JPS5939720A - Solid compound - Google Patents

Abstract

PURPOSE:To obtain a solid compound capable of forming a thin film with high alkali ionic conductivity suitable for an electrochromic display element by mixing the fluoride of an alkali metal with the fluoride of a bivalent metal in a specified weight ratio and by sintering the mixture. CONSTITUTION:Lithium fluoride and/or sodium fluoride (A) and >=1 kind of fluoride (B) selected from the anhydrous difluorides of Cr, Fe, Co, Ni, Cu and Zn are weighed so as to obtain stoichiometrically a compound having a composition represented by the formula (where MI is Li and/or Na; MII is at least one among Cr, Fe, Co, Ni, Cu and Zn; 0.3<=a<=0.999; and b=1-a). They are mixed, compressed, sintered, and crushed to obtain a solid compound having a composition represented by the formula. The solid compound has high alkali ionic conductivity and can give a stable thin film in the air.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solid compound that is a fluoride of an alkali metal and a divalent metal, and particularly to a solid compound that is a fluoride of an alkali metal and a divalent metal and is suitable for an alkali ion conductor. It is something.

In order to produce a solid-state ion device such as an all-solid-state electrochromic display device, a lithium ion device must have a lithium ion conductivity of 1×10 S/m or more at room temperature, be stable in the atmosphere, and have a thickness of 0.1 to 100 S/m or more. It is necessary to be able to form micron thin films. Conventionally, materials that meet this purpose include LlxNal-x beta alumina, LisN
etc. were considered. However, the former had drawbacks such as difficulty in forming a thin film, and the latter was unstable in the atmosphere.

An object of the present invention is to provide a solid compound capable of forming a thin film with high alkali ion conductivity.

One of the inventors previously proposed a'Lix/Na1-x/F
-b'AIF3 (where a' is 0.45 to 0.7
b' is a numerical value in the range of 0.6 to 0.55, X is 0.1≦X 1. It has been found that an amorphous compound having a composition corresponding to a value in the range of O) is an excellent lithium ion conductor. Furthermore, the general formula, a''M1
F-b''MuIF3 (here, M represents at least one element selected from the group consisting of Li and Na, MIH represents Sc, T
i, V, CrS Fe, Rh1, In, Ga
, yJ represents at least one element selected from the group consisting of; "=1-a
We have found that a composition represented by "a numerical value) is an excellent alkali ion conductor. Based on these findings, we have found that a fluorine composition containing two or more types of metal ions that can achieve similar conductivity. The present invention was achieved as a result of experimental studies on combinations of alkali metal ions and divalent metal ions.

The solid compounds of the invention according to the above have the general formula, T
n a M , F-bM F2 (here, M represents at least one element selected from the group consisting of Li and Na, Mll represents Cr, Fe, Co, Ni
represents at least one element selected from the group consisting of , Cu, and Zn; a is a numerical value in the range of 0.6 and a<0.999; b is a numerical value expressed by b=1-a ) is a solid compound that generally has an amorphous structure.

From the viewpoint of the inherent crystal structure, the solid compound of the present invention has the following characteristics:
It can be classified into the following three types (i), M
F structure. MF2 is forcibly dissolved in solid solution. The vacancies created by replacing two M by one Mu increase the diffusion coefficient of M1 ions, that is, the M1 ion conductivity.

(2) M12MIIF4 structure. This compound has a spinel structure (small ionic radius M' =
For Li, for example L12NIF4) or K2
N r F4 structure (large ionic radius M = K, R
b, limited to the case of Cs, no corresponding compound exists for M = Na, and the perovskite structure K N +
(which can be regarded as a layered structure of F3 and KF), and in either case, it can become a two-dimensional ionic conductor.

(3) MMF, structure. This compound has a perovskite structure (e.g., NaFeF3, NaN1F3, N
a Z n F3, no corresponding compound exists for M = Li with a small ionic radius), and can become a six-dimensional ionic conductor.

As described above, although the inherent crystal structure changes depending on the molar ratio of MIF and MIIF2, it is expected that the M1 ion conductivity will increase in either case.

Hereinafter, the present invention will be specifically explained in further detail using test examples.

In addition, in the following test examples, in test example 1.2, a comparative example that is not according to the present invention is described together with an example of the present invention, and in test example 6.4.5, , only examples according to the invention have been described.

Test Example 1 Weighed, mixed, pressed, and sintered (750°C
), then crushed, placed in a Knudsensel type evaporation vessel (made of tantalum, but preferably made of platinum when evaporating a mixture containing NiF or CuF2), heated to approximately 900 ° C. Vacuum deposition was performed at a vacuum degree of about 500 μPa. At this time, the substrate used was a slide glass coated with an aluminum evaporated film serving as the lower electrode, and the substrate temperature was kept at room temperature.

The vapor-deposited film thus formed with a thickness of 0.5 microns was colorless and transparent, had a smooth surface, had no fine structure, and had no defects such as cracks or peeling.

Chemical analysis of these thin films revealed that they had the compositions shown in the compound column of Table 1.

Moreover, the results of X-ray diffraction of these thin films showed that they were all amorphous.

In Table 1, the compositions in parentheses in the compound column are those of comparative examples not according to the present invention, and the other compositions are those of examples of the present invention.

Next, lithium and aluminum were sequentially deposited on these thin films to form a layered film, which was used as an upper electrode.

When a DC voltage within ±2 V was applied between these lower and upper electrodes, a large current flowed only when positively charged lithium ions were considered to be moving, and the conductivities at that time were as shown in Table 1. It was determined as shown in the electrical conductivity column. On the other hand, under conditions where lithium ions cannot move (for example, when all lithium ions are directly under the upper electrode and an electric field is applied such that the upper electrode is negative and the lower electrode is positive), , the current is extremely small, and the conductivity at that time is approximately 10-10 S/m, regardless of the type of compound prepared.
Met. This electrical conductivity is believed to be due to electronic conduction.

On the other hand, among the conductivities listed in Table 1, the large conductivity values are considered to be due to lithium ion conduction. therefore,
Among these, Ll:Mn 99.9: 0.1 60
An amorphous solid compound thin film having a composition in the range of =70 is considered to be an excellent lithium ion conductor.

In Table 1, the composition of the compounds is expressed in molar parts.

Test Example 2 Select from chromium, iron, cobalt, nickel, copper, zinc difluoride, and sodium fluoride according to the prescription.
Each was weighed, mixed, pressed, sintered, and crushed, and a colorless, transparent, amorphous thin film with a thickness of about 0.5 microns was produced in the same manner as in Test Example 1.

These were subjected to chemical analysis, and the conductivity of sodium ions was measured in the same manner as in Test Example 1 (however, metallic sodium was evaporated in place of metallic lithium). In addition, at the same time, a comb-shaped electrode (made of a chromium-gold layered film) facing the plane was provided on the fluoride thin film with a thickness of about 0.5 microns, which had been previously formed on a slide glass (not coated with an aluminum vapor-deposited film). The AC conductivity of the thin film was measured by a method of measuring impedance while applying an AC of 20 Hz to 500 kHz. Both measured values agreed within a range of ±30%, and the values are shown in Table 2 together with the results of the above chemical analysis.

In Table 2, the compositions in parentheses in the compound column are those of comparative examples not according to the present invention, and the other compositions are those of examples of the present invention.

Margin table below 2 Compound Electrical conductivity (S/m) (1[]Q
NaF) 1/1O-1199NaF
1CrF2 2/ 10”6ONaF 4
0CrF2 1/10-495NaF5
FeF24/ 1O-567NaF 33FeF2
8/ 1O-549NaF 51COF2
6/ 10 ”99.13NaF 092NiF
7/10”61NaF 39NIF2
8/ 1O-55QNaF 5QNiF
1/10-4 (15NaF 85NI F2)
4/1O-866NaF 34CuF2
1/10 '93NaF 2ZnF2
6/10' Test Example 3 This test example is an example according to the present invention.

Using a sample selected from chromium, iron, cobalt, nickel, copper, zinc difluoride, lithium butoxide, and sodium butoxide, the sample was pretreated in the same manner as in Test Example 1, and then treated in the same manner as in Test Example 1. A similar deposited film with a thickness of about 0.5 microns was prepared in a similar manner. These were subjected to chemical analysis, and the AC conductivity was measured in the same manner as in Test Example 2 above. As a result, the values shown in Table 6 were obtained.

Table 6 Compound Conductivity (87m) 41LiF1
7NaF42CrF28/1O-536LiF16Na
F48FeF26/10520LiF16NaF64C
oF24/1o-5iQLiF4QNaF5ONiF2
1/1O-415LiF2QNaF65CuF+ 5
/1O-460Li F 35NaF 5ZnF28/
1(:J 4 Test Example 4 This test example is an example according to the present invention.

Thin films of similar ternary compounds were prepared in the same manner as in Test Example 6 above, and tests were conducted on them to obtain the results shown in Table 4.

All of the ternary compounds shown in Table 4 exhibit high ionic conductivity.

Compound Conductivity (87m) 50Li
F25CrF225FeF2 1/1O-
447L+F 26CrF224COF2 8/
10-548LtF 2QCrF2 2NiF2
3/10-451LiF 29CrF220CL
IF2 1/10 '51LiF 33Cr
F216ZnF2 9/ 10-551 LiF
26FeF223CoF27/10530LiF
40FeF23QNiF28/ 1Q 552LIF
20FeF228NIF2 2/ 1Q-45
0LIF 23FeF222COF26/1O-449
I, +F 41 FeF210ZnF2 1 /
10~485LiF 5CoF21ONiF2
3/ 10 '9[]LiF 6CoF 4CuF
2 7 / 1Q-591LiF 4CoF
25ZnF2 8/10”95LiF2
NiF23CuF2 1/1O-491
LiF7NiF 2ZnF 2/104
2 97LiF 1cuF 2ZnF2 7/
10''Test Example 5 This test example is an example according to the present invention.

In the same manner as in Test Example 6 above, thin films of similar quaternary or higher compounds were prepared and tested, and the results shown in Table 5 were obtained.

All of the quaternary or higher compounds shown in Table 5 exhibit high ionic conductivity.

Table 5 Compound conductivity (87m)51
LiF 15CrF25FeF229NiF2 4/
1O-470LiF 13CrF21CoF216C
uF2 2/ 10 '8[]L+F 5FeF21
3NIF22ZnF2 4/ 10 '95LiF
lN1F 2CuF 2ZnF 2/1
042 2 2 71] Lip 15crF21[lNiF23CuF2
2ZnF24/1Q-4 Test Example The test example in 2ZnF24/1Q-4 test example is an example according to the present invention.

Using the same method as in Test Example 6 above, thin films of similar quaternary or higher compounds were prepared and tested. Table 6
The results shown are obtained.

All of the quaternary or higher compounds shown in Table 6 showed high ionic conductivity.

Table 6 Compound conductivity (8/m) 7Q
NaF 15CrF21ONiF25ZnF2 1
/ 1O-440LiF 18NaF 5FeF237
NiF'23/ 10'70LiF21NaF3Cr
F24NiF22CuF23/10' As can be seen from the comparison with the examples of the present invention in the above test examples, especially the comparative examples, the effects of the present invention are extremely remarkable.

As described above, the amorphous thin film according to the present invention made of a solid compound having a composition of lithium sodium butoxide or a mixed crystal thereof mixed with a suitable divalent transition metal atomide has a crystallinity of about 10 S/ Since they exhibit a large cationic conductivity of m or more at room temperature, they can be applied to electrochromic display elements, and have great industrial benefits. Moreover,
According to the present invention, the amount of mixed crystals of divalent transition metal fragments is 0.
Since the above-mentioned excellent characteristics can be obtained over a wide range from 1 mol to 70 mol, strict control of the thin film composition is no longer necessary, which has the effect of reducing device manufacturing costs.

Claims (1)

[Claims] General formula: aM1F-bMIIF2, (where Ml represents at least one element selected from the group consisting of Ll and Na, and M represents Cr, F
represents at least one element selected from the group consisting of e, Co, Ni, C'u, and Zn, and a is 0.3
<a,, (is a numerical value in the range of 0,999, b is b=
A solid compound characterized by being composed of a compound represented by (the numerical value represented by 1-a).