When a fibrous binder is used, the diameter of the fiber of the binder is preferably 10 μm or less, more preferably 5 μm or less, fibrils (ultrafine fibers), and fibrid-like (tentacle-like ultrafine fibers). Powder with fibrils)
Is particularly preferred.

The mixing ratio of the carbonaceous material and the binder is preferably from 0.1 to 100 parts by weight of the carbonaceous material.
It is 30 parts by weight, more preferably 0.5 to 20 parts by weight, further preferably 1 to 10 parts by weight.

Further, an alkali metal as an active material, particularly a metal capable of forming an alloy with lithium, for example, aluminum can be mixed with the above mixture. Alternatively, an alloy composed of such a metal and an alkali metal, particularly lithium, for example, a lithium aluminum alloy can be used as a mixture. Such a metal or alloy may be in the form of particles, in the form of a thin layer coated on the surface of a carbonaceous material, or in the form of being contained inside a carbonaceous material.

The mixing ratio of such a metal or alloy is as follows:
The metal or alloy is preferably 70 parts by weight or less, more preferably 5 to 60 parts by weight, further preferably 10 to 50 parts by weight, particularly preferably 15 to 40 parts by weight, based on 100 parts by weight of the carbonaceous material.

The carbonaceous material used in the present invention is a mixture with the above-mentioned binder; or a mixture of a metal capable of forming an alloy with the above-mentioned active material or an alloy of the metal and the active material. , And the electrode material is directly formed into an electrode shape by a method such as roll molding or compression molding to obtain an electrode molded body. Or,
These components may be dispersed in a solvent and applied to a metal current collector or the like. The shape of the electrode molding is sheet-like,
It can be set arbitrarily, such as a pellet.

An alkali metal, preferably a lithium metal, which is an active material, is added to the electrode molded body thus obtained.
It can be carried prior to or during assembly of the battery.

As a method for supporting the active material on the carrier, there are a chemical method, an electrochemical method, a physical method and the like. For example, the electrode molded body is immersed in an electrolyte containing a predetermined concentration of alkali metal cation, preferably Li ion,
In addition, a method of electrolytic impregnation using lithium as a counter electrode and using the electrode molded body as an anode, a method of mixing an alkali metal powder, preferably a lithium powder in the process of obtaining the electrode molded body, and the like can be applied.

Alternatively, a method of electrically contacting a lithium metal and an electrode molded body is also used. In this case, it is preferable that the lithium metal and the carbonaceous material in the electrode compact are brought into contact with each other via the lithium ion conductive polymer composition.

The amount of lithium previously supported on the electrode molded body in this manner is preferably 0.030 to 0.250 parts by weight, more preferably 0.060 to 0.200 parts by weight, per part by weight of the support. Part, more preferably 0.1 part.
070-0.150 parts by weight, particularly preferably 0.075
-0.120 parts by weight, most preferably 0.080-0.02 parts by weight.
100 parts by weight.

The electrode of the present invention using such an electrode material is usually used as a negative electrode of a secondary battery, and is opposed to a positive electrode via a separator.

The material of the positive electrode body is not particularly limited.
For example, charge and discharge alkali metal cations such as Li ions
Metal chalcogen compounds released or acquired with the reaction
It is preferably made of a material. Such a metal chalcogen
Compounds include vanadium oxide and vanadium sulfate.
Oxide, molybdenum oxide, molybdenum sulfide, man
Gun oxide, chromium oxide, titanium oxide, titanium
Sulfides and their composite oxides and sulfides
No. Preferably Cr_Three O₈ , V_Two O_Five, V₆ O
₁₃, VO_Two , Cr_Two O_Five , MnO_Two , TiO_Two , MoV
_Two O₈ ; TiS _Two , V_Two S_Five , MoS_Two , MoS_Three , V
S_Two , Cr_0.25V_0.75S_Two , Cr_0.5 V_0.5 S_Two Etc
is there. Also, LiCoO_Two , WO_Three Oxides such as; Cu
S, Fe_0.25V_0.75S_Two , Na_0.1 CrS_Two Such as sulfurization
Object; NiPS_Three , FePS_Three Such as phosphorus and sulfur compounds
Object; VSe_Two , NbSe_Three For selenium compounds
Can also be.

Further, conductive polymers such as polyaniline and polypyrrole can be used.

The separator holding the electrolytic solution is generally made of a material having excellent liquid retaining properties, for example, a non-woven fabric of a polyolefin resin, using ethylene carbonate, propylene carbonate, 1,3-dioxolan, 1,2
LiClO ₄ , LiBF in an aprotic organic solvent such as dimethoxyethane and 2-methyltetrahydrofuran
_4. Impregnated with a non-aqueous electrolyte having a predetermined concentration in which an electrolyte such as LiAsF ₆ or LiPF ₆ is dissolved.

Further, a solid electrolyte which is a conductor of an alkali metal cation such as Li ion may be interposed between the positive electrode body and the negative electrode body.

[0069]

In the battery thus constructed, the active material ions are carried on the carrier at the time of charging at the negative electrode,
At the time of discharge, the active material ions in the carrier are released, so that a charge / discharge electrode reaction proceeds.

On the other hand, when a metal chalcogen compound is used in the positive electrode, active material ions are released to the positive electrode body during charging, and the active material ions are carried during discharging, so that the charging / discharging electrode reaction proceeds.

Alternatively, when a conductive polymer such as polyaniline is used for the positive electrode, a counter ion of an active material ion is carried on the positive electrode body during charging, and a counter ion of the active material ion is released from the positive electrode body during discharging. As a result, the electrode reaction proceeds.

As described above, the battery reaction accompanying the charge and discharge of the battery proceeds by the combination of the electrode reactions of the positive electrode body and the negative electrode body.

[0073]

The electrode material of the present invention, when used as an electrode for a secondary battery by being formed into an electrode molded article by using the above-described carbonaceous material as a main component, has an electrode capacity. It is large and exhibits excellent charge / discharge cycle characteristics.

[0074]

The present invention will be described below with reference to examples and comparative examples. Note that the present invention is not limited to this embodiment. In these examples, all parts are by weight.

The X-ray wide angle diffraction, the measurement of the true density, and the differential thermal analysis performed in the following examples were performed as follows.

[X-Ray Wide Angle Diffraction] (1) Spacing between ( ₀₀₂ ) planes (d ₀₀₂ ) When the carbonaceous material is powder, it is powdered as it is, and when it is a fine flake, it is powdered in an agate mortar. About 15% by weight of high-purity silicon powder for X-ray standard as an internal standard substance, mixed and packed in a sample cell, and using a CuKα ray monochromatized with a graphite monochromator as a radiation source, by a reflection type diffractometer method. A wide angle X-ray diffraction curve was measured. To correct the curve, so-called Lorentz, deflection factor,
No correction is made for absorption factors, atomic scattering factors, etc.
The following simple method was used. That is, the baseline of the curve corresponding to the (002) diffraction was drawn, and the substantial intensity from the baseline was re-plotted to obtain a (002) plane correction curve. Find the midpoint of the line where the line parallel to the angle axis drawn to two-thirds the height of the peak height of the curve intersects the diffraction curve,
The angle of the middle point was corrected by an internal standard, and the angle was set to twice the diffraction angle, and d ₀₀₂ was determined from the wavelength λ of CuKα ray by the following Bragg equation. d ₀₀₂ = λ / 2 sin θ [Å] where λ: 1.5418Å θ: diffraction angle corresponding to d ₀₀₂

(2) Crystallite size in the c-axis direction (Lc) In the corrected diffraction curve obtained in the preceding section, the so-called half-value width β at half the peak height is used to calculate the crystallite size in the c-axis direction. The size was determined from the following equation. Lc = K · λ / (β · cos θ) [Å]

The shape factor K used was 0.90. λ and θ have the same meaning as in the previous section.

"True density" was measured by a gas displacement method using helium gas using a multipycnometer manufactured by Yuasa Ionics Co., Ltd.

[Differential Thermal Analysis] Measurement was carried out at a heating rate of 10 ° C./min while flowing air using a thermal analysis system SSC5000 manufactured by Seiko Denshi Kogyo KK.

Example 1 (1) Synthesis of Carbonaceous Material About 100 mg of perylene-3,4,9,10-tetracarboxylic dianhydride powder was placed in a nitrogen stream at 10 ° C. /
The temperature is raised to 900 ° C at a heating rate of min.
Hold for minutes. This was further heated to 2,800 ° C. at a rate of 20 ° C./min, and kept at that temperature for 1 hour.

The carbonaceous material thus formed is represented by X
In line wide angle diffraction, d ₀₀₂ was 3.39 ° and L _C was 25.
It was 0 °. The true density was 2.20 g / cm ³ and the average particle size was 5 μm.

The carbonaceous material particles and perylene-3.4,
Mixing 9,10-tetracarboxylic dianhydride powder,
The temperature was raised to 570 ° C. at a rate of 10 ° C./min.
The dianhydride was sublimated by holding at 30 ° C. for 30 minutes, and thermally decomposed to form a new surface layer of the carbonaceous material on the surface with the above-described carbonaceous material particles as nuclei. Further, the temperature was raised to 900 ° C. at a rate of 10 ° C./min and maintained at that temperature for 30 minutes to complete the formation of the surface carbonaceous material. As a result, carbonaceous material particles comprising 50 parts by weight of the core carbonaceous material and 50 parts by weight of the surface carbonaceous material were obtained.

The carbonaceous material thus obtained had a true density of 2.10 g / cm ³ by the above-mentioned measuring method. Further, in the Raman spelling torr analysis using an argon ion laser beam, it has a peak at 1,600Cm ^-1 and 1,360Cm ^-1, the peak intensity ratio R of both was 1.0. Also, by differential thermal analysis, 824 ° C., 769 ° C., 662 ° C.
And 630 ° C.

(2) Preparation of Electrode Molded Product Particles 95 of the carbonaceous material having a multiphase structure obtained in (1)
5 parts by weight of polyethylene powder were mixed with the parts by weight, and the mixture was pressed on a nickel wire net to prepare a sheet-like electrode having a thickness of 0.25 mm. This was dried by heating to 130 ° C. in a vacuum to obtain an electrode compact. The amount of the carbonaceous material in this compact was 17 mg.

(3) Evaluation of Electrode A propylene carbonate solution of LiClO ₄ having a concentration of 1 mol / liter was placed in a glass cell, and the electrode formed body prepared in (2) was suspended from the upper part of the cell to form one electrode. An electrode obtained by crimping lithium metal on a nickel wire mesh was used as an electrode facing this.

The operation of charging to 0 V with a constant current of 5 mA between both electrodes and discharging to 1.5 V was repeated. Table 1 shows the performance at the third cycle and the 30th cycle.

[0088]

[Table 1]

Comparative Example 1 Approximately 100 mg of perylene-3,4,9,10-tetracarboxylic dianhydride powder was placed in a nitrogen stream at 10 ° C.
The temperature is raised to 900 ° C at a heating rate of min.
Hold for minutes. This was further heated to 2,800 ° C. at a rate of 20 ° C./min, and kept at that temperature for 1 hour.

The carbonaceous material thus formed has a true density of 2.21 g / cm ³ , and the Raman spectrum using argon ion laser light is 1,580 cm ⁻¹ and 1,580 cm ⁻¹ .
It has a peak at 360 cm ^-1 and a peak intensity ratio R of 0.20
Met. In addition, a peak was observed around 863 ° C. by differential thermal analysis.

Using the carbonaceous material thus obtained, an electrode compact was prepared in the same manner as in Example 1, and the electrode was evaluated in the same manner as in Example 1 using this. Table 1 shows the results.

Comparative Example 2 Approximately 100 mg of perylene-3,4,9,10-tetracarboxylic dianhydride powder was placed in a nitrogen stream at 10 ° C. /
The temperature is raised to 900 ° C at a heating rate of min.
Hold for minutes.

The carbonaceous material thus formed has a true density of 1.85 g / cm ³ , and the Raman spectrum using argon ion laser light is 1,600 cm ⁻¹ and 1,600 cm ⁻¹ .
It had a peak at 360 cm ^-1 and the peak intensity ratio R was 1.0. Also, the peaks were shown at 762 ° C. and 671 ° C. by differential thermal analysis.

Using the carbonaceous material thus obtained, an electrode compact was prepared in the same manner as in Example 1, and the electrode was evaluated in the same manner as in Example 1 using this. Table 1 shows the results.

Comparative Example 3 80 parts by weight of the carbonaceous material synthesized in Comparative Example 1 and 20 parts by weight of the carbonaceous material synthesized in Comparative Example 2 were mixed. The true density of this mixed carbonaceous material is 2.14 g / cm ³ , and the peak intensity ratio R is 0.
36. In addition, by differential thermal analysis, 1
The peak of the book was shown.

Using the carbonaceous material thus obtained, an electrode compact was prepared in the same manner as in Example 1, and the electrode was evaluated in the same manner as in Example 1 using this. Table 1 shows the results.

Example 2 The particles of the carbonaceous material synthesized in Comparative Example 1 were immersed in a solution of poly (α-fluoroacrylonitrile) dissolved in acetone, and the surface of the carbonaceous material was poly (α-fluoroacrylonitrile). Covered. This was heated to 900 ° C. at a rate of 10 ° C./min in a nitrogen stream and kept at that temperature for 30 minutes. This is further reduced to 20 ° C / min.
The temperature was raised to 1,600 ° C. at the temperature raising rate, and maintained at that temperature for 1 hour. Thus, carbonaceous material particles having a core of 53 parts by weight and a surface layer of 47 parts by weight were obtained.

The carbonaceous material thus obtained has a true density of 2.08 g / cm ³ , and the Raman spectrum using argon ion laser light is 1,600 cm ⁻¹ and 1,3 cm 3.
It had a peak at 60 cm ² and the peak intensity ratio R was 1.0. Also, the peaks were observed at 824 ° C. and 778 ° C. by differential thermal analysis.

Using the carbonaceous material thus obtained, an electrode compact was prepared in the same manner as in Example 1, and the electrode was evaluated in the same manner as in Example 1 using this. Table 1 shows the results.

Example 3 Particles of the carbonaceous material synthesized in Comparative Example 1 were immersed in a solution in which pitch, which is a mixture of condensed polycyclic hydrocarbons, was dissolved in toluene to coat the surface of the hydrocarbon with the pitch. did. This was heated in a nitrogen stream to 1,100 ° C. at a rate of 10 ° C./min, and kept at that temperature for 30 minutes. Thus, carbonaceous material particles having a core of 65 parts by weight and a surface layer of 35 parts by weight were obtained.

The carbonaceous material thus formed has a true density of 2.16 g / cm ³ , and Raman spectrum using an argon ion laser beam is 1,600 cm ⁻¹ and 1,600 cm ⁻¹ .
It has a peak at 360 cm ^-1 and the peak intensity ratio R is 0.92.
Met. Further, the peaks were observed at 823 ° C. and 767 ° C. by differential thermal analysis.

Using the carbonaceous material thus obtained, an electrode compact was prepared in the same manner as in Example 1, and the electrode was evaluated in the same manner as in Example 1 using this. Table 1 shows the results.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing an example of a multiphase structure of a carbonaceous material used in the present invention.

[Explanation of symbols]

 1 core 2 surface

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-2-66856 (JP, A) JP-A-4-368778 (JP, A) JP-A-63-121261 (JP, A) JP-A-63-1988 304572 (JP, A) WO 90/13924 (WO, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 4/02-4/04 H01M 4/58 H01M 10/40

Claims (3)

(57) [Claims] 1. A carbonaceous material having a multiphase structure comprising at least two phases of a carbonaceous material forming a surface layer and a carbonaceous material included therein to form a nucleus, and satisfying the following (1) and (2): An electrode for a secondary battery in which an alkali metal as an active material is supported on a support mainly composed of (1) The true density is 1.80 g / cm ³ or more. (2) In the differential thermal analysis, at least two exothermic peaks are shown, and the exothermic peak corresponding to the surface carbonaceous material is 81
The temperature is lower than 0 ° C., and the exothermic peak corresponding to the core carbonaceous material is 810 ° C. or higher. 2. A secondary battery comprising the secondary battery electrode according to claim 1. 3. A carbonaceous material having a multiphase structure comprising at least two phases of a carbonaceous material forming a surface layer and a carbonaceous material included therein to form a nucleus, and satisfying the following (1) and (2): An electrode material for a secondary battery comprising, as a main component, (1) The true density is 1.80 g / cm ³ or more. (2) In the differential thermal analysis, at least two exothermic peaks are shown, and the exothermic peak corresponding to the surface carbonaceous material is 81
The temperature is lower than 0 ° C., and the exothermic peak corresponding to the core carbonaceous material is 810 ° C. or higher.