JPH03233860A - Organic electrolyte battery - Google Patents

Abstract

PURPOSE:To make possible charge and discharge of an organic electrolyte battery over a long period by using lithium as negative electrode active material, and using as a negative electrode a heat treated specific aromatic condensed polymer consisting of carbon, hydrogen and oxygen. CONSTITUTION:An organic electrolyte battery is provided with a positive electrode 1, a negative electrode 2 and an electrolyte 4 and a heat treated aromatic condensed polymer consisting of carbon, hydrogen and oxygen is used as the negative electrode 2. The aromatic condensed polymer is selected from among (a) a condensate of an aromatic hydrocarbon compound having phenol hydroxyl group, (b) a condensate of an aromatic hydrocarbon compound having phenol hydroxyl group, an aromatic hydrocarbon compound not having phenol hydroxyl group and aldehyde, and (c) furan resin. A molding or heat treated molding containing a thermosetting resin and an insoluble and infusible base substance containing a polyacene skeleton structure in which the ratio of hydrogen atom to carbon atom is 0.50 to 0.05 after heat treatment is used, which carries lithium therein by more than 3mol percentage. The long-range cycle characteristic of the battery is thereby bettered.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to all solutions, and more specifically, an insoluble and infusible substrate having a polyacene skeleton structure and a thermosetting resin are used as a negative electrode. The present invention relates to an organic electrolyte battery using a molded body containing lithium or a heat-treated product of the molded body that supports lithium.

(Prior Art) In recent years, batteries using S-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 lengthen with repeated charging and discharging, and eventually both poles are short-circuited, resulting in the end of 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 the generation of dendrites is extremely small, there is a problem in that the structure changes significantly when lithium is added or removed, resulting in a decrease in cycle characteristics.

In general, battery electrodes use active materials in powder form, such as polytetrafluoroethylene binder polyethylene,
Kneading with thermoplastic resin binder such as polypropylene,
Pressure molded products are
Preferably used.

However, when lithium is supported on a molded article obtained by molding the above-mentioned insoluble and infusible substrate in powder form by the above-mentioned method! The electrodes were significantly loosened, and problems remained with the battery characteristics, especially the rapid discharge characteristics and 5-cycle characteristics.

(Problems to be Solved by the Invention) The present inventors have completed the present invention as a result of diligent research in view of the above-mentioned problems.The purpose of the present invention is to enable charging and discharging over a long period of time. To provide secondary batteries.

Another object of the present invention is to provide a secondary battery with good rapid discharge characteristics.

Still another object of the present invention is to provide a secondary battery that is easy to manufacture.

(Means for Solving the Problems) The above object of the present invention is to provide a negative electrode active material in 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. A heat-treated product of an aromatic condensation polymer in which lithium is used as a negative electrode and carbon, hydrogen, and oxygen are used as a negative electrode, the aromatic condensation polymer is a condensation product of (a) an aromatic hydrocarbon compound having a phenolic hydroxyl group and an aldehyde. (b) an aromatic hydrocarbon compound having a phenolic hydroxyl group, a condensate of an aromatic hydrocarbon compound having no phenolic hydroxyl group and an aldehyde, and (c) a furan resin; /The atomic ratio of carbon atoms is 0.50~
'h? with 0.05? ) Adding 3% lithium (mole percentage) to a molded article containing thermosetting resin or a heat-treated product of the molded article, in which an insoluble and infusible substrate containing a polyacene skeleton structure is thermosetted.
I11 characterized in that the above supported material is used.
Achieved by electrolyte batteries.

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 JP-A-59-3806 filed by the applicant of the present application. Obtained by heat treatment under specific conditions.

In addition, PAS having a specific surface area of 600 mt/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. condensates, (b) aromatic hydrocarbon compounds with phenolic hydroxyl groups, such as xylene-modified phenol, formaldehyde resin (phenol partially replaced with xylene), aromatic hydrocarbon compounds without phenolic hydroxyl groups; Preferred examples include condensates of hydrogen compounds and aldehydes, and (c) furan resins.

The aromatic condensation polymer is gradually heated to an appropriate 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.
50-0.05, preferably 0.35 to 0.10, PAS can be obtained. 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 above-mentioned aromatic condensation polymer. It varies depending on the shape and performance of the target electrode, but
The weight ratio is preferably 10/1 to 1/7.

The mixture of inorganic salt and aromatic condensation polymer thus obtained is usually cured by heating at a temperature of 50-180°C for 2-90 minutes, although it varies depending on the composition of the polymer, the type of inorganic salt, etc. The obtained cured product is then heated in a non-oxidizing atmosphere to a temperature of 350 to 800°C, preferably 400t to 750°C, and the obtained cured product 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 preferably 0.35 to 0.10 (7) 600 m” /
PAS having a specific surface area of more than g is obtained.

The PAS used in the present invention has a main peak position of 2θ of 24° or less in X41 diffraction (CuKc X-ray),
In addition, those showing a broad peak at 2θ between 41 and 46° C. are preferable.

In addition, in the present invention, PAS absorbs infrared; (absorbance ratio (D) expressed by the following formula obtained from the vector;
Dz*oo~2,4° is the absorbance determined from the maximum absorption peak in the range of 2900 to 2940 Kaiser in the infrared absorption spectrum, DIS66~. 4° is the absorbance determined from the maximum absorption peak in the range of 1560 to 1640 Kaiser in the infrared absorption spectrum, is 0.5
Below, those of 0.3 or less are particularly suitable.

(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 polyacene 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 PAS used in the present invention is manufactured in the shape of powder, short fibers, etc., or manufactured in an appropriate shape, and processed into the shape of powder, short fibers, etc., so that it can be easily molded.

In the present invention, a molded article containing at least PAS supporting lithium and a thermosetting resin can be produced by the following two methods.

The first method is to knead PAS in a mixed form such as powder or short tal and an initial condensate of a thermosetting resin, adding a solvent such as methanol, toluene, or water if necessary, and then
This is a method of curing under heating at 50°C to 200 tons and pressure molding at the same time.The second method is to first prepare PAS in the above form,
For example, it is mixed with a binder commonly used for battery electrodes such as polytetrafluoroethylene, polyethylene, polypropylene, etc., or kneaded and molded as necessary, and then the molded body is added to an initial condensate solution of a thermosetting resin. This is a method in which after impregnation, drying and curing are performed by heating or the like.

Examples of the thermosetting resin in the present invention include those that can firmly adhere PAS powder and the like and prevent loosening of the electrode, such as phenol resin, melamine resin, furan resin, and the like. The molded product thus obtained may be used after being heat-treated in an inert atmosphere (including vacuum), depending on the case.

For example, when phenolic resin is used as a thermosetting resin, there are large amounts of hydroxyl groups, carbonyl groups, etc. that easily react with lithium, and extra lithium is required to support lithium, so heat treatment removes these functional groups in advance. It is advantageous to keep the groups depleted. The heating temperature is 15
The temperature is 0°C or higher, preferably 250°C to 500°C, and as the temperature increases, the electrode strength decreases and it becomes difficult to obtain the original effects of the present invention.

The proportion of thermosetting resin in the molded body is determined by the shape of PAS, P
Specific surface area of AS, amount of other binders.

It is determined by the amount of lithium carried, etc., but preferably the proportion of lithium in the T-type cow is 1% or more and 70% or less by weight,
More preferably, it is 5% or more and 50% or less. If it is less than 90%,! The effect of suppressing the loosening of the pole is small, 70
%, the amount of PAS will naturally decrease,
Sufficient lithium cannot be supported, resulting in a decrease in battery capacity.

The negative electrode applied to the organic electrolyte of the present invention is a molded article containing PAS obtained by the above method and a thermosetting resin or! ! Lithium is supported on the heat-treated product.

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

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

When using the gas phase method, for example, P is added to the atmosphere of lithium.
The AS rod is exposed, or when a liquid phase method is used, a complex containing, for example, lithium ions is reacted with an insoluble and infusible substrate. 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 IO% or more, expressed as a molar percentage (percentage of lithium to one carbon atom of PAS). The amount of lithium varies depending on the specific surface area of PAS, and it is desirable to support lithium so that the potential of the PAS shape body supporting lithium is 1.0~0■ with respect to Li/Li. If the amount is small, the capacity of the battery of the present invention will be reduced, and if the amount is large, excessive lithium will precipitate on the surface of the PAS molded body, which is not preferable.

When lithium is supported on a PASFi shape formed by forming the bottom of the above-mentioned PAS powder etc. using a conventionally known method, the looseness of the electrode is large, and the plate-like or film-like PAS
The internal resistance of the battery increased compared to the case where lithium was used as a lithium carrier, making rapid discharge difficult, and furthermore, sufficient cycle characteristics could not be obtained.

In particular, when PAS with a high comparative surface area is used, the electrode tends to loosen in the conventional method due to the large amount of lithium supported, and the effects of the present invention are minutely manifested. That is 6
PA with specific surface area measured by BET method of 00m'/g or more
Although it has been confirmed that S can reduce the internal resistance of a battery due to the fast diffusion rate of Lj in the substrate, there were problems with the molding method and it could not be put into practical use. However, by using the method of the present invention, , a high-performance battery can be obtained.

Furthermore, since the present invention uses a thermosetting resin as the main binder, it is possible to remove moisture, which is the main cause of deterioration of lithium batteries, in a short time at high temperatures of, for example, 300°C or higher, making it a practical molding method. be.

As the solvent constituting the electrolytic solution used in the present invention, an aprotic 111 solvent is used. Examples of the aprotic organic solvent include ethylene carbonate, propylene carbonate, T-butyrolactone, dimethylformamide, dimethyl acedoide, dimethyl sulfoxide, acetonitrile, dimethoxyethane, tetrahydrofuran, dioxolane, methylene chloride, sulfolane, or these aprotic organic solvents. Any mixture of two or more 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 as, for example, Lil LiC10.
a, LiAsP*, LiBFa, or LjHFz.

The above electrolyte and solvent are mixed in a sufficiently dehydrated state to form an electrolytic solution, and the concentration of pre-0 electrolyte in the electrolytic solution is at least 0.1 mol in order to reduce the internal resistance caused by the electrolytic solution. /1 or more is desirable, usually 0.2
It is more preferable to set it to 1.5 mol/1.

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 polyacene organic semiconductors, which are heat-treated products of polyaniline and aromatic condensation polymers. When used as a 1i electrode material, stability and bottom shape are extremely important from a practical standpoint, and from this point of view, polymers of polyacene organic semiconductors and anilines are particularly preferred.

Metal oxides that can be preferably used as positive electrodes include vanadium, chromium, and manganese, which can reversibly introduce and remove lithium ions by intercalating silane or deintercalating silane (referred to as doping or and-doping in the present invention). , molybdenum, and bismuth.

For example, VzOs, VhO+s, Cr5L,
One or more types of Mn0t+ MOO3°CutVtOt, etc. are used. The structure of these transition metal oxides may be in a crystalline state or 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.
e5t, Mo5g+F'IoSs. The structure of these metal sulfides may be in a crystalline state or an amorphous state.

Among the positive electrodes mentioned above, the most preferred is a polyacene organic semiconductor (Japanese Patent Application Laid-open No. 170163/1983). This semiconductor has particularly excellent stability, and the use of this semiconductor as a positive electrode is 4.0 It is also possible to create a high-voltage battery having a voltage of

As a current collector for extracting a current to the outside of the battery, a conductive material that is resistant to corrosion by the doping agent and the electrolytic solution, such as carbon, nickel, stainless steel, etc., can be used.

Next, an example of an embodiment of the present invention will be explained with reference to the drawings. 1st
The figure is a basic configuration diagram of a battery according to the present invention. In FIG. 1, (1) is the positive electrode, and (2) is the negative electrode.
(3) and (3') are current collectors, which are connected to each electrode and external terminals (7) and (7') so as not to cause a voltage drop. (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 solution 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 thin 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 appropriately determined depending on the shape and performance of the intended battery.

(Effects of the Invention) The organic electrolyte battery of the present invention has rapid discharge characteristics, by using as a negative electrode an insoluble and infusible substrate containing a polyacene skeleton structure carrying lithium and bonded with a thermosetting resin. This is a secondary battery with excellent long-term cycle characteristics.

The present invention will be specifically explained below using Examples.

Example (1) Method for producing PAS 1 Novolank type phenolic resin silicone was placed in an electric furnace and heated at 650°C (PASll) and 800°C (PASll) under a nitrogen atmosphere.
ASI-2) was heat-treated at a heating rate of 10° C./hour, and pulverized with a disk mill to obtain PAS powder.

(2) PAS manufacturing method 2 An aqueous solution prepared by mixing a water-soluble resol (approximately 60% concentration), zinc chloride, and water in a weight ratio of 10:25:4 was coated on a glass plate using a film applicator. Next, a glass plate was placed over the formed aqueous solution to prevent moisture from evaporating, and then heated at a temperature of about 100° C. for 1 hour to cure 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.
(PAS2-1), heat treatment was performed up to 750t (PAS2-2).

Next, the heat-treated product was washed with dilute hydrochloric acid, then water, and then dried to obtain a PAS film with a high specific surface area.

PAS powder was obtained by pulverizing this PAS film with a disk mill.

(PAS manufacturing method 3...positive electrode) A film is formed on a glass plate using a film applicator with an aqueous solution containing water-soluble resol (approximately 60% concentration), zinc chloride, and water mixed in a weight ratio of 10:25:4. After covering the aqueous solution formed in the 0th order with glass to prevent moisture from evaporating, the film was heated at a temperature of about 100° C. for I hours to harden it.

The phenolic resin film was placed in a siliconite electric furnace and heated at a rate of 40°C/hour under a nitrogen stream to 500°C.
Heat treatment was performed to ℃. Next, the heat-treated product was washed with dilute hydrochloric acid, then water, and then dried to obtain an insoluble and infusible substrate.

Powder 100 obtained by pulverizing the insoluble and infusible substrate with a disk mill
15 parts of acetylene black and 10 parts of tetrafluoroethylene powder were thoroughly kneaded and then formed into a film of about 500 μm using a roller.

(PAS3) (Negative electrode manufacturing method 1) PAS 1-1. PASI-2 each powder 1
00 parts, the first resol type phenolic resin! 40 parts of a methanol solution (approximately 65% concentration) of the +1 condensate was thoroughly mixed, and the mixture was heated at 150 tons at 50 kg/am.
'' for 15 minutes to form a film of about 500 μm.

A t9i gold working electrode is used, lithium metal is used as a counter electrode and a tllit electrode, and sufficiently dehydrated propylene carbonate is used as LiCj! An electrochemical cell was assembled using a 1 mol/1 solution of O, as an electrolyte, and a voltage of 0.2 V was applied to lithium for 12 hours to support lithium on an insoluble and infusible substrate. I let it happen.

The amount of lithium supported is expressed as a percentage of the number of lithium per carbon atom of PAS, and 37% and 31% of lithium were supported on the PASI-■ molded body and 31% on the PASI-2 molded body, respectively. l, Asahi 2).

(Negative electrode manufacturing method 2) PAS2-1. After thoroughly mixing and kneading 10 parts of polytetrafluoroethylene powder with 100 parts of each PAS2-2 powder, the mixture was formed into a film of about 500 μm using a roller. Vt resol type phenolic resin first FJ
Methanol solution of compound Ii (10%, 20%, 30%,
45% concentration) to impregnate the molded body with phenolic resin. The impregnated film was dried for 100 t'-250' day and night.
Heat treatment was performed at a temperature of C for 4 hours under a nitrogen atmosphere.

A metal foil of 300 μm (lithium loading amount: approximately 80
%〉 and 1 mol/I LiCl0
When it was left in a propylene carbonate solution for 48 hours, the Li gold gh foil completely disappeared, and all the Li was able to maintain the PAS shape.

The phenol resin content in the molded article was calculated from the weight before impregnation with the phenol resin and after the impregnation, drying and hardening.

(Creation of II Pond) A battery was assembled as shown in FIG. 1 by using PAS 3 as a positive electrode and combining it with negative electrodes N11i to 4.

A stainless wire mesh was used as the current collector, and felt made of glass fiber was used as the separator. A battery was assembled using a 1 mol/l LiCl0n propylene carbonate solution as the electrolyte.

(Measurement of cycle characteristics) 4. A voltage of OV was applied for about 1 hour to perform charging, and then discharged to 2.OV at a current density of 1 mA/cm'' to determine the initial capacity.Furthermore, this charge/discharge cycle was repeated, and the initial capacity reached 80% of the initial capacity. The number of times this happened was measured.

(Measurement of rapid discharge characteristics) The charging method was the same as the measurement of cycle characteristics.
Discharge to 2.OV at a current density of 1mA
/cm" compared with the capacity at the time of discharge.

The result is (capacity at 5mA/cm")/(1mA/cm")
It is shown in the figure of time.

Table 1 shows the physical properties of PAS, Table 2 shows the physical properties of the negative electrode obtained by negative electrode manufacturing method 2, and Table 3 shows the test results of the present invention.

Table 1 Table 3 Comparative Example I PASI-1, PASI-2, PAS2-1゜PAS2
10 parts (per weight) of polytetrafluoroethylene (PTFE) powder was mixed and kneaded with respect to each of the powders in Example 2-2, and then rolled into a film having a thickness of 500 μm. Lithium was supported by the method described in negative electrode manufacturing method 2 without impregnating it with phenol resin. However, PASI-1,P
For ASI-2, 150μ (approximately 40% lithium loading) lithium foil was used.

A battery was assembled in the same manner as in the example, and cycle characteristics and two-speed discharge characteristics were measured.

The results are summarized in Table 4.

Table 4

[Brief explanation of drawings]

FIG. 1 is a basic configuration diagram of a battery according to the present invention, (1)
is a positive electrode, (2) is a negative electrode, (3) and (3') are current collectors,
(4) represents the electrolyte, (5) the separator, (6> battery case, and (7) and (7') the external terminals. Fig. 1

Claims (1)

[Claims] (1) In 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, the negative electrode active material is lithium, and the negative electrode is an aromatic compound consisting of carbon, hydrogen, and oxygen. A heat-treated product of an aromatic condensation polymer, the aromatic condensation polymer comprises (a) a condensate of an aromatic hydrocarbon compound having a phenolic hydroxyl group and an aldehyde, (b) an aromatic hydrocarbon compound having a phenolic hydroxyl group, Aromatic hydrocarbon compounds having no phenolic hydroxyl groups and condensates of aldehydes and (c
) An insoluble and infusible substrate containing a polyacene skeleton structure selected from furan resins and having an atomic ratio of hydrogen atoms/carbon atoms of the heat-treated product of 0.50 to 0.05, and a thermosetting resin. An organic electrolyte battery characterized by using a molded article or a heat-treated product of the molded article that supports lithium in a molar percentage of 3% or more.