JP2000100244A - High molecular solid electrolyte - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use an electrolyte as a new key material to improve film formability, an insulating property and fracture strength by forming it by adding an inorganic salt to a complex of poly(ethylene glycol)-bis-(carboxymethyl)ether and pyrazine or 4,4'-dipyridyl or 1,3,5-triazine. SOLUTION: One mol of poly(ethylene glycol)-bis-(carboxymethyl)ether (abbreviated symbol: PEO-CA) is compounded with, preferably, a nitrogen containing heterocyclic compound of one mol of pyrazine or 4,4'-dipyridyl, or two mol of 1,3,5-triazine. The ion conductivity of this electrolyte is preferably maximized at room temperature when 0.03 mol of lithium perchlorate that is an inorganic salt having a high degree of dissociation per oxyethylene unit of the PEO-CA is added and is high when the PEO-CA is in an amorphous form having a molecular weight of 200-650. It has flexibility due to hydrogen bond. Both the compounding and the addition of the inorganic salt are performed by means of stirring at around 60 deg.C for four hours in an atmosphere of argon or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a solid polymer electrolyte using a new base material.

[0002] A polymer material that dissociates salts, keeps the generated ions stable, and conducts them quickly is called "polymer solid electrolyte" or "ion conductive polymer". Since this material enables ionic conduction in a solid state without using a solvent, it can be used, for example, as a solid electrolyte having a diaphragm function of an all-solid-state battery called a film battery or a paper battery.

[0003] The first substances used as the base material for polyelectrolytes are polyethers, in particular polyethylene glycols. Polyethers solvate ions through the dipole moment of ether oxygen, much like a polymer of water molecules. Moreover, since the polyether has a low Tg, the segmental movement of the chain is active at room temperature. Ions surrounded by ether oxygen can move according to this segmental motion. This is the principle of ionic conduction of the polyether solid electrolyte.

[0004] Poly (ethylene glycol) bis (carboxymethyl) ether in which the terminal OH group of polyethylene glycol is carboxymethyl etherified (hereinafter referred to as “PEO”)
-CA) or its polymer metal salt is used as a film of an all-solid battery, and is not satisfactory in performance such as film formability and dielectric strength, and further improvement is desired.

[0005]

DISCLOSURE OF THE INVENTION In order to satisfy the above demands, the present invention provides
A complex of EO-CA and a nitrogen-containing heterocyclic compound is used. Compounds that can be used include pyrazine (abbreviation: Py),
4,4′-dipyridyl (abbreviation: Bpy), and 1,
3,5-triazine (abbreviation: Tri). PEA-
CA is bifunctional, and these nitrogen-containing heterocyclic compounds have two or three ring nitrogen atoms per molecule.
In the case of y and Bpy, a complex having a molar ratio of 1: 1 is formed with PEO-CA, and Tri is mixed with PEO-CA at a molar ratio of 1: 2.
To form a complex.

The solid polymer electrolyte of the present invention can be obtained by adding a monovalent inorganic metal salt to the composite. The inorganic metal salt to be added is a salt having a high degree of dissociation, and usually lithium perchlorate LiClO ₄ is used. It is known that the ionic conductivity in a solid polymer depends on the salt concentration. In the present invention, it has been observed that the conductivity at room temperature reaches a maximum when the salt concentration per PEO unit is about 0.03 mol.

[0007] The ionic conductivity also depends on the molecular weight of PEO-CA. In general, the higher the molecular weight, the higher the conductivity. However, in order to maintain an amorphous state in which ions can move quickly along the segmental motion of the molecular chain, the molecular weight is 20%.
It is suitably in the range of 0 to 650 (average degree of polymerization of PEO 3 to 15).

In the case of Py and Bpy, the complex of PEO-CA and the nitrogen-containing heterocyclic compound is in a molar ratio of 1: 1.
In the case of Tri, the reaction is performed at a molar ratio of Tri: PEO-CA = 1: 2. The reaction is carried out in an inert atmosphere, for example in a glove box filled with argon gas, by stirring the mixture of the two under heating (about 60 ° C.) for about 4 hours. The resulting complexes are all brown gels. By comparison of IR spectra, peaks due to expansion and contraction of C の O at 1746 cm ⁻¹ observed in the spectrum of PEO-CA were 3 to 6 in the spectrum of the composite, respectively.
The shift to the lower wavelength side by about cm ⁻¹ confirms the formation of hydrogen bonds.

A complex of a metal ion such as a lithium ion and a complex (the polymer solid electrolyte of the present invention) is similarly added to a predetermined amount of perchlorine in an inert atmosphere such as a glove box filled with argon. It can be synthesized by adding lithium oxide and stirring under heating (about 60 ° C.) for about 4 hours. It is important that the lithium perchlorate be added, for example, by drying it in a vacuum line at 40 ° C. for 3 days to substantially completely remove water in advance.
As mentioned earlier, LiClO ₄ / PEO units = 0.0
Complex 3 exhibited the highest ionic conductivity at room temperature.

EXAMPLES (1) Synthesis of PEO-CA: Py complex PEO-CA (Mw 250 Aldrich) 7.7
g (3.1 × 10 ^-2 mol) and pyrazine (Wako C)
o. 3.2 g (3.1 × 10 ^-2 mol) was placed in a sample bottle and stirred at about 60 ° C. for 4 hours in a glove box filled with argon gas.

(2) Synthesis of PEO-CA: Bpy complex As in (1), anhydrous 4,4'-bipyridyl (Kanto Chemical Co.) was added to PEO-CA at a molar ratio of 1: 1. The mixture was stirred at about 60 ° C. for 4 hours in a glove box filled with argon gas.

(3) Synthesis of PEO-CA: Tri complex 1,3,5-Triazine (Kanto Chemical) was added to 4.3 g (1.7 × 10 ^-2 mol) of PEO-CA.
l Co. ) 700 mg (8.6 × 10 ⁻³ mol) was added, and the mixture was stirred at about 60 ° C. for 4 hours in a glove box filled with argon gas using a hot stirrer.

(4) Synthesis of lithium ion complex In a glove box filled with argon gas, PEO-CA and P synthesized by (1), (2) and (3) were used.
Each of the EO-CA: Py complex, the PEO-CA: Bpy complex, and the PEO-CA: Tri complex was placed in a sample bottle, and dried at 40 ° C for 3 days in a vacuum line at lithium perchlorate (Kanto Chemical Co., Ltd.). .)
With the molar ratio [LiClO ₄ ] / [PEUnit] =
The contents were adjusted to 0.01, 0.03, 0.06, and 0.1, and the mixture was heated and stirred at 60 ° C. for 4 hours using a hot stirrer to synthesize a lithium complex.

Ionic conduction of the synthesized lithium ion complex
After measuring the resistance of the sample bulk of each solid polymer electrolyte four polyelectrolytes synthesized in Comparative Example of the ion conductivity of sex Test (1) PEO-CA and PEO-CA complexes, ionic conductivity I asked. FIG. 1 shows [Li
The graph shows the temperature dependence of the polymer electrolyte when ClO ₄ ] / [PEUnit] = 0.03. At this time, PEO-CA, PEO-CA: Py complex, PEO-
The ionic conductivity of -CA: Bpy complex and the ionic conductivity of PEO-CA: Tri complex are 3.6 × 10 ⁻⁵ Scm ⁻¹ ,
4.4 × 10 ⁻⁶ Scm ⁻¹ , 6.2 × 10 ⁻⁶ Scm ⁻¹ ,
It was 4.7 × 10 ⁻⁶ Scm ⁻¹ . The decrease in ionic conductivity of these composites as compared to PEO-CA is due to a decrease in the mobility of carrier ions due to solidification of the system, but the ionic conductivity is equivalent to that using the PEO cross-linked product. Rate was obtained. PEO-CA and PE
The Arrhenius plot of the O-CA complex is
At 0 ° C., it showed a linear type. That is, these composites have properties as a liquid. Generally PEO
The allenium plot of the crosslinked product shows an upwardly convex curve, and is known to exhibit rubbery properties. Therefore, it was found that the use of hydrogen bonding provided flexibility that could not be obtained by conventional covalent bonding.

(2) Comparison of ionic conductivities of polymer solid electrolytes with different amounts of lithium perchlorate introduced PEO-CA, P
FIGS. 2 to 5 show changes in the ionic conductivity of the EO-CA: Py composite, the PEO-CA: Bpy composite, and the PEO-CA: Tri composite. From these results, at room temperature, [LiClO ₄ ] / [PEOuni] was obtained for all the composites.
t] = 0.03, the ionic conductivity shows a maximum value,
At around 100 ° C., the maximum value was exhibited when the molar ratio was 0.06. When the molar ratio was 0.1, it was greatly reduced. In order to explain the reason, the value of Tg of each polymer electrolyte is shown in FIG. This figure shows that the value of Tg increases as lithium perchlorate is introduced. In the low-concentration region, as lithium perchlorate is added, lithium ions coordinate to oxygen atoms of PEO-CA and a lithium complex is formed, so that the segment motion of the main chain is greatly reduced and the value of Tg is greatly increased. The effect of lithium ion generation surpassed this due to complex formation, resulting in an increase in conductivity.However, in the high concentration region, lithium complex formation approaches a saturated state, so repulsion of lithium ions occurs and dissociation does not easily occur. For this reason, a large decrease in conductivity was observed. In addition to this reason, it is considered that the precipitation of lithium perchlorate as crystals also contributes to the decrease in conductivity.

(3) Comparison of Ionic Conductivity of PEO-CA Polymer Solid Electrolytes with Different Molecular Weights In order to know how a change in molecular weight affects the ionic conductivity, a PEO-CA polymer solid having a molecular weight of 600 is used. Electrolyte ([LiClO ₄ ] / [PEUnit] = 0.
03) was synthesized, and its ionic conductivity was measured, as shown in FIG. From this result, PEO of molecular weight 600
The -CA polymer solid electrolyte showed a higher value of ionic conductivity than the molecular weight of 250. The reason for this is that PEO-C
Although the crystal state of A may be different, a molecular weight of 600
It is believed that the low viscosity of PEO-CA was the largest cause of high ionic conductivity. In general, a polymer compound tends to increase in viscosity as the molecular weight increases, but it is inferred that this did not occur, but PEO-CA having a molecular weight of 600 has a longer main chain than that of a molecular weight of 250. It is thought that the viscosity was low because the interaction between the carboxylic acids became small.

[Brief description of the drawings]

FIG. 1 [LiClO ₄ ] / [PEO unit] = 0.0
3 is a graph showing the temperature dependence of the ionic conductivity of the polymer electrolyte in FIG.

FIG. 2

FIG. 5: PEO- based on the amount of lithium perchlorate introduced
CA, PEO-CA: Py complex, PEO-CA: Bp
The graph which shows the change of the ionic conductivity of y composite, PEO-CA: Tri composite.

FIG. 6 is a graph showing a change in Tg of each polymer electrolyte depending on the amount of lithium perchlorate introduced.

FIG. 7 is a graph comparing the ionic conductivities of PEO-CA polymer solid electrolytes having different molecular weights.

Claims (6)

[Claims] 1. Poly (ethylene glycol) bis (carboxymethyl) ether (PEO-CA) and pyrazine (Py) or 4,4'-bipyridyl (Bpy) or 1,3,5-triazine (Tri) A polymer solid electrolyte obtained by adding an inorganic salt to a composite. 2. The complex comprises 1 mol of PEO-CA and Py
2. The polymer solid electrolyte according to claim 1, which is a complex with 1 mol. 3. The complex comprises 1 mol of PEO-CA and Bp
2. The polymer solid electrolyte according to claim 1, which is a complex with 1 mol of y. 4. The complex is composed of 2 mol of PEO-CA and Tr
2. The solid polymer electrolyte according to claim 1, which is a complex with 1 mol of i. 5. The polymer solid electrolyte according to claim 1, wherein said inorganic salt is lithium perchlorate. 6. The amount of lithium perchlorate added is PEO-CA.
6. The polymer solid electrolyte according to claim 5, wherein the amount is about 0.03 mol per oxyethylene unit.