JP2646462B2 - Organic electrolyte battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electrolyte battery,
More specifically, the present invention relates to an organic electrolyte battery in which, as a negative electrode, a molded product obtained by impregnating a cured insoluble and infusible substrate having a polyacene skeleton structure with a thermosetting resin solution and carrying lithium on the molded product is applied.

[0002]

2. Description of the Related Art In recent years, batteries using a conductive polymer, a transition metal oxide or activated carbon as a positive electrode have been proposed. When lithium is used as the negative electrode of these batteries, a secondary battery for an energy source having a high voltage, a large capacity and a high energy density can be obtained. However, when a battery using lithium for such a negative electrode is put into practical use, there is a problem that the charge / discharge cycle life is reduced due to the generation of dendrite. Dendrite is a dendritic or moss-like lithium crystal generated on the surface of a lithium negative electrode during charging. The dendrite grows with the repetition of charge and discharge, and eventually the two electrodes are short-circuited, resulting in a long cycle life. Therefore, it is important to suppress the generation of the dendrite when the battery is put to practical use. Recently, carbon materials such as graphite,
Research on lithium batteries in which lithium is supported on a conductive polymer such as polyacetylene or polyparaphenylene has been advanced. However, although the generation of dendrites is extremely small, there is a problem that a change in the structure is large with respect to lithium in / out, and the cycle characteristics are deteriorated.
In general, a battery electrode is obtained by kneading an active material in the form of a powder or the like with a thermoplastic resin binder such as a polytetrafluoroethylene binder, polyethylene, or polypropylene, and press-molding, thereby improving productivity and dimensional stability. From the viewpoint of, it is preferably used.

On the other hand, an insoluble and infusible substrate already containing a polyacene skeleton structure has been proposed as a stable negative electrode material for a secondary battery (JP-A-59-3806 and JP-A-60-170163). In the case where lithium is supported on a compact obtained by molding the above-described insoluble and infusible substrate in the form of a powder or the like by the above-described method, the electrode is remarkably loosened, and there is a problem in battery characteristics, particularly rapid charge / discharge characteristics and cycle characteristics. Was left.

[0004]

DISCLOSURE OF THE INVENTION The present inventors have made intensive studies in view of the above problems and completed the present invention. An object of the present invention is to provide a secondary battery which can be charged and discharged for a long period of time and has a good rapid charging characteristic.
Another object of the present invention is to provide a secondary battery having good rapid discharge characteristics. Still another object of the present invention is to provide a secondary battery which is easy to manufacture.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to provide an organic electrolyte battery comprising a positive electrode, a negative electrode and a solution of a lithium salt in an aprotic organic solvent as an electrolyte,
The negative electrode is a heat-treated product of an aromatic condensed polymer composed of carbon, hydrogen and oxygen, and has an atomic ratio of hydrogen atoms / carbon atoms of 0.5.
After molding an insoluble and infusible substrate containing a polyacene-based skeletal structure of about 0.05 to 0.05% using a binder, a thermosetting resin solution is impregnated and cured to obtain a molded article containing 3% by mole of lithium. The present invention is achieved by an organic electrolyte battery which is supported as described above, and wherein the molded article satisfies the following formula. V _a ≧ 0.2 (cc) (V _a : Void volume of 100 ° or more per 1 cc of a molded article obtained by molding an insoluble and infusible substrate with a binder. V _b : Molded article 1 after impregnated with a thermosetting resin solution and cured.
Pore volume of more than 100mm per cc)

The insoluble and infusible substrate having a polyacene skeleton structure (hereinafter referred to as PAS) according to the present invention is an aromatic base described in Japanese Patent Application Laid-Open No. 59-3806 filed by the present applicant. It is obtained by subjecting the condensation polymer to heat treatment under specific conditions. PAS having a specific surface area of 600 m ² / g or more according to the BET method can be obtained by the method described in Japanese Patent Application Laid-Open No. Sho 60-170163 filed by the present applicant. Specifically, when a high specific surface area is not required, the aromatic condensation polymer used in the present invention includes (a) an aromatic hydrocarbon compound having a phenolic hydroxyl group, such as a phenol-formaldehyde resin, and an aldehyde. Aromatic hydrocarbon compounds having a phenolic hydroxyl group, such as condensates, (b) xylene-modified phenol, formaldehyde resin (a part of phenol substituted with xylene), and aromatic hydrocarbons having no phenolic hydroxyl group Condensates of hydrogen compounds and aldehydes and (c) furan resins are preferred.

The aromatic condensation polymer is gradually heated to a suitable temperature of 400 ° C. to 1000 ° C., preferably 600 ° C. to 800 ° C. in a non-oxidizing atmosphere (including a vacuum state) to form a hydrogen atom. / The atomic ratio of carbon atoms (hereinafter referred to as H / C) is 0.50 to 0.05, preferably 0.35 to
When the heat treatment is performed at 0.10, PAS is obtained. 600
PAS having a specific surface area of at least m ² / g by the BET method
In the case of the above, an inorganic salt such as zinc chloride or sodium phosphate is mixed with the above-mentioned aromatic condensation polymer. The amount to be mixed is
The ratio by weight is preferably from 10/1 to 1/7, though it depends on the type of the inorganic salt and the shape and performance of the intended electrode. The mixture of the inorganic salt and the aromatic condensation polymer thus obtained varies depending on the composition of the polymer, the kind of the inorganic salt and the like, but is usually cured at a temperature of 50 to 180 ° C. by heating for 2 to 90 minutes, thus. The obtained cured body is then heated in a non-oxidizing atmosphere to a temperature of 350 to 800 ° C., preferably 400 to 750 ° C., and the obtained heat-treated body is sufficiently washed with water or dilute hydrochloric acid. ,
The inorganic salt contained in the heat-treated body is removed. afterwards,
When this is dried, a PAS having a specific surface area of 600 m ² / g or more of H / C = 0.50 to 0.05, preferably 0.35 to 0.10 is obtained. The PAS used in the present invention is preferably one in which the position of the main peak occurs at 24 or less at 2θ in X-ray diffraction (Cukα ray) and shows a broad peak at 41 from 46 ° to 2θ.

[0008] PAS suggests that the aromatic polycyclic structure is moderately developed, and that the average distance of the planar polyacene skeleton structure is relatively large, so that PAS can stably carry lithium. If the H / C is less than 0.05, the structure of the base is likely to change when lithium is carried or when lithium is taken in and out (during charging and discharging), and the cycle characteristics deteriorate. When H / C exceeds 0.5, lithium cannot be stably supported.
A battery manufactured using a negative electrode having lithium supported thereon has a large self-discharge. The PAS in the present invention is manufactured in the form of powder, short fiber or the like or manufactured in an appropriate shape so as to be easily molded, and is processed into the form of powder, short fiber or the like.
Is used. In the method for producing a negative electrode according to the present invention, the PAS in the above-described form is mixed with a binder generally used for battery electrodes such as polytetrafluoroethylene, polyethylene, polypropylene, or the like, or kneaded and molded as necessary. Then, after obtaining a preformed body, the formed body is impregnated with a solution of an initial condensate of a thermosetting resin, and then dried and cured by heating or the like. As the thermosetting resin in the present invention, for example, phenol resin, melamine resin, furan resin and the like are preferably used. The impregnated molded body thus obtained can suppress the loosening of the electrode with respect to lithium loading. In addition, the impregnated molded body may be used after being heat-treated in an inert atmosphere (including a vacuum) in some cases.

For example, when a phenol resin is used as the thermosetting resin, a large amount of hydroxyl groups, carbonyl groups, etc., which easily react with lithium are present, and extra lithium is required when carrying lithium. It is advantageous to keep these functional groups reduced. Heating temperature is 150 ° C or higher, preferably 250 ° C to 500 ° C
However, as the temperature increases, the strength of the electrode decreases, and it becomes difficult to obtain the original effect of the present invention. Pore volume in the negative electrode of the present invention is defined by the mercury porosimetry 100Å or more pore volume per shaped body 1cc measured in (porosimeter) (cc), the pore volume of the preform V _a, When the pore volume of the impregnated molded body is _Vb ,

[0010] For V _a <0.2 (cc), since the pore volume of the preform itself be devised how impregnation is small, the pore volume of the impregnated molded body is also naturally reduced, the electrode active material Since the amount of electrolyte near the PAS is small,
Poor chargeability. When such impregnation is performed, quick chargeability is deteriorated. In the present invention, the proportion of the thermosetting resin in the impregnated molded article is P
It is determined by the shape of the AS, the specific surface area of the PAS, the amount of lithium to be supported, and the like. is there. If this ratio is less than 1%, even if the pore volume is within the range of the present invention, the effect of suppressing the loosening of the electrode is small, which is not preferable.

The negative electrode used in the organic electrolyte battery of the present invention is obtained by supporting lithium on a PAS-impregnated compact obtained by the above-described method or a heat-treated product of the compact. The method for supporting lithium may be appropriately selected from known methods such as an electrolytic method, a gas phase method, a liquid phase method, and an ion implantation method. For example, when lithium is supported by an electrolytic method, the PAS molded body is immersed in an electrolyte containing lithium ions as a working electrode, and a current is applied or a voltage is applied between the counter electrode in the same electrolyte. I do. Further, it can also be supported by a method in which an appropriate amount of lithium foil is brought into direct contact with the above-mentioned molded body. When the gas phase method is used, the PAS compact is exposed to, for example, lithium vapor. When the liquid phase method is used, for example, a complex containing lithium ions is reacted with an insoluble and infusible substrate. Examples of the complex used in this reaction include, but are not limited to, an alkali metal naphthalene complex and an alkoxide. The amount of lithium supported on the PAS by the above method is 3% or more, preferably 10% or more, expressed as a molar percentage (percentage of the number of lithium to one carbon atom of the PAS). The amount of lithium also depends on the specific surface area of the PAS, and the potential of the PAS compact supporting lithium is L
It is desirable to support lithium so that i / Li ⁺ becomes 1.0 to ⁰ V. If the amount of lithium is small,
If the capacity of the battery of the present invention is reduced, and if the capacity is large, excessive lithium is undesirably deposited on the surface of the PAS molded body.

An aprotic organic solvent is used as a solvent constituting the electrolytic solution used in the present invention. Examples of the aprotic organic solvent include, for example, ethylene carbonate, propylene carbonate, γ-butyrolactone, dimethylformamide, dimethylacetamide, dimethylsulfoxide, acetonitrile, dimethoxyethane, tetrahydrofuran, dioxolan, methylene chloride, sulfolane, or a mixture of these aprotic organic solvents. Any mixture of more than one species may be used. The electrolyte mixed or dissolved in a single solvent may be any electrolyte capable of generating lithium ions. Such an electrolyte is, for example, LiI, LiClO ₄ , LiAsF ₆ , LiBF ₄ or LiHF ₂ . The above electrolyte and solvent are mixed in a sufficiently dehydrated state to form an electrolyte. The concentration of the electrolyte in the electrolyte is at least 0.1 mol / l or more in order to reduce the internal resistance due to the electrolyte. And more preferably 0.2 to 1.5 mol / l.

As the positive electrode of the organic electrolyte battery of the present invention,
For example, a conductive polymer, metal oxide, or the like, which can be electrochemically doped and undoped, which will be described later, can be used. Examples of conductive polymers that can be electrochemically doped and undoped include polyacetylene, polythiophene, polyaniline, and polyacene-based organic semiconductors that are heat-treated aromatic condensation polymers. When used as an electrode material, stability and a molded body are extremely important in practical use, and from this viewpoint, a polymer of a polyacene-based organic semiconductor and an aniline is particularly preferable. Metal oxides which can be preferably used as the positive electrode can reversibly enter and leave lithium ions by intercalation or deintercalation (referred to as doping or undoping in the present invention), for example, vanadium, chromium,
An oxide of a transition metal such as manganese. The most preferable of the positive electrodes is a polyacene-based organic semiconductor (Japanese Patent Application Laid-Open No. Sho 60-170163). The semiconductor is particularly excellent in stability and is a positive electrode excellent in rapid chargeability.
It is also possible to produce a high-voltage battery having the following voltage, and there is almost no deterioration due to repeated charging and discharging, and a battery having excellent cycle characteristics can be produced. As a current collector for extracting a current to the outside of the battery, a conductive material having corrosion resistance to a doping agent and an electrolytic solution, for example, carbon, platinum, nickel, stainless steel, or the like can be used.

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram of a basic configuration of a battery according to the present invention. In FIG. 1, (1) is a positive electrode, and (2) is a negative electrode. (3) and (3 ') are current collectors, which are connected to each electrode and the external terminals (7) and (7') so as not to cause a voltage drop. (4) is an electrolytic solution in which the above-mentioned compound capable of generating ions that can be doped is dissolved in an aprotic organic solvent. The electrolyte is usually liquid, but may be used in a gel or solid state to prevent liquid leakage. (5) is a separator arranged for the purpose of preventing contact between the positive and negative electrodes and holding the electrolytic solution. The separator is a non-electron-conductive porous body having continuous air holes that are durable with respect to the electrolytic solution or the electrode active material such as a doping agent or an alkali metal. Usually, cloth, nonwoven fabric or porous body made of glass fiber, polyethylene or polypropylene is used. The thickness of the separator is preferably thin in order to reduce the internal resistance of the battery, but is determined in consideration of the amount of retained electrolyte, flowability, strength, and the like. The positive and negative electrodes and the separator are fixed in the battery case (6) so that there is no practical problem. The shape, size, and the like of the electrode are appropriately determined depending on the shape and performance of the intended battery.

[0015]

The organic electrolyte battery of the present invention uses a negative electrode obtained by molding an insoluble and infusible substrate having a polyacene skeleton structure so as to have a specific pore volume, thereby achieving a rapid charge characteristic, A secondary battery with excellent long-term cycle characteristics.

[0016]

【Example】

(1) Production of preform (PAS1,2,3) A glass plate is prepared by mixing an aqueous solution obtained by mixing a water-soluble resol (about 60% concentration), zinc chloride and water at a weight ratio of 10: 25: 4 with a film applicator. A film was formed thereon. Next, a glass was put on the formed aqueous solution so that water did not evaporate, and then heated at a temperature of about 100 ° C. for 1 hour to be cured. The phenol resin film was placed in a siliconite electric furnace, and heated at a rate of 10 ° C./hour under a nitrogen stream to heat-treat to 650 ° C. Next, after washing the heat-treated product with dilute hydrochloric acid,
By washing with water and then drying, a high specific surface area PA
An S film was obtained. The (hydrogen atom) / (carbon atom) atomic ratio of this PAS was 0.17, and was measured by the BET method. The specific surface area was 1840 m ² / g. Subsequently, this PAS film was pulverized with a disk mill, and three types of PAS powders were obtained by changing the pulverization time. To 100 parts of this PAS powder, 8 parts of polytetrafluoroethylene powder was added, kneaded well, and then formed into a sheet to obtain a preform (PAS1, PAS2, PAS3).

(2) Measurement of Pore Volume The pore volume is PORESIZER 9310 (MICRO)
MERITICS, U.S.A. S. It measured by the mercury intrusion method with a porosimeter using A). In the present invention, the volume of pores of 100 ° or more contained per 1 (cc) of the molded body was measured and defined as the pore volume. The pore volume V _a of the preform PAS1~3 shown in Table 1.

[0018]

[Table 1]

(3) Production of Impregnated Molded Articles The preformed articles PAS1 to 3 were impregnated by dipping them in a methanol solution of a resol-type phenolic resin precondensate having a predetermined concentration shown in Table 2 for about 10 minutes. Then 1
By drying and curing at a temperature of 00 ° C. for about 2 hours, an impregnated molded body was obtained. Table 2 shows the results of measuring the pore volume by the method (2).

(4) Production of Positive Electrode An aqueous solution in which a water-soluble resol (about 60% concentration), zinc chloride and water were mixed at a weight ratio of 10: 25: 4 was formed on a glass plate using a film applicator. Next, a glass was put on the formed aqueous solution so that water did not evaporate, and then heated at a temperature of about 100 ° C. for 1 hour to be cured. The phenol resin film was placed in a siliconite electric furnace, heated at a rate of 40 ° C./hour under a nitrogen stream, and heat-treated to 500 ° C. Next, the heat-treated product was washed with diluted hydrochloric acid, washed with water, and then dried to obtain an insoluble and infusible substrate. (Hydrogen atom) / (carbon atom) = 0.
25. The specific surface area measured by the BET method was 2100 m ² / g. After 100 parts of the powder obtained by pulverizing the insoluble and infusible substrate with a disk mill, 15 parts of acetylene black, and 10 parts of ethylene tetrafluoride powder were sufficiently kneaded, the mixture was rolled using a roller for about 50 parts.
Formed into a 0μ film.

(5) Preparation of Battery No. 2 in Table 2 below 1 to No. A battery was prepared for each of the 7 impregnated molded bodies. The electrochemical method was used to carry Li on the impregnated molded body. In the electrochemical cell used, the impregnated molded body was used as a working electrode, lithium metal was used as a counter electrode and a reference electrode, and a 1 mol / l solution of LiClO ₄ dissolved in sufficiently dehydrated propylene carbonate was used as an electrolyte. By applying a voltage of 0.2 V to lithium for 12 hours,
Lithium was supported. The amount of lithium carried was determined by integrating the current flowing through the electrochemical cell. No.
1 to No. Table 2 shows the loading ratio of lithium of No. 7. A battery was assembled as shown in FIG. 1 by combining the seven types of negative electrodes thus obtained and the positive electrode obtained in (5). A stainless steel wire mesh was used as a current collector, and a felt made of glass fiber was used as a separator. 1 mol / l as electrolyte
A battery was assembled using the LiClO ₄ -propylene carbonate solution. The initial voltage of the battery is about 2.7 V in each case
Met.

(6) Measurement of rapid chargeability A voltage of 4.0 V was applied to the above-mentioned battery from an external power source for about 12 hours to perform charging, and then discharged at a current density of 1 mA / cm ² to 2.0 V. The capacity was determined. Subsequently, the charging time was set to 30 minutes, and the same measurement was performed to obtain the capacity at the time of quick charging. The quick charge rate was calculated as a ratio of (capacity during quick charge) / (initial capacity) and is shown in Table 2.

[0023]

[Table 2]

[0024] . As for No. 5, it can be seen that the quick chargeability is as low as 0.7 or less.

[0025]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram of a basic configuration of a battery according to the present invention.
(1) is a positive electrode, (2) a negative electrode, (3) and (3 ') are current collectors, (4) is an electrolyte, (5) is a separator, (6) a battery case, (7) and (7'). ) Indicates an external terminal.

Claims (1)

(57) [Claims] 1. An organic electrolyte battery comprising a positive electrode, a negative electrode and a solution of a lithium salt in an aprotic organic solvent as an electrolytic solution, wherein the negative electrode is a heat-treated product of an aromatic condensation polymer comprising carbon, hydrogen and oxygen. An insoluble and infusible substrate containing a polyacene-based skeleton having an atomic ratio of hydrogen atom / carbon atom of 0.5 to 0.05 is molded using a binder, and then impregnated with a thermosetting resin solution and cured. An organic electrolyte battery, wherein lithium is supported on the obtained molded body in a molar percentage of 3% or more, and the molded body satisfies the following formula. V _a ≧ 0.2 (cc) (However, V _a : a void volume of 100 ° or more per 1 cc of a molded article obtained by molding an insoluble and infusible substrate with a binder V _b : a molded article 1 after impregnating and curing a thermosetting resin solution
Pore volume of more than 100mm per cc)