JPH09283173A - Metal oxide-fullerence storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize high capacity and high density by regulating charging weight ratio of a positive electrode and a negative electrode. SOLUTION: In this battery, Fullerence compound is used for the negative electrode, and the metal oxide is used for the positive electrode. Charging weight ratio thereof is regulated so that the negative electrode per one part by weight of the positive electrode is set in a range at 0.2-0.5. The Fullerence compound is expressed with a general formula Cn , and 60<=n<=82, and C60 and C70 exist 0<C60 /(C60 +C70 )<1, and at least any one of 12 kinds of metal such as Li is included in the negative electrode active material, and desirably expressed with a general formula Mx Cn (M means metal kind, 1<=x<=3, 60<=n<=82), and the charged Fullerence hydride is desirably expressed with a general formula Cn Hy (Y means an even number, 0<y/n<=0.8 60<=n<=82). Electrochemical absorption and discharge of hydrogen of this hydride is performed so as to obtain a light battery at a high energy density.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal oxide / fullerene storage battery using a fullerene capable of electrochemically storing and releasing hydrogen.

[0002]

2. Description of the Related Art In recent years, portable devices have been increasingly miniaturized, and there is an inevitably demand for a high-density storage battery as a power source. In addition, since applications of devices are diversifying, a battery having stable performance in a wide temperature range is desired.

A nickel-cadmium storage battery using a nickel oxide as a positive electrode active material and cadmium as a negative electrode active material has been widely used in a storage battery using an alkaline electrolyte. Concerned, nickel-hydrogen storage batteries using hydrogen storage alloys as alternatives have been put to practical use. This can attain the high capacity and high density required for the storage battery at the same time. In addition, especially for batteries for portable power equipment such as communication, information and AV, the weight energy density of nickel-cadmium and nickel-hydrogen storage batteries is about 70 Wh.
However, due to the development of a lithium ion storage battery having more than that, it is expected that the battery will be smaller and lighter.

However, nonaqueous storage batteries such as lithium ion storage batteries in a wide temperature range as described above are not yet stable, and there are great expectations for storage batteries using an alkaline electrolyte. ing.

[0005]

For a storage battery using an alkaline electrolyte, a battery having a higher energy density and a lighter weight than that of the battery system described above is required. Current nickel
The specific gravity of the negative electrode of the hydrogen storage battery is about 8.0 g / cm ³ , and it is difficult to further improve the weight energy density because it uses a hydrogen storage alloy. Therefore, there has been a demand for a material that is more weight efficient than the alloy type.

The present invention is intended to solve the above problems,
An object is to provide a storage battery capable of high capacity and high density.

[0007]

In order to achieve the above object, the present invention uses a fullerene compound for the negative electrode, and the filling weight ratio in the metal oxide / fullerene storage battery using the metal oxide as the positive electrode is positive. The negative electrode was used in the range of 0.2 to 0.5 per part by weight.

The fullerene compound has the general formula C
n is 60 ≦ n ≦ 82, and C ₆₀ and C ₇₀ are 0 <C
₆₀ / (C ₆₀ + C ₇₀ ) <1 and Li, Na, Mg, K, Ca, Ni, Fe, Co, R in the negative electrode active material.
at least one of b, Cs, Sr, and Ba metals
And a general formula MxCn (M is a metal species, x is a stoichiometric composition ratio, 1 ≦ x ≦ 3, and n is the number of carbon atoms).
Is represented by the general formula CnHy (y represents a stoichiometric composition ratio and is an even number, and the degree of hydrogenation is 0 <y / n ≦ 0.8). 60
It is preferable that it is represented by ≦ n ≦ 82).

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to the schematic configuration diagram of a nickel fullerene storage battery shown in FIG.

In FIG. 1, 1 is a negative electrode plate using the fullerene of the present invention as a main component, 2 is a positive electrode plate using nickel hydroxide as a main component, 3 is a separator, 4 is a case, 5 is an insulating plate, 6 Is a safety valve, 7 is a sealing plate, 8 is a positive electrode terminal, and 9 is a positive electrode lead.

First, a method for producing the fullerene compound used for the negative electrode will be described. The basic manufacturing mechanism is the arc discharge method, in which potassium carbonate and graphite powder are mixed in advance and solidified at a pitch to form an electrode, the container is evacuated, and helium gas (about 200To
rr) is introduced and a DC voltage of 23 V is applied to the electrodes,
An electric current of about mA was applied to generate an arc discharge. As a result of analyzing the carbon material deposited in the container, the yield of the fullerene compound was 18%. A fullerene compound having a purity of about 90% was separated from this carbon material by solvent extraction, and this was used as a negative electrode material. This fullerene compound is a crystalline solid in which fullerenes and metals have a periodicity, and has a general formula Mx
When expressed by Cn, 1 ≦ x ≦ 3. In addition, this fullerene compound was heated at 1200 ° C. in an argon gas atmosphere for 5 hours.
By irradiating a YAG laser of 32 nm, a metal-containing fullerene in which metal atoms were included in the hollow of fullerene was also produced and used as a negative electrode material.

The negative electrode plate 1 was prepared by adding a 1 wt% aqueous solution of carboxymethyl cellulose to a fullerene compound to form a paste, which was filled in a foamed nickel porous body having a porosity of about 95%. This was dried and then pressed to a predetermined thickness to produce a fullerene electrode having a porosity of 20%. In addition,
The theoretical capacity of this fullerene electrode is C, which is fullerene.
The amount of n that can react with hydrogen to the maximum, that is, CnHn when fully charged, is calculated from this amount of hydrogen, and CnHn is calculated.
It was 2061 mAh per gram.

For the positive electrode plate 2, a foamed nickel porous body having a porosity of about 95% was filled with nickel hydroxide, a zinc compound and a cobalt compound were added, and the product was pressed to have a porosity of 25%. Further, a nickel lead was welded to the positive electrode and connected to the sealing plate. The separator is made of a non-woven polypropylene fabric that has been subjected to sulfonation to form an electrode group, which is inserted into a metal case and injected with a 30 wt% potassium hydroxide aqueous solution as an electrolytic solution. A sealed nickel oxide / fullerene storage battery was produced.

Fullerene having a spherical shell-like molecular structure is described in H.H.
W. Kroto et al. (Nature, 318, 162 (1
985)) and typically C ₆₀
There are other fullerenes such as C ₇₀ , C ₇₆ , C ₇₈ ,
Some are formed with carbon numbers of C ₈₀ , C ₈₂ , or higher. All of these fullerenes are composed of a 5-membered ring and a 6-membered ring, and the general production ratio of each of them is 85% for C ₆₀ , 13% for C ₇₀ , and the rest are higher than that. It is reported to be the next fullerene. In addition, since fullerene is spherical, it has semiconducting properties unlike ordinary semi-metallic graphite having a planar structure, and exhibits semiconductor-like properties.

[0015] The reason is that different electron density state of the pi-electrons of the electron structure at the outer and inner sphere, tended to be lower in the high inside the outside, to further sigma orbital is mixed, simple sp ² hybridized This is because the orbit cannot be defined and a band gap occurs in the conduction band and the valence band. However, it is known that distorted pi-electrons due to sigma-orbital hybridization are advantageous for reactions such as addition reactions in which sp ³ hybridization occurs after the reaction. Therefore, alkali metal, alkaline earth metal or 3d is present between the fullerene crystal lattices.
When the like transition metal is encapsulated metal inside doping or fullerene molecule, the t _1u orbital (icosahedral symmetry to form a conduction band of the fullerene, the triple degeneration resulting from trajectory 11 LUMO (lowest unoccupied state) Orbit that forms the
Electrons in, improving electron density and electron conductivity,
As a result, hydrogen ions, which have a high electron affinity, easily exchange electrons (charge transfer) from this orbit, and are occluded by fullerenes in the negatively charged electronic state.

This hydride is generally produced by dissociation of the carbon-carbon double bond of fullerene outside the spherical shell to form a carbon-hydrogen bond, so that it is not affected by steric hindrance and the like. A stable structure can be easily obtained when the degree of hydrogenation (hydrogen number / carbon number ratio) is 0.8 or less. From these facts, a metal oxide / fullerene storage battery which has a high energy density and can be used as a battery negative electrode material replacing an hydrogen storage alloy by electrochemically storing and releasing hydrogen is provided. It becomes possible.

[0017]

EXAMPLE The positive electrode plate 2 was filled with nickel hydroxide in various amounts within the range of 0.05 (a) to 0.7 (h) parts by weight relative to 1 part by weight of the above negative electrode, and a zinc compound was further added. And a cobalt compound were added and pressed to a porosity of 25%.

[0018]

[Table 1]

The charge / discharge reaction formula of the positive and negative electrodes in the alkaline electrolyte is shown below. Can be expressed as

Here, Cn: fullerene (n = 60 to 8)
2), y: means the number of reaction electrons. Therefore, the battery as a whole is expressed by the following equation.

[0021] From the formula shown above, the amount of hydrogen y that can react with fullerene in a charged state is 0 because the maximum amount is CnHn.
It can be considered that <y / n ≦ 1.0.

FIG. 2 shows the positive / negative electrode weight ratios (a) to (h).
Discharge capacity with respect to the number of cycles in the
After charging 0%, charging / discharging was performed under the cycle condition that the final voltage was 1.0 V and the discharging was performed at a 5-hour rate current.

The initial capacity of each battery is 100
Is shown as. FIG. 2 shows the composition ratio of the negative electrode R = C ₆₀ / (C
₆₀ + C ₇₀ ) is 0.8, and the above-mentioned positive / negative electrode weight ratio gives the results shown in the figure.
For this reason, although the reason is not clear with respect to the specific capacity of the positive electrode / negative electrode relative to the specific capacity of the positive electrode per unit weight, the filling weight ratio of the negative electrode is in the range of 0.2 to 0.5 parts by weight per 1 part by weight of the positive electrode. Good characteristics can be obtained by using.

Further, FIG. 3 shows the discharge capacity when the composition ratio R of the negative electrode was changed by changing the filling weight ratio of the negative electrode to 0.3 parts by weight per 1 part by weight of the positive electrode. Good characteristics were obtained in the range of 1 ≦ R ≦ 0.9.
Here, it is considered that similar results can be obtained in the range of R <0.1 or 0.9 <R, but the composition in such a range is very difficult in synthesis and separation by chromatography. Is known and lacks in practicality.

Also, even when the doping metal species are different, the filling weight ratio of the negative electrode to the positive electrode is 0.1. Good results are obtained in the range of 2 to 0.5 parts by weight, and further, such results are obtained when a metal-encapsulated fullerene is used and when a metal-doped fullerene is mixed with a metal-encapsulated fullerene. Also obtained similar characteristics.

When the metal was not doped or included, the capacity balance between the positive and negative electrodes was lost, and good characteristics could not be obtained.

[0027]

As described above, according to the present invention, the filling weight ratio of the negative electrode to the specific capacity per unit weight of the positive electrode in the filling capacity ratio of the positive and negative electrodes is 0.2 to 1 part by weight of the positive electrode.
When used in the range of 0.5 parts by weight, a nickel fullerene storage battery can be provided.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a nickel fullerene storage battery according to an embodiment of the present invention.

FIG. 2 is a graph showing the discharge capacity with respect to the number of cycles in the nickel-fullerene storage battery prepared in this example.

FIG. 3 is a diagram showing the discharge capacity with respect to the number of cycles in the nickel-fullerene storage battery prepared in this example.

[Explanation of symbols]

 1 Negative electrode plate using fullerene compound 2 Nickel hydroxide positive electrode plate 3 Separator 4 Case 5 Insulating plate 6 Safety valve 7 Sealing plate 8 Positive electrode terminal 9 Positive electrode lead

Claims (5)

[Claims] 1. A positive electrode using a metal oxide, a negative electrode using a fullerene compound, and an alkaline electrolyte, wherein the filling weight ratio of the positive electrode to the negative electrode is 0.2 per 1 part by weight of the positive electrode.
To 0.5, a metal oxide / fullerene storage battery. 2. The metal oxide / fullerene storage battery according to claim 1, wherein the fullerene used for the negative electrode active material is represented by the general formula Cn (n is the number of carbon atoms) and 60 ≦ n ≦ 82. 3. Fullerene used for the negative electrode active material is R = C
The metal oxide / fullerene storage battery according to claim 1, wherein the composition ratio of ₆₀ / (C ₆₀ + C ₇₀ ) is in the range of 0 <R <1. 4. Li, Na, Mg, K, C in the negative electrode active material.
a, Ni, Fe, Co, Rb, Cs, Sr, or Ba containing at least one kind of metal, and having the general formula MxCn
(M represents a metal species, x represents a stoichiometric composition ratio, and 1 ≦ x ≦ 3
And n representing the number of carbon atoms is represented by 60 ≦ n ≦ 82), wherein the metal oxide / fullerene storage battery according to claim 1. 5. A fullerene hydride in a charged state has a general formula CnHy (y represents a stoichiometric composition ratio and is an even number, and the degree of hydrogenation is 0 <y / n ≦ 0.8 and 60 ≦ n ≦ 82). The metal oxide / fullerene storage battery according to claim 1, wherein