JPH05306117A - Amorphous lithium ion conductive solid electrolyte and its synthesizing method - Google Patents

Abstract

PURPOSE:To provide a lithium ion conductive solid electrolyte which improves conventional problems including low chemical stability causing low conductivity or reduction of conductivity. CONSTITUTION:An amorphous lithium ion conductive solid electrolyte aLi3 PO4.bLi2S.cX.dZ wherein a+b+c+d=1, X is one or more kinds of sulfides selected from SiS2, GeS2, P2S5 and B2S3, and Z is plural kinds of lithium halides, is obtd. by mixing plural kinds of lithium halides with an amorphous compd. expressed by a'Li3PO4.b'Li2S.c'X wherein a'+b'+c'=1 and X is one or more kinds of sulfides selected from SiS2, GeS2, P2S5 and B2S3, then heating and melting the mixture, followed by rapid cooling.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium ion conductive solid electrolyte used as an electrolyte for electrochemical devices such as all-solid-state batteries, capacitors and solid electrochromic display devices.

[0002]

2. Description of the Related Art In recent years, much research has been conducted on the development of lithium secondary batteries using organic lithium electrolytes. To develop a lithium secondary battery using an organic electrolyte,
It is necessary to develop an active material material having excellent reversibility as a positive electrode or a negative electrode, and today, such materials are actively searched. For example, with respect to the negative electrode material, the use of lithium metal alone or a lithium alloy has been progressing toward the use of a reaction in which lithium is reversibly taken in and out between carbon layers by using special carbon.

Similarly, with respect to the positive electrode material, a material in which Li ions in the electrolyte enter and leave the active material has come to be used from a material accompanied by a chemical change due to electrochemical redox of the active material. ..

On the other hand, regarding the electrolyte, a lithium ion conductive solid electrolyte is required in order to improve the reliability of the battery. However, at present, there is no excellent lithium-ion conductive solid electrolyte, and research and development of new solid electrolyte materials are actively conducted.

As one of the studies on such a solid electrolyte, Li ₂ S.X (X is SiS ₂ , GeS ₂ , P
One or more sulfide-based sulfide glasses selected from the group of ₂ S ₅ and B ₂ S ₃ have been extensively studied because they show excellent ionic conductivity.

Li ₂ S.X (X is SiS ₂ , GeS ₂ ,
One or more sulfide-based sulfide glasses selected from the group of P ₂ S ₅ and B ₂ S ₃ are Li ₂ S.Si in which X is SiS _2.
It has a particularly high conductivity value in the S ₂ system, and its value is
It is about 5 × 10 ⁻⁴ S / cm.

In addition, Li₂S / X sulfide glass with iodine
LiI · Li with lithium fluoride added ₂With S / X type glass
Is 10^-3Has a relatively high ionic conductivity of about S / cm
Known as one.

[0008]

Problems to be Solved by the Invention Li ₂ S.X (X is S
The conductivity of at least one sulfide-based sulfide glass selected from the group of iS ₂ , GeS ₂ , P ₂ S ₅ , and B ₂ S ₃ is as high as 5 × 10 ⁻⁴ S / cm as described above. Shows the value,
The ionic conductivity is still low for application to electrochemical devices,
Furthermore, the chemical stability of the material is insufficient.

In the LiI / Li ₂ S / X system, 10
^It has a high ionic conductivity of about ^-3 S / cm, but its chemical stability has not been resolved, such as the solid electrolyte being reduced due to contact with lithium metal and the conductivity being reduced. There were many problems in application development to electrochemical devices.

The present invention is intended to provide a lithium ion conductive solid electrolyte and a method for synthesizing the same, which solves the conventional problems of low conductivity or chemical stability leading to a decrease in conductivity.

[0011]

The present invention provides a'Li ₃ P
O ₄ · b'Li ₂ S · c'X (however, a '+ b' + c '
Is 1 and X is SiS ₂ , GeS ₂ , P ₂ S ₅ , B
_A plurality of kinds of lithium halide Z are mixed with an amorphous compound represented by one or more sulfides selected from the group of ₂ S ₃ ), the mixture is heated and melted, and then rapidly cooled to obtain a new amorphous form. Lithium ion conductive solid electrolyte aLi ₃ PO
₄ · bLi ₂ S · cX · dZ (where a + b + c + d is 1 and X is SiS ₂ , GeS ₂ , P ₂ S ₅ , B ₂
A sulfide of one or more kinds selected from the group of S _3, Z combines the lithium halide) of a plurality of types, and amorphous lithium ion conductive solid electrolyte.

The above general formula aLi ₃ PO ₄ .bLi ₂
S · cX · dZ (where a + b + c + d is 1,
Amorphous lithium ion conduction represented by X is one or more sulfides selected from the group of SiS ₂ , GeS ₂ , P ₂ S ₅ , and B ₂ S ₃ , and Z is a plurality of lithium halides). -Based solid electrolyte has a composition ratio of a, b and c of 0.9 ≧ a + b
When + c ≧ 0.4 and d satisfies 0.1 ≦ d ≦ 0.6, the chemical stability is particularly excellent.

[0013]

It is known that Li ₃ PO ₄ has a crystal structure with high ionic conductivity in a high temperature region, but the structure changes due to phase transfer at around room temperature, resulting in a decrease in ionic conductivity.

However, Li ₃ PO ₄ is added to a material exhibiting an amorphous state at room temperature, and these are once made amorphous at a high temperature state and then returned to the room temperature state to obtain Li ₃ PO 4.
It is considered that the state of ₄ can be maintained in an amorphous state even at room temperature, and high ionic conductivity can be provided even at room temperature.

This is due to the amorphous state,
That is, the atomic arrangement of the crystal structure has a somewhat disordered structure.
Therefore, unlike crystalline materials, lithium ions move freely.
As a result, the ionic conductivity is improved.
Conceivable. In particular, a'Li ₃PO_Four・ B'Li₂S
C'X (provided that a '+ b' + c 'is 1 and X is
SiS₂, GeS₂, P₂S_Five, B₂S₃Select from the group of
One or more sulfides)
Mix several kinds of lithium halide Z and heat the mixture
By melting and then quenching, a new synthetic
Amorphous lithium ion conductive solid electrolyte aLi₃PO_Four・
bLi₂S ・ cX ・ dZ (where a + b + c + d is 1
Yes, X is SiS₂, GeS₂, P₂S_Five, B₂S₃
Is one or more sulfides selected from the group
Species of lithium halide) is a freely moving lithium ion
As a result of increasing the number of ONs, a'Li₃PO_Four・ B'Li₂S
C'X (provided that a '+ b' + c 'is 1 and X is
SiS₂, GeS₂, P₂S _Five, B₂S₃Select from the group of
Amorphous compound material represented by one or more sulfides
Lithium-ion conductive solid state battery with higher ionic conductivity than
It becomes a demerit.

[0016]

EXAMPLE A lithium ion conductive solid electrolyte of the present invention is a'Li ₃ PO ₄ .b'Li ₂ S.c'X (however,
a ′ + b ′ + c ′ is 1 and X is SiS ₂ , GeS
₂ , an amorphous compound represented by one or more sulfides selected from the group of P ₂ S ₅ and B ₂ S ₃ ) is used as a base material, and a plurality of types of lithium halide Z (here Z = LiI, LiCl or LiBr) is used. However, since the amorphous compound as the base material, the raw material thereof and the synthesized solid electrolyte are easily decomposed by oxygen and moisture in the atmosphere, all handling is performed with dry argon. It was conducted in a dry box under an atmosphere.

Here, lithium halide and other reagents used were all of special grade, and LiI, LiCl and the like were used after drying at 400 ° C. for 6 hours under reduced pressure.

Hereinafter, the present invention will be described in more detail with reference to specific examples. (Example 1) of the amorphous lithium ion conductive solid electrolyte according to the present _{invention, aLi 3 PO 4 · bLi 2} S · cSi
S ₂ based non amorphous lithium with amorphous material ion conductive solid electrolyte _{aLi 3 PO 4 · bLi 2 S} · cSiS 2 ·
An example of dZ will be described.

First, b "Li ₂ S.c" SiS ₂ (b "
+ C ″ = 1) was synthesized. This synthesis was performed using lithium sulfide (L
i ₂ S) and silicon sulfide (SiS ₂ ) with b ″ = 0.3 to 0.
8 to mix, and put the mixed powder in a glassy carbon crucible, melt this in an argon stream at 950 ° C for 1.5 hours to react, and then put into liquid nitrogen to quench. , B "Li ₂ S · c" SiS ₂ (b "+ c" =
1) was obtained.

Next, this was crushed to obtain lithium phosphate (L
i ₃ PO ₄₎ to _{a'Li 3 PO 4 · b'Li 2 S} · c '
SiS ₂ was added and mixed so that a ′ = 0.01 to 0.3, the powder was put into a glassy carbon crucible, and this was melted at 950 ° C. for 1.5 hours in an argon stream. After the reaction, put it into liquid nitrogen to quench it,
Li ₃ PO ₄ b'Li ₂ S c'SiS ₂ (a '+
b ′ + c ′ = 1) was synthesized.

The obtained a'Li₃PO_Four・ B'Li₂S
・ C'SiS₂Depending on the amount of material y, multiple halogenated solutions
Lithium iodide (LiI) as lithium Z, lithium chloride
A mixture of 0.7: 0.3
After mixing so that y + d becomes 1, the mixed powder is mixed.
Place in a carbon-like carbon crucible, and put this in an argon stream.
After melting and reacting at 50 ° C for 1.5 hours, in liquid nitrogen
Charge and cool aLi ₃PO_Four・ BLi₂S ・ cSiS
₂-DZ (a + b + c + d = 1) was obtained.

To investigate the characteristics of the synthesized solid electrolyte,
The ionic conductivity was measured by the AC impedance method.

The obtained results are shown in FIG. The vertical axis represents ionic conductivity, and the horizontal axis represents (0.03Li ₃ PO ₄ .0.
58Li ₂ S.0.39SiS ₂ ) lithium halide Z consisting of a plurality of species (where Z is lithium iodide (LiI), lithium chloride (LiCl) 0.7: 0.3).
The amount of addition (mol%) of the mixture (1) was shown. It is shown from FIG. 1 that the ionic conductivity increases with the addition of lithium halide Z, then reaches a maximum and then decreases, and the ionic conductivity becomes maximum.
0.75 (0.03Li ₃ PO ₄ 0.58Li ₂ S
0.39SiS ₂ ) ・ 0.25 (0.7LiI, 0.3
LiCl) and its ionic conductivity value is 2.3 × 1.
It was 0 ^-3 S / cm.

On the other hand, 0.03Li ₃ PO ₄ .0.58Li ₂ S.
The ionic conductivity of 0.39SiS ₂ is 7 × 10 ⁻⁴ S / cm.
Met.

Next, in order to investigate the chemical stability of the electrolyte with respect to lithium metal, the synthesized electrolytes of various compositions were press-molded into a disk 1 having a thickness of 0.5 mm and a diameter of 10 mm, and further, on both surfaces of the disk 1. The lithium metal disks 2 and 2'were pressure-bonded to prepare a sealed cell 3 as shown in FIG. The chemical stability of these sealed cells 3 is 60 ° C.
The sample was stored in the constant temperature bath for 500 hours, and the change with time of the internal impedance of each sealed cell 3 was measured.

FIG. 3 shows the obtained results, and the vertical axis shows the impedance change normalized by the internal impedance before storage. As is clear from this result, it was found that when the lithium halide was 0.6 or more, the change in internal impedance with time was significantly large, and when it was less than that, the increase in internal impedance was small.

(Example 2) In Example 1, a'Li
₃ PO ₄ · b′Li ₂ S · c′SiS _{2 The} amount of the material y is 0.7: 0.3 of lithium iodide (LiI) and lithium chloride (LiCl) as a plurality of types of lithium halide Z to be added. A mixture of lithium iodide (LiI) 0.75: lithium bromide (L) was used here.
iBr) 0.25 except that the amount of d was changed to aLi ₃ PO ₄ .bLi ₂ S.
cSiS ₂ · dZ (a + b + c + d = 1) was obtained.

To investigate the characteristics of the synthesized solid electrolyte,
The ionic conductivity was measured by the AC impedance method.

The obtained results are shown in FIG. The vertical axis represents ionic conductivity, and the horizontal axis represents (0.03Li ₃ PO ₄ .0.
58 Li ₂ S.0.39SiS ₂ ) lithium halide Z composed of a plurality of types (where Z is lithium iodide (LiI) and lithium bromide (LiBr) is 0.75:
0.25 mixture). It is shown from FIG. 4 that the ionic conductivity increases with the addition of lithium halide Z, then reaches a maximum and then decreases, and the ionic conductivity becomes maximum.
0.80 (0.03Li ₃ PO ₄ 0.58Li ₂ S
0.39SiS ₂ ) · 0.20 (0.75LiI, 0.
25 LiBr) and its ionic conductivity value is 2.6.
It was × 10 ^-3 S / cm.

(Example 3) In Example 1, a'Li
₃ PO ₄ · b′Li ₂ S · c′SiS _{2 The} amount of the material y is 0.7: 0.3 of lithium iodide (LiI) and lithium chloride (LiCl) as a plurality of types of lithium halide Z to be added. Was used, which was used here as lithium iodide (LiI) 0.7: lithium bromide (Li
Br) 0.1: Lithium chloride (LiCl) 0.2 In the same manner as in Example 1 except that the amount of d was changed,
aLi ₃ PO ₄ · bLi ₂ S · cSiS ₂ · dZ (a +
b + c + d = 1) was obtained.

In order to investigate the characteristics of the synthesized solid electrolyte,
The ionic conductivity was measured by the AC impedance method.

The obtained results are shown in FIG. The vertical axis is Io
Conductivity and the horizontal axis is (0.03Li₃PO_Four・ 0.
58Li₂S ・ 0.39SiS₂) From multiple species
Lithium halide Z (where Z is lithium iodide
(LiI) 0.7, lithium bromide (LiBr) 0.1,
Amount of lithium chloride (LiCl) 0.2 mixture)
(Mol%) is shown. From Figure 5, ionic conductivity
Is maximum after increasing with the addition of lithium halide Z
It has been shown that the ionic conductivity decreases after
Is the largest at 0.80 (0.03Li₃PO
_Four・ 0.58Li ₂S ・ 0.39SiS₂) ・ 0.20
(0.7LiI, 0.1LiBr, 0.2LiCl)
Yes, its ionic conductivity value is 1.8 × 10^-3S / cm
Met.

Example 4 aLi ₃ PO ₄ .bLi ₂ S
· CGeS ₂ based amorphous lithium ion conductive solid electrolyte with amorphous material _{aLi 3 PO 4 · bLi 2 S} · cG
An example of eS ₂ · dZ will be described.

First, 0.6Li ₂ S.0.4Ge
S ₂ glass was synthesized as in Example 1. That is, lithium sulfide (Li ₂ S) and germanium sulfide (GeS ₂ ) were mixed at a molar ratio of 3: 2, the material powder was put in a glassy carbon crucible, and this was put in an argon stream at 950 ° C. for 1. after 5 hours of reaction was quenched put into liquid nitrogen to synthesize a material 0.6Li ₂ S · 0.4GeS ₂ composition. Then, the material 0.6Li ₂ S.0.4 obtained in this way
GeS ₂ was pulverized, lithium phosphate (Li ₃ PO ₄ ) was mixed at a molar ratio of 97: 3, the powder was put into a glassy carbon crucible, and the mixture was reacted in an argon stream at 950 ° C. for 1.5 hours. It was After that, put it in liquid nitrogen and quench it,
0.03Li ₃ PO ₄ , 0.58Li ₂ S, 0.39G
An amorphous material designated eS ₂ was synthesized.

The obtained 0.03Li ₃ PO ₄ .0.58
Li ₂ S.0.39 GeS ₂ material y amount, lithium iodide (Li
I) and lithium chloride (LiCl) in a ratio of 0.8: 0.2 are mixed in a d amount, and y + d is mixed to be 1;
The material powder was put into a glassy carbon crucible, and this was melted and reacted at 950 ° C. for 1.5 hours in an argon stream, and then poured into liquid nitrogen and rapidly cooled aLi ₃ PO ₄ .bL
i ₂ S · cGeS ₂ · dZ (a + b + c + d = 1) was obtained.

In order to investigate the characteristics of the synthesized solid electrolytes of various compositions, the ionic conductivity was measured by the AC impedance method.

The obtained results are shown in FIG. The vertical axis is Io
Conductivity and the horizontal axis is (0.03Li₃PO_Four・ 0.
58Li₂S ・ 0.39GeS₂) Multiple ha
It shows the addition amount (mol%) of lithium rogenide Z.
is there. From FIG. 6, the ionic conductivity of lithium halide Z is
After increasing with addition, it goes through a maximum and then decreases.
It is shown that the highest ionic conductivity is
0.85 (0.03Li ₃PO_Four・ 0.58Li₂S ・
0.39GeS₂) ・ 0.15 (0.8LiI, 0.2
LiCl) and its ionic conductivity value is 1.2 × 1.
0^-3It was S / cm.

On the other hand, 0.03Li ₃ PO ₄ .0.58Li ₂ S
The ionic conductivity of 0.39 GeS ₂ is 2.0 × 10 ⁻⁴ S /
It was cm.

Next, the chemical stability of the electrolyte with respect to lithium metal was examined in the same manner as in Example 1.

As with the results obtained in Example 1, it was found that when the lithium halide was 0.6 or more, the change in internal impedance with time was significantly large, and when it was less than that, the increase in internal impedance was small.

(Example 5) In Example 4, a'Li
₃ PO ₄ · b′Li ₂ S · c′GeS ₂ Material y amount of lithium iodide (LiI) and lithium chloride (LiCl) 0.8: 0.2 as plural kinds of lithium halide Z to be added. A mixture of lithium iodide (LiI) 0.75: lithium bromide (L) was used here.
IBR) 0.15: In the same manner, except that a mixture of lithium chloride (LiCl) 0.1 was changed to d amount as in Example _{4, aLi 3 PO 4 · bLi} 2 S · cGeS 2 · dZ
(A + b + c + d = 1) was obtained.

In order to investigate the characteristics of the synthesized solid electrolyte,
The ionic conductivity was measured by the AC impedance method.

The obtained results are shown in FIG. The vertical axis represents ionic conductivity, and the horizontal axis represents (0.03Li ₃ PO ₄ .0.
58Li ₂ S.0.39GeS ₂ ) lithium halide Z consisting of plural kinds (where Z is lithium iodide (LiI) 0.75 and lithium bromide (LiBr) 0.1).
5, the mixture amount (mol%) of lithium chloride (LiCl 0.1) is shown. From FIG. 7, it is shown that the ionic conductivity increases with the addition of lithium halide Z, then reaches a maximum and then decreases, and the maximum ionic conductivity is 0.75 (0.03 Li ₃ P
O ₄ , 0.58 Li ₂ S, 0.39GeS ₂ ), 0.2
5 (0.75LiI, 0.15LiBr, 0.10Li
Cl) and its ionic conductivity value is 1.1 × 10 ⁻³
It was S / cm.

Example 6 aLi ₃ PO ₄ .bLi ₂ S
· CP ₂ S ₅ based non amorphous lithium with amorphous material ion conductive solid electrolyte _{aLi 3 PO 4 · bLi 2 S} · cP
An example of ₂ S ₅ · dZ will be described.

First, 0.67 Li ₂ S.0.33
P ₂ S ₅ glass was synthesized as in Example 1. That is, lithium sulfide (Li ₂ S) and phosphorus sulfide (P ₂ S ₅ ) were mixed at a molar ratio of 2: 1 and the material powder was put into a glassy carbon crucible and the mixture was placed in an argon stream at 500 ° C. After reacting for 12 hours and then at 800 ° C. for 2 hours, the mixture was put into liquid nitrogen and rapidly cooled to 0.67Li ₂ S.0.33P _2.
A material of S ₅ composition was synthesized. Subsequently, the material 0.67Li ₂ S.0.33P ₂ S ₅ thus obtained was pulverized and lithium phosphate (Li ₃ PO ₄ ) was mixed at a molar ratio of 97: 3, and the powder was mixed with a glassy carbon crucible. It was put in the inside and reacted at 950 ° C. for 1.5 hours in an argon stream. After that, it is put into liquid nitrogen and rapidly cooled to 0.03 Li ₃ PO ₄
The amorphous material represented by 0.65Li ₂ S · 0.32P ₂ S ₅ were synthesized.

The obtained 0.03 Li ₃ PO ₄ .0.65
Li ₂ S.0.32P ₂ S ₅ material y amount, lithium iodide (Li
I) and lithium chloride (LiCl) of 0.7: 0.3 are mixed in a d amount and mixed so that y + d is 1,
Put the mixed powder in a glassy carbon crucible,
After melting and reacting at 950 ° C for 1.5 hours in an argon stream, the mixture was poured into liquid nitrogen and rapidly cooled aLi ₃ PO ₄ · b.
Li ₂ S · cP ₂ S ₅ · dZ (a + b + c + d = 1) was obtained.

In order to investigate the characteristics of the synthesized solid electrolytes of various compositions, the ionic conductivity was measured by the AC impedance method and the chemical stability of the solid electrolyte to lithium metal was examined.

The obtained results are shown in FIG. The vertical axis represents ionic conductivity, and the horizontal axis represents (0.03Li ₃ PO ₄ .0.
More of lithium halide (lithium iodide for _{65Li 2 S · 0.32P 2 S 5} ), illustrates the addition amount of lithium chloride mixture) (mol%). The composition showing the largest ionic conductivity is 0.75 (0.03
_{Li 3 PO 4 · 0.65Li 2 S} · 0.32P 2 S 5)
-0.25 (0.7LiI, 0.3LiCl),
The value of its ionic conductivity was 1.2 × 10 ⁻³ S / cm.

On the other hand, 0.03Li ₃ PO ₄ .0.6Li ₂ S
The ionic conductivity of 0.32P ₂ S ₅ is 4.2 × 10 ⁻⁴ S /
It was cm.

Next, the chemical stability of the electrolyte against lithium metal was examined in the same manner as in Example 1.

As with the results obtained in Example 1, it was found that the change in internal impedance with time is significantly large when the plural kinds of lithium halides are 0.6 or more, and the increase in the internal impedance is small when the amount is less than that. ..

Example 7 In Example 6, a'Li
_{3 PO 4 · b'Li 2 S ·} c'P 2 S 5 material y amount to a plurality of kinds of lithium iodide as a lithium halide Z adding (LiI), lithium chloride (LiCl) is 0.7: 0 A mixture of 0.3.3 was used, but in this case, lithium iodide (LiI) 0.75 and lithium bromide (L
IBR) 0.1, a mixture of lithium chloride (LiCl) 0.15 in the same manner as in Example 6 except for changing the d _{quantity, aLi 3 PO 4 · bLi 2} S · cP 2 S 5 · dZ
(A + b + c + d = 1) was obtained.

To investigate the characteristics of the synthesized solid electrolyte,
The ionic conductivity was measured by the AC impedance method.

The obtained results are shown in FIG. The vertical axis represents ionic conductivity, and the horizontal axis represents (0.03Li ₃ PO ₄ .0.
65 Li ₂ S.0.32P ₂ S ₅ ) and a plurality of types of lithium halide Z (provided that Z is lithium iodide (LiI) 0.75, lithium bromide (LiBr) 0.
1 shows the addition amount (mol%) of 1, a mixture of lithium chloride (LiCl) 0.15). From FIG. 9, the ionic conductivity increases with the addition of lithium halide Z, and
It has been shown that after reaching the maximum, it decreases, and the maximum ionic conductivity is 0.85 (0.01 Li _{3
PO 4 · 0.64Li 2 S · 0.35P} 2 S 5) · 0.
15 (0.75LiI, 0.1LiBr, 0.15Li
Cl) and its ionic conductivity value is 1.7 × 10 ⁻³
It was S / cm.

Example 8 aLi ₃ PO ₄ .bLi ₂ S
· CB ₂ S ₃ based amorphous lithium material using an ion-conductive solid electrolyte _{aLi 3 PO 4 · bLi 2 S} · cB 2 S 3
An example of dZ will be described.

First, 0.5Li ₂ S.0.5B ₂
S ₃ glass was synthesized as in Example 1. That is, lithium sulfide (Li ₂ S) and boron sulfide (B ₂ S ₃ ) were mixed at a molar ratio of 1: 1 and the material powder was put into a glassy carbon crucible, which was placed in an argon stream at 500 ° C. in 12 hours, followed by after reacting for 3 hours at 800 ° C, was synthesized material was quenched put in liquid nitrogen 0.5Li ₂ S · 0.5B ₂ S ₃ composition. Then the material 0.5 thus obtained
Li ₂ S.0.5B ₂ S ₃ was crushed, lithium phosphate (Li ₃ PO ₄ ) was mixed at a molar ratio of 96: 4, and the powder was put into a glassy carbon crucible and was placed in an argon stream at 80
The reaction was carried out at 0 ° C for 3 hours. After that, it was put into liquid nitrogen and rapidly cooled to 0.04Li ₃ PO ₄ .0.48Li ₂ S
An amorphous material represented by 0.48B ₂ S ₃ was synthesized.

The obtained 0.04 Li ₃ PO ₄ .0.48
Li ₂ S.0.48B ₂ S ₃ Material y amount of lithium iodide (Li
I) and lithium chloride (LiCl) are 0.65: 0.35
After d amount of the mixture of (1) and (1) were mixed so that y + d was 1, the mixed powder was put into a glassy carbon crucible, and this was melted and reacted at 800 ° C. for 1.5 hours in an argon stream, and then reacted. , Put into liquid nitrogen and rapidly cooled aLi ₃ PO ₄
・ BLi ₂ S ・ cB ₂ S ₃・ dZ (a + b + c + d =
1) was obtained.

In order to investigate the characteristics of the synthesized solid electrolytes of various compositions, the ionic conductivity was measured by the AC impedance method, and the chemical stability of this solid electrolyte against lithium metal was examined.

The obtained results are shown in FIG. The vertical axis represents ionic conductivity, and the horizontal axis represents (0.04Li ₃ PO ₄ ·.
It illustrates amount of a plurality of types of lithium halide (molar%) of _{0.48Li 2 S · 0.48B 2 S 3} ). The composition with the highest ionic conductivity is
_{0.75 (0.03Li 3 PO 4 · 0.65Li} 2 S ·
0.32B ₂ S ₃ ) 0.25 (0.65LiI, 0.
35 LiCl) and its ionic conductivity value is 1.8.
It was × 10 ^-3 S / cm.

On the other hand, 0.03Li ₃ PO ₄ .0.65Li to which plural kinds of lithium halides are not added
The ionic conductivity of ₂ S / 0.32B ₂ S ₃ is 3.0 × 10.
It was ^-4 S / cm.

Next, the chemical stability of the electrolyte against lithium metal was examined in the same manner as in Example 1.

Similar to Example 1, the obtained results show that the change of the internal impedance with time becomes significantly large when the addition amount of the plural kinds of halogen lithium is 0.6 or more, and the increase of the internal impedance decreases when the addition amount is less than that. Do you get it.

[0063]

Lithium ion conductive solid electrolyte of the present invention _{exhibits, Li 3 PO 4 · Li 2} S · X (X is SiS _2, G
eS ₂ , P ₂ S ₅ , and one or more sulfides selected from the group of B ₂ S ₃ ) -based sulfides An amorphous material obtained by adding a mixture of a plurality of types of lithium halides. Yes, the base material Li ₂ S · X (X is SiS ₂ , G
Compared with one or more sulfide-based amorphous materials selected from the group consisting of eS ₂ , P ₂ S ₅ , and B ₂ S ₃ , it exhibits higher lithium ion conductivity and is chemically dependent on contact with lithium metal. It is possible to provide a solid electrolyte with little static change.

As a result, even if the lithium ion conductive solid electrolyte is used as an electrolyte for electrochemical devices such as batteries, capacitors and electrochromic display devices, it is possible to produce an electrochemical device having extremely high practicality. There is expected.

In the synthesis of the solid electrolyte in the examples of the present invention, the amorphous material was successively synthesized to obtain the intended lithium ion conductive solid electrolyte of the present invention. It was an attempt to find the best conditions, and it is self-evident that simplification can be achieved by selecting various conditions such as electrolyte composition, synthesis temperature, and temperature rising conditions. It belongs to the category of invention. Further, although a single kind is used as a mixing ratio of a plurality of kinds of halides, an ion conductive solid electrolyte can be obtained even at a mixing ratio of other compositions. Therefore, it goes without saying that the electrolyte having a mixing ratio of other composition also belongs to the category of the present invention.

[Brief description of drawings]

FIG. 1 a'Li ₃ PO ₄ b'Li ₂ S c'SiS
₂ kinds of lithium halide (LiI, LiCl
Diagram showing the change in conductivity due to the addition of

FIG. 2 is a cross-sectional view of a sealed cell used for measuring internal impedance.

FIG. 3 is a characteristic diagram showing chemical stability against lithium metal.

FIG. 4 a'Li ₃ PO ₄ b'Li ₂ S c'SiS
₂ kinds of lithium halides (LiI, LiBr
Diagram showing the change in conductivity due to the addition of

FIG. 5: a'Li ₃ PO ₄ / b'Li ₂ S / c'SiS
₂ types of lithium halides (LiI, LiB
Characteristic diagram showing the change in conductivity due to the addition of r, a mixture of LiCl)

FIG. 6 a'Li ₃ PO ₄ b'Li ₂ S c'GeS
₂ kinds of lithium halide (LiI, LiCl
Diagram showing the change in conductivity due to the addition of

FIG. 7: a'Li ₃ PO ₄ / b'Li ₂ S / c'GeS
₂ types of lithium halides (LiI, LiB
Characteristic diagram showing the change in conductivity due to the addition of r, a mixture of LiCl)

FIG. 8: a'Li ₃ PO ₄ b'Li ₂ S c'P ₂ S
₅ kinds of lithium halides (LiI, LiCl
Diagram showing the change in conductivity due to the addition of

FIG. 9: a'Li ₃ PO ₄ / b'Li ₂ S / c'P ₂ S
₅ kinds of lithium halides (LiI, LiB
Characteristic diagram showing the change in conductivity due to the addition of r, a mixture of LiCl)

FIG. 10 a'Li ₃ PO ₄ / b'Li ₂ S / c'B ₂
Several kinds of lithium halides (LiI, LiC) to S ₃
Characteristic diagram showing the change in conductivity due to the addition of

[Explanation of symbols]

 1 Electrolyte Disk 2 Lithium Metal Disk 2'Lithium Metal Disk 3 Sealed Cell

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display area H01M 10/36 A

Claims (3)

[Claims] 1. A general formula aLi ₃ PO ₄ .bLi ₂ S.c.
X · dZ (where a + b + c + d is 1 and X is S
Amorphous lithium ion conductive solid represented by one or more sulfides selected from the group of iS ₂ , GeS ₂ , P ₂ S ₅ , and B ₂ S ₃ , and Z is a plurality of lithium halides. Electrolytes. 2. The sum of composition ratios a, b and c is 0.9 ≧ a + b.
The amorphous lithium ion conductive solid electrolyte according to claim 1, wherein + c ≧ 0.4 and d satisfies 0.1 ≦ d ≦ 0.6. 3. The amorphous liquid according to claim 1 or 2.
A method for synthesizing a solid electrolyte containing thion ion, comprising:
No, a'Li₃PO_Four・ B'Li₂S · c'X (however,
a '+ b' + c 'is 1 and X is SiS₂, GeS
₂, P₂S_Five, B ₂S₃One or more selected from the group of
After synthesizing an amorphous compound represented by (sulfide), the amorphous
A plurality of types of lithium halide Z to the organic compound,
The mixture is heated and melted and then quenched to synthesize it.
Amorphous lithium-ion conductive solid state electrode characterized by
Synthesis method of disintegration.