JP3134595B2 - Sulfide-based 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 a solid electrochemical device such as an all solid battery, a capacitor, and a solid electrochromic display device.

[0002]

2. Description of the Related Art In recent years, studies on all solidification of a lithium battery using a lithium ion conductive solid electrolyte have been actively conducted. This is because a lithium battery using lithium or the like as the negative electrode active material has a high energy density, and since the electrolyte is solidified, there is no liquid leakage, and it is excellent in safety and reliability, and can be made smaller and thinner. Therefore, the demand is high and development is desired.

As one of such lithium ion conductive solid electrolytes, Li ₂ SX (X is SiS ₂ , GeS ₂ ,
At least one sulfide of P ₂ S ₅ and B ₂ S ₃ )
Based sulfide glass is present. The Li ₂ SX-based sulfide glass has the highest conductivity value even in the Li ₂ S-SiS ₂ system in which X is SiS ₂ , and the value is 5 × 10 ⁻⁴ S / cm.
It is about.

Further, in order to obtain higher ionic conductivity, Li _{3 obtained} by adding lithium iodide (LiI) or lithium phosphate (Li ₃ PO ₄ ) to these sulfide glasses.
Proposals have been made for PO ₄ -Li ₂ S-SiS ₂ pseudo-ternary glass.

[0005] For example, Li ₃
In the case of PO ₄ —Li ₂ S—SiS ₂ pseudo-ternary glass, the process is performed as follows. Lithium phosphate (Li ₃ PO ₄ ),
Lithium sulfide (Li ₂ S) and silicon sulfide (SiS ₂ ) are mixed in a desired molar ratio, and the mixed powder is heated in an argon stream to cause eutectic. Then, the melt is cooled by throwing it into liquid nitrogen, and Li ₃ PO ₄ —Li ₂ SS
iS ₂ pseudo ternary glass is obtained.

[0006]

When these solid electrolytes are used as an electrolyte for an electrochemical device, for example, in order to enable rapid charging and discharging in the case of a battery, and to improve the response speed in the case of a sensor. Therefore, it is necessary to further improve the ionic conductivity.

[0007] In view of the above problems, an object of the present invention is to provide a solid electrolyte having higher lithium ion conductivity.

[0008]

In order to solve these problems, a sulfide-based lithium ion conductive solid electrolyte according to the present invention is obtained by dispersing an oxide dielectric fine powder in a sulfide-based lithium ion conductive solid electrolyte. General formula aLi ₂ S · b
X.cLi ₃ PO ₄ .dLiI.eY (a + b + c + d +
e = 1), wherein X is SiS ₂ , GeS ₂ , P ₂ S ₅ and B ₂
At least one member selected from the group consisting of S _3,
Y is at least one selected from the group consisting of Al ₂ O ₃ , ZrO ₂ , TiO ₂ and SiO ₂ .

The general formula aLi_TwoS ・ bX ・ cLi_ThreeP
O_Four(However, X is SiS_Two, GeS_Two, P_TwoS_FiveAnd B_TwoS_Three
Represented by at least one sulfide of
Obtained by sintering ionic conductive solid electrolyte, LiI and Y
The general formula dLiI.eY (where Y is Al_TwoO_Three, Zr
O_Two, TiO_TwoAnd SiO_TwoAt least one of
Lithium ion conductivity expressed by oxide dielectric fine powder)
Mix and crush solid electrolyte and heat and melt the mixed powder
After cooling, the general formula aLi_TwoS ・ bX ・ cLi_ThreePO _Four
Lithium ion conductive solid represented by dLiIeY
It synthesizes an electrolyte.

Alternatively, the general formula aLi_TwoS ・ bX ・ cL
i_ThreePO_Four(However, X is SiS_Two, GeS _Two, P_TwoS_FiveAnd B
_TwoS_ThreeRepresented by at least one of the sulfides
Sintering of lithium ion conductive solid electrolyte, LiI and Y
General formula dLiI.eY (where Y is Al_TwoO_Three, Zr
O_Two, TiO_TwoAnd SiO_TwoAt least one of
Lithium ion conductivity expressed by oxide dielectric fine particles)
Mixing and grinding with a solid electrolyte and glass transition of the mixed powder
By heating and sintering below the temperature, the general formula aLi
_TwoS ・ bX ・ cLi_ThreePO_Four· Represented by dLiI · eY
For synthesizing a lithium ion conductive solid electrolyte
You.

[0011]

When the oxide dielectric fine powder is dispersed in the sulfide-based lithium ion conductive solid electrolyte, V ′ is formed at the interface between the sulfide-based lithium ion conductive solid electrolyte and the oxide dielectric fine powder. It is considered that a space charge layer is formed by lithium ion vacancies or interstitial lithium ions represented by _Li or Li @ i, which contribute to ionic conduction and improve ionic conductivity. For this reason,
General formula aLi ₂ S · bX · cL in which oxide dielectric fine powder is dispersed in a sulfide-based lithium ion conductive solid electrolyte
i ₃ PO ₄ .dLiI.eY (a + b + c + d + e = 1)
The lithium ion conductive solid electrolyte represented by the formula has higher lithium ion conductivity. Among the sulfide-based lithium ion conductive solid electrolytes, the SiS ₂ system has the highest ionic conductivity, and is particularly effective when Al ₂ O ₃ is used as the oxide dielectric fine powder, and the higher ionic conductivity is obtained. Can be achieved.

In order to form a space charge layer, it is preferable that the surfaces of the oxide dielectric particles are covered with highly conductive LiI. Therefore, the mixed powder of LiI and the oxide dielectric fine powder is heated and sintered in advance, and the surfaces of the oxide dielectric particles are coated with LiI. Then, this powder is mixed with a sulfide-based lithium ion conductive solid electrolyte, and the mixed powder is heated and melted, cooled, or heated and sintered at a temperature equal to or lower than the glass transition temperature, to thereby form an oxide dielectric having a surface coated with LiI. A sulfide-based lithium ion conductive solid electrolyte in which body powder is dispersed is synthesized. Even higher ionic conductivity can be achieved by the method for synthesizing the sulfide-based ion-conductive solid electrolyte.

[0013]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to specific examples, but the present invention is not limited to these examples.

Incidentally, the particle diameter of the oxide dielectric fine powder added for improving the ionic conductivity of LiI or CuCl is generally 10 to 500 nm. Therefore, in this embodiment, the oxide dielectric fine powder (Al ₂ O ₃ , ZrO ₂ , T
iO ₂ , SiO ₂ ) has an average particle diameter of 50 n for each dielectric.
m.

(Example 1) Among the sulfide-based lithium ion conductive solid electrolytes according to the present invention, aLi ₂ S.bSi
A sulfide-based lithium ion conductive solid electrolyte represented by S ₂ .cLi ₃ PO ₄ .dLiI.eAl ₂ O ₃ was converted to Al ₂ O ₃
Is changed in the range of 0 ≦ e ≦ 0.5, and A
The composition ratio of components other than l ₂ O ₃ is 0.2 ≦ a / (a + b + c)
+ D) ≦ 0.7, 0.15 ≦ b / (a + b + c + d) ≦
0.6, 0 ≦ c / (a + b + c + d) ≦ 0.1, 0 ≦ d
/(A+b+c+d)≦0.4, and synthesized according to the following procedure.

First, a material powder obtained by mixing lithium phosphate (Li ₃ PO ₄ ), lithium sulfide (Li ₂ S) and silicon sulfide (SiS ₂ ) is placed in a glassy carbon crucible so as to have a predetermined composition. , At 950 ° C in an argon stream for 2 hours.
After in time melt reaction, was put into liquid nitrogen _{cooled, a'Li 2 S · b'SiS 2 ·} c'Li 3 PO 4 based lithium ion conductive solid electrolyte (a '+ b' + c '= 1)
Was synthesized. Further, a material powder obtained by mixing lithium iodide (LiI) and alumina (Al ₂ O ₃ ) fine powder so as to have a predetermined composition is put into a glassy carbon crucible, which is heated at 550 ° C. for 15 hours in an argon gas stream. Sintered, Al
D'LiI.e'Al ₂ O ₃ with the surface of ₂ O ₃ covered with LiI
Based lithium ion conductive solid electrolyte (d '+ e' = 1)
Was synthesized. Next, these composites were synthesized by two kinds of methods to obtain a sulfide-based lithium ion conductive solid electrolyte. In the first synthesis method, these synthesized products are pulverized, and a material powder sufficiently mixed so as to have a desired composition is put into a glassy carbon crucible, which is melted and reacted at 950 ° C. for 2 hours in an argon stream. , Poured into liquid nitrogen and cooled, a
Li ₂ S.bSiS ₂ .cLi ₃ PO ₄ .dLiI.eAl
_{A 2} O ₃ sulfide-based lithium ion conductive solid electrolyte was synthesized (hereinafter, the synthesis method in this step is referred to as a melting method). The second synthesis method is a′Li ₂ S.b′SiS ₂ .c′Li ₃
PO ₄ -based lithium ion conductive solid electrolyte and d'LiI
・ E'Al ₂ O ₃ -based lithium ion conductive solid electrolyte is pulverized, and a material powder sufficiently mixed so as to have a desired composition is put into a glassy carbon crucible and heated at 350 ° C. for 20 hours to obtain aLi ₂ S.bSiS. ₂・ cLi ₃ PO ₄・ dLiI ・
An eAl ₂ O ₃ sulfide-based lithium ion conductive solid electrolyte was synthesized (hereinafter, the synthesis method in this step is referred to as a sintering method).

The ionic conductivity of the solid electrolyte synthesized as described above was measured by an AC impedance method.

FIG. 1 shows main measurement results of the solid electrolyte synthesized by the melting method. ALi according to the invention
₂ S.bSiS ₂ .cLi ₃ PO ₄ .dLiI.eAl ₂ O ₃
The ionic conductivity of the sulfide-based lithium ion conductive solid electrolyte represented by the formula (I) increases with the amount of Al ₂ O ₃ dispersed,
The maximum was shown when the composition ratio e of l ₂ O ₃ was 0.15. However, when the amount of dispersion is larger than the above, the ionic conductivity decreases, and when the composition ratio of Al ₂ O ₃ is e = 0.5, the ionic conductivity is lower than e = 0. Also, for other compositions,
Similar results were obtained. Furthermore, the same results were obtained for the solid electrolyte synthesized by the sintering method as for the solid electrolyte synthesized by the melting method.

Example 2 Among the sulfide-based lithium ion conductive solid electrolytes according to the present invention, aLi ₂ S.bGe
A sulfide-based lithium ion conductive solid electrolyte represented by S ₂ .cLi ₃ PO ₄ .dLiI.eAl ₂ O ₃ was converted to SiS ₂
Synthesis was performed in the same manner as in Example 1 except that GeS ₂ was used instead.

The ionic conductivity of the solid electrolyte synthesized as described above was measured by an AC impedance method.

FIG. 2 shows main measurement results of the solid electrolyte synthesized by the melting method. ALi according to the invention
₂ S ・ bGeS ₂・ cLi ₃ PO ₄・ dLiI ・ eAl ₂ O ₃
The ionic conductivity of the sulfide-based lithium ion conductive solid electrolyte represented by the formula (I) increases with the amount of Al ₂ O ₃ dispersed,
When the composition ratio of l ₂ O ₃ was e = 0.2, the maximum was exhibited, and when the dispersion amount was larger than that, the ionic conductivity was reduced. Similar results were obtained for other compositions. Furthermore, the same results were obtained for the solid electrolyte synthesized by the sintering method as for the solid electrolyte synthesized by the melting method.

Embodiment 3 Among the sulfide-based lithium ion conductive solid electrolytes according to the present invention, aLi ₂ S.bP ₂ S
The _{5 · cLi 3 PO 4 · dLiI} · eAl 2 O 3 in the sulfide-based lithium ion conductive solid electrolyte represented, except for using the P ₂ S ₅ in place of SiS ₂ in a manner similar to Example 1 Synthesized.

The ionic conductivity of the solid electrolyte synthesized as described above was measured by an AC impedance method.

FIG. 3 shows main measurement results of the solid electrolyte synthesized by the melting method. ALi according to the invention
_{2 S · bP 2 S 5 ·} cLi 3 PO 4 · dLiI · eAl 2 O 3
The ionic conductivity of the sulfide-based lithium ion conductive solid electrolyte represented by the formula (I) increases with the amount of Al ₂ O ₃ dispersed,
When the composition ratio of l ₂ O ₃ was e = 0.1, the maximum was exhibited, and when the dispersion amount was larger than that, the ionic conductivity was lowered. Similar results were obtained for other compositions. Furthermore, the same results were obtained for the solid electrolyte synthesized by the sintering method as for the solid electrolyte synthesized by the melting method.

Example 4 Among the sulfide-based lithium ion conductive solid electrolytes according to the present invention, aLi ₂ S.bB ₂ S
₃ - The _{cLi 3 PO 4 · dLiI · eAl} 2 O 3 in the sulfide-based lithium ion conductive solid electrolyte represented, except for using the B ₂ S ₃ instead of SiS ₂ in a manner similar to Example 1 Synthesized.

The ionic conductivity of the solid electrolyte synthesized as described above was measured by an AC impedance method.

FIG. 4 shows main measurement results of the solid electrolyte synthesized by the melting method. ALi according to the invention
₂ S.bB ₂ S ₃ .cLi ₃ PO ₄ .dLiI.eAl ₂ O ₃
The ionic conductivity of the sulfide-based lithium ion conductive solid electrolyte represented by the formula (I) increases with the amount of Al ₂ O ₃ dispersed,
When the composition ratio e of l ₂ O ₃ was e = 0.15, the maximum was exhibited, and when the dispersion amount was larger than that, the ionic conductivity was reduced. Also,
Similar results were obtained for other compositions. Furthermore, the same results were obtained for the solid electrolyte synthesized by the sintering method as for the solid electrolyte synthesized by the melting method.

Embodiment 5 Among the sulfide-based lithium ion conductive solid electrolytes according to the present invention, aLi ₂ S.bSi
A sulfide-based lithium ion conductive solid electrolyte represented by S ₂ · cLi ₃ PO ₄ · dLiI · eZrO ₂ was synthesized in the same manner as in Example 1 except that ZrO ₂ was used instead of Al ₂ O _3. did.

The ionic conductivity of the solid electrolyte synthesized as described above was measured by an AC impedance method.

FIG. 5 shows main measurement results of the solid electrolyte synthesized by the melting method. ALi according to the invention
₂ S.bSiS ₂ .cLi ₃ PO ₄ .dLiI.eZrO ₂
The ionic conductivity of the sulfide-based lithium ion conductive solid electrolyte represented by the formula (I) increases with the amount of ZrO ₂ dispersed,
The maximum was exhibited when the composition ratio of rO ₂ was e = 0.2, and the ionic conductivity was lowered when the dispersion amount was larger than that. Similar results were obtained for other compositions. Furthermore, the same results were obtained for the solid electrolyte synthesized by the sintering method as for the solid electrolyte synthesized by the melting method.

Embodiment 6 Among the sulfide-based lithium ion conductive solid electrolytes according to the present invention, aLi ₂ S.bGe
The sulfide-based lithium ion conductive solid electrolyte represented by S ₂ · cLi ₃ PO ₄ · dLiI · eZrO ₂ was replaced by GeS _{2 in place} of SiS ₂ and ZrO _{2 in place} of Al ₂ O ₃ . Except for the above, it was synthesized in the same manner as in Example 1.

The ionic conductivity of the solid electrolyte synthesized as described above was measured by an AC impedance method.

FIG. 6 shows main measurement results of the solid electrolyte synthesized by the melting method. ALi according to the invention
₂ S ・ bGeS ₂・ cLi ₃ PO ₄・ dLiI ・ eZrO ₂
The ionic conductivity of the sulfide-based lithium ion conductive solid electrolyte represented by the formula (I) increases with the amount of ZrO ₂ dispersed,
The maximum was exhibited when the composition ratio e of rO ₂ was 0.25, and when the dispersion amount was larger than that, the ionic conductivity decreased. Also,
Similar results were obtained for other compositions. Furthermore, the same results were obtained for the solid electrolyte synthesized by the sintering method as for the solid electrolyte synthesized by the melting method.

Embodiment 7 Among the sulfide-based lithium ion conductive solid electrolytes according to the present invention, aLi ₂ S.bP ₂ S
Use the _{5 · cLi 3 PO 4 · dLiI} · eZrO 2 sulfide-based lithium-ion conductive solid electrolyte represented, with P ₂ S ₅ in place of SiS _2, also the ZrO ₂ instead of Al ₂ O ₃ The synthesis was carried out in the same manner as in Example 1 except for the difference.

The ionic conductivity of the solid electrolyte synthesized as described above was measured by an AC impedance method.

FIG. 7 shows main measurement results of the solid electrolyte synthesized by the melting method. ALi according to the invention
Ionic conductivity of _{2 S · bP 2 S 5 ·} cLi 3 PO 4 · dLiI · eZrO represented by ₂ sulfide based lithium ion conductive solid electrolyte, improves with dispersion amount of ZrO _2, Zr
The maximum was exhibited when the composition ratio e of O ₂ was 0.15, and when the dispersion amount was larger than that, the ionic conductivity was reduced. Similar results were obtained for other compositions. Furthermore, the same results were obtained for the solid electrolyte synthesized by the sintering method as for the solid electrolyte synthesized by the melting method.

Example 8 Among the sulfide-based lithium ion conductive solid electrolytes according to the present invention, aLi ₂ S.bB ₂ S
Use a _{3 · cLi 3 PO 4 · dLiI} · eZrO 2 sulfide-based lithium-ion conductive solid electrolyte represented, using the B ₂ S ₃ instead of SiS _2, also the ZrO ₂ instead of Al ₂ O ₃ The synthesis was carried out in the same manner as in Example 1 except for the difference.

The ionic conductivity of the solid electrolyte synthesized as described above was measured by an AC impedance method.

FIG. 8 shows main measurement results of the solid electrolyte synthesized by the melting method. ALi according to the invention
_The ionic conductivity of the sulfide-based lithium ion conductive solid electrolyte represented by ₂ S.bB ₂ S ₃ .cLi ₃ PO ₄ .dLiI.eZrO ₂ increases with the dispersion amount of ZrO ₂ ,
The maximum was exhibited when the composition ratio of O ₂ was e = 0.2, and the ionic conductivity was lowered with a larger amount of dispersion. Similar results were obtained for other compositions. further,
For the solid electrolyte synthesized by the sintering method, almost the same results as in the case of the solid electrolyte synthesized by the melting method were obtained.

Embodiment 9 Among the sulfide-based lithium ion conductive solid electrolytes according to the present invention, aLi ₂ S.bSi
A sulfide-based lithium ion conductive solid electrolyte represented by S ₂ · cLi ₃ PO ₄ · dLiI · eTiO ₂ was synthesized in the same manner as in Example 1 except that TiO ₂ was used instead of Al ₂ O _3. did.

The ionic conductivity of the solid electrolyte synthesized as described above was measured by an AC impedance method.

FIG. 9 shows main measurement results of the solid electrolyte synthesized by the melting method. ALi according to the invention
₂ S.bSiS ₂ .cLi ₃ PO ₄ .dLiI.eTiO ₂
The ionic conductivity of the sulfide-based lithium ion conductive solid electrolyte represented by the formula (I) increases with the amount of TiO ₂ dispersed,
The maximum was exhibited when the composition ratio e of iO ₂ was 0.1, and the ionic conductivity decreased when the dispersion amount was larger than that. Similar results were obtained for other compositions. Furthermore, the same results were obtained for the solid electrolyte synthesized by the sintering method as for the solid electrolyte synthesized by the melting method.

Example 10 Among the sulfide-based lithium ion conductive solid electrolytes according to the present invention, aLi ₂ S.bG
A sulfide-based lithium ion conductive solid electrolyte represented by eS ₂ .cLi ₃ PO ₄ .dLiI.eTiO ₂ was converted to SiS ₂
GeS ₂ was used instead of TiO ₂ and TiO ₂ was used instead of Al ₂ O ₃
Was synthesized in the same manner as in Example 1 except that

The ionic conductivity of the solid electrolyte synthesized as described above was measured by the AC impedance method.

FIG. 10 shows main measurement results of the solid electrolyte synthesized by the melting method. AL according to the invention
i ₂ S ・ bGeS ₂・ cLi ₃ PO ₄・ dLiI ・ eTiO
_The ionic conductivity of the sulfide-based lithium ion conductive solid electrolyte represented by ₂ increases with the amount of TiO ₂ dispersed,
The maximum was exhibited when the composition ratio e of TiO ₂ was 0.15, and when the amount of dispersion was larger than that, the ionic conductivity decreased. Similar results were obtained for other compositions.
Furthermore, the same results were obtained for the solid electrolyte synthesized by the sintering method as for the solid electrolyte synthesized by the melting method.

Example 11 Among the sulfide-based lithium ion conductive solid electrolytes according to the present invention, aLi ₂ S.bP ₂
The _{S 5 · cLi 3 PO 4 ·} dLiI · eTiO 2 sulfide-based lithium-ion conductive solid electrolyte represented, with P ₂ S ₅ in place of SiS _2, also the TiO ₂ instead of Al ₂ O ₃ The synthesis was carried out in the same manner as in Example 1, except for using.

The ionic conductivity of the solid electrolyte synthesized as described above was measured by an AC impedance method.

FIG. 11 shows main measurement results of the solid electrolyte synthesized by the melting method. AL according to the invention
_{i 2 S · bP 2 S 5} · cLi 3 PO 4 · dLiI · eTiO 2
The ionic conductivity of the sulfide-based lithium ion conductive solid electrolyte represented by the formula (I) increases with the amount of TiO ₂ dispersed,
The maximum was exhibited when the composition ratio of iO ₂ was e = 0.05, and the ionic conductivity decreased when the dispersion amount was larger than that. Also,
Similar results were obtained for other compositions. Furthermore, the same results were obtained for the solid electrolyte synthesized by the sintering method as for the solid electrolyte synthesized by the melting method.

Example 12 Among the sulfide-based lithium ion conductive solid electrolytes according to the present invention, aLi ₂ S.bB ₂
The _{S 3 · cLi 3 PO 4 ·} dLiI · eTiO 2 sulfide-based lithium-ion conductive solid electrolyte represented, using the B ₂ S ₃ instead of SiS _2, also the TiO ₂ instead of Al ₂ O ₃ The synthesis was carried out in the same manner as in Example 1, except for using.

The ionic conductivity of the solid electrolyte synthesized as described above was measured by the AC impedance method.

FIG. 12 shows main measurement results of the solid electrolyte synthesized by the melting method. AL according to the invention
_{i 2 S · bB 2 S 3} · cLi 3 PO 4 · dLiI · eTiO 2
The ionic conductivity of the sulfide-based lithium ion conductive solid electrolyte represented by the formula (I) increases with the amount of TiO ₂ dispersed,
The maximum was exhibited when the composition ratio e of iO ₂ was 0.1, and the ionic conductivity decreased when the dispersion amount was larger than that. Similar results were obtained for other compositions. Furthermore, the same results were obtained for the solid electrolyte synthesized by the sintering method as for the solid electrolyte synthesized by the melting method.

Embodiment 13 Among the sulfide-based lithium ion conductive solid electrolytes according to the present invention, aLi ₂ S.bS
A sulfide-based lithium ion conductive solid electrolyte represented by iS ₂ .cLi ₃ PO ₄ .dLiI.eSiO ₂ was converted to Al ₂ O ₃
Synthesis was performed in the same manner as in Example 1 except that SiO ₂ was used instead.

The ionic conductivity of the solid electrolyte synthesized as described above was measured by the AC impedance method.

FIG. 13 shows main measurement results of the solid electrolyte synthesized by the melting method. AL according to the invention
i ₂ S.bSiS ₂ .cLi ₃ PO ₄ .dLiI.eSiO
_The ionic conductivity of the sulfide-based lithium ion conductive solid electrolyte represented by ₂ improves with the amount of SiO ₂ dispersed,
The maximum was exhibited when the composition ratio e of SiO ₂ was 0.25, and when the dispersion amount was larger than that, the ionic conductivity decreased. Similar results were obtained for other compositions.
Furthermore, the same results were obtained for the solid electrolyte synthesized by the sintering method as for the solid electrolyte synthesized by the melting method.

(Example 14) Among the sulfide-based lithium ion conductive solid electrolytes according to the present invention, aLi ₂ S.bG
A sulfide-based lithium ion conductive solid electrolyte represented by eS ₂ .cLi ₃ PO ₄ .dLiI.eSiO ₂ was converted to SiS ₂
GeS ₂ was used instead of SiO ₂ and SiO ₂ was used instead of Al ₂ O ₃
Was synthesized in the same manner as in Example 1 except that

The ionic conductivity of the solid electrolyte synthesized as described above was measured by the AC impedance method.

FIG. 14 shows main measurement results of the solid electrolyte synthesized by the melting method. AL according to the invention
i ₂ S ・ bGeS ₂・ cLi ₃ PO ₄・ dLiI ・ eSiO
_The ionic conductivity of the sulfide-based lithium ion conductive solid electrolyte represented by ₂ improves with the amount of SiO ₂ dispersed,
The maximum was exhibited when the composition ratio of SiO ₂ was e = 0.3, and the ionic conductivity was reduced when the dispersion amount was larger than that. Also,
Similar results were obtained for other compositions. Furthermore, the same results were obtained for the solid electrolyte synthesized by the sintering method as for the solid electrolyte synthesized by the melting method.

Example 15 Among the sulfide-based lithium ion conductive solid electrolytes according to the present invention, aLi ₂ S.bP ₂
The _{S 5 · cLi 3 PO 4 ·} dLiI · eSiO 2 sulfide-based lithium-ion conductive solid electrolyte represented, with P ₂ S ₅ in place of SiS _2, also the SiO ₂ instead of Al ₂ O ₃ The synthesis was carried out in the same manner as in Example 1, except for using.

The ionic conductivity of the solid electrolyte synthesized as described above was measured by the AC impedance method.

FIG. 15 shows main measurement results of the solid electrolyte synthesized by the melting method. AL according to the invention
_{i 2 S · bP 2 S 5} · cLi 3 PO 4 · dLiI · eSiO 2
Ion conductivity of in represented by sulfide-based lithium ion conductive solid electrolyte, improves with the amount of dispersion of SiO _2, S
The maximum was exhibited when the composition ratio e of iO ₂ was 0.2, and when the amount of dispersion was larger than that, the ionic conductivity decreased. Similar results were obtained for other compositions. Furthermore, the same results were obtained for the solid electrolyte synthesized by the sintering method as for the solid electrolyte synthesized by the melting method.

Example 16 Among the sulfide-based lithium ion conductive solid electrolytes according to the present invention, aLi ₂ S.bB ₂
The _{S 3 · cLi 3 PO 4 ·} dLiI · eSiO 2 sulfide-based lithium-ion conductive solid electrolyte represented, using the B ₂ S ₃ instead of SiS _2, also the SiO ₂ instead of Al ₂ O ₃ The synthesis was carried out in the same manner as in Example 1, except for using.

The ionic conductivity of the solid electrolyte synthesized as described above was measured by the AC impedance method.

FIG. 16 shows main measurement results of the solid electrolyte synthesized by the melting method. AL according to the invention
_{i 2 S · bB 2 S 3} · cLi 3 PO 4 · dLiI · eSiO 2
Ion conductivity of in represented by sulfide-based lithium ion conductive solid electrolyte, improves with the amount of dispersion of SiO _2, S
The maximum was exhibited when the composition ratio e of iO ₂ was 0.25, and the ionic conductivity was lowered with a larger dispersion amount. Also,
Similar results were obtained for other compositions. Furthermore, the same results were obtained for the solid electrolyte synthesized by the sintering method as for the solid electrolyte synthesized by the melting method.

In the examples of the present invention, the general formula aLi
As a sulfide-based lithium ion conductive solid electrolyte represented by _{2 S · bX · cLi 3 PO} 4 · dLiI · eY, X is about what is _{SiS 2, GeS 2, P 2} S 5, B 2 S 3 described The same result can be obtained by using a mixture of a plurality of sulfides selected from SiS ₂ , GeS ₂ , P ₂ S ₅ , and B ₂ S ₃ such as a mixture of SiS ₂ and GeS ₂ as X. Needless to say, the present invention is not limited to a single sulfide as X.

In the examples of the present invention, the general formula aLi
As a sulfide-based lithium ion conductive solid electrolyte represented by _{2 S · bX · cLi 3 PO} 4 · dLiI · eY, been described and Y is _{Al 2 O 3, ZrO 2,} TiO 2, SiO 2 However, similar results can be obtained even when a mixture of a plurality of oxides selected from Al ₂ O ₃ , ZrO ₂ , TiO ₂ , and SiO ₂ such as a mixture of Al ₂ O ₃ and ZrO ₂ is used as Y. Needless to say, the present invention is not limited to a single oxide as Y.

[0066]

As described above, according to the present invention, an oxide dielectric fine powder is dispersed in a sulfide-based lithium ion conductive solid electrolyte, and the general formula aLi ₂ S.bX.cLi ₃ PO _4.
dLiIeY (where X is SiS ₂ , GeS ₂ , P ₂ S ₅ ,
At least one sulfide of B ₂ S ₃ , Y is Al ₂ O ₃ ,
It is possible to obtain a lithium ion conductive solid electrolyte having high ionic conductivity represented by at least one oxide dielectric fine powder of ZrO ₂ , TiO ₂ , and SiO ₂ . In particular, when the composition ratio e of Y is 0.4 or less, high ionic conductivity is exhibited, and the effect appears.

By using SiS ₂ as X and using Al ₂ O ₃ as Y, a sulfide-based lithium ion conductive solid electrolyte having higher ion conductivity can be obtained.

Also, a mixed powder of LiI and oxide dielectric fine powder is heated and sintered in advance, and the surfaces of the oxide dielectric particles are coated with LiI. This powder was mixed with a sulfide-based lithium ion conductive solid electrolyte, and the mixed powder was heated and melted, cooled, or heated at or below the glass transition temperature to disperse the oxide dielectric powder coated with LiI on the surface. By synthesizing a sulfide-based lithium ion conductive solid electrolyte, higher ionic conductivity can be achieved.

[Brief description of the drawings]

The composition ratio of [1] _{Al 2 O 3, aLi 2 S} · bSiS 2 ·
Diagram of ionic conductivity of cLi ₃ PO ₄ .dLiI.eAl ₂ O ₃

The composition ratio of [2] _{Al 2 O 3, aLi 2 S} · bGeS 2 ·
Diagram of ionic conductivity of cLi ₃ PO ₄ .dLiI.eAl ₂ O ₃

[3] the composition ratio of _{Al 2 O 3, aLi 2 S} · bP 2 S 5 ·
Diagram of ionic conductivity of cLi ₃ PO ₄ .dLiI.eAl ₂ O ₃

FIG. 4 shows the composition ratio of Al ₂ O ₃ and aLi ₂ S.bB ₂ S _3.
Diagram of ionic conductivity of cLi ₃ PO ₄ .dLiI.eAl ₂ O ₃

And Figure 5 ZrO ₂ composition ratio, aLi ₂ S · bSiS ₂ ·
Relationship between ionic conductivity of cLi ₃ PO ₄ .dLiI.eZrO ₂

And Figure 6 ZrO ₂ composition ratio, aLi ₂ S · bGeS ₂ ·
Relationship between ionic conductivity of cLi ₃ PO ₄ .dLiI.eZrO ₂

[7] and ZrO ₂ composition _{ratio, aLi 2 S · bP 2 S} 5 · c
Relationship between Li ₃ PO ₄ · dLiI · eZrO ₂ and ionic conductivity

FIG. 8 shows the composition ratio of ZrO ₂ and aLi ₂ S.bB ₂ S ₃ .c
Relationship between Li ₃ PO ₄ · dLiI · eZrO ₂ and ionic conductivity

And [9] TiO ₂ composition ratio, aLi ₂ S · bSiS ₂ ·
Relationship between ionic conductivity of cLi ₃ PO ₄ .dLiI.eTiO ₂

[Figure 10] and TiO ₂ composition ratio, aLi ₂ S · bGeS ₂
・ Relationship between ionic conductivity of cLi ₃ PO ₄・ dLiI ・ eTiO ₂

[11] and TiO ₂ composition _{ratio, aLi 2 S · bP 2 S} 5 ·
Relationship between ionic conductivity of cLi ₃ PO ₄ .dLiI.eTiO ₂

FIG. 12 shows the composition ratio of TiO ₂ and aLi ₂ S.bB ₂ S _3.
Relationship between ionic conductivity of cLi ₃ PO ₄ .dLiI.eTiO ₂

[13] and the SiO ₂ compositional ratio, aLi ₂ S · bSiS ₂
・ Relationship between ionic conductivity of cLi ₃ PO ₄・ dLiI ・ eSiO ₂

[Figure 14] and SiO ₂ compositional ratio, aLi ₂ S · bGeS ₂
・ Relationship between ionic conductivity of cLi ₃ PO ₄・ dLiI ・ eSiO ₂

[15] and the SiO ₂ compositional _{ratio, aLi 2 S · bP 2 S} 5 ·
Relationship between ionic conductivity of cLi ₃ PO ₄ .dLiI.eSiO ₂

FIG. 16 shows the composition ratio of SiO ₂ and aLi ₂ S.bB ₂ S _3.
Relationship between ionic conductivity of cLi ₃ PO ₄ .dLiI.eSiO ₂

Continuation of the front page (72) Inventor Shigeo Kondo 1006 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. (56) References JP-A-6-271332 (JP, A) JP-A-5-310417 (JP) , A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C03C 1/00-14/00 H01M 10/36 H01M 6/18 H01B 1/06 JICST file (JOIS)

Claims (6)

(57) [Claims] 1. A general formula aLi _{2 wherein} an oxide dielectric fine powder is dispersed in a sulfide-based lithium ion conductive solid electrolyte.
S.bX.cLi ₃ PO ₄ .dLiI.eY (a + b + c
+ D + e = 1), wherein X is at least one selected from the group consisting of SiS ₂ , GeS ₂ , P ₂ S ₅ and B ₂ S ₃ ; Is at least one member selected from the group consisting of Al ₂ O ₃ , ZrO ₂ , TiO ₂ and SiO ₂ . 2. The formula aLi ₂ S.bX.cLi ₃ PO ₄
2. The sulfide-based lithium ion conductive solid electrolyte according to claim 1, wherein the composition ratio e of the lithium ion conductive solid electrolyte represented by dLiI.eY is 0.4 or less. 3. The general formula aLi ₂ S.bX.cLi ₃ PO ₄
- represented among the lithium ion conductive solid electrolyte is at dLiI · eY, claim 1 or 2 with SiS ₂ to X
The sulfide-based lithium ion conductive solid electrolyte described in the above. 4. The general formula aLi ₂ S.bX.cLi ₃ PO ₄
- represented among the lithium ion conductive solid electrolyte is at dLiI · eY, sulfide-based lithium ion conductive solid electrolyte according to any one of claims 1 to 3 using Al ₂ O ₃ in the Y. 5. The general formula aLi_TwoS ・ bX ・ cLi_ThreePO_Four
(However, X is SiS_Two, GeS_Two, P_TwoS_FiveAnd B_TwoS_ThreeHorse
Lithium ion represented by at least one sulfide
General information obtained by sintering LiI and Y
Formula dLiI.eY (where Y is Al_TwoO_Three, ZrO_Two, Ti
O_Two, SiO_TwoAt least one oxide dielectric fine
Powder) and a lithium ion conductive solid electrolyte
After mixing and crushing, heating and melting the mixed powder, cooling and general
Formula aLi_TwoS ・ bX ・ cLi_ThreePO _Four・ With dLiI ・ eY
Lithium ion conductive solid electrolyte to obtain the electrolyte represented
Synthesis method. 6. The formula aLi ₂ S.bX.cLi ₃ PO ₄
(Where X is at least one sulfide of SiS ₂ , GeS ₂ , P ₂ S _5, and B ₂ S ₃ ), and a lithium ion conductive solid electrolyte, which is obtained by sintering LiI and Y. General formula dLiI.eY (where Y is Al ₂ O ₃ , ZrO ₂ , Ti
And a lithium ion conductive solid electrolyte represented by at least one oxide dielectric fine powder of O ₂ and SiO ₂ ), and the mixed powder is heated at a glass transition temperature or lower to obtain a general formula aLi ₂ S ・ bX ・ cLi ₃ PO ₄・ dL
A method for synthesizing a lithium ion conductive solid electrolyte to obtain an electrolyte represented by iI.eY.