JPH06283206A - Microcapsule contained battery - Google Patents

Abstract

PURPOSE:To provide a lithium secondary battery which has high safety and high energy density. CONSTITUTION:A lithium secondary battery consists of, at least, a negative electrode active material 101, a separator 108, a positive electrode active material 103, electrolyte 105, collectors 102, 107 and a battery case 109. Microcapsules are dispersed into the electrolyte or the separator to release chemical substances with hydroxyl groups or chemical substrates as polymerization initiator when temperature rise occurs in the battery. In this way, the lithium secondary battery can be manufactured which has high energy density and safety even after charge and discharge are repeated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery having improved safety, and more particularly to a secondary battery having high safety and high energy density.

[0002]

2. Description of the Related Art Recently, it is predicted that global warming will occur due to the greenhouse effect due to an increase in CO ₂ , and it will become difficult to construct a new thermal power plant. It has been devised to carry out so-called load leveling, in which a load is stored in a secondary battery installed in a general household and the load is leveled and used efficiently. In addition, there is a demand for the development of small, lightweight, high energy density secondary batteries for electric vehicles that do not emit air pollutants, and high performance as a power source for portable devices such as book-type personal computers, word processors, video cameras and mobile phones. The demand for such secondary batteries is increasing.

As the above high performance secondary battery, a rocking chair type lithium ion battery in which lithium ion is introduced into an intercalation compound as a positive electrode active material and carbon as a negative electrode active material has been developed and partially put into practical use. It's starting. However, a lithium ion battery has a lower energy density than a lithium battery using metallic lithium as a negative electrode active material.

The reason why high-capacity lithium storage batteries using lithium metal for the negative electrode have not yet been put to practical use has been successful in suppressing the generation of lithium dendrites, which are the main cause of short circuits due to repeated charging and discharging. It seems that there is no. As lithium dendrites grow,
Since the negative electrode and the positive electrode are short-circuited and the energy of the battery is consumed in a short time, heat is generated, the solvent of the electrolyte solution is decomposed and gas is generated, which may cause an internal pressure to be high and explode after all. There is a problem that such an accident rarely occurs. Therefore, it is desired to develop a safe lithium storage battery that does not cause the above accident.

Further, it is desired to develop a safe battery which does not cause the above-mentioned accident even in a battery which may be ignited by a chemical reaction.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned conventional problems, to provide a highly safe battery, and to provide a highly safe and high energy density lithium secondary battery.

[0007]

The present inventor has conducted extensive studies to solve the above conventional problems, and as a result, the temperature of a chemical substance that reacts with lithium rises in the electrolyte solution (electrolyte solution) of a lithium battery. By including microcapsules that are released when the battery is discharged, it is possible to decompose the dendrite of lithium that has grown to a short-circuit state by repeating charge and discharge, release the short-circuit state, and prevent energy from being consumed and ignition or explosion to occur in a short time. I found it reusable. In addition, by including microcapsules that release a chemical substance that causes a curing reaction such as a polymerization reaction or a cross-linking reaction when the temperature rises, the electrolyte is solidified when the temperature rises to an abnormal temperature. It has been found that the internal resistance can be increased to prevent energy from being consumed in a short period of time, resulting in ignition or rupture.

The present invention has a negative electrode having a negative electrode active material, a positive electrode having a positive electrode active material sandwiching the negative electrode active material and a separator, and an electrolyte solution between the negative electrode and the positive electrode, and the separator. And / or a microcapsule-containing battery characterized by having microcapsules containing a chemical substance in an electrolyte solution. Further, the microcapsule-containing battery is a microcapsule-containing battery that is a lithium secondary battery, the chemical substance is a microcapsule-containing battery having at least a compound having a hydroxyl group, the chemical substance, polymerization initiation A microcapsule-containing battery having at least an agent or a cross-linking agent, wherein the micro-capsule contains at least one or more selected from a monomer, an olegomer, and a polymer in addition to a polymerization initiator or a cross-linking agent. The battery is a containing battery, the chemical substance is a microcapsule-containing battery having at least an acid, the microcapsule is a microcapsule-containing battery having at least a flame retardant, the negative electrode active material The surface of the negative electrode composed of the A microcapsule-containing battery that is coated with a coating that passes over, the surface of the positive electrode made of the positive electrode active material facing the negative electrode is a microcapsule-containing battery that is coated with a coating that transmits at least lithium ions, and A microcapsule-containing battery whose film is a flame-retardant material or a non-combustible material, and the negative electrode active material is lithium or a lithium alloy.

Further, the melting point of the microcapsules is 70.
A microcapsule-containing battery having a temperature of ~ 150 ° C,
In addition, the microcapsule is a microcapsule-containing battery in which the size is 1 to 500 μm, and the mixing amount of the microcapsule is 1 to 2 with respect to the electrolyte solution.
It is a battery containing 0% by weight of microcapsules.

By putting the above-mentioned chemical substance monomers, olegomers, and polymers in the microcapsules, it becomes easy to increase the internal resistance of the battery when the temperature of the battery rises abnormally. In addition, by putting a flame retardant in the microcapsules, it becomes possible to further suppress ignition when the battery temperature rises abnormally.

(Battery Structure) FIG. 1 shows a basic structure of the secondary battery of the present invention. In FIG. 1, 101 is a negative electrode made of a negative electrode active material, 102 is a negative electrode current collector, 103 is a positive electrode made of a positive electrode active material, 104 is a positive electrode current collector, 105 is an electrolyte solution (electrolyte solution), 106 is a negative electrode terminal, 107 is a positive electrode terminal, 108 is a separator, 109 is a battery case, 1
Reference numeral 10 is a microcapsule containing a chemical substance.

(Battery Reaction) In a lithium battery in which the negative electrode active material of the negative electrode 101 is lithium or a lithium alloy,
During the discharge reaction, lithium ions in the electrolytic solution 105 permeate the separator 108 and enter the layers of the positive electrode active material of the positive electrode 103, and at the same time, lithium ions are dissolved in the electrolyte 105 from the negative electrode active material. On the other hand, in the charging reaction, lithium ions in the electrolytic solution 105 permeate the separator 108 to be deposited as lithium metal on the negative electrode active material (at this time, dendrites easily grow), and at the same time, lithium ions between the positive electrode active material 103 layers of the positive electrode are separated. It dissolves in the electrolyte 105.

(Heat generation of battery) When the dendrite grows and short-circuits inside the battery, when the battery is damaged and short-circuited,
When a short circuit occurs, such as when an external circuit connected to the battery is short-circuited, the battery will generate heat. In the battery of the present invention, when the temperature of the battery rises, the microcapsules in the battery are melted or broken and opened to release the chemical substance. When the released chemical substance is a substance that reacts with lithium, the lithium in the short circuit part reacts and is removed to release the short circuit, or an insulating reaction product is formed on the lithium surface and the internal resistance of the battery As a result, the current is reduced and excessive heat generation is suppressed. When the lithium in the short circuit portion reacts and is removed and the short circuit is released, the lithium battery can be used again.
If the released chemical is a radical generator,
When the temperature rises to the decomposition temperature of the radical generator, the polymerization reaction of the solvent of the electrolytic solution and the like occurs in the battery, and the internal resistance of the battery increases, so that the current decreases and excessive heat generation is suppressed.

The above-mentioned safety technique using the microcapsules of the present invention is effective not only in the secondary battery but also in various primary batteries as long as they are generated by heat or the microcapsules are opened.

Chemical Substance Reacting with Lithium Examples of the chemical substance reacting with lithium used in the present invention include a compound having a hydroxyl group and an acid. A compound having a hydroxyl group and an acid are appropriately mixed and used according to the material of the microcapsule and the structure of the battery. Examples of the compound having a hydroxyl group include water, alcohol, glycol, glycerin and the like.

As the alcohol, methyl alcohol, ethyl alcohol, and higher alcohols such as ceryl alcohol can be used. As the glycol, ethylene glycol, propylene glycol, 1,10-decanediol and the like can be used. As the acid, an inorganic acid such as hydrochloric acid, an organic acid such as acetic acid or a fatty acid can be used.

Since the above chemical substances generate hydrogen when reacting with lithium, even if the internal pressure of the battery rises due to the generated hydrogen, the reaction with lithium does not occur so that the safety valve provided in the battery can follow and operate. It is necessary to select the type and concentration of slowly progressing chemical substances.

Chemical Substance that Causes Polymerization or Cross- Linking Reaction As another example of the chemical substance that reacts with lithium used in the present invention, a radical generator that generates radicals by thermal decomposition can be used. The radical generator causes a polymerization reaction and a cross-linking reaction. As the radical generator, peroxide,
There are azo compounds and metal compounds, and specific examples include benzoyl peroxide, azobisisobutyronitrile,
And so on.

[0019] The wall film material of the microcapsule microcapsules, when the battery reaches a abnormal temperature, opened solved or microcapsules is broken, use a material capable of releasing the chemicals. Specific materials include linear polyethylene, olefins such as olefins, poly-benzylidene thiodecamethylene sulfide, poly-1,2-cyclohexylene sulfide, poly-cyclopropylene dimethylene terephthalate, poly-decamethylene phthalamide. , Poly-ethylene 2,2'-dibenzoate, poly- (oxydiethylene) -oxy-p-phenylene oxide, calcium stearate, carnauba wax and the like can be used. The olegomers of the above olefins include olego (methylene),
Repeating units such as olego (ethylene), olego (cyclme alkane), olego (perfluoro-n-alkane), olego (ω-chloro-perfluoro-n-alkane), olego (semi-fluorinated n-alkane), etc. It can be used with a value of 10 to 500.

As the material for the wall film of the microcapsules, it is necessary to select a material that is insoluble in the electrolytic solution of the battery. It is also necessary to select the wall film material from the material melting points in accordance with the maximum temperature at which battery safety can be maintained.

The melting point of the wall film material of the microcapsules is preferably selected from the range of 70 to 150 ° C., and more preferably selected from the range of 100 to 130 ° C.

The size of the microcapsules and the amount of the microcapsules maintain the safety without deteriorating the battery performance. Therefore, the size of the microcapsules is preferably 1 to 500 μm, more preferably 5 to 50 μm. It is the size. The amount of microcapsules mixed is preferably 1 to 20% by weight with respect to the electrolyte solution.

(Microencapsulation of Chemical Substance) As an example of the method of microencapsulating the chemical substance, the chemical substance is directly added to a solution in which the wall film material of the microcapsule is dissolved in a solvent, or the wall film of the microcapsule. After adding and dispersing a chemical substance dissolved in a solvent in which the material does not dissolve, drop the dispersion into a solvent such as water or alcohol while stirring, filter or centrifuge, and dry under reduced pressure to remove the chemical substance-containing microbe. There is a method of preparing capsules. In addition to the aforementioned chemical substances, monomers and flame retardants may be mixed in the microcapsules.

Flame Retardant In addition to the above chemical substances, the microcapsules may contain a flame retardant. By using the flame retardant, it is possible to suppress ignition of the electrolytic solution when the battery heats up.

As the flame retardant, a phosphorus-based flame retardant which is a phosphorus compound, a halogen-based flame retardant of iodine, bromine, chlorine, a halogen compound, a flame retardant containing phosphorus and a halogen element, and the like can be used. . The halogen-based flame retardant is particularly effective because perfluorocarbon, which is a fluorine compound inert liquid, does not affect the electrolytic reaction.

The above-mentioned perfluorocarbon is C _{5
F 12, C 6 F 14,} C 7 F 16, C 8 F 18, perfluorobutyl tetrahydrofuran: C ₈ F ₁₆ O, _{perfluorotributylamine: (C 4 F 9) 3} N, perfluorotripropylamine :( C ₃ F _{7) 3} N, perfluorooctanol Rinei Incorporated ether, perfluoro methyl decalin, perfluorodecalin, and the like.

Examples of the phosphorus-based flame retardant include red phosphorus, trimethyl phosphate, triethyl phosphate, tris (chloroethyl) phosphate, tri (dichloropropyl) phosphate, and the like.

Current collectors Current collector materials include carbon, stainless steel,
Conductive materials such as titanium, nickel, copper, platinum and gold are used. As the shape of the current collector, a fibrous shape, a porous shape or a mesh shape can be used.

Positive Electrode A positive electrode is formed by mixing a positive electrode active material, a conductive powder and a binder, adding a solvent if necessary, and molding the current collector.

[Positive Electrode Active Material] As the positive electrode active material, metal oxides such as nickel oxide, cobalt oxide, titanium oxide, iron oxide, vanadium oxide, manganese oxide, molybdenum oxide, chromium oxide, and tungsten oxide in which lithium is intercalated. Compounds, metal sulfides such as molybdenum sulfide, iron sulfide and titanium sulfide, hydroxides such as iron oxyhydroxide, and conductive polymers such as polyacetylene, polyaniline, polypyrrole and polythiophene.

Here, the metal element of the metal oxide or metal sulfide is a transition metal element having a partial d-shell or f-shell, and includes Sc, Y, lanthanoids, actinides, and T.
i, Zr, Hf, V, Nb, Ta, Cr, Mo, W, M
n, Tc, Re, Fe, Ru, Os, Co, Rh, I
r, Ni, Pd, Pt, Cu, Ag, and Au are used. Mainly, Ti, V, Cr, Mn, and F of the first transition series metals
e, Co, Ni, Cu are used.

The role of conductor powder conductive powder, when the active material is poor conductivity, to assist electron conduction is to facilitate current collection.

As the conductor powder, acetylene black,
Various carbon materials such as Ketjen black and graphite powder, and metal materials such as nickel, titanium, copper and stainless steel can be used. The weight mixing ratio of the conductor powder to the active material is preferably 1 or less.

Binder The binder has a role of adhering the active material powders to each other when the moldability of the active material is poor, and preventing the active material powders from cracking and falling off from the current collector during charge / discharge cycles. ing. Examples of the binder material include solvent-stable fluororesins, polyethylene, polypropylene, and silicone resins. When the above resin is in a liquid or solution form or has a low melting point, the content of the binder in the electrode can be reduced, and the capacity of the battery can be improved. Specific examples of the resin that is liquid or soluble in a solvent include, in addition to polyethylene and polypropylene, fluororesins and silicone resins having an ether bond. In particular, when a fluororesin having an ether bond is used, it can be dissolved in a solvent and used at a low concentration, so that the content in the positive electrode can be reduced and the porosity can be increased.

Negative Electrode Active Material As the negative electrode active material, lithium or lithium alloy,
And so on. Examples of the lithium alloy include alloys of magnesium, aluminum, potassium, sodium, calcium, zinc, lead, and the like with lithium.

Separator The separator has a role of preventing a short circuit between the negative electrode and the positive electrode. It may also have a role of holding the electrolytic solution. Since the separator has pores through which the ions involved in the battery reaction can move and must be insoluble and stable in the electrolytic solution, a non-woven fabric such as glass, polypropylene, polyethylene, or fluororesin or a material with a micropore structure is used. Has been. Further, a metal oxide film having fine pores or a resin film in which a metal oxide is composited can also be used. In particular, when a metal oxide film having a multi-layered structure is used, it is difficult for dendrites to penetrate, which is effective in preventing short circuits. When a fluororesin film which is a flame retardant material or a glass or metal oxide film which is a nonflammable material is used, the safety can be further enhanced.

[0037] The electrolyte electrolyte in addition to the case of using as it is, to use those immobilized by adding a gelling agent such as a solution or solution polymer dissolved in a solvent. Usually, an electrolyte solution (electrolyte solution) in which an electrolyte is dissolved in a solvent is used while being retained in a porous separator.

The higher the conductivity of the electrolyte or the electrolytic solution, the more preferable, and the conductivity at least at 25 ° C. is 1 × 1.
It is preferably 0 ^-3 S / cm or more, 5 × 10 ^-3 S / cm
More preferably, it is at least cm.

The electrolyte contains lithium ions (Li ⁺ ) and Lewis acid ions (BF ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , Cl).
O ₄ ^- salt consisting of), and use of these mixed salts. In addition to the above supporting electrolyte, a salt of a cation such as sodium ion, potassium ion, tetraalkylammonium ion and Lewis acid ion can also be used. It is desirable that the salt be heated under reduced pressure to be sufficiently dehydrated and deoxidized.

As the solvent of the electrolyte, acetonitrile,
Benzonitrile, propylene carbonate, ethylene carbonate, dimethylformamide, tetrahydrofuran, nitrobenzene, dichloroethane, diethoxyethane, chlorobenzene, γ-butyrolactone, dioxolane, sulfolane, nitromethane, dimethylsulfide, dimethylsulfoxide, dimethoxyethane, methyl formate, 3-methyl. -2-Oxazolidinone, 2-methyltetrahydrofuran, sulfur dioxide, phosphoryl chloride,
Thionyl chloride, sulfuryl chloride, etc., and mixtures thereof can be used.

The solvent is dehydrated with activated alumina, molecular sieves, phosphorus pentoxide, calcium chloride or the like, or depending on the solvent, it is distilled in an inert gas in the presence of an alkali metal to remove impurities and dehydrate. Is good.

Gelation is desirable in order to prevent leakage of the electrolytic solution. As the gelling agent, it is desirable to use a polymer that absorbs the solvent of the electrolytic solution and swells,
Polymers such as polyethylene oxide, polyvinyl alcohol and polyacrylamide are used.

(Coating of Negative Electrode or Positive Electrode) When the negative electrode active material is lithium, dendrite, which causes a short circuit, occurs during charging. To prevent this, the negative electrode or the positive electrode or the surface of the negative electrode and the positive electrode is prevented. It is possible to extend the cycle life of the battery by coating with a film that allows lithium ions to permeate.

As the coating material, a polymer of a macrocyclic compound derivative, a polymer of an aromatic hydrocarbon derivative, a fluororesin, a silicone resin, a titanium resin, a polyolefin, or an inorganic oxide, a nitride, a carbide or a halide can be used. . Covering with a flame-retardant material or a non-combustible material such as a fluororesin, polyphosphazene, an inorganic oxide, a nitride, a carbide, or a halide is effective for further improving the safety of the lithium secondary battery.

(Battery Shape and Structure) Actual battery shapes include flat type, cylindrical type, rectangular type and sheet type batteries. In the spiral cylindrical type, the electrode area can be increased by winding a separator between the negative electrode and the positive electrode, and a large current can be passed during charging and discharging. Further, in the rectangular parallelepiped type, it is possible to effectively use the storage space of the device that stores the secondary battery. As for the structure, there are structures such as a single layer type and a multilayer type.

2 and 3 are examples of schematic sectional views of a single-layer flat type battery and a spiral structure cylindrical battery, respectively. 2 and 3, 201 and 301 are negative electrodes made of a negative electrode active material, 202 and 302 are negative electrode current collectors, 203 and 303 are positive electrodes made of a positive electrode active material, 304 is a positive electrode current collector, and 206 and 306 are negative electrodes. Terminal (negative electrode cap), 20
Reference numerals 7 and 307 denote outer case (positive electrode can) and battery case, 208 and 308 are separators holding microcapsules containing a chemical substance and an electrolytic solution, 210 and 310 are insulating packings, and 311 is an insulating plate.

As an example of assembling the battery shown in FIGS. 2 and 3,
After the separators 208 and 308 are sandwiched between the negative electrodes 201 and 301 and the positive electrodes 203 and 303, they are incorporated into positive electrode cans 207 and 307, and an electrolyte solution in which microcapsules containing a chemical substance are dispersed is injected, and then negative electrode caps 206 and 306.
The insulating packings 210 and 310 are assembled and caulked to produce a battery.

The preparation of the lithium battery material and the assembly of the battery are preferably carried out in dry air from which water has been sufficiently removed or in a dry inert gas.

Battery Case (Exterior Can) As the battery case, a plastic resin material case can be used as well as a metal external can that also serves as an output terminal.

As the material of the positive electrode cans 207 and 307 and the negative electrode caps 206 and 306 of the actual battery, stainless steel, particularly titanium clad stainless steel, copper clad stainless steel, nickel plated steel plate and the like are used.

2 and 3, the positive electrode cans 207 and 307 also serve as the battery case, but as the material of the battery case,
In addition to stainless steel, aluminum and other metals,
A plastic such as polypropylene or a composite material of metal or glass fiber and plastic can be used.

[0052] As the material for the insulating packing insulating packing 210 and 310, fluorine resins, polyamide resins, polysulfone resins, and various rubbers can be used.

[0053] As the sealing sealing method, in addition to caulking using a gasket such as insulating packing also adhesives, welding, soldering, methods such as glass sealing tube is used.

[0054] As the material of the insulating plate 311 used for the insulating isolation within the insulation board battery, various organic resin materials and ceramics are used.

Safety valve Although not shown in FIGS. 2 and 3, as a safety measure when the internal pressure of the battery increases, a safety valve using rubber, springs, metal balls or the like is provided.

(Battery safety evaluation) As a battery safety evaluation test, a short circuit test was conducted at 25 ° C. and 85 ° C., after charging, the positive electrode and the negative electrode were short-circuited with a copper wire to ignite even if the battery temperature increased. Confirmation test for the presence of. Nailing test A charged battery is penetrated by a nail with a diameter of 3 mm to confirm whether or not it bursts or ignites even when the battery temperature rises. Combustion test A test to confirm that violent combustion does not occur by dropping a charged battery during carbonization. Immersion test in water A test to confirm that no rupture or ignition occurs by immersing in tap water at a temperature of 25 ° C for 14 days. High temperature storage test Store the battery at 100 ℃ for 5 hours and the battery temperature is 13
Confirmation test that the temperature does not rise above 0 ° C and that there is no smoke, burst, or ignition. Terminal voltage 5.0V at 10 hours overcharge rate, 24 at cutoff
A test to confirm that there is no ignition even if the battery temperature rises after charging for an hour. And

[0057]

EXAMPLES The present invention will be described in detail below based on examples. The present invention is not limited to these examples.

Example 1 First, microcapsules were prepared by the following method using linear polyethylene as the wall covering material of the capsule and 1,4-butanediol as the chemical substance. A solution prepared by dropping 1,4-butanediol into a linear polyethylene xylene solution was dropped into ethyl alcohol to prepare a microcapsule colloidal ethyl alcohol solution. The obtained colloidal solution was separated and filtered, and then dried under reduced pressure to prepare microcapsules.

Next, a lithium secondary battery having the schematic cross-sectional structure shown in FIG. 3 was produced.

As the positive electrode active material, electrolytic manganese dioxide and lithium carbonate were mixed at a ratio of 1: 0.4, and then 80
A lithium-manganese oxide was prepared by heating at 0 ° C.
The prepared lithium-manganese oxide was mixed with graphite and powder fluororesin paint Super Konak (made by NOF CORPORATION), and then pressure-molded on nickel mesh 304 to obtain 170.
The positive electrode 303 was formed by performing a heat treatment at ℃.

In a dry argon gas atmosphere, a titanium mesh current collector 30 with leads was attached to the lithium metal foil from the back side.
2 was pressure-bonded and further coated with a fluororesin paint Lumiflon thin film (manufactured by Asahi Glass Co., Ltd.) to prepare a lithium negative electrode 301. The electrolytic solution was prepared by dissolving 1 M (mol / l) of lithium tetrafluoroborate salt in a mixed solvent of propylene carbonate (PC) and dimethoxyethane (DME) in an equal amount,
10% by weight of the microcapsules prepared by the above method were mixed to prepare a microcapsule dispersion liquid.

As the separator 308, a sandwich of an alumina film, a polypropylene non-woven fabric and a polypropylene fine hole separator was used.

Assembling was performed by sandwiching and winding a separator 308 between a negative electrode 301 and a positive electrode 303, and then inserting it into a positive electrode can 307 made of a titanium clad stainless material and connecting a current collecting lead to an electrolytic solution in which microcapsules were dispersed. After the injection, was sealed with a negative electrode cap 306 made of a titanium clad stainless material with a safety valve and an insulating packing 310 made of fluororubber to produce a spiral cylindrical lithium secondary battery.

Example 2 Orego (semi-fluorinated n-alkane): F- [CF ₂ ] _m- [CH ₂ ] _n -H was added to the capsule wall film material.
Microcapsules of (m = 12, n = 20) were prepared by the following method using azobisisobutyronitrile as a chemical substance. Orego (semi-fluorinated n-
A solution prepared by adding azobisisobutyronitrile to a dimethyl sulfoxide solution of alkane) was added dropwise to ethyl alcohol to prepare a colloidal ethyl alcohol solution of microcapsules. The obtained colloidal solution was separated and filtered, and then dried under reduced pressure to prepare microcapsules.

In the same manner as in Example 1, the spiral cylindrical lithium secondary battery shown in FIG. 3 was produced.

As the positive electrode active material, electrolytic manganese dioxide and lithium carbonate were mixed at a ratio of 1: 0.4, and then 80
A lithium-manganese oxide was prepared by heating at 0 ° C.
After the graphite and the tetrafluoroethylene powder were mixed with the prepared lithium-manganese oxide, the nickel mesh 304 was pressure-molded at 250 ° C. to form the positive electrode 303.

In a dry argon gas atmosphere, a titanium mesh current collector 30 with leads was attached to the lithium metal foil from the back side.
0 is pressure bonded, and then polyphosphazene PPZ-R100
1 thin film (manufactured by Idemitsu Petrochemical Co., Ltd.) was coated to prepare a lithium negative electrode 301. The electrolytic solution was prepared by dissolving 1M (mol / l) of lithium tetrafluoroborate salt in a mixed solvent of propylene carbonate (PC) and dimethoxyethane (DME) in an equal amount, and the microcapsules prepared by the above method. 3% by weight was mixed to prepare a microcapsule dispersion liquid.

As the separator 308, a sandwich of polypropylene non-woven fabric and polypropylene micropore separator was used.

Assembling was carried out by sandwiching a separator 308 between a negative electrode 301 and a positive electrode 303, inserting the separator 308 into a positive electrode can 307 made of a titanium clad stainless material, connecting a current collecting lead, and connecting a microcapsule to an electrolytic solution. After injecting, was sealed with a negative electrode cap 306 made of a titanium clad stainless material with a safety valve and an insulating packing 310 made of fluororubber to manufacture a lithium secondary battery.

Example 3 Orego (ethylene): H [CH ₂ ] _n was added to the capsule wall film material.
Microcapsules of H (n = 288) were prepared by the following method using cyclohexanol as a chemical substance. A solution prepared by adding cyclohexanol and red phosphorus to a xylene solution of Orego (ethylene) was dropped into ethyl alcohol to prepare a colloidal ethyl alcohol solution of microcapsules. The obtained colloidal solution was separated and filtered, and then dried under reduced pressure to prepare microcapsules.

In the same manner as in Example 1, the spiral cylindrical lithium secondary battery shown in FIG. 3 was produced.

As the positive electrode active material, electrolytic manganese dioxide and lithium carbonate were mixed at a ratio of 1: 0.4, and then 80
A lithium-manganese oxide was prepared by heating at 0 ° C.
Acetylene black and tetrafluoroethylene powder were mixed with the prepared lithium-manganese oxide, and the nickel mesh 304 was pressure-molded at 250 ° C. to form the positive electrode 303.

In a dry argon gas atmosphere, a titanium metal current collector 30 with leads was attached to the lithium metal foil from the back side.
2 was pressure-bonded to prepare a lithium negative electrode 301. As the electrolytic solution, 1 M (mol / l) of tetrafluoroboric acid lithium salt was dissolved in an equal amount mixed solvent of propylene carbonate (PC) and dimethoxyethane (DME), and prepared by the above method. 5% by weight of the prepared microcapsules were mixed to prepare a microcapsule dispersion liquid.

As the separator 308, a sandwich of a titanium oxide film, a polypropylene non-woven fabric and a polypropylene fine hole separator was used.

Assembling was performed by sandwiching and winding a separator 308 between a negative electrode 301 and a positive electrode 303, inserting it into a positive electrode can 307 made of titanium clad stainless material, connecting a current collecting lead, and connecting a microcapsule to an electrolytic solution. After injecting, was sealed with a negative electrode cap 306 made of a titanium clad stainless material with a safety valve and an insulating packing 310 made of fluororubber to manufacture a lithium secondary battery.

Comparative Example 1 A lithium secondary battery was prepared in the same manner as in Example 3 except that the negative electrode was made of lithium foil in which microcapsules were not dispersed at all and surface treatment was not applied.

Example 4 Orego (semi-fluorinated n-alkane): F- [CF ₂ ] _m- [CH ₂ ] _n -H was added to the capsule wall film material.
Microcapsules of (m = 12, n = 20) were prepared by the following method using benzoyl peroxide as a chemical substance. A solution prepared by adding benzoyl peroxide to a dimethyl sulfoxide solution of Orego (semi-fluorinated n-alkane) was added dropwise to ethyl alcohol to prepare a colloidal ethyl alcohol solution of microcapsules. After separating and filtering the obtained colloidal solution,
Microcapsules were prepared by drying under reduced pressure.

In the same manner as in Example 1, the spiral cylindrical lithium secondary battery shown in FIG. 3 was produced.

As the positive electrode active material, electrolytic manganese dioxide and lithium carbonate were mixed at a ratio of 1: 0.4, and then 80
A lithium-manganese oxide was prepared by heating at 0 ° C.
Acetylene black and tetrafluoroethylene powder were mixed with the prepared lithium-manganese oxide, and the nickel mesh 304 was pressure-molded at 250 ° C. to form the positive electrode 303.

In a dry argon gas atmosphere, the titanium mesh current collector 30 with leads was attached to the lithium metal foil from the back side.
2 by pressure bonding, and then polyphosphazene PPZ-R100
1 thin film (manufactured by Idemitsu Petrochemical Co., Ltd.) was coated to prepare a lithium negative electrode 301. For the electrolytic solution, 1M (mol / l) of lithium tetrafluoroborate salt was added to an equal amount mixed solvent of propylene carbonate (PC) and dimethoxyethane (DME).
Using the dissolved product, 5% by weight of the microcapsule prepared by the above method was mixed to prepare a microcapsule dispersion liquid.

As the separator 308, a sandwich of a glass non-woven fabric, a polypropylene non-woven fabric and a polypropylene micro-hole separator was used.

Assembling was performed by sandwiching and winding a separator 308 between a negative electrode 301 and a positive electrode 303, inserting the separator 308 into a positive electrode can 307 made of a titanium clad stainless material, connecting a current collecting lead, and dispersing a microcapsule in an electrolytic solution. After injecting, was sealed with a negative electrode cap 306 made of a titanium clad stainless material with a safety valve and an insulating packing 310 made of fluororubber to manufacture a lithium secondary battery.

(Evaluation of Safety of Lithium Secondary Battery) Each lithium secondary battery produced in Examples 1, 2, 3, 4 and Comparative Example 1 was charged and discharged repeatedly for 20 cycles, and then the safety was evaluated. Was evaluated by the following test method. Good test results could be obtained for the lithium secondary batteries of any of the examples. Short circuit test After charging at 25 ° C and 85 ° C, the positive electrode and the negative electrode were short-circuited with a copper wire, and it was confirmed that the battery did not ignite even when the battery temperature increased. Nailing test A charged battery was penetrated with a nail having a diameter of 3 mm, and it was confirmed that the battery did not burst or ignite even when the battery temperature increased. Combustion test It was confirmed that no violent combustion occurred by dropping the charged battery during carbonization. Immersion test in water It was immersed in tap water at a temperature of 25 ° C. for 14 days, and it was confirmed that neither burst nor ignition occurred. High temperature storage test Store the battery at 100 ℃ for 5 hours and the battery temperature is 13
It was confirmed that the temperature did not rise above 0 ° C and that no smoke, rupture, or ignition occurred. Terminal voltage 5.0V at 10 hours overcharge rate, 24 at cutoff
After charging for an hour, it was confirmed that it did not ignite even when the battery temperature rose.

However, in Comparative Example 1, in the short circuit test, the temperature was 10 to 30 ° C. as compared with the batteries manufactured in Examples.
An abnormal temperature rise was observed. Further, in the overcharge test, some of the 10 batteries produced by the same method were found to emit smoke.

From the results of the above safety evaluation test, it is found that the lithium secondary battery of the present invention has high safety even after repeated charge and discharge, even though metallic lithium is used as the negative electrode active material. all right. Similarly, it was found that other batteries have high safety.

[0086]

According to the present invention, it is possible to supply a highly safe battery without danger of ignition. In addition, the charge and discharge can be repeated while maintaining safety at a high energy density using metallic lithium as the negative electrode active material. A lithium secondary battery can be supplied.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of a lithium secondary battery of the present invention.

FIG. 2 is a schematic cross-sectional view of a flat battery that is an embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view of a cylindrical battery that is another embodiment of the present invention.

[Explanation of symbols]

101,201,301 Negative electrode 102,202,302 Negative electrode current collector 103,203,303 Positive electrode 104,304 Positive electrode current collector 105 Electrolyte 106,206,306 Negative electrode terminal 107,207,307 Positive electrode terminal 108 Separator 208,308 Separator holding an electrolytic solution in which microcapsules are dispersed 109 Battery case 110 Microcapsules containing chemical substances 210, 310 Insulation packing 311 Insulation plate

Claims (14)

[Claims] 1. A negative electrode having a negative electrode active material, a positive electrode having a positive electrode active material sandwiching the negative electrode active material and a separator, and an electrolyte solution between the negative electrode and the positive electrode, and / or the separator. A microcapsule-containing battery characterized by having microcapsules containing a chemical substance in an electrolyte solution. 2. The microcapsule-containing battery according to claim 1, wherein the microcapsule-containing battery is a lithium secondary battery. 3. The microcapsule-containing battery according to claim 1, wherein the chemical substance has at least a compound having a hydroxyl group. 4. The microcapsule-containing battery according to claim 1, wherein the chemical substance has at least a polymerization initiator or a cross-linking agent. 5. The microcapsule-containing battery according to claim 4, wherein the microcapsule contains at least one or more selected from a monomer, an olegomer, and a polymer in addition to a polymerization initiator or a crosslinking agent. . 6. The microcapsule-containing battery according to claim 1, wherein the chemical substance includes at least an acid. 7. The microcapsule-containing battery according to claim 1, wherein the microcapsule contains at least a flame retardant. 8. The micro according to claim 1, wherein a surface of the negative electrode made of the negative electrode active material facing the positive electrode is coated with a film that transmits at least lithium ions. Capsule-containing battery. 9. The micro according to claim 1, wherein the surface of the positive electrode made of the positive electrode active material facing the negative electrode is coated with a film that transmits at least lithium ions. Capsule-containing battery. 10. The microcapsule-containing battery according to claim 8, wherein the film is made of a flame-retardant material or a non-combustible material. 11. The microcapsule-containing battery according to claim 1, wherein the negative electrode active material is lithium or a lithium alloy. 12. The melting point of the microcapsules is 70.
12. The microcapsule-containing battery according to any one of claims 1 to 11, which has a temperature of up to 150 ° C. 13. The microcapsules are sized in the range of 1 to 500 microns.
The microcapsule-containing battery according to 2. 14. The microcapsule-containing battery according to claim 1, wherein the mixing amount of the microcapsules is 1 to 20% by weight with respect to the electrolyte solution.