JPH02236908A - Solid electrolytic thin film and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a solid electrolytic thin film having anisotropy of ion conductance by forming a monomolecular film of a prescribed compound on the surface of the water or on the liquid level while being able to transfer it on to a substrate. CONSTITUTION:A hydrophobic part 1 is composed of one piece, two pieces and three pieces of linear chain alkyl, alkenyl, alkynil and fluoroalkyl radicals having the carbon number 10 to 30, a connection part 2 has various constructions according to the number of the alkyl chain, a polarity part 3 has the proper chain length and contains an oligomer or a polymer of the formula 1 at least as a part of its construction for becoming a migration path of ions. By using a material having such a molecular construction, a thin film having a regular lamination construction can be obtained, in which ions migrate only in the arrow direction through the polarity part 3 while the tin film comes to have anisotropy of ion conductance.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to various sensors, electrochromic devices,
This article relates to a solid electrolytic thin film that can be used for diaphragms in batteries, electric double layer capacitors, memories, etc. [Prior art and its problems] Substances that exhibit conductivity through the movement of ions rather than electrons in solids, that is, solid electrolytes, are used in all-solid-state batteries, ion sensors, humidity sensors, electrochromic devices, etc. It is indispensable as a component of RT gas double layer capacitors and memories, and so far, inorganic solid electrolytes such as stabilized zirconia,
Organic polymer solid M. typified by polyethylene oxide alkali metal salt hybrid. - Known for its quality, etc. “For example, Chemistry, Vol. 38, No. 6, 40G-41
1 and pp. 418-426 (1983), etc.] The latter organic solid electrolytes are slightly inferior to inorganic ones in terms of ionic conductivity, but they have excellent moldability, so
It has high industrial utility. By the way, these conventional polymer solid electrolytes are made into thin films by dissolving the polymer and inorganic salt in a common solvent and then evaporating the solvent, but the thin film obtained in this way is usually is completely isotropic. In other words, there is no difference in physical properties such as ionic conductivity due to the difference in direction within the thin film (particularly between parallel and perpendicular directions to the film surface), and there is no difference in which direction ions move within the film. can also move with exactly the same flickering ease. However, is ion conduction in the horizontal direction and perpendicular direction to the membrane surface? 1 is very different,
In other words, if a solid electrolyte thin film with anisotropy can be obtained, its range of applications will further expand. For example, in various sensors, by moving ions in only one direction, it will be possible to obtain better sensitivity and response speed than conventional sensors, and in electrocomic devices, conventional static However, by using an anisotropic solid electrolyte thin film, it becomes easy to independently drive display elements consisting of many pixels. In addition, not only the performance of batteries has improved, but also the construction of vertically stacked batteries and batteries using microelectrodes has become easier. It can provide useful materials for constructing devices used for.

However, no solid electrolyte thin film with such anisotropy has been obtained so far.

[Means for solving the problem] The present invention has been made in order to provide a solid electrolyte having anisotropy of ionic conductivity in view of the above situation. Instead of the casting method that has often been used in the past for molecular solid electrolytes, Langmui makes it easy to control the molecular orientation in the membrane and relatively easily obtain layered molecular arrangements.
The solution to this problem is to use the r-B Iodgett method as a film forming method. That is, by forming a monomolecular film of a compound capable of forming a solid ffiM substance on the water surface or liquid surface and transferring it onto a solid substrate, a solid having anisotropy of ionic conductivity is formed. This is to obtain an electrolyte lotus membrane. The material for the thin film created by this method may be any material that exhibits ionic conductivity, is solid, and forms a stable monomolecular film on the water surface or an appropriate liquid surface, but based on experience, Preferably, a substance having a molecular structure as schematically shown in FIG. 1 is used (1), by which a thin film with a regular laminated structure as shown in FIG. With that width, ions move only in the direction of the arrow through the polar region 3, so the thin film has anisotropy of ion conduction W1.Here, the hydrophobic region 1 in Fig. 1 is 1, 2
Consists of one or three linear alkyl, alkenyl, alkynyl, or fluoroalkyl groups having 10 to 30 carbon atoms. Further, the connecting portion 2 can have various structures depending on the number of alkyl chains thereof, and examples include the following. Furthermore, the polar portion 3 includes at least a part of its structure as an oligomer or polymer as described below having an appropriate chain length, and provides a portion that becomes a vJ path for ion movement.

-(OCl!2CH2 fan('oc H2C HtC Heh IOC II - CH2CH2C H s {'NHCIIzCHa light 4: N HC H2C H2C Hp light Also, when making such a substance into a thin film, It is desirable to contain therein a metal salt that provides ions to be charged carriers by any method, preferably 1-ICIO4t
L I B Fag L i C F ssOi+
LiSCN, NaSCN, N&I. By dissolving an alkali metal salt such as KSCN in the lower phase water in advance and forming a monomolecular film of the target compound on the water surface, ions can be easily and appropriately incorporated into the film. Can be done. Alternatively, metal ions can be incorporated in the same way by dissolving an alkali metal salt together with a membrane material in an appropriate solvent and dropping it onto pure water. In general, it is well known that many so-called amphiphilic substances, which have both a long-chain alkyl group and a polar group asymmetrically, are easy to create LBIII (for example, "New Experimental Chemistry Course Volume 18" Colloids) Chapter 6, Maruzen, etc.) introduced isomeric electrolysis by introducing ionic conductive oligomers or polymers as polar groups of these substances. ! There is no example of it being used as a thin film, and one feature of the present invention is to do so as a means to solve the problem. Also, this kind of thing is
Films can also be formed by methods other than the LB method, such as the casting method, and because the films obtained in this way have a stacked structure of bilayer films, some of the ion conductivity of N is reduced. Although it exhibits anisotropy, as will be described later in Examples, films formed by the LB method exhibit much higher anisotropy and are also more useful. Now, by taking the measures mentioned above,
An ionically conductive organic thin film having a regular layered structure as schematically shown in FIG. 2 was obtained. In addition, it has been found through experience that thin films with good properties can be obtained relatively easily, especially by using an amphipathic compound represented by the following general formula (1). General formula (!) where n is a natural number of 4 to 100, and R represents a linear alkyl, alkenyl, alkynyl, or fluoroalkyl group having 10 to 30 carbon atoms. The fact that this thin film actually has a layered structure can be easily confirmed by X-ray diffraction. [Function] In such a solid electrolyte thin film, ion movement occurs only through the polar part, that is, a part of the oligomer or polymer, and ions and electrons move through the densely packed hydrophobic part. As a result, it is extremely difficult to conduct ions in the direction parallel to the membrane. It has been found that an anisotropic solid electrolyte thin film having a high lt rate and low ionic conductivity in the direction perpendicular to the membrane surface, that is, ions move two-dimensionally, can be obtained.

For example, the compound represented by the general formula (T) (R is C+@
1 lithium atom per 4 ethylene oxide units.
Incorporate LiCIO4 in a proportion of LB
In the case of a 10-layer thin film formed by the method, the conductivity in the direction perpendicular to the film surface is 1.6X10-''S/cm, while the conductivity in the direction downward to the film surface is 3. 4X
It showed anisotropy of 10-'S/cm, on the order of 107. Furthermore, by using this solid electrolyte thin film, we were able to construct a sensor with excellent responsiveness. [Examples] Hereinafter, the present invention will be explained in more detail based on Examples. (Example!) As an example of compound synthesis, a method for synthesizing a compound having the structural formula shown below is shown. This compound is one of the thin film materials showing the best properties. 48.54 g of stearyl alcohol, 12.12 g of L-glutamine, and 38.85 g of p-toluenesulfonic acid.
The mixture was reacted in toluene 2001 at reflux temperature for 4 hours.

After the reaction, toluene was distilled off and the residue was recrystallized from acetone to obtain L-glutamic acid dihebutadecyl ester p-}luenesulfonate of white scales 40.48
I got g. (Yield 68.5 $) Next, this synthetic product 10
．． 05 g and 25.00 g of terephthaloyl chloride were reacted in the presence of triethylamine (4.93 g) in tetrahydrofuran!801 at room temperature for 3 days. After removing the by-produced triethylamine hydrochloride and distilling off the solvent. ,
Recrystallization from n-hebutane gave 17.3 g of acid chloride in the form of white bulk crystals. (Yield 73.4X) After #1, this compound 6. 9 4g, polyoxyethylene (molecular weight 458.5) 4.31g, and triethylamine 1.298g were dissolved in tetrahydrofuran 401, and after reacting at room temperature for 7 days, the temperature was raised to 40°C and further 1.
The reaction was allowed to proceed for 2 hours. After removing the triethylamine hydrochloride formed and distilling off the solvent, the residue was recrystallized from acetone to obtain 5.28 g of the desired N-(ω-methoxyborioxyethylene terephthalate) L-glutamic acid dihebutadecyl ester. Obtained. (Yield 50.H) Infrared absorption (IR): 3300Cl-' (
ν 訃H), 1730cr' (ν coo ester), 1640cm-' (ν c.o
rmit゛) 1100ca+-' (V c
-o-e X-ter) proton nuclear magnetic resonance absorption (NM
R): Not shown in Figure 3.

Example 2) Method for creating an LB film For example, the compound synthesized in Example 1 was dissolved in a mixed solvent of benzene:ethanol (volume ratio 9:1) and tfu, and the mixture was poured into a Teflon-coated water tank filled with water (
However, if necessary, t. an alkali metal salt such as iclo, in an appropriate amount, e.g. (previously dissolved at a concentration of 14 M) was gently dropped onto the water surface to form a monomolecular film on the water surface. The water temperature at this time was 20℃. Next, while monitoring the surface pressure of the monomolecular film using a Wilhelmy type surface pressure meter, the area covered by the monomolecular film was reduced by a barrier provided on the water tank, and when the surface pressure reached 25 mN/m, I controlled the barrier so that I was always afraid of its surface pressure. While maintaining this state, move a suitable TFF-clean substrate such as quartz, silicon wafer alumina, gold Tt electrode, sapphire, etc. vertically up and down through the monomolecular film at a speed of 150 mm/win. Accordingly, A. Minute T-membranes were laminated. At this time, it has been observed that the film does not adhere to the substrate while the substrate is being lowered, and the film adheres only when the substrate is being lifted up, which is the so-called Z
I found out that the model LBIII is loud. In addition, each time one layer was accumulated, the absorbance of the film at 257 nm was measured, and the correlation with the number of layers was investigated. As shown in Section 4C21, a good linear relationship was obtained, indicating a regular It was found that a significant accumulation was occurring. (Example 3) Ionic conductivity measurement An LB film 6 of the compound shown in Example 1 ( IOFI, containing Ll ions) was created.
From above, as shown in Figure 6(b),
i7 was vacuum-deposited and used as a sample for ionic conductivity measurement.
For measuring conductivity, Yokogawa Hewlett Vac Card 419
Using a 2A Invi7 dance analyzer, the conductivity in the direction perpendicular to the film surface was measured using a Sanderch type Wj. The conductivity was measured in the direction parallel to the film surface. As shown in Fig. 7, the gap electrode type electrode has a gap @ 4.5 x 1 0-”
cm). Measurements were performed in vacuum at 24°C. Also, in this case, AC conductivity was measured, and the measurement was performed at a frequency in the range of 10 Hz to 10 MH2. As a result, as shown in the table below, it was found that a solid electrolyte thin film with large ionic conductivity anisotropy in the parallel and perpendicular directions to the film surface was obtained. Furthermore, in this case, it was confirmed that one lithium ion was incorporated for every four ethylene oxide units. However, σe is the electrical conductivity in the direction perpendicular to the film surface, σ7
indicates the conductivity in the direction parallel to the film surface. (Comparative example 1
) An example of thinning film using the casting method is shown. The compound synthesized by the method of Example 1 and LIC irises were mixed at a predetermined ratio, and the mixture was dissolved in a mixed solvent of tetrahydrofuran: dioxane: water (volume ratio 2: 6: 3). ．． Next, it was cast onto a gold electrode substrate 1 as shown in FIG. 5, and the solvent was gradually evaporated at room temperature (for about a week) to form a thin film. Mixing ratio with L1 ion (0/L
Various versions of i) were prepared and the anisotropy of conductivity was examined in the same manner as in Example 3, and the values shown in the table below were obtained. Although films with anisotropy can also be produced by the casting method, it was confirmed that the film created by the LB method (Example 3) has greater anisotropy and is more useful. [Effects of the Invention] As is clear from what has been described above, in the present invention, it is easy to create a thin film with a regular layered structure.
By using Method B and chemically modifying the membrane material to suit the method, we have created a solid electrolyte with ionic conductivity anisotropy of the order of 10▼, which has never been achieved before. We were able to provide a thin film. This material is particularly useful as a material for sensors, electric double layer capacitors, and memories. Although several organic thin films with conductivity anisotropy have been obtained so far, all of them are based on electronic conduction, not ionic conduction, and the present invention is based on the properties Please note that both have different uses.

[Brief explanation of drawings]

Figure 1 is a schematic diagram showing the chemical structure of a substance that can form a thin film with anisotropy of ionic conductivity. Second [! I am
FIG. 1 is a schematic diagram showing the regular layered structure of the thin film of the present invention and the ion conduction paths within it. Figure 3 is a proton nuclear magnetic resonance spectrum diagram of N-(6》-methoxyboryoxyethylene terephthalate) L-glutamic acid dihebutadecyl ester, which is one of the typical samples. FIG. 4 is a graph showing the relationship between the accumulated number of LB film layers and the absorbance of the film at 257 nm. FIG. 5 is a schematic diagram showing the shape of an electrode for measuring conductivity. FIGS. 6 and 7 are schematic diagrams illustrating methods for measuring ionic conductivity in a direction perpendicular to the membrane surface and in a direction parallel to the membrane surface, respectively. l. Hydrophobic part 2. Connecting part 3. Polar part 4. Gold etched electrode 5
．． Support substrate 6. LB film 7. Kinden F! i8
．． Impedance analyzer Atsushi 2 ports

Claims (6)

[Claims] (1) Anisotropy of ionic conductivity obtained by forming a monomolecular film of a compound capable of forming a solid electrolyte on the water or liquid surface and transferring it onto a solid substrate. solid electrolyte thin film. (2) A compound having the ability to form a solid electrolyte is
A compound having at least one linear alkyl, alkenyl, alkynyl, or fluoroalkyl group having 10 to 30 carbon atoms as a hydrophobic part, and one or more of the repeating structures shown below as a polar part,
The solid electrolyte thin film according to claim 1. (Repeating structure) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ ▲There are mathematical formulas, chemical formulas, tables, etc.▼ However, n is any natural number. (3) A compound having the ability to form a solid electrolyte is
Claim 1, which is a compound represented by the following general formula (I)
The solid electrolyte thin film described. (General Formula I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ However, n is a natural number from 4 to 100, and R represents a linear alkyl, alkenyl, alkynyl, or fluoroalkyl group having 10 to 30 carbon atoms. . (4) Water containing alkali metal ions is used as the lower phase water, and a monomolecular film of a compound having the ability to form a solid electrolyte is formed on the water surface. 3. The method for producing a solid electrolyte thin film as described in 3. (5) Claim 1, 2 or 3, characterized in that a mixed solution of a compound capable of forming a solid electrolyte and an alkali metal salt is dropped onto the water surface to form a monomolecular film.
The method for producing a solid electrolyte thin film described above. (6) The solid electrolyte thin film according to claim 2 or 3, produced by the method according to claim 4 or 5.