JP3004789B2 - Rechargeable battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery, and more particularly, to a secondary battery having high capacity and excellent long-term charge / discharge cycle characteristics.
The present invention relates to a secondary battery which can repeat charge and discharge of a large current, has excellent overcharge and overdischarge recovery characteristics, and has high safety.

[0002]

2. Description of the Related Art Attention has been paid to the development of lithium secondary batteries capable of obtaining high capacity.

It has been proposed to use a conductive polymer such as polyacetylene as an electrode for such a lithium secondary battery. However, conductive polymers lack Li ion doping ability and stability of charge / discharge cycle 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.

[0005] That is, at the time of discharging the battery, lithium is converted from the negative electrode body into Li ions and moves into the electrolytic solution. At the time of charging, the Li ions become metallic lithium and are deposited again on the negative electrode body. Is repeated, the metal lithium deposited therewith becomes dendritic. Since the dendritic lithium metal is an extremely active substance, it decomposes the electrolytic solution, and as a result, disadvantageously deteriorates the charge / discharge cycle characteristics of the battery.
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.
Therefore, the charge / discharge cycle life is short.

In order to solve such a problem, a carbonaceous material obtained by firing an organic compound is used as a negative electrode as a support,
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.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a high-capacity, long-lasting charge / discharge cycle characteristic and a large current charge / discharge cycle under the above technical background. An object of the present invention is to provide a safe secondary battery that has excellent recovery characteristics against charge and overdischarge, and that is free from ignition or explosion due to a short circuit or the like.

[0008]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have conducted intensive studies on a negative electrode and a positive electrode combined with the negative electrode. As a result, a negative electrode containing an improved specific carbonaceous material described later will be described. The present inventors have found that a secondary battery comprising a combination of a positive electrode containing a specific carbonaceous material and the positive electrode is extremely effective for the above purpose, and have accomplished the present invention.

That is, a secondary battery of the present invention is a secondary battery including a rechargeable positive electrode and a rechargeable negative electrode, wherein the positive electrode is made of a carbonaceous material satisfying the following requirement (A). And the negative electrode contains a carbonaceous material satisfying the following requirement (B). (A) Spacing d of (002) plane by X-ray wide-angle diffraction method
₀₀₂ is 3.45 ° or more and the specific surface area is 10 m ² / g or more. (B) It has a multiphase structure in which a surface layer of a carbonaceous material satisfying the following requirement (b) is formed on the surface of a particulate or fibrous core of the carbonaceous material satisfying the following requirement (a). (A) Spacing d of (002) plane by X-ray wide-angle diffraction method
₀₀₂ is 3.35 ° or more and less than 3.45 °. (B) In Raman spectrum analysis using an argon ion laser beam having a wave number of 5145 °, 1580 to 162
Range of 0 cm ^-1 to the peak P _A, has a peak P _B in the range of 1350 ^-1, is R value defined by formula (I) is 0.4 or more. Strength R = in I _B / I _A (I) formula, I _A is the peak P _A, I _B represents the intensity of peak P _B.

The secondary battery of the present invention has a rechargeable positive electrode and a rechargeable negative electrode, and is a separator holding an electrolytic solution between the two or a conductor of alkali metal ions, particularly lithium ions. It has a solid electrolyte interposed.

[0011] The rechargeable positive electrode used in the present invention comprises:
It is composed mainly of the following carbonaceous materials.

That is, the X-ray wide angle diffraction method (00
2) The plane spacing d ₀₀₂ of the diffraction lines of the plane is 3.45 ° or more, preferably 3.50 ° or more, and more preferably 3.5.
5 ° or more, more preferably 3.60 ° or more, particularly preferably 3.60 to 3.90 °, most preferably 3.7.
0 to 3.80 °.

The size L _C of the crystallite in the c-axis direction is
Preferably 100 ° or less, more preferably 50 ° or less,
More preferably 30 ° or less, particularly preferably 5 to 2 °
0 °, most preferably 7-15 °.

[0014] The specific surface area is at 10m ² / g or more, preferably 50m ² / g or more, more preferably 100m ² /
g or more, more preferably 500 m ² / g or more, and most preferably 1,000 m ² / g or more.

The carbonaceous material used for the positive electrode of the present invention may be in any form such as a particle or a fiber, but is preferably in the form of a particle or a fiber.

The rechargeable negative electrode used in the present invention comprises:
It is composed mainly of a carbonaceous material having the following multiphase structure. That is, (002) by the X-ray wide-angle diffraction method.
Raman using an argon ion laser beam with a wavelength of 5145 ° is obtained by carbonizing an organic compound on the surface of a carbonaceous material particle or fiber having a surface spacing d ₀₀₂ of 3.35 ° or more and less than 3.45 ° as a nucleus. It is a carbonaceous material having a multiphase structure obtained by forming a surface layer of a carbonaceous material having a peak intensity ratio R of 0.4 or more in spectrum analysis.

Particles or fibers of the carbonaceous material serving as a nucleus have a plane spacing d _{002 of} a diffraction line of the (002) plane by the X-ray wide angle diffraction method.
However, as described above, it is not less than 3.35 ° and less than 3.45 °, preferably from 3.35 to 3.43 °, more preferably from 3.36 to 3.42 °, and still more preferably from 3.37 to 3.43 °.
3.41 °.

The crystallite size L _C in the c-axis direction is
Preferably at least 100 °, more preferably at least 150 °, even more preferably at least 180 °, most preferably 2 °
20-1,000 °.

The true density of the particles or fibers of the carbonaceous material as a core is preferably 2.00 g / cm ³ or more, more preferably 2.05 g / cm ³ or more, more preferably 2.10～
2.25 g / cm ³ , particularly preferably 2.15 to 2.2
5 g / cm ³ , most preferably 2.18 to 2.23 g / cm
³

The shape of the core carbonaceous material may be particulate or fibrous. In the case of particles, the volume average particle size is preferably 1 to 50 μm, more preferably 2 to 30 μm.
μm, more preferably 3 to 15 μm, and particularly preferably 4 to 10 μm. In the case of fibers, the average diameter is preferably 0.5 to 20 μm, more preferably 1 to 20 μm.
It is 10 μm, more preferably 2 to 8 μm.

Using such carbonaceous material particles or fibers as nuclei, an organic compound is decomposed and carbonized on the surface to form a surface layer made of carbonaceous material having the following properties.

That is, in Raman spectrum analysis using an argon ion laser having a wavelength of 5145 °, 1
Peak P _{A in} the range of 580 to 1620 cm ⁻¹ , 1350 to
Has a peak P _B in the range of 1370 cm ^-1, the ratio R = I _B / I _A of the intensity I _B of P _B with respect to the intensity I _A of the P _A is,
0.4 or more, preferably 0.6 or more, more preferably 0.9 or more, particularly preferably 0.90 to 1.5
A carbonaceous material having 0, most preferably 0.90 to 1.30 is formed as a surface layer.

The true density of the carbon material in the surface layer is preferably lower than the true density of the core carbonaceous material. That is,
The true density of the carbon material in the surface layer is less than 2.10 g / ml, more preferably 2.05 g / ml or less, and further preferably 1.
30 to 2.05 g / ml, particularly preferably 1.40 to
2.05 g / ml, most preferably 1.80 to 2.03 g
/ Ml, preferably 0.10 to 0.70 g / ml, more preferably 0.15 g / ml, more than the true density of the core carbonaceous material.
-0.50 g / ml, more preferably 0.18-0.4
0 g / ml, particularly preferably 0.19 to 0.35 g / m
l, most preferably control to a value smaller by 0.20 to 0.30 g / ml.

The carbonaceous material formed as the surface layer is X
In the line wide-angle diffraction, the spacing d ₀₀₂ of the (002) plane is
It is preferably at least 3.45 °, more preferably at least 3.47 °.
3.75 °, more preferably 3.49 to 3.70 °.
It is particularly preferably controlled at 3.50 to 3.65 °, most preferably at 3.56 to 3.60 °.

Further, the crystallite size L _{C in the} c-axis direction
Is preferably 100 ° or less, more preferably 70 ° or less, further preferably 50 ° or less, particularly preferably 1 ° or less.
It is controlled at 0 to 30 °, most preferably at 15 to 30 °.

The thickness of the surface layer is preferably 100 ° to 5 μm.
m, more preferably from 200 to 4 μm, even more preferably from 300 to 3 μm, particularly preferably from 500 to 2 μm.
m, most preferably from 800 ° to 1 μm.

As a result of forming such a surface layer, the ratio of the surface layer portion to the entire carbonaceous material is preferably 3 to 80.
% By weight, more preferably 5 to 60% by weight, still more preferably 8 to 50% by weight, particularly preferably 10 to 45% by weight, and most preferably 12 to 40% by weight.

Such a carbonaceous material is a multiphase in which one or more nuclei composed of a granular or fibrous carbonaceous material are included in a surface layer composed of a granular or fibrous carbonaceous material having another crystal structure. Take the structure. FIG. 1 shows an example of a schematic diagram of the shape.
Shown in Note that the core and the surface layer may each be composed of a plurality of layers.

The carbonaceous material can take any shape such as a particle shape or a fiber shape as a whole, but is preferably a particle shape or a fiber shape, and particularly preferably a particle shape.

In the case of particles, the volume average particle size is preferably 1 to 100 μm, more preferably 2 to 50 μm, further preferably 3 to 30 μm, particularly preferably 4 to 20 μm.
μm, most preferably 5 to 15 μm. If fibrous, the diameter is preferably 0.5-25 μm, more preferably 1-20 μm, even more preferably 2-10 μm, most preferably 3-5 μm; the length is preferably 1-5 μm.
It is 0 mm or less, more preferably 5 mm or less, and still more preferably 3 mm or less.

[0031] The specific surface area determined by the BET method is preferably 0.5 m ² / g or more, more preferably 1 m ²
/ G or more, more preferably ² to 100 m ² / 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 for 1,000 hours.
0 to 3,000 ° C, preferably 2,000 to 3,000
It is decomposed by heating at a temperature of ° C., carbonized and graphitized, and d ₀₀₂ is 3.35 ° in the X-ray wide-angle diffraction diagram.
As described above, a carbonaceous material of less than 3.45 ° is obtained and used as a nucleus. This carbonaceous material may take any of a particle shape and a fibrous shape.

Next, using the carbonaceous material obtained as described above as a nucleus, the organic compound is decomposed by heating under an inert gas flow or under vacuum, carbonized, and new carbon is deposited on the surface of the nucleus. The surface layer of the substance is formed. Alternatively, the surface layer may be formed by a similar method using natural graphite or artificial graphite particles as nuclei.

The heating temperature varies depending on the kind of the organic compound, but a temperature at which the true density and the crystal structure of the core carbonaceous material do not change is used, and is usually 500 to 2,500 ° C., preferably 600 to 1,500. It is selected from the range of ° C.

As a method for forming a surface layer on the surface of the carbonaceous material serving as a nucleus, there are the following methods, which can be arbitrarily selected.

The first method is a method in which an organic compound is thermally decomposed in a gas phase on the surface of a carbonaceous material serving as a nucleus to form a surface carbonaceous material. Examples of the organic compound used in this method include aliphatic saturated hydrocarbons such as propane, aliphatic unsaturated hydrocarbons such as propylene, and aromatic hydrocarbons such as benzene, toluene, xylene, naphthalene, and perylene. Further, carboxylic acids, carboxylic anhydrides, carboxylic imides, and the like derived from these aromatic hydrocarbons can also be used.

The second method is a method in which an organic compound is carbonized from a liquid phase on the surface of a carbonaceous material serving as a nucleus to form a surface carbonaceous material. Examples of the organic compound used in this method include monocyclic hydrocarbon compounds having three or more ring members such as naphthalene, phenanthrene, acenaphthylene, anthracene, triphenylene, pyrene, chrysene, naphthacene, picene, perylene, pentaphene, and pentacene. A condensed polycyclic hydrocarbon compound obtained by condensing at least one compound; or a derivative of the above compound such as carboxylic acid, carboxylic anhydride, or carboxylic imide; and a pitch mainly containing a mixture of the above compounds. Examples of the pitch include crude oil pitch, naphtha pitch, asphalt pitch, coal tar pitch, as well as cracked pitch obtained by cracking polyvinyl chloride or polyvinylidene chloride.

As the organic compound used as a starting material, a 3- or more-membered heteromonocyclic compound such as indole, isoindole, quinoline, isoquinoline, quinoxaline, phthalazine, carbazole, acridine, phenazine and phenanthridine can be used. At least two with each other
A condensed heterocyclic compound formed by bonding to one or more monocyclic hydrocarbon compounds having one or more three-membered rings or more is also exemplified.

In a third method, the surface of a carbonaceous material serving as a nucleus is coated with a polymer substance, and then heated and decomposed to carbonize in a solid phase to form a carbonaceous material in a surface layer. Is the way. As the polymer substance used in this method, phenol resin; furfuryl alcohol resin; cellulose; acrylic resin such as polyacrylonitrile and poly (α-acrylonitrile halide); polyvinyl chloride, polyvinylidene chloride, chlorinated polyvinyl chloride And any organic polymer compound such as a conjugated resin such as polyacetylene, poly (p-phenylene), and poly (p-phenylenevinylene).

Further, the above-mentioned carbonaceous material can be used by mixing an alkali metal as an active material, particularly a metal capable of forming an alloy with lithium, for example, aluminum. 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 particles of carbonaceous material, or in the form of being contained inside particles of carbonaceous material. . The particles of the metal or its alloy capable of forming an alloy with the above active material preferably have a volume average particle diameter of 1 to 50 μm, more preferably 2 to 2 μm.
0 μm, more preferably 3 to 10 μm.

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, based on 100 parts by weight of the carbonaceous material.
More preferably, it is 10 to 50 parts by weight, particularly preferably 15 to 40 parts by weight, and most preferably 20 to 30 parts by weight.

The carbonaceous material used as a positive electrode or a negative electrode is usually mixed with a polymer binder 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, ethylene / propylene rubber and butyl 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 ionic conductive polymer composition has an ionic conductivity at room temperature of preferably 10 ^-8.
S · cm ⁻¹ or more, more preferably 10 ⁻⁶ S · cm ⁻¹ or more, further preferably 10 ^-5 S · cm ⁻¹ or more, particularly preferably 10 ^-4 S · cm ⁻¹ or more, and most preferably 10 ^-4 S · cm ⁻¹ or more. ^-3 S · cm ⁻¹ or more is used. Specifically, polyethylene oxide, polypropylene oxide, polyepichlorohydrin, polyphosphazene, polyvinylidene fluoride, a polymer compound such as polyacrylonitrile, a system in which a lithium salt or a lithium-based alkali metal salt is compounded,
Alternatively, a system in which an organic compound having a high dielectric constant such as propylene carbonate, ethylene carbonate, and γ-butyrolactone is further blended can be used. The polyphosphazene preferably has a polyether chain, particularly a polyoxyethylene chain in a side chain.

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 a fibrous binder is entangled with the carbonaceous material particles, or the above rubber-like polymer, thermoplastic elastomer, soft resin, ion-conductive polymer Examples include a form in which a binder such as a composition is attached to the surface of particles of a carbonaceous material.

When a fibrous binder is used, the fiber diameter of the binder is preferably 10 μm or less, more preferably 5 μm or less, fibrils (ultrafine fibers), and fibrids (tentacle-like ultrafine fibers). It is particularly preferable that the powder is a powder having fibrils.

The mixing ratio of the carbonaceous material and the binder is preferably from 0.1 to 100 parts by weight of the carbonaceous material.
30 parts by weight, more preferably 0.5 to 20 parts by weight, further preferably 1 to 10 parts by weight, particularly preferably 2 to 7 parts by weight
Parts by weight.

The carbonaceous material obtained as described above is mixed with the above-mentioned binder; or a metal capable of forming an alloy with the above-mentioned active material, or an alloy of the active material and the above-mentioned metal. An electrode formed body can be obtained by forming an electrode material made of a mixture obtained by blending, and forming the electrode material as it is into a shape of an electrode by a method such as roll molding or compression molding. Alternatively, these components are dispersed in a solvent and applied to a metal current collector or the like to form electrodes in various shapes such as pellets and sheets. As the metal current collector, a thin layer of a metal such as Ni, Cu, or stainless steel, a wire mesh, or the like can be used.

As a separator interposed between the positive electrode and the negative electrode obtained as described above and holding the electrolytic solution, a material having excellent liquid retention properties, for example, polyethylene,
A nonwoven fabric of a polyolefin-based resin such as polypropylene can be used. Examples of the electrolyte to be impregnated therein include aprotic organic solvents such as ethylene carbonate, propylene carbonate, 1,3-dioxolan, 1,2-dimethoxyethane, and 2-methyltetrahydrofuran, and LiClO ₄ , LiBF ₄ , and LiAsF.
₆ , LiPF ₆ , LiSO ₃ CF ₃ , LiN (SO ₂ C
A non-aqueous electrolyte having a predetermined concentration in which an electrolyte such as F ₃ ) ₂ is dissolved is used.

[0051]

In the secondary battery constructed as described above, the negative electrode carries the carbon dioxide in the electrolytic solution at the time of charging, and releases the carbon during the discharging, so that the charging / discharging electrode reaction proceeds.

On the other hand, in the positive electrode, the anion in the electrolytic solution is carried on the positive electrode body during charging, and the anion is released during discharging, so that the charging and discharging electrode reaction proceeds.

[0053]

As described above, the secondary battery of the present invention has excellent battery capacity and long-term charge / discharge cycle characteristics due to the combination of the positive electrode and the negative electrode as described above. It has excellent charge / discharge characteristics at high and low temperatures and excellent recovery characteristics against overcharge and overdischarge.
Furthermore, since the secondary battery of the present invention does not contain a large amount of lithium metal, there is no risk of ignition or explosion due to short-circuit or the like, and therefore, the secondary battery is extremely excellent in safety.

[0054]

EXAMPLES In the following examples, wide-angle X-ray diffraction and measurement of true density were performed as follows.

"X-Ray Wide Angle Diffraction" (1) Spacing between ( ₀₀₂ ) planes (d ₀₀₂ ) When the carbonaceous material is a powder, it is powdered in an agate mortar when it is a fine flake, 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,
The following simple method was used without correcting the absorption factor and the atomic scattering factor. 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 correction curve for the (002) plane.
A line parallel to the angle axis drawn to two-thirds of the peak height of this curve finds the midpoint of the line segment that intersects the diffraction curve, and corrects the angle of the midpoint with an internal standard. The diffraction angle was set to twice, and d ₀₀₂ was determined from the wavelength λ of the CuKα ray by the following Bragg equation. d ₀₀₂ = λ / 2 sin θ [Å] where λ: 1.5418 ° θ: diffraction angle corresponding to d ₀₀₂

(2) Crystallite size in the c-axis direction (L _c ) In the corrected diffraction curve obtained in the preceding section, the so-called half-width β at half the peak height is used to calculate the crystallite size in the c-axis direction. Was determined from the following equation. L _c = K · λ / (β · cos θ) [Å] 0.90 was used as the shape factor K. λ and θ have the same meaning as in the previous section.

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

Hereinafter, the present invention will be described 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.

Example 1 (1) Synthesis of Carbonaceous Material for Negative Electrode About 100 parts of a powder of naphthalene-1,4,5,8-tetracarboxylic dianhydride was placed in a nitrogen stream at 10 ° C. /
The temperature is raised to 380 ° C at a heating rate of
Hold for minutes. The temperature was further increased to 2,300 ° C. at a rate of 20 ° C./min, and maintained at that temperature for 1 hour.
Particles of carbonaceous material were formed.

[0060] The carbonaceous material particles, the X-ray wide angle diffraction, d ₀₀₂ is 3.390Å, L _C was 220 Å.
The true density was 2.22 g / cm ³ .

The thus obtained particulate carbonaceous material having an average particle size of 6 μm is used as a core, and 300 parts of a pitch, which is a mixture of condensed polycyclic hydrocarbon compounds, is mixed with toluene 867.
Immersed in the solution obtained by dissolving in
To coat the pitch on the surface of the carbonaceous material particles. This was heated to 1,000 ° C. at a rate of 20 ° C./min in a nitrogen stream, kept at that temperature for 30 minutes, and then lightly pulverized. In this way, a particulate carbonaceous material having a multilayer structure in which the above carbonaceous material particles are nuclei and a surface layer made of the carbonaceous material was formed on the surface thereof and having an average particle size of 6.8 μm was obtained. .

The carbonaceous material thus obtained had a multiphase structure consisting of a core and a surface layer, and the ratio of the surface layer was 28 parts to 100 parts of the core.

[0063] The carbonaceous material, in the Raman spectrum analysis using an argon ion laser beam of 5415A, the peak P _B in 1360 cm ^-1, a peak P _A in the 1600 cm ^-1, the intensity ratio R of the both 0. 95.
The density of the carbonaceous material was 2.16 g / ml.

(2) Preparation of Negative Electrode Particles of carbonaceous material having a multiphase structure obtained in (1) 9
Six parts were mixed with 4 parts of polyethylene powder, and the mixture was pressed on a nickel wire mesh to prepare a pellet electrode having a diameter of 16 mm. This was dried by heating to 130 ° C. in a vacuum to obtain a negative electrode.

(3) Synthesis of Carbonaceous Material for Positive Electrode The phenol resin particles were mixed at 10 ° C./min in a nitrogen stream.
The temperature was raised to 1,000 ° C. at the temperature rising rate, and maintained at that temperature for 1 hour. Thereafter, the particles were activated in steam at 800 ° C.

The carbonaceous material particles thus obtained had a (002) plane spacing d ₀₀₂ of 3.80 ° and a crystallite size L _{c in the} c-axis direction of 8 ° by X-ray wide angle diffraction of 8 °. Was. The specific surface area by BET was 800 m ² / g.

(4) Preparation of Positive Electrode 500 parts of the carbonaceous material obtained in (3), 25 parts of polytetrafluoroethylene powder and 25 parts of carbon black were kneaded and pressed on a titanium wire mesh to form a pellet electrode having a diameter of 16 mm. A positive electrode was prepared.

(5) Assembly of Experimental Cell and Evaluation of Battery Performance The positive electrode obtained in (4) and the negative electrode obtained in (2) were
A pair of electrodes was formed to face a glass cell containing a 1 mol / liter LiClO ₄ propylene carbonate solution to form an experimental cell. The operation of applying a constant current of ² mA / cm ² between both electrodes and charging to 4.0 V and discharging to 1.5 V was repeated, and the change in battery capacity for each cycle was tracked.

FIG. 2 shows the relationship between battery capacity and charge / discharge cycle.
Was as shown in FIG.

Comparative Example 1 The same as Example 1 except that the carbonaceous material serving as a nucleus synthesized in the first stage of (1) of Example 1 was used as it was as a carbonaceous material for a negative electrode without forming a surface layer. And then
A positive electrode and a negative electrode were prepared, and they were combined to form an experimental cell in the same manner as in Example 1, and the battery performance was evaluated. The result is shown in FIG.

COMPARATIVE EXAMPLE 2 The pitch was heated to 1,000 ° C. in a nitrogen stream at a rate of 20 ° C./min, and kept at that temperature for 30 minutes to be carbonized. A particulate carbonaceous material having a particle size of 6.8 μm was obtained. The carbonaceous material obtained in this manner had a d ₀₀₂ of 3.56 ° and an L _c of 1 by X-ray wide-angle diffraction.
8 °, and the true density was 1.90 g / cm ³ .

Using this carbonaceous material, a negative electrode was prepared in the same manner as in Example 1, and then, in the same manner as in Example 1, a positive electrode was prepared, the configuration of an experimental cell, and the battery performance were evaluated.
The result is shown in FIG.

Comparative Example 3 100 parts of the carbonaceous material used for the negative electrode in Comparative Example 1 and Comparative Example 2
Was mixed with 35 parts of the carbonaceous material used for the negative electrode. Using this mixture, a negative electrode was prepared in the same manner as in Example 1;
As in Example 1, the preparation of the positive electrode, the configuration of the experimental cell, and the evaluation of the battery performance were performed. The result is shown in FIG.

[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.

FIG. 2 is a graph showing battery capacity for each charge / discharge cycle as an evaluation result of battery performance in Examples and Comparative Examples.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Core 2 Surface layer A Example 1 B Comparative example 1 C Comparative example 2 D Comparative example 3

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-102167 (JP, A) JP-A-59-87777 (JP, A) JP-A-4-368778 (JP, A) JP-A-5-87 94838 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 4/36-4/62 H01M 4/00-4/04

Claims (1)

(57) [Claims] 1. A secondary battery comprising a rechargeable positive electrode and a rechargeable negative electrode, wherein the positive electrode contains a carbonaceous material satisfying the following requirement (A), and the negative electrode comprises the following ( A secondary battery comprising a carbonaceous material satisfying the requirement of B). (A) Spacing d of (002) plane by X-ray wide-angle diffraction method
₀₀₂ is 3.45 ° or more and the specific surface area is 10 m ² / g or more. (B) It has a multiphase structure in which a surface layer of a carbonaceous material satisfying the following requirement (b) is formed on the surface of a particulate or fibrous core of the carbonaceous material satisfying the following requirement (a). (A) Spacing d of (002) plane by X-ray wide-angle diffraction method
₀₀₂ is 3.35 ° or more and less than 3.45 °. (B) In Raman spectrum analysis using an argon ion laser beam having a wave number of 5145 °, 1580 to 162
Range of 0 cm ^-1 to the peak P _A, has a peak P _B in the range of 1350 ^-1, is R value defined by formula (I) is 0.4 or more. Strength R = in I _B / I _A (I) formula, I _A is the peak P _A, I _B represents the intensity of peak P _B.