JP2001102062A - Lithium ion conductive polymer film using dna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium ion conductive polymer film using DNA as raw material. SOLUTION: A film of DNA sodium is immersed into an organic solvent solution including lithium salt and doped of the lithium salt into DNA. A single ion conductive film of DNA is produced by immersing a film of DNA lipid 4 class ammonium salt into an organic solvent solution of lithium salt and displacing 4 class ammonium cation bonded with DNA phosphoric acid into lithium.

Description

DETAILED DESCRIPTION OF THE INVENTION [Background of the present invention]

[0001] The present invention relates to a lithium ion conductive polymer film and a method for producing the film.

[0002] For all solid lithium batteries, lithium ion conductive polymers are used in place of the usual battery electrolyte solution.

As such a polymer, a polymer obtained by impregnating a high-polarity polymer matrix with a polar high-boiling solvent containing a lithium salt and a polymer obtained by doping a polyether-based polymer with a lithium salt have been known. .

The present invention relates to a film of a lithium ion conductive polymer which is completely different from the ion conductive polymers known hitherto, and a method for producing the same.

[0005]

DISCLOSURE OF THE INVENTION The present invention relates to a film made of a lithium ion-conducting polymer comprising a complex of a lithium salt doped in DNA or a lithium salt of DNA, and a method for producing the film.

As is well known, DNA has a double helix structure, in which the base portion of one strand is connected to the base portion of the other strand which is complementary to the base portion by hydrogen bonding, and such a base is formed. Many of the pairs stack perpendicular to the helical axis. Attempts have been made to intercalate various molecules or compounds between these base pairs of DNA to form intercalation compounds. The present inventors thought that if this principle was applied, DNA could be doped with a lithium salt.

Okahata et al. Am. Chem. So
c. , 118: 10679 (1996).
A DNA salt soluble in an organic solvent is formed by ion exchange between sodium A and lipid, and the dye is intercalated between base pairs of DNA by immersing an independent membrane of this DNA salt in an aqueous solution of ethidium bromide dye. Have reported that.

However, it is not appropriate to apply this method as it is to lithium salt doping. The lithium salt dope must be used in the form of an organic solvent solution so that lithium ions do not form hydrated ions. This is because the lipid DNA membrane of Okahata et al. Is dissolved in many organic solvents. DNA sodium, on the other hand, does not dissolve in organic solvents such as methanol, ethanol, and acetone.

Therefore, the present invention employs a method in which a film is formed using sodium DNA and the film is immersed in a lithium salt solution in an insoluble organic solvent. The method for producing a lithium ion conductive film according to the present invention includes the following steps. a) casting an aqueous solution of DNA sodium in the form of a film on a support and removing at least most of the water by evaporation; b) the film containing the lithium salt together with the support of the pulled-up film does not dissolve Dipping in a polar organic solvent solution, c) removing the solvent from the pulled-up film by evaporation and optionally peeling it off the support.

As the polar solvent, methanol, ethanol, isopropanol, acetone and the like can be used. As the lithium salt, lithium perchlorate is generally used, but other lithium salts such as lithium chloride, lithium p-toluenesulfonate, lithium trifluorosulfonate and lithium ditrifluorosulfonate may be used.

The rate at which the amount of lithium salt to be doped reaches the saturation limit is a function of the salt concentration in the solution and the immersion time. For example, in the case of a 1 molar solution of lithium perchlorate in acetone, the immersion time is one day and night. It is enough.

Although DNA of any origin can be used, DNA sodium salt extracted from salmon sperm is readily available. DNA films can be made by dissolving the sodium salt in water to a concentration suitable for casting, and casting this solution onto a substrate having a smooth surface. It is preferable to use a substrate having releasability, such as Teflon. Then, after removing at least most of the water from the film, the film is then immersed in a polar solvent solution containing a lithium salt, pulled up, the solvent is removed, and the film is separated from the substrate to obtain an independent film.

When producing a composite membrane having high mechanical strength, a porous plastic film is used instead of the substrate used in the production of the independent membrane, and finally the ion conductive film is used without peeling. .

By using the lipid DNA membrane of Okahata et al., A single ion conductive (cation conductive) polymer film made of a lithium salt of DNA can be produced.

[0015] The lipid DNA membrane of Okahata et al.
The sodium bonded to the phosphate group of DNA is exchanged with a quaternary ammonium cation by the reaction of sodium salt A with an amphiphilic quaternary ammonium salt, and a solution of the lipid quaternary ammonium salt of DNA obtained in an organic solvent is cast. It is made by things. When this membrane is immersed in a solution of a lithium salt such as lithium chloride dissolved in an organic solvent in which the membrane is insoluble but the lithium salt is soluble (eg, methanol, ethanol, acetone, etc.), the quaternary ammonium cations bound to DNA are Replaced by lithium.

This film is substantially the same as the above-described ion-conducting film made of lithium salt-doped DNA, except that lipid DNA is preliminarily prepared from DNA sodium salt and its organic solvent solution is cast on a support. It can be manufactured according to the process.

The quaternary ammonium salts that can be used for the reaction with DNA sodium salt are the N, N, N-
It contains not only trimethyl-N- (3,6,9,12-tetraoxadocosyl) ammonium bromide but also quaternary ammonium salts having a hydrophobic hydrocarbon group such as a long-chain aliphatic group. Examples are cationic surfactants such as alkyltrimethylammonium chloride, benzethonium chloride, benzalkonium chloride and their corresponding bromides.

In the electrode reaction, it is extremely important that the ion conductive film has excellent adhesion to the electrode. However, the lithium ion conductive film of the present invention is flexible and has a very good adhesion to the electrode. Have.

Hereinafter, the present invention will be described in detail with reference to examples.

Example 1 A 5% aqueous solution of commercially available salmon sperm DNA sodium salt was cast on a Teflon plate (10 cm × 10 cm).
Most of the water was removed by air drying. The obtained film was immersed together with the support in 1 L of a 1 molar solution of lithium perchlorate in acetone for 24 hours and pulled up. After removing the solvent from the film by air drying, the film was 10 ⁻² at 100 ° C.
After drying for 6 hours under a reduced pressure of a torr, the film was gently peeled from the support to obtain a translucent film having a thickness of about 100 μm.

The ionic conductivity of this film is 20 ° C.
The result was 5.5 × 10 ⁻⁶ S · cm ⁻¹ , confirming that the polymer was an excellent ion-conductive polymer.

Example 2 Commercially available 1% aqueous solution of salmon sperm DNA sodium salt 100
ml of N, N, N-trimethyl-N- (3,6,
5 g of 9,12-tetraoxadocosyl) ammonium bromide was added and stirred to produce a white precipitate.
The precipitate was collected by filtration, washed well with water, and after removing impurities by dialysis, freeze-dried to obtain a DNA quaternary ammonium salt as a white powder. A 5% chloroform solution of this DNA quaternary ammonium salt was placed on a Teflon plate (10 cm).
X 10 cm) and the solvent was evaporated at room temperature to give a clear film.

This film was immersed together with the support in 1 L of a 1 molar methanol solution of lithium chloride for 24 hours and pulled up. After removing the solvent from the film by air drying, the film was dried at 100 ° C. under a reduced pressure of 10 ⁻² torr for 6 hours, and the film was gently peeled from the support to obtain a translucent film having a thickness of about 100 μm.

The ionic conductivity of this film is 5.8 × 1
0 ⁻⁶ S · cm ⁻¹ , confirming that the polymer was an excellent ion conductive polymer.

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Claims (4)

[Claims] 1. A lithium ion conductive polymer film made of a complex in which DNA is doped with a lithium salt. 2. A lithium ion conductive polymer film made of DNA lithium salt. 3. A DNA sodium salt film is immersed in a lithium salt solution dissolved in a solvent in which the film is insoluble,
2. The method for producing a lithium ion conductive polymer film according to claim 1, comprising drying. 4. The method for producing a lithium ion conductive polymer film according to claim 2, wherein the film of the DNA lipid quaternary ammonium salt is immersed in a solution of a lithium salt dissolved in a solvent in which the film is insoluble and dried. .