JP3151925B2 - Amorphous lithium ion conductive solid electrolyte and its synthesis method - Google Patents

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 state electrochromic display devices.

[0002]

2. Description of the Related Art In recent years, research on the development of lithium secondary batteries using an organic lithium electrolyte has been actively conducted. For the development of lithium secondary batteries using organic electrolytes,
It is necessary to develop an active material having excellent reversibility as a positive electrode or a negative electrode, and such materials are being actively searched for today. For example, with regard to the negative electrode material, the use of lithium metal alone or a lithium alloy has been used, and special carbon has been used, and a reaction for reversibly bringing lithium in and out of the carbon layer has been used.

[0003] Similarly, as for the positive electrode material, a material in which Li ions in the electrolyte enter and exit the active material from those accompanied by a chemical change by electrochemical oxidation-reduction of the active material has been used. .

On the other hand, as for 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 being actively conducted.

As one of the studies on such solid electrolytes, Li ₂ SX (X is SiS ₂ , GeS ₂ , P
It is actively studied since it shows a ₂ S _5, B ₂ S sulfide least one selected from the group of ₃₎ based sulfide glass is excellent ion conductivity.

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

In addition, Li_TwoIodine on S / X sulfide glass
LiI.Li with lithium chloride added _TwoWith SX glass
Is 10^-3Has relatively high ionic conductivity of about S / cm
Known as one.

[0008]

SUMMARY OF THE INVENTION Li ₂ SX (X is S
The conductivity of one or more sulfide-based sulfide glasses selected from the group consisting 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. Indicates 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 SX system, 10
^Despite high ionic conductivity of about ^-3 S / cm, chemical stability has not been solved, for example, the solid electrolyte is reduced by contact with lithium metal and the conductivity is reduced. The development of application to electrochemical devices had many problems.

An object of the present invention is to provide a lithium ion conductive solid electrolyte which has solved the problems of chemical stability that causes a low conductivity or a decrease in conductivity, which is a conventional problem, and a method for synthesizing the same.

[0011]

According to the present invention, there is provided an 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 lithium halides Z are mixed with an amorphous compound represented by one or more sulfides selected from the group of ₂ S ₃ ), and the mixture is heated and melted, and then rapidly cooled to form a new amorphous material. 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
It is one or more sulfides selected from the group of S ₃ , and Z is a compound of a plurality of types of lithium halides to form an amorphous lithium ion conductive solid electrolyte.

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

[0013]

[Function] Li ₃ PO ₄ has a crystal structure with high ion conductivity in a high temperature region, but it is known that the structure changes due to phase transfer near room temperature, and the ion conductivity decreases.

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

This is because the amorphous state is obtained.
In other words, the structure of atoms in the crystal structure is slightly disordered.
Therefore, unlike crystalline materials, lithium ions move freely.
As a result, ion conductivity is improved.
Conceivable. In particular, a'Li _ThreePO_Four・ B'Li_TwoS
C'X (where a '+ b' + c 'is 1 and X is
SiS_Two, GeS_Two, P_TwoS_Five, B_TwoS_ThreeSelect from group
Or more than one sulfide)
Mix several kinds of lithium halides Z and heat the mixture
By melting and then quenching, the new synthesized
Amorphous lithium ion conductive solid electrolyte aLi_ThreePO_Four・
bLi_TwoS · cX · dZ (where a + b + c + d is 1
And X is SiS_Two, GeS_Two, P_TwoS_Five, B_TwoS_Three
Is at least one sulfide selected from the group consisting of
Species of lithium halides)
As a result of more on, a′Li_ThreePO_Four・ B'Li_TwoS
C'X (where a '+ b' + c 'is 1 and X is
SiS_Two, GeS_Two, P_TwoS _Five, B_TwoS_ThreeSelect from group
Compound material represented by one or more sulfides
Lithium-ion conductive solid state electrode with higher ion conductivity than
It will be degraded.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The lithium ion conductive solid electrolyte of the present invention comprises a'Li ₃ PO ₄ .b'Li ₂ S'c'X (provided that
a ′ + b ′ + c ′ is 1 and X is SiS ₂ , GeS
_{2, P 2 S 5, B} 2 using the S least one sulfide selected from the group of ₃₎ amorphous compound represented by a matrix, a plurality of kinds of lithium halide Z as the compound added (here Z = LiI, LiCl or LiBr) is used, but since the amorphous compound serving 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. Performed in a dry box under atmosphere.

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

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

First, b "Li ₂ S.c" SiS ₂ (b "
+ C "= 1). This synthesis is based on lithium sulfide (L
i ₂ S) and silicon sulfide (SiS ₂ ) with b ″ = 0.3 to 0.
8, and the mixed powder was placed in a glassy carbon crucible. The mixture was melted in an argon gas stream at 950 ° C. for 1.5 hours to react, then put into liquid nitrogen and quenched. , B ”Li ₂ S · c” SiS ₂ (b ″ + c ″ =
1) was obtained.

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

The obtained a'Li_ThreePO_Four・ B'Li_TwoS
・ C'SiS_TwoMultiple kinds of halogenated resin
Lithium iodide (LiI), lithium chloride
The mixture (LiCl) having a ratio of 0.7: 0.3 is d-weighted,
After mixing so that y + d becomes 1, the mixed powder is mixed
Into a carbon crucible, and put it in an argon stream.
After melting and reacting at 50 ° C for 1.5 hours,
ALi _ThreePO_Four・ BLi_TwoS ・ cSiS
_TwoDZ (a + b + c + d = 1) was obtained.

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

FIG. 1 shows the obtained results. The vertical axis indicates ionic conductivity, and the horizontal axis indicates (0.03Li ₃ PO ₄ .0.
58Li ₂ S.0.39SiS ₂ ) composed of plural kinds of lithium halides Z (where Z is lithium iodide (LiI), lithium chloride (LiCl) 0.7: 0.3)
(A mixture of the above) was used (mol%). FIG. 1 shows that the ionic conductivity increases with the addition of lithium halide Z, then decreases through a local maximum, and the ionic conductivity becomes the largest
_{0.75 (0.03Li 3 PO 4 · 0.58Li} 2 S ·
_{0.39SiS 2) · 0.25 (0.7LiI,} 0.3
LiCl) whose ionic conductivity is 2.3 × 1
It was 0 ^-3 S / cm.

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

Next, in order to examine the chemical stability of the electrolyte with respect to lithium metal, the synthesized electrolytes having various compositions were pressed into a disc 1 having a thickness of 0.5 mm and a diameter of 10 mm. The lithium metal disks 2 and 2 ′ were crimped to form a sealed cell 3 as shown in FIG. The chemical stability is that these sealed cells 3 are kept at 60 ° C.
For 500 hours, and the change over time in the internal impedance of each sealed cell 3 was measured.

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

(Example 2) In Example 1, a′Li
0.7: 0.3 of lithium iodide (LiI) and lithium chloride (LiCl) as a plurality of kinds of lithium halides Z to be added to the amount of ₃ PO ₄ .b'Li ₂ S.c'SiS ₂ material y. Here, a mixture of lithium iodide (LiI) 0.75: lithium bromide (L
iLi) In the same manner as in Example 1 except that the mixture consisting of 0.25 was changed to the amount of d, aLi ₃ PO ₄ .bLi ₂ S.
cSiS ₂ .dZ (a + b + c + d = 1) was obtained.

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

FIG. 4 shows the obtained results. The vertical axis indicates ionic conductivity, and the horizontal axis indicates (0.03Li ₃ PO ₄ .0.
58Li ₂ S.0.39SiS ₂ ) composed of a plurality of kinds of lithium halides Z (where Z is lithium iodide (LiI) and lithium bromide (LiBr) 0.75:
(A mixture of 0.25). FIG. 4 shows that the ionic conductivity increases with the addition of the lithium halide Z, then decreases through a local maximum, and the ionic conductivity is highest.
_{0.80 (0.03Li 3 PO 4 · 0.58Li} 2 S ·
0.39SiS ₂ ) .0.20 (0.75LiI, 0.
25LiBr), and its ionic conductivity value is 2.6.
× 10 ^-3 S / cm.

(Example 3) In Example 1, a′Li
0.7: 0.3 of lithium iodide (LiI) and lithium chloride (LiCl) as a plurality of kinds of lithium halides Z to be added to the amount of ₃ PO ₄ .b'Li ₂ S.c'SiS ₂ material y. Here, a mixture of lithium iodide (LiI) 0.7: lithium bromide (Li) was used.
Br) 0.1: Same as Example 1 except that the mixture consisting of lithium chloride (LiCl) 0.2 was changed to d amount.
aLi ₃ PO ₄ .bLi ₂ S.cSiS ₂ .dZ (a +
b + c + d = 1) was obtained.

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

FIG. 5 shows the obtained results. The vertical axis is Io
The horizontal axis indicates (0.03Li)._ThreePO_Four・ 0.
58Li_TwoS ・ 0.39SiS_TwoFrom multiple species
Lithium halide Z (where Z is lithium iodide
(LiI) 0.7, lithium bromide (LiBr) 0.1,
Lithium chloride (LiCl) 0.2 mixture)
(Mol%). Figure 5 shows the ionic conductivity
Increases with the addition of lithium halide Z and then reaches a maximum
It is shown that the ionic conductivity has decreased
Is largest at 0.80 (0.03Li_ThreePO
_Four・ 0.58Li _TwoS ・ 0.39SiS_Two) ・ 0.20
(0.7LiI, 0.1LiBr, 0.2LiCl)
And its ionic conductivity value is 1.8 × 10^-3S / cm
Met.

Example 4 aLi ₃ PO ₄ .bLi ₂ S
・ Amorphous lithium ion conductive solid electrolyte aLi ₃ PO ₄・ bLi ₂ S ・ cG using cGeS ₂ -based amorphous material
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 ) are mixed at a molar ratio of 3: 2, and the material powder is placed in a glassy carbon crucible. after 5 hours of reaction was quenched put into liquid nitrogen to synthesize a material 0.6Li ₂ S · 0.4GeS ₂ composition. Subsequently, the thus obtained material 0.6Li ₂ S.0.4
GeS ₂ was pulverized, lithium phosphate (Li ₃ PO ₄ ) was mixed at a molar ratio of 97: 3, and the powder was placed in a glassy carbon crucible and reacted at 950 ° C. for 1.5 hours in a stream of argon. Was. After that, put into liquid nitrogen and quench,
_{0.03Li 3 PO 4 · 0.58Li 2 S} · 0.39G
The amorphous material represented by eS ₂ were synthesized.

The obtained 0.03Li ₃ PO ₄ .0.58
Li ₂ S · 0.39GeS _{2 With} respect to the amount of the material y, lithium iodide (Li
I), after taking a mixture of lithium chloride (LiCl) 0.8: 0.2 with d amount and mixing so that y + d becomes 1,
The material powder was placed in a glassy carbon crucible, which was melted and reacted at 950 ° C. for 1.5 hours in an argon gas stream, and then poured into liquid nitrogen to be rapidly cooled to aLi ₃ PO ₄ .bL.
i ₂ S.cGeS ₂ .dZ (a + b + c + d = 1) was obtained.

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

FIG. 6 shows the obtained results. The vertical axis is Io
The horizontal axis indicates (0.03Li)._ThreePO_Four・ 0.
58Li_TwoS ・ 0.39GeS_TwoMultiple kinds of c
It shows the amount (mol%) of lithium logenide Z added.
is there. FIG. 6 shows that the ionic conductivity of lithium halide Z
After increasing with the addition, it has decreased through the maximum
It is shown that the ionic conductivity is highest
0.85 (0.03Li _ThreePO_Four・ 0.58Li_TwoS.
0.39GeS_Two) .0.15 (0.8LiI, 0.2
LiCl) whose ionic conductivity is 1.2 × 1
0^-3S / 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 /
cm.

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

The obtained results show that, as in Example 1, when lithium halide is 0.6 or more, the change with time of the internal impedance is extremely large, and when it is less than 0.6, the increase in the internal impedance is small.

(Example 5) In Example 4, a′Li
Lithium iodide (LiI) and lithium chloride (LiCl) as a plurality of kinds of lithium halides Z to be added are 0.8: 0.2 with respect to the amount of the ₃ PO ₄ .b'Li ₂ S.c'GeS ₂ material y. Here, a mixture of lithium iodide (LiI) 0.75: lithium bromide (L
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 examine the characteristics of the synthesized solid electrolyte,
The ionic conductivity was measured by the AC impedance method.

FIG. 7 shows the obtained results. The vertical axis indicates ionic conductivity, and the horizontal axis indicates (0.03Li ₃ PO ₄ .0.
58Li ₂ S.0.39GeS ₂ ) composed of plural kinds of lithium halides Z (where Z is lithium iodide (LiI) 0.75, lithium bromide (LiBr) 0.1
5, a mixture of lithium chloride (LiCl) 0.1) (mol%). FIG. 7 shows that the ionic conductivity increased with the addition of lithium halide Z, then decreased through a local maximum, and the ionic conductivity was maximized at 0.75 (0.03Li ₃ P
_{O 4 · 0.58Li 2 S · 0.39GeS} 2) · 0.2
5 (0.75LiI, 0.15LiBr, 0.10Li
Cl) whose ionic conductivity value is 1.1 × 10 ^−3.
S / cm.

Example 6 aLi ₃ PO ₄ .bLi ₂ S
Amorphous lithium ion conductive solid electrolyte aLi ₃ PO ₄ · bLi ₂ S · cP using cP ₂ S ₅ amorphous material
Example of ₂ S ₅ · dZ 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 ) are mixed at a molar ratio of 2: 1 and the material powder is placed in a glassy carbon crucible, which is placed in an argon stream at 500 ° C. After reacting for 12 hours and then at 800 ° C. for 2 hours, the mixture is poured into liquid nitrogen and quenched, and 0.67Li ₂ S.0.33P ₂
It was synthesized material S ₅ composition. Subsequently, the material 0.67Li ₂ S.0.33P ₂ S ₅ thus obtained was pulverized, 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. The reaction was carried out at 950 ° C. for 1.5 hours in an argon stream. After that, it is poured into liquid nitrogen and quenched, and then 0.03Li ₃ PO _4.
The amorphous material represented by 0.65Li ₂ S · 0.32P ₂ S ₅ were synthesized.

The obtained 0.03Li ₃ PO ₄ · 0.65
Li ₂ S · 0.32 P ₂ S _{5 With} respect to the amount of material y, lithium iodide (Li)
I), after taking a mixture of lithium chloride (LiCl) 0.7: 0.3 in d amount and mixing so that y + d becomes 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 to aLi ₃ PO ₄ .b.
Li ₂ S.cP ₂ S ₅ .dZ (a + b + c + d = 1) was obtained.

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

FIG. 8 shows the obtained results. The vertical axis indicates ionic conductivity, and the horizontal axis indicates (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 in which the ionic conductivity showed the largest value was 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 the ionic conductivity was 1.2 × 10 ⁻³ S / cm.

On the other hand, 0.03Li ₃ PO ₄ · 0.65Li ₂ S ·
The ionic conductivity of 0.32P ₂ S ₅ is 4.2 × 10 ⁻⁴ S /
cm.

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

The obtained results show that, as in Example 1, the variation of the internal impedance with time is remarkably large when a plurality of types of lithium halides are 0.6 or more, and when the content is less than 0.6, the increase of the internal impedance is small. .

(Example 7) In Example 6, a'Li
_With respect to the amount of y of ₃ PO ₄ .b'Li ₂ S.c'P ₂ S ₅ , lithium iodide (LiI) and lithium chloride (LiCl) 0.7-0 as a plurality of kinds of lithium halides Z to be added are added. .3 was used. Here, the mixture was prepared using lithium iodide (LiI) 0.75, lithium bromide (L
aLi ₃ PO ₄ .bLi ₂ S.cP ₂ S ₅ .dZ in the same manner as in Example 6 except that the mixture consisting of iBr) 0.1 and lithium chloride (LiCl) 0.15 was changed to d amount.
(A + b + c + d = 1) was obtained.

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

FIG. 9 shows the obtained results. The vertical axis indicates ionic conductivity, and the horizontal axis indicates (0.03Li ₃ PO ₄ .0.
65Li ₂ S.0.32P ₂ S ₅ ) composed of a plurality of kinds of lithium halides Z (where Z is lithium iodide (LiI) 0.75, lithium bromide (LiBr) 0.1.
1, a mixture of lithium chloride (LiCl) 0.15). FIG. 9 shows that the ionic conductivity increased with the addition of lithium halide Z,
It is shown that the ionic conductivity has decreased after passing through the maximum, and the ionic conductivity becomes the largest at 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.
S / cm.

Example 8 aLi ₃ PO ₄ .bLi ₂ S
Lithium ion conductive solid electrolyte aLi ₃ PO ₄ bLi ₂ S cB ₂ S ₃ using cB ₂ S ₃ amorphous material
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 ) are mixed at a molar ratio of 1: 1 and the material powder is placed in a glassy carbon crucible, which is 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. Subsequently, the thus obtained material 0.5
Li ₂ S.0.5B ₂ S ₃ is pulverized, lithium phosphate (Li ₃ PO ₄ ) is mixed at a molar ratio of 96: 4, and the powder is placed in a glassy carbon crucible and placed in an argon gas stream.
The reaction was performed at 0 ° C. for 3 hours. After that, it is poured into liquid nitrogen and quenched, and then 0.04Li ₃ PO ₄ .0.48Li ₂ S
· 0.48B ₂ was synthesized amorphous material represented by S _3.

The resulting 0.04Li ₃ PO ₄ .0.48
Li ₂ S · 0.48B ₂ S _{3 The} amount of the material y is changed to lithium iodide (Li)
I), lithium chloride (LiCl) 0.65: 0.35
After mixing d so that y + d is 1, the mixed powder is put into a glassy carbon crucible, and the mixture is melted at 800 ° C. for 1.5 hours in an argon stream to react. , Quenched in liquid nitrogen and aLi ₃ PO _{4
· BLi 2 S · cB 2 S} 3 · dZ (a + b + c + d =
1) was obtained.

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

FIG. 10 shows the obtained results. The vertical axis indicates the ionic conductivity, and the horizontal axis indicates (0.04Li ₃ PO _4.
It shows the amounts (mol%) of a plurality of types of lithium halides added to 0.48Li ₂ S · 0.48B ₂ S ₃ ). The composition with the highest value of ionic conductivity is
_{0.75 (0.03Li 3 PO 4 · 0.65Li} 2 S ·
0.32B ₂ S ₃ ) .0.25 (0.65 LiI, 0.
35LiCl), and its ionic conductivity value is 1.8.
× 10 ^-3 S / cm.

On the other hand, 0.03Li ₃ PO ₄ .0.65Li without addition of a plurality of types of lithium halides was used.
Ionic conductivity of ₂ S · 0.32B ₂ S ₃ is 3.0 × 10
^-4 S / cm.

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

The obtained results show that, as in Example 1, when the amount of addition of a plurality of types of lithium lithium is 0.6 or more, the change with time of the internal impedance becomes remarkably large, and when it is less than 0.6, the increase in the internal impedance is small. 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 B ₂ S ₃ are obtained by adding a mixture of a plurality of types of lithium halides to one or more sulfide-based sulfide amorphous materials selected from the group of B ₂ S _3. Yes, the base material Li ₂ SX (X is SiS ₂ , G
It shows higher lithium ion conductivity than one or more sulfide-based amorphous materials selected from the group consisting of eS ₂ , P ₂ S ₅ , and B ₂ S ₃ , and exhibits chemical chemistry even by contact with lithium metal. It is possible to provide a solid electrolyte with little change in the target.

As a result, even if this lithium ion conductive solid electrolyte is used for an electrolyte of an electrochemical device such as a battery, a capacitor, and an electrochromic display device, an extremely practical electrochemical device can be manufactured. There is expected.

In the synthesis of the solid electrolyte according to the embodiment of the present invention, an amorphous material was sequentially synthesized to obtain the intended lithium ion conductive solid electrolyte of the present invention. It was obvious that the simplification could be achieved by selecting various conditions such as the electrolyte composition, the synthesis temperature, and the heating condition. It belongs to the category of the invention. 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 with a mixing ratio of another composition. Therefore, it goes without saying that an electrolyte having a mixing ratio of another composition also belongs to the category of the present invention.

[Brief description of the drawings]

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

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

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

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

FIG. 10: a'Li ₃ PO ₄ .b'Li ₂ S.c'B ₂
More of lithium halide to S ₃ (LiI, LiC
characteristic diagram showing the change in conductivity due to the addition of

[Description of Signs] 1 electrolyte disk 2 lithium metal disk 2 'lithium metal disk 3 sealed cell

Continuation of front page (56) References JP-A-2-304805 (JP, A) JP-A-3-269079 (JP, A) JP-A-4-162306 (JP, A) (58) Fields investigated (Int) .Cl. ⁷ , DB name) C01B 25/30 H01B 1/06 H01M 6/18

Claims (3)

(57) [Claims] 1. The formula aLi ₃ PO ₄ .bLi ₂ S.c
X · dZ (where a + b + c + d is 1 and X is S
an amorphous lithium ion conductive solid represented by at least one sulfide selected from the group consisting of iS ₂ , GeS ₂ , P ₂ S ₅ and B ₂ S ₃ , wherein Z is a plurality of lithium halides Electrolytes. 2. The sum of the composition ratios a, b, and c is 0.9 ≧ a + b.
2. 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 resin according to claim 1 or 2, wherein
A method for synthesizing a lithium ion conductive solid electrolyte, comprising:
A'Li_ThreePO_Four・ B'Li_TwoS · c′X (however,
a '+ b' + c 'is 1 and X is SiS_Two, GeS
_Two, P_TwoS_Five, B _TwoS_ThreeMore than one kind selected from the group of
After synthesizing an amorphous compound represented by
Mixed with a plurality of lithium halides Z, and
The mixture is heated and melted, and then quenched to synthesize.
Amorphous lithium ion conductive solid state electrode
Synthetic method of resolving.