JPS63168973A - Electric cell - Google Patents

Abstract

PURPOSE:To realize a compact, lightweight, and thin-type cell, and to make the flatness of the voltage excellent, by adding iodine or bromine to an active carbon and/or organic nonaqueous type polar solvent. CONSTITUTION:In a cell composed by soaking an active carbon positive electrode and a metallic negative electrode in an organic nonaqueous type polar solvent, iodine or bromine is added to either the active carbon or the organic nonaqueous polar solvent, or to both of them. The adding amount of the iodine or bromine to the active carbon is 10wt.% or more, preferably 50wt.% or more. On the other hand, the content amount of the element in the polar solvent is most preferably to dissolve 0.5M/l or more of the iodine (I2) or the bromine (Br2). And when the iodine or bromine is contained in both the polar solvent and the active carbon, especially the voltage flatness of the cell is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a battery that has significantly improved charging and discharging characteristics and durability against repeated charging and discharging.

[Conventional technology]

Aqueous secondary batteries, such as nickel-cadmium storage batteries and lead-acid batteries, have drawbacks such as the inability to obtain high voltage due to the low decomposition voltage of the electrolyte, and the generation of gas during charging and discharging reactions. was. In order to fundamentally improve these drawbacks, a secondary battery using an organic non-aqueous polar solvent (hereinafter abbreviated as non-aqueous solvent) has been proposed.

There are expectations for a secondary battery that uses a non-aqueous solvent, has a high terminal voltage, and does not generate gas.

In particular, carbon fibers, which have a large contact area with electrolytes, have been actively researched recently because they can absorb many ions. In order to increase the amount of ions adsorbed onto the carbon fibers, studies are being conducted from two main directions. One approach is to electrochemically store various ions between the layers of graphite, which is a layered compound, by increasing the degree of graphitization of carbon fibers (Japanese Patent Laid-Open No. 6O-36315).

In the other direction, the specific surface area of carbon fibers is made extremely large (100d19 or more), thereby increasing the storage capacity based on the formation of an electric double layer, which is an interfacial phenomenon. Electric double layer capacitor with increased storage capacity by using activated carbon fiber with a large specific surface area (JP 58-206116% JP 55-9
9714) or secondary battery (JP 59-14616
5% Japanese Patent Publication No. 60-25152) Various methods have been proposed.

[Problem that the invention seeks to solve]

Among carbon materials, carbon fiber is a material that is expected to have particularly high performance as a positive electrode for batteries using non-aqueous organic electrolytes.

Carbon materials exist in various forms such as powder, Ill-like, and film forms, but the fibrous form is particularly excellent as an electrode, considering that the contact area with the electrolyte can be increased. When it is made into a fibrous form, it can also have a diameter of about 10 μm.

However, in reality, the amount of ions that can be stably adsorbed and desorbed to carbon fibers is extremely small when ordinary carbon fibers are used. In this case, being able to stably adsorb and desorb ions means that ions can be adsorbed (including intercalation reactions) without destroying the ion adsorption and desorption mechanism of carbon fibers, and that ions can be adsorbed in a region of at least 80 or more in terms of charge efficiency. This means that it is possible to adsorb and desorb.

In order to improve the performance of carbon fiber electrodes, methods of increasing the degree of graphitization of carbon fibers have been proposed (for example, in Japanese Patent Application Laid-Open No. 1983-1999).
No. 36315). However, when ions are adsorbed and desorbed to graphite using an electrochemical method in an electrolytic solution (in this case, an intercalation reaction is performed), the amount of ions that can be stably adsorbed and desorbed is at most 1 mol terres per carbon atom of graphite. However, if the amount of ion adsorption is increased to 1 molti or more, the ion adsorption/desorption mechanism of graphite is destroyed [Denki Kagaku, 4
6, A (1978) 438-441]. For this reason, even when studies were conducted to improve the electrode performance of carbon fibers in order to bring them closer to graphite, the level at which carbon fibers could be stably adsorbed and desorbed was at most 1 mol.

A silium secondary battery can be produced by using carbon fiber (activated carbon fiber) with a large specific surface area for the positive electrode and metallic lithium for the negative electrode [Synthetic Metal (S)]
'nthetic Metals), 10 (1985
) 222-234, 26th Battery Symposium (1985) Lecture Abstracts, p. 57 (IA-15)). When activated carbon fibers are used, the amount of stable ion adsorption can be increased compared to when highly graphitized carbon fibers are used, but this is not the case with activated carbon fibers that have been studied in the past.

It was about 1 to 4 molt at most. Furthermore, although the charging and discharging mechanism of activated carbon fiber is said to be based on an electric double layer, it has been pointed out that when used as a positive electrode in a lithium secondary battery, an intercalation reaction occurs [26th Battery Discussion (1985) Lecture Abstracts 57 (IA-15))
.

Furthermore, lithium secondary batteries that use activated carbon for the positive electrode have the disadvantage that they do not have a voltage leveling part during discharge (the open circuit voltage depends on the amount of stored charge) (Summary of the 26th Battery Symposium) Collection 2A-05 and IA-15). Also, because there are some high-voltage parts where the terminal voltage is 3.8V or more, electrolysis occurs even in non-aqueous solvents, resulting in large self-discharge! The disadvantage was that gas was generated.

Furthermore, when used as a secondary battery, the fact that the discharge voltage is not flat is subject to usage limitations. For example, when used to drive an electric circuit such as a microcomputer or a small motor, the fact that the discharge voltage is not flat is a major drawback.

[Means for solving problems]

According to research conducted by the present inventors, in a battery formed by immersing an activated carbon positive electrode and a metal negative electrode in an organic non-aqueous polar solvent, it is possible to add iodine or bromine to either or both of the activated carbon and the organic non-aqueous polar solvent. It was recognized that the above objectives could be achieved.

In the present invention, the method of adding iodine or bromine (hereinafter sometimes referred to as iodine etc.) to activated carbon is not particularly limited. For example, it is easiest to adsorb iodine, etc. to activated carbon by (2) contacting activated carbon with vapor of iodine, etc., or (2) soaking activated carbon in a solution containing iodine, etc. If the bromine is in liquid form, activated carbon can be directly added to the bromine liquid to adsorb it, or if it is solid like iodine, iodine can be kneaded into activated carbon or molded into an active substance using various binders. It is also good to include it in a product.The method of adding iodine etc. to a polar solvent is not particularly limited.If the iodine etc. is sufficiently dissolved in the polar solvent, it is possible to add iodine etc. to make a homogeneous solution.On the other hand, One-hedral iodine (usually powder) may be in a separated state without being dissolved.Iodine, etc. added to activated carbon and/or solvent may be a substance that reacts to produce iodine (iodine or bromine source). ).Also, a mixture of iodine and bromine may be added.

The amount of iodine etc. added to the activated carbon and/or the polar solvent is not particularly limited. Generally, the effect of addition becomes more significant as the content increases. The content of iodine, etc. is 10% by weight or more, preferably 20% by weight, based on the content of activated carbon.
weight - or more, particularly preferably 50% by weight or more. On the other hand, the content in the polar solvent is preferably 0.1M/A+ or more, usually 0.2M/II or more, particularly preferably 0.5M/1 or more of iodine (Process 2) or bromine (Br2).
) is dissolved. In the present invention, when iodine or the like is contained in both the polar solvent and the activated carbon, the voltage flatness of the battery is particularly large.

According to the present invention, the halogen to be added to the positive electrode or the polar solvent is iodine (2) or bromine (Br2), and is not an ion. According to the research of the present inventors, compared to the case where iodine ions (Ni) or bromine ions (B) are adsorbed in a polar solvent and/or on activated carbon, when iodine etc. are added, the It has been confirmed that the voltage flatness is extremely good. For example, activated carbon in which bromine ions (Br-) are adsorbed by an electrochemical method at a rate of 0 mole per carbon atom (approximately 60 wj% increase) Even when bromine (Br2) was used as the positive electrode, no voltage flatness was obtained in the secondary battery using this.On the other hand, when bromine (Br2) adsorbed on activated carbon was used as the positive electrode, the discharge The voltages are quite flat.Also, for a similar comparison, there is a case where LiBr is used as an electrolyte and a case where a solvent is used without using anything generally considered to be an electrolyte (salt consisting of cations and anions). If we consider the case where only bromine (Brz) is added in the electrolyte, the difference between the two becomes extremely clear.In other words, when LiBr is used as the electrolyte, voltage flatness cannot be expressed at any concentration of LiBr. When bromine is added, the concentration of bromine is at least about 0.1 M/n or more, preferably 1 M/1
If it is above that, the discharge voltage becomes completely flat.

The above results described for bromine are also similar for iodine. Specifically, the case where iodine ions are used is a, and the case where an electrolyte containing iodine ions (for example LiI) is used is b.

It is classified into three types: when iodine ions (1) are adsorbed onto activated carbon by an electrochemical method and are used as the positive electrode, and when both a and b are used.

For example, even if the method described above is used, this tendency does not change, and even if activated carbon, on which about 20 molti of iodine ions are adsorbed in advance by an electrochemical method, is used as the positive electrode, the voltage level during charging and discharging does not change. The supported portion was extremely small, and no effect of adsorbing iodine ions was observed. On the other hand, in advance, iodine
) adsorbed on activated carbon is used as the positive electrode, it is possible to charge and discharge with a flat discharge voltage even at an adsorption/desorption level of about 10 molti, although the results will vary depending on the structure of the activated carbon used. Such high performance could not be obtained at all when iodine ions were adsorbed on activated carbon.

It is not necessarily clear why battery performance is significantly improved when iodine (■2) or bromine (Br2) is adsorbed compared to when iodine ions or bromine ions are used, but it is When iodine or bromine is adsorbed, the structure is simply activated carbon with ions adsorbed, whereas when iodine or bromine is adsorbed, the activated carbon and these halogens are integrated into one structure. I think this is because they have completely different structures.

The organic solvent as the electrolytic solution used in the present invention is an organic non-aqueous solvent, preferably an aprotic one and a high dielectric constant. Specific examples include propylene carbonate, γ-butyrolactone, dimethylsulf7oxide, dimethylformamide, acetonitrile, ethylene carbonate,
Examples include, but are not limited to, tetrahydro-7rane, dimethoxyethane, dichloroethane, and the like. Among these solvents, those having low reactivity with iodine or bromine are preferred. Further, these organic solvents may be used alone or as a mixed solvent of two or more.

Although an electrolyte is not particularly necessary in the secondary battery of the present invention, an auxiliary electrolyte may be added. The auxiliary electrolyte to be added is not particularly limited, but examples include salts of cations and anions such as metal cations, quaternary ammonium, carbonium cations, oxonium cations and pyridinium cations. The anion used here is Cl0a-1BF4-1SbF6-1sb c
x;, AgF2-1PF6-1HF2-, Ni, Br
-, etc., and particularly preferred anions include Ni and Br-. Specific electrolytes include LiCIO4, LiBF4, LiAsF6. Na
BF4. NaClO4, Bu4N'ClO4, KBF
Examples include 4% LiI, LiBr, and the like. Particularly preferred is LiI%LiBr.

When LiI%Li Br is used as an auxiliary electrolyte, a secondary battery with good voltage flatness and a high level of ion adsorption and desorption that can be charged and discharged is obtained compared to when other auxiliary electrolytes are used. be able to.

The concentration of the auxiliary electrolyte in the solvent is not particularly limited, but is usually about 1 M/n to 2 M/It.

The secondary battery of the present invention has poor battery performance even immediately after assembly.
- It has the characteristic of being useful as a secondary battery.

The metal used as the negative electrode of the present invention is not particularly limited, but alkali metals, alkaline earth metals, metals of Group 3 and Group 4 of the periodic table, etc. are preferable, such as Li, N, etc.
a%, Rh, Cs%Be%Mg, Ca%Sr.

Ba % Se b Y % La , Tt s Zr
-AlsPb%Bx%Y, Ni, etc. can be used. Or alloys of the above metals, such as Li-homogeneous alloys, Li-AI-Mg alloys, Li-Hg alloys,
Examples include Li-Al alloy and Li-Pb alloy.

It is also possible to use conductive polymers such as carbon fibers, activated carbon fibers, polyacetylene, polyphenylene, etc., on which the metals are supported.

Among the above-mentioned metals and alloys, lithium-based metals are particularly preferably used in view of high voltage and weight reduction of the battery. Examples of materials containing lithium-based metals include, in addition to metallic lithium, alloys containing metallic lithium or materials in which metallic lithium is supported on the surface.

The activated carbon used in the present invention is not particularly limited, and raw materials include natural organic polymers, synthetic organic polymers, and pitch. Natural organic polymers include palm oil, shirugashi, and the like. Synthetic organic polymers include purely synthetic polymers such as polyvinyl alcohol, phenolic resin, polyacrylonitrile, etc., as well as semi-synthetic polymers such as fiber-based conductors.

"Activity" as used in the present invention means that the specific surface area is large. Generally, the specific surface area measured by the BET method is 100 d19 or more. The larger the specific surface area is, the larger the contact area with the electrolyte becomes, and thus the battery performance improves. A preferable specific surface area is 500 d/Q or more, more preferably 1000 d19 or more.

Further, as a result of various studies, we have found that the less developed the graphitic crystal structure of the activated carbon used in the present invention is, the better the battery performance is. In researching the structure of activated carbon, the X-ray diffraction method is used as the main experimental method along with the specific surface area in the BET method. It was selected as appropriate.

X-ray diffraction is the main experimental method used to study the microscopic structure of carbon materials, including carbon fibers (graphite and Kerr 1A). A study is underway [Carbon Materials (Materials Science Series, Kyoritsu Publishing), Chapter 4].

The height of the X-ray diffraction peak of the carbon material corresponding to the (002) plane of graphite crystal indicates the degree of crystallinity caused by the aromatic condensed ring, and the half-width indicates the size and uniformity of the crystallites. (
Journal of the Chemical Society of Japan, 1975, (9), 1551-1554
page).

A method for analyzing the structure of carbon using diffraction of the (002) plane from an actual X-ray diffraction intensity curve (CuKα) will be described. 1st
The figure shows an X-ray diffraction intensity curve of polyacrylonitrile activated carbon fiber (specific surface area: 1000rd/9). (00
2) Draw a tangent line β to both sides of the X-ray diffraction peak of the surface, and rewrite the difference between the measured curve and the tangent line on the baseline to obtain a curved line. Diffraction angle 2θ showing maximum value Ip and Ip of curved line
Furthermore, the intensity IO is determined by subtracting the air scattering intensity from the intensity of the measured curve at the diffraction angle 2θ. The air scattering intensity was obtained by scanning under the same conditions without a sample. Here, Ip is X due to the graphitic crystalline structure.
It is the line diffraction peak intensity, and (Io-IP) is the X-ray scattering intensity due to the defective structure. In general, the diffraction peak intensity indicates the degree of development of crystals, which increases as the crystal size and crystallinity of crystallites increases. The crystal size is determined by the sharpness of the peak (X-ray Diff, Process
In many activated carbons, the microcrystallite size in the direction perpendicular to the (002) plane was 10-16A. Crystallinity is generally the ratio of the total crystal scattering intensity to the total scattering intensity, and means the volume fraction of crystals in the X-ray irradiation volume [Journal of the Japan Textile Science Society, 3
1 (1975), P2O3-p214).

However, in the case of carbon materials, the crystalline portion and the amorphous portion are not clearly separated structurally [J.

Appl, Phy, 13 (1942), P 3
64-P371, Basics of Carbonization Engineering (Ohmsha) No. 1
Chapter, Carbon Materials (Kyoritsu Publishing) Chapter 4], the internal structure cannot simply be understood as a two-phase structure consisting of a crystalline part and an amorphous part, as is the case with ordinary crystalline polymers. In the case of activated carbon, microcrystallites with extremely low degree of perfection are dispersed in an amorphous sea [Chapter 2 of Activated Carbon Industry (Kyoritsu Publishing)], and coherent scattering from graphitic crystalline regions of their texture occurs. IP
sb, the incoherent scattering from the non-quality region is (Io-Ip
).

IP/I is a parameter used in the present invention.

indicates the degree of development of graphitic crystalline structure, Ip
/Io is called the graphitic crystalline structure parameter.

However, as mentioned above, there is a big difference between the degree of development of the crystalline structure in activated carbon and the so-called degree of crystallinity in the case of ordinary polymer materials. It is not clearly defined structurally. For a fully developed, nearly perfect graphite crystal, Ip/Io is 0.96.
That's all.

According to a detailed study, there is no clear correlation between Ip/Io and specific surface area. For example, the Ip/Io of a commercially available phenolic activated carbon fiber with a specific surface area of 26,004 g is 0.37, whereas the Ip/Io of a polyvinyl alcohol-based activated carbon fiber with almost the same specific surface area is 0.07, which is extremely small. Ta. That is, it is recognized that Ip/Io is greatly influenced by the starting material of activated carbon fiber.

When used as polyvinyl alcohol-1t material, Ip/I
It is possible to make o extremely small, but even in this case there is no clear correlation between the specific surface area and Ip/Io, and even though the specific surface area is 2000 d19 or more, Ip/Io is 0.4 or more. There are also 1.

The activated carbon used in the present invention is not particularly limited, but preferably has an Ip/IO of 0.5 or less, preferably 0.4 or less, particularly preferably 0635 or less. By using such activated carbon, a secondary battery with particularly excellent performance can be obtained.

No CH absorption is observed in the external absorption spectrum.

When Ip/Io is 0.35 or less, the battery performance further improves significantly, and even though the discharge voltage is almost constant at 6.0 ■ for iodine-based batteries, the ion adsorption/desorption level remains at an extremely high level of 12 mol. Stable charging and discharging was possible.

Even when Ip/Io was 0.5 or more, stable charging and discharging could be performed at an ion adsorption/desorption level of about 5 mol. There have been various reports on secondary batteries using activated carbon, especially activated carbon fibers, but it should be taken into consideration that when using commonly used activated carbon, the level at which stable adsorption and desorption can be achieved is at most about 1 molt. It can be said that the present invention has significantly improved the adsorption/desorption level of ions.

A method for producing activated carbon with a particularly low Np/Io is described in Japanese Patent Application No. 61-244719 by the same applicant.

The activated carbon used in the present invention may have any shape, such as fibrous or powder, but is generally preferably fibrous. When the powder is in the form of powder, it can be used by binding it with various binders, such as an aqueous dispersion of fluororesin, and molding it into any shape such as a sheet or film. Moreover, when the activated carbon is fibrous, it may be in any shape such as felt, cloth, or paper. These are used as positive electrodes of batteries after being subjected to any known treatment, for example, by providing a current collector with a net or vapor-deposited film of aluminum, titanium, etc.

The battery according to the present invention can be charged and discharged at a higher level of ion adsorption and desorption than conventional secondary batteries using activated carbon. For example, when using LiCl0a or LiBF4, which are commonly used as electrolytes in lithium secondary batteries with acrylic or rayon activated carbon fiber as the positive electrode, the level at which they can be stably adsorbed and desorbed is at most 1 carbon atom. ~2 mol% (26th Battery Symposium Abstracts Collection IA-15), but by using the method of the present invention, it is possible to increase the level at which stable charging and discharging is possible to 4 to 6 mol%. Ta. Furthermore, there was also the effect that the discharge voltage could be leveled out.

When using activated carbon fibers with an Ip/Io of 0.3 or less and mainly consisting of an amorphous structure, the method of the present invention can be used to flatten the voltage during discharge and further eliminate the high voltage portion during charging and discharging. I was able to do it.

In the secondary battery of the present invention, especially when metallic lithium is used as the negative electrode and iodine is used, the voltage during discharge is approximately 3. It was constant at Ov. Further, when bromine was used, the voltage during discharge was constant at about 6.5V.

In the secondary battery of the present invention, oxygen and moisture present in the electrolyte or solvent may reduce the performance of the battery, so it is best to sufficiently purify it in advance.

In the present invention, if necessary, a porous membrane made of synthetic resin such as polyethylene, polypropylene, Teflon, etc. or natural fiber may be used as a diaphragm between the two electrodes. It is also preferable that the battery be sealed to prevent oxygen and moisture from entering the battery from the outside world.

〔Example〕

The present invention will be explained in more detail below using Examples.

Synthesis Example 1 [Synthesis of activated carbon fiber using polyvinyl alcohol fiber as a starting material] P was spun by a high-humidity spinning method from a PVA (polyvinyl alcohol) aqueous solution with an average degree of polymerization of 1700 as a starting material.
VA fiber (denier 1800d, number of filaments 100
A woven fabric obtained from a fabric with a strength of 10.5 g/d and an elongation of 7% was used. Next, as a dehydration/carbonizing agent /Q4 s (NH4)2 SO4 and (NH4)2HPO4 each 50%
9 was dissolved in 1000 g of water, this aqueous solution was heated to 60°, the woven fabric was immersed in it for 5 minutes, and then the liquid was squeezed out with a mangle and dried at 105°C for 3 minutes. The adhesion rate of the dehydrating agent was 10% by weight. When heating the woven fabric with this dehydrating agent attached at 210°C for 30 minutes, Bs per 1a width of the woven fabric
The shrinkage rate of the fiber was controlled to 40% by applying a low tension of 0 g. Furthermore, the carbonization condition is 630℃×10
During heating in two steps: 1 minute and then 400° C. for 20 minutes, a low tension of 30 q per 1 cI 1 width of the woven fabric was applied to make the shrinkage rate of the fiber 60 cm as seen from the starting PVA fiber. The weight reduction rate at that time was 55 inches. As described above, a dehydrated and carbonized carbon fiber sheet was obtained. B with N2 gas
The specific surface area of the ET method was 2300 vf/Q. The X-ray diffraction intensity curve of this activated carbon fiber was measured using a rotating anode cathode type X-ray diffractometer T)'pe RAD-rA manufactured by Rigaku Denki Co., Ltd. The measurement conditions were 40 kV 100 mA,
CuKa line (λ = 1.5418 people), slit 1/2°
, 0.15m, scanning speed 1°/-i, full scale 80
Measured in transmission at 0 cps. The graph obtained in this manner is shown in FIG. It was found that the peak based on the (002) plane that should exist near 2θ of 25° almost disappeared, and carbon fibers with a non-standard structure were mainly produced (Ip/Io = 0 .07
). The internal fine structure was measured by the MAS GATE method using solid-state high-resolution NMR. Measurements were performed under the following conditions: 8K data points, 1.5 sampling points, and 10,000 scans. This result is the third
Shown in the figure. Since a curve having a peak around 140 ppm was obtained, it was confirmed that the structure was centered on a graphite-like six-membered ring skeleton.

The surface reflection infrared results are shown in Figure 4, and no C-H absorption was observed, confirming almost complete carbonization. In addition, by changing the activation conditions, Ip/
Several samples with different Io were synthesized (Table 1).

Synthesis Example 2 [Synthesis of activated carbon fibers using phenolic fibers, acrylic fibers, and rayon fibers as raw materials] Fabrics made of fibrous phenol resin were made, and after making them carbonaceous, they were heated at 1000°C in steam. I activated it for 1 hour. The specific surface area of the obtained activated carbon fiber was 2300 tons,
Ip/Io was o and 37.2θ was 23.7°. In addition, solid-state high-resolution NM is used to examine even finer structures.
R and surface reflection infrared measurements were also carried out (Figures 5 and 6).

There was no structural difference between the phenol-based activated carbon fiber and the polyvinyl alcohol-based fiber except for a larger Ip/Io.

A woven fabric was made from a spun yarn such as rayon fiber, and this woven fabric was soaked in an aqueous solution of ammonium phosphate ((NH4)2PO4), dried, impregnated with 10 grams of ammonium phosphate, and then heated at 270°C. Heat in N2 gas for 30 minutes,
Subsequently, the temperature was raised from 270°C to 850°C over a period of 90 minutes. 10 in N2 gas containing 40 ml of water vapor.
Activation was performed at 00°C for 60 minutes.

This resulted in activated carbon fibers having a surface area of 1650 vf/9 and an IP/Io of 0.54.

10% ammonium phosphate ((NH4)2804) was attached to a fabric made from spun acrylic fiber yarn at 270°C.
By fully oxidizing the fibers in air for 2 hours with free shrinkage and then activating them at 1000°C for 1 hour, activated carbon fibers with a specific surface area of 1080 m/g and Ip/Io of 0.66 were obtained. . Table 2 shows the relationship between the activation conditions of the above sample and the structure of the obtained product. In addition, by changing the activation conditions, the specific surface area can be reduced25) Synthesis Example 3 [Synthesis of activated carbon fibers with a mainly non-structural structure using phenolic fibers as a starting material] Fabrics made of fibrous phenolic resin After making it into carbonaceous material, it was activated in steam at 1000° C. for 1 hour. The obtained activated carbon fiber had a specific surface area of 2300 vl/9 and II)/Io of 0.37. The yield at this time was 14%. Furthermore, steam 900
Activation was performed for 1 hour and 50 minutes at ℃. Ip/Io of the obtained activated carbon fiber was 0.20. The yield at this time was 3.

Synthesis Example 4 [Preparation of Activated Carbon Powder] The activated carbon fibers obtained in Synthesis Example 1 (Synthesis Experiment No. 1), which mainly have a non-virtual structure, are ground in a ball mill for 24 hours to produce powdered activated carbon, which mainly has a non-virtual structure. I got it. The particle size distribution was 99.6 inches below 350 mesh.

Example 1 [Secondary battery using activated carbon fibers with iodine adsorbed on the positive electrode and metallic lithium on the negative electrode] Polyvinyl alcohol-based activated carbon fiber sheet obtained in Synthesis Example 1 (Ip/I
o = o, o 7.2600 g) was placed in a vacuum line, evacuated, and then exposed to iodine vapor to adsorb iodine. Exposure to iodine vapor for 40 minutes at room temperature resulted in a weight increase of 60 wt%. A secondary battery was fabricated in an argon atmosphere using the activated carbon fibers adsorbed with iodine thus obtained as a positive electrode and metallic lithium as a negative electrode. Activated carbon fiber and metallic lithium were placed on both electrodes via a glass fiber filter with a thickness of 0.5 nm. The electrolytic solution used was one in which lithium perchlorate was dissolved in propylene carbonate at a concentration of 1 M/II and iodine (Process 2) was dissolved at a concentration of 0.2 mol/l. Platinum mesh was used for both the positive and negative electrodes for current collection. The size of the iodine adsorption activated carbon fiber sheet used was 1J.
x 1 cIl and the weight was approximately 9.5% + (activated carbon fiber 6 cape 9).

The constant current charging and discharging characteristics of this secondary battery were measured.

The Voc (open circuit voltage) immediately after the secondary battery cell was assembled was 3.0■.The current density was Q for the activated carbon fiber,
Q677A/9 was charged for 2 hours and then discharged with a current. The adsorption and desorption of ions corresponding to the amount of ions occurred), and the discharge was carried out for 1 hour and 55 minutes. Further, when the cell voltage during discharging decreased to 2 Vt, discharging was stopped at that point and charging started.

The charging/discharging curve became stable from the third time of repeated charging/discharging. 7th
The figure shows the charge/discharge curve for the fifth time. Moreover, the relationship between charge efficiency and number of repetitions is shown in FIG. It was also confirmed that charging and discharging could be repeated up to about 200 times and that it was possible to charge and discharge for more than 200 times.

Comparative Example 1 [Secondary battery using activated carbon fiber for the positive electrode and metallic lithium for the negative electrode] Polyvinyl alcohol-based activated carbon fiber sheet obtained in Synthesis Example 1 (Ip/Io = 0.07.250On?/
A secondary battery cell was produced using Example 1 as the positive electrode and a 1M/II solution of lithium perchlorate in propylene carbonate as the electrolyte, with the other conditions being the same as in Example 1. Further, a charge/discharge curve was measured under the same conditions as in Example 1, and the results are shown in FIG.

Example 2 [Charging and discharging experiment when the ion adsorption/desorption level is 12 molti] Same method as Example 1 (same sample, same sample preparation conditions)
A charging/discharging experiment was conducted using the ion adsorption/desorption level of 12 mol. After charging the activated carbon fiber for 4 hours at a current density of 0.0677 A/g -
Discharge was performed using electric current. Discharge was performed for 3 hours and 50 minutes. Further, when the cell voltage during discharging decreased to 2V, discharging was stopped at that point and charging started.

The charge/discharge curve is shown in FIG. 9, and the relationship between the charge efficiency and the number of repetitions is shown in FIG.

Comparative Example 2 [Secondary battery using activated carbon fiber for the positive electrode and metallic lithium for the negative electrode] Using the same method as Comparative Example 1, the ion adsorption/desorption level was 1.
The charge/discharge curve in the case of 2 molti is shown in FIG.

By using activated carbon fiber with iodine adsorbed as the positive electrode, it was possible to level out the discharge voltage. Also, the so-called high voltage part where the voltage during charging and discharging is 3.8V or more could be eliminated.

Example 3 [Secondary battery using activated carbon fibers with bromine adsorbed as the positive electrode and metallic lithium as the negative electrode] Polyvinyl alcohol-based activated carbon fiber sheet obtained in Synthesis Example 1 (IP/Io
= 0.07.2500d/9) was immersed in a propylene carbonate solution of bromine at a concentration of 5M/l for 1 hour to adsorb bromine onto the activated carbon fiber. A secondary battery was fabricated in an argon atmosphere using the activated carbon fibers adsorbed with bromine thus obtained as a positive electrode and metallic lithium as a negative electrode.

A cell was prepared in the same manner as in Example 1 except that an electrolytic solution containing bromine dissolved in propylene carbonate at a concentration of 5 M/l and lithium bromide dissolved at a concentration of IMA was used. Further, the charge/discharge curve measured under the same conditions as in Example 1 is shown in FIG. 10, and the cyclic stability is shown in FIG. 11.

Even when bromine was used, the discharge voltage could be leveled as in the case of iodine. However, in the case of bromine, the discharge voltage (using negative electrode lithium) was 3.5V (open circuit voltage), which was constant at 0.5V higher than that of iodine. Furthermore, a charge/discharge test was also conducted at an ion adsorption/desorption level of 12 molti, and a charge/discharge curve almost identical to that shown in FIG. 10 was shown. In addition, cycle charging and discharging could be performed stably.

Comparative Example 3 [Activated carbon fiber lithium secondary battery using lithium iodide as the electrolyte] A secondary battery was produced in the same manner as in Comparative Example 1, except that a propylene carbonate solution of lithium iodide with a concentration of 1 M/l was used as the electrolyte. A battery cell was produced. Further, a charge/discharge curve was measured under the same conditions as in Example 1. The charge/discharge curve is shown in FIG. 12, and the cycle stability is shown in FIG. 11.

Comparative Example 4 [Activated carbon fiber lithium secondary battery using lithium bromide as the electrolyte] A secondary battery was produced in the same manner as in Comparative Example 1, except that a propylene carbonate solution of lithium bromide with a concentration of 1M/II was used as the electrolyte. A battery cell was produced. Further, a charge/discharge curve was measured under the same conditions as in Example 1.

The charge/discharge curve is shown in FIG. 12, and the cycle stability is shown in FIG. 11.

Comparative Example 5 [Lithium secondary battery using activated carbon fiber adsorbed with iodide ions (I'-) as a positive electrode] Propylene carbonate solution of lithium iodide (IM#
), an activated carbon fiber sheet similar to that used in Example 1 was used as the positive electrode, and the sheet was taken out from the solution under constant current conditions.

A secondary battery was fabricated using the thus obtained material as a positive electrode and a negative electrode (3 metal lithium).Also, as an electrolyte, lithium iodide glopylene carbonate IM/
l solution was used. The charge-discharge curve was measured in the same manner as in Example 1. The charge/discharge curve was almost the same as that of Comparative Example 3, and the voltage level portion was extremely small, and almost no effect of adsorbing iodine ions was observed.

Example 4 [Iodine-based lithium secondary battery without using auxiliary electrolyte] Example 1 except that lithium perchlorate is not added to the solvent
A secondary battery was produced in the same manner as above. The charge/discharge curve of this secondary battery was exactly the same as that shown in Example 1 (FIG. 7), and the cycle stability was also very good as in Example 1.

Example 5 A secondary battery was produced in the same manner as in Example 3. The charge/discharge curve of this secondary battery was exactly the same as that shown in Example 6 (FIG. 10). In addition, the cycle stability was also measured in Example 3.
As in the case of , the results were extremely good.

Example 6 [Secondary battery performance when γ-butyrolactone is used as a secondary battery resistance medium] A lithium secondary battery was produced in the same manner as in Example 1 except that γ-butyrolactone was used as a battery solvent. , the charge-discharge characteristics were measured.

The charge/discharge curve was the same as in Example 1, and the cycle stability was also very good.

Example 7 Li borofluoride (Li BF4) as an auxiliary electrolyte
) was used, but a lithium secondary battery was produced in the same manner as in Example 1, and the charge/discharge characteristics were measured.

The charge/discharge curve was the same as in Example 1, and the cycle stability was also very good.

Comparative Example 6 [Secondary battery using carbon fibers with a specific surface area smaller than 100 vl/9] Using the carbon fibers obtained in Synthesis No. 6 with a specific surface area smaller than 100 trilQ, iodine was added in the same manner as in Example 1. However, in this case, the amount of iodine adsorbed onto the carbon fiber was at most about 5wt4, and no more iodine could be adsorbed. A lithium secondary battery was produced under exactly the same conditions except for the above, and the charge/discharge curve (second charge/discharge) is shown in FIG. The charge efficiency was only about 30%, and stable charging and discharging could not be performed at all.

Similar experiments were conducted on samples with synthesis numbers 7, 11, and 12, and the results were exactly the same as in the case of synthesis number 6.

From the above experimental results, it was found that a carbon fiber having a specific surface area smaller than 1 o vf/f cannot produce a good secondary battery even if it adsorbs iodine.

Example 8 60 weight of iodine was added according to Example 1 except that the activated carbon fibers obtained in Synthesis Examples 2 to 5 and 8 to 10 were used in place of the polyvinyl alcohol-based activated carbon obtained in Synthesis Example 1. % adsorbed activated carbon fibers were obtained. Next, a battery was assembled in exactly the same manner as in Example 1, and a repeated charge/discharge test was conducted in the same manner as in Example 1.

In either case, the number of cycles of charging and discharging became stable after the third cycle. The charge/discharge curve at that time was almost the same as in Example 1. The discharge voltage leveled off at an open end voltage of 3.0 .mu.m. The cycle stability results are shown in Figure 14 and Figure 1.
It is shown in Figure 5.

According to the above results, in the battery of the present invention, there is no clear correlation between the specific surface area of the activated carbon fiber used and the battery performance.In fact, activated carbon made from polyvinyl alcohol has a stable cycle stability. It was recognized that the battery performance including battery performance was excellent.

Example 9 When the battery assembled in Example 8 was charged and discharged with the ion adsorption/desorption level increased to 12 molti, the activated carbon fiber sheet with synthesis number 2 showed a flat discharge voltage and 100 ml of activated carbon fiber sheet. Approximately 8 times the charge/discharge cycle
Stable charging and discharging was possible with a charge efficiency of 0 or more.

On the other hand, in other batteries, as Ip/Io increased, the stability against charging and discharging increased.

Example 10 Bromine was added under exactly the same conditions as in Example 3, except that activated carbon fibers obtained in Synthesis Examples 2 to 5 and 8 to 10 were used in place of the polyvinyl alcohol-based activated carbon obtained in Synthesis Example 1. Activated carbon fibers adsorbed were obtained. Next, a battery was assembled in exactly the same manner as in Example 5, and repeated charging and discharging tests were conducted in the same manner as in Example 3.

When the ion adsorption/desorption level was set to 6M, the open circuit voltage during discharge was 3.5V, and this value was stable throughout the discharge period. Further, the stability against cycle charging and discharging was almost the same as that of Example 8 in which iodine was adsorbed, and was extremely stable.

A battery using activated carbon fiber of synthesis number 2 was charged and discharged at an ion adsorption/desorption level of 12 molti, but after repeated charging and discharging, it showed an open circuit voltage of 3.5V, and the voltage Even charging and discharging was possible.

Comparative Example 7 Activated carbon fibers obtained in synthesis numbers 8 to 10 were used as a positive electrode,
A lithium secondary battery was produced in the same manner as in Example 1 except that a jM/1 solution of lithium perchlorate was used as the electrolyte. The cycle stability at an ion adsorption/desorption level of 6 molti is shown in FIG.

By comparison with Example 8, it can be confirmed that the electrode performance is significantly improved by adsorbing iodine to activated carbon.

Example 11 1 wt % of Teflon binder was added to the activated carbon powder bed obtained in Synthesis Example 4, and the mixture was compressed at a temperature of 170°C to form a pellet (diameter 1 cM). Next, 60% by weight of iodine was adsorbed onto this as in Example 1, and a lithium secondary battery was produced using this as a positive electrode. As in the case of Example 1, stable charging and discharging could be performed at a charge efficiency of 90 cm or higher at an adsorption/desorption level of 6 molar.

Example 12 About 60vrt% of iodine was adsorbed onto the activated carbon fiber obtained in Synthesis Example 1, and a coin-type lithium secondary battery using this as a positive electrode was assembled in an argon-substituted glow box. The electrolytic solution used was a propylene carbonate solution of lithium perchlorate that did not contain iodine (AM/11).

The charging/discharging performance was measured, and the same charging/discharging curve and cycle stability as in Example 1 could be obtained.

〔Effect of the invention〕

The battery of the present invention can be easily made small, lightweight, and thin, and has a high energy density, so it is industrially very important as a secondary battery for power needle mice. Further, the battery of the present invention is characterized by extremely good voltage uniformity.

The cycle stability and charge efficiency of the secondary battery of the present invention are as follows:
When the adsorption/desorption rate of ions is 6 mol/carbon atom, charging/discharging cycles can be performed at least 200 times at extremely high efficiency of 94 to 100%. Also 1
Even in the case of 2 molti, it is possible to charge and discharge the battery 100 times or more.

As described above, the major features of the battery of the present invention are high charge efficiency and good cycle stability at a high ion adsorption/desorption rate, and furthermore, excellent voltage flatness. In addition, the battery of the present invention has an output density of 10 to 20 KW/# and a lead secondary battery (1
, 2KW/#) 0:) It is extremely large, about 10 to 20 times.

[Brief explanation of the drawing]

Figures 1 to 6 are diagrams for confirming the structure of activated carbon suitably used in the present invention. Figure 1 is an X-ray diffraction intensity curve of acrylic activated carbon fiber, and Figure 2 is mainly a X-ray diffraction intensity curve of activated carbon fiber consisting of quality structure,
Figure 3 is a solid-state high-resolution NMR spectrum of an activated carbon fiber mainly consisting of a non-standard structure, Figure 4 is a surface reflection infrared spectrum, Figure 5 is a solid-state high-resolution NMR spectrum of a phenolic activated carbon fiber, and Figure 6 is the surface reflection infrared spectrum. FIGS. 7 to 16 are diagrams for comparing the performance of batteries in examples of the present invention and comparative examples, and FIGS.
Figures 10, 12, and 13 show the charge/discharge curves of the secondary battery, and Figures 8, 11, and 14 to 16 show the cycle stability of the secondary battery. .

Claims (5)

[Claims] (1) A battery comprising an activated carbon positive electrode and a metal negative electrode immersed in an organic non-aqueous polar solvent, characterized in that iodine or bromine is added to the activated carbon and/or the organic non-aqueous polar solvent. (2) Claim 1, in which the activated carbon has a fibrous form.
Batteries listed in section. (3) The battery according to claim 1 or 2, in which the activated carbon is made from polyvinyl alcohol resin as a starting material. (4) The battery according to claim 1, 2, or 3, in which a lithium-based metal is used as the negative electrode. (5) Graphitic crystalline structure parameter Ip/at the diffraction peak of the (002) plane of the X-ray diffraction intensity curve of the activated carbon
The battery according to claims 1 to 5, characterized in that Io is 0.35 or less.