JPH0864251A - Organic electrolyte battery - Google Patents

Abstract

PURPOSE: To provide high capacity and high voltage by using metal oxide for a positive electrode, using insoluble and infusible substrate having a polyacene group skeletal structure for a negative electrode, properly controlling quantity of lithium in a battery, and selecting a carrying method for lithium derived from the negative electrode. CONSTITUTION: Metal oxide containing lithium is used for a positive electrode 1, while a substance composed of insoluble and infusible substrate (PAS) is used for a negative electrode 2. In other words, PAS used for the negative electrode 2 is prepared by heating aromatic group condensation polymer and is provided with an atomic ratio of hydrogen atoms to carbon atoms of 0.5-0.05 and a polyacene group skeletal structure. To the negative electrode 2PAS, total quantity of lithium contained in a battery is 500mAh/g or more, while quantity of lithium derived from the negative electrode 2 is 100mAh/g or more, and lithium derived from the negative electrode 2 is electrochemically carried by impressing potential equal to that of Li metal or less. According to proper control of quantity of lithium and proper selection of a carrying method for lithium derived from the electrode 2 PAS, production is facilitated while the battery provided with high capacity and high voltage can be obtained.

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 having a high capacity and a high voltage, which uses an insoluble and infusible substrate having a polyacene skeleton structure for a negative electrode and a metal oxide for a positive electrode.

[0002]

2. Description of the Related Art In recent years, secondary batteries using a conductive polymer, a transition metal oxide or the like as a positive electrode and a lithium metal or a lithium alloy as a negative electrode have a high energy density.
It has been proposed as an alternative to i-Cd batteries and lead batteries. However, when these secondary batteries are repeatedly charged and discharged, the capacity decreases due to deterioration of the positive electrode or the negative electrode, and a problem remains for practical use. In particular, the deterioration of the negative electrode is accompanied by the generation of moss-like lithium crystals called dendrites, and the dendrites eventually penetrate the separator due to repeated charging and discharging, causing a short circuit inside the battery, and in some cases the battery bursts. There was also a problem in terms of safety.

Recently, in order to solve the above problems, a battery using a carbon material such as graphite for the negative electrode and a lithium-containing metal oxide such as LiCoO _{2 for} the positive electrode has been proposed. The battery is a so-called rocking chair type battery in which lithium is supplied from the lithium-containing metal oxide of the positive electrode to the negative electrode by charging after the battery is assembled, and the negative electrode lithium is returned to the positive electrode by discharging. Although the battery is characterized by high voltage and high capacity, its capacity is 80 to 90 mA at maximum.
h / cc (based on the total volume of the electrode, separator, and current collector)
However, the high energy density characteristic of lithium batteries has not been obtained yet. On the other hand, aromatic condensation polymers
Which is a heat-treated product and has an atomic ratio of hydrogen atoms / carbon atoms of 0.
The insoluble infusible substrate having a polyacene-based skeleton structure of 5 to 0.05 is capable of doping lithium in a large amount as compared with a general carbon material. When the above-mentioned rocking chair type battery using a lithium-containing oxide for the positive electrode was assembled, a high capacity was obtained as compared with the carbon material, but the capacity was unsatisfactory. In order to solve the above-mentioned problems, Japanese Patent Application No. 5-259403 of the same applicant as the present application has not yet been published, but a positive electrode, a negative electrode, and an aprotic organic solvent solution of a lithium salt are provided as an electrolytic solution. An organic electrolyte battery,
(1) A polyacene-based skeleton structure in which the positive electrode contains a metal oxide and (2) the negative electrode is a heat-treated product of an aromatic condensed polymer and the atomic ratio of hydrogen atoms / carbon atoms is 0.5 to 0.05. The insoluble and infusible substrate (hereinafter referred to as PAS) having (3) the total amount of lithium contained in the battery is 50 relative to the negative electrode PAS.
0 mAh / g or more, and the lithium derived from the negative electrode is 1
An organic electrolyte battery has been proposed which is characterized in that it is at least 00 mAh / g. Although the battery has a high capacity, the time required for carrying the lithium derived from the negative electrode is long, and a problem remains in practical use.

[0004]

The inventors of the present invention have completed the present invention as a result of intensive research in view of the above problems, and an object of the present invention is to provide a secondary battery having a high capacity and a high voltage. To provide batteries. Another object of the present invention is to provide a secondary battery which can be charged and discharged for a long period of time and is excellent in safety. Still another object of the present invention is to provide a secondary battery having a low internal resistance. Still another object of the present invention is to provide a secondary battery that is easy to manufacture. Still other objects of the present invention will be apparent from the following description.

[0005]

The present inventors have used a metal oxide for the positive electrode and an insoluble and infusible substrate having a polyacene skeleton structure for the negative electrode, and appropriately control the amount of lithium in the battery. At the same time, the present invention was completed by selecting the supporting method (dope method) derived from the negative electrode. That is, the present invention is an organic electrolyte battery comprising a positive electrode, a negative electrode, and an aprotic organic solvent solution of a lithium salt as an electrolytic solution,
(1) A polyacene-based skeleton structure in which the positive electrode contains a metal oxide and (2) the negative electrode is a heat-treated product of an aromatic condensed polymer and the atomic ratio of hydrogen atoms / carbon atoms is 0.5 to 0.05. The insoluble and infusible substrate (hereinafter referred to as PAS) having (3) the total amount of lithium contained in the battery is 50 relative to the negative electrode PAS.
0 mAh / g or more, and the lithium derived from the negative electrode is 1
Lithium derived from the negative electrode is
It is an organic electrolyte battery characterized in that it is electrochemically supported by applying a potential equal to or lower than the potential of i metal.

The aromatic condensation polymer in the present invention is a condensation product of an aromatic hydrocarbon compound and aldehydes. As the aromatic hydrocarbon compound, so-called phenols such as phenol, cresol and xylenol are suitable. For example, the following formula

Embedded image (Where x and y are each independently 0, 1 or 2
Methylene bisphenols represented by the formula), or hydroxy biphenyls and hydroxynaphthalenes. Of these, phenols, particularly phenol, are practically preferred.
As the aromatic condensation polymer in the present invention, a part of the above aromatic hydrocarbon compound having a phenolic hydroxyl group is substituted with an aromatic hydrocarbon compound having no phenolic hydroxyl group, for example, xylene, toluene, aniline and the like. It is also possible to use a modified aromatic condensation polymer such as a condensation product of phenol, xylene and formaldehyde.
Further, a modified aromatic polymer substituted with melamine or urea can also be used. Furan resin is also suitable. Aldehydes such as formaldehyde, acetaldehyde and furfural can be used as the aldehyde, but formaldehyde is preferred. The phenol-formaldehyde condensate may be a novolac type, a resol type, or a mixture thereof.

The insoluble and infusible substrate in the present invention is obtained by heat-treating the above aromatic polymer.
All of the insoluble and infusible substrates having a polyacene-based skeleton structure described in JP-A-44212, JP-B-3-24024, etc. can be used. For example, they can be produced as follows. The aromatic condensation polymer is
400 ° C to 8 in a non-oxidizing atmosphere (including vacuum)
By gradually heating to an appropriate temperature of 00 ° C, the atomic ratio of hydrogen atoms / carbon atoms (hereinafter referred to as H / C) is 0.
It is possible to obtain an insoluble and infusible substrate of 50 to 0.05, preferably 0.35 to 0.10. In addition, Japanese Examined Patent Publication 3-24
In the method described in Japanese Patent No. 024, etc., 600 m ² /
It is also possible to obtain an insoluble and infusible substrate having a BET specific surface area of g or more. For example, an aromatic condensation polymer
A solution containing the precondensate and the inorganic salt such as zinc chloride is prepared, and the solution is heated and cured in a mold. The cured product thus obtained is subjected to a non-oxidizing atmosphere (including vacuum),
Up to a temperature of 350 ° C to 800 ° C, preferably 400
After gradually heating to an appropriate temperature of ° C to 750 ° C,
By sufficiently washing with water or dilute hydrochloric acid, an insoluble infusible substrate having the above H / C and having a specific surface area by the BET method of, for example, 600 m ² / g or more can be obtained.

The insoluble and infusible substrate used in the present invention has a main peak position of 2θ according to X-ray diffraction (CuKα).
In addition to the main peak, there is another broad peak between 41 and 46 °. That is, it is suggested that the insoluble and infusible substrate has a polyacene skeleton structure in which an aromatic polycyclic structure is appropriately developed, and has an amorphous structure, and lithium can be stably doped so that an active material for a battery can be obtained. Is useful as When H / C exceeds 0.50, the aromatic polycyclic structure is not sufficiently developed, and therefore lithium doping,
The de-doping cannot be smoothly performed, and the charge / discharge efficiency is reduced when the battery is assembled. Also, H / C is 0.0
When it is 5 or less, the capacity of the battery of the present invention decreases, which is not preferable.

The negative electrode of the present invention comprises the above-mentioned insoluble and infusible substrate (hereinafter referred to as PAS), and is formed from a PAS having a shape such as powder, granules, short fibers, etc., which can be easily molded, with a binder. As the binder, a fluorine-containing resin such as polytetrafluoroethylene or polyvinylidene fluoride, a thermoplastic resin such as polypropylene or polyethylene can be used, but a fluorine-based binder is preferable, and a fluorine atom / Atomic ratio of carbon atoms (hereinafter referred to as F / C)
Is preferably less than 1.5 and 0.75 or more, and particularly preferably less than 1.3 and 0.75 or more. Examples of the fluorine-based binder include polyvinylidene fluoride, vinylidene fluoride-3 fluoroethylene copolymer, ethylene-4 fluoroethylene copolymer, propylene-4 fluoroethylene copolymer, and the like. Further, a fluorine-containing polymer in which hydrogen in the main chain is replaced with an alkyl group can also be used. In the case of polyvinylidene fluoride, the F / C is 1, and in the case of vinylidene fluoride-3 fluoroethylene copolymer, the F / C is 50% and 50%, respectively, when the vinylidene fluoride mole fraction is 50%. 1.25 and 1.1, and in the case of propylene-4 fluoroethylene copolymer, the propylene mole fraction is 50%.
At that time, the F / C is 0.75. Among them, polyvinylidene fluoride and a vinylidene fluoride-3 fluoroethylene copolymer having a molar fraction of vinylidene fluoride of 50% or more are preferable, and polyvinylidene fluoride is practically preferable. When these binders are used, the dope capacity (capacity) of lithium that PAS has can be fully utilized.

As the positive electrode of the organic electrolyte battery of the present invention,
For example, Li _X CoO _2, Li _X NiO _2, Li _X Mn
O _2, Li _X FeO _2, etc. Li _X M _y O _Z (M is a metal,
Lithium-containing metal oxide capable of electrochemically doping or dedoping lithium, or a transition metal oxide such as cobalt, manganese, or nickel, which can be represented by the general formula Use things. Particularly, a lithium-containing oxide having a voltage of 4 V or more with respect to lithium metal is preferable. Of these, lithium-containing cobalt oxide and lithium-containing nickel oxide are preferable. The positive electrode in the present invention is
The active material and, if necessary, a conductive material and a binder are added and molded, and the types and compositions of the conductive material and the binder may be appropriately set.

The kind of the conductive agent may be a metal powder such as metallic nickel, but carbon-based ones such as activated carbon, carbon black, acetylene black and graphite are particularly preferable. The mixing ratio varies depending on the electric conductivity of the active material, the shape of the electrode, etc., but it is appropriate to add 2 to 40% to the active material. Further, the kind of binder may be one that is insoluble in the electrolytic solution used in the present invention described later, for example, a rubber-based binder such as SBR, a fluorine-containing resin such as polytetrafluoroethylene, polyvinylidene fluoride, Thermoplastic resins such as polypropylene and polyethylene are preferable, and the mixing ratio thereof is preferably 20% or less.

The shape of the positive and negative electrodes used in the present invention is as follows:
Depending on the intended battery, various shapes such as a plate shape, a film shape, a column shape, or molding on a metal foil can be adopted. In particular, the one formed on a metal foil is preferable as it can be applied to various batteries as a collector-integrated electrode.

The battery of the present invention can be remarkably improved in capacity as compared with a conventional battery by using the above PAS as a negative electrode and appropriately controlling the amount of lithium contained in the battery. In the present invention, the total amount of lithium in the battery is the total amount of lithium derived from the positive electrode, lithium derived from the electrolytic solution, and lithium derived from the negative electrode. The lithium derived from the positive electrode is lithium contained in the positive electrode during battery assembly, and a part or all of the lithium is supplied to the negative electrode by an operation (charging or the like) of passing a current from an external circuit. The lithium derived from the electrolytic solution is lithium in the electrolytic solution contained in the separator, the positive electrode, the negative electrode and the like. In addition, the lithium derived from the negative electrode is lithium supported on the negative electrode PAS of the present invention (lithium derived from the positive electrode, lithium other than lithium derived from the electrolytic solution). In the present invention, the method of supporting lithium on the negative electrode PAS is, for example, before the battery is assembled,
Lithium can be preliminarily loaded on the negative electrode PAS by applying a constant current, applying a constant voltage, or a combination thereof in an electrochemical cell having a lithium metal counter electrode. At this time, what is important is that the potential of the lithium metal is applied to the negative electrode PAS at least once with respect to the potential of the lithium metal. The applied voltage depends on the target amount of lithium derived from the negative electrode, PAS, type and shape of electrode, type and shape of electrolytic cell, but is 0 mV with respect to the potential of lithium metal.
To -1000 mV are preferred, and -10 is more preferred.
mV to -300 mV. Importantly, it is permissible to choose a potential that is lower than that of the lithium metal, and in some cases, it is possible to initially support lithium at a potential below the potential of the lithium metal and gradually increase it. A method of increasing the voltage and finally ending at a positive potential, or a method of initially supporting at a positive potential and later supporting at a potential equal to or lower than the potential of lithium metal can be performed.

In the present invention, the total amount of lithium in the battery is
500 mAh / g or more, preferably 6 with respect to the negative electrode PAS
When the amount is 00 mAh / g or more and less than 500 mAh / g, sufficient capacity cannot be obtained. Further, the lithium derived from the negative electrode in the present invention is 100 mAh / g with respect to the negative electrode PAS.
Or more, preferably 150 mAh / g or more, and 100
If it is less than mAh / g, the total amount of lithium is negative electrode PA.
Even if it is 500 mAh / g or more with respect to S, a sufficient capacity cannot be obtained. Further, when a lithium-containing oxide is used for the positive electrode, the lithium derived from the negative electrode is the negative electrode PA.
It is practical to set S to 600 mAh / g or less. The lithium derived from the positive electrode and the lithium derived from the electrolytic solution in the present invention may satisfy the above conditions, but the lithium derived from the positive electrode is preferably 300 mAh / g or more based on the negative electrode PAS.

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 ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, acetonitrile, dimethoxyethane, tetrahydrofuran, dioxolane, methylene chloride, and sulfolane. Furthermore,
Mixtures of two or more of these aprotic organic solvents can also be used.

The electrolyte mixed or dissolved in a single solvent may be any electrolyte capable of producing lithium ions. As such an electrolyte, for example, Li
I, LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiP
F ₆ or LiHF ₂ may, for example, be mentioned. The above electrolyte and solvent are mixed in a sufficiently dehydrated state to form an electrolytic solution, and the concentration of the electrolyte in the electrolytic solution is at least 0.1 mol / l or more in order to reduce the internal resistance of the electrolytic solution. It is preferable that the amount is usually 0.2 to 1.5 mol / l.

Examples of the current collector for extracting the electric current to the outside of the battery include carbon, platinum, nickel, stainless steel,
Aluminum, copper or the like can be used, and when a foil-shaped or net-shaped current collector is used, it can be used as a current collector-integrated electrode by molding the electrode on the current collector.

Next, an example of an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating the basic configuration of a battery according to the present invention. In FIG. 1, (1) is a positive electrode and (2) is a negative electrode. Current collectors (3) and (3 ') are connected to the electrodes 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 a dopable ion is dissolved in an aprotic organic solvent. The electrolytic solution is usually liquid, but it may be used in the form of gel or solid 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 porous body having no continuous electron-permeation holes, which has durability to the electrolytic solution or the electrode active material, and is usually a cloth or non-woven fabric made of glass fiber, polyethylene or polypropylene. Alternatively, a porous body is used. The thickness of the separator is preferably thin to reduce the internal resistance of the battery, but the amount of electrolyte retained, flowability,
It is decided in consideration of strength etc. The positive and negative electrodes and the separator are fixed in the battery case (6) so that there is no practical problem. The shape and size of the electrode are appropriately determined according to the shape and performance of the target battery. Examples of the battery shape of the present invention include a coin shape, a cylinder shape, a square shape, and a box shape, which satisfy the above basic configuration, and the shape thereof is not particularly limited.

[0020]

INDUSTRIAL APPLICABILITY The organic electrolyte battery of the present invention uses PA as the negative electrode.
S, a metal oxide is used for the positive electrode, both the amount of lithium in the battery and the amount of lithium derived from the negative electrode PAS are appropriately controlled, and a method for supporting lithium derived from the negative electrode PAS is selected to facilitate production. It is a high capacity and high voltage battery. Hereinafter, the present invention will be specifically described with reference to examples.

[0021]

Example 1 A phenol resin molded plate having a thickness of 0.5 mm was placed in a silicon knit electric furnace, heated in a nitrogen atmosphere at a rate of 10 ° C./hour, and heat-treated to 650 ° C. to form an insoluble and infusible substrate. (Denoted as PAS) was synthesized. P thus obtained
A PAS powder having an average particle size of about 15 μm was obtained by grinding the AS plate with a disk mill. The H / C ratio was 0.22. Next, 100 parts by weight of the above PAS powder and 100 parts by weight of a solution prepared by dissolving 10 parts by weight of polyvinylidene fluoride powder in 90 parts by weight of N, N-dimethylformamide were sufficiently mixed to obtain a slurry. The slurry was applied on a copper foil (negative electrode current collector) having a thickness of 10 μm using an applicator, dried and pressed to obtain a PAS negative electrode having a thickness of 210 μm in which PAS was applied on both sides. Commercial LiCoO
_{2 to} 100 parts (made by Strem Co.) and 5 parts of graphite,
A slurry was obtained by sufficiently mixing 10 parts by weight of polyvinylidene fluoride powder and 50 parts by weight of a solution dissolved in 90 parts by weight of N, N-dimethylformamide. The slurry
Is coated on an aluminum foil (positive electrode current collector) having a thickness of 20 μm using an applicator, dried and pressed, and LiCo is coated on both sides.
A positive electrode 1 having a thickness of 280 μm coated with O ₂ was obtained.

Lithium is used as a counter electrode for the negative electrode, and the electrolyte solution contains propylene carbonate and diethyl carbonate at a ratio of 1 :.
1 (weight ratio) liquid mixture to a concentration of 1 mol / l LiPF ₆
An electrolytic cell having a lithium reference electrode was assembled using a solution in which was dissolved. For the lithium reference electrode, the PAS negative electrode is
+20 mV, 0 mV, -20 mV, -50 mV, -10
A constant voltage is applied so that it becomes 0 mV, and 300 mAh /
The time during which g (lithium derived from the negative electrode) can be supported was measured. The results are shown in Table 1. The above positive electrode 1 and negative electrode (both are 1
× 1 cm ² ) and a battery as shown in FIG. 1 was assembled. A 25 μm thick polypropylene separator was used as the separator. The total amount of lithium with respect to the negative electrode PAS in the battery was 1040 mAh / g. 0.
It is charged at a constant current of 25 mAh until the battery voltage reaches 4.3 V, and then at a constant current of 0.25 mAh, the battery voltage is 2.
It discharged until it became 5V. This 4.3V-2.5V cycle was repeated, and the volume capacity (mAh / cc) was evaluated in the third discharge. As the volume reference, the total of the electrode volume, the separator volume, and the current collector volume was used.
The results are shown in Table 1.

[0023]

[Table 1]

[0024]

Comparative Example 1 In Example 1, lithium metal (about 20
0 μm) was attached to a negative electrode PAS, sandwiched between polypropylene plates having a thickness of 2 mm, and lithium derived from the negative electrode was supported in the same electrolytic solution as in Example 1. When the lithium metal was peeled off from the PAS negative electrode in about 40 minutes, 300
It was possible to dope mAh / g of lithium. It takes more time than when a negative voltage is applied.

[0025]

Comparative Example 2 In Example 1, the negative electrode PAS was made to carry lithium derived from the negative electrode by short-circuiting the counter electrode lithium metal (about 200 μm) and the negative electrode PAS. It was possible to dope 300 mAh / g lithium in about 35 minutes. It takes more time than when a negative voltage is applied.

[0026]

[Comparative Example 3] A 0.5 mm-thick phenol resin molded plate was placed in a siliconit electric furnace, heated at a rate of 10 ° C / hour in a nitrogen atmosphere, and heat-treated to 1000 ° C to obtain a carbonaceous material. It was The PAS plate thus obtained was pulverized with a disc mill to obtain a carbonaceous material powder having an average particle size of about 13 μm. The H / C ratio was 0.02. The carbonaceous material was used as an electrode in the same manner as in Example 1, and lithium derived from the negative electrode was loaded with lithium in the same manner as in Example 1.
+20 mV, loading time is 50 minutes, 0
In the case of mV, the time required for loading is 45 minutes and is -20
When mV, -50 mV, and -100 mV were applied, lithium metal was deposited on the negative electrode carbon material. When left as it was, the lithium metal disappeared after about 30 hours, but it cannot be said to be practical as a method for supporting lithium derived from the negative electrode. A battery similar to that of Example 1 was assembled using the negative electrode prepared at +20 mV and evaluated. After 3 cycles, a large amount of lithium metal was deposited on the negative electrode.

[Brief description of 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 2 Negative electrode 3, 3'collector 4 Electrolyte solution 5 Separator 6 Battery case 7, 7'External terminal

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Noriyuki Hato, No. 6 2-305, Tomobuchi-cho, Miyakojima-ku, Osaka (72) Inventor Shizuka Yada 2-6-13 Miyanishi, Harima-cho, Kako-gun, Hyogo Prefecture

Claims (2)

[Claims] 1. An organic electrolyte battery comprising a positive electrode, a negative electrode and an aprotic organic solvent solution of a lithium salt as an electrolytic solution, wherein (1) the positive electrode contains a metal oxide and (2) the negative electrode is an aromatic condensation. (3) Negative electrode P, which is a heat-treated polymer and is an insoluble and infusible substrate having a polyacene-based skeleton structure in which the atomic ratio of hydrogen atoms / carbon atoms is 0.5 to 0.05.
The total amount of lithium contained in the battery is 500 m compared to AS
Ah / g or more and the amount of lithium derived from the negative electrode is 100
An organic electrolyte battery characterized in that lithium derived from a negative electrode, which is mAh / g or more, is electrochemically supported by applying a potential lower than that of Li metal. 2. The organic electrolyte battery according to claim 1, wherein a lithium-containing metal oxide is used as a positive electrode.