JPS61168512A - Electrode material - Google Patents

Abstract

PURPOSE:To provide a low-cost electrode material enabling the production of a light-weight pollution-free cell having high energy density and maximum output density, by calcining an acrylonitrile polymer, a phenolic resin, a cellulosic resin or pitch. CONSTITUTION:The objective electrode material satisfying the following two conditions is produced by calcining a polyacrylonitrile, a phenolic resin, a cellulosic resin or pitch. The conditions are (1) the atomic ratio of H/C is <=0.20 and (2) the g value determined from the first-order differential absorption curve of electron spin resonance spectrum (at 23 deg.C) has a signal having a line width (DELTAHpp) of >=100Gauss within the range of 1.970-2.020, or is devoid of the signal having a line width of <100Gauss.

Description

Detailed Description of the Invention (Field of Application) The present invention relates to an electrode material that is lightweight, has a high energy density, a high maximum output density, and can be industrially produced at low cost, making it possible to manufacture non-polluting batteries. .

(Prior Art) In recent years, there has been a rapid movement in research and development aimed at improving the performance of batteries. One of these is research on rechargeable secondary batteries that use carbonaceous materials as electrodes and electrochemical doping. The ninth example is when using KLi metal as the negative electrode and graphite as the positive electrode.
Anions such as ClO:, BF4-, etc. can be doped between the graphite layers by charging, and the electromotive force generated at this time can be used for application as a battery. During discharge, these ions are dedoped from between the graphite layers, allowing current to flow out. In this way, it can be used as a secondary battery that can be charged and discharged repeatedly (Electrochemistry 46, 438 (1978), etc.).

However, in this case, there is a limit to the amount of doping, probably due to repulsion between ions doped between the graphite layers, and the energy density is low, making graphite insufficient as a positive electrode.

Furthermore, Li metal as a negative electrode is insufficient as a negative electrode because it cannot increase the number of charge/discharge cycles due to dendrites that grow on the Li metal electrode as the charge/discharge cycles are repeated.

In addition, when graphite is used as a negative electrode, it is possible to dope cations such as Li ions between the eyebrows, but it is unstable under extreme pressure in the electrolyte and reacts with the electrolyte, making it unsuitable as an electrode material ( J, Elec-trochem,
5ociety, 125, 687 (1978)
).

Furthermore, a battery using commercially available activated carbon fibers for both electrodes has been proposed in Japanese Patent Application Laid-Open No. 58-35881. However, as proposed in Japanese Unexamined Patent Publication No. 55-99714, an electric double layer capacitor using activated carbon fibers for both poles, rather than accumulating and releasing charges through ion doping and dedoping, It utilizes an electric double layer in which positive and negative charges are distributed across an extremely short distance at the interface between the activated carbon electrode and the solution, so the energy density does not increase and self-emission is more likely to occur, resulting in long-term discharge. It has several important problems, such as not being able to withstand high temperatures and not being able to achieve voltage flatness.

On the other hand, there is also a great deal of interest in research into rechargeable secondary batteries that utilize electrochemical doping with conductive polymers such as polyacetylene as electrodes. For example, JP-A-57-121168 proposes a battery using an acetylene polymer. However, polyacetylene is unstable due to oxidative deterioration in the air, and deteriorates when reacting with trace amounts of moisture and oxygen contained in the solvent, making it less stable as an electrode. In particular, the polyacetylene used as the negative electrode deteriorates severely in the electrolyte.

Therefore, a battery using polyacetylene as both electrodes has severe self-discharge and poor charging/discharging efficiency, making it difficult to obtain a high-performance and highly reliable IE battery.

In a battery that uses Li metal as the negative electrode and polyacetylene as the positive electrode, problems such as charge efficiency during charging and discharging are improved compared to batteries that use polyacetylene for both electrodes, but in this case as well, the charging and discharging efficiency is improved. Problems arise, such as the inability to increase the number of charge/discharge cycles due to dendrites that grow on the Li metal electrode as the process progresses.

(Summary of the Invention) In view of the current situation, the present inventors have developed a lightweight, high energy density, high maximum output density, non-polluting secondary battery that is stable against ion doping and dedoping and requires a large amount of Recognizing that good positive and negative electrode materials that can be doped with ions are important, and the most important point being the development of materials that have excellent performance as negative electrodes, HC has developed excellent materials for negative electrodes. We have worked hard to develop. As a result, we have arrived at the present invention.

That is, the present invention is an electrode material that does not contain an acrylonitrile polymer, a phenol resin, a cellulose resin, or c. pitch, and satisfies the following (1) and (2).

(1) The atomic ratio of hydrogen/carbon atoms is 0.20 or less.

(2) The binary value obtained from the first-order differential absorption curve of the electron spin resonance spectrum (measured at 23°C) is 1.970 to 2.0.
Have a signal with a line width of 100 Gauss or more in the range of 20, or have no signal with a line width of less than 10 Gauss.

The electrode material of the present invention exhibits excellent battery performance when used as a negative electrode.

(Detailed Description of the Invention) In the present invention, the negative electrode refers to an electrode that is connected to the cathode of an external power source to which electrons are sent and doped with cations during charging.

The phenolic resin used in the synthesis of the electrode material of the present invention means a condensate obtained by condensing an aromatic hydrocarbon compound having a phenolic hydroxyl group and an aldehyde compound in the presence of a dispersive or basic catalyst.

Examples of the aromatic hydrocarbon compound having a phenolic hydroxyl group include phenol, orthocresol, para-cresol, metacresol, xylenol such as 3,5-xylenol, alkylphenol such as para-tert-glutylphenol, para-phenylphenol,
Bisphenol A, resorcinol, etc. are used.

Examples of aldehyde compounds include formaldehyde, paraformaldehyde, trioxane, acetaldehyde, furfural, and acrolein.

In particular, formaldehyde, paraformaldehyde, and trioxane are commonly used.

The condensate obtained by condensing the above-mentioned aromatic hydrocarbon compound having a phenolic hydroxyl group and an aldehyde compound in the presence of an acidic or basic catalyst can undergo an appropriate curing reaction with a curing agent or simply by heating. It is desirable to have them do this. By allowing a curing reaction to occur after shaping into an appropriate shape, the shape of the electrode material obtained after thermal firing can be selected.

That is, the novolac type phenol resin obtained by condensing the above-mentioned aromatic hydrocarbon compound having a phenolic hydroxyl group and an aldehyde compound in the presence of an acidic catalyst further contains formaldehyde, paraformaldehyde, acetaldehyde, furfural, acrolein, and hexanemethylenetetramine. The curing reaction can be carried out using a crosslinking agent such as trimethylolphosphine oxyto fZ. It is also possible to use epoxy-based compounds, such as epoxy resins, as hardeners. Furthermore, a resol type phenol resin obtained by reacting phenol with an aldehyde compound in the presence of an alkali catalyst can be cured by reacting it with the above-mentioned novolac type phenol resin.

Furthermore, a resol type phenolic resin obtained by reacting an aromatic hydrocarbon compound having a phenolic hydroxyl group and an aldehyde compound in the presence of a basic catalyst can be heated to cause a curing reaction.

As the phenolic resin used in the synthesis of the electrode material of the present invention, a polymer containing a phenol group tM combination unit such as polyP-vinylphenol or polyisopropenylphenol can be used. Usually, these polymers are appropriately cured using a compound having an epoxy group such as formaldehyde, paraformaldehyde, acetaldehyde, furfural, acrolein, hexamethylenetetramine, trimethylolphosphine oxide, epoxy resin, or resol.

The polyacrylonitrile used in the synthesis of the electrode material of the present invention means a homopolymer of acrylonitrile or a copolymer obtained by copolymerizing acrylonitrile with a small proportion of other comonomers. A homopolymer of acrylonitrile or a copolymer of acrylonitrile and α-halogenated acrylonitrile is preferred, and common 1 is copolymerized with L/%O acrylonitrile.
- When using a hexamer other than α-halogenated acrylonitrile or β-halogenated acrylonitrile, the proportion of comonomer in the copolymer is 20 mol or less,
It is preferable to suppress it to less than 1Omolti.

The cellulose resin used in the present invention means cellulose and cellulose derivatives. Cellulose includes cotton,
These include natural celluloses such as hemp and 2M, pulps obtained from wood, bamboo, linters, etc., and regenerated celluloses such as viscose rayon, polynosic, cuprammonium rayon, etc. Cellulose derivatives include those obtained by esterifying or etherifying cellulose, such as cellulose acetate, cellulose acetate butyrate, cellulose acetate globionate, and ethyl cellulose.

As the cellulose resin, the above-mentioned cellulose is usually used.

The pitch used in the present invention is crude oil pitch produced during the cracking of crude oil, ethylene heavy end pitch produced during the cracking of naphtha, asphalt cracked pitch produced during the cracking of asphalt, or coal pitch produced during the thermal cracking of coal. It is an isotropic pitch that contains a mixture of compounds consisting of carbon and hydrogen and is substantially free of quinoline solvents. This isotropic pitch can be heated under a flow of inert gas to increase the menphase content and then used as the pitch used in the present invention.The pitch used in the present invention is produced by thermally baking it. Filling the electrode material,
In view of the balance between discharge characteristics and mechanical strength as an electrode, those having a mesophase content of 0 to 60 inches are usually used. The Men7Aze content was determined by polarizing microscopic observation at room temperature, and indicates the ratio of the area occupied by the anisotropic portion in the polarizing microscopic field of view of the pitch sample.

The electrode material of the present invention is obtained by thermally firing the above-mentioned polyacrylonitrile, phenol resin, cellulose resin, or pitch. Polyacrylonitrile, phenol resin, and cellulose resin are preferred from the viewpoint of charge/discharge characteristics and electrode strength.

Polyacrylonitrile has a 200 to 40
It is desirable to perform flameproofing treatment by heating in an active atmosphere such as air at a temperature of 0°C.

It is also preferable that the pitch be subjected to an infusible treatment by heating it in an active atmosphere such as air at a temperature of 200 to 400° C. before thermal baking.

Thermal firing is carried out in a vacuum or under an inert gas (nitrogen, argon, etc.) flow, an oxidizing gas (air etc.) flow, or a mixed gas flow of both. It is usually fired under vacuum or under a flow of inert gas.

The thermal calcination temperature is closely related to the hydrogen/carbon atomic ratio of the polymer conjugated system to be produced, and the thermal calcination temperature is selected so that this atomic ratio is 0.20 or less. Usually 500~
Thermal firing is carried out at a temperature of 3000°C, preferably 1000 to 2800°C, more preferably 1500 to 2700°C.

The polymer before thermal baking is used in various forms such as fibrous, powder, granular, and film forms.

The electrode material of the present invention is preferably used after increasing its specific surface area by a known method such as thermally baking and then steam activation, or making the material porous before thermally baking.

The specific surface area of the electrode material of the present invention is preferably i.

rl/If or more, more preferably KIFf or more than 100-79, particularly preferably Id:, 1000 nl/ or more.

The electrode material of the present invention has a hydrogen/carbon atom atomic ratio determined from elemental analysis of 0.20 or less, preferably 0.15 or less, and more preferably 0.1θ to 0.01. If the atomic ratio of hydrogen/carbon atoms exceeds 0.20, overvoltage during the charging and discharging process will be large as a negative electrode material, and good charging and discharging characteristics will not be obtained.

The electrode material of the present invention has an electron spin resonance spectrum (23℃
When the f-value determined from the first-order differential absorption curve (measured at 1) is 1.
has a signal in the range of 9700 to 2.0200, and the line width (ΔHpp) of the signal is 100 Gauss or more,
Preferably 200 Gauss or more, preferably 300 Gauss or more, or electron spin resonance spectrum (23°C
When the f-value determined from the first-order differential absorption curve (measured at 1) is 1.
The line width of the signal (ΔHp
Those having no signal with p) less than 100 Gauss, preferably less than 200 Gauss, more preferably less than 300 Gauss are used.

The t value determined from the first-order differential absorption curve of the electron spin resonance spectrum (measured at 23°C) is 1.9700 to 2.02.
0, there is no signal with a signal width of 100 Gauss or more, or the signal width is 100 Gauss or more.
When the negative electrode material has a signal less than Gauss, the overvoltage during the charging and discharging process is large and good charging and discharging characteristics cannot be obtained.

The electrode material of the present invention may have two or more electron spin resonance spectrum signals in some cases, and in that case, at least one of the signals has a t value in the range of 1.970 to 2.020. ), the signal width of which is 100 Gauss or more is used.

Furthermore, the electrode material of the present invention has an electron spin resonance spectrum (
In some cases, the line width of the signal of the first-order differential absorption curve (measured at 23°C) becomes extremely wide, making it difficult to distinguish the signal. In this case, the i value of the first-order differential absorption curve of the electron spin resonance spectrum (measured at 23°C) is 1.9700-2.
0100, with no signal having a signal linewidth of less than 100 Gauss is used.

Furthermore, the electrode material of the present invention has a pseudographite structure quantified using X-ray wide-angle diffraction, and the interplanar spacing d of the (002) plane...
is 3.405λ or more, preferably 3°41 GA or more,
More preferably 3.415λ or more, and the crystallite size Lc) in the C-axis direction is 55A or less, preferably 50^
Below, 1ctIF or 45A or less is desirable.

Furthermore, the electrode material of the present invention has an interplanar spacing (dx
lo) O2 times the distance (2doox) is 2.460
^ or less, preferably 2.455^ or less, and the crystallite size La) in the a-axis direction is 17λ or more, preferably 1
A value of 9 or more, more preferably 21^ or more is desirable.

The electrode material of the present invention has the above-mentioned pseudographite structure and does not have the regular laminated structure developed to so-called graphite K.

The electrode material of the present invention can be used as an electrode in various shapes either alone or with the addition of a conductive material such as carbon fiber, a reinforcing material, etc.

A battery incorporating the electrode material of the present invention has the following configuration. That is, the electrode material of the present invention is used as the main active material in the negative electrode. For the positive electrode, an electrode material having relatively good properties as a positive electrode material, such as activated carbon fiber, is selected.

As an electrolyte, L i C/0. ,l,j C1,L
i Pk'6, KCNS, NaPF, , LiBF, , N
Known salts such as alkali metal salts, alkaline earth metal salts, and tetraalkylammonium salts such as (Bu), (JO4, N(Bu)4C1), propylene carbonate, ethylene carbonate, acetonitrile, r-butyrolactone, dimethylformamide, Usually, a solution containing one or more organic solvents commonly used in batteries, such as dimethyl sulfoxide, ethyl ether, tetrahydrofuran, glyme, etc., is used.The point of view is to use a solvent that increases the decomposition voltage. Propylene carbonate, ethylene carbonate, etc. are preferred as organic solvents.

In addition, in order to obtain a compact battery that does not leak,
It is preferable to use a solid electrolyte at room temperature b, which is the operating temperature of the battery.

When a battery with the above configuration is charged by applying a constant voltage to both poles from an external power supply or by regulating the voltage so that a constant current flows, anions are generated at the positive electrode and positive at the negative electrode. When doped with ions, it can be used as a battery by utilizing the electromotive force generated at both the P-type electrode and the nm-type electrode. During discharge, each tS
The quality ions are dedoped from each electrode, and a current is generated. By repeating these charging and discharging cycles, it can be used as a secondary battery.Also, even if ＼-type electrodes with different doping amounts are used, an electromotive force is generated; .

This is lower than when a 7Vl electrode is included.

Hereinafter, the present invention will be specifically explained with reference to Examples. Note that elemental analysis, electron spin resonance spectroscopy, and X-ray wide-angle diffraction measurements are carried out by the following methods.

[Elemental analysis]

The sample was dried under reduced pressure at 120°C for about 15 hours, then dried under reduced pressure at 100°C on a hot plate in a dry box for 1 hour, sampled in an aluminum cup under argon, and measured using a Perkin Elmer 240C elemental analyzer. did.

[Electron spin resonance spectrum]

The first-order differential absorption vector of electron spin resonance is JEOL
Measurement is performed in the X band using a JB8-Fn IX nsR spectrometer. Powdered samples are left as they are, and minute flake samples are pulverized in an agate mortar, placed in a capillary tube with an outer diameter of 2 m, and the capillary tube is further placed in an ESRWK with an outer diameter of 5 m. The modulation width of the high-frequency magnetic field is assumed to be 6.3 Gauss. All of the above is carried out at 23° C. in an air atmosphere. The linewidth (ΔHpp) between the peaks of the first-order differential absorption spectrum is determined using an MP/MfO standard sample.

(X-ray wide-angle diffraction) The (002) lattice spacing d ooz employed in the present invention
, the crystallite size LC in the C-axis direction, the (110) interplanar spacing drt·, and the crystallite size La in the a-axis direction were measured by the following methods.

[1] Interplanar spacing between (002) planes If the d oox sample is a powder, use it as is, or if it is in the form of small pieces, powder it in an agate mortar and add high-purity silicon powder for X-ray standards with a weight of about 15% to the sample. is added as an internal standard substance, mixed, packed into a sample cell, and made monochromatic with a graphite monochromator.The wide-angle X-ray diffraction curve is measured using the reflection diffractometer method.To correct the 0 curve, , so-called Lorentz, polarization factors, absorption factors, atomic scattering factors, etc. are not corrected, and the following simple method is used.

That is, by drawing the baseline of the curve corresponding to (002) diffraction and replotting the real intensity from the baseline, we get (
002 plane) is obtained. Find the midpoint of the line segment where a line parallel to the angular axis drawn at two-thirds of the peak height of this curve intersects with the diffraction curve, correct the angle at the midpoint using an internal standard, and calculate this. By taking care to double the input, d ooz is obtained from CuKd and the wavelength of the line by the following Bragg equation.

λ doox=-17- (A) 231nθ λ: 1.5418A 08 Diffraction angle (2) Size of crystallite in C-axis direction 2LC In the corrected diffraction curve obtained in the previous section, at the position half the peak height Using the so-called half value β, the size of the crystallite in the C-axis direction is determined by the following formula.

There are various discussions about the shape factor K, but K=0.90
Use. λ and θ have the same meaning as in the previous section.

(3) Interplanar spacing do of (110) plane・d oos above
The crystallite size La in the 0(4) a-axis direction was based on the measurement method described above (Lc).

Example 1 Polyacrylonitrile fibers (acrylonitrile or 101) were set in an electric processing device and heated to 300°C at a rate of 10°C/min under vacuum. The black substrate was further heated to 1600° C. at a rate of 20° C./min under nitrogen flow. Further, the temperature was maintained at 1600° C. for 1 hour under nitrogen flow. The hydrogen/carbon atomic ratio determined from elemental analysis of the sample thus obtained is shown in Table 1, the first-order differential absorption curve of the electron spin resonance spectrum is shown in the gt diagram, and the plane of the (002) plane determined from X-ray wide-angle diffraction. Distance do・1 Crystallite size in C-axis direction Lc),
The interplanar spacing do・ of the (110) plane and the crystallite size La) in the a-axis direction are shown in Table 2IC.0 From these data, the hydrogen/carbon atomic ratio of the above sample is 0.040, and from the electron spin resonance spectrum The half width (ΔHpp) of the signal with the determined t value of 1.982 was 4000 Gauss or more. Also, the interplanar spacing d ooz of the (002) plane obtained from X-ray wide-angle diffraction is 3.45λ, the crystallite size Lc) in the C-axis direction is 42.3^, and the interplanar spacing d of the (110) plane
11G twice the distance 2 d no is 2.43^, a
The crystallite size (La) in the axial direction was 37.6^.

[Battery using the above sample as the negative electrode]

The above sample 8 cape was wrapped in a 55-mesh platinum wire mesh and used as one electrode. In addition, 8 capes of cellulose-based activated carbon fiber felt (KF-1600 manufactured by Toyobo Co., Ltd.) were similarly wrapped in a 55-mesh platinum wire mesh and used as the other electrode. A 0.5-inch thick glass fiber filter paper was placed between both electrodes as a diaphragm. A platinum wire was connected between both electrodes as a lead wire.

An electrode in which the above sample was wrapped in a platinum wire mesh was connected to the cathode of a potentiostat/galvanostat (HA-501 manufactured by Hokuto Denko Co., Ltd.), and an electrode in which cellulose-based activated carbon fiber felt was wrapped in a platinum wire mesh was connected to the anode. , KO between both electrodes,
It was charged by flowing a constant current of 15 mA. 3. Coulomb meter reading. Charging stopped when the charge of OO coulombs was charged. The average voltage during charging was 3.4v. Thereafter, the circuit was left open for 130 minutes, but the cell voltage decreased by only 0.04 V compared to immediately after charging. Thereafter, a 1 KΩ resistor was connected between the two electrodes to perform constant resistance discharge, and the amount of charge discharged until the cell voltage reached 1.0 VIC was 2.00 coulombs. In addition, for the charge amount during discharging of 3.00 coulombs and the average cell voltage of 3.2 VK,
Discharge charge amount 2. After charging for the 906th time with IO coulombs and average cell voltage of 2.4V, it was left for 15 hours and then IKΩ constant resistance discharge was performed, and discharged with charge amount of 3.00 coulombs and average cell voltage of 3.2V. The charge amount is 1.50 coulombs, and the average cell voltage is 2. OV Comparative Example 1 The hydrogen/carbon atomic ratio determined from elemental analysis of commercially available polyacrylonitrile activated carbon fiber (FGWT3A manufactured by Toho Rayon Co., Ltd.) is shown in Table 1. Hydrogen/carbon atomic ratio is 0.30
It was 7.

A battery was constructed in the same manner as in Example 1 except that this commercially available polyacrylonitrile activated carbon fiber (F'GWT3A manufactured by Toho Rayon Co., Ltd.) was used as the negative electrode material.
Charging was carried out in the same manner as in Example 1. When the coulomb meter indicated a value of 3.0 coulombs, the battery was completely charged. The average cell voltage during charging was 3.7v. After that, the circuit was left open for 30 minutes, but the cell voltage decreased by 0.4V compared to immediately after charging. After that IKΩ
A constant resistance discharge is performed by connecting a resistor between the two electrodes until the cell voltage reaches 1. The amount of charge discharged until OVK was reached was 1.40 coulombs. Also, the average cell voltage during discharge is 2.3V
Met.

Repeat the above charging and discharging operations until the fifth charge amount is 3.
．． 00 coulombs and an average cell voltage of 3.6v, the amount of discharged charge was 1.40 coulombs and the average cell voltage was 2.2v. After the 6th charge, the battery was left for 15 hours, and then a constant resistance discharge of IKΩ was carried out.The charge amount was 3.00 coulombs and the average cell voltage was 3.5V, whereas the discharged charge amount was 1.10 coulombs and the average cell voltage was 1. It was 6v.

Example 2 Phenol fibers (Kynor Mata Rufelt 3-504 manufactured by Nippon Kynor Co., Ltd.) were set in an electrically heated INK and heated to 1700° C. at a rate of 20° C./min under nitrogen flow. The hydrogen/carbon atomic ratio determined from elemental analysis of the sample thus obtained is shown in Table 1, and the first-order differential absorption curve of the electron spin resonance spectrum is shown in Figure 2. Planar spacing duet of (002) plane determined from line wide-angle diffraction, crystallite size in C-axis direction LC), (
110) Interplanar spacing dsx·, crystallite size in the a-axis direction La)'t - shown in Table 2. From these data, the hydrogen/carbon atomic ratio of the sample was 0.048, and the half width (ΔHpp) of the signal with a t value of 1.980 determined from the electron beam/resonance spectrum was 305 glass. Also, X
Interplanar spacing of (002) plane determined from line wide-angle diffraction d ooz
is 3.62^, and the crystallite size Lc) in the C-axis direction is 1
1.2A, the distance twice the distance of the (110) plane do.''
The distance 2d+1o was 2.43^, and the crystallite size La) in the a-axis direction was 22.7;

[Battery using the above sample as the negative electrode]

A battery was constructed in the same manner as in Example 1 except that Sample 811Q was used as the negative electrode. 0.1 between both electrodes
A constant current of 5 mA was applied, and charging was terminated when a charge of 3.00 coulombs was reached as indicated by the coulomb meter. The average voltage during charging was 3.3V. After that, the circuit was left open for 30 minutes, but the cell voltage decreased by only 0.03V compared to immediately after charging. After that, a constant resistance discharge was performed by connecting a resistor of IKΩ between the two poles, and the cell voltage was 1. The amount of charge discharged before reaching OV is 2.
It was 0.07 coulombs. Also, the average cell voltage during discharge is 2.
It was 6v.

Repeat the above charging and discharging operation until the fifth charge amount is 3.
．． 00 coulombs and the average cell voltage was 3.2 vlc, whereas the discharge charge amount was 2.08 coulombs and the average cell voltage was 2.5 v. After the 6th charge, it was left to stand for 15 hours and then a constant resistance discharge of rKΩ was carried out.The charged charge amount was 3.00 coulombs and the average cell voltage was 3.2VK, whereas the discharged charge amount was 1.60 coulombs and the average cell voltage was 2. ．． It was OV.

Comparative Example 2 Commercially available 7-enol activated carbon fiber (Japan Kynor Co., Ltd. #A
The hydrogen/carbon atomic ratio determined from elemental analysis of CN-504) is shown in Table 1. The hydrogen/carbon atomic ratio was 0.230.

A battery was constructed in the same manner as in Example 1, except that 8 wg of this commercially available 7-enol activated carbon fiber (ACN-504 manufactured by Nippon Kynor Co., Ltd.) was used as the negative electrode material, and charged in the same manner as in Example 2. did.

The average cell voltage at the time of zero charging was 3.5 V, which was the point at which charging was completed when a charge of 3.00 coulombs was charged as indicated by the coulomb meter. After that, I left the circuit open for 30 minutes, but the cell voltage was at the bottom of charging, and after that it was 0.3
After the cell voltage decreased to 0, a constant resistance discharge was performed by connecting a 1KΩ resistor between the two poles, and the cell voltage decreased to 1. The amount of charge discharged until reaching oV was 1.50 coulombs. Further, the average cell voltage during discharge was 2.1 V.

Repeat the above charging and discharging operations for the fifth time.
The discharge charge amount was 1.50 coulombs and the average cell voltage was 2.1 cm, whereas the discharge charge amount was 1.50 coulombs and the average cell voltage was 2.1 cm. After the 6th charge, it was left to stand for 15 hours and then a constant resistance discharge of IKΩ was carried out, and the charge amount was 3°0θ coulombs, the average cell voltage was 3.4VK, the discharged charge amount was 1.20 coulombs, and the average cell voltage was 1. 7 I met with V.

The temperature was raised to 1700°C at a flow rate of 20°C/min.

Further, the temperature was maintained at 1700° C. under nitrogen flow for 1 hour. The hydrogen/carbon atomic ratio determined from elemental analysis of the sample thus obtained is shown in Table 1. The first-order differential absorption curve of the C electron spin resonance spectrum is shown in Figure 3. The interplanar spacing of the (002) plane determined from X-ray wide-angle diffraction is , the crystallite size in the C-axis direction LC) (
Table 2 shows the interplanar spacing of the 110) planes (duoSa), the crystallite size in the axial direction (La).

According to these data, the hydrogen/carbon atomic ratio of the above sample is 0.
0, determined from the first-order differential absorption curve of the electron spin resonance spectrum? There is no signal with a signal width (ΔHpp) of less than 100 Gauss in the value range of 1.970 to 2',020, and the interplanar spacing doo* of the (002) plane determined from X-ray wide-angle diffraction is 3. .53^, the crystallite size in the C-axis direction Lc) is 24.6^, the interplanar spacing d of the (110) plane
The distance 2duo, which is twice xto, is 2o43^, and the crystallite size La in the a-axis direction is 23. ．． 4^ was 0 [Battery using the above sample as the negative electrode] All examples were Example 1 except that the above sample 8 was used as the negative electrode.
The battery was constructed in a similar manner. A constant current of 0.15 A is passed between both electric currents, and the coulomb meter reading is 3.0.
The charge was exhausted when the charge of 0 coulombs was charged.

The average voltage during charging was 3.3V. After that, the circuit was left open for 30 minutes, but the cell voltage remained at K, which was 0.04 ■ lower than immediately after charging. Then IK
A constant resistance discharge is performed by connecting a resistor of Ω between the two poles, and the cell voltage reaches 1. The amount of charge discharged until it reaches o V is 2.04
It was Coulomb. Also, the average cell voltage during discharge is 2.6
It was V.

Repeat the above charging and discharging operation until the fifth charge amount is 3.
．． 00 coulombs and an average cell voltage of 3.2v, the amount of discharged charge was 2.05 coulombs and the average cell voltage was 2.5v. After the 6th charge, it was left to stand for 15 hours, and then a constant resistance discharge of IKΩ was carried out.The charged charge amount was 3.00 l4-ron, and the average cell voltage was 3.2V, while the discharged charge amount was 1.57 coulombs.
The average cell voltage is 2. It was IV.

Comparative Example 3 The hydrogen/carbon atomic ratio determined from elemental analysis of graphitic carbon fiber is shown in Table 1, the first-order differential absorption curve of the electron spin resonance spectrum is shown in Figure 4, and the (0
Table 2 shows the interplanar spacing d ooa of the 02 plane), the crystallite size f in the C-axis direction, and c). From these data, the hydrogen/carbon atomic ratio of the sample was 0.040 or less, and the half-width (.Hpp) of the signal with an f value of 2.003 determined from the electron spin resonance spectrum was 50 Gauss. Also, X
The interplanar spacing doom of the (002) plane determined from line wide-angle diffraction was 3.402λ, and the crystallite size Lc) in the C-axis direction was 165^.

[Battery using the above sample as the negative electrode button]

All Example 1 except that the above Sample 8 Misaki was used as the negative electrode.
A battery was constructed in the same manner as in Example 1, and charged in the same manner as in Example 1. Charging was completed when the charge of 3.00 coulombs was charged as indicated by the coulomb meter. The average cell voltage during charging was 4.2v. After that, the circuit was left open for 30 minutes, but the cell voltage decreased by 1.5 V compared to immediately after charging. Thereafter, a constant resistance discharge was performed by connecting a resistor of IKΩ between the two electrodes, and the amount of charge discharged until the cell voltage reached z,o V was 1.20 coulombs.

Also, the average cell voltage during discharge is 2. It was Ov.

Repeat the above charging and discharging operation until the fifth charge amount is 3.
．． 00 coulombs, average cell voltage 4. Ov, discharge charge t was 1.16 coulombs, and average cell voltage was 1.9 . After the 6th charge, the cell was left to stand for 15 hours, and then a constant resistance discharge of IKΩ was carried out.The charged charge amount was 3゜00 coulombs, the average cell voltage was 4.2 VK, and the discharged charge amount was i, o o coulombs.
Average cell voltage was 1.2v.

[Comparison of Examples 1, 2.3 and Comparative Examples 1, 2.3] Overvoltage of Examples 1, 2.3 and Comparative Examples 1, 2.3 (cell voltage immediately after charging and 30 minutes with the circuit open) Table 3 shows the difference in cell voltage after standing and the charge efficiency of charging and discharging.

The samples of Examples 1 and 2.3 had lower overvoltages than Comparative Examples 1 and 2.3, and had higher charge efficiencies during charging and discharging for 1 cycle, 5 cycles, and 6 cycles (after being left for 15 hours). It can be seen that the battery performance is excellent.

[Brief explanation of the drawing]

Figures 1, 2, 3, and 4 show electron spin resonance spectra of electrode materials obtained in the first example, second example, third example, and third comparative example, respectively. This is the first-order differential absorption curve of . Patent applicant Mitsubishi Yuka Co., Ltd. Agent Patent attorney Hidetoshi Furukawa (TL or one person)

Claims (1)

[Claims] 1. Made by thermally firing polyacrylonitrile, phenol resin, cellulose resin, or pitch, and comprising the following (
An electrode material characterized by satisfying 1) and (2). (1) The atomic ratio of hydrogen/carbon atoms is 0.20 or less. (2) The g value determined from the first-order differential absorption curve of electron spin resonance spectrum (measured at 23°C) is 1.970 to 2.0
20, have a signal with a line width (ΔHpp) of 100 Gauss or more, or have no signal with a line width (ΔHpp) of 100 Gauss or less.