JPH07153446A - Electrode and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide an electrode having an extremely large electric capacity and excellent in charge/discharge cyclic characteristics by feeding a hydrocarbon compound acted with a specific characteristic group to hydrocarbon to a reaction system, and using a carbon deposit as an electrode active material. CONSTITUTION:A hydrocarbon compound added or substituted with a characteristic group containing at least one element among oxygen, nitrogen, sulfur, and halogen to hydrocarbon or part of hydrocarbon is fed to a reaction system. A carbon deposit deposited in the vapor phase by thermal decomposition in the reaction system is used as an electrode active material to manufacture a target electrode. This electrode is mainly made of a carbon material having a layer structure expressed by the average spacing of the hexagonal net face of graphite at 3.37-3.55 and the ratio of the peak strength of 1360cm<-1> against the peak strength of 1580cm<-1> in the argon laser Raman spectrum and some irregular layer structure. Doping and dedoping of a dopant material occur more easily as compared with a conventional high-graphite carbon body, and the electric capacity is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode and a method for producing the same, and more particularly to a battery electrode using an alkali metal such as lithium (Li) or potassium (K), an alkaline earth metal, a rare earth metal or a transition metal as a dopant substance. The present invention relates to an active material or an electrode active material of a battery using halogen, a halogen compound or oxyacid as a dopant material.

[0002]

2. Description of the Related Art In recent years, research has been actively conducted to apply carbon materials to battery electrodes.

For example, JP-A-60-182670 describes a chargeable / dischargeable battery using activated carbon or activated carbon fiber for the positive electrode, graphite or graphitized carbon fiber for the negative electrode, and an organic material as an electrolytic solution. Has been done.

Further, in Japanese Patent Laid-Open No. 60-20466, chlorination of graphite fiber obtained by heat treatment of carbon fiber having a structure in which the hexagonal mesh plane of carbon is arranged substantially parallel to the fiber axis and in a ring shape. There is a description of a battery active material containing a nickel graphite intercalation compound.

Further, Japanese Patent Laid-Open No. 60-36315 discloses a secondary battery using a carbon fiber structure.

[0006]

The graphite used as the electrode material has a hexagonal mesh plane formed by carbon atoms arranged regularly and is called a graphite structure.
This has a layered structure in which hexagonal mesh plane carbon layers are laminated in parallel. This layered structure with high regularity is called graphite, but in the case of simply carbon materials, the layered structure called amorphous carbon such as activated carbon is completely irregular, so it is highly ordered like graphite. It is known that there is a very wide range of properties, including those in which the carbon atoms are arranged by sex.

However, at present, it is considered that the graphite material used as the electrode material must have a high crystallinity.

That is, the above-mentioned JP-A-60-18267.
In the case of the publication No. 0, the Raman spectra by argon ion laser light are 1350 cm ^-1 and 1580 cm ^-1.
A highly graphitized carbon body having a high crystallinity, in which the ratio of the peak intensity appearing in and is 0.4 or less is used. Similarly, JP-A-6
In the case of JP-A No. 0-36315, the demand for this crystallinity is even higher, which is 136 for a Raman intensity of 1580 cm ^−1.
An extremely high graphitized carbon layer having a Raman intensity ratio of 1/10 at 0 cm ⁻¹ is used.

Further, in the case of Japanese Patent Laid-Open No. 60-20466, the carbon fibers grown on the substrate are 2700-300.
Graphitized at a high temperature of 0 ° C. to further grow graphite crystallites to obtain highly graphitized fibers for use.

As described above, it is generally believed that graphite as an electrode material generally requires high crystallinity. However, in the case of graphite having perfect crystallinity,
The layer spacing is relatively narrow at 3.354Å. However, when graphite is used as an electrode material to form an intercalation compound, the dopant substance enters and leaves between the layers. In the case of a highly graphitized carbon body (graphite material having high crystallinity), Since the layer spacing is narrow and the hexagonal mesh planes are stacked very regularly, there has been a problem that the amount of the dopant substance doped is reduced near room temperature.

Therefore, the present invention has been made in view of the above-mentioned problems, and has an electrode having a remarkably large electric capacity as compared with the conventional carbon material and excellent charge-discharge repeating characteristics, and a method for manufacturing the same. The purpose is to provide.

[0012]

[Means for Solving the Problems] In order to achieve the above object, the inventors of the present invention have conducted extensive studies and as a result, have found that a layered structure is used instead of carbon having a highly oriented graphite structure (carbon with high crystallinity). By using a material with a slight disordered layer structure or carbon with selective orientation as the electrode material, the electric capacity was greater than that of the conventional one and the charge / discharge repetition characteristics were excellent. The knowledge that an electrode can be obtained was able to be obtained. The degree of disordered layer structure or selective orientation of the carbon material is objectively expressed as follows.

That is, the carbon plane has a layer spacing of 3.37Å to 3.55Å by X-ray diffractometry, and does not show a sharp peak like graphite, but shows a considerably wide diffraction peak.

Furthermore, the laser Raman spectrum of 15
Peak intensity ratio of 1360 cm ^-1 to the peak intensity of 80 cm ^-1 is of 0.4 to 1.0.

Each physical property value is well known as a physical property value showing the degree of graphitization, but the physical property of a material can be expressed by combining the physical property value obtained from Raman scattering and the physical property value obtained from X-ray diffraction. As is well known, the physical property value obtained from Raman scattering is information on an extremely surface about 50 nm from the surface of a carbon material, and the physical property value obtained from X-ray diffraction is a certain depth of about several tens of μm including the surface. It is information as the average so far. That is, the structure in the depth direction can be grasped by combining these two physical property values.

The crystallite size obtained from the half-width of the diffraction peak is such that the crystallite size in the C-axis direction from the diffraction peak of the (002) plane is 20Å to 1000Å.
The diffraction peak of the (110) plane hardly appears, or even if it appears, it is very broad, so that the crystallite size in the ab axis direction is recognized to be very small. Note that the backscattered electron diffraction pattern has a broad ring shape, which reflects that the crystallites are very fine. These rings correspond to the (002), (004), (006) reflections of the graphite structure. Also, the siege of each crystallite is not random,
The (001) planes of each crystallite are aligned in a specific direction, and the relative inclination in the C-axis direction between the crystallites is within ± 75 degrees.

As described above, a carbon body having a larger interplanar spacing, a smaller crystallite size and a certain degree of orientation as compared with the highly graphitized carbon body exhibits good characteristics as an electrode material.

The carbon body having the above characteristics can be obtained, for example, by the following production method. That is, a hydrocarbon or a hydrocarbon compound can be used as a starting material, which is supplied to a reaction system and formed on a substrate by a vapor phase volume method by thermal decomposition.

As the hydrocarbon compound, a compound obtained by adding or substituting a characteristic group containing at least one element selected from oxygen, nitrogen, sulfur or halogen to a part of hydrocarbon can be used.

[0020]

When the above-mentioned carbon material is used for an electrode of a battery containing an alkali metal or the like as a dopant substance, the dopant substance is more likely to be doped and dedoped than the conventional highly graphitized carbon body, resulting in a large electric capacity. Become. Moreover, since the above-mentioned carbon body can be directly formed on the substrate as a thin film, the internal resistance is small and the utilization factor of the active material is high. Further, since it can be formed in an arbitrary shape, there is an effect that the electrode can be made thinner.

[0021]

【Example】

(Embodiment 1) Hereinafter, the present invention will be described in detail by way of an embodiment with reference to the drawings.

FIG. 1 is a carbon body C used for the electrode of the present invention.
It is an X-ray diffraction diagram which uses uKα as a light source. From this diffraction peak, the following Bragg equation (Equation 1)

[0023]

[Equation 1]

The average interplanar spacing of the (002) plane is found to be 3.45Å, and from the half-value width β of the peak, the following equation (Equation 2)

[0025]

[Equation 2]

The crystallite size in the C-axis direction was found to be 27.2Å.

FIG. 2 is a Raman spectrum of this carbon body using an argon laser. As is clear from this figure, the peak intensity at 1580 cm ^-1 is 1360c.
The peak intensity at m ^-1 is 0.8.

Reflection high-energy electron diffraction (RHEED)
(002), (00)
The 4) and (006) reflections show broad spots, the orientation of each crystallite is fairly good, and the distribution in the C-axis direction is within ± 18 degrees.

This carbon body (a film in which a carbon material was formed on a substrate) was sandwiched by a collecting net to form an electrode. This is designated as test pole A. A test electrode A was arranged in an electrolytic cell as shown in FIG. 3, and a lithium metal was used as a counter electrode and lithium was used as a dopant substance to perform a charge / discharge test by doping / dedoping lithium element. In FIG. 3, 12 is an electrode (test electrode A) made of the carbon body according to the present invention, 13 is a current collector, 14 is a counter electrode, 15 is lithium used as a reference electrode, and 16 is propylene in which 1 mol of lithium perhydrochloride is dissolved. An electrolytic solution made of carbonate, and 17 is an electrolytic cell.

FIG. 4 shows various carbon materials doped with lithium.
FIG. 7 is a potential change diagram with respect to a lithium reference electrode at 25 ° C. when dedoped. Curve A in FIG. 4 is a potential change curve of the electrode of the present invention. In curve A, the potential is 0V
The direction closer to is the doping (charging), and the direction becoming the high voltage is the dedoping (discharging).

FIG. 5 shows changes in discharge capacity in a test in which various carbon materials are charged and discharged with a constant current between 0 V and 2.5 V with respect to a lithium reference electrode. Curve A in FIG. 5 is a curve showing the electrode characteristics of the present invention. As is clear from this result, there is almost no capacity deterioration due to repeated charging and discharging, and the repeating characteristics are very good.

As described above, by using the carbon body of the present invention, a negative electrode of a non-aqueous lithium secondary battery that can be charged and discharged can be constructed.

An example of the method for producing the above carbon material will be described below with reference to the drawings.

FIG. 6 is a block diagram of a carbon material producing apparatus used for producing the carbon material used for the electrode of the present invention.

Hydrocarbons used as starting materials and hydrocarbon compounds partially containing various characteristic groups include, for example, aliphatic hydrocarbons, preferably unsaturated hydrocarbons, aromatic compounds and alicyclic compounds. These are pyrolyzed at 1000 ° C. Specifically, acetylene, diphenyl, acetylene, acrylonitrile, 1.2-dibromoethylene, 2
Butyne, benzene, toluene, pyridine, aniline,
Examples thereof include phenol, diphenyl, anthracene, pyrene, hixamethylbenzene, styrene, allylbenzene, cyclohexane, normal hexane, pyrrole and thiophene.

Depending on the type of hydrocarbon compound used,
The supply method to the reaction tube, which will be described later, is a bubbler method, an evaporation method or a sublimation method and is controlled to a supply amount of several millimoles or less per hour. Soot-like carbon volume is generated when the supply amount is large,
The carbon material required for the electrode structure of the present invention cannot be obtained. It is necessary that the volume of the carbon material and the substrate on which it is generated do not deteriorate at the reaction temperature of about 1000 ° C.

The manufacturing process will be described below.

Argon gas is supplied from an argon gas control system 2 into a bubble container 1 containing benzene which has been subjected to a purification operation by vacuum distillation to bubble benzene, and a benzene bubble is passed through a Pyrex glass tube 3 to a quartz reaction tube 4. Feed benzene molecules. At this time, the temperature of the liquid benzene in the bubble container 1 is kept constant and the flow rate of argon gas is adjusted by the bubble 5 to control the supply amount of benzene molecules into the reaction tube 4 to several millimoles per hour. On the other hand, argon gas is caused to flow from the dilution line 6 to optimize the number density and flow rate of benzene molecules in the argon gas in the glass tube 3 immediately before being fed to the reaction tube 4. A heating furnace 8 is provided around the outside of the reaction tube 4. The heating furnace 8 holds the volume generating substrate in the reaction tube 4 at a temperature of about 1000 ° C.

When the benzene molecule is fed into the reaction tube 4, the benzene molecule is thermally decomposed in the reaction tube 4 and a carbon volume product is formed on the substrate. Gas into the reaction tube 4 is exhaust pipe 9
It is introduced into the exhaust system 10 via and is removed from the reaction tube 4. About 1000 benzene molecules were introduced into the reaction tube 4.
It is heated at a temperature of ° C to be thermally decomposed and sequentially grown and formed on the substrate. In this case, the grown carbon becomes a thin film having a metallic luster, and since the reaction proceeds at a lower temperature than the method of forming a graphite material by a conventional manufacturing method, a carbon material having good physical properties is manufactured. be able to. In addition,
With this method, the anisotropy and the like can be arbitrarily controlled by selecting the starting material, the supply amount of the starting material, the supply rate, and the reaction temperature.

Example 2 Various characteristics of the carbon film of the second example are as follows. That is, the average interplanar spacing of the (002) plane is 3.37Å as shown in FIG. 7, which is ¹ with respect to the peak intensity of 1580 cm ⁻¹ by the Raman spectrum.
The peak intensity ratio at 360 cm ^-1 is 0.50 as shown in FIG.
Met. The distribution of each crystallite in the c-axis direction by reflection high-energy electron diffraction was within ± 60 degrees.

A lead wire was taken out from this carbon film formed on the substrate and used as an electrode, which was used as a test electrode B. This is Example 1
A charging / discharging test by doping / dedoping was performed by using lithium as a dopant substance in the same manner as in. Curve B in FIG.
3 is a potential change curve of the carbon material according to this example. Curve B in FIG. 5 shows the change in discharge capacity in the repeated test of the carbon material according to this example. As is clear from this result, the discharge capacity and the repeating characteristics are very good.

In this example, 1 mol of lithium perchlorate was used as the electrolyte and propylene carbonate was used as the electrolytic solution, but it is not necessary to limit to this, and other electrolytes such as lithium hexafluorosulfate and borofluoride can be used. Lithium fluoride, lithium trifluorosulfonate, and the like, and as the electrolytic solution, dimethyl sulfoxide, gamma-butyl lactone, sulfolane tetrahydrofuran, 2-methyltetrahydrofuran, 1.2-dimethoxyethane, 1.3-.
Examples include organic solvents such as dioxolane and water, and these can be used alone or in combination.

Comparative Example 1 A carbon body deposited on a quartz substrate at 1200 ° C. was peeled from the substrate and then heat treated at 2800 ° C. for comparison with a graphitized carbon body of the present invention.

FIG. 9 shows the X-ray diffraction data of this carbon body. The spacing between (002) planes of this carbon body was 3.36Å. Moreover, in Raman spectrum, it is 1580 cm.
^The ratio of the peak intensity at 1360 cm ^{-1 to} the peak intensity at ^-1 was 0.1 (Fig. 10). This carbon body was used as an electrode and used as a test electrode C in the same manner as in Example 1. Test pole C is shown in FIG.
The charging / discharging test was performed in the same manner as in Example 1 by disposing in the electrolytic cell as shown in FIG. Curve c in FIG. 4 is a potential change curve of the carbon material according to this comparative example. As a result, the discharge capacity was smaller than that of the electrodes of Examples 1 and 2 and it was unsuitable as an electrode material.

Comparative Example 2 Crude petroleum coke obtained by removing volatile components from crude oil was heat-treated at 500 ° C. The X-ray diffraction pattern of this carbon powder body is shown in FIG. From this diffraction peak, the average interplanar spacing of the (002) plane was 3.45Å. Further, the peak intensity ratio of 1360 cm ^-1 to the peak intensity of 1580 cm ^-1 in the Raman spectrum was 0.8. The result is shown in FIG. Further, according to the diffraction pattern of the electrode obtained by pressing this carbon body by reflection high-energy electron diffraction, it was found that each ring of the diffraction pattern was uniform and had no orientation. A foamed nickel substrate was filled with this carbon body and pressed to obtain an electrode, which was used as a test electrode D. The test electrode D was placed in an electrolytic cell as shown in FIG. 3, and a charge / discharge test was conducted in the same manner as in Example 1. Curve D in FIG. 4 is a potential curve of the carbon material according to this comparative example. From this result, the discharge capacity is smaller than those in Examples 1 and 2. However, the initial charge / discharge characteristics were better than those of Comparative Example 1.

The test electrode D was subjected to a repeated charging / discharging test in the same manner as in Example 1. Curve D in FIG. 5 shows the result of this comparative example. From this result, it is recognized that the electrode having no crystallite orientation at all has a deterioration in capacity due to repeated charging and discharging, and cannot withstand long-term use.

[0047]

According to the present invention, doping and de-doping of the dopant substance are more likely to occur than in the conventional highly graphitized carbon body, and the electric capacity is increased. Moreover, since the above-mentioned carbon body can be directly formed on the substrate as a thin film, the internal resistance is small and the utilization factor of the active material is high. Further, since it can be manufactured in an arbitrary shape, there is a remarkable effect that the electrode can be made thinner.

[Brief description of drawings]

FIG. 1 is an X-ray diffraction diagram of a carbon material of the present invention.

FIG. 2 is a diagram showing a Raman spectrum of the carbon material of the present invention.

FIG. 3 is a schematic view of an apparatus for measuring the electrode characteristics of the carbon material of the present invention.

FIG. 4 is a charge / discharge characteristic diagram of the carbon material of the present invention and the existing carbon material.

FIG. 5 is a cycle characteristic diagram of the charge and discharge capacities of the carbon material of the present invention and the existing carbon material.

FIG. 6 is a block configuration diagram of a carbon material generation device used for describing an embodiment of the present invention.

FIG. 7 is an X-ray diffraction pattern of the carbon material of the present invention.

FIG. 8 is a diagram showing a Raman spectrum of the carbon material of the present invention.

FIG. 9 is an X-ray diffraction diagram of an existing carbon material.

FIG. 10 is a diagram showing a Raman spectrum of an existing carbon material.

FIG. 11 is an X-ray diffraction diagram of an existing carbon material.

FIG. 12 is a diagram showing a Raman spectrum of an existing carbon material.

[Explanation of symbols]

 12 Test Electrode A 13 Current Collector 14 Counter Electrode 15 Reference Electrode 16 Electrolyte 17 Electrolyzer

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoshimitsu Tajima 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within Sharp Corporation (72) Yoshikazu Yoshimoto 22-22 Nagaike-cho, Abeno-ku, Osaka, Osaka (72) Inventor Shigeo Nakajima 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Prefecture Sharp Corporation (72) Inventor, Sansei Kasahara 22-22, Nagaike-cho, Abeno-ku, Osaka City, Osaka Prefecture

Claims (3)

[Claims] 1. The average interplanar spacing of graphite hexagonal mesh planes is 3.37.
Å to 3.55Å, 1360c for peak intensity at 1580 cm ^-1 in Argon laser Raman spectrum
An electrode comprising, as a main component, a carbon material having a slight disordered layer structure in a layer structure represented by a ratio of m ⁻¹ peak intensities of 0.4 or more and 1.0 or less. 2. The average interplanar spacing of hexagonal mesh planes of graphite is 3.37.
Å to 3.55Å, 1360c for peak intensity at 1580 cm ^-1 in Argon laser Raman spectrum
The layer structure represented by the ratio of the peak intensity of m ⁻¹ of 0.4 or more and 1.0 or less has a slight disordered layer structure, and the diffraction pattern of the (002) plane in reflection high-energy electron diffraction shows An electrode comprising a carbon material as a main component, which has a selective orientation with a relative inclination in the C-axis direction between crystallites of ± 75 ° or less. 3. A hydrocarbon or a part of the hydrocarbon is oxygen,
A hydrocarbon compound having a characteristic group added or substituted with at least one element selected from nitrogen, sulfur, or halogen is supplied to a reaction system, and vapor-phase-deposited carbon deposit by thermal decomposition in the reaction system Is used as an electrode active material.