JP2968097B2 - 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, as a negative electrode, a molded article containing an insoluble infusible substrate having a polyacene-based skeleton structure, acetylene black and a thermosetting resin, or a heat-treated product of the molded article, in which lithium was supported was used. The present invention relates to an organic electrolyte battery.

[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.

[0003] Recently, research on lithium batteries in which lithium is supported on a carbon material such as graphite, or a conductive polymer such as polyacetylene or polyparaphenylene has been conducted.
However, although the generation of dendrites is remarkably small, the change in the structure is large with respect to the inflow and outflow of lithium.
There was a problem that the cycle characteristics deteriorated. In general, a battery electrode comprises an active material in the form of a powder, a binder such as a polytetrafluoroethylene binder, a thermoplastic resin binder such as polyethylene and polypropylene, and a conductive material such as graphite and carbon black. Kneaded and pressure-formed products are preferably used from the viewpoint of productivity and dimensional stability.

On the other hand, an insoluble and infusible substrate having a polyacene skeleton structure has already been proposed as a stable negative electrode material for secondary batteries (JP-A-59-3806 and JP-A-60-170163). And the like, when lithium is supported on a molded product obtained by molding an insoluble and infusible substrate having a polyacene-based skeleton structure such as a powder, the electrode is remarkably loosened, and furthermore, a conductive material such as graphite or carbon black is used. In addition to deterioration, battery characteristics, especially internal resistance,
Problems remained in the storage characteristics.

[0005]

DISCLOSURE OF THE INVENTION In view of the above-mentioned problems, the present inventors have made intensive studies and completed the present invention. It is an object of the present invention to provide a secondary battery that can be charged and discharged over a long period. Another object of the present invention is to provide a secondary battery having good storage characteristics. 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.

[0006]

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 an aprotic organic solvent solution of a lithium salt as an electrolyte, wherein the negative electrode has at least (a) A) an insoluble infusible substrate containing a polyacene skeleton structure having a hydrogen atom / carbon atom ratio of 0.5 to 0.05, which is a heat-treated product of an aromatic condensation polymer comprising carbon, hydrogen and oxygen; A molded article containing (b) acetylene black and (c) a thermosetting resin,
Alternatively, it is achieved by an organic electrolyte battery, characterized in that a heat-treated product of the molded body supports lithium.

The insoluble and infusible substrate (hereinafter referred to as PAS) containing a polyacene-based skeleton structure in the present invention is an aromatic-based insoluble substrate 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 compounds having no phenolic hydroxyl group Condensates of hydrocarbon compounds and aldehydes and (c) furan resins are preferred.

The aromatic condensation polymer is gradually heated in a non-oxidizing atmosphere (including a vacuum state) to a temperature of 400 ° C. to 1000 ° C., preferably to an appropriate temperature of 600 ° C. to 800 ° C. / 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.
Cured by heating for 90 minutes, the cured body thus obtained is then heated in a non-oxidizing atmosphere to a temperature of 350 to 800 ° C., preferably 400 to 750 ° C. Alternatively, the inorganic salt contained in the heat-treated body is removed by sufficiently washing with dilute hydrochloric acid or the like. Then, when this is dried, H / C = 0.5.
0-0.05, preferably 0.35-0.10 600m
A PAS having a specific surface area of ² / g or more is obtained. In the PAS used in the present invention, the position of the main peak in X-ray diffraction (CuKα ray) occurs at 24 or less at 2θ and 2θ.
It is preferable that the peak shows a broad peak between 41 ° and 46 °.

[0010] 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 are degraded. When H / C exceeds 0.5,
Lithium cannot be stably supported.
A battery manufactured using a negative electrode in which AS carries lithium 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 that it can be easily formed, and is processed into the shape of powder or short fiber.
AS is used.

The molded article used for the negative electrode in the present invention contains PAS, acetylene black and a thermosetting resin, and the molded article can be roughly divided into the following two methods. The first method is to knead PAS in the form of powder, short fiber, etc., which is easy to mix, and an initial condensate of acetylene black and a thermosetting resin, if necessary, by adding a solvent such as methanol, toluene or water. The second method is to simultaneously form the mixture of PAS and acetylene black in the above-mentioned form, for example, by using polytetrafluoroethylene, polyethylene, polypropylene or the like. A method of mixing with a binder commonly used for battery electrodes or kneading and molding as necessary, followed by impregnating the molded body with a solution of an initial condensate of a thermosetting resin, followed by drying and curing by heating or the like. It is.

Acetylene black used in the present invention is a conductive material used to reduce the internal resistance of a battery. In general, graphite and carbon black typified by acetylene black are used as a conductive material of a battery electrode.The present inventors use carbon black, particularly acetylene black, as a conductive material, and use a thermosetting resin to form the electrode. We have found that a stable negative electrode with small internal resistance can be obtained by suppressing loosening. The acetylene black in the present invention is preferably mixed with PAS by preferably 5 to 50%, more preferably 10 to 40% by weight. If the amount of acetylene black is too small, the internal resistance of the prepared battery increases. On the other hand, if the amount is too large, it becomes difficult to suppress the deterioration of acetylene black itself due to charge and discharge even in an electrode hardened with a thermosetting resin.

The thermosetting resin in the present invention is PA
S powder and acetylene black can be firmly bonded to prevent loosening of the electrode, such as phenol resin, melamine resin and furan resin. The molded body thus obtained can be optionally used after heat treatment in an inert atmosphere (including vacuum). For example, when a phenolic resin is used as a thermosetting resin, a large amount of hydroxyl groups, carbonyl groups, and the like that easily react with lithium are present, and extra lithium is required when lithium is supported. It is advantageous to keep the groups reduced. The heating temperature is 150 ° C. or higher, preferably 25
The temperature is 0 ° C. to 500 ° C., and the higher the temperature, the lower the electrode strength, and it is difficult to obtain the original effect of the present invention. The ratio of the thermosetting resin in the molded article is determined by the shape of the PAS, the amount of acetylene black, the specific surface area of the PAS, the amount of another type of binder, the amount of lithium to be supported, and the like. The weight ratio is 1% or more and 70% or less, more preferably 5% or more and 50% or less. If the amount is too small, the effect of suppressing the loosening of the electrode is small. On the other hand, if the amount is too large, the amount of the PAS is naturally small, so that sufficient lithium cannot be carried and the battery capacity is reduced.

The negative electrode applied to the organic electrolyte of the present invention comprises:
A molded article containing PAS, acetylene black, and a thermosetting resin obtained by the above-described method, or a heat-treated product of the molded article (hereinafter referred to as a PAS molded article), on which lithium is supported. As a method for supporting lithium, an electrolytic method,
The method may be appropriately selected from known methods such as 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 varies depending on the specific surface area of the PAS. The lithium is supported such that the potential of the PAS molded body supporting lithium is 1.0 to ⁰ V with respect to Li / Li ⁺ . It is desirable. When the amount of lithium is small, the capacity of the battery of the present invention is reduced.
Deposits on the surface of the compact.

In the organic electrolyte battery according to the present invention, the use of the PAS compact supporting lithium as the negative electrode allows the negative electrode reaction to proceed by doping and undoping of Li, so that no dendrite is generated.
A battery with excellent long-term reliability. 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 electrolytes include, for example, LiI, LiClO ₄ , LiAs
F ₆ , LiBF ₄ , or LiHF ₂ .

The above-mentioned 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 in order to reduce the internal resistance due to the electrolyte. / L or 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 or a metal oxide 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 moldability are extremely important in practical use, and from this viewpoint, a polymer of a polyacene-based organic semiconductor and an aniline is particularly preferable.

Examples of the metal oxide which can be preferably used as the positive electrode include, for example, vanadium, chromium, which can reversibly enter and leave lithium ions by intercalation or deintercalation (in the present invention, called doping or undoping). And oxides of transition metals such as manganese. The most preferred of the above positive electrodes is a polyacene-based organic semiconductor (Japanese Patent Application Laid-Open No. 60-17 / 1985).
No. 0163). The semiconductor is particularly excellent in stability, and it is possible to produce a high-voltage battery having a voltage of 4.0 V by using the semiconductor as a positive electrode. A battery having excellent characteristics can be produced.

[0018]

According to the organic electrolyte battery of the present invention, acetylene black is used as the conductive material of the PAS of the negative electrode, and the electrode is made of a thermosetting resin. It is a secondary battery. Hereinafter, the present invention will be described specifically with reference to examples.

[0019]

【Example】

(1) Method for producing PAS 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 into a film on a glass plate using a film applicator. Next, a glass plate was placed on the formed aqueous solution to prevent moisture from evaporating, and then cured by heating at a temperature of about 100 ° C. for 1 hour. 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 550 ° C.
(PAS1) Heat treatment was performed to 750 ° C. (PAS2). Next, the heat-treated product was washed with dilute hydrochloric acid, washed with water, and then dried to obtain a PAS film having a high specific surface area. This PAS film was pulverized with a disk mill to obtain a PAS powder. Elemental analysis of PAS1 and PAS2 revealed that the respective atomic ratios of hydrogen atoms / carbon atoms were 0.22 and 0.11, and the specific surface values by the BET method were 1900 m ² / g and 1620 m ² , respectively.
/ G.

(2) Production of Negative Electrode A predetermined amount of acetylene black (Denka Black, manufactured by Denki Kagaku Kogyo) and 100 parts of polytetrafluoroethylene were sufficiently mixed and kneaded with 100 parts of each powder of PAS1 and PAS2. It was formed into a film of about 400 μm using a roller. Subsequently, the molded body was immersed in a methanol solution (20% concentration) of a resol-type phenol resin precondensate to impregnate the phenol resin. The impregnated film was dried and cured at 100 ° C. to obtain a negative electrode.

(3) Production of positive electrode 100 parts of PAS1, 25 parts of acetylene black and 10 parts of polytetrafluoroethylene were sufficiently mixed and kneaded, and a film having a thickness of about 800 μm was obtained using a roller.

(4) Preparation of Battery The 2020 type coin battery shown in FIG. 1 was assembled. In the figure,
(1) is a positive electrode can and (2) is a negative electrode can made of stainless steel. (3) is a positive electrode (15 mmφ, 0.8 mmt), and a lithium foil (5) (14 mmφ, 0.15 mm) on the separator side on the negative electrode (15 mmφ, 0.4 mmt) of (4).
mmt). The pressed lithium foil is the negative electrode (4)
It is carried inside and disappears within a few days after battery assembly. Between the positive electrode can (1) and the positive electrode (3), and between the negative electrode can (2) and the negative electrode (4), a stainless steel mesh (0.08 mmt) (6) as a current collector was disposed. Was welded. The separator (7) used a glass fiber nonwoven fabric. (2) The electrode sheet obtained in (3) was punched out to a predetermined size, dried at 150 ° C. for 2 hours under vacuum, and then a 1M-LiClO ₄ / propylene carbonate solution was used as an electrolyte to produce the above-mentioned 2020 type battery. did. All operations were performed in an Ar box. When the battery was disassembled 200 hours after its preparation, it was confirmed that all the lithium crimped on the negative electrode had disappeared.

(5) Measurement of battery After the battery was left at room temperature for 200 hours, the internal resistance became 1
It was measured as an AC impedance at KHz. Subsequently, the internal resistance after storage in a thermostat at 60 ° C. for 500 hours was measured and compared with the initial value.

[0024]

[Comparative Examples] In the examples, PAS1 was used, acetylene black was not used, phenol resin was not used, and graphite (manufactured by Wako Pure Chemical Industries) and furnace black (Ketjen Bla) were used instead of acetylene black.
ck), Channel Black (Black Pearl)
s 2000, manufactured by Cabot) was evaluated in the same manner as in the example. Table 1 shows the results of Examples and Comparative Examples. By using acetylene black as the conductive material and solidifying it with a phenol resin, a battery having low internal resistance and excellent storage characteristics was obtained.

[0025]

[Table 1]

[0026]

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a basic configuration of a battery according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Positive electrode can 2 Negative electrode can 3 Positive electrode 4 Negative electrode 5 Lithium foil (supported in the negative electrode of (4) 'and lost after completion of battery) 6 Current collector 7 Separator 8 Packing

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-301460 (JP, A) JP-A-63-218157 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01M 4/02 H01M 4/60-4/62 H01M 10/40

Claims (1)

(57) [Claims] 1. An organic electrolyte battery comprising a positive electrode, a negative electrode, and an electrolytic solution containing an aprotic organic solvent solution of a lithium salt as the electrolytic solution, wherein the negative electrode comprises at least (a) an aromatic substance comprising carbon, hydrogen, and oxygen. The hydrogen atom / carbon atom ratio, which is a heat-treated product of the group III condensation polymer, is 0.5
A molded article containing (b) acetylene black and (c) a thermosetting resin, or a heat-treated product of the molded article; An organic electrolyte battery using lithium.