JP2001338689A - Liquid crystal electrolyte and secondary cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolyte with anisotropic ion conductivity for the use of electrolyte at the field of electronics such as cell, sensor device, or the like. SOLUTION: The liquid crystal electrolyte contains discotic liquid crystal compound with lyotropic liquid crystal property, for example, a compound shown by the formula (1), and metal salt. The metal salt is alkaline metal salt. As to a liquid crystal compound, it is preferable to polymerize the side chain of triphenylene group compound with copolymerizable compound like acryl group, methacryl group and the like. As to the metal salt, MCIO4, MBF4 (M represents Li, Na, and K) or the like are preferable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel compound, a liquid crystal electrolyte used in the field of electronics such as a battery device, a photochromic device, and a sensor device, and a secondary battery using the same.

[0002]

2. Description of the Related Art In 1973, Wright et al.
The ionic conduction properties of a complex of polyethylene oxide (PEO) and an alkali metal salt were reported.
The discovery of the potential of electrolytes for batteries by nd et al. has led to widespread research on solid electrolytes worldwide. Since the solid electrolyte is not liquid in shape, there is no leakage to the outside, and it is more advantageous than the liquid electrolyte for heat resistance, reliability, safety, and miniaturization of the device. In addition, since the organic substance is more flexible than the inorganic substance, there is an advantage that processing is easy.

In general, the ionic conductivity of an electrolyte is represented by the product of carrier density, charge, and ion mobility. Therefore, a high polarity for dissociating ions and a low viscosity for moving dissociated ions are required. From that viewpoint, it cannot be said that PEO has sufficient characteristics as a solid electrolyte. In the first place, the ion transport mechanism of PEO is based on ligand exchange in which ions dissociated by coordination to a donor polar group portion are successively handed over by segmental movement due to heat. Therefore, it is susceptible to temperature dependence. Further, when a large amount of metal ions are dissolved to increase the carrier density, crystallization occurs, and conversely, the ion mobility decreases. In order to prevent this crystallization, PEO (MW
atanabe et al, “Solid Stat
e Ionics ", 28-30, 911, 198
8) Further, PEO (“40th Polymer Symposium Preliminary Proceedings”, 3766, 1991) in which a side chain is introduced into a crosslinked portion in order to improve ion mobility at low temperatures has been developed.
Recently, a molten salt type P in which a salt is introduced into the terminal of PEO is used.
EO (K. Ito et al., "Solid St"
ate Ionics ", 86-88, 325, 199
6, K. Ito et al. , “Electroc
him. Acta ", 42, 1561, 1997). However, at present, sufficient ionic conductivity cannot be obtained yet, so that an electrolyte or a mixture of a high-dielectric-constant organic solvent and a low-viscosity solvent may be used. Gel electrolytes immobilized with molecules are the mainstream, and when a solid electrolyte is used as a battery device, the efficiency of the electrochemical reaction at the interface with the electrode as well as the ion transport efficiency becomes a problem. I have.

On the other hand, the discotic liquid crystal phase has 197
7 years in S. (“Prana” 9 , 471 (1977)), a liquid crystal phase discovered by Chandrasekhar et al. For example, by the authors, "Disco
tic Liquid Crystals ”and“ Rep. Prog. Phys. " 53 (1990) 5
7 or as described in Shunsuke Takenaka entitled “Design and Synthesis of Discotic Liquid Crystal Molecules”, edited by The Chemical Society of Japan, “Quarterly Review of Chemistry,” Vol. 22, p. 60, compared to disc-shaped cores. It is found in compounds with multiple long side chains.

[0005] The types of the compounds can be mainly classified according to the structure of the core. Derivatives of 6-substituted benzene and 3-substituted benzene, phthalocyanine and porphyrin derivatives, triphenylene, tolcene, pyrylium derivatives, and tribenzocyclononene derivatives Azacrown derivatives, cyclohexane derivatives and the like.

Several reports have been made in the past suggesting the application to devices from the structural characteristics of discotic liquid crystals. In systems with conjugated pi electrons, such as phthalocyanine and triphenylene, the application of electron (or hole) channels (Pieocki et a
l. : “J. Am. Chem. Soc.” 1982, 1
04, pp5245), when the core is a ring like azacrown, an application of a molecular channel in which a molecule selectively passes through a central void portion (“J. Chem. Soc., Ch.
em. Commun. ", 1985, 1794," J.
Chem. Soc. Chem. Commun. ", 1
995, 117, 9957) and the like.

Also, recently, US Pat. No. 5,370,082
As shown in No. 0, a method of improving the electron conductivity by adding an oxidizing agent or a reducing agent to the discotic liquid crystal by several percent is also employed.

On the other hand, a lyotropic liquid crystal is a liquid crystal that is developed by mixing two components, unlike a thermotropic liquid crystal. Often one component is water or a solvent such as ethanol. Lyotropic liquid crystals are widely used as surfactants and the like, and their polymer liquid crystals are also used as structural materials for aircraft. For lyotropic discotic liquid crystals, see "Liquid Cr".
ysta1s ", 1986, Vo1.1, No. 2, 1
Some are shown on pages 09 to 125, but there is no description regarding the properties as an electrolyte.

[0009]

DISCLOSURE OF THE INVENTION The present invention has been made in view of such a prior art, and contains a discotic liquid crystal compound having lyotropic liquid crystallinity and a metal salt, and has an anisotropic ionic conductivity. It is an object of the present invention to provide a liquid crystal electrolyte and a secondary battery using the liquid crystal electrolyte.

[0010]

That is, the present invention provides a liquid crystal electrolyte comprising a discotic liquid crystal compound having lyotropic liquid crystallinity and a metal salt.

It is preferable that the discotic liquid crystal compound is polymerized by a polymerization reaction. Preferably, the metal salt is an alkali metal salt.

Further, the present invention is a secondary battery using the above liquid crystal electrolyte.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The liquid crystal electrolyte of the present invention is characterized by containing a discotic liquid crystal compound having lyotropic liquid crystal properties and a metal salt.

The above liquid crystal compound is preferably a discotic liquid crystal compound having a columnar phase. Further, it is preferable that these discotic liquid crystal compounds are polymerized and polymerized. In this case, a method of polymerizing a polymer having a polymerizable group such as an acryl group, a methacryl group, an epoxy group, or a vinyl group at a terminal of a liquid crystal side chain, and a method of copolymerizing with another polymerizable compound are preferable. The other polymerizable compound is not particularly limited, and examples thereof include an acrylic acid derivative, a methacrylic acid derivative, a vinyl derivative, a styrene derivative, a urethane derivative, and an epoxy derivative.

The metal salt is preferably an alkali metal salt,
For example, MCLO_Four, MBF_Four, MPF ₆, MCF_ThreeSO
_Two(M represents Li, Na, K.)
Genus salt, CuSO_Four, Ni (NO_Three)_Two, Ni (BF_Four)
_Two And the like. Especially preferred
Or LiClO_Four, LiBF_Four, LiPF₆, LiC
F_ThreeSO_Two, Li (CF_ThreeSO_Two)_TwoLithium metal salts such as N
It is.

The content of the metal salt contained in the liquid crystal electrolyte of the present invention is usually 0.01 to 50% by weight, preferably 0.1 to 30% by weight.

Further, the lyotropic liquid crystal of the present invention is preferably one that is developed by mixing with water.

Next, specific structural formulas of the discotic liquid crystal compound having lyotropic liquid crystallinity used in the present invention are shown in Tables 1 to 3, but the present invention is not limited to these.

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

[Table 3]

Next, a secondary battery will be described as an application example of the liquid crystal electrolyte of the present invention. FIG. 1 is a schematic configuration example of a secondary battery. 41 and 42 are negative and positive electrodes, respectively. 43 is an electrolyte layer using a liquid crystal electrolyte,
Using this layer as a channel, ions of a specific polarity are transmitted from the negative electrode to the positive electrode or from the positive electrode to the negative electrode. Since the negative and positive electrodes are required to have various functions such as ion emission and absorption functions, cooperation functions with external devices (for example, electronic conductivity functions), mechanical support functions, etc., they are usually separated from each other. Often, it becomes a composite composed of a plurality of members.

The negative electrode 41 is formed by coating a negative electrode active material 412 on an electron conductive support 411 such as copper, aluminum, gold, or platinum which also has an electronic connection function with an external circuit. Alternatively, a negative electrode active material that also functions as a support can be used. As the negative electrode active material, a material having the ability to release cations such as alkali ions such as Li ions, Na ions, and K ions, alkaline earth ions, and hydrogen ions. Alloys and the like, polyacetylene, polythiophene, poly p-phenylene, polyacene and the like, preferably doped with n-type from polymer materials, and derivatives thereof, and graphite (graphite), pitch, coke, A sintered body of an organic polymer or a composite of these materials and an organic polymer is appropriately and selectively used.

The positive electrode 42 is formed by coating a positive electrode active material 422 on an electron conductive support 421 such as copper, aluminum, gold, or platinum which also has an electronic connection function with an external circuit. Alternatively, a positive electrode active material that also functions as a support can be used. Among the positive electrode active material materials, among inorganic materials, chalcogen compounds and oxides of transition metals such as cobalt, vanadium, titanium, molybdenum, iron, and manganese, and composites of these with lithium are used as graphite and fluorine among carbon-based materials. A series of layered compounds such as activated carbon, or a composite of these materials and an organic polymer, is preferably a p-type or n-type doped polyacetylene, polyaniline, polypyrrole, polythiophene, poly-p-phenylene from a polymer material. , Polyacene, polyphthalocyanine, polypyridine, and the like, and their derivatives are appropriately and selectively used.

[0025]

The present invention will be described in more detail with reference to the following Examples and Synthesis Examples, but the present invention is not limited to these Examples.

Synthesis Example 1 2,3,6,7,10,11-hexa (1,4,7-trioxaoctyl) triphenylene (Exemplified Compound L-
Production of 5) (1) Production of 1,4,7-trioxaoctyl p-toluenesulfonic acid 3.0 g of 3,6-dioxaheptanol (2
5 mmol1) and 5.93 g (75 mmol) of pyridine were added, and 5.24 g (27.5 mmol) of p-toluenesulfonic acid chloride was added thereto in an ice bath, and the mixture was stirred for 1 hour and further stirred at room temperature for 3 hours. After the reaction, 3N-
After adding HC1 to make it acidic, it was extracted twice with toluene.
After the extract was washed with water, anhydrous sodium sulfate was added and dried. After distilling off the solvent, silica gel column chromatography (elution solvent: toluene / ethyl acetate = 3 /
1), p-toluenesulfonic acid 1,4,7
6.57 g (24 mmol) of trioxaoctyl were obtained. 96% yield

(2) Production of 2,3,6,7,10,11-hexa (1,4,7-trioxaoctyl) triphenylene Dry N, N-dimethylformamide (DM
F) 15 ml and sodium hydride (60% in oi
1 (mineral oil)) 0.77 g (19.3 mmol)
In a water bath, 0.92 g of 2,3,6,7,10,11-hexahydroxytriphenylene (2.84 mmol
1) was added and stirred for 1 hour. Thereafter, 6.4 g of 1,4,7-trioxaoctyl p-toluenesulfonate (2
A mixture of 3.3 mmol) and 5 ml of dry DMF was added dropwise, and the mixture was stirred at 80 ° C for 5 hours. After the reaction was completed, water was added, and the mixture was extracted twice with toluene. After the extract was washed with water, anhydrous sodium sulfate was added and dried.

After distilling off the solvent, the residue was purified by silica gel column chromatography (elution solvent: chloroform / ethanol = 200/1) three times to obtain 2,3,6,7,1.
0,11-hexa (1,4,7-trioxaoctyl)
0.95 g (1.0 mmol) of triphenylene was obtained.
Yield 25%, melting point 51.6 ° C

Example 1 Preparation of lyotropic liquid crystal 2,3,6,7,10,11-hexa (1,4,7-trioxaoctyl) triphenylene 60 mg (0.06
50 mg (2.78 ml) of H ₂ O was added to 4 mmol), and the mixture was heated and stirred at 60 ° C. to prepare a lyotropic liquid crystal A.

The phase transition temperature of the obtained lyotropic liquid crystal A is shown. Temperature rise process Cry (−15 ° C.) Xl (2 ° C.) Dh (26 ° C.) Iso Cooling process Iso (24 ° C.) Dh (0 ° C.) Xl (<−50 ° C.) Cr
y Cry: crystalline phase, X1: unidentified phase, Dh: discotic columnar phase, Iso: isotropic phase

Preparation of Liquid Crystal Electrolyte A 2,3,6,7,10,11-hexa (1,4,7-trioxaoctyl) triphenylene 60 mg (0.06
A liquid crystal electrolyte A was prepared by adding 25 mg of a 1.6 mol / 1 aqueous solution of LiClO ₄ to ₄ mmol) and heating and stirring at 60 ° C.

The phase transition temperature of the obtained liquid crystal electrolyte A is shown. Temperature rising process Cry (4 ° C.) Dh (22 ° C.) Iso Cooling process Iso (18 ° C.) Dh (0 ° C.) Cry Cry: crystalline phase, Dh: discotic columnar phase,
Iso: Isotropic phase

Example 2 A pair of glass substrates each having a thickness of 1.1 mm on which an ITO film having a thickness of 700 ° was formed as a transparent electrode was prepared. On the transparent electrode of the glass substrate, as a spacer on one substrate,
Silica beads having an average particle size of 2.4 μm were sprayed to produce cells having a uniform cell gap. The liquid crystal electrolyte A prepared in Example 1 was injected into this cell in an isotropic liquid state, and cooled from the isotropic phase at 20 ° C./h to a temperature showing a discotic columnar phase. Observation of the texture of the cell under crossed Nicols with a polarizing microscope revealed that a dark field was obtained, indicating that the discotic columnar phase had homeotropic orientation.

Next, 0.001 to 100 kHz, 10 mV
The complex impedance was measured by measuring the current when the AC voltage was applied, and the ionic conductivity was calculated. The results are shown below. Measurement temperature Ion conductivity 10 ° C 1.3 × 10 ^-8 S / cm

Next, instead of using silica beads having an average particle size of 2.4 μm, a recell was prepared by the same method except that silica beads having an average particle size of 40 μm were used. When the texture was observed with, multi-domain orientation was observed, and it was found that the discotic columnar phase was randomly oriented.

Further, the complex impedance was measured in the same manner, and the ionic conductivity was calculated. The results are shown below. Measurement temperature Ion conductivity 10 ° C 3.6 × 10 ^-9 S / cm

Example 3 Preparation of Liquid Crystal Electrolyte B 2,3,6,7,10,11-hexa (1,4,7-trioxaoctyl) triphenylene 60 mg (0.06
30 mg of a 1.6 mol / 1 aqueous solution of LiClO ₄ was added to ₄ mmol), and the mixture was heated and stirred at 60 ° C. to prepare a liquid crystal electrolyte B.

The phase transition temperature of the obtained liquid crystal electrolyte B is shown. Temperature rising process Cry (4 ° C.) Dh (20 ° C.) Iso Cooling process Iso (16 ° C.) Dh (0 ° C.) Cry Cry: crystalline phase, Dh: discotic columnar phase,
Iso: Isotropic phase

Example 4 Two kinds of cells were prepared and injected by the same method as in Example 2 except that the liquid crystal electrolyte B was used instead of the liquid crystal electrolyte A, and the texture was observed with a polarizing microscope. The cell made of 0.4 μm silica beads provided a dark field, indicating that the discotic columnar phase had homeotropic orientation. On the other hand, average particle size 40μ
It was found that the cell made of m silica beads had a multi-domain orientation, and the discotic columnar phase had a random orientation.

The complex impedance was measured in the same manner as in Example 2, and the ionic conductivity was calculated. The results are shown below. Average particle size 2.4 μm silica bead cell Measurement temperature Ion conductivity 10 ° C. 8.7 × 10 ⁻⁸ S / cm Average particle size 40 μm silica bead cell Measurement temperature Ion conductivity 10 ° C. 7.6 × 10 ⁻⁹ S / cm

[0041]

As described above, according to the present invention, a liquid crystal electrolyte having anisotropic ionic conductivity in an electrolyte used in the field of electronics such as batteries and sensor devices,
And a secondary battery using the liquid crystal electrolyte.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a secondary battery.

[Explanation of symbols]

 41 Negative electrode 42 Positive electrode 43 Electrolyte layer 411, 421 Electron conductive support 412 Negative active material 422 Positive active material

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J002 BQ001 DE186 DK006 5G301 CA30 CD01 5H029 AJ01 AK02 AK03 AK04 AL06 AL07 AL08 AL12 AL16 AM16 DJ09

Claims (4)

[Claims] 1. A liquid crystal electrolyte comprising a discotic liquid crystal compound having lyotropic liquid crystal properties and a metal salt. 2. The liquid crystal electrolyte according to claim 1, wherein the discotic liquid crystal compound is polymerized by a polymerization reaction. 3. The liquid crystal electrolyte according to claim 1, wherein the metal salt is an alkali metal salt. 4. A secondary battery using the liquid crystal electrolyte according to claim 1.