JPH0434870A - Organic electrolyte battery - Google Patents

Abstract

PURPOSE:To enable charge and discharge for a long period by applying specified quantity of lithium to insoluble infusible substrate which includes polyacene construction on a negative electrode, and adhering the negative electrode to a negative electrode current collector with conductive paste having Ni as its main ingredient. CONSTITUTION:In an organic electrolytic battery equipped with electrolyte, including a positive electrode, negative electrode and solution prepared by dissolving lithium salt in aprotic solvent, the negative electrode is constructed by applying 3% or more of lithium by mole percentage to an insoluble infusible substrate including a polyacene structure in which a ratio between the number of hydrogen atoms and the number of carbon atoms in a heat treated material is 0.50 to 0.05, which heat treated material consisting of aromatic condensed polymer, made of carbon, hydrogen, and oxygen. Then, the negative electrode is adhered to a negative electrode current collector with conductive paste having Ni as its main ingredient.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an organic electrolyte battery, and more specifically, the present invention relates to an organic electrolyte battery, and more specifically, the negative electrode is one in which lithium is supported on an insoluble and infusible substrate containing a polyacene structure. , relates to an organic electrolyte battery in which the negative electrode is adhered to a negative electrode current collector with a conductive paste containing Ni as a main component.

(Prior Art) In recent years, batteries using conductive polymers, transition metal oxides, or activated carbon as positive electrodes have been proposed. When lithium is used as the negative electrode of these batteries, secondary batteries for energy sources with high voltage, capacity, and energy density can be obtained. However, when such a battery using lithium as a negative electrode is put into practical use, there is a problem in that the charge/discharge cycle life is reduced due to the generation of dendrites. Dendrites are dendritic or moss-like lithium crystals that form on the surface of a lithium negative electrode during charging. The dendrites grow with repeated charging and discharging, and eventually the two electrodes are short-circuited, shorting the cycle life. Therefore, it is important to suppress the generation of dendrites when putting the battery into practical use.

Recently, research has been progressing on lithium batteries in which lithium is supported on carbon materials such as graphite, and conductive polymers such as polyacetylene and polyparaphenylene. However, although orders for dendrites are extremely small, However, there was a problem in that the structure changed significantly and the cycle characteristics deteriorated.

On the other hand, an insoluble and infusible substrate containing a polyacene skeleton structure has been reported as an electrode material that is more stable than the above-mentioned conductive polymer. (Special Publication No. 1-44212. Japanese Patent Publication No. 60-170163, 5ynth, Met, +
18 (1987) 645) The insoluble and infusible substrate can be doped not only with an electron-donating dopant (P-type doping) but also with an electron-accepting dopant such as lithium (N-type doping). When supported by doping, the potential of the insoluble and infusible substrate approaches that of lithium metal;
Since it has good reversibility against and-pumping, it can be considered as a negative electrode material in place of lithium.

However, when lithium is supported on an insoluble and infusible substrate having a polyacene skeleton structure by doping and used as a negative electrode, and a battery is assembled, compared to using lithium metal,
The problem of high internal resistance remained.

(Problems to be solved by the invention) The inventors of the present invention have conducted intensive research in view of the above-mentioned problems, and as a result, have found that:
This completes the present invention.

An object of the present invention is to provide a secondary battery with low internal resistance.

Another object of the present invention is to provide a secondary battery that can be charged and discharged for a long period of time.

(Means for Solving the Problems) The above-mentioned object of the present invention is to provide an organic electrolyte battery equipped with a positive electrode, a negative electrode, and an electrolytic solution containing a solution of a lithium salt dissolved in an aprotic organic solvent, in which the negative electrode is made of carbon. is a heat-treated product of an aromatic condensation polymer consisting of hydrogen and oxygen, and the atomic ratio of hydrogen atoms/carbon atoms of the heat-treated product is 0.50.
The negative electrode is made of an insoluble and infusible substrate containing a polyacene skeleton structure of ~0.05 and carrying lithium in a molar percentage of 3% or more, and the negative electrode has conductivity mainly composed of Nj on the negative electrode current collector. This is achieved by an organic electrolyte battery characterized by being bonded with a paste.

The insoluble and infusible substrate containing a polyacene skeleton structure (hereinafter referred to as PAS) in the present invention is an aromatic condensation polymer described in Japanese Patent Publication No. 1-44212 filed by the applicant of the present application. It can be obtained by heat treatment under the following conditions.

In addition, PAS having a specific surface area of 600 m"/g or more by the BET method is
It is obtained by the method described in Japanese Patent No. 170163.

Specifically, when a high specific surface area is not required, the aromatic condensation polymer used in the present invention is (a) a combination of an aromatic hydrocarbon compound having a phenolic hydroxyl group and an aldehyde, such as a phenol-formaldehyde resin. (b) Aromatic hydrocarbon compounds having a phenolic hydroxyl group, such as xylene-modified phenol and formaldehyde resin (phenol partially substituted with xylene).

Suitable examples include aromatic hydrocarbon compounds having no phenolic hydroxyl group, condensates of aldehydes, and (c) furan resins.

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 hydrogen atoms/carbon atoms. The atomic ratio (hereinafter referred to as H/C) is 0.
PAS is obtained when the heat-treated product has a molecular weight of 50 to 0.05, preferably 0.35 to 0.10. In the case of PAS having a specific surface area determined by the BET method of 600 m"/g or more, an inorganic salt such as zinc chloride or sodium phosphate is mixed with the aromatic condensation polymer described above. The amount to be mixed depends on the type and purpose of the inorganic salt. Although it varies depending on the shape and performance of the electrode, a weight ratio of 1071 to 1/7 is preferable.

The mixture of inorganic salt and aromatic condensation polymer thus obtained is usually cured by heating at a temperature of 50 to 180°C for 2 to 90 minutes, although it varies depending on the composition of the polymer, the type of inorganic salt, etc. The thus obtained cured body is then heated to a temperature of 350 to 800°C, preferably 400 to 750°C in a non-oxidizing atmosphere, and the resulting heat-treated body is thoroughly washed with water or dilute hydrochloric acid. to remove inorganic salts contained in the heat-treated body.

After that, when this is dried, H/C=0.50~0.0
5 A PAS having a specific surface area of 600 m''78 or more, preferably 0.35 to 0.10, is obtained.

It is preferable that the PAS used in the present invention has a main peak position of 20° and 24° or less in X-ray diffraction (CuKα ray) and a broad peak at 2θ between 41° and 46°C.

In addition, in the present invention, PAS is determined from an infrared absorption spectrum and is expressed by the following formula (D):
16411, where I) t's. . -2,4° is the absorbance determined from the maximum absorption peak in the range of 2900 to 2940 Kaiser in the infrared absorption spectrum, Dlsho-
Iha. is 1560-16 in the infrared absorption spectrum
The absorbance determined from the maximum absorption peak in the range of 40 Kaiser is preferably 0.5 or less, particularly 0.3 or less.

(Details of the method for calculating the above absorbance ratio (D) are described in Example 1 of JP-A-59-3806.) PAS has a suitably developed aromatic polycyclic structure, and It is suggested that the average distance of the planar boriacene-based skeleton structure is relatively large, and lithium can be stably supported.

When the above-mentioned average distance is small, that is, as it approaches the graphite crystal, changes are more likely to occur in the substrate structure when lithium is supported or when lithium is put in and taken out (during charging and discharging), and the cycle characteristics deteriorate.

Furthermore, if the aromatic polycyclic structure is not developed, lithium cannot be stably supported, and a battery manufactured using a negative electrode in which lithium is supported on such PAS will have a large self-discharge.

The negative electrode used in the present invention is one in which 3% or more of lithium is supported on the above-mentioned PAS.

PAS can be manufactured in the form of a plate or film and used as is.

Further, as a practical method, PAS is manufactured in the form of powder, short fibers, etc., or manufactured in an appropriate shape, and the PAS processed into the shape of powder, short fibers, etc. is molded and used as an electrode.

Although the negative electrode of the present invention has 3% or more of lithium supported on PAS, it is more practical to adhere to the negative electrode current collector before supporting lithium. The negative electrode current collector is made of metal that does not alloy with lithium, such as stainless steel or nickel, and its shape is plate-like or mesh-like.

Punching metal etc. are not particularly limited. When the exterior material itself serves as a current collector, such as in a coin-type battery, it may be directly adhered to the inner surface of the exterior material.

The electrically conductive paste mainly composed of Ni used for the adhesive of the present invention uses Ni particles or Ni-plated particles as the electrically conductive filler, and the binder is made of silicone resin, phenolic resin, etc., which is a synthetic resin that does not easily deteriorate even when it comes into contact with lithium. It uses resin.

In addition to the conductive paste of the present invention, products using conductive fillers such as carbon, graphite, copper, silver, and aluminum are already on the market, but among these, those using Ni have a negative electrode with a potential close to that of lithium metal. Excellent adhesion when

The method for supporting lithium may be appropriately selected from known methods such as electrolytic method, gas phase method, liquid phase method, and ion implantation. For example, when supporting lithium by electrolytic method, lithium containing PAS or a PAS molded body is immersed in an electrolytic solution as a working electrode, and a current is passed or a voltage is applied between it and a counter electrode in the same electrolytic solution.

It can also be supported by a method in which an appropriate amount of lithium foil is brought into direct contact with PAS or a PAS molded body.

When using a gas phase method, for example, lithium vapor is added with P.
The AS or PAS molded body is exposed, or when a liquid phase method is used, a complex containing lithium ions is allowed to react with the PAS or PAS molded body. Examples of the complex used in this reaction include, but are not limited to, alkali metal naphthalene complexes and alkoxides.

The amount of lithium supported on PAS by the above method is 3% or more, preferably 10%, expressed as a molar percentage (percentage of the number of lithium to one carbon atom of PA, S).
That's all. The amount of lithium differs depending on the specific surface area of PAS.
The potential of the S molded body is 1.
It is desirable to support lithium in such a way that the amount of lithium is 0 to 0. If the amount of lithium is small, the capacity of the battery of the present invention will be reduced, and if it is large, excess lithium will be supported by PAS or PAS.
It precipitates on the surface of the AS molded body, which is not preferable.

As the positive electrode of the organic electrolyte battery of the present invention, for example, conductive polymers, metal oxides, metal sulfides, activated carbon, etc. which can be electrochemically doped and undoped, which will be described later, can be used.

Conductive polymers that can be electrochemically doped and undoped include polyacetylene, polythiophene,
Examples include boriacene organic semiconductors, which are heat-treated products of polyaniline and aromatic condensation polymers. When used as an electrode material, stability and formability are extremely important in practical terms.
From this viewpoint, polymers of boriacene-based organic semiconductors and anilines are particularly preferred.

Metal oxides that can be preferably used as the positive electrode include vanadium, chromium, manganese, It is an oxide of transition metals such as molybdenum and bismuth.

For example, VzOs, V&O+s, CT sos, M
n Ox.

One or more types of M o O, Cu, VA01, etc. are used. Even in the crystalline state, the structure of these transition metal oxides is
Alternatively, it may be made into an amorphous state by heat treatment or the like.

An example of a metal sulfide that can be preferably used as a positive electrode is T.
Examples include f St, M OSt, and M o 33.

The structure of these metal sulfides may be in a crystalline state or an amorphous state.

Among the above positive electrodes, the most preferred is a boriacene organic semiconductor (Japanese Unexamined Patent Publication No. 60-170163). This semiconductor has particularly excellent stability, and 4. It is also possible to create a high-voltage battery having a voltage of Ov, and it is also possible to create a battery with excellent cycle characteristics with almost no deterioration due to repeated charging and discharging.

As the electrolytic solution of the present invention, one in which a lithium salt is dissolved in an aprotic organic solvent is used. Examples of the aprotic organic solvent include ethylene carbonate, propylene carbonate, γ-butyrolactone, dimethylformamide, dimethylacetamide, dimethylsulfoxide, acetonitrile, dimethoxyethane, and tetrahydrofuran.

Any of dioxolane, methylene chloride, sulfolane, or a mixture of two or more of these aprotic organic solvents may be used.

Further, the electrolyte dissolved in the above mixed or single solvent may be any electrolyte capable of producing lithium ions. Such electrolytes include, for example, Li I, LiCj! O
a, LiAsFi, LiBFn, or LiHFz.

The above electrolyte and solvent are mixed in a sufficiently dehydrated state to form an electrolyte solution, and the concentration of the former electrolyte in the electrolyte solution is at least 0.1 mol/1 or more in order to reduce the internal resistance due to the electrolyte solution. It is desirable to set it as 0.2, usually 0.2
It is more preferable to set it to 1.5 mol/l.

Next, an example of an embodiment of the present invention will be explained with reference to the drawings.

FIG. 1 is an explanatory diagram showing the basic configuration of a battery according to the present invention. In Figure 1, (1) is the positive electrode, (2) is the negative electrode, (3
), (3') is a current collector, and (3') is a negative electrode current collector.
3') and the negative electrode (2) are bonded together with a conductive paste containing Ni as a main component. As the positive electrode current collector, a conductive material that is resistant to corrosion by the doping agent and the electrolytic solution, such as carbon, platinum, nickel, stainless steel, etc., can be used.

(4) is an electrolytic solution in which the above-mentioned compound that can generate ions that can be doped is dissolved in an aprotic organic solvent. The electrolyte is usually in liquid form, but it can also be used in gel or solid form to prevent leakage. (5
) is a separator placed for the purpose of preventing contact between the positive and negative electrodes and retaining the electrolyte.

The separator is a porous body with no electronic conductivity and has continuous pores that are durable to the electrolytic solution or electrode active material such as a doping agent or an alkali metal. Generally, cloth, nonwoven fabric, or porous material made of glass fiber, polyethylene, polypropylene, or the like is used.

The thickness of the separator is preferably thinner in order to reduce the internal resistance of the battery, but it is determined by taking into account the amount of electrolyte retained, flowability, strength, etc. The positive and negative electrodes and the separator are fixed in the battery case (6) so as not to cause any practical problems. The shape, size, etc. of the electrodes are determined as appropriate depending on the shape and performance of the intended battery.

(Effects of the Invention) In the organic electrolyte battery of the present invention, a negative electrode made of an insoluble and infusible substrate containing a polyacene skeleton structure on which lithium is supported and a negative electrode current collector are formed using a conductive paste mainly composed of Ni. Because it is bonded, it is a secondary battery with low internal resistance.

The present invention will be specifically explained below using Examples.

Example (Preparation of IIPAs) Zero-order formation was performed by forming a film on a glass plate using a film applicator using an aqueous solution containing a water-soluble resol (approximately 60% concentration), zinc chloride, and water mixed in a weight ratio of lO:2S:4. After covering the filmed aqueous solution with a glass plate to prevent moisture from evaporating, it was heated at a temperature of about 100° C. for 1 hour to harden it.

The phenolic resin film was placed in a siliconite electric furnace and heated to 550°C at a rate of 10°C/hour under a nitrogen stream.
Heat treatment was performed until.

Next, the heat-treated product was washed with dilute hydrochloric acid, water, and then dried to obtain a PAS film with a thickness of 500 μm (PAS-1). The H/C of this film was 0.22, and the B
The specific surface area value determined by the ET method was 2000 m2/g.

Furthermore, a PAS film with a thickness of 500μ was obtained in exactly the same manner except that the heat treatment temperature was changed to 750°C (P
AS-2).

The H/C of this film is 0.11, and the specific surface area is 1850.
m”/g.

PAS 1-2 was ground in a disc mill to obtain PAS powder, 10 parts of polytetrafluoroethylene powder was added to 100 parts of this PAS powder, and after thorough kneading, it was molded with a roller to form a PAS powder with a thickness of 500μ. Got the film. (PAS2) (2) Preparation of battery The PAS or PAS molded body obtained in (1) was adhered to a Ni plate with the conductive paste shown in Table 1, and then dried under vacuum at 250°C for 4 hours and then dried. Lithium was supported on PAS by electrochemically doping 20% lithium in the box. At this time, the electrolyte is 1
m o l / ILiCj! O,-propylene carbonate solution, lithium was used as the counter electrode, 1 mA
/cm'' at a flow density of 1.

Next, using PASI-1 as the positive electrode, 5US304 mesh as the positive electrode current collector, and felt made of glass fiber as the separator, a battery was assembled as shown in Figure 1 by combining with the above-mentioned negative electrode. /j!
LiCj! 0 using O,-propylene carbonate
The internal resistance of the produced battery was measured as AC impedance at 1 kHz. The results are shown in Table 1.

For comparison, when a conductive paste containing carbon as the main component was used to bond the negative electrode, when lithium was bonded to a Ni plate for the negative electrode, and when the negative electrode was made without using a conductive paste, Na~ In No. 6, the internal resistance of the battery was approximately 1/2 that of the case without adhesion.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the basic configuration of a battery according to the present invention, in which (1) is a positive electrode, (2) is a negative electrode, (3), (3'
) is a current collector, (4) is an electrolyte, (5) is a separator,
(6) represents a battery case, and (7) and (7') represent external terminals.

Claims (1)

[Claims] In an organic electrolyte battery comprising a positive electrode, a negative electrode, and an electrolytic solution containing a solution of a lithium salt dissolved in an aprotic organic solvent, the negative electrode is a heat-treated product of an aromatic condensation polymer consisting of carbon, hydrogen, and oxygen; The negative electrode is made of an insoluble and infusible substrate containing a polyacene skeleton structure in which the atomic ratio of hydrogen atoms/carbon atoms of the heat-treated product is 0.50 to 0.05, and lithium is supported in a molar percentage of 3% or more. An organic electrolyte battery characterized in that the electrode is bonded to a negative electrode current collector with a conductive paste containing Ni as a main component.