JPH10302835A - Polymeric battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate thinning and area enlargement, have superior retentiveness of electrolytic solution within wide temperature range and ensure long stability and improvement in mechanical strength by constituting a polymeric battery of a non-proton electrolytic thin film with a poly-olefin fine porous membrane being a base material and positive and negative electrodes. SOLUTION: A polymeric battery comprises a non-proton electrolytic thin film in which a non-proton solution is solidified in a poly-olefin fine porous membrane and positive and negative electrodes. In particular, as at least one of the positive and negative electrodes, a solidified liquid membrane conductor in which an electrolytic solution is solidified in a polyolefin fine porous membrane containing an electronic conductive material is constituted in combination. The poly-olefin fine porous membrane is 1 to 1,000 μm or preferably 5 to 500 μm in thickness, and a membrane cavity rate is preferably within a range of 30 to 95%. A rupture strength is preferably 200 kg/cm<2> . By employing this conductive thin film, a polymeric battery in which stability can be improved in overcharging can be provided without significantly lowering electronic conductivity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrolyte for a battery, comprising at least one of an aprotic electrolyte thin film, a positive electrode and a negative electrode.
Finally, the present invention relates to a polymer battery using an immobilized liquid film conductor, particularly to a lithium-based battery, particularly to a rechargeable lithium secondary battery.

[0002]

2. Description of the Related Art The performance of portable electronic devices such as mobile phones and personal digital assistants largely depends on not only the semiconductor elements and electronic circuits mounted thereon but also rechargeable rechargeable batteries. -It is desired to achieve compactness at the same time. Until now, lead batteries and nickel cadmium batteries have been used, but it has been difficult to cope with a reduction in weight and size due to insufficient energy density.
Therefore, a nickel-metal hydride battery having an energy density twice as high as that of a nickel cadmium battery has been developed, and then a lithium-ion battery having an energy density even higher than that has been developed and attracted attention. However, all of the batteries use a liquid electrolyte and are filled in a metal can in order to prevent liquid leakage, and thus have limitations in thickness and weight.

[0003] Therefore, attention has been focused on polymer batteries in which a liquid electrolyte is solidified. In particular, as a gel polymer in which a polymer matrix is impregnated with a salt and solvent solution similar to that of a conventional liquid type lithium battery, Technology for using cross-linked polyalkylene oxide for electrolyte (US
P4, 303, 748, etc., and technology for gelling polyallyllate and using it as an electrolyte (US Pat. No. 4,830,939)
Etc.) have been proposed. Recently, a technique using a polymer gel obtained by impregnating a carbonate-based solution obtained by dissolving a lithium salt in a copolymer of polyvinylidene fluoride and hexafluoropropylene as an electrolyte, and a copolymer of polyvinylidene fluoride and hexafluoropropylene LiMn ₂
A technique (USP 5,296,318, etc.) in which a polymer gel impregnated with a carbonate-based solution in which O ₄ and carbon black or petroleum coke and carbon black are mixed and in which a lithium salt is dissolved has been proposed has been proposed and is promising. It has been observed that there is a problem of electrolyte oozing out due to gel shrinkage at high temperature, and it is not a complete solution for solvent retention.

In order to reduce the effective resistance, thinning is also one of the solutions, and the liquid ionic conductivity is reduced by utilizing capillary condensation in fine pores of 0.1 μm or less of a solid polymer porous thin film of 50 μm or less. Method for fixing body (Japanese Patent Laid-Open No. 1-158)
However, this alone cannot fundamentally solve the problem of operating temperature. In Japanese Patent Application Laid-Open No. Hei 3-87096, Ketjen Black is mixed with a plasticizer solution of polyethylene, and after forming and stretching a sheet, an electrolytic solution is fixed to the porous thin film from which the plasticizer has been removed by utilizing the capillary condensation force. However, this is not a complete solution for electrolyte retention.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems, is easy to make a thin film and has a large area, has excellent aprotic electrolyte solvent retention over a wide temperature range, and has a long-term stability. Another object of the present invention is to provide a polymer battery using at least one of an aprotic electrolyte thin film having improved mechanical strength and an immobilized liquid membrane conductor, and a method for producing the same.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to overcome the above-mentioned prior art, and have found that an electrolyte thin film using a specific microporous polyolefin membrane as a base material and a specific microporous polyolefin membrane are used. It has been found that the above object can be achieved by using the immobilized liquid film conductor used as the base material in combination. That is, the present invention is a polymer battery comprising an aprotic electrolyte thin film based on a polyolefin microporous membrane as a base material and a positive / negative electrode, and a polyolefin microporous membrane containing an electronic conductive material as at least one of the positive / negative electrodes. This is a polymer battery comprising an immobilized liquid film conductor as a base material.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The polymer battery of the present invention is a battery comprising an aprotic electrolyte thin film in which an aprotic solution is immobilized on a microporous polyolefin membrane and a positive electrode and a negative electrode. This is a battery configured by combining an immobilized liquid membrane conductor in which an electrolyte solution is immobilized on a microporous polyolefin membrane containing an electronic conductive material. The details will be described below.

A. Aprotic electrolyte thin film The aprotic electrolyte thin film used in the present invention is obtained by immobilizing the aprotic electrolyte solution on a polyolefin microporous membrane containing a substance having an affinity for the aprotic electrolyte solution. As a method for producing a microporous polyolefin membrane containing a substance having an affinity for an aprotic electrolyte solution, a method of graft-polymerizing a substance having an affinity for an aprotic electrolyte solution on a polyolefin microporous membrane, an aprotic There is a method of forming a film from a composition blended with a substance having an affinity for an electrolyte solution, a method of coating the surface of a substance having an affinity for an aprotic electrolyte solution, and the like. Are obtained by immobilizing For example, it can be manufactured by the following method.

1. Polyolefin microporous membrane a. Polyolefin Polyolefins include polyethylene, polypropylene, ethylene-propylene copolymer, polybutene-1,
Poly-4-methylpentene-1 and the like. Of these, polyethylene is preferred. As the polyethylene, those made of ultra-high molecular weight polyethylene, high density polyethylene, medium-low density polyethylene can be used, but those containing ultra-high molecular weight polyethylene or components thereof from the viewpoint of strength, safety, film forming property, etc. It is preferable to use The polyolefin has a weight average molecular weight of 5 × 10 ⁵ or more, preferably 1 × 10 ⁶ to 1 × 10 5.
^It is preferred that the ultrahigh molecular weight component ⁷ is contained in an amount of 1% by weight or more and the molecular weight distribution (weight average molecular weight / number average molecular weight) is 10 to 300. When the content of the ultrahigh molecular weight polyolefin component is less than 1% by weight, the portion which contributes to the improvement of the stretchability of the film is insufficient. On the other hand, the upper limit is not particularly limited. On the other hand, if the molecular weight distribution exceeds 300, breakage due to low molecular weight components occurs, and the strength of the entire thin film decreases, which is not preferable.

B. Method for producing microporous polyolefin membrane A microporous polyolefin membrane can be obtained by forming a polyolefin membrane. The film formation is described in JP-A-60-2
42035 and JP-A-3-64334. For example, it can be performed as follows.
A polyolefin containing an ultrahigh molecular weight polyolefin is heated and dissolved in a solvent such as liquid paraffin at 10 to 50% by weight to form a uniform solution. After forming a sheet from this solution and cooling it into a gel-like sheet, the sheet is heated at a temperature equal to or lower than the melting point of the polyolefin plus 10 degrees, and stretched to an area magnification of 3 times or more. The solvent contained in the stretched film is extracted and removed with a volatile solvent such as methylene chloride, and then dried and heat-set. In addition, the polyolefin microporous membrane, if necessary, antioxidants, ultraviolet absorbers, lubricants, antiblocking agents, pigments, dyes, various additives such as inorganic fillers,
It can be added in a range that does not impair the purpose of the present invention.

C. Physical properties The polyolefin microporous membrane has a thickness of 1 to 1000 μm, preferably 5 to 500 μm. If the thickness is less than 1 μm, it is difficult to practically use from the viewpoint of mechanical strength and handling. On the other hand, if it exceeds 1000 μm, the effective resistance becomes large and the volume efficiency becomes disadvantageous. The porosity of the film is not limited, but is in the range of 30 to 95%, more preferably 50 to 90%. 30% porosity
If the porosity is less than 95%, the immobilization of the aprotic electrolyte solution may be insufficient. On the other hand, if the porosity exceeds 95%, the mechanical strength of the membrane becomes small, resulting in poor practicability. Further, the average pore size is preferably 1 μm or less. If it exceeds 1 μm, it becomes difficult to prevent the active material and the reaction product from diffusing when the amount of graft polymerization is small. Although the lower limit is not limited, if the average pore diameter is less than 0.005 μm, there may be a problem in uniformity and polymerization rate in graft polymerization by plasma. Further, the microporous polyolefin membrane preferably has a breaking strength of 200 kg / cm ² or more. Break strength 2
By setting it to be not less than 00 kg / cm ^{2, the} deformation resistance against swelling when the aprotic electrolyte solution is dissolved in the graft polymer becomes sufficient.

2. A method for imparting affinity to an aprotic electrolyte solution to the surface of a microporous polyolefin membrane and the surface of pores by a graft polymerization method. a. Graft Polymerization Monomer As a monomer having an affinity for the aprotic electrolyte solution, acrylic acid, methacrylic acid, acrylate, methacrylate, acrylamide, acrylonitrile, styrene and derivatives thereof are used. Specifically, for example, acrylates include methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate,
Lauryl acrylate, stearyl acrylate, ethyl decyl acrylate, ethyl hexadecyl acrylate, 2-ethoxyethyl acrylate, tetrahydrofurfuryl acrylate, trimethylolpropane triacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl acrylate
Examples include acrylic monomers such as hydroxypropyl acrylate, 1,4-butanediol diacrylate, and 1,6-hexanediol diacrylate. Examples of methacrylates include methyl methacrylate, ethyl methacrylate, butyl methacrylate, and methacrylic acid. Examples include methacrylic monomers such as 2-ethylhexyl, tridecyl methacrylate, stearyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, glycidyl methacrylate, and ethylene glycol dimethacrylate. Can be One or more of these can be selected and used. If necessary, a crosslinkable monomer such as vinyl acrylate, vinyl methacrylate, divinylbenzene, and vinyl butyl acrylate can also be used. Among the above-mentioned monomers, it is preferable to use a monomer composed of acrylic acid, methacrylic acid, or an ester thereof, or an acrylic monomer composed of acrylamide or a derivative thereof.

B. Graft Polymerization Method As a method for graft-polymerizing the above polymer onto the surface of the microporous polyolefin membrane and the surface of the pores, a radiation graft polymerization method such as plasma or electron beam or γ-ray is used. A post-polymerization method in which radicals are generated in the polyolefin microporous membrane and then contacted with a selected monomer, or a simultaneous polymerization method in which radicals are generated in a state in contact with the monomers may be used. Specific examples of plasma graft polymerization include:
In the presence of a gas such as argon, helium, nitrogen, or air at a pressure of 10 ^{-2 to} 10 mbar, the polyolefin porous membrane has a frequency of 10 to 30 MHz and an output of 1 to 10
Plasma treatment is performed at 00 W for 1 to 1000 seconds. Next, an inorganic or organic solvent containing the selected monomer in an amount of 1 to 10% by volume and, if necessary, 0.01 to 2% by volume of a crosslinking aid (the monomer and the crosslinking aid are dissolved or suspended in this solvent). ), And the graft polymerization reaction is performed at 20 to 100 ° C for 1 to 60 minutes while bubbling with a nitrogen gas, an argon gas, or the like. In addition, as a solvent, water, alcohol such as methanol, an alcohol aqueous solution, or the like can be used.

As the electron beam graft polymerization method, the above-mentioned microporous polyolefin membrane, the simultaneous irradiation method in which the selected monomer and the cross-linking aid are coexistent, and the simultaneous irradiation with an electron beam, After irradiating the film with an electron beam, there is a pre-irradiation method in which the selected monomer is reacted in the presence of the cross-linking aid, but the pre-irradiation method is used because the homopolymerization of the selected monomer is suppressed. Is preferred. In the pre-irradiation method, the microporous polyolefin membrane is preferably irradiated with an electron beam having an acceleration voltage of 100 to 5000 KeV, more preferably 200 to 800 KeV. Note that the electron beam irradiation can be performed in an air atmosphere. The irradiation amount is suitably from 10 to 500 KGy, preferably from 50 to 200 KGy. 10K
If it is less than Gy, the grafting of the selected monomer is insufficient, while if it exceeds 500 KGy, the microporous polyolefin membrane may deteriorate.

Next, the electron beam-irradiated polyolefin microporous membrane is immersed in the selected monomer solution in the presence of the crosslinking aid to form a graft polymer.
By such graft polymerization, a graft polymer is selectively formed on the surface of the microporous polyolefin membrane, or a graft polymer is selectively formed on the inner surface of the pore, or on either the surface or the inner surface of the pore. Can also form a graft polymer. The homopolymer by-produced in the course of the graft polymerization may be left as it is, but it may be completely washed away using a solvent such as toluene, and only the graft polymer is removed from the surface of the polyolefin microporous membrane and its pores. It may be left on the inner surface.

C. Graft Polymerization Amount The amount of graft polymerization can be controlled by conditions such as the amount of radical generation or monomer concentration, the contact time, and the temperature. Graft polymerization amount (graft amount of polymer polymerized per unit area) is preferably 0.02~35mg / cm ^2, more preferably 0.03~30mg / cm ^2. Although it depends on the thickness of the microporous polyolefin membrane, it may be in the range of 0.1 to 1.0.
02mg / cm dissolution by electrolyte is less than ^2, the swelling effect is insufficient, preventing deformation of the polyolefin porous membrane, the effect of reduction in strength prevent insufficient exceeds 35 mg / cm ^2. With an increase in the amount of graft polymerization, the micropores of the polyolefin microporous membrane are gradually closed, the porosity is gradually lost, and finally, the membrane is substantially completely closed.

3. Method of adding terminally modified polypropylene to impart affinity to aprotic electrolyte solution a. Terminal-modified polypropylene Terminal-modified polypropylene is a polypropylene having a functional group structure at the terminal. Here, as polypropylene,
Not limited to propylene homopolymer, propylene and other α-
One or more block copolymer rubbers with olefins (eg, ethylene, 1-butene, 1-hexene, 4-methyl-1-pentene, etc.) are included.

The polypropylene having a functional group structure at the terminal can be produced as follows. That is, it is produced by reacting a living polypropylene obtained by living polymerization of propylene with a functional group-containing monomer in the presence of a catalyst comprising a specific vanadium compound and an organoaluminum compound. As the vanadium compound, V (acetylacetonato) ₃ , V (2-methyl-1,3-butanedionato) ₃ and V (1,3-butanedionato) ₃ are preferable. As the organic aluminum compound, a compound having 1 to 1 carbon atoms
An organoaluminum compound having 8, preferably 2 to 6 carbon atoms, or a mixture or complex compound thereof, such as dialkylaluminum monohalide, monoalkylaluminum dihalide, and alkylaluminum sesquihalide.

The polymerization reaction is inert to the polymerization reaction,
It is preferable to carry out the reaction in a solvent which is liquid at the time of polymerization. Such solvents include saturated aliphatic hydrocarbons, saturated alicyclic hydrocarbons, and aromatic hydrocarbons. The amount of the polymerization catalyst used in the polymerization of propylene is 1 × 10 ^{−4 to} 0.1 mol, preferably 5 × 10 ^{−4 to} 5 × 10 ⁻² mol of the vanadium compound per mol of propylene, and 1 mol of the organic aluminum compound. × 10 ^{-4 to} 0.5 mol, preferably 1 × 10 ^-3
~ 0.1 mol. The organic aluminum compound is preferably used in an amount of 4 to 100 mol per 1 mol of the vanadium compound.

The living polymerization is usually carried out at -100 ° C to 100 ° C.
C. for 0.5 to 50 hours. The molecular weight of the obtained living polypropylene can be adjusted by changing the reaction temperature and the reaction time. Lower the polymerization temperature, especially -30
By setting the temperature to not more than ° C, a polymer having a molecular weight distribution close to monodispersion can be obtained. Mw below -50 ° C
(Weight average molecular weight) / Mn (number average molecular weight) is 1.05
It can be a living polymer of from 1.40 to 1.40. As described above, living polypropylene having a number average molecular weight of about 800 to 400,000 and nearly monodisperse can be produced.

Next, in order to introduce a functional group structure into the terminal, living polypropylene is reacted with a functional group-containing monomer. As the monomers to be introduced, the same monomers as in the case of the graft polymerization method are used. The amount of a single monomer or a plurality of monomers forming a living polymer is adjusted according to the solvent of the electrolytic solution. By doing so, the gel is effectively swollen and gelled in the electrolytic solution, and it can be firmly fixed. Here, the porous thin film containing the terminal-modified living polymer selectively incorporates an electrolyte solvent having an affinity for the living polymerization functional group covering the surface and the pore surface, but the main skeleton has a solvent resistance. Since it is made of polyethylene having excellent properties, its swelling is appropriately suppressed as a whole, and large deformation and reduction in strength can be prevented.

The reaction between the living polypropylene and the functional group-containing monomer is carried out by supplying the monomer to a reaction system in which the living polypropylene exists. Reaction is usually -1
It is performed at a temperature of 00 ° C to 150 ° C for 5 minutes to 50 hours. By increasing the reaction temperature or lengthening the reaction time, it is possible to increase the modification ratio of the polypropylene terminal with the monomer unit. Usually, 1 to 1,000 mol of a monomer is used per 1 mol of living polypropylene.

The terminal-modified polypropylene obtained as described above has a number average molecular weight (Mn) of about 800 to 500,000, and has a very narrow molecular weight distribution (Mw / Mn) following the living polypropylene itself. =
1.05 to 1.40). In addition, the terminal has an average of 0.1 to 500, preferably 0.5 to 100 terminal structures of the monomers at the terminal. One feature of the end-modified polypropylene thus produced is that the syndiotactic dyad fraction is 0.6 or more. The amount of the terminal-modified living polymerized polypropylene is 1 to 50% by weight of the polyolefin, preferably
３０30% by weight. If it is less than 1% by weight, the effect of impregnation and immobilization of the solvent in the electrolytic solution cannot be expected. On the other hand, if it exceeds 50% by weight, the mechanical strength is significantly reduced.

B. Method for producing microporous polyolefin membrane containing terminal-modified polypropylene As a method for producing a microporous polyolefin membrane containing terminal-modified polypropylene, a method for producing a microporous membrane from a composition obtained by blending the above-mentioned terminal-modified polypropylene with polyolefin, There is a method in which a microporous membrane is produced from polyolefin, and the surface is coated with a terminal-modified polypropylene. The method for producing a microporous membrane from the composition obtained by blending the above-mentioned terminal-modified polypropylene with the polyolefin can be carried out according to the method for producing the above-mentioned microporous polyolefin membrane. Producing a microporous membrane from polyolefin,
The method of coating the surface with terminal-modified polypropylene,
According to the method described in the above patent, the surface of the obtained polyolefin microporous membrane, the terminal-modified polypropylene aromatic hydrocarbon, paraffin hydrocarbon, chloroform,
Impregnation with a solution dissolved in a solvent such as tetrahydrofuran,
It is a method of coating by coating or spraying or the like.

4. Method of adding affinity to aprotic electrolyte solution by containing wax a. Waxes As waxes having an affinity for aprotic electrolyte solutions, natural waxes such as vegetable waxes, animal waxes, mineral waxes, petroleum waxes, synthetic hydrocarbons,
Synthetic waxes such as modified waxes, hydrogenated waxes, fatty acids, acid amides, esters and ketones can be used. Among them, the ester [RCOO (CH ₂ CH ₂ ) _n CO
OR ′], a synthetic wax such as an ester wax represented by [RCOOR ′], a monohydric alcohol fatty acid ester represented by [RCOOOR ′], [RCOOCH ₂ CH (OH) CH ₂ OH]
A glycerin fatty acid ester represented by the formula [RCOOCH
₂ CH ₂ OH], an ethylene glycol ester represented by the formula:
Fatty oil-based synthetic waxes such as sorbitan fatty acid esters are expected to not only have an affinity for aprotic electrolyte solutions, but also form a kind of complex with lithium ions to promote ionic conduction.

B. Method for Producing Wax-Containing Polyolefin Microporous Membrane The method for producing the aprotic electrolyte thin film used in the present invention includes:
There are two methods, a method of coating a wax on a polyolefin microporous membrane and a method of manufacturing a microporous membrane from a polyolefin composition containing a wax. Method for coating wax on microporous polyolefin membrane Wax is diluted with a diluting solvent and coated on the above-mentioned microporous polyolefin membrane. As the coating method, impregnation, application, spraying, or the like can be used alone or in combination. In addition, as a diluting solvent,
Hydrocarbons such as pentane, hexane, heptane, and toluene; chlorinated hydrocarbons such as methylene chloride and carbon tetrachloride;
Examples thereof include fluorinated hydrocarbons such as ethane trichloride, ethers such as diethyl ether and dioxane, and alcohols such as methanol and ethanol.

Method for Producing Microporous Membrane from Wax-Containing Polyolefin Composition The composition ratio of the ultra-high molecular weight polyolefin alone or the polyolefin composition with the polyolefin and the wax is such that the wax is 1 to 50% by weight based on the total resin composition. %, Preferably 3 to 30% by weight. If it is less than 1% by weight, the effect of immobilizing the solvent in the electrolyte solution cannot be expected. on the other hand,
If it exceeds 50% by weight, the mechanical strength is significantly reduced.
A method for producing a microporous polyolefin membrane from a wax-containing polyolefin composition can be carried out in the same manner as described above.

5. A method for imparting affinity to an aprotic electrolyte solution by containing an organopolysiloxane a. Organopolysiloxane The organopolysiloxane used in the present invention is a polymer having at least one silicon-carbon bond per silicon and having a silicon-oxygen bond (→ Si—O—Si ←) as a repeating unit. Compound. For example, commercially available silicone oils and silicone rubbers having a degree of polymerization of 10 or more, preferably 10 to 10,000 can be used. If the degree of polymerization is less than 10, volatilization and dissipation cannot be ignored, which is not preferable. On the other hand, if the degree of polymerization greatly exceeds 100, the viscosity becomes high and it becomes difficult to uniformly fill the gel-like molded product. Therefore, dilution with a volatile solvent is preferred.

Specific examples of the organopolysiloxane include polydimethylsiloxane in which the organic group is a methyl group, and hydrogen or hydrogen at the terminal or inside of the polysiloxane chain.
Modified polysiloxane to which vinyl group, hydroxyl group, amino group, carboxyl group, epoxy group, methacryloxy group, mercapto group, long-chain alkyl group, phenyl group, chlorine or fluorine are bonded, and non-polysiloxane part in main chain Examples thereof include an alkylene oxide-modified polysiloxane, a silicone-modified copolymer, and an alkoxysilane-modified polymer. Polymethylvinylsiloxane, polymethylphenylvinylsiloxane, polymethylfluorovinylsiloxane, or a modified polysiloxane in which a vinyl group or a hydroxyl group is bonded to the inside or end of a polysiloxane chain, such as a polydimethylsiloxane having a hydroxyl group blocked, may also be used. Yes, but-(CH
₂ CH ₂ O) _n modified polysiloxane or with an ether-based group in the side chain, such as -R - [(CH _{2) m} COO (CH
₂ ) A modified polysiloxane having an ester group such as _n ] -R is expected to have not only an affinity with an aprotic electrolyte solution but also a kind of complex with lithium ions to promote ion conduction.

As the volatile solvent for diluting the organopolysiloxane having a high degree of polymerization, pentane, hexane,
Hydrocarbons such as heptane and toluene, chlorinated hydrocarbons such as methylene chloride and carbon tetrachloride, fluorinated hydrocarbons such as ethane trichloride ethane, ethers such as diethyl ether and dioxane, and others such as methanol and ethanol Alcohols. The above-mentioned organopolysiloxane or its diluted solution may contain, if necessary, a crosslinking agent for the organopolysiloxane, for example, an organic peroxide, an organosilicon compound having three or more functional groups, an alkyl orthosilicate, a metal catalyst. Alternatively, a small amount of a reinforcing material such as synthetic silica and other additives may be prepared.

B. Manufacturing method of organopolysiloxane-containing microporous polyolefin membrane Manufacturing method of organopolysiloxane-containing polyolefin microporous membrane is a method of coating organopolysiloxane on polyolefin microporous membrane, and filling organopolysiloxane into gel-like molded product composed of polyolefin composition. And a method of forming a film. Coating method of organopolysiloxane As a coating method of organopolysiloxane,
Spraying and applying a solution of an organopolysiloxane dissolved in an organic solvent which is a non-solvent to the above-mentioned microporous polyolefin membrane to the polyolefin microporous membrane, or dipping the membrane into the liquid, and other coating operations. More preferably, the film obtained by evaporating and solidifying the organic solvent is further crosslinked. The thickness of the coating is from 1 to
Preferably it is 1000 μm.

A method for filling a gel-like molded product comprising a polyolefin composition with an organopolysiloxane to form a film and fixing an electrolyte solution to obtain a gel-like sheet comprising a polyolefin composition, and then removing the solvent in the gel-like sheet Remove. Examples of the removal method include removal of the solvent by evaporation of the gel-like sheet by heating, removal by compression, extraction and removal of the solvent by a volatile solvent, and removal of the solvent while maintaining the network structure of the gel-like sheet by freeze-drying. However, in order to remove the solvent without significantly changing the structure of the gel-like sheet, extraction and removal with a volatile solvent is preferable. Further, it is preferable to remove the solvent in the gel-like sheet to 1% by weight or less.

The filling of the organopolysiloxane is carried out by immersing the gelled sheet subjected to the desolvation treatment in an organopolysiloxane solution or a dilute solution thereof in the presence or absence of a volatile solvent for the desolvation treatment, or by immersing the gel sheet. This is done by coating. Further, even in the case of an untreated gel-like sheet that has not been subjected to a solvent removal treatment, it can be filled by injecting an organopolysiloxane solution or a diluted solution thereof. However, it is more preferable to immerse the gel-like sheet in the presence of the volatile solvent after the desolvation treatment, because it can be easily filled.

The dilution concentration of the dilute organopolysiloxane solution varies depending on the amount of the organopolysiloxane to be filled in the gel sheet, but is preferably at least 0.05% by weight or more, particularly preferably 0.5% by weight or more. If the concentration is less than 0.05% by weight, the amount of the organopolysiloxane filled in the gel-like sheet is insufficient, and pinholes are easily generated during stretching. The solution viscosity is 5 at 25 ° C. in order to uniformly fill the entire gel sheet.
It is preferably less than 00 cSt, particularly preferably less than 100 cSt. The filling amount of the organopolysiloxane in the gel sheet is preferably from 5 to 90% by weight, particularly preferably from 10 to 80% by weight. Next, the obtained organopolysiloxane-containing gel-like sheet is stretched to obtain a polyolefin microporous membrane containing an organopolysiloxane.

6. Immobilization of aprotic electrolyte solution on polyolefin microporous membrane having affinity for aprotic electrolyte solution a. Electrolyte solution As an electrolyte of the aprotic electrolyte solution, an alkali metal salt, an alkaline earth metal salt is used, for example, LiF,
NaI, LiI, LiClO ₄ , LiAsF ₆ , LiPF
₆ , LiBF ₄ , LiCF ₃ SO ₃ , NaSCN and the like. Further, as the aprotic solvent for dissolving the electrolyte of the aprotic electrolyte solution, a solvent stable to an alkali metal, specifically, propylene carbonate, ethylene carbonate, γ-butyrolactone, dimethoxyethane, acetonitrile, form An aprotic high dielectric constant solvent such as amide, tetrahydrofuran, diethyl ether or the like is used alone or in combination of two or more.

B. Immobilization Method As a method of immobilizing an aprotic electrolyte solution on a polyolefin microporous membrane to form an aprotic electrolyte thin film, impregnation, coating, spraying or the like can be used alone or in combination. In addition, the electrolyte solution may be fixed before being incorporated into the battery, during the battery assembly process, or at the final battery assembly process. Among them, in view of the ease of handling during battery assembly, the prevention of wrinkles and the like, the adhesion to the positive and negative electrode surfaces, and the fact that the conventional battery assembly process can be applied as it is, the electrolyte may be used during the battery assembly process or the final battery assembly process. The method of immobilizing the solution is preferred.

B. Immobilized liquid membrane conductor The immobilized liquid membrane conductor used in the present invention fixes an aprotic electrolyte solution to a polyolefin microporous membrane containing an electron conductive material and a substance having an affinity for an aprotic electrolyte solution. It can be manufactured by A method for producing a microporous polyolefin membrane containing an electron conductive material and a substance having an affinity for an aprotic electrolyte solution includes a non-proton microporous membrane obtained from a polyolefin composition containing an electronic conductive material. Method of graft-polymerizing a substance having affinity for aprotic electrolyte solution, method of forming a film from a composition in which a polyolefin containing an electroconductive material is blended with a substance having affinity for aprotic electrolyte solution, aprotic electrolyte solution There is a method of coating the surface with a substance having an affinity for, and the like, which can be obtained by immobilizing an aprotic electrolyte solution on the obtained microporous membrane. These methods can be carried out in accordance with the above-mentioned method for producing an aprotic electrolyte thin film by blending an electronic conductive material described below with polyolefin.

A. Electronic conductive material Examples of the electronic conductive material include various metals and semiconductors, oxide and sulfide electronic conductive materials, and carbon or graphite. These may be in any shape such as a particle shape, a fiber shape, a fibril shape, a whisker shape and the like. Particularly preferred are TiS ₃ , TiS ₂ ,
TiO ₂ , V ₂ O ₅ , NbSe ₃ , MnO ₂ , LiCoO ₂ ,
Battery positive electrode active materials such as LiNiO ₂ , LiMn ₂ O ₄ , PbO ₂ , NiOOH, petroleum coke, natural graphite,
Battery negative electrode active materials such as carbon fiber, Pb and Cd, acetylene black, Ketjen black (Akz
oChemic), carbon whiskers, graphite whiskers, graphite fibrils and the like.

B. The specific conductivity of the immobilized liquid film conductor The immobilized liquid film conductor of the present invention constituted by the above,
It has a specific conductivity of 10 ^-5 Scm ^-1 or more, preferably 10 ^-3 Scm ^-1 or more. If the specific conductivity is less than 10 ^-5 Scm ^-1 , the effective resistance becomes large and is not practical. For example, film thickness 1μ
m, the effective resistance is 1 μm / 10 ⁻⁵ Scm ⁻¹ , that is, 1
It becomes 0 Ωcm ² .

C. Polymer Battery A polymer battery is obtained by combining the above-obtained aprotic electrolyte thin film, which is a gel electrolyte, with a conventional cathode and anode. In particular, the aprotic electrolyte thin film obtained above is at least one of a positive electrode fixed liquid film conductor containing a positive electrode active material of an electron conductive material and a negative electrode fixed liquid film conductor containing a negative electrode active material as an electron conductive material. By combining them, a polymer battery that is safer and more economical than a battery using a conventional liquid electrolyte can be obtained.

That is, the conductive thin film or the immobilized liquid film conductor is applied, a lightweight and highly flexible composite electrode is used, the electrolyte solvent is immobilized by the solubility of the filling polymer, and the polyolefin is used. By suppressing the excessive swelling by the porous membrane substrate skeleton, the electrolyte solvent can be stably held in a wide temperature range, and the evaporation rate of the electrolyte solvent can be kept extremely low, Good conductivity can be maintained over a wide temperature range.
That is, it is possible to manufacture a polymer battery capable of improving safety in overcharging without significantly lowering the electronic conductivity.

Thus, the organic electrolyte can be contained in the pores of the lithium ion conductive polymer membrane, so that lithium ions can pass not only in the electrolyte but also in the polymer electrolyte. It is possible to discharge at a higher rate than a battery. In addition, the electrolyte in the pores of the porous polymer electrolyte secures a passage through which ions diffuse rapidly, so that a higher rate of discharge can be achieved than in a conventional polymer electrolyte lithium battery. In addition, by covering a part or the whole of the interface between the positive electrode and the negative electrode and the electrolyte with a porous lithium ion conductive polymer, oxidation and reduction of the organic electrolytic solution by the positive electrode and the negative electrode, which are problematic for a high-voltage battery, can be prevented. The charge and discharge characteristics can be improved. Also in this case, since the lithium ion conductive polymer is porous, high-rate discharge is possible.

[0043]

EXAMPLES The present invention will be described in more detail with reference to the following specific examples, but the present invention is not particularly limited to these examples. In addition, the test method in an Example is as follows. (1) Film thickness: The cross section was measured by a scanning electron microscope. (2) Porosity: measured by a gravimetric method. (3) Tensile strength: measured according to ASTM D882.

Example 1 Microporous polyethylene membrane (weight average molecular weight 1.1 million, molecular weight distribution 20, film thickness 25 μm, porosity 40%, tensile strength 1
049 kg / cm ² ), and methyl acrylate was polymerized by a plasma graft polymerization method. Under an argon atmosphere, plasma irradiation was performed at 0.1 mbar, 10 W, and 60 seconds, and the polymer was brought into contact with a methyl acrylate aqueous solution (water concentration was 4 vol% and water was used as a solvent) at 30 ° C. for 15 minutes to perform graft polymerization. After the reaction, the resultant was washed with toluene and dried in an oven at 50 ° C. From the weight change before and after the polymerization, the amount of the graft polymer polymerized per unit base material area was 3.9 mg / cm ² . The obtained graft-polymerized microporous PE membrane 10 × 10 mm square is 25
It was immersed in propylene carbonate containing 1M LiPF ₆ at 1 ° C. for 1 hour to obtain an aprotic electrolyte thin film having a swelling ratio (weight increase ratio) of 134%.

12 parts by weight of polyethylene (10 parts by weight of polyethylene having a weight average molecular weight of 400,000, and 2 parts by weight of polyethylene having a weight average molecular weight of 2,000,000), 15 parts by weight of petroleum coke powder, 3 parts by weight of Ketjen black powder, and 70 parts by weight of liquid paraffin 10 parts by weight of a mixture containing 0.1 parts by weight of an antioxidant.
37 parts by weight were added and the mixture was heated and kneaded with a twin screw extruder. This was discharged from a die having a rectangular die and taken up by a chill roll to form a 1 mm thick sheet. This sheet was simultaneously biaxially stretched 5 × 5 times at a temperature of 120 ° C. using a batch type biaxial stretching machine, and the remaining liquid paraffin was washed with n-hexane and then fixed at 120 ° C. while being fixed to a metal frame. After drying and heat setting, a polyethylene film containing an electronic conductive material was obtained. The obtained polyethylene film (thickness: 30 μm) containing the electronic conductive material was coated with 0.1 mba under an argon atmosphere.
Irradiated with plasma for 10 seconds at 10 W for 30 minutes at 30 ° C. for 15 minutes with a methyl acrylate aqueous solution (having a monomer concentration of 4 vol% and using water as a solvent) to perform graft polymerization. After the completion of the reaction, the resultant was washed with toluene and dried in a 50 ° C. oven to obtain a polyethylene film containing a graft-polymerized electronic conductive material. From the weight change before and after the polymerization, the amount of the graft polymer polymerized per unit area was 2.5 mg / cm ² . The obtained polyethylene film containing the electroconductive material subjected to the graft polymerization is immersed in a propylene carbonate solution containing 1 M LiPF ₆ at 25 ° C. for 1 hour, and the swelling ratio (weight increase ratio) is 126%.
Of the negative electrode-immobilized liquid film conductor was obtained.

Similarly, polyethylene (weight average molecular weight 4
100,000 polyethylene 10 parts by weight and weight average molecular weight 200
2 parts by weight of polyethylene) 12 parts by weight and LiMn ₂ O ₄
0.37 parts by weight of an antioxidant was added to 10 parts by weight of a mixture containing 15 parts by weight, 3 parts by weight of Ketjen black powder and 70 parts by weight of liquid paraffin, and the mixture was heated and kneaded by a twin screw extruder. This was discharged from a die having a rectangular die and taken up by a chill roll to form a 1 mm thick sheet. The sheet was subjected to 5 × 5 at 120 ° C. using a batch type biaxial stretching machine.
The film was simultaneously biaxially stretched twice, and the remaining liquid paraffin was washed with n-hexane, dried at 120 ° C. while being fixed to a metal frame, and heat-set to obtain a polyethylene film containing an electronic conductive material. A polyethylene film (thickness: 30 μm) containing the obtained electronically conductive material was coated with 0.1 μm under an argon atmosphere.
Irradiated with mbar, 10 W, 60 seconds plasma, and contacted with methyl acrylate aqueous solution (monomer concentration was 4 vol%, water was used as solvent) at 30 ° C. for 15 minutes to perform graft polymerization. After the reaction is complete, wash with toluene and
After drying in an oven at 0 ° C., a polyethylene film containing an electron conductive material subjected to graft polymerization was obtained. From the weight change before and after the polymerization, the amount of the graft polymer polymerized per unit area was 3.1 mg / cm ² . The resulting polyethylene film containing the graft-polymerized electronic conductive material is immersed in a propylene carbonate solution containing 1 M LiPF ₆ at 25 ° C. for 1 hour, and a swelling ratio (weight increase ratio) of 1 is obtained.
A positive electrode-immobilized liquid film conductor of 04% was obtained.

The obtained negative electrode fixing liquid film conductor (film thickness 57
μm, 40 × 30 mm) and a positive electrode-immobilized liquid membrane conductor (51 μm, 40 × 30 mm) and an aprotic electrolyte thin film (49 μm, 42 × 33 mm). , And the ends were sealed. It had a capacity of about 400 mAh at a discharge of 2 mA, and charging and discharging were repeated 50 times, but no deterioration of the capacity was observed.

[0048]

In the battery according to the present invention, lithium ions can pass not only in the electrolyte but also in the polymer electrolyte, and discharge at a higher rate than the conventional liquid electrolyte lithium battery is possible. Further, in the battery according to the present invention, the electrolyte solution in the pores of the porous polymer electrolyte secures a path through which ions diffuse rapidly,
Discharge at a higher rate than conventional polymer electrolyte lithium batteries is possible. In addition, by covering a part or the whole of the interface between the positive electrode and the negative electrode and the electrolyte with a porous lithium ion conductive polymer, oxidation and reduction of the organic electrolytic solution by the positive electrode and the negative electrode, which are problematic for a high-voltage battery, can be prevented. The charge and discharge characteristics can be improved. Also in this case, since the lithium ion conductive polymer is porous, high-rate discharge is possible. This makes it possible to provide a polymer battery having better high-rate discharge performance at low temperatures and less self-discharge even at high temperatures than conventional non-aqueous electrolyte batteries, and having excellent long-term charge storage characteristics.

Claims (2)

[Claims] 1. A polymer battery comprising an aprotic electrolyte thin film based on a microporous polyolefin membrane and positive and negative electrodes. 2. The polymer battery according to claim 1, wherein at least one of the positive and negative electrodes comprises an immobilized liquid film conductor having a microporous polyolefin film containing an electron conductive material as a base material.