JPH08239218A - Oxide composition and solid electrolyte - Google Patents

Abstract

PURPOSE: To obtain an oxide composition stable in the atmosphere, providing a solid electrolyte having high ionic conductivity, glass transition temperature, etc., comprising an oxide selected from Nb2 O5 , Ta2 O5 and WO3 , Li2 O4 and SiO2 . CONSTITUTION: This oxide composition is shown by the formula (M is an oxide selected from Nb2 O5 , Ta2 O5 and WO3 ; x+y+z=1) and is obtained by mixing an oxide selected from Nb2 O5 , Ta2 O5 and WO3 with lithium carbonate and silicon dioxide, heating, melting and cooling the mixture. The oxide composition is preferably glassy. In the formula, the values of (x), (y) and (z) are preferably in 1/10<=x<=2/3; 1/10<=y<=4/5; 1/50<=z<=1/2. The prepared oxide composition has excellent thermal stability, has high crystallization temperature and can be suitably used as a solid electrolyte for the whole solid type electrochemical element such as a gas sensor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxide composition and a solid electrolyte, and in particular, it is preferably used as an electrolyte for an all-solid-state electrochemical device such as a solid-state battery, an electrochromic device and a gas sensor. The present invention relates to a lithium ion conductive glassy solid electrolyte having high electrical conductivity and excellent thermal stability.

[0002]

2. Description of the Related Art Li ₂ S-SiS ₂ and Li ₂ S-P ₂ are known lithium ion conductive glassy solid electrolytes.
S ₅ -LiI, there is a compound mainly composed of a sulfide such as _{Li 2 S-B 2 S 3} -LiI. However, since these compounds are mainly composed of sulfides, they have high hygroscopicity and are unstable, and it is difficult to handle them in the atmosphere.

Further, as an oxide type lithium ion conductive glass solid electrolyte which is relatively stable in the atmosphere, L
i ₂ O-P ₂ O ₅ -Ta ₂ O ₅ system and Li ₂ O-P ₂ O ₅
-Nb ₂ O ₅ based solid electrolytes have been proposed by BVR Chowdari et al. (J. Non-Crystalline Solids 108
(1989) 323-332 and J. Non-Crystalline Solids 110.
(1989) 101-110). Although these oxide systems have relatively good ionic conductivity, they have low glass transition temperature and crystallization temperature and lack thermal stability for use as solid electrolytes such as gas sensors operating at high temperatures. ing.

Therefore, an object of the present invention is to provide an oxide composition which is stable in the air and has a high glass transition temperature and a high crystallization temperature, and a lithium ion conductive material which has a high ionic conductivity and a high glass transition temperature and a high crystallization temperature. To provide a viscous solid electrolyte.

[0005]

As a result of earnest research, the present inventor has found that the general formula (Li ₂ O) _x- (SiO ₂ ) _y -M _z (M is Nb ₂ O ₅ , Ta ₂ O ₅ and At least one oxide selected from the group consisting of WO ₃ and x +
y + z = 1. It was found that the oxide composition represented by the formula (1) provides a lithium ion conductive glassy solid electrolyte which is stable in the air, has a high ionic conductivity, and has a high glass transition temperature and a high crystallization temperature.

Therefore, according to the present invention, the general formula (Li ₂ O) _x- (SiO ₂ ) _y -M _z (M is selected from the group consisting of Nb ₂ O ₅ , Ta ₂ O ₅ and WO _3. At least one or more oxides, x +
y + z = 1. The oxide composition shown by these is provided.

The oxide composition is preferably glassy.

In the above general formula, the values of x, y and z are preferably 1 / 10≤x≤2 / 3, respectively.
1/10 ≦ y ≦ 4/5 and 1/50 ≦ z ≦ 1/2.

According to the present invention, the general formula (Li ₂ O) _x- (SiO ₂ ) _y -M _z (M is selected from the group consisting of Nb ₂ O ₅ , Ta ₂ O ₅ and WO _3. At least one or more oxides, x +
y + z = 1. The solid electrolyte which consists of a glassy oxide composition shown by these is provided.

The values of x, y and z are preferably 1 / 10≤x≤2 / 3 and 1 / 10≤y≤4 / 5, 1 respectively.
/ 50 ≦ z ≦ 1/2.

The oxide composition of the present invention has excellent stability in the air, high thermal stability, and high ionic conductivity.

In the oxide composition and solid electrolyte of the present invention, Nb ₂ O ₅ , Ta ₂ O ₅ and WO ₃ may coexist or may be used separately. That is, in the above general formula, three components of Nb ₂ O ₅ , Ta ₂ O ₅ and WO ₃ as M may be present in one composition at the same time, and two of these components may be contained in one composition at the same time. It may be present in the object. In addition, Nb ₂ O ₅ , Ta ₂ O ₅
And only one component of WO ₃ may be used as M in the above general formula. Specifically, {Li ₂ O} _x − {S
_{iO 2} y - {(Nb} 2 O 5) a (Ta 2 O 5) b (W
_{O 3) c} z, {} Li 2 O} x - {SiO 2} y -
{(Nb ₂ O ₅ ) _d (Ta ₂ O ₅ ) _e ) _z , {Li ₂ O}
_{x - {SiO 2} y -} {(Nb 2 O 5) f (WO 3)
_{g} z, {Li 2 O} } x - {SiO 2} y - {(Ta 2
_{O 5) h (WO 3)} i} z, (Li 2 O) x - (SiO 2
_{) Y - (Nb 2 O 5} ) z, (Li 2 O) x - (SiO 2
_{) Y - (Ta 2 O 5} ) z or _{(Li 2 O) x - (} S
_{iO 2) y - (WO 3} ) composition of _z it can be used. Here, a + b + c = 1, d + e = 1, f + g = 1,
h + i = 1.

In the oxide composition and solid electrolyte of the present invention, when M is Nb ₂ O ₅ , the glassy solid electrolyte is less likely to be distorted, and is easy to handle, and the ionic conductivity and the crystallization temperature are high. When M is Ta ₂ O ₅ , the ionic conductivity is highest and the crystallization temperature is also highest. When M is WO ₃ , distortion is unlikely to occur as in the case of Nb ₂ O ₅ .

In the oxide composition and solid electrolyte of the present invention, the values of x, y and z are preferably 1/10 ≦ x.
≦ 2/3, 1/10 ≦ y ≦ 4/5, 1/50 ≦ z ≦ 1 /
It is 2. When x is in the range of 1/10 or more and 2/3 or less, vitrification becomes easy, and the crystallization temperature T
_c also becomes higher and it can be used at high temperature. y is 1/1
In the range of 0 or more and 4/5 or less, crystallization is easy and the crystallization temperature T _c is high. When z is in the range of 1/50 or more and 1/2 or less, the ionic conductivity increases. More preferable ranges of x, y, and z are 0.4 ≦ x ≦ 0.6 and 0.4 ≦ y ≦
0.6 and 0.05 ≦ z ≦ 0.2. This is because in this range, the ionic conductivity is high and the crystallization temperature is high.
In the present invention, x, y and z represent the molar ratio of each oxide.

The oxide composition and the glassy solid electrolyte of the present invention are preferably produced by the following method.

The first method is to measure a predetermined amount of a powdered reagent such as silicon dioxide, lithium carbide, niobium oxide, tantalum oxide, or tungsten oxide as a starting material, mix them well in a mortar, and then put them in a platinum crucible and put them in an electric furnace. Is melted for a certain period of time, and then the solution is quickly poured onto a SUS plate or the like and rapidly cooled to obtain the vitreous oxide composition or vitreous solid electrolyte of the present invention. A crystalline oxide composition can be obtained by slow cooling after melting.

The second method is a method for producing a thin film oxide composition or solid electrolyte by using a high frequency sputtering method. As the target, a sintered body or a molten body of lithium metasilicate or lithium orthosilicate is used. In this case, niobium oxide, tantalum oxide, tungsten oxide,
Sputtering is performed by placing a sintered or molten chip of lithium niobate, lithium tantalate, or the like on the target. If necessary, oxygen gas is introduced to carry out reactive sputtering.

In the first method, an arbitrary shape can be easily produced and the workability is excellent. The second method is a kind of ultra-quenching method in which a solid is directly produced from a gas phase, and it is possible to extend the vitrification range to a region where the lithium composition is large.

The lithium ion conductive glassy solid electrolyte containing the oxide composition of the present invention as a main component is suitably used for a solid-state battery, an electrochromic element, a gas sensor such as a carbon dioxide sensor, and the like.

For example, a carbon dioxide gas sensor using the solid electrolyte of the present invention can have a structure as shown in FIG.
In the carbon dioxide sensor 10 of FIG. 1, the layered solid electrolyte 3 is provided on the layered metal carbonate 1 in which the mesh-shaped noble metal electrode 2 is embedded, and the noble metal electrode 4 is provided on the solid electrolyte 3. There is. Lead wires 5 and 6 are connected to the noble metal electrodes 2 and 4, respectively.

The metal carbonate 1 is preferably
Lithium carbonate, sodium carbonate, potassium carbonate, barium carbonate, strontium carbonate, calcium carbonate are used. Particularly preferably, lithium carbonate, or a two-component system of lithium carbonate and another carbonate is used. The layer thickness of the metal carbonate 1 depends on the kind of the metal carbonate, but is generally 0.01 to 3 mm, preferably 0.05 to 1 m.
m.

As the solid electrolyte 3, the solid electrolyte of the present invention is used. The thickness of the solid electrolyte 3 is 0.5 to 10 μm,
Particularly, 1 to 5 μm is preferable.

Platinum, gold, silver or the like is preferably used for the noble metal electrodes 2 and 4, and platinum or gold is particularly preferably used.

Platinum, gold, silver or the like is preferably used for the lead wires 5 and 6, and platinum or gold is particularly preferably used.

[0025]

【Example】

(Example 1) Lithium carbonate, silicon dioxide, and niobium pentoxide powder reagents were weighed so as to have a molar ratio of 4: 5: 1 and thoroughly mixed in a mortar. Transfer to a platinum crucible, put in an electric furnace, heat to 1400 ° C and melt for 5 hours, then add S
The melt was rapidly cooled by dropping it on a US plate and sandwiching it with another SUS plate to obtain a flat glassy solid electrolyte. The composition of this glassy solid electrolyte is (Li ₂ O) _0.4 −
It was (Nb ₂ O _{5) 0.1} (molar ratio) - (SiO _{2) 0.5.}

Upper and lower ends of this flat glass solid electrolyte
With # 2000 polishing paper to a thickness of 2 mm,
A platinum electrode was formed on the edge by sputtering, and the ionic conductivity of
The measurement was performed. In addition, the glass transition temperature is small
It measured using the glass piece of. Fabricated vitreous solid state electrode
Ionic conductivity σ at room temperature of decomposition_RTIs 3.5 × 10 ^-7
S / cm, glass transition temperature T_g 513 ℃, crystal
Temperature T_C Was 691 ° C. Note that the conductivity σ_RTExchange
Glass transition temperature T_g Conclude with
Crystallization temperature T_C Was measured by the DTA (differential thermal analysis) method.

Example 2 Lithium carbonate, silicon dioxide,
The molar ratio of each powdered reagent of niobium pentoxide was 4.5: 4.5:
After weighing so as to have a composition of 1, a glass solid electrolyte was prepared in the same manner as in Example 1. The composition of the glass solid electrolyte _{(Li 2 O) 0.45 - (} SiO 2)
_0.45 - was (Nb ₂ O _{5) 0.1} (molar ratio). σ _RT ,
As a result of measuring T _g and T _C in the same manner as in Example 1, the results were 1.8 × 10 ⁻⁶ S / cm, 498 ° C. and 6 respectively.
It was 26 ° C.

(Example 3) Lithium carbonate, silicon dioxide,
Each powdered reagent of tantalum pentoxide was weighed so as to have a composition of 4: 5: 1 in molar ratio, and then a glassy solid electrolyte was prepared in the same manner as in Example 1. The composition of the glass solid electrolyte _{(Li 2 O) 0.4 - (} SiO 2) 0.5 -
It was (Ta ₂ O ₅ ) _0.1 (molar ratio). σ _RT , T _g ,
As a result of measuring T _C in the same manner as in Example 1, the results were 6.1 × 10 ⁻⁷ S / cm, 547 ° C., and 716 ° C., respectively.

(Example 4) Lithium carbonate, silicon dioxide,
Tungsten trioxide powder reagents in a molar ratio of 4: 5: 1
After being weighed so as to have the composition of, a glass solid electrolyte was prepared in the same manner as in Example 1. The composition of the glass solid electrolyte _{(Li 2 O) 0.4 - (} SiO 2) 0.5
- it was (WO _{3) 0.1} (molar ratio). σ _RT , T _g , T
_{When C} was measured in the same manner as in Example 1, the results were 1.7 × 10 ⁻⁷ S / cm, 520 ° C., and 699 ° C., respectively.

Comparative Example 1 Lithium carbonate, phosphorus pentoxide, and niobium pentoxide powder reagents were weighed so as to have a molar ratio of 6: 3: 1, and then the same procedure as in Example 1 was performed. A vitreous solid electrolyte was prepared. σ _RT , T _g , and T _C were measured in the same manner as in Example 1, and the results were 2.
The temperature was 4 × 10 ⁻⁶ S / cm, 364 ° C., and 455 ° C.

Comparative Example 2 Lithium carbonate, phosphorus pentoxide, and tantalum pentoxide powder reagents were weighed so that the molar ratio was 6: 3: 1, and then the same procedure as in Example 1 was performed. A vitreous solid electrolyte was prepared. σ _RT , T _g , and T _C were measured in the same manner as in Example 1, and
It was 2.3 * 10 < ^-6 > S / cm, 465 degreeC, and 559 degreeC.

COMPARATIVE EXAMPLE 3 Lithium carbonate, phosphorus pentoxide, and tungsten trioxide powder reagents were weighed so that the molar ratio was 6: 3: 1, and then the same procedure as in Example 1 was performed. A vitreous solid electrolyte was prepared. σ _RT , T _g , T _C
Was measured in the same manner as in Example 1, and the results were 1.7 × 10 ⁻⁶ S / cm, 363 ° C., and 425 ° C., respectively.

As described above, the glassy solid electrolyte containing the oxide composition of the present invention as the main component has a high glass transition temperature and a high crystallization temperature, and also has a high ionic conductivity and exhibits excellent characteristics.

[0034]

According to the oxide composition and solid electrolyte of the present invention, a lithium ion conductive glassy solid electrolyte which is stable in the air, has a high ionic conductivity, and has a high glass transition temperature and a high crystallization temperature can be obtained. can get. When the oxide composition or solid electrolyte of the present invention is used, all-solid-state electrochemical devices such as gas sensors, solid-state batteries, electrochromic devices, etc. having excellent properties can be obtained.

[Brief description of drawings]

FIG. 1 is a view for explaining the structure of a carbon dioxide gas sensor using the solid electrolyte of the present invention.

[Explanation of symbols]

 1 ... Metal carbonate 2, 4 ... Noble metal electrode 3 ... Solid electrolyte 5, 6 ... Lead wire

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H01M 6/18 G01N 27/46 376

Claims (6)

[Claims] 1. A general formula (Li ₂ O) _x — (SiO ₂ ) _y —M _z (M is at least one oxide selected from the group consisting of Nb ₂ O ₅ , Ta ₂ O ₅ and WO ₃ . And x +
y + z = 1. ) The oxide composition shown by. 2. The oxide composition according to claim 1, wherein the oxide composition is glassy. 3. The values of x, y and z are each 1/10 ≦ x.
≦ 2/3, 1/10 ≦ y ≦ 4/5, 1/50 ≦ z ≦ 1 /
The oxide composition according to claim 1 or 2, which is 2. 4. A compound represented by the general formula (Li ₂ O) _x — (SiO ₂ ) _y —M _z (M is at least one oxide selected from the group consisting of Nb ₂ O ₅ , Ta ₂ O ₅ and WO ₃ ). And x +
y + z = 1. ) A solid electrolyte comprising a glassy oxide composition represented by 5. The values of x, y and z are each 1/10 ≦ x.
≦ 2/3, 1/10 ≦ y ≦ 4/5, 1/50 ≦ z ≦ 1 /
The solid electrolyte according to claim 4, which is 2. 6. A gas sensor using the solid electrolyte according to claim 4.